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rfc:rfc5977

Internet Engineering Task Force (IETF) A. Bader Request for Comments: 5977 L. Westberg Category: Experimental Ericsson ISSN: 2070-1721 G. Karagiannis

                                                  University of Twente
                                                            C. Kappler
                                                ck technology concepts
                                                             T. Phelan
                                                                 Sonus
                                                          October 2010
            RMD-QOSM: The NSIS Quality-of-Service Model
                for Resource Management in Diffserv

Abstract

 This document describes a Next Steps in Signaling (NSIS) Quality-of-
 Service (QoS) Model for networks that use the Resource Management in
 Diffserv (RMD) concept.  RMD is a technique for adding admission
 control and preemption function to Differentiated Services (Diffserv)
 networks.  The RMD QoS Model allows devices external to the RMD
 network to signal reservation requests to Edge nodes in the RMD
 network.  The RMD Ingress Edge nodes classify the incoming flows into
 traffic classes and signals resource requests for the corresponding
 traffic class along the data path to the Egress Edge nodes for each
 flow.  Egress nodes reconstitute the original requests and continue
 forwarding them along the data path towards the final destination.
 In addition, RMD defines notification functions to indicate overload
 situations within the domain to the Edge nodes.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for examination, experimental implementation, and
 evaluation.
 This document defines an Experimental Protocol for the Internet
 community.  This document is a product of the Internet Engineering
 Task Force (IETF).  It represents the consensus of the IETF
 community.  It has received public review and has been approved for
 publication by the Internet Engineering Steering Group (IESG).  Not
 all documents approved by the IESG are a candidate for any level of
 Internet Standard; see Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc5977.

Bader, et al. Experimental [Page 1] RFC 5977 RMD-QOSM October 2010

Copyright Notice

 Copyright (c) 2010 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1. Introduction ....................................................4
 2. Terminology .....................................................6
 3. Overview of RMD and RMD-QOSM ....................................7
    3.1. RMD ........................................................7
    3.2. Basic Features of RMD-QOSM ................................10
         3.2.1. Role of the QNEs ...................................10
         3.2.2. RMD-QOSM/QoS-NSLP Signaling ........................11
         3.2.3. RMD-QOSM Applicability and Considerations ..........13
 4. RMD-QOSM, Detailed Description .................................15
    4.1. RMD-QSPEC Definition ......................................16
         4.1.1. RMD-QOSM <QoS Desired> and <QoS Reserved> ..........16
         4.1.2. PHR Container ......................................17
         4.1.3. PDR Container ......................................20
    4.2. Message Format ............................................23
    4.3. RMD Node State Management .................................23
         4.3.1. Aggregated Operational and Reservation
                States at the QNE Edges ............................23
         4.3.2. Measurement-Based Method ...........................25
         4.3.3. Reservation-Based Method ...........................27
    4.4. Transport of RMD-QOSM Messages ............................28
    4.5. Edge Discovery and Message Addressing .....................31
    4.6. Operation and Sequence of Events ..........................32
         4.6.1. Basic Unidirectional Operation .....................32
                4.6.1.1. Successful Reservation ....................34
                4.6.1.2. Unsuccessful Reservation ..................46
                4.6.1.3. RMD Refresh Reservation ...................50
                4.6.1.4. RMD Modification of Aggregated
                         Reservations ..............................54
                4.6.1.5. RMD Release Procedure .....................55
                4.6.1.6. Severe Congestion Handling ................64

Bader, et al. Experimental [Page 2] RFC 5977 RMD-QOSM October 2010

                4.6.1.7. Admission Control Using Congestion
                         Notification Based on Probing .............70
         4.6.2. Bidirectional Operation ............................73
                4.6.2.1. Successful and Unsuccessful Reservations ..77
                4.6.2.2. Refresh Reservations ......................82
                4.6.2.3. Modification of Aggregated Intra-Domain
                         QoS-NSLP Operational Reservation States ...82
                4.6.2.4. Release Procedure .........................83
                4.6.2.5. Severe Congestion Handling ................84
                4.6.2.6. Admission Control Using Congestion
                         Notification Based on Probing .............87
    4.7. Handling of Additional Errors .............................89
 5. Security Considerations ........................................89
    5.1. Introduction ..............................................89
    5.2. Security Threats ..........................................91
         5.2.1. On-Path Adversary ..................................92
         5.2.2. Off-Path Adversary .................................94
    5.3. Security Requirements .....................................94
    5.4. Security Mechanisms .......................................94
 6. IANA Considerations ............................................97
    6.1. Assignment of QSPEC Parameter IDs .........................97
 7. Acknowledgments ................................................97
 8. References .....................................................97
    8.1. Normative References ......................................97
    8.2. Informative References ....................................98
 Appendix A. Examples .............................................101
    A.1. Example of a Re-Marking Operation during Severe
         Congestion in the Interior Nodes .........................101
    A.2. Example of a Detailed Severe Congestion Operation in the
         Egress Nodes .............................................107
    A.3. Example of a Detailed Re-Marking Admission Control
         (Congestion Notification) Operation in Interior Nodes ....111
    A.4. Example of a Detailed Admission Control (Congestion
         Notification) Operation in Egress Nodes ..................112
    A.5. Example of Selecting Bidirectional Flows for Termination
         during Severe Congestion .................................113
    A.6. Example of a Severe Congestion Solution for
         Bidirectional Flows Congested Simultaneously on Forward
         and Reverse Paths ........................................113
    A.7. Example of Preemption Handling during Admission Control ..117
    A.8. Example of a Retransmission Procedure within the RMD
         Domain ...................................................120
    A.9. Example on Matching the Initiator QSPEC to the Local
         RMD-QSPEC ................................................122

Bader, et al. Experimental [Page 3] RFC 5977 RMD-QOSM October 2010

1. Introduction

 This document describes a Next Steps in Signaling (NSIS) QoS Model
 for networks that use the Resource Management in Diffserv (RMD)
 framework ([RMD1], [RMD2], [RMD3], and [RMD4]).  RMD adds admission
 control to Diffserv networks and allows nodes external to the
 networks to dynamically reserve resources within the Diffserv
 domains.
 The Quality-of-Service NSIS Signaling Layer Protocol (QoS-NSLP)
 [RFC5974] specifies a generic protocol for carrying QoS signaling
 information end-to-end in an IP network.  Each network along the end-
 to-end path is expected to implement a specific QoS Model (QOSM)
 specified by the QSPEC template [RFC5975] that interprets the
 requests and installs the necessary mechanisms, in a manner that is
 appropriate to the technology in use in the network, to ensure the
 delivery of the requested QoS.  This document specifies an NSIS QoS
 Model for RMD networks (RMD-QOSM), and an RMD-specific QSPEC (RMD-
 QSPEC) for expressing reservations in a suitable form for simple
 processing by internal nodes.
 They are used in combination with the QoS-NSLP to provide QoS
 signaling service in an RMD network.  Figure 1 shows an RMD network
 with the respective entities.
                        Stateless or reduced-state        Egress
 Ingress                RMD Nodes                         Node
 Node                   (Interior Nodes; I-Nodes)        (Stateful
 (Stateful              |          |            |         RMD QoS
 RMD QoS-NLSP           |          |            |         NSLP Node)
 Node)                  V          V            V
 +-------+   Data +------+      +------+       +------+     +------+
 |-------|--------|------|------|------|-------|------|---->|------|
 |       |   Flow |      |      |      |       |      |     |      |
 |Ingress|        |I-Node|      |I-Node|       |I-Node|     |Egress|
 |       |        |      |      |      |       |      |     |      |
 +-------+        +------+      +------+       +------+     +------+
          =================================================>
          <=================================================
                                Signaling Flow
                 Figure 1: Actors in the RMD-QOSM
 Many network scenarios, such as the "Wired Part of Wireless Network"
 scenario, which is described in Section 8.4 of [RFC3726], require
 that the impact of the used QoS signaling protocol on the network
 performance should be minimized.  In such network scenarios, the
 performance of each network node that is used in a communication path

Bader, et al. Experimental [Page 4] RFC 5977 RMD-QOSM October 2010

 has an impact on the end-to-end performance.  As such, the end-to-end
 performance of the communication path can be improved by optimizing
 the performance of the Interior nodes.  One of the factors that can
 contribute to this optimization is the minimization of the QoS
 signaling protocol processing load and the minimization of the number
 of states on each Interior node.
 Another requirement that is imposed by such network scenarios is that
 whenever a severe congestion situation occurs in the network, the
 used QoS signaling protocol should be able to solve them.  In the
 case of a route change or link failure, a severe congestion situation
 may occur in the network.  Typically, routing algorithms are able to
 adapt and change their routing decisions to reflect changes in the
 topology and traffic volume.  In such situations, the rerouted
 traffic will have to follow a new path.  Interior nodes located on
 this new path may become overloaded, since they suddenly might need
 to support more traffic than for which they have capacity.  These
 severe congestion situations will severely affect the overall
 performance of the traffic passing through such nodes.
 RMD-QOSM is an edge-to-edge (intra-domain) QoS Model that, in
 combination with the QoS-NSLP and QSPEC specifications, is designed
 to support the requirements mentioned above:
    o Minimal impact on Interior node performance;
    o Increase of scalability;
    o Ability to deal with severe congestion
 Internally to the RMD network, RMD-QOSM together with QoS-NSLP
 [RFC5974] defines a scalable QoS signaling model in which per-flow
 QoS-NSLP and NSIS Transport Layer Protocol (NTLP) states are not
 stored in Interior nodes but per-flow signaling is performed (see
 [RFC5974]) at the Edges.
 In the RMD-QOSM, only routers at the Edges of a Diffserv domain
 (Ingress and Egress nodes) support the (QoS-NSLP) stateful operation;
 see Section 4.7 of [RFC5974].  Interior nodes support either the
 (QoS-NSLP) stateless operation or a reduced-state operation with
 coarser granularity than the Edge nodes.
 After the terminology in Section 2, we give an overview of RMD and
 the RMD-QOSM in Section 3.  This document specifies several RMD-QOSM/
 QoS-NSLP signaling schemes.  In particular, Section 3.2.3 identifies
 which combination of sections are used for the specification of each
 RMD-QOSM/QoS-NSLP signaling scheme.  In Section 4 we give a detailed
 description of the RMD-QOSM, including the role of QoS NSIS entities

Bader, et al. Experimental [Page 5] RFC 5977 RMD-QOSM October 2010

 (QNEs), the definition of the QSPEC, mapping of QSPEC generic
 parameters onto RMD-QOSM parameters, state management in QNEs, and
 operation and sequence of events.  Section 5 discusses security
 issues.

2. Terminology

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].
 The terminology defined by GIST [RFC5971] and QoS-NSLP [RFC5974]
 applies to this document.
 In addition, the following terms are used:
 NSIS domain: an NSIS signaling-capable domain.
 RMD domain: an NSIS domain that is capable of supporting the RMD-QOSM
 signaling and operations.
 Edge node: a QoS-NSLP node on the boundary of some administrative
 domain that connects one NSIS domain to a node in either another NSIS
 domain or a non-NSIS domain.
 NSIS-aware node: a node that is aware of NSIS signaling and RMD-QOSM
 operations, such as severe congestion detection and Differentiated
 Service Code Point (DSCP) marking.
 NSIS-unaware node: a node that is unaware of NSIS signaling, but is
 aware of RMD-QOSM operations such as severe congestion detection and
 DSCP marking.
 Ingress node: an Edge node in its role in handling the traffic as it
 enters the NSIS domain.
 Egress node: an Edge node in its role in handling the traffic as it
 leaves the NSIS domain.
 Interior node: a node in an NSIS domain that is not an Edge node.
 Congestion: a temporal network state that occurs when the traffic (or
 when traffic associated with a particular Per-Hop Behavior (PHB))
 passing through a link is slightly higher than the capacity allocated
 for the link (or allocated for the particular PHB).  If no measures
 are taken, then the traffic passing through this link may temporarily
 slightly degrade in QoS.  This type of congestion is usually solved
 using admission control mechanisms.

Bader, et al. Experimental [Page 6] RFC 5977 RMD-QOSM October 2010

 Severe congestion: the congestion situation on a particular link
 within the RMD domain where a significant increase in its real packet
 queue situation occurs, such as when due to a link failure rerouted
 traffic has to be supported by this particular link.

3. Overview of RMD and RMD-QOSM

3.1. RMD

 The Differentiated Services (Diffserv) architecture ([RFC2475],
 [RFC2638]) was introduced as a result of efforts to avoid the
 scalability and complexity problems of IntServ [RFC1633].
 Scalability is achieved by offering services on an aggregate rather
 than per-flow basis and by forcing as much of the per-flow state as
 possible to the Edges of the network.  The service differentiation is
 achieved using the Differentiated Services (DS) field in the IP
 header and the Per-Hop Behavior (PHB) as the main building blocks.
 Packets are handled at each node according to the PHB indicated by
 the DS field in the message header.
 The Diffserv architecture does not specify any means for devices
 outside the domain to dynamically reserve resources or receive
 indications of network resource availability.  In practice, service
 providers rely on short active time Service Level Agreements (SLAs)
 that statically define the parameters of the traffic that will be
 accepted from a customer.
 RMD was introduced as a method for dynamic reservation of resources
 within a Diffserv domain.  It describes a method that is able to
 provide admission control for flows entering the domain and a
 congestion handling algorithm that is able to terminate flows in case
 of congestion due to a sudden failure (e.g., link, router) within the
 domain.
 In RMD, scalability is achieved by separating a fine-grained
 reservation mechanism used in the Edge nodes of a Diffserv domain
 from a much simpler reservation mechanism needed in the Interior
 nodes.  Typically, it is assumed that Edge nodes support per-flow QoS
 states in order to provide QoS guarantees for each flow.  Interior
 nodes use only one aggregated reservation state per traffic class or
 no states at all.  In this way, it is possible to handle large
 numbers of flows in the Interior nodes.  Furthermore, due to the
 limited functionality supported by the Interior nodes, this solution
 allows fast processing of signaling messages.
 The possible RMD-QOSM applicabilities are described in Section 3.2.3.
 Two main basic admission control modes are supported: reservation-
 based and measurement-based admission control that can be used in

Bader, et al. Experimental [Page 7] RFC 5977 RMD-QOSM October 2010

 combination with a severe congestion-handling solution.  The severe
 congestion-handling solution is used in the situation that a
 link/node becomes severely congested due to the fact that the traffic
 supported by a failed link/node is rerouted and has to be processed
 by this link/node.  Furthermore, RMD-QOSM supports both
 unidirectional and bidirectional reservations.
 Another important feature of RMD-QOSM is that the intra-domain
 sessions supported by the Edges can be either per-flow sessions or
 per-aggregate sessions.  In the case of the per-flow intra-domain
 sessions, the maintained per-flow intra-domain states have a one-to-
 one dependency to the per-flow end-to-end states supported by the
 same Edge.  In the case of the per-aggregate sessions the maintained
 per-aggregate states have a one-to-many relationship to the per-flow
 end-to-end states supported by the same Edge.
 In the reservation-based method, each Interior node maintains only
 one reservation state per traffic class.  The Ingress Edge nodes
 aggregate individual flow requests into PHB traffic classes, and
 signal changes in the class reservations as necessary.  The
 reservation is quantified in terms of resource units (or bandwidth).
 These resources are requested dynamically per PHB and reserved on
 demand in all nodes in the communication path from an Ingress node to
 an Egress node.
 The measurement-based algorithm continuously measures traffic levels
 and the actual available resources, and admits flows whose resource
 needs are within what is available at the time of the request.  The
 measurement-based algorithm is used to support a predictive service
 where the service commitment is somewhat less reliable than the
 service that can be supported by the reservation-based method.
 A main assumption that is made by such measurement-based admission
 control mechanisms is that the aggregated PHB traffic passing through
 an RMD Interior node is high and therefore, current measurement
 characteristics are considered to be an indicator of future load.
 Once an admission decision is made, no record of the decision need be
 kept at the Interior nodes.  The advantage of measurement-based
 resource management protocols is that they do not require pre-
 reservation state nor explicit release of the reservations at the
 Interior nodes.  Moreover, when the user traffic is variable,
 measurement-based admission control could provide higher network
 utilization than, e.g., peak-rate reservation.  However, this can
 introduce an uncertainty in the availability of the resources.  It is
 important to emphasize that the RMD measurement-based schemes
 described in this document do not use any refresh procedures, since
 these approaches are used in stateless nodes; see Section 4.6.1.3.

Bader, et al. Experimental [Page 8] RFC 5977 RMD-QOSM October 2010

 Two types of measurement-based admission control schemes are
 possible:
  • Congestion notification function based on probing:
 This method can be used to implement a simple measurement-based
 admission control within a Diffserv domain.  In this scenario, the
 Interior nodes are not NSIS-aware nodes.  In these Interior nodes,
 thresholds are set for the traffic belonging to different PHBs in the
 measurement-based admission control function.  In this scenario, an
 end-to-end NSIS message is used as a probe packet, meaning that the
 <DSCP> field in the header of the IP packet that carries the NSIS
 message is re-marked when the predefined congestion threshold is
 exceeded.  Note that when the predefined congestion threshold is
 exceeded, all packets are re-marked by a node, including NSIS
 messages.  In this way, the Edges can admit or reject flows that are
 requesting resources.  The frequency and duration that the congestion
 level is above the threshold resulting in re-marking is tracked and
 used to influence the admission control decisions.
  • NSIS measurement-based admission control:
 In this case, the measurement-based admission control functionality
 is implemented in NSIS-aware stateless routers.  The main difference
 between this type of admission control and the congestion
 notification based on probing is related to the fact that this type
 of admission control is applied mainly on NSIS-aware nodes.  With the
 measurement-based scheme, the requested peak bandwidth of a flow is
 carried by the admission control request.  The admission decision is
 considered as positive if the currently carried traffic, as
 characterized by the measured statistics, plus the requested
 resources for the new flow exceeds the system capacity with a
 probability smaller than a value alpha.  Otherwise, the admission
 decision is negative.  It is important to emphasize that due to the
 fact that the RMD Interior nodes are stateless, they do not store
 information of previous admission control requests.
 This could lead to a situation where the admission control accuracy
 is decreased when multiple simultaneous flows (sharing a common
 Interior node) are requesting admission control simultaneously.  By
 applying measuring techniques, e.g., see [JaSh97] and [GrTs03], which
 use current and past information on NSIS sessions that requested
 resources from an NSIS-aware Interior node, the decrease in admission
 control accuracy can be limited.  RMD describes the following
 procedures:

Bader, et al. Experimental [Page 9] RFC 5977 RMD-QOSM October 2010

  • classification of an individual resource reservation or a resource

query into Per-Hop Behavior (PHB) groups at the Ingress node of the

   domain,
  • hop-by-hop admission control based on a PHB within the domain.

There are two possible modes of operation for internal nodes to

   admit requests.  One mode is the stateless or measurement-based
   mode, where the resources within the domain are queried.  Another
   mode of operation is the reduced-state reservation or reservation-
   based mode, where the resources within the domain are reserved.
  • a method to forward the original requests across the domain up to

the Egress node and beyond.

  • a congestion-control algorithm that notifies the Egress Edge nodes

about congestion. It is able to terminate the appropriate number

   of flows in the case a of congestion due to a sudden failure (e.g.,
   link or router failure) within the domain.

3.2. Basic Features of RMD-QOSM

3.2.1. Role of the QNEs

 The protocol model of the RMD-QOSM is shown in Figure 2.  The figure
 shows QoS NSIS initiator (QNI) and QoS NSIS Receiver (QNR) nodes, not
 part of the RMD network, that are the ultimate initiator and receiver
 of the QoS reservation requests.  It also shows QNE nodes that are
 the Ingress and Egress nodes in the RMD domain (QNE Ingress and QNE
 Egress), and QNE nodes that are Interior nodes (QNE Interior).
 All nodes of the RMD domain are usually QoS-NSLP-aware nodes.
 However, in the scenarios where the congestion notification function
 based on probing is used, then the Interior nodes are not NSIS aware.
 Edge nodes store and maintain QoS-NSLP and NTLP states and therefore
 are stateful nodes.  The NSIS-aware Interior nodes are NTLP
 stateless.  Furthermore, they are either QoS-NSLP stateless (for NSIS
 measurement-based operation) or reduced-state nodes storing per PHB
 aggregated QoS-NSLP states (for reservation-based operation).
 Note that the RMD domain MAY contain Interior nodes that are not
 NSIS-aware nodes (not shown in the figure).
 These nodes are assumed to have sufficient capacity for flows that
 might be admitted.  Furthermore, some of these NSIS-unaware nodes MAY
 be used for measuring the traffic congestion level on the data path.
 These measurements can be used by RMD-QOSM in the congestion control
 based on probing operation and/or severe congestion operation (see
 Section 4.6.1.6).

Bader, et al. Experimental [Page 10] RFC 5977 RMD-QOSM October 2010

 |------|   |-------|                           |------|   |------|
 | e2e  |<->| e2e   |<------------------------->| e2e  |<->| e2e  |
 | QoS  |   | QoS   |                           | QoS  |   | QoS  |
 |      |   |-------|                           |------|   |------|
 |      |   |-------|   |-------|   |-------|   |------|   |      |
 |      |   | local |<->| local |<->| local |<->| local|   |      |
 |      |   | QoS   |   |  QoS  |   |  QoS  |   |  QoS |   |      |
 |      |   |       |   |       |   |       |   |      |   |      |
 | NSLP |   | NSLP  |   | NSLP  |   | NSLP  |   | NSLP |   | NSLP |
 |st.ful|   |st.ful |   |st.less/   |st.less/   |st.ful|   |st.ful|
 |      |   |       |   |red.st.|   |red.st.|   |      |   |      |
 |      |   |-------|   |-------|   |-------|   |------|   |      |
 |------|   |-------|   |-------|   |-------|   |------|   |------|
 ------------------------------------------------------------------
 |------|   |-------|   |-------|   |-------|   |------|   |------|
 | NTLP |<->| NTLP  |<->| NTLP  |<->| NTLP  |<->| NTLP |<->|NTLP  |
 |st.ful|   |st.ful |   |st.less|   |st.less|   |st.ful|   |st.ful|
 |------|   |-------|   |-------|   |-------|   |------|   |------|
   QNI         QNE        QNE         QNE          QNE       QNR
 (End)     (Ingress)   (Interior)  (Interior)   (Egress)    (End)
     st.ful: stateful, st.less: stateless
     st.less red.st.: stateless or reduced-state
  Figure 2: Protocol model of stateless/reduced-state operation

3.2.2. RMD-QOSM/QoS-NSLP Signaling

 The basic RMD-QOSM/QoS-NSLP signaling is shown in Figure 3.  The
 signaling scenarios are accomplished using the QoS-NSLP processing
 rules defined in [RFC5974], in combination with the Resource
 Management Function (RMF) triggers sent via the QoS-NSLP-RMF API
 described in [RFC5974].
 Due to the fact that within the RMD domain a QoS Model that is
 different than the end-to-end QoS Model applied at the Edges of the
 RMD domain can be supported, the RMD Interior node reduced-state
 reservations can be updated independently of the per-flow end-to-end
 reservations (see Section 4.7 of [RFC5974]).  Therefore, two
 different RESERVE messages are used within the RMD domain.  One
 RESERVE message that is associated with the per-flow end-to-end
 reservations and is used by the Edges of the RMD domain and one that
 is associated with the reduced-state reservations within the RMD
 domain.
 A RESERVE message is created by a QNI with an Initiator QSPEC
 describing the reservation and forwarded along the path towards the
 QNR.

Bader, et al. Experimental [Page 11] RFC 5977 RMD-QOSM October 2010

 When the original RESERVE message arrives at the Ingress node, an
 RMD-QSPEC is constructed based on the initial QSPEC in the message
 (usually the Initiator QSPEC).  The RMD-QSPEC is sent in a intra-
 domain, independent RESERVE message through the Interior nodes
 towards the QNR.  This intra-domain RESERVE message uses the GIST
 datagram signaling mechanism.  Note that the RMD-QOSM cannot directly
 specify that the GIST Datagram mode SHOULD be used.  This can however
 be notified by using the GIST API Transfer-Attributes, such as
 unreliable, low level of security and use of local policy.
 Meanwhile, the original RESERVE message is sent to the Egress node on
 the path to the QNR using the reliable transport mode of NTLP.  Each
 QoS-NSLP node on the data path processes the intra-domain RESERVE
 message and checks the availability of resources with either the
 reservation-based or the measurement-based method.
     QNE Ingress     QNE Interior     QNE Interior   QNE Egress
   NTLP stateful  NTLP stateless  NTLP stateless  NTLP stateful
          |               |               |              |
  RESERVE |               |               |              |
 -------->| RESERVE       |               |              |
          +--------------------------------------------->|
          | RESERVE'      |               |              |
          +-------------->|               |              |
          |               | RESERVE'      |              |
          |               +-------------->|              |
          |               |               | RESERVE'     |
          |               |               +------------->|
          |               |               |     RESPONSE'|
          |<---------------------------------------------+
          |               |               |              | RESERVE
          |               |               |              +------->
          |               |               |              |RESPONSE
          |               |               |              |<-------
          |               |               |     RESPONSE |
          |<---------------------------------------------+
  RESPONSE|               |               |              |
 <--------|               |               |              |
   Figure 3: Sender-initiated reservation with reduced-state
             Interior nodes
 When the message reaches the Egress node, and the reservation is
 successful in each Interior node, an intra-domain (local) RESPONSE'
 is sent towards the Ingress node and the original (end-to-end)
 RESERVE message is forwarded to the next domain.  When the Egress
 node receives a RESPONSE message from the downstream end, it is
 forwarded directly to the Ingress node.

Bader, et al. Experimental [Page 12] RFC 5977 RMD-QOSM October 2010

 If an intermediate node cannot accommodate the new request, it
 indicates this by marking a single bit in the message, and continues
 forwarding the message until the Egress node is reached.  From the
 Egress node, an intra-domain RESPONSE' and an original RESPONSE
 message are sent directly to the Ingress node.
 As a consequence, in the stateless/reduced-state domain only sender-
 initiated reservations can be performed and functions requiring per-
 flow NTLP or QoS-NSLP states, like summary and reduced refreshes,
 cannot be used.  If per-flow identification is needed, i.e.,
 associating the flow IDs for the reserved resources, Edge nodes act
 on behalf of Interior nodes.

3.2.3. RMD-QOSM Applicability and Considerations

 The RMD-QOSM is a Diffserv-based bandwidth management methodology
 that is not able to provide a full Diffserv support.  The reason for
 this is that the RMD-QOSM concept can only support the (Expedited
 Forwarding) EF-like functionality behavior, but is not able to
 support the full set of (Assured Forwarding) AF-like functionality.
 The bandwidth information REQUIRED by the EF-like functionality
 behavior can be supported by RMD-QOSM carrying the bandwidth
 information in the <QoS Desired> parameter (see [RFC5975]).  The full
 set of (Assured Forwarding) AF-like functionality requires
 information that is specified in two token buckets.  The RMD-QOSM is
 not supporting the use of two token buckets and therefore, it is not
 able to support the full set of AF-functionality.  Note however, that
 RMD-QOSM could also support a single AF PHB, when the traffic or the
 upper limit of the traffic can be characterized by a single bandwidth
 parameter.  Moreover, it is considered that in case of tunneling, the
 RMD-QOSM supports only the uniform tunneling mode for Diffserv (see
 [RFC2983]).
 The RMD domain MUST be engineered in such a way that each QNE Ingress
 maintains information about the smallest MTU that is supported on the
 links within the RMD domain.
 A very important consideration on using RMD-QOSM is that within one
 RMD domain only one of the following RMD-QOSM schemes can be used at
 a time.  Thus, an RMD router can never process and use two different
 RMD-QOSM signaling schemes at the same time.
 However, all RMD QNEs supporting this specification MUST support the
 combination of the "per-flow RMD reservation-based" and the "severe
 congestion handling by proportional data packet marking" scheme.  If
 the RMD QNEs support more RMD-QOSM schemes, then the operator of that
 RMD domain MUST preconfigure all the QNE Edge nodes within one domain
 such that the <SCH> field included in the "PHR container" (Section

Bader, et al. Experimental [Page 13] RFC 5977 RMD-QOSM October 2010

 4.1.2) and the "PDR Container" (Section 4.1.3) will always use the
 same value, such that within one RMD domain only one of the below
 described RMD-QOSM schemes is used at a time.
 The congestion situations (see Section 2) are solved using an
 admission control mechanism, e.g., "per-flow congestion notification
 based on probing", while the severe congestion situations (see
 Section 2), are solved using the severe congestion handling
 mechanisms, e.g., "severe congestion handling by proportional data
 packet marking".
 The RMD domain MUST be engineered in such a way that RMD-QOSM
 messages could be transported using the GIST Query and DATA messages
 in Q-mode; see [RFC5971].  This means that the Path MTU MUST be
 engineered in such a way that the RMD-QOSM message are transported
 without fragmentation.  Furthermore, the RMD domain MUST be
 engineered in such a way to guarantee capacity for the GIST Query and
 Data messages in Q-mode, within the rate control limits imposed by
 GIST; see [RFC5971].
 The RMD domain has to be configured such that the GIST context-free
 flag (C-flag) MUST be set (C=1) for QUERY messages and DATA messages
 sent in Q-mode; see [RFC5971].
 Moreover, the same deployment issues and extensibility considerations
 described in [RFC5971] and [RFC5978] apply to this document.
 It is important to note that the concepts described in Sections
 4.6.1.6.2, 4.6.2.5.2, 4.6.1.6.2, and 4.6.2.5.2 contributed to the PCN
 WG standardization.
 The available RMD-QOSM/QoS-NSLP signaling schemes are:
  • "per-flow congestion notification based on probing" (see Sections

4.3.2, 4.6.1.7, and 4.6.2.6). Note that this scheme uses, for

   severe congestion handling, the "severe congestion handling by
   proportional data packet marking" (see Sections 4.6.1.6.2 and
   4.6.2.5.2).  Furthermore, the Interior nodes are considered to be
   Diffserv aware, but NSIS-unaware nodes (see Section 4.3.2).
  • "per-flow RMD NSIS measurement-based admission control" (see

Sections 4.3.2, 4.6.1, and 4.6.2). Note that this scheme uses, for

   severe congestion handling, the "severe congestion handling by
   proportional data packet marking" (see Sections 4.6.1.6.2 and
   4.6.2.5.2).  Furthermore, the Interior nodes are considered to be
   NSIS-aware nodes (see Section 4.3.2).

Bader, et al. Experimental [Page 14] RFC 5977 RMD-QOSM October 2010

  • "per-flow RMD reservation-based" in combination with the "severe

congestion handling by the RMD-QOSM refresh" procedure (see

   Sections 4.3.3, 4.6.1, 4.6.1.6.1, and 4.6.2.5.1).  Note that this
   scheme uses, for severe congestion handling, the "severe congestion
   handling by the RMD-QOSM refresh" procedure (see Sections 4.6.1.6.1
   and 4.6.2.5.1).  Furthermore, the intra-domain sessions supported
   by the Edge nodes are per-flow sessions (see Section 4.3.3).
  • "per-flow RMD reservation-based" in combination with the "severe

the congestion handling by proportional data packet marking"

   procedure (see Sections 4.3.3, 4.6.1, 4.6.1.6.2, and 4.6.2.5.2).
   Note that this scheme uses, for severe congestion handling, the
   "severe congestion handling by proportional data packet marking"
   procedure (see Sections 4.6.1.6.2 and 4.6.2.5.2).  Furthermore, the
   intra-domain sessions supported by the Edge nodes are per-flow
   sessions (see Section 4.3.3).
  • "per-aggregate RMD reservation-based" in combination with the

"severe congestion handling by the RMD-QOSM refresh" procedure (see

   Sections 4.3.1, 4.6.1, 4.6.1.6.1, and 4.6.2.5.1).  Note that this
   scheme uses, for severe congestion handling, the "severe congestion
   handling by the RMD-QOSM refresh" procedure (see Sections 4.6.1.6.1
   and 4.6.2.5.1).  Furthermore, the intra-domain sessions supported
   by the Edge nodes are per-aggregate sessions (see Section 4.3.1).
   Moreover, this scheme can be considered to be a reservation-based
   scheme, since the RMD Interior nodes are reduced-state nodes, i.e.,
   they do not store NTLP/GIST states, but they do store per PHB-
   aggregated QoS-NSLP reservation states.
  • "per-aggregate RMD reservation-based" in combination with the

"severe congestion handling by proportional data packet marking"

   procedure (see Sections 4.3.1, 4.6.1, 4.6.1.6.2, and 4.6.2.5.2).
   Note that this scheme uses, for severe congestion handling, the
   "severe congestion handling by proportional data packet marking"
   procedure (see Sections 4.6.1.6.2 and 4.6.2.5.2).  Furthermore, the
   intra-domain sessions supported by the Edge nodes are per-aggregate
   sessions (see Section 4.3.1).  Moreover, this scheme can be
   considered to be a reservation-based scheme, since the RMD Interior
   nodes are reduced-state nodes, i.e., they do not store NTLP/GIST
   states, but they do store per PHB-aggregated QoS-NSLP reservation
   states.

4. RMD-QOSM, Detailed Description

 This section describes the RMD-QOSM in more detail.  In particular,
 it defines the role of stateless and reduced-state QNEs, the RMD-QOSM
 QSPEC Object, the format of the RMD-QOSM QoS-NSLP messages, and how
 QSPECs are processed and used in different protocol operations.

Bader, et al. Experimental [Page 15] RFC 5977 RMD-QOSM October 2010

4.1. RMD-QSPEC Definition

 The RMD-QOSM uses the QSPEC format specified in [RFC5975].  The
 Initiator/Local QSPEC bit, i.e., <I> is set to "Local" (i.e., "1")
 and the <QSPEC Proc> is set as follows:
  • Message Sequence = 0: Sender initiated
  • Object combination = 0: <QoS Desired> for RESERVE and

<QoS Reserved> for RESPONSE

 The <QSPEC Version> used by RMD-QOSM is the default version, i.e.,
 "0", see [RFC5975].  The <QSPEC Type> value used by the RMD-QOSM is
 specified in [RFC5975] and is equal to "2".  The <Traffic Handling
 Directives> contains the following fields:
 <Traffic Handling Directives> = <PHR container> <PDR container>
 The Per-Hop Reservation container (PHR container) and the Per-Domain
 Reservation container (PDR container) are specified in Sections 4.1.2
 and 4.1.3, respectively.  The <PHR container> contains the traffic
 handling directives for intra-domain communication and reservation.
 The <PDR container> contains additional traffic handling directives
 that are needed for edge-to-edge communication.  The parameter IDs
 used by the <PHR container> and <PDR container> are assigned by IANA;
 see Section 6.
 The RMD-QOSM <QoS Desired> and <QoS Reserved>, are specified in
 Section 4.1.1.  The RMD-QOSM <QoS Desired> and <QoS Reserved> and the
 <PHR container> are used and processed by the Edge and Interior
 nodes.  The <PDR container> field is only processed by Edge nodes.

4.1.1. RMD-QOSM <QoS Desired> and <QoS Reserved>

 The RESERVE message contains only the <QoS Desired> object [RFC5975].
 The <QoS Reserved> object is carried by the RESPONSE message.
 In RMD-QOSM, the <QoS Desired> and <QoS Reserved> objects contain the
 following parameters:
 <QoS Desired> = <TMOD-1> <PHB Class> <Admission Priority>
 <QoS Reserved> = <TMOD-1> <PHB Class> <Admission Priority>
 The bit format of the <PHB Class> (see [RFC5975] and Figures 4 and 5)
 and <Admission Priority> complies with the bit format specified in
 [RFC5975].

Bader, et al. Experimental [Page 16] RFC 5977 RMD-QOSM October 2010

 Note that for the RMD-QOSM, a reservation established without an
 <Admission Priority> parameter is equivalent to a reservation
 established with an <Admission Priority> whose value is 1.
  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | DSCP      |0 0 0 0 0 0 0 0 X 0|
 +---+---+---+---+---+---+---+---+
    Figure 4: DSCP parameter
  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    PHB ID code        |0 0 X X|
 +---+---+---+---+---+---+---+---+
    Figure 5: PHB ID Code parameter

4.1.2. PHR Container

 This section describes the parameters used by the PHR container,
 which are used by the RMD-QOSM functionality available at the
 Interior nodes.
 <PHR container> = <O> <K> <S> <M>, <Admitted Hops>, <B> <Hop_U> <Time
 Lag> <SCH> <Max Admitted Hops>
 The bit format of the PHR container can be seen in Figure 6.  Note
 that in Figure 6 <Hop_U> is represented as <U>.  Furthermore, in
 Figure 6, <Max Admitted Hops> is represented as <Max Adm Hops>.
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |M|E|N|r|       Parameter ID    |r|r|r|r|          2            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |S|M| Admitted  Hops|B|U| Time  Lag     |O|K| SCH |             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Max Adm  Hops |                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                      Figure 6: PHR container
 Parameter ID: 12-bit field, indicating the PHR type:
 PHR_Resource_Request, PHR_Release_Request, PHR_Refresh_Update.

Bader, et al. Experimental [Page 17] RFC 5977 RMD-QOSM October 2010

 "PHR_Resource_Request" (Parameter ID = 17): initiate or update the
 traffic class reservation state on all nodes located on the
 communication path between the QNE(Ingress) and QNE(Egress) nodes.
 "PHR_Release_Request" (Parameter ID = 18): explicitly release, by
 subtraction, the reserved resources for a particular flow from a
 traffic class reservation state.
 "PHR_Refresh_Update" (Parameter ID = 19): refresh the traffic class
 reservation soft state on all nodes located on the communication path
 between the QNE(Ingress) and QNE(Egress) nodes according to a
 resource reservation request that was successfully processed during a
 previous refresh period.
 <S> (Severe Congestion): 1 bit.  In the case of a route change,
 refreshing RESERVE messages follow the new data path, and hence
 resources are requested there.  If the resources are not sufficient
 to accommodate the new traffic, severe congestion occurs.  Severe
 congested Interior nodes SHOULD notify Edge QNEs about the congestion
 by setting the <S> bit.
 <O> (Overload): 1 bit.  This field is used during the severe
 congestion handling scheme that is using the RMD-QOSM refresh
 procedure.  This bit is set when an overload on a QNE Interior node
 is detected and when this field is carried by the
 "PHR_Refresh_Update" container.  <O> SHOULD be set to"1" if the <S>
 bit is set.  For more details, see Section 4.6.1.6.1.
 <M>: 1 bit.  In the case of unsuccessful resource reservation or
 resource query in an Interior QNE, this QNE sets the <M> bit in order
 to notify the Egress QNE.
 <Admitted Hops>: 8-bit field.  The <Admitted Hops> counts the number
 of hops in the RMD domain where the reservation was successful.  The
 <Admitted Hops> is set to "0" when a RESERVE message enters a domain
 and it MUST be incremented by each Interior QNE, provided that the
 <Hop_U> bit is not set.  However, when a QNE that does not have
 sufficient resources to admit the reservation is reached, the <M> bit
 is set, and the <Admitted Hops> value is frozen, by setting the
 <Hop_U> bit to "1".  Note that the <Admitted Hops> parameter in
 combination with the <Max Admitted Hops> and <K> parameters are used
 during the RMD partial release procedures (see Section 4.6.1.5.2).
 <Hop_U> (NSLP_Hops unset): 1 bit.  The QNE(Ingress) node MUST set the
 <Hop_U> parameter to 0.  This parameter SHOULD be set to "1" by a
 node when the node does not increase the <Admitted Hops> value.  This
 is the case when an RMD-QOSM reservation-based node is not admitting
 the reservation request.  When <Hop_U> is set to "1", the <Admitted

Bader, et al. Experimental [Page 18] RFC 5977 RMD-QOSM October 2010

 Hops> SHOULD NOT be changed.  Note that this flag, in combination
 with the <Admitted Hops> flag, are used to locate the last node that
 successfully processed a reservation request (see Section 4.6.1.2).
 <B>: 1 bit.  When set to "1", it indicates a bidirectional
 reservation.
 <Time Lag>: It represents the ratio between the "T_Lag" parameter,
 which is the time difference between the departure time of the last
 sent "PHR_Refresh_Update" control information container and the
 departure time of the "PHR_Release_Request" control information
 container, and the length of the refresh period, "T_period", see
 Section 4.6.1.5.
 <K>: 1 bit.  When set to "1", it indicates that the
 resources/bandwidth carried by a tearing RESERVE MUST NOT be
 released, and the resources/bandwidth carried by a non-tearing
 RESERVE MUST NOT be reserved/refreshed.  For more details, see
 Section 4.6.1.5.2.
 <Max Admitted Hops>: 8 bits.  The <Admitted Hops> value that has been
 carried by the <PHR container> field used to identify the RMD
 reservation-based node that admitted or processed a
 "PHR_Resource_Request".
 <SCH>: 3 bits.  The <SCH> value that is used to specify which of the
 6 RMD-QOSM scenarios (see Section 3.2.3) MUST be used within the RMD
 domain.  The operator of an RMD domain MUST preconfigure all the QNE
 Edge nodes within one domain such that the <SCH> field included in
 the "PHR container", will always use the same value, such that within
 one RMD domain only one of the below described RMD-QOSM schemes can
 be used at a time.  All the QNE Interior nodes MUST interpret this
 field before processing any other PHR container payload fields.  The
 currently defined <SCH> values are:
 o  0:     RMD-QOSM scheme MUST be "per-flow congestion notification
           based on probing";
 o  1:     RMD-QOSM scheme MUST be "per-flow RMD NSIS measurement-
           based admission control",
 o  2:     RMD-QOSM scheme MUST be "per-flow RMD reservation-based" in
           combination with the "severe congestion handling by the
           RMD-QOSM refresh" procedure;
 o  3 :    RMD-QOSM scheme MUST be "per-flow RMD reservation-based" in
           combination with the "severe congestion handling by
           proportional data packet marking" procedure;

Bader, et al. Experimental [Page 19] RFC 5977 RMD-QOSM October 2010

 o  4:     RMD-QOSM scheme MUST be "per-aggregate RMD reservation-
           based" in combination with the "severe congestion handling
           by the RMD-QOSM refresh" procedure;
 o  5:     RMD-QOSM scheme MUST be "per-aggregate RMD reservation-
           based" in combination with the "severe congestion handling
           by proportional data packet marking" procedure;
 o  6 - 7: reserved.
 The default value of the <SCH> field MUST be set to the value equal
 to 3.

4.1.3. PDR Container

 This section describes the parameters of the PDR container, which are
 used by the RMD-QOSM functionality available at the Edge nodes.
 The bit format of the PDR container can be seen in Figure 7.
 <PDR container> = <O>  <S> <M>
 <Max Admitted Hops> <B> <SCH> [<PDR Bandwidth>]
 In Figure 7, note that <Max Admitted Hops> is represented as <Max Adm
 Hops>.
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |M|E|N|r|   Parameter ID        |r|r|r|r|          2            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |S|M| Max Adm  Hops |B|O| SCH |        EMPTY                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |PDR Bandwidth(32-bit IEEE floating point.number)               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                      Figure 7: PDR container
 Parameter ID: 12-bit field identifying the type of <PDR container>
 field.
 "PDR_Reservation_Request" (Parameter ID = 20): generated by the
 QNE(Ingress) node in order to initiate or update the QoS-NSLP per-
 domain reservation state in the QNE(Egress) node.

Bader, et al. Experimental [Page 20] RFC 5977 RMD-QOSM October 2010

 "PDR_Refresh_Request" (Parameter ID = 21): generated by the
 QNE(Ingress) node and sent to the QNE(Egress) node to refresh, in
 case needed, the QoS-NSLP per-domain reservation states located in
 the QNE(Egress) node.
 "PDR_Release_Request" (Parameter ID = 22): generated and sent by the
 QNE(Ingress) node to the QNE(Egress) node to release the per-domain
 reservation states explicitly.
 "PDR_Reservation_Report" (Parameter ID = 23): generated and sent by
 the QNE(Egress) node to the QNE(Ingress) node to report that a
 "PHR_Resource_Request" and a "PDR_Reservation_Request" traffic
 handling directive field have been received and that the request has
 been admitted or rejected.
 "PDR_Refresh_Report" (Parameter ID = 24) generated and sent by the
 QNE(Egress) node in case needed, to the QNE(Ingress) node to report
 that a "PHR_Refresh_Update" traffic handling directive field has been
 received and has been processed.
 "PDR_Release_Report" (Parameter ID = 25) generated and sent by the
 QNE(Egress) node in case needed, to the QNE(Ingress) node to report
 that a "PHR_Release_Request" and a "PDR_Release_Request" traffic
 handling directive field have been received and have been processed.
 "PDR_Congestion_Report" (Parameter ID = 26): generated and sent by
 the QNE(Egress) node to the QNE(Ingress) node and used for congestion
 notification.
 <S> (PDR Severe Congestion): 1 bit.  Specifies if a severe congestion
 situation occurred.  It can also carry the <S> parameter of the
 <PHR_Resource_Request> or <PHR_Refresh_Update> fields.
 <O> (Overload): 1 bit.  This field is used during the severe
 congestion handling scheme that is using the RMD-QOSM refresh
 procedure.  This bit is set when an overload on a QNE Interior node
 is detected and when this field is carried by the
 "PDR_Congestion_Report" container.  <O> SHOULD be set to "1" if the
 <S> bit is set.  For more details, see Section 4.6.1.6.1.
 <M> (PDR Marked): 1 bit.  Carries the <M> value of the
 "PHR_Resource_Request" or "PHR_Refresh_Update" traffic handling
 directive field.
 <B>: 1 bit.  Indicates bidirectional reservation.

Bader, et al. Experimental [Page 21] RFC 5977 RMD-QOSM October 2010

 <Max Admitted Hops>: 8 bits.  The <Admitted Hops> value that has been
 carried by the <PHR container> field used to identify the RMD
 reservation-based node that admitted or processed a
 "PHR_Resource_Request".
 <PDR Bandwidth>: 32 bits.  This field specifies the bandwidth that
 either applies when the <B> flag is set to "1" and when this
 parameter is carried by a RESPONSE message or when a severe
 congestion occurs and the QNE Edges maintain an aggregated intra-
 domain QoS-NSLP operational state and it is carried by a NOTIFY
 message.  In the situation that the <B> flag is set to "1", this
 parameter specifies the requested bandwidth that has to be reserved
 by a node in the reverse direction and when the intra-domain
 signaling procedures require a bidirectional reservation procedure.
 In the severe congestion situation, this parameter specifies the
 bandwidth that has to be released.
 <SCH>: 3 bits.  The <SCH> value that is used to specify which of the
 6 RMD scenarios (see Section 3.2.3) MUST be used within the RMD
 domain.  The operator of an RMD domain MUST preconfigure all the QNE
 Edge nodes within one domain such that the <SCH> field included in
 the "PDR container", will always use the same value, such that within
 one RMD domain only one of the below described RMD-QOSM schemes can
 be used at a time.  All the QNE Interior nodes MUST interpret this
 field before processing any other <PDR container> payload fields.
 The currently defined <SCH> values are:
 o  0:     RMD-QOSM scheme MUST be "per-flow congestion notification
           based on probing";
 o  1:     RMD-QOSM scheme MUST be "per-flow RMD NSIS measurement-
           based admission control";
 o  2:     RMD-QOSM scheme MUST be "per-flow RMD reservation-based" in
           combination with the "severe congestion handling by the
           RMD-QOSM refresh" procedure;
 o  3 :    RMD-QOSM scheme MUST be "per-flow RMD reservation-based" in
           combination with the "severe congestion handling by
           proportional data packet marking" procedure;
 o  4:     RMD-QOSM scheme MUST be "per-aggregate RMD reservation-
           based" in combination with the "severe congestion handling
           by the RMD-QOSM refresh" procedure;
 o  5:     RMD-QOSM scheme MUST be "per-aggregate RMD reservation-
           based" in combination with the "severe congestion handling
           by proportional data packet marking" procedure;

Bader, et al. Experimental [Page 22] RFC 5977 RMD-QOSM October 2010

 o  6 - 7: reserved.
 The default value of the <SCH> field MUST be set to the value equal
 to 3.

4.2. Message Format

 The format of the messages used by the RMD-QOSM complies with the
 QoS-NSLP and QSPEC template specifications.  The QSPEC used by RMD-
 QOSM is denoted in this document as RMD-QSPEC and is described in
 Section 4.1.

4.3. RMD Node State Management

 The QoS-NSLP state creation and management is specified in [RFC5974].
 This section describes the state creation and management functions of
 the Resource Management Function (RMF) in the RMD nodes.

4.3.1. Aggregated Operational and Reservation States at the QNE Edges

 The QNE Edges maintain both the intra-domain QoS-NSLP operational and
 reservation states, while the QNE Interior nodes maintain only
 reservation states.  The structure of the intra-domain QoS-NSLP
 operational state used by the QNE Edges is specified in [RFC5974].
 In this case, the intra-domain sessions supported by the Edges are
 per-aggregate sessions that have a one-to-many relationship to the
 per-flow end-to-end states supported by the same Edge.
 Note that the method of selecting the end-to-end sessions that form
 an aggregate is not specified in this document.  An example of how
 this can be accomplished is by monitoring the GIST routing states
 used by the end-to-end sessions and grouping the ones that use the
 same <PHB Class>, QNE Ingress and QNE Egress addresses, and the value
 of the priority level.  Note that this priority level should be
 deduced from the priority parameters carried by the initial QSPEC
 object.
 The operational state of this aggregated intra-domain session MUST
 contain a list with BOUND-SESSION-IDs.
 The structure of the list depends on whether a unidirectional
 reservation or a bidirectional reservation is supported.
 When the operational state (at QNE Ingress and QNE Egress) supports
 unidirectional reservations, then this state MUST contain a list with
 BOUND-SESSION-IDs maintaining the <SESSION-ID> values of its bound
 end-to-end sessions.  The Binding_Code associated with this BOUND-

Bader, et al. Experimental [Page 23] RFC 5977 RMD-QOSM October 2010

 SESSION-ID is set to code (Aggregated sessions).  Thus, the
 operational state maintains a list of BOUND-SESSION-ID entries.  Each
 entry is created when an end-to-end session joins the aggregated
 intra-domain session and is removed when an end-to-end session leaves
 the aggregate.
 It is important to emphasize that, in this case, the operational
 state (at QNE Ingress and QNE Egress) that is maintained by each end-
 to-end session bound to the aggregated intra-domain session MUST
 contain in the BOUND-SESSION-ID, the <SESSION-ID> value of the bound
 tunneled intra-domain (aggregate) session.  The Binding_Code
 associated with this BOUND-SESSION-ID is set to code (Aggregated
 sessions).
 When the operational state (at QNE Ingress and QNE Egress) supports
 bidirectional reservations, the operational state MUST contain a list
 of BOUND-SESSION-ID sets.  Each set contains two BOUND-SESSION-IDs.
 One of the BOUND-SESSION-IDs maintains the <SESSION-ID> value of one
 of bound end-to-end session.  The Binding_Code associated with this
 BOUND-SESSION-ID is set to code (Aggregated sessions).  Another
 BOUND-SESSION-ID, within the same set entry, maintains the SESSION-ID
 of the bidirectional bound end-to-end session.  The Binding_Code
 associated with this BOUND-SESSION-ID is set to code (Bidirectional
 sessions).
 Note that, in each set, a one-to-one relation exists between each
 BOUND-SESSION-ID with Binding_Code set to (Aggregate sessions) and
 each BOUND-SESSION-ID with Binding_Code set to (bidirectional
 sessions).  Each set is created when an end-to-end session joins the
 aggregated operational state and is removed when an end-to-end
 session leaves the aggregated operational state.
 It is important to emphasize that, in this case, the operational
 state (at QNE Ingress and QNE Egress) that is maintained by each end-
 to-end session bound to the aggregated intra-domain session it MUST
 contain two types of BOUND-SESSION-IDs.  One is the BOUND-SESSION-ID
 that MUST contain the <SESSION-ID> value of the bound tunneled
 aggregated intra-domain session that is using the Binding_Code set to
 (Aggregated sessions).  The other BOUND-SESSION-ID maintains the
 SESSION-ID of the bound bidirectional end-to-end session.  The
 Binding_Code associated with this BOUND-SESSION-ID is set to code
 (Bidirectional sessions).
 When the QNE Edges use aggregated QoS-NSLP reservation states, then
 the <PHB Class> value and the size of the aggregated reservation,
 e.g., reserved bandwidth, have to be maintained.  Note that this type
 of aggregation is an edge-to-edge aggregation and is similar to the
 aggregation type specified in [RFC3175].

Bader, et al. Experimental [Page 24] RFC 5977 RMD-QOSM October 2010

 The size of the aggregated reservations needs to be greater or equal
 to the sum of bandwidth of the inter-domain (end-to-end)
 reservations/sessions it aggregates (e.g., see Section 1.4.4 of
 [RFC3175]).
 A policy can be used to maintain the amount of REQUIRED bandwidth on
 a given aggregated reservation by taking into account the sum of the
 underlying inter-domain (end-to-end) reservations, while endeavoring
 to change reservation less frequently.  This MAY require a trend
 analysis.  If there is a significant probability that in the next
 interval of time the current aggregated reservation is exhausted, the
 Ingress router MUST predict the necessary bandwidth and request it.
 If the Ingress router has a significant amount of bandwidth reserved,
 but has very little probability of using it, the policy MAY predict
 the amount of bandwidth REQUIRED and release the excess.  To increase
 or decrease the aggregate, the RMD modification procedures SHOULD be
 used (see Section 4.6.1.4).
 The QNE Interior nodes are reduced-state nodes, i.e., they do not
 store NTLP/GIST states, but they do store per PHB-aggregated QoS-NSLP
 reservation states.  These reservation states are maintained and
 refreshed in the same way as described in Section 4.3.3.

4.3.2. Measurement-Based Method

 The QNE Edges maintain per-flow intra-domain QoS-NSLP operational and
 reservation states that contain similar data structures as those
 described in Section 4.3.1.  The main difference is associated with
 the different types of the used Message-Routing-Information (MRI) and
 the bound end-to-end sessions.  The structure of the maintained
 BOUND-SESSION-IDs depends on whether a unidirectional reservation or
 a bidirectional reservation is supported.
 When unidirectional reservations are supported, the operational state
 associated with this per-flow intra-domain session MUST contain in
 the BOUND-SESSION-ID the <SESSION-ID> value of its bound end-to-end
 session.  The Binding_Code associated with this BOUND-SESSION-ID is
 set to code (Tunneled and end-to-end sessions).
 When bidirectional reservations are supported, the operational state
 (at QNE Ingress and QNE Egress) MUST contain two types of BOUND-
 SESSION-IDs.  One is the BOUND-SESSION-ID that maintains the
 <SESSION-ID> value of the bound tunneled per-flow intra-domain
 session.  The Binding_Code associated with this BOUND-SESSION-ID is
 set to code (Tunneled and end-to-end sessions).

Bader, et al. Experimental [Page 25] RFC 5977 RMD-QOSM October 2010

 The other BOUND-SESSION-ID maintains the SESSION-ID of the bound
 bidirectional end-to-end session.  The Binding_Code associated with
 this BOUND-SESSION-ID is set to code (Bidirectional sessions).
 Furthermore, the QoS-NSLP reservation state maintains the <PHB Class>
 value, the value of the bandwidth requested by the end-to-end session
 bound to the intra-domain session, and the value of the priority
 level.
 The measurement-based method can be classified in two schemes:
  • Congestion notification based on probing:
 In this scheme, the Interior nodes are Diffserv-aware but not NSIS-
 aware nodes.  Each Interior node counts the bandwidth that is used by
 each PHB traffic class.  This counter value is stored in an RMD_QOSM
 state.  For each PHB traffic class, a predefined congestion
 notification threshold is set.  The predefined congestion
 notification threshold is set according to an engineered bandwidth
 limitation based, e.g., on a Service Level Agreement or a capacity
 limitation of specific links.  The threshold is usually less than the
 capacity limit, i.e., admission threshold, in order to avoid
 congestion due to the error of estimating the actual traffic load.
 The value of this threshold SHOULD be stored in another RMD_QOSM
 state.
 In this scenario, an end-to-end NSIS message is used as a probe
 packet.  In this case, the <DSCP> field of the GIST message is re-
 marked when the predefined congestion notification threshold is
 exceeded in an Interior node.  It is required that the re-marking
 happens to all packets that belong to the congested PHB traffic class
 so that the probe can't pass the congested router without being re-
 marked.  In this way, it is ensured that the end-to-end NSIS message
 passed through the node that is congested.  This feature is very
 useful when flow-based ECMP (Equal Cost Multiple Path) routing is
 used to detect only flows that are passing through the congested
 node.
  • NSIS measurement-based admission control:
 The measurement-based admission control is implemented in NSIS-aware
 stateless routers.  Thus, the main difference between this type of
 the measurement-based admission control and the congestion
 notification-based admission control is the fact that the Interior
 nodes are NSIS-aware nodes.  In particular, the QNE Interior nodes
 operating in NSIS measurement-based mode are QoS-NSLP stateless
 nodes, i.e., they do not support any QoS-NSLP or NTLP/GIST states.
 These measurement-based nodes store two RMD-QOSM states per PHR

Bader, et al. Experimental [Page 26] RFC 5977 RMD-QOSM October 2010

 group.  These states reflect the traffic conditions at the node and
 are not affected by QoS-NSLP signaling.  One state stores the
 measured user traffic load associated with the PHR group and another
 state stores the maximum traffic load threshold that can be admitted
 per PHR group.  When a measurement-based node receives a intra-domain
 RESERVE message, it compares the requested resources to the available
 resources (maximum allowed minus current load) for the requested PHR
 group.  If there are insufficient resources, it sets the <M> bit in
 the RMD-QSPEC.  No change to the RMD-QSPEC is made when there are
 sufficient resources.

4.3.3. Reservation-Based Method

 The QNE Edges maintain intra-domain QoS-NSLP operational and
 reservation states that contain similar data structures as described
 in Section 4.3.1.
 In this case, the intra-domain sessions supported by the Edges are
 per-flow sessions that have a one-to-one relationship to the per-flow
 end-to-end states supported by the same Edge.
 The QNE Interior nodes operating in reservation-based mode are QoS-
 NSLP reduced-state nodes, i.e., they do not store NTLP/GIST states
 but they do store per PHB-aggregated QoS-NSLP states.
 The reservation-based PHR installs and maintains one reservation
 state per PHB, in all the nodes located in the communication path.
 This state is identified by the <PHB Class> value and it maintains
 the number of currently reserved resource units (or bandwidth).
 Thus, the QNE Ingress node signals only the resource units requested
 by each flow.  These resource units, if admitted, are added to the
 currently reserved resources per PHB.
 For each PHB, a threshold is maintained that specifies the maximum
 number of resource units that can be reserved.  This threshold could,
 for example, be statically configured.
 An example of how the admission control and its maintenance process
 occurs in the Interior nodes is described in Section 3 of [CsTa05].
 The simplified concept that is used by the per-traffic class
 admission control process in the Interior nodes, is based on the
 following equation:
      last + p <= T,

Bader, et al. Experimental [Page 27] RFC 5977 RMD-QOSM October 2010

 where p is the requested bandwidth rate, T is the admission
 threshold, which reflects the maximum traffic volume that can be
 admitted in the traffic class, and last is a counter that records the
 aggregated sum of the signaled bandwidth rates of previous admitted
 flows.
 The PHB group reservation states maintained in the Interior nodes are
 soft states, which are refreshed by sending periodic refresh intra-
 domain RESERVE messages, which are initiated by the Ingress QNEs.  If
 a refresh message corresponding to a number of reserved resource
 units (i.e., bandwidth) is not received, the aggregated reservation
 state is decreased in the next refresh period by the corresponding
 amount of resources that were not refreshed.  The refresh period can
 be refined using a sliding window algorithm described in [RMD3].
 The reserved resources for a particular flow can also be explicitly
 released from a PHB reservation state by means of a intra-domain
 RESERVE release/tear message, which is generated by the Ingress QNEs.
 The use of explicit release enables the instantaneous release of the
 resources regardless of the length of the refresh period.  This
 allows a longer refresh period, which also reduces the number of
 periodic refresh messages.
 Note that both in the case of measurement- and (per-flow and
 aggregated) RMD reservation-based methods, the way in which the
 maximum bandwidth thresholds are maintained is out of the
 specification of this document.  However, when admission priorities
 are supported, the Maximum Allocation [RFC4125] or the Russian Dolls
 [RFC4127] bandwidth allocation models MAY be used.  In this case,
 three types of priority traffic classes within the same PHB, e.g.,
 Expedited Forwarding, can be differentiated.  These three different
 priority traffic classes, which are associated with the same PHB, are
 denoted in this document as PHB_low_priority, PHB_normal_priority,
 and PHB_high_priority, and are identified by the <PHB Class> value
 and the priority value, which is carried in the <Admission Priority>
 RMD-QSPEC parameter.

4.4. Transport of RMD-QOSM Messages

 As mentioned in Section 1, the RMD-QOSM aims to support a number of
 additional requirements, e.g., Minimal impact on Interior node
 performance.  Therefore, RMD-QOSM is designed to be very lightweight
 signaling with regard to the number of signaling message round trips
 and the amount of state established at involved signaling nodes with
 and without reduced state on QNEs.  The actions allowed by a QNE
 Interior node are minimal (i.e., only those specified by the RMD-
 QOSM).

Bader, et al. Experimental [Page 28] RFC 5977 RMD-QOSM October 2010

 For example, only the QNE Ingress and the QNE Egress nodes are
 allowed to initiate certain signaling messages.  QNE Interior nodes
 are, for example, allowed to modify certain signaling message
 payloads.  Moreover, RMD signaling is targeted towards intra-domain
 signaling only.  Therefore, RMD-QOSM relies on the security and
 reliability support that is provided by the bound end-to-end session,
 which is running between the boundaries of the RMD domain (i.e., the
 RMD-QOSM QNE Edges), and the security provided by the D-mode.  This
 implies the use of the Datagram Mode.
 Therefore, the intra-domain messages used by the RMD-QOSM are
 intended to operate in the NTLP/GIST Datagram mode (see [RFC5971]).
 The NSLP functionality available in all RMD-QOSM-aware QoS-NSLP nodes
 requires the intra-domain GIST, via the QoS-NSLP RMF API see
 [RFC5974], to:
  • operate in unreliable mode. This can be satisfied by passing this

requirement from the QoS-NSLP layer to the GIST layer via the API

   Transfer-Attributes.
  • not create a message association state. This requirement can be

satisfied by a local policy, e.g., the QNE is configured to not

   create a message association state.
  • not create any NTLP routing state by the Interior nodes. This can

be satisfied by passing this requirement from the QoS-NSLP layer to

   the GIST layer via the API.  However, between the QNE Egress and
   QNE Ingress routing states SHOULD be created that are associated
   with intra-domain sessions and that can be used for the
   communication of GIST Data messages sent by a QNE Egress directly
   to a QNE Ingress.  This type of routing state associated with an
   intra-domain session can be generated and used in the following
   way:
  • When the QNE Ingress has to send an initial intra-domain RESERVE

message, the QoS-NSLP sends this message by including, in the GIST

   API SendMessage primitive, the Unreliable and No security
   attributes.  In order to optimize this procedure, the RMD domain
   MUST be engineered in such a way that GIST will piggyback this NSLP
   message on a GIST Query message.  Furthermore, GIST sets the C-flag
   (C=1), see [RFC5971] and uses the Q-mode.  The GIST functionality
   in each QNE Interior node will receive the GIST Query message and
   by using the RecvMessage GIST API primitive it will pass the intra-
   domain RESERVE message to the QoS-NSLP functionality.  At the same
   time, the GIST functionality uses the Routing-State-Check boolean
   to find out if the QoS-NSLP needs to create a routing state.  The
   QoS-NSLP sets this boolean to inform GIST to not create a routing
   state and to forward the GIST Query further downstream with the

Bader, et al. Experimental [Page 29] RFC 5977 RMD-QOSM October 2010

   modified QoS-NSLP payload, which will include the modified intra-
   domain RESERVE message.  The intra-domain RESERVE is sent in the
   same way up to the QNE Egress.  The QNE Egress needs to create a
   routing state.
   Therefore, at the same moment that the GIST functionality passes
   the intra-domain RESERVE message, via the GIST RecvMessage
   primitive, to the QoS-NSLP, the QoS-NSLP sets the Routing-State-
   Check boolean such that a routing state is created.  The GIST
   creates the routing state using normal GIST procedures.  After this
   phase, the QNE Ingress and QNE Egress have, for the particular
   session, routing states that can route traffic directly from QNE
   Ingress to QNE Egress and from QNE Egress to QNE Ingress.  The
   routing state at the QNE Egress can be used by the QoS-NSLP and
   GIST to send an intra-domain RESPONSE or intra-domain NOTIFY
   directly to the QNE Ingress using GIST Data messages.  Note that
   this routing state is refreshed using normal GIST procedures.  Note
   that in the above description, it is considered that the QNE
   Ingress can piggyback the initial RESERVE (NSLP) message on the
   GIST Query message.  If the piggybacking of this NSLP (initial
   RESERVE) message would not be possible on the GIST Query message,
   then the GIST Query message sent by the QNE Ingress node would not
   contain any NSLP data.  This GIST Query message would only be
   processed by the QNE Egress to generate a routing state.
   After the QNE Ingress is informed that the routing state at the QNE
   Egress is initiated, it would have to send the initial RESERVE
   message using similar procedures as for the situation that it would
   send an intra-domain RESERVE message that is not an initial
   RESERVE, see next bullet.  This procedure is not efficient and
   therefore it is RECOMMENDED that the RMD domain MUST be engineered
   in such a way that the GIST protocol layer, which is processed on a
   QNE Ingress, will piggyback an initial RESERVE (NSLP) message on a
   GIST Query message that uses the Q-mode.
  • When the QNE Ingress needs to send an intra-domain RESERVE message

that is not an initial RESERVE, then the QoS-NSLP sends this

   message by including in the GIST API SendMessage primitive such
   attributes that the use of the Datagram Mode is implied, e.g., the
   Unreliable attribute.  Furthermore, the Local policy attribute is
   set such that GIST sends the intra-domain RESERVE message in a
   Q-mode even if there is a routing state at the QNE Ingress.  In
   this way, the GIST functionality uses its local policy to send the
   intra-domain RESERVE message by piggybacking it on a GIST Data
   message and sending it in Q-mode even if there is a routing state
   for this session.  The intra-domain RESERVE message is piggybacked
   on the GIST Data message that is forwarded and processed by the QNE
   Interior nodes up to the QNE Egress.

Bader, et al. Experimental [Page 30] RFC 5977 RMD-QOSM October 2010

 The transport of the original (end-to-end) RESERVE message is
 accomplished in the following way:
 At the QNE Ingress, the original (end-to-end) RESERVE message is
 forwarded but ignored by the stateless or reduced-state nodes, see
 Figure 3.
 The intermediate (Interior) nodes are bypassed using multiple levels
 of NSLPID values (see [RFC5974]).  This is accomplished by marking
 the end-to-end RESERVE message, i.e., modifying the QoS-NSLP default
 NSLPID value to another NSLPID predefined value.
 The marking MUST be accomplished by the Ingress by modifying the
 QoS_NSLP default NSLPID value to a NSLPID predefined value.  In this
 way, the Egress MUST stop this marking process by reassigning the
 QoS-NSLP default NSLPID value to the original (end-to-end) RESERVE
 message.  Note that the assignment of these NSLPID values is a QoS-
 NSLP issue, which SHOULD be accomplished via IANA [RFC5974].

4.5. Edge Discovery and Message Addressing

 Mainly, the Egress node discovery can be performed by using either
 the GIST discovery mechanism [RFC5971], manual configuration, or any
 other discovery technique.  The addressing of signaling messages
 depends on which GIST transport mode is used.  The RMD-QOSM/QoS-NSLP
 signaling messages that are processed only by the Edge nodes use the
 peer-peer addressing of the GIST Connection (C) mode.
 RMD-QOSM/QoS-NSLP signaling messages that are processed by all nodes
 of the Diffserv domain, i.e., Edges and Interior nodes, use the end-
 to-end addressing of the GIST Datagram (D) mode.  Note that the RMD-
 QOSM cannot directly specify that the GIST Connection or the GIST
 Datagram mode SHOULD be used.  This can only be specified by using,
 via the QoS-NSLP-RMF API, the GIST API Transfer-Attributes, such as
 Reliable or Unreliable, high or low level of security, and by the use
 of local policies.  RMD QoS signaling messages that are addressed to
 the data path end nodes are intercepted by the Egress nodes.  In
 particular, at the ingress and for downstream intra-domain messages,
 the RMD-QOSM instructs the GIST functionality, via the GIST API to do
 the following:
  • use unreliable and low level security Transfer-Attributes,
  • do not create a GIST routing state, and
  • use the D-mode MRI.

Bader, et al. Experimental [Page 31] RFC 5977 RMD-QOSM October 2010

 The intra-domain RESERVE messages can then be transported by using
 the Query D-mode; see Section 4.4.
 At the QNE Egress, and for upstream intra-domain messages, the RMD-
 QOSM instructs the GIST functionality, via the GIST API, to use among
 others:
  • unreliable and low level security Transfer-Attributes
  • the routing state associated with the intra-domain session to send

an upstream intra-domain message directly to the QNE Ingress; see

   Section 4.4.

4.6. Operation and Sequence of Events

4.6.1. Basic Unidirectional Operation

 This section describes the basic unidirectional operation and
 sequence of events/triggers of the RMD-QOSM.  The following basic
 operation cases are distinguished:
  • Successful reservation (Section 4.6.1.1),
  • Unsuccessful reservation (Section 4.6.1.2),
  • RMD refresh reservation (Section 4.6.1.3),
  • RMD modification of aggregated reservation (Section 4.6.1.4),
  • RMD release procedure (Section 4.6.1.5.),
  • Severe congestion handling (Section 4.6.1.6.),
  • Admission control using congestion notification based on probing

(Section 4.6.1.7.).

 The QNEs at the Edges of the RMD domain support the RMD QoS Model and
 end-to-end QoS Models, which process the RESERVE message differently.
 Note that the term end-to-end QoS Model applies to any QoS Model that
 is initiated and terminated outside the RMD-QOSM-aware domain.
 However, there might be situations where a QoS Model is initiated
 and/or terminated by the QNE Edges and is considered to be an end-to-
 end QoS Model.  This can occur when the QNE Edges can also operate as
 either QNI or as QNR and at the same time they can operate as either
 sender or receiver of the data path.
 It is important to emphasize that the content of this section is used
 for the specification of the following RMD-QOSM/QoS-NSLP signaling
 schemes, when basic unidirectional operation is assumed:
  • "per-flow congestion notification based on probing";
  • "per-flow RMD NSIS measurement-based admission control";

Bader, et al. Experimental [Page 32] RFC 5977 RMD-QOSM October 2010

  • "per-flow RMD reservation-based" in combination with the "severe

congestion handling by the RMD-QOSM refresh" procedure;

  • "per-flow RMD reservation-based" in combination with the "severe

congestion handling by proportional data packet marking" procedure;

  • "per-aggregate RMD reservation-based" in combination with the

"severe congestion handling by the RMD-QOSM refresh" procedure;

  • "per-aggregate RMD reservation-based" in combination with the

"severe congestion handling by proportional data packet marking"

   procedure.
 For more details, please see Section 3.2.3.
 In particular, the functionality described in Sections 4.6.1.1,
 4.6.1.2, 4.6.1.3, 4.6.1.5, 4.6.1.4, and 4.6.1.6 applies to the RMD
 reservation-based and to the NSIS measurement-based admission control
 methods.  The described functionality in Section 4.6.1.7 applies to
 the admission control procedure that uses the congestion notification
 based on probing.  The QNE Edge nodes maintain either per-flow QoS-
 NSLP operational and reservation states or aggregated QoS-NSLP
 operational and reservation states.
 When the QNE Edges maintain aggregated QoS-NSLP operational and
 reservation states, the RMD-QOSM functionality MAY accomplish an RMD
 modification procedure (see Section 4.6.1.4), instead of the
 reservation initiation procedure that is described in this
 subsection.  Note that it is RECOMMENDED that the QNE implementations
 of RMD-QOSM process the QoS-NSLP signaling messages with a higher
 priority than data packets.  This can be accomplished as described in
 Section 3.3.4 of [RFC5974] and it can be requested via the QoS-NSLP-
 RMF API described in [RFC5974].  The signaling scenarios described in
 this section are accomplished using the QoS-NSLP processing rules
 defined in [RFC5974], in combination with the RMF triggers sent via
 the QoS-NSLP-RMF API described in [RFC5974].
 According to Section 3.2.3, it is specified that only the "per-flow
 RMD reservation-based" in combination with the "severe congestion
 handling by proportional data packet marking" scheme MUST be
 implemented within one RMD domain.  However, all RMD QNEs supporting
 this specification MUST support the combination the "per-flow RMD
 reservation-based" in combination with the "severe congestion
 handling by proportional data packet marking" scheme.  If the RMD
 QNEs support more RMD-QOSM schemes, then the operator of that RMD
 domain MUST preconfigure all the QNE Edge nodes within one domain
 such that the <SCH> field included in the "PHR container" (Section

Bader, et al. Experimental [Page 33] RFC 5977 RMD-QOSM October 2010

 4.1.2) and the "PDR Container" (Section 4.1.3) will always use the
 same value, such that within one RMD domain only one of the below
 described RMD-QOSM schemes is used at a time.
 All QNE nodes located within the RMD domain MUST read and interpret
 the <SCH> field included in the "PHR container" before processing all
 the other "PHR container" payload fields.  Moreover, all QNE Edge
 nodes located at the boarder of the RMD domain, MUST read and
 interpret the <SCH> field included in the "PDR container" before
 processing all the other <PDR container> payload fields.

4.6.1.1. Successful Reservation

 This section describes the operation of the RMD-QOSM where a
 reservation is successfully accomplished.
 The QNI generates the initial RESERVE message, and it is forwarded by
 the NTLP as usual [RFC5971].

4.6.1.1.1. Operation in Ingress Node

 When an end-to-end reservation request (RESERVE) arrives at the
 Ingress node (QNE) (see Figure 8), it is processed based on the end-
 to-end QoS Model.  Subsequently, the combination of <TMOD-1>, <PHB
 Class>, and <Admission Priority> is derived from the <QoS Desired>
 object of the initial QSPEC.
 The QNE Ingress MUST maintain information about the smallest MTU that
 is supported on the links within the RMD domain.
 The <Maximum Packet Size-1 (MPS)> value included in the end-to-end
 QoS Model <TMOD-1> parameter is compared with the smallest MTU value
 that is supported by the links within the RMD domain.  If the
 "Maximum Packet Size-1 (MPS)" is larger than this smallest MTU value
 within the RMD domain, then the end-to-end reservation request is
 rejected (see Section 4.6.1.1.2).  Otherwise, the admission process
 continues.
 The <TMOD-1> parameter contained in the original initiator QSPEC is
 mapped into the equivalent RMD-Qspec <TMOD-1> parameter representing
 only the peak bandwidth in the local RMD-QSPEC.  This can be
 accomplished by setting the RMD-QSPEC <TMOD-1> fields as follows:
 token rate (r) = peak traffic rate (p), the bucket depth (b) = large,
 and the minimum policed unit (m) = large.
 Note that the bucket size, (b), is measured in bytes.  Values of this
 parameter may range from 1 byte to 250 gigabytes; see [RFC2215].
 Thus, the maximum value that (b) could be is in the order of 250

Bader, et al. Experimental [Page 34] RFC 5977 RMD-QOSM October 2010

 gigabytes.  The minimum policed unit, [m], is an integer measured in
 bytes and must be less than or equal to the Maximum Packet Size
 (MPS).  Thus, the maximum value that (m) can be is (MPS).  [Part94]
 and [TaCh99] describe a method of calculating the values of some
 Token Bucket parameters, e.g., calculation of large values of (m) and
 (b), when the token rate (r), peak rate (p), and MPS are known.
 The <Peak Data Rate-1 (p)> value of the end-to-end QoS Model <TMOD-1>
 parameter is copied into the <Peak Data Rate-1 (p)> value of the
 <Peak Data Rate-1 (p)> value of the local RMD-Qspec <TMOD-1>.
 The MPS value of the end-to-end QoS Model <TMOD-1> parameter is
 copied into the MPS value of the local RMD-Qspec <TMOD-1>.
 If the initial QSPEC does not contain the <PHB Class> parameter, then
 the selection of the <PHB Class> that is carried by the intra-domain
 RMD-QSPEC is defined by a local policy similar to the procedures
 discussed in [RFC2998] and [RFC3175].
 For example, in the situation that the initial QSPEC is used by the
 IntServ Controlled Load QOSM, then the Expedited Forwarding (EF) PHB
 is appropriate to set the <PHB Class> parameter carried by the intra-
 domain RMD-QSPEC (see [RFC3175]).
 If the initial QSPEC does not carry the <Admission Priority>
 parameter, then the <Admission Priority> parameter in the RMD-QSPEC
 will not be populated.  If the initial QSPEC does not carry the
 <Admission Priority> parameter, but it carries other priority
 parameters, then it is considered that Edges, as being stateful
 nodes, are able to control the priority of the sessions that are
 entering or leaving the RMD domain in accordance with the priority
 parameters.
 Note that the RMF reservation states (see Section 4.3) in the QNE
 Edges store the value of the <Admission Priority> parameter that is
 used within the RMD domain in case of preemption and severe
 congestion situations (see Section 4.6.1.6).
 If the RMD domain supports preemption during the admission control
 process, then the QNE Ingress node can support the building blocks
 specified in [RFC5974] and during the admission control process use
 the example preemption handling algorithm described in Appendix A.7.
 Note that in the above described case, the QNE Egress uses, if
 available, the tunneled initial priority parameters, which can be
 interpreted by the QNE Egress.

Bader, et al. Experimental [Page 35] RFC 5977 RMD-QOSM October 2010

 If the initial QSPEC carries the <Excess Treatment> parameter, then
 the QNE Ingress and QNE Egress nodes MUST control the excess traffic
 that is entering or leaving the RMD domain in accordance with the
 <Excess Treatment> parameter.  Note that the RMD-QSPEC does not carry
 the <Excess Treatment> parameter.
 If the requested <TMOD-1> parameter carried by the initial QSPEC,
 cannot be satisfied, then an end-to-end RESPONSE message has to be
 generated.  However, in order to decide whether the end-to-end
 reservation request was locally (at the QNE Ingress) satisfied, a
 local (at the QNE_Ingress) RMD-QOSM admission control procedure also
 has to be performed.  In other words, the RMD-QOSM functionality has
 to verify whether the value included in the <Peak Data Rate-1 (p)>
 field of RMD-QOSM <TMOD-1> can be reserved and stored in the RMD-QOSM
 reservation states (see Sections 4.6.1.1.2 and 4.3).
 An initial QSPEC object MUST be included in the end-to-end RESPONSE
 message.  The parameters included in the QSPEC <QoS Reserved> object
 are copied from the original <QoS Desired> values.
 The <E> flag associated with the QSPEC <QoS Reserved> object and the
 <E> flag associated with the local RMD-QSPEC <TMOD-1> parameter are
 set.  In addition, the <INFO-SPEC> object is included in the end-to-
 end RESPONSE message.  The error code used by this <INFO-SPEC> is:
 Error severity class: Transient Failure Error code value: Reservation
 failure
 Furthermore, all of the other RESPONSE parameters are set according
 to the end-to-end QoS Model or according to [RFC5974] and [RFC5975].
 If the request was satisfied locally (see Section 4.3), the Ingress
 QNE node generates two RESERVE messages: one intra-domain and one
 end-to-end RESERVE message.  Note however, that when the aggregated
 QoS-NSLP operational and reservation states are used by the QNE
 Ingress, then the generation of the intra-domain RESERVE message
 depends on the availability of the aggregated QoS-NSLP operational
 state.  If this aggregated QoS-NSLP operational state is available,
 then the RMD modification of aggregated reservations described in
 Section 4.6.1.4 is used.
 It is important to note that when the "per-flow RMD reservation-
 based" scenario is used within the RMD domain, the retransmission
 within the RMD domain SHOULD be disallowed.  The reason for this is
 related to the fact that the QNI Interior nodes are not able to
 differentiate between a retransmitted RESERVE message associated with
 a certain session and an initial RESERVE message belonging to another
 session.  However, the QNE Ingress have to report a failure situation

Bader, et al. Experimental [Page 36] RFC 5977 RMD-QOSM October 2010

 upstream.  When the QNE Ingress transmits the (intra-domain or end-
 to-end) RESERVE with the <RII> object set, it waits for a RESPONSE
 from the QNE Egress for a QOSNSLP_REQUEST_RETRY period.
 If the QNE Ingress transmitted an intra-domain or end-to-end RESERVE
 message with the <RII> object set and it fails to receive the
 associated intra-domain or end-to-end RESPONSE, respectively, after
 the QOSNSLP_REQUEST_RETRY period expires, it considers that the
 reservation failed.  In this case, the QNE Ingress SHOULD generate an
 end-to-end RESPONSE message that will include, among others, an
 <INFO-SPEC> object.  The error code used by this <INFO-SPEC> object
 is:
    Error severity class: Transient Failure
    Error code value: Reservation failure
 Furthermore, all of the other RESPONSE parameters are set according
 to the end-to-end QoS Model or according to [RFC5974] and [RFC5975].
 Note however, that if the retransmission within the RMD domain is not
 disallowed, then the procedure described in Appendix A.8 SHOULD be
 used on QNE Interior nodes; see also [Chan07].  In this case, the
 stateful QNE Ingress uses the retransmission procedure described in
 [RFC5974].
 If a rerouting takes place, then the stateful QNE Ingress is
 following the procedures specified in [RFC5974].
 At this point, the intra-domain and end-to-end operational states
 MUST be initiated or modified according to the REQUIRED binding
 procedures.  The way of how the BOUND-SESSION-IDs are initiated and
 maintained in the intra-domain and end-to-end QoS-NSLP operational
 states is described in Sections 4.3.1 and 4.3.2.
 These two messages are bound together in the following way.  The end-
 to-end RESERVE SHOULD contain, in the BOUND-SESSION-ID, the SESSION-
 ID of its bound intra-domain session.
 Furthermore, if the QNE Edge nodes maintain intra-domain per-flow
 QoS-NSLP reservation states, then the value of Binding_Code MUST be
 set to code "Tunnel and end-to-end sessions" (see Section 4.3.2).
 In addition to this, the intra-domain and end-to-end RESERVE messages
 are bound using the Message binding procedure described in [RFC5974].

Bader, et al. Experimental [Page 37] RFC 5977 RMD-QOSM October 2010

 In particular the <MSG-ID> object is included in the intra-domain
 RESERVE message and its bound <BOUND-MSG-ID> object is carried by the
 end-to-end RESERVE message.  Furthermore, the <Message_Binding_Type>
 flag is SET (value is 1), such that the message dependency is
 bidirectional.
 If the QoS-NSLP Edges maintain aggregated intra-domain QoS-NSLP
 operational states, then the value of Binding_Code MUST be set to
 code "Aggregated sessions".
 Furthermore, in this case, the retransmission within the RMD domain
 is allowed and the procedures described in Appendix A.8 SHOULD be
 used on QNE Interior nodes.  This is necessary due to the fact that
 when retransmissions are disallowed, then the associated with (micro)
 flows belonging to the aggregate will loose their reservations.  Note
 that, in this case, the stateful QNE Ingress uses the retransmission
 procedure described in [RFC5974].
 The intra-domain RESERVE message is associated with the (local NTLP)
 SESSION-ID mentioned above.  The selection of the IP source and IP
 destination address of this message depends on how the different
 inter-domain (end-to-end) flows are aggregated by the QNE Ingress
 node (see Section 4.3.1).  As described in Section 4.3.1, the QNE
 Edges maintain either per-flow, or aggregated QoS-NSLP reservation
 states for the RMD QoS Model, which are identified by (local NTLP)
 SESSION-IDs (see [RFC5971]).  Note that this NTLP SESSION-ID is a
 different one than the SESSION-ID associated with the end-to-end
 RESERVE message.
 If no QoS-NSLP aggregation procedure at the QNE Edges is supported,
 then the IP source and IP destination address of this message MUST be
 equal to the IP source and IP destination addresses of the data flow.
 The intra-domain RESERVE message is sent using the NTLP datagram mode
 (see Sections 4.4 and 4.5).  Note that the GIST Datagram mode can be
 selected using the unreliable GIST API Transfer-Attributes.  In
 addition, the intra-domain RESERVE (RMD-QSPEC) message MUST include a
 PHR container (PHR_Resource_Request) and the RMD QOSM <QoS Desired>
 object.
 The end-to-end RESERVE message includes the initial QSPEC and it is
 sent towards the Egress QNE.
 Note that after completing the initial discovery phase, the GIST
 Connection mode can be used between the QNE Ingress and QNE Egress.
 Note that the GIST Connection mode can be selected using the reliable
 GIST API Transfer-Attributes.

Bader, et al. Experimental [Page 38] RFC 5977 RMD-QOSM October 2010

 The end-to-end RESERVE message is forwarded using the GIST forwarding
 procedure to bypass the Interior stateless or reduced-state QNE
 nodes; see Figure 8.  The bypassing procedure is described in Section
 4.4.
 At the QNE Ingress, the end-to-end RESERVE message is marked, i.e.,
 modifying the QoS-NSLP default NSLPID value to another NSLPID
 predefined value that will be used by the GIST message carrying the
 end-to-end RESPONSE message to bypass the QNE Interior nodes.  Note
 that the QNE Interior nodes (see [RFC5971]) are configured to handle
 only certain NSLP-IDs (see [RFC5974]).
 Furthermore, note that the initial discovery phase and the process of
 sending the end-to-end RESERVE message towards the QNE Egress MAY be
 done simultaneously.  This can be accomplished only if the GIST
 implementation is configured to perform that, e.g., via a local
 policy.  However, the selection of the discovery procedure cannot be
 selected by the RMD-QOSM.
 The (initial) intra-domain RESERVE message MUST be sent by the QNE
 Ingress and it MUST contain the following values (see the QoS-NSLP-
 RMF API described in [RFC5974]):
  • the <RSN> object, whose value is generated and processed as

described in [RFC5974];

  • the <SCOPING> flag MUST NOT be set, meaning that a default

scoping of the message is used. Therefore, the QNE Edges MUST

       be configured as RMD boundary nodes and the QNE Interior nodes
       MUST be configured as Interior (intermediary) nodes;
  • the <RII> MUST be included in this message, see [RFC5974];
  • the <REPLACE> flag MUST be set to FALSE = 0;
  • The value of the <Message ID> value carried by the <MSG-ID> object

is set according to [RFC5974]. The value of the

    <Message_Binding_Type> is set to "1".
  • the value of the <REFRESH-PERIOD> object MUST be calculated and

set by the QNE Ingress node as described in Section 4.6.1.3;

  • the value of the <PACKET-CLASSIFIER> object is associated with the

path-coupled routing Message Routing Message (MRM), since RMD-QOSM

    is used with the path-coupled MRM.  The flag that has to be set is
    the <T> flag (traffic class) meaning that the packet
    classification of packets is based on the <DSCP> value included in
    the IP header of the packets.  Note that the <DSCP> value used in

Bader, et al. Experimental [Page 39] RFC 5977 RMD-QOSM October 2010

    the MRI can be derived by the value of <PHB Class> parameter,
    which MUST be carried by the intra-domain RESERVE message.  Note
    that the QNE Ingress being a QNI for the intra-domain session it
    can pass this value to GIST, via the GIST API.
  • the PHR resource units MUST be included in the <Peak Data Rate-1

(p)> field of the local RMD-QSPEC <TMOD-1> parameter of the <QoS

    Desired> object.
    When the QNE Edges use per-flow intra-domain QoS-NSLP states, then
    the <Peak Data Rate-1 (p)> value included in the initial QSPEC
    <TMOD-1> parameter is copied into the <Peak Data Rate-1 (p)> value
    of the local RMD-QSPEC <TMOD-1> parameter.
    When the QNE Edges use aggregated intra-domain QoS-NSLP
    operational states, then the <Peak Data Rate-1 (p)> value of the
    local RMD-QSPEC <TMOD-1> parameter can be obtained by using the
    bandwidth aggregation method described in Section 4.3.1;
  • the value of the <PHB Class> parameter can be defined by using the

method of copying the <PHB Class> parameter carried by the initial

    QSPEC into the <PHB Class> carried by the RMD-QSPEC, which is
    described above in this subsection.
  • the value of the <Parameter ID> field of the PHR container MUST be

set to "17", (i.e., PHR_Resource_Request).

  • the value of the <Admitted Hops> parameter in the PHR container

MUST be set to "1". Note that during a successful reservation,

    each time an RMD-QOSM-aware node processes the RMD-QSPEC, the
    <Admitted Hops> parameter is increased by one.
  • the value of the <Hop_U> parameter in the PHR container MUST be

set to "0".

  • the value of the <Max Admitted Hops> is set to "0".
  • If the initial QSPEC carried an <Admission Priority> parameter,

then this parameter SHOULD be copied into the RMD-QSPEC and

    carried by the (initiating) intra-domain RESERVE.
    Note that for the RMD-QOSM, a reservation established without an
    <Admission Priority> parameter is equivalent to a reservation with
    <Admission Priority> value of 1.

Bader, et al. Experimental [Page 40] RFC 5977 RMD-QOSM October 2010

    Note that, in this case, each admission priority is associated
    with a priority traffic class.  The three priority traffic classes
    (PHB_low_priority, PHB_normal_priority, and PHB_high_priority) MAY
    be associated with the same PHB (see Section 4.3.3).
  • In a single RMD domain case, the PDR container MAY not be included

in the message.

 Note that the intra-domain RESERVE message does not carry the <BOUND-
 SESSION-ID> object.  The reason for this is that the end-to-end
 RESERVE carries, in the <BOUND-SESSION-ID> object, the <SESSION-ID>
 value of the intra-domain session.
 When an end-to-end RESPONSE message is received by the QNE Ingress
 node, which was sent by a QNE Egress node (see Section 4.6.1.1.3),
 then it is processed according to [RFC5974] and end-to-end QoS Model
 rules.
 When an intra-domain RESPONSE message is received by the QNE Ingress
 node, which was sent by a QNE Egress (see Section 4.6.1.1.3), it uses
 the QoS-NSLP procedures to match it to the earlier sent intra-domain
 RESERVE message.  After this phase, the RMD-QSPEC has to be
 identified and processed.
 The RMD QOSM reservation has been successful if the <M> bit carried
 by the "PDR Container" is equal to "0" (i.e., not set).
 Furthermore, the <INFO-SPEC> object is processed as defined in the
 QoS-NSLP specification.  In the case of successful reservation, the
 <INFO-SPEC> object MUST have the following values:
  • Error severity class: Success
  • Error code value: Reservation successful
 If the end-to-end RESPONSE message has to be forwarded to a node
 outside the RMD-QOSM-aware domain, then the values of the objects
 contained in this message (i.e., <RII> <RSN>, <INFO-SPEC>, [<QSPEC>])
 MUST be set by the QoS-NSLP protocol functions of the QNE.  If an
 end-to-end QUERY is received by the QNE Ingress, then the same
 bypassing procedure has to be used as the one applied for an end-to-
 end RESERVE message.  In particular, it is forwarded using the GIST
 forwarding procedure to bypass the Interior stateless or reduced-
 state QNE nodes.

Bader, et al. Experimental [Page 41] RFC 5977 RMD-QOSM October 2010

4.6.1.1.2. Operation in the Interior Nodes

 Each QNE Interior node MUST use the QoS-NSLP and RMD-QOSM parameters
 of the intra-domain RESERVE (RMD-QSPEC) message as follows (see QoS-
 NSLP-RMF API described in [RFC5974]):
  • the values of the <RSN>, <RII>, <PACKET-CLASSIFIER>, <REFRESH-

PERIOD>, objects MUST NOT be changed.

    The Interior node is informed by the <PACKET-CLASSIFIER> object
    that the packet classification SHOULD be done on the <DSCP> value.
    The flag that has to be set in this case is the <T> flag (traffic
    class).  The value of the <DSCP> value MUST be obtained via the
    MRI parameters that the QoS-NSLP receives from GIST.  A QNE
    Interior MUST be able to associate the value carried by the RMD-
    QSPEC <PHB Class> parameter and the <DSCP> value obtained via
    GIST.  This is REQUIRED, because there are situations in which the
    <PHB Class> parameter is not carrying a <DSCP> value but a PHB ID
    code, see Section 4.1.1.
  • the flag <REPLACE> MUST be set to FALSE = 0;
  • when the RMD reservation-based methods, described in Section 4.3.1

and 4.3.3, are used, the <Peak Data Rate-1 (p)> value of the local

    RMD-QSPEC <TMOD-1> parameter is used by the QNE Interior node for
    admission control.  Furthermore, if the <Admission Priority>
    parameter is carried by the RMD-QOSM <QoS Desired> object, then
    this parameter is processed as described in the following bullets.
  • in the case of the RMD reservation-based procedure, and if these

resources are admitted (see Sections 4.3.1 and 4.3.3), they are

    added to the currently reserved resources.  Furthermore, the value
    of the <Admitted Hops> parameter in the PHR container has to be
    increased by one.
  • If the bandwidth allocated for the PHB_high_priority traffic is

fully utilized, and a high priority request arrives, other

    policies on allocating bandwidth can be used, which are beyond the
    scope of this document.
  • If the RMD domain supports preemption during the admission control

process, then the QNE Interior node can support the building

    blocks specified in the [RFC5974] and during the admission control
    process use the preemption handling algorithm specified in
    Appendix A.7.

Bader, et al. Experimental [Page 42] RFC 5977 RMD-QOSM October 2010

  • in the case of the RMD measurement-based method (see Section

4.3.2), and if the requested into the <Peak Data Rate-1 (p)> value

    of the local RMD-QSPEC <TMOD-1> parameter is admitted, using a
    measurement-based admission control (MBAC) algorithm, then the
    number of this resource will be used to update the MBAC algorithm
    according to the operation described in Section 4.3.2.

4.6.1.1.3. Operation in the Egress Node

 When the end-to-end RESERVE message is received by the egress node,
 it is only forwarded further, towards QNR, if the processing of the
 intra-domain RESERVE(RMD-QSPEC) message was successful at all nodes
 in the RMD domain.  In this case, the QNE Egress MUST stop the
 marking process that was used to bypass the QNE Interior nodes by
 reassigning the QoS-NSLP default NSLPID value to the end-to-end
 RESERVE message (see Section 4.4).  Furthermore, the carried <BOUND-
 SESSION-ID> object associated with the intra-domain session MUST be
 removed after processing.  Note that the received end-to-end RESERVE
 was tunneled within the RMD domain.  Therefore, the tunneled initial
 QSPEC carried by the end-to-end RESERVE message has to be
 processed/set according to the [RFC5975] specification.
 If a rerouting takes place, then the stateful QNE Egress is following
 the procedures specified in [RFC5974].
 At this point, the intra-domain and end-to-end operational states
 MUST be initiated or modified according to the REQUIRED binding
 procedures.
 The way in which the BOUND-SESSION-IDs are initiated and maintained
 in the intra-domain and end-to-end QoS-NSLP operational states is
 described in Sections 4.3.1 and 4.3.2.
 If the processing of the intra-domain RESERVE(RMD-QSPEC) was not
 successful at all nodes in the RMD domain, then the inter-domain
 (end-to-end) reservation is considered to have failed.
 Furthermore, if the initial QSPEC object used an object combination
 of type 1 or 2 where the <QoS Available> is populated, and the intra-
 domain RESERVE(RMD-QSPEC) was not successful at all nodes in the RMD
 domain MUST be considered that the <QoS Available> is not satisfied
 and that the inter-domain (end-to-end) reservation is considered to
 have failed.
 Furthermore, note that when the QNE Egress uses per-flow intra-domain
 QoS-NSLP operational states (see Sections 4.3.2 and 4.3.3), the QNE
 Egress SHOULD support the message binding procedure described in
 [RFC5974], which can be used to synchronize the arrival of the end-

Bader, et al. Experimental [Page 43] RFC 5977 RMD-QOSM October 2010

 to-end RESERVE and the intra-domain RESERVE (RMD-QSPEC) messages, see
 Section 5.7, and QoS-NSLP-RMF API described in [RFC5974].  Note that
 the intra-domain RESERVE message carries the <MSG-ID> object and its
 bound end-to-end RESERVE message carries the <BOUND-MSG-ID> object.
 Both these objects carry the <Message_Binding_Type> flag set to the
 value of "1".  If these two messages do not arrive during the time
 defined by the MsgIDWait timer, then the reservation is considered to
 have failed.  Note that the timer has to be preconfigured and it has
 to have the same value in the RMD domain.  In this case, an end-to-
 end RESPONSE message, see QoS-NSLP-RMF API described in [RFC5974], is
 sent towards the QNE Ingress with the following <INFO-SPEC> values:
 Error class: Transient Failure
 Error code: Mismatch synchronization between end-to-end RESERVE
 and intra-domain RESERVE
 When the intra-domain RESERVE (RMD-QSPEC) is received by the QNE
 Egress node of the session associated with the intra-domain
 RESERVE(RMD-QSPEC) (the PHB session) with the session included in its
 <BOUND-SESSION-ID> object MUST be bound according to the
 specification given in [RFC5974].  The SESSION-ID included in the
 BOUND-SESSION-ID parameter stored in the intra-domain QoS-NSLP
 operational state object is the SESSION-ID of the session associated
 with the end-to-end RESERVE message(s).  Note that if the QNE Edge
 nodes maintain per-flow intra-domain QoS-NSLP operational states,
 then the value of Binding_Code = (Tunnel and end-to-end sessions) is
 used.  If the QNE Edge nodes maintain per-aggregated QoS-NSLP intra-
 domain reservation states, then the value of Binding_Code =
 (Aggregated sessions), see Sections 4.3.1 and 4.3.2.
 If the RMD domain supports preemption during the admission control
 process, then the QNE Egress node can support the building blocks
 specified in the [RFC5974] and during the admission control process
 use the example preemption handling algorithm described in Appendix
 A.7.
 The end-to-end RESERVE message is generated/forwarded further
 upstream according to the [RFC5974] and [RFC5975] specifications.
 Furthermore, the <B> (BREAK) QoS-NSLP flag in the end-to-end RESERVE
 message MUST NOT be set, see the QoS-NSLP-RMF API described in QoS-
 NSLP.

Bader, et al. Experimental [Page 44] RFC 5977 RMD-QOSM October 2010

QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress) NTLP stateful NTLP stateless NTLP stateless NTLP stateful

  |                    |                   |                    |

RESERVE | | | —>| | | RESERVE |

  |------------------------------------------------------------>|
  |RESERVE(RMD-QSPEC)  |                   |                    |
  |------------------->|                   |                    |
  |                    |RESERVE(RMD-QSPEC) |                    |
  |                    |------------------>|                    |
  |                    |                   | RESERVE(RMD-QSPEC) |
  |                    |                   |------------------->|
  |                    |RESPONSE(RMD-QSPEC)|                    |
  |<------------------------------------------------------------|
  |                    |                   |                RESERVE
  |                    |                   |                    |-->
  |                    |                   |                RESPONSE
  |                    |                   |                    |<--
  |                    |RESPONSE           |                    |
  |<------------------------------------------------------------|

RESPONSE | | | ←–| | | |

Figure 8: Basic operation of successful reservation procedure
          used by the RMD-QOSM
 The QNE Egress MUST generate an intra-domain RESPONSE (RMD-Qspec)
 message.  The intra-domain RESPONSE (RMD-QSPEC) message MUST be sent
 to the QNE Ingress node, i.e., the previous stateful hop by using the
 procedures described in Sections 4.4 and 4.5.
 The values of the RMD-QSPEC that are carried by the intra-domain
 RESPONSE message MUST be used and/or set in the following way (see
 the QoS-NSLP-RMF API described in [RFC5974]):
  • the <RII> object carried by the intra-domain RESERVE message, see

Section 4.6.1.1.1, has to be copied and carried by the intra-

    domain RESPONSE message.
  • the value of the <Parameter ID> field of the PDR container MUST be

set to "23" (i.e., PDR_Reservation_Report);

  • the value of the <M> field of the PDR container MUST be equal to

the value of the <M> parameter of the PHR container that was

    carried by its associated intra-domain RESERVE(RMD-QSPEC) message.
    This is REQUIRED since the value of the <M> parameter is used to
    indicate the status if the RMD reservation request to the Ingress
    Edge.

Bader, et al. Experimental [Page 45] RFC 5977 RMD-QOSM October 2010

 If the binding between the intra-domain session and the end-to-end
 session uses a Binding_Code that is (Aggregated sessions), and there
 is no aggregated QoS-NSLP operational state associated with the
 intra-domain session available, then the RMD modification of
 aggregated reservation procedure described in Section 4.6.1.4 can be
 used.
 If the QNE Egress receives an end-to-end RESPONSE message, it is
 processed and forwarded towards the QNE Ingress.  In particular, the
 non-default values of the objects contained in the end-to-end
 RESPONSE message MUST be used and/or set by the QNE Egress as follows
 (see the QoS-NSLP-RMF API described in [RFC5974]):
  • the values of the <RII>, <RSN>, <INFO-SPEC>, [<QSPEC>] objects are

set according to [RFC5974] and/or [RFC5975]. The <INFO-SPEC>

    object SHOULD be set by the QoS-NSLP functionality.  In the case
    of successful reservation, the <INFO-SPEC> object SHOULD have the
    following values:
    Error severity class: Success Error code value: Reservation
    successful
  • furthermore, an initial QSPEC object MUST be included in the end-

to-end RESPONSE message. The parameters included in the QSPEC

    <QoS Reserved> object are copied from the original <QoS Desired>
    values.
 The end-to-end RESPONSE message is delivered as normal, i.e., is
 addressed and sent to its upstream QoS-NSLP neighbor, i.e., the QNE
 Ingress node.
 Note that if a QNE Egress receives an end-to-end QUERY that was
 bypassed through the RMD domain, it MUST stop the marking process
 that was used to bypass the QNE Interior nodes.  This can be done by
 reassigning the QoS-NSLP default NSLPID value to the end-to-end QUERY
 message; see Section 4.4.

4.6.1.2. Unsuccessful Reservation

 This subsection describes the operation where a request for
 reservation cannot be satisfied by the RMD-QOSM.
 The QNE Ingress, the QNE Interior, and QNE Egress nodes process and
 forward the end-to-end RESERVE message and the intra-domain
 RESERVE(RMD-QSPEC) message in a similar way, as specified in Section
 4.6.1.1.  The main difference between the unsuccessful operation and
 successful operation is that one of the QNE nodes does not admit the

Bader, et al. Experimental [Page 46] RFC 5977 RMD-QOSM October 2010

 request, e.g., due to lack of resources.  This also means that the
 QNE Edge node MUST NOT forward the end-to-end RESERVE message towards
 the QNR node.
 Note that the described functionality applies to the RMD reservation-
 based methods (see Sections 4.3.1 and 4.3.2) and to the NSIS
 measurement-based admission control method (see Section 4.3.2).
 The QNE Edge nodes maintain either per-flow QoS-NSLP reservation
 states or aggregated QoS-NSLP reservation states.  When the QNE Edges
 maintain aggregated QoS-NSLP reservation states, the RMD-QOSM
 functionality MAY accomplish an RMD modification procedure (see
 Section 4.6.1.4), instead of the reservation initiation procedure
 that is described in this subsection.

4.6.1.2.1. Operation in the Ingress Nodes

 When an end-to-end RESERVE message arrives at the QNE Ingress and if
 (1) the "Maximum Packet Size-1 (MPS)" included in the end-to-end QoS
 Model <TMOD-1> is larger than this smallest MTU value within the RMD
 domain or (2) there are no resources available, the QNE Ingress MUST
 reject this end-to-end RESERVE message and send an end-to-end
 RESPONSE message back to the sender, as described in the QoS-NSLP
 specification, see [RFC5974] and [RFC5975].
 When an end-to-end RESPONSE message is received by an Ingress node
 (see Section 4.6.1.2.3), the values of the <RII>, <RSN>, <INFO-SPEC>,
 and [<QSPEC>] objects are processed according to the QoS-NSLP
 procedures.
 If the end-to-end RESPONSE message has to be forwarded upstream to a
 node outside the RMD-QOSM-aware domain, then the values of the
 objects contained in this message (i.e., <RII<, <RSN>, <INFO-SPEC>,
 [<QSPEC>]) MUST be set by the QoS-NSLP protocol functions of the QNE.
 When an intra-domain RESPONSE message is received by the QNE Ingress
 node, which was sent by a QNE Egress (see Section 4.6.1.2.3), it uses
 the QoS-NSLP procedures to match it to the intra-domain RESERVE
 message that was previously sent.  After this phase, the RMD-QSPEC
 has to be identified and processed.  Note that, in this case, the RMD
 Resource Management Function (RMF) is notified that the reservation
 has been unsuccessful, by reading the <M> parameter of the PDR
 container.  Note that when the QNE Edges maintain a per-flow QoS-NSLP
 reservation state, the RMD-QOSM functionality, has to start an RMD
 release procedure (see Section 4.6.1.5).  When the QNE Edges maintain
 aggregated QoS-NSLP reservation states, the RMD-QOSM functionality
 MAY start an RMD modification procedure (see Section 4.6.1.4).

Bader, et al. Experimental [Page 47] RFC 5977 RMD-QOSM October 2010

4.6.1.2.2. Operation in the Interior Nodes

 In the case of the RMD reservation-based scenario, and if the intra-
 domain reservation request is not admitted by the QNE Interior node,
 then the <Hop_U> and <M> parameters of the PHR container MUST be set
 to "1".  The <Admitted Hops> counter MUST NOT be increased.
 Moreover, the value of the <Max Admitted Hops> counter MUST be set
 equal to the <Admitted Hops> value.
 Furthermore, the <E> flag associated with the QSPEC <QoS Desired>
 object and the <E> flag associated with the local RMD-QSPEC <TMOD-1>
 parameter SHOULD be set.  In the case of the RMD measurement-based
 scenario, the <M> parameter of the PHR container MUST be set to "1".
 Furthermore, the <E> flag associated with the QSPEC <QoS Desired>
 object and the <E> flag associated with the local RMD-QSPEC <TMOD-1>
 parameter SHOULD be set.  Note that the <M> flag seems to be set in a
 similar way to the <E> flag used by the local RMD-QSPEC <TMOD-1>
 parameter.  However, the ways in which the two flags are processed by
 a QNE are different.
 In general, if a QNE Interior node receives an RMD-QSPEC <TMOD-1>
 parameter with the <E> flag set and a PHR container type
 "PHR_Resource_Request", with the <M> parameter set to "1", then this
 "PHR Container" and the RMD-QOSM <QoS Desired> object) MUST NOT be
 processed.  Furthermore, when the <K> parameter that is included in
 the "PHR Container" and carried by a RESERVE message is set to "1",
 then this "PHR Container" and the RMD-QOSM <QoS Desired> object) MUST
 NOT be processed.

4.6.1.2.3. Operation in the Egress Nodes

 In the RMD reservation-based (Section 4.3.3) and RMD NSIS
 measurement-based scenarios (Section 4.3.2), when the <M> marked
 intra-domain RESERVE(RMD-QSPEC) is received by the QNE Egress node
 (see Figure 9), the session associated with the intra-domain
 RESERVE(RMD-QSPEC) (the PHB session) and the end-to-end session MUST
 be bound.
 Moreover, if the initial QSPEC object (used by the end-to-end QoS
 Model) used an object combination of type 1 or 2 where the <QoS
 Available> is populated, and the intra-domain RESERVE(RMD-QSPEC) was
 not successful at all nodes in the RMD domain, i.e., the intra-domain
 RESERVE(RMD-QSPEC) message is marked, it MUST be considered that the
 <QoS Available> is not satisfied and that the inter-domain (end-to-
 end) reservation is considered as to have failed.

Bader, et al. Experimental [Page 48] RFC 5977 RMD-QOSM October 2010

 When the QNE Egress uses per-flow intra-domain QoS-NSLP operational
 states (see Sections 4.3.2 and 4.3.3), then the QNE Egress node MUST
 generate an end-to-end RESPONSE message that has to be sent to its
 previous stateful QoS-NSLP hop (see the QoS-NSLP-RMF API described in
 [RFC5974]).
  • the values of the <RII>, <RSN> and <INFO-SPEC> objects are set by

the standard QoS-NSLP protocol functions. In the case of an

    unsuccessful reservation, the <INFO-SPEC> object SHOULD have the
    following values:
    Error severity class: Transient Failure
    Error code value: Reservation failure
 The QSPEC that was carried by the end-to-end RESERVE message that
 belongs to the same session as this end-to-end RESPONSE message is
 included in this message.
 In particular, the parameters included in the QSPEC <QoS Reserved>
 object of the end-to-end RESPONSE message are copied from the initial
 <QoS Desired> values included in its associated end-to-end RESERVE
 message.  The <E> flag associated with the QSPEC <QoS Reserved>
 object and the <E> flag associated with the <TMOD-1> parameter
 included in the end-to-end RESPONSE are set.
 In addition to the above, similar to the successful operation, see
 Section 4.6.1.1.3, the QNE Egress MUST generate an intra-domain
 RESPONSE message that has to be sent to its previous stateful QoS-
 NSLP hop.
 The values of the <RII>, <RSN> and <INFO-SPEC> objects are set by the
 standard QoS-NSLP protocol functions.  In the case of an unsuccessful
 reservation, the <INFO-SPEC> object SHOULD have the following values
 (see the QoS-NSLP-RMF API described in [RFC5974]):
 Error severity class: Transient Failure
 Error code value: Reservation failure

Bader, et al. Experimental [Page 49] RFC 5977 RMD-QOSM October 2010

QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress) NTLP stateful NTLP stateless NTLP stateless NTLP stateful

  |                    |                   |                    |

RESERVE | | | —>| | | RESERVE |

  |------------------------------------------------------------>|
  |RESERVE(RMD-QSPEC:M=0)                  |                    |
  |------------------->|                   |                    |
  |                    |RESERVE(RMD-QSPEC:M=1)                  |
  |                    |------------------>|                    |
  |                    |                   | RESERVE(RMD-QSPEC:M=1)
  |                    |                   |------------------->|
  |                    |RESPONSE(RMD-QOSM) |                    |
  |<------------------------------------------------------------|
  |                    |RESPONSE           |                    |
  |<------------------------------------------------------------|

RESPONSE | | | ←–| | | | RESERVE(RMD-QSPEC: Tear=1, M=1, <Admitted Hops>=<Max Admitted Hops>

  |------------------->|                   |                    |
                       |RESERVE(RMD-QSPEC: Tear=1, M=1, K=1)    |
  |                    |------------------>|                    |
                       |    RESERVE(RMD-QSPEC: Tear=1, M=1, K=1)|
  |                    |                   |------------------->|
   Figure 9: Basic operation during unsuccessful reservation
             initiation used by the RMD-QOSM
 The values of the RMD-QSPEC MUST be used and/or set in the following
 way (see the QoS-NSLP-RMF API described in [RFC5974]):
  • the value of the <PDR Control Type> of the PDR container MUST be

set to "23" (PDR_Reservation_Report);

  • the value of the <Max Admitted Hops> parameter of the PHR

container included in the received <M> marked intra-domain RESERVE

    (RMD-QSPEC) MUST be included in the <Max Admitted Hops> parameter
    of the PDR container;
  • the value of the <M> parameter of the PDR container MUST be "1".

4.6.1.3. RMD Refresh Reservation

 In the case of the RMD measurement-based method, see Section 4.3.2,
 QoS-NSLP reservation states in the RMD domain are not typically
 maintained, therefore, this method typically does not use an intra-
 domain refresh procedure.

Bader, et al. Experimental [Page 50] RFC 5977 RMD-QOSM October 2010

 However, there are measurement-based optimization schemes, see
 [GrTs03], that MAY use the refresh procedures described in Sections
 4.6.1.3.1 and 4.6.1.3.3.  However, this measurement-based
 optimization scheme can only be applied in the RMD domain if the QNE
 Edges are configured to perform intra-domain refresh procedures and
 if all the QNE Interior nodes are configured to perform the
 measurement-based optimization schemes.
 In the description given in this subsection, it is assumed that the
 RMD measurement-based scheme does not use the refresh procedures.
 When the QNE Edges maintain aggregated or per-flow QoS-NSLP
 operational and reservation states (see Sections 4.3.1 and 4.3.3),
 then the refresh procedures are very similar.  If the RESERVE
 messages arrive within the soft state timeout period, the
 corresponding number of resource units are not removed.  However, the
 transmission of the intra-domain and end-to-end (refresh) RESERVE
 message are not necessarily synchronized.  Furthermore, the
 generation of the end-to-end RESERVE message, by the QNE Edges,
 depends on the locally maintained refreshed interval (see [RFC5974]).

4.6.1.3.1. Operation in the Ingress Node

 The Ingress node MUST be able to generate an intra-domain (refresh)
 RESERVE(RMD-QSPEC) at any time defined by the refresh period/timer.
 Before generating this message, the RMD QoS signaling model
 functionality is using the RMD traffic class (PHR) resource units for
 refreshing the RMD traffic class state.
 Note that the RMD traffic class refresh periods MUST be equal in all
 QNE Edge and QNE Interior nodes and SHOULD be smaller (default: more
 than two times smaller) than the refresh period at the QNE Ingress
 node used by the end-to-end RESERVE message.  The intra-domain
 RESERVE (RMD-QSPEC) message MUST include an RMD-QOSM <QoS Desired>
 and a PHR container (i.e., PHR_Refresh_Update).
 An example of this refresh operation can be seen in Figure 10.

Bader, et al. Experimental [Page 51] RFC 5977 RMD-QOSM October 2010

QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress) NTLP stateful NTLP stateless NTLP stateless NTLP stateful

  |                    |                   |                    |
  |RESERVE(RMD-QSPEC)  |                   |                    |
  |------------------->|                   |                    |
  |                    |RESERVE(RMD-QSPEC) |                    |
  |                    |------------------>|                    |
  |                    |                   | RESERVE(RMD-QSPEC) |
  |                    |                   |------------------->|
  |                    |                   |                    |
  |                    |RESPONSE(RMD-QSPEC)|                    |
  |<------------------------------------------------------------|
  |                    |                   |                    |
 Figure 10: Basic operation of RMD-specific refresh procedure
 Most of the non-default values of the objects contained in this
 message MUST be used and set by the QNE Ingress in the same way as
 described in Section 4.6.1.1.  The following objects are used and/or
 set differently:
  • the PHR resource units MUST be included in the <Peak Data Rate-1

(p)> field of the local RMD-QSPEC <TMOD-1> parameter. The <Peak

    Data Rate-1 (p)> field value of the local RMD-QSPEC <TMOD-1>
    parameter depends on how the different inter-domain (end-to-end)
    flows are aggregated by the QNE Ingress node (e.g., the sum of all
    the PHR-requested resources of the aggregated flows); see Section
    4.3.1.  If no QoS-NSLP aggregation is accomplished by the QNE
    Ingress node, the <Peak Data Rate-1 (p)> value of the local RMD-
    QSPEC <TMOD-1> parameter SHOULD be equal to the <Peak Data Rate-1
    (p)> value of the local RMD-QSPEC <TMOD-1> parameter of its
    associated new (initial) intra-domain RESERVE (RMD-QSPEC) message;
    see Section 4.3.3.
  • the value of the Container field of the <PHR Container> MUST be

set to "19", i.e., "PHR_Refresh_Update".

 When the intra-domain RESPONSE (RMD-QSPEC) message (see Section
 4.6.1.3.3), is received by the QNE Ingress node, then:
  • the values of the <RII>, <RSN>, <INFO-SPEC>, and [RFC5975] objects

are processed by the standard QoS-NSLP protocol functions (see

    Section 4.6.1.1);
  • the "PDR Container" has to be processed by the RMD-QOSM

functionality in the QNE Ingress node. The RMD-QOSM functionality

    is notified by the <PDR M> parameter of the PDR container that the
    refresh procedure has been successful or unsuccessful.  All

Bader, et al. Experimental [Page 52] RFC 5977 RMD-QOSM October 2010

    sessions associated with this RMD-specific refresh session MUST be
    informed about the success or failure of the refresh procedure.
    (When aggregated QoS-NSLP operational and reservation states are
    used (see Section 4.3.1), there will be more than one session.)
    In the case of failure, the QNE Ingress node has to generate (in a
    standard QoS-NSLP way) an error end-to-end RESPONSE message that
    will be sent towards the QNI.

4.6.1.3.2. Operation in the Interior Node

 The intra-domain RESERVE (RMD-QSPEC) message is received and
 processed by the QNE Interior nodes.  Any QNE Edge or QNE Interior
 node that receives a <PHR_Refresh_Update> field MUST identify the
 traffic class state (PHB) (using the <PHB Class> parameter).  Most of
 the parameters in this refresh intra-domain RESERVE (RMD-QSPEC)
 message MUST be used and/or set by a QNE Interior node in the same
 way as described in Section 4.6.1.1.
 The following objects are used and/or set differently:
  • the <Peak Data Rate-1 (p)> value of the local RMD-QSPEC <TMOD-1>

parameter of the RMD-QOSM <QoS Desired> is used by the QNE

    Interior node for refreshing the RMD traffic class state.  These
    resources (included in the <Peak Data Rate-1 (p)> value of local
    RMD-QSPEC <TMOD-1>), if reserved, are added to the currently
    reserved resources per PHB and therefore they will become a part
    of the per-traffic class (PHB) reservation state (see Sections
    4.3.1 and 4.3.3).  If the refresh procedure cannot be fulfilled
    then the <M> and <S> fields carried by the PHR container MUST be
    set to "1".
  • furthermore, the <E> flag associated with <QoS Desired> object and

the <E> flag associated with the local RMD-QSPEC <TMOD-1>

    parameter SHOULD be set.
 Any PHR container of type "PHR_Refresh_Update", and its associated
 local RMD-QSPEC <TMOD-1>, whether or not it is marked and independent
 of the <E> flag value of the local RMD-QSPEC <TMOD-1> parameter, is
 always processed, but marked bits are not changed.

4.6.1.3.3. Operation in the Egress Node

 The intra-domain RESERVE(RMD-QSPEC) message is received and processed
 by the QNE Egress node.  A new intra-domain RESPONSE (RMD-QSPEC)
 message is generated by the QNE Egress node and MUST include a PDR
 (type PDR_Refresh_Report).

Bader, et al. Experimental [Page 53] RFC 5977 RMD-QOSM October 2010

 The (refresh) intra-domain RESPONSE (RMD-QSPEC) message MUST be sent
 to the QNE Ingress node, i.e., the previous stateful hop.  The
 (refresh) intra-domain RESPONSE (RMD-QSPEC) message MUST be
 explicitly routed to the QNE Ingress node, i.e., the previous
 stateful hop, using the procedures described in Section 4.5.
  • the values of the <RII>, <RSN>, and <INFO-SPEC> objects are set by

the standard QoS-NSLP protocol functions, see [RFC5974].

  • the value of the <PDR Control Type> parameter of the PDR container

MUST be set "24" (i.e., PDR_Refresh_Report). In case of

    successful reservation, the <INFO-SPEC> object SHOULD have the
    following values:
    Error severity Class: Success
    Error code value: Reservation successful
  • In the case of unsuccessful reservation the <INFO-SPEC> object

SHOULD have the following values:

    Error severity class: Transient Failure
    Error code value: Reservation failure
 The RMD-QSPEC that was carried by the intra-domain RESERVE belonging
 to the same session as this intra-domain RESPONSE is included in the
 intra-domain RESPONSE message.  The parameters included in the QSPEC
 <QoS Reserved> object are copied from the original <QoS Desired>
 values.  If the reservation is unsuccessful, then the <E> flag
 associated with the QSPEC <QoS Reserved> object and the <E> flag
 associated with the local RMD-QSPEC <TMOD-1> parameter are set.
 Furthermore, the <M> and <S> PDR container bits are set to "1".

4.6.1.4. RMD Modification of Aggregated Reservations

 In the case when the QNE Edges maintain QoS-NSLP-aggregated
 operational and reservation states and the aggregated reservation has
 to be modified (see Section 4.3.1) the following procedure is
 applied:
  • When the modification request requires an increase of the reserved

resources, the QNE Ingress node MUST include the corresponding

    value into the <Peak Data Rate-1 (p)> value of the local RMD-QSPEC
    <TMOD-1> parameter of the RMD-QOSM <QoS Desired>, which is sent
    together with a "PHR_Resource_Request" control information.  If a
    QNE Edge or QNE Interior node is not able to reserve the number of
    requested resources, the "PHR_Resource_Request" that is associated
    with the local RMD-QSPEC <TMOD-1> parameter MUST be <M> marked,

Bader, et al. Experimental [Page 54] RFC 5977 RMD-QOSM October 2010

    i.e., the <M> bit is set to the value of "1".  In this situation,
    the RMD-specific operation for unsuccessful reservation will be
    applied (see Section 4.6.1.2).
  • When the modification request requires a decrease of the reserved

resources, the QNE Ingress node MUST include this value into the

    <Peak Data Rate-1 (p)> value of the local RMD-QSPEC <TMOD-1>
    parameter of the RMD-QOSM <QoS Desired>.  Subsequently, an RMD
    release procedure SHOULD be accomplished (see Section 4.6.1.5).
    Note that if the complete bandwidth associated with the aggregated
    reservation maintained at the QNE Ingress does not have to be
    released, then the <TEAR> flag MUST be set to OFF.  This is
    because the NSLP operational states associated with the aggregated
    reservation states at the Edge QNEs MUST NOT be turned off.
    However, if the complete bandwidth associated with the aggregated
    reservation maintained at the QNE Ingress has to be released, then
    the <TEAR> flag MUST be set to ON.
 It is important to emphasize that this RMD modification scheme only
 applies to the following two RMD-QOSM schemes:
  • "per-aggregate RMD reservation-based" in combination with the

"severe congestion handling by the RMD-QOSM refresh" procedure;

  • "per-aggregate RMD reservation-based" in combination with the

"severe congestion handling by proportional data packet marking"

    procedure.

4.6.1.5. RMD Release Procedure

 This procedure is applied to all RMD mechanisms that maintain
 reservation states.  If a refresh RESERVE message does not arrive at
 a QNE Interior node within the refresh timeout period, then the
 bandwidth requested by this refresh RESERVE message is not updated.
 This means that the reserved bandwidth associated with the reduced
 state is decreased in the next refresh period by the amount of the
 corresponding bandwidth that has not been refreshed, see Section
 4.3.3.
 This soft state behavior provides certain robustness for the system
 ensuring that unused resources are not reserved for a long time.
 Resources can be removed by an explicit release at any time.
 However, in the situation that an end-to-end (tear) RESERVE is
 retransmitted (see Section 5.2.4 in [RFC5974]), then this message
 MUST NOT initiate an intra-domain (tear) RESERVE message.  This is
 because the amount of bandwidth within the RMD domain associated with

Bader, et al. Experimental [Page 55] RFC 5977 RMD-QOSM October 2010

 the (tear) end-to-end RESERVE has already been released, and
 therefore, this amount of bandwidth within the RMD domain MUST NOT
 once again be released.
 When the RMD-RMF of a QNE Edge or QNE Interior node processes a
 "PHR_Release_Request" PHR container, it MUST identify the <PHB Class>
 parameter and estimate the time period that elapsed after the
 previous refresh, see also Section 3 of [CsTa05].
 This MAY be done by indicating the time lag, say "T_Lag", between the
 last sent "PHR_Refresh_Update" and the "PHR_Release_Request" control
 information container by the QNE Ingress node, see [RMD1] and
 [CsTa05] for more details.  The value of "T_Lag" is first normalized
 to the length of the refresh period, say "T_period".  The ratio
 between the "T_Lag" and the length of the refresh period, "T_period",
 is calculated.  This ratio is then introduced into the <Time Lag>
 field of the "PHR_Release_Request".  When the above mentioned
 procedure of indicating the "T_Lag" is used and when a node (QNE
 Egress or QNE Interior) receives the "PHR_Release_Request" PHR
 container, it MUST store the arrival time.  Then, it MUST calculate
 the time difference, "T_diff", between the arrival time and the start
 of the current refresh period, "T_period".  Furthermore, this node
 MUST derive the value of the "T_Lag", from the <Time Lag> parameter.
 "T_Lag" can be found by multiplying the value included in the <Time
 Lag> parameter with the length of the refresh period, "T_period".  If
 the derived time lag, "T_Lag", is smaller than the calculated time
 difference, "T_diff", then this node MUST decrease the PHB
 reservation state with the number of resource units indicated in the
 <Peak Data Rate-1 (p)> field of the local RMD-QSPEC <TMOD-1>
 parameter of the RMD-QOSM <QoS Desired> that has been sent together
 with the "PHR_Release_Request" "PHR Container", but not below zero.
 An RMD-specific release procedure can be triggered by an end-to-end
 RESERVE with a <TEAR> flag set to ON (see Section 4.6.1.5.1), or it
 can be triggered by either an intra-domain RESPONSE, an end-to-end
 RESPONSE,
  or an end-to-end NOTIFY message that includes a marked (i.e., PDR
 <M> and/or PDR <S> parameters are set to ON) "PDR_Reservation_Report"
 or "PDR_Congestion_Report" and/or an <INFO-SPEC> object.

4.6.1.5.1. Triggered by a RESERVE Message

 This RMD-explicit release procedure can be triggered by a tear
 (<TEAR> flag set to ON) end-to-end RESERVE message.  When a tear
 (<TEAR> flag set ON) end-to-end RESERVE message arrives to the QNE
 Ingress, the QNE Ingress node SHOULD process the message in a
 standard QoS-NSLP way (see [RFC5974]).  In addition to this, the RMD
 RMF is notified, as specified in [RFC5974].

Bader, et al. Experimental [Page 56] RFC 5977 RMD-QOSM October 2010

 Like the scenario described in Section 4.6.1.1., a bypassing
 procedure has to be initiated by the QNE Ingress node.  The bypassing
 procedure is performed according to the description given in Section
 4.4.  At the QNE Ingress, the end-to-end RESERVE message is marked,
 i.e., modifying the QoS-NSLP default NSLPID value to another NSLPID
 predefined value that will be used by the GIST message that carries
 the end-to-end RESERVE message to bypass the QNE Interior nodes.
 Before generating an intra-domain tear RESERVE, the RMD-QOSM has to
 release the requested RMD-QOSM bandwidth from the RMD traffic class
 state maintained at the QNE Ingress.
 This can be achieved by identifying the traffic class (PHB) and then
 subtracting the amount of RMD traffic class requested resources,
 included in the <Peak Data Rate-1 (p)> field of the local RMD-QSPEC
 <TMOD-1> parameter, from the total reserved amount of resources
 stored in the RMD traffic class state.  The <Time Lag> is used as
 explained in the introductory part of Section 4.6.1.5.

QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress) NTLP stateful NTLP stateless NTLP stateless NTLP stateful

  |                    |                   |                    |

RESERVE | | | —>| | | RESERVE |

  |------------------------------------------------------------>|
  |RESERVE(RMD-QSPEC:Tear=1)               |                    |
  |------------------->|                   |                    |
  |                    |RESERVE(RMD-QSPEC:Tear=1)               |
  |                    |------------------->|                   |
  |                    |                 RESERVE(RMD-QSPEC:Tear=1)
  |                    |                   |------------------->|
  |                    |                   |                RESERVE
  |                    |                   |                    |-->
Figure 11: Explicit release triggered by RESERVE used by the
           RMD-QOSM
 After that, the REQUIRED bandwidth is released from the RMD-QOSM
 traffic class state at the QNE Ingress, an intra-domain RESERVE (RMD-
 QOSM) message has to be generated.  The intra-domain RESERVE (RMD-
 QSPEC) message MUST include an <RMD QoS object combination> field and
 a PHR container, (i.e., "PHR_Release_Request") and it MAY include a
 PDR container, (i.e., PDR_Release_Request).  An example of this
 operation can be seen in Figure 11.

Bader, et al. Experimental [Page 57] RFC 5977 RMD-QOSM October 2010

 Most of the non-default values of the objects contained in the tear
 intra-domain RESERVE message are set by the QNE Ingress node in the
 same way as described in Section 4.6.1.1.  The following objects are
 set differently (see the QoS-NSLP-RMF API described in [RFC5974]):
  • The <RII> object MUST NOT be included in this message. This is

because the QNE Ingress node does not need to receive a response

    from the QNE Egress node;
  • if the release procedure is not applied for the RMD modification

of aggregated reservation procedure (see Section 4.6.1.4), then

    the <TEAR> flag MUST be set to ON;
  • the PHR resource units MUST be included into the <Peak Data Rate-1

(p)> value of the local RMD-QSPEC <TMOD-1> parameter of the RMD-

    QOSM <QoS Desired>;
  • the value of the <Admitted Hops> parameter MUST be set to "1";
  • the value of the <Time Lag> parameter of the PHR container is

calculated by the RMD-QOSM functionality (see Section 4.6.1.5) the

    value of the <Control Type> parameter of the PHR container is set
    to "18" (i.e., PHR_Release_Request).
 Any QNE Interior node that receives the combination of the RMD-QOSM
 <QoS Desired> object and the "PHR_Release_Request" control
 information container MUST identify the traffic class (PHB) and
 release the requested resources included in the <Peak Data Rate-1
 (p)> value of the local RMD-QSPEC <TMOD-1> parameter.  This can be
 achieved by subtracting the amount of RMD traffic class requested
 resources, included in the <Peak Data Rate-1 (p)> field of the local
 RMD-QSPEC <TMOD-1> parameter, from the total reserved amount of
 resources stored in the RMD traffic class state.  The value of the
 <Time Lag> parameter of the "PHR_Release_Request" container is used
 during the release procedure as explained in the introductory part of
 Section 4.6.1.5.
 The intra-domain tear RESERVE (RMD-QSPEC) message is received and
 processed by the QNE Egress node.  The RMD-QOSM <QoS Desired> and the
 "PHR RMD-QOSM control" container (and if available the "PDR
 Container") are read and processed by the RMD QoS node.
 The value of the <Peak Data Rate-1 (p)> field of the local RMD-QSPEC
 <TMOD-1> parameter of the RMD-QOSM <QoS Desired> and the value of the
 <Time Lag> field of the PHR container MUST be used by the RMD release
 procedure.

Bader, et al. Experimental [Page 58] RFC 5977 RMD-QOSM October 2010

 This can be achieved by subtracting the amount of RMD traffic class
 requested resources, included in the <Peak Data Rate-1 (p)> field
 value of the local RMD-QSPEC <TMOD-1> parameter, from the total
 reserved amount of resources stored in the RMD traffic class state.
 The end-to-end RESERVE message is forwarded by the next hop (i.e.,
 the QNE Egress) only if the intra-domain tear RESERVE (RMD-QSPEC)
 message arrives at the QNE Egress node.  Furthermore, the QNE Egress
 MUST stop the marking process that was used to bypass the QNE
 Interior nodes by reassigning the QoS-NSLP default NSLPID value to
 the end-to-end RESERVE message (see Section 4.4).
 Note that when the QNE Edges maintain aggregated QoS-NSLP reservation
 states, the RMD-QOSM functionality MAY start an RMD modification
 procedure (see Section 4.6.1.4) that uses the explicit release
 procedure, described above in this subsection.  Note that if the
 complete bandwidth associated with the aggregated reservation
 maintained at the QNE Ingress has to be released, then the <TEAR>
 flag MUST be set to ON.  Otherwise, the <TEAR> flag MUST be set to
 OFF, see Section 4.6.1.4.

4.6.1.5.2. Triggered by a Marked RESPONSE or NOTIFY Message

 This RMD explicit release procedure can be triggered by either an
 intra-domain RESPONSE message with a PDR container carrying among
 others the <M> and <S> parameters with values <M>=1 and <S>=0 (see
 Section 4.6.1.2), an intra-domain (refresh) RESPONSE message carrying
 a PDR container with <M>=1 and <S>=1  (see Section 4.6.1.6.1), or an
 end-to-end NOTIFY message (see Section 4.6.1.6) with an <INFO-SPEC>
 object with the following values:
 Error severity class: Informational
 Error code value: Congestion situation
 When the aggregated intra-domain QoS-NSLP operational states are
 used, an end-to-end NOTIFY message used to trigger an RMD release
 procedure MAY contain a PDR container that carries an <M> and an <S>
 with values <M>=1 and <S>=1, and a bandwidth value in the <PDR
 Bandwidth> parameter included in a "PDR_Refresh_Report" or
 "PDR_Congestion_Report" container.
 Note that in all explicit release procedures, before generating an
 intra-domain tear RESERVE, the RMD-QOSM has to release the requested
 RMD-QOSM bandwidth from the RMD traffic class state maintained at the
 QNE Ingress.  This can be achieved by identifying the traffic class
 (PHB) and then subtracting the amount of RMD traffic class requested

Bader, et al. Experimental [Page 59] RFC 5977 RMD-QOSM October 2010

 resources, included in the <Peak Data Rate-1 (p)> field of the local
 RMD-QSPEC <TMOD-1> parameter, from the total reserved amount of
 resources stored in the RMD traffic class state.
 Figure 12 shows the situation that the intra-domain tear RESERVE is
 generated after being triggered by either an intra-domain (refresh)
 RESPONSE message that carries a PDR container with <M>=1 and <S>=1 or
 by an end-to-end NOTIFY message that does not carry a PDR container,
 but an <INFO-SPEC> object.  The error code values carried by this
 NOTIFY message are:
 Error severity class: Informational
 Error code value: Congestion situation
 Most of the non-default values of the objects contained in the tear
 intra-domain RESERVE(RMD-QSPEC) message are set by the QNE Ingress
 node in the same way as described in Section 4.6.1.1.
 The following objects MUST be used and/or set differently (see the
 QoS-NSLP-RMF described in [RFC5974]):
  • the value of the <M> parameter of the PHR container MUST be set to

"1".

  • the value of the <S> parameter of the "PHR container" MUST be set

to "1".

  • the RESERVE message MAY include a PDR container. Note that this

is needed if a bidirectional scenario is used; see Section 4.6.2.

QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress) NTLP stateful NTLP stateless NTLP stateless NTLP stateful

  |                  |                  |                  |
  | NOTIFY           |                  |                  |
  |<-------------------------------------------------------|
  |RESERVE(RMD-QSPEC:Tear=1,M=1,S=1)    |                  |
  | ---------------->|RESERVE(RMD-QSPEC:Tear=1,M=1,S=1)    |
  |                  |                  |                  |
  |                  |----------------->|                  |
  |                  |           RESERVE(RMD-QSPEC:Tear=1,M=1,S=1)
  |                  |                  |----------------->|
Figure 12: Basic operation during RMD-explicit release procedure
           triggered by NOTIFY used by the RMD-QOSM
 Note that if the values of the <M> and <S> parameters included in the
 PHR container carried by a intra-domain tear RESERVE(RMD-QOSM) are
 set as ((<M>=0 and <S>=1) or (<M>=0 and <S>=0) or (<M>=1 and <S>=1)),

Bader, et al. Experimental [Page 60] RFC 5977 RMD-QOSM October 2010

 then the <Max Admitted Hops> value SHOULD NOT be compared to the
 <Admitted Hops> value and the value of the <K> field MUST NOT be set.
 Any QNE Edge or QNE Interior node that receives the intra-domain tear
 RESERVE MUST check the <K> field included in the PHR container.  If
 the <K> field is "0", then the traffic class state (PHB) has to be
 identified, using the <PHB Class> parameter, and the requested
 resources included in the <Peak Data Rate-1 (p)> field of the local
 RMD-QSPEC <TMOD-1> parameter have to be released.
 This can be achieved by subtracting the amount of RMD traffic class
 requested resources, included in the <Peak Data Rate-1 (p)> field of
 the local RMD-QSPEC <TMOD-1> parameter, from the total reserved
 amount of resources stored in the RMD traffic class state.  The value
 of the <Time Lag> parameter of the PHR field is used during the
 release procedure, as explained in the introductory part of Section
 4.6.1.5.  Afterwards, the QNE Egress node MUST terminate the tear
 intra-domain RESERVE(RMD-QSPEC) message.
 The RMD-specific release procedure that is triggered by an intra-
 domain RESPONSE message with an <M>=1 and <S>=0 PDR container (see
 Section 4.6.1.2) generates an intra-domain tear RESERVE message that
 uses the combination of the <Max Admitted Hops> and <Admitted_Hops>
 fields to calculate and specify when the <K> value carried by the
 "PHR Container" can be set.  When the <K> field is set, then the "PHR
 Container" and the RMD-QOSM <QoS Desired> carried by an intra-domain
 tear RESERVE MUST NOT be processed.
 The RMD-specific explicit release procedure that uses the combination
 of <Max Admitted Hops>, <Admitted_Hops> and <K> fields to release
 resources/bandwidth in only a part of the RMD domain, is denoted as
 RMD partial release procedure.
 This explicit release procedure can be used, for example, during
 unsuccessful reservation (see Section 4.6.1.2).  When the RMD-
 QOSM/QoS-NSLP signaling model functionality of a QNE Ingress node
 receives a PDR container with values <M>=1 and <S>=0, of type
 "PDR_Reservation_Report", it MUST start an RMD partial release
 procedure.
 In this situation, after the REQUIRED bandwidth is released from the
 RMD-QOSM traffic class state at the QNE Ingress, an intra-domain
 RESERVE (RMD-QOSM) message has to be generated.  An example of this
 operation can be seen in Figure 13.
 Most of the non-default values of the objects contained in the tear
 intra-domain RESERVE(RMD-QSPEC) message are set by the QNE Ingress
 node in the same way as described in Section 4.6.1.1.

Bader, et al. Experimental [Page 61] RFC 5977 RMD-QOSM October 2010

 The following objects MUST be used and/or set differently:
  • the value of the <M> parameter of the PHR container MUST be set to

"1".

  • the RESERVE message MAY include a PDR container.
  • the value of the <Max Admitted Hops> carried by the "PHR

Container" MUST be set equal to the <Max Admitted Hops> value

    carried by the "PDR Container" (with <M>=1 and <S>=0) carried by
    the received intra-domain RESPONSE message that triggers the
    release procedure.
 Any QNE Edge or QNE Interior node that receives the intra-domain tear
 RESERVE has to check the value of the <K> field in the "PHR
 Container" before releasing the requested resources.
 If the value of the <K> field is "1", then all the QNEs located
 downstream, including the QNE Egress, MUST NOT process the carried
 "PHR Container" and the RMD-QOSM <QoS Desired> object by the intra-
 domain tearing RESERVE.

QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress)

                                   Node that marked
                                  PHR_Resource_Request
                                     <PHR> object

NTLP stateful NTLP stateless NTLP stateless NTLP stateful

  |                    |                   |                    |
  |                    |                   |                    |
  | RESPONSE (RMD-QSPEC: M=1)              |                    |
  |<------------------------------------------------------------|

RESERVE(RMD-QSPEC: Tear=1, M=1, <Admit Hops>=<Max Admitted Hops>, K=0)

  |------------------->|                   |                    |
  |                    |RESERVE(RMD-QSPEC: Tear=1, M=1, K=1)    |
  |                    |------------------>|                    |
  |                    |    RESERVE(RMD-QSPEC: Tear=1, M=1, K=1)|
  |                    |                   |------------------->|
  |                    |                   |                    |
Figure 13: Basic operation during RMD explicit release procedure
           triggered by RESPONSE used by the RMD-QOSM
 If the <K> field value is "0", any QNE Edge or QNE Interior node that
 receives the intra-domain tear RESERVE can release the resources by
 subtracting the amount of RMD traffic class requested resources,
 included in the <Peak Data Rate-1 (p)> field of the local RMD-QSPEC
 <TMOD-1> parameter, from the total reserved amount of resources

Bader, et al. Experimental [Page 62] RFC 5977 RMD-QOSM October 2010

 stored in the RMD traffic class state.  The value of the <Time Lag>
 parameter of the PHR field is used during the release procedure as
 explained in the introductory part of Section 4.6.1.5.
 Furthermore, the QNE MUST perform the following procedures.
 If the values of the <M> and <S> parameters included in the
 "PHR_Release_Request" PHR container are (<M=1> and <S>=0) then the
 <Max Admitted Hops> value MUST be compared with the calculated
 <Admitted Hops> value.  Note that each time that the intra-domain
 tear RESERVE is processed and before being forwarded by a QNE, the
 <Admitted Hops> value included in the PHR container is increased by
 one.
 When these two values are equal, the intra-domain RESERVE(RMD-QSPEC)
 that is forwarded further towards the QNE Egress MUST set the <K>
 value of the carried "PHR Container" to "1".
 The reason for doing this is that the QNE node that is currently
 processing this message was the last QNE node that successfully
 processed the RMD-QOSM <QoS Desired>) and PHR container of its
 associated initial reservation request (i.e., initial intra-domain
 RESERVE(RMD-QSPEC) message).  Its next QNE downstream node was unable
 to successfully process the initial reservation request; therefore,
 this QNE node marked the <M> and <Hop_U> parameters of the
 "PHR_Resource_Request".
 Finally, note that the QNE Egress node MUST terminate the intra-
 domain RESERVE(RMD-QSPEC) message.
 Moreover, note that the above described RMD partial release procedure
 applies to the situation that the QNE Edges maintain a per-flow QoS-
 NSLP reservation state.
 When the QNE Edges maintain aggregated intra-domain QoS-NSLP
 operational states and a severe congestion occurs, then the QNE
 Ingress MAY receive an end-to-end NOTIFY message (see Section
 4.6.1.6) with a PDR container that carries the <M>=0 and <S>=1 fields
 and a bandwidth value in the <PDR Bandwidth> parameter included in a
 "PDR_Congestion_Report" container.  Furthermore, the same end-to-end
 NOTIFY message carries an <INFO-SPEC> object with the following
 values:
 Error severity class: Informational
 Error code value: Congestion situation

Bader, et al. Experimental [Page 63] RFC 5977 RMD-QOSM October 2010

 The end-to-end session associated with this NOTIFY message maintains
 the BOUND-SESSION-ID of the bound aggregated session; see Section
 4.3.1.  The RMD-QOSM at the QNE Ingress MUST start an RMD
 modification procedures (see Section 4.6.1.4) that uses the RMD
 explicit release procedure, described above in this section.  In
 particular, the RMD explicit release procedure releases the bandwidth
 value included in the <PDR Bandwidth> parameter, within the
 "PDR_Congestion_Report" container, from the reserved bandwidth
 associated with the aggregated intra-domain QoS-NSLP operational
 state.

4.6.1.6. Severe Congestion Handling

 This section describes the operation of the RMD-QOSM when a severe
 congestion occurs within the Diffserv domain.
 When a failure in a communication path, e.g., a router or a link
 failure occurs, the routing algorithms will adapt to failures by
 changing the routing decisions to reflect changes in the topology and
 traffic volume.  As a result, the rerouted traffic will follow a new
 path, which MAY result in overloaded nodes as they need to support
 more traffic.  This MAY cause severe congestion in the communication
 path.  In this situation, the available resources, are not enough to
 meet the REQUIRED QoS for all the flows along the new path.
 Therefore, one or more flows SHOULD be terminated, or forwarded in a
 lower priority queue.
 Interior nodes notify Edge nodes by data marking or marking the
 refresh messages.

4.6.1.6.1. Severe Congestion Handling by the RMD-QOSM Refresh Procedure

 This procedure applies to all RMD scenarios that use an RMD refresh
 procedure.  The QoS-NSLP and RMD are able to cope with congested
 situations using the refresh procedure; see Section 4.6.1.3.
 If the refresh is not successful in an QNE Interior node, Edge nodes
 are notified by setting <S>=1 (<M>=1) marking the refresh messages
 and by setting the <O> field in the "PHR_Refresh_Update" container,
 carried by the intra-domain RESERVE message.
 Note that the overload situation can be detected by using the example
 given in Appendix A.1.  In this situation, when the given
 signaled_overload_rate parameter given in Appendix A.1 is higher than
 0, the value of the <Overload> field is set to "1".  The calculation

Bader, et al. Experimental [Page 64] RFC 5977 RMD-QOSM October 2010

 of this is given in Appendix A.1 and denoted as the
 signaled_overload_rate parameter.  The flows can be terminated by the
 RMD release procedure described in Section 4.6.1.5.
 The intra-domain RESPONSE message that is sent by the QNE Egress
 towards the QNE Ingress will contain a PDR container with a Parameter
 ID = 26, i.e., "PDR_Congestion_Report".  The values of the <M>, <S>,
 and <O> fields of this container SHOULD be set equal to the values of
 the <M>, <S>, and <O> fields, respectively, carried by the
 "PHR_Refresh_Update" container.  Part of the flows, corresponding to
 the <O>, are terminated, or forwarded in a lower priority queue.
 The flows can be terminated by the RMD release procedure described in
 Section 4.6.1.5.
 Furthermore, note that the above functionalities also apply to the
 scenario in which the QNE Edge nodes maintain either per-flow QoS-
 NSLP reservation states or aggregated QoS-NSLP reservation states.
 In general, relying on the soft state refresh mechanism solves the
 congestion within the time frame of the refresh period.  If this
 mechanism is not fast enough, additional functions SHOULD be used,
 which are described in Section 4.6.1.6.2.

4.6.1.6.2. Severe Congestion Handling by Proportional Data Packet

          Marking
 This severe congestion handling method requires the following
 functionalities.

4.6.1.6.2.1. Operation in the Interior Nodes

 The detection and marking/re-marking functionality described in this
 section applies to NSIS-aware and NSIS-unaware nodes.  This means
 however, that the "not NSIS-aware" nodes MUST be configured such that
 they can detect the congestion/severe congestion situations and re-
 mark packets in the same way the "NSIS-aware" nodes do.
 The Interior node detecting severe congestion re-marks data packets
 passing the node.  For this re-marking, two additional DSCPs can be
 allocated for each traffic class.  One DSCP MAY be used to indicate
 that the packet passed a congested node.  This type of DSCP is
 denoted in this document as an "affected DSCP" and is used to
 indicate that a packet passed through a severe congested node.
 The use of this DSCP type eliminates the possibility that, e.g., due
 to flow-based ECMP-enabled (Equal Cost Multiple Paths) routing, the
 Egress node either does not detect packets passed a severely

Bader, et al. Experimental [Page 65] RFC 5977 RMD-QOSM October 2010

 congested node or erroneously detects packets that actually did not
 pass the severely congested node.  Note that this type of DSCP MUST
 only be used if all the nodes within the RMD domain are configured to
 use it.  Otherwise, this type of DSCP MUST NOT be applied.  The other
 DSCP MUST be used to indicate the degree of congestion by marking the
 bytes proportionally to the degree of congestion.  This type of DSCP
 is denoted in this document as "encoded DSCP".
 In this document, note that the terms "marked packets" or "marked
 bytes" refer to the "encoded DSCP".  The terms "unmarked packets" or
 "unmarked bytes" represent the packets or the bytes belonging to
 these packets that their DSCP is either the "affected DSCP" or the
 original DSCP.  Furthermore, in the algorithm described below, it is
 considered that the router MAY drop received packets.  The
 counting/measuring of marked or unmarked bytes described in this
 section is accomplished within measurement periods.  All nodes within
 an RMD domain use the same, fixed-measurement interval, say T
 seconds, which MUST be preconfigured.
 It is RECOMMENDED that the total number of additional (local and
 experimental) DSCPs needed for severe congestion handling within an
 RMD domain SHOULD be as low as possible, and it SHOULD NOT exceed the
 limit of 8.  One possibility to reduce the number of used DSCPs is to
 use only the "encoded DSCP" and not to use "affected DSCP" marking.
 Another possible solution is, for example, to allocate one DSCP for
 severe congestion indication for each of the AF classes that can be
 supported by RMD-QOSM.
 An example of a re-marking procedure can be found in Appendix A.1.

4.6.1.6.2.2. Operation in the Egress Nodes

 When the QNE Edges maintain a per-flow intra-domain QoS-NSLP
 operational state (see Sections 4.3.2 and 4.3.3), then the following
 procedure is followed.  The QNE Egress node applies a predefined
 policy to solve the severe congestion situation, by selecting a
 number of inter-domain (end-to-end) flows that SHOULD be terminated
 or forwarded in a lower priority queue.
 When the RMD domain does not use the "affected DSCP" marking, the
 Egress MUST generate an Ingress/Egress pair aggregated state, for
 each Ingress and for each supported PHB.  This is because the Edges
 MUST be able to detect in which Ingress/Egress pair a severe
 congestion occurs.  This is because, otherwise, the QNE Egress will
 not have any information on which flows or groups of flows were
 affected by the severe congestion.

Bader, et al. Experimental [Page 66] RFC 5977 RMD-QOSM October 2010

 When the RMD domain supports the "affected DSCP" marking, the Egress
 is able to detect all flows that are affected by the severe
 congestion situation.  Therefore, when the RMD domain supports the
 "affected DSCP" marking, the Egress MAY not generate and maintain the
 Ingress/Egress pair aggregated reservation states.  Note that these
 aggregated reservation states MAY not be associated with aggregated
 intra-domain QoS-NSLP operational states.
 The Ingress/Egress pair aggregated reservation state can be derived
 by detecting which flows are using the same PHB and are sent by the
 same Ingress (via the per-flow end-to-end QoS-NSLP states).
 Some flows, belonging to the same PHB traffic class might get other
 priority than other flows belonging to the same PHB traffic class.
 This difference in priority can be notified to the Egress and Ingress
 nodes by either the RESERVE message that carries the QSPEC associated
 with the end-to-end QoS Model, e.g.,, <Preemption Priority> and
 <Defending Priority> parameter or using a locally defined policy.
 The priority value is kept in the reservation states (see Section
 4.3), which might be used during admission control and/or severe
 congestion handling procedures.  The terminated flows are selected
 from the flows having the same PHB traffic class as the PHB of the
 marked (as "encoded DSCP") and "affected DSCP" (when applied in the
 complete RMD domain) packets and (when the Ingress/Egress pair
 aggregated states are available) that belong to the same
 Ingress/Egress pair aggregate.
 For flows associated with the same PHB traffic class, the priority of
 the flow plays a significant role.  An example of calculating the
 number of flows associated with each priority class that have to be
 terminated is explained in Appendix A.2.
 For the flows (sessions) that have to be terminated, the QNE Egress
 node generates and sends an end-to-end NOTIFY message to the QNE
 Ingress node (its upstream stateful QoS-NSLP peer) to indicate the
 severe congestion in the communication path.
 The non-default values of the objects contained in the NOTIFY message
 MUST be set by the QNE Egress node as follows (see QoS-NSLP-RMF API
 described in [RFC5974]):
  • the values of the <INFO-SPEC> object is set by the standard QoS-

NSLP protocol functions.

  • the <INFO-SPEC> object MUST include information that notifies that

the end-to-end flow MUST be terminated. This information is as

    follows:

Bader, et al. Experimental [Page 67] RFC 5977 RMD-QOSM October 2010

      Error severity class: Informational
      Error code value: Congestion situation
    When the QNE Edges maintain a per-aggregate intra-domain QoS-NSLP
    operational state (see Section 4.3.1), the QNE Edge has to
    calculate, per each aggregate intra-domain QoS-NSLP operational
    state, the total bandwidth that has to be terminated in order to
    solve the severe congestion.  The total bandwidth to be released
    is calculated in the same way as in the situation in which the QNE
    Edges maintain per-flow intra-domain QoS-NSLP operational states.
    Note that for the aggregated sessions that are affected, the QNE
    Egress node generates and sends one end-to-end NOTIFY message to
    the QNE Ingress node (its upstream stateful QoS-NSLP peer) to
    indicate the severe congestion in the communication path.  Note
    that this end-to-end NOTIFY message is associated with one of the
    end-to-end sessions that is bound to the aggregated intra-domain
    QoS-NSLP operational state.
    The non-default values of the objects contained in the NOTIFY
    message MUST be set by the QNE Egress node in the same way as the
    ones used by the end-to-end NOTIFY message described above for the
    situation that the QNE Egress maintains a per-flow intra-domain
    operational state.  In addition to this, the end-to-end NOTIFY
    MUST carry the RMD-QSPEC, which contains a PDR container with a
    Parameter ID = 26, i.e., "PDR_Congestion_Report".  The value of
    the <S> SHOULD be set.  Furthermore, the value of the <PDR
    Bandwidth> parameter MUST contain the bandwidth associated with
    the aggregated QoS-NSLP operational state, which has to be
    released.
    Furthermore, the number of end-to-end sessions that have to be
    terminated will be calculated as in the situation that the QNE
    Edges maintain per-flow intra-domain QoS-NSLP operational states.
    Similarly for each, to be terminated, ongoing flow, the Egress
    will notify the Ingress in the same way as in the situation that
    the QNE Edges maintain per-flow intra-domain QoS-NSLP operational
    states.
    Note that the QNE Egress SHOULD restore the original <DSCP> values
    of the re-marked packets; otherwise, multiple actions for the same
    event might occur.  However, this value MAY be left in its re-
    marking form if there is an SLA agreement between domains that a
    downstream domain handles the re-marking problem.
    An example of a detailed severe congestion operation in the Egress
    Nodes can be found in Appendix A.2.

Bader, et al. Experimental [Page 68] RFC 5977 RMD-QOSM October 2010

4.6.1.6.2.3. Operation in the Ingress Nodes

 Upon receiving the (end-to-end) NOTIFY message, the QNE Ingress node
 resolves the severe congestion by a predefined policy, e.g., by
 refusing new incoming flows (sessions), terminating the affected and
 notified flows (sessions), and blocking their packets or shifting
 them to an alternative RMD traffic class (PHB).
 This operation is depicted in Figure 14, where the QNE Ingress, for
 each flow (session) to be terminated, receives a NOTIFY message that
 carries the "Congestion situation" error code.
 When the QNE Ingress node receives the end-to-end NOTIFY message, it
 associates this NOTIFY message with its bound intra-domain session
 (see Sections 4.3.2 and 4.3.3) via the BOUND-SESSION-ID information
 included in the end-to-end per-flow QoS-NSLP state.  The QNE Ingress
 uses the operation described in Section 4.6.1.5.2 to terminate the
 intra-domain session.

QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress)

user  |                  |                 |                  |
data  |  user data       |                 |                  |

——>|—————–>| user data | user data |

      |                  |---------------->S(# marked bytes)  |
      |                  |                 S----------------->|
      |                  |                 S(# unmarked bytes)|
      |                  |                 S----------------->|Term.
      |                 NOTIFY             S                  |flow?
      |<-----------------|-----------------S------------------|YES
      |RESERVE(RMD-QSPEC:Tear=1,M=1,S=1)   S                  |
      | ---------------->|RESERVE(RMD-QSPEC:T=1,M=1,S=1)      |
      |                  |                 S                  |
      |                  |---------------->S                  |
      |                  |       RESERVE(RMD-QSPEC:Tear=1,M=1,S=1)
      |                  |                 S----------------->|
       Figure 14:  RMD severe congestion handling
 Note that the above functionality applies to the RMD reservation-
 based (see Section 4.3.3) and to both measurement-based admission
 control methods (i.e., congestion notification based on probing and
 the NSIS measurement-based admission control; see Section 4.3.2).
 In the case that the QNE Edges support aggregated intra-domain QoS-
 NSLP operational states, the following actions take place.  The QNE
 Ingress MAY receive an end-to-end NOTIFY message with a PDR container
 that carries an <S> marked and a bandwidth value in the <PDR

Bader, et al. Experimental [Page 69] RFC 5977 RMD-QOSM October 2010

 Bandwidth> parameter included in a "PDR_Congestion_Report" container.
 Furthermore, the same end-to-end NOTIFY message carries an <INFO-
 SPEC> object with the "Congestion situation" error code.
 When the QNE Ingress node receives this end-to-end NOTIFY message, it
 associates the NOTIFY message with the aggregated intra-domain QoS-
 NSLP operational state via the BOUND-SESSION-ID information included
 in the end-to-end per-flow QoS-NSLP operational state, see Section
 4.3.1.
 The RMD-QOSM at the QNE Ingress node by using the total bandwidth
 value to be released included in the <PDR Bandwidth> parameter MUST
 reduce the bandwidth associated and reserved by the RMD aggregated
 session.  This is accomplished by triggering the RMD modification for
 aggregated reservations procedure described in Section 4.6.1.4.
 In addition to the above, the QNE Ingress MUST select a number of
 inter-domain (end-to-end) flows (sessions) that MUST be terminated.
 This is accomplished in the same way as in the situation that the QNE
 Edges maintain per-flow intra-domain QoS-NSLP operational states.
 The terminated end-to-end sessions are selected from the end-to-end
 sessions bound to the aggregated intra-domain QoS-NSLP operational
 state.  Note that the end-to-end session associated with the received
 end-to-end NOTIFY message that notified the severe congestion MUST
 also be selected for termination.
 For the flows (sessions) that have to be terminated, the QNE Ingress
 node generates and sends an end-to-end NOTIFY message upstream
 towards the sender (QNI).  The values carried by this message are:
  • the values of the <INFO-SPEC> object set by the standard QoS-NSLP

protocol functions.

  • the <INFO-SPEC> object MUST include information that notifies that

the end-to-end flow MUST be terminated. This information is as

    follows:
      Error severity class: Informational
      Error code value: Congestion situation

4.6.1.7. Admission Control Using Congestion Notification Based on

        Probing
 The congestion notification function based on probing can be used to
 implement a simple measurement-based admission control within a
 Diffserv domain.  At Interior nodes along the data path, congestion

Bader, et al. Experimental [Page 70] RFC 5977 RMD-QOSM October 2010

 notification thresholds are set in the measurement-based admission
 control function for the traffic belonging to different PHBs.  These
 Interior nodes are not NSIS-aware nodes.

4.6.1.7.1. Operation in Ingress Nodes

 When an end-to-end reservation request (RESERVE) arrives at the
 Ingress node (QNE), see Figure 15, it is processed based on the
 procedures defined by the end-to-end QoS Model.
 The <DSCP> field of the GIST datagram message that is used to
 transport this probe RESERVE message, SHOULD be marked with the same
 value of DSCP as the data path packets associated with the same
 session.  In this way, it is ensured that the end-to-end RESERVE
 (probe) packet passed through the node that it is congested.  This
 feature is very useful when ECMP-based routing is used to detect only
 flows that are passing through the congested router.
 When a (end-to-end) RESPONSE message is received by the Ingress
 node,it will be processed based on the procedures defined by the end-
 to-end QoS Model.

4.6.1.7.2. Operation in Interior nodes

 These Interior nodes do not need to be NSIS-aware nodes and they do
 not need to process the NSIS functionality of NSIS messages.  Note
 that the "not NSIS-aware" nodes MUST be configured such that they can
 detect the congestion/severe congestion situations and re-mark
 packets in the same way the "NSIS-aware" nodes do.
 Using standard functionalities, congestion notification thresholds
 are set for the traffic that belongs to different PHBs (see Section
 4.3.2).  The end-to-end RESERVE message, see Figure 15, is used as a
 probe packet.
 The <DSCP> field of all data packets and of the GIST message carrying
 the RESERVE message will be re-marked when the corresponding
 "congestion notification" threshold is exceeded (see Section 4.3.2).
 Note that when the data rate is higher than the congestion
 notification threshold, the data packets are also re-marked.  An
 example of the detailed operation of this procedure is given in
 Appendix A.2.

4.6.1.7.3. Operation in Egress Nodes

 As emphasized in Section 4.6.1.6.2.2, the Egress node, by using the
 per-flow end-to-end QoS-NSLP states, can derive which flows are using
 the same PHB and are sent by the same Ingress.

Bader, et al. Experimental [Page 71] RFC 5977 RMD-QOSM October 2010

 For each Ingress, the Egress SHOULD generate an Ingress/Egress pair
 aggregated (RMF) reservation state for each supported PHB.  Note that
 this aggregated reservation state does not require that an aggregated
 intra-domain QoS-NSLP operational state is needed also.
 Appendix A.4 contains an example of how and when a (probe) RESERVE
 message that arrives at the Egress is admitted or rejected.
 If the request is rejected, then the Egress node SHOULD generate an
 (end-to-end) RESPONSE message to notify that the reservation is
 unsuccessful.  In particular, it will generate an <INFO-SPEC> object
 of:
   Error severity class: Transient Failure
   Error code value: Reservation failure
 The QSPEC that was carried by the end-to-end RESERVE that belongs to
 the same session as this end-to-end RESPONSE is included in this
 message.  The parameters included in the QSPEC <QoS Reserved> object
 are copied from the original <QoS Desired> values.  The <E> flag
 associated with the <QoS Reserved> object and the <E> flag associated
 with local RMD-QSPEC <TMOD-1> parameter are also set.  This RESPONSE
 message will be sent to the Ingress node and it will be processed
 based on the end-to-end QoS Model.
 Note that the QNE Egress SHOULD restore the original <DSCP> values of
 the re-marked packets; otherwise, multiple actions for the same event
 might occur.  However, this value MAY be left in its re-marking form
 if there is an SLA agreement between domains that a downstream domain
 handles the re-marking problem.  Note that the break <B> flag carried
 by the end-to-end RESERVE message MUST NOT be set.

Bader, et al. Experimental [Page 72] RFC 5977 RMD-QOSM October 2010

QNE(Ingress) Interior Interior QNE(Egress)

                  (not NSIS aware) (not NSIS aware)
user  |                  |                 |                  |
data  |  user data       |                 |                  |

——>|—————–>| user data | |

      |                  |---------------->| user data        |
      |                  |                 |----------------->|
user  |                  |                 |                  |
data  |  user data       |                 |                  |

——>|—————–>| user data | user data |

      |                  |---------------->S(# marked bytes)  |
      |                  |                 S----------------->|
      |                  |                 S(# unmarked bytes)|
      |                  |                 S----------------->|
      |                  |                 S                  |

RESERVE | | S | ——→| | S |

      |----------------------------------->S                  |
      |                  |           RESERVE(re-marked DSCP in GIST)
      |                  |                 S----------------->|
      |                  |RESPONSE(unsuccessful INFO-SPEC)    |
      |<------------------------------------------------------|

RESPONSE(unsuccessful INFO-SPEC) | | ←—–| | | |

Figure 15:  Using RMD congestion notification function for
            admission control based on probing

4.6.2. Bidirectional Operation

 This section describes the basic bidirectional operation and sequence
 of events/triggers of the RMD-QOSM.  The following basic operation
 cases are distinguished:
  • Successful and unsuccessful reservation (Section 4.6.2.1);
  • Refresh reservation (Section 4.6.2.2);
  • Modification of aggregated reservation (Section 4.6.2.3);
  • Release procedure (Section 4.6.2.4);
  • Severe congestion handling (Section 4.6.2.5);
  • Admission control using congestion notification based on probing

(Section 4.6.2.6).

 It is important to emphasize that the content of this section is used
 for the specification of the following RMD-QOSM/QoS-NSLP signaling
 schemes, when basic unidirectional operation is assumed:
  • "per-flow congestion notification based on probing";

Bader, et al. Experimental [Page 73] RFC 5977 RMD-QOSM October 2010

  • "per-flow RMD NSIS measurement-based admission control",
  • "per-flow RMD reservation-based" in combination with the "severe

congestion handling by the RMD-QOSM refresh" procedure;

  • "per-flow RMD reservation-based" in combination with the "severe

congestion handling by proportional data packet marking"

    procedure;
  • "per-aggregate RMD reservation-based" in combination with the

"severe congestion handling by the RMD-QOSM refresh" procedure;

  • "per-aggregate RMD reservation-based" in combination with the

"severe congestion handling by proportional data packet marking"

    procedure.
 For more details, please see Section 3.2.3.
 In particular, the functionality described in Sections 4.6.2.1,
 4.6.2.2, 4.6.2.3, 4.6.2.4, and 4.6.2.5 applies to the RMD
 reservation-based and NSIS measurement-based admission control
 methods.  The described functionality in Section 4.6.2.6 applies to
 the admission control procedure that uses the congestion notification
 based on probing.  The QNE Edge nodes maintain either per-flow QoS-
 NSLP operational and reservation states or aggregated QoS-NSLP
 operational and reservation states.
 RMD-QOSM assumes that asymmetric routing MAY be applied in the RMD
 domain.  Combined sender-receiver initiated reservation cannot be
 efficiently done in the RMD domain because upstream NTLP states are
 not stored in Interior routers.
 Therefore, the bidirectional operation SHOULD be performed by two
 sender-initiated reservations (sender&sender).  We assume that the
 QNE Edge nodes are common for both upstream and downstream
 directions, therefore, the two reservations/sessions can be bound at
 the QNE Edge nodes.  Note that if this is not the case, then the
 bidirectional procedure could be managed and maintained by nodes
 located outside the RMD domain, by using other procedures than the
 ones defined in RMD-QOSM.
 This (intra-domain) bidirectional sender&sender procedure can then be
 applied between the QNE Edge (QNE Ingress and QNE Egress) nodes of
 the RMD QoS signaling model.  In the situation in which a security
 association exists between the QNE Ingress and QNE Egress nodes (see
 Figure 15), and the QNE Ingress node has the REQUIRED <Peak Data
 Rate-1 (p)> values of the local RMD-QSPEC <TMOD-1> parameters for
 both directions, i.e., QNE Ingress towards QNE Egress and QNE Egress

Bader, et al. Experimental [Page 74] RFC 5977 RMD-QOSM October 2010

 towards QNE Ingress, then the QNE Ingress MAY include both <Peak Data
 Rate-1 (p)> values of the local RMD-QSPEC <TMOD-1> parameters (needed
 for both directions) into the RMD-QSPEC within a RESERVE message.  In
 this way, the QNE Egress node is able to use the QoS parameters
 needed for the "Egress towards Ingress" direction (QoS-2).  The QNE
 Egress is then able to create a RESERVE with the right QoS parameters
 included in the QSPEC, i.e., RESERVE (QoS-2).  Both directions of the
 flows are bound by inserting <BOUND-SESSION-ID> objects at the QNE
 Ingress and QNE Egress, which will be carried by bound end-to-end
 RESERVE messages.
   |------ RESERVE (QoS-1, QoS-2)----|
   |                                 V
   |           Interior/stateless QNEs
               +---+     +---+
      |------->|QNE|-----|QNE|------
      |        +---+     +---+     |
      |                            V
    +---+                        +---+
    |QNE|                        |QNE|
    +---+                        +---+
       ^                           |
    |  |       +---+     +---+     V
    |  |-------|QNE|-----|QNE|-----|
    |          +---+     +---+
 Ingress/                         Egress/
 stateful  QNE                    stateful QNE
                                   |
 <--------- RESERVE (QoS-2) -------|
 Figure 16: The intra-domain bidirectional reservation scenario
            in the RMD domain
 Note that it is RECOMMENDED that the QNE implementations of RMD-QOSM
 process the QoS-NSLP signaling messages with a higher priority than
 data packets.  This can be accomplished as described in Section 3.3.4
 in [RFC5974] and the QoS-NSLP-RMF API [RFC5974].
 A bidirectional reservation, within the RMD domain, is indicated by
 the PHR <B> and PDR <B> flags, which are set in all messages.  In
 this case, two <BOUND-SESSION-ID> objects SHOULD be used.
 When the QNE Edges maintain per-flow intra-domain QoS-NSLP
 operational states, the end-to-end RESERVE message carries two BOUND-
 SESSION-IDs.  One BOUND-SESSION-ID carries the SESSION-ID of the
 tunneled intra-domain (per-flow) session that is using a Binding_Code
 with value set to code (Tunneled and end-to-end sessions).  Another

Bader, et al. Experimental [Page 75] RFC 5977 RMD-QOSM October 2010

 BOUND-SESSION-ID carries the SESSION-ID of the bound bidirectional
 end-to-end session.  The Binding_Code associated with this BOUND-
 SESSION-ID is set to code (Bidirectional sessions).
 When the QNE Edges maintain aggregated intra-domain QoS-NSLP
 operational states, the end-to-end RESERVE message carries two BOUND-
 SESSION-IDs.  One BOUND-SESSION-ID carries the SESSION-ID of the
 tunneled aggregated intra-domain session that is using a Binding_Code
 with value set to code (Aggregated sessions).  Another BOUND-SESSION-
 ID carries the SESSION-ID of the bound bidirectional end-to-end
 session.  The Binding_Code associated with this BOUND-SESSION-ID is
 set to code (Bidirectional sessions).
 The intra-domain and end-to-end QoS-NSLP operational states are
 initiated/modified depending on the binding type (see Sections 4.3.1,
 4.3.2, and 4.3.3).
 If no security association exists between the QNE Ingress and QNE
 Egress nodes, the bidirectional reservation for the sender&sender
 scenario in the RMD domain SHOULD use the scenario specified in
 [RFC5974] as "bidirectional reservation for sender&sender scenario".
 This is because in this scenario, the RESERVE message sent from the
 QNE Ingress to QNE Egress does not have to carry the QoS parameters
 needed for the "Egress towards Ingress" direction (QoS-2).
 In the following sections, it is considered that the QNE Edge nodes
 are common for both upstream and downstream directions and therefore,
 the two reservations/sessions can be bound at the QNE Edge nodes.
 Furthermore, it is considered that a security association exists
 between the QNE Ingress and QNE Egress nodes, and the QNE Ingress
 node has the REQUIRED <Peak Data Rate-1 (p)> value of the local RMD-
 QSPEC <TMOD-1> parameters for both directions, i.e., QNE Ingress
 towards QNE Egress and QNE Egress towards QNE Ingress.
 According to Section 3.2.3, it is specified that only the "per-flow
 RMD reservation-based" in combination with the "severe congestion
 handling by proportional data packet marking" scheme MUST be
 implemented within one RMD domain.  However, all RMD QNEs supporting
 this specification MUST support the combination the "per-flow RMD
 reservation-based" in combination with the "severe congestion
 handling by proportional data packet marking" scheme.  If the RMD
 QNEs support more RMD-QOSM schemes, then the operator of that RMD
 domain MUST preconfigure all the QNE Edge nodes within one domain
 such that the <SCH> field included in the "PHR Container" (Section
 4.1.2) and the "PDR Container" (Section 4.1.3) will always use the
 same value, such that within one RMD domain, only one of the below
 described RMD-QOSM schemes is used at a time.

Bader, et al. Experimental [Page 76] RFC 5977 RMD-QOSM October 2010

 All QNE nodes located within the RMD domain MUST read and interpret
 the <SCH> field included in the "PHR Container" before processing all
 the other <PHR Container> payload fields.  Moreover, all QNE Edge
 nodes located at the boarder of the RMD domain, MUST read and
 interpret the <SCH> field included in the "PDR container" before
 processing all the other <PDR Container> payload fields.

4.6.2.1. Successful and Unsuccessful Reservations

 This section describes the operation of the RMD-QOSM where an RMD
 Intra-domain bidirectional reservation operation, see Figure 16 and
 Section 4.6.2, is either successfully or unsuccessfully accomplished.
 The bidirectional successful reservation is similar to a combination
 of two unidirectional successful reservations that are accomplished
 in opposite directions, see Figure 17.  The main differences of the
 bidirectional successful reservation procedure with the combination
 of two unidirectional successful reservations accomplished in
 opposite directions are as follows.  Note also that the intra-domain
 and end-to-end QoS-NSLP operational states generated and maintained
 by the end-to-end RESERVE messages contain, compared to the
 unidirectional reservation scenario, a different BOUND-SESSION-ID
 data structure (see Sections 4.3.1, 4.3.2, and 4.3.3).  In this
 scenario, the intra-domain RESERVE message sent by the QNE Ingress
 node towards the QNE Egress node is denoted in Figure 17 as RESERVE
 (RMD-QSPEC): "forward".  The main differences between the intra-
 domain RESERVE (RMD-QSPEC): "forward" message used for the
 bidirectional successful reservation procedure and a RESERVE (RMD-
 QSPEC) message used for the unidirectional successful reservation are
 as follows (see the QoS-NSLP-RMF API described in [RFC5974]):
  • the <RII> object MUST NOT be included in the message. This is

because no RESPONSE message is REQUIRED.

  • the <B> bit of the PHR container indicates a bidirectional

reservation and it MUST be set to "1".

  • the PDR container is also included in the RESERVE(RMD-QSPEC):

"forward" message. The value of the Parameter ID is "20", i.e.,

    "PDR_Reservation_Request".  Note that the response PDR container
    sent by a QNE Egress to a QNE Ingress node is not carried by an
    end-to-end RESPONSE message, but it is carried by an intra-domain
    RESERVE message that is sent by the QNE Egress node towards the
    QNE Ingress node (denoted in Figure 16 as RESERVE(RMD-QSPEC):
    "reverse").
  • the <B> PDR bit indicates a bidirectional reservation and is set

to "1".

Bader, et al. Experimental [Page 77] RFC 5977 RMD-QOSM October 2010

  • the <PDR Bandwidth> field specifies the requested bandwidth that

has to be used by the QNE Egress node to initiate another intra-

    domain RESERVE message in the reverse direction.
 The RESERVE(RMD-QSPEC): "reverse" message is initiated by the QNE
 Egress node at the moment that the RESERVE(RMD-QSPEC): "forward"
 message is successfully processed by the QNE Egress node.
 The main differences between the RESERVE(RMD-QSPEC): "reverse"
 message used for the bidirectional successful reservation procedure
 and a RESERVE(RMD-QSPEC) message used for the unidirectional
 successful reservation are as follows:

QNE(Ingress) QNE (int.) QNE (int.) QNE (int.) QNE(Egress) NTLP stateful NTLP st.less NTLP st.less NTLP st.less NTLP stateful

  |                |               |               |              |
  |                |               |               |              |
  |RESERVE(RMD-QSPEC)              |               |              |
  |"forward"       |               |               |              |
  |                |    RESERVE(RMD-QSPEC):        |              |
  |--------------->|    "forward"  |               |              |
  |                |------------------------------>|              |
  |                |               |               |------------->|
  |                |               |               |              |
  |                |               |RESERVE(RMD-QSPEC)            |
  |      RESERVE(RMD-QSPEC)        | "reverse"     |<-------------|
  |      "reverse" |               |<--------------|              |
  |<-------------------------------|               |              |
   Figure 17: Intra-domain signaling operation for successful
              bidirectional reservation
  • the <RII> object is not included in the message. This is because

no RESPONSE message is REQUIRED;

  • the value of the <Peak Data Rate-1 (p)> field of the local RMD-

QSPEC <TMOD-1> parameter is set equal to the value of the <PDR

    Bandwidth> field included in the RESERVE(RMD-QSPEC): "forward"
    message that triggered the generation of this RESERVE(RMD-QSPEC):
    "reverse" message;
  • the <B> bit of the PHR container indicates a bidirectional

reservation and is set to "1";

  • the PDR container is included into the RESERVE(RMD-QSPEC):

"reverse" message. The value of the Parameter ID is "23", i.e.,

    "PDR_Reservation_Report";

Bader, et al. Experimental [Page 78] RFC 5977 RMD-QOSM October 2010

  • the <B> PDR bit indicates a bidirectional reservation and is set

to "1".

 Figures 18 and 19 show the flow diagrams used in the case of an
 unsuccessful bidirectional reservation.  In Figure 18, the QNE that
 is not able to support the requested <Peak Data Rate-1 (p)> value of
 local RMD-QSPEC <TMOD-1> is located in the direction QNE Ingress
 towards QNE Egress.  In Figure 19, the QNE that is not able to
 support the requested <Peak Data Rate-1 (p)> value of local RMD-QSPEC
 <TMOD-1> is located in the direction QNE Egress towards QNE Ingress.
 The main differences between the bidirectional unsuccessful procedure
 shown in Figure 18 and the bidirectional successful procedure are as
 follows:
  • the QNE node that is not able to reserve resources for a certain

request is located in the "forward" path, i.e., the path from the

    QNE Ingress towards the QNE Egress.
  • the QNE node that is not able to support the requested <Peak Data

Rate-1 (p)> value of local RMD-QSPEC <TMOD-1> MUST mark the <M>

    bit, i.e., set to value "1", of the RESERVE(RMD-QSPEC): "forward".

QNE(Ingress) QNE (int.) QNE (int.) QNE (int.) QNE(Egress) NTLP stateful NTLP st.less NTLP st.less NTLP st.less NTLP stateful

  |                |             |              |               |
  |RESERVE(RMD-QSPEC):           |              |               |
  |  "forward"     |  RESERVE(RMD-QSPEC):       |               |
  |--------------->|  "forward"  |              M RESERVE(RMD-QSPEC):
  |                |--------------------------->M  "forward-M marked"
  |                |             |              M-------------->|
  |                |           RESPONSE(PDR)    M               |
  |                |        "forward - M marked"M               |
  |<------------------------------------------------------------|
  |RESERVE(RMD-QSPEC, K=0)       |              M               |
  |"forward - T tear"            |              M               |
  |--------------->|             |              M               |
  |                    RESERVE(RMD-QSPEC, K=1)  M               |
  |                |   "forward - T tear"       M               |
  |                |--------------------------->M               |
  |                |                  RESERVE(RMD-QSPEC, K=1)   |
  |                |                 "forward - T tear"         |
  |                |                            M-------------->|
Figure 18: Intra-domain signaling operation for unsuccessful
           bidirectional reservation (rejection on path
           QNE(Ingress) towards QNE(Egress))

Bader, et al. Experimental [Page 79] RFC 5977 RMD-QOSM October 2010

 The operation for this type of unsuccessful bidirectional reservation
 is similar to the operation for unsuccessful unidirectional
 reservation, shown in Figure 9.
 The main differences between the bidirectional unsuccessful procedure
 shown in Figure 19 and the in bidirectional successful procedure are
 as follows:
  • the QNE node that is not able to reserve resources for a certain

request is located in the "reverse" path, i.e., the path from the

    QNE Egress towards the QNE Ingress.
  • the QNE node that is not able to support the requested <Peak Data

Rate-1 (p)> value of local RMD-QSPEC <TMOD-1> MUST mark the <M>

    bit, i.e., set to value "1", the RESERVE(RMD-QSPEC): "reverse".

Bader, et al. Experimental [Page 80] RFC 5977 RMD-QOSM October 2010

QNE(Ingress) QNE (int.) QNE (int.) QNE (int.) QNE(Egress) NTLP stateful NTLP st.less NTLP st.less NTLP st.less NTLP stateful

  |                |                |                |              |
  |RESERVE(RMD-QSPEC)               |                |              |
  |"forward"       |  RESERVE(RMD-QSPEC):            |              |
  |--------------->|  "forward"     |           RESERVE(RMD-QSPEC): |
  |                |-------------------------------->|"forward"     |
  |                |   RESERVE(RMD-QSPEC):           |------------->|
  |                |    "reverse"   |                |              |
  |                |              RESERVE(RMD-QSPEC) |              |
  |    RESERVE(RMD-QSPEC):          M      "reverse" |<-------------|
  |   "reverse - M marked"          M<---------------|              |
  |<--------------------------------M                |              |
  |                |                M                |              |
  |RESERVE(RMD-QSPEC, K=0):         M                |              |
  |"forward - T tear"               M                |              |
  |--------------->|  RESERVE(RMD-QSPEC, K=0):       |              |
  |                |  "forward - T tear"             |              |
  |                |-------------------------------->|              |
  |                |                M                |------------->|
  |                |                M         RESERVE(RMD-QSPEC, K=0):
  |                |                M            "reverse - T tear" |
  |                |                M                |<-------------|
  |                                 M RESERVE(RMD-QSPEC, K=1)       |
  |                |                M "forward - T tear"            |
  |                |                M<---------------|              |
  |          RESERVE(RMD-QSPEC, K=1)M                |              |
  |          "forward - T tear"     M                |              |
  |<--------------------------------M                |              |
Figure 19: Intra-domain signaling normal operation for unsuccessful
           bidirectional reservation (rejection on path QNE(Egress)
           towards QNE(Ingress)
  • the QNE Ingress uses the information contained in the received PHR

and PDR containers of the RESERVE(RMD-QSPEC): "reverse" and

    generates a tear intra-domain RESERVE(RMD-QSPEC): "forward - T
    tear" message.  This message carries a "PHR_Release_Request" and
    "PDR_Release_Request" control information.  This message is sent
    to the QNE Egress node.  The QNE Egress node uses the information
    contained in the "PHR_Release_Request" and the
    "PDR_Release_Request" control info containers to generate a
    RESERVE(RMD-QSPEC): "reverse - T tear" message that is sent
    towards the QNE Ingress node.

Bader, et al. Experimental [Page 81] RFC 5977 RMD-QOSM October 2010

4.6.2.2. Refresh Reservations

 This section describes the operation of the RMD-QOSM where an RMD
 intra-domain bidirectional refresh reservation operation is
 accomplished.
 The refresh procedure in the case of an RMD reservation-based method
 follows a scheme similar to the successful reservation procedure,
 described in Section 4.6.2.1 and depicted in Figure 17, and how the
 refresh process of the reserved resources is maintained and is
 similar to the refresh process used for the intra-domain
 unidirectional reservations (see Section 4.6.1.3).
 Note that the RMD traffic class refresh periods used by the bound
 bidirectional sessions MUST be equal in all QNE Edge and QNE Interior
 nodes.
 The main differences between the RESERVE(RMD-QSPEC): "forward"
 message used for the bidirectional refresh procedure and a
 RESERVE(RMD-QSPEC): "forward" message used for the bidirectional
 successful reservation procedure are as follows:
  • the value of the Parameter ID of the PHR container is "19", i.e.,

"PHR_Refresh_Update".

  • the value of the Parameter ID of the PDR container is "21", i.e.,

"PDR_Refresh_Request".

 The main differences between the RESERVE(RMD-QSPEC): "reverse"
 message used for the bidirectional refresh procedure and the RESERVE
 (RMD-QSPEC): "reverse" message used for the bidirectional successful
 reservation procedure are as follows:
  • the value of the Parameter ID of the PHR container is "19", i.e.,

"PHR_Refresh_Update".

  • the value of the Parameter ID of the PDR container is "24", i.e.,

"PDR_Refresh_Report".

4.6.2.3. Modification of Aggregated Intra-Domain QoS-NSLP Operational

        Reservation States
 This section describes the operation of the RMD-QOSM where RMD intra-
 domain bidirectional QoS-NSLP aggregated reservation states have to
 be modified.

Bader, et al. Experimental [Page 82] RFC 5977 RMD-QOSM October 2010

 In the case when the QNE Edges maintain, for the RMD QoS Model, QoS-
 NSLP aggregated reservation states and if such an aggregated
 reservation has to be modified (see Section 4.3.1), then similar
 procedures to Section 4.6.1.4 are applied.  In particular:
  • When the modification request requires an increase of the reserved

resources, the QNE Ingress node MUST include the corresponding

    value into the <Peak Data Rate-1 (p)> field local RMD-QSPEC
    <TMOD-1> parameter of the RMD-QOSM <QoS Desired>), which is sent
    together with "PHR_Resource_Request" control information.  If a
    QNE Edge or QNE Interior node is not able to reserve the number of
    requested resources, then the "PHR_Resource_Request" associated
    with the local RMD-QSPEC <TMOD-1> parameter MUST be marked.  In
    this situation, the RMD-specific operation for unsuccessful
    reservation will be applied (see Section 4.6.2.1).  Note that the
    value of the <PDR Bandwidth> parameter, which is sent within a
    "PDR_Reservation_Request" container, represents the increase of
    the reserved resources in the "reverse" direction.
  • When the modification request requires a decrease of the reserved

resources, the QNE Ingress node MUST include this value into the

    <Peak Data Rate-1 (p)> field of the local RMD-QSPEC <TMOD-1>
    parameter of the RMD-QOSM <QoS Desired>).  Subsequently, an RMD
    release procedure SHOULD be accomplished (see Section 4.6.2.4).
    Note that the value of the <PDR Bandwidth> parameter, which is
    sent within a "PDR_Release_Request" container, represents the
    decrease of the reserved resources in the "reverse" direction.

4.6.2.4. Release Procedure

 This section describes the operation of the RMD-QOSM, where an RMD
 intra-domain bidirectional reservation release operation is
 accomplished.  The message sequence diagram used in this procedure is
 similar to the one used by the successful reservation procedures,
 described in Section 4.6.2.1 and depicted in Figure 17.  However, how
 the release of the reservation is accomplished is similar to the RMD
 release procedure used for the intra-domain unidirectional
 reservations (see Section 4.6.1.5 and Figures 18 and 19).
 The main differences between the RESERVE (RMD-QSPEC): "forward"
 message used for the bidirectional release procedure and a RESERVE
 (RMD-QSPEC): "forward" message used for the bidirectional successful
 reservation procedure are as follows:
  • the value of the Parameter ID of the PHR container is "18",

i.e."PHR_Release_Request";

Bader, et al. Experimental [Page 83] RFC 5977 RMD-QOSM October 2010

  • the value of the Parameter ID of the PDR container is "22", i.e.,

"PDR_Release_Request";

 The main differences between the RESERVE (RMD-QSPEC): "reverse"
 message used for the bidirectional release procedure and the RESERVE
 (RMD-QSPEC): "reverse" message used for the bidirectional successful
 reservation procedure are as follows:
  • the value of the Parameter ID of the PHR container is "18", i.e.,

"PHR_Release_Request";

  • the PDR container is not included in the RESERVE (RMD-QSPEC):

"reverse" message.

4.6.2.5. Severe Congestion Handling

 This section describes the severe congestion handling operation used
 in combination with RMD intra-domain bidirectional reservation
 procedures.  This severe congestion handling operation is similar to
 the one described in Section 4.6.1.6.

4.6.2.5.1. Severe Congestion Handling by the RMD-QOSM Bidirectional

          Refresh Procedure
 This procedure is similar to the severe congestion handling procedure
 described in Section 4.6.1.6.1.  The difference is related to how the
 refresh procedure is accomplished (see Section 4.6.2.2) and how the
 flows are terminated (see Section 4.6.2.4).

4.6.2.5.2. Severe Congestion Handling by Proportional Data Packet

          Marking
 This section describes the severe congestion handling by proportional
 data packet marking when this is combined with an RMD intra-domain
 bidirectional reservation procedure.  Note that the detection and
 marking/re-marking functionality described in this section and used
 by Interior nodes, applies to NSIS-aware but also to NSIS-unaware
 nodes.  This means however, that the "not NSIS-aware" Interior nodes
 MUST be configured such that they can detect the congestion
 situations and re-mark packets in the same way as the Interior "NSIS-
 aware" nodes do.
 This procedure is similar to the severe congestion handling procedure
 described in Section 4.6.1.6.2.  The main difference is related to
 the location of the severe congested node, i.e., "forward" or
 "reverse" path.  Note that when a severe congestion situation occurs,
 e.g., on a forward path, and flows are terminated to solve the severe
 congestion in forward path, then the reserved bandwidth associated

Bader, et al. Experimental [Page 84] RFC 5977 RMD-QOSM October 2010

 with the terminated bidirectional flows will also be released.
 Therefore, a careful selection of the flows that have to be
 terminated SHOULD take place.  An example of such a selection is
 given in Appendix A.5.
 Furthermore, a special case of this operation is associated with the
 severe congestion situation occurring simultaneously on the forward
 and reverse paths.  An example of this operation is given in Appendix
 A.6.
 Simulation results associated with these procedures can be found in
 [DiKa08].

QNE(Ingress) QNE (int.) QNE (int.) QNE (int.) QNE(Egress) NTLP stateful NTLP st.less NTLP st.less NTLP st.less NTLP stateful user| | | | | data| user | | | | —>| data | user data | |user data |

  |--------------->|             |              S               |
  |                |--------------------------->S (#marked bytes)
  |                |             |              S-------------->|
  |                |             |              S(#unmarked bytes)
  |                |             |              S-------------->|Term
  |                |             |              S               |flow?
  |                |          NOTIFY (PDR)      S               |YES
  |<------------------------------------------------------------|
  |RESERVE(RMD-QSPEC)            |              S               |
  |"forward - T tear"            |              S               |
  |--------------->|             |           RESERVE(RMD-QSPEC):|
  |                |--------------------------->S"forward - T tear"
  |                |             |              S-------------->|
  |                |             |          RESERVE(RMD-QSPEC): |
  |                |             |           "reverse - T tear" |
  | RESERVE(RMD-QSPEC):          |              |<--------------|
  |"reverse - T tear"            |<-------------S               |
  |<-----------------------------|              S               |
Figure 20: Intra-domain RMD severe congestion handling for
           bidirectional reservation (congestion on path
           QNE(Ingress) towards QNE(Egress))
 Figure 20 shows the scenario in which the severely congested node is
 located in the "forward" path.  The QNE Egress node has to generate
 an end-to-end NOTIFY (PDR) message.  In this way, the QNE Ingress
 will be able to receive the (#marked and #unmarked) that were
 measured by the QNE Egress node on the congested "forward" path.
 Note that in this situation, it is assumed that the "reverse" path is
 not congested.

Bader, et al. Experimental [Page 85] RFC 5977 RMD-QOSM October 2010

 This scenario is very similar to the severe congestion handling
 scenario described in Section 4.6.1.6.2 and shown in Figure 14.  The
 difference is related to the release procedure, which is accomplished
 in the same way as described in Section 4.6.2.4.
 Figure 21 shows the scenario in which the severely congested node is
 located in the "reverse" path.  Note that in this situation, it is
 assumed that the "forward" path is not congested.  The main
 difference between this scenario and the scenario shown in Figure 20
 is that no end-to-end NOTIFY (PDR) message has to be generated by the
 QNE Egress node.
 This is because now the severe congestion occurs on the "reverse"
 path and the QNE Ingress node receives the (#marked and #unmarked)
 user data passing through the severely congested "reverse" path.  The
 QNE Ingress node will be able to calculate the number of flows that
 have to be terminated or forwarded in a lower priority queue.

Bader, et al. Experimental [Page 86] RFC 5977 RMD-QOSM October 2010

QNE(Ingress) QNE (int.) QNE (int.) QNE (int.) QNE(Egress) NTLP stateful NTLP st.less NTLP st.less NTLP st.less NTLP stateful user| | | | | data| user | | | | —>| data | user data | |user data |

  |--------------->|                |           |               |
  |                |--------------------------->|user data      |user
  |                |                |           |-------------->|data
  |                |                |           |               |--->
  |                |                |  user     |               |<---
  |   user data    |                |  data     |<--------------|
  | (#marked bytes)|                S<----------|               |
  |<--------------------------------S           |               |
  | (#unmarked bytes)               S           |               |

Term|←——————————-S | | Flow? | S | | YES |RESERVE(RMD-QSPEC): S | |

  |"forward - T tear"               s           |               |
  |--------------->|  RESERVE(RMD-QSPEC):       |               |
  |                |  "forward - T tear"        |               |
  |                |--------------------------->|               |
  |                |                S           |-------------->|
  |                |                S         RESERVE(RMD-QSPEC):
  |                |                S       "reverse - T tear"  |
  |      RESERVE(RMD-QSPEC)         S           |<--------------|
  |      "reverse - T tear"         S<----------|               |
  |<--------------------------------S           |               |
Figure 21: Intra-domain RMD severe congestion handling for
           bidirectional reservation (congestion on path
           QNE(Egress) towards QNE(Ingress))
 For the flows that have to be terminated, a release procedure, see
 Section 4.6.2.4, is initiated to release the reserved resources on
 the "forward" and "reverse" paths.

4.6.2.6. Admission Control Using Congestion Notification Based on

        Probing
 This section describes the admission control scheme that uses the
 congestion notification function based on probing when RMD intra-
 domain bidirectional reservations are supported.

Bader, et al. Experimental [Page 87] RFC 5977 RMD-QOSM October 2010

QNE(Ingress) Interior QNE (int.) Interior QNE(Egress) NTLP stateful not NSIS aware not NSIS aware not NSIS aware NTLP stateful user| | | | | data| | | | | —>| | user data | |user data |

  |-------------------------------------------->S (#marked bytes)
  |                |             |              S-------------->|
  |                |             |              S(#unmarked bytes)
  |                |             |              S-------------->|
  |                |             |              S               |
  |                |           RESERVE(re-marked DSCP in GIST)):|
  |                |             |              S               |
  |-------------------------------------------->S               |
  |                |             |              S-------------->|
  |                |             |              S               |
  |                |          RESPONSE(unsuccessful INFO-SPEC)  |
  |<------------------------------------------------------------|
  |                |             |              S               |
Figure 22: Intra-domain RMD congestion notification based on
           probing for bidirectional admission control (congestion
           on path from QNE(Ingress) towards QNE(Egress))
 This procedure is similar to the congestion notification for
 admission control procedure described in Section 4.6.1.7.  The main
 difference is related to the location of the severe congested node,
 i.e., "forward" path (i.e., path between QNE Ingress towards QNE
 Egress) or "reverse" path (i.e., path between QNE Egress towards QNE
 Ingress).
 Figure 22 shows the scenario in which the severely congested node is
 located in the "forward" path.  The functionality of providing
 admission control is the same as that described in Section 4.6.1.7,
 Figure 15.
 Figure 23 shows the scenario in which the congested node is located
 in the "reverse" path.  The probe RESERVE message sent in the
 "forward" direction will not be affected by the severely congested
 node, while the <DSCP> value in the IP header of any packet of the
 "reverse" direction flow and also of the GIST message that carries
 the probe RESERVE message sent in the "reverse" direction will be re-
 marked by the congested node.  The QNE Ingress is, in this way,
 notified that a congestion occurred in the network, and therefore it
 is able to refuse the new initiation of the reservation.

Bader, et al. Experimental [Page 88] RFC 5977 RMD-QOSM October 2010

 Note that the "not NSIS-aware" Interior nodes MUST be configured such
 that they can detect the congestion/severe congestion situations and
 re-mark packets in the same way as the Interior "NSIS-aware" nodes
 do.

QNE(Ingress) Interior QNE (int.) Interior QNE(Egress) NTLP stateful not NSIS aware NTLP st.less not NSIS aware NTLP stateful user| | | | | data| | | | | —>| | user data | | |

  |-------------------------------------------->|user data      |user
  |                |                |           |-------------->|data
  |                |                |           |               |--->
  |                |                |           |               |user
  |                |                |           |               |data
  |                |                |           |               |<---
  |                S                | user data |               |
  |                S  user data     |<--------------------------|
  |   user data    S<---------------|           |               |
  |<---------------S                |           |               |
  |  user data     S                |           |               |
  | (#marked bytes)S                |           |               |
  |<---------------S                |           |               |
  |                S           RESERVE(unmarked DSCP in GIST)): |
  |                S                |           |               |
  |----------------S------------------------------------------->|
  |                S          RESERVE(re-marked DSCP in GIST)   |
  |                S<-------------------------------------------|
  |<---------------S                |           |               |
Figure 23: Intra-domain RMD congestion notification for
           bidirectional admission control (congestion on path
           QNE(Egress) towards QNE(Ingress))

4.7. Handling of Additional Errors

 During the QSPEC processing, additional errors MAY occur.  The way in
 which these additional errors are handled and notified is specified
 in [RFC5975] and [RFC5974].

5. Security Considerations

5.1. Introduction

 A design goal of the RMD-QOSM protocol is to be "lightweight" in
 terms of the number of exchanged signaling message and the amount of
 state established at involved signaling nodes (with and without
 reduced-state operation).  A side effect of this design decision is

Bader, et al. Experimental [Page 89] RFC 5977 RMD-QOSM October 2010

 to introduce second-class signaling nodes, namely QNE Interior nodes,
 that are restricted in their ability to perform QoS signaling
 actions.  Only the QNE Ingress and the QNE Egress nodes are allowed
 to initiate certain signaling messages.
 Moreover, RMD focuses on an intra-domain deployment only.
 The above description has the following implications for security:
 1) QNE Ingress and QNE Egress nodes require more security and fault
    protection than QNE Interior nodes because their uncontrolled
    behavior has larger implications for the overall stability of the
    network.  QNE Ingress and QNE Egress nodes share a security
    association and utilize GIST security for protection of their
    signaling messages.  Intra-domain signaling messages used for RMD
    signaling do not use GIST security, and therefore they do not
    store security associations.
 2) The focus on intra-domain QoS signaling simplifies trust
    management and reduces overall complexity.  See Section 2 of RFC
    4081 for a more detailed discussion about the complete set of
    communication models available for end-to-end QoS signaling
    protocols.  The security of RMD-QOSM does not depend on Interior
    nodes, and hence the cryptographic protection of intra-domain
    messages via GIST is not utilized.
 It is important to highlight that RMD always uses the message
 exchange shown in Figure 24 even if there is no end-to-end signaling
 session.  If the RMD-QOSM is triggered based on an end-to-end (E2E)
 signaling exchange, then the RESERVE message is created by a node
 outside the RMD domain and will subsequently travel further (e.g., to
 the data receiver).  Such an exchange is shown in Figure 3.  As such,
 an evaluation of an RMD's security always has to be seen as a
 combination of the two signaling sessions, (1) and (2) of Figure 24.
 Note that for the E2E message, such as the RESERVE and the RESPONSE
 message, a single "hop" refers to the communication between the QNE
 Ingress and the QNE Egress since QNE Interior nodes do not
 participate in the exchange.

Bader, et al. Experimental [Page 90] RFC 5977 RMD-QOSM October 2010

        QNE             QNE             QNE            QNE
      Ingress         Interior        Interior        Egress
  NTLP stateful  NTLP stateless  NTLP stateless  NTLP stateful
         |               |               |              |
         | RESERVE (1)   |               |              |
         +--------------------------------------------->|
         | RESERVE' (2)  |               |              |
         +-------------->|               |              |
         |               | RESERVE'      |              |
         |               +-------------->|              |
         |               |               | RESERVE'     |
         |               |               +------------->|
         |               |               | RESPONSE' (2)|
         |<---------------------------------------------+
         |               |               | RESPONSE (1) |
         |<---------------------------------------------+
                Figure 24: RMD message exchange
 Authorizing quality-of-service reservations is accomplished using the
 Authentication, Authorization, and Accounting (AAA) framework and the
 functionality is inherited from the underlying NSIS QoS NSLP, see
 [RFC5974], and not described again in this document.  As a technical
 solution mechanism, the Diameter QoS application [RFC5866] may be
 used.  The end-to-end reservation request arriving at the Ingress
 node will trigger the authorization procedure with the backend AAA
 infrastructure.  The end-to-end reservation is typically triggered by
 a human interaction with a software application, such as a voice-
 over-IP client when making a call.  When authorization is successful
 then no further user initiated QoS authorization check is expected to
 be performed within the RMD domain for the intra-domain reservation.

5.2. Security Threats

 In the RMD-QOSM, the Ingress node constructs both end-to-end and
 intra-domain signaling messages based on the end-to-end message
 initiated by the sender end node.
 The Interior nodes within the RMD network ignore the end-to-end
 signaling message, but they process, modify, and forward the intra-
 domain signaling messages towards the Egress node.  In the meantime,
 resource reservation states are installed, modified, or deleted at
 each Interior node along the data path according to the content of
 each intra-domain signaling message.  The Edge nodes of an RMD
 network are critical components that require strong security
 protection.

Bader, et al. Experimental [Page 91] RFC 5977 RMD-QOSM October 2010

 Therefore, they act as security gateways for incoming and outgoing
 signaling messages.  Moreover, a certain degree of trust has to be
 placed into Interior nodes within the RMD-QOSM network, such that
 these nodes can perform signaling message processing and take the
 necessary actions.
 With the RMD-QOSM, we assume that the Ingress and the Egress nodes
 are not controlled by an adversary and the communication between the
 Ingress and the Egress nodes is secured using standard GIST security,
 (see Section 6 of [RFC5971]) mechanisms and experiences integrity,
 replay, and confidentiality protection.
 Note that this only affects messages directly addressed by these two
 nodes and not any other message that needs to be processed by
 intermediaries.  The <SESSION-ID> object of the end-to-end
 communication is visible, via GIST, to the Interior nodes.  In order
 to define the security threats that are associated with the RMD-QOSM,
 we consider that an adversary that may be located inside the RMD
 domain and could drop, delay, duplicate, inject, or modify signaling
 packets.
 Depending on the location of the adversary, we speak about an on-path
 adversary or an off-path adversary, see also RFC 4081 [RFC4081].

5.2.1. On-Path Adversary

 The on-path adversary is a node, which supports RMD-QOSM and is able
 to observe RMD-QOSM signaling message exchanges.
 1) Dropping signaling messages
 An adversary could drop any signaling messages after receiving them.
 This will cause a failure of reservation request for new sessions or
 deletion of resource units (bandwidth) for ongoing sessions due to
 states timeout.
 It may trigger the Ingress node to retransmit the lost signaling
 messages.  In this scenario, the adversary drops selected signaling
 messages, for example, intra-domain reserve messages.  In the RMD-
 QOSM, the retransmission mechanism can be provided at the Ingress
 node to make sure that signaling messages can reach the Egress node.
 However, the retransmissions triggered by the adversary dropping
 messages may cause certain problems.  Therefore, disabling the use of
 retransmissions in the RMD-QOSM-aware network is recommended, see
 also Section 4.6.1.1.1.

Bader, et al. Experimental [Page 92] RFC 5977 RMD-QOSM October 2010

 2) Delaying Signaling Messages
 Any signaling message could be delayed by an adversary.  For example,
 if RESERVE' messages are delayed over the duration of the refresh
 period, then the resource units (bandwidth) reserved along the nodes
 for corresponding sessions will be removed.  In this situation, the
 Ingress node does not receive the RESPONSE within a certain period,
 and considers that the signaling message has failed, which may cause
 a retransmission of the "failed" message.  The Egress node may
 distinguish between the two messages, i.e., the delayed message and
 the retransmitted message, and it could get a proper response.
 However, Interior nodes suffer from this retransmission and they may
 reserve twice the resource units (bandwidth) requested by the Ingress
 node.
 3) Replaying Signaling Messages
 An adversary may want to replay signaling messages.  It first stores
 the received messages and decides when to replay these messages and
 at what rate (packets per second).
 When the RESERVE' message carried an <RII> object, the Egress will
 reply with a RESPONSE' message towards the Ingress node.  The Ingress
 node can then detect replays by comparing the value of <RII> in the
 RESPONSE' messages with the stored value.
 4) Injecting Signaling Messages
 Similar to the replay-attack scenario, the adversary may store a part
 of the information carried by signaling messages, for example, the
 <RSN> object.  When the adversary injects signaling messages, it puts
 the stored information together with its own generated parameters
 (RMD-QSPEC <TMOD-1> parameter, <RII>, etc.) into the injected
 messages and then sends them out.  Interior nodes will process these
 messages by default, reserve the requested resource units (bandwidth)
 and pass them to downstream nodes.
 It may happen that the resource units (bandwidth) on the Interior
 nodes are exhausted if these injected messages consume too much
 bandwidth.
 5) Modifying Signaling Messages
 On-path adversaries are capable of modifying any part of the
 signaling message.  For example, the adversary can modify the <M>,
 <S>, and <O> parameters of the RMD-QSPEC messages.  The Egress node
 will then use the SESSION-ID and subsequently the <BOUND-SESSION-ID>

Bader, et al. Experimental [Page 93] RFC 5977 RMD-QOSM October 2010

 objects to refer to that flow to be terminated or set to lower
 priority.  It is also possible for the adversary to modify the RMD-
 QSPEC <TMOD-1> parameter and/or <PHB Class> parameter, which could
 cause a modification of an amount of the requested resource units
 (bandwidth) changes.

5.2.2. Off-Path Adversary

 In this case, the adversary is not located on-path and it does not
 participate in the exchange of RMD-QOSM signaling messages, and
 therefore is unable to eavesdrop signaling messages.  Hence, the
 adversary does not know valid <RII>s, <RSN>s, and <SESSION-ID>s.
 Hence, the adversary has to generate new parameters and constructs
 new signaling messages.  Since Interior nodes operate in reduced-
 state mode, injected signaling messages are treated as new once,
 which causes Interior nodes to allocate additional reservation state.

5.3. Security Requirements

 The following security requirements are set as goals for the intra-
 domain communication, namely:
  • Nodes, which are never supposed to participate in the NSIS

signaling exchange, must not interfere with QNE Interior nodes.

    Off-path nodes (off-path with regard to the path taken by a
    particular signaling message exchange) must not be able to
    interfere with other on-path signaling nodes.
  • The actions allowed by a QNE Interior node should be minimal

(i.e., only those specified by the RMD-QOSM). For example, only

    the QNE Ingress and the QNE Egress nodes are allowed to initiate
    certain signaling messages.  QNE Interior nodes are, for example,
    allowed to modify certain signaling message payloads.
 Note that the term "interfere" refers to all sorts of security
 threats, such as denial-of-service, spoofing, replay, signaling
 message injection, etc.

5.4. Security Mechanisms

 An important security mechanism that was built into RMD-QOSM was the
 ability to tie the end-to-end RESERVE and the RESERVE' messages
 together using the BOUND-SESSION-ID and to allow the Ingress node to
 match the RESERVE' with the RESPONSE' by using the <RII>.  These
 mechanisms enable the Edge nodes to detect unexpected signaling
 messages.

Bader, et al. Experimental [Page 94] RFC 5977 RMD-QOSM October 2010

 We assume that the RESERVE/RESPONSE is sent with hop-by-hop channel
 security provided by GIST and protected between the QNE Ingress and
 the QNE Egress.  GIST security mechanisms MUST be used to offer
 authentication, integrity, and replay protection.  Furthermore,
 encryption MUST be used to prevent an adversary located along the
 path of the RESERVE message from learning information about the
 session that can later be used to inject a RESERVE' message.
 The following messages need to be mapped to each other to make sure
 that the occurrence of one message is not without the other:
 a) the RESERVE and the RESERVE' relate to each other at the QNE
    Egress; and
 b) the RESPONSE and the RESERVE relate to each other at the QNE
    Ingress; and
 c) the RESERVE' and the RESPONSE' relate to each other.  The <RII> is
    carried in the RESERVE' message and the RESPONSE' message that is
    generated by the QNE Egress node contains the same <RII> as the
    RESERVE'.  The <RII> can be used by the QNE Ingress to match the
    RESERVE' with the RESPONSE'.  The QNE Egress is able to determine
    whether the RESERVE' was created by the QNE Ingress node since the
    intra-domain session, which sent the RESERVE', is bound to an end-
    to-end session via the <BOUND-SESSION-ID> value included in the
    intra-domain QoS-NSLP operational state maintained at the QNE
    Egress.
 The RESERVE and the RESERVE' message are tied together using the
 BOUND-SESSION-ID(s) maintained by the intra-domain and end-to-end
 QoS-NSLP operational states maintained at the QNE Edges (see Sections
 4.3.1, 4.3.2, and 4.3.3).  Hence, there cannot be a RESERVE' without
 a corresponding RESERVE.  The SESSION-ID can fulfill this purpose
 quite well if the aim is to provide protection against off-path
 adversaries that do not see the SESSION-ID carried in the RESERVE and
 the RESERVE' messages.
 If, however, the path changes (due to rerouting or due to mobility),
 then an adversary could inject RESERVE' messages (with a previously
 seen SESSION-ID) and could potentially cause harm.
 An off-path adversary can, of course, create RESERVE' messages that
 cause intermediate nodes to create some state (and cause other
 actions) but the message would finally hit the QNE Egress node.  The
 QNE Egress node would then be able to determine that there is
 something going wrong and generate an error message.

Bader, et al. Experimental [Page 95] RFC 5977 RMD-QOSM October 2010

 The severe congestion handling can be triggered by intermediate nodes
 (unlike other messages).  In many cases, however, intermediate nodes
 experiencing congestion use refresh messages modify the <S> and <O>
 parameters of the message.  These messages are still initiated by the
 QNE Ingress node and carry the SESSION-ID.  The QNE Egress node will
 use the SESSION-ID and subsequently the BOUND-SESSION-ID, maintained
 by the intra-domain QoS-NSLP operational state, to refer to a flow
 that might be terminated.  The aspect of intermediate nodes
 initiating messages for severe congestion handling is for further
 study.
 During the refresh procedure, a RESERVE' creates a RESPONSE', see
 Figure 25.  The <RII> is carried in the RESERVE' message and the
 RESPONSE' message that is generated by the QNE Egress node contains
 the same <RII> as the RESERVE'.
 The <RII> can be used by the QNE Ingress to match the RESERVE' with
 the RESPONSE'.
 A further aspect is marking of data traffic.  Data packets can be
 modified by an intermediary without any relationship to a signaling
 session (and a SESSION-ID).  The problem appears if an off-path
 adversary injects spoofed data packets.
   QNE Ingress    QNE Interior   QNE Interior    QNE Egress
 NTLP stateful  NTLP stateless  NTLP stateless  NTLP stateful
        |               |               |              |
        | REFRESH RESERVE'              |              |
        +-------------->| REFRESH RESERVE'             |
        | (+RII)        +-------------->| REFRESH RESERVE'
        |               | (+RII)        +------------->|
        |               |               | (+RII)       |
        |               |               |              |
        |               |               |     REFRESH  |
        |               |               |     RESPONSE'|
        |<---------------------------------------------+
        |               |               |     (+RII)   |
          Figure 25: RMD REFRESH message exchange
 The adversary thereby needs to spoof data packets that relate to the
 flow identifier of an existing end-to-end reservation that SHOULD be
 terminated.  Therefore, the question arises how an off-path adversary
 SHOULD create a data packet that matches an existing flow identifier
 (if a 5-tuple is used).  Hence, this might not turn out to be simple
 for an adversary unless we assume the previously mentioned
 mobility/rerouting case where the path through the network changes
 and the set of nodes that are along a path changes over time.

Bader, et al. Experimental [Page 96] RFC 5977 RMD-QOSM October 2010

6. IANA Considerations

 This section defines additional codepoint assignments in the QSPEC
 Parameter ID registry, in accordance with BCP 26 [RFC5226].

6.1. Assignment of QSPEC Parameter IDs

 This document specifies the following QSPEC containers in the QSPEC
 Parameter ID registry created in [RFC5975]:
 <PHR_Resource_Request> (Section 4.1.2 above, ID=17)
 <PHR_Release_Request> (Section 4.1.2 above, ID=18)
 <PHR_Refresh_Update> (Section 4.1.2 above, ID=19)
 <PDR_Reservation_Request> (Section 4.1.3 above, ID=20)
 <PDR_Refresh_Request> (Section 4.1.3 above, ID=21)
 <PDR_Release_Request> (Section 4.1.3 above, ID=22)
 <PDR_Reservation_Report> (Section 4.1.3 above, ID=23)
 <PDR_Refresh_Report> (Section 4.1.3 above, ID=24)
 <PDR_Release_Report> (Section 4.1.3 above, ID=25)
 <PDR_Congestion_Report> (Section 4.1.3 above, ID=26)

7. Acknowledgments

 The authors express their acknowledgement to people who have worked
 on the RMD concept: Z. Turanyi, R. Szabo, G. Pongracz, A. Marquetant,
 O. Pop, V. Rexhepi, G. Heijenk, D. Partain, M. Jacobsson, S.
 Oosthoek, P. Wallentin, P. Goering, A. Stienstra, M. de Kogel, M.
 Zoumaro-Djayoon, M. Swanink, R. Klaver G. Stokkink, J. W. van
 Houwelingen, D. Dimitrova, T. Sealy, H. Chang, and J. de Waal.

8. References

8.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2983]  Black, D., "Differentiated Services and Tunnels", RFC
            2983, October 2000.

Bader, et al. Experimental [Page 97] RFC 5977 RMD-QOSM October 2010

 [RFC5971]  Schulzrinne, H. and R. Hancock, "GIST: General Internet
            Signaling Transport", RFC 5971, October 2010.
 [RFC5974]  Manner, J., Karagiannis, G., and A. McDonald, "NSIS
            Signaling Layer Protocol (NSLP) for Quality-of-Service
            Signaling", RFC 5974, October 2010.
 [RFC5975]  Ash, G., Bader, A., Kappler C., and D. Oran, "QSPEC
            Template for the Quality-of-Service NSIS Signaling Layer
            Protocol (NSLP)", RFC 5975, October 2010.

8.2. Informative References

 [AdCa03]   Adler, M., Cai, J.-Y., Shapiro, J. K., Towsley, D.,
            "Estimation of congestion price using probabilistic packet
            marking", Proc. IEEE INFOCOM, pp. 2068-2078, 2003.
 [AnHa06]   Lachlan L. H. Andrew and Stephen V. Hanly, "The Estimation
            Error of Adaptive Deterministic Packet Marking", 44th
            Annual Allerton Conference on Communication, Control and
            Computing, 2006.
 [AtLi01]   Athuraliya, S., Li, V. H., Low, S. H., Yin, Q., "REM:
            active queue management", IEEE Network, vol. 15, pp.
            48-53, May/June 2001.
 [Chan07]   H. Chang, "Security support in RMD-QOSM", Masters thesis,
            University of Twente, 2007.
 [CsTa05]   Csaszar, A., Takacs, A., Szabo, R., Henk, T., "Resilient
            Reduced-State Resource Reservation", Journal of
            Communication and Networks, Vol. 7, No. 4, December 2005.
 [DiKa08]   Dimitrova, D., Karagiannis, G., de Boer, P.-T., "Severe
            congestion handling approaches in NSIS RMD domains with
            bi-directional reservations", Journal of Computer
            Communications, Elsevier, vol. 31, pp. 3153-3162, 2008.
 [JaSh97]   Jamin, S., Shenker, S., Danzig, P., "Comparison of
            Measurement-based Admission Control Algorithms for
            Controlled-Load Service", Proceedings IEEE Infocom '97,
            Kobe, Japan, April 1997.
 [GrTs03]   Grossglauser, M., Tse, D.N.C, "A Time-Scale Decomposition
            Approach to Measurement-Based Admission Control",
            IEEE/ACM Transactions on Networking, Vol. 11, No. 4,
            August 2003.

Bader, et al. Experimental [Page 98] RFC 5977 RMD-QOSM October 2010

 [Part94]   C. Partridge, Gigabit Networking, Addison Wesley
            Publishers (1994).
 [RFC1633]  Braden, R., Clark, D., and S. Shenker, "Integrated
            Services in the Internet Architecture: an Overview", RFC
            1633, June 1994.
 [RFC2215]  Shenker, S. and J. Wroclawski, "General Characterization
            Parameters for Integrated Service Network Elements", RFC
            2215, September 1997.
 [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
            and W. Weiss, "An Architecture for Differentiated
            Service", RFC 2475, December 1998.
 [RFC2638]  Nichols, K., Jacobson, V., and L. Zhang, "A Two-bit
            Differentiated Services Architecture for the Internet",
            RFC 2638, July 1999.
 [RFC2998]  Bernet, Y., Ford, P., Yavatkar, R., Baker, F., Zhang, L.,
            Speer, M., Braden, R., Davie, B., Wroclawski, J., and E.
            Felstaine, "A Framework for Integrated Services Operation
            over Diffserv Networks", RFC 2998, November 2000.
 [RFC3175]  Baker, F., Iturralde, C., Le Faucheur, F., and B. Davie,
            "Aggregation of RSVP for IPv4 and IPv6 Reservations", RFC
            3175, September 2001.
 [RFC3726]  Brunner, M., Ed., "Requirements for Signaling Protocols",
            RFC 3726, April 2004.
 [RFC4125]  Le Faucheur, F. and W. Lai, "Maximum Allocation Bandwidth
            Constraints Model for Diffserv-aware MPLS Traffic
            Engineering", RFC 4125, June 2005.
 [RFC4127]  Le Faucheur, F., Ed., "Russian Dolls Bandwidth Constraints
            Model for Diffserv-aware MPLS Traffic Engineering", RFC
            4127, June 2005.
 [RFC4081]  Tschofenig, H. and D. Kroeselberg, "Security Threats for
            Next Steps in Signaling (NSIS)", RFC 4081, June 2005.
 [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
            IANA Considerations Section in RFCs", BCP 26, RFC 5226,
            May 2008.

Bader, et al. Experimental [Page 99] RFC 5977 RMD-QOSM October 2010

 [RFC5866]  Sun, D., Ed., McCann, P., Tschofenig, H., Tsou, T., Doria,
            A., and G. Zorn, Ed., "Diameter Quality-of-Service
            Application", RFC 5866, May 2010.
 [RFC5978]  Manner, J., Bless, R., Loughney, J., and E. Davies, Ed.,
            "Using and Extending the NSIS Protocol Family", RFC 5978,
            October 2010.
 [RMD1]     Westberg, L., et al., "Resource Management in Diffserv
            (RMD): A Functionality and Performance Behavior Overview",
            IFIP PfHSN 2002.
 [RMD2]     G. Karagiannis, et al., "RMD - a lightweight application
            of NSIS" Networks 2004, Vienna, Austria.
 [RMD3]     Marquetant A., Pop O., Szabo R., Dinnyes G., Turanyi Z.,
            "Novel Enhancements to Load Control - A Soft-State,
            Lightweight Admission Control Protocol", Proc. of the 2nd
            Int. Workshop on Quality of Future Internet Services,
            Coimbra, Portugal, Sept 24-26, 2001, pp. 82-96.
 [RMD4]     A. Csaszar et al., "Severe congestion handling with
            resource management in diffserv on demand", Networking
            2002.
 [TaCh99]   P. P. Tang, T-Y Charles Tai, "Network Traffic
            Characterization Using Token Bucket Model", IEEE Infocom
            1999, The Conference on Computer Communications, no. 1,
            March 1999, pp. 51-62.
 [ThCo04]   Thommes, R. W., Coates, M. J., "Deterministic packet
            marking for congestion packet estimation" Proc. IEEE
            Infocom, 2004.

Bader, et al. Experimental [Page 100] RFC 5977 RMD-QOSM October 2010

Appendix A. Examples

A.1. Example of a Re-Marking Operation during Severe Congestion in the

    Interior Nodes
 This appendix describes an example of a re-marking operation during
 severe congestion in the Interior nodes.
 Per supported PHB, the Interior node can support the operation states
 depicted in Figure 26, when the per-flow congestion notification
 based on probing signaling scheme is used in combination with this
 severe congestion type.  Figure 27 depicts the same functionality
 when the per-flow congestion notification based on probing scheme is
 not used in combination with the severe congestion scheme.  The
 description given in this and the following appendices, focuses on
 the situation where: (1) the "notified DSCP" marking is used in
 congestion notification state, and (2) the "encoded DSCP" and
 "affected DSCP" markings are used in severe congestion state.  In
 this case, the "notified DSCP" marking is used during the congestion
 notification state to mark all packets passing through an Interior
 node that operates in the congestion notification state.  In this
 way, and in combination with probing, a flow-based ECMP solution can
 be provided for the congestion notification state.  The "encoded
 DSCP" marking is used to encode and signal the excess rate, measured
 at Interior nodes, to the Egress nodes.  The "affected DSCP" marking
 is used to mark all packets that are passing through a severe
 congested node and are not "encoded DSCP" marked.
 Another possible situation could be derived in which both congestion
 notification and severe congestion state use the "encoded DSCP"
 marking, without using the "notified DSCP" marking.  The "affected
 DSCP" marking is used to mark all packets that pass through an
 Interior node that is in severe congestion state and are not "encoded
 DSCP" marked.  In addition, the probe packet that is carried by an
 intra-domain RESERVE message and pass through Interior nodes SHOULD
 be "encoded DSCP" marked if the Interior node is in congestion
 notification or severe congestion states.  Otherwise, the probe
 packet will remain unmarked.  In this way, an ECMP solution can be
 provided for both congestion notification and severe congestion
 states.  The"encoded DSCP" packets signal an excess rate that is not
 only associated with Interior nodes that are in severe congestion
 state, but also with Interior nodes that are in congestion
 notification state.  The algorithm at the Interior node is similar to
 the algorithm described in the following appendix sections.  However,
 this method is not described in detail in this example.

Bader, et al. Experimental [Page 101] RFC 5977 RMD-QOSM October 2010

  1. ——————————————–

| event B |

        |                                             V
     ----------             -------------           ----------
    | Normal   |  event A  | Congestion  | event B | Severe   |
    |  state   |---------->| notification|-------->|congestion|
    |          |           |  state      |         |  state   |
     ----------             -------------           ----------
      ^  ^                       |                     |
      |  |      event C          |                     |
      |   -----------------------                      |
      |         event D                                |
       ------------------------------------------------
 Figure 26: States of operation, severe congestion combined with
            congestion notification based on probing
  1. ——— ————-

| Normal | event B | Severe |

    |  state   |-------------->| congestion  |
    |          |               |  state      |
     ----------                 -------------
         ^                           |
         |      event E              |
          ---------------------------
 Figure 27: States of operation, severe congestion without
            congestion notification based on probing
 The terms used in Figures 26 and 27 are:
 Normal state: represents the normal operation conditions of the node,
 i.e., no congestion.
 Severe congestion state: represents the state in which the Interior
 node is severely congested related to a certain PHB.  It is important
 to emphasize that one of the targets of the severe congestion state
 solution to change the severe congestion state behavior directly to
 the normal state.
 Congestion notification: state in which the load is relatively high,
 close to the level when congestion can occur.
 event A: this event occurs when the incoming PHB rate is higher than
 the "congestion notification detection" threshold and lower than the
 "severe congestion detection".  This threshold is used by the
 congestion notification based on probing scheme, see Sections 4.6.1.7
 and 4.6.2.6.

Bader, et al. Experimental [Page 102] RFC 5977 RMD-QOSM October 2010

 event B: this event occurs when the incoming PHB rate is higher than
 the "severe congestion detection" threshold.
 event C: this event occurs when the incoming PHB rate is lower than
 or equal to the "congestion notification detection" threshold.
 event D: this event occurs when the incoming PHB rate is lower than
 or equal to the "severe_congestion_restoration" threshold.  It is
 important to emphasize that this even supports one of the targets of
 the severe congestion state solution to change the severe congestion
 state behavior directly to the normal state.
 event E: this event occurs when the incoming PHB rate is lower than
 or equal to the "severe congestion restoration" threshold.
 Note that the "severe congestion detection", "severe congestion
 restoration" and admission thresholds SHOULD be higher than the
 "congestion notification detection" threshold, i.e., "severe
 congestion detection" > "congestion notification detection" and
 "severe congestion restoration" > "congestion notification
 detection".
 Furthermore, the "severe congestion detection" threshold SHOULD be
 higher than or equal to the admission threshold that is used by the
 reservation-based and NSIS measurement-based signaling schemes.
 "severe congestion detection" >= admission threshold.
 Moreover, the "severe congestion restoration" threshold SHOULD be
 lower than or equal to the "severe congestion detection" threshold
 that is used by the reservation-based and NSIS measurement-based
 signaling schemes, that is:
 "severe congestion restoration" <= "severe congestion detection"
 During severe congestion, the Interior node calculates, per traffic
 class (PHB), the incoming rate that is above the "severe congestion
 restoration" threshold, denoted as signaled_overload_rate, in the
 following way:
  • A severe congested Interior node SHOULD take into account that

packets might be dropped. Therefore, before queuing and

    eventually dropping packets, the Interior node SHOULD count the
    total number of unmarked and re-marked bytes received by the
    severe congested node, denote this number as total_received_bytes.
    Note that there are situations in which more than one Interior
    node in the same path become severely congested.  Therefore, any
    Interior node located behind a severely congested node MAY receive
    marked bytes.

Bader, et al. Experimental [Page 103] RFC 5977 RMD-QOSM October 2010

 When the "severe congestion detection" threshold per PHB is set equal
 to the maximum capacity allocated to one PHB used by the RMD-QOSM, it
 means that if the maximum capacity associated to a PHB is fully
 utilized and a packet belonging to this PHB arrives, then it is
 assumed that the Interior node will not forward this packet
 downstream.
 In other words, this packet will either be dropped or set to another
 PHB.  Furthermore, this also means that after the severe congestion
 situation is solved, then the ongoing flows will be able to send
 their associated packets up to a total rate equal to the maximum
 capacity associated with the PHB.  Therefore, when more than one
 Interior node located on the same path will be severely congested and
 when the Interior node receives "encoded DSCP" marked packets, it
 means that an Interior node located upstream is also severely
 congested.
 When the "severe congestion detection" threshold per PHB is set equal
 to the maximum capacity allocated to one PHB, then this Interior node
 MUST forward the "encoded DSCP" marked packets and it SHOULD NOT
 consider these packets during its local re-marking process.  In other
 words, the Egress should see the excess rates encoded by the
 different severely congested Interior nodes as independent, and
 therefore, these independent excess rates will be added.
 When the "severe congestion detection" threshold per PHB is not set
 equal to the maximum capacity allocated to one PHB, this means that
 after the severe congestion situation is solved, the ongoing flows
 will not be able to send their associated packets up to a total rate
 equal to the maximum capacity associated with the PHB, but only up to
 the "severe_congestion_threshold".  When more than one Interior node
 located on the same communication path is severely congested and when
 one of these Interior node receives "encoded_DSCP" marked packets,
 this Interior node SHOULD NOT mark unmarked, i.e., either "original
 DSCP" or "affected DSCP" or "notified DSCP" encoded packets, up to a
 rate equal to the difference between the maximum PHB capacity and the
 "severe congestion threshold", when the incoming "encoded DSCP"
 marked packets are already able to signal this difference.  In this
 case, the "severe congestion threshold" SHOULD be configured in all
 Interior nodes, which are located in the RMD domain, and equal to:
 "severe_congestion_threshold" =
    Maximum PHB capacity - threshold_offset_rate
 The threshold_offset_rate represents rate and SHOULD have the same
 value in all Interior nodes.

Bader, et al. Experimental [Page 104] RFC 5977 RMD-QOSM October 2010

  • before queuing and eventually dropping the packets, at the end of

each measurement interval of T seconds, calculate the current

    estimated overloaded rate, say measured_overload_rate, by using
    the following equation:
 measured_overload_rate =
 =((total_received_bytes)/T)-severe_congestion_restoration)
 To provide a reliable estimation of the encoded information, several
 techniques can be used; see [AtLi01], [AdCa03], [ThCo04], and
 [AnHa06].  Note that since marking is done in Interior nodes, the
 decisions are made at Egress nodes, and the termination of flows is
 performed by Ingress nodes, there is a significant delay until the
 overload information is learned by the Ingress nodes (see Section 6
 of [CsTa05]).  The delay consists of the trip time of data packets
 from the severely congested Interior node to the Egress, the
 measurement interval, i.e., T, and the trip time of the notification
 signaling messages from Egress to Ingress.  Moreover, until the
 overload decreases at the severely congested Interior node, an
 additional trip time from the Ingress node to the severely congested
 Interior node MUST expire.  This is because immediately before
 receiving the congestion notification, the Ingress MAY have sent out
 packets in the flows that were selected for termination.  That is, a
 terminated flow MAY contribute to congestion for a time longer that
 is taken from the Ingress to the Interior node.  Without considering
 the above, Interior nodes would continue marking the packets until
 the measured utilization falls below the severe congestion
 restoration threshold.  In this way, in the end, more flows will be
 terminated than necessary, i.e., an overreaction takes place.
 [CsTa05] provides a solution to this problem, where the Interior
 nodes use a sliding window memory to keep track of the signaling
 overload in a couple of previous measurement intervals.  At the end
 of a measurement interval, T, before encoding and signaling the
 overloaded rate as "encoded DSCP" packets, the actual overload is
 decreased with the sum of already signaled overload stored in the
 sliding window memory, since that overload is already being handled
 in the severe congestion handling control loop.  The sliding window
 memory consists of an integer number of cells, i.e., n = maximum
 number of cells.  Guidelines for configuring the sliding window
 parameters are given in [CsTa05].
 At the end of each measurement interval, the newest calculated
 overload is pushed into the memory, and the oldest cell is dropped.
 If Mi is the overload_rate stored in ith memory cell (i = [1..n]),
 then at the end of every measurement interval, the overload rate that
 is signaled to the Egress node, i.e., signaled_overload_rate is
 calculated as follows:

Bader, et al. Experimental [Page 105] RFC 5977 RMD-QOSM October 2010

 Sum_Mi =0
 For i =1 to n
 {
 Sum_Mi = Sum_Mi + Mi
 }
 signaled_overload_rate = measured_overload_rate - Sum_Mi,
 where Sum_Mi is calculated as above.
 Next, the sliding memory is updated as follows:
     for i = 1..(n-1): Mi <- Mi+1
     Mn <- signaled_overload_rate
 The bytes that have to be re-marked to satisfy the signaled overload
 rate: signaled_remarked_bytes, are calculated using the following
 pseudocode:
 IF severe_congestion_threshold <> Maximum PHB capacity
 THEN
  {
   IF (incoming_encoded-DSCP_rate <> 0) AND
      (incoming_encoded-DSCP_rate =< termination_offset_rate)
   THEN
      { signaled_remarked_bytes =
       = ((signaled_overload_rate - incoming_encoded-DSCP_rate)*T)/N
      }
   ELSE IF (incoming_encoded-DSCP_rate > termination_offset_rate)
   THEN signaled_remarked_bytes =
       = ((signaled_overload_rate - termination_offset_rate)*T)/N
   ELSE IF (incoming_encoded-DSCP_rate =0)
   THEN signaled_remarked_bytes =
       = signaled_overload_rate*T/N
   }
  ELSE signaled_remarked_bytes =  signaled_overload_rate *T/N
  Where the incoming "encoded DSCP" rate is calculated as follows:
  incoming_encoded-DSCP_rate =
   = (received number of "encoded_DSCP" during T) * N)/T;
 The signal_remarked_bytes also represents the number of the outgoing
 packets (after the dropping stage) that MUST be re-marked, during
 each measurement interval T, by a node when operates in severe
 congestion mode.

Bader, et al. Experimental [Page 106] RFC 5977 RMD-QOSM October 2010

 Note that, in order to process an overload situation higher than 100%
 of the maintained severe congestion threshold, all the nodes within
 the domain MUST be configured and maintain a scaling parameter, e.g.,
 N used in the above equation, which in combination with the marked
 bytes, e.g., signaled_remarked_bytes, such a high overload situation
 can be calculated and represented.  N can be equal to or higher than
 1.
 Note that when incoming re-marked bytes are dropped, the operation of
 the severe congestion algorithm MAY be affected, e.g., the algorithm
 MAY become, in certain situations, slower.  An implementation of the
 algorithm MAY assure as much as possible that the incoming marked
 bytes are not dropped.  This could for example be accomplished by
 using different dropping rate thresholds for marked and unmarked
 bytes.
 Note that when the "affected DSCP" marking is used by a node that is
 congested due to a severe congestion situation, then all the outgoing
 packets that are not marked (i.e., by using the "encoded DSCP") have
 to be re-marked using the "affected DSCP" marking.
 The "encoded DSCP" and the "affected DSCP" marked packets (when
 applied in the whole RMD domain) are propagated to the QNE Edge
 nodes.
 Furthermore, note that when the congestion notification based on
 probing is used in combination with severe congestion, then in
 addition to the possible "encoded DSCP" and "affected DSCP", another
 DSCP for the re-marking of the same PHB is used (see Section
 4.6.1.7).  This additional DSCP is denoted in this document as
 "notified DSCP".  When an Interior node operates in the severe
 congested state (see Figure 27), and receives "notified DSCP"
 packets, these packets are considered to be unmarked packets (but not
 "affected DSCP" packets).  This means that during severe congestion,
 also the "notified DSCP" packets can be re-marked and encoded as
 either "encoded DSCP" or "affected DSCP" packets.

A.2. Example of a Detailed Severe Congestion Operation in the Egress

    Nodes
 This appendix describes an example of a detailed severe congestion
 operation in the Egress nodes.
 The states of operation in Egress nodes are similar to the ones
 described in Appendix A.1.  The definition of the events, see below,
 is however different than the definition of the events given in
 Figures 26 and 27:

Bader, et al. Experimental [Page 107] RFC 5977 RMD-QOSM October 2010

  • event A: when the Egress receives a predefined rate of "notified

DSCP" marked bytes/packets, event A is activated (see Sections

    4.6.1.7 and A.4).  The predefined rate of "notified DSCP" marked
    bytes is denoted as the congestion notification detection
    threshold.  Note this congestion notification detection threshold
    can also be zero, meaning that the event A is activated when the
    Egress node, during an interval T, receives at least one "notified
    DSCP" packet.
  • event B: this event occurs when the Egress receives packets marked

as either "encoded DSCP" or "affected DSCP" (when "affected DSCP"

    is applied in the whole RMD domain).
  • event C: this event occurs when the rate of incoming "notified

DSCP" packets decreases below the congestion notification

    detection threshold.  In the situation that the congestion
    notification detection threshold is zero, this will mean that
    event C is activated when the Egress node, during an interval T,
    does not receive any "notified DSCP" marked packets.
  • event D: this event occurs when the Egress, during an interval T,

does not receive packets marked as either "encoded DSCP" or

    "affected DSCP" (when "affected DSCP" is applied in the whole RMD
    domain).  Note that when "notified DSCP" is applied in the whole
    RMD domain for the support of congestion notification, this event
    could cause the following change in operation state.
    When the Egress, during an interval T, does not receive (1)
    packets marked as either "encoded DSCP" or "affected DSCP" (when
    "affected DSCP" is applied in the whole RMD domain) and (2) it
    does NOT receive "notified DSCP" marked packets, the change in the
    operation state occurs from the severe congestion state to normal
    state.
    When the Egress, during an interval T, does not receive (1)
    packets marked as either "encoded DSCP" or "affected DSCP" (when
    "affected DSCP" is applied in the whole RMD domain) and (2) it
    does receive "notified DSCP" marked packets, the change in the
    operation state occurs from the severe congestion state to the
    congestion notification state.
  • event E: this event occurs when the Egress, during an interval T,

does not receive packets marked as either "encoded DSCP" or

    "affected DSCP" (when "affected DSCP" is applied in the whole RMD
    domain).

Bader, et al. Experimental [Page 108] RFC 5977 RMD-QOSM October 2010

 An example of the algorithm for calculation of the number of flows
 associated with each priority class that have to be terminated is
 explained by the pseudocode below.
 The Edge nodes are able to support severe congestion handling by: (1)
 identifying which flows were affected by the severe congestion and
 (2) selecting and terminating some of these flows such that the
 quality of service of the remaining flows is recovered.
 The "encoded DSCP" and the "affected DSCP" marked packets (when
 applied in the whole RMD domain) are received by the QNE Edge node.
 The QNE Edge nodes keep per-flow state and therefore they can
 translate the calculated bandwidth to be terminated, to number of
 flows.  The QNE Egress node records the excess rate and the identity
 of all the flows, arriving at the QNE Egress node, with "encoded
 DSCP" and with "affected DSCP" (when applied in the whole RMD
 domain); only these flows, which are the ones passing through the
 severely congested Interior node(s), are candidates for termination.
 The excess rate is calculated by measuring the rate of all the
 "encoded DSCP" data packets that arrive at the QNE Egress node.  The
 measured excess rate is converted by the Egress node, by multiplying
 it by the factor N, which was used by the QNE Interior node(s) to
 encode the overload level.
 When different priority flows are supported, all the low priority
 flows that arrived at the Egress node are terminated first.  Next,
 all the medium priority flows are stopped and finally, if necessary,
 even high priority flows are chosen.  Within a priority class both
 "encoded DSCP" and "affected DSCP" are considered before the
 mechanism moves to higher priority class.  Finally, for each flow
 that has to be terminated the Egress node, sends a NOTIFY message to
 the Ingress node, which stops the flow.
 Below, this algorithm is described in detail.
 First, when the Egress operates in the severe congestion state, the
 total amount of re-marked bandwidth associated with the PHB traffic
 class, say total_congested_bandwidth, is calculated.  Note that when
 the node maintains information about each Ingress/Egress pair
 aggregate, then the total_congested_bandwidth MUST be calculated per
 Ingress/Egress pair reservation aggregate.  This bandwidth represents
 the severely congested bandwidth that SHOULD be terminated.  The
 total_congested_bandwidth can be calculated as follows:
 total_congested_bandwidth = N*input_remarked_bytes/T

Bader, et al. Experimental [Page 109] RFC 5977 RMD-QOSM October 2010

 Where, input_remarked_bytes represents the number of "encoded DSCP"
 marked bytes that arrive at the Egress, during one measurement
 interval T, N is defined as in Sections 4.6.1.6.2.1 and A.1.  The
 term denoted as terminated_bandwidth is a temporal variable
 representing the total bandwidth that has to be terminated, belonging
 to the same PHB traffic class.  The terminate_flow_bandwidth
 (priority_class) is the total bandwidth associated with flows of
 priority class equal to priority_class.  The parameter priority_class
 is an integer fulfilling:
 0 =< priority_class =< Maximum_priority.
 The QNE Egress node records the identity of the QNE Ingress node that
 forwarded each flow, the total_congested_bandwidth and the identity
 of all the flows, arriving at the QNE Egress node, with "encoded
 DSCP" and "affected DSCP" (when applied in whole RMD domain).  This
 ensures that only these flows, which are the ones passing through the
 severely overloaded QNE Interior node(s), are candidates for
 termination.  The selection of the flows to be terminated is
 described in the pseudocode that is given below, which is realized by
 the function denoted below as calculate_terminate_flows().
 The calculate_terminate_flows() function uses the
 <terminate_bandwidth_class> value and translates this bandwidth value
 to number of flows that have to be terminated.  Only the "encoded
 DSCP" flows and "affected DSCP" (when applied in whole RMD domain)
 flows, which are the ones passing through the severely overloaded
 Interior node(s), are candidates for termination.
 After the flows to be terminated are selected, the
 <sum_bandwidth_terminate(priority_class)> value is calculated that is
 the sum of the bandwidth associated with the flows, belonging to a
 certain priority class, which will certainly be terminated.
 The constraint of finding the total number of flows that have to be
 terminated is that sum_bandwidth_terminate(priority_class), SHOULD be
 smaller or approximately equal to the variable
 terminate_bandwidth(priority_class).

Bader, et al. Experimental [Page 110] RFC 5977 RMD-QOSM October 2010

 terminated_bandwidth = 0;
 priority_class = 0;
 while terminated_bandwidth < total_congested_bandwidth
  {
   terminate_bandwidth(priority_class) =
   = total_congested_bandwidth - terminated_bandwidth
   calculate_terminate_flows(priority_class);
   terminated_bandwidth =
   = sum_bandwidth_terminate(priority_class) + terminated_bandwidth;
   priority_class = priority_class + 1;
  }
 If the Egress node maintains Ingress/Egress pair reservation
 aggregates, then the above algorithm is performed for each
 Ingress/Egress pair reservation aggregate.
 Finally, for each flow that has to be terminated, the QNE Egress node
 sends a NOTIFY message to the QNE Ingress node to terminate the flow.

A.3. Example of a Detailed Re-Marking Admission Control (Congestion

    Notification) Operation in Interior Nodes
 This appendix describes an example of a detailed re-marking admission
 control (congestion notification) operation in Interior nodes.  The
 predefined congestion notification threshold, see Appendix A.1, is
 set according to, and usually less than, an engineered bandwidth
 limitation, i.e., admission threshold, e.g., based on a Service Level
 Agreement or a capacity limitation of specific links.
 The difference between the congestion notification threshold and the
 engineered bandwidth limitation, i.e., admission threshold, provides
 an interval where the signaling information on resource limitation is
 already sent by a node but the actual resource limitation is not
 reached.  This is due to the fact that data packets associated with
 an admitted session have not yet arrived, which allows the admission
 control process available at the Egress to interpret the signaling
 information and reject new calls before reaching congestion.
 Note that in the situation when the data rate is higher than the
 preconfigured congestion notification rate, data packets are also re-
 marked (see Section 4.6.1.6.2.1).  To distinguish between congestion
 notification and severe congestion, two methods MAY be used (see
 Appendix A.1):
  • using different <DSCP> values (re-marked <DSCP> values). The re-

marked DSCP that is used for this purpose is denoted as "notified

    DSCP" in this document.  When this method is used and when the
    Interior node is in "congestion notification" state, see Appendix

Bader, et al. Experimental [Page 111] RFC 5977 RMD-QOSM October 2010

    A.1, then the node SHOULD re-mark all the unmarked bytes passing
    through the node using the "notified DSCP".  Note that this method
    can only be applied if all nodes in the RMD domain use the
    "notified" DSCP marking.  In this way, probe packets that will
    pass through the Interior node that operates in congestion
    notification state are also encoded using the "notified DSCP"
    marking.
  • Using the "encoded DSCP" marking for congestion notification and

severe congestion. This method is not described in detail in this

    example appendix.

A.4. Example of a Detailed Admission Control (Congestion Notification)

    Operation in Egress Nodes
 This appendix describes an example of a detailed admission control
 (congestion notification) operation in Egress nodes.
 The admission control congestion notification procedure can be
 applied only if the Egress maintains the Ingress/Egress pair
 aggregate.  When the operation state of the Ingress/Egress pair
 aggregate is the "congestion notification", see Appendix A.2, then
 the implementation of the algorithm depends on how the congestion
 notification situation is notified to the Egress.  As mentioned in
 Appendix A.3, two methods are used:
  • using the "notified DSCP". During a measurement interval T, the

Egress counts the number of "notified DSCP" marked bytes that

    belong to the same PHB and are associated with the same
    Ingress/Egress pair aggregate, say input_notified_bytes.  We
    denote the rate as incoming_notified_rate.
  • using the "encoded DSCP". In this case, during a measurement

interval T, the Egress measures the input_notified_bytes by

    counting the "encoded DSCP" bytes.
 Below only the detail description of the first method is given.
 The incoming congestion_rate can be then calculated as follows:
    incoming_congestion_rate = input_notified_bytes/T
 If the incoming_congestion_rate is higher than a preconfigured
 congestion notification threshold, then the communication path
 between Ingress and Egress is considered to be congested.  Note that
 the pre-congestion notification threshold can be set to "0".  In this

Bader, et al. Experimental [Page 112] RFC 5977 RMD-QOSM October 2010

 case, the Egress node will operate in congestion notification state
 at the moment that it receives at least one "notified DSCP" encoded
 packet.
 When the Egress node operates in "congestion notification" state and
 if the end-to-end RESERVE (probe) arrives at the Egress, then this
 request SHOULD be rejected.  Note that this happens only when the
 probe packet is either "notified DSCP" or "encoded DSCP" marked.  In
 this way, it is ensured that the end-to-end RESERVE (probe) packet
 passed through the node that is congested.  This feature is very
 useful when ECMP-based routing is used to detect only flows that are
 passing through the congested router.
 If such an Ingress/Egress pair aggregated state is not available when
 the (probe) RESERVE message arrives at the Egress, then this request
 is accepted if the DSCP of the packet carrying the RESERVE message is
 unmarked.  Otherwise (if the packet is either "notified DSCP" or
 "encoded DSCP" marked), it is rejected.

A.5. Example of Selecting Bidirectional Flows for Termination during

    Severe Congestion
 This appendix describes an example of selecting bidirectional flows
 for termination during severe congestion.
 When a severe congestion occurs, e.g., in the forward path, and when
 the algorithm terminates flows to solve the severe congestion in the
 forward path, then the reserved bandwidth associated with the
 terminated bidirectional flows is also released.  Therefore, a
 careful selection of the flows that have to be terminated SHOULD take
 place.  A possible method of selecting the flows belonging to the
 same priority type passing through the severe congestion point on a
 unidirectional path can be the following:
  • the Egress node SHOULD select, if possible, first unidirectional

flows instead of bidirectional flows.

  • the Egress node SHOULD select, if possible, bidirectional flows

that reserved a relatively small amount of resources on the path

    reversed to the path of congestion.

A.6. Example of a Severe Congestion Solution for Bidirectional Flows

    Congested Simultaneously on Forward and Reverse Paths
 This appendix describes an example of a severe congestion solution
 for bidirectional flows congested simultaneously on forward and
 reverse paths.

Bader, et al. Experimental [Page 113] RFC 5977 RMD-QOSM October 2010

 This scenario describes a solution using the combination of the
 severe congestion solutions described in Section 4.6.2.5.2.  It is
 considered that the severe congestion occurs simultaneously in
 forward and reverse directions, which MAY affect the same
 bidirectional flows.
 When the QNE Edges maintain per-flow intra-domain QoS-NSLP
 operational states, the steps can be the following, see Figure A.3.
 Consider that the Egress node selects a number of bidirectional flows
 to be terminated.  In this case, the Egress will send, for each
 bidirectional flow, a NOTIFY message to Ingress.  If the Ingress
 receives these NOTIFY messages and its operational state (associated
 with reverse path) is in the severe congestion state (see Figures 26
 and 27), then the Ingress operates in the following way:
  • For each NOTIFY message, the Ingress SHOULD identify the

bidirectional flows that have to be terminated.

  • The Ingress then calculates the total bandwidth that SHOULD be

released in the reverse direction (thus not in forward direction)

    if the bidirectional flows will be terminated (preempted), say
    "notify_reverse_bandwidth".  This bandwidth can be calculated by
    the sum of the bandwidth values associated with all the end-to-end
    sessions that received a (severe congestion) NOTIFY message.
  • Furthermore, using the received marked packets (from the reverse

path) the Ingress will calculate, using the algorithm used by an

    Egress and described in Appendix A.2, the total bandwidth that has
    to be terminated in order to solve the congestion in the reverse
    path direction, say "marked_reverse_bandwidth".
  • The Ingress then calculates the bandwidth of the additional flows

that have to be terminated, say "additional_reverse_bandwidth", in

    order to solve the severe congestion in reverse direction, by
    taking into account:
  • * the bandwidth in the reverse direction of the bidirectional flows

that were appointed by the Egress (the ones that received a NOTIFY

    message) to be preempted, i.e., "notify_reverse_bandwidth".
  • * the total amount of bandwidth in the reverse direction that has

been calculated by using the received marked packets, i.e.,

    "marked_reverse_bandwidth".

Bader, et al. Experimental [Page 114] RFC 5977 RMD-QOSM October 2010

QNE(Ingress) NE (int.) NE (int.) NE (int.) QNE(Egress) NTLP stateful NTLP stateful data| user | | | | —>| data | #unmarked bytes| | |

  |--------------->S #marked bytes  |           |               |
  |                S--------------------------->|               |
  |                |                |           |-------------->|data
  |                |                |           |               |--->
  |                |                |           |              Term.?
  |            NOTIFY               |           |               |Yes
  |<------------------------------------------------------------|
  |                |                |           |               |data
  |                |                |  user     |               |<---
  |   user data    |                |  data     |<--------------|
  | (#marked bytes)|                S<----------|               |
  |<--------------------------------S           |               |
  | (#unmarked bytes)               S           |               |

Term|←——————————-S | | Flow? | S | | YES |RESERVE(RMD-QSPEC): S | |

  |"forward - T tear"               s           |               |
  |--------------->|  RESERVE(RMD-QSPEC):       |               |
  |                |  "forward - T tear"        |               |
  |                |--------------------------->|               |
  |                |                S           |-------------->|
  |                |                S         RESERVE(RMD-QSPEC):
  |                |                S       "reverse - T tear"  |
  |      RESERVE(RMD-QSPEC)         S           |<--------------|
  |      "reverse - T tear"         S<----------|               |
  |<--------------------------------S           |               |
Figure 28: Intra-domain RMD severe congestion handling for
           bidirectional reservation (congestion in both forward
           and reverse direction)
 This additional bandwidth can be calculated using the following
 algorithm:
 IF ("marked_reverse_bandwidth" > "notify_reverse_bandwidth") THEN
 "additional_reverse_bandwidth" =
  = "marked_reverse_bandwidth"- "notify_reverse_bandwidth";
 ELSE
 "additional_reverse_bandwidth" = 0
  • Ingress terminates the flows that experienced a severe congestion

in the forward path and received a (severe congestion) NOTIFY

    message.

Bader, et al. Experimental [Page 115] RFC 5977 RMD-QOSM October 2010

  • If possible, the Ingress SHOULD terminate unidirectional flows

that use the same Egress-Ingress reverse direction

       communication path to satisfy the release of a total bandwidth
       up equal to the "additional_reverse_bandwidth", see Appendix
       A.5.
  • If the number of REQUIRED unidirectional flows (to satisfy the

above issue) is not available, then a number of bidirectional

       flows that are using the same Egress-Ingress reverse direction
       communication path MAY be selected for preemption in order to
       satisfy the release of a total bandwidth equal up to the
       "additional_reverse_bandwidth".  Note that using the guidelines
       given in Appendix A.5, first the bidirectional flows that
       reserved a relatively small amount of resources on the path
       reversed to the path of congestion SHOULD be selected for
       termination.
       When the QNE Edges maintain aggregated intra-domain QoS-NSLP
       operational states, the steps can be the following.
  • The Egress calculates the bandwidth to be terminated using the

same method as described in Section 4.6.1.6.2.2. The Egress

       includes this bandwidth value in a <PDR Bandwidth> within a
       "PDR_Congestion_Report" container that is carried by the end-
       to-end NOTIFY message.
  • The Ingress receives the NOTIFY message and reads the <PDR

Bandwidth> value included in the "PDR_Congestion_Report"

       container.  Note that this value is denoted as
       "notify_reverse_bandwidth" in the situation that the QNE Edges
       maintain per-flow intra-domain QoS-NSLP operational states, but
       is calculated differently.  The variables
       "marked_reverse_bandwidth" and "additional_reverse_bandwidth"
       are calculated using the same steps as explained for the
       situation that the QNE Edges maintain per-flow intra-domain
       QoS-NSLP states.
  • Regarding the termination of flows that use the same Egress-

Ingress reverse direction communication path, the Ingress can

       follow the same procedures as the situation that the QNE Edges
       maintain per-flow intra-domain QoS-NSLP operational states.
       The RMD-aggregated (reduced-state) reservations maintained by
       the Interior nodes, can be reduced in the "forward" and
       "reverse" directions by using the procedure described in
       Section 4.6.2.3 and including in the <Peak Data Rate-1 (p)>
       value of the local RMD-QSPEC <TMOD-1> parameter of the RMD-QOSM
       <QoS Desired> field carried by the forward intra-domain RESERVE

Bader, et al. Experimental [Page 116] RFC 5977 RMD-QOSM October 2010

       the value equal to <notify_reverse_bandwidth> and by including
       the <additional_reverse_bandwidth> value in the <PDR Bandwidth>
       parameter within the "PDR_Release_Request" container that is
       carried by the same intra-domain RESERVE message.

A.7. Example of Preemption Handling during Admission Control

 This appendix describes an example of how preemption handling is
 supported during admission control.
 This section describes the mechanism that can be supported by the QNE
 Ingress, QNE Interior, and QNE Egress nodes to satisfy preemption
 during the admission control process.
 This mechanism uses the preemption building blocks specified in
 [RFC5974].

A.7.1. Preemption Handling in QNE Ingress Nodes

 If a QNE Ingress receives a RESERVE for a session that causes other
 session(s) to be preempted, for each of these to-be-preempted
 sessions, then the QNE Ingress follows the following steps:
 Step_1:
 The QNE Ingress MUST send a tearing RESERVE downstream and add a
 BOUND-SESSION-ID, with <Binding_Code> value equal to "Indicated
 session caused preemption" that indicates the SESSION-ID of the
 session that caused the preemption.  Furthermore, an <INFO-SPEC>
 object with error code value equal to "Reservation preempted" has to
 be included in each of these tearing RESERVE messages.
 The selection of which flows have to be preempted can be based on
 predefined policies.  For example, this selection process can be
 based on the MRI associated with the high and low priority sessions.
 In particular, the QNE Ingress can select low(er) priority session(s)
 where their MRI is "close" (especially the target IP) to the one
 associated with the higher priority session.  This means that
 typically the high priority session and the to-be-preempted lower
 priority sessions are following the same communication path and are
 passing through the same QNE Egress node.
 Furthermore, the amount of lower priority sessions that have to be
 preempted per each high priority session, has to be such that the
 requested resources by the higher priority session SHOULD be lower or
 equal than the sum of the reserved resources associated with the
 lower priority sessions that have to be preempted.

Bader, et al. Experimental [Page 117] RFC 5977 RMD-QOSM October 2010

 Step_2:
 For each of the sent tearing RESERVE(s) the QNE Ingress will send a
 NOTIFY message with an <INFO-SPEC> object with error code value equal
 to "Reservation preempted" towards the QNI.
 Step_3:
 After sending the preempted (tearing) RESERVE(s), the Ingress QNE
 will send the (reserving) RESERVE, which caused the preemption,
 downstream towards the QNE Egress.

A.7.2. Preemption Handling in QNE Interior Nodes

 The QNE Interior upon receiving the first (tearing) RESERVE that
 carries the <BOUND-SESSION-ID> object with <Binding_Code> value equal
 to "Indicated session caused preemption" and an <INFO-SPEC> object
 with error code value equal to "Reservation preempted" it considers
 that this session has to be preempted.
 In this case, the QNE Interior creates a so-called "preemption
 state", which is identified by the SESSION-ID carried in the
 preemption-related <BOUND-SESSION-ID> object.  Furthermore, this
 "preemption state" will include the SESSION-ID of the session
 associated with the (tearing) RESERVE.  Subsequently, if additional
 tearing RESERVE(s) are arriving including the same values of BOUND-
 SESSION-ID and <INFO-SPEC> objects, then the associated SESSION-IDs
 of these (tearing) RESERVE message will be included in the already
 created "preemption state".  The QNE will then set a timer, with a
 value that is high enough to ensure that it will not expire before
 the (reserving) RESERVE arrives.
 Note that when the "preemption state" timer expires, the bandwidth
 associated with the preempted session(s) will have to be released,
 following a normal RMD-QOSM bandwidth release procedure.  If the QNE
 Interior node will not receive all the to-be-preempted (tearing)
 RESERVE messages sent by the QNE Ingress before their associated
 (reserving) RESERVE message arrives, then the (reserving) RESERVE
 message will not reserve any resources and this message will be "M"
 marked (see Section 4.6.1.2).  Note that this situation is not a
 typical situation.  Typically, this situation can only occur when at
 least one of (tearing) the RESERVE messages is dropped due to an
 error condition.

Bader, et al. Experimental [Page 118] RFC 5977 RMD-QOSM October 2010

 Otherwise, if the QNE Interior receives all the to-be-preempted
 (tearing) RESERVE messages sent by the QNE Ingress, then the QNE
 Interior will remove the pending resources, and make the new
 reservation using normal RMD-QOSM bandwidth release and reservation
 procedures.

A.7.3. Preemption Handling in QNE Egress Nodes

 Similar to the QNE Interior operation, the QNE Egress, upon receiving
 the first (tearing) RESERVE that carries the <BOUND-SESSION-ID>
 object with the <Binding_Code> value equal to "Indicated session
 caused preemption" and an <INFO-SPEC> object with error code value
 equal to "Reservation preempted", it considers that this session has
 to be preempted.  Similar to the QNE Interior operation the QNE
 Egress creates a so called "preemption state", which is identified by
 the SESSION-ID carried in the preemption-related <BOUND-SESSION-ID>
 object.  This "preemption state" will store the same type of
 information and use the same timer value as specified in Appendix
 A.7.2.
 Subsequently, if additional tearing RESERVE(s) are arriving including
 the same values of BOUND-SESSION-ID and <INFO-SPEC> objects, then the
 associated SESSION-IDs of these (tearing) RESERVE message will be
 included in the already created "preemption state".
 If the (reserving) RESERVE message sent by the QNE Ingress node
 arrived and is not "M" marked, and if all the to-be-preempted
 (tearing) RESERVE messages arrived, then the QNE Egress will remove
 the pending resources and make the new reservation using normal RMD-
 QOSM procedures.
 If the QNE Egress receives an "M" marked RESERVE message, then the
 QNE Egress will use the normal partial RMD-QOSM procedure to release
 the partial reserved resources associated with the "M" marked RESERVE
 (see Section 4.6.1.2).
 If the QNE Egress will not receive all the to-be-preempted (tearing)
 RESERVE messages sent by the QNE Ingress before their associated and
 not "M" marked (reserving) RESERVE message arrives, then the
 following steps can be followed:
  • If the QNE Egress uses an end-to-end QOSM that supports the

preemption handling, then the QNE Egress has to calculate and

    select new lower priority sessions that have to be terminated.
    How the preempted sessions are selected and signaled to the
    downstream QNEs is similar to the operation specified in Appendix
    A.7.1.

Bader, et al. Experimental [Page 119] RFC 5977 RMD-QOSM October 2010

  • If the QNE Egress does not use an end-to-end QOSM that supports

the preemption handling, then the QNE Egress has to reject the

    requesting (reserving) RESERVE message associated with the high
    priority session (see Section 4.6.1.2).
 Note that typically, the situation in which the QNE Egress does not
 receive all the to-be-preempted (tearing) RESERVE messages sent by
 the QNE Ingress can only occur when at least one of the (tearing)
 RESERVE messages are dropped due to an error condition.

A.8. Example of a Retransmission Procedure within the RMD Domain

 This appendix describes an example of a retransmission procedure that
 can be used in the RMD domain.
 If the retransmission of intra-domain RESERVE messages within the RMD
 domain is not disallowed, then all the QNE Interior nodes SHOULD use
 the functionality described in this section.
 In this situation, we enable QNE Interior nodes to maintain a replay
 cache in which each entry contains the <RSN>, <SESSION-ID> (available
 via GIST), <REFRESH-PERIOD> (available via the QoS NSLP [RFC5974]),
 and the last received "PHR Container" <Parameter ID> carried by the
 RMD-QSPEC for each session [RFC5975].  Thus, this solution uses
 information carried by <QoS-NSLP> objects [RFC5974] and parameters
 carried by the RMD-QSPEC "PHR Container".  The following phases can
 be distinguished:
 Phase 1: Create Replay Cache Entry
 When an Interior node receives an intra-domain RESERVE message and
 its cache is empty or there is no matching entry, it reads the
 <Parameter ID> field of the "PHR Container" of the received message.
 If the <Parameter ID> is a PHR_RESOURCE_REQUEST, which indicates that
 the intra-domain RESERVE message is a reservation request, then the
 QNE Interior node creates a new entry in the cache and copies the
 <RSN>, <SESSION-ID> and <Parameter ID> to the entry and sets the
 <REFRESH-PERIOD>.
 By using the information stored in the list, the Interior node
 verifies whether or not the received intra-domain RESERVE message is
 sent by an adversary.  For example, if the <SESSION-ID> and <RSN> of
 a received intra-domain RESERVE message match the values stored in
 the list then the Interior node checks the <Parameter ID> part.

Bader, et al. Experimental [Page 120] RFC 5977 RMD-QOSM October 2010

 If the <Parameter ID> is different, then:
 Situation D1: <Parameter ID> in its own list is
    PHR_RESOURCE_REQUEST, and <Parameter ID> in the message is
    PHR_REFRESH_UPDATE;
 Situation D2: <Parameter ID> in its own list is
    PHR_RESOURCE_REQUEST or PHR_REFRESH_UPDATE, and <Parameter ID>
    in the message is PHR_RELEASE_REQUEST;
 Situation D3: <Parameter ID> in its own list is PHR_REFRESH_UPDATE,
    and <Parameter ID> in the message is PHR_RESOURCE_REQUEST;
 For Situation D1, the QNE Interior node processes this message by
 RMD-QOSM default operation, reserves bandwidth, updates the entry,
 and passes the message to downstream nodes.  For Situation D2, the
 QNE Interior node processes this message by RMD-QOSM default
 operation, releases bandwidth, deletes all entries associated with
 the session and passes the message to downstream nodes.  For
 situation D3, the QNE Interior node does not use/process the local
 RMD-QSPEC <TMOD-1> parameter carried by the received intra-domain
 RESERVE message.  Furthermore, the <K> flag in the "PHR Container"
 has to be set such that the local RMD-QSPEC <TMOD-1> parameter
 carried by the intra-domain RESERVE message is not processed/used by
 a QNE Interior node.
 If the <Parameter ID> is the same, then:
    Situation S1: <Parameter ID> is equal to PHR_RESOURCE_REQUEST;
    Situation S2: <Parameter ID> is equal to PHR_REFRESH_UPDATE;
    For situation S1, the QNE Interior node does not process the
    intra-domain RESERVE message, but it just passes it to downstream
    nodes, because it might have been retransmitted by the QNE Ingress
    node.  For situation S2, the QNE Interior node processes the first
    incoming intra-domain (refresh) RESERVE message within a refresh
    period and updates the entry and forwards it to the downstream
    nodes.
 If only <Session-ID> is matched to the list, then the QNE Interior
 node checks the <RSN>.  Here also two situations can be
 distinguished:
 If a rerouting takes place (see Section 5.2.5.2 in [RFC5974]), the
 <RSN> in the message will be equal to either <RSN + 2> in the stored
 list if it is not a tearing RESERVE or <RSN -1> in the stored list if
 it is a tearing RESERVE:

Bader, et al. Experimental [Page 121] RFC 5977 RMD-QOSM October 2010

 The QNE Interior node will check the <Parameter ID> part;
 If the <RSN> in the message is equal to <RSN + 2> in the stored list
 and the <Parameter ID> is a PHR_RESOURCE_REQUEST or
 PHR_REFRESH_UPDATE, then the received intra-domain RESERVE message
 has to be interpreted and processed as a typical (non-tearing)
 RESERVE message, which is caused by rerouting, see Section 5.2.5.2 in
 [RFC5974].
 If the <RSN> in the message is equal to <RSN-1> in the stored list
 and the <Parameter ID> is a PHR_RELEASE_REQUEST, then the received
 intra-domain RESERVE message has to be interpreted and processed as a
 typical (tearing) RESERVE message, which is caused by rerouting (see
 Section 5.2.5.2 in [RFC5974]).
 If other situations occur than the ones described above, then the QNE
 Interior node does not use/process the local RMD-QSPEC <TMOD-1>
 parameter carried by the received intra-domain RESERVE message.
 Furthermore, the <K> parameter has to be set, see above.
 Phase 2: Update Replay Cache Entry
 When a QNE Interior node receives an intra-domain RESERVE message, it
 retrieves the corresponding entry from the cache and compares the
 values.  If the message is valid, the Interior node will update
 <Parameter ID> and <REFRESH-PERIOD> in the list entry.
 Phase 3: Delete Replay Cache Entry
 When a QNE Interior node receives an intra-domain (tear) RESERVE
 message and an entry in the replay cache can be found, then the QNE
 Interior node will delete this entry after processing the message.
 Furthermore, the Interior node will delete cache entries, if it did
 not receive an intra-domain (refresh) RESERVE message during the
 <REFRESH-PERIOD> period with a <Parameter ID> value equal to
 PHR_REFRESH_UPDATE.

A.9. Example on Matching the Initiator QSPEC to the Local RMD-QSPEC

 Section 3.4 of [RFC5975] describes an example of how the QSPEC can be
 Used within QoS-NSLP.  Figure 29 illustrates a situation where a QNI
 and a QNR are using an end-to-end QOSM, denoted in this context as
 Z-e2e.  It is considered that the QNI access network side is a
 wireless access network built on a generation "X" technology with QoS
 support as defined by generation "X", while QNR access network is a
 wired/fixed access network with its own defined QoS support.

Bader, et al. Experimental [Page 122] RFC 5977 RMD-QOSM October 2010

 Furthermore, it is considered that the shown QNE Edges are located at
 the boundary of an RMD domain and that the shown QNE Interior nodes
 are located inside the RMD domain.
 The QNE Edges are able to run both the Z-e2e QOSM and the RMD-QOSM,
 while the QNE Interior nodes can only run the RMD-QOSM.  The QNI is
 considered to be a wireless laptop, for example, while the QNR is
 considered to be a PC.
 |------|   |------|                           |------|   |------|
 |Z-e2e |<->|Z-e2e |<------------------------->|Z-e2e |<->|Z-e2e |
 | QOSM |   | QOSM |                           | QOSM |   | QOSM |
 |      |   |------|   |-------|   |-------|   |------|   |      |
 | NSLP |   | NSLP |<->| NSLP  |<->| NSLP  |<->| NSLP |   | NSLP |
 |Z-e2e |   |  RMD |   |  RMD  |   |  RMD  |   | RMD  |   | Z-e2e|
 | QOSM |   | QOSM |   | QOSM  |   | QOSM  |   | QOSM |   | QOSM |
 |------|   |------|   |-------|   |-------|   |------|   |------|
 -----------------------------------------------------------------
 |------|   |------|   |-------|   |-------|   |------|   |------|
 | NTLP |<->| NTLP |<->| NTLP  |<->| NTLP  |<->| NTLP |<->| NTLP |
 |------|   |------|   |-------|   |-------|   |------|   |------|
   QNI         QNE        QNE         QNE         QNE       QNR
 (End)  (Ingress Edge) (Interior)  (Interior) (Egress Edge)  (End)
  Figure 29. Example of initiator and local domain QOSM operation
 The QNI sets <QoS Desired> and <QoS Available> QSPEC objects in the
 initiator QSPEC, and initializes <QoS Available> to <QoS Desired>.
 In this example, the <Minimum QoS> object is not populated.  The QNI
 populates QSPEC parameters to ensure correct treatment of its traffic
 in domains down the path.  Additionally, to ensure correct treatment
 further down the path, the QNI includes <PHB Class> in <QoS Desired>.
 The QNI therefore includes in the QSPEC.
   <QoS Desired> = <TMOD-1> <PHB Class>
   <QoS Available> = <TMOD-1> <Path Latency>
 In this example, it is assumed that the <TMOD-1> parameter is used to
 encode the traffic parameters of a VoIP application that uses RTP and
 the G.711 Codec, see Appendix B in [RFC5975].  The below text is
 copied from [RFC5975].
    In the simplest case the Minimum Policed Unit m is the sum of the
    IP-, UDP- and RTP- headers + payload.  The IP header in the IPv4
    case has a size of 20 octets (40 octets if IPv6 is used).  The UDP
    header has a size of 8 octets and RTP uses a 12 octet header.  The

Bader, et al. Experimental [Page 123] RFC 5977 RMD-QOSM October 2010

    G.711 Codec specifies a bandwidth of 64 kbit/s (8000 octets/s).
    Assuming RTP transmits voice datagrams every 20 ms, the payload
    for one datagram is 8000 octets/s * 0.02 s = 160 octets.
    IPv4+UDP+RTP+payload: m=20+8+12+160 octets = 200 octets
    IPv6+UDP+RTP+payload: m=40+8+12+160 octets = 220 octets
    The Rate r specifies the amount of octets per second.  50
    datagrams are sent per second.
    IPv4: r = 50 1/s * m = 10,000 octets/s
    IPv6: r = 50 1/s * m = 11,000 octets/s
    The bucket size b specifies the maximum burst.  In this example, a
    burst of 10 packets is used.
    IPv4: b = 10 * m = 2000 octets
    IPv6: b = 10 * m = 2200 octets
 In our example, we will assume that IPV4 is used and therefore, the
 <TMOD-1> values will be set as follows:
 m = 200 octets
 r = 10000 octets/s
 b = 2000 octets
 The <Peak Data Rate-1 (p)> and MPS are not specified above, but in
 our example we will assume:
 p = r = 10000 octets/s
 MPS = 220 octets
 The <PHB Class> is set in such a way that the Expedited Forwarding
 (EF) PHB is used.
 Since <Path Latency> and <QoS Class> are not vital parameters from
 the QNI's perspective, it does not raise their <M> flags.
 Each QNE, which supports the Z-e2e QOSM on the path, reads and
 interprets those parameters in the initiator QSPEC.
 When an end-to-end RESERVE message is received at a QNE Ingress node
 at the RMD domain border, the QNE Ingress can "hide" the initiator
 end-to-end RESERVE message so that only the QNE Edges process the
 initiator (end-to-end) RESERVE message, which then bypasses
 intermediate nodes between the Edges of the domain, and issues its
 own local RESERVE message (see Section 6).  For this new local
 RESERVE message, the QNE Ingress node generates the local RMD-QSPEC.

Bader, et al. Experimental [Page 124] RFC 5977 RMD-QOSM October 2010

 The RMD-QSPEC corresponding to the RMD-QOSM is generated based on the
 original initiator QSPEC according to the procedures described in
 Section 4.5 of [RFC5974] and in Section 6 of this document.  The RMD
 QNE Ingress maps the <TMOD-1> parameters contained in the original
 Initiator QSPEC into the equivalent <TMOD-1> parameter representing
 only the peak bandwidth in the local RMD-QSPEC.
 In this example, the initial <TMOD-1> parameters are mapped into the
 RMD-QSPEC <TMOD-1> parameters as follows.
 As specified, the RMD-QOSM bandwidth equivalent <TMOD-1> parameter of
 RMD-QSPEC should have:
    r = p of initial e2e <TMOD-1> parameter
    m = large;
    b = large;
 For the RMD-QSPEC <TMOD-1> parameter, the following values are
 calculated:
    r = p of initial e2e <TMOD-1> parameter = 10000 octets/s
    m is set in this example to large as follows:
    m = MPS of initial e2e <TMOD-1> parameter = 220 octets
 The maximum value of b = 250 gigabytes, but in our example this value
 is quite large.  The b parameter specifies the extent to which the
 data rate can exceed the sustainable level for short periods of time.
 In order to get a large b, in this example we consider that for a
 period of certain period of time the data rate can exceed the
 sustainable level, which in our example is the peak rate (p).
 Thus, in our example, we calculate b as:
    b = p * "period of time"
 For this VoIP example, we can assume that this period of time is 1.5
 seconds, see below:
    b = 10000 octets/s * 1.5 seconds = 15000 octets
 Thus, the local RMD-QSPEC <TMOD-1> values are:
    r = 10000 octets/s
    p = 10000 octets/s
    m = 220 octets
    b = 15000 octets
    MPS = 220 octets

Bader, et al. Experimental [Page 125] RFC 5977 RMD-QOSM October 2010

 The bit level format of the RMD-QSPEC is given in Section 4.1.  In
 particular, the Initiator/Local QSPEC bit, i.e., <I> is set to
 "Local" (i.e., "1") and the <Qspec Proc> is set as follows:
  • Message Sequence = 0: Sender initiated
  • Object combination = 0: <QoS Desired> for RESERVE and

<QoS Reserved> for RESPONSE

 The <QSPEC Version> used by RMD-QOSM is the default version, i.e.,
 "0", see [RFC5975].  The <QSPEC Type> value used by the RMD-QOSM is
 specified in [RFC5975] and is equal to: "2".
 The <Traffic Handling Directives> contains the following fields:
 <Traffic Handling Directives> = <PHR container> <PDR container>
 The Per-Hop Reservation container (PHR container) and the Per-Domain
 Reservation container (PDR container) are specified in Sections 4.1.2
 and 4.1.3, respectively.  The <PHR container> contains the traffic
 handling directives for intra-domain communication and reservation.
 The <PDR container> contains additional traffic handling directives
 that are needed for edge-to-edge communication.  The RMD-QOSM <QoS
 Desired> and <QoS Reserved>, are specified in Section 4.1.1.
 In RMD-QOSM the <QoS Desired> and <QoS Reserved> objects contain the
 following parameters:
 <QoS Desired> = <TMOD-1> <PHB Class> <Admission Priority>
 <QoS Reserved> = <TMOD-1> <PHB Class> <Admission Priority>
 The bit format of the <PHB Class> (see [RFC5975] and Figures 4 and 5)
 and <Admission Priority> complies to the bit format specified in
 [RFC5975].
 In this example, the RMD-QSPEC <TMOD-1> values are the ones that were
 calculated and given above.  Furthermore, the <PHB Class>, represents
 the EF PHB class.  Moreover, in this example the RMD reservation is
 established without an <Admission Priority> parameter, which is
 equivalent to a reservation established with an <Admission Priority>
 whose value is 1.
 The RMD QNE Egress node updates <QoS Available> on behalf of the
 entire RMD domain if it can.  If it cannot (since the <M> flag is not
 set for <Path Latency>) it raises the parameter-specific, "not-
 supported" flag, warning the QNR that the final latency value in <QoS
 Available> is imprecise.

Bader, et al. Experimental [Page 126] RFC 5977 RMD-QOSM October 2010

 In the "Y" access domain, the initiator QSPEC is processed by the QNR
 in the similar was as it was processed in the "X" wireless access
 domain, by the QNI.
 If the reservation was successful, eventually the RESERVE request
 arrives at the QNR (otherwise, the QNE at which the reservation
 failed would have aborted the RESERVE and sent an error RESPONSE back
 to the QNI).  If the <RII> was included in the QoS-NSLP message, the
 QNR generates a positive RESPONSE with QSPEC objects <QoS Reserved>
 and <QoS Available>.  The parameters appearing in <QoS Reserved> are
 the same as in <QoS Desired>, with values copied from <QoS
 Available>.  Hence, the QNR includes the following QSPEC objects in
 the RESPONSE message:
    <QoS Reserved> = <TMOD-1> <PHB Class>
    <QoS Available> = <TMOD-1> <Path Latency>

Contributors

 Attila Takacs
 Ericsson Research
 Ericsson Hungary Ltd.
 Laborc 1, Budapest, Hungary, H-1037
 EMail: Attila.Takacs@ericsson.com
 Andras Csaszar
 Ericsson Research
 Ericsson Hungary Ltd.
 Laborc 1, Budapest, Hungary, H-1037
 EMail: Andras.Csaszar@ericsson.com

Bader, et al. Experimental [Page 127] RFC 5977 RMD-QOSM October 2010

Authors' Addresses

 Attila Bader
 Ericsson Research
 Ericsson Hungary Ltd.
 Laborc 1, Budapest, Hungary, H-1037
 EMail: Attila.Bader@ericsson.com
 Lars Westberg
 Ericsson Research
 Torshamnsgatan 23
 SE-164 80 Stockholm, Sweden
 EMail: Lars.Westberg@ericsson.com
 Georgios Karagiannis
 University of Twente
 P.O. Box 217
 7500 AE Enschede, The Netherlands
 EMail: g.karagiannis@ewi.utwente.nl
 Cornelia Kappler
 ck technology concepts
 Berlin, Germany
 EMail: cornelia.kappler@cktecc.de
 Hannes Tschofenig
 Nokia Siemens Networks
 Linnoitustie 6
 Espoo 02600
 Finland
 EMail: Hannes.Tschofenig@nsn.com
 URI: http://www.tschofenig.priv.at
 Tom Phelan
 Sonus Networks
 250 Apollo Dr.
 Chelmsford, MA 01824 USA
 EMail: tphelan@sonusnet.com

Bader, et al. Experimental [Page 128]

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