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rfc:rfc4804

Network Working Group F. Le Faucheur, Ed. Request for Comments: 4804 Cisco Systems, Inc. Category: Standards Track February 2007

        Aggregation of Resource ReSerVation Protocol (RSVP)
              Reservations over MPLS TE/DS-TE Tunnels

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The IETF Trust (2007).

Abstract

 RFC 3175 specifies aggregation of Resource ReSerVation Protocol
 (RSVP) end-to-end reservations over aggregate RSVP reservations.
 This document specifies aggregation of RSVP end-to-end reservations
 over MPLS Traffic Engineering (TE) tunnels or MPLS Diffserv-aware
 MPLS Traffic Engineering (DS-TE) tunnels.  This approach is based on
 RFC 3175 and simply modifies the corresponding procedures for
 operations over MPLS TE tunnels instead of aggregate RSVP
 reservations.  This approach can be used to achieve admission control
 of a very large number of flows in a scalable manner since the
 devices in the core of the network are unaware of the end-to-end RSVP
 reservations and are only aware of the MPLS TE tunnels.

Faucheur Standards Track [Page 1] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

Table of Contents

 1. Introduction ....................................................3
 2. Specification of Requirements ...................................7
 3. Definitions .....................................................7
 4. Operations of RSVP Aggregation over TE with
    Pre-established Tunnels .........................................8
    4.1. Reference Model ............................................9
    4.2. Receipt of E2E Path Message by the Aggregator ..............9
    4.3. Handling of E2E Path Message by Transit LSRs ..............11
    4.4. Receipt of E2E Path Message by the Deaggregator ...........11
    4.5. Handling of E2E Resv Message by the Deaggregator ..........12
    4.6. Handling of E2E Resv Message by the Aggregator ............12
    4.7. Forwarding of E2E Traffic by the Aggregator ...............14
    4.8. Removal of E2E Reservations ...............................14
    4.9. Removal of the TE Tunnel ..................................14
    4.10. Example Signaling Flow ...................................15
 5. IPv4 and IPv6 Applicability ....................................16
 6. E2E Reservations Applicability .................................16
 7. Example Deployment Scenarios ...................................16
    7.1. Voice and Video Reservations Scenario .....................16
    7.2. PSTN/3G Voice Trunking Scenario ...........................17
 8. Security Considerations ........................................18
 9. Acknowledgments ................................................20
 10. Normative References ..........................................20
 11. Informative References ........................................21
 Appendix A - Optional Use of RSVP Proxy on RSVP Aggregator ........23
 Appendix B - Example Usage of RSVP Aggregation over DSTE Tunnels
              for VoIP Call Admission Control (CAC) ................25

Faucheur Standards Track [Page 2] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

1. Introduction

 The Integrated Services (Intserv) [INT-SERV] architecture provides a
 means for the delivery of end-to-end Quality of Service (QoS) to
 applications over heterogeneous networks.
 [RSVP] defines the Resource reSerVation Protocol that can be used by
 applications to request resources from the network.  The network
 responds by explicitly admitting or rejecting these RSVP requests.
 Certain applications that have quantifiable resource requirements
 express these requirements using Intserv parameters as defined in the
 appropriate Intserv service specifications ([GUARANTEED],
 [CONTROLLED]).
 The Differentiated Services (DiffServ) architecture ([DIFFSERV]) was
 then developed to support the differentiated treatment of packets in
 very large scale environments.  In contrast to the per-flow
 orientation of Intserv and RSVP, Diffserv networks classify packets
 into one of a small number of aggregated flows or "classes", based on
 the Diffserv codepoint (DSCP) in the packet IP header.  At each
 Diffserv router, packets are subjected to a "per-hop behavior" (PHB),
 which is invoked by the DSCP.  The primary benefit of Diffserv is its
 scalability.  Diffserv eliminates the need for per-flow state and
 per-flow processing, and therefore scales well to large networks.
 However, DiffServ does not include any mechanism for communication
 between applications and the network.  Thus, as detailed in
 [INT-DIFF], significant benefits can be achieved by using Intserv
 over Diffserv including resource-based admission control, policy-
 based admission control, assistance in traffic
 identification/classification, and traffic conditioning.  As
 discussed in [INT-DIFF], Intserv can operate over Diffserv in
 multiple ways.  For example, the Diffserv region may be statically
 provisioned or RSVP aware.  When it is RSVP aware, several mechanisms
 may be used to support dynamic provisioning and topology-aware
 admission control, including aggregate RSVP reservations, per-flow
 RSVP, or a bandwidth broker.  The advantage of using aggregate RSVP
 reservations is that it offers dynamic, topology-aware admission
 control over the Diffserv region without per-flow reservations and
 the associated level of RSVP signaling in the Diffserv core.  In
 turn, this allows dynamic, topology-aware admission control of flows
 requiring QoS reservations over the Diffserv core even when the total
 number of such flows carried over the Diffserv core is extremely
 large.
 [RSVP-AGG] and [RSVP-GEN-AGG] describe in detail how to perform such
 aggregation of end-to-end RSVP reservations over aggregate RSVP
 reservations in a Diffserv cloud.  They establish an architecture

Faucheur Standards Track [Page 3] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 where multiple end-to-end RSVP reservations sharing the same ingress
 router (Aggregator) and egress router (Deaggregator) at the edges of
 an "aggregation region" can be mapped onto a single aggregate
 reservation within the aggregation region.  This considerably reduces
 the amount of reservation state that needs to be maintained by
 routers within the aggregation region.  Furthermore, traffic
 belonging to aggregate reservations is classified in the data path
 purely using Diffserv marking.
 [MPLS-TE] describes how MPLS Traffic Engineering (TE) tunnels can be
 used to carry arbitrary aggregates of traffic for the purposes of
 traffic engineering.  [RSVP-TE] specifies how such MPLS TE tunnels
 can be established using RSVP-TE signaling.  MPLS TE uses
 Constraint-Based Routing to compute the path for a TE tunnel.  Then,
 Admission Control is performed during the establishment of TE tunnels
 to ensure they are granted their requested resources.
 [DSTE-REQ] presents the Service Providers requirements for support of
 Diffserv-aware MPLS Traffic Engineering (DS-TE).  With DS-TE,
 separate DS-TE tunnels can be used to carry different Diffserv
 classes of traffic, and different resource constraints can be
 enforced for these different classes.  [DSTE-PROTO] specifies RSVP-TE
 signaling extensions as well as OSPF and Intermediate System to
 Intermediate System (IS-IS) extensions for support of DS-TE.
 In the rest of this document we will refer to both TE tunnels and
 DS-TE tunnels simply as "TE tunnels".
 TE tunnels have much in common with the aggregate RSVP reservations
 used in [RSVP-AGG] and [RSVP-GEN-AGG]:
  1. A TE tunnel is subject to Admission Control and thus is

effectively an aggregate bandwidth reservation.

  1. In the data plane, packet scheduling relies exclusively on

Diffserv classification and PHBs.

  1. Both TE tunnels and aggregate RSVP reservations are controlled

by "intelligent" devices on the edge of the "aggregation core"

      (Head-end and Tail-end in the case of TE tunnels; Aggregator and
      Deaggregator in the case of aggregate RSVP reservations.
  1. Both TE tunnels and aggregate RSVP reservations are signaled

using the RSVP protocol (with some extensions defined in

      [RSVP-TE] and [DSTE-PROTO] respectively for TE tunnels and DS-TE
      tunnels).

Faucheur Standards Track [Page 4] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 This document provides a detailed specification for performing
 aggregation of end-to-end RSVP reservations over MPLS TE tunnels
 (which act as aggregate reservations in the core).  This document
 builds on the RSVP Aggregation procedures defined in [RSVP-AGG] and
 [RSVP-GEN-AGG], and only changes those where necessary to operate
 over TE tunnels.  With [RSVP-AGG] and [RSVP-GEN-AGG], a lot of
 responsibilities (such as mapping end-to-end reservations to
 Aggregate reservations and resizing the Aggregate reservations) are
 assigned to the Deaggregator (which is the equivalent of the tunnel
 Tail-end) while with TE, the tunnels are controlled by the tunnel
 Head-end.  Hence, the main change over the RSVP Aggregations
 procedures defined in [RSVP-AGG] and [RSVP-GEN-AGG] is to modify
 these procedures to reassign responsibilities from the Deaggregator
 to the Aggregator (i.e., the tunnel Head-end).
 [LSP-HIER] defines how to aggregate MPLS TE Label Switched Paths
 (LSPs) by creating a hierarchy of such LSPs.  This involves nesting
 of end-to-end LSPs into an aggregate LSP in the core (by using the
 label stack construct).  Since end-to-end TE LSPs are themselves
 signaled with RSVP-TE and reserve resources at every hop, this can be
 looked at as a form of aggregation of RSVP(-TE) reservations over
 MPLS TE tunnels.  This document capitalizes on the similarities
 between nesting of TE LSPs over TE tunnels and RSVP aggregation over
 TE tunnels, and reuses the procedures of [LSP-HIER] wherever
 possible.
 This document also builds on the "RSVP over Tunnels" concepts of RFC
 2746 [RSVP-TUN].  It differs from that specification in the following
 ways:
  1. This document describes operation over MPLS tunnels, whereas RFC

2746 describes operation with IP tunnels. One consequence of

      this difference is the need to deal with penultimate hop popping
      (PHP).
  1. MPLS-TE tunnels inherently reserve resources, whereas the

tunnels in RFC 2746 do not have resource reservations by

      default.  This leads to some simplifications in the current
      document.
  1. This document builds on the fact that there is exactly one

aggregate reservation per MPLS-TE tunnel, whereas RFC 2746

      permits a model where one reservation is established on the
      tunnel path for each end-to-end flow.

Faucheur Standards Track [Page 5] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

  1. We have assumed in the current document that a given MPLS-TE

tunnel will carry reserved traffic and nothing but reserved

      traffic, which negates the requirement of RFC 2746 to
      distinguish reserved and non-reserved traffic traversing the
      same tunnel by using distinct encapsulations.
  1. There may be several MPLS-TE tunnels that share common Head-end

and Tail-end routers, with the Head-end policy determining which

      tunnel is appropriate for a particular flow.  This scenario does
      not appear to be addressed in RFC 2746.
 At the same time, this document does have many similarities with RFC
 2746.  MPLS-TE tunnels are "type 2 tunnels" in the nomenclature of
 RFC 2746:
    "The (logical) link may be able to promise that some overall level
    of resources is available to carry traffic, but not to allocate
    resources specifically to individual data flows".
 Aggregation of end-to-end RSVP reservations over TE tunnels combines
 the benefits of [RSVP-AGG] and [RSVP-GEN-AGG] with the benefits of
 MPLS, including the following:
  1. Applications can benefit from dynamic, topology-aware,

resource-based admission control over any segment of the end-

      to-end path, including the core.
  1. As per regular RSVP behavior, RSVP does not impose any burden on

routers where such admission control is not needed (for example,

      if the links upstream and downstream of the MPLS TE core are
      vastly over-engineered compared to the core capacity, admission
      control is not required on these over-engineered links and RSVP
      need not be processed on the corresponding router hops).
  1. The core scalability is not affected (relative to the

traditional MPLS TE deployment model) since the core remains

      unaware of end-to-end RSVP reservations and only has to maintain
      aggregate TE tunnels since the datapath classification and
      scheduling in the core relies purely on the Diffserv mechanism
      (or more precisely the MPLS Diffserv mechanisms, as specified in
      [DIFF-MPLS]).
  1. The aggregate reservation (and thus the traffic from the

corresponding end to end reservations) can be network engineered

      via the use of Constraint based routing (e.g., affinity,
      optimization on different metrics) and when needed can take
      advantage of resources on other paths than the shortest path.

Faucheur Standards Track [Page 6] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

  1. The aggregate reservations (and thus the traffic from the

corresponding end-to-end reservations) can be protected against

      failure through the use of MPLS Fast Reroute.
 This document, like [RSVP-AGG] and [RSVP-GEN-AGG], covers aggregation
 of unicast sessions.  Aggregation of multicast sessions is for
 further study.

2. Specification of Requirements

 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 [KEYWORDS].

3. Definitions

 For readability, a number of definitions from [RSVP-AGG] as well as
 definitions for commonly used MPLS TE terms are provided here:
 Aggregator       This is the process in (or associated with) the
                  router at the ingress edge of the aggregation region
                  (with respect to the end-to-end RSVP reservation)
                  and behaving in accordance with [RSVP-AGG].  In this
                  document, it is also the TE tunnel Head-end.
 Deaggregator     This is the process in (or associated with) the
                  router at the egress edge of the aggregation region
                  (with respect to the end-to-end RSVP reservation)
                  and behaving in accordance with [RSVP-AGG].  In this
                  document, it is also the TE tunnel Tail-end
 E2E              End to end
 E2E Reservation  This is an RSVP reservation such that:
                  (i)   corresponding Path messages are initiated
                        upstream of the Aggregator and terminated
                        downstream of the Deaggregator, and
                  (ii)  corresponding Resv messages are initiated
                        downstream of the Deaggregator and terminated
                        upstream of the Aggregator, and
                  (iii) this RSVP reservation is aggregated over an
                        MPLS TE tunnel between the Aggregator and
                        Deaggregator.

Faucheur Standards Track [Page 7] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

                  An E2E RSVP reservation may be a per-flow
                  reservation.  Alternatively, the E2E reservation may
                  itself be an aggregate reservation of various types
                  (e.g., Aggregate IP reservation, Aggregate IPsec
                  reservation).  See Section 5 and 6 for more details
                  on the types of E2E RSVP reservations.  As per
                  regular RSVP operations, E2E RSVP reservations are
                  unidirectional.
 Head-end         This is the Label Switch Router responsible for
                  establishing, maintaining, and tearing down a given
                  TE tunnel.
 Tail-end         This is the Label Switch Router responsible for
                  terminating a given TE tunnel.
 Transit LSR      This is a Label Switch Router that is on the path of
                  a given TE tunnel and is neither the Head-end nor
                  the Tail-end.

4. Operations of RSVP Aggregation over TE with Pre-established Tunnels

 [RSVP-AGG] and [RSVP-GEN-AGG] support operations both in the case
 where aggregate RSVP reservations are pre-established and where
 Aggregators and Deaggregators have to dynamically discover each other
 and dynamically establish the necessary aggregate RSVP reservations.
 Similarly, RSVP Aggregation over TE tunnels could operate both in the
 case where the TE tunnels are pre-established and where the tunnels
 need to be dynamically established.
 In this document we provide a detailed description of the procedures
 in the case where TE tunnels are already established.  These
 procedures are based on those defined in [LSP-HIER].  The routing
 aspects discussed in Section 3 of [LSP-HIER] are not relevant here
 because those aim at allowing the constraint based routing of end-
 to-end TE LSPs to take into account the (aggregate) TE tunnels.  In
 the present document, the end-to-end RSVP reservations to be
 aggregated over the TE tunnels rely on regular SPF routing.  However,
 as already mentioned in [LSP-HIER], we note that a TE tunnel may be
 advertised into IS-IS or OSPF, to be used in normal SPF by nodes
 upstream of the Aggregator.  This would affect SPF routing and thus
 routing of end-to-end RSVP reservations.  The control of aggregation
 boundaries discussed in Section 6 of [LSP-HIER] is also not relevant
 here.  This uses information exchanged in GMPLS protocols to
 dynamically discover the aggregation boundary.  In this document, TE
 tunnels are pre-established, so that the aggregation boundary can be
 easily inferred.  The signaling aspects discussed in Section 6.2 of

Faucheur Standards Track [Page 8] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 [LSP-HIER] apply to the establishment/termination of the aggregate TE
 tunnels when this is triggered by GMPLS mechanisms (e.g., as a result
 of an end-to-end TE LSP establishment request received at the
 aggregation boundary).  As this document assumes pre-established
 tunnels, those aspects are not relevant here.  The signaling aspects
 discussed in Section 6.1 of [LSP-HIER] relate to the
 establishment/maintenance of the end-to-end TE LSPs over the
 aggregate TE tunnel.  This document describes how to use the same
 procedures as those specified in Section 6.1 of [LSP-HIER], but for
 the establishment of end-to-end RSVP reservations (instead of end-
 to-end TE LSPs) over the TE tunnels.  This is covered further in
 Section 4 of the present document.
 Pre-establishment of the TE tunnels may be triggered by any
 mechanisms including; for example, manual configuration or automatic
 establishment of a TE tunnel mesh through dynamic discovery of TE
 Mesh membership as allowed in [AUTOMESH].
 Procedures in the case of dynamically established TE tunnels are for
 further studies.

4.1. Reference Model

    |----|                                          |----|
 H--| R  |\ |-----|                       |------| /| R  |--H
 H--|    |\\|     |       |---|           |      |//|    |--H
    |----| \| He/ |       | T |           | Te/  |/ |----|
            | Agg |=======================| Deag |
           /|     |       |   |           |      |\
 H--------//|     |       |---|           |      |\\--------H
 H--------/ |-----|                       |------| \--------H
 H       = Host requesting end-to-end RSVP reservations
 R       = RSVP router
 He/Agg  = TE tunnel Head-end/Aggregator
 Te/Deag = TE tunnel Tail-end/Deaggregator
 T       = Transit LSR
  1. - = E2E RSVP reservation

== = TE tunnel

4.2. Receipt of E2E Path Message by the Aggregator

 The first event is the arrival of the E2E Path message at the
 Aggregator.  The Aggregator MUST follow traditional RSVP procedures
 for the processing of this E2E path message augmented with the
 extensions documented in this section.

Faucheur Standards Track [Page 9] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 The Aggregator MUST first attempt to map the E2E reservation onto a
 TE tunnel.  This decision is made in accordance with routing
 information as well as any local policy information that may be
 available at the Aggregator.  Examples of such policies appear in the
 following paragraphs.  Just for illustration purposes, among many
 other criteria, such mapping policies might take into account the
 Intserv service type, the Application Identity [RSVP-APPID], and/or
 the signaled preemption [RSVP-PREEMP] of the E2E reservation (for
 example, the aggregator may take into account the E2E reservations
 RSVP preemption priority and the MPLS TE tunnel setup and/or hold
 priorities when mapping the E2E reservation onto an MPLS TE tunnel).
 There are situations where the Aggregator is able to make a final
 mapping decision.  That would be the case, for example, if there is a
 single TE tunnel toward the destination and if the policy is to map
 any E2E RSVP reservation onto TE tunnels.
 There are situations where the Aggregator is not able to make a final
 determination.  That would be the case, for example, if routing
 identifies two DS-TE tunnels toward the destination, one belonging to
 DS-TE Class-Type 1 and one to Class-Type 0, if the policy is to map
 Intserv Guaranteed Services reservations to a Class-Type 1 tunnel and
 Intserv Controlled Load reservations to a Class-Type 0 tunnel, and if
 the E2E RSVP Path message advertises both Guaranteed Service and
 Controlled Load.
 Whether final or tentative, the Aggregator makes a mapping decision
 and selects a TE tunnel.  Before forwarding the E2E Path message
 toward the receiver, the Aggregator SHOULD update the ADSPEC inside
 the E2E Path message to reflect the impact of the MPLS TE cloud onto
 the QoS achievable by the E2E flow.  This update is a local matter
 and may be based on configured information, on the information
 available in the MPLS TE topology database, on the current TE tunnel
 path, on information collected via RSVP-TE signaling, or a
 combination thereof.  Updating the ADSPEC allows receivers that take
 into account the information collected in the ADSPEC within the
 network (such as delay and bandwidth estimates) to make more informed
 reservation decisions.
 The Aggregator MUST then forward the E2E Path message to the
 Deaggregator (which is the Tail-end of the selected TE tunnel).  In
 accordance with [LSP-HIER], the Aggregator MUST send the E2E Path
 message with an IF_ID RSVP_HOP object instead of an RSVP_HOP object.
 The data interface identification MUST identify the TE tunnel.

Faucheur Standards Track [Page 10] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 To send the E2E Path message, the Aggregator MUST address it directly
 to the Deaggregator by setting the destination address in the IP
 Header of the E2E Path message to the Deaggregator address.  The
 Router Alert is not set in the E2E Path message.
 Optionally, the Aggregator MAY also encapsulate the E2E Path message
 in an IP tunnel or in the TE tunnel itself.
 Regardless of the encapsulation method, the Router Alert is not set.
 Thus, the E2E Path message will not be visible to routers along the
 path from the Aggregator to the Deaggregator.  Therefore, in contrast
 to the procedures of [RSVP-AGG] and [RSVP-GEN-AGG], the IP Protocol
 number does not need to be modified to "RSVP-E2E-IGNORE"; it MUST be
 left as is (indicating "RSVP") by the Aggregator.
 In some environments, the Aggregator and Deaggregator MAY also act as
 IPsec Security Gateways in order to provide IPsec protection to E2E
 traffic when it transits between the Aggregator and the Deaggregator.
 In that case, to transmit the E2E Path message to the Deaggregator,
 the Aggregator MUST send the E2E Path message into the relevant IPsec
 tunnel terminating on the Deaggregator.
 E2E PathTear and ResvConf messages MUST be forwarded by the
 Aggregator to the Deaggregator exactly like Path messages.

4.3. Handling of E2E Path Message by Transit LSRs

 Since the E2E Path message is addressed directly to the Deaggregator
 and does not have Router Alert set, it is hidden from all transit
 LSRs.

4.4. Receipt of E2E Path Message by the Deaggregator

 Upon receipt of the E2E Path message addressed to it, the
 Deaggregator will notice that the IP Protocol number is set to "RSVP"
 and will thus perform RSVP processing of the E2E Path message.
 As with [LSP-HIER], the IP TTL vs. RSVP TTL check MUST NOT be made.
 The Deaggregator is informed that this check is not to be made
 because of the presence of the IF_ID RSVP HOP object.
 The Deaggregator MAY support the option to perform the following
 checks (defined in [LSP-HIER]) by the receiver Y of the IF_ID
 RSVP_HOP object:
 1.  Make sure that the data interface identified in the IF_ID
     RSVP_HOP object actually terminates on Y.

Faucheur Standards Track [Page 11] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 2.  Find the "other end" of the above data interface, i.e., X.  Make
     sure that the PHOP in the IF_ID RSVP_HOP object is a control
     channel address that belongs to the same node as X.
 The information necessary to perform these checks may not always be
 available to the Deaggregator.  Hence, the Deaggregator MUST support
 operations in such environments where the checks cannot be made.
 The Deaggregator MUST forward the E2E Path downstream toward the
 receiver.  In doing so, the Deaggregator sets the destination address
 in the IP header of the E2E Path message to the IP address found in
 the destination address field of the Session object.  The
 Deaggregator also sets the Router Alert.
 An E2E PathErr sent by the Deaggregator in response to the E2E Path
 message (which contains an IF_ID RSVP_HOP object) SHOULD contain an
 IF_ID RSVP_HOP object.

4.5. Handling of E2E Resv Message by the Deaggregator

 As per regular RSVP operations, after receipt of the E2E Path, the
 receiver generates an E2E Resv message which travels upstream hop-
 by-hop towards the sender.
 Upon receipt of the E2E Resv, the Deaggregator MUST follow
 traditional RSVP procedures on receipt of the E2E Resv message.  This
 includes performing admission control for the segment downstream of
 the Deaggregator and forwarding the E2E Resv message to the PHOP
 signaled earlier in the E2E Path message and which identifies the
 Aggregator.  Since the E2E Resv message is directly addressed to the
 Aggregator and does not carry the Router Alert option (as per
 traditional RSVP Resv procedures), the E2E Resv message is hidden
 from the routers between the Deaggregator and the Aggregator which,
 therefore, handle the E2E Resv message as a regular IP packet.
 If the Aggregator and Deaggregator are also acting as IPsec Security
 Gateways, the Deaggregator MUST send the E2E Resv message into the
 relevant IPsec tunnel terminating on the Aggregator.

4.6. Handling of E2E Resv Message by the Aggregator

 The Aggregator is responsible for ensuring that there is sufficient
 bandwidth available and reserved over the appropriate TE tunnel to
 the Deaggregator for the E2E reservation.
 On receipt of the E2E Resv message, the Aggregator MUST first perform
 the final mapping onto the final TE tunnel (if the previous mapping
 was only a tentative one).

Faucheur Standards Track [Page 12] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 If the tunnel did not change during the final mapping, the Aggregator
 continues the processing of the E2E Resv as described in the four
 following paragraphs.
 The aggregator calculates the size of the resource request using
 traditional RSVP procedures.  That is, it follows the procedures in
 [RSVP] to determine the resource requirements from the Sender Tspec
 and the Flowspec contained in the Resv.  Then it compares the
 resource request with the available resources of the selected TE
 tunnel.
 If sufficient bandwidth is available on the final TE tunnel, the
 Aggregator MUST update its internal understanding of how much of the
 TE tunnel is in use and MUST forward the E2E Resv messages to the
 corresponding PHOP.
 As noted in [RSVP-AGG], a range of policies MAY be applied to the
 re-sizing of the aggregate reservation (in this case, the TE tunnel).
 For example, the policy may be that the reserved bandwidth of the
 tunnel can only be changed by configuration.  More dynamic policies
 are also possible, whereby the aggregator may attempt to increase the
 reserved bandwidth of the tunnel in response to the amount of
 allocated bandwidth that has been used by E2E reservations.
 Furthermore, to avoid the delay associated with the increase of the
 tunnel size, the Aggregator may attempt to anticipate the increases
 in demand and adjust the TE tunnel size ahead of actual needs by E2E
 reservations.  In order to reduce disruptions, the Aggregator SHOULD
 use "make-before-break" procedures as described in [RSVP-TE] to alter
 the TE tunnel bandwidth.
 If sufficient bandwidth is not available on the final TE tunnel, the
 Aggregator MUST follow the normal RSVP procedure for a reservation
 being placed with insufficient bandwidth to support it.  That is, the
 reservation is not installed and a ResvError is sent back toward the
 receiver.
 If the tunnel did change during the final mapping, the Aggregator
 MUST first resend to the Deaggregator an E2E Path message with the
 IF_ID RSVP_HOP data interface identification identifying the final TE
 tunnel.  If needed, the ADSPEC information in this E2E Path message
 SHOULD be updated.  Then the Aggregator MUST
  1. either drop the E2E Resv message
  1. or proceed with the processing of the E2E Resv in the same

manner as in the case where the tunnel did not change (described

      above).

Faucheur Standards Track [Page 13] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 In the former case, admission control over the final TE tunnel (and
 forwarding of E2E Resv message upstream toward the sender) would only
 occur when the Aggregator received the subsequent E2E Resv message
 (that will be sent by the Deaggregator in response to the resent E2E
 Path).  In the latter case, admission control over the final tunnel
 is carried out immediately by the Aggregator, and if successful the
 E2E Resv message is generated upstream toward the sender.
 Upon receipt of an E2E ResvConf from the Aggregator, the Deaggregator
 MUST forward the E2E ResvConf downstream toward the receiver.  In
 doing so, the Deaggregator sets the destination address in the IP
 header of the E2E ResvConf message to the IP address found in the
 RESV_CONFIRM object of the corresponding Resv.  The Deaggregator also
 sets the Router Alert.

4.7. Forwarding of E2E Traffic by the Aggregator

 When the Aggregator receives a data packet belonging to an E2E
 reservations currently mapped over a given TE tunnel, the Aggregator
 MUST encapsulate the packet into that TE tunnel.
 If the Aggregator and Deaggregator are also acting as IPsec Security
 Gateways, the Aggregator MUST also encapsulate the data packet into
 the relevant IPsec tunnel terminating on the Deaggregator before
 transmission into the MPLS TE tunnel.

4.8. Removal of E2E Reservations

 E2E reservations are removed in the usual way via PathTear, ResvTear,
 timeout, or as the result of an error condition.  When a reservation
 is removed, the Aggregator MUST update its local view of the
 resources available on the corresponding TE tunnel accordingly.

4.9. Removal of the TE Tunnel

 Should a TE tunnel go away (presumably due to a configuration change,
 route change, or policy event), the Aggregator behaves much like a
 conventional RSVP router in the face of a link failure.  That is, it
 may try to forward the Path messages onto another tunnel, if routing
 and policy permit, or it may send Path_Error messages to the sender
 if a suitable tunnel does not exist.  In case the Path messages are
 forwarded onto another tunnel, which terminates on a different
 Deaggregator, or the reservation is torn down via Path Error
 messages, the reservation state established on the router acting as
 the Deaggregator before the TE tunnel went away, will time out since
 it will no longer be refreshed.

Faucheur Standards Track [Page 14] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

4.10. Example Signaling Flow

             Aggregator                      Deaggregator
                (*)
                           RSVP-TE Path
                     =========================>
                           RSVP-TE Resv
                     <=========================
               (**)
 E2E Path
   -------------->
                (1)
                           E2E Path
                  ------------------------------->
                                                 (2)
                                                     E2E Path
                                                     ----------->
                                                         E2E Resv
                                                     <-----------
                                                  (3)
                           E2E Resv
                   <-----------------------------
                (4)
       E2E Resv
   <-------------
   (*)  Aggregator is triggered to pre-establish the TE tunnel(s)
   (**) TE tunnel(s) are pre-established
   (1)  Aggregator tentatively selects the TE tunnel and forwards
        E2E path to Deaggregator
   (2)  Deaggregator forwards the E2E Path toward the receiver
   (3)  Deaggregator forwards the E2E Resv to the Aggregator
   (4)  Aggregator selects final TE tunnel, checks that there is
        sufficient bandwidth on TE tunnel, and forwards E2E Resv to
        PHOP.  If final tunnel is different from tunnel tentatively
        selected, the Aggregator re-sends an E2E Path with an updated
        IF_ID RSVP_HOP and possibly an updated ADSPEC.

Faucheur Standards Track [Page 15] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

5. IPv4 and IPv6 Applicability

 The procedures defined in this document are applicable to all the
 following cases:
    (1)  Aggregation of E2E IPv4 RSVP reservations over IPv4 TE
         tunnels.
    (2)  Aggregation of E2E IPv6 RSVP reservations over IPv6 TE
         tunnels.
    (3)  Aggregation of E2E IPv6 RSVP reservations over IPv4 TE
         tunnels, provided a mechanism such as [6PE] is used by the
         Aggregator and Deaggregator for routing of IPv6 traffic over
         an IPv4 MPLS core.
    (4)  Aggregation of E2E IPv4 RSVP reservations over IPv6 TE
         tunnels, provided a mechanism is used by the Aggregator and
         Deaggregator for routing IPv4 traffic over IPv6 MPLS.

6. E2E Reservations Applicability

 The procedures defined in this document are applicable to many types
 of E2E RSVP reservations including the following cases:
    (1)  The E2E RSVP reservation is a per-flow reservation where the
         flow is characterized by the usual 5-tuple
    (2)  The E2E reservation is an aggregate reservation for multiple
         flows as described in [RSVP-AGG] or [RSVP-GEN-AGG] where the
         set of flows is characterized by the <source address,
         destination address, DSCP>
    (3)  The E2E reservation is a reservation for an IPsec protected
         flow.  For example, where the flow is characterized by the
         <source address, destination address, SPI> as described in
         [RSVP-IPSEC].

7. Example Deployment Scenarios

7.1. Voice and Video Reservations Scenario

 An example application of the procedures specified in this document
 is admission control of voice and video in environments with a very
 high number of hosts.  In the example illustrated below, hosts
 generate E2E per-flow reservations for each of their video streams
 associated with a video-conference, each of their audio streams
 associated with a video-conference and each of their voice calls.

Faucheur Standards Track [Page 16] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 These reservations are aggregated over MPLS DS-TE tunnels over the
 packet core.  The mapping policy defined by the user may be that all
 the reservations for audio and voice streams are mapped onto DS-TE
 tunnels of Class-Type 1, while reservations for video streams are
 mapped onto DS-TE tunnels of Class-Type 0.
  1. —– ——

| H |# ——- ——– #| H |

 |    |\#|     |          -----           |      |#/|    |
 -----| \| Agg |          | T |           | Deag |/ ------
         |     |==========================|      |
 ------ /|     |::::::::::::::::::::::::::|      |\ ------
 | H  |/#|     |          -----           |      |#\| H  |
 |    |# -------                          -------- #|    |
 ------                                             ------
 H     = Host
 Agg   = Aggregator (TE tunnel Head-end)
 Deagg = Deaggregator (TE tunnel Tail-end)
 T     = Transit LSR
 /     = E2E RSVP reservation for a Voice flow
 #     = E2E RSVP reservation for a Video flow
 ==    = DS-TE tunnel from Class-Type 1
 ::    = DS-TE tunnel from Class-Type 0

7.2. PSTN/3G Voice Trunking Scenario

 An example application of the procedures specified in this document
 is voice call admission control in large-scale telephony trunking
 environments.  A Trunk VoIP Gateway may generate one aggregate RSVP
 reservation for all the calls in place toward another given remote
 Trunk VoIP Gateway (with resizing of this aggregate reservation in a
 step function depending on the current number of calls).  In turn,
 these reservations may be aggregated over MPLS TE tunnels over the
 packet core so that tunnel Head-ends act as Aggregators and perform
 admission control of Trunk Gateway reservations into MPLS TE tunnels.
 The MPLS TE tunnels may be protected by MPLS Fast Reroute.  This
 scenario is illustrated below:

Faucheur Standards Track [Page 17] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

  1. —– ——

| GW |\ ——- ——– /| GW |

 |    |\\|     |          -----           |      |//|    |
 -----| \| Agg |          | T |           | Deag |/ ------
         |     |==========================|      |
 ------ /|     |          |   |           |      |\ ------
 | GW |//|     |          -----           |      |\\| GW |
 |    |/ -------                          -------- \|    |
 ------                                             ------
 GW    = VoIP Gateway
 Agg   = Aggregator (TE tunnel Head-end)
 Deagg = Deaggregator (TE tunnel Tail-end)
 T     = Transit LSR
 /     = Aggregate Gateway to Gateway E2E RSVP reservation
 ==    = TE tunnel

8. Security Considerations

 In the environments concerned by this document, RSVP messages are
 used to control resource reservations for E2E flows outside the MPLS
 region as well as to control resource reservations for MPLS TE
 tunnels inside the MPLS region.  To ensure the integrity of the
 associated reservation and admission control mechanisms, the
 mechanisms defined in [RSVP-CRYPTO1] and [RSVP-CRYPTO2] can be used.
 The mechanisms protect the integrity of RSVP messages hop-by-hop and
 provide node authentication, thereby protecting against corruption
 and spoofing of RSVP messages.  These hop-by-hop integrity mechanisms
 can naturally be used to protect the RSVP messages used for E2E
 reservations outside the MPLS region, to protect RSVP messages used
 for MPLS TE tunnels inside the MPLS region, or for both.  These hop-
 by-hop RSVP integrity mechanisms can also be used to protect RSVP
 messages used for E2E reservations when those transit through the
 MPLS region.  This is because the Aggregator and Deaggregator behave
 as RSVP neighbors from the viewpoint of the E2E flows (even if they
 are not necessarily IP neighbors nor RSVP-TE neighbors).  In that
 case, the Aggregator and Deaggregator need to use a pre-shared
 secret.
 As discussed in Section 6 of [RSVP-TE], filtering of traffic
 associated with an MPLS TE tunnel can only be done on the basis of an
 MPLS label, instead of the 5-tuple of conventional RSVP reservation
 as per [RSVP].  Thus, as explained in [RSVP-TE], an administrator may
 wish to limit the domain over which TE tunnels (which are used for
 aggregation of RSVP E2E reservations as per this specification) can
 be established.  See Section 6 of [RSVP-TE] for a description of how

Faucheur Standards Track [Page 18] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 filtering of RSVP messages associated with MPLS TE tunnels can be
 deployed to that end.
 This document is based in part on [RSVP-AGG], which specifies
 aggregation of RSVP reservations.  Section 5 of [RSVP-AGG] raises the
 point that because many E2E flows may share an aggregate reservation,
 if the security of an aggregate reservation is compromised, there is
 a multiplying effect in the sense that it can in turn compromise the
 security of many E2E reservations whose quality of service depends on
 the aggregate reservation.  This concern applies also to RSVP
 Aggregation over TE tunnels as specified in the present document.
 However, the integrity of MPLS TE tunnels operation can be protected
 using the mechanisms discussed in the previous paragraphs.  Also,
 while [RSVP-AGG] specifies RSVP Aggregation over dynamically
 established aggregate reservations, the present document restricts
 itself to RSVP Aggregation over pre-established TE tunnels.  This
 further reduces the security risks.
 In the case where the Aggregators dynamically resize the TE tunnels
 based on the current level of reservation, there are risks that the
 TE tunnels used for RSVP aggregation hog resources in the core, which
 could prevent other TE tunnels from being established.  There are
 also potential risks that such resizing results in significant
 computation and signaling as well as churn on tunnel paths.  Such
 risks can be mitigated by configuration options allowing control of
 TE tunnel dynamic resizing (maximum TE tunnel size, maximum resizing
 frequency, etc.), and/or possibly by the use of TE preemption.
 Section 5 of [RSVP-AGG] also discusses a security issue specific to
 RSVP aggregation related to the necessary modification of the IP
 Protocol number in RSVP E2E Path messages that traverses the
 aggregation region.  This security issue does not apply to the
 present document since aggregation of RSVP reservation over TE
 tunnels does not use this approach of changing the protocol number in
 RSVP messages.
 Section 7 of [LSP-HIER] discusses security considerations stemming
 from the fact that the implicit assumption of a binding between data
 interface and the interface over which a control message is sent is
 no longer valid.  These security considerations are equally
 applicable to the present document.
 If the Aggregator and Deaggregator are also acting as IPsec Security
 Gateways, the Security Considerations of [SEC-ARCH] apply.

Faucheur Standards Track [Page 19] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

9. Acknowledgments

 This document builds on the [RSVP-AGG], [RSVP-TUN], and [LSP-HIER]
 specifications.  We would like to thank Tom Phelan, John Drake, Arthi
 Ayyangar, Fred Baker, Subha Dhesikan, Kwok-Ho Chan, Carol Iturralde,
 and James Gibson for their input into this document.

10. Normative References

 [CONTROLLED]   Wroclawski, J., "Specification of the Controlled-Load
                Network Element Service", RFC 2211, September 1997.
 [DIFFSERV]     Blake, S., Black, D., Carlson, M., Davies, E., Wang,
                Z., and W. Weiss, "An Architecture for Differentiated
                Service", RFC 2475, December 1998.
 [DSTE-PROTO]   Le Faucheur, F., "Protocol Extensions for Support of
                Diffserv-aware MPLS Traffic Engineering", RFC 4124,
                June 2005.
 [GUARANTEED]   Shenker, S., Partridge, C., and R. Guerin,
                "Specification of Guaranteed Quality of Service", RFC
                2212, September 1997.
 [INT-DIFF]     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.
 [INT-SERV]     Braden, R., Clark, D., and S. Shenker, "Integrated
                Services in the Internet Architecture: an Overview",
                RFC 1633, June 1994.
 [KEYWORDS]     Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.
 [LSP-HIER]     Kompella, K. and Y. Rekhter, "Label Switched Paths
                (LSP) Hierarchy with Generalized Multi-Protocol Label
                Switching (GMPLS) Traffic Engineering (TE)", RFC 4206,
                October 2005.
 [MPLS-TE]      Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and
                J. McManus, "Requirements for Traffic Engineering Over
                MPLS", RFC 2702, September 1999.

Faucheur Standards Track [Page 20] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 [RSVP]         Braden, R., Zhang, L., Berson, S., Herzog, S., and S.
                Jamin, "Resource ReSerVation Protocol (RSVP) --
                Version 1 Functional Specification", RFC 2205,
                September 1997.
 [RSVP-AGG]     Baker, F., Iturralde, C., Le Faucheur, F., and B.
                Davie, "Aggregation of RSVP for IPv4 and IPv6
                Reservations", RFC 3175, September 2001.
 [RSVP-CRYPTO1] Baker, F., Lindell, B., and M. Talwar, "RSVP
                Cryptographic Authentication", RFC 2747, January 2000.
 [RSVP-CRYPTO2] Braden, R. and L. Zhang, "RSVP Cryptographic
                Authentication -- Updated Message Type Value", RFC
                3097, April 2001.
 [RSVP-TE]      Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan,
                V., and G. Swallow, "RSVP-TE: Extensions to RSVP for
                LSP Tunnels", RFC 3209, December 2001.
 [SEC-ARCH]     Kent, S. and K. Seo, "Security Architecture for the
                Internet Protocol", RFC 4301, December 2005.

11. Informative References

 [6PE]          De Clercq, J., Ooms, D., Prevost, S., and F. Le
                Faucheur, "Connecting IPv6 Islands over IPv4 MPLS
                using IPv6 Provider Edge Routers (6PE)", RFC 4798,
                February 2007.
 [AUTOMESH]     Vasseur and Leroux, "Routing extensions for discovery
                of Multiprotocol (MPLS) Label Switch Router (LSR)
                Traffic Engineering (TE) mesh membership", Work in
                Progress.
 [DIFF-MPLS]    Le Faucheur, F., Wu, L., Davie, B., Davari, S.,
                Vaananen, P., Krishnan, R., Cheval, P., and J.
                Heinanen, "Multi-Protocol Label Switching (MPLS)
                Support of Differentiated Services", RFC 3270, May
                2002.
 [DSTE-REQ]     Le Faucheur, F. and W. Lai, "Requirements for Support
                of Differentiated Services-aware MPLS Traffic
                Engineering", RFC 3564, July 2003.
 [L-RSVP]       Manner, et al., Localized RSVP for Controlling RSVP
                Proxies, Work in Progress.

Faucheur Standards Track [Page 21] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 [RSVP-APPID]   Yadav, S., Yavatkar, R., Pabbati, R., Ford, P., Moore,
                T., Herzog, S., and R. Hess, "Identity Representation
                for RSVP", RFC 3182, October 2001.
 [RSVP-GEN-AGG] Le Faucheur, R., Davie, B., Bose, P., Martin, L.,
                Christou, C., Davenport, M., and A. Hamilton, "Generic
                Aggregate Resource ReSerVation Protocol (RSVP)
                Reservations", Work in Progress, January 2007.
 [RSVP-IPSEC]   Berger, L. and T. O'Malley, "RSVP Extensions for IPSEC
                Data Flows", RFC 2207, September 1997.
 [RSVP-PREEMP]  Herzog, S., "Signaled Preemption Priority Policy
                Element", RFC 3181, October 2001.
 [RSVP-PROXY1]  Gai, et al., RSVP Proxy, Work in Progress.
 [RSVP-PROXY2]  Le Faucheur, et al., RSVP Proxy Approaches, Work in
                Progress.
 [RSVP-TUN]     Terzis, A., Krawczyk, J., Wroclawski, J., and L.
                Zhang, "RSVP Operation Over IP Tunnels", RFC 2746,
                January 2000.
 [SIP-RSVP]     Camarillo, G., Marshall, W., and J. Rosenberg,
                "Integration of Resource Management and Session
                Initiation Protocol (SIP)", RFC 3312, October 2002.

Faucheur Standards Track [Page 22] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

Appendix A - Optional Use of RSVP Proxy on RSVP Aggregator

 A number of approaches ([RSVP-PROXY1],[RSVP-PROXY2], [L-RSVP]) have
 been, or are being, discussed in the IETF in order to allow a network
 node to behave as an RSVP proxy which:
  1. originates the Resv Message (in response to the Path message) on

behalf of the destination node

  1. originates the Path message (in response to some trigger) on

behalf of the source node.

 We observe that such approaches may optionally be used in conjunction
 with the aggregation of RSVP reservations over MPLS TE tunnels as
 specified in this document.  In particular, we consider the case
 where the RSVP Aggregator/Deaggregator also behaves as the RSVP
 proxy.
 The information in this Appendix is purely informational and
 illustrative.
 As discussed in [RSVP-PROXY1]:
 "The proxy functionality does not imply merely generating a single
 Resv message.  Proxying the Resv involves installing state in the
 node doing the proxy i.e. the proxying node should act as if it had
 received a Resv from the true endpoint.  This involves reserving
 resources (if required), sending periodic refreshes of the Resv
 message and tearing down the reservation if the Path is torn down."
 Hence, when behaving as the RSVP Proxy, the RSVP Aggregator may
 effectively perform resource reservation over the MPLS TE tunnel (and
 hence over the whole segment between the RSVP Aggregator and the RSVP
 Deaggregator) even if the RSVP signaling only takes place upstream of
 the MPLS TE tunnel (i.e., between the host and the RSVP aggregator).
 Also, the RSVP Proxy can generate the Path message on behalf of the
 remote source host in order to achieve reservation in the return
 direction (i.e., from RSVP aggregator/Deaggregator to host).

Faucheur Standards Track [Page 23] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 The resulting Signaling Flow is illustrated below, covering
 reservations for both directions:
 |----|       |--------------|  |------|   |--------------|     |----|
 |    |       | Aggregator/  |  | MPLS |   | Aggregator/  |     |    |
 |Host|       | Deaggregator/|  | cloud|   | Deaggregator/|     |Host|
 |    |       | RSVP Proxy   |  |      |   | RSVP Proxy   |     |    |
 |----|       |--------------|  |------|   |--------------|     |----|
                    ==========TE Tunnel==========>
                    <========= TE Tunnel==========
   Path                                                      Path
  ------------> (1)-\                          /-(i)  <----------
         Resv       |                         |        Resv
  <------------ (2)-/                          \-(ii) ------------>
         Path                                            Path
  <------------ (3)                              (iii) ------------>
   Resv                                                        Resv
  ------------>                                        <------------
 (1)(i)  : Aggregator/Deaggregator/Proxy receives Path message,
           selects the TE tunnel, performs admission control over the
           TE tunnel.  (1) and (i) happen independently of each other.
 (2)(ii)  : Aggregator/Deaggregator/Proxy generates the Resv message
           toward Host.  (2) is triggered by (1) and (ii) is triggered
           by (i).  Before generating this Resv message, the
           Aggregator/Proxy performs admission control of the
           corresponding reservation over the TE tunnel that will
           eventually carry the corresponding traffic.
 (3)(iii) : Aggregator/Deaggregator/Proxy generates the Path message
           toward Host for reservation in return direction.  The
           actual trigger for this depends on the actual RSVP proxy
           solution.  As an example, (3) and (iii) may simply be
           triggered respectively by (1) and (i).
 Note that the details of the signaling flow may vary slightly
 depending on the actual approach used for RSVP Proxy.  For example,
 if the [L-RSVP] approach was used instead of [RSVP-PROXY1], an
 additional PathRequest message would be needed from host to
 Aggregator/Deaggregator/Proxy in order to trigger the generation of
 the Path message for return direction.
 But regardless of the details of the call flow and of the actual RSVP
 Proxy approach, RSVP proxy may optionally be deployed in combination
 with RSVP Aggregation over MPLS TE tunnels, in such a way that

Faucheur Standards Track [Page 24] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 ensures (when used on both the Host-Aggregator and Deaggregator-Host
 sides, and when both end systems support RSVP):
    (i)   admission control and resource reservation is performed on
          every segment of the end-to-end path (i.e., between source
          host and Aggregator, over the TE tunnel between the
          Aggregator and Deaggregator that itself has been subject to
          admission control by MPLS TE, between Deaggregator and
          destination host).
    (ii)  this is achieved in both directions.
    (iii) RSVP signaling is localized between hosts and
          Aggregator/Deaggregator, which may result in significant
          reduction in reservation establishment delays (and in turn
          in post-dial delay in the case where these reservations are
          pre-conditions for voice call establishment), particularly
          in the case where the MPLS TE tunnels span long distances
          with high propagation delays.

Appendix B - Example Usage of RSVP Aggregation over DSTE Tunnels for

           VoIP Call Admission Control (CAC)
 This Appendix presents an example scenario where the mechanisms
 described in this document are used, in combination with other
 mechanisms specified by the IETF, to achieve Call Admission Control
 (CAC) of Voice over IP (VoIP) traffic over the packet core.
 The information in this Appendix is purely informational and
 illustrative.
 Consider the scenario depicted in Figure B1.  VoIP Gateways GW1 and
 GW2 are both signaling and media gateways.  They are connected to an
 MPLS network via edge routers PE1 and PE2, respectively.  In each
 direction, a DSTE tunnel passes from the Head-end edge router,
 through core network P routers, to the Tail-end edge router.  GW1 and
 GW2 are RSVP-enabled.  The RSVP reservations established by GW1 and
 GW2 are aggregated by PE1 and PE2 over the DS-TE tunnels.  For
 reservations going from GW1 to GW2, PE1 serves as the
 Aggregator/Head-end and PE2 serves as the Deaggregator/Tail-end.  For
 reservations going from GW2 to GW2, PE2 serves as the
 Aggregator/Head-end and PE1 serves as the Deaggregator/Tail-end.
 To determine whether there is sufficient bandwidth in the MPLS core
 to complete a connection, the originating and destination GWs each
 send for each connection a Resource Reservation Protocol (RSVP)
 bandwidth request to the network PE router to which it is connected.
 As part of its Aggregator role, the PE router effectively performs

Faucheur Standards Track [Page 25] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 admission control of the bandwidth request generated by the GW onto
 the resources of the corresponding DS-TE tunnel.
 In this example, in addition to behaving as Aggregator/Deaggregator,
 PE1 and PE2 behave as RSVP proxy.  So when a PE receives a Path
 message from a GW, it does not propagate the Path message any
 further.  Rather, the PE performs admission control of the bandwidth
 signaled in the Path message over the DSTE tunnel toward the
 destination.  Assuming there is enough bandwidth available on that
 tunnel, the PE adjusts its bookkeeping of remaining available
 bandwidth on the tunnel and generates a Resv message back toward the
 GW to confirm resources have been reserved over the DSTE tunnel.
                             ,-.     ,-.
                       _.---'   `---'   `-+
                   ,-''   +------------+  :
                  (       |            |   `.
                   \     ,'    CCA     `.    :
                    \  ,' |            | `.  ;
                     ;'   +------------+   `._
                   ,'+                     ; `.
                 ,' -+   Application Layer'    `.
            SIP,'     `---+       |    ;         `.SIP
             ,'            `------+---'            `.
           ,'                                        `.
         ,'                                            `.
       ,'                  ,-.        ,-.                `.
     ,'                ,--+   `--+--'-   --'\              `._
  +-`--+_____+------+  {   +----+   +----+   `. +------+_____+----+
  |GW1 | RSVP|      |______| P  |___| P  |______|      | RSVP|GW2 |
  |    |-----| PE1  |  {   +----+   +----+    /+| PE2  |-----|    |
  |    |     |      |==========================>|      |     |    |
  +-:--+ RTP |      |<==========================|      | RTP +-:--+
   _|..__    +------+  {     DSTE Tunnels    ;  +------+ __----|--.
 _,'    \-|          ./                    -'._          /         |
 | Access  \         /        +----+           \,        |_ Access |
 | Network   |       \_       | P  |             |       /  Network |
 |          /          `|     +----+            /        |         '
 `--.  ,.__,|           |    IP/MPLS Network   /         '---'- ----'
    '`'  ''             ' .._,,'`.__   _/ '---'                |
     |                             '`'''                       |
     C1                                                        C2
        Figure B1.  Integration of SIP Resource Management and
                 RSVP Aggregation over MPLS TE Tunnels
 [SIP-RSVP] discusses how network quality of service can be made a
 precondition for establishment of sessions initiated by the Session

Faucheur Standards Track [Page 26] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

 Initiation Protocol (SIP).  These preconditions require that the
 participant reserve network resources before continuing with the
 session.  The reservation of network resources are performed through
 a signaling protocol such as RSVP.
 Through the collaboration between SIP resource management, RSVP
 signaling, RSVP Aggregation and DS-TE as described above, we see
 that:
    a) the PE and GW collaborate to determine whether there is enough
       bandwidth on the tunnel between the calling and called GWs to
       accommodate the connection,
    b) the corresponding accept/reject decision is communicated to the
       GWs on a connection-by-connection basis, and
    c) the PE can optimize network resources by dynamically adjusting
       the bandwidth of each tunnel according to the load over that
       tunnel.  For example, if a tunnel is operating at near
       capacity, the network may dynamically adjust the tunnel size
       within a set of parameters.
 We note that admission Control of voice calls over the core network
 capacity is achieved in a hierarchical manner whereby:
  1. DSTE tunnels are subject to Admission Control over the resources

of the MPLS TE core

  1. Voice calls are subject to CAC over the DSTE tunnel bandwidth
 This hierarchy is a key element in the scalability of this CAC
 solution for voice calls over an MPLS Core.
 It is also possible for the GWs to use aggregate RSVP reservations
 themselves instead of per-call RSVP reservations.  For example,
 instead of setting one reservation for each call GW1 has in place
 toward GW2, GW1 may establish one (or a small number of) aggregate
 reservations as defined in [RSVP-AGG] or [RSVP-GEN-AGG], which is
 used for all (or a subset of all) the calls toward GW2.  This
 effectively provides an additional level of hierarchy whereby:
  1. DSTE tunnels are subject to Admission Control over the resources

of the MPLS TE core

  1. Aggregate RSVP reservations (for the calls from one GW to

another GW) are subject to Admission Control over the DSTE

      tunnels (as per the "RSVP Aggregation over TE Tunnels"
      procedures defined in this document)

Faucheur Standards Track [Page 27] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

  1. Voice calls are subject to CAC by the GW over the aggregate

reservation toward the appropriate destination GW.

 This pushes even further the scalability limits of this voice CAC
 architecture.

Faucheur Standards Track [Page 28] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

Contributing Authors

 This document was the collective work of several authors.  The text
 and content were contributed by the editor and the co-authors listed
 below.
 Michael DiBiasio
 Cisco Systems, Inc.
 300 Beaver Brook Road
 Boxborough, MA 01719
 USA
 EMail: dibiasio@cisco.com
 Bruce Davie
 Cisco Systems, Inc.
 300 Beaver Brook Road
 Boxborough, MA 01719
 USA
 EMail: bdavie@cisco.com
 Christou Christou
 Booz Allen Hamilton
 8283 Greensboro Drive
 McLean, VA 22102
 USA
 EMail: christou_chris@bah.com
 Michael Davenport
 Booz Allen Hamilton
 8283 Greensboro Drive
 McLean, VA 22102
 USA
 EMail: davenport_michael@bah.com
 Jerry Ash
 AT&T
 200 Laurel Avenue
 Middletown, NJ 07748
 USA
 EMail: gash@att.com
 Bur Goode
 AT&T
 32 Old Orchard Drive
 Weston, CT 06883
 USA
 EMail: bgoode@att.com

Faucheur Standards Track [Page 29] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

Editor's Address

 Francois Le Faucheur
 Cisco Systems, Inc.
 Village d'Entreprise Green Side - Batiment T3
 400, Avenue de Roumanille
 06410 Biot Sophia-Antipolis
 France
 EMail: flefauch@cisco.com

Faucheur Standards Track [Page 30] RFC 4804 RSVP Aggregation over MPLS TE Tunnels February 2007

Full Copyright Statement

 Copyright (C) The IETF Trust (2007).
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 contained in BCP 78, and except as set forth therein, the authors
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Faucheur Standards Track [Page 31]

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