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rfc:rfc3726

Network Working Group M. Brunner, Ed. Request for Comments: 3726 NEC Category: Informational April 2004

               Requirements for Signaling Protocols

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

 This document defines requirements for signaling across different
 network environments, such as across administrative and/or technology
 domains.  Signaling is mainly considered for Quality of Service (Qos)
 such as the Resource Reservation Protocol (RSVP).  However, in recent
 years, several other applications of signaling have been defined.
 For example, signaling for label distribution in Multiprotocol Label
 Switching (MPLS) or signaling to middleboxes.  To achieve wide
 applicability of the requirements, the starting point is a diverse
 set of scenarios/use cases concerning various types of networks and
 application interactions.  This document presents the assumptions
 before listing the requirements.  The requirements are grouped
 according to areas such as architecture and design goals, signaling
 flows, layering, performance, flexibility, security, and mobility.

Brunner Informational [Page 1] RFC 3726 Requirements for Signaling Protocols April 2004

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.1.  Keywords . . . . . . . . . . . . . . . . . . . . . . . .  5
 2.  Terminology. . . . . . . . . . . . . . . . . . . . . . . . . .  5
 3.  Problem Statement and Scope. . . . . . . . . . . . . . . . . .  6
 4.  Assumptions and Exclusions . . . . . . . . . . . . . . . . . .  8
     4.1.  Assumptions and Non-Assumptions. . . . . . . . . . . . .  8
     4.2.  Exclusions . . . . . . . . . . . . . . . . . . . . . . .  9
 5.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.1.  Architecture and Design Goals. . . . . . . . . . . . . . 11
           5.1.1.  NSIS SHOULD Provide Availability Information
                   on Request . . . . . . . . . . . . . . . . . . . 11
           5.1.2.  NSIS MUST be Designed Modularly. . . . . . . . . 11
           5.1.3.  NSIS MUST Decouple Protocol and Information. . . 12
           5.1.4.  NSIS MUST Support Independence of Signaling and
                   Network Control Paradigm . . . . . . . . . . . . 12
           5.1.5.  NSIS SHOULD be Able to Carry Opaque Objects. . . 12
     5.2.  Signaling Flows. . . . . . . . . . . . . . . . . . . . . 12
           5.2.1.  The Placement of NSIS Initiator, Forwarder, and
                   Responder Anywhere in the Network MUST be
                   Allowed. . . . . . . . . . . . . . . . . . . . . 12
           5.2.2.  NSIS MUST Support Path-Coupled and MAY Support
                   Path-Decoupled Signaling . . . . . . . . . . . . 13
           5.2.3.  Concealment of Topology and Technology
                   Information SHOULD be Possible . . . . . . . . . 13
           5.2.4.  Transparent Signaling Through Networks SHOULD be
                   Possible . . . . . . . . . . . . . . . . . . . . 13
     5.3.  Messaging. . . . . . . . . . . . . . . . . . . . . . . . 13
           5.3.1.  Explicit Erasure of State MUST be Possible . . . 13
           5.3.2.  Automatic Release of State After Failure MUST be
                   Possible . . . . . . . . . . . . . . . . . . . . 14
           5.3.3.  NSIS SHOULD Allow for Sending Notifications
                   Upstream . . . . . . . . . . . . . . . . . . . . 14
           5.3.4.  Establishment and Refusal to set up State MUST
                   be Notified. . . . . . . . . . . . . . . . . . . 15
           5.3.5.  NSIS MUST Allow for Local Information Exchange . 15
     5.4.  Control Information. . . . . . . . . . . . . . . . . . . 16
           5.4.1.  Mutability Information on Parameters SHOULD be
                   Possible . . . . . . . . . . . . . . . . . . . . 16
           5.4.2.  It SHOULD be Possible to Add and Remove Local
                   Domain Information . . . . . . . . . . . . . . . 16
           5.4.3.  State MUST be Addressed Independent of Flow
                   Identification . . . . . . . . . . . . . . . . . 16
           5.4.4.  Modification of Already Established State SHOULD
                   be Seamless. . . . . . . . . . . . . . . . . . . 16
           5.4.5.  Grouping of Signaling for Several Micro-Flows
                   MAY be Provided. . . . . . . . . . . . . . . . . 17

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     5.5.  Performance. . . . . . . . . . . . . . . . . . . . . . . 17
           5.5.1.  Scalability. . . . . . . . . . . . . . . . . . . 17
           5.5.2.  NSIS SHOULD Allow for Low Latency in Setup . . . 18
           5.5.3.  NSIS MUST Allow for Low Bandwidth Consumption
                   for the Signaling Protocol . . . . . . . . . . . 18
           5.5.4.  NSIS SHOULD Allow to Constrain Load on Devices . 18
           5.5.5.  NSIS SHOULD Target the Highest Possible Network
                   Utilization. . . . . . . . . . . . . . . . . . . 18
     5.6.  Flexibility. . . . . . . . . . . . . . . . . . . . . . . 19
           5.6.1.  Flow Aggregation . . . . . . . . . . . . . . . . 19
           5.6.2.  Flexibility in the Placement of the NSIS
                   Initiator/Responder. . . . . . . . . . . . . . . 19
           5.6.3.  Flexibility in the Initiation of State Change. . 19
           5.6.4.  SHOULD Support Network-Initiated State Change. . 19
           5.6.5.  Uni / Bi-directional State Setup . . . . . . . . 20
     5.7.  Security . . . . . . . . . . . . . . . . . . . . . . . . 20
           5.7.1.  Authentication of Signaling Requests . . . . . . 20
           5.7.2.  Request Authorization. . . . . . . . . . . . . . 20
           5.7.3.  Integrity Protection . . . . . . . . . . . . . . 20
           5.7.4.  Replay Protection. . . . . . . . . . . . . . . . 21
           5.7.5.  Hop-by-Hop Security. . . . . . . . . . . . . . . 21
           5.7.6.  Identity Confidentiality and Network Topology
                   Hiding . . . . . . . . . . . . . . . . . . . . . 21
           5.7.7.  Denial-of-Service Attacks. . . . . . . . . . . . 21
           5.7.8.  Confidentiality of Signaling Messages. . . . . . 22
           5.7.9.  Ownership of State . . . . . . . . . . . . . . . 22
     5.8.  Mobility . . . . . . . . . . . . . . . . . . . . . . . . 22
           5.8.1.  Allow Efficient Service Re-Establishment After
                   Handover . . . . . . . . . . . . . . . . . . . . 22
     5.9.  Interworking with Other Protocols and Techniques . . . . 22
           5.9.1.  MUST Interwork with IP Tunneling . . . . . . . . 22
           5.9.2.  MUST NOT Constrain Either to IPv4 or IPv6. . . . 23
           5.9.3.  MUST be Independent from Charging Model. . . . . 23
           5.9.4.  SHOULD Provide Hooks for AAA Protocols . . . . . 23
           5.9.5.  SHOULD work with Seamless Handoff Protocols. . . 23
           5.9.6.  MUST Work with Traditional Routing . . . . . . . 23
     5.10. Operational. . . . . . . . . . . . . . . . . . . . . . . 23
           5.10.1. Ability to Assign Transport Quality to Signaling
                   Messages . . . . . . . . . . . . . . . . . . . . 23
           5.10.2. Graceful Fail Over . . . . . . . . . . . . . . . 24
           5.10.3. Graceful Handling of NSIS Entity Problems. . . . 24
 6.  Security Considerations. . . . . . . . . . . . . . . . . . . . 24
 7.  Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 24
 8.  Appendix: Scenarios/Use Cases. . . . . . . . . . . . . . . . . 26
     8.1.  Terminal Mobility. . . . . . . . . . . . . . . . . . . . 26
     8.2.  Wireless Networks. . . . . . . . . . . . . . . . . . . . 28
     8.3.  An Example Scenario for 3G Wireless Networks . . . . . . 29
     8.4.  Wired Part of Wireless Network . . . . . . . . . . . . . 31

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     8.5.  Session Mobility . . . . . . . . . . . . . . . . . . . . 33
     8.6.  QoS Reservation/Negotiation from Access to Core Network. 34
     8.7.  QoS Reservation/Negotiation Over Administrative
           Boundaries . . . . . . . . . . . . . . . . . . . . . . . 34
     8.8.  QoS Signaling Between PSTN Gateways and Backbone Routers 35
     8.9.  PSTN Trunking Gateway. . . . . . . . . . . . . . . . . . 36
     8.10. An Application Requests End-to-End QoS Path from the
           Network. . . . . . . . . . . . . . . . . . . . . . . . . 38
     8.11. QOS for Virtual Private Networks . . . . . . . . . . . . 39
           8.11.1. Tunnel End Points at the Customer Premises . . . 39
           8.11.2. Tunnel End Points at the Provider Premises . . . 39
 9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 40
     9.1.  Normative References . . . . . . . . . . . . . . . . . . 40
     9.2.  Informative References . . . . . . . . . . . . . . . . . 40
 10. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 41
 11. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 42

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1. Introduction

 This document is the product of the Next Steps in Signaling (NSIS)
 Working Group.  It defines requirements for signaling across
 different network environments.  It does not list any problems of
 existing signaling protocols such as [RSVP].
 In order to derive requirements for signaling it is necessary to
 first have an idea of the scope within which they are applicable.
 Therefore, we list use cases and scenarios where an NSIS protocol
 could be applied.  The scenarios are used to help derive requirements
 and to test the requirements against use cases.
 The requirements listed are independent of any application.  However,
 resource reservation and QoS related issues are used as examples
 within the text.  However, QoS is not the only field where signaling
 is used in the Internet.  Signaling might also be used as a
 communication protocol to setup and maintain the state in middleboxes
 [RFC3234].
 This document does not cover requirements in relation to some
 networking areas, in particular, interaction with host and site
 multihoming.  We leave these for future analysis.

1.1. Keywords

 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 BCP 14, RFC 2119
 [KEYWORDS].

2. Terminology

 We list the most often used terms in the document.  However, they
 cannot be made precise without a more complete architectural model,
 and they are not meant to prescribe any solution in the document.
 Where applicable, they will be defined in protocol documents.
 NSIS Entity (NE): The function within a node, which implements an
 NSIS protocol.  In the case of path-coupled signaling, the NE will
 always be on the data path.
 NSIS Forwarder (NF): NSIS Entity between a NI and NR, which may
 interact with local state management functions in the network.  It
 also propagates NSIS signaling further through the network.
 NSIS Initiator (NI): NSIS Entity that starts NSIS signaling to set up
 or manipulate network state.

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 NSIS Responder (NR): NSIS Entity that terminates NSIS signaling and
 can optionally interact with applications as well.
 Flow: A traffic stream (sequence of IP packets between two end
 systems) for which a specific packet level treatment is provided.
 The flow can be unicast (uni- or bi-directional) or multicast.  For
 multicast, a flow can diverge into multiple flows as it propagates
 toward the receiver.  For multi-sender multicast, a flow can also
 diverge when viewed in the reverse direction (toward the senders).
 Data Path: The route across the networks taken by a flow or
 aggregate, i.e., which domains/subdomains it passes through and the
 egress/ingress points for each.
 Signaling Path: The route across the networks taken by a signaling
 flow or aggregate, i.e., which domains/subdomains it passes through
 and the egress/ingress points for each.
 Path-coupled signaling: A mode of signaling where the signaling
 messages follow a path that is tied to the data packets.  Signaling
 messages are routed only through nodes (NEs) that are in the data
 path.
 Path-decoupled signaling: Signaling with independent data and
 signaling paths.  Signaling messages are routed to nodes (NEs) which
 are not assumed to be on the data path, but which are (presumably)
 aware of it.  Signaling messages will always be directly addressed to
 the neighbor NE, and the NI/NR may have no relation at all with the
 ultimate data sender or receiver.
 Service: A generic something provided by one entity and consumed by
 another.  It can be constructed by allocating resources.  The network
 can provide it to users or a network node can provide it to packets.

3. Problem Statement and Scope

 We provide in the following a preliminary architectural picture as a
 basis for discussion.  We will refer to it in the following
 requirement sections.
 Note that this model is intended not to constrain the technical
 approach taken subsequently, simply to allow concrete phrasing of
 requirements (e.g., requirements about placement of the NSIS
 Initiator.)

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 Roughly, the scope of NSIS is assumed to be the interaction between
 the NSIS Initiator, NSIS Forwarder(s), and NSIS Responder including a
 protocol to carry the information, and the syntax/semantics of the
 information that is exchanged.  Further statements on
 assumptions/exclusions are given in the next Section.
 The main elements are:
 1. Something that starts the request for state to be set up in the
    network, the NSIS Initiator.
    This might be in the end system or within some other part of the
    network.  The distinguishing feature of the NSIS Initiator is that
    it acts on triggers coming (directly or indirectly) from the
    higher layers in the end systems.  It needs to map the services
    requested by them, and also provides feedback information to the
    higher layers, which might be used by transport layer algorithms
    or adaptive applications.
 2. Something that assists in managing state further along the
    signaling path, the NSIS Forwarder.
    The NSIS Forwarder does not interact with higher layers, but
    interacts with the NSIS Initiator, NSIS Responder, and possibly
    one or more NSIS Forwarders on the signaling path, edge-to-edge or
    end-to-end.
 3. Something that terminates the signaling path, the NSIS Responder.
    The NSIS responder might be in an end-system or within other
    equipment.  The distinguishing feature of the NSIS Responder is
    that it responds to requests at the end of a signaling path.
 4. The signaling path traverses an underlying network covering one or
    more IP hops.  The underlying network might use locally different
    technology.  For instance, QoS technology has to be provisioned
    appropriately for the service requested.  In the QoS example, an
    NSIS Forwarder maps service-specific information to technology-
    related QoS parameters and receives indications about success or
    failure in response.
 5. We can see the network at the level of domains/subdomains rather
    than individual routers (except in the special case that the
    domain contains one link).  Domains are assumed to be
    administrative entities.  So security requirements might apply
    differently for the signaling between the domains and within a
    domain.  Both cases we deal with in this document.

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4. Assumptions and Exclusions

4.1. Assumptions and Non-Assumptions

 1. The NSIS signaling could run end-to-end, end-to-edge, or edge-to-
    edge, or network-to-network (between providers), depending on what
    point in the network acts as NSIS initiator, and how far towards
    the other end of the network the signaling propagates.  In
    general, we could expect NSIS Forwarders to become more 'dense'
    towards the edges of the network, but this is not a requirement.
    For example, in the case of QoS, an over-provisioned domain might
    contain no NSIS Forwarders at all (and be NSIS transparent); at
    the other extreme, NSIS Forwarders might be placed at every
    router.  In the latter case, QoS provisioning can be carried out
    in a local implementation-dependent way without further signaling,
    whereas in the case of remote NSIS Forwarders, a protocol might be
    needed to control the routers along the path.  This protocol is
    then independent of the end-to-end NSIS signaling.
 2. We do not consider 'pure' end-to-end signaling that is not
    interpreted anywhere within the network.  Such signaling is a
    higher-layer issue and IETF protocols such as SIP etc. can be
    used.
 3. Where the signaling does cover several domains, we do not exclude
    that different signaling protocols are used in each domain.  We
    only place requirements on the universality of the control
    information that is being transported.  (The goals here would be
    to allow the use of signaling protocols, which are matched to the
    characteristics of the portion of the network being traversed.)
    Note that the outcome of NSIS work might result in various flavors
    of the same protocol.
 4. We assume that the service definitions a NSIS Initiator can ask
    for are known in advance of the signaling protocol running.  For
    instance in the QoS example, the service definition includes QoS
    parameters, lifetime of QoS guarantee etc., or any other service-
    specific parameters.
    There are many ways service requesters get to know about available
    services.  There might be standardized services, the definition
    can be negotiated together with a contract, the service definition
    is published in some on-line directory (e.g., at a Web page), and
    so on.
 5. We assume that there are means for the discovery of NSIS entities
    in order to know the signaling peers (solutions include static
    configuration, automatically discovered, or implicitly runs over

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    the right nodes along the data path, etc.).  The discovery of the
    NSIS entities has security implications that need to be addressed
    properly.  For some security mechanisms (i.e., Kerberos, pre-
    shared secret) it is required to know the identity of the other
    entity.  Hence the discovery mechanism may provide means to learn
    this identity, which is then later used to retrieve the required
    keys and parameters.
 6. NSIS assumes layer 3 routing and the determination of next data
    node selection is not done by NSIS.

4.2. Exclusions

 1.  Development of specific mechanisms and algorithms for application
     and transport layer adaptation are not considered, nor are the
     protocols that would support it.
 2.  Specific mechanisms (APIs and so on) for interaction between
     transport/applications and the network layer are not considered,
     except to clarify the requirements on the negotiation
     capabilities and information semantics that would be needed of
     the signaling protocol.
 3.  Specific mechanisms and protocols for provisioning or other
     network control functions within a domain/subdomain are not
     considered.  The goal is to reuse existing functions and
     protocols unchanged.  However, NSIS itself can be used for
     signaling within a domain/subdomain.
     For instance in the QoS example, it means that the setting of QoS
     mechanisms in a domain is out of scope, but if we have a tunnel,
     NSIS could also be used for tunnel setup with QoS guarantees.  It
     should be possible to exploit these mechanisms optimally within
     the end-to-end context.  Consideration of how to do this might
     generate new requirements for NSIS however.  For example, the
     information needed by a NSIS Forwarder to manage a radio
     subnetwork needs to be provided by the NSIS solution.
 4.  Specific mechanisms (APIs and so on) for interaction between the
     network layer and underlying provisioning mechanisms are not
     considered.
 5.  Interaction with resource management or other internal state
     management capabilities is not considered.  Standard protocols
     might be used for this.  This may imply requirements for the sort
     of information that should be exchanged between the NSIS
     entities.

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 6.  Security implications related to multicasting are outside the
     scope of the signaling protocol.
 7.  Service definitions and in particular QoS services and classes
     are out of scope.  Together with the service definition any
     definition of service specific parameters are not considered in
     this document.  Only the base NSIS signaling protocol for
     transporting the service information are addressed.
 8.  Similarly, specific methods, protocols, and ways to express
     service information in the Application/Session level are not
     considered (e.g., SDP, SIP, RTSP, etc.).
 9.  The specification of any extensions needed to signal information
     via application level protocols (e.g., SDP), and the mapping to
     NSIS information are considered outside of the scope of NSIS
     working group, as this work is in the direct scope of other IETF
     working groups (e.g., MMUSIC).
 10. Handoff decision and trigger sources: An NSIS protocol is not
     used to trigger handoffs in mobile IP, nor is it used to decide
     whether to handoff or not.  As soon as or in some situations even
     before a handoff happened, an NSIS protocol might be used for
     signaling for the particular service again.  The basic underlying
     assumption is that the route comes first (defining the path) and
     the signaling comes after it (following the path).  This doesn't
     prevent a signaling application at some node interacting with
     something that modifies the path, but the requirement is then
     just for NSIS to live with that possibility.  However, NSIS must
     interwork with several protocols for mobility management.
 11. Service monitoring is out of scope.  It is heavily dependent on
     the type of the application and or transport service, and in what
     scenario it is used.

5. Requirements

 This section defines more detailed requirements for a signaling
 solution, respecting the problem statement, scoping assumptions, and
 terminology considered earlier.  The requirements are in subsections,
 grouped roughly according to general technical aspects: architecture
 and design goals, topology issues, parameters, performance, security,
 information, and flexibility.
 Two general (and potentially contradictory) goals for the solution
 are that it should be applicable in a very wide range of scenarios,
 and at the same time be lightweight in implementation complexity and
 resource consumption requirements in NSIS Entities.  We use the terms

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 'access' and 'core' informally in the discussion of some particular
 requirements to refer to deployment conditions where particular
 protocol attributes, especially performance characteristics, have
 special importance.  Specifically, 'access' refers to lower capacity
 networks with fewer users and sessions.  'Core' refers to high
 capacity networks with a large number of users and sessions.
 One approach to this is that the solution could deal with certain
 requirements via modular components or capabilities, which are
 optional to implement or use in individual nodes.

5.1. Architecture and Design Goals

 This section contains requirements related to desirable overall
 characteristics of a solution, e.g., enabling flexibility, or
 independence of parts of the framework.

5.1.1. NSIS SHOULD Provide Availability Information on Request

 NSIS SHOULD provide a mechanism to check whether state to be setup is
 available without setting it up.  For the resource reservation
 example this translates into checking resource availability without
 performing resource reservation.  In some scenarios, e.g., the mobile
 terminal scenario, it is required to query, whether resources are
 available, without performing a reservation on the resource.

5.1.2. NSIS MUST be Designed Modularly

 A modular design allows for more lightweight implementations, if
 fewer features are needed.  Mutually exclusive solutions are
 supported.  Examples for modularity:
  1. Work over any kind of network (narrowband versus broadband,

error-prone versus reliable, …). This implies low bandwidth

    signaling, and elimination of redundant information MUST be
    supported if necessary.
  1. State setup for uni- and bi-directional flows is possible.
  1. Extensible in the future with different add-ons for certain

environments or scenarios.

  1. Protocol layering, where appropriate. This means NSIS MUST

provide a base protocol, which can be adapted to different

    environments.

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5.1.3. NSIS MUST Decouple Protocol and Information

 The signaling protocol MUST be clearly separated from the control
 information being transported.  This provides for the independent
 development of these two aspects of the solution, and allows for this
 control information to be carried within other protocols, including
 application layer ones, existing ones or those being developed in the
 future.  The flexibility gained in the transport of information
 allows for the applicability of the same protocol in various
 scenarios.
 However, note that the information carried needs to be standardized;
 otherwise interoperability is difficult to achieve.

5.1.4. NSIS MUST Support Independence of Signaling and Network Control

      Paradigm
 The signaling MUST be independent of the paradigm and mechanism of
 network control.  E.g., in the case of signaling for QoS, the
 independence of the signaling protocol from the QoS provisioning
 allows for using the NSIS protocol together with various QoS
 technologies in various scenarios.

5.1.5. NSIS SHOULD be Able to Carry Opaque Objects

 NSIS SHOULD be able to pass around opaque objects, which are
 interpreted only by some NSIS-capable nodes.

5.2. Signaling Flows

 This section contains requirements related to the possible signaling
 flows that should be supported, e.g., over what parts of the flow
 path, between what entities (end-systems, routers, middleboxes,
 management systems), in which direction.

5.2.1. The placement of NSIS Initiator, Forwarder, and Responder

      Anywhere in the Network MUST be Allowed
 The protocol MUST work in various scenarios such as host-to-network-
 to-host, edge-to-edge, (e.g., just within one provider's domain),
 user-to-network (from end system into the network, ending, e.g., at
 the entry to the network and vice versa), and network-to-network
 (e.g., between providers).
 Placing the NSIS Forwarder and NSIS Initiator functions at different
 locations allows for various scenarios to work with the same
 protocol.

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5.2.2. NSIS MUST Support Path-Coupled and MAY Support Path-Decoupled

      Signaling.
 The path-coupled signaling mode MUST be supported.  NSIS signaling
 messages are routed only through nodes (NEs) that are in the data
 path.
 However, there is a set of scenarios, where signaling is not on the
 data path.  Therefore, NSIS MAY support the path-decoupled signaling
 mode, where signaling messages are routed to nodes (NEs), which are
 not assumed to be on the data path, but which are aware of it.

5.2.3. Concealment of Topology and Technology Information SHOULD be

      Possible
 The NSIS protocol SHOULD allow for hiding the internal structure of a
 NSIS domain from end-nodes and from other networks.  Hence an
 adversary should not be able to learn the internal structure of a
 network with the help of the signaling protocol.
 In various scenarios, topology information should be hidden for
 various reasons.  From a business point of view, some administrations
 don't want to reveal the topology and technology used.

5.2.4. Transparent Signaling Through Networks SHOULD be Possible

 It SHOULD be possible that the signaling for some flows traverses
 path segments transparently, i.e., without interpretation at NSIS
 Forwarders within the network.  An example would be a subdomain
 within a core network, which only interpreted signaling for
 aggregates established at the domain edge, with the signaling for
 individual flows passing transparently through it.
 In other words, NSIS SHOULD work in hierarchical scenarios, where big
 pipes/trunks are setup using NSIS signaling, but also flows which run
 within that big pipe/trunk are setup using NSIS.

5.3. Messaging

5.3.1. Explicit Erasure of State MUST be Possible

 When state along a path is no longer necessary, e.g., because the
 application terminates, or because a mobile host experienced a hand-
 off, it MUST be possible to erase the state explicitly.

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5.3.2. Automatic Release of State After Failure MUST be Possible

 When the NSIS Initiator goes down, the state it requested in the
 network SHOULD be released, since it will most likely no longer be
 necessary.
 After detection of a failure in the network, any NSIS
 Forwarder/Initiator MUST be able to release state it is involved in.
 For example, this may require signaling of the "Release after
 Failure" message upstream as well as downstream, or soft state timing
 out.
 The goal is to prevent stale state within the network and add
 robustness to the operation of NSIS.  So in other words, an NSIS
 signaling protocol or mechanisms MUST provide means for an NSIS
 entity to discover and remove local stale state.
 Note that this might need to work together with a notification
 mechanism.  Note as well, that transient failures in NSIS processing
 shouldn't necessarily have to cause all state to be released
 immediately.

5.3.3. NSIS SHOULD Allow for Sending Notifications Upstream

 NSIS Forwarders SHOULD notify the NSIS Initiator or any other NSIS
 Forwarder upstream, if there is a state change inside the network.
 There are various types of network changes for instance among them:
 Recoverable errors: the network nodes can locally repair this type
 error.  The network nodes do not have to notify the users of the
 error immediately.  This is a condition when the danger of
 degradation (or actual short term degradation) of the provided
 service was overcome by the network (NSIS Forwarder) itself.
 Unrecoverable errors: the network nodes cannot handle this type of
 error, and have to notify the users as soon as possible.
 Service degradation: In case the service cannot be provided
 completely but only partially.
 Repair indication: If an error occurred and it has been fixed, this
 triggers the sending of a notification.
 Service upgrade available: If a previously requested better service
 becomes available.

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 The content of the notification is very service specific, but it is
 must at least carry type information.  Additionally, it may carry the
 location of the state change.
 The notifications may or may not be in response to a NSIS message.
 This means an NSIS entity has to be able to handle notifications at
 any time.
 Note however, that there are a number of security consideration needs
 to be solved with notification, even more important if the
 notification is sent without prior request (asynchronously).  The
 problem basically is, that everybody could send notifications to any
 NSIS entity and the NSIS entity most likely reacts on the
 notification.  For example, if it gets an error notification it might
 erase state, even if everything is ok.  So the notification might
 depend on security associations between the sender of the
 notification and its receiver.  If a hop-by-hop security mechanism is
 chosen, this implies also that notifications need to be sent on the
 reverse path.

5.3.4. Establishment and Refusal to Set Up State MUST be Notified

 A NR MUST acknowledge establishment of state on behalf of the NI
 requesting establishment of that state.  A refusal to set up state
 MUST be replied with a negative acknowledgement by the NE refusing to
 set up state.  It MUST be sent to the NI.  Depending on the signaling
 application the (positive or negative) notifications may have to pass
 through further NEs upstream.  Information on the reason of the
 refusal to set up state MAY be made available.  For example, in the
 resource reservation example, together with a negative answer, the
 amount of resources available might also be returned.

5.3.5. NSIS MUST Allow for Local Information Exchange

 The signaling protocol MUST be able to exchange local information
 between NSIS Forwarders located within one single administrative
 domain.  The local information exchange is performed by a number of
 separate messages not belonging to an end-to-end signaling process.
 Local information might, for example, be IP addresses, notification
 of successful or erroneous processing of signaling messages, or other
 conditions.
 In some cases, the NSIS signaling protocol MAY carry identification
 of the NSIS Forwarders located at the boundaries of a domain.
 However, the identification of edge should not be visible to the end
 host (NSIS Initiator) and only applies within one administrative
 domain.

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5.4. Control Information

 This section contains requirements related to the control information
 that needs to be exchanged.

5.4.1. Mutability Information on Parameters SHOULD be Possible

 It is possible that nodes modify parameters of a signaling message.
 However, it SHOULD be possible for the NSIS Initiator to control the
 mutability of the signaled information.  For example, the NSIS
 Initiator should be able to control what is requested end-to-end,
 without the request being gradually mutated as it passes through a
 sequence of nodes.

5.4.2. It SHOULD be Possible to Add and Remove Local Domain Information

 It SHOULD be possible to add and remove local scope elements.
 Compared to Requirement 5.3.5 this requirement does use the normal
 signaling process and message exchange for transporting local
 information.  For example, at the entrance to a domain, domain-
 specific information is added information is added, which is used in
 this domain only, and the information is removed again when a
 signaling message leaves the domain.  The motivation is in the
 economy of re-using the protocol for domain internal signaling of
 various information pieces.  Where additional information is needed
 within a particular domain, it should be possible to carry this at
 the same time as the end-to-end information.

5.4.3. State MUST be Addressed Independent of Flow Identification

 Addressing or identifying state MUST be independent of the flow
 identifier (flow end-points, topological addresses).  Various
 scenarios in the mobility area require this independence because
 flows resulting from handoff might have changed end-points etc. but
 still have the same service requirement.  Also several proxy-based
 signaling methods profit from such independence, though these are not
 chartered work items for NSIS.

5.4.4. Modification of Already Established State SHOULD be Seamless

 In many case, the established state needs to be updated (in QoS
 example upgrade or downgrade of resource usage).  This SHOULD happen
 seamlessly without service interruption.  At least the signaling
 protocol should allow for it, even if some data path elements might
 not be capable of doing so.

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5.4.5. Grouping of Signaling for Several Micro-Flows MAY be Provided

 NSIS MAY group signaling information for several micro-flows into one
 signaling message.  The goal of this is the optimization in terms of
 setup delay, which can happen in parallel.  This helps applications
 requesting several flows at once.  Also potential refreshes (in case
 of a soft state solution) might profit from grouping.
 However, the network need not know that a relationship between the
 grouped flows exists.  There MUST NOT be any transactional semantic
 associated with the grouping.  It is only meant for optimization
 purposes.

5.5. Performance

 This section discusses performance requirements and evaluation
 criteria and the way in which these could and should be traded off
 against each other in various parts of the solution.
 Scalability is always an important requirement for signaling
 protocols.  However, the type of scalability and its importance
 varies from one scenario to another.
 Note that many of the performance issues are heavily dependent on the
 scenario assumed and are normally a trade-off between speed,
 reliability, complexity, and scalability.  The trade-off varies in
 different parts of the network.  For example, in radio access
 networks low bandwidth consumption will outweigh the low latency
 requirement, while in core networks it may be reverse.

5.5.1. Scalability

 NSIS MUST be scalable in the number of messages received by a
 signaling communication partner (NSIS Initiator, NSIS Forwarder, and
 NSIS Responder).  The major concern lies in the core of the network,
 where large numbers of messages arrive.
 It MUST be scalable in number of hand-offs in mobile environments.
 This mainly applies in access networks, because the core is
 transparent to mobility in most cases.
 It MUST be scalable in the number of interactions for setting up
 state.  This applies for end-systems setting up several states.  Some
 servers might be expected to setup a large number of states.
 Scalability in the amount of state per entity MUST be achieved for
 NSIS Forwarders in the core of the network.

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 Scalability in CPU usage MUST be achieved on end terminals and
 intermediate nodes in case of many state setup processes at the same
 time.
 Specifically, NSIS MUST work in Internet scale deployments, where the
 use of signaling by hosts becomes universal.  Note that requirement
 5.2.4 requires the functionality of transparently signaling through
 networks without interpretation.  Additionally, requirement 5.6.1
 lists the capability to aggregate.  Furthermore, requirement 5.5.4
 states that NSIS should be able to constrain the load on devices.
 Basically, the performance of the signaling MUST degrade gracefully
 rather than catastrophically under overload conditions.

5.5.2. NSIS SHOULD Allow for Low Latency in Setup

 NSIS SHOULD allow for low latency setup of states.  This is only
 needed in scenarios where state setups are required on a short time
 scale (e.g., handover in mobile environments), or where human
 interaction is immediately concerned (e.g., voice communication setup
 delay).

5.5.3. NSIS MUST Allow for Low Bandwidth Consumption for the Signaling

      Protocol
 NSIS MUST allow for low bandwidth consumption in certain access
 networks.  Again only small sets of scenarios call for low bandwidth,
 mainly those where wireless links are involved.

5.5.4. NSIS SHOULD Allow to Constrain Load on Devices

 The NSIS architecture SHOULD give the ability to constrain the load
 (CPU load, memory space, signaling bandwidth consumption and
 signaling intensity) on devices where it is needed.  One of the
 reasons is that the protocol handling should have a minimal impact on
 interior (core) nodes.
 This can be achieved by many different methods.  Examples include
 message aggregation, header compression, minimizing functionality, or
 ignoring signaling in core nodes.  NSIS may choose any method as long
 as the requirement is met.

5.5.5. NSIS SHOULD Target the Highest Possible Network Utilization

 This requirement applies specifically to QoS signaling.

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 There are networking environments that require high network
 utilization for various reasons, and the signaling protocol SHOULD to
 its best ability support high resource utilization while maintaining
 appropriate service quality.
 In networks where resources are very expensive (as is the case for
 many wireless networks), efficient network utilization for signaling
 traffic is of critical financial importance.  On the other hand there
 are other parts of the network where high utilization is not
 required.

5.6. Flexibility

 This section lists the various ways the protocol can flexibly be
 employed.

5.6.1. Flow Aggregation

 NSIS MUST allow for flow aggregation, including the capability to
 select and change the level of aggregation.

5.6.2. Flexibility in the Placement of the NSIS Initiator/Responder

 NSIS MUST be flexible in placing an NSIS Initiator and NSIS
 Responder.  The NSIS Initiator might be located at the sending or the
 receiving side of a data stream, and the NSIS Responder naturally on
 the other side.
 Also network-initiated signaling and termination MUST be allowed in
 various scenarios such as PSTN gateways, some VPNs, and mobility.
 This means the NSIS Initiator and NSIS Responder might not be at the
 end points of the data stream.

5.6.3. Flexibility in the Initiation of State Change

 The NSIS Initiator or the NSIS Responder SHOULD be able to initiate a
 change of state.  In the example of resource reservation this is
 often referred to as resource re-negotiation.  It can happen due to
 various reasons, such as local resource shortage (CPU, memory on
 end-system) or a user changed application preference/profiles.

5.6.4. SHOULD Support Network-Initiated State Change

 NSIS SHOULD support network-initiated state change.  In the QoS
 example, this is used in cases, where the network is not able to
 further guarantee resources and wants to e.g., downgrade a resource
 reservation.

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5.6.5. Uni / Bi-Directional State Setup

 Both unidirectional as well as bi-direction state setup SHOULD be
 possible.  With bi-directional state setup we mean that the state for
 bi-directional data flows is setup.  The bi-directional data flows
 have the same end-points, but the path in the two directions does not
 need to be the same.
 The goal of a bi-directional state setup is mainly an optimization in
 terms of setup delay.  There is no requirements on constrains such as
 use of the same data path etc.

5.7. Security

 This section discusses security-related requirements.  The NSIS
 protocol MUST provide means for security, but it MUST be allowed that
 nodes implementing NSIS signaling do not have to use the security
 means.

5.7.1. Authentication of Signaling Requests

 A signaling protocol MUST make provision for enabling various
 entities to be authenticated against each other using strong
 authentication mechanisms.  The term strong authentication points to
 the fact that weak plain-text password mechanisms must not be used
 for authentication.

5.7.2. Request Authorization

 The signaling protocol MUST provide means to authorize state setup
 requests.  This requirement demands a hook to interact with a policy
 entity to request authorization data.  This allows an authenticated
 entity to be associated with authorization data and to verify the
 request.  Authorization prevents state setup by unauthorized
 entities, setups violating policies, and theft of service.
 Additionally it limits denial of service attacks against parts of the
 network or the entire network caused by unrestricted state setups.
 Additionally it might be helpful to provide some means to inform
 other protocols of participating nodes within the same administrative
 domain about a previous successful authorization event.

5.7.3. Integrity Protection

 The signaling protocol MUST provide means to protect the message
 payloads against modifications.  Integrity protection prevents an
 adversary from modifying parts of the signaling message and from
 mounting denial of service or theft of service type of attacks
 against network elements participating in the protocol execution.

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5.7.4. Replay Protection

 To prevent replay of previous signaling messages the signaling
 protocol MUST provide means to detect old i.e., already transmitted
 signaling messages.  A solution must cover issues of synchronization
 problems in the case of a restart or a crash of a participating
 network element.

5.7.5. Hop-by-Hop Security

 Channel security between signaling entities MUST be implemented.  It
 is a well known and proven concept in Quality of Service and other
 signaling protocols to have intermediate nodes that actively
 participate in the protocol to modify the messages as it is required
 by processing rules.  Note that this requirement does not exclude
 end-to-end or network-to-network security of a signaling message.
 End-to-end security between the NSIS Initiator and the NSIS Responder
 may be used to provide protection of non-mutable data fields.
 Network-to-network security refers to the protection of messages over
 various hops but not in an end-to-end manner i.e., protected over a
 particular network.

5.7.6. Identity Confidentiality and Network Topology Hiding

 Identity confidentiality SHOULD be supported.  It enables privacy and
 avoids profiling of entities by adversary eavesdropping the signaling
 traffic along the path.  The identity used in the process of
 authentication may also be hidden to a limited extent from a network
 to which the initiator is attached.  However the identity MUST
 provide enough information for the nodes in the access network to
 collect accounting data.
 Network topology hiding MAY be supported to prevent entities along
 the path to learn the topology of a network.  Supporting this
 property might conflict with a diagnostic capability.

5.7.7. Denial-of-Service Attacks

 A signaling protocol SHOULD provide prevention of Denial-of-service
 attacks.  To effectively prevent denial-of-service attacks it is
 necessary that the used security and protocol mechanisms MUST have
 low computational complexity to verify a state setup request prior to
 authenticating the requesting entity.  Additionally the signaling
 protocol and the used security mechanisms SHOULD NOT require large
 resource consumption on NSIS Entities (for example main memory or
 other additional message exchanges) before a successful
 authentication is done.

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5.7.8. Confidentiality of Signaling Messages

 Based on the signaling information exchanged between nodes
 participating in the signaling protocol an adversary may learn both
 the identities and the content of the signaling messages.  Since the
 ability to listen to signaling channels is a major guide to what data
 channels are interesting ones.
 To prevent this from happening, confidentiality of the signaling
 message in a hop-by-hop manner SHOULD be provided.  Note that most
 messages must be protected on a hop-by-hop basis, since entities,
 which actively participate in the signaling protocol, must be able to
 read and eventually modify the signaling messages.

5.7.9. Ownership of State

 When existing states have to be modified then there is a need to use
 a session identifier to uniquely identify the established state.  A
 signaling protocol MUST provide means of security protection to
 prevent adversaries from modifying state.

5.8. Mobility

5.8.1. Allow Efficient Service Re-Establishment After Handover

 Handover is an essential function in wireless networks.  After
 handover, the states may need to be completely or partially re-
 established due to route changes.  The re-establishment may be
 requested by the mobile node itself or triggered by the access point
 that the mobile node is attached to.  In the first case, the
 signaling MUST allow efficient re-establishment after handover.  Re-
 establishment after handover MUST be as quick as possible so that the
 mobile node does not experience service interruption or service
 degradation.  The re-establishment SHOULD be localized, and not
 require end-to-end signaling.

5.9. Interworking with Other Protocols and Techniques

 Hooks SHOULD be provided to enable efficient interworking between
 various protocols and techniques including the following listed.

5.9.1. MUST Interwork with IP Tunneling

 IP tunneling for various applications MUST be supported.  More
 specifically IPSec tunnels are of importance.  This mainly impacts
 the identification of flows.  When using IPSec, parts of information
 commonly used for flow identification (e.g., transport protocol
 information and ports) may not be accessible due to encryption.

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5.9.2. MUST NOT Constrain Either to IPv4 or IPv6

5.9.3. MUST be Independent from Charging Model

 Signaling MUST NOT be constrained by charging models or the charging
 infrastructure used.

5.9.4. SHOULD Provide Hooks for AAA Protocols

 The NSIS protocol SHOULD be developed with respect to be able to
 collect usage records from one or more network elements.

5.9.5. SHOULD Work with Seamless Handoff Protocols

 An NSIS protocol SHOULD work with seamless handoff protocols such as
 context transfer and candidate access router (CAR) discovery.

5.9.6. MUST Work with Traditional Routing

 NSIS assumes traditional L3 routing, which is purely based on L3
 destination addresses.  NSIS MUST work with L3 routing, in particular
 it MUST work in case of route changes.  This means state on the old
 route MUST be released and state on the new route MUST be established
 by an NSIS protocol.
 Networks, which do non-traditional routing, should not break NSIS
 signaling.  NSIS MAY work for some of these situations.
 Particularly, combinations of NSIS unaware nodes and routing other
 then traditional one causes some problems.  Non-traditional routing
 includes, for example, routing decisions based on port numbers, other
 IP header fields than the destination address, or splitting traffic
 based on header hash values.  These routing environments result in
 the signaling path being potentially different than the data path.

5.10. Operational

5.10.1. Ability to Assign Transport Quality to Signaling Messages

 The NSIS architecture SHOULD allow the network operator to assign the
 NSIS protocol messages a certain transport quality.  As signaling
 opens up the possibility of denial-of-service attacks, this
 requirement gives the network operator a means, but also the
 obligation, to trade-off between signaling latency and the impact
 (from the signaling messages) on devices within the network.  From
 protocol design this requirement states that the protocol messages
 SHOULD be detectable, at least where the control and assignment of
 the messages priority is done.

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 Furthermore, the protocol design must take into account reliability
 concerns.  Communication reliability is seen as part of the quality
 assigned to signaling messages.  So procedures MUST be defined for
 how an NSIS signaling system behaves if some kind of request it sent
 stays unanswered.  The basic transport protocol to be used between
 adjacent NSIS Entities MAY ensure message integrity and reliable
 transport.

5.10.2. Graceful Fail Over

 Any unit participating in NSIS signaling MUST NOT cause further
 damage to other systems involved in NSIS signaling when it has to go
 out of service.

5.10.3. Graceful Handling of NSIS Entity Problems

 NSIS entities SHOULD be able to detect a malfunctioning peer.  It may
 notify the NSIS Initiator or another NSIS entity involved in the
 signaling process.  The NSIS peer may handle the problem itself e.g.,
 switching to a backup NSIS entity.  In the latter case note that
 synchronization of state between the primary and the backup entity is
 needed.

6. Security Considerations

 Section 5.7 of this document provides security related requirements
 of a signaling protocol.

7. Acknowledgments

 Quite a number of people have been involved in the discussion of the
 document, adding some ideas, requirements, etc.  We list them without
 a guarantee on completeness: Changpeng Fan (Siemens), Krishna Paul
 (NEC), Maurizio Molina (NEC), Mirko Schramm (Siemens), Andreas
 Schrader (NEC), Hannes Hartenstein (NEC), Ralf Schmitz (NEC), Juergen
 Quittek (NEC), Morihisa Momona (NEC), Holger Karl (Technical
 University Berlin), Xiaoming Fu (Technical University Berlin), Hans-
 Peter Schwefel (Siemens), Mathias Rautenberg (Siemens), Christoph
 Niedermeier (Siemens), Andreas Kassler (University of Ulm), Ilya
 Freytsis.
 Some text and/or ideas for text, requirements, scenarios have been
 taken from an Internet Draft written by the following authors: David
 Partain (Ericsson), Anders Bergsten (Telia Research), Marc Greis
 (Nokia), Georgios Karagiannis (Ericsson), Jukka Manner (University of
 Helsinki), Ping Pan (Juniper), Vlora Rexhepi (Ericsson), Lars
 Westberg (Ericsson), Haihong Zheng (Nokia).  Some of those have
 actively contributed new text to this document as well.

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 Another Internet Draft impacting this document has been written by
 Sven Van den Bosch, Maarten Buchli, and Danny Goderis (all Alcatel).
 These people contributed also new text.
 Thanks also to Kwok Ho Chan (Nortel) for text changes.  And finally
 thanks Alison Mankin for the thorough AD review and thanks to Harald
 Tveit Alvestrand and Steve Bellovin for the IESG review comments.

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8. Appendix: Scenarios/Use Cases

 In the following we describe scenarios, which are important to cover,
 and which allow us to discuss various requirements.  Some regard this
 as use cases to be covered defining the use of a signaling protocol.
 In general, these scenarios consider the specific case of signaling
 for QoS (resource reservation), although many of the issues carry
 over directly to other signaling types.

8.1. Terminal Mobility

 The scenario we are looking at is the case where a mobile terminal
 (MT) changes from one access point to another access point.  The
 access points are located in separate QoS domains.  We assume Mobile
 IP to handle mobility on the network layer in this scenario and
 consider the various extensions (i.e., IETF proposals) to Mobile IP,
 in order to provide 'fast handover' for roaming Mobile Terminals.
 The goal to be achieved lies in providing, keeping, and adapting the
 requested QoS for the ongoing IP sessions in case of handover.
 Furthermore, the negotiation of QoS parameters with the new domain
 via the old connection might be needed, in order to support the
 different 'fast handover' proposals within the IETF.
 The entities involved in this scenario include a mobile terminal,
 access points, an access network manager, and communication partners
 of the MT (the other end(s) of the communication association).  From
 a technical point of view, terminal mobility means changing the
 access point of a mobile terminal (MT).  However, technologies might
 change in various directions (access technology, QoS technology,
 administrative domain).  If the access points are within one specific
 QoS technology (independent of access technology) we call this
 intra-QoS technology handoff.  In the case of an inter-QoS technology
 handoff, one changes from e.g., a DiffServ to an IntServ domain,
 however still using the same access technology.  Finally, if the
 access points are using different access technologies we call it
 inter-technology hand-off.
 The following issues are of special importance in this scenario:
 1) Handoff decision
  1. The QoS management requests handoff. The QoS management can

decide to change the access point, since the traffic conditions of

    the new access point are better supporting the QoS requirements.
    The metric may be different (optimized towards a single or a
    group/class of users).  Note that the MT or the network (see
    below) might trigger the handoff.

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  1. The mobility management forces handoff. This can have several

reasons. The operator optimizes his network, admission is no

    longer granted (e.g., emptied prepaid condition).  Or another
    example is when the MT is reaching the focus of another base
    station.  However, this might be detected via measurements of QoS
    on the physical layer and is therefore out of scope of QoS
    signaling in IP.  Note again that the MT or the network (see
    below) might trigger the handoff.
  1. This scenario shows that local decisions might not be enough. The

rest of the path to the other end of the communication needs to be

    considered as well.  Hand-off decisions in a QoS domain do not
    only depend on the local resource availability, e.g., the wireless
    part, but involve the rest of the path as well.  Additionally,
    decomposition of an end-to-end signaling might be needed, in order
    to change only parts of it.
 2) Trigger sources
  1. Mobile terminal: If the end-system QoS management identifies

another (better-suited) access point, it will request the handoff

    from the terminal itself.  This will be especially likely in the
    case that two different provider networks are involved.  Another
    important example is when the current access point bearer
    disappears (e.g., removing the Ethernet cable).  In this case, the
    NSIS Initiator is basically located on the mobile terminal.
  1. Network (access network manager): Sometimes, the handoff trigger

will be issued from the network management to optimize the overall

    load situation.  Most likely this will result in changing the
    base-station of a single providers network.  Most likely the NSIS
    Initiator is located on a system within the network.
 3) Integration with other protocols
  1. Interworking with other protocol must be considered in one or the

other form. E.g., it might be worth combining QoS signaling

    between different QoS domains with mobility signaling at hand-
    over.
 4) Handover rates
 In mobile networks, the admission control process has to cope with
 far more admission requests than call setups alone would generate.
 For example, in the GSM (Global System for Mobile communications)
 case, mobility usually generates an average of one to two handovers

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 per call.  For third generation networks (such as UMTS), where it is
 necessary to keep radio links to several cells simultaneously
 (macro-diversity), the handover rate is significantly higher.
 5) Fast state installation
 Handover can also cause packet losses.  This happens when the
 processing of an admission request causes a delayed handover to the
 new base station.  In this situation, some packets might be
 discarded, and the overall speech quality might be degraded
 significantly.  Moreover, a delay in handover may cause degradation
 for other users.  In the worst-case scenario, a delay in handover may
 cause the connection to be dropped if the handover occurred due to
 bad air link quality.  Therefore, it is critical that QoS signaling
 in connection with handover be carried out very quickly.
 6) Call blocking in case of overload
 Furthermore, when the network is overloaded, it is preferable to keep
 states for previously established flows while blocking new requests.
 Therefore, the resource reservation requests in connection with
 handover should be given higher priority than new requests for
 resource reservation.

8.2. Wireless Networks

 In this scenario, the user is using the packet services of a wireless
 system (such as the 3rd generation wireless system 3GPP/UMTS,
 3GPP2/cdma2000).  The region between the End Host and the Edge Node
 (Edge Router) connecting the wireless network to another QoS domain
 is considered to be a single QoS domain.
 The issues in such an environment regarding QoS include:
 1) The wireless networks provide their own QoS technology with
    specialized parameters to coordinate the QoS provided by both the
    radio access and wired access networks.  Provisioning of QoS
    technologies within a wireless network can be described mainly in
    terms of calling bearer classes, service options, and service
    instances.  These QoS technologies need to be invoked with
    suitable parameters when higher layers trigger a request for QoS.
    Therefore these involve mapping of the requested higher layer QoS
    parameters onto specific bearer classes or service instances.  The
    request for allocation of resources might be triggered by
    signaling at the IP level that passes across the wireless system,
    and possibly other QoS domains.  Typically, wireless network
    specific messages are invoked to setup the underlying bearer

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    classes or service instances in parallel with the IP layer QoS
    negotiation, to allocate resources within the radio access
    network.
 2) The IP signaling messages are initiated by the NSIS initiator and
    interpreted by the NSIS Forwarder.  The most efficient placement
    of the NSIS Initiator and NSIS Forwarder has not been determined
    in wireless networks, but a few potential scenarios can be
    envisioned. The NSIS Initiator could be located at the End Host
    (e.g., 3G User equipment (UE)), the Access Gateway or at a node
    that is not directly on the data path, such as a Policy Decision
    Function.  The Access Gateway could act as a proxy NSIS Initiator
    on behalf of the End Host.  The Policy Decision Function that
    controls per-flow/aggregate resources with respect to the session
    within its QoS domain (e.g., the 3G wireless network) may act as a
    proxy NSIS Initiator for the end host or the Access Gateway.
    Depending on the placement of the NSIS Initiator, the NSIS
    Forwarder may be located at an appropriate point in the wireless
    network.
 3) The need for re-negotiation of resources in a new wireless domain
    due to host mobility.  In this case the NSIS Initiator and the
    NSIS Forwarder should detect mobility events and autonomously
    trigger re-negotiation of resources.

8.3. An Example Scenario for 3G Wireless Networks

 The following example is a pure hypothetical scenario, where an NSIS
 signaling protocol might be used in a 3G environment.  We do not
 impose in any way, how a potential integration might be done.  Terms
 from the 3GPP architecture are used (P-CSCF, IMS, expanded below) in
 order to give specificity, but in a hypothetical design, one that
 reflects neither development nor review by 3GPP.  The example should
 help in the design of a NSIS signaling protocol such that it could be
 used in various environments.
 The 3G wireless access scenario is shown in Figure 1.  The Proxy-Call
 State Control Function (P-CSCF) is the outbound SIP proxy (only used
 in IP Multimedia Subsystems (IMS)).  The Access Gateway is the egress
 router of the 3G wireless domain and it connects the radio access
 network to the Edge Router (ER) of the backbone IP network.  The
 Policy Decision Function (PDF) is an entity responsible for
 controlling bearer level resource allocations/de-allocations in
 relation to session level services e.g., SIP.  The Policy Decision
 Function may also control the Access Gateway to open and close the
 gates and to configure per-flow policies, i.e., to authorize or
 forbid user traffic.  The P-CSCF (only used in IMS) and the Access
 Gateway communicate with the Policy Decision Function, for network

Brunner Informational [Page 29] RFC 3726 Requirements for Signaling Protocols April 2004

 resource allocation/de-allocation decisions.  The User Equipment (UE)
 or the Mobile Station (MS) consists of a Mobile Terminal (MT) and
 Terminal Equipment (TE), e.g., a laptop.
                   +--------+
        +--------->| P-CSCF |---------> SIP signaling
       /           +--------+
      / SIP            |
     |                 |
     |              +-----+            +----------------+
     |              | PDF |<---------->| NSIS Forwarder |<--->
     |              +-----+            +----------------+
     |                 |                  ^
     |                 |                  |
     |                 |                  |
     |                 |COPS              |
     |                 |                  |
 +------+          +---------+            |
 | UE/MS|----------| Access  |<-----------+     +----+
 +------+          | Gateway |------------------| ER |
                   +---------+                  +----+
          Figure 1: 3G wireless access scenario
 The PDF has all the required QoS information for per-flow or
 aggregate admission control in 3G wireless networks.  It receives
 resource allocation/de-allocation requests from the P-CSCF and/or
 Access Gateway etc. and responds with policy decisions.  Hence the
 PDF may be a candidate entity to host the functionality of the NSIS
 Initiator, initiating the NSIS QoS signaling towards the backbone IP
 network.  On the other hand, the UE/MS may act as the NSIS Initiator
 or the Access Gateway may act as a Proxy NSIS Initiator on behalf of
 the UE/MS.  In the former case, the P-CSCF/PDF has to do the mapping
 from codec types and media descriptors (derived from SIP/SDP
 signaling) to IP traffic descriptor.  In the latter case, the UE/MS
 may use any appropriate QoS signaling mechanism as the NSIS
 Initiator.  If the Access Gateway is acting as the Proxy NSIS
 initiator on behalf of the UE/MS, then it may have to do the mapping
 of parameters from radio access specific QoS to IP QoS traffic
 parameters before forwarding the request to the NSIS Forwarder.
 The NSIS Forwarder is currently not part of the standard 3G wireless
 architecture.  However, to achieve end-to-end QoS a NSIS Forwarder is
 needed such that the NSIS Initiators can request a QoS connection to
 the IP network.  As in the previous example, the NSIS Forwarder could
 manage a set of pre-provisioned resources in the IP network, i.e.,
 bandwidth pipes, and the NSIS Forwarder perform per-flow admission
 control into these pipes.  In this way, a connection can be made

Brunner Informational [Page 30] RFC 3726 Requirements for Signaling Protocols April 2004

 between two 3G wireless access networks, and hence, end-to-end QoS
 can be achieved.  In this case the NSIS Initiator and NSIS Forwarder
 are clearly two separate logical entities.  The Access Gateway or/and
 the Edge Router in Fig.1 may contain the NSIS Forwarder
 functionality, depending upon the placement of the NSIS Initiator as
 discussed in scenario 2 in section 8.2.  This use case clearly
 illustrates the need for an NSIS QoS signaling protocol between NSIS
 Initiator and NSIS Forwarder.  An important application of such a
 protocol may be its use in the end-to-end establishment of a
 connection with specific QoS characteristics between a mobile host
 and another party (e.g., end host or content server).

8.4. Wired Part of Wireless Network

 A wireless network, seen from a QoS domain perspective, usually
 consists of three parts: a wireless interface part (the "radio
 interface"), a wired part of the wireless network (i.e., Radio Access
 Network) and the backbone of the wireless network, as shown in Figure
 2.  Note that this figure should not be seen as an architectural
 overview of wireless networks but rather as showing the conceptual
 QoS domains in a wireless network.
 In this scenario, a mobile host can roam and perform a handover
 procedure between base stations/access routers.  In this scenario the
 NSIS QoS protocol can be applied between a base station and the
 gateway (GW).  In this case a GW can also be considered as a local
 handover anchor point.  Furthermore, in this scenario the NSIS QoS
 protocol can also be applied either between two GWs, or between two
 edge routers (ER).

Brunner Informational [Page 31] RFC 3726 Requirements for Signaling Protocols April 2004

                        |--|
                        |GW|
 |--|                   |--|
 |MH|---                 .
 |--|  / |-------|       .
      /--|base   | |--|  .
         |station|-|ER|...
         |-------| |--|  . |--| back- |--|  |---|              |----|
                         ..|ER|.......|ER|..|BGW|.."Internet"..|host|
      -- |-------| |--|  . |--| bone  |--|  |---|              |----|
 |--| \  |base   |-|ER|...     .
 |MH|  \ |station| |--|        .
 |--|--- |-------|             .          MH  = mobile host
                            |--|          ER  = edge router
    <---->                  |GW|          GW  = gateway
   Wireless link            |--|          BGW = border gateway
                                          ... = interior nodes
          <------------------->
     Wired part of wireless network
 <---------------------------------------->
              Wireless Network
    Figure 2. QoS architecture of wired part of wireless network
 Each of these parts of the wireless network impose different issues
 to be solved on the QoS signaling solution being used:
 1) Wireless interface: The solution for the air interface link has to
    ensure flexibility and spectrum efficient transmission of IP
    packets.  However, this link layer QoS can be solved in the same
    way as any other last hop problem by allowing a host to request
    the proper QoS profile.
 2) Wired part of the wireless network:  This is the part of the
    network that is closest to the base stations/access routers.  It
    is an IP network although some parts logically perform tunneling
    of the end user data.  In cellular networks, the wired part of the
    wireless network is denoted as a radio access network.
    This part of the wireless network has different requirements for
    signaling protocol characteristics when compared to traditional IP
    networks:
  1. The network must support mobility. Many wireless networks are

able to provide a combination of soft and hard handover

       procedures.  When handover occurs, reservations need to be
       established on new paths.  The establishment time has to be as

Brunner Informational [Page 32] RFC 3726 Requirements for Signaling Protocols April 2004

       short as possible since long establishment times for s degrade
       the performance of the wireless network.  Moreover, for maximal
       utilization of the radio spectrum, frequent handover operations
       are required.
  1. These links are typically rather bandwidth-limited.
  1. The wired transmission in such a network contains a relatively

high volume of expensive leased lines. Overprovisioning might

       therefore be prohibitively expensive.
  1. The radio base stations are spread over a wide geographical

area and are in general situated a large distance from the

       backbone.
 3) Backbone of the wireless network: the requirements imposed by this
    network are similar to the requirements imposed by other types of
    backbone networks.
 Due to these very different characteristics and requirements, often
 contradictory, different QoS signaling solutions might be needed in
 each of the three network parts.

8.5. Session Mobility

 In this scenario, a session is moved from one end-system to another.
 Ongoing sessions are kept and QoS parameters need to be adapted,
 since it is very likely that the new device provides different
 capabilities.  Note that it is open which entity initiates the move,
 which implies that the NSIS Initiator might be triggered by different
 entities.
 User mobility (i.e., a user changing the device and therefore moving
 the sessions to the new device) is considered to be a special case
 within the session mobility scenario.
 Note that this scenario is different from terminal mobility.  The
 terminal (end-system) has not moved to a different access point.
 Both terminals are still connected to an IP network at their original
 points.
 The issues include:
 1) Keeping the QoS guarantees negotiated implies that the end-
    point(s) of communication are changed without changing the s.
 2) The trigger of the session move might be the user or any other
    party involved in the session.

Brunner Informational [Page 33] RFC 3726 Requirements for Signaling Protocols April 2004

8.6. QoS Reservation/Negotiation from Access to Core Network

 The scenario includes the signaling between access networks and core
 networks in order to setup and change reservations together with
 potential negotiation.
 The issues to be solved in this scenario are different from previous
 ones.
 1) The entity of reservation is most likely an aggregate.
 2) The time scales of states might be different (long living states
    of aggregates, less often re-negotiation).
 3) The specification of the traffic (amount of traffic), a particular
    QoS is guaranteed for, needs to be changed.  E.g., in case
    additional flows are added to the aggregate, the traffic
    specification of the flow needs to be added if it is not already
    included in the aggregates specification.
 4) The flow specification is more complex including network addresses
    and sets of different address for the source as well as for the
    destination of the flow.

8.7. QoS Reservation/Negotiation Over Administrative Boundaries

 Signaling between two or more core networks to provide QoS is handled
 in this scenario.  This might also include access to core signaling
 over administrative boundaries.  Compared to the previous one it adds
 the case, where the two networks are not in the same administrative
 domain.  Basically, it is the inter-domain/inter-provider signaling
 which is handled in here.
 The domain boundary is the critical issue to be resolved.  Which of
 various flavors of issues a QoS signaling protocol has to be
 concerned with.
 1) Competing administrations: Normally, only basic information should
    be exchanged, if the signaling is between competing
    administrations.  Specifically information about core network
    internals (e.g., topology, technology, etc.) should not be
    exchanged.  Some information exchange about the "access points" of
    the core networks (which is topology information as well) may be
    required, to be exchanged, because it is needed for proper
    signaling.
 2) Additionally, as in scenario 4, signaling most likely is based on
    aggregates, with all the issues raise there.

Brunner Informational [Page 34] RFC 3726 Requirements for Signaling Protocols April 2004

 3) Authorization: It is critical that the NSIS Initiator is
    authorized to perform a QoS path setup.
 4) Accountability: It is important to notice that signaling might be
    used as an entity to charge money for, therefore the
    interoperation with accounting needs to be available.

8.8. QoS Signaling Between PSTN Gateways and Backbone Routers

 A PSTN gateway (i.e., host) requires information from the network
 regarding its ability to transport voice traffic across the network.
 The voice quality will suffer due to packet loss, latency and jitter.
 Signaling is used to identify and admit a flow for which these
 impairments are minimized.  In addition, the disposition of the
 signaling request is used to allow the PSTN GW to make a call routing
 decision before the call is actually accepted and delivered to the
 final destination.
 PSTN gateways may handle thousands of calls simultaneously and there
 may be hundreds of PSTN gateways in a single provider network.  These
 numbers are likely to increase as the size of the network increases.
 The point being that scalability is a major issue.
 There are several ways that a PSTN gateway can acquire assurances
 that a network can carry its traffic across the network.  These
 include:
 1. Over-provisioning a high availability network.
 2. Handling admission control through some policy server that has a
    global view of the network and its resources.
 3. Per PSTN GW pair admission control.
 4. Per call admission control (where a call is defined as the 5-tuple
    used to carry a single RTP flow).
 Item 1 requires no signaling at all and is therefore outside the
 scope of this working group.
 Item 2 is really a better informed version of 1, but it is also
 outside the scope of this working group as it relies on a particular
 telephony signaling protocol rather than a packet admission control
 protocol.
 Item 3 is initially attractive, as it appears to have reasonable
 scaling properties, however, its scaling properties only are
 effective in cases where there are relatively few PSTN GWs.  In the

Brunner Informational [Page 35] RFC 3726 Requirements for Signaling Protocols April 2004

 more general case where a PSTN GW reduces to a single IP phone
 sitting behind some access network, the opportunities for aggregation
 are reduced and the problem reduces to item 4.
 Item 4 is the most general case.  However, it has the most difficult
 scaling problems.  The objective here is to place the requirements on
 Item 4 such that a scalable per-flow admission control protocol or
 protocol suite may be developed.
 The case where per-flow signaling extends to individual IP end-points
 allows the inclusion of IP phones on cable, DSL, wireless or other
 access networks in this scenario.
 Call Scenario
 A PSTN GW signals end-to-end for some 5-tuple defined flow a
 bandwidth and QoS requirement.  Note that the 5-tuple might include
 masking/wildcarding.  The access network admits this flow according
 to its local policy and the specific details of the access
 technology.
 At the edge router (i.e., border node), the flow is admitted, again
 with an optional authentication process, possibly involving an
 external policy server.  Note that the relationship between the PSTN
 GW and the policy server and the routers and the policy server is
 outside the scope of NSIS.  The edge router then admits the flow into
 the core of the network, possibly using some aggregation technique.
 At the interior nodes, the NSIS host-to-host signaling should either
 be ignored or invisible as the Edge router performed the admission
 control decision to some aggregate.
 At the inter-provider router (i.e., border node), again the NSIS
 host-to-host signaling should either be ignored or invisible, as the
 Edge router has performed an admission control decision about an
 aggregate across a carrier network.

8.9. PSTN Trunking Gateway

 One of the use cases for the NSIS signaling protocol is the scenario
 of interconnecting PSTN gateways with an IP network that supports
 QoS.

Brunner Informational [Page 36] RFC 3726 Requirements for Signaling Protocols April 2004

 Four different scenarios are considered here.
 1. In-band QoS signaling is used.  In this case the Media Gateway
    (MG) will be acting as the NSIS Initiator and the Edge Router (ER)
    will be the NSIS Forwarder.  Hence, the ER should do admission
    control (into pre-provisioned traffic trunks) for the individual
    traffic flows.  This scenario is not further considered here.
 2. Out-of-band signaling in a single domain, the NSIS forwarder is
    integrated in the Media Gateway Controller (MGC).  In this case no
    NSIS protocol is required.
 3. Out-of-band signaling in a single domain, the NSIS forwarder is a
    separate box.  In this case NSIS signaling is used between the MGC
    and the NSIS Forwarder.
 4. Out-of-band signaling between multiple domains, the NSIS Forwarder
    (which may be integrated in the MGC) triggers the NSIS Forwarder
    of the next domain.
 When the out-of-band QoS signaling is used the Media Gateway
 Controller (MGC) will be acting as the NSIS Initiator.
 In the second scenario the voice provider manages a set of traffic
 trunks that are leased from a network provider.  The MGC does the
 admission control in this case.  Since the NSIS Forwarder acts both
 as a NSIS Initiator and a NSIS Forwarder, no NSIS signaling is
 required.  This scenario is shown in Figure 3.
  +-------------+    ISUP/SIGTRAN     +-----+              +-----+
  | SS7 network |---------------------| MGC |--------------| SS7 |
  +-------------+             +-------+-----+---------+    +-----+
        :                    /           :             \
        :                   /            :              \
        :                  /    +--------:----------+    \
        :          MEGACO /    /         :           \    \
        :                /    /       +-----+         \    \
        :               /    /        | NMS |          \    \
        :              /     |        +-----+          |     \
        :              :     |                         |     :
 +--------------+  +----+    |   bandwidth pipe (SLS)  |  +----+
 | PSTN network |--| MG |--|ER|======================|ER|-| MG |--
 +--------------+  +----+     \                       /   +----+
                               \     QoS network     /
                                +-------------------+
              Figure 3: PSTN trunking gateway scenario

Brunner Informational [Page 37] RFC 3726 Requirements for Signaling Protocols April 2004

 In the third scenario, the voice provider does not lease traffic
 trunks in the network.  Another entity may lease traffic trunks and
 may use a NSIS Forwarder to do per-flow admission control.  In this
 case the NSIS signaling is used between the MGC and the NSIS
 Forwarder, which is a separate box here.  Hence, the MGC acts only as
 a NSIS Initiator.  This scenario is depicted in Figure 4.
  +-------------+    ISUP/SIGTRAN     +-----+              +-----+
  | SS7 network |---------------------| MGC |--------------| SS7 |
  +-------------+             +-------+-----+---------+    +-----+
        :                    /           :             \
        :                   /         +-----+           \
        :                  /          | NF  |            \
        :                 /           +-----+             \
        :                /               :                 \
        :               /       +--------:----------+       \
        :       MEGACO :       /         :           \       :
        :              :      /       +-----+         \      :
        :              :     /        | NMS |          \     :
        :              :     |        +-----+          |     :
        :              :     |                         |     :
 +--------------+  +----+    |   bandwidth pipe (SLS)  |  +----+
 | PSTN network |--| MG |--|ER|======================|ER|-| MG |--
 +--------------+  +----+     \                       /   +----+
                               \     QoS network     /
                                +-------------------+
             Figure 4: PSTN trunking gateway scenario
 In the fourth scenario multiple transport domains are involved.  In
 the originating network either the MGC may have an overview on the
 resources of the overlay network or a separate NSIS Forwarder will
 have the overview.  Hence, depending on this either the MGC or the
 NSIS Forwarder of the originating domain will contact the NSIS
 Forwarder of the next domain.  The MGC always acts as a NSIS
 Initiator and may also be acting as a NSIS Forwarder in the first
 domain.

8.10. An Application Requests End-to-End QoS Path from the Network

 This is actually the conceptually simplest case.  A multimedia
 application requests a guaranteed service from an IP network.  We
 assume here that the application is somehow able to specify the
 network service.  The characteristics here are that many hosts might
 do it, but that the requested service is low capacity (bounded by the
 access line).  Note that there is an issue of scaling in the number
 of applications requesting this service in the core of the network.

Brunner Informational [Page 38] RFC 3726 Requirements for Signaling Protocols April 2004

8.11. QOS for Virtual Private Networks

 In a Virtual Private Network (VPN), a variety of tunnels might be
 used between its edges.  These tunnels could be for example, IPSec,
 GRE, and IP-IP.  One of the most significant issues in VPNs is
 related to how a flow is identified and what quality a flow gets.  A
 flow identification might consist among others of the transport
 protocol port numbers.  In an IP-Sec tunnel this will be problematic
 since the transport protocol information is encrypted.
 There are two types of L3 VPNs, distinguished by where the endpoints
 of the tunnels exist.  The endpoints of the tunnels may either be on
 the customer (CPE) or the provider equipment or provider edge (PE).
 Virtual Private networks are also likely to request bandwidth or
 other type of service in addition to the premium services the PSTN GW
 are likely to use.

8.11.1. Tunnel End Points at the Customer Premises

 When the endpoints are the CPE, the CPE may want to signal across the
 public IP network for a particular amount of bandwidth and QoS for
 the tunnel aggregate.  Such signaling may be useful when a customer
 wants to vary their network cost with demand, rather than paying a
 flat rate.  Such signaling exists between the two CPE routers.
 Intermediate access and edge routers perform the same exact call
 admission control, authentication and aggregation functions performed
 by the corresponding routers in the PSTN GW scenario with the
 exception that the endpoints are the CPE tunnel endpoints rather than
 PSTN GWs and the 5-tuple used to describe the RTP flow is replaced
 with the corresponding flow spec to uniquely identify the tunnels.
 Tunnels may be of any variety (e.g., IP-Sec, GRE, IP-IP).
 In such a scenario, NSIS would actually allow partly for customer
 managed VPNs, which means a customer can setup VPNs by subsequent
 NSIS signaling to various end-point.  Plus the tunnel end-points are
 not necessarily bound to an application.  The customer administrator
 might be the one triggering NSIS signaling.

8.11.2. Tunnel End Points at the Provider Premises

 In the case were the tunnel end-points exist on the provider edge,
 requests for bandwidth may be signaled either per flow, where a flow
 is defined from a customers address space, or between customer sites.
 In the case of per flow signaling, the PE router must map the
 bandwidth request to the tunnel carrying traffic to the destination
 specified in the flow spec.  Such a tunnel is a member of an

Brunner Informational [Page 39] RFC 3726 Requirements for Signaling Protocols April 2004

 aggregate to which the flow must be admitted.  In this case, the
 operation of admission control is very similar to the case of the
 PSTN GW with the additional level of indirection imposed by the VPN
 tunnel.  Therefore, authentication, accounting and policing may be
 required on the PE router.
 In the case of per site signaling, a site would need to be
 identified.  This may be accomplished by specifying the network
 serviced at that site through an IP prefix.  In this case, the
 admission control function is performed on the aggregate to the PE
 router connected to the site in question.

9. References

9.1. Normative References

 [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.

9.2. Informative References

 [RSVP]     Braden, R., Ed., Zhang, L., Berson, S., Herzog, S. and S.
            Jamin, "Resource Protocol (RSVP) -- Version 1 Functional
            Specification", RFC 2205, September 1997.
 [RFC3234]  Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and
            Issues", RFC 3234, February 2002.

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10. Authors' Addresses

 Marcus Brunner (Editor)
 NEC Europe Ltd.
 Network Laboratories
 Kurfuersten-Anlage 36
 D-69115 Heidelberg
 Germany
 EMail: brunner@netlab.nec.de
 Robert Hancock
 Roke Manor Research Ltd
 Romsey, Hants, SO51 0ZN
 United Kingdom
 EMail: robert.hancock@roke.co.uk
 Eleanor Hepworth
 Roke Manor Research Ltd
 Romsey, Hants, SO51 0ZN
 United Kingdom
 EMail: eleanor.hepworth@roke.co.uk
 Cornelia Kappler
 Siemens AG
 Berlin 13623
 Germany
 EMail: cornelia.kappler@siemens.com
 Hannes Tschofenig
 Siemens AG
 Otto-Hahn-Ring 6
 81739 Munchen
 Germany
 EMail: Hannes.Tschofenig@mchp.siemens.de

Brunner Informational [Page 41] RFC 3726 Requirements for Signaling Protocols April 2004

11. Full Copyright Statement

 Copyright (C) The Internet Society (2004).  This document is subject
 to the rights, licenses and restrictions contained in BCP 78 and
 except as set forth therein, the authors retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
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 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
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 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
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Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Brunner Informational [Page 42]

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