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Network Working Group S. Yasukawa, Ed. Request for Comments: 4461 NTT Category: Informational April 2006

           Signaling Requirements for Point-to-Multipoint
        Traffic-Engineered MPLS Label Switched Paths (LSPs)

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 (2006).

Abstract

 This document presents a set of requirements for the establishment
 and maintenance of Point-to-Multipoint (P2MP) Traffic-Engineered (TE)
 Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs).
 There is no intent to specify solution-specific details or
 application-specific requirements in this document.
 The requirements presented in this document not only apply to
 packet-switched networks under the control of MPLS protocols, but
 also encompass the requirements of Layer Two Switching (L2SC), Time
 Division Multiplexing (TDM), lambda, and port switching networks
 managed by Generalized MPLS (GMPLS) protocols.  Protocol solutions
 developed to meet the requirements set out in this document must
 attempt to be equally applicable to MPLS and GMPLS.

Yasukawa Informational [Page 1] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

Table of Contents

 1. Introduction ....................................................3
    1.1. Non-Objectives .............................................6
 2. Definitions .....................................................6
    2.1. Acronyms ...................................................6
    2.2. Terminology ................................................6
         2.2.1. Terminology for Partial LSPs ........................8
    2.3. Conventions ................................................9
 3. Problem Statement ...............................................9
    3.1. Motivation .................................................9
    3.2. Requirements Overview ......................................9
 4. Detailed Requirements for P2MP TE Extensions ...................11
    4.1. P2MP LSP ..................................................11
    4.2. P2MP Explicit Routing .....................................12
    4.3. Explicit Path Loose Hops and Widely Scoped
         Abstract Nodes ............................................13
    4.4. P2MP TE LSP Establishment, Teardown, and
         Modification Mechanisms ...................................14
    4.5. Fragmentation .............................................14
    4.6. Failure Reporting and Error Recovery ......................15
    4.7. Record Route of P2MP TE LSP ...............................16
    4.8. Call Admission Control (CAC) and QoS Control
         Mechanism of P2MP TE LSPs .................................17
    4.9. Variation of LSP Parameters ...............................17
    4.10. Re-Optimization of P2MP TE LSPs ..........................18
    4.11. Merging of Tree Branches .................................18
    4.12. Data Duplication .........................................19
    4.13. IPv4/IPv6 Support ........................................20
    4.14. P2MP MPLS Label ..........................................20
    4.15. Advertisement of P2MP Capability .........................20
    4.16. Multi-Access LANs ........................................21
    4.17. P2MP MPLS OAM ............................................21
    4.18. Scalability ..............................................21
          4.18.1. Absolute Limits ..................................22
    4.19. Backwards Compatibility ..................................24
    4.20. GMPLS ....................................................24
    4.21. P2MP Crankback Routing ...................................25
 5. Security Considerations ........................................25
 6. Acknowledgements ...............................................26
 7. References .....................................................26
    7.1. Normative References ......................................26
    7.2. Informative References ....................................26

Yasukawa Informational [Page 2] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

1. Introduction

 Existing MPLS traffic engineering (MPLS-TE) allows for strict QoS
 guarantees, resource optimization, and fast failure recovery, but it
 is limited to point-to-point (P2P) LSPs.  There is a desire to
 support point-to-multipoint (P2MP) services using traffic-engineered
 LSPs, and this clearly motivates enhancements of the base MPLS-TE
 tool box in order to support P2MP MPLS-TE LSPs.
 A P2MP TE LSP is a TE LSP (per [RFC2702] and [RFC3031]) that has a
 single ingress LSR and one or more egress LSRs, and is
 unidirectional.  P2MP services (that deliver data from a single
 source to one or more receivers) may be supported by any combination
 of P2P and P2MP LSPs depending on the degree of optimization required
 within the network, and such LSPs may be traffic-engineered again
 depending on the requirements of the network.  Further, multipoint-
 to-multipoint (MP2MP) services (which deliver data from more than one
 source to one or more receivers) may be supported by a combination of
 P2P and P2MP LSPs.
 [RFC2702] specifies requirements for traffic engineering over MPLS.
 In Section 2, it describes traffic engineering in some detail, and
 those definitions are equally applicable to traffic engineering in a
 point-to-multipoint service environment.  They are not repeated here,
 but it is assumed that the reader is fully familiar with them.
 Section 3.0 of [RFC2702] also explains how MPLS is particularly
 suited to traffic engineering; it presents the following eight
 reasons.
    1. Explicit label switched paths that are not constrained by the
       destination-based forwarding paradigm can be easily created
       through manual administrative action or through automated
       action by the underlying protocols.
    2. LSPs can potentially be maintained efficiently.
    3. Traffic trunks can be instantiated and mapped onto LSPs.
    4. A set of attributes can be associated with traffic trunks that
       modulate their behavioral characteristics.
    5. A set of attributes can be associated with resources that
       constrain the placement of LSPs and traffic trunks across them.
    6. MPLS allows for both traffic aggregation and disaggregation,
       whereas classical destination-only-based IP forwarding permits
       only aggregation.
    7. It is relatively easy to integrate a "constraint-based routing"
       framework with MPLS.
    8. A good implementation of MPLS can offer significantly lower
       overhead than competing alternatives for traffic engineering.

Yasukawa Informational [Page 3] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 These points are equally applicable to point-to-multipoint traffic
 engineering.  Points 1 and 7 are particularly important.  Note that
 point 3 implies that the concept of a point-to-multipoint traffic
 trunk is defined and is supported by (or mapped onto) P2MP LSPs.
 That is, the traffic flow for a point-to-multipoint LSP is not
 constrained to the path or paths that it would follow during
 multicast routing or shortest path destination-based routing, but it
 can be explicitly controlled through manual or automated action.
 Further, the explicit paths that are used may be computed using
 algorithms based on a variety of constraints to produce all manner of
 tree shapes.  For example, an explicit path may be cost-based
 [STEINER], shortest path, or QoS-based, or it may use some fair-cost
 QoS algorithm.
 [RFC2702] also describes the functional capabilities required to
 fully support traffic engineering over MPLS in large networks.
 This document presents a set of requirements for Point-to-Multipoint
 (P2MP) traffic engineering (TE) extensions to Multiprotocol Label
 Switching (MPLS).  It specifies functional requirements for solutions
 to deliver P2MP TE LSPs.
 Solutions that specify procedures for P2MP TE LSP setup MUST satisfy
 these requirements.  There is no intent to specify solution-specific
 details or application-specific requirements in this document.
 The requirements presented in this document apply equally to packet-
 switched networks under the control of MPLS protocols and to packet-
 switched, TDM, lambda, and port-switching networks managed by
 Generalized MPLS (GMPLS) protocols.  Protocol solutions developed to
 meet the requirements set out in this document MUST attempt to be
 equally applicable to MPLS and GMPLS.
 Existing MPLS TE mechanisms such as [RFC3209] do not support P2MP TE
 LSPs, so new mechanisms need to be developed.  This SHOULD be
 achieved with maximum re-use of existing MPLS protocols.
 Note that there is a separation between routing and signaling in MPLS
 TE.  In particular, the path of the MPLS TE LSP is determined by
 performing a constraint-based computation (such as CSPF) on a traffic
 engineering database (TED).  The contents of the TED may be collected
 through a variety of mechanisms.

Yasukawa Informational [Page 4] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 This document focuses on requirements for establishing and
 maintaining P2MP MPLS TE LSPs through signaling protocols; routing
 protocols are out of scope.  No assumptions are made about how the
 TED used as the basis for path computations for P2MP LSPs is formed.
 This requirements document assumes the following conditions for P2MP
 MPLS TE LSP establishment and maintenance:
 o A P2MP TE LSP will be set up with TE constraints and will allow
   efficient packet or data replication at various branching points in
   the network.  Although replication is a data plane issue, it is the
   responsibility of the control plane (acting in conjunction with the
   path computation component) to install LSPs in the network such
   that replication can be performed efficiently.  Note that the
   notion of "efficient" replication is relative and may have
   different meanings depending on the objectives (see Section 4.2).
 o P2MP TE LSP setup mechanisms must include the ability to add/remove
   receivers to/from the P2MP service supported by an existing P2MP TE
   LSP.
 o Tunnel endpoints of P2MP TE LSP will be modified by adding/removing
   egress LSRs to/from an existing P2MP TE LSP.  It is assumed that
   the rate of change of leaves of a P2MP LSP (that is, the rate at
   which new egress LSRs join, or old egress LSRs are pruned) is "not
   so high" because P2MP TE LSPs are assumed to be utilized for TE
   applications.  This issue is discussed at greater length in Section
   4.18.1.
 o A P2MP TE LSP may be protected by fast error recovery mechanisms to
   minimize disconnection of a P2MP service.
 o A set of attributes of the P2MP TE LSP (e.g., bandwidth, etc.)  may
   be modified by some mechanism (e.g., make-before-break, etc.)  to
   accommodate attribute changes to the P2MP service without impacting
   data traffic.  These issues are discussed in Sections 4.6 and 4.10.
 It is not a requirement that the ingress LSR must control the
 addition or removal of leaves from the P2MP tree.
 It is this document's objective that a solution compliant to the
 requirements set out in this document MUST operate these P2MP TE
 capabilities in a scalable fashion.

Yasukawa Informational [Page 5] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

1.1. Non-Objectives

 For clarity, this section lists some items that are out of scope of
 this document.
 It is assumed that some information elements describing the P2MP TE
 LSP are known to the ingress LSR prior to LSP establishment.  For
 example, the ingress LSRs know the IP addresses that identify the
 egress LSRs of the P2MP TE LSP.  The mechanisms by which the ingress
 LSR obtains this information is outside the scope of P2MP TE
 signaling and so is not included in this document.  Other documents
 may complete the description of this function by providing automated,
 protocol-based ways of passing this information to the ingress LSR.
 This document does not specify any requirements for the following
 functions.
  1. Non-TE LSPs (such as per-hop, routing-based LSPs).
  2. Discovery of egress leaves for a P2MP LSP.
  3. Hierarchical P2MP LSPs.
  4. OAM for P2MP LSPs.
  5. Inter-area and inter-AS P2MP TE LSPs.
  6. Applicability of P2MP MPLS TE LSPs to service scenarios.
  7. Specific application or application requirements.
  8. Algorithms for computing P2MP distribution trees.
  9. Multipoint-to-point LSPs.
  10. Multipoint-to-multipoint LSPs.
  11. Routing protocols.
  12. Construction of the traffic engineering database.
  13. Distribution of the information used to construct the traffic

engineering database.

2. Definitions

2.1. Acronyms

 P2P:  Point-to-point
 P2MP: Point-to-multipoint

2.2. Terminology

 The reader is assumed to be familiar with the terminology in
 [RFC3031] and [RFC3209].
 The following terms are defined for use in the context of P2MP TE
 LSPs only.

Yasukawa Informational [Page 6] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 P2MP tree:
    The ordered set of LSRs and TE links that comprise the path of a
    P2MP TE LSP from its ingress LSR to all of its egress LSRs.
 ingress LSR:
    The LSR that is responsible for initiating the signaling messages
    that set up the P2MP TE LSP.
 egress LSR:
    One of potentially many destinations of the P2MP TE LSP.  Egress
    LSRs may also be referred to as leaf nodes or leaves.
 bud LSR:
   An LSR that is an egress LSR, but also has one or more directly
   connected downstream LSRs.
 branch LSR:
    An LSR that has more than one directly connected downstream LSR.
 P2MP-ID (P2ID):
    A unique identifier of a P2MP TE LSP, which is constant for the
    whole LSP regardless of the number of branches and/or leaves.
 source:
    The sender of traffic that is carried on a P2MP service supported
    by a P2MP LSP.  The sender is not necessarily the ingress LSR of
    the P2MP LSP.
 receiver:
    A recipient of traffic carried on a P2MP service supported by a
    P2MP LSP.  A receiver is not necessarily an egress LSR of the P2MP
    LSP.  Zero, one, or more receivers may receive data through a
    given egress LSR.

Yasukawa Informational [Page 7] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

2.2.1. Terminology for Partial LSPs

 It is convenient to sub-divide P2MP trees for functional and
 representational reasons.  A tree may be divided in two dimensions:
  1. A division may be made along the length of the tree. For example,

the tree may be split into two components each running from the

   ingress LSR to a discrete set of egress LSRs.  Upstream LSRs (for
   example, the ingress LSR) may be members of both components.
  1. A tree may be divided at a branch LSR (or any transit LSR) to

produce a component of the tree that runs from the branch (or

   transit) LSR to all egress LSRs downstream of this point.
 These two methods of splitting the P2MP tree can be combined, so it
 is useful to introduce some terminology to allow the partitioned
 trees to be clearly described.
 Use the following designations:
    Source (ingress) LSR - S
    Leaf (egress) LSR - L
    Branch LSR - B
    Transit LSR - X (any single, arbitrary LSR that is not a source,
                     leaf or branch)
    All - A
    Partial (i.e., not all) - P
 Define a new term:
    Sub-LSP:
       A segment of a P2MP TE LSP that runs from one of the LSP's LSRs
       to one or more of its other LSRs.
 Using these new concepts, we can define any combination or split of
 the P2MP tree.  For example:
    S2L sub-LSP:
       The path from the source to one specific leaf.
    S2PL sub-LSP:
       The path from the source to a set of leaves.
    B2AL sub-LSP:
       The path from a branch LSR to all downstream leaves.

Yasukawa Informational [Page 8] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

    X2X sub-LSP:
       A component of the P2MP LSP that is a simple path that does not
       branch.
    Note that the S2AL sub-LSP is equivalent to the P2MP LSP.

2.3. Conventions

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].

3. Problem Statement

3.1. Motivation

 As described in Section 1, traffic engineering and constraint-based
 routing (including Call Admission Control (CAC), explicit source
 routing, and bandwidth reservation) are required to enable efficient
 resource usage and strict QoS guarantees.  Such mechanisms also make
 it possible to provide services across a congested network where
 conventional "shortest path first" forwarding paradigms would fail.
 Existing MPLS TE mechanisms [RFC3209] and GMPLS TE mechanisms
 [RFC3473] only provide support for P2P TE LSPs.  While it is possible
 to provide P2MP TE services using P2P TE LSPs, any such approach is
 potentially suboptimal since it may result in data replication at the
 ingress LSR, or in duplicate data traffic within the network.
 Hence, to provide P2MP MPLS TE services in a fully efficient manner,
 it is necessary to specify specific requirements.  These requirements
 can then be used when defining mechanisms for the use of existing
 protocols and/or extensions to existing protocols and/or new
 protocols.

3.2. Requirements Overview

 This document states basic requirements for the setup of P2MP TE
 LSPs.  The requirements apply to the signaling techniques only, and
 no assumptions are made about which routing protocols are run within
 the network, or about how the information that is used to construct
 the Traffic Engineering Database (TED) is distributed.  These factors
 are out of the scope of this document.
 A P2MP TE LSP path computation will take into account various
 constraints such as bandwidth, affinities, required level of
 protection and so on.  The solution MUST allow for the computation of
 P2MP TE LSP paths that satisfy constraints, with the objective of

Yasukawa Informational [Page 9] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 supporting various optimization criteria such as delays, bandwidth
 consumption in the network, or any other combinations.  This is
 likely to require the presence of a TED, as well as the ability to
 signal the explicit path of an LSP.
 A desired requirement is also to maximize the re-use of existing MPLS
 TE techniques and protocols where doing so does not adversely impact
 the function, simplicity, or scalability of the solution.
 This document does not restrict the choice of signaling protocol used
 to set up a P2MP TE LSP, but note that [RFC3468] states
   ...the consensus reached by the Multiprotocol
   Label Switching (MPLS) Working Group within the IETF to focus its
   efforts on "Resource Reservation Protocol (RSVP)-TE: Extensions to
   RSVP for Label-Switched Paths (LSP) Tunnels" (RFC 3209) as the MPLS
   signalling protocol for traffic engineering applications...
 The P2MP TE LSP setup mechanism MUST include the ability to
 add/remove egress LSRs to/from an existing P2MP TE LSP and MUST allow
 for the support of all the TE LSP management procedures already
 defined for P2P TE LSP.  Further, when new TE LSP procedures are
 developed for P2P TE LSPs, equivalent or identical procedures SHOULD
 be developed for P2MP TE LSPs.
 The computation of P2MP trees is implementation dependent and is
 beyond the scope of the solutions that are built with this document
 as a guideline.
 Consider the following figure.
                       Source 1 (S1)
                             |
                           I-LSR1
                           |   |
                           |   |
          R2----E-LSR3--LSR1   LSR2---E-LSR2--Receiver 1 (R1)
                           |   :
                R3----E-LSR4   E-LSR5
                           |   :
                           |   :
                          R4   R5
                         Figure 1
 Figure 1 shows a single ingress LSR (I-LSR1), and four egress LSRs
 (E-LSR2, E-LSR3, E-LSR4, and E-LSR5).  I-LSR1 is attached to a
 traffic source that is generating traffic for a P2MP application.

Yasukawa Informational [Page 10] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 Receivers R1, R2, R3, and R4 are attached to E-LSR2, E-LSR3, and
 E-LSR4.
 The following are the objectives of P2MP LSP establishment and use.
    a) A P2MP tree that satisfies various constraints is pre-
       determined, and details are supplied to I-LSR1.
       Note that no assumption is made about whether the tree is
       provided to I-LSR1 or computed by I-LSR1.  The solution SHOULD
       also allow for the support of a partial path by means of loose
       routing.
       Typical constraints are bandwidth requirements, resource class
       affinities, fast rerouting, and preemption.  There should not
       be any restriction on the possibility of supporting the set of
       constraints already defined for point-to-point TE LSPs.  A new
       constraint may specify which LSRs should be used as branch LSRs
       for the P2MP LSR in order to take into account LSR capabilities
       or network constraints.
    b) A P2MP TE LSP is set up from I-LSR1 to E-LSR2, E-LSR3, and
       E-LSR4 using the tree information.
    c) In this case, the branch LSR1 should replicate incoming packets
       or data and send them to E-LSR3 and E-LSR4.
    d) If a new receiver (R5) expresses an interest in receiving
       traffic, a new tree is determined, and a B2L sub-LSP from LSR2
       to E-LSR5 is grafted onto the P2MP TE LSP.  LSR2 becomes a
       branch LSR.

4. Detailed Requirements for P2MP TE Extensions

4.1. P2MP LSP

 The P2MP TE extensions MUST be applicable to the signaling of LSPs
 for different switching types.  For example, it MUST be possible to
 signal a P2MP TE LSP in any switching medium, whether it is packet or
 non-packet based (including frame, cell, TDM, lambda, etc.).
 As with P2P MPLS technology [RFC3031], traffic is classified with a
 FEC in this extension.  All packets that belong to a particular FEC
 and that travel from a particular node MUST follow the same P2MP
 tree.

Yasukawa Informational [Page 11] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 In order to scale to a large number of branches, P2MP TE LSPs SHOULD
 be identified by a unique identifier (the P2MP ID or P2ID) that is
 constant for the whole LSP regardless of the number of branches
 and/or leaves.

4.2. P2MP Explicit Routing

 Various optimizations in P2MP tree formation need to be applied to
 meet various QoS requirements and operational constraints.
 Some P2MP applications may request a bandwidth-guaranteed P2MP tree
 that satisfies end-to-end delay requirements.  And some operators may
 want to set up a cost-minimum P2MP tree by specifying branch LSRs
 explicitly.
 The P2MP TE solution therefore MUST provide a means of establishing
 arbitrary P2MP trees under the control of an external tree
 computation process, path configuration process, or dynamic tree
 computation process located on the ingress LSR.  Figure 2 shows two
 typical examples.
             A                                      A
             |                                    /   \
             B                                   B     C
             |                                  / \   / \
             C                                 D   E  F   G
             |                                / \ / \/ \ / \
 D--E*-F*-G*-H*-I*-J*-K*--L                  H  I J KL M N  O
      Steiner P2MP tree                        SPF P2MP tree
              Figure 2: Examples of P2MP TE LSP topology
 One example is the Steiner P2MP tree (cost-minimum P2MP tree)
 [STEINER].  This P2MP tree is suitable for constructing a cost-
 minimum P2MP tree so as to minimize the bandwidth consumption in the
 core.  To realize this P2MP tree, several intermediate LSRs must be
 both MPLS data terminating LSRs and transit LSRs (LSRs E, F, G, H, I,
 J, and K in Figure 2).  Therefore, the P2MP TE solution MUST support
 a mechanism that can set up this kind of bud LSR between an ingress
 LSR and egress LSRs.  Note that this includes constrained Steiner
 trees that allow for the computation of a minimal cost trees with
 some other constraints such as a bounded delay between the source and
 every receiver.

Yasukawa Informational [Page 12] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 Another example is a CSPF (Constraint Shortest Path First) P2MP tree.
 By some metric (which can be set upon any specific criteria like the
 delay, bandwidth, or a combination of those), one can calculate a
 shortest-path P2MP tree.  This P2MP tree is suitable for carrying
 real-time traffic.
 The solution MUST allow the operator to make use of any tree
 computation technique.  In the former case, an efficient/optimal tree
 is defined as a minimal cost tree (Steiner tree), whereas in the
 later case, it is defined as the tree that provides shortest path
 between the source and any receiver.
 To support explicit setup of any reasonable P2MP tree shape, a P2MP
 TE solution MUST support some form of explicit source-based control
 of the P2MP tree that can explicitly include particular LSRs as
 branch LSRs.  This can be used by the ingress LSR to set up the P2MP
 TE LSP.  For instance, a P2MP TE LSP can be represented simply as a
 whole tree or by its individual branches.

4.3. Explicit Path Loose Hops and Widely Scoped Abstract Nodes

 A P2MP tree is completely specified if all the required branches and
 hops between a sender and leaf LSR are indicated.
 A P2MP tree is partially specified if only a subset of intermediate
 branches and hops is indicated.  This may be achieved using loose
 hops in the explicit path, or using widely scoped abstract nodes
 (that is, abstract nodes that are not simple [RFC3209]) such as IPv4
 prefixes shorter than 32 bits, or AS numbers.  A partially specified
 P2MP tree might be particularly useful in inter-area and inter-AS
 situations, although P2MP requirements for inter-area and inter-AS
 are beyond the scope of this document.
 Protocol solutions SHOULD include a way to specify loose hops and
 widely scoped abstract nodes in the explicit source-based control of
 the P2MP tree as defined in the previous section.  Where this support
 is provided, protocol solutions MUST allow downstream LSRs to apply
 further explicit control to the P2MP tree to resolve a partially
 specified tree into a (more) completely specified tree.
 Protocol solutions MUST allow the P2MP tree to be completely
 specified at the ingress LSR where sufficient information exists to
 allow the full tree to be computed and where policies along the path
 (such as at domain boundaries) support full specification.

Yasukawa Informational [Page 13] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 In all cases, the egress LSRs of the P2MP TE LSP must be fully
 specified either individually or through some collective identifier.
 Without this information, it is impossible to know where the TE LSP
 should be routed to.
 In case of a tree being computed by some downstream LSRs (e.g., the
 case of hops specified as loose hops), the solution MUST provide
 protocol mechanisms for the ingress LSR of the P2MP TE LSP to learn
 the full P2MP tree.  Note that this information may not always be
 obtainable owing to policy considerations, but where part of the path
 remains confidential, it MUST be reported through aggregation (for
 example, using an AS number).

4.4. P2MP TE LSP Establishment, Teardown, and Modification Mechanisms

 The P2MP TE solution MUST support establishment, maintenance, and
 teardown of P2MP TE LSPs in a manner that is at least scalable in a
 linear way.  This MUST include both the existence of very many LSPs
 at once, and the existence of very many destinations for a single
 P2MP LSP.
 In addition to P2MP TE LSP establishment and teardown mechanisms, the
 solution SHOULD support a partial P2MP tree modification mechanism.
 For the purpose of adding sub-P2MP TE LSPs to an existing P2MP TE
 LSP, the extensions SHOULD support a grafting mechanism.  For the
 purpose of deleting a sub-P2MP TE LSPs from an existing P2MP TE LSP,
 the extensions SHOULD support a pruning mechanism.
 It is RECOMMENDED that these grafting and pruning operations cause no
 additional processing in nodes that are not along the path to the
 grafting or pruning node, or that are downstream of the grafting or
 pruning node toward the grafted or pruned leaves.  Moreover, both
 grafting and pruning operations MUST NOT disrupt traffic currently
 forwarded along the P2MP tree.
 There is no assumption that the explicitly routed P2MP LSP remains on
 an optimal path after several grafts and prunes have occurred.  In
 this context, scalable refers to the signaling process for the P2MP
 TE LSP.  The TE nature of the LSP allows that re-optimization may
 take place from time to time to restore the optimality of the LSP.

4.5. Fragmentation

 The P2MP TE solution MUST handle the situation where a single
 protocol message cannot contain all the information necessary to
 signal the establishment of the P2MP LSP.  It MUST be possible to
 establish the LSP in these circumstances.

Yasukawa Informational [Page 14] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 This situation may arise in either of the following circumstances.
    a. The ingress LSR cannot signal the whole tree in a single
       message.
    b. The information in a message expands to be too large (or is
       discovered to be too large) at some transit node.  This may
       occur because of some increase in the information that needs to
       be signaled or because of a reduction in the size of signaling
       message that is supported.
 The solution to these problems SHOULD NOT rely on IP fragmentation of
 protocol messages, and it is RECOMMENDED to rely on some protocol
 procedures specific to the signaling solution.
 In the event that fragmented IP packets containing protocol messages
 are received, it is NOT RECOMMENDED that they are reassembled at the
 receiving LSR.

4.6. Failure Reporting and Error Recovery

 Failure events may cause egress LSRs or sub-P2MP LSPs to become
 detached from the P2MP TE LSP.  These events MUST be reported
 upstream as for a P2P LSP.
 The solution SHOULD provide recovery techniques, such as protection
 and restoration, allowing recovery of any impacted sub-P2MP TE LSPs.
 In particular, a solution MUST provide fast protection mechanisms
 applicable to P2MP TE LSP similar to the solutions specified in
 [RFC4090] for P2P TE LSPs.  Note also that no assumption is made
 about whether backup paths for P2MP TE LSPs should or should not be
 shared with P2P TE LSPs backup paths.
 Note that the functions specified in [RFC4090] are currently specific
 to packet environments and do not apply to non-packet environments.
 Thus, while solutions MUST provide fast protection mechanisms similar
 to those specified in [RFC4090], this requirement is limited to the
 subset of the solution space that applies to packet-switched networks
 only.
 Note that the requirements expressed in this document are general to
 all MPLS TE P2MP signaling, and any solution that meets them will
 therefore be general.  Specific applications may have additional
 requirements or may want to relax some requirements stated in this
 document.  This may lead to variations in the solution.

Yasukawa Informational [Page 15] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 The solution SHOULD also support the ability to meet other network
 recovery requirements such as bandwidth protection and bounded
 propagation delay increase along the backup path during failure.
 A P2MP TE solution MUST support the P2MP fast protection mechanism to
 handle P2MP applications sensitive to traffic disruption.
 If the ingress LSR is informed of the failure of delivery to fewer
 than all the egress LSRs, this SHOULD NOT cause automatic teardown of
 the P2MP TE LSP.  That is, while some egress LSRs remain connected to
 the P2MP tree, it SHOULD be a matter of local policy at the ingress
 LSR whether the P2MP LSP is retained.
 When all egress LSRs downstream of a branch LSR have become
 disconnected from the P2MP tree, and some branch LSR is unable to
 restore connectivity to any of them by means of some recovery or
 protection mechanisms, the branch LSR MAY remove itself from the P2MP
 tree provided that it is not also an egress LSR (that is, a bud).
 Since the faults that severed the various downstream egress LSRs from
 the P2MP tree may be disparate, the branch LSR MUST report all such
 errors to its upstream neighbor.  An upstream LSR or the ingress LSR
 can then decide to re-compute the path to those particular egress
 LSRs around the failure point.
 Solutions MAY include the facility for transit LSRs and particularly
 branch LSRs to recompute sub-P2MP trees to restore them after
 failures.  In the event of successful repair, error notifications
 SHOULD NOT be reported to upstream nodes, but the new paths are
 reported if route recording is in use.  Crankback requirements are
 discussed in Section 4.21.

4.7. Record Route of P2MP TE LSP

 Being able to identify the established topology of P2MP TE LSP is
 very important for various purposes such as management and operation
 of some local recovery mechanisms like Fast Reroute [RFC4090].  A
 network operator uses this information to manage P2MP TE LSPs.
 Therefore, the P2MP TE solution MUST support a mechanism that can
 collect and update P2MP tree topology information after the P2MP LSP
 establishment and modification process.
 It is RECOMMENDED that the information is collected in a data format
 that allows easy recognition of the P2MP tree topology.
 The solution MUST support mechanisms for the recording of both
 outgoing interfaces and node-ids.

Yasukawa Informational [Page 16] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 The solution MUST gracefully handle scaling issues concerned with the
 collection of P2MP tree information, including the case where the
 collected information is too large to be carried in a single protocol
 message.

4.8. Call Admission Control (CAC) and QoS Control Mechanism of

    P2MP TE LSPs
 P2MP TE LSPs may share network resource with P2P TE LSPs.  Therefore,
 it is important to use CAC and QoS in the same way as P2P TE LSPs for
 easy and scalable operation.
 P2MP TE solutions MUST support both resource sharing and exclusive
 resource utilization to facilitate coexistence with other LSPs to the
 same destination(s).
 P2MP TE solutions MUST be applicable to DiffServ-enabled networks
 that can provide consistent QoS control in P2MP LSP traffic.
 Any solution SHOULD also satisfy the DS-TE requirements [RFC3564] and
 interoperate smoothly with current P2P DS-TE protocol specifications.
 Note that this requirement document does not make any assumption on
 the type of bandwidth pool used for P2MP TE LSPs, which can either be
 shared with P2P TE LSP or be dedicated for P2MP use.

4.9. Variation of LSP Parameters

 Certain parameters (such as priority and bandwidth) are associated
 with an LSP.  The parameters are installed by the signaling exchanges
 associated with establishing and maintaining the LSP.
 Any solution MUST NOT allow for variance of these parameters within a
 single P2MP LSP.  That is:
  1. No attributes set and signaled by the ingress LSR of a P2MP LSP may

be varied by downstream LSRs.

  1. There MUST be homogeneous QoS from the root to all leaves of a

single P2MP LSP.

 Changing the parameters for the whole tree MAY be supported, but the
 change MUST apply to the whole tree from ingress LSR to all egress
 LSRs.

Yasukawa Informational [Page 17] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

4.10. Re-Optimization of P2MP TE LSPs

 The detection of a more optimal path (for example, one with a lower
 overall cost) is an example of a situation where P2MP TE LSP re-
 routing may be required.  While re-routing is in progress, an
 important requirement is to avoid double bandwidth reservation (over
 the common parts between the old and new LSP) thorough the use of
 resource sharing.
 Make-before-break MUST be supported for a P2MP TE LSP to ensure that
 there is minimal traffic disruption when the P2MP TE LSP is re-
 routed.
 Make-before-break that only applies to a sub-P2MP tree without
 impacting the data on all the other parts of the P2MP tree MUST be
 supported.
 The solution SHOULD allow for make-before-break re-optimization of
 any subdivision of the P2MP LSP (S2PL sub-LSP, S2X sub-LSP, S2L sub-
 LSP, X2AL sub-LSP, B2PL sub-LSP, X2AL sub-LSP, or B2AL tree).
 Further, it SHOULD do so by minimizing the signaling impact on the
 rest of the P2MP LSP, and without affecting the ability of the
 management plane to manage the LSP.
 The solution SHOULD also provide the ability for the ingress LSR to
 have strict control over the re-optimization process.  The ingress
 LSR SHOULD be able to limit all re-optimization to be source-
 initiated.
 Where sub-LSP re-optimization is allowed by the ingress LSR, such
 re-optimization MAY be initiated by a downstream LSR that is the root
 of the sub-LSP that is to be re-optimized.  Sub-LSP re-optimization
 initiated by a downstream LSR MUST be carried out with the same
 regard to minimizing the impact on active traffic as was described
 above for other re-optimization.

4.11. Merging of Tree Branches

 It is possible for a single transit LSR to receive multiple signaling
 messages for the same P2MP LSP but for different sets of
 destinations.  These messages may be received from the same or
 different upstream nodes and may need to be passed on to the same or
 different downstream nodes.
 This situation may arise as the result of the signaling solution
 definition or implementation options within the signaling solution.
 Further, it may happen during make-before-break re-optimization
 (Section 4.10).

Yasukawa Informational [Page 18] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 It is even possible that it is necessary to construct distinct
 upstream branches in order to achieve the correct label choices in
 certain switching technologies managed by GMPLS (for example,
 photonic cross-connects where the selection of a particular lambda
 for the downstream branches is only available on different upstream
 switches).
 The solution MUST support the case where multiple signaling messages
 for the same P2MP LSP are received at a single transit LSR and refer
 to the same upstream interface.  In this case, the result of the
 protocol procedures SHOULD be a single data flow on the upstream
 interface.
 The solution SHOULD support the case where multiple signaling
 messages for the same P2MP LSP are received at a single transit LSR
 and refer to different upstream interfaces, and where each signaling
 message results in the use of different downstream interfaces.  This
 case represents data flows that cross at the LSR but that do not
 merge.
 The solution MAY support the case where multiple signaling messages
 for the same P2MP LSP are received at a single transit LSR and refer
 to different upstream interfaces, and where the downstream interfaces
 are shared across the received signaling messages.  This case
 represents the merging of data flows.  A solution that supports this
 case MUST ensure that data is not replicated on the downstream
 interfaces.
 An alternative to supporting this last case is for the signaling
 protocol to indicate an error such that the merge may be resolved by
 the upstream LSRs.

4.12. Data Duplication

 Data duplication refers to the receipt by any recipient of duplicate
 instances of the data.  In a packet environment, this means the
 receipt of duplicate packets.  Although small-scale packet
 duplication (that is, a few packets over a relatively short period of
 time) should be a harmless (if inefficient) situation, certain
 existing and deployed applications will not tolerate packet
 duplication.  Sustained packet duplication is, at best, a waste of
 network and processing resources and, at worst, may cause congestion
 and the inability to process the data correctly.
 In a non-packet environment, data duplication means the duplication
 of some part of the signal that may lead to the replication of data
 or to the scrambling of data.

Yasukawa Informational [Page 19] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 Data duplication may legitimately arise in various scenarios
 including re-optimization of active LSPs as described in the previous
 section, and protection of LSPs.  Thus, it is impractical to regulate
 against data duplication in this document.
 Instead, the solution:
  1. SHOULD limit to bounded transitory conditions the cases where

network bandwidth is wasted by the existence of duplicate delivery

   paths.
  1. MUST limit the cases where duplicate data is delivered to an

application to bounded transitory conditions.

4.13. IPv4/IPv6 Support

 Any P2MP TE solution MUST support IPv4 and IPv6 addressing.

4.14. P2MP MPLS Label

 A P2MP TE solution MUST allow the continued use of existing
 techniques to establish P2P LSPs (TE and otherwise) within the same
 network, and MUST allow the coexistence of P2P LSPs within the same
 network as P2MP TE LSPs.
 A P2MP TE solution MUST be specified in such a way that it allows
 P2MP and P2P TE LSPs to be signaled on the same interface.

4.15. Advertisement of P2MP Capability

 Several high-level requirements have been identified to determine the
 capabilities of LSRs within a P2MP network.  The aim of such
 information is to facilitate the computation of P2MP trees using TE
 constraints within a network that contains LSRs that do not all have
 the same capability levels with respect to P2MP signaling and data
 forwarding.
 These capabilities include, but are not limited to:
  1. The ability of an LSR to support branching.
  2. The ability of an LSR to act as an egress LSR and a branch LSR for

the same LSP.

  1. The ability of an LSR to support P2MP MPLS-TE signaling.

Yasukawa Informational [Page 20] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

4.16. Multi-Access LANs

 P2MP MPLS TE may be used to traverse network segments that are
 provided by multi-access media such as Ethernet.  In these cases, it
 is also possible that the entry point to the network segment is a
 branch LSR of the P2MP LSP.
 Two options clearly exist:
  1. the branch LSR replicates the data and transmits multiple copies

onto the segment.

  1. the branch LSR sends a single copy of the data to the segment and

relies on the exit points to determine whether to receive and

   forward the data.
 The first option has a significant data plane scaling issue since all
 replicated data must be sent through the same port and carried on the
 same segment.  Thus, a solution SHOULD provide a mechanism for a
 branch LSR to send a single copy of the data onto a multi-access
 network to reach multiple (adjacent) downstream nodes.  The second
 option may have control plane scaling issues.

4.17. P2MP MPLS OAM

 The MPLS and GMPLS MIB modules MUST be enhanced to provide P2MP TE
 LSP management in line with whatever signaling solutions are
 developed.
 In order to facilitate correct management, P2MP TE LSPs MUST have
 unique identifiers, since otherwise it is impossible to determine
 which LSP is being managed.
 Further discussions of OAM are out of scope for this document.  See
 [P2MP-OAM] for more details.

4.18. Scalability

 Scalability is a key requirement in P2MP MPLS systems.  Solutions
 MUST be designed to scale well with an increase in the number of any
 of the following:
  1. the number of recipients
  2. the number of egress LSRs
  3. the number of branch LSRs
  4. the number of branches
 Both scalability of control plane operation (setup, maintenance,
 modification, and teardown) MUST be considered.

Yasukawa Informational [Page 21] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 Key considerations MUST include:
  1. the amount of refresh processing associated with maintaining a P2MP

TE LSP.

  1. the amount of protocol state that must be maintained by ingress and

transit LSRs along a P2MP tree.

  1. the number of protocol messages required to set up or tear down a

P2MP LSP as a function of the number of egress LSRs.

  1. the number of protocol messages required to repair a P2MP LSP after

failure or to perform make-before-break.

  1. the amount of protocol information transmitted to manage a P2MP TE

LSP (i.e., the message size).

  1. the amount of additional data distributed in potential routing

extensions.

  1. the amount of additional control plane processing required in the

network to detect whether an add/delete of a new branch is

   required, and in particular, the amount of processing in steady
   state when no add/delete is requested
 - the amount of control plane processing required by the ingress,
   transit, and egress LSRs to add/delete a branch LSP to/from an
   existing P2MP LSP.
 It is expected that the applicability of each solution will be
 evaluated with regards to the aforementioned scalability criteria.

4.18.1. Absolute Limits

 In order to achieve the best solution for the problem space, it is
 helpful to clarify the boundaries for P2MP TE LSPs.
  1. Number of egress LSRs.
   A scaling bound is placed on the solution mechanism such that a
   P2MP TE LSP MUST reduce to similar scaling properties as a P2P LSP
   when the number of egress LSRs reduces to one.  That is,
   establishing a P2MP TE LSP to a single egress LSR should cost
   approximately as much as establishing a P2P LSP.
   It is important to classify the issues of scaling within the
   context of traffic engineering.  It is anticipated that the initial
   deployments of P2MP TE LSPs will be limited to a maximum of around
   a hundred egress LSRs, but that within five years deployments may
   increase this to several hundred, and that future deployments may
   require significantly larger numbers.
   An acceptable upper bound for a solution, therefore, is one that
   scales linearly with the number of egress LSRs.  It is expected
   that solutions will scale better than linearly.

Yasukawa Informational [Page 22] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

   Solutions that scale worse than linearly (that is, exponentially or
   polynomially) are not acceptable whatever the number of egress LSRs
   they could support.
  1. Number of branch LSRs.
   Solutions MUST support all possibilities from one extreme of a
   single branch LSR that forks to all leaves on a separate branch, to
   the greatest number of branch LSRs which is (n-1) for n egress
   LSRs.  Assumptions MUST NOT be made in the solution regarding which
   topology is more common, and the solution MUST be designed to
   ensure scalability in all topologies.
  1. Dynamics of P2MP tree.
   Recall that the mechanisms for determining which egress LSRs should
   be added to an LSP and for adding and removing egress LSRs from
   that group are out of the scope of this document.  Nevertheless, it
   is useful to understand the expected rates of arrival and departure
   of egress LSRs, since this can impact the selection of solution
   techniques.
   Again, this document is limited to traffic engineering, and in this
   model the rate of change of LSP egress LSRs may be expected to be
   lower than the rate of change of recipients in an IP multicast
   group.
   Although the absolute number of egress LSRs coming and going is the
   important element for determining the scalability of a solution,
   note that a percentage may be a more comprehensible measure, but
   that this is not as significant for LSPs with a small number of
   recipients.
   A working figure for an established P2MP TE LSP is less than 10%
   churn per day; that is, a relatively slow rate of churn.
   We could say that a P2MP LSP would be shared by multiple multicast
   groups, so the dynamics of the P2MP LSP would be relatively small.
   Solutions MUST optimize for such relatively low rates of change and
   are not required to optimize for significantly higher rates of
   change.
  1. Rate of change within the network.
   It is also important to understand the scaling with regard to
   changes within the network.  That is, one of the features of a P2MP
   TE LSP is that it can be robust or protected against network

Yasukawa Informational [Page 23] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

   failures, and it can be re-optimized to take advantage of newly
   available network resources.
   It is more important that a solution be optimized for scaling with
   respect to recovery and re-optimization of the LSP than for change
   in the egress LSRs, because P2MP is used as a TE tool.
   The solution MUST follow this distinction and optimize accordingly.

4.19. Backwards Compatibility

 It SHOULD be an aim of any P2MP solution to offer as much backward
 compatibility as possible.  An ideal that is probably impossible to
 achieve would be to offer P2MP services across legacy MPLS networks
 without any change to any LSR in the network.
 If this ideal cannot be achieved, the aim SHOULD be to use legacy
 nodes as both transit non-branch LSRs and egress LSRs.
 It is a further requirement for the solution that any LSR that
 implements the solution SHALL NOT be prohibited by that act from
 supporting P2P TE LSPs using existing signaling mechanisms.  That is,
 unless doing so is administratively prohibited, P2P TE LSPs MUST be
 supported through a P2MP network.
 Also, it is a requirement that P2MP TE LSPs MUST be able to coexist
 with IP unicast and IP multicast networks.

4.20. GMPLS

 The requirement for P2MP services for non-packet switch interfaces is
 similar to that for Packet-Switch Capable (PSC) interfaces.
 Therefore, it is a requirement that reasonable attempts must be made
 to make all the features/mechanisms (and protocol extensions) that
 will be defined to provide MPLS P2MP TE LSPs equally applicable to
 P2MP PSC and non-PSC TE-LSPs.  If the requirements of non-PSC
 networks over-complicate the PSC solution a decision may be taken to
 separate the solutions.
 Solutions for MPLS P2MP TE-LSPs, when applied to GMPLS P2MP PSC or
 non-PSC TE-LSPs, MUST be compatible with the other features of GMPLS
 including:
  1. control and data plane separation;
  2. full support of numbered and unnumbered TE links;
  3. use of the arbitrary labels and labels for specific technologies,

as well as negotiation of labels, where necessary, to support

   limited label processing and swapping capabilities;

Yasukawa Informational [Page 24] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

  1. the ability to apply external control to the labels selected on

each hop of the LSP, and to control the next hop

   label/port/interface for data after it reaches the egress LSR;
 - support for graceful and alarm-free enablement and termination of
   LSPs;
 - full support for protection including link-level protection,
   end-to-end protection, and segment protection;
 - the ability to teardown an LSP from a downstream LSR, in
   particular, from the egress LSR;
 - handling of Graceful Deletion procedures; and
 - support for failure and restart or reconnection of the control
   plane without any disruption of the data plane.
 In addition, since non-PSC TE-LSPs may have to be processed in
 environments where the "P2MP capability" could be limited, specific
 constraints may also apply during the P2MP TE Path computation.
 Being technology specific, these constraints are outside the scope of
 this document.  However, technology-independent constraints (i.e.,
 constraints that are applicable independently of the LSP class)
 SHOULD be allowed during P2MP TE LSP message processing.  It has to
 be emphasized that path computation and management techniques shall
 be as close as possible to those being used for PSC P2P TE LSPs and
 P2MP TE LSPs.

4.21. P2MP Crankback Routing

 P2MP solutions SHOULD support crankback requirements as defined in
 [CRANKBACK].  In particular, they SHOULD provide sufficient
 information to a branch LSR from downstream LSRs to allow the branch
 LSR to re-route a sub-LSP around any failures or problems in the
 network.

5. Security Considerations

 This requirements document does not define any protocol extensions
 and does not, therefore, make any changes to any security models.
 It is a requirement that any P2MP solution developed to meet some or
 all of the requirements expressed in this document MUST include
 mechanisms to enable the secure establishment and management of P2MP
 MPLS-TE LSPs.  This includes, but is not limited to:
  1. mechanisms to ensure that the ingress LSR of a P2MP LSP is

identified;

  1. mechanisms to ensure that communicating signaling entities can

verify each other's identities;

  1. mechanisms to ensure that control plane messages are protected

against spoofing and tampering;

Yasukawa Informational [Page 25] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

  1. mechanisms to ensure that unauthorized leaves or branches are not

added to the P2MP LSP; and

  1. mechanisms to protect signaling messages from snooping.
 Note that P2MP signaling mechanisms built on P2P RSVP-TE signaling
 are likely to inherit all the security techniques and problems
 associated with RSVP-TE.  These problems may be exacerbated in P2MP
 situations where security relationships may need to maintained
 between an ingress LSR and multiple egress LSRs.  Such issues are
 similar to security issues for IP multicast.
 It is a requirement that documents offering solutions for P2MP LSPs
 MUST have detailed security sections.

6. Acknowledgements

 The authors would like to thank George Swallow, Ichiro Inoue, Dean
 Cheng, Lou Berger, and Eric Rosen for their review and suggestions.
 Thanks to Loa Andersson for his help resolving the final issues in
 this document and to Harald Alvestrand for a thorough GenArt review.

7. References

7.1. Normative References

 [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2702]     Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and
               J. McManus, "Requirements for Traffic Engineering Over
               MPLS", RFC 2702, September 1999.
 [RFC3031]     Rosen, E., Viswanathan, A., and R. Callon,
               "Multiprotocol Label Switching Architecture", RFC 3031,
               January 2001.
 [RFC3209]     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.

7.2. Informative References

 [RFC3468]     Andersson, L. and G. Swallow, "The Multiprotocol Label
               Switching (MPLS) Working Group decision on MPLS
               signaling protocols", RFC 3468, February 2003.

Yasukawa Informational [Page 26] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 [RFC3473]     Berger, L., "Generalized Multi-Protocol Label Switching
               (GMPLS) Signaling Resource ReserVation Protocol-Traffic
               Engineering (RSVP-TE) Extensions", RFC 3473, January
               2003.
 [RFC3564]     Le Faucheur, F. and W. Lai, "Requirements for Support
               of Differentiated Services-aware MPLS Traffic
               Engineering", RFC 3564, July 2003.
 [RFC4090]     Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
               Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May
               2005.
 [STEINER]     H. Salama, et al., "Evaluation of Multicast Routing
               Algorithm for Real-Time Communication on High-Speed
               Networks," IEEE Journal on Selected Area in
               Communications, pp.332-345, 1997.
 [CRANKBACK]   A. Farrel, A. Satyanarayana, A. Iwata, N. Fujita, G.
               Ash, S. Marshall, "Crankback Signaling Extensions for
               MPLS Signaling", Work in Progress, May 2005.
 [P2MP-OAM]    S. Yasukawa, A. Farrel, D. King, and T. Nadeau, "OAM
               Requirements for Point-to-Multipoint MPLS Networks",
               Work in Progress, February 2006.

Yasukawa Informational [Page 27] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

Editor's Address

 Seisho Yasukawa
 NTT Corporation
 9-11, Midori-Cho 3-Chome
 Musashino-Shi, Tokyo 180-8585,
 Japan
 Phone: +81 422 59 4769
 EMail: yasukawa.seisho@lab.ntt.co.jp

Authors' Addresses

 Dimitri Papadimitriou
 Alcatel
 Francis Wellensplein 1,
 B-2018 Antwerpen,
 Belgium
 Phone : +32 3 240 8491
 EMail: dimitri.papadimitriou@alcatel.be
 JP Vasseur
 Cisco Systems, Inc.
 300 Beaver Brook Road
 Boxborough, MA 01719,
 USA
 EMail: jpv@cisco.com
 Yuji Kamite
 NTT Communications Corporation
 Tokyo Opera City Tower
 3-20-2 Nishi Shinjuku, Shinjuku-ku,
 Tokyo 163-1421,
 Japan
 EMail: y.kamite@ntt.com

Yasukawa Informational [Page 28] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

 Rahul Aggarwal
 Juniper Networks
 1194 North Mathilda Ave.
 Sunnyvale, CA 94089
 EMail: rahul@juniper.net
 Alan Kullberg
 Motorola Computer Group
 120 Turnpike Rd.
 Southborough, MA 01772
 EMail: alan.kullberg@motorola.com
 Adrian Farrel
 Old Dog Consulting
 Phone: +44 (0) 1978 860944
 EMail: adrian@olddog.co.uk
 Markus Jork
 Quarry Technologies
 8 New England Executive Park
 Burlington, MA 01803
 EMail: mjork@quarrytech.com
 Andrew G. Malis
 Tellabs
 2730 Orchard Parkway
 San Jose, CA 95134
 Phone: +1 408 383 7223
 EMail: andy.malis@tellabs.com
 Jean-Louis Le Roux
 France Telecom
 2, avenue Pierre-Marzin
 22307 Lannion Cedex
 France
 EMail: jeanlouis.leroux@francetelecom.com

Yasukawa Informational [Page 29] RFC 4461 Signaling Requirements for P2MP TE MPLS LSPs April 2006

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 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is provided by the IETF
 Administrative Support Activity (IASA).

Yasukawa Informational [Page 30]

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