path: root/doc/rfc/rfc6006.txt

Internet Engineering Task Force (IETF)                      Q. Zhao, Ed.
Request for Comments: 6006                             Huawei Technology
Category: Standards Track                                   D. King, Ed.
ISSN: 2070-1721                                       Old Dog Consulting
                                                            F. Verhaeghe
                                             Thales Communication France
                                                               T. Takeda
                                                         NTT Corporation
                                                                  Z. Ali
                                                     Cisco Systems, Inc.
                                                               J. Meuric
                                                          France Telecom
                                                          September 2010


                             Extensions to
       the Path Computation Element Communication Protocol (PCEP)
    for Point-to-Multipoint Traffic Engineering Label Switched Paths

Abstract

   Point-to-point Multiprotocol Label Switching (MPLS) and Generalized
   MPLS (GMPLS) Traffic Engineering Label Switched Paths (TE LSPs) may
   be established using signaling techniques, but their paths may first
   need to be determined.  The Path Computation Element (PCE) has been
   identified as an appropriate technology for the determination of the
   paths of point-to-multipoint (P2MP) TE LSPs.

   This document describes extensions to the PCE communication Protocol
   (PCEP) to handle requests and responses for the computation of paths
   for P2MP TE LSPs.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6006.






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Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1. Introduction ....................................................3
      1.1. Terminology ................................................4
      1.2. Requirements Language ......................................5
   2. PCC-PCE Communication Requirements ..............................5
   3. Protocol Procedures and Extensions ..............................6
      3.1. P2MP Capability Advertisement ..............................6
           3.1.1. P2MP Computation TLV in the Existing PCE
                  Discovery Protocol ..................................6
           3.1.2. Open Message Extension ..............................7
      3.2. Efficient Presentation of P2MP LSPs ........................7
      3.3. P2MP Path Computation Request/Reply Message Extensions .....8
           3.3.1. The Extension of the RP Object ......................8
           3.3.2. The New P2MP END-POINTS Object ......................9
      3.4. Request Message Format ....................................12
      3.5. Reply Message Format ......................................12
      3.6. P2MP Objective Functions and Metric Types .................13
           3.6.1. New Objective Functions ............................13
           3.6.2. New Metric Object Types ............................14
      3.7. Non-Support of P2MP Path Computation ......................14



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      3.8. Non-Support by Back-Level PCE Implementations .............15
      3.9. P2MP TE Path Reoptimization Request .......................15
      3.10. Adding and Pruning Leaves to/from the P2MP Tree ..........16
      3.11. Discovering Branch Nodes .................................19
           3.11.1. Branch Node Object ................................19
      3.12. Synchronization of P2MP TE Path Computation Requests .....19
      3.13. Request and Response Fragmentation .......................20
           3.13.1. Request Fragmentation Procedure ...................21
           3.13.2. Response Fragmentation Procedure ..................21
           3.13.3. Fragmentation Examples ............................21
      3.14. UNREACH-DESTINATION Object ...............................22
      3.15. P2MP PCEP-ERROR Objects and Types ........................23
      3.16. PCEP NO-PATH Indicator ...................................24
   4. Manageability Considerations ...................................25
      4.1. Control of Function and Policy ............................25
      4.2. Information and Data Models ...............................25
      4.3. Liveness Detection and Monitoring .........................25
      4.4. Verifying Correct Operation ...............................25
      4.5. Requirements for Other Protocols and Functional
           Components ................................................26
      4.6. Impact on Network Operation ...............................26
   5. Security Considerations ........................................26
   6. IANA Considerations ............................................27
      6.1. PCEP TLV Type Indicators ..................................27
      6.2. Request Parameter Bit Flags ...............................27
      6.3. Objective Functions .......................................27
      6.4. Metric Object Types .......................................27
      6.5. PCEP Objects ..............................................28
      6.6. PCEP-ERROR Objects and Types ..............................29
      6.7. PCEP NO-PATH Indicator ....................................30
      6.8. SVEC Object Flag ..........................................30
      6.9. OSPF PCE Capability Flag ..................................30
   7. Acknowledgements ...............................................30
   8. References .....................................................30
      8.1. Normative References ......................................30
      8.2. Informative References ....................................32

1.  Introduction

   The Path Computation Element (PCE) defined in [RFC4655] is an entity
   that is capable of computing a network path or route based on a
   network graph, and applying computational constraints.  A Path
   Computation Client (PCC) may make requests to a PCE for paths to be
   computed.

   [RFC4875] describes how to set up point-to-multipoint (P2MP) Traffic
   Engineering Label Switched Paths (TE LSPs) for use in Multiprotocol
   Label Switching (MPLS) and Generalized MPLS (GMPLS) networks.



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   The PCE has been identified as a suitable application for the
   computation of paths for P2MP TE LSPs [RFC5671].

   The PCE communication Protocol (PCEP) is designed as a communication
   protocol between PCCs and PCEs for point-to-point (P2P) path
   computations and is defined in [RFC5440].  However, that
   specification does not provide a mechanism to request path
   computation of P2MP TE LSPs.

   A P2MP LSP is comprised of multiple source-to-leaf (S2L) sub-LSPs.
   These S2L sub-LSPs are set up between ingress and egress Label
   Switching Routers (LSRs) and are appropriately overlaid to construct
   a P2MP TE LSP.  During path computation, the P2MP TE LSP may be
   determined as a set of S2L sub-LSPs that are computed separately and
   combined to give the path of the P2MP LSP, or the entire P2MP TE LSP
   may be determined as a P2MP tree in a single computation.

   This document relies on the mechanisms of PCEP to request path
   computation for P2MP TE LSPs.  One path computation request message
   from a PCC may request the computation of the whole P2MP TE LSP, or
   the request may be limited to a sub-set of the S2L sub-LSPs.  In the
   extreme case, the PCC may request the S2L sub-LSPs to be computed
   individually with it being the PCC's responsibility to decide whether
   to signal individual S2L sub-LSPs or combine the computation results
   to signal the entire P2MP TE LSP.  Hence the PCC may use one path
   computation request message or may split the request across multiple
   path computation messages.

1.1.  Terminology

   Terminology used in this document:

      TE LSP: Traffic Engineering Label Switched Path.

      LSR: Label Switching Router.

      OF: Objective Function: A set of one or more optimization criteria
      used for the computation of a single path (e.g., path cost
      minimization), or for the synchronized computation of a set of
      paths (e.g., aggregate bandwidth consumption minimization).

      P2MP: Point-to-Multipoint.

      P2P: Point-to-Point.

   This document also uses the terminology defined in [RFC4655],
   [RFC4875], and [RFC5440].




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1.2.  Requirements Language

   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 RFC 2119 [RFC2119].

2.  PCC-PCE Communication Requirements

   This section summarizes the PCC-PCE communication requirements for
   P2MP MPLS-TE LSPs described in [RFC5862].  The numbering system
   corresponds to the requirement numbers used in [RFC5862].

   1.  The PCC MUST be able to specify that the request is a P2MP path
       computation request.

   2.  The PCC MUST be able to specify that objective functions are to
       be applied to the P2MP path computation request.

   3.  The PCE MUST have the capability to reject a P2MP path request
       and indicate non-support of P2MP path computation.

   4.  The PCE MUST provide an indication of non-support of P2MP path
       computation by back-level PCE implementations.

   5.  A P2MP path computation request MUST be able to list multiple
       destinations.

   6.  A P2MP path computation response MUST be able to carry the path
       of a P2MP LSP.

   7.  By default, the path returned by the PCE SHOULD use the
       compressed format.

   8.  It MUST be possible for a single P2MP path computation request or
       response to be conveyed by a sequence of messages.

   9.  It MUST NOT be possible for a single P2MP path computation
       request to specify a set of different constraints, traffic
       parameters, or quality-of-service requirements for different
       destinations of a P2MP LSP.

   10. P2MP path modification and P2MP path diversity MUST be supported.

   11. It MUST be possible to reoptimize existing P2MP TE LSPs.

   12. It MUST be possible to add and remove P2MP destinations from
       existing paths.




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   13. It MUST be possible to specify a list of applicable branch nodes
       to use when computing the P2MP path.

   14. It MUST be possible for a PCC to discover P2MP path computation
       capability.

   15. The PCC MUST be able to request diverse paths when requesting a
       P2MP path.

3.  Protocol Procedures and Extensions

   The following section describes the protocol extensions required to
   satisfy the requirements specified in Section 2 ("PCC-PCE
   Communication Requirements") of this document.

3.1.  P2MP Capability Advertisement

3.1.1.  P2MP Computation TLV in the Existing PCE Discovery Protocol

   [RFC5088] defines a PCE Discovery (PCED) TLV carried in an OSPF
   Router Information Link State Advertisement (LSA) defined in
   [RFC4970] to facilitate PCE discovery using OSPF.  [RFC5088]
   specifies that no new sub-TLVs may be added to the PCED TLV.  This
   document defines a new flag in the OSPF PCE Capability Flags to
   indicate the capability of P2MP computation.

   Similarly, [RFC5089] defines the PCED sub-TLV for use in PCE
   Discovery using IS-IS.  This document will use the same flag
   requested for the OSPF PCE Capability Flags sub-TLV to allow IS-IS to
   indicate the capability of P2MP computation.

   The IANA assignment for a shared OSPF and IS-IS P2MP Capability Flag
   is documented in Section 6.9 ("OSPF PCE Capability Flag") of this
   document.

   PCEs wishing to advertise that they support P2MP path computation
   would set the bit (10) accordingly.  PCCs that do not understand this
   bit will ignore it (per [RFC5088] and [RFC5089]).  PCEs that do not
   support P2MP will leave the bit clear (per the default behavior
   defined in [RFC5088] and [RFC5089]).

   PCEs that set the bit to indicate support of P2MP path computation
   MUST follow the procedures in Section 3.3.2 ("The New P2MP END-POINTS
   Object") to further qualify the level of support.







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3.1.2.  Open Message Extension

   Based on the Capabilities Exchange requirement described in
   [RFC5862], if a PCE does not advertise its P2MP capability during
   discovery, PCEP should be used to allow a PCC to discover, during the
   Open Message Exchange, which PCEs are capable of supporting P2MP path
   computation.

   To satisfy this requirement, we extend the PCEP OPEN object by
   defining a new optional TLV to indicate the PCE's capability to
   perform P2MP path computations.

   IANA has allocated value 6 from the "PCEP TLV Type Indicators" sub-
   registry, as documented in Section 6.1 ("PCEP TLV Type Indicators").
   The description is "P2MP capable", and the length value is 2 bytes.
   The value field is set to default value 0.

   The inclusion of this TLV in an OPEN object indicates that the sender
   can perform P2MP path computations.

   The capability TLV is meaningful only for a PCE, so it will typically
   appear only in one of the two Open messages during PCE session
   establishment.  However, in case of PCE cooperation (e.g.,
   inter-domain), when a PCE behaving as a PCC initiates a PCE session
   it SHOULD also indicate its path computation capabilities.

3.2.  Efficient Presentation of P2MP LSPs

   When specifying additional leaves, or optimizing existing P2MP TE
   LSPs as specified in [RFC5862], it may be necessary to pass existing
   P2MP LSP route information between the PCC and PCE in the request and
   reply messages.  In each of these scenarios, we need new path objects
   for efficiently passing the existing P2MP LSP between the PCE and
   PCC.

   We specify the use of the Resource Reservation Protocol Traffic
   Engineering (RSVP-TE) extensions Explicit Route Object (ERO) to
   encode the explicit route of a TE LSP through the network.  PCEP ERO
   sub-object types correspond to RSVP-TE ERO sub-object types.  The
   format and content of the ERO object are defined in [RFC3209] and
   [RFC3473].

   The Secondary Explicit Route Object (SERO) is used to specify the
   explicit route of a S2L sub-LSP.  The path of each subsequent S2L
   sub-LSP is encoded in a P2MP_SECONDARY_EXPLICIT_ROUTE object SERO.
   The format of the SERO is the same as an ERO defined in [RFC3209] and
   [RFC3473].




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   The Secondary Record Route Object (SRRO) is used to record the
   explicit route of the S2L sub-LSP.  The class of the P2MP SRRO is the
   same as the SRRO defined in [RFC4873].

   The SERO and SRRO are used to report the route of an existing TE LSP
   for which a reoptimization is desired.  The format and content of the
   SERO and SRRO are defined in [RFC4875].

   A new PCEP object class and type are requested for SERO and SRRO.

   Object-Class Value    29
   Name                  SERO
   Object-Type           1: SERO
                         2-15: Unassigned
   Reference             RFC 6006

   Object-Class Value    30
   Name                  SRRO
   Object-Type           1: SRRO
                         2-15: Unassigned
   Reference             RFC 6006

   The IANA assignment is documented in Section 6.5 ("PCEP Objects").

   Since the explicit path is available for immediate signaling by the
   MPLS or GMPLS control plane, the meanings of all of the sub-objects
   and fields in this object are identical to those defined for the ERO.

3.3.  P2MP Path Computation Request/Reply Message Extensions

   This document extends the existing P2P RP (Request Parameters) object
   so that a PCC can signal a P2MP path computation request to the PCE
   receiving the PCEP request.  The END-POINTS object is also extended
   to improve the efficiency of the message exchange between PCC and PCE
   in the case of P2MP path computation.

3.3.1.  The Extension of the RP Object

   The PCE path computation request and reply messages will need the
   following additional parameters to indicate to the receiving PCE that
   the request and reply messages have been fragmented across multiple
   messages, that they have been requested for a P2MP path, and whether
   the route is represented in the compressed or uncompressed format.

   This document adds the following flags to the RP Object:






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   The F-bit is added to the flag bits of the RP object to indicate to
   the receiver that the request is part of a fragmented request, or is
   not a fragmented request.

   o  F (RP fragmentation bit - 1 bit):

      0: This indicates that the RP is not fragmented or it is the last
         piece of the fragmented RP.

      1: This indicates that the RP is fragmented and this is not the
         last piece of the fragmented RP.  The receiver needs to wait
         for additional fragments until it receives an RP with the same
         RP-ID and with the F-bit set to 0.

   The N-bit is added in the flag bits field of the RP object to signal
   the receiver of the message that the request/reply is for P2MP or is
   not for P2MP.

   o  N (P2MP bit - 1 bit):

      0: This indicates that this is not a PCReq or PCRep message for
         P2MP.

      1: This indicates that this is a PCReq or PCRep message for P2MP.

   The E-bit is added in the flag bits field of the RP object to signal
   the receiver of the message that the route is in the compressed
   format or is not in the compressed format.  By default, the path
   returned by the PCE SHOULD use the compressed format.

   o  E (ERO-compression bit - 1 bit):

      0: This indicates that the route is not in the compressed format.

      1: This indicates that the route is in the compressed format.

   The IANA assignment is documented in Section 6.2 ("Request Parameter
   Bit Flags") of this document.

3.3.2.  The New P2MP END-POINTS Object

   The END-POINTS object is used in a PCReq message to specify the
   source IP address and the destination IP address of the path for
   which a path computation is requested.  To represent the end points
   for a P2MP path efficiently, we define two new types of END-POINTS
   objects for the P2MP path:





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   o  Old leaves whose path can be modified/reoptimized;

   o  Old leaves whose path must be left unchanged.

   With the new END-POINTS object, the PCE path computation request
   message is expanded in a way that allows a single request message to
   list multiple destinations.

   In total, there are now 4 possible types of leaves in a P2MP request:

   o  New leaves to add (leaf type = 1)

   o  Old leaves to remove (leaf type = 2)

   o  Old leaves whose path can be modified/reoptimized (leaf type = 3)

   o  Old leaves whose path must be left unchanged (leaf type = 4)

   A given END-POINTS object gathers the leaves of a given type.  The
   type of leaf in a given END-POINTS object is identified by the END-
   POINTS object leaf type field.

   Using the new END-POINTS object, the END-POINTS portion of a request
   message for the multiple destinations can be reduced by up to 50% for
   a P2MP path where a single source address has a very large number of
   destinations.

   Note that a P2MP path computation request can mix the different types
   of leaves by including several END-POINTS objects per RP object as
   shown in the PCReq Routing Backus-Naur Form (RBNF) [RFC5511] format
   in Section 3.4 ("Request Message Format").




















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   The format of the new END-POINTS object body for IPv4 (Object-Type 3)
   is as follows:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Leaf type                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Source IPv4 address                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  Destination IPv4 address                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~                           ...                                 ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  Destination IPv4 address                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 1.  The New P2MP END-POINTS Object Body Format for IPv4

   The format of the END-POINTS object body for IPv6 (Object-Type 4) is
   as follows:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Leaf type                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                Source IPv6 address (16 bytes)                 |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |              Destination IPv6 address (16 bytes)              |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~                           ...                                 ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |              Destination IPv6 address (16 bytes)              |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 2.  The New P2MP END-POINTS Object Body Format for IPv6

   The END-POINTS object body has a variable length.  These are
   multiples of 4 bytes for IPv4, and multiples of 16 bytes, plus 4
   bytes, for IPv6.




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3.4.  Request Message Format

   The PCReq message is encoded as follows using RBNF as defined in
   [RFC5511].

   Below is the message format for the request message:

           <PCReq Message>::= <Common Header>
                                 <request>
        where:
                <request>::= <RP>
                                <end-point-rro-pair-list>
                                [<OF>]
                                [<LSPA>]
                                [<BANDWIDTH>]
                                [<metric-list>]
                                [<IRO>]
                                [<LOAD-BALANCING>]

        where:

                <end-point-rro-pair-list>::=
                                   <END-POINTS>[<RRO-List>][<BANDWIDTH>]
                                   [<end-point-rro-pair-list>]

                <RRO-List>::=<RRO>[<BANDWIDTH>][<RRO-List>]
                <metric-list>::=<METRIC>[<metric-list>]

           Figure 3.  The Message Format for the Request Message

   Note that we preserve compatibility with the [RFC5440] definition of
   <request>.  At least one instance of <endpoints> MUST be present in
   this message.

   We have documented the IANA assignment of additional END-POINTS
   Object-Types in Section 6.5 ("PCEP Objects") of this document.

3.5.  Reply Message Format

   The PCRep message is encoded as follows using RBNF as defined in
   [RFC5511].










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   Below is the message format for the reply message:

          <PCRep Message>::= <Common Header>
                                <response>
          <response>::=<RP>
                          [<end-point-path-pair-list>]
                          [<NO-PATH>]
                          [<attribute-list>]

        where:

           <end-point-path-pair-list>::=
                   [<END-POINTS>]<path>[<end-point-path-pair-list>]

          <path> ::= (<ERO>|<SERO>) [<path>]

          <attribute-list>::=[<OF>]
                               [<LSPA>]
                               [<BANDWIDTH>]
                               [<metric-list>]
                               [<IRO>]

            Figure 4.  The Message Format for the Reply Message

   The optional END-POINTS object in the reply message is used to
   specify which paths are removed, changed, not changed, or added for
   the request.  The path is only needed for the end points that are
   added or changed.

   If the E-bit (ERO-Compress bit) was set to 1 in the request, then the
   path will be formed by an ERO followed by a list of SEROs.

   Note that we preserve compatibility with the [RFC5440] definition of
   <response> and the optional <end-point-path-pair-list> and <path>.

3.6.  P2MP Objective Functions and Metric Types

3.6.1.  New Objective Functions

   Six objective functions have been defined in [RFC5541] for P2P path
   computation.

   This document defines two additional objective functions -- namely,
   SPT (Shortest Path Tree) and MCT (Minimum Cost Tree) that apply to
   P2MP path computation.  Hence two new objective function codes have
   to be defined.

   The description of the two new objective functions is as follows.



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   Objective Function Code: 7

      Name: Shortest Path Tree (SPT)

      Description: Minimize the maximum source-to-leaf cost with respect
      to a specific metric or to the TE metric used as the default
      metric when the metric is not specified (e.g., TE or IGP metric).

   Objective Function Code: 8

      Name: Minimum Cost Tree (MCT)

      Description: Minimize the total cost of the tree, that is the sum
      of the costs of tree links, with respect to a specific metric or
      to the TE metric used as the default metric when the metric is not
      specified.

   Processing these two new objective functions is subject to the rules
   defined in [RFC5541].

3.6.2.  New Metric Object Types

   There are three types defined for the <METRIC> object in [RFC5440] --
   namely, the IGP metric, the TE metric, and the hop count metric.
   This document defines three additional types for the <METRIC> object:
   the P2MP IGP metric, the P2MP TE metric, and the P2MP hop count
   metric.  They encode the sum of the metrics of all links of the tree.
   We propose the following values for these new metric types:

   o  P2MP IGP metric: T=8

   o  P2MP TE metric: T=9

   o  P2MP hop count metric: T=10

3.7.  Non-Support of P2MP Path Computation

   o  If a PCE receives a P2MP path request and it understands the P2MP
      flag in the RP object, but the PCE is not capable of P2MP
      computation, the PCE MUST send a PCErr message with a PCEP-ERROR
      object and corresponding Error-Value.  The request MUST then be
      cancelled at the PCC.  New Error-Types and Error-Values are
      requested in Section 6 ("IANA Considerations") of this document.

   o  If the PCE does not understand the P2MP flag in the RP object,
      then the PCE MUST send a PCErr message with Error-value=2
      (capability not supported).




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3.8.  Non-Support by Back-Level PCE Implementations

   If a PCE receives a P2MP request and the PCE does not understand the
   P2MP flag in the RP object, and therefore the PCEP P2MP extensions,
   then the PCE SHOULD reject the request.

3.9.  P2MP TE Path Reoptimization Request

   A reoptimization request for a P2MP TE path is specified by the use
   of the R-bit within the RP object as defined in [RFC5440] and is
   similar to the reoptimization request for a P2P TE path.  The only
   difference is that the user MUST insert the list of RROs and SRROs
   after each type of END-POINTS in the PCReq message, as described in
   the "Request Message Format" section (Section 3.4) of this document.

   An example of a reoptimization request and subsequent PCReq message
   is described below:

           Common Header
           RP with P2MP flag/R-bit set
           END-POINTS for leaf type 3
             RRO list
           OF (optional)

            Figure 5.  PCReq Message Example 1 for Optimization

   In this example, we request reoptimization of the path to all leaves
   without adding or pruning leaves.  The reoptimization request would
   use an END-POINT type 3.  The RRO list would represent the P2MP LSP
   before the optimization, and the modifiable path leaves would be
   indicated in the END-POINTS object.

   It is also possible to specify distinct leaves whose path cannot be
   modified.  An example of the PCReq message in this scenario would be:

           Common Header
           RP with P2MP flag/R-bit set
           END-POINTS for leaf type 3
             RRO list
           END-POINTS for leaf type 4
             RRO list
           OF (optional)

            Figure 6.  PCReq Message Example 2 for Optimization







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3.10.  Adding and Pruning Leaves to/from the P2MP Tree

   When adding new leaves to or removing old leaves from the existing
   P2MP tree, by supplying a list of existing leaves, it SHOULD be
   possible to optimize the existing P2MP tree.  This section explains
   the methods for adding new leaves to or removing old leaves from the
   existing P2MP tree.

   To add new leaves, the user MUST build a P2MP request using END-
   POINTS with leaf type 1.

   To remove old leaves, the user must build a P2MP request using END-
   POINTS with leaf type 2.  If no type-2 END-POINTS exist, then the PCE
   MUST send an error type 17, value=1: The PCE is not capable of
   satisfying the request due to no END-POINTS with leaf type 2.

   When adding new leaves to or removing old leaves from the existing
   P2MP tree, the PCC must also provide the list of old leaves, if any,
   including END-POINTS with leaf type 3, leaf type 4, or both.  New
   PCEP-ERROR objects and types are necessary for reporting when certain
   conditions are not satisfied (i.e., when there are no END-POINTS with
   leaf type 3 or 4, or in the presence of END-POINTS with leaf type 1
   or 2).  A generic "Inconsistent END-POINT" error will be used if a
   PCC receives a request that has an inconsistent END-POINT (i.e., if a
   leaf specified as type 1 already exists).  These IANA assignments are
   documented in Section 6.6 ("PCEP-ERROR Objects and Types") of this
   document.

   For old leaves, the user MUST provide the old path as a list of RROs
   that immediately follows each END-POINTS object.  This document
   specifies error values when specific conditions are not satisfied.

   The following examples demonstrate full and partial reoptimization of
   existing P2MP LSPs:

   Case 1: Adding leaves with full reoptimization of existing paths

           Common Header
           RP with P2MP flag/R-bit set
           END-POINTS for leaf type 1
             RRO list
           END-POINTS for leaf type 3
             RRO list
           OF (optional)







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   Case 2: Adding leaves with partial reoptimization of existing paths

           Common Header
           RP with P2MP flag/R-bit set
           END-POINTS for leaf type 1
           END-POINTS for leaf type 3
             RRO list
           END-POINTS for leaf type 4
             RRO list
           OF (optional)

   Case 3: Adding leaves without reoptimization of existing paths

           Common Header
           RP with P2MP flag/R-bit set
           END-POINTS for leaf type 1
             RRO list
           END-POINTS for leaf type 4
             RRO list
           OF (optional)

   Case 4: Pruning Leaves with full reoptimization of existing paths

           Common Header
           RP with P2MP flag/R-bit set
           END-POINTS for leaf type 2
             RRO list
           END-POINTS for leaf type 3
             RRO list
           OF (optional)

   Case 5: Pruning leaves with partial reoptimization of existing paths

           Common Header
           RP with P2MP flag/R-bit set
           END-POINTS for leaf type 2
             RRO list
           END-POINTS for leaf type 3
             RRO list
           END-POINTS for leaf type 4
             RRO list
           OF (optional)









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   Case 6: Pruning leaves without reoptimization of existing paths

           Common Header
           RP with P2MP flag/R-bit set
           END-POINTS for leaf type 2
             RRO list
           END-POINTS for leaf type 4
             RRO list
           OF (optional)

   Case 7: Adding and pruning leaves with full reoptimization of
   existing paths

           Common Header
           RP with P2MP flag/R-bit set
           END-POINTS for leaf type 1
           END-POINTS for leaf type 2
             RRO list
           END-POINTS for leaf type 3
             RRO list
           OF (optional)

   Case 8: Adding and pruning leaves with partial reoptimization of
   existing paths

           Common Header
           RP with P2MP flag/R-bit set
           END-POINTS for leaf type 1
           END-POINTS for leaf type 2
             RRO list
           END-POINTS for leaf type 3
             RRO list
           END-POINTS for leaf type 4
             RRO list
           OF (optional)

   Case 9: Adding and pruning leaves without reoptimization of existing
   paths

           Common Header
           RP with P2MP flag/R-bit set
           END-POINTS for leaf type 1
           END-POINTS for leaf type 2
             RRO list
           END-POINTS for leaf type 4
             RRO list
           OF (optional)




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3.11.  Discovering Branch Nodes

   Before computing the P2MP path, a PCE may need to be provided means
   to know which nodes in the network are capable of acting as branch
   LSRs.  A PCE can discover such capabilities by using the mechanisms
   defined in [RFC5073].

3.11.1.  Branch Node Object

   The PCC can specify a list of nodes that can be used as branch nodes
   or a list of nodes that cannot be used as branch nodes by using the
   Branch Node Capability (BNC) Object.  The BNC Object has the same
   format as the Include Route Object (IRO) defined in [RFC5440], except
   that it only supports IPv4 and IPv6 prefix sub-objects.  Two Object-
   types are also defined:

   o  Branch node list: List of nodes that can be used as branch nodes.

   o  Non-branch node list: List of nodes that cannot be used as branch
      nodes.

   The object can only be carried in a PCReq message.  A Path Request
   may carry at most one Branch Node Object.

   The Object-Class and Object-types have been allocated by IANA.  The
   IANA assignment is documented in Section 6.5 ("PCEP Objects").

3.12.  Synchronization of P2MP TE Path Computation Requests

   There are cases when multiple P2MP LSPs' computations need to be
   synchronized.  For example, one P2MP LSP is the designated backup of
   another P2MP LSP.  In this case, path diversity for these dependent
   LSPs may need to be considered during the path computation.

   The synchronization can be done by using the existing Synchronization
   VECtor (SVEC) functionality defined in [RFC5440].















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   An example of synchronizing two P2MP LSPs, each having two leaves for
   Path Computation Request Messages, is illustrated below:

           Common Header
           SVEC for sync of LSP1 and LSP2
           OF (optional)
           END-POINTS1 for P2MP
             RRO1 list
           END-POINTS2 for P2MP
             RRO2 list

           Figure 7.  PCReq Message Example for Synchronization

   This specification also defines two new flags to the SVEC Object Flag
   Field for P2MP path dependent computation requests.  The first new
   flag is to allow the PCC to request that the PCE should compute a
   secondary P2MP path tree with partial path diversity for specific
   leaves or a specific S2L sub-path to the primary P2MP path tree.  The
   second flag, would allow the PCC to request that partial paths should
   be link direction diverse.

   The following flags are added to the SVEC object body in this
   document:

   o  P (Partial Path Diverse bit - 1 bit):

      When set, this would indicate a request for path diversity for a
      specific leaf, a set of leaves, or all leaves.

   o  D (Link Direction Diverse bit - 1 bit):

      When set, this would indicate a request that a partial path or
      paths should be link direction diverse.

   The IANA assignment is referenced in Section 6.8 of this document.

3.13.  Request and Response Fragmentation

   The total PCEP message length, including the common header, is
   16 bytes.  In certain scenarios the P2MP computation request may not
   fit into a single request or response message.  For example, if a
   tree has many hundreds or thousands of leaves, then the request or
   response may need to be fragmented into multiple messages.








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   The F-bit has been outlined in "The Extension of the RP Object"
   (Section 3.3.1) of this document.  The F-bit is used in the RP object
   header to signal that the initial request or response was too large
   to fit into a single message and will be fragmented into multiple
   messages.  In order to identify the single request or response, each
   message will use the same request ID.

3.13.1.  Request Fragmentation Procedure

   If the initial request is too large to fit into a single request
   message, the PCC will split the request over multiple messages.  Each
   message sent to the PCE, except the last one, will have the F-bit set
   in the RP object to signify that the request has been fragmented into
   multiple messages.  In order to identify that a series of request
   messages represents a single request, each message will use the same
   request ID.

   The assumption is that request messages are reliably delivered and in
   sequence, since PCEP relies on TCP.

3.13.2.  Response Fragmentation Procedure

   Once the PCE computes a path based on the initial request, a response
   is sent back to the PCC.  If the response is too large to fit into a
   single response message, the PCE will split the response over
   multiple messages.  Each message sent to the PCE, except the last
   one, will have the F-bit set in the RP object to signify that the
   response has been fragmented into multiple messages.  In order to
   identify that a series of response messages represents a single
   response, each message will use the same response ID.

   Again, the assumption is that response messages are reliably
   delivered and in sequence, since PCEP relies on TCP.

3.13.3.  Fragmentation Examples

   The following example illustrates the PCC sending a request message
   with Req-ID1 to the PCE, in order to add one leaf to an existing tree
   with 1200 leaves.  The assumption used for this example is that one
   request message can hold up to 800 leaves.  In this scenario, the
   original single message needs to be fragmented and sent using two
   smaller messages, which have the Req-ID1 specified in the RP object,
   and with the F-bit set on the first message, and cleared on the
   second message.







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           Common Header
           RP1 with Req-ID1 and P2MP=1 and F-bit=1
           OF (optional)
           END-POINTS1 for P2MP
             RRO1 list

           Common Header
           RP2 with Req-ID1 and P2MP=1 and F-bit=0
           OF (optional)
           END-POINTS1 for P2MP
             RRO1 list

              Figure 8.  PCReq Message Fragmentation Example

   To handle a scenario where the last fragmented message piece is lost,
   the receiver side of the fragmented message may start a timer once it
   receives the first piece of the fragmented message.  When the timer
   expires and it has not received the last piece of the fragmented
   message, it should send an error message to the sender to signal that
   it has received an incomplete message.  The relevant error message is
   documented in Section 3.15 ("P2MP PCEP-ERROR Objects and Types").

3.14.  UNREACH-DESTINATION Object

   The PCE path computation request may fail because all or a subset of
   the destinations are unreachable.

   In such a case, the UNREACH-DESTINATION object allows the PCE to
   optionally specify the list of unreachable destinations.

   This object can be present in PCRep messages.  There can be up to one
   such object per RP.

   The following UNREACH-DESTINATION objects will be required:

   UNREACH-DESTINATION Object-Class is 28.
   UNREACH-DESTINATION Object-Type for IPv4 is 1.
   UNREACH-DESTINATION Object-Type for IPv6 is 2.













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   The format of the UNREACH-DESTINATION object body for IPv4 (Object-
   Type=1) is as follows:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Destination IPv4 address                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                           ...                                 ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Destination IPv4 address                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 9.  UNREACH-DESTINATION Object Body for IPv4

   The format of the UNREACH-DESTINATION object body for IPv6 (Object-
   Type=2) is as follows:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |            Destination IPv6 address (16 bytes)                |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          ...                                  ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |              Destination IPv6 address (16 bytes)              |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 10.  UNREACH-DESTINATION Object Body for IPv6

3.15.  P2MP PCEP-ERROR Objects and Types

   To indicate an error associated with policy violation, a new error
   value "P2MP Path computation not allowed" should be added to the
   existing error code for policy violation (Error-Type=5) as defined in
   [RFC5440]:









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   Error-Type=5; Error-Value=7: if a PCE receives a P2MP path
   computation request that is not compliant with administrative
   privileges (i.e., "The PCE policy does not support P2MP path
   computation"), the PCE MUST send a PCErr message with a PCEP-ERROR
   object (Error-Type=5) and an Error-Value (Error-Value=7).  The
   corresponding P2MP path computation request MUST also be cancelled.

   To indicate capability errors associated with the P2MP path request,
   a new Error-Type (16) and subsequent error-values are defined as
   follows for inclusion in the PCEP-ERROR object:

   Error-Type=16; Error-Value=1: if a PCE receives a P2MP path request
   and the PCE is not capable of satisfying the request due to
   insufficient memory, the PCE MUST send a PCErr message with a PCEP-
   ERROR object (Error-Type=16) and an Error-Value (Error-Value=1).  The
   corresponding P2MP path computation request MUST also be cancelled.

   Error-Type=16; Error-Value=2: if a PCE receives a P2MP path request
   and the PCE is not capable of P2MP computation, the PCE MUST send a
   PCErr message with a PCEP-ERROR object (Error-Type=16) and an Error-
   Value (Error-Value=2).  The corresponding P2MP path computation
   request MUST also be cancelled.

   To indicate P2MP message fragmentation errors associated with a P2MP
   path request, a new Error-Type (17) and subsequent error-values are
   defined as follows for inclusion in the PCEP-ERROR object:

   Error-Type=18; Error-Value=1: if a PCE has not received the last
   piece of the fragmented message, it should send an error message to
   the sender to signal that it has received an incomplete message
   (i.e., "Fragmented request failure").  The PCE MUST send a PCErr
   message with a PCEP-ERROR object (Error-Type=18) and an Error-Value
   (Error-Value=1).

3.16.  PCEP NO-PATH Indicator

   To communicate the reasons for not being able to find P2MP path
   computation, the NO-PATH object can be used in the PCRep message.

   One new bit is defined in the NO-PATH-VECTOR TLV carried in the
   NO-PATH Object:

   bit 24: when set, the PCE indicates that there is a reachability
   problem with all or a subset of the P2MP destinations.  Optionally,
   the PCE can specify the destination or list of destinations that are
   not reachable using the new UNREACH-DESTINATION object defined in
   Section 3.14.




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4.  Manageability Considerations

   [RFC5862] describes various manageability requirements in support of
   P2MP path computation when applying PCEP.  This section describes how
   manageability requirements mentioned in [RFC5862] are supported in
   the context of PCEP extensions specified in this document.

   Note that [RFC5440] describes various manageability considerations in
   PCEP, and most of the manageability requirements mentioned in
   [RFC5862] are already covered there.

4.1.  Control of Function and Policy

   In addition to PCE configuration parameters listed in [RFC5440], the
   following additional parameters might be required:

   o  The ability to enable or disable P2MP path computations on the
      PCE.

   o  The PCE may be configured to enable or disable the advertisement
      of its P2MP path computation capability.  A PCE can advertise its
      P2MP capability via the IGP discovery mechanism discussed in
      Section 3.1.1 ("P2MP Computation TLV in the Existing PCE Discovery
      Protocol"), or during the Open Message Exchange discussed in
      Section 3.1.2 ("Open Message Extension").

4.2.  Information and Data Models

   A number of MIB objects have been defined for general PCEP control
   and monitoring of P2P computations in [PCEP-MIB].  [RFC5862]
   specifies that MIB objects will be required to support the control
   and monitoring of the protocol extensions defined in this document.
   A new document will be required to define MIB objects for PCEP
   control and monitoring of P2MP computations.

4.3.  Liveness Detection and Monitoring

   There are no additional considerations beyond those expressed in
   [RFC5440], since [RFC5862] does not address any additional
   requirements.

4.4.  Verifying Correct Operation

   There are no additional requirements beyond those expressed in
   [RFC4657] for verifying the correct operation of the PCEP sessions.
   It is expected that future MIB objects will facilitate verification
   of correct operation and reporting of P2MP PCEP requests, responses,
   and errors.



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4.5.  Requirements for Other Protocols and Functional Components

   The method for the PCE to obtain information about a PCE capable of
   P2MP path computations via OSPF and IS-IS is discussed in
   Section 3.1.1 ("P2MP Computation TLV in the Existing PCE Discovery
   Protocol") of this document.

   The subsequent IANA assignments are documented in Section 6.9 ("OSPF
   PCE Capability Flag") of this document.

4.6.  Impact on Network Operation

   It is expected that the use of PCEP extensions specified in this
   document will not significantly increase the level of operational
   traffic.  However, computing a P2MP tree may require more PCE state
   compared to a P2P computation.  In the event of a major network
   failure and multiple recovery P2MP tree computation requests being
   sent to the PCE, the load on the PCE may also be significantly
   increased.

5.  Security Considerations

   As described in [RFC5862], P2MP path computation requests are more
   CPU-intensive and also utilize more link bandwidth.  In the event of
   an unauthorized P2MP path computation request, or a denial of service
   attack, the subsequent PCEP requests and processing may be disruptive
   to the network.  Consequently, it is important that implementations
   conform to the relevant security requirements of [RFC5440] that
   specifically help to minimize or negate unauthorized P2MP path
   computation requests and denial of service attacks.  These mechanisms
   include:

   o  Securing the PCEP session requests and responses using TCP
      security techniques (Section 10.2 of [RFC5440]).

   o  Authenticating the PCEP requests and responses to ensure the
      message is intact and sent from an authorized node (Section 10.3
      of [RFC5440]).

   o  Providing policy control by explicitly defining which PCCs, via IP
      access-lists, are allowed to send P2MP path requests to the PCE
      (Section 10.6 of [RFC5440]).

   PCEP operates over TCP, so it is also important to secure the PCE and
   PCC against TCP denial of service attacks.  Section 10.7.1 of
   [RFC5440] outlines a number of mechanisms for minimizing the risk of
   TCP based denial of service attacks against PCEs and PCCs.




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   PCEP implementations SHOULD consider the additional security provided
   by the TCP Authentication Option (TCP-AO) [RFC5925].

6.  IANA Considerations

   IANA maintains a registry of PCEP parameters.  A number of IANA
   considerations have been highlighted in previous sections of this
   document.  IANA has made the following allocations.

6.1.  PCEP TLV Type Indicators

   As described in Section 3.1.2., the newly defined P2MP capability TLV
   allows the PCE to advertise its P2MP path computation capability.
   IANA has made the following allocation from the "PCEP TLV Type
   Indicators" sub-registry.

      Value       Description          Reference
      6           P2MP capable         RFC 6006

6.2.  Request Parameter Bit Flags

   As described in Section 3.3.1, three new RP Object Flags have been
   defined.  IANA has made the following allocations from the PCEP "RP
   Object Flag Field" sub-registry:

      Bit      Description                         Reference

      18       Fragmentation (F-bit)               RFC 6006
      19       P2MP (N-bit)                        RFC 6006
      20       ERO-compression (E-bit)             RFC 6006

6.3.  Objective Functions

   As described in Section 3.6.1, two new Objective Functions have been
   defined.  IANA has made the following allocations from the PCEP
   "Objective Function" sub-registry:

      Code Point        Name        Reference

      7                 SPT         RFC 6006
      8                 MCT         RFC 6006

6.4.  Metric Object Types

   As described in Section 3.6.2, three new metric object T fields have
   been defined.  IANA has made the following allocations from the PCEP
   "METRIC Object T Field" sub-registry:




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      Value           Description               Reference

      8               P2MP IGP metric           RFC 6006
      9               P2MP TE metric            RFC 6006
      10              P2MP hop count metric     RFC 6006

6.5.  PCEP Objects

   As discussed in Section 3.3.2, two new END-POINTS Object-Types are
   defined.  IANA has made the following Object-Type allocations from
   the "PCEP Objects" sub-registry:

      Object-Class Value    4
      Name                  END-POINTS
      Object-Type           3: IPv4
                            4: IPv6
                            5-15: Unassigned
      Reference             RFC 6006

   As described in Section 3.2, Section 3.11.1, and Section 3.14, four
   PCEP Object-Classes and six PCEP Object-Types have been defined.
   IANA has made the following allocations from the "PCEP Objects" sub-
   registry:

      Object-Class Value    28
      Name                  UNREACH-DESTINATION
      Object-Type           1: IPv4
                            2: IPv6
                            3-15: Unassigned
      Reference             RFC 6006

      Object-Class Value    29
      Name                  SERO
      Object-Type           1: SERO
                            2-15: Unassigned
      Reference             RFC 6006

      Object-Class Value    30
      Name                  SRRO
      Object-Type           1: SRRO
                            2-15: Unassigned
      Reference             RFC 6006









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      Object-Class Value    31
      Name                  Branch Node Capability Object
      Object-Type           1: Branch node list
                            2: Non-branch node list
                            3-15: Unassigned
      Reference             RFC 6006

6.6.  PCEP-ERROR Objects and Types

   As described in Section 3.15, a number of new PCEP-ERROR Object Error
   Types and Values have been defined.  IANA has made the following
   allocations from the PCEP "PCEP-ERROR Object Error Types and Values"
   sub-registry:

      Error
      Type  Meaning                                            Reference

      5     Policy violation
              Error-value=7:                                   RFC 6006
                P2MP Path computation is not allowed

      16    P2MP Capability Error
              Error-Value=0: Unassigned                        RFC 6006
              Error-Value=1:                                   RFC 6006
                The PCE is not capable to satisfy the request
                due to insufficient memory
              Error-Value=2:                                   RFC 6006
                The PCE is not capable of P2MP computation

      17    P2MP END-POINTS Error
              Error-Value=0: Unassigned                        RFC 6006
              Error-Value=1:                                   RFC 6006
                The PCE is not capable to satisfy the request
                due to no END-POINTS with leaf type 2
              Error-Value=2:                                   RFC 6006
                The PCE is not capable to satisfy the request
                due to no END-POINTS with leaf type 3
              Error-Value=3:                                   RFC 6006
                The PCE is not capable to satisfy the request
                due to no END-POINTS with leaf type 4
              Error-Value=4:                                   RFC 6006
                The PCE is not capable to satisfy the request
                due to inconsistent END-POINTS

      18    P2MP Fragmentation Error
              Error-Value=0: Unassigned                        RFC 6006
              Error-Value=1:                                   RFC 6006
                Fragmented request failure



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6.7.  PCEP NO-PATH Indicator

   As discussed in Section 3.16, a new NO-PATH-VECTOR TLV Flag Field has
   been defined.  IANA has made the following allocation from the PCEP
   "NO-PATH-VECTOR TLV Flag Field" sub-registry:

      Bit    Description                               Reference

      24     P2MP Reachability Problem                 RFC 6006

6.8.  SVEC Object Flag

   As discussed in Section 3.12, two new SVEC Object Flags are defined.
   IANA has made the following allocation from the PCEP "SVEC Object
   Flag Field" sub-registry:

      Bit      Description                              Reference

      19       Partial Path Diverse                     RFC 6006
      20       Link Direction Diverse                   RFC 6006

6.9.  OSPF PCE Capability Flag

   As discussed in Section 3.1.1, a new OSPF Capability Flag is defined
   to indicate P2MP path computation capability.  IANA has made the
   following assignment from the OSPF Parameters "Path Computation
   Element (PCE) Capability Flags" registry:

      Bit      Description                              Reference

      10       P2MP path computation                    RFC 6006

7.  Acknowledgements

   The authors would like to thank Adrian Farrel, Young Lee, Dan Tappan,
   Autumn Liu, Huaimo Chen, Eiji Okim, Nick Neate, Suresh Babu K, Dhruv
   Dhody, Udayasree Palle, Gaurav Agrawal, Vishwas Manral, Dan
   Romascanu, Tim Polk, Stewart Bryant, David Harrington, and Sean
   Turner for their valuable comments and input on this document.

8.  References

8.1.  Normative References

   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.





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   [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.

   [RFC3473]   Berger, L., Ed., "Generalized Multi-Protocol Label
               Switching (GMPLS) Signaling Resource ReserVation
               Protocol-Traffic Engineering (RSVP-TE) Extensions",
               RFC 3473, January 2003.

   [RFC4873]   Berger, L., Bryskin, I., Papadimitriou, D., and A.
               Farrel, "GMPLS Segment Recovery", RFC 4873, May 2007.

   [RFC4875]   Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
               Yasukawa, Ed., "Extensions to Resource Reservation
               Protocol - Traffic Engineering (RSVP-TE) for Point-to-
               Multipoint TE Label Switched Paths (LSPs)", RFC 4875, May
               2007.

   [RFC4970]   Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R.,
               and S. Shaffer, "Extensions to OSPF for Advertising
               Optional Router Capabilities", RFC 4970, July 2007.

   [RFC5073]   Vasseur, J., Ed., and J. Le Roux, Ed., "IGP Routing
               Protocol Extensions for Discovery of Traffic Engineering
               Node Capabilities", RFC 5073, December 2007.

   [RFC5088]   Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
               Zhang, "OSPF Protocol Extensions for Path Computation
               Element (PCE) Discovery", RFC 5088, January 2008.

   [RFC5089]   Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
               Zhang, "IS-IS Protocol Extensions for Path Computation
               Element (PCE) Discovery", RFC 5089, January 2008.

   [RFC5511]   Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
               Used to Form Encoding Rules in Various Routing Protocol
               Specifications", RFC 5511, April 2009.

   [RFC5440]   Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path
               Computation Element (PCE) Communication Protocol (PCEP)",
               RFC 5440, March 2009.

   [RFC5541]   Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
               Objective Functions in the Path Computation Element
               Communication Protocol (PCEP)", RFC 5541, June 2009.






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8.2.  Informative References

   [RFC4655]   Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
               Computation Element (PCE)-Based Architecture", RFC 4655,
               August 2006.

   [RFC4657]   Ash, J., Ed., and J. Le Roux, Ed., "Path Computation
               Element (PCE) Communication Protocol Generic
               Requirements", RFC 4657, September 2006.

   [RFC5671]   Yasukawa, S. and A. Farrel, Ed., "Applicability of the
               Path Computation Element (PCE) to Point-to-Multipoint
               (P2MP) MPLS and GMPLS Traffic Engineering (TE)",
               RFC 5671, October 2009.

   [RFC5862]   Yasukawa, S. and A. Farrel, "Path Computation Clients
               (PCC) - Path Computation Element (PCE) Requirements for
               Point-to-Multipoint MPLS-TE", RFC 5862, June 2010.

   [RFC5925]   Touch, J., Mankin, A., and R. Bonica, "The TCP
               Authentication Option", RFC 5925, June 2010.

   [PCEP-MIB]  Koushik, K., Stephan, E., Zhao, Q., and D. King, "PCE
               communication protocol (PCEP) Management Information
               Base", Work in Progress, July 2010.

Contributors

   Jean-Louis Le Roux
   France Telecom
   2, Avenue Pierre-Marzin
   22307 Lannion Cedex
   France
   EMail: jeanlouis.leroux@orange-ftgroup.com


   Mohamad Chaitou
   France
   EMail: mohamad.chaitou@gmail.com












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Authors' Addresses

   Quintin Zhao (editor)
   Huawei Technology
   125 Nagog Technology Park
   Acton, MA  01719
   US
   EMail: qzhao@huawei.com


   Daniel King (editor)
   Old Dog Consulting
   UK
   EMail: daniel@olddog.co.uk


   Fabien Verhaeghe
   Thales Communication France
   160 Bd Valmy 92700 Colombes
   France
   EMail: fabien.verhaeghe@gmail.com


   Tomonori Takeda
   NTT Corporation
   3-9-11, Midori-Cho
   Musashino-Shi, Tokyo 180-8585
   Japan
   EMail: takeda.tomonori@lab.ntt.co.jp


   Zafar Ali
   Cisco Systems, Inc.
   2000 Innovation Drive
   Kanata, Ontario  K2K 3E8
   Canada
   EMail: zali@cisco.com


   Julien Meuric
   France Telecom
   2, Avenue Pierre-Marzin
   22307 Lannion Cedex
   France
   EMail: julien.meuric@orange-ftgroup.com






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