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Versions: (draft-raggarwa-mpls-rsvp-te-p2mp) 00 01 02 03 04 05 06 07 RFC 4875

Network Working Group                               R. Aggarwal (Editor)
Internet Draft                                          Juniper Networks
Expiration Date: January 2006
                                               D. Papadimitriou (Editor)
                                                                 Alcatel

                                                    S. Yasukawa (Editor)
                                                                     NTT

                                                               July 2005


         Extensions to RSVP-TE for Point to Multipoint TE LSPs


                  draft-ietf-mpls-rsvp-te-p2mp-02.txt

Status of this Memo

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Abstract

   This document describes extensions to Resource Reservation Protocol -
   Traffic Engineering (RSVP-TE) for the setup of Traffic Engineered
   (TE) point-to-multipoint (P2MP) Label Switched Paths (LSPs) in Multi-
   Protocol Label Switching (MPLS) and Generalized MPLS (GMPLS)
   networks.  The solution relies on RSVP-TE without requiring a
   multicast routing protocol in the Service Provider core. Protocol



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   elements and procedures for this solution are described. There can be
   various applications for P2MP TE LSPs such as IP multicast.
   Specification of how such applications will use a P2MP TE LSP is
   outside the scope of this document.















































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Table of Contents

 1          Conventions used in this document  .....................   5
 2          Terminology  ...........................................   5
 3          Introduction  ..........................................   5
 4          Mechanism  .............................................   5
 4.1        P2MP Tunnels  ..........................................   6
 4.2        P2MP LSP   .............................................   6
 4.3        Sub-Groups  ............................................   6
 4.4        S2L Sub-LSPs  ..........................................   7
 4.4.1      Representation of a S2L Sub-LSP  .......................   7
 4.4.2      S2L Sub-LSPs and Path Messages  ........................   7
 4.5        Explicit Routing  ......................................   8
 5          Path Message  ..........................................  10
 5.1        Path Message Format  ...................................  10
 5.2        Path Message Processing  ...............................  11
 5.2.1      Multiple Path Messages  ................................  12
 5.2.2      Multiple S2L Sub-LSPs in one Path message  .............  13
 5.2.3      Transit Fragmentation  .................................  14
 5.2.4      Control of Branch Fate Sharing  ........................  15
 5.3        Grafting  ..............................................  15
 6          Resv Message  ..........................................  16
 6.1        Resv Message Format  ...................................  16
 6.2        Resv Message Processing  ...............................  17
 6.2.1      Resv Message Throttling  ...............................  18
 6.3        Record Routing  ........................................  18
 6.3.1      RRO Processing  ........................................  18
 6.4        Reservation Style  .....................................  19
 7          PathTear Message  ......................................  19
 7.1        PathTear Message Format  ...............................  19
 7.2        Pruning  ...............................................  20
 7.2.1      Implicit S2L Sub-LSP Teardown  .........................  20
 7.2.2      Explicit S2L Sub-LSP Teardown   ........................  20
 8          Notify and ResvConf Messages  ..........................  21
 9          Refresh Reduction  .....................................  21
10          State Management  ......................................  22
10.1        Incremental State Update  ..............................  22
10.2        Combining Multiple Path Messages  ......................  23
11          Error Processing  ......................................  24
11.1        PathErr Messages  ......................................  24
11.2        ResvErr Messages  ......................................  24
11.3        Branch Failure Handling  ...............................  25
12          Admin Status Change  ...................................  26
13          Label Allocation on LANs with Multiple Downstream Nodes  ...26
14          P2MP LSP and Sub-LSP Re-optimization  ..................  26



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14.1        Make-before-break  .....................................  27
14.2        Sub-Group Based Re-optimization  .......................  27
15          Fast Reroute  ..........................................  27
15.1        Facility Backup  .......................................  28
15.2        One to One Backup  .....................................  29
16          Support for LSRs that are not P2MP Capable  ............  29
17          Reduction in Control Plane Processing with LSP Hierarchy  ..31
18          P2MP LSP Remerging and Cross-Over  .....................  31
19          New and Updated Message Objects  .......................  34
19.1        SESSION Object  ........................................  34
19.1.1      P2MP LSP Tunnel IPv4 SESSION Object  ...................  34
19.1.2      P2MP LSP Tunnel IPv6 SESSION Object  ...................  35
19.2        SENDER_TEMPLATE object  ................................  35
19.2.1      P2MP LSP Tunnel IPv4 SENDER_TEMPLATE Object  ...........  35
19.2.2      P2MP LSP Tunnel IPv6 SENDER_TEMPLATE Object  ...........  36
19.3        S2L SUB-LSP Object  ....................................  37
19.3.1      S2L SUB-LSP IPv4 Object  ...............................  37
19.3.2      S2L SUB-LSP IPv6 Object  ...............................  38
19.4        FILTER_SPEC Object  ....................................  38
19.4.1      P2MP LSP_IPv4 FILTER_SPEC Object  ......................  38
19.4.2      P2MP LSP_IPv4 FILTER_SPEC Object  ......................  38
19.5        P2MP SECONDARY_EXPLICIT_ROUTE Object (SERO)  ...........  38
19.6        P2MP_SECONDARY_RECORD_ROUTE Object (SRRO)  .............  39
20          IANA Considerations  ...................................  39
20.1        New Class Numbers  .....................................  39
20.2        New Class Types  .......................................  39
20.3        New Error Codes  .......................................  40
20.4        LSP Attributes Flags  ..................................  40
21          Security Considerations  ...............................  41
22          Acknowledgements  ......................................  41
23          Appendix  ..............................................  41
23.1        Example  ...............................................  41
24          References  ............................................  42
24.1        Normative References  ..................................  42
24.2        Informative References  ................................  43
25          Author Information  ....................................  44
25.1        Editor Information  ....................................  44
25.2        Contributor Information  ...............................  45
26          Intellectual Property  .................................  47
27          Full Copyright Statement  ..............................  48
28          Acknowledgement  .......................................  48










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1. Conventions used in this document

   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 [KEYWORDS].


2. Terminology

   This document uses terminologies defined in [RFC3031], [RFC2205],
   [RFC3209], [RFC3473] and [P2MP-REQ].


3. Introduction

   [RFC3209] defines a mechanism for setting up P2P TE LSPs in MPLS net-
   works. [RFC3473] defines extensions to [RFC3209] for setting up P2P
   TE LSPs in GMPLS networks. However these specifications do not pro-
   vide a mechanism for building P2MP TE LSPs.

   This document defines extensions to RSVP-TE protocol [RFC3209,
   RFC3473] to support P2MP TE LSPs satisfying the set of requirements
   described in [P2MP-REQ].

   This document relies on the semantics of RSVP that RSVP-TE inherits
   for building P2MP LSPs. A P2MP LSP  is comprised of multiple S2L sub-
   LSPs. These S2L sub-LSPs are set up between the ingress and egress
   LSRs and are appropriately combined by the branch LSRs using RSVP
   semantics to result in a P2MP TE LSP. One Path message may signal one
   or multiple S2L sub-LSPs. Hence the S2L sub-LSPs belonging to a P2MP
   LSP can be signaled using one Path message or split across multiple
   Path messages.

   Path computation and P2MP application specific aspects are outside of
   the scope of this document.


4. Mechanism

   This document describes a solution that optimizes data replication by
   allowing non-ingress nodes in the network to be replication/branch
   nodes. A branch node is a LSR that is capable of replicating the
   incoming data on two or more outgoing interfaces. The solution uses
   RSVP-TE in the core of the network for setting up a P2MP TE LSP.

   The P2MP TE LSP is set up by associating multiple S2L TE sub-LSPs and
   relying on data replication at branch nodes. This is described fur-
   ther in the following sub-sections by describing P2MP Tunnels and how



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   they relate to S2L sub-LSPs.


4.1. P2MP Tunnels

   The specific aspect related to P2MP TE LSP is the action required at
   a branch node, where data replication occurs. For instance, in the
   MPLS case, incoming labeled data is appropriately replicated to sev-
   eral outgoing interfaces which may have different labels.

   A P2MP TE Tunnel comprises of one or more P2MP LSPs. A P2MP TE Tunnel
   is identified by a P2MP SESSION object. This object contains the
   identifier of the P2MP Session which includes the P2MP ID, a tunnel
   ID and an extended tunnel ID.

   The fields of a P2MP SESSION object are identical to those of the
   SESSION object defined in [RFC3209] except that the Tunnel Endpoint
   Address field is replaced by the P2MP Identifier (P2MP ID) field.

   The P2MP ID provides an identifier for the set of destinations of the
   P2MP TE Tunnel.


4.2. P2MP LSP

   A P2MP LSP  is identified by the combination of the P2MP ID, Tunnel
   ID, and Extended Tunnel ID that are part of the P2MP SESSION object,
   and the tunnel sender address and LSP ID fields of the P2MP
   SENDER_TEMPLATE object. The new P2MP SENDER_TEMPLATE object is
   defined in section 20.2.


4.3. Sub-Groups

   As with all other RSVP controlled LSPs, P2MP LSP  state is managed
   using RSVP messages. While use of RSVP messages is the same, P2MP LSP
   state differs from P2P LSP state in a number of ways. The two most
   notable differences are that a P2MP LSP  comprises multiple S2L Sub-
   LSPs and that, as a result of this, it may not be possible to repre-
   sent full state in a single IP datagram and even more likely that it
   can't fit into a single IP packet. It must also be possible to effi-
   ciently add and remove endpoints to and from P2MP TE LSPs. An addi-
   tional issue is that P2MP LSP must also handle the state "remerge"
   problem, see [P2MP-REQ].

   These differences in P2MP state are addressed through the addition of
   a sub-group identifier (Sub-Group ID) and sub-group originator (Sub-
   Group Originator ID) to the SENDER_TEMPLATE and FILTER_SPEC objects.



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   Taken together the Sub-Group ID and Sub-Group Originator ID are
   referred to as the Sub-Group fields.

   The Sub-Group fields, together with rest of the SENDER_TEMPLATE and
   SESSION objects, are used to represent a portion of a P2MP LSP's
   state.  This portion of a P2MP LSP's state refers only to signaling
   state and not data plane replication or branching. For example, it is
   possible for a node to "branch" signaling state for a P2MP LSP, but
   to not branch the data associated with the P2MP LSP. Typical applica-
   tions for generation and use of multiple subgroups are adding an
   egress and semantic fragmentation to ensure that a Path message
   remains within a single IP packet.


4.4. S2L Sub-LSPs

   A P2MP LSP is constituted of one or more S2L sub-LSPs.


4.4.1. Representation of a S2L Sub-LSP

   A S2L sub-LSP exists within the context of a P2MP LSP. Thus it is
   identified by the P2MP ID, Tunnel ID, and Extended Tunnel ID that are
   part of the P2MP SESSION, the tunnel sender address and LSP ID fields
   of the P2MP SENDER_TEMPLATE object, and the S2L sub-LSP destination
   address that is part of the S2L_SUB_LSP object. The S2L_SUB_LSP
   object is defined in section 20.3.

   An EXPLICIT_ROUTE Object (ERO) or P2MP SECONDARY_EXPLICIT_ROUTE
   Object (SERO) is used to optionally specify the explicit route of a
   S2L sub-LSP. Each ERO or a SERO that is signaled corresponds to a
   particular S2L_SUB_LSP object. Details of explicit route encoding are
   specified in section 4.5. The SECONDARY_EXPLICIT_ROUTE Object is
   defined in [RECOVERY], a new P2MP SECONDARY_EXPLICIT_ROUTE Object C-
   type is defined in Section 20.5 and a matching P2MP SEC-
   ONDARY_RECORD_ROUTE Object C-type is defined in Section 20.6.


4.4.2. S2L Sub-LSPs and Path Messages

   The mechanism in this document allows a P2MP LSP to be signaled using
   one or more Path messages. Each Path message may signal one or more
   S2L sub-LSPs. Support for multiple Path messages is desirable as one
   Path message may not be large enough to fit all the S2L sub-LSPs; and
   they also allow separate manipulation of sub-trees of the P2MP LSP.
   The reason for allowing a single Path message, to signal multiple S2L
   sub-LSPs, is to optimize the number of control messages needed to
   setup a P2MP LSP.



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4.5. Explicit Routing

   When a Path message signals a single S2L sub-LSP (that is, the Path
   message is only targeting a single leaf in the P2MP tree), the
   EXPLICIT_ROUTE object encodes the path from the ingress LSR to the
   egress LSR. The Path message also includes the S2L_SUB_LSP object for
   the S2L sub-LSP being signaled. The < [<EXPLICIT_ROUTE>],
   <S2L_SUB_LSP> > tuple represents the S2L sub-LSP and is referred to
   as the sub-LSP descriptor.  The absence of the ERO should be inter-
   preted as requiring hop-by-hop routing for the sub-LSP based on the
   S2L sub-LSP destination address field of the S2L_SUB_LSP object.

   When a Path message signals multiple S2L sub-LSPs the path of the
   first S2L sub-LSP, from the ingress LSR to the egress LSR, is encoded
   in the ERO. The first S2L sub-LSP is the one that corresponds to the
   first S2L_SUB_LSP object in the Path message. The S2L sub-LSPs corre-
   sponding to the S2L_SUB_LSP objects that follow are termed as subse-
   quent S2L sub-LSPs.  One approach to encode the explicit route of a
   subsequent S2L sub-LSP is to include all the hops from the ingress to
   the egress of the S2L sub-LSP. However this implies potential repeti-
   tion of hops that can be learned from the ERO or explicit routes of
   other S2L sub-LSPs. Explicit route compression using SEROs attempts
   to minimize such repetition.

   The path of each subsequent S2L sub-LSP is encoded in a P2MP SEC-
   ONDARY_EXPLICIT_ROUTE object (SERO). The format of the SERO is the
   same as an ERO (as defined in [RFC3209]). Each subsequent S2L sub-LSP
   is represented by tuples of the form < [<P2MP SEC-
   ONDARY_EXPLICIT_ROUTE>] <S2L_SUB_LSP> >. There is a one to one corre-
   spondence between a S2L_SUB_LSP object and a SERO. A SERO for a par-
   ticular S2L sub-LSP includes only the path from a certain branch LSR
   to the egress LSR if the path to that branch LSR can be derived from
   the ERO or other SEROs. The absence of a SERO should be interpreted
   as requiring hop-by-hop routing for that S2L sub-LSP. Note that the
   destination address is carried in the S2L sub-LSP object. The encod-
   ing of the SERO and S2L sub-LSP object are described in detail in
   section 20.

   Explicit route compression is illustrated using the following figure.


                                    A
                                    |
                                    |
                                    B
                                    |
                                    |
                          C----D----E



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                          |    |    |
                          |    |    |
                          F    G    H-------I
                               |    |\      |
                               |    | \     |
                               J    K   L   M
                               |    |   |   |
                               |    |   |   |
                               N    O   P   Q--R


                        Figure 1. Explicit Route Compression

   Figure 1. shows a P2MP LSP with LSR A as the ingress LSR and six
   egress LSRs: (F, N, O, P, Q and R). When all the six S2L sub-LSPs are
   signaled in one Path message let us assume that the S2L sub-LSP to
   LSR F is the first S2L sub-LSP and the rest are subsequent S2L sub-
   LSPs. Following is one way for the ingress LSR A to encode the S2L
   sub-LSP explicit routes using compression:

      S2L sub-LSP-F:   ERO = {B, E, D, C, F},  S2L_SUB_LSP Object-F
      S2L sub-LSP-N:   SERO = {D, G, J, N}, S2L_SUB_LSP Object-N
      S2L sub-LSP-O:   SERO = {E, H, K, O}, S2L_SUB_LSP Object-O
      S2L sub-LSP-P:   SERO = {H, L, P}, S2L_SUB_LSP Object-P,
      S2L sub-LSP-Q:   SERO = {H, I, M, Q}, S2L_SUB_LSP Object-Q,
      S2L sub-LSP-R:   SERO = {Q, R}, S2L_SUB_LSP Object-R,

   After LSR E processes the incoming Path message from LSR B it sends a
   Path message to LSR D with the S2L sub-LSP explicit routes encoded as
   follows:

      S2L sub-LSP-F:   ERO = {D, C, F},  S2L_SUB_LSP Object-F
      S2L sub-LSP-N:   SERO = {D, G, J, N}, S2L_SUB_LSP Object-N

   LSR E also sends a Path message to LSR H and following is one way to
   encode the S2L sub-LSP explicit routes using compression:

      S2L sub-LSP-O:   ERO = {H, K, O}, S2L_SUB_LSP Object-O
      S2L sub-LSP-P:   SERO = {H, L, P}, S2L_SUB_LSP Object-P,
      S2L sub-LSP-Q:   SERO = {H, I, M, Q}, S2L_SUB_LSP Object-Q,
      S2L sub-LSP-R:   SERO = {Q, R}, S2L_SUB_LSP Object-R,

   After LSR H processes the incoming Path message from E it sends a
   Path message to LSR K, LSR L and LSR I. The encoding for the Path
   message to LSR K is as follows:

      S2L sub-LSP-O:   ERO  = {K, O}, S2L_SUB_LSP Object-O




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   The encoding of the Path message sent by LSR H to LSR L is as fol-
   lows:

      S2L sub-LSP-P:   ERO = {L, P}, S2L_SUB_LSP Object-P,

   Following is one way for LSR H to encode the S2L sub-LSP explicit
   routes in the Path message sent to LSR I:

      S2L sub-LSP-Q:   ERO = {I, M, Q}, S2L_SUB_LSP Object-Q,
      S2L sub-LSP-R:   SERO = {Q, R}, S2L_SUB_LSP Object-R,

   The explicit route encodings in the Path messages sent by LSRs D and
   Q are left as an exercise to the reader.

   This compression mechanism reduces the Path message size. It also
   reduces extra processing that can result if explicit routes are
   encoded from ingress to egress for each S2L sub-LSP. No assumptions
   are placed on the ordering of the subsequent S2L sub-LSPs and hence
   on the ordering of the SEROs in the Path message. All LSRs need to
   process the ERO corresponding to the first S2L sub-LSP. A LSR needs
   to process a S2L sub-LSP descriptor for a subsequent S2L sub-LSP only
   if the first hop in the corresponding SERO is a local address of that
   LSR. The branch LSR that is the first hop of a SERO propagates the
   corresponding S2L sub-LSP downstream.


5. Path Message

5.1. Path Message Format

   This section describes modifications made to the Path message format
   as specified in [RFC3209] and [RFC3473]. The Path message is enhanced
   to signal one or more S2L sub-LSPs. This is done by including the S2L
   sub-LSP descriptor list in the Path message as shown below.

   <Path Message> ::=     <Common Header> [ <INTEGRITY> ]
                          [ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>] ...]
                          [ <MESSAGE_ID> ]
                          <SESSION> <RSVP_HOP>
                          <TIME_VALUES>
                          [ <EXPLICIT_ROUTE> ]
                          <LABEL_REQUEST>
                          [ <PROTECTION> ]
                          [ <LABEL_SET> ... ]
                          [ <SESSION_ATTRIBUTE> ]
                          [ <NOTIFY_REQUEST> ]
                          [ <ADMIN_STATUS> ]
                          [ <POLICY_DATA> ... ]



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                          <sender descriptor>
                          [<S2L sub-LSP descriptor list>]


   Following is the format of the S2L sub-LSP descriptor list.

   <S2L sub-LSP descriptor list> ::= <S2L sub-LSP descriptor>
                                     [ <S2L sub-LSP descriptor list> ]

   <S2L sub-LSP descriptor> ::= <S2L_SUB_LSP> [ <P2MP SEC-
   ONDARY_EXPLICIT_ROUTE> ]

   Each LSR MUST use the common objects in the Path message and the S2L
   sub-LSP descriptors to process each S2L sub-LSP represented by the
   S2L sub-LSP object and the SUB-/EXPLICIT_ROUTE object combination.

   The first S2L_SUB_LSP object's explicit route is specified by the
   ERO. Explicit routes of subsequent S2L sub-LSPs are specified by the
   corresponding SERO. A SERO corresponds to the following S2L_SUB_LSP
   object.

   The RRO in the sender descriptor contains the hops traversed by the
   Path message and applies to all the S2L sub-LSPs signaled in the Path
   message.

   Path message processing is described in the next section.


5.2. Path Message Processing

   The ingress-LSR initiates the set up of a S2L sub-LSP to each egress-
   LSR that is the destination of the P2MP LSP. Each S2L sub-LSP is
   associated with the same P2MP LSP using common P2MP SESSION object
   and <Source Address, LSP-ID> fields in the P2MP SENDER_TEMPLATE
   object.  Hence it can be combined with other S2L sub-LSPs to form a
   P2MP LSP.  Another S2L sub-LSP belonging to the same instance of this
   S2L sub-LSP (i.e.  the same P2MP LSP) shares resources with this S2L
   sub-LSP. The session corresponding to the P2MP TE tunnel is deter-
   mined based on the P2MP SESSION object. Each S2L sub-LSP is identi-
   fied using the S2L_SUB_LSP object. Explicit routing for the S2L sub-
   LSPs is achieved using the ERO and SEROs.

   As mentioned earlier, it is possible to signal S2L sub-LSPs for a
   given P2MP LSP in one or more Path messages. And a given Path message
   can contain one or more S2L sub-LSPs. A LSR that supports RSVP-TE
   signaled P2MP LSPs MUST be able to receive and process multiple Path
   messages for the same P2MP LSP and multiple S2L sub-LSPs in one Path
   message. This implies that a LSR MUST be able to receive and process



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   all objects listed in section 20.


5.2.1. Multiple Path Messages

   As described in section 3, either the <EXPLICIT_ROUTE> <S2L SUB-LSP>
   or the <P2MP SECONDARY_EXPLICIT_ROUTE> <S2L_SUB_LSP> tuple is used to
   specify a S2L sub-LSP. Multiple Path messages can be used to signal a
   P2MP LSP. Each Path message can signal one or more S2L sub-LSPs. If a
   Path message contains only one S2L sub-LSP, each LSR along the S2L
   sub-LSP follows [RFC3209] procedures for processing the Path message
   besides the S2L SUB-LSP object processing described in this document.

   Processing of Path messages containing more than one S2L sub-LSP is
   described in Section 5.2.2.

   An ingress LSR may use multiple Path messages for signaling a P2MP
   LSP.  This may be because a single Path message may not be large
   enough to signal the P2MP LSP. Or it may be while adding leaves to
   the P2MP LSP the new leaves are signaled in a new Path message. Or an
   ingress LSR MAY choose to break the P2MP tree into separate manage-
   able P2MP trees.  These trees share the same root and may share the
   trunk and certain branches.  The scope of this management decomposi-
   tion of P2MP trees is bounded by a single tree (the P2MP Tree) and
   multiple trees with a single leaf each (S2L sub-LSPs).  Per [P2MP-
   REQ], a P2MP LSP MUST have consistent attributes across all portions
   of a tree. This implies that each Path message that is used to signal
   a P2MP LSP is signaled using the same signaling attributes with the
   exception of the S2L sub-LSP information.

   The resulting sub-LSPs from the different Path messages belonging to
   the same P2MP LSP SHOULD share labels and resources where they share
   hops to prevent multiple copies of the data being sent.

   In certain cases a transit LSR may need to generate multiple Path
   messages to signal state corresponding to a single received Path mes-
   sage. For instance ERO expansion may result in an overflow of the
   resultant Path message. In this case the message can be decomposed
   into multiple Path messages such that each of the messages carry a
   subset of the X2L sub-tree carried by the incoming message.

   Multiple Path messages generated by a LSR that signal state for the
   same P2MP LSP are signaled with the same SESSION object and have the
   same <Source address, LSP-ID> in the SENDER_TEMPLATE object. In order
   to disambiguate these Path messages a <Sub-Group Originator ID, sub-
   Group ID> tuple is introduced (also referred to as the Sub-Group
   field) and encoded in the SENDER_TEMPLATE object. Multiple Path mes-
   sages generated by a LSR to signal state for the same P2MP LSP have



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   the same Sub-Group Originator ID and have a different sub-Group ID.
   The Sub-Group Originator ID SHOULD be set to the TE Router ID of the
   LSR that originates the Path message. This is either the ingress LSR
   or a LSR which re-originates the Path message with its own Sub-Group
   Originator ID. Cases when a transit LSR may change the Sub-Group
   Originator ID of an incoming Path message are described below. The
   <Sub-Group Originator ID, sub-Group ID> tuple is globally unique. The
   sub-Group ID space is specific to the Sub-Group Originator ID. There-
   fore the combination <Sub-Group Originator ID, sub-Group ID> is net-
   work-wide unique. Also, a router that changes the Sub-Group origina-
   tor ID of an incoming Path message MUST use the same value of the
   Sub-Group Originator ID for all outgoing Path messages, for a partic-
   ular P2MP LSP, and SHOULD not vary it during the life of the P2MP
   LSP.


5.2.2. Multiple S2L Sub-LSPs in one Path message

   The S2L sub-LSP descriptor list allows the signaling of one or more
   S2L sub-LSPs in one Path message. It is possible to signal multiple
   S2L sub-LSP object and ERO/SERO combinations in a single Path mes-
   sage. Note that these two objects are the ones that differentiate a
   S2L sub-LSP.

   All LSRs MUST process the ERO corresponding to the first S2L sub-LSP
   when the ERO is present. If one or more SEROs are present an ERO MUST
   be present.  The first S2L sub-LSP MUST be propagated in a Path mes-
   sage by each LSR along the explicit route specified by the ERO. A LSR
   MUST process a S2L sub-LSP descriptor for a subsequent S2L sub-LSP
   only if the first hop in the corresponding SERO is a local address of
   that LSR. If this is not the case the S2L sub-LSP descriptor MUST be
   included in the Path message sent to LSR that is the next hop to
   reach the first hop in the SERO. This next hop is determined by using
   the ERO or other SEROs that encode the path to the SERO's first hop.
   If this is the case and the LSR is also the egress, the S2L sub-LSP
   descriptor MUST NOT be propagated downstream. If this is the case and
   the LSR is not the egress the S2L sub-LSP descriptor MUST be included
   in a Path message sent to the next-hop determined from the SERO.
   Hence a branch LSR MUST only propagate the relevant S2L sub-LSP
   descriptors on each downstream link. A S2L sub-LSP descriptor list
   that is propagated on a downstream link MUST only contain those S2L
   sub-LSPs that are routed using that link. This processing MAY result
   in a subsequent S2L sub-LSP in an incoming Path message to become the
   first S2L sub-LSP in an outgoing Path message.

   Note that if one or more SEROs contain loose hops, expansion of such
   loose hops MAY result in overflowing the Path message size. Section
   5.2.3 describes how signaling of the set of S2L sub-LSPs can be split



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   in more than one Path message.

   The Record Route Object (RRO) contains the hops traversed by the Path
   message and applies to all the S2L sub-LSPs signaled in the path mes-
   sage. A transit LSR MUST append its address in an incoming RRO and
   propagate it downstream. A branch LSR MUST form a new RRO for each of
   the outgoing Path messages. Each such updated RRO MUST be formed
   using the rules in [RFC3209].

   If a LSR is unable to support a S2L sub-LSP in a Path message, a
   PathErr message MUST be sent for the impacted S2L sub-LSP, and normal
   processing of the rest of the P2MP LSP SHOULD continue. The default
   behavior is that the remainder of the LSP is not impacted (that is,
   all other branches are allowed to set up) and the failed branches are
   reported in PathErr messages in which the Path_State_Removed flag
   MUST NOT be set. However, the ingress LSR may set a LSP Integrity
   flag to request that if there is a setup failure on any branch the
   entire LSP should fail to set up. This is described further in sec-
   tion 12.


5.2.3. Transit Fragmentation

   In certain cases a transit LSR may need to generate multiple Path
   messages to signal state corresponding to a single received Path mes-
   sage. For instance ERO expansion may result in an overflow of the
   resultant Path message. It is desirable not to rely on IP fragmenta-
   tion in this case. In order to achieve this, the multiple Path mes-
   sages generated by the transit LSR, are signaled with the Sub-Group
   Originator ID set to the TE Router ID of the transit LSR and a dis-
   tinct sub-Group ID. Thus each distinct Path message that is generated
   by the transit LSR for the P2MP LSP carries a distinct <Sub-Group
   Originator ID, Sub-Group ID> tuple.

   When multiple Path messages are used by an ingress or transit node,
   each Path message SHOULD be identical with the exception of the S2L
   sub-LSP related information (e.g., SERO), message and hop information
   (e.g., INTEGRITY, MESSAGE_ID and RSVP_HOP), and the sub-group fields
   of the SENDER_TEMPLATE objects. Except when performing a  make-
   before-break operation, the tunnel sender address and LSP ID fields
   MUST be the same in each message, and for transit nodes, the same as
   the values in the received Path message.

   As described above one case in which the Sub-Group Originator ID of a
   received Path message is changed is that of transit fragmentation.
   The Sub-Group Originator ID of a received Path message may also be
   changed in the outgoing Path message and set to that of the LSR orig-
   inating the Path message based on a local policy. For instance a LSR



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   may decide to always change the Sub-Group Originator ID while per-
   forming ERO expansion. The Sub-Group ID MUST not be changed if the
   Sub-Group Originator ID is not being changed.


5.2.4. Control of Branch Fate Sharing

   An ingress LSR can control the behavior of an LSP if there is a fail-
   ure during LSP setup or after an LSP has been established. The
   default behavior is that only the branches downstream of the failure
   are not established, but the ingress may request 'LSP integrity' such
   that any failure anywhere within the LSP tree causes the entire P2MP
   LSP to fail.

   The ingress LSP may request 'LSP integrity' by setting bit [TBA] of
   the Attributes Flags TLV. The bit is set if LSP integrity is
   required.

   It is RECOMMENDED to use the LSP_ATTRIBUTES Object for this flag and
   not the LSP_REQUIRED_ATTRIBUTES Object.

   A branch LSR that supports the Attributes Flags TLV and recognizes
   this bit MUST support LSP integrity or reject the LSP setup with a
   PathErr carrying the error "Routing Error"/"Unsupported LSP
   Integrity"


5.3. Grafting

   The operation of adding egress LSR(s) to an existing P2MP LSP is
   termed as grafting. This operation allows egress nodes to join a P2MP
   LSP at different points in time.

   There are two methods to add S2L sub-LSPs to a P2MP LSP.  The first
   is to add new S2L sub-LSPs to the P2MP LSP by adding them to an
   existing Path message and refreshing the entire Path message. Path
   message processing described in section 4 results in adding these S2L
   sub-LSPs to the P2MP LSP. Note that as a result of adding one or more
   S2L sub-LSPs to a Path message the ERO compression encoding may have
   to be recomputed.

   The second is to use incremental updates described in section 10.1.
   The egress LSRs can be added by signaling only the impacted S2L sub-
   LSPs in a new Path message. Hence other S2L sub-LSPs do not have to
   be re-signaled.






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6. Resv Message

6.1. Resv Message Format

   The Resv message follows the [RFC3209] and [RFC3473] format:

   <Resv Message> ::=    <Common Header> [ <INTEGRITY> ]
                         [ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>] ... ]
                         [ <MESSAGE_ID> ]
                         <SESSION> <RSVP_HOP>
                         <TIME_VALUES>
                         [ <RESV_CONFIRM> ]  [ <SCOPE> ]
                         [ <NOTIFY_REQUEST> ]
                         [ <ADMIN_STATUS> ]
                         [ <POLICY_DATA> ... ]
                         <STYLE> <flow descriptor list>


   <flow descriptor list> ::= <FF flow descriptor list>
                              | <SE flow descriptor>


   <FF flow descriptor list> ::= <FF flow descriptor>
                                 | <FF flow descriptor list>
                                 <FF flow descriptor>


   <SE flow descriptor> ::= <FLOWSPEC> <SE filter spec list>

   <SE filter spec list> ::= <SE filter spec>
                            | <SE filter spec list> <SE filter spec>

   The FF flow descriptor and SE filter spec are modified as follows to
   identify the S2L sub-LSPs that they correspond to:

   <FF flow descriptor> ::= [ <FLOWSPEC> ] <FILTER_SPEC> <LABEL>
                            [ <RECORD_ROUTE> ] [ <S2L sub-LSP descriptor
   list> ]

   <SE filter spec> ::=     <FILTER_SPEC> <LABEL> [ <RECORD_ROUTE> ]
                            [ <S2L sub-LSP descriptor list> ]

   <S2L sub-LSP descriptor list> ::= <S2L sub-LSP descriptor>
                                     [ <S2L sub-LSP descriptor list> ]

   <S2L sub-LSP descriptor> ::= <S2L_SUB_LSP> [ <P2MP SEC-
   ONDARY_EXPLICIT_ROUTE> ]




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   FILTER_SPEC is defined in section 20.4.

   The S2L sub-LSP descriptor has the same format as in section 4.1 with
   the difference that a P2MP_SECONDARY_RECORD_ROUTE object is used in
   place of a P2MP SECONDARY_EXPLICIT_ROUTE object. The P2MP_SEC-
   ONDARY_RECORD_ROUTE objects follow the same compression mechanism as
   the P2MP SECONDARY_EXPLICIT_ROUTE objects. Note that that a Resv mes-
   sage can signal multiple S2L sub-LSPs that may belong to the same
   FILTER_SPEC object or different FILTER_SPEC objects. The same label
   SHOULD be allocated if the <Source Address, LSP-ID> fields of the
   FILTER_SPEC object are the same.

   However different upstream labels are allocated if the <Source
   Address, LSP-ID> of the FILTER_SPEC object is different as that
   implies different P2MP LSP.


6.2. Resv Message Processing

   The egress LSR MUST follow normal RSVP procedures while originating a
   Resv message. The Resv message carries the label allocated by the
   egress LSR.

   A subsequent node MUST allocates its own label and pass it in the
   Resv message upstream. The node MAY combine multiple flow descrip-
   tors, from different Resv messages received from downstream, in one
   Resv message sent upstream. A Resv message MUST NOT be sent upstream
   until at least one Resv message has been received from a downstream
   neighbor. When the integrity bit is set in the LSP_ATTRIBUTE object,
   no Resv message MUST be sent upstream until all Resv messages have
   been received from the downstream neighbors.

   Each FF flow descriptor or SE filter spec sent upstream in a Resv
   message includes a S2L sub-LSP descriptor list. Each such FF flow
   descriptor or SE filter spec for the same P2MP LSP (whether on one or
   multiple Resv messages) MUST be allocated the same label.

   This label is associated by that node with all the labels received
   from downstream Resv messages for that P2MP LSP. Note that a transit
   node may become a replication point in the future when a branch is
   attached to it.  Hence this results in the setup of a P2MP LSP from
   the ingress-LSR to the egress LSRs.

   The ingress LSR may need to understand when all desired egresses have
   been reached. This is achieved using <S2L_SUB_LSP> objects.

   Each branch node can potentially send one Resv message upstream for
   each of the downstream receivers. This MAY result in overflowing the



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   Resv message, particularly when considering that the number of mes-
   sages increases the closer the branch node is to the ingress.

   Transit nodes MUST replace the Sub-Group ID fields received in the
   FILTER_SPEC objects with the value that was received in the Sub-Group
   ID field of the Path message from the upstream neighbor, when the
   node set the Sub-Group Originator field in the associated Path mes-
   sage.  ResvErr messages generation is unmodified.  Nodes propagating
   a received ResvErr message MUST use the Sub-Group field values car-
   ried in the corresponding Resv message.


6.2.1. Resv Message Throttling

   A branch node may have to send the Resv message being sent upstream
   whenever there is a change in a Resv message for a S2L sub-LSP
   received from downstream. This can result in excessive Resv messages
   sent upstream, particularly when the S2L sub-LSPs are established for
   the first time.  In order to mitigate this situation, branch nodes
   can limit their transmission of Resv messages. Specifically, in the
   case where the only change being sent in a Resv message is in one or
   more SRRO objects, the branch node SHOULD transmit the Resv message
   only after a delay time has passed since the transmission of the pre-
   vious Resv message for the same session. This delayed Resv message
   SHOULD include SRROs for all branches. Specific mechanisms for Resv
   message throttling are implementation dependent and are outside the
   scope of this document.


6.3. Record Routing

6.3.1. RRO Processing

   A Resv message contains a record route per S2L sub-LSP that is being
   signaled by the Resv message if the sender node requests route
   recording by including a RRO in the Path message. The same rule is
   used during signaling of P2MP LSP i.e. insertion of the RRO in the
   Path message used to signal one or more S2L sub-LSP triggers the
   inclusion of an RRO for each sub-LSP.

   The record route of the first S2L sub-LSP is encoded in the RRO.
   Additional RROs for the subsequent S2L sub-LSPs are referred to as
   P2MP_SECONDARY_RECORD_ROUTE objects (SRROs). Their format is speci-
   fied in section 20.5. The ingress node then receives the RRO and
   possibly the SRRO  corresponding to each subsequent S2L sub-LSP. Each
   S2L_SUB_LSP object is followed by the RRO/SRRO. The ingress node can
   then determine the record route corresponding to a particular S2L
   sub-LSP. The RRO and SRROs can be used to construct the end to end



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   Path for each S2L sub-LSP.


6.4. Reservation Style

   Considerations about the reservation style in a Resv message apply as
   described in [RFC3209]. The reservation style in the Resv messages
   can either be FF or SE. All P2MP LSP that belong to the same P2MP
   Tunnel MUST be signaled with the same reservation style. Irrespective
   of whether the reservation style is FF or SE, the S2L sub-LSPs that
   belong to the same P2MP LSP SHOULD share labels where they share
   hops. If the S2L sub-LSPs that belong to the same P2MP LSP share
   labels then they MUST share resources. The S2L sub-LSPs that belong
   to different P2MP LSP MUST NOT share labels. If the reservation style
   is FF than S2L Sub-LSPs that belong to different P2MP LSP MUST NOT
   share resources. If the reservation style is SE than S2L sub-LSPs
   that belong to different P2MP LSP and the same P2MP Tunnel SHOULD
   share resources where they share hops, but MUST not share labels.


7. PathTear Message

7.1. PathTear Message Format

   The format of the PathTear message is as follows:

   <PathTear Message> ::= <Common Header> [ <INTEGRITY> ]
                           [ [ <MESSAGE_ID_ACK> |
                               <MESSAGE_ID_NACK> ... ]
                           [ <MESSAGE_ID> ]
                           <SESSION> <RSVP_HOP>
                           [ <sender descriptor> ]
                           [ <S2L sub-LSP descriptor list> ]

                 <sender descriptor> ::= (see earlier definition)

   Note: it is assumed that the S2L sub-LSP descriptor will not include
   the P2MP SECONDARY_EXPLICIT_ROUTE object associated with each
   S2L_SUB_LSP being deleted












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7.2. Pruning

   The operation of removing egress LSR(s) from an existing P2MP LSP is
   termed as pruning. This operation allows egress nodes to be removed
   from a P2MP LSP at different points in time. This section describes
   the mechanisms to perform pruning.


7.2.1. Implicit S2L Sub-LSP Teardown

   Implicit teardown uses standard RSVP message processing. Per standard
   RSVP processing, a S2L sub-LSP may be removed from a P2MP TE LSP by
   sending a modified message for the Path or Resv message that previ-
   ously advertised the S2L sub-LSP. This message MUST list all S2L sub-
   LSPs that are not being removed. When using this approach, a node
   processing a message that removes a S2L sub-LSP from a P2MP TE LSP
   MUST ensure that the S2L sub-LSP is not included in any other Path
   state associated with session before interrupting the data path to
   that egress.  All other message processing remains unchanged.

   When implicit teardown is used to delete one or more S2L sub-LSPs, by
   modifying a Path message, a transit LSR may have to generate a
   PathTear message downstream to delete one or more of these S2L sub-
   LSPs. This can happen if as a result of the implicit deletion of S2L
   sub-LSP(s) there are no remaining S2L sub-LSPs to send in the corre-
   sponding Path message downstream.


7.2.2. Explicit S2L Sub-LSP Teardown

   Explicit S2L Sub-LSP teardown relies on generating a PathTear message
   for the corresponding Path message. The PathTear message is signaled
   with the SESSION and SENDER_TEMPLATE objects corresponding to the
   P2MP LSP and the <Sub-Group Originator ID, Sub-Group ID> tuple corre-
   sponding to the Path message. This approach SHOULD be used when all
   the egresses signaled by a Path message need to be removed from the
   P2MP LSP. Other S2L sub-LSPs, from other sub-groups signaled using
   other Path messages, are not affected by the PathTear.

   A transit LSR that propagates the PathTear message downstream MUST
   ensure that it sets the <Sub-Group Originator ID, Sub-Group ID> tuple
   in the PathTear message to the values used to generate the previous
   Path message that corresponds to the S2L sub-LSPs being deleted by it
   in the PathTear message.  The transit LSR may need to generate multi-
   ple PathTear messages for an incoming PathTear message if it had per-
   formed transit fragmentation for the corresponding incoming Path mes-
   sage.




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   When a P2MP LSP is removed by the ingress, a PathTear message MUST be
   generated for each Path message used to signal the P2MP LSP.


8. Notify and ResvConf Messages

   This section is currently under discussion between the authors and
   will be updated in the next revision.

   Notify Request and Notify messages are described in [RFC3473].  If a
   transit router sets the sub-group originator ID in the SENDER_TEM-
   PLATE object of a Path message to its own address and the Path mes-
   sage carries a Notify Request object then the router MUST set the
   notify node address in the Notify Request object to its own address.
   If this router receives a corresponding Notify message from down-
   stream than it MUST generate a Notify message upstream towards the
   Notify node address that the router had received in the incoming Path
   message. The receiver of a Notify message MUST identify the sender
   state referenced in the message based on the SESSION and SENDER_TEM-
   PLATE objects.

   ResvConf messages are described in [RFC2205]. An egress LSR may
   include a RESV_CONFIRM object that contains the egress LSR's address.
   If a transit LSR is merging Resv messages received from more than
   egress LSR and one or more of these Resv messages contain a RESV_CON-
   FIRM object than the transit LSR MUST set its own address in the
   RESV_CONFIRM object in the Resv message that it generates. Also if
   the transit LSR changes the sub-group originator ID in the generated
   Resv message and it includes a RESV_CONFIRM object in the Resv mes-
   sage, it MUST set its own address in the RESV_CONFIRM object.  Upon
   receiving a ResvConf message from upstream the transit LSR MUST gen-
   erate a ResvConf message towards each of the downstream LSRs that had
   included RESV_CONFIRM objects in the corresponding Resv messages.  As
   with Notify messages, the receiver of a ResvConf message MUST iden-
   tify the state referenced in the message based on the SESSION and
   FILTER_SPEC objects.


9. Refresh Reduction

   The refresh reduction procedures described in [RFC2961] are equally
   applicable to P2MP LSP described in this document. Refresh reduction
   applies to individual messages and the state they install/maintain,
   and that continues to be the case for P2MP LSP.







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10. State Management

   State signaled by a P2MP Path message is managed by a local implemen-
   tation using the <P2MP ID, Tunnel ID, Extended Tunnel ID> as part of
   the SESSION object and <Tunnel Sender Address, LSP ID, Sub-Group
   Originator ID, Sub-Group ID> as part of the SENDER_TEMPLATE object.

   Additional information signaled in the Path message is part of the
   state created by a local implementation. This mandatorily includes
   PHOP and SENDER_TSPEC object.


10.1. Incremental State Update

   RSVP as defined in [RFC2205] and as extended by RSVP-TE [RFC3209] and
   GMPLS [RFC3473] uses the same basic approach to state communication
   and synchronization, namely full state is sent in each state adver-
   tisement message. Per [RFC2205] Path and Resv messages are idempo-
   tent. Also, [RFC2961] categorizes RSVP messages into two types: trig-
   ger and refresh messages and improves RSVP message handling and scal-
   ing of state refreshes but does not modify the full state advertise-
   ment nature of Path and Resv messages. The full state advertisement
   nature of Path and Resv messages has many benefits, but also has some
   drawbacks. One notable drawback is when an incremental modification
   is being made to a previously advertised state. In this case, there
   is the message overhead of sending the full state and the cost of
   processing it. It is desirable to overcome this drawback and
   add/delete S2L sub-LSPs to a P2MP LSP by incrementally updating the
   existing state.

   It is possible to use the procedures described in this document to
   allow S2L sub-LSPs to be incrementally added or deleted from the P2MP
   LSP by allowing a Path or a PathTear message to incrementally change
   the existing P2MP LSP Path state.

   As described in section 4.2, multiple Path messages can be used to
   signal a P2MP LSP. The Path messages are distinguished by different
   <Sub-Group Originator ID, sub-Group ID> tuples in the SENDER_TEMPLATE
   object.  In order to perform incremental S2L sub-LSP state addition a
   separate Path message with a new sub-Group ID is used to add the new
   S2L sub-LSPs, by the ingress LSR. The Sub-Group Originator ID MUST be
   set to the TE Router ID [RFC3477] of the node that sets the Sub-Group
   ID.

   This maintains the idempotent nature of RSVP Path messages; avoids
   keeping track of individual S2L sub-LSP state expiration and provides
   the ability to perform incremental P2MP LSP state updates.




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10.2. Combining Multiple Path Messages

   There is a tradeoff between the number of Path messages used by the
   ingress to maintain the P2MP LSP and the processing imposed by full
   state messages when adding S2L sub-LSPs to an existing Path message.
   It is possible to combine S2L sub-LSPs previously advertised in dif-
   ferent Path messages in a single Path message in order to reduce the
   number of Path messages needed to maintain the P2MP LSP. This can
   also be done by a transit node that performed fragmentation and at a
   later point is able to combine multiple Path messages that it gener-
   ated into a single Path message. This may happen when one or more S2L
   sub-LSPs are pruned from the existing Path states.

   The new Path message is signaled by the node that is combining multi-
   ple Path messages with all the S2L sub-LSPs that are being combined
   in a single Path message. This Path message MAY contain a new Sub-
   Group ID field value.  When a new Path and Resv message that is sig-
   naled for an existing S2L sub-LSP is received by a transit LSR, state
   including the new instance of the S2L sub-LSP is created.

   The S2L sub-LSP SHOULD continue to be advertised in both the old and
   new Path messages until a Resv message listing the S2L sub-LSP and
   corresponding to the new Path message is received by the combining
   node. Hence until this point state for the S2L sub-LSP SHOULD be
   maintained as part of the Path state for both the old and the new
   Path message [Section 3.1.3, 2205]. At that point the S2L sub-LSP
   SHOULD be deleted from the old Path state using the procedures of
   section 7.

   A Path message with a sub-Group_ID(n) may signal a set of S2L sub-
   LSPs that belong partially or entirely to an already existing Sub-
   Group_ID(i), the SESSION object and <Sender Tunnel Address, LSP-ID,
   Sub-Group Originator ID> being the same. Or it may signal a strictly
   non-overlapping new set of S2L sub-LSPs with a strictly higher sub-
   Group_ID value.

   1) If sub-Group_ID(i) = sub-Group_ID(n), then either a full refresh
   is indicated by the Path message or a S2L Sub-LSP is added to/deleted
   from the group signaled by sub-Group_ID(n)

   2) If sub-Group_ID(i) != sub-Group_ID(n), then the Path message is
   signaling a set of S2L sub-LSPs that belong partially or entirely to
   an already existing Sub-Group_ID(i) or a strictly non-overlapping set
   of S2L sub-LSPs.







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11. Error Processing

   PathErr and ResvErr messages are processed as per RSVP-TE procedures.
   Note that a LSR on receiving a PathErr/ResvErr message for a particu-
   lar S2L sub-LSP changes the state only for that S2L sub-LSP. Hence
   other S2L sub-LSPs are not impacted. In case the ingress node
   requests the maintenance of the 'LSP integrity', any error reported
   within the P2MP TE LSP must be reported at (least at) any other
   branching nodes belonging to this LSP. Therefore, reception of an
   error message for a particular S2L sub-LSP MAY change the state of
   any other S2L sub- LSP of the same P2MP TE LSP.


11.1. PathErr Messages

   The PathErr message will include one or more S2L_SUB_LSP objects. The
   resulting modified format for a PathErr Message is:

   <PathErr Message> ::=    <Common Header> [ <INTEGRITY> ]
                             [ [<MESSAGE_ID_ACK> |
                                <MESSAGE_ID_NACK>] ... ]
                             [ <MESSAGE_ID> ]
                             <SESSION> <ERROR_SPEC>
                             [ <ACCEPTABLE_LABEL_SET> ... ]
                             [ <POLICY_DATA> ... ]
                             <sender descriptor>
                             [ <S2L sub-LSP descriptor list> ]

   PathErr messages generation is unmodified, but nodes that set the
   Sub-Group Originator field and propagate a received PathErr message
   upstream MUST replace the Sub-Group fields received in the PathErr
   message with the value that was received in the Sub-Group fields of
   the Path message from the upstream neighbor.  Note the receiver of a
   PathErr message is able to identify the errored outgoing Path mes-
   sage, and outgoing interface, based on the Sub-Group fields received
   in the PathErr message.


11.2. ResvErr Messages

   The ResvErr message will include one or more S2L_SUB_LSP objects. The
   resulting modified format for a ResvErr Message is:

   <ResvErr Message> ::=    <Common Header> [ <INTEGRITY> ]
                             [ [<MESSAGE_ID_ACK> |
                                <MESSAGE_ID_NACK>] ... ]
                             [ <MESSAGE_ID> ]
                             <SESSION> <RSVP_HOP>



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                             <ERROR_SPEC> [ <SCOPE> ]
                             [ <ACCEPTABLE_LABEL_SET> ... ]
                             [ <POLICY_DATA> ... ]
                             <STYLE> <flow descriptor list>

   ResvErr messages generation is unmodified, but nodes that set the
   Sub-Group Originator field and propagate a received ResvErr message
   downstream MUST replace the Sub-Group fields received in the ResvErr
   message with the value that was set in the Sub-Group fields of the
   Path message sent to the downstream neighbor. Note the receiver of a
   ResvErr message is able to identify the errored outgoing Path mes-
   sage, and outgoing interface, based on the Sub-Group fields received
   in the ResvErr message.


11.3. Branch Failure Handling

   During setup and during normal operation, PathErr messages may be
   received at a branch node. In all cases, a received PathErr message
   is first processed per standard processing rules. That is: the
   PathErr message is sent hop-by-hop to the ingress/branch LSR for that
   Path message.  Intermediate nodes until this ingress/branch LSR MAY
   inspect this message but take no action upon it. The behavior of a
   branch LSR that generates a PathErr message is under the control of
   the ingress LSR.

   The default behavior is that the PathErr does not have the
   Path_State_Removed flag set. However, if the ingress LSR has set the
   'LSP integrity' flag on the Path message (see LSP_ATTRIBUTE object in
   section 20) and if the Path_State_Removed flag is supported, the LSR
   generating a PathErr to report the failure of a branch of the P2MP
   LSP SHOULD set the Path_State_Removed flag.

   A branch LSR that receives a PathErr message with the
   Path_State_Removed flag set MUST act according to the wishes of the
   ingress LSR. The default behavior is that the branch LSR clears the
   Path_State_Removed flag on the PathErr and sends it further upstream.
   It does not tear any other branches of the LSP. However, if the LSP
   integrity flag is set on the Path message, the branch LSR MUST send
   PathTear on all downstream branches and send the PathErr message
   upstream with the Path_State_Removed flag set.

   A branch LSR that receives a PathErr message with the
   Path_State_Removed flag clear MUST act according to the wishes of the
   ingress LSR. The default behavior is that the branch LSR forwards the
   PathErr upstream and takes no further action. However, if the LSP
   integrity flag is set on the Path message, the branch LSR MUST send
   PathTear on all downstream branches and send the PathErr upstream



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   with the Path_State_Removed flag set (per [RFC3473]).

   In all cases, the PathErr message forwarded by a branch LSR MUST con-
   tain the S2L sub-LSP identification and explicit routes of all
   branches that are reported by received PathErr messages and all
   branches that are explicitly torn by the branch LSR.


12. Admin Status Change

   A branch node that receives an ADMIN_STATUS object processes it nor-
   mally and also relays the ADMIN_STATUS object in a Path on every
   branch. All Path messages may be concurrently sent to the downstream
   neighbors.

   Downstream nodes process the change in the status object per
   [RFC3473], including generation of Resv messages. When the last
   received upstream ADMIN_STATUS object had the R bit set, branch nodes
   wait for a Resv message with a matching ADMIN_STATUS object to be
   received (or a corresponding PathErr or ResvTear messsage) on all
   branches before relaying a corresponding Resv message upstream.


13. Label Allocation on LANs with Multiple Downstream Nodes

   A sender on a LAN uses a different label for sending traffic to each
   node on the LAN that belongs to the P2MP LSP. Thus the sender per-
   forms replication. It may be considered desirable on a LAN to use the
   same label for sending traffic to multiple nodes belonging to the
   same P2MP LSP, to avoid replication. Procedures for doing this are
   for further study.


14. P2MP LSP and Sub-LSP Re-optimization

   It is possible to change the path used by P2MP LSPs to reach the des-
   tinations of the P2MP Tunnel. There are two methods that can be used
   to accomplish this.  The first is  make-before-break, defined in
   [RFC3209], and the second uses the sub-groups defined above.












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14.1. Make-before-break

   In this case all the S2L sub-LSPs are signaled with a different LSP
   ID by the ingress-LSR and follow make-before-break procedure defined
   in [RFC3209]. Thus a new P2MP LSP is established. Each S2L sub-LSP is
   signaled with a different LSP ID, corresponding to the new P2MP LSP.
   After moving traffic to the new P2MP LSP, the ingress can tear down
   the old P2MP LSP. This procedure can be used to re-optimize the path
   of the entire P2MP LSP or paths to a subset of the destinations of
   the P2MP LSP. When modifying just a portion of the P2MP LSP this
   approach requires the entire P2MP LSP to be resignaled.


14.2. Sub-Group Based Re-optimization

   Any node may initiate re-optimization of a set of S2L sub-LSPs by
   using the incremental state update and then, optionally, combining
   multiple path messages.

   To alter the path taken by a particular set of S2L sub-LSPs the node
   initiating the path change initiates one or more separate Path mes-
   sages, for the same P2MP LSP, each with a new sub-Group ID. The gen-
   eration of these Path messages, each with one or more S2L sub-LSPs,
   follows procedures in section 5.2. As is the case in Section 10.2, a
   particular egress continues to be advertised in both the old and new
   Path messages until a Resv message listing the egress and correspond-
   ing to the new Path message is received by the re-optimizing node. At
   that point the egress SHOULD be deleted from the old Path state using
   the procedures of section 7.  Sub-tree re-optimization is then com-
   pleted.

   As is always the case, a node may choose to combine multiple path
   messages as described in section 10.2.


15. Fast Reroute

   [RSVP-FR] extensions can be used to perform fast reroute for the
   mechanism described in this document.












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15.1. Facility Backup

   Facility backup as described in [RSVP-FR] can be used to protect P2MP
   LSPs.


   If link protection is desired, a bypass tunnel is used to protect the
   link between the PLR and next-hop. Thus all S2L sub-LSPs that use the
   link can be protected in the event of link failure. Note that all
   such S2L sub-LSPs belonging to a particular instance of a P2MP tunnel
   will share the same outgoing label on the link between the PLR and
   the next-hop. This is the P2MP LSP label on the link. Label stacking
   is used to send data for each P2MP LSP in the bypass tunnel. The
   inner label is the P2MP LSP label allocated by the nhop. During fail-
   ure Path messages for each S2L sub-LSP, that is effected, will be
   sent to the MP, by the PLR. It is recommended that the PLR use the
   sender template specific method to identify these Path messages.
   Hence the PLR will set the source address in the sender template to a
   local PLR address. The MP will use the LSP-ID to identify the corre-
   sponding S2L sub-LSPs.

   The MP MUST not use the <sub-group originator ID, sub-group ID> while
   identifying the corresponding S2L sub-LSPs.

   In order to further process a S2L sub-LSP it will determine the pro-
   tected S2L sub-LSP using the LSP-id and the S2L sub-LSP object.

   If node protection is desired, the bypass P2P tunnel must intersect
   the path of the protected S2L sub-LSPs on a LSR that is downstream
   from the PLR. This constrains the set of S2L sub-LSPs being backed-up
   via that bypass tunnel to those S2L sub-LSPs that pass through a com-
   mon downstream MP. This MP is the destination of the bypass tunnel.
   The MP will allocate the same label to all such S2L sub-LSPs belong-
   ing to a particular instance of a P2MP tunnel. This will be the inner
   label used during label stacking by the PLR when it sends data for
   each P2MP LSP in the bypass tunnel.  The outer label is the bypass
   tunnel label. During failure of the protected node the PLR will send
   Path messages for the protected S2L Sub-LSPs to the MP using proce-
   dures that are same as the link protection procedures described
   above. Node protection may require the PLR to be branch capable as
   multiple bypass tunnels may be required to backup the set of S2L sub-
   LSPs passing through the protected node. Else all the S2L sub-LSPs
   passing through the protected node must also pass through a MP that
   is downstream from the protected node.







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15.2. One to One Backup

   One to one backup as described in [RSVP-FR] can be used to protect a
   particular S2L sub-LSP against link and next-hop failure. Protection
   may be used for one or more S2L sub-LSPs between the PLR and the
   next-hop. All the S2L sub-LSPs corresponding to the same instance of
   the P2MP tunnel, between the PLR and the next-hop share the same P2MP
   LSP label.

   All or some of these S2L sub-LSPs may be protected.

   The detour S2L sub-LSPs may or may not share labels, depending on the
   detour path. Thus the set of outgoing labels and next-hops for a P2MP
   LSP that was using a single next-hop and label between the PLR and
   next-hop before protection, may change once protection is triggerred.

   Its is recommended that the path specific method be used to identify
   a backup S2L sub-LSP. Hence the DETOUR object will be inserted in the
   backup Path message. A backup S2L sub-LSP MUST be treated as belong-
   ing to a different P2MP tunnel instance than the one specified by the
   LSP-id. Furthermore multiple backup S2L sub-LSPs MUST be treated as
   part of the same P2MP tunnel instance if they have the same LSP-id
   and the same DETOUR objects. Note that as specified in section 4 S2L
   sub-LSPs between different P2MP tunnel instances use different
   labels.

   If there is only one S2L sub-LSP in the Path message, the DETOUR
   object applies to that sub-LSP. If there are multiple S2L sub-LSPs in
   the Path message the DETOUR applies to all the S2L sub-LSPs.


16. Support for LSRs that are not P2MP Capable

   It may be that some LSRs in a network are capable of processing the
   P2MP extensions described in this document, but do not support P2MP
   branching in the data plane. If such an LSR is requested to become a
   branch LSR by a received Path message, it MUST respond with a PathErr
   message carrying the Error Value "Routing Error" and Error Code
   "Unable to Branch".

   Its also conceivable that some LSRs, in a network deploying P2MP
   capability, may not support the extensions described in this docu-
   ment.  If a Path message for the establishment of a P2MP LSP reaches
   such an LSR it will reject it with a PathErr because it will not rec-
   ognize the C-Type of the P2MP SESSION object.

   LSRs that do not support the P2MP extensions in this document may be
   included as transit LSRs by the use of LSP-stitching [LSP-STITCH] and



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   LSP-hierarchy [LSP-HIER]. Note that LSRs that are required to play
   any other role in the network (ingress, branch or egress) MUST sup-
   port the extensions defined in this document.

   The use of LSP-stitching and LSP-hierarchy [LSP-HIER] allows to build
   P2MP LSPs in such an environment. A P2P LSP segment is signaled from
   the previous P2MP capable hop of a legacy LSR to the next P2MP capa-
   ble hop. Of course this assumes that intermediate legacy LSRs are
   transit LSRs and cannot act as P2MP branch points. Transit LSRs along
   this LSP segment do not process control plane messages associated
   with a P2MP LSP. Furthermore these LSRs also do not need to have P2MP
   data plane capability as they only need to process data belonging to
   the P2P LSP segment. Hence these LSRs do not need to support P2MP
   MPLS. This P2P LSP segment is stitched to the incoming P2MP LSP.
   After the P2P LSP segment is established the P2MP Path message is
   sent to the next P2MP capable LSR as a directed Path  message. The
   next P2MP capable LSR stitches the P2P LSP segment to the outgoing
   P2MP LSP.

   In packet networks, the S2L sub-LSPs may be nested inside the outer
   P2P LSP. Hence label stacking can be used to enable use of the same
   LSP segment for multiple P2MP LSP. Stitching and nesting considera-
   tions and procedures are described further in [INT-REG].

   It may be an overhead for an operator to configure the P2P LSP seg-
   ments in advance, when it is desired to support legacy LSRs. It may
   be desirable to do this dynamically. The ingress can use IGP exten-
   sions to determine non P2MP capable LSRs [TE-NODE-CAP]. It can use
   this information to compute S2L sub-LSP paths such that they avoid
   these legacy LSRs. The explicit route object of a S2L sub-LSP path
   may contain loose hops if there are legacy LSRs along the path. The
   corresponding explicit route contains a list of objects upto the P2MP
   capable LSR that is adjacent to a legacy LSR followed by a loose
   object with the address of the next P2MP capable LSR. The P2MP capa-
   ble LSR expands the loose hop using its TED. When doing this it
   determines that the loose hop expansion requires a P2P LSP to tunnel
   through the legacy LSR. If such a P2P LSP exists, it uses that P2P
   LSP. Else it establishes the P2P LSP.  The P2MP Path message is sent
   to the next P2MP capable LSR using non-adjacent signaling. The P2MP
   capable LSR that initiates the non-adjacent signaling message to the
   next P2MP capable LSR may have to employ a fast detection mechanism
   such as [BFD] to the next P2MP capable LSR.

   This may be needed for the directed Path message Head-End to use node
   protection FRR when the protected node is the directed Path message
   tail.

   Note that legacy LSRs along a P2P LSP segment cannot perform node



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   protection of the tail of the P2P LSP segment.


17. Reduction in Control Plane Processing with LSP Hierarchy

   It is possible to take advantage of LSP hierarchy [LSP-HIER] while
   setting up P2MP LSP, as described in the previous section, to reduce
   control plane processing along transit LSRs that are P2MP capable.
   This is applicable only in environments where LSP hierarchy can be
   used. Transit LSRs along a P2P LSP segment, being used by a P2MP LSP,
   do not process control plane messages associated with the P2MP LSP.
   Infact they are not aware of these messages as they are tunneled over
   the P2P LSP segment. This reduces the amount of control plane pro-
   cessing required on these transit LSRs.

   Note that the P2P LSP segments can be dynamically setup as described
   in the previous section or preconfigured. For example in Figure 2,
   PE1 can setup a P2P LSP to P1 and use that as a LSP segment. The Path
   messages for PE3 and PE4 can now be tunneled over the LSP segment.
   Thus P3 is not aware of the P2MP LSP and does not process the P2MP
   control messages.


18. P2MP LSP Remerging and Cross-Over

   This section is currently under discussion between the authors and
   will be updated in the next revision.

   The functional description described so far assumes that multiple
   Path messages received by a LSR for the same P2MP LSP arrive on the
   same incoming interface. However this may not always be the case.

   P2MP tree remerging or cross-over occurs when a transit or egress
   node receives the signaling state i.e. Path message for the same P2MP
   TE LSP from more than one previous hop. If the remerged S2L sub-LSPs
   are sent out on different interfaces there is no data plane issue.
   However if the remerged S2L sub-LSPs are sent out on the same inter-
   face it can result in data duplication downstream. In order to
   describe identification of cross over and remerging by a LSR let us
   list the various cases when state for a S2L sub-LSP is received by a
   LSR.

   Case1: S2L sub-LSP already exist as part of an existing Path state.
   The following are the various sub-cases.
      a) The new S2L sub-LSP uses the same PHOP and outgoing interface
   as the existing S2L sub-LSP. This is either a refresh or can occur
   when multiple existing Path messages are combined in a new Path mes-
   sage.



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      b) The new S2L sub-LSP uses the same PHOP but different outgoing
   interface as the existing S2L sub-LSP. This is a case of re-routing.
      c) The new S2L sub-LSP uses a different PHOP and same outgoing
   interface as the existing S2L sub-LSP. This is a case of re-routing.
      d) The new S2L sub-LSP uses a different PHOP and a different out-
   going interface as compared to the existing S2L sub-LSP. This is a
   case of re-routing.

   Case2: S2L sub-LSP does not exist as part of an existing Path state.
   The following are the sub-cases.
      a) The new S2L sub-LSP uses a PHOP and outgoing interface that is
   same as the PHOP and outgoing interface used by an existing S2L sub-
   LSP that belongs to the same P2MP LSP. This is a legal case of sig-
   naling a new S2L sub-LSP.
      b) The new S2L sub-LSP uses a PHOP that is same as that used by an
   existing S2L sub-LSP. However the outgoing interface is different
   from the outgoing interfaces used by existing S2L sub-LSPs belonging
   to the same P2MP LSP. This is a legal case of signaling a new S2L
   sub-LSP.
      c) The new S2L sub-LSP uses a different PHOP than that used by any
   of the existing S2L sub-LSP that belong to the same P2MP LSP . How-
   ever the outgoing interface is same as the outgoing interface used by
   an existing S2L sub-LSPs. This is a case of remerging.
      d) The new S2L sub-LSP uses a different PHOP than that used by any
   of the existing S2L sub-LSP that belong to the same P2MP LSP. Also
   the outgoing interface is different from the outgoing interfaces used
   by existing S2L sub-LSPs. This is a case of cross-over.

   Case 2(d) above identifies cross-over and this is considered legal.
   Case 2(c) above identifies remerging in the data plane. If the LSR is
   capable of remerging in the data plane this is considered legal.

   The below procedure applies for remerging.

   The remerge error case is detected by checking incoming Path messages
   that represent new P2MP TE LSP state and seeing if they represent
   both known LSP state and a different S2L sub-LSP list. Specifically,
   the remerge check MUST be performed when processing Path messages
   that contain SESSION, SENDER_TEMPLATE and RSVP_HOP objects that have
   not previously been seen on a particular interface. The remerge check
   consists of attempting to locate state that has the same values in
   the SESSION object and in the tunnel sender address and LSP ID fields
   of the SENDER_TEMPLATE object.

   If no matching state is located, then there is no remerge condition.

   If matching state is found, then the list of S2L Sub-LSPs associated
   with the new Path message is compared against the list present in the



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   located state.  If any addresses in the lists of S2L sub-LSPs match,
   then it is the legal LSP rerouting case mentioned here above.

   If there are no overlap in the lists, the node checks whether any of
   the outgoing interfaces, as identified by the ERO/SUB_EROs, are an
   outgoing interface already associated with the existing P2MP LSP. If
   not, then legal LSP crossing is being performed. Else re-merging has
   occurred and if the LSR is capable of remerging in the data plane,
   this is considered legal. In that case the LSR will return the label
   already associated with the existing S2L sub-LSP with the matching
   egress interface, in the Resv message it sends upstream. If the LSR
   is not capable of remerging in the data plane the new Path message
   MUST be handled according to remerge error processing as described
   below.

   The LSR generates a PathErr message with Error Code "Routing Prob-
   lem/P2MP Remerge Detected" towards the upstream node (i.e.  the node
   that sent the Path message) until it reaches the node that caused the
   remerge condition.  Identification of the offending node requires
   special processing by the nodes upstream of the error.  A node that
   receives a PathErr message that contains the error "Routing Prob-
   lem/P2MP Remerge Detected" MUST check to see if it is the offending
   node. This check is done by comparing the S2L sub-LSPs listed in the
   PathErr message with existing LSP state. If any of the egresses are
   already present in any Path state associated with the P2MP TE LSP
   other than the one associated with the <SESSION, SENDER_TEMPLATE>
   objects signaled in the PathErr message, then the node is the signal-
   ing branch node that caused the remerge condition. This node SHOULD
   then correct the remerge condition by adding all S2L sub-LSPs listed
   in the offending Path state to the Path state (and Path message)
   associated to these S2L sub-LSPs. Note that the new Path state may be
   sent out the same outgoing interface in different Path messages in
   order to meet IP packet size limitations.  If use of a new outgoing
   interface violates one or more SERO constraint, then a PathErr mes-
   sage containing the associated egresses and any identified valid
   egresses SHOULD be generated with the error code "Routing Problem"
   and error value of "ERO Resulted in Remerge".

   This process may continue hop-by-hop until the ingress is reached.
   The only case where this process will fail is when all the listed S2L
   sub-LSPs are deleted prior to the PathErr message propagating to the
   ingress. In this case, the whole process will be corrected on the
   next (refresh or trigger) transmission of the offending Path message.

   In all cases where a remerge error is not detected, normal processing
   continues.





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19. New and Updated Message Objects

   This section presents the RSVP object formats as modified by this
   document.


19.1. SESSION Object

   A P2MP LSP SESSION object is used. This object uses the existing SES-
   SION C-Num. New C-Types are defined to accommodate a logical P2MP
   destination identifier of the P2MP Tunnel. This SESSION object has a
   similar structure as the existing point to point RSVP-TE SESSION
   object. However the destination address is set to the P2MP ID instead
   of the unicast Tunnel Endpoint address. All S2L sub-LSPs part of the
   same P2MP LSP share the same SESSION object. This SESSION object
   identifies the P2MP Tunnel.

   The combination of the SESSION object, the SENDER_TEMPLATE object and
   the S2L SUB-LSP object, identifies each S2L sub-LSP. This follows the
   existing P2P RSVP-TE notion of using the SESSION object for identify-
   ing a P2P Tunnel which in turn can contain multiple LSPs, each dis-
   tinguished by a unique SENDER_TEMPLATE object.


19.1.1. P2MP LSP Tunnel IPv4 SESSION Object

   Class = SESSION, P2MP_LSP_TUNNEL_IPv4 C-Type = TBA

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       P2MP ID                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  MUST be zero                 |      Tunnel ID                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Extended Tunnel ID                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   P2MP ID

      A 32-bit identifier used in the SESSION object that remains
      constant over the life of the P2MP tunnel. It encodes the
      P2MP ID and identifies the set of destinations of the P2MP
      Tunnel.

   Tunnel ID




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      A 16-bit identifier used in the SESSION object that remains
      constant over the life of the P2MP tunnel.

   Extended Tunnel ID

      A 32-bit identifier used in the SESSION object that remains
      constant over the life of the P2MP tunnel.  Normally set to
      all zeros. Ingress nodes that wish to narrow the scope of a
      SESSION to the ingress-PID pair may place their IPv4 address
      here as a globally unique identifier [RFC3209].


19.1.2. P2MP LSP Tunnel IPv6 SESSION Object

   This is same as the P2MP IPv4 LSP SESSION Object with the difference
   that the extended tunnel ID may be set to a 16 byte identifier
   [RFC3209].


19.2. SENDER_TEMPLATE object

   The sender template contains the ingress-LSR source address. LSP ID
   can be can be changed to allow a sender to share resources with
   itself. Thus multiple instances of the P2MP tunnel can be created,
   each with a different LSP ID. The instances can share resources with
   each other, but use different labels. The S2L sub-LSPs corresponding
   to a particular instance use the same LSP ID.

   As described in section 4.2 it is necessary to distinguish different
   Path messages that are used to signal state for the same P2MP LSP by
   using a <Sub-Group ID Originator ID, Sub-Group ID> tuple. The
   SENDER_TEMPLATE object is modified to carry this information as shown
   below.


19.2.1. P2MP LSP Tunnel IPv4 SENDER_TEMPLATE Object

   Class = SENDER_TEMPLATE, P2MP_LSP_TUNNEL_IPv4 C-Type = TBA

         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                   IPv4 tunnel sender address                  |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |       Reserved                |            LSP ID             |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                   Sub-Group Originator ID                     |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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        |       Reserved                |            Sub-Group ID       |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


        IPv4 tunnel sender address
            See [RFC3209]

        Sub-Group Originator ID
            The Sub-Group Originator ID is set to the TE Router ID of
            the LSR that originates the Path message. This is either the
            ingress LSR or a LSR which re-originates the Path message
            with its own Sub-Group Originator ID.

        Sub-Group ID
            An identifier of a Path message used to differentiate
            multiple Path messages that signal state for the same P2MP
            LSP. This may be seen as identifying a group of one or more
            egress nodes targeted by this Path message.

        LSP ID
           See [RFC3209]


19.2.2. P2MP LSP Tunnel IPv6 SENDER_TEMPLATE Object

   Class = SENDER_TEMPLATE, P2MP_LSP_TUNNEL_IPv6 C-Type = TBA


         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        +                                                               +
        |                   IPv6 tunnel sender address                  |
        +                                                               +
        |                            (16 bytes)                         |
        +                                                               +
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |       Reserved                |            LSP ID             |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        +                                                               +
        |                   Sub-Group Originator ID                     |
        +                                                               +
        |                            (16 bytes)                         |
        +                                                               +
        |                                                               |



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        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |       Reserved                |            Sub-Group ID       |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


        IPv6 tunnel sender address
           See [RFC3209]

        Sub-Group Originator ID
            The Sub-Group Originator ID is set to the IPv6 TE Router ID
            of the LSR that originates the Path message. This is either
            the ingress LSR or a LSR which re-originates the Path
            message with its own Sub-Group Originator ID.

        Sub-Group ID
           As above.

        LSP ID
           See [RFC3209]


19.3. S2L SUB-LSP Object

   A new S2L Sub-LSP object identifies a particular S2L sub-LSP belong-
   ing to the P2MP LSP.


19.3.1. S2L SUB-LSP IPv4 Object

   SUB_LSP Class = 50, S2L_SUB_LSP_IPv4 C-Type = TBA

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   IPv4 S2L Sub-LSP destination address        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   IPv4 Sub-LSP destination address

      IPv4 address of the S2L sub-LSP destination.










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19.3.2. S2L SUB-LSP IPv6 Object

   SUB_LSP Class = 50, S2L_SUB_LSP_IPv6 C-Type = TBA

   This is same as the S2L IPv4 Sub-LSP object, with the difference that
   the destination address is a 16 byte IPv6 address.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   IPv6 S2L Sub-LSP destination address        |
      |                        ....                                   |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


19.4. FILTER_SPEC Object

   The FILTER_SPEC object is canonical to the P2MP SENDER_TEMPLATE
   object.


19.4.1. P2MP LSP_IPv4 FILTER_SPEC Object

   Class = FILTER SPEC, P2MP LSP_IPv4 C-Type = TBA

   The format of the P2MP LSP_IPv4 FILTER_SPEC object is identical to
   the P2MP LSP_IPv4 SENDER_TEMPLATE object.


19.4.2. P2MP LSP_IPv4 FILTER_SPEC Object

   Class = FILTER SPEC, P2MP LSP_IPv6 C-Type = TBA

   The format of the P2MP LSP_IPv6 FILTER_SPEC object is identical to
   the P2MP LSP_IPv6 SENDER_TEMPLATE object.


19.5. P2MP SECONDARY_EXPLICIT_ROUTE Object (SERO)

   The P2MP Secondary Explicit Route Object (SERO) is defined as identi-
   cal to the ERO.  The class of the P2MP SERO is the same as the SERO
   defined in [RECOVERY] (TBA).  The P2MP SERO C-Type = TBA The sub-
   objects are identical to those defined for the ERO.







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19.6. P2MP SECONDARY_RECORD_ROUTE Object (SRRO)

   The P2MP Secondary Record Route Object (SRRO) is defined as identical
   to the ERO.  The class of the P2MP SRRO is the same as the SRRO
   defined in [RECOVERY] (TBA).  The P2MP SRRO C-Type = TBA.  The sub-
   objects are identical to those defined for the RRO.


20. IANA Considerations

20.1. New Class Numbers

   IANA is requested to assign the following Class Numbers for the new
   object classes introduced. The Class Types for each of them are to be
   assigned via standards action. The sub-object types for the P2MP SEC-
   ONDARY_EXPLICIT_ROUTE and P2MP_SECONDARY_RECORD_ROUTE follow the same
   IANA considerations as those of the ERO and RRO [RFC3209].

   50  Class Name = SUB_LSP

   C-Type
      1   S2L_SUB_LSP_IPv4 C-Type
      2   S2L_SUB_LSP_IPv6 C-Type


20.2. New Class Types

   IANA is requested to assign the following C-Type values:

   Class Name = SESSION

   C-Type
     13    P2MP_LSP_IPv4 C-Type
     14    P2MP_LSP_IPv6 C-Type

   Class Name = SENDER_TEMPLATE

   C-Type
     12    P2MP_LSP_IPv4 C-Type
     13    P2MP_LSP_IPv6 C-Type

   Class Name = FILTER_SPEC

   C-Type
     12    P2MP LSP_IPv4 C-Type
     13    P2MP LSP_IPv6 C-Type

   Class Name = SECONDARY_EXPLICIT_ROUTE



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   C-Type
      2  P2MP SECONDARY_EXPLICIT_ROUTE C-Type

   Class Name = SECONDARY_RECORD_ROUTE

   C-Type
      2  P2MP_SECONDARY_RECORD_ROUTE C-Type


20.3. New Error Codes

   Four new Error Codes are defined for use with the Error Value "Rout-
   ing Problem". IANA is requested to assign values.

   The Error Code "Unable to Branch" indicates that a P2MP branch cannot
   be formed by the reporting LSR. IANA is requested to assign value 20
   to this Error Code.

   The Error Code "Unsupported LSP Integrity" indicates that a P2MP
   branch does not support the requested LSP integrity function. IANA is
   requested to assign value 21 to this Error Code.

   The Error Code "P2MP Remerge Detected" indicates that a node has
   detected remerge. IANA is requested to assign value 22 to this Error
   Code.


20.4. LSP Attributes Flags

   IANA has been asked to manage the space of flags in the Attibutes
   Flags TLV carried in the LSP_ATTRIBUTES Object [LSP-ATTRIB]. This
   document defines two new flags as follows:


   Suggested Bit Number:             3
   Meaning:                          LSP Integrity Required
   Used in Attributes Flags on Path: Yes
   Used in Attributes Flags on Resv: No
   Used in Attributes Flags on RRO:  No
   Referenced Section of this Doc:   10











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21. Security Considerations

   This document does not introduce any new security issues. The secu-
   rity issues identified in [RFC3209] and [RFC3473] are still relevant.


22. Acknowledgements

   This document is the product of many people. The contributors are
   listed in Section 27.2.

   Thanks to Yakov Rekhter, Der-Hwa Gan, Arthi Ayyanger and Nischal
   Sheth for their suggestions and comments. Thanks also to Dino Farni-
   nacci for his comments.


23. Appendix

23.1. Example

   Following is one example of setting up a P2MP LSP using the proce-
   dures described in this document.


                   Source 1 (S1)
                     |
                    PE1
                   |   |
                   |L5 |
                   P3  |
                   |   |
                L3 |L1 |L2
       R2----PE3--P1   P2---PE2--Receiver 1 (R1)
                  | L4
          PE5----PE4----R3
                  |
                  |
                 R4

                Figure 2.


   The mechanism is explained using Figure 2. PE1 is the ingress-LSR.
   PE2, PE3 and PE4 are Egress-LSRs.

   a) PE1 learns that PE2, PE3 and PE4 are interested in joining a P2MP
   tree with a P2MP ID of P2MP ID1. We assume that PE1 learns of the
   egress-LSRs at different points.



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   b) PE1 computes the P2P path to reach PE2.

   c) PE1 establishes the S2L sub-LSP to PE2 along <PE1, P2, PE2>

   d) PE1 computes the P2P path to reach PE3 when it discovers PE3. This
   path is computed to share the same links where possible with the sub-
   LSP to PE2 as they belong to the same P2MP session.

   e) PE1 establishes the S2L sub-LSP to PE3 along <PE1, P3, P1, PE3>

   f) PE1 computes the P2P path to reach PE4 when it discovers PE4. This
   path is computed to share the same links where possible with the sub-
   LSPs to PE2 and PE3 as they belong to the same P2MP session.

   g) PE1 signals the Path message for PE4 sub-LSP along <PE1, P3, P1,
   PE4>

   e) P1 receives a Resv message from PE4 with label L4. It had previ-
   ously received a Resv message from PE3 with label L3. It had allo-
   cated a label L1 for the sub-LSP to PE3. It uses the same label and
   sends the Resv messages to P3. Note that it may send only one Resv
   message with multiple flow descriptors in the flow descriptor list.
   If this is the case and FF style is used, the FF flow descriptor will
   contain the S2L sub-LSP descriptor list with two entries: one for PE4
   and the other for PE3. For SE style, the SE filter spec will contain
   this S2L sub-LSP descriptor list. P1 also creates a label mapping of
   (L1 -> {L3, L4}). P3 uses the existing label L5 and sends the Resv
   message to PE1, with label L5. It reuses the label mapping of {L5 ->
   L1}.


24. References

24.1. Normative References

      [LSP-HIER] K. Kompella, Y. Rekhter, "LSP Hierarchy with Generalized
                 MPLS TE", draft-ietf-mpls-lsp-hierarchy-08.txt, work in
                 progress.

      [LSP-ATTR] A. Farrel, et. al. , "Encoding of
                 Attributes for Multiprotocol Label Switching (MPLS)
                 Label Switched Path (LSP) Establishment Using RSVP-TE",
                 draft-ietf-mpls-rsvpte-attributes-05.txt, March 2004,
                 work in progress.

      [RFC3209]  D. Awduche, L. Berger, D. Gan, T. Li, V. Srinivasan,
                 G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels",
                 RFC3209, December 2001, work in progress.



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

      [RFC2205]  Braden, R., Zhang, L., Berson, S., Herzog, S. and S. Jamin,
                 "Resource ReSerVation Protocol (RSVP) -- Version 1,
                 Functional Specification", RFC 2205, September 1997, work in
                 progress.

      [RFC3471]  Lou Berger, et al., "Generalized MPLS - Signaling Functional
                 Description", RFC 3471, January 2003, work in progress.

      [RFC3473]  L. Berger et.al., "Generalized MPLS Signaling - RSVP-TE
                 Extensions", RFC 3473, January 2003, work in progress.

      [RFC2961]  L. Berger, D. Gan, G. Swallow, P. Pan, F. Tommasi,
                 S. Molendini, "RSVP Refresh Overhead Reduction Extensions",
                 RFC 2961, April 2001, work in progress.

      [RFC3031]  Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol
                 Label Switching Architecture", RFC 3031, January 2001, work in
                 progress.

      [RFC4090]  P. Pan, G. Swallow, A. Atlas (Editors), "Fast Reroute Extensions
                 to RSVP-TE for LSP Tunnels", work in progress.

      [RFC3477]  K. Kompella, Y. Rekther, "Signalling Unnumbered Links in
                 Resource ReSerVation Protocol - Traffic Engineering (RSVP-TE)",
                 work in progress .

      [P2MP-REQ] S. Yasukawa, Editor "Signaling Requirements for
                 Point-to-Multipoint Traffic Engineered MPLS LSPs",
                 draft-ietf-mpls-p2mp-sig-requirement-02.txt, work in progress.

      [RECOVERY] "GMPLS Based Segment Recovery",
                 draft-ietf-ccamp-gmpls-segment-recovery-02.txt


24.2. Informative References

      [BFD]      D. Katz, D. Ward, "Bidirectional Forwarding Detection",
              draft-katz-ward-bfd-01.txt, work in progress.

      [BFD-MPLS] R. Aggarwal, K. Kompella, T. Nadeau, G. Swallow, "BFD for MPLS
                 LSPs", draft-ietf-bfd-mpls-00.txt, work in progress.

      [IPR-1]    Bradner, S., "IETF Rights in Contributions", BCP 78,
                 RFC 3667, February 2004, work in progress.



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      [IPR-2]    Bradner, S., Ed., "Intellectual Property Rights in IETF
                 Technology", BCP 79, RFC 3668, February 2004, work in progress.

      [INT-REG]  JP Vasseur, A. Ayyangar, "Inter-area and Inter-AS MPLS Traffic
                 Engineering",  draft-vasseur-ccamp-inter-area-as-te-00.txt,
                 work in progress.

      [RFC2209]  R. Braden, L. Zhang, "Resource Reservation Protocol (RSVP)
                 Version 1 Message Processing Rules", RFC 2209, work in progress.

      [LSP-STITCH] A. Ayyanger, J.P. Vasseur, "Label Switched Path Stitching
                   with Generalized MPLS Traffic Engineering",
                   draft-ietf-ccamp-lsp-stitching-00.txt, April 2005
                   work in progress

      [TE-NODE-CAP] JP Vasseur, JL Le Roux, et al. "Routing extensions for
                    discovery of Traffic Engineering Node Capabilities",
                    draft-vasseur-ccamp-te-node-cap-00.txt, February 2005,
                    work in progress



25. Author Information

25.1. Editor Information

   Rahul Aggarwal
   Juniper Networks
   1194 North Mathilda Ave.
   Sunnyvale, CA 94089
   Email: rahul@juniper.net

   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

   Dimitri Papadimitriou
   Alcatel
   Francis Wellesplein 1,
   B-2018 Antwerpen, Belgium
   Phone: +32 3 240-8491
   Email: Dimitri.Papadimitriou@alcatel.be






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25.2. Contributor Information

   John Drake
   Calient Networks
   Email: jdrake@calient.net

   Alan Kullberg
   Motorola Computer Group
   120 Turnpike Road 1st Floor
   Southborough, MA  01772
   EMail: alan.kullberg@motorola.com

   Lou Berger
   Movaz Networks, Inc.
   7926 Jones Branch Drive
   Suite 615
   McLean VA, 22102
   Phone: +1 703 847-1801
   EMail: lberger@movaz.com

   Liming Wei
   Redback Networks
   350 Holger Way
   San Jose, CA 95134
   Email: lwei@redback.com

   George Apostolopoulos
   Redback Networks
   350 Holger Way
   San Jose, CA 95134
   Email: georgeap@redback.com

   Kireeti Kompella
   Juniper Networks
   1194 N. Mathilda Ave
   Sunnyvale, CA 94089
   Email: kireeti@juniper.net

   George Swallow
   Cisco Systems, Inc.
   300 Beaver Brook Road
   Boxborough , MA - 01719
   USA
   Email: swallow@cisco.com

   JP Vasseur
   Cisco Systems, Inc.
   300 Beaver Brook Road



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   Boxborough , MA - 01719
   USA
   Email: jpv@cisco.com

   Dean Cheng
   Cisco Systems Inc.
   170 W Tasman Dr.
   San Jose, CA 95134
   Phone 408 527 0677
   Email:  dcheng@cisco.com

   Markus Jork
   Avici Systems
   101 Billerica Avenue
   N. Billerica, MA 01862
   Phone: +1 978 964 2142
   EMail: mjork@avici.com

   Hisashi Kojima
   NTT Corporation
   9-11, Midori-Cho 3-Chome
   Musashino-Shi, Tokyo 180-8585 Japan
   Phone: +81 422 59 6070
   EMail: kojima.hisashi@lab.ntt.co.jp

   Andrew G. Malis
   Tellabs
   2730 Orchard Parkway
   San Jose, CA 95134
   Phone: +1 408 383 7223
   Email: Andy.Malis@tellabs.com

   Koji Sugisono
   NTT Corporation
   9-11, Midori-Cho 3-Chome
   Musashino-Shi, Tokyo 180-8585 Japan
   Phone: +81 422 59 2605
   EMail: sugisono.koji@lab.ntt.co.jp

   Masanori Uga
   NTT Corporation
   9-11, Midori-Cho 3-Chome
   Musashino-Shi, Tokyo 180-8585 Japan
   Phone: +81 422 59 4804
   EMail: uga.masanori@lab.ntt.co.jp

   Igor Bryskin
   Movaz Networks, Inc.



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   7926 Jones Branch Drive
   Suite 615
   McLean VA, 22102

   Adrian Farrel
   Old Dog Consulting
   Phone: +44 0 1978 860944
   EMail: adrian@olddog.co.uk

   Jean-Louis Le Roux
   France Telecom
   2, avenue Pierre-Marzin
   22307 Lannion Cedex
   France
   E-mail: jeanlouis.leroux@francetelecom.com



26. Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any assur-
   ances of licenses to be made available, or the result of an attempt
   made to obtain a general license or permission for the use of such
   proprietary rights by implementers or users of this specification can
   be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at ietf-
   ipr@ietf.org.










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27. Full Copyright Statement

   Copyright (C) The Internet Society (2005). This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.


   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


28. Acknowledgement

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































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