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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 (Juniper)
Internet Draft                              D. Papadimitriou (Alcatel)
Expiration Date: June 2005                  S. Yasukawa (NTT)
                                            Editors

         Extensions to RSVP-TE for Point to Multipoint TE LSPs

                  draft-ietf-mpls-rsvp-te-p2mp-01.txt


Status of this Memo

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   RFC 3668.

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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
   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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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].


Authors' Note

   Some of the text in the document needs further discussion between
   authors and feedback from MPLS WG. This has been pointed out when
   applicable. A change log and reviewed/updated text will be made
   available online.


Table of Contents

       1      Terminology............................................. 4
       2      Introduction.............................................4
       3      Mechanisms.............................................. 4
       3.1    P2MP Tunnels............................................ 5
       3.2    P2MP LSP Tunnels........................................ 5
       3.3    Sub-Groups.............................................. 5
       3.4    S2L Sub-LSPs............................................ 6
       3.4.1  Representation of a S2L sub-LSP......................... 6
       3.4.2  S2L Sub-LSPs and Path Messages.......................... 6
       3.5    Explicit Routing........................................ 7
       4      Path Message............................................ 9
       4.1    Path Message Format..................................... 9
       4.2    Path Message Processing................................. 10
       4.2.1  Multiple Path Messages.................................. 11
       4.2.2  Multiple S2L Sub-LSPs in One Path Message............... 12
       4.2.3  Transit Fragmentation................................... 13
       4.3    Grafting................................................ 14
       4.3.1  Addition of S2L Sub-LSP................................. 14
       5      Resv Message............................................ 14
       5.1    Resv Message Format..................................... 14
       5.2    Resv Message Processing................................. 15
       5.2.1  Resv Message Throttling................................. 16
       5.3    Record Routing.......................................... 17
       5.3.1  RRO Processing.......................................... 17
       6      Reservation Style....................................... 17
       7      Path Tear Message....................................... 17
       7.1    Path Tear Message Format................................ 17
       7.2    Pruning................................................. 17
       7.2.1  Explicit S2L Sub-LSP Teardown........................... 17
       7.2.2  Implicit S2L Sub-LSP Teardown........................... 18
       7.2.1  P2MP TE LSP Teardown.................................... 19



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       8      Notify and ResvConf Messages............................ 20
       9      Error Processing........................................ 20
       9.1    PathErr Message Format.................................. 20
       9.2    Handling of Failures at Branch LSRs..................... 21
       10     Refresh Reduction....................................... 22
       11     State Management........................................ 22
       11.1   Incremental State Update................................ 22
       11.2   Combining Multiple Path Messages........................ 23
       12     Control of Branch Fate Sharing.......................... 24
       13     Admin Status Change..................................... 24
       14     Label Allocation on LANs with Multiple Downstream Nodes. 25
       15     Make-Before-Break....................................... 25
       15.1   P2MP Tree re-optimization............................... 25
       15.2   Re-optimization of a subset of S2L sub-LSPs ............ 25
       16     Fast Reroute............................................ 26
       16.1   Facility Backpup........................................ 26
       16.2   One to One Backup....................................... 26
       17     Support for LSRs that are not P2MP Capable.............. 27
       18     Reduction in Control Plane Processing with LSP Hierarchy 29
       19     P2MP LSP Tunnel Remerging and Cross-Over................ 29
       20     New and Updated Message Objects......................... 31
       20.1   P2MP SESSION Object..................................... 31
       20.2   P2MP LSP Tunnel SENDER_TEMPLATE Object.................. 32
       20.2.1 P2MP LSP Tunnel IPv4 SENDER_TEMPLATE Object............. 33
       20.2.2 P2MP LSP Tunnel IPv6 SENDER_TEMPLATE Object............. 33
       20.3   S2L SUB-LSP Object...................................... 34
       20.3.1 S2L IPv4 SUB-LSP Object................................. 34
       20.3.2 S2L IPv6 SUB-LSP Object................................. 35
       20.4   FILTER_SPEC Object...................................... 35
       20.5   SUB EXPLICIT ROUTE Object (SERO)........................ 36
       20.6   SUB RECORD ROUTE Object (SRRO).......................... 36
       21     IANA Considerations..................................... 37
       22     Security Considerations................................. 37
       23     Acknowledgements........................................ 37
       24     Example P2MP LSP Establishment ......................... 37
       25     References.............................................. 39
       26     Authors................................................. 40
       27     Intellectual Property................................... 43
       28     Full Copyright Statement................................ 43
       29     Acknowledgement......................................... 44











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1. Terminology

   This document uses terminologies defined in [RFC3031], [RFC2205],
   [RFC3209], [RFC3473] and [P2MP-REQ]. In particular, this document
   uses the notation defined in [P2MP-REQ] for describing the components
   on a P2MP LSP between root, branches and leaves.


2. Introduction

   [RFC3209] defines a mechanism for setting up point-to-point (P2P)
   Traffic Engineered (TE) LSPs in MPLS networks. [RFC3473] defines
   extensions to [RFC3209] for setting up P2P TE LSPs in GMPLS networks.
   However these specifications do not provide a mechanism for building
   point-to-multipoint P2MP TE LSPs.

   This document defines extensions to RSVP-TE [RFC3209] and [RFC3473]
   protocol 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 LSP Tunnels. A P2MP LSP Tunnel 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 Tunnel 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.


3. 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
   further in the following sub-sections by describing P2MP tunnels and
   how they relate to S2L sub-LSPs.






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3.1. P2MP Tunnels

   The specific aspect related to P2MP TE LSP is the action required at
   a branch node, where data replication occurs. Incoming labeled data
   is appropriately replicated to several outgoing interfaces which may
   have different labels.

   A P2MP TE tunnel comprises of one or more P2MP LSPs referred to as
   P2MP LSP tunnels. A P2MP TE Tunnel is identified by a P2MP SESSION
   object. This object contains an identifier of the P2MP session
   defined as a 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. The P2MP SESSION object is defined in section 20.1.

3.2. P2MP LSP Tunnel

   A P2MP LSP Tunnel 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.

3.3. Sub-Groups

   As with all other RSVP controlled LSP Tunnels, P2MP LSP Tunnel state
   is managed using RSVP messages. While use of RSVP messages is the
   same, P2MP LSP Tunnel state differs from P2P LSP state in a number of
   ways. A notable difference is that a P2MP LSP Tunnel is comprised of
   multiple S2L Sub-LSPs As a result of this, it may not be possible to
   signal a P2MP LSP Tunnel in a single RSVP-TE Path/Resv message. It is
   also possible that such a signaling message can not fit into a single
   IP packet. It must also be possible to efficiently add and remove
   endpoints to and from P2MP TE LSPs. An additional issue is that P2MP
   LSP Tunnels must also handle the state "remerge" problem [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.
   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
   Tunnel's state. The portion of P2MP LSP Tunnel state identified by



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   specific subgroup field values is referred to as a signaling sub-
   tree. It is important to note that the term "signaling sub-tree"
   refers only to signaling state and not data plane replication or
   branching. For example, it is possible for a node to "split"
   signaling state for a P2MP LSP Tunnel, but to not branch the data
   associated with the P2MP LSP Tunnel. Typical applications 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.

3.4. S2L Sub-LSPs

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

3.4.1. Representation of a S2L Sub-LSP

   A S2L sub-LSP exists within the context of a P2MP LSP Tunnel. 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.

   Additionally, a sub-LSP ID contained in the S2L_SUB_LSP object may be
   used depending on further discussions about the make-before-break
   procedures described in section 14.

   An EXPLICIT_ROUTE Object (ERO) or SUB_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 3.5.

3.4.2. S2L Sub-LSPs and Path Messages

   The mechanism in this document allows a P2MP LSP Tunnel 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 Tunnel. 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 Tunnel.








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3.5. 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 may encode the path 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. The absence of the ERO should be
   interpreted 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, 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
   corresponding to the S2L_SUB_LSP objects that follow are termed as
   subsequent S2L sub-LSPs.  One approach to encode the explicit route
   of a subsequent S2L sub-LSP is to include the path from the ingress
   to the egress of the S2L sub-LSP. However this implies potential
   repetition of hops that could be learned from the ERO or explicit
   routes of other S2L sub-LSPs. Explicit route compression using SEROs
   attempts to minimize such repetition and is described below.

   The path of each subsequent S2L sub-LSP is encoded in a
   SUB_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 [<SUB_EXPLICIT_ROUTE>]
   <S2L_SUB_LSP>. There is a one to one correspondence between a
   S2L_SUB_LSP object and a SERO. A SERO for a particular 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 encoding 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 Tunnel 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

   The encoding of the Path message sent by LSR H to LSR L is as
   follows:



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      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 the 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 SERO 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.


4. Path Message

4.1. 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> ... ]
                          <sender descriptor>
                          [S2L sub-LSP descriptor list]




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   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> [ <SUB_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.

4.2. 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 Tunnel. Each S2L sub-LSP
   is associated with the same P2MP LSP Tunnel using common P2MP SESSION
   object and <Source Address, LSP-ID> fields in the SENDER_TEMPLATE
   object.  Hence it can be combined with other S2L sub-LSPs to form a
   P2MP LSP Tunnel.  Another S2L sub-LSP belonging to the same instance
   of this S2L sub-LSP (i.e.  the same P2MP LSP Tunnel) can share
   resources with this LSP. The session corresponding to the P2MP TE
   tunnel is determined based on the P2MP SESSION object. Each S2L sub-
   LSP is identified 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 Tunnel in one or more Path messages. And a given Path
   message can contain one or more S2L sub-LSPs.

4.2.1. Multiple Path messages

   As described in section 3, {<EXPLICIT_ROUTE>, <S2L SUB-LSP>} or
   {<SUB_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
   Tunnel. 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



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   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 4.3.

   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 Tunnel. Or it may be while adding
   leaves to the P2MP LSP Tunnel the new leaves are signaled in a new
   Path message. Or an ingress LSR MAY choose to break the P2MP tree
   into separate manageable S2L sub-trees.  These trees share the same
   root and may share the trunk and certain branches.  The scope of this
   management decomposition of P2MP trees is bounded by a single tree
   and multiple S2L sub-trees with a single leaf each. As defined in
   [P2MP-REQ], a P2MP LSP Tunnel must have consistent attributes across
   all portions of a tree. This implies that each Path message that is
   used to signal a P2MP LSP Tunnel is signaled using the same signaling
   attributes with the exception of the S2L sub-LSP information.

   The resulting S2L sub-LSPs from the different Path messages belonging
   to the same P2MP LSP Tunnel 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
   message. For instance ERO expansion may result in an overflow of the
   resultant Path message. There are two cases occurring in such
   circumstances, either the message can be decomposed into multiple
   Path messages such that each of the message carries a subset of the
   incoming S2L sub-LSPs carried by the incoming message, or the message
   can not be decomposed such that each of the outgoing Path message
   fits its maximum size value.

   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).  Multiple Path messages generated by a LSR to signal state
   for the same P2MP LSP have 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 network-wide unique. The sub-Group ID space is specific
   to the Sub-Group Originator ID. Therefore the combination <Sub-Group



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   Originator ID, sub-Group ID> is network-wide unique. Also, a router
   that changes the Sub-Group Originator ID MUST use the same Sub-Group
   Originator ID on all Path messages for the same P2MP LSP Tunnel and
   SHOULD not vary the value during the life of the P2MP LSP Tunnel.

   Note: This version of the document assumes that these additional
   fields, i.e. <Sub-Group Originator ID, sub-Group ID>, are part of the
   SENDER_TEMPLATE object.

4.2.2. 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 objects and ERO/SERO combinations in a single Path
   message. Note that these objects are the ones that differentiate a
   S2L sub-LSP. Each LSR can use the common objects in the Path message
   and the S2L sub-LSP descriptors to process each S2L sub-LSP.

   All LSRs need to 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 signaling information for the first S2L sub-LSP
   is propagated in a Path message by each LSR along the explicit route
   specified by the ERO. 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. If this is not the
   case the S2L sub-LSP descriptor is 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 is not propagated
   downstream. If this is the case and the LSR is not the egress the S2L
   sub-LSP descriptor is included in a Path message sent to the next-hop
   determined from the SERO. Hence a branch LSR only propagates the
   relevant S2L sub-LSP descriptors on each downstream link. A S2L sub-
   LSP descriptor that is propagated on a downstream link only contains
   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 contains loose hops, expansion of such
   loose hops may result in overflowing the Path message size.  Section
   4.2.3 describes how signaling of the set of S2L sub-LSPs can be split
   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
   message. A transit LSR appends its address in an incoming RRO and
   propagates it downstream. A branch LSR forms a new RRO for each of



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   the outgoing Path messages. Each such updated RRO is formed using the
   rules in [RFC3209].

   If a LSR is unable to support a S2L sub-LSP setup, a PathErr message
   MUST be sent for the impacted S2L sub-LSP, and normal processing of
   the rest of the P2MP LSP Tunnel 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_Reomved flag MUST NOT be
   set. However, the ingress LSR may set a LSP Integrity flag (see
   section 21.3) to request that if there is a setup failure on any
   branch the entire LSP should fail to set up.

4.2.3. Transit Fragmentation

   In certain cases a transit LSR may need to generate multiple Path
   messages to signal state corresponding to a single received Path
   message. For instance ERO expansion may result in an overflow of the
   resultant Path message. It is desirable not to rely on IP
   fragmentation in this case. In order to achieve this, the multiple
   Path messages generated by the transit LSR, MUST be signaled with the
   Sub-Group Originator ID set to the TE Router ID of the transit LSR
   and a distinct sub-Group ID. Thus each distinct Path message that is
   generated by the transit LSR for the P2MP LSP Tunnel 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 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 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
   originating the Path message based on a local policy. For instance a
   LSR may decide to always change the Sub-Group Originator ID while
   performing ERO expansion. The Sub-Group ID MUST not be changed if the
   Sub-Group Originator ID is not being changed.








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4.3. Grafting

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

4.3.1. Addition of S2L Sub-LSPs

   There are two methods to add S2L sub-LSPs to a P2MP LSP Tunnel.  The
   first is to add new S2L sub-LSPs to the P2MP LSP Tunnel 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 Tunnel. 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 11.1.
   The egress LSRs can be added/removed 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.


5. Resv Message

5.1. 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>




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   <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> ]

   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 SUB_RECORD_ROUTE object is used in place of a
   SUB_EXPLICIT_ROUTE object.

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

   <S2L sub-LSP filte descriptor> ::= <S2L_SUB_LSP> [ <SUB_RECORD_ROUTE>
   ]

   The SUB_RECORD_ROUTE objects follow the same compression mechanism as
   the SUB_EXPLICIT_ROUTE objects. Note that a Resv message can signal
   multiple S2L sub-LSPs that may belong to the same FILTER_SPEC object
   or different FILTER_SPEC objects. The same label is allocated if the
   FILTER_SPEC object is 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 Tunnels.

5.2. Resv Message Processing

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

   A subsequent node allocates its own label and passes it upstream in
   the Resv message. The node may combine multiple flow descriptors,
   from different Resv messages received from downstream, in one Resv



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   message sent upstream. A Resv message is not sent upstream by a
   transit LSR until at least one Resv message has been received from a
   downstream neighbor except when the integrity bit is set in the
   LSP_ATTRIBUTE object.

   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 Tunnel (whether on
   one or multiple Resv messages) is allocated the same label.

   This label is associated by that node with all the labels received
   from downstream Resv messages for that P2MP LSP Tunnel. 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 Tunnel 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
   Resv message, particularly when considering that the number of
   messages 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
   message.  ResvErr message generation is unmodified.  Nodes
   propagating a received ResvErr message MUST use the Sub-Group field
   values carried in the corresponding Resv message.

   The solution for this issue is for further discussion.

5.2.1. Resv Message Throttling

   A branch node needs 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
   MAY 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
   previous 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



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   scope of this document.

5.3. Record Routing

5.3.1. RRO Processing

   A Resv message contains a recorded 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 Tunnels. Thus insertion of the RRO
   in the Path message used to signal one or more S2L sub-LSPs triggers
   the inclusion of an RRO for each sub-LSP signaled in that Path
   message or any derivative Path message.

   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
   SUB_RECORD_ROUTE objects (SRROs). Their format is specified in
   section 20.6. 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 recorded route corresponding to a particular S2L
   sub-LSP. The RRO and SRROs can be used to construct the end-to-end
   Path for each S2L sub-LSP.


6. Reservation Style

   TBD


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 SUB_EXPLICIT_ROUTE object associated with each S2L_SUB_LSP being



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   deleted

7.2. Pruning

   The operation of removing egress LSR(s) from an existing P2MP LSP
   Tunnel is termed pruning. This operation allows egress nodes to
   leave  a P2MP LSP Tunnel at different points in time. This section
   describes various mechanisms to perform pruning. Further discussion
   and feedback is needed to finesse these mechanisms.

7.2.1. Explicit S2L Sub-LSP Teardown

   The S2L sub-LSP(s) being removed from the P2MP LSP Tunnel are
   signaled in a PathTear message. The PathTear message includes the S2L
   sub-LSP descriptor list which is included before the sender
   descriptor. Note that the PathTear message contains only the S2L sub-
   LSP(s) being removed and rest of the P2MP LSP Tunnel does not have to
   be re-signaled. This results in removal of the state corresponding to
   these S2L sub-LSPs. State for rest of the S2L sub-LSPs is not
   modified.

   In the first mechanism in order to delete one or more S2L Sub-LSPs, a
   PathTear message is sent with the list of S2L sub-LSPs being deleted.
   This is a form of explicit tear down. A single PathTear message can
   only contain S2L sub-LSPs that were signaled by the ingress using the
   same <Sub-Group Originator ID, Sub-Group ID> tuple. The PathTear
   message is signaled with the SESSION and SENDER_TEMPLATE objects
   corresponding to the P2MP LSP Tunnel and the <Sub-Group Originator
   ID, Sub-Group ID> tuple corresponding to the S2L sub-LSPs that are
   being deleted. 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 last Path message that corresponds to the S2L sub-LSPs
   signaled in the PathTear message that it generates. The transit LSR
   may need to generate multiple PathTear messages for an incoming
   PathTear message if it had performed transit fragmentation for the
   corresponding incoming Path message.

   The Path messages from which the S2L sub-LSPs were deleted need to be
   refreshed with the remaining S2L sub-LSPs. Note that as a result of
   deleting one or more S2L sub-LSPs from a Path message the ERO
   compression encoding may have to be recomputed.

   When the last S2L sub-LSP is to be removed from a Path state, i.e.,
   there are no remaining S2L sub-LSPs to send in a Path message, a
   PathTear message SHOULD be sent carrying the Sub-Group ID of the Path
   message that no longer has any S2L sub-LSPs.




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   The second mechanism is an explicit teardown mechanism that defines
   new syntax and semantics for a PathTear message. This new mechanism
   minimizes signaling required to remove a subset of S2L sub-LSPs set
   signaled in a Path message, and thereby reduces associated
   processing.  When using this mechanism each identified S2L sub-LSP is
   removed from the P2MP LSP Tunnel state, even if the S2L sub-LSP is
   advertised in multiple Path message.

   When using this approach, a PathTear message is generated. The
   PathTear message MUST identify each S2L sub-LSP to be removed, via a
   S2L_SUB_LSP object per S2L Sub-LSP, and include a SENDER_TEMPLATE
   object corresponding to the Path state being modified. The Sub-Group
   ID valued contained in the SENDER_TEMPLATE object message MUST be set
   to zero (0). Subsequent Path messages associated with the P2MP LSP
   Tunnel MUST NOT contain the removed S2L sub-LSPs, unless that S2L
   sub-LSP is being re-added to the P2MP LSP.

   To support the second mechanism, the receiver of PathTear message
   that is associated with a P2MP LSP Tunnel MUST check the value of a
   received Sub-Group ID fields.  When there is no SENDER_TEMPLATE
   object present or the value of the Sub-Group ID fields is non-zero,
   then PathTear processing as defined in the above explicit tear down
   mechanism must be followed.  When the Sub-Group ID field is zero (0),
   then the processing node MUST remove the identified egresses from all
   control plane state associated with the P2MP LSP Tunnel and adjust
   the data path appropriately.

7.2.2. Implicit S2L Sub-LSP Teardown

   The third mechanism to delete S2L sub-LSPs is implicit teardown which
   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 previously 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.

7.2.3. P2MP TE LSP Teardown

   This operation is accomplished by listing all the S2L sub-LSPs in a
   PathTear message.

   A PathTear message must be generated for each Path message used to
   signal the P2MP LSP Tunnel.




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8. Notify and ResvConf Messages

   Notify messages, see [RFC3473], may contain either SENDER_TEMPLATE or
   FILTER_SPEC objects, but are sent in a targeted fashion. This means
   that the Sub-Group fields cannot be updated in transit and is
   unlikely to provide any value to the Notify message recipient.
   Therefore, the receiver of a Notify message MUST identify the sender
   state referenced in the message based on the Source address and LSP
   ID contained in the received SENDER_TEMPLATE or FILTER_SPEC objects
   rather than, as is normally done, based on the whole objects.

   ResvConf messages may contain FILTER_SPEC objects and may also be
   sent in a targeted fashion.  As with Notify messages, the receiver of
   a ResvConf message MUST identify the state referenced in the message
   based on the address and LSP ID contained in the received FILTER_SPEC
   object rather than, as is normally done, based on the whole objects.


9. Error Processing

   Note that a LSR on receiving a PathErr/ResvErr message for a
   particular 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.

9.1. PathErr Message Format

   A PathErr message will include one or more S2L_SUB_LSP objects. The
   resulting modified format of 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



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   the Path message from the upstream neighbor. Note the receiver of a
   PathErr message is able to identify the errored outgoing Path
   message, and outgoing interface, based on the Sub-Group fields
   received in the error message.

9.2. Handling of Failures at Branch LSRs

   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 21.3) 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 Tunnel SHOULD set the Path_State_Removed flag.

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

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
















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10. Refresh Reduction

   The refresh reduction procedures described in [RFC2961] are equally
   applicable to P2MP LSP Tunnels 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
   Tunnels.


11. State Management

   State signaled by a P2MP Path message is managed by an implementation
   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 an implementation. This mandatorily includes PHOP
   and SENDER_TSPEC objects.

11.1. 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
   advertisement message. Per [RFC2205] Path and Resv messages are
   idempotent. Also, [RFC2961] categorizes RSVP messages into two types:
   trigger and refresh messages and improves RSVP message handling and
   scaling of state refreshes but does not modify the full state
   advertisement 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 Tunnel 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 Tunnel Path state.

   As described in section 4.2, multiple Path messages can be used to
   signal a P2MP LSP Tunnel. 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



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   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 Tunnel state updates.

11.2. Combining Multiple Path Messages

   There is a tradeoff between the number of Path messages used by the
   ingress to maintain the P2MP LSP Tunnel and using full state refresh
   to add S2L sub-LSPs. It is possible to combine S2L sub-LSPs
   previously advertised in different Path messages into 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 generated 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
   multiple Path messages with all the S2L sub-LSPs that are being
   combined in a single Path message. This Path message contains a new
   Sub-Group ID field value. When a new Path and Resv message that is
   signaled 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 a PathTear message.
   The S2L sub-LSP should also be removed from the old Path message and
   the old Path message should be signaled again, if there are other
   remaining S2L sub-LSPs in the old Path message.

   A Path message with a Sub-Group_ID(n+1) may signal a set of S2L sub-
   LSPs that belong partially or entirely to an already existing Sub-
   Group_ID(i), i <= n, 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+1), i =< n then either a full
   refresh is indicated by the Path message or a S2L Sub-LSP is added



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   to/deleted from the group signaled by Sub-Group_ID(n+1)

   2) If Sub-Group_ID(i) != Sub-Group_ID(n+1), i =< 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.


12. Control of Branch Fate Sharing

   An ingress LSR can control the behavior of an LSP if there is a
   failure 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 Tunnel to fail.

   The ingress LSP may request 'LSP integrity' by setting bit [section
   21.3] 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"


13. Admin Status Change

   A branch node that receives an ADMIN_STATUS object processes it
   normally 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 ADMIN_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.








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14. 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 Tunnel. Thus the sender
   performs 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 Tunnel, to avoid replication. Procedures for doing this
   are for further study. Given the relatively small number of receivers
   on LANs typically deployed in MPLS networks, this is not currently
   seen as a practical problem. Furthermore avoiding replication at the
   sender on a LAN requires significant complexity in the control plane.
   Given the tradeoff we propose the use of replication by the sender on
   a LAN.


15. Make-before-break

   Let's consider the following cases where make-before-break is needed:

15.1. P2MP Tree Re-optimization

   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
   [RFC3209].  Thus a new P2MP LSP Tunnel instance is established. Each
   S2L sub-LSP is signaled with a different LSP ID, corresponding to the
   new P2MP TE LSP. The ingress can, after moving traffic to the new
   instance, tear down the previous P2MP LSP Tunnel instance.

15.2. Re-optimization of a subset of S2L sub-LSPs

   One way to accomplish re-optimization of a subset of S2L sub-LSPs
   that belong to a P2MP LSP Tunnel is to resignal the entire tree with
   a new LSP-ID as described in the previous subsection.

   (There is NO-CONSENSUS between the authors on rest of the text in
   this subsection and it needs further discussion.)

   It is possible to accomplish re-optimization of one or more S2L sub-
   LSPs without re-signaling rest of the P2MP LSP. To achieve this a
   sub-LSP ID is used to identify each S2L sub-LSP. This is encoded in
   the S2L sub-LSP object. Each re-optimized S2L sub-LSP is signaled
   with a different sub-LSP ID and hence a new S2L sub-LSP is
   established. Once the new setup is complete, the old S2L sub-LSP can
   be torn down. In some cases this may result in transient data
   duplication.






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16. Fast Reroute

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

16.1. Facility Backup

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

   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 Tunnel label allocated by the nhop.
   During failure 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 corresponding 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
   protected S2L sub-LSP using the LSP-id and the S2L sub-LSP object.

   If node protection is desired, the bypass tunnel must intersect the
   path of the protected S2L sub-LSPs somewhere downstream of the PLR.
   This constrains the set of S2L sub-LSPs being backed-up via that
   bypass tunnel to those that pass through a common downstream MP. The
   MP will allocate the same label to all such S2L sub-LSPs belonging to
   a particular instance of a P2MP tunnel. This will be the inner label
   used during label stacking. This 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 being backed up must pass through the same MP.

16.2. 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



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   the P2MP tunnel, between the PLR and the next-hop share the same P2MP
   LSP Tunnel 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 Tunnel 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
   belonging 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 3 S2L sub-LSPs between different P2MP tunnel instances use
   different labels.

   If there is only 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.


17. 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
   document.  If a Path message for the establishment of a P2MP LSP
   Tunnel reaches such an LSR it will reject it with a PathErr because
   it will not recognize 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 and LSP-
   hierarchy [LSP-HIER]. Note that LSRs that are required to play any
   other role in the network (ingress, branch or egress) MUST support
   the extensions defined in this document.

   The use of LSP-stitching and LSP-hierarchy [LSP-HIER] allows P2MP LSP



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   Tunnels to be built in such an environment. A P2P LSP segment is
   signaled from the previous P2MP capable hop of a legacy LSR to the
   next P2MP capable 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 Tunnel. 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 Tunnel. 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 Tunnel.

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

   It may be an overhead for an operator to configure the P2P LSP
   segments in advance, when it is desired to support legacy LSRs. It
   may be desirable to do this dynamically. The ingress can use IGP
   extensions to determine non P2MP capable LSRs. 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
   capable 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
   protection of the tail of the P2P LSP segment.






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18. Reduction in Control Plane Processing with LSP Hierarchy

   It is possible to take advantage of LSP hierarchy [LSP-HIER] while
   setting up P2MP LSP Tunnels, 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 Tunnel, do not process control plane messages associated
   with the P2MP LSP Tunnel. Infact they are not aware of these messages
   as they are tunneled over the P2P LSP segment. This reduces the
   amount of control plane processing required on these transit LSRs.

   Note that the P2P LSP segments can be dynamically set up 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 Tunnel and does not process the
   P2MP control messages.


19. P2MP LSP Tunnel Remerging and Cross-Over

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

   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 re-merged S2L sub-LSPs
   are sent out on different interfaces there is no data plane issue.
   However if the re-merged S2L sub-LSPs are sent out on the same
   interface 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 message.

   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



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   interface as the existing S2L sub-LSP. This is a case of re-merging.

   d) The new S2L sub-LSP uses a different PHOP and a different outgoing
   interface as compared to the existing S2L sub-LSP. This is a case of
   cross-over.

   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. This is a legal case of signaling 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. 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. However 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. Also the outgoing interface is different
   from the outgoing interfaces used by existing S2L sub-LSPs. This is a
   case of cross-over.

   Cases 1(d) and 2(d) above identify cross-over and this is considered
   legal.  Cases 1(c) and 2(c) above identify 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



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   with the new Path message is compared against the list present in the
   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, and the LSR is capable of
   remerging in the data plane, this is considered legal. Else 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
   Problem/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 a the error
   "Routing Problem/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 signaling 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 message 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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20. New and Updated Message Objects

   This section presents the new and updated RSVP message objects used
   by this document.

20.1. P2MP LSP Tunnel SESSION Object

   A P2MP LSP Tunnel SESSION object is used. This object uses the
   existing SESSION 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 Tunnel 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
   identifying a P2P Tunnel which in turn can contain multiple LSP
   Tunnels, each distinguished by a unique SENDER_TEMPLATE object.

20.1.1. P2MP IPv4 LSP SESSION Object

   Class = SESSION, P2MP_LSP_TUNNEL_IPv4 C-Type = TBD

       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
      LSP Tunnel.

   Tunnel ID

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



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   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].

20.1.2. P2MP IPv6 LSP 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].

20.2. SENDER_TEMPLATE object

   The sender template contains the ingress-LSR source address. LSP ID
   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
   Tunnel by using a <Sub-Group ID Originator ID, Sub-Group ID> tuple.
   There are various methods to encode this information. This document
   proposes the use of the SENDER_TEMPLATE object and modifies it to
   carry this information as shown below. This encoding is subject to
   review by the MPLS WG.

20.2.1. P2MP IPv4 LSP Tunnel SENDER_TEMPLATE Object

   Class = SENDER_TEMPLATE, P2MP_LSP_TUNNEL_IPv4 C-Type = TBD

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





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        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. If the third
            mechanism for pruning is used as described in section 7.2,
            the Sub-Group ID value of zero (0) has special meaning and
            MUST NOT be used with P2MP LSP Tunnels in messages other
            than PathTear messages. Use of a Sub-Group ID value of zero
            (0) in PathTear messages is defined below.

        LSP ID
           See [RFC3209]

20.2.2. P2MP LSP Tunnel IPv6 SENDER_TEMPLATE Object

   Class = SENDER_TEMPLATE, P2MP_LSP_TUNNEL_IPv6 C-Type = TBD


         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]

20.3. S2L SUB-LSP IPv4 Object

   A new S2L Sub-LSP object identifies a particular S2L sub-LSP
   belonging to the P2MP LSP Tunnel.

20.3.1. S2L SUB-LSP IPv4 Object

   SUB_LSP Class = TBD, S2L_SUB_LSP_IPv4 C-Type = TBD

       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        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  MUST be zero                 |            Sub-LSP ID         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   IPv4 Sub-LSP destination address

      IPv4 address of the S2L sub-LSP destination.

   (There is NO-CONSENSUS amongst the authors on the sub-LSP ID
   described below and it needs more discussion)

   Sub-LSP ID

      A 16-bit identifier that identifies a particular instance



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      of a S2L sub-LSP. It can be varied for S2L sub-LSP
      make-before-break. Different S2L sub-LSPs, with the same SESSION
      object and LSP ID, follow the label merge semantics described in
      section 3 to form a particular instance of the P2MP tunnel.

20.3.2. S2L SUB-LSP IPv6 Object

   SUB_LSP Class = TBD, S2L_SUB_LSP_IPv6 C-Type = TBD

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

20.4. FILTER_SPEC Object

   The FILTER_SPEC object is canonical to the P2MP SENDER_TEMPLATE
   object.

20.4.1. P2MP LSP_TUNNEL_IPv4 FILTER_SPEC Object

   Class = FILTER SPEC, P2MP LSP_TUNNEL_IPv4 C-Type = TBD

   The format of the P2MP LSP_TUNNEL_IPv4 FILTER_SPEC object is
   identical to the P2MP LSP_TUNNEL_IPv4 SENDER_TEMPLATE object.

20.4.2. P2MP LSP_TUNNEL_IPv4 FILTER_SPEC Object

   Class = FILTER SPEC, P2MP LSP_TUNNEL_IPv6 C_Type = TBD

   The format of the P2MP LSP_TUNNEL_IPv6 FILTER_SPEC object is
   identical to the P2MP LSP_TUNNEL_IPv6 SENDER_TEMPLATE object.

20.5. SUB_EXPLICIT_ROUTE Object (SERO)

   The SERO is defined as identical to the ERO.  The CNums are TBD and
   TBD of the form 11bbbbbb.

20.6. SUB_RECORD_ROUTE Object (SRRO)

   The SRRO is defined as identical to the RRO.  The CNums are TBD and
   TBD of the form 11bbbbbb.











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21. IANA Considerations

21.1. New Message Objects

   IANA considerations for new message objects will be specified after
   the objects used are decided upon.

21.2. New Error Codes

   Two new Error Codes are defined for use with the Error Value "Routing
   Error". IANA is requested to assign values.

   The Error Code "Unable to Branch" indicates that a P2MP branch cannot
   be formed by the reporting LSR.

   The Error Code "Unsupported LSP Integrity" indicates that a P2MP
   branch does not support the requested LSP integrity function.

21.3. 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 Document:   12

   Suggested Bit Number:             4
   Meaning:                          Branch Reoptimization Allowed
   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 Document: TBD













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22. Security Considerations

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


23. Acknowledgements

   This document is the product of many people. The contributors are
   listed in Section 25.

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


24. Example P2MP LSP Establishment

   Following is one example of setting up a P2MP LSP Tunnel using the
   procedures 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
   previously received a Resv message from PE3 with label L3. It had
   allocated 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}.


25. References

25.1. Normative References


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

      [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-03.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



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

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

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

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

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

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

      [RSVP-FRR] P. Pan, G. Swallow, A. Atlas (Editors), "Fast Reroute Extensions
                 to RSVP-TE for LSP Tunnels",
                 draft-ietf-mpls-rsvp-lsp-fastreroute-07.txt.

      [P2MP-REQ] S. Yasukawa, et. al., "Requirements for Point-to-Multipoint
                 capability extension to MPLS",
                 draft-ietf-mpls-p2mp-sig-requirement-00.txt.



25.2. Informative References


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

      [BFD-MPLS] R. Aggarwal, K. Kompella, "BFD for MPLS LSPs",
                 draft-raggarwa-mpls-bfd-00.txt

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

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

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




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

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



26. Author Information

26.1. 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


26.2. 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



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   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
   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



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   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.
   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



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   France
   E-mail: jeanlouis.leroux@francetelecom.com



27. 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
   assurances 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.


28. Full Copyright Statement

   Copyright (C) The Internet Society (2004). This document is subject
   to the rights, licenses and restrictions contained in BCP 78 and
   except as set forth therein, the authors retain all their rights.


   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUNG 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.







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29. Acknowledgement

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















































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