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Versions: (draft-tsaad-mpls-p2mp-loose-path-reopt) 00 01 draft-ietf-teas-p2mp-loose-path-reopt

MPLS Working Group                                       Tarek Saad, Ed.
Internet-Draft                                        Rakesh Gandhi, Ed.
Intended status: Standards Track                               Zafar Ali
Expires: April 3, 2015                               Cisco Systems, Inc.
                                                       Robert H. Venator
                                      Defense Information Systems Agency
                                                             Yuji Kamite
                                          NTT Communications Corporation
                                                      September 30, 2014


    Extensions to Resource Reservation Protocol For Re-optimization
     of Loosely Routed Point-to-Multipoint Traffic Engineering LSPs
                draft-ietf-mpls-p2mp-loose-path-reopt-01


Abstract

   For a Traffic Engineered (TE) point-to-multipoint (P2MP) Label
   Switched Path (LSP), it is preferable in some cases to re-evaluate
   and re-optimize the entire P2MP-TE LSP by re-signaling all its
   Source-to-Leaf (S2L) sub-LSP(s).  Existing mechanisms, a mechanism
   for an ingress Label Switched Router (LSR) to trigger a new path re-
   evaluation request and a mechanism for a mid-point LSR to notify an
   availability of a preferred path, operate on an individual or a sub-
   group of S2L sub-LSP(s) basis only.

   This document defines RSVP-TE signaling extensions to allow an
   ingress node of a P2MP-TE LSP to request the re-evaluation of the
   entire LSP tree containing one or more S2L sub-LSPs whose paths are
   loose (or abstract) hop expanded, and for a mid-point LSR to notify
   to the ingress node that a preferable tree exists for the entire
   P2MP-TE LSP.  This document also defines markers to indicate
   beginning and end of a S2L sub-LSP descriptor list when RSVP message
   needs to be fragmented due to large number of S2L sub-LSPs when
   performing re-optimization.


Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.




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   Internet-Drafts are draft documents valid for a maximum of six months
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Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Existing Mechanism For Re-optimizing Loosely Routed
           P2MP-TE LSP  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Combining Multiple Path Messages for Re-optimization . . .  5
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     2.1.  Abbreviations  . . . . . . . . . . . . . . . . . . . . . .  7
     2.2.  Nomenclatures  . . . . . . . . . . . . . . . . . . . . . .  7
     2.3.  Conventions Used in This Document  . . . . . . . . . . . .  7
   3.  Signaling Procedure For Loosely Routed P2MP-TE LSP
       Re-optimization  . . . . . . . . . . . . . . . . . . . . . . .  8
     3.1.  Tree Based Re-optimization . . . . . . . . . . . . . . . .  8
     3.2.  Sub-group Based Re-optimization  . . . . . . . . . . . . .  8
   4.  RSVP Signaling Extensions  . . . . . . . . . . . . . . . . . .  9
     4.1.  P2MP-TE Tree Re-evaluation Request Flag  . . . . . . . . .  9
     4.2.  Preferable P2MP-TE Tree Exists Path Error Sub-code . . . . 10
     4.3.  Markers For S2L sub-LSP Descriptor . . . . . . . . . . . . 10
   5.  Compatibility  . . . . . . . . . . . . . . . . . . . . . . . . 11
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
     7.1.  P2MP-TE Tree Re-evaluation Request Flag  . . . . . . . . . 12
     7.2.  Preferable P2MP-TE Tree Exists Path Error Sub-code . . . . 12
     7.3.  BEGIN and END Markers For S2L sub-LSP Descriptor . . . . . 12
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 13
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 14
   Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15






















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1.  Introduction

   This document defines Resource Reservation Protocol - Traffic
   Engineering (RSVP-TE) [RFC2205] [RFC3209] signaling extensions for
   re-optimizing loosely routed Point-to-Multipoint (P2MP) Traffic
   Engineered (TE) Label Switched Paths (LSPs) [RFC4875] in an
   Multi-Protocol Label Switching (MPLS) and/or Generalized MPLS (GMPLS)
   networks.

   A P2MP-TE LSP is comprised of one or more source-to-leaf (S2L)
   sub-LSPs.  A loosely routed P2MP-TE S2L sub-LSP is defined as one
   whose path does not contain the full explicit route identifying each
   node along the path to the egress node at the time of its signaling
   by the ingress node.  Such an S2L sub-LSP is signaled with no
   Explicit Route Object (ERO) [RFC3209], or with an ERO that contains
   at least one loose hop, or with an ERO that contains an abstract node
   that is not a simple abstract node (that is, an abstract node that
   identifies more than one node).  This is often the case with
   inter-domain P2MP-TE LSPs where Path Computation Element (PCE) is not
   used [RFC5440].

   As per [RFC4875], an ingress node may re-optimize the entire P2MP-TE
   LSP by re-signaling all its S2L sub-LSP(s) or may re-optimize
   individual or group of S2L sub-LSP(s) i.e. individual or group of
   destination(s).


1.1.  Existing Mechanism For Re-optimizing Loosely Routed P2MP-TE LSP

   [RFC4736] defines RSVP signaling extensions for re-optimizing loosely
   routed P2P TE LSP(s) as follows.

   - A mid-point LSR that expands loose next-hop(s) sends a solicited or
   unsolicited PathErr with the Notify error code (25 as defined in
   [RFC3209]) with sub-code 6 to indicate "Preferable Path Exists" to
   the ingress node.

   - An ingress node triggers a path re-evaluation request at all
   mid-point LSR(s) that expands loose next-hop(s) by setting the "Path
   Re-evaluation Request" flag (0x20) in SESSION_ATTRIBUTES Object in
   the Path message.

   - The ingress node upon receiving this PathErr either solicited or
   unsolicited initiates re-optimization of the LSP.


   [RFC4736] does not define signaling extensions specific for
   re-optimizing entire P2MP-TE LSP tree.  Mechanisms defined in



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   [RFC4736] can be used for signaling the re-optimization of individual
   or group of S2L sub-LSP(s).  However, to use [RFC4736] mechanisms for
   re-optimizing an entire P2MP-TE LSP tree, an ingress node needs to
   send the path re-evaluation requests on all (typically 100s of) S2L
   sub-LSPs and the mid-point LSR to notify PathErrs for all S2L
   sub-LSPs.  Such a procedure may lead to the following issues:

   - A mid-point LSR that expands loose next-hop(s) may have to
   accumulate the received path re-evaluation request(s) for all S2L
   sub-LSPs (e.g, by using a wait timer) and interpret them as a
   re-optimization request for the whole P2MP-TE LSP tree.  Otherwise, a
   mid-point LSR may prematurely notify "Preferable Path Exists" for one
   or a sub-set of S2L sub-LSPs.

   - The ingress node that receives (un)solicited PathErr
   notification(s) for individual S2L sub-LSP(s), may prematurely start
   re-optimizing the sub-set of S2L sub-LSPs.  However, as mentioned in
   [RFC4875] Section 14.2, such sub-group based re-optimization
   procedure may result in data duplication that can be avoided if the
   entire P2MP-TE LSP tree is re-optimized using a different LSP-ID,
   especially if the ingress node eventually receives PathErr
   notifications for all S2L sub-LSPs of the P2MP-TE LSP tree.

   - The ingress node may have to heuristically determine when to
   perform entire P2MP-TE LSP tree re-optimization versus per S2L sub-
   LSP re-optimization, for example, to delay re-optimization long
   enough to allow all PathErr(s) to be received.  Once all PathErr(s)
   are received, the ingress node has to accumulate them to see if re-
   optimization of the entire P2MP-TE is necessary.  Such procedures may
   produce undesired results due to timing related issues.  This may be
   easily avoided by the RSVP signaling messages defined in this
   document.


1.2.  Combining Multiple Path Messages for Re-optimization

   Based on [RFC4875] (Section 14.2 "Sub-Group-Based Re-Optimization"),
   an ingress node may trigger path re-evaluation requests for a set of
   S2L sub-LSPs by combining multiple Path messages using S2L sub-LSP
   descriptor list.  A mid-point LSR may send a PathErr message
   containing a list of S2L sub-LSPs transiting through the LSR to
   notify the ingress node.  This method can alleviate the scale issue
   associated with sending RSVP messages for individual S2L sub-LSPs.
   This method is useful for re-optimizing a sub-group of S2L sub-LSPs
   within an LSP tree.  However, this procedure can lead to following
   issues:

   - Path message that is intended to carry the path re-evaluation



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   request as defined in [RFC4736] with a full list of S2L sub-LSPs in
   S2L sub-LSPs descriptor list will be decomposed at branching LSRs,
   and only a subset of the S2L sub-LSPs that are routed over the same
   next-hop will be added in the descriptor list of the Path message
   propagated to downstream mid-point LSRs.  Consequently, when a
   preferable path exists at such mid-point LSRs, the PathErr can only
   include the sub-set of S2L sub-LSPs traversing the LSR.  In this
   case, at the ingress node there is no way to distinguish which mode
   of re-optimization to invoke, i.e. sub-group based re-optimization
   using the same LSP-ID or tree based re-optimization using a different
   LSP-ID.

   - An LSR may fragment a large RSVP message (when a combined message
   may not be large enough to fit all S2L sub-LSPs).  In this case, the
   ingress node may receive multiple PathErrs with sub-sets of S2L
   sub-LSPs in each (either due to the combined Path message got
   fragmented or combined PathErr message got fragmented) and would
   require additional logic to infer to re-optimize the tree (for
   example, waiting for some time to aggregate all possible PathErr
   messages before taking an action).



   As discussed in Section 1.1 and Section 1.2 of this document, there
   is a requirement to align re-optimization of P2MP-TE LSP with P2P LSP
   [RFC4736] to have a mechanism to trigger re-optimization of the LSP
   tree by re-signaling all S2L sub-LSPs with a different LSP-ID.  There
   is also a need to define markers to indicate beginning and end of the
   S2L sub-LSP descriptor list when an RSVP message is fragmented due to
   large number of S2L sub-LSPs in the message.

   This document defines RSVP-TE signaling extensions for the ingress
   node of a P2MP-TE LSP to trigger the re-evaluation of the P2MP LSP
   tree on every hop that has a next hop defined as a loose or abstract
   hop for one or more S2L sub-LSP path, and a mid-point LSR to signal
   to the ingress node that a preferable LSP tree exists (compared to
   the current path) or that the whole P2MP-TE LSP must be re-optimized
   (because of maintenance required on the TE LSP path).  This document
   also defines markers to indicate beginning and end of a S2L sub-LSP
   descriptor list when RSVP message needs to be fragmented due to large
   number of S2L sub-LSPs when performing re-optimization.










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2.  Terminology

2.1.  Abbreviations

   ABR: Area Border Router.

   AS: Autonomous System.

   ERO: Explicit Route Object.

   LSR: Label Switching Router.

   TE LSP: Traffic Engineering Label Switched Path.

   TE LSP ingress: Head-end/source of the TE LSP.

   TE LSP egress: Tail-end/destination of the TE LSP.

2.2.  Nomenclatures

   Domain: Routing or administrative domain such as an IGP area and an
   autonomous system.

   Interior Gateway Protocol Area (IGP Area): OSPF Area or IS-IS level.

   Inter-area TE LSP: A TE LSP whose path transits across at least two
   different IGP areas.

   Inter-AS MPLS TE LSP: A TE LSP whose path transits across at least
   two different Autonomous Systems (ASes) or sub-ASes (BGP
   confederations).

   S2L sub-LSP: Source-to-leaf sub Label Switched Path.

2.3.  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 [RFC2119].  The reader
   is assumed to be familiar with the terminology in [RFC4875] and
   [RFC4736].










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3.  Signaling Procedure For Loosely Routed P2MP-TE LSP Re-optimization

3.1.  Tree Based Re-optimization

   To evaluate an entire P2MP-TE LSP tree on mid-point LSRs that expand
   loose next-hop(s), an ingress node MAY send a Path message with
   "P2MP-TE Tree Re-evaluation Request" defined in this document.  An
   ingress node SHOULD select one of the S2L sub-LSPs of the P2MP-TE LSP
   tree transiting a mid-point LSR to trigger the re-evaluation request.

   A mid-point LSR that expands loose next-hop(s) for one or more S2L
   sub-LSP path(s), and that receives a Path message with the "P2MP-TE
   Tree Re-evaluation Request" bit set, SHOULD check for a preferable
   P2MP-TE LSP tree by re-evaluating all S2L sub-LSP(s) that are
   expanded paths of the loose next-hops of the P2MP-TE LSP.  If a
   preferable P2MP-TE LSP tree is found, the mid-point LSR MAY send an
   RSVP PathErr to the ingress node with Error code 25 (Notify defined
   in [RFC3209] and Error sub-code defined in this document "Preferable
   P2MP-TE Tree Exists".  The mid-point LSR, in turn, SHOULD not
   propagate the "P2MP-TE Tree Re-evaluation Request" bit in subsequent
   RSVP Path messages sent downstream for the re-evaluated P2MP-TE LSP.
   The sending of an RSVP PathErr Notify message "Preferable P2MP-TE
   Tree Exists" to the ingress node SHALL notify the ingress node of the
   existence of a preferable P2MP-TE LSP tree.  In addition, a mid-point
   LSR MAY send an unsolicited PathErr message with "Preferable P2MP-TE
   Tree Exists" PathErr code 25 to the ingress node to notify of a
   preferred the P2MP-TE LSP tree when it determines it exists.  In this
   case, the mid-point LSR that expands loose next-hop(s) for one or
   more S2L sub-LSP path(s) SHOULD select one of the S2L sub-LSP(s) of
   the P2MP-TE LSP tree to send this PathErr message to the ingress
   node.

   If no preferable tree for P2MP-TE LSP can be found, the recommended
   mode is that the mid-point LSR that expands loose next-hop(s) for one
   or more S2L sub-LSP path(s) SHOULD propagate the request downstream
   by setting the "P2MP-TE Tree Re-evaluation Request" bit in the
   LSP_ATTRIBUTES Object of RSVP Path message.

3.2.  Sub-group Based Re-optimization

   It might be preferable, as per [RFC4875], to re-optimize the entire
   P2MP-TE LSP by re-signaling all of its S2L sub-LSP(s) (Section 14.1,
   "Make-before-Break") or to re-optimize individual or group of S2L
   sub-LSP(s) i.e. individual or group of destination(s) (Section 14.2
   "Sub-Group-Based Re-Optimization" in [RFC4875]), both using the same
   LSP-ID.  For loosely routed S2L sub-LSPs, this can be achieved by
   using the procedures defined in [RFC4736] to re-optimize one or more
   S2L sub-LSP(s) of the P2MP-TE LSP.



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   An ingress node may trigger path re-evaluation requests for a set of
   S2L sub-LSPs by combining multiple Path messages using S2L sub-LSP
   descriptor list [RFC4875].  An S2L sub-LSP descriptor list is created
   using a series of S2L_SUB_LSP Objects as defined in [RFC4875].
   Similarly, a mid-point LSR may send a PathErr message containing a
   list of S2L sub-LSPs transiting through the LSR to notify the ingress
   node of preferable paths available.

   As per [RFC4875] (Section 5.2.3, "Transit Fragmentation of Path State
   Information"), when a Path message is not large enough to fit all S2L
   sub-LSPs in the descriptor list, an LSR may fragment the message.  In
   this case, the LSR MAY add S2L_SUB_LSP_MARKER_BEGIN and
   S2L_SUB_LSP_MARKER_END Objects defined in this document at the
   beginning and at the end of the S2L sub-LSP descriptor list,
   respectively.

   Both S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END Objects
   defined in this document are optional.  However, a node MUST add the
   S2L_SUB_LSP_MARKER_END Object if it has added
   S2L_SUB_LSP_MARKER_BEGIN Object in the S2L sub-LSP descriptor list.

   A mid-point LSR SHOULD wait to accumulate all S2L sub-LSPs before
   attempting to re-evaluate preferable path when a Path message for
   "Path Re-evaluation Request" is received with
   S2L_SUB_LSP_MARKER_BEGIN.  An ingress node SHOULD wait to accumulate
   all S2L sub-LSPs before attempting to trigger re-optimization when a
   PathErr message with "Preferable Path Exists" is received with
   S2L_SUB_LSP_MARKER_BEGIN.

   New objects S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END
   defined in this document have a wider applicability than the P2MP-TE
   LSP re-optimization but it is outside the scope of this document.


4.  RSVP Signaling Extensions

4.1.  P2MP-TE Tree Re-evaluation Request Flag

   In order to trigger a tree re-evaluation request, a new flag is
   defined in Attributes Flags TLV of the LSP_ATTRIBUTES Object
   [RFC5420] as follows:

      Bit Number (to be assigned by IANA): P2MP-TE Tree Re-evaluation
            Request flag


   The "P2MP-TE Tree Re-evaluation Request" flag is meaningful in a Path
   message of a P2MP-TE S2L sub-LSP and is inserted by the ingress node.



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4.2.  Preferable P2MP-TE Tree Exists Path Error Sub-code

   In order to indicate to an ingress node that a preferable P2MP-TE LSP
   tree exists, the following new sub-code for PathErr code 25 (Notify
   Error) [RFC3209] is defined:

      Sub-code (to be assigned by IANA): Preferable P2MP-TE Tree Exists
            sub-code


   When a preferable path for P2MP-TE LSP tree exists, the mid-point LSR
   sends a solicited or unsolicited "Preferable P2MP-TE Tree Exists"
   PathErr notification to the ingress node of the P2MP-TE LSP.

4.3.  Markers For S2L sub-LSP Descriptor

   An S2L_SUB_LSP Object [RFC4875] identifies a particular S2L sub-LSP
   belonging to the P2MP-TE LSP.  An S2L sub-LSP descriptor list is
   created using a series of S2L_SUB_LSP Objects as defined in
   [RFC4875].

   In order to indicate the beginning and end of the S2L sub-LSP
   descriptor list when the RSVP message needs to be fragmented due to
   large number of S2L sub-LSPs, the following new types are defined for
   the S2L_SUB_LSP Object [RFC4875].

   S2L_SUB_LSP_MARKER_BEGIN :

         Class-Num 50, C-Type TBA by IANA

   +-----------------+---------------+--------------------------+
   | Length (4 bytes)| Class_Num 50  | S2L_SUB_LSP_MARKER_BEGIN |
   +-----------------+---------------+--------------------------+

   S2L_SUB_LSP_MARKER_END :

         Class-Num 50, C-Type TBA by IANA

   +-----------------+---------------+--------------------------+
   | Length (4 bytes)| Class_Num 50  | S2L_SUB_LSP_MARKER_END   |
   +-----------------+---------------+--------------------------+


   The S2L_SUB_LSP_MARKER_BEGIN Object is added before adding the first
   S2L_SUB_LSP_IPv4 or S2L_SUB_LSP_IPv6 Object and the
   S2L_SUB_LSP_MARKER_END Object is added after adding the last
   S2L_SUB_LSP_IPv4 or S2L_SUB_LSP_IPv6 Object in the S2L sub-LSP
   descriptor list.



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5.  Compatibility

   The LSP_ATTRIBUTES Object has been defined in [RFC5420] with class
   numbers in the form 11bbbbbb, which ensures compatibility with
   non-supporting nodes.  Per [RFC2205], nodes not supporting this
   extension will ignore the new flag defined in this document but
   forward it without modification.

   The S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END Objects have
   been defined with class numbers in the form 11bbbbbb, which ensures
   compatibility with non-supporting nodes.  Per [RFC2205], nodes not
   supporting new S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END
   Objects will ignore them but forward it without modification.


6.  Security Considerations

   This document defines a mechanism for a mid-point LSR to notify the
   ingress node of a P2MP-TE LSP of the existence of a preferable tree.
   As per [RFC4736], in the case of a P2MP-TE LSP S2L sub-LSP spanning
   multiple domains, it may be desirable for a mid-point LSR to modify
   the RSVP PathErr message defined in this document to maintain
   confidentiality across different domains.  Furthermore, an ingress
   node may decide to ignore this PathErr message coming from a
   mid-point LSR residing in another domain.  Similarly, an mid-point
   LSR may decide to ignore the tree re-evaluation request originating
   from another ingress domain.


7.  IANA Considerations

   IANA is requested to administer assignment of new values for
   namespace defined in this document and summarized in this section.

   IANA maintains a name space for RSVP-TE TE parameters "Resource
   Reservation Protocol-Traffic Engineering (RSVP-TE) Parameters" (see
   http://www.iana.org/assignments/rsvp-te-parameters/rsvp-te-
   parameters.xml).  From the registries in this name space "Attribute
   Flags", allocation of new flag is requested (Section 4.1).

   IANA also maintains a name space for RSVP protocol parameters
   "Resource Reservation Protocol (RSVP) Parameters" (see
   http://www.iana.org/assignments/rsvp-parameters/rsvp-parameters.xml).
   From the sub-registry "Sub-Codes - 25 Notify Error" in registry
   "Error Codes and Globally-Defined Error Value Sub-Codes", allocation
   of a new error code is requested (Section 4.2).  Also, from the
   sub-registry "Class Types or C-Types 50 S2L_SUB_LSP" in registry
   "Class Names, Class Numbers, and Class Types", allocation of new



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   C-Types is requested (Section 4.3).


7.1.  P2MP-TE Tree Re-evaluation Request Flag

   The following new flag is defined for the Attributes Flags TLV in the
   LSP_ATTRIBUTES Object [RFC5420].  The numeric value is to be assigned
   by IANA.

   o  P2MP-TE Tree Re-evaluation Request Flag:

   +--------+---------------+---------+---------+---------+------------+
   | Bit No | Attribute     | Carried | Carried | Carried | Reference  |
   |        | Flag Name     | in Path | in Resv | in RRO  |            |
   +--------+---------------+---------+---------+---------+------------+
   | TBA by | P2MP-TE Tree  | Yes     | No      | No      | This       |
   | IANA   | Re-evaluation |         |         |         | document   |
   +--------+---------------+---------+---------+---------+------------+



7.2.  Preferable P2MP-TE Tree Exists Path Error Sub-code

   As defined in [RFC3209], the Error Code 25 in the ERROR SPEC Object
   corresponds to a Notify Error PathErr.  This document adds a new
   sub-code as follows for this PathErr:

   o  Preferable P2MP-TE Tree Exists sub-code:

   +----------+--------------------+---------+---------+-----------+
   | Sub-code | Sub-code           | PathErr | PathErr | Reference |
   | value    | Description        | Code    | Name    |           |
   +----------+--------------------+---------+---------+-----------+
   | TBA by   | Preferable P2MP-TE | 25      | Notify  | This      |
   | IANA     | Tree Exists        |         | Error   | document  |
   +----------+--------------------+---------+---------+-----------+




7.3.  BEGIN and END Markers For S2L sub-LSP Descriptor

   As defined in [RFC4875], S2L_SUB_LSP Object is defined with
   Class-Number 50 to identify a particular S2L sub-LSP belonging to the
   P2MP-TE LSP.  This document adds two new object types for this object
   as follows:





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   o  S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END Object types:

   +---------------+---------------------------+-----------------+
   | C-Type value  | Description               | Reference       |
   +---------------+---------------------------+-----------------+
   | TBA by IANA   | S2L_SUB_LSP_MARKER_BEGIN  | This document   |
   +---------------+---------------------------+-----------------+
   | TBA by IANA   | S2L_SUB_LSP_MARKER_END    | This document   |
   +---------------+---------------------------+-----------------+


8.  Acknowledgments

   The authors would like to thank Loa Andersson, Sriganesh Kini, Curtis
   Villamizar, Dimitri Papadimitriou and Nobo Akiya for reviewing this
   document.



































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9.  References

9.1.  Normative References

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

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, December 2001.

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

   [RFC5420]  Farrel, A., Papadimitriou, D., Vasseur, JP., and A.
              Ayyangarps, "Encoding of Attributes for MPLS LSP
              Establishment Using Resource Reservation Protocol Traffic
              Engineering (RSVP-TE)", RFC 5420, February 2009.

9.2.  Informative References

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

   [RFC4736]  Vasseur, JP., Ikejiri, Y. and Zhang, R, "Reoptimization of
              Multiprotocol Label Switching (MPLS) Traffic Engineering
              (TE) Loosely Routed Label Switched Path (LSP)", RFC 4736,
              November 2006.

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
















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Author's Addresses


   Tarek Saad (editor)
   Cisco Systems

   Email: tsaad@cisco.com


   Rakesh Gandhi (editor)
   Cisco Systems

   Email: rgandhi@cisco.com


   Zafar Ali
   Cisco Systems

   Email: zali@cisco.com


   Robert H. Venator
   Defense Information Systems Agency

   Email: robert.h.venator.civ@mail.mil


   Yuji Kamite
   NTT Communications Corporation

   Email: y.kamite@ntt.com




















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