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Versions: (draft-ietf-mpls-p2mp-loose-path-reopt) 00 01 02 03 04 05 06 07 08 09 RFC 8149

TEAS Working Group                                          T. Saad, Ed.
Internet-Draft                                            R. Gandhi, Ed.
Intended status: Standards Track                                  Z. Ali
Expires: November 26, 2015                           Cisco Systems, Inc.
                                                              R. Venator
                                      Defense Information Systems Agency
                                                               Y. Kamite
                                          NTT Communications Corporation
                                                            May 25, 2015


         RSVP Extensions For Re-optimization of Loosely Routed
  Point-to-Multipoint Traffic Engineering Label Switched Paths (LSPs)
                draft-ietf-teas-p2mp-loose-path-reopt-03


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 Resource Reservation Protocol (RSVP) 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.  For re-optimizing a group of S2L
   sub-LSP(s) in a tree, an S2L sub-LSP descriptor list can be used to
   signal one or more S2L sub-LSPs in an RSVP message.  This document
   defines markers to indicate beginning and end of an S2L sub-LSP
   descriptor list when the RSVP message needs to be fragmented due to
   large number of S2L sub-LSPs in the message when performing sub-group
   based 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



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   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.


   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
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Copyright Notice

   Copyright (c) 2015 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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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



























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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Loosely Routed Inter-domain P2MP-TE LSP Tree . . . . . . .  5
     1.2.  Existing Mechanism For Tree-Based P2MP-TE LSP
           Re-optimization  . . . . . . . . . . . . . . . . . . . . .  5
     1.3.  Existing Mechanism For Sub-Group-Based P2MP-TE LSP
           Re-optimization  . . . . . . . . . . . . . . . . . . . . .  6
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  7
     2.1.  Key Word Definitions . . . . . . . . . . . . . . . . . . .  7
     2.2.  Abbreviations  . . . . . . . . . . . . . . . . . . . . . .  7
     2.3.  Nomenclatures  . . . . . . . . . . . . . . . . . . . . . .  8
   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 Using Markers  . . . . . .  9
   4.  Message and Object Definitions . . . . . . . . . . . . . . . . 10
     4.1.  P2MP-TE Tree Re-evaluation Request Flag  . . . . . . . . . 10
     4.2.  Preferable P2MP-TE Tree Exists Path Error Sub-code . . . . 10
     4.3.  Markers For S2L sub-LSP Descriptor . . . . . . . . . . . . 11
   5.  Compatibility  . . . . . . . . . . . . . . . . . . . . . . . . 11
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
     6.1.  P2MP-TE Tree Re-evaluation Request Flag  . . . . . . . . . 12
     6.2.  Preferable P2MP-TE Tree Exists Path Error Sub-code . . . . 12
     6.3.  BEGIN and END Markers For S2L sub-LSP Descriptor . . . . . 13
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 15
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . . . 16
   Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16




















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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).

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

   o  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.

   o  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.

   o  The ingress node upon receiving this PathErr either solicited or
   unsolicited initiates re-optimization of the LSP with a different
   LSP-ID.


   Following sections discuss the issues that may arise when using
   existing mechanisms defined in [RFC4736] for re-optimizing loosely
   routed P2MP-TE LSPs.




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1.1.  Loosely Routed Inter-domain P2MP-TE LSP Tree

   An example of a loosely routed inter-domain P2MP-TE LSP tree is shown
   in Figure 1.  In this example, the P2MP-TE LSP tree consists of 3 S2L
   sub-LSPs, to destinations (i.e. leafs) R10, R11 and R12 from the
   ingress node (i.e. source) R1.  Nodes R2 and R5 are branch nodes and
   nodes ABR3, ABR4, ABR7, ABR8 and ABR9 are area border routers.  For
   the S2L sub-LSP to destination R10, nodes ABR3, ABR7 and R10 are
   defined as loose hops.  For the S2L sub-LSP to destination R11, nodes
   ABR3, ABR8 and R11 are defined as loose hops.  For the S2L sub-LSP to
   destination R12, nodes ABR4, ABR9 and R12 are defined as loose hops.


         <--area1--><--area0--><-area2->

                              ABR7---R10
                             /
                            /
                   ABR3---R5
                  /         \
                 /           \
          R1---R2             ABR8---R11
                 \
                  \
                   ABR4---R6
                            \
                             \
                              ABR9---R12


   Figure 1: An Example of Loosely Routed Inter-domain P2MP-TE LSP Tree


1.2.  Existing Mechanism For Tree-Based P2MP-TE LSP Re-optimization

   [RFC4736] does not define signaling extensions specific for
   re-optimizing entire P2MP-TE LSP tree.  Mechanisms defined in
   [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 mechanisms may lead to the following issues:

   o  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



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   mid-point LSR may prematurely notify "Preferable Path Exists" for one
   or a sub-set of S2L sub-LSPs.

   o  Similarly, 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.  Such procedures
   may produce undesired results due to timing related issues.

   o  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.


   In order to address above mentioned issues and to align
   re-optimization of P2MP-TE LSP with P2P LSP [RFC4736], there is a
   need for a mechanism to trigger re-optimization of the LSP tree by
   re-signaling all S2L sub-LSPs with a different LSP-ID.  To meet this
   requirement, this document defines RSVP-TE signaling extensions for
   the ingress node 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).


1.3.  Existing Mechanism For Sub-Group-Based P2MP-TE LSP Re-optimization

   Based on [RFC4875] (Section 14.2 "Sub-Group-Based Re-Optimization"),
   an ingress node may trigger path re-evaluation requests using the
   procedures defined in [RFC4736] for a set of S2L sub-LSPs and
   combining multiple Path messages using S2L sub-LSP descriptor list.
   Similarly, a mid-point LSR may send a PathErr message (with Error
   code 25, sub-code 6) containing a list of S2L sub-LSPs transiting
   through the LSR using an S2L sub-LSP descriptor list to notify the
   ingress node.  This method can be used for re-optimizing a sub-group
   of S2L sub-LSPs within an LSP tree using the same LSP-ID.  This
   method can alleviate the scale issue associated with sending RSVP
   messages for individual S2L sub-LSPs.  However, this procedure can
   lead to the following issues when used to re-optimize the LSP tree:

   o  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.

   o  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 LSP tree (for
   example, waiting for some time to aggregate all possible PathErr
   messages before taking an action).


   In order to address the above mentioned issue due to the RSVP message
   fragmentation, this document defines markers to indicate beginning
   and end of an S2L sub-LSP descriptor list when combining large number
   of S2L sub-LSPs in an RSVP message.


2.  Conventions Used in This Document

2.1.  Key Word Definitions

   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].

2.2.  Abbreviations

   ABR: Area Border Router.

   AS: Autonomous System.

   ERO: Explicit Route Object.

   LSR: Label Switching Router.

   TE LSP: Traffic Engineering Label Switched Path.




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

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

2.3.  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.


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

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.  The
   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.
    The ingress node MAY send a re-evaluation request to each border LSR
   on the path of the LSP tree.

   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:

   o  The mid-point LSR 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.

   o  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 sub-code "Preferable P2MP-TE Tree Exists"
   defined in this document.  The mid-point LSR, in turn, SHOULD NOT



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   propagate the "P2MP-TE Tree Re-evaluation Request" bit in subsequent
   RSVP Path messages sent downstream for the re-evaluated P2MP-TE LSP.

   o  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.


   A mid-point LSR MAY send an unsolicited PathErr message with
   "Preferable P2MP-TE Tree Exists" PathErr to the ingress node to
   notify of a preferred 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.

   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 and upon receiving this
   PathErr, the ingress node MAY trigger re-optimization of the LSP
   using a different LSP-ID.

3.2.  Sub-Group-Based Re-optimization Using Markers

   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.

   An ingress node may trigger path re-evaluation requests using the
   procedures defined in [RFC4736] for a set of S2L sub-LSPs by
   combining multiple Path messages using an 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 (with Error code 25, sub-code 6,
   Preferable Path Exists) containing a list of S2L sub-LSPs transiting
   through the LSR using an S2L sub-LSP descriptor list 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



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   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 Object.  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 Object.

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

4.  Message and Object Definitions

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.

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





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   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.

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



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   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.  IANA Considerations

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

6.1.  P2MP-TE Tree Re-evaluation Request Flag

   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).  From the
   registries in this name space "Attribute Flags", allocation of new
   flag is requested (Section 4.1).

   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   |
   +--------+---------------+---------+---------+---------+------------+



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

   IANA maintains a name space for RSVP protocol parameters "Resource
   Reservation Protocol (RSVP) Parameters" (see
   http://www.iana.org/assignments/rsvp-parameters).  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).

   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 for this PathErr as follows:



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   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  |
   +----------+--------------------+---------+---------+-----------+


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

   IANA maintains a name space for RSVP protocol parameters "Resource
   Reservation Protocol (RSVP) Parameters" (see
   http://www.iana.org/assignments/rsvp-parameters).  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
   C-Types is requested (Section 4.3).

   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:


   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   |
   +---------------+---------------------------+-----------------+
















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7.  Security Considerations

   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, and for a mid-point LSR to notify the ingress node
   of the existence of a preferable tree by sending a PathErr.  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 preserve confidentiality
   across domains.  Furthermore, an ingress node may decide to ignore
   this PathErr message coming from a mid-point LSR residing in another
   domain.  Similarly, a mid-point LSR may decide to ignore the P2MP-TE
   tree re-evaluation request originating from another ingress domain.

   This document also defines markers to indicate beginning and end of
   an S2L sub-LSP descriptor list when combining large number of S2L
   sub-LSPs in an RSVP message and the message needs to be fragmented.
   The introduction of these markers, by themselves, introduce no
   additional information to signaling.  For a general discussions on
   MPLS and GMPLS related security issues, see the MPLS/GMPLS security
   framework [RFC5920].






























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8.  References

8.1.  Normative References

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

   [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.

   [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.

   [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.


8.2.  Informative References

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

   [RFC5920]  Fang, L., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, July 2010.












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Acknowledgments

   The authors would like to thank Loa Andersson, Sriganesh Kini, Curtis
   Villamizar, Dimitri Papadimitriou and Nobo Akiya for reviewing this
   document.  The authors would also like to thank Ling Zeng for
   implementing mechanisms defined in this document.


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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