[Docs] [txt|pdf] [Tracker] [WG] [Email] [Nits] [IPR]

Versions: 00 01 02 03 draft-ietf-mpls-p2mp-loose-path-reopt

MPLS Working Group                                            Tarek Saad
Internet-Draft                                             Rakesh Gandhi
Intended status: Informational                                 Zafar Ali
Expires: July 28, 2014                               Cisco Systems, Inc.
                                                       Robert H. Venator
                                      Defense Information Systems Agency
                                                             Yuji Kamite
                                          NTT Communications Corporation
                                                        January 24, 2014


       Reoptimization of Point-to-Multipoint Traffic Engineering
                          Loosely Routed LSPs

             draft-tsaad-mpls-p2mp-loose-path-reopt-00.txt


Abstract

   This document defines signaling extensions to Resource
   Reservation Protocol - Traffic Engineering (RSVP-TE) for reoptimizing
   loosely routed point-to-multipoint (P2MP) Traffic Engineered (TE)
   Label Switched Path (LSP) in an Multi-Protocol Label Switching (MPLS)
   and Generalized MPLS (GMPLS) networks.


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/.

   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
   material or to cite them other than as "work in progress."











Saad, et al.             Expires July 28, 2014                  [Page 1]


Internet-Draft  Reoptimizing P2MP-TE Loosely Routed LSP January 24, 2014


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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.










Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1 Conventions used in this document  . . . . . . . . . . . . .  4
   3. Procedure for Reoptimization of a Loosely Routed P2MP-TE LSP  .  4
   4. RSVP Signaling Extensions . . . . . . . . . . . . . . . . . . .  5
     4.1.  P2MP-TE Tree Re-evaluation Request . . . . . . . . . . . .  5
     4.2.  Preferable P2MP-TE Tree Exists Error sub-code  . . . . . .  5
   5.  Compatibility  . . . . . . . . . . . . . . . . . . . . . . . .  6
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  6
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  6
     7.1 P2MP-TE Tree Re-evaluation Request Flag  . . . . . . . . . .  6
     7.2 Preferable P2MP-TE Tree Exists sub-code  . . . . . . . . . .  7
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  7
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     8.1.  Normative References . . . . . . . . . . . . . . . . . . .  7
     8.2.  Informative References . . . . . . . . . . . . . . . . . .  7
   Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . .  8








Saad, et al.             Expires July 28, 2014                  [Page 2]


Internet-Draft  Reoptimizing P2MP-TE Loosely Routed LSP January 24, 2014


1.  Introduction

   This document defines RSVP signaling extensions for the
   reoptimization of loosely routed point-to-multipoint (P2MP) MPLS and
   GMPLS (Generalized Multiprotocol Label Switching) Traffic Engineered
   (TE) Label Switched Path (LSP).

   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 at the time of its signaling by the
   ingress node. Such an S2L sub-LSP is signaled with no Explicit Route
   Object (ERO), 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).

   [RFC4736] defines RSVP signaling extensions for reoptimizing loosely
   routed P2P TE LSP(s). Specifically, an ingress node sends a "path re-
   evaluation request" to a border node by setting a flag (0x20) in
   SESSION_ATTRIBUTES object in the Path message. A border node sends a
   PathErr code 25 (notify error defined in [RFC3209]) with sub-code 6
   to indicate "preferable path exists" to the ingress node. The ingress
   node upon receiving this PathErr initiates reoptimization of the LSP.

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

   [RFC4736] does not define signaling extensions specific for
   reoptimizing entire P2MP-TE LSP tree. Mechanisms defined in [RFC4736]
   can be used for signaling the reoptimization of individual S2L sub-
   LSP(s). However, to use [RFC4736] mechanisms for reoptimizing an
   entire P2MP-TE LSP tree, an ingress node needs to send the query on
   all (typically 100s of) S2L sub-LSPs and a border node needs to
   notify PathErrs for all S2L sub-LSPs. In addition, a border node has
   to accumulate the received queries on all S2L sub-LSPs (using a wait
   timer) and interpret them as a reoptimization request for the P2MP-TE
   LSP tree. Furthermore, when the ingress node gradually receives
   unsolicited PathErr(s) notifications for individual S2L sub-LSP(s),
   it may prematurely start reoptimizing these sub-set of sub-LSPs.
   However, as mentioned in [RFC4875] Section 14.2, such reoptimization
   procedure may result in data duplication that can be avoided if the
   entire P2MP-TE LSP tree is reoptimized, especially if the ingress
   node eventually receives PathErr(s) notifications for all S2L sub-
   LSP(s) of the P2MP-TE LSP tree. In such cases, the ingress node may
   have to heuristically determine when to perform P2MP-TE LSP tree
   reoptimization or per S2L sub-LSP reoptimization, for example, to



Saad, et al.             Expires July 28, 2014                  [Page 3]


Internet-Draft  Reoptimizing P2MP-TE Loosely Routed LSP January 24, 2014


   wait long enough time to accumulate all PathErr(s) to be received.
   Such methods may produce undesired results that can be avoided by the
   proposed RSVP signaling extensions in this draft.

   This document defines required RSVP signaling extensions to query and
   notify for reoptimizing loosely routed P2MP-TE LSP tree.

2.  Terminology

   ABR: Area Border Router.

   ERO: Explicit Route Object.

   TE LSP: Traffic Engineering Label Switched Path.

   TE LSP ingress: head/source of the TE LSP.

   TE LSP egress: tail/destination of the TE LSP.

   S2L: Source-to-leaf.

   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).

2.1 Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119]. The reader
   is assumed to be familiar with the terminology in [RFC4875] and
   [RFC4736].

3. Procedure for Reoptimization of a Loosely Routed P2MP-TE LSP

   As per [RFC4875], an ingress node may prefer to reoptimize the entire
   P2MP-TE LSP by resignaling all its S2L sub-LSP(s) (Section 14.1,
   "Make-before- Break") or reoptimize individual S2L sub-LSP(s) i.e.
   individual destination(s) (Section 14.2 "Sub-Group-Based Re-
   Optimization").

   Procedures defined in [RFC4736] are used by an ingress node to
   reoptimize the S2L sub-LSP individually.



Saad, et al.             Expires July 28, 2014                  [Page 4]


Internet-Draft  Reoptimizing P2MP-TE Loosely Routed LSP January 24, 2014


   To reoptimize entire P2MP-TE LSP tree, in order to query border nodes
   to check if a preferable P2MP-TE LSP tree exists, an ingress node
   sends a Path message with "P2MP-TE Tree Re-evaluation Request"
   defined in this document.

   A border node receiving the "P2MP-TE Tree Re-evaluation Request"
   checks for a preferable P2MP-TE LSP tree by re-evaluating loosely
   expanded paths for all S2L sub-LSP(s) of the P2MP-TE LSP. If a
   preferable P2MP-TE LSP tree is found, the border node immediately
   sends 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". At this point, the border node does
   not propagate this bit in subsequent RSVP Path messages sent
   downstream for the re-evaluated TE LSP. The sending of an RSVP
   PathErr Notify message "Preferable P2MP-TE Tree Exists" to the
   ingress node will notify the ingress node of the existence of a
   preferable P2MP-TE LSP tree. If no preferable path can be found, the
   recommended mode is for the border node to relay the request (by
   setting the "P2MP-TE Tree Re-evaluation Request" bit in the
   LSP_ATTRIBUTES TLV of RSVP path message sent downstream).

   A border node MAY also send "Preferable P2MP-TE Tree Exists" with
   PathErr code 25 to the ingress node to reoptimize the entire P2MP-TE
   LSP tree with an unsolicited PathErr message.

4. RSVP Signaling Extensions

4.1.  P2MP-TE Tree Re-evaluation Request

   In order to query border nodes to check if a preferable P2MP-TE LSP
   tree exists, 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 an S2L sub-LSP and is inserted by the ingress node.

4.2.  Preferable P2MP-TE Tree Exists Error sub-code

   In order to indicate to an ingress node that a preferable P2MP-TE LSP
   tree is available, 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




Saad, et al.             Expires July 28, 2014                  [Page 5]


Internet-Draft  Reoptimizing P2MP-TE Loosely Routed LSP January 24, 2014


   When a preferable P2MP-TE LSP tree is found, the border node MUST
   send "Preferable P2MP-TE Tree Exists" PathErr to the ingress node in
   order to reoptimize the entire P2MP-TE LSP.

5.  Compatibility

   The LSP_ATTRIBUTES TLV 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,
   unexamined and unmodified, in all messages resulting from this
   message.

6.  Security Considerations

   This document does not introduce any additional security issues above
   those identified in [RFC3209] and [RFC4875].

7.  IANA Considerations

   IANA maintains a name space for RSVP-TE TE parameters "Resource
   Reservation Protocol-Traffic Engineering (RSVP-TE) Parameters". From
   the registries in this name space "Attribute Flags" allocation of new
   flag is requested (sections 4.1).

   IANA also maintains a name space for RSVP protocol parameters
   "Resource Reservation Protocol (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).

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 values are to be
   assigned by IANA.

   o  P2MP-TE Tree Re-evaluation Request Flag:

        - Bit Number: To be assigned by IANA.

        - Attribute flag carried in Path message: Yes

        - Attribute flag carried in Resv message: No







Saad, et al.             Expires July 28, 2014                  [Page 6]


Internet-Draft  Reoptimizing P2MP-TE Loosely Routed LSP January 24, 2014


7.2 Preferable P2MP-TE Tree Exists 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 for Notify PathErr code 25. To be assigned by
         IANA.

8.  Acknowledgments

        TBA.

8.  References

8.1.  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.

8.2.  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.





Saad, et al.             Expires July 28, 2014                  [Page 7]


Internet-Draft  Reoptimizing P2MP-TE Loosely Routed LSP January 24, 2014


Author's Addresses


   Tarek Saad
   Cisco Systems

   Email: tsaad@cisco.com


   Rakesh Gandhi
   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




















Saad, et al.             Expires July 28, 2014                  [Page 8]


Html markup produced by rfcmarkup 1.129b, available from https://tools.ietf.org/tools/rfcmarkup/