Internet DRAFT - draft-he-pce-pcep-associated-lsp-extensions

draft-he-pce-pcep-associated-lsp-extensions






PCE Working Group                                            WJ. He, Ed.
Internet-Draft                                                       ZTE
Intended status: Standards Track                       November 14, 2011
Expires: May 17, 2012


Extensions to the Path Computation Element Communication Protocol (PCEP)
                    for Associated Bidirectional LSP
             draft-he-pce-pcep-associated-lsp-extensions-01

Abstract

   The MPLS Transport Profile (MPLS-TP) requirements document[RFC5654],
   describes that MPLS-TP MUST support associated bidirectional point-
   to-point LSPs.  Path Computation Element (PCE), see [RFC4655], may be
   used for path computation of an associated bidirectional LSP.  This
   document defines the Path Computation Element Protocol (PCEP)-based
   [RFC5440] extensions for associated bidirectional LSP.

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."

   This Internet-Draft will expire on May 17, 2012.

Copyright Notice

   Copyright (c) 2011 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



He                        Expires May 17, 2012                  [Page 1]

Internet-Draft  PCEP Ext for Associated Bidirectional Lsp  November 2011


   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Conventions used in this document . . . . . . . . . . . . . . . 3
   3.  Processing  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     3.1.  Concurrent Computation  . . . . . . . . . . . . . . . . . . 4
     3.2.  Successive Computation  . . . . . . . . . . . . . . . . . . 4
   4.  PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . . 5
     4.1.  Extended ASSOCIATION Object . . . . . . . . . . . . . . . . 5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   7.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     8.1.  Normative  References . . . . . . . . . . . . . . . . . . . 6
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 7































He                        Expires May 17, 2012                  [Page 2]

Internet-Draft  PCEP Ext for Associated Bidirectional Lsp  November 2011


1.  Introduction

   The MPLS Transport Profile (MPLS-TP) requirements [RFC5654] and
   control plane framework documents[RFC6373]describe that MPLS-TP MUST
   support associated bidirectional point-to-point LSPs.  Path
   Computation Element (PCE), see [RFC4655], may be used for path
   computation of a GMPLS LSP, see
   [I-D.ietf-pce-gmpls-pcep-extensions],and consequently an associated
   bidirectional LSP, across domains and in a single domain.

   Dependent path computations are requests that need to be synchronized
   in order to meet specific objectives, see [RFC6007].  For associated
   bidirectional LSP, if the forward LSP and the backward LSP are
   computed concurrently, the PCE can find the optimum path.

   This document defines the Path Computation Element Protocol (PCEP)-
   based [RFC5440] extensions for associated bidirectional LSP.


2.  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].


3.  Processing

   Consider the topology described in Figure 1.  (An example of
   associated bidirectional LSP).  The LSP1 [via nodes A,D,B] (from A to
   B) and LSP2 [via nodes B,D,C,A] (from B to A) need to be established,
   which can form an associated bidirectional LSP deployed by Single
   Sided Provisioning model or Double Sided Provisioning
   model[I-D.ietf-ccamp-mpls-tp-rsvpte-ext-associated-lsp].  Node A, the
   ingress LSR of LSP1, can play the role of a PCC and request the PCE
   to compute the LSP1 or the associated bidirectional LSP.


                                A-------D-------B
                                 \     /
                                  \   /
                                   \ /
                                    C


           Figure 1 : An example of associated bidirectional LSP

   The path computation for associated bidirectional LSP can be realized



He                        Expires May 17, 2012                  [Page 3]

Internet-Draft  PCEP Ext for Associated Bidirectional Lsp  November 2011


   by the concurrent or successive computation.  The concurrent
   computation means that the head-end submits the computation request
   for both two directional LSPs concurrently, which is applicable to
   the Single Sided Provisioning model.  As to the successive
   computation, the head-end and the tail-end send the forward LSP and
   backward LSP computation requests separately, which is applicable to
   both the Single Sided Provisioning model and the Double Sided
   Provisioning model.

3.1.  Concurrent Computation

   The PCC sends the PCReq message to PCE for computing an associated
   bidirectional LSP, whose forward and backward paths are computed
   concurrently.  Concurrent computation can ensure that the paths for
   the associated bidirectional LSP is optimal [RFC5557].

   The SVEC object described in [RFC6007] can be used to synchronize the
   requests about the forward and backward LSPs, and get the optimal
   path for the associated bidirectional LSP.

3.2.  Successive Computation

   For the Successive computation, the PCCs submit the path computation
   request for the forward LSP and the backward LSP separately, then,
   the path for the associated bidirectional LSP may be not optimal.  So
   that the two reverse LSPs should be associated, the ASSOCIATION
   object [I-D.ietf-ccamp-assoc-ext]may be useful.  The stateful PCE
   [RFC4655] can coordinate the two reverse LSPs to get the optimal path
   for the associated bidirectional LSP through the ASSOCIATION object,
   if both the head-end and the tail-end PCCs delegate their respective
   LSPs (forward and backward) to the PCE .

   When the PCC submits the path computation request for the forward LSP
   or the backward LSP, the PCReq message may carry Extended ASSOCIATION
   object to indicate there is a reverse LSP to be associated, see
   [I-D.ietf-ccamp-mpls-tp-rsvpte-ext-associated-lsp].  At the same
   time, both the head-end and the tail-end PCCs delegate their
   respective LSPs (forward and backward) to the PCE using PCRpt
   messages[I-D.crabbe-pce-stateful-pce].

   Upon receipt of the PCReq message,the PCE will locate the reverse LSP
   with the same association information.  If there is no matched
   reverse LSP, the PCE will compute the LSP independently.  Otherwise,
   the PCE will coordinate the two reverse LSPs and compute path for the
   associated bidirectional LSP.  After the successful computation, the
   PCE will trigger the head-end to setup the forward LSP and the tail-
   end to setup the backward LSP using PCUpd messages.  The PCC will use
   make-before-break whenever possible in the re-signaling



He                        Expires May 17, 2012                  [Page 4]

Internet-Draft  PCEP Ext for Associated Bidirectional Lsp  November 2011


   operation,[I-D.crabbe-pce-stateful-pce].


4.  PCEP Extensions

4.1.  Extended ASSOCIATION Object

   The Extended ASSOCIATION Object is used to associate the two reverse
   LSPs, which form an associated bidirectional LSP.  The Extended
   ASSOCIATION Object is carried within a PCRep message to locate the
   reverse LSP, and the PCE will coordinate the forward LSP and the
   backward LSP to get the optimal path for the associated bidirectional
   LSP.

   The contents of this object are identical in encoding to the contents
   of the RSVP-TE Extended ASSOCIATION Object defined in
   [I-D.ietf-ccamp-assoc-ext] and
   [I-D.ietf-ccamp-mpls-tp-rsvpte-ext-associated-lsp].

   PCEP Extended ASSOCIATION object types correspond to RSVP-TE Extended
   ASSOCIATION object types.

   Extended ASSOCIATION Object-Class is TBD.

   Extended ASSOCIATION Object-Type is TBD.


5.  IANA Considerations

   TBD


6.  Security Considerations

   TBD


7.  Acknowledgement

   The author would like to thank Jan Medved for his valuable comments
   on the double sided provisioning, Cyril for the discussion of the
   concurrent computation.  At the same time, the author would also like
   to acknowledge the contributions of Fei Zhang for the discussions.


8.  References





He                        Expires May 17, 2012                  [Page 5]

Internet-Draft  PCEP Ext for Associated Bidirectional Lsp  November 2011


8.1.  Normative  References

   [I-D.crabbe-pce-stateful-pce]
              Crabbe, E., Medved, J., and R. Varga, "PCEP Extensions for
              Stateful PCE", draft-crabbe-pce-stateful-pce-01 (work in
              progress), October 2011.

   [I-D.ietf-ccamp-assoc-ext]
              Berger, L., Faucheur, F., and A. Narayanan, "RSVP
              Association Object Extensions",
              draft-ietf-ccamp-assoc-ext-01 (work in progress),
              October 2011.

   [I-D.ietf-ccamp-mpls-tp-rsvpte-ext-associated-lsp]
              Zhang, F. and R. Jing, "RSVP-TE Extensions for Associated
              Bidirectional LSPs",
              draft-ietf-ccamp-mpls-tp-rsvpte-ext-associated-lsp-02
              (work in progress), October 2011.

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

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

8.2.  Informative References

   [I-D.ietf-pce-gmpls-pcep-extensions]
              Margaria, C., Dios, O., and F. Zhang, "PCEP extensions for
              GMPLS", draft-ietf-pce-gmpls-pcep-extensions-04 (work in
              progress), October 2011.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655, August 2006.

   [RFC5557]  Lee, Y., Le Roux, JL., King, D., and E. Oki, "Path
              Computation Element Communication Protocol (PCEP)
              Requirements and Protocol Extensions in Support of Global
              Concurrent Optimization", RFC 5557, July 2009.

   [RFC5654]  Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
              and S. Ueno, "Requirements of an MPLS Transport Profile",
              RFC 5654, September 2009.

   [RFC6007]  Nishioka, I. and D. King, "Use of the Synchronization
              VECtor (SVEC) List for Synchronized Dependent Path
              Computations", RFC 6007, September 2010.



He                        Expires May 17, 2012                  [Page 6]

Internet-Draft  PCEP Ext for Associated Bidirectional Lsp  November 2011


   [RFC6373]  Andersson, L., Berger, L., Fang, L., Bitar, N., and E.
              Gray, "MPLS Transport Profile (MPLS-TP) Control Plane
              Framework", RFC 6373, September 2011.


Author's Address

   Wenjuan He (editor)
   ZTE

   Email: he.wenjuan1@zte.com.cn








































He                        Expires May 17, 2012                  [Page 7]