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Network Working Group                                          A. Takacs
Internet-Draft                                               B. Tremblay
Intended status: Standards Track                                Ericsson
Expires: January 8, 2009                                    July 7, 2008


  GMPLS RSVP-TE recovery extension for data plane initiated reversion
                   draft-takacs-ccamp-revertive-ps-00

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Copyright Notice

   Copyright (C) The IETF Trust (2008).














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Abstract

   RSVP-TE recovery extensions are specified in [RFC4872] and [RFC4873].
   Currently these extensions cannot signal request for revertive
   protection to the remote endpoint.  This document defines a new bit
   to signal this request and a new field to specify a wait-to-restore
   interval.












































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Requirements Language

   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


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  PROTECTION object extension  . . . . . . . . . . . . . . . . .  6
   3.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   5.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
   Intellectual Property and Copyright Statements . . . . . . . . . . 11



































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1.  Introduction

   Reversion refers to the process of moving normal traffic back to the
   original working LSP after the failure is cleared and the path is
   repaired [RFC4426][RFC4427][RFC4872].  Reversion is desirable since
   the protection path may not be optimal from a routing and resource
   consumption point of view, additionally, moving traffic back to the
   working LSP allows the protection resources to be used to protect
   other LSPs.  On the other hand, reversion requires that the working
   resources remain allocated during failure.  The operator needs to
   have the choice between revertive and non-revertive protection to
   balance the pros and cons in a given situation.

   [RFC4426] and [RFC4872] describes control plane signalling procedures
   for reversion.  This signaling can be used to initiate the actual
   reversion in the data plane; or simply to synchronise control plane
   states after data plane actions.  This latter case, when
   independently from the control plane, data plane mechanisms
   autonomously initiate reversion is not detailed further in the
   documents.

   [RFC4426] and [RFC4872] assumed that signalling the revertive
   property of protection is not needed between protection endpoints.
   This assumption holds for uni- and bidirectional LSPs in the
   following cases.

   o  The control plane is responsible to execute reversion and trigger
      data plane switch-over.

   o  In the case of data plane initiated reversion there is a dedicated
      protocol for protection switching (e.g., Automatic Protection
      Switching (APS)) synchronising the switch-over of the data plane
      endpoints.

   In these cases, only one side: the ingress LER needs to be provided
   with information about the revertive property of protection.  Hence,
   there is no need to signal any information in RSVP-TE to the remote
   endpoint.

   However, GMPLS may be applied in a scenario where the data plane
   autonomously executes reversion but it has no mechanism to
   communicate the revertive property of protection between the
   endpoints.  Such an example is protection switching of bidirectional
   connections in Ethernet PBB-TE [IEEE-PBBTE] (currently under
   standardisation in IEEE).  In this case revertiveness needs to be
   signalled by RSVP-TE during LSP establishment to properly setup the
   remote data plane endpoint.  Further, although wait-to-restore (WTR)
   intervals may be pre-configured, it may be beneficial to signal the



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   desired WTR value as well.


















































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2.  PROTECTION object extension

   In [RFC4872] and [RFC4873] the PROTECTION object is specified to
   support end-to-end and segment recovery.  This document introduces a
   new bit: "V" Revertive; to signal that the protection requested is to
   be revertive.  The "V" bit can only be set if the "N" Notification is
   set as well.  Once the data plane autonomously initiated reversion,
   it notifies the control plane which then can invoke the signalling
   specified in [RFC4872] to syncronise control plane LSP states to
   reflect the actual path taken by normal traffic.

   In order that traffic is not switched back and fort between worker
   and protection LSPs during transients, a wait to restore (WTR) timer
   is usually applied delaying the reversion until the recovered path is
   considered stable again.  To support autonomous data plane recovery,
   the wait to restore time can be signalled in the new WTR field.  The
   WTR field defines the wait to restore delay in minutes.  The
   additions to the PROTECTION object are depicted below.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |S|P|N|O|V| Reserved| LSP Flags |  Reserved |  WTR  | Link Flags|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   V - Revertive bit, when set the protection is to be revertive, and if
   supported the data plane should be configured to autonomously execute
   reversion.

   WTR - Wait to Restore, it specifies the WTR delay before reversion in
   minutes.




















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3.  IANA Considerations

   This document specifies a new bit "V" and a new field "WTR" to be
   carried in the PROTECTION object.















































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4.  Security Considerations

   This document introduces no new security issues.  The considerations
   in [RFC4872] and [RFC4873] apply.















































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5.  References

   [IEEE-PBBTE]
              "IEEE 802.1Qay Draft Standard for Provider Backbone
              Bridging Traffic Engineering",  work in progress.

   [RFC4426]  "Generalized Multi-Protocol Label Switching (GMPLS)
              Recovery Functional Specification", RFC 4426, March 2006.

   [RFC4427]  "Recovery (Protection and Restoration) Terminology for
              Generalized Multi-Protocol Label Switching (GMPLS)",
              RFC 4427, March 2006.

   [RFC4872]  "RSVP-TE Extensions in Support of End-to-End Generalized
              Multi-Protocol Label Switching (GMPLS) Recovery",
              RFC 4872, May 2007.

   [RFC4873]  "GMPLS Segment Recovery", RFC 4873, May 2007.

































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Authors' Addresses

   Attila Takacs
   Ericsson
   Laborc u. 1.
   Budapest,   1037
   Hungary

   Email: attila.takacs@ericsson.com


   Benoit Tremblay
   Ericsson
   8400 Decarie.
   Montreal, Quebec  H4P 2N2
   Canada

   Email: benoit.c.tremblay@ericsson.com

































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