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Network Working Group                                          A. Takacs
Internet-Draft                                               F. Fondelli
Intended status: Standards Track                             B. Tremblay
Expires: May 7, 2009                                            Ericsson
                                                        November 3, 2008

  GMPLS RSVP-TE recovery extension for data plane initiated reversion

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   GMPLS RSVP-TE recovery extensions are specified in [RFC4872] and
   [RFC4873].  Currently these extensions cannot signal request for
   revertive protection neither values for the associated timers to the
   remote endpoint.  This document defines two new fields in the
   PROTECTION Object to specify wait-to-restore and hold-off intervals.

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Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  PROTECTION object extension  . . . . . . . . . . . . . . . . .  6
   3.  Error handling . . . . . . . . . . . . . . . . . . . . . . . .  7
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
   Intellectual Property and Copyright Statements . . . . . . . . . . 12

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1.  Introduction

   Generalised MPLS (GMPLS) extends MPLS to include support of different
   switching technologies [RFC3471].  These switching technologies
   provide several protection schemes [RFC4426][RFC4427] (e.g. 1+1, 1:N,
   M:N).  Many characteristics of those protection schemes are common
   disregarding of the switching technology (e.g.  TDM, LSC, etc).
   GMPLS RSVP-TE signalling has been extended to support the various
   protection schemes and establish connections (Label Switched Paths
   (LSPs)) configuring its specific protection characteristics

   Currently RSVP-TE extensions do not address the configuration of
   protection switching timers neither provide information on the
   protection switching operation mode (i.e., revertive or non-

   The Hold-off time (HOFF) is defined as the time between the reporting
   of signal fail or degrade, and the initialization of the recovery
   switching operation [RFC4427].  This timer is useful to limit the
   number of switch actions when multiple layers of recovery are being
   used, or in case of 1+1 unidirectional protection scheme [G.808.1] to
   prevent too early switching due to the differential delay difference
   between the short and long path.

   The Wait-to-Restore time (WTR) is defined as a period of time that
   must elapse after a recovered fault before an LSP can be used again
   to transport the normal traffic and/or to select the normal traffic
   from the LSP [RFC4427].  The WTR time is fundamental in revertive
   mode of operation, to prevent frequent operation of the protection
   switch due to an intermittent defect [G.808.1].

   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].  In transport networks
   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

   WTR and HOFF timers must be accurately configured at both ends of the
   LSP.  Operators may need to tune these timers on a per LSP basis to
   ensure best protection switching performance (e.g., account for
   differential delays between worker and protection paths).  Currently

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   these values are either pre-configured to a default value (and so may
   be suboptimal for some of the LSPs) or need to be manually set/tuned
   after the connections have been established.  Since these parameters
   are important for recovery in transport networks, it is desirable
   that GMPLS RSVP-TE protection signalling carries the necessary

   This document adds two new fields to the PROTECTION Object to carry
   WTR and HOFF values.

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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.  Two new fields are defined
   WTR and HOFF.  This is 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| Reserved  | LSP Flags |      Reserved     | Link Flags|
       |I|R|    Reserved   | Seg.Flags | Resv.   |  WTR  |    HOFF     |

   WTR - Wait-to-Restore time field specifies the WTR time.  If the WTR
   field is 0 the protection switching operation modes is non-revertive,
   otherwise revertive operation with the signalled timer is requested.
   9 values for WTR are permitted:

      WTR value        timer
          0      non-revertive mode
          1            5min
         2-7    6-11min in 1min steps
          8            12min

   HOFF - Hold-off time field specifies the HOFF time.  The following
   values are permitted:

      HOFF value           timer
          0              no HOFF
          1               100ms
         2-99    200ms-9900ms with 100ms steps
         100              10sec

   In order to ensure that the new fields are properly handled by the
   nodes a new C-Type (3, IANA to assigned) is used to explicitly
   indicate the presence of WTR and HOFF fields.

   In the case of end-to-end protection the PROTECTION Object is
   inserted at the top level in the Path message, the WTR and HOFF
   fields correspond to the end-to-end protection.  In the case when a
   segment of the LSP is to be protected and the WTR and HOFF timers for
   the protection segment are to be set by signalling, explicit segment
   recovery control has to be used, i.e., the PROTECTION Object with the
   desired timers set must be inserted in the appropriate Secondary
   Explicit Route Object (SERO).

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3.  Error handling

   In the case a specific configuration of the timers is not supported
   the corresponding error should be generated and sent in the PathErr
   message: "Routing Problem/Unsupported WTR value" and/or "Routing
   Problem/Unsupported HOFF value".

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4.  IANA Considerations

   A new C-Type (3) is to be assigned for the modified PROTECTION Object
   in the "Class Names, Class Numbers, and Class Types " Registry.

   New error values need to be added to "Error Codes and Globally-
   Defined Error Value Sub-Codes " Registry for the "Routing Problem"
   Error Code: "Unsupported WTR value" and "Unsupported HOFF value".

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5.  Security Considerations

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

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6.  References

   [G.808.1]  "Generic protection switching -- Linear trail and
              subnetwork protection", ITU-T Recommendation G.808.1,
              March 2006.

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

   [RFC3471]  "Generalized Multi-Protocol Label Switching (GMPLS)
              Signaling Functional Description", RFC 3471, January 2003.

   [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
   Laborc u. 1.
   Budapest,   1037

   Email: attila.takacs@ericsson.com

   Francesco Fondelli
   Via Negrone
   Genova,   16153

   Email: francesco.fondelli.ericsson.com

   Benoit Tremblay
   8400 Decarie.
   Montreal, Quebec  H4P 2N2

   Email: benoit.c.tremblay@ericsson.com

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