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Network Working Group                                          A. Takacs
Internet-Draft                                               F. Fondelli
Intended status: Standards Track                             B. Tremblay
Expires: April 28, 2011                                         Ericsson
                                                        October 25, 2010


GMPLS RSVP-TE Recovery Extension for data plane initiated reversion and
                      protection timer signalling
                   draft-takacs-ccamp-revertive-ps-05

Abstract

   GMPLS RSVP-TE recovery extensions are specified in [RFC4872] and
   [RFC4873].  Currently recovery signalling does not support the
   request for revertive protection, neither the configuration of
   recovery timers.  This document extends the PROTECTION Object format
   allowing sub-TLVs, and defines two sub-TLVs to carry wait-to-restore
   and hold-off intervals.
































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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

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
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   This Internet-Draft will expire on April 28, 2011.

Copyright Notice

   Copyright (c) 2010 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
   2.  Updated PROTECTION Object format and sub-TLVs  . . . . . . . .  6
   3.  Error handling . . . . . . . . . . . . . . . . . . . . . . . .  8
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12










































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1.  Introduction

   Generalised MPLS (GMPLS) extends MPLS to include support for
   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 disregard 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
   [RFC4426][RFC4872].

   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-
   revertive).

   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
   situation.

   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
   information.

   This document extends the PROTECTION Object format allowing sub-TLVs,
   and defines two sub-TLVs to carry WTR and HOFF values.










































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2.  Updated PROTECTION Object format and sub-TLVs

   In [RFC4872] and [RFC4873] the PROTECTION object is specified to
   support end-to-end and segment recovery.  In order to ease addition
   of protection attributes the PROTECTION Object is extended to carry
   sub-TLVs.  The new format updates the PROTECTION Object format of
   C-Type 2.  The updated format is depicted below.  IANA is requested
   to maintain the TLV space for the PROTECTION Object.

   We retained C-Type to ensure that nodes not capable of interpreting
   the new format (sub-TLVs) will still be able to process the object
   without being required to generate an error; while nodes recognising
   the new format will process the TLVs accordingly.  The processed sub-
   TLV MUST be included in the PROTECTION Object sent in the Resv
   message upstream, to ensure that the sender can maintain a consistent
   view of the actual protection configuration of the LSP.


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Length             | Class-Num(37) |   C-Type(2)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |S|P|N|O| Reserved  | LSP Flags |      Reserved     | Link Flags|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |I|R|   Reserved    | Seg.Flags |           Reserved            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                           sub-TLVs                            ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This document specifies two new sub-TLVs.

   WTR - Wait-to-Restore time sub-TLV specifies the WTR time.  If the
   WTR field is 0 the protection switching operation mode is non-
   revertive, otherwise revertive operation with the signalled timer (in
   milliseconds) is requested.  The value 0xffffffff is reserved, and
   refers to a locally pre-configured WTR value.


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Type (1) (IANA)     |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              WTR                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   HOFF - Hold-off time sub-TLV specifies the HOFF time.  The values are
   in milliseconds.  The value 0xffffffff is reserved, and refers to a
   locally pre-configured HOFF value.


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Type (2) (IANA)     |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             HOFF                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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 TLV space needs to be opened and maintained for the 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-PBBTE]
              "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
   Ericsson
   Laborc u. 1.
   Budapest,   1037
   Hungary

   Email: attila.takacs@ericsson.com


   Francesco Fondelli
   Ericsson
   Via Negrone
   Genova,   16153
   Italy

   Email: francesco.fondelli.ericsson.com


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

   Email: benoit.c.tremblay@ericsson.com
























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