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Versions: 00 01 02 03 draft-ietf-mpls-tp-aps-updates

MPLS Working Group                                               J. Ryoo
Internet-Draft                                                 T. Cheung
Updates: 7271 (if approved)                                         ETRI
Intended status: Standards Track                         H. van Helvoort
Expires: April 19, 2016                                   Hai Gaoming BV
                                                                 I. Busi
                                                                 G. Weng
                                                     Huawei Technologies
                                                        October 17, 2015


    Updates to MPLS Transport Profile (MPLS-TP) Linear Protection in
               Automatic Protection Switching (APS) Mode
                 draft-ryoo-mpls-tp-aps-updates-01.txt

Abstract

   This document contains updates to MPLS Transport Profile (MPLS-TP)
   linear protection in Automatic Protection Switching (APS) mode
   defined in RFC 7271.  The updates provide rules related to the
   initialization of the Protection State Coordination (PSC) Control
   Logic, in which the state machine resides, when operating in APS
   mode.

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 April 19, 2016.

Copyright Notice

   Copyright (c) 2015 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



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   (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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   3
   3.  Updates . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Initialization Behavior . . . . . . . . . . . . . . . . .   3
     3.2.  State Transition Modification . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   MPLS Transport Profile (MPLS-TP) linear protection in Automatic
   Protection Switching (APS) mode is defined in RFC 7271 [RFC7271].
   The actions being performed at the initialization of the Protection
   State Coordination (PSC) Control Logic are not described in either
   [RFC7271] or RFC 6378 [RFC6378].  Although it is a common perception
   that the state machine starts at the Normal state (but, not
   explicitly specified in any of the documents), various questions have
   been raised concerning the detailed actions that the PSC Control
   Logic should take.

   The state machine described in [RFC7271] operates under the
   assumption that both end nodes of linear protection domain start in
   the Normal state.  In the case that one node reboots while the other
   node is still in operation, various scenarios may arise resulting in
   problematic situations.  This document is intended to resolve all the
   problematic cases and to minimize traffic disruptions related to
   initialization including both cold and warm reboots that require re-
   initialization of the PSC Control Logic.

   This document contains updates to the MPLS Transport Profile (MPLS-
   TP) linear protection in Automatic Protection Switching (APS) mode
   defined in [RFC7271].  The updates provide rules related to
   initialization of the PSC Control Logic, in which the state machine
   resides, when operating in APS mode.  The updates also include



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   modifications to the state transition table defined in Section 11.2
   of [RFC7271].  The changes in the state transition table were
   examined to make sure that they do not introduce any new problems.

   This document does not introduce backward compatibility issues with
   implementations of [RFC7271].  In case a node implementing this
   document restarts, the new state changes will not cause problems at
   the remote node implementing [RFC7271] and the two ends will converge
   to the same local and remote states.  In case a node implementing
   [RFC7271] restarts, the two ends behave as of today.

   The reader of this document is assumed to be familiar with [RFC7271].
   This document shares the acronyms defined in Section 3 of [RFC7271].

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 RFC 2119 [RFC2119].

3.  Updates

   This document updates [RFC7271] by specifying the actions that will
   be performed at the initialization of the PSC Control Logic and
   modifies the state transition table defined in Section 11.2 of
   [RFC7271].

3.1.  Initialization Behavior

   When the PSC Control Logic is initialized, the following actions MUST
   be performed:

   o  Stop the WTR timer if it is running.

   o  Clear any operator command in the Local Request Logic.

   o  If an SF-W or SF-P exists as the highest local request, transit to
      the PF:W:L or UA:P:L state, respectively.

   o  When the node being initialized has no local request:

      *  If the node being initialized does not remember the active path
         or if the node being initialized remembers the working path as
         the active path, send NR(0,0) in Normal state.

      *  If the node being initialized remembers the protection path as
         the active path, send either NR(0,1) in WTR state or DNR(0,1)
         in DNR state depending on the configuration.



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   o  Any local SD MUST be ignored and the detection of a local SD MUST
      be (re-)started after the local node completes the initialization
      and responds to the first protocol message received from the
      remote node.

   o  When the local node receives an EXER message as the first protocol
      message after rebooting and the remote EXER becomes the top-
      priority global request, align the position of the bridge and
      selector with the Path value in the EXER message and transit to
      the E::R state .

   Remembering the active path in case of no local request is intended
   to minimize traffic switchovers in case that the other node is still
   in operation and does not cause any problem even if the remembered
   active path is not valid any more due to any local input at the other
   node while the initializing node is out of operation.

   Note that while the local SD input is being ignored and there exist
   no other local requests, the local node restats with no local
   request.  Since the equal priority resolution stated in Section 7.4
   of [RFC7271] does not converge when the active paths that two nodes
   remember are different from each other.  an SD detection needs to be
   (re-)started after both nodes converge to the same view on their
   active paths.

   It is worth noting that in some restart scenarios (e.g., cold
   rebooting), no valid SF/SD indications may be present at the input of
   the Local Request logic.  In this case, the PSC Control Logic would
   restart as if no local requests are present.  If a valid SF/SD
   indication is detected later on, this would be notified to the PSC
   Control Logic and trigger state change.

3.2.  State Transition Modification

   State transition by remote message defined in Section 11.2 of
   [RFC7271] MUST be modified as follows (only modified cells are
   shown):

           | MS-W    | MS-P    | WTR | EXER | RR | DNR  | NR
   --------+---------+---------+-----+------+----+------+----
   N       |         |         | (13)|      |    | DNR  |
   PF:W:R  |         |         |     |      |    | DNR  |
   PF:DW:R |         |         |     |      |    | DNR  |








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4.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

5.  Security Considerations

   No specific security issue is raised in addition to those ones
   already documented in [RFC7271]

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC7271]  Ryoo, J., Ed., Gray, E., Ed., van Helvoort, H.,
              D'Alessandro, A., Cheung, T., and E. Osborne, "MPLS
              Transport Profile (MPLS-TP) Linear Protection to Match the
              Operational Expectations of Synchronous Digital Hierarchy,
              Optical Transport Network, and Ethernet Transport Network
              Operators", RFC 7271, DOI 10.17487/RFC7271, June 2014,
              <http://www.rfc-editor.org/info/rfc7271>.

6.2.  Informative References

   [RFC6378]  Weingarten, Y., Ed., Bryant, S., Osborne, E., Sprecher,
              N., and A. Fulignoli, Ed., "MPLS Transport Profile (MPLS-
              TP) Linear Protection", RFC 6378, DOI 10.17487/RFC6378,
              October 2011, <http://www.rfc-editor.org/info/rfc6378>.

Authors' Addresses

   Jeong-dong Ryoo
   ETRI

   EMail: ryoo@etri.re.kr


   Taesik Cheung
   ETRI

   EMail: cts@etri.re.kr



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   Huub van Helvoort
   Hai Gaoming BV

   EMail: huubatwork@gmail.com


   Italo Busi
   Huawei Technologies

   EMail: Italo.Busi@huawei.com


   Guangjuan Weng
   Huawei Technologies

   EMail: wenguangjuan@huawei.com



































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