Pseudowire Preferential Forwarding Status Bit
RFC 6870

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Internet Engineering Task Force (IETF)                     P. Muley, Ed.
Request for Comments: 6870                              M. Aissaoui, Ed.
Updates: 4447                                             Alcatel-Lucent
Category: Standards Track                                  February 2013
ISSN: 2070-1721

             Pseudowire Preferential Forwarding Status Bit

Abstract

   This document describes a mechanism for signaling the active and
   standby status of redundant Pseudowires (PWs) between their
   termination points.  A set of Redundant PWs is configured between
   Provider Edge (PE) nodes in single-segment pseudowire (SS-PW)
   applications or between Terminating Provider Edge (T-PE) nodes in
   Multi-Segment Pseudowire (MS-PW) applications.

   In order for the PE/T-PE nodes to indicate the preferred PW to use
   for forwarding PW packets to one another, a new status bit is
   defined.  This bit indicates a Preferential Forwarding status with a
   value of active or standby for each PW in a redundant set.

   In addition, a second status bit is defined to allow peer PE nodes to
   coordinate a switchover operation of the PW.

   Finally, this document updates RFC 4447 by adding details to the
   handling of the PW status code bits in the PW Status TLV.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6870.

Muley & Aissaoui             Standards Track                    [Page 1]
RFC 6870          PW Preferential Forwarding Status Bit    February 2013

Copyright Notice

   Copyright (c) 2013 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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Muley & Aissaoui             Standards Track                    [Page 2]
RFC 6870          PW Preferential Forwarding Status Bit    February 2013

Table of Contents

   1. Introduction ....................................................4
      1.1. Requirements Language ......................................4
   2. Motivation and Scope ............................................4
   3. Terminology .....................................................7
   4. PE Architecture .................................................9
   5. Modes of Operation ..............................................9
      5.1. Independent Mode ...........................................9
      5.2. Master/Slave Mode .........................................12
   6. PW State Transition Signaling Procedures .......................14
      6.1. PW Standby Notification Procedures in Independent Mode ....14
      6.2. PW Standby Notification Procedures in Master/Slave Mode ...15
           6.2.1. PW State Machine ...................................16
      6.3. Coordination of PW Switchover .............................17
           6.3.1. Procedures at the Requesting Endpoint ..............18
           6.3.2. Procedures at the Receiving Endpoint ...............20
   7. Status Mapping .................................................20
      7.1. AC Defect State Entry/Exit ................................21
      7.2. PW Defect State Entry/Exit ................................21
   8. Applicability and Backward Compatibility .......................21
   9. Security Considerations ........................................22
   10. MIB Considerations ............................................22
   11. IANA Considerations ...........................................22
      11.1. Status Code for PW Preferential Forwarding Status ........22
      11.2. Status Code for PW Request Switchover Status .............23
   12. Contributors ..................................................23
   13. Acknowledgments ...............................................24
   14. References ....................................................24
      14.1. Normative References .....................................24
      14.2. Informative References ...................................24