Virtual Circuit Connectivity Verification (VCCV) Capability Advertisement for MPLS Transport Profile (MPLS-TP)
RFC 7189

Internet Engineering Task Force (IETF)                         G. Mirsky
Request for Comments: 7189                                      Ericsson
Category: Standards Track                                     March 2014
ISSN: 2070-1721

            Virtual Circuit Connectivity Verification (VCCV)
     Capability Advertisement for MPLS Transport Profile (MPLS-TP)

Abstract

   This document specifies how signaling and selection processes for
   Pseudowire (PW) Virtual Circuit Connectivity Verification (VCCV) are
   modified to ensure backward compatibility and allow use of proactive
   Connectivity Verification (CV), Continuity Check (CC), and Remote
   Defect Indication (RDI) over MPLS Transport Profile (MPLS-TP) PWs.
   This document introduces four new CV types and, to accommodate them,
   a new VCCV Extended CV parameter for PW Interface Parameters Sub-TLV
   is defined.

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/rfc7189.

Copyright Notice

   Copyright (c) 2014 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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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   2
       1.1.1.  Terminology . . . . . . . . . . . . . . . . . . . . .   2
       1.1.2.  Requirements Language . . . . . . . . . . . . . . . .   3
   2.  MPLS-TP CC-CV on Pseudowires  . . . . . . . . . . . . . . . .   3
     2.1.  VCCV Extended CV Advertisement Sub-TLV  . . . . . . . . .   3
     2.2.  MPLS-TP CC-CV Types . . . . . . . . . . . . . . . . . . .   3
     2.3.  MPLS-TP CC-CV Type Operation  . . . . . . . . . . . . . .   4
     2.4.  CV Type Selection . . . . . . . . . . . . . . . . . . . .   4
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  VCCV Extended CV Types  . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Proactive Connectivity Verification (CV), Continuity Check (CC), and
   Remote Defect Indication (RDI) for the MPLS Transport Profile
   [RFC6428] are applicable to all constructs of the MPLS-TP, including
   pseudowires (PWs).  If the control plane is used to operate and
   manage PWs then the procedures defined in [RFC5085] and [RFC5885]
   should be used to select the proper type of Control Channel and the
   corresponding type of Connectivity Verification.  This document
   specifies how signaling and selection processes are modified to
   ensure backward compatibility and allow use of proactive CV-CC-RDI
   over MPLS-TP PWs.

1.1.  Conventions Used in This Document

1.1.1.  Terminology

   BFD: Bidirectional Forwarding Detection

   CC: Continuity Check

   CV: Connectivity Verification

   PE: Provider Edge

   VCCV: Virtual Circuit Connectivity Verification

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1.1.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

2.  MPLS-TP CC-CV on Pseudowires

   PW VCCV can support several CV Types, and it can support an arbitrary
   combination of CV modes advertised in the CV Types field of the VCCV
   Interface Parameter sub-TLV [RFC4446] [RFC4447].  Currently, six
   types of CV have been defined for PW VCCV.  This document introduces
   four new CV types and, to accommodate them, a new VCCV Extended CV
   parameter for the PW Interface Parameters Sub-TLV is defined.

2.1.  VCCV Extended CV Advertisement Sub-TLV

   The format of the VCCV Extended CV Advertisement is a TLV where the
   format is as follows:

    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 = 0x19 |    Length     |   CV Type    |   Reserved     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 1: VCCV Extended CV Parameter Format

   The Length field is the length of the sub-TLV, including type and the
   Length field itself.  The minimum length is 4.  It is recommended
   that extensions to the sub-TLV be done in 4-byte increments.

   The Reserved field MUST be set to zeroes on transmit and ignored on
   receive.

   The CV Type field is a bitmask that lists types of CV monitoring that
   a PE is capable of supporting.  The VCCV Extended CV parameter sub-
   TLV MUST appear in combination with the VCCV parameter sub-TLV.  If
   the VCCV parameter sub-TLV is missing, then the VCCV Extended CV
   parameter sub-TLV SHOULD be ignored.

2.2.  MPLS-TP CC-CV Types

   [RFC6428] defines coordinated and independent modes of monitoring
   point-to-point bidirectional connection that can be applied to
   monitoring PWs.  At the same time, [RFC6310] defines how BFD-based

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   Operations, Administration, and Maintenance (OAM) can map to the
   status of an Attachment Circuit.  Thus, there could be four MPLS-TP
   CV types for each combination of mode and functionality:

   +----------------+-------------------+------------------------------+
   |     Modes      |  Fault Detection  |  Fault Detection and Status  |
   |                |        Only       |          Signaling           |
   +----------------+-------------------+------------------------------+
   |  Independent   |        0x01       |             0x02             |
   |      Mode      |                   |                              |
   |  Coordinated   |        0x04       |             0x08             |
   |      Mode      |                   |                              |
   +----------------+-------------------+------------------------------+

               Table 1: Bitmask Values for MPLS-TP CV Types

2.3.  MPLS-TP CC-CV Type Operation

   According to [RFC6428], connectivity verification is part of MPLS-TP
   CC/CV operation that can be used with VCCV Control Channel Type 1
   [RFC5085].  If VCCV Control Channel Type 1 is selected, then PEs MAY
   select one of the MPLS-TP CC-CV types as the VCCV CV mechanism to be
   used for this PW.

2.4.  CV Type Selection

   CV selection rules that have been defined in Section 7 of [RFC5085]
   and updated in Section 4 of [RFC5885] are augmented in this document.

   If VCCV Control Channel Type 1 is chosen according to Section 7 of
   [RFC5085] and a common set of proactive CV types that are advertised
   by both PEs includes MPLS-TP CC-CV types and some BFD CV types, then
   MPLS-TP CC-CV takes precedence over any type of BFD CV.  If multiple
   MPLS-TP CV types are advertised by both PEs, then the following list
   (ordered by descending priority) is used:

   1.  0x08 - Coordinated mode for PW Fault Detection and AC/PW Fault
       Status Signaling

   2.  0x04 - Coordinated mode for PW Fault Detection only

   3.  0x02 - Independent mode for PW Fault Detection and AC/PW Fault
       Status Signaling

   4.  0x01 - Independent mode for PW Fault Detection only

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3.  IANA Considerations

   The PW Interface Parameters Sub-TLV registry is defined in [RFC4446].

   IANA has reserved a new PW Interface Parameters Sub-TLV type as
   follows:

   +-----------+----------+----------------------------+---------------+
   | Parameter | Length   |        Description         | Reference     |
   |     ID    |          |                            |               |
   +-----------+----------+----------------------------+---------------+
   |    0x19   | variable | VCCV Extended CV Parameter | This document |
   +-----------+----------+----------------------------+---------------+

               Table 2: New PW Interface Parameters Sub-TLV

3.1.  VCCV Extended CV Types

   IANA has set up a registry of VCCV Extended CV Types.  These are
   8-bit values.  Extended CV Type values 0x01, 0x02, 0x04, and 0x08 are
   specified in Section 2.2 of this document.  The remaining values
   (0x10 through 0x80) are to be assigned by IANA using the "IETF
   Review" policy defined in [RFC5226].  A VCCV Extended Connectivity
   Verification Type description and a reference to an RFC approved by
   the IESG are required for any assignment from this registry.

   +--------------+----------------------------------------------------+
   |  Bit(Value)  | Description                                        |
   +--------------+----------------------------------------------------+
   | Bit 0 (0x01) | Independent mode for PW Fault Detection only       |
   | Bit 1 (0x02) | Independent mode for PW Fault Detection and AC/PW  |
   |              | Fault Status Signaling                             |
   | Bit 2 (0x04) | Coordinated mode for PW Fault Detection only       |
   | Bit 3 (0x08) | Coordinated mode for PW Fault Detection and AC/PW  |
   |              | Fault Status Signaling                             |
   | Bit 4 (0x10) | Unassigned                                         |
   | Bit 5 (0x20) | Unassigned                                         |
   | Bit 6 (0x40) | Unassigned                                         |
   | Bit 7 (0x80) | Unassigned                                         |
   +--------------+----------------------------------------------------+

        Table 3: VCCV Extended Connectivity Verification (CV) Types

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4.  Security Considerations

   Routers that implement the additional CV Type defined herein are
   subject to the same security considerations as defined in [RFC5085],
   [RFC5880], [RFC5881], and [RFC6428].  This specification does not
   raise any additional security issues beyond those.

5.  Acknowledgements

   The author gratefully acknowledges the thoughtful review, comments,
   and explanations provided by Dave Allan and Carlos Pignataro.

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4446]  Martini, L., "IANA Allocations for Pseudowire Edge to Edge
              Emulation (PWE3)", BCP 116, RFC 4446, April 2006.

   [RFC4447]  Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
              Heron, "Pseudowire Setup and Maintenance Using the Label
              Distribution Protocol (LDP)", RFC 4447, April 2006.

   [RFC5085]  Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
              Connectivity Verification (VCCV): A Control Channel for
              Pseudowires", RFC 5085, December 2007.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, June 2010.

   [RFC5881]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June
              2010.

   [RFC5885]  Nadeau, T. and C. Pignataro, "Bidirectional Forwarding
              Detection (BFD) for the Pseudowire Virtual Circuit
              Connectivity Verification (VCCV)", RFC 5885, June 2010.

   [RFC6310]  Aissaoui, M., Busschbach, P., Martini, L., Morrow, M.,
              Nadeau, T., and Y(J). Stein, "Pseudowire (PW) Operations,
              Administration, and Maintenance (OAM) Message Mapping",
              RFC 6310, July 2011.

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   [RFC6428]  Allan, D., Swallow Ed. , G., and J. Drake Ed. , "Proactive
              Connectivity Verification, Continuity Check, and Remote
              Defect Indication for the MPLS Transport Profile", RFC
              6428, November 2011.

6.2.  Informative References

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

Author's Address

   Greg Mirsky
   Ericsson

   EMail: gregory.mirsky@ericsson.com

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