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Versions: 00 01

Network Working Group                                          T. Nadeau
Internet-Draft                                           CA Technologies
Intended status: Standards Track
Expires: July 27, 2012                                        L. Martini
                                                     Cisco Systems, Inc.

                                                        January 27, 2012


              A Unified Control Channel for Pseudowires
                 draft-ietf-pwe3-vccv-for-gal-00.txt

Abstract

   This document describes a unified mode of operation for Virtual
   Circuit Connectivity Verification (VCCV), which provides a control
   channel that is associated with a pseudowire (PW). VCCV applies to
   all supported access circuit and transport types currently defined
   for PWs, as well as those being transported by The MPLS Transport
   Profile. This new mode is intended to augment those described in
   RFC5085, but this document describes new rules requiring this mode
   to be used as the default/mandatory mode of operation for
   VCCV. The older types will remain optional.


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 RFC 2119 [RFC2119].


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 July 27, 2012.

Copyright Notice





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   Copyright (c) 2012 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.


Table of Contents
   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   1.2.  Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  VCCV Control Channel When The Control Word is Used . . . . . .  6
   3.  VCCV Control Channel When The Control Word is Not Used . . . .  6
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
     4.1.  VCCV Interface Parameters Sub-TLV  . . . . . . . . . . . . 19
       4.1.1.  MPLS VCCV Control Channel (CC) Type 4  . . . . . . . . 19
   5. Security Considerations   . . . . . . . . . . . . . . . . . . . 24
   6. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 25
   7. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 26
     7.1. Normative References  . . . . . . . . . . . . . . . . . . . 26
     7.2. Informative References  . . . . . . . . . . . . . . . . . . 26




1.  Introduction

   There is a need for fault detection and diagnostic mechanisms that
   can be used for end-to-end fault detection and diagnostics for a
   Pseudowire, as a means of determining the PW's true operational
   state.  Operators have indicated in [RFC4377], [RFC3916].
   that such a tool is required for PW operation and maintenance. To
   this end, the IETF's PWE3 Working Group defined The Virtual
   Circuit Connectivity Verification Protocol (VCCV) in [RFC5085].
   Since then a number of interoperability issues have arisen with the
   protocol as it is defined.

   Over time, a variety of VCCV options or "modes" have been created to
   support legacy hardware, the use of the control word in some cases,
   while in others not. The difficulty of operating these
   different combinations of "modes" have been detailed in an
   implementation survey the PWE3 Working Group conducted. Many of the
   motivations of this survey are detailed in [MAN-CW]. This document



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   and the implementation survey concluded that operators have had
   difficulty deploying the protocol given the number of combinations
   and options for its use.

   In addition to the implementation issues just described, the ITU-T
   and IETF have set out to enhance MPLS to make it suitable as an
   optical transport protocol. The requirements for this protocol are
   defined as the MPLS Transport Profile (MPLS-TP). The requirements
   for this protocol can be found in [RFC5654]. In order to support
   VCCV when an MPLS-TP PSN is in use, the GAL-ACH had to be created;
   this effectively resulted in another mode of operation.

   This document defines two modes of operation of VCCV: 1) with
   a control word or 2) without a control word, but
   with a ACH encapsulation making it possible to handle all of the
   other cases handled by the other modes of VCCV. In either case, it
   will be mandatory to implement and use that mode under that
   scenario.

   Figure 1 depicts the architecture of a pseudowire as defined in
   [RFC3985].  It further depicts where the VCCV control channel resides
   within this architecture, which will be discussed in detail shortly.


            |<-------------- Emulated Service ---------------->|
            |          |<---------- VCCV ---------->|          |
            |          |<------- Pseudowire ------->|          |
            |          |                            |          |
            |          |    |<-- PSN Tunnel -->|    |          |
            |          V    V                  V    V          |
            V    AC    +----+                  +----+     AC   V
      +-----+    |     | PE1|==================| PE2|     |    +-----+
      |     |----------|............PW1.............|----------|     |
      | CE1 |    |     |    |                  |    |     |    | CE2 |
      |     |----------|............PW2.............|----------|     |
      +-----+  ^ |     |    |==================|    |     | ^  +-----+
            ^  |       +----+                  +----+     | |  ^
            |  |   Provider Edge 1         Provider Edge 2  |  |
            |  |                                            |  |
      Customer |                                            | Customer
      Edge 1   |                                            | Edge 2
               |                                            |
               |                                            |
         Native service                               Native service

               Figure 1: PWE3 VCCV Operation Reference Model

   From Figure 1, Customer Edge (CE) routers CE1 and CE2 are attached to



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   the emulated service via Attachment Circuits (ACs), and to each of
   the Provider Edge (PE) routers (PE1 and PE2, respectively).  An AC
   can be a Frame Relay Data Link Connection Identifier (DLCI), an ATM
   Virtual Path Identifier / Virtual Channel Identifier (VPI/VCI), an
   Ethernet port, etc.  The PE devices provide pseudowire emulation,
   enabling the CEs to communicate over the PSN.  A pseudowire exists
   between these PEs traversing the provider network.  VCCV provides
   several means of creating a control channel over the PW, between the
   PE routers that attach the PW.

   Figure 2 depicts how the VCCV control channel is associated with the
   pseudowire protocol stack.

       +-------------+                                +-------------+
       |  Layer2     |                                |  Layer2     |
       |  Emulated   |       < Emulated Service >     |  Emulated   |
       |  Services   |                                |  Services   |
       +-------------+                                +-------------+
       |             |            VCCV/PW             |             |
       |Demultiplexer|       < Control Channel >      |Demultiplexer|
       +-------------+                                +-------------+
       |    PSN      |          < PSN Tunnel >        |    PSN      |
       +-------------+                                +-------------+
       |  Physical   |                                |  Physical   |
       +-----+-------+                                +-----+-------+
             |                                              |
             |             ____     ___       ____          |
             |           _/    \___/   \    _/    \__       |
             |          /               \__/         \_     |
             |         /                               \    |
             +--------|     MPLS/MPLS-TP or IP Network  |---+
                       \                               /
                        \   ___      ___     __      _/
                         \_/   \____/   \___/  \____/

     Figure 2: PWE3 Protocol Stack Reference Model including the VCCV
                              Control Channel

   VCCV messages are encapsulated using the PWE3 encapsulation as
   described in Sections 2 and 3, so that they are handled and processed
   in the same manner (or in some cases, a similar manner) as the PW
   PDUs for which they provide a control channel.  These VCCV messages
   are exchanged only after the capability (expressed as two VCCV type
   spaces, namely the VCCV Control Channel and Connectivity Verification
   Types) and desire to exchange such traffic has been advertised
   between the PEs (see Sections 5.3 and 6.3), and VCCV types chosen.





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1.2.  Acronyms

   AC      Attachment Circuit [RFC3985].

   AVP     Attribute Value Pair [RFC3931].

   CC      Control Channel (used as CC Type).

   CE      Customer Edge.

   CV      Connectivity Verification (used as CV Type).

   CW      Control Word [RFC3985].

   L2SS    L2-Specific Sublayer [RFC3931].

   LCCE    L2TP Control Connection Endpoint [RFC3931].

   OAM     Operation and Maintenance.

   PE      Provider Edge.

   PSN     Packet Switched Network [RFC3985].

   PW      Pseudowire [RFC3985].

   PW-ACH  PW Associated Channel Header [RFC4385].

   VCCV    Virtual Circuit Connectivity Verification [RFC5085].


2. VCCV Control Channel When The Control Word is Used

   When the PWE3 Control Word is used to encapsulate pseudowire
traffic, the rules described for encapsulating VCCV CC Type 1 as
specified in section 9.5.1 [RFC6073] and section 5.1.1 of [RFC5085]
MUST be used.  In this case the advertised CC Type is 1, and
Associated Channel Types of 21, 07, or 57 are allowed.


3. VCCV Control Channel When The Control Word is Not Used

   When the PWE3 Control Word is not used a new CC Type 4 is
defined 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



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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                            PW Label                           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                              GAL                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version|   Reserved    |  Associated Channel Type      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
~                        VCCV Message Body                      ~
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The PW Label must set the TTL field to 1. In the case
of multi-segment pseudo-wires, the PW Label TTL MUST be set to the
correct value to reach the intended destination PE as described
in [RFC6073].

   The GAL field MUST contain the reserved label as defined in
[RFC5586].

   The first nibble of the next field is set to 0001b to indicate
an ACH associated with a pseudowire (see Section 5 of [RFC4385]
and Section 3.6 of [RFC4446]) instead of PW data.  The Version and
the Reserved fields MUST be set to 0, and the Channel Type is
set to 0x0021 for IPv4, 0x0057 for IPv6 payloads [RFC5085] or
0x0007 for BFD payloads [RFC5885].

    The "VCCV Message Body" field is defined based on the Associated
Channel Type and defined therein.


4. VCCV Capability Advertisement

    The capability advertisement MUST match that c-bit setting
that is advertised in the PW FEC element. If the c-bit is set,
indicating the use of the control word, type 1 MUST be advertised
and type 4 MUST NOT be advertised. If the c-bit is not set,
indicating that the control word is not in use, type 4 MUST
be advertised, and type 1 MUST NOT be advertised.

    A PE supporting Type 4 MAY advertise other CC types
as defined in RFC5085. If the remote PE also supports Type
4, then Type 4 MUST be used superceding the Capability
Advertisement Selection rules of section 7 from RFC5085.
If a remote PE does not support Type 4, then the rules
from section 7 of RFC5085 apply. If a CW is in use, then
Type 4 is not applicable, and therefore the normal



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capability advertisement selection rules of section 7
from RFC5085 apply.


4.  IANA Considerations

4.1.  VCCV Interface Parameters Sub-TLV

   The VCCV Interface Parameters Sub-TLV codepoint is defined in
   [RFC4446].  IANA has created and will maintain registries for the CC
   Types and CV Types (bitmasks in the VCCV Parameter ID).  The CC Type
   and CV Type new registries (see Sections 8.1.1 and 8.1.2,
   respectively) have been created in the Pseudo Wires Name Spaces,
   reachable from [IANA.pwe3-parameters].  The allocations must be done
   using the "IETF Consensus" policy defined in [RFC5226].

4.1.1.  MPLS VCCV Control Channel (CC) Type 4

   IANA is requested to augment the registry of "MPLS VCCV Control
   Channel Types" with the new type defined below. As defined in
   RFC5058, this new bitfield is to be assigned by IANA using
   the "IETF Consensus" policy defined in [RFC5226].  A VCCV
   Control Channel Type description and a reference to an RFC approved
   by the IESG are required for any assignment from this registry.

      MPLS Control Channel (CC) Types:

      Bit (Value)    Description
      ============   ==========================================
      Bit 3 (0x08) - Type 4


   The most significant (high order) bit is labeled Bit 7, and the least
   significant (low order) bit is labeled Bit 0, see parenthetical
   "Value".


5.  Security Considerations

   This document does not by itself raise any particular security
   considerations that differ from those described in RFC5085.


6.  Acknowledgements

7.  References

7.1.  Normative References



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

   [RFC3931]  Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
              Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.

   [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, February 2006.

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

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

   [RFC5586]  Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
              "MPLS Generic Associated Channel", RFC 5586, June 2009.

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

   [RFC5654]  Niven-Jenkins, B., Brungard, D., and M. Betts,
              "Requirements of an MPLS Transport Profile", RFC 5654,
              September 2009

   [RFC6073]  Martini, L., Metz, C., Nadeau, T., Bocci, M., and
              M. Aissaoui, "Segmented Pseudowire", RFC 6073,
              January 2011.

12.2.  Informative References

   [IANA.l2tp-parameters]
              Internet Assigned Numbers Authority, "Layer Two Tunneling
              Protocol "L2TP"", April 2007,
              <http://www.iana.org/assignments/l2tp-parameters>.

   [IANA.pwe3-parameters]
              Internet Assigned Numbers Authority, "Pseudo Wires Name
              Spaces", June 2007,
              <http://www.iana.org/assignments/pwe3-parameters>.

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



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              RFC 5226, May 2008.

   [RFC3916]  Xiao, X., McPherson, D., and P. Pate, "Requirements for
              Pseudo-Wire Emulation Edge-to-Edge (PWE3)", RFC 3916,
              September 2004.

   [RFC3985]  Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-
              Edge (PWE3) Architecture", RFC 3985, March 2005.

   [RFC4377]  Nadeau, T., Morrow, M., Swallow, G., Allan, D., and S.
              Matsushima, "Operations and Management (OAM) Requirements
              for Multi-Protocol Label Switched (MPLS) Networks",
              RFC 4377, February 2006.

   [MAN-CW]   Del Regno, N., Nadeau, T., Manral, V., Ward, D.,
              "Mandatory Use of Control Word for PWE3 Encapsulations",
              "Work in progress", October 2010.


8.  Authors' Addresses

   Thomas D. Nadeau
   CA Technologies
   273 Corporate Drive, Portsmouth, NH, USA

   Email: thomas.nadeau@ca.com


   Luca Martini
   Cisco Systems, Inc.
   9155 East Nichols Avenue, Suite 400
   Englewood, CO, 80112 USA

   EMail: lmartini@cisco.com

















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