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Versions: 00 01 02 draft-ietf-pals-vccv-for-gal

PWE3                                                           T. Nadeau
Internet-Draft                                               lucidvision
Updates: 5085 (if approved)                                   L. Martini
Intended status: Standards Track                               S. Bryant
Expires: March 6, 2015                                     Cisco Systems
                                                       September 2, 2014


               A Unified Control Channel for Pseudowires
                    draft-ietf-pwe3-vccv-for-gal-02

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.  It describes new rules requiring this mode to be used as
   the default/mandatory mode of operation for VCCV.  The older VCCV
   types will remain optional.

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 March 6, 2015.

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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   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.  Requirements Language and Terminology . . . . . . . . . . . .   2
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  VCCV Control Channel When The Control Word is Used  . . . . .   5
   4.  VCCV Control Channel When The Control Word is Not Used  . . .   6
   5.  VCCV Capability Advertisement . . . . . . . . . . . . . . . .   7
   6.  Manageability Considerations  . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  VCCV Interface Parameters Sub-TLV . . . . . . . . . . . .   7
     8.2.  MPLS VCCV Control Channel (CC) Type 4 . . . . . . . . . .   7
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Requirements Language and Terminology

   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].

   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].




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   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.  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], and [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, these modes use of the CW in some cases,
   while in others the CW is not used.  The difficulty of operating
   these different combinations of "modes" have been detailed in an
   implementation survey conducted by the PWE3 Working Group and
   documented in [RFC7079].  The implementation survey and the PWE3
   Working Group have concluded that operators have difficulty deploying
   the VCCV OAM protocol due to 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 MPLS-TP 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 [RFC5586].
   This resulted in yet another mode of VCCV operation.

   This document defines two modes of operation of VCCV: 1) with a
   control word or 2) without a control word, both with a ACH
   encapsulation making it possible to handle all of the other cases
   handled by the other modes of VCCV.  The modes of operation defined
   in this document MUST be implemented.




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   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 later in
   this document.

              |<-------------- 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
   the emulated service via Attachment Circuits (AC), 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, or any other attachment type for which a PW is defined.  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.










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          +-------------+                                +-------------+
          |  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 Section 3 and Section 4, so that they are handled and
   processed in the same manner (or in some cases, a similar manner) the
   PW PDUs for which they provide a control channel.  These VCCV
   messages are exchanged only after the capability (the VCCV Control
   Channel and Connectivity Verification types) and the desire to
   exchange VCCV traffic has been advertised between the PEs (see
   Sections 5.3 and 6.3 of [RFC5085]), and VCCV type to use have been
   chosen.

   [EDITOR'S NOTE - Why are we talking about 6.3 which is L2TPv3 related
   in a text on GAL?]

3.  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 of [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.






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4.  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

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

   EDITOR's note = when we wrote RFC3985 I seem to remember that TTL=1
   was problematic do we want to specify TTL=1 in the text below?

   EDITOR's note = not sure if it should be MUST or SHOULD in the text
   below.

   When the PW is a single segment PW, the TTL field of the PW Label
   Stack Entry (LSE) SHOULD be set to 1.  In the case of multi-segment
   pseudo-wires, the PW LSE TTL SHOULD be set to the value needed to
   reach the intended destination PE as described in [RFC6073].

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

   As defined in [RFC4385] and [RFC4446] the first nibble of the next
   field is set to 0001b to indicate an ACH associated with a pseudowire
   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 Associated Channel Type defines how the "VCCV Message Body" field
   is to be interpreted by the receiver.








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5.  VCCV Capability Advertisement

   The capability advertisement MUST match the 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 superseding 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 capability
   advertisement selection rules of section 7 from [RFC5085] apply.

6.  Manageability Considerations

   Editor's note - this is a placeholder - I am not sure if it sis
   needed

7.  Security Considerations

   This document does not by itself raise any new security
   considerations beyond those described in [RFC5085].

8.  IANA Considerations

8.1.  VCCV Interface Parameters Sub-TLV

   EDITOR'S NOTE ASFAICS this section can be deleted.

   The VCCV Interface Parameters Sub-TLV code point is defined in
   [RFC4446].  IANA has created and will maintain registries for the CC
   Types and CV Types (bit masks in the VCCV Parameter ID).  The CC Type
   and CV Type new registries (see Sections 8.1.1 and 8.1.2,
   respectively of[RFC5085] ) have been created in the Pseudo Wires Name
   Spaces, . The allocations must be done using the "IETF Review" policy
   defined in [RFC5226].

8.2.  MPLS VCCV Control Channel (CC) Type 4

   IANA is requested to assign a new bit from the MPLS VCCV Control
   Channel (CC) Types registry in the PWE3-parameters name space in
   order to identify VCCV type 4.  It is recommended that Bit 3 be
   assigned to this purpose which would have a value of 0x08.




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   MPLS VCCV Control Channel (CC) Types

         Bit (Value)    Description   Reference
         ============   ===========   ====================
         Bit X (0x0Y)   Type 4        [This Specification]

9.  Acknowledgements

10.  References

10.1.  Normative References

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

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

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

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

10.2.  Informative References

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



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   [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.

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

   [RFC7079]  Del Regno, N. and A. Malis, "The Pseudowire (PW) and
              Virtual Circuit Connectivity Verification (VCCV)
              Implementation Survey Results", RFC 7079, November 2013.

Authors' Addresses

   Thomas D. Nadeau
   lucidvision

   Email: tnadeau@lucidvision.com


   Luca Martini
   Cisco Systems

   Email: lmartini@cisco.com


   Stewart Bryant
   Cisco Systems

   Email: stbryant@cisco.com

















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