[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-gp-pals-seamless-vccv) 00 01 02 03 RFC 7885

Internet Engineering Task Force                              V. Govindan
Internet-Draft                                              C. Pignataro
Updates: 5885 (if approved)                                        Cisco
Intended status: Standards Track                          April 28, 2016
Expires: October 30, 2016


                         Seamless BFD for VCCV
                    draft-ietf-pals-seamless-vccv-03

Abstract

   This document extends the procedures and Connectivity Verification
   (CV) types already defined for Bidirectional Forwarding Detection
   (BFD) for Virtual Circuit Connectivity Verification (VCCV) to define
   Seamless BFD (S-BFD) for VCCV.  This document updates RFC 5885,
   extending the CV Values and the Capability Selection.

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 October 30, 2016.

Copyright Notice

   Copyright (c) 2016 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




Govindan & Pignataro    Expires October 30, 2016                [Page 1]


Internet-Draft            Seamless BFD for VCCV               April 2016


   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  S-BFD Connectivity Verification . . . . . . . . . . . . . . .   3
     2.1.  Co-existence of S-BFD and BFD Capabilites . . . . . . . .   4
     2.2.  S-BFD CV Operation  . . . . . . . . . . . . . . . . . . .   4
       2.2.1.  S-BFD Initiator Operation . . . . . . . . . . . . . .   4
       2.2.2.  S-BFD Reflector Operation . . . . . . . . . . . . . .   5
         2.2.2.1.  Demultiplexing  . . . . . . . . . . . . . . . . .   5
         2.2.2.2.  Transmission of Control Packets . . . . . . . . .   5
         2.2.2.3.  Advertisement of Target Discriminators Using LDP    5
         2.2.2.4.  Advertisement of Target Discriminators Using L2TP   5
         2.2.2.5.  Provisioning of Target Discriminators . . . . . .   6
     2.3.  S-BFD Encapsulation . . . . . . . . . . . . . . . . . . .   6
     2.4.  S-BFD CV Types  . . . . . . . . . . . . . . . . . . . . .   6
   3.  Capability Selection  . . . . . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  MPLS CV Types for the VCCV Interface Parameters Sub-TLV .   7
     5.2.  L2TPv3 CV Types for the VCCV Capability AVP . . . . . . .   8
     5.3.  PW Associated Channel Type  . . . . . . . . . . . . . . .   8
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Background

   BFD for VCCV [RFC5885] defines the CV types for BFD using VCCV,
   protocol operation and the required packet encapsulation formats.
   This document extends those procedures, CV type values to enable
   S-BFD [I-D.ietf-bfd-seamless-base] operation for VCCV.

   The new S-BFD CV Types are Pseudowire (PW) demultiplexer-agnostic,
   and hence applicable for both MPLS and Layer Two Tunneling Protocol
   version 3 (L2TPv3) pseudowire demultiplexers.  This document concerns
   itself with the S-BFD VCCV operation over single-segment pseudowires
   (SS-PWs).  The scope of this document is as follows:

      This specification describes procedures only for S-BFD
      asynchronous mode.




Govindan & Pignataro    Expires October 30, 2016                [Page 2]


Internet-Draft            Seamless BFD for VCCV               April 2016


      S-BFD Echo mode is outside the scope of this specification.

      S-BFD operation for fault detection and status signaling is
      outside the scope of this specification.

   This document specifies the use of a single S-BFD discriminator per
   Pseudowire.  There are cases where multiple S-BFD discriminators per
   PW can be useful.  One such cases is using different S-BFD
   discriminators per Flow within a FAT PW [RFC6391]; however, the
   mapping between Flows and discriminators is a prerequisite.  FAT PWs
   can be supported as described in Section 7 of [RFC6391].

1.1.  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.  S-BFD Connectivity Verification

   S-BFD protocol provides continuity check services by monitoring the
   S-BFD control packets sent and received over the VCCV channel of the
   PW.  The term "Connectivity Verification" is used throughout this
   document to be consistent with [RFC5885].

   This section defines the CV types to be used for S-BFD.  It also
   defines the procedures for the S-BFD reflector and S-BFD Initiator
   operation.

   Two CV Types are defined for S-BFD.  Table 1 summarizes the S-BFD CV
   Types, grouping them by encapsulation (i.e., with versus without IP/
   UDP headers) for fault detection only.  S-BFD for fault detection and
   status signaling is outside the scope of this specification.

















Govindan & Pignataro    Expires October 30, 2016                [Page 3]


Internet-Draft            Seamless BFD for VCCV               April 2016


   +----------------------------------------+-----------+--------------+
   |                                        |   Fault   |    Fault     |
   |                                        | Detection |  Detection   |
   |                                        |    Only   |  and Status  |
   |                                        |           |  Signaling   |
   +----------------------------------------+-----------+--------------+
   |      S-BFD, IP/UDP Encapsulation (with |    TBD1   |     N/A      |
   |                        IP/UDP Headers) |           |              |
   |                                        |           |              |
   | S-BFD, PW-ACH Encapsulation when using |    TBD2   |     N/A      |
   | MPLS PW or L2-Specific Sublayer (L2SS) |           |              |
   |       Encapsulation when using L2TP PW |           |              |
   |               (without IP/UDP Headers) |           |              |
   +----------------------------------------+-----------+--------------+

                 Table 1: Bitmask Values for BFD CV Types

   Two new bits are requested from IANA to indicate S-BFD operation.

2.1.  Co-existence of S-BFD and BFD Capabilites

   Since the CV types for S-BFD and BFD are unique, BFD and S-BFD
   capabilities can be advertised concurrently.

2.2.  S-BFD CV Operation

2.2.1.  S-BFD Initiator Operation

   The S-BFD Initiator SHOULD bootstrap S-BFD sessions after it learns
   the discriminator of the remote target identifier.  This can be
   achieved, for example but not limited to, through one or more of the
   following methods:

   1.  Advertisements of S-BFD discriminators made through a PW
       signaling protocol, for example AVP/TLVs defined in L2TP/LDP.

   2.  Provisioning of S-BFD discriminators by manual configuration of
       the PE/LCCEs.

   3.  Assignment of S-BFD discriminators by a controller.

   4.  Probing remote S-BFD discriminators through a mechanism such as
       S-BFD Alert discriminators [I-D.akiya-bfd-seamless-alert-discrim]

   S-BFD Initiator operation MUST be according to the specifications in
   Section 7.2 of [I-D.ietf-bfd-seamless-base].





Govindan & Pignataro    Expires October 30, 2016                [Page 4]


Internet-Draft            Seamless BFD for VCCV               April 2016


2.2.2.  S-BFD Reflector Operation

      When a pseudowire signaling protocol such as LDP or L2TPv3 is in
      use, the S-BFD Reflector can advertise its target discriminators
      using that signaling protocol.  When static PWs are in use the
      target discriminator of S-BFD needs to be provisioned on the S-BFD
      Initiator nodes.

      All point to point pseudowires are bidirectional, the S-BFD
      Reflector therefore reflects the S-BFD packet back to the
      Initiator using the VCCV channel of the reverse direction of the
      PW on which it was received.

      It is observed that the reflector has enough information to
      reflect the S-BFD Async packet received by it back to the S-BFD
      initiator using the PW context (e.g., fields of the L2TPv3
      headers).

      S-BFD Reflector operation for BFD protocol fields MUST be
      according to the specifications of [I-D.ietf-bfd-seamless-base].

2.2.2.1.  Demultiplexing

   Demultiplexing of S-BFD is achieved using the PW context, following
   the procedures in Section 7.1 of [I-D.ietf-bfd-seamless-base].

2.2.2.2.  Transmission of Control Packets

   The procedures of S-BFD Reflector described in
   [I-D.ietf-bfd-seamless-base] apply for S-BFD using VCCV.

2.2.2.3.  Advertisement of Target Discriminators Using LDP

   The advertisement of the target discriminator using LDP is left for
   further study.  It should be noted that S-BFD can still be used with
   signaled PWs over an MPLS PSN, by provisioning of the S-BFD
   discriminators or by learning the S-BFD discriminators by other
   means.

2.2.2.4.  Advertisement of Target Discriminators Using L2TP

   The S-BFD Reflector MUST use the AVP
   [I-D.ietf-l2tpext-sbfd-discriminator] defined for advertising its
   target discriminators using L2TP.







Govindan & Pignataro    Expires October 30, 2016                [Page 5]


Internet-Draft            Seamless BFD for VCCV               April 2016


2.2.2.5.  Provisioning of Target Discriminators

   S-BFD target discriminators MAY be provisioned when static PWs are
   used.

2.3.  S-BFD Encapsulation

   Unless specified differently below, the encapsulation of S-BFD
   packets is identical to the method specified in Section 3.2 [RFC5885]
   and in [RFC5880] for the encapsulation of BFD packets.

   o  IP/UDP BFD Encapsulation (BFD with IP/UDP Headers)

      *  The destination UDP port for the IP encapsulated S-BFD packet
         MUST be 7784 [I-D.ietf-bfd-seamless-ip].

      *  The encapsulation of the S-BFD header fields MUST be according
         to Section 7.3.2 of [I-D.ietf-bfd-seamless-base].

      *  The Time to Live (TTL) (IPv4) or Hop Limit (IPv6) is set to
         255.

   o  PW-ACH/ L2SS BFD Encapsulation (BFD without IP/UDP Headers)

      *  The encapsulation of S-BFD packets using this format MUST be
         according to Section 3.2 of [RFC5885] with the exception of the
         value for the PW-ACH/L2SS type.

      *  When VCCV carries PW-ACH/ L2SS-encapsulated S-BFD (i.e., "raw"
         S-BFD), the PW-ACH (pseudowire CW's) or L2SS' Channel Type MUST
         be set to TBD3 to indicate "S-BFD Control, PW-ACH/ L2SS-
         encapsulated" (i.e., S-BFD without IP/UDP headers; see
         Section 5.3).  This is to allow the identification of the
         encased S-BFD payload when demultiplexing the VCCV control
         channel.

2.4.  S-BFD CV Types

3.  Capability Selection

   When multiple S-BFD CV Types are advertised, and after applying the
   rules in [RFC5885], the set that both ends of the pseudowire have in
   common is determined.  If the two ends have more than one S-BFD CV
   Type in common, the following list of S-BFD CV Types is considered in
   the order of the lowest list number CV Type to the highest list
   number CV Type, and the CV Type with the lowest list number is used:

   1.  TBD1 - S-BFD IP/UDP-encapsulated, for PW Fault Detection only.



Govindan & Pignataro    Expires October 30, 2016                [Page 6]


Internet-Draft            Seamless BFD for VCCV               April 2016


   2.  TBD2 - S-BFD PW-ACH/ L2SS-encapsulated (without IP/UDP headers),
       for PW Fault Detection only.

   The order of capability selection between S-BFD and BFD is defined as
   follows:

   +----------------------------+---------+----------+-----------------+
   | Advertised capabilities of |   BFD   |   SBFD   |  Both S-BFD and |
   |          PE1/ PE2          |   Only  |   Only   |       BFD       |
   +----------------------------+---------+----------+-----------------+
   |          BFD Only          |   BFD   |   None   |     BFD Only    |
   |                            |         |          |                 |
   |         S-BFD Only         |   None  |  S-BFD   |    S-BFD only   |
   |                            |         |          |                 |
   |     Both S-BFD and BFD     |   BFD   |  S-BFD   |  Both SBFD and  |
   |                            |   only  |   only   |       BFD       |
   +----------------------------+---------+----------+-----------------+

          Table 2: Capability Selection Matrix for BFD and S-BFD

4.  Security Considerations

   Security considerations for VCCV are addressed in Section 10 of
   [RFC5085].  The introduction of the S-BFD Connectivity Verification
   (CV) Types introduces no new security risks for VCCV.
   Implementations of the additional CV Types defined herein are subject
   to the same security considerations as defined in [RFC5085] as well
   as [I-D.ietf-bfd-seamless-base].

   The IP/UDP encasulation of S-BFD makes use of the TTL/Hop Limit
   procedures described in the Generalized TTL Security Mechanism (GTSM)
   [RFC5082]) as a security mechanism.

   This specification does not raise any additional security issues
   beyond these.

5.  IANA Considerations

5.1.  MPLS CV Types for the VCCV Interface Parameters Sub-TLV

   The VCCV Interface Parameters Sub-TLV codepoint is defined in
   [RFC4446], and the VCCV CV Types registry is defined in [RFC5085].

   This section lists the new BFD CV Types.

   IANA has augmented the "MPLS VCCV Connectivity Verification (CV)
   Types" registry in the Pseudowire Name Spaces reachable from




Govindan & Pignataro    Expires October 30, 2016                [Page 7]


Internet-Draft            Seamless BFD for VCCV               April 2016


   [IANA-PWE3].  These are bitfield values.  CV Type values are
   specified in Section 2 of this document.

         MPLS Connectivity Verification (CV) Types:

      Bit (Value)  Description                       Reference
      ===========  ===========                       ==============
      TBD1(0xY)    S-BFD IP/UDP-encapsulated,        This document
                   for PW Fault Detection only
      TBD2(0xZ)    S-BFD PW-ACH-encapsulated,        This document
                   for PW Fault Detection only

5.2.  L2TPv3 CV Types for the VCCV Capability AVP

   This section lists the new requests for S-BFD "L2TPv3 Connectivity
   Verification (CV) Types" to be added to the existing "VCCV Capability
   AVP" registry in the L2TP name spaces.  The Layer Two Tunneling
   Protocol "L2TP" Name Spaces are reachable from [IANA-L2TP].  IANA is
   requested to assign the following L2TPv3 Connectivity Verification
   (CV) Types in the VCCV Capability AVP Values registry.

      VCCV Capability AVP (Attribute Type 96) Values
      ----------------------------------------------

      L2TPv3 Connectivity Verification (CV) Types:

      Bit (Value)  Description                  Reference
      ===========  ===========                  ==============
      TBD1(0xY)    S-BFD IP/UDP-encapsulated,   This document
                   for PW Fault Detection only
      TBD2(0xZ)    S-BFD L2SS-encapsulated,     This document
                   for PW Fault Detection only

5.3.  PW Associated Channel Type

   As per the IANA considerations in [RFC5586], IANA is requested to
   allocate the following Channel Types in the "MPLS Generalized
   Associated Channel (G-ACh) Types" registry:

   IANA has reserved a new Pseudowire Associated Channel Type value as
   follows:










Govindan & Pignataro    Expires October 30, 2016                [Page 8]


Internet-Draft            Seamless BFD for VCCV               April 2016


   Registry:
                                                TLV
    Value   Description                         Follows  Reference
    ------  ----------------------------------  -------  ---------------
    TBD3    S-BFD Control, PW-ACH/L2SS          No       [This document]
            encapsulation
            (without IP/UDP Headers)



6.  Acknowledgments

   The authors would like to thank Nobo Akiya, Stewart Bryant, Greg
   Mirsky, and Pawel Sowinski, Yuanlong, Andrew Malis, and Alexander
   Vainshtein for providing input to this document and for performing
   thorough reviews and useful comments.

7.  Contributors

   Mallik Mudigonda
   Cisco Systems, Inc.

   Email: mmudigon@cisco.com

8.  References

8.1.  Normative References

   [I-D.ietf-bfd-seamless-base]
              Akiya, N., Pignataro, C., Ward, D., Bhatia, M., and J.
              Networks, "Seamless Bidirectional Forwarding Detection
              (S-BFD)", draft-ietf-bfd-seamless-base-09 (work in
              progress), April 2016.

   [I-D.ietf-bfd-seamless-ip]
              Akiya, N., Pignataro, C., and D. Ward, "Seamless
              Bidirectional Forwarding Detection (S-BFD) for IPv4, IPv6
              and MPLS", draft-ietf-bfd-seamless-ip-04 (work in
              progress), April 2016.

   [I-D.ietf-l2tpext-sbfd-discriminator]
              Govindan, V. and C. Pignataro, "Advertising Seamless
              Bidirectional Forwarding Detection (S-BFD) Discriminators
              in Layer Two Tunneling Protocol, Version 3 (L2TPv3)",
              draft-ietf-l2tpext-sbfd-discriminator-05 (work in
              progress), April 2016.





Govindan & Pignataro    Expires October 30, 2016                [Page 9]


Internet-Draft            Seamless BFD for VCCV               April 2016


   [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>.

   [RFC4446]  Martini, L., "IANA Allocations for Pseudowire Edge to Edge
              Emulation (PWE3)", BCP 116, RFC 4446,
              DOI 10.17487/RFC4446, April 2006,
              <http://www.rfc-editor.org/info/rfc4446>.

   [RFC5082]  Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
              <http://www.rfc-editor.org/info/rfc5082>.

   [RFC5085]  Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
              Circuit Connectivity Verification (VCCV): A Control
              Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
              December 2007, <http://www.rfc-editor.org/info/rfc5085>.

   [RFC5586]  Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
              "MPLS Generic Associated Channel", RFC 5586,
              DOI 10.17487/RFC5586, June 2009,
              <http://www.rfc-editor.org/info/rfc5586>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <http://www.rfc-editor.org/info/rfc5880>.

   [RFC5885]  Nadeau, T., Ed. and C. Pignataro, Ed., "Bidirectional
              Forwarding Detection (BFD) for the Pseudowire Virtual
              Circuit Connectivity Verification (VCCV)", RFC 5885,
              DOI 10.17487/RFC5885, June 2010,
              <http://www.rfc-editor.org/info/rfc5885>.

8.2.  Informative References

   [I-D.akiya-bfd-seamless-alert-discrim]
              Akiya, N., Pignataro, C., and D. Ward, "Seamless
              Bidirectional Forwarding Detection (S-BFD) Alert
              Discriminator", draft-akiya-bfd-seamless-alert-discrim-03
              (work in progress), October 2014.

   [IANA-L2TP]
              Internet Assigned Numbers Authority, "Layer Two Tunneling
              Protocol "L2TP"", May 2015,
              <http://www.iana.org/assignments/l2tp-parameters>.




Govindan & Pignataro    Expires October 30, 2016               [Page 10]


Internet-Draft            Seamless BFD for VCCV               April 2016


   [IANA-PWE3]
              Internet Assigned Numbers Authority, "Pseudowire Name
              Spaces (PWE3)", January 2016,
              <http://www.iana.org/assignments/pwe3-parameters>.

   [RFC6391]  Bryant, S., Ed., Filsfils, C., Drafz, U., Kompella, V.,
              Regan, J., and S. Amante, "Flow-Aware Transport of
              Pseudowires over an MPLS Packet Switched Network",
              RFC 6391, DOI 10.17487/RFC6391, November 2011,
              <http://www.rfc-editor.org/info/rfc6391>.

Authors' Addresses

   Vengada Prasad Govindan
   Cisco Systems, Inc.

   Email: venggovi@cisco.com


   Carlos Pignataro
   Cisco Systems, Inc.

   Email: cpignata@cisco.com




























Govindan & Pignataro    Expires October 30, 2016               [Page 11]


Html markup produced by rfcmarkup 1.123, available from https://tools.ietf.org/tools/rfcmarkup/