Internet Engineering Task Force (IETF)                       V. Govindan
Internet-Draft
Request for Comments: 7885                                  C. Pignataro
Updates: 5885 (if approved)                                                      Cisco
Intended status:
Category: Standards Track                          April 28, 2016
Expires: October 30,                                      June 2016
ISSN: 2070-1721

          Seamless BFD Bidirectional Forwarding Detection (S-BFD)
          for VCCV
                    draft-ietf-pals-seamless-vccv-03 Virtual Circuit Connectivity Verification (VCCV)

Abstract

   This document extends defines Seamless BFD (S-BFD) for VCCV by extending 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. (VCCV).

   This document updates RFC 5885, 5885 by extending the CV Values Type values and
   the Capability Selection. 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 an Internet Standards Track document.

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   This Internet-Draft will expire on October 30, 2016.
   http://www.rfc-editor.org/info/rfc7885.

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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 . Capabilities  . . . . . . .   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   5
     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  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Contributors
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     6.2.  Informative References  . . . . . .   9
   8.  References . . . . . . . . . . .  10
   Acknowledgements  . . . . . . . . . . . . . .   9
     8.1.  Normative References . . . . . . . . . .  10
   Contributors  . . . . . . . . .   9
     8.2.  Informative References . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Background

   BFD

   Bidirectional Forwarding Detection (BFD) for VCCV Virtual Circuit
   Connectivity Verification (VCCV) [RFC5885] defines the CV types Types for
   BFD using VCCV, protocol operation operation, and the required packet
   encapsulation formats.  This document extends those procedures, procedures and
   CV type Type values to enable
   S-BFD [I-D.ietf-bfd-seamless-base] Seamless BFD (S-BFD) [RFC7880] operation
   for VCCV.

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

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

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

   o  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 Discriminator per
   Pseudowire.
   PW.  There are cases where multiple S-BFD discriminators Discriminators per PW can
   be useful.  One such cases is case involves using different S-BFD
   discriminators
   Discriminators per Flow within a FAT Flow-Aware Transport (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
   [RFC6391], which details Operations, Administration, and Maintenance
   (OAM) considerations for FAT PWs.

   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

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

   This section defines the CV types Types to be used for S-BFD.  It also
   defines the procedures for the S-BFD reflector and S-BFD Initiator 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 IP/UDP headers,
   without IP/
   UDP IP/UDP headers) for fault detection only.  S-BFD for fault
   detection and status signaling is outside the scope of this
   specification.

   +----------------------------------------+-----------+--------------+

   +-----------------------------------------+-----------+-------------+
   |                                         |   Fault   |    Fault    |
   |                                         | Detection |  Detection  |
   |                                         |    Only   |  and Status |
   |                                         |           |  Signaling  |
   +----------------------------------------+-----------+--------------+
   +-----------------------------------------+-----------+-------------+
   |      S-BFD, S-BFD IP/UDP Encapsulation encapsulation (with IP/UDP |    TBD1    0x40   |     N/A     |
   |                        IP/UDP Headers)                                headers) |           |             |
   |                                         |           |             |
   | S-BFD,   S-BFD PW-ACH Encapsulation encapsulation when using |    TBD2    0x80   |     N/A     |
   |   MPLS PW or S-BFD L2-Specific Sublayer (L2SS) |           |             |
   |       Encapsulation (L2SS) encapsulation when using L2TP PW |           |             |
   |                (without IP/UDP Headers) headers) |           |             |
   +----------------------------------------+-----------+--------------+
   +-----------------------------------------+-----------+-------------+

                Table 1: Bitmask Values for BFD S-BFD CV Types

   Two

   IANA has assigned two new bits are requested from IANA to indicate S-BFD operation.

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

   Since the CV types 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 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, example, through one or more of the following methods: methods.
   (This list is not exhaustive.)

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

   2.  Provisioning of S-BFD discriminators Discriminators by manual configuration of
       the PE/LCCEs. Provider Edge (PE) or L2TP Control Connection Endpoints
       (LCCEs).

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

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

   The S-BFD Initiator initiator operation MUST be according to the specifications done as specified in
   Section 7.2 7.3 of [I-D.ietf-bfd-seamless-base]. [RFC7880].

2.2.2.  S-BFD Reflector Operation

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

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

      It is observed that the

   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).

   The S-BFD Reflector reflector operation for BFD protocol fields MUST be
      according to the specifications of [I-D.ietf-bfd-seamless-base].
   performed as specified in [RFC7880].

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]. [RFC7880].

2.2.2.2.  Transmission of Control Packets

   The procedures of

   S-BFD Reflector reflector procedures as described in
   [I-D.ietf-bfd-seamless-base] [RFC7880] 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, Packet Switched Network (PSN) by
   provisioning of the S-BFD
   discriminators Discriminators or by learning the S-BFD discriminators by
   Discriminators via some other means.

2.2.2.4.  Advertisement of Target Discriminators Using L2TP

   The S-BFD Reflector reflector MUST use the AVP
   [I-D.ietf-l2tpext-sbfd-discriminator] defined in [RFC7886] for
   advertising its target discriminators using L2TP.

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 of
   [RFC5885] and in [RFC5880] for the encapsulation of BFD packets.

   o  IP/UDP BFD Encapsulation encapsulation (BFD with IP/UDP Headers) headers):

      *  The destination UDP port for the IP encapsulated IP-encapsulated S-BFD packet
         MUST be 7784 [I-D.ietf-bfd-seamless-ip]. [RFC7881].

      *  The encapsulation contents of the S-BFD header fields Control packets MUST be set according
         to Section 7.3.2 of [I-D.ietf-bfd-seamless-base]. [RFC7880].

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

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

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

      *  When VCCV carries PW-ACH/ L2SS-encapsulated PW-ACH/L2SS-encapsulated S-BFD (i.e., "raw"
         S-BFD), the PW-ACH (pseudowire CW's) or L2SS' Channel Type of PW-ACH (the PW Control Word (CW))
         or L2SS MUST be set to TBD3 0x0008 to indicate "S-BFD Control, PW-ACH/ L2SS-
         encapsulated"
         PW-ACH/L2SS-encapsulated" (i.e., S-BFD without IP/UDP headers;
         see Section 5.3).  This is done to allow the identification of
         the
         encased encapsulated 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 PW 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 order,
   from 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  0x40 - S-BFD IP/UDP-encapsulated, for PW Fault Detection only.

   2.  TBD2  0x80 - S-BFD PW-ACH/ L2SS-encapsulated 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   S-BFD   |  Both S-BFD and |
   |          PE1/ PE2         of PE1/PE2        |   Only  |    Only   |       BFD       |
   +----------------------------+---------+----------+-----------------+
   +---------------------------+---------+-----------+-----------------+
   |          BFD Only         |   BFD   |    None   |     BFD Only    |
   |                           |         |           |                 |
   |         S-BFD Only        |   None  |   S-BFD   |    S-BFD only Only   |
   |                           |         |           |                 |
   |     Both S-BFD and BFD    |   BFD   |   S-BFD   |  Both SBFD S-BFD and |
   |                           |   only   Only  |   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) CV Types introduces no does not present
   any new security risks for VCCV.  Implementations of the additional
   CV Types defined herein are subject to the same security
   considerations as those defined in [RFC5085] as well as [I-D.ietf-bfd-seamless-base]. [RFC7880].

   The IP/UDP encasulation encapsulation of S-BFD makes use of the TTL/Hop TTL / Hop Limit
   procedures described in the Generalized TTL Security Mechanism (GTSM)
   [RFC5082])
   specification [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 "MPLS VCCV CV Types Connectivity Verification (CV) Types"
   registry is defined in [RFC5085].

   This section lists the new BFD S-BFD CV Types.

   IANA has augmented the "MPLS VCCV Connectivity Verification (CV)
   Types" registry in the Pseudowire "Pseudowire Name Spaces reachable from (PWE3)" registry
   [IANA-PWE3].  These are bitfield values.  CV Type values are
   specified in Section 2 of this document.

      MPLS VCCV Connectivity Verification (CV) Types:

      Bit (Value)  Description                       Reference
      ===========  ===========                       ==============
      TBD1(0xY)
      6 (0x40)     S-BFD IP/UDP-encapsulated,        This document        RFC 7885
                   for PW Fault Detection only
      TBD2(0xZ)

      7 (0x80)     S-BFD PW-ACH-encapsulated,        This document        RFC 7885
                   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 that have been added to the existing "VCCV Capability
   AVP" AVP
   (Attribute Type 96) Values" registry in the L2TP name spaces.  The Layer "Layer Two Tunneling
   Protocol "L2TP" Name Spaces are reachable from 'L2TP'" registry [IANA-L2TP].  IANA is
   requested to assign has assigned the
   following L2TPv3 Connectivity Verification (CV) Types in the VCCV "VCCV
   Capability AVP Values (Attribute Type 96) Values" registry.

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

      L2TPv3 Connectivity Verification (CV) Types:

      Bit (Value)  Description                  Reference
      ===========  ===========                  ==============
      TBD1(0xY)
      6 (0x40)     S-BFD IP/UDP-encapsulated,   This document   RFC 7885
                   for PW Fault Detection only
      TBD2(0xZ)

      7 (0x80)     S-BFD L2SS-encapsulated,     This document     RFC 7885
                   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 has allocated a
   Channel Types Type in the "MPLS Generalized Associated Channel (G-ACh) Types" registry:
   Types (including Pseudowire Associated Channel Types)" registry
   [IANA-G-ACh].

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

   Registry:
                                                TLV

    Value   Description                         Follows                          Reference
    ------  ----------------------------------  -------   ---------------
    TBD3
    0x0008  S-BFD Control, PW-ACH/L2SS          No       [This document]           RFC 7885
            encapsulation
            (without IP/UDP Headers)

8.

6.  References

8.1.

6.1.  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.

   [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]

   [RFC7880]  Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
              Pallagatti, "Seamless Bidirectional Forwarding Detection
              (S-BFD)", RFC 7880, DOI 10.17487/RFC7880, June 2016,
              <http://www.rfc-editor.org/info/rfc7880>.

   [RFC7881]  Pignataro, C., and D. Ward, D., and N. Akiya, "Seamless
              Bidirectional Forwarding Detection (S-BFD) Alert
              Discriminator", draft-akiya-bfd-seamless-alert-discrim-03
              (work for IPv4, IPv6,
              and MPLS", RFC 7881, DOI 10.17487/RFC7881, June 2016,
              <http://www.rfc-editor.org/info/rfc7881>.

   [RFC7886]  Govindan, V. and C. Pignataro, "Advertising Seamless
              Bidirectional Forwarding Detection (S-BFD) Discriminators
              in progress), October 2014. the Layer Two Tunneling Protocol Version 3 (L2TPv3)",
              RFC 7886, DOI 10.17487/RFC7886, June 2016,
              <http://www.rfc-editor.org/info/rfc7886>.

6.2.  Informative References

   [IANA-G-ACh]
              Internet Assigned Numbers Authority, "MPLS Generalized
              Associated Channel (G-ACh) Types (including Pseudowire
              Associated Channel Types)",
              <http://www.iana.org/assignments/g-ach-parameters>.

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

   [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>.

6.  Acknowledgments

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

Acknowledgements

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

7.

Contributors

   Mallik Mudigonda
   Cisco Systems, Inc.

   Email: mmudigon@cisco.com

Authors' Addresses

   Vengada Prasad Govindan
   Cisco Systems, Inc.

   Email: venggovi@cisco.com

   Carlos Pignataro
   Cisco Systems, Inc.

   Email: cpignata@cisco.com