TRILL                                                           M. Zhang
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                           S. Pallagatti
Expires: May 26, 2017                                   Juniper Networks
                                                             V. Govindan
                                                           Cisco Systems
                                                       November 22, 2016


                TRILL Support of Point to Multipoint BFD
                      draft-ietf-trill-p2mp-bfd-03

Abstract

   Point to multipoint (P2MP) BFD is designed to verify multipoint
   connectivity.  This document specifies the support of P2MP BFD in
   TRILL.  Similar to TRILL point-to-point BFD, BFD Control packets in
   TRILL P2MP BFD are transmitted using RBridge Channel message.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on December 11, 2015.

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
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   include Simplified BSD License text as described in Section 4.e of



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

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Acronyms and Terminology . . . . . . . . . . . . . . . . . . .  2
     2.1.  Acronyms . . . . . . . . . . . . . . . . . . . . . . . . .  2
     2.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Bootstrapping  . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  A New RBridge Channel Message for P2MP BFD . . . . . . . . . .  3
   5.  Discriminators and Packet Demultiplexing . . . . . . . . . . .  4
   6.  Tracking Active Tails  . . . . . . . . . . . . . . . . . . . .  4
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  4
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  5
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  5
   10.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  5
     10.1.  Normative References  . . . . . . . . . . . . . . . . . .  5
     10.2.  Informative References  . . . . . . . . . . . . . . . . .  6
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  7



1.  Introduction

   TRILL supports multicast forwarding.  Applications based on TRILL
   multicast may need quick detection of multicast failures using P2MP
   BFD.  This document specifies TRILL support of P2MP BFD.

   To use P2MP BFD, the head end needs to periodically transmit BFD
   Control packets to all tails using TRILL multicast.  A new RBridge
   Channel message is allocated for this purpose.

   In order to execute the global protection of distribution used for
   multicast forwarding [I-D.ietf-trill-resilient-trees], the head needs
   to track the active status of tails
   [I-D.ietf-bfd-multipoint-active-tail].  If the tail loses
   connectivity of the new RBridge Channel message from the head, the
   tail should notify the head of the lack of multipoint connectivity
   with unicast BFD Control packets.  These unicast BFD Control packets
   are transmitted using the existing RBridge Channel message assigned
   to BFD Control [RFC7175].

2.  Acronyms and Terminology

2.1.  Acronyms

   Data Label: VLAN or Fine Grained Label [RFC7172].



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   BFD: Bidirectional Forwarding Detection

   P2MP: Point to Multi-Point

   TRILL: Transparent Interconnection of Lots of Links or Tunneled
   Routing in the Link Layer

2.2.  Terminology

   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 [RFC2119].

   Familiarity with [RFC6325], [RFC7175], and [RFC7178] is assumed in
   this document.

3.  Bootstrapping

   The TRILL adjacency mechanism bootstraps the establishment of the BFD
   session [RFC7177].  A slight wording update to the second sentence in
   Section 6 of [RFC7177] is required.

   It currently read:

      If an RBridge supports BFD [RFC7175], it will have learned whether
      the other RBridge has BFD enabled by whether or not a BFD-Enabled
      TLV [RFC6213] was included in its Hellos.

   Now it should read:

      If an RBridge supports BFD [RFC7175] [this document], it will have
      learned whether the other RBridge has BFD enabled by whether or
      not a BFD-Enabled TLV [RFC6213] was included in its Hellos.

4.  A New RBridge Channel Message for P2MP BFD

   RBridge Channel message protocol 0x002 is defined for TRILL point-to-
   point BFD Control packets in [RFC7175].  If the M bit of the TRILL
   Header of the RBridge channel packet containing a BFD Control packet
   is non-zero, the packet MUST be dropped [RFC7175].  In P2MP BFD, the
   head is required to probe tails using multicast.  This means the M
   bit will be set to 1.  For this reason, a new RBridge Channel
   message, whose protocol code point is TBD, is specified in this
   document.  An RBridge that supports P2MP BFD MUST support the new
   RBridge Channel message for P2MP BFD. The capability to support the
   RBridge Channel message for P2MP BFD, and therefore support
   performing P2MP BFD, is announced within the "RBridge Channel
   Protocols Sub-TLV" in LSPs [RFC7176].



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   As specified in [RFC7178], when the tail receives TRILL Data packets
   sent as BFD RBridge channel messages, it will absorb the packets
   itself rather than deliver these packets to its attached end-
   stations.

5.  Discriminators and Packet Demultiplexing

   The processing in Section 3.2 of [RFC7175] applies except that the
   test on the M bit in the TRILL Header is reversed.  If the M bit is
   zero, the packet is discarded.  If the M bit is one, it is processed.

   After the Section 3.2 of [RFC7175] processing, the tail demultiplexes
   incoming BFD packets based on a combination of the source address and
   My Discriminator as specified in [I-D.ietf-bfd-multipoint].  In
   addition to this combination, TRILL P2MP BFD that requires the tail
   use the Data Label, which is either the inner VLAN or the Fine
   Grained Label [RFC7172], for demultiplexing.  If the tail needs to
   notify the head about the failure of a multipath, the tail is
   required to send unicast BFD Control packets using the same Data
   Label as used by the head.

6.  Tracking Active Tails

   According to[I-D.ietf-bfd-multipoint], the head has a session of type
   MultipointHead that is bound to a multipoint path.  Multipoint BFD
   Control packets are sent by this session over the multipoint path,
   and no BFD Control packets are received by it.  Each tail dynamically
   creates a MultipointTail per a multipoint path.  MultipointTail
   sessions receive BFD Control packets from the head over multipoint
   paths.

   If the head is keeping track of some or all of the tails
   [I-D.ietf-trill-resilient-trees], it has a session of type
   MultipointClient per tail that it cares about
   [I-D.ietf-bfd-multipoint-active-tail].  See
   [I-D.ietf-bfd-multipoint-active-tail] for detail operations of
   tacking active tails.

7.  Security Considerations

   P2MP BFD control packets can be encapsulated as the payload of the
   RBridge Channel Tunnel [RFC7978].  In that case, the security option
   of RBridge Channel Tunnel can secure the transmission of BFD control
   packets.

   The demultiplexing of TRILL P2MP BFD at the tail is Data Label aware.
   This enhances the security of the dynamic creation of MultipointTail
   sessions at tails.  In order to forge BFD Control packets, the



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   attacker has to acquire the right Data Label that the head uses for
   P2MP BFD.

   For general multipoint BFD security considerations, see
   [I-D.ietf-bfd-multipoint].

   For general RBridge Channel security considerations, see [RFC7178].

8.  IANA Considerations

   IANA is required to allocate one RBridge Channel protocol number from
   the Standards Action range, as follows:

          Protocol          Number
          ----------------  ------
          P2MP BFD Control  TBD

9.  Acknowledgements

   Authors would like to thank the comments and suggestions from Gayle
   Noble and Donald Eastlake.

10.  References

10.1.  Normative References

   [I-D.ietf-bfd-multipoint]
              Katz, D., Ward, D., and J. Networks, "BFD for Multipoint
              Networks", draft-ietf-bfd-multipoint (work in progress).

   [I-D.ietf-bfd-multipoint-active-tail]
              Katz, D., Ward, D., and J. Networks, "BFD Multipoint
              Active Tails.", draft-ietf-bfd-multipoint-active-tail
              (work in progress).

   [I-D.ietf-trill-resilient-trees]
              Zhang, M., Senevirathne, T., Pathangi, J., Banerjee, A.,
              and A. Ghanwani, "TRILL Resilient Distribution Trees",
              draft-ietf-trill-resilient-trees (work in progress).

   [RFC7978]  Eastlake 3rd, D., Umair, M., and Y. Li, "Transparent
              Interconnection of Lots of Links (TRILL): RBridge Channel
              Header Extension", RFC 7978, DOI 10.17487/RFC7978,
              September 2016, <http://www.rfc-editor.org/info/rfc7978>.

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




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   [RFC6325]  Perlman, R., Eastlake, D., Dutt, D., Gai, S., and A.
              Ghanwani, "Routing Bridges (RBridges): Base Protocol
              Specification", RFC 6325, July 2011.

   [RFC7172]  Eastlake, D., Zhang, M., Agarwal, P., Perlman, R., and D.
              Dutt, "Transparent Interconnection of Lots of Links
              (TRILL): Fine-Grained Labeling", RFC 7172, May 2014.

   [RFC7175]  Manral, V., Eastlake, D., Ward, D., and A. Banerjee,
              "Transparent Interconnection of Lots of Links (TRILL):
              Bidirectional Forwarding Detection (BFD) Support", RFC
              7175, May 2014.

   [RFC7176]  Eastlake, D., Senevirathne, T., Ghanwani, A., Dutt, D.,
              and A. Banerjee, "Transparent Interconnection of Lots of
              Links (TRILL) Use of IS-IS", RFC 7176, May 2014.

   [RFC7177]  Eastlake, D., Perlman, R., Ghanwani, A., Yang, H., and V.
              Manral, "Transparent Interconnection of Lots of Links
              (TRILL): Adjacency", RFC 7177, May 2014.

   [RFC7178]  Eastlake, D., Manral, V., Li, Y., Aldrin, S., and D. Ward,
              "Transparent Interconnection of Lots of Links (TRILL):
              RBridge Channel Support", RFC 7178, May 2014.

10.2.  Informative References

   [RFC6213]  Hopps, C. and L. Ginsberg, "IS-IS BFD-Enabled TLV", RFC
              6213, April 2011.






















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Authors' Addresses


   Mingui Zhang
   Huawei Technologies
   No.156 Beiqing Rd. Haidian District
   Beijing  100095
   P.R. China

   Email: zhangmingui@huawei.com


   Santosh Pallagatti
   Juniper Networks
   Embassy Business Park
   Bangalore  KA 560093
   India

   Email: santoshpk@juniper.net


   Vengada Prasad Govindan
   Cisco Systems

   Email: venggovi@cisco.com


























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