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Versions: (draft-eastlake-trill-rbridge-bfd) 00 01 02 03 04 05 06 07 RFC 7175

Network Working Group                                          V. Manral
Internet-Draft                                             HP Networking
Intended status: Standards Track                             D. Eastlake
Expires: November 3, 2011                                         Huawei
                                                                 D. Ward
                                                        Juniper Networks
                                                             A. Banerjee
                                                           Cisco Systems
                                                            May 02, 2011

  Rbridges: Bidirectional Forwarding Detection (BFD) support for TRILL


   This document specifies use of the BFD (Bidirectional Forwarding
   Detection) protocol in RBridge campuses based on the Rbridge Channel
   extension to the TRILL (TRansparent Interconnection of Lots of Links)

   BFD is a widely deployed (Operations, Administration and Maintenance)
   OAM mechanism in IP and MPLS networks.  However, in the present form
   a BFD packet cannot be sent over a TRILL network as it is either IP/
   UDP encapsulated or encapsulated directly over Multi Protocol Label
   Switching (MPLS) or using Associated Channel Header (ACH)
   encapsulation.  This document defines BFD encapsulation over TRILL to
   address this shortcoming.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [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

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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 3, 2011.

Copyright Notice

   Copyright (c) 2011 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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   (http://trustee.ietf.org/license-info) in effect on the date of
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   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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   3.  BFD over TRILL  . . . . . . . . . . . . . . . . . . . . . . . . 5
   4.  Sessions and Initialization . . . . . . . . . . . . . . . . . . 5
   5.  Relationship to MPLS OAM  . . . . . . . . . . . . . . . . . . . 6
   6.  TRILL BFD Control Protocol  . . . . . . . . . . . . . . . . . . 6
     6.1.  One-Hop TRILL BFD Control . . . . . . . . . . . . . . . . . 7
     6.2.  BFD Control Frame Processing  . . . . . . . . . . . . . . . 7
   7.  TRILL BFD Echo Protocol . . . . . . . . . . . . . . . . . . . . 8
     7.1.  BFD Echo Frame Processing . . . . . . . . . . . . . . . . . 8
   8.  Management and Operations Considerations  . . . . . . . . . . . 9
   9.  Security Considerations . . . . . . . . . . . . . . . . . . . . 9
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 9
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 9
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   12.1.  Normative References   . . . . . . . . . . . . . . . . . . . 10
   12.1.  Informative References   . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 11

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1.  Introduction

   Faster convergence is a very critical feature of TRILL networks.  The
   TRILL IS-IS Hellos [TRILLAdj] used between RBridges provide a basic
   neighbor and continuity check for TRILL links.  However, failure
   detection by non-receipt of such Hellos is based on the holding time
   parameter which is commonly set to a value of tens of seconds and, in
   any case, has a minimum expressible value of one second.

   Some applications, including Voice over IP, may wish, with high
   probability, to detect interruptions in continuity within a much
   shorter time period.  In some cases physical layer failures can be
   detected very rapidly but this is not always possible, such as when
   there is a failure between two bridges that are in turn between two
   RBridges.  There are also many subtle failures possible at higher
   levels.  For example, some forms of failure could affect unicast
   frames while still letting multicast frames through; since all TRILL
   IS-IS Hellos are multicast such a failure cannot be detected with
   Hellos.  Thus, a low overhead method for frequently testing
   continuity for the TRILL Data between neighbor RBridges is necessary
   for some applications.  BFD protocol provides a low-overhead, short-
   duration detection of failures in the path between forwarding

   This document describes a TRILL encapsulation for BFD packets between
   Rbridges using the Rbridge Channel facility [TRILLChannel].

2.  Terminology

   ACH: Assiciated Channel Header

   BFD: Bi-directional Forwarding Detection

   GTSM: Generalized TTL Security Mechanism

   IP: Internet Protocol

   IS-IS: Intermediate-System to Intermediate-System

   MPLS: Multi Protocol Label Switching

   OAM: Operations, Administration, and Maintenance

   PPP: Point-to-Point Protocol

   TRILL: Transparent Interconnection of Lots of Links

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   TTL: Time To Live

   UDP: User Datagram Protocol

3.  BFD over TRILL

   TRILL supports neighbor BFD Echo and one-hop and multi-hop BFD
   Control, as specified below, over the TRILL Rbridge Channel facility.
   Multi-destination BFD is beyond the scope of this document.  The
   Rbridge Channel facility is specified in [TRILLChannel].

   BFD over TRILL support is similar to BFD over IP support except where
   it is explicitly so mentioned.  When running BFD over TRILL both
   Single Hop as well as in Multi Hop sessions are supported.

   Asynchronous mode is supported, and the demand mode is not supported
   for TRILL.  BFD over TRILL supports the Echo function, however this
   can be used for only Single hop sessions.

   The TRILL Header Hop Count in the BFD packets is sent out with a
   value of 63.  To reduce spoofing attacks, the TRILL Hop Count of a
   received frame is checked.  For a Single Hop session if the Hop count
   is less than 63 the packet is discarded if the GTSM mode [RFC5082] is
   set.  For Multi Hop sessions the Hop count check can be disabled or
   the bfdTrillAcceptedHopCount value can be configured.  If a packet is
   received with a hop count of less than bfdTrillAcceptedHopCount, the
   packet is discarded.

   Like in BFD for IP the format of the Echo Packet is not defined.

   A new channel type for the BFD TRILL Control frame as well as for BFD
   Echo packet is defined.

   Authentication mechanisms as supported in BFD are also supported for
   BFD running over TRILL.

4.  Sessions and Initialization

   Within an RBridge campus, there will be only a single TRILL BFD
   Control session between two RBridges over a given link visible to
   TRILL.  This BFD session must be bound to this link.  Any BFD packet
   from the remote machine with a zero value of Your Discriminator MUST
   be associated with the session bound to the remote system and link.

   Note that TRILL BFD provides OAM facilities for the TRILL Data plane.
   This is above whatever protocol is in use on a particular link, such

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   as a Point-to-Point Protocol (PPP) [TrillPPP] link or an Ethernet
   link.  Link technology specific OAM protocols may be used on a link
   between neighbor RBridges, for example Continuity Fault Management
   [802.1ag] if the link is Ethernet.  But such link layer OAM and
   coordination between it and TRILL data plane layer OAM, such as TRILL
   BFD, is beyond the scope of this document.

   If lower level mechanisms, such as link aggregation [802.1AX], are in
   use that present a single logical interface to TRILL IS-IS, only a
   single TRILL BFD session can be established to any other RBridge over
   this logical interface.  However, lower layer OAM could be aware of
   and/or run separately on each of the components of an aggregation.

5.  Relationship to MPLS OAM

   TRILL BFD uses the TRILL Rbridge Channel [TRILLChannel] in the same
   way that MPLS OAM protocols use the MPLS Generic Associated Channel
   [RFC5586].  However, the RBridges that implement TRILL are IS-IS
   [IS-IS] based routers, not label switched routers; thus TRILL BFD is
   closer to IPv4/IPv6 BFD than to MPLS BFD.

   TRILL BFD optionally includes support of BFD Echo which is not
   specified for MPLS BFD.

6.  TRILL BFD Control Protocol

   TRILL BFD Control frames are unicast TRILL OAM Message Channel frames
   [TRILLChannel].  The TRILL Rbridge Protocol value is given in Section

   The protocol specific data associated with the TRILL BFD Control
   protocol is as shown below.  See [RFC5880] for further information on
   these fields.

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    TRILL BFD Control Protocol Data:
       |Vers |  Diag   |Sta|P|F|C|A|D|M|  Detect Mult  |    Length     |
       |                       My Discriminator                        |
       |                      Your Discriminator                       |
       |                    Desired Min TX Interval                    |
       |                   Required Min RX Interval                    |
       |                 Required Min Echo RX Interval                 |
    Optional Authentication Section:
       |   Auth Type   |   Auth Len    |    Authentication Data...     |

6.1.  One-Hop TRILL BFD Control

   One-hop TRILL BFD Control is typically used to rapidly detect link
   and RBridge failures.  TRILL BFD frames over one hop for such
   purposes SHOULD be sent with priority 7.

   For neighbor RBridges RB1 and RB2, each RBridge sends one-hop TRILL
   BFD Control frames to the other only if TRILL IS-IS has detected bi-
   directional connectivity, that is, the adjacency is in the Two-Way or
   report states [TRILLAdj] and both RBridges indicate support of TRILL
   BFD is enabled.  The BFD Enabled TLV is used to indicate this as
   specified in [RFC6213].

6.2.  BFD Control Frame Processing

   The following tests MUST be performed on received TRILL BFD Control
   frames before generic BFD processing.

   If the M bit in the TRILL Header is non-zero, discard the frame.
   TRILL support of multi-destination BFD Control is beyond the scope of
   this document.

   If the OAM Header MH flag is zero, indicating one-hop, test that the
   TRILL Header hop count received was 0x3F (i.e., is 0x3E if it has
   already been decremented) and if it is any other value discard the
   frame.  If the MH OAM flag is one, indicating multi-hop, test that
   the TRILL Header hop count received was not less than a configurable
   value (bfdTrillAcceptedHopCount) that defaults to 0x30.  If it is
   less, discard the frame.

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7.  TRILL BFD Echo Protocol

   A TRILL BFD Echo frame is a unicast TRILL Rbridge Channel frame, as
   specified in [TRILLChannel], which should be bounced back by an
   immediate neighbor because both the ingress and egress nicknames are
   set to a nickname of the originating RBridge.  Normal TRILL Data
   frame forwarding will cause the frame to be returned.  The Rbridge
   Channel protocol number for BFD Echo is given in Section 10.

   TRILL BFD Echo frames SHOULD only be sent on a link if

   1.  A TRILL BFD Control session has been established,

   2.  TRILL BFD Echo support is indicated by the potentially echo
   responding RBridge, and

   3.  The adjacency is in the Report state [TRILLAdj], and

   4.  The TRILL BFD Echo originating RBridge wishes to make use of this
   optional feature.

   Since the originating RBridge is the RBridge that will be processing
   a returned Echo frame, the entire TRILL BFD Echo protocol specific
   data area is considered opaque and left to the discretion of the
   originating RBridge.  Nevertheless, it is RECOMMENDED that this data
   include information by which the originating RBridge can authenticate
   the returned BFD Echo frame and confirm the neighbor that echoed the
   frame back.  For example, it could include its own SystemID, the
   neighbor's SystemID, a session identifier and a sequence count as
   well as a Message Authentication Code.

7.1.  BFD Echo Frame Processing

   The following tests MUST be performed on returned TRILL BFD Echo
   frames before other processing.  The RBridge Channel document now
   requires that the information in the TRILL Header be given to the OAM

   If the M-bit in the TRILL Header is non-zero, discard the frame.
   TRILL support of multi-destination BFD Echo is beyond the scope of
   this document.

   The TRILL BFD Echo frame should have gone exactly two hops so test
   that the TRILL Header hop count as received was 0x3E (i.e., 0x3D if
   it has already been decremented) and if it is any other value discard
   the frame.  The TRILL Rbridge Channel Header in the frame should have
   the MH bit equal to one and if it is zero, the frame is discarded.

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8.  Management and Operations Considerations

   The TRILL BFD parameters on an RBridge are configurable.  The default
   values are the same as in the IP BFD case, except where specified in
   this document i.e.  Hop Count.

   It is required that the operator of an RBridge campus configure the
   rates at which TRILL BFD frames are transmitted on a link to avoid
   congestion (e.g., link, I/O, CPU) and false failure detection.

9.  Security Considerations

   This draft raises no new security considerations than those already
   mentioned in the BFD [RFC5880].  By keeping a seperate flag for
   Single Hop and Multihop sessions it allows the TTL check to be
   performed thus making harder the spoofing of BFD packets.

   However the same is possible even without the changes mentioned in
   this document.  A device should rate limit the BFD packets redirected
   to the CPU so that the CPU is not overwhelmed.

10.  IANA Considerations

   IANA is request to allocate two TRILL Rbridge Channel numbers from
   the range allocated by Standards Actions, as follows:

       Protocol     Number
       --------     ------
       BFD Control   TBD (2 suggested)
       BFD Echo      TBD (3 suggested)

11.  Acknowledgements

   The authors would like to thank a lot of folks.  Names will be
   disclosed soon.

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  12.  References

  12.1.  Normative References

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

   [RFC5082]  Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, October 2007.

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

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, June 2010.

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

   [TRILLAdj] Eastlake, D., R. Perlman, A. Ghanwani, D. Dutt, V. Manral,
               "RBridges: Adjacency", draft-ietf-trill-adj, work
              in progress.

   [TRILLChannel] Eastlake, D., V. Manral, Y. Li, S. Aldrin, D. Ward,
              "RBridges: RBridge Channel Support in TRILL",
              draft-ietf-trill-rbridge-channel, work in progress.

12.2.  Informative References

   [802.1AX]  IEEE, "IEEE Standard for Local and metropolitan area
              networks / Link Aggregation", 802.1AX-2008,
              1 January 2008.

   [802.1ag]  IEEE, "IEEE Standard for Local and metropolitan area
              networks / Virtual Bridged Local Area Networks /
              Connectivity Fault Management", 802.1ag-2007, 17
              December 2007.

   [TrillPPP]  Carlson, J., "PPP TRILL Protocol Control Protocol",
              draft-ietf-pppext-trill-protocol-02.txt, work in progress,
              May 2010.

   [IS-IS] ISO/IEC 10589:2002, "Intermediate system to Intermediate
           system routeing information exchange protocol for use in
           conjunction with the Protocol for providing the
           Connectionless-mode NetworkService (ISO 8473),"
           ISO/IEC 10589:2002.

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Authors' Addresses

   Vishwas Manral
   HP Networking
   19111 Pruneridge Ave.
   Cupertino, CA  95014

   Phone: 408-777-0693
   Email: vishwas.manral@hp.com

   Donald Eastlake 3rd
   155 Beaver Street
   Milford, MA  01757

   Phone: 508-333-2270
   Email: d3e3e3@gmail.com

   Dave Ward
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089-1206

   Phone: 408-745-2000
   Email: dward@juniper.net

   Ayan Banerjee
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95138

   Phone: 408-525-8781
   Email: ayabaner@cisco.com

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