wdiff rfc7886.alt-original rfc7886.txt


Networking Working Group
Internet Engineering Task Force (IETF)                       V. Govindan
Internet-Draft
Request for Comments: 7886                                  C. Pignataro
Intended status:
Category: Standards Track                                          Cisco
Expires: October 17, 2016                                 April 15,
ISSN: 2070-1721                                                June 2016

    Advertising Seamless Bidirectional Forwarding Detection (S-BFD)
 Discriminators in the Layer Two Tunneling Protocol, Protocol Version 3 (L2TPv3)
                draft-ietf-l2tpext-sbfd-discriminator-05

Abstract

   This document defines a new Attribute Value Attribute-Value Pair (AVP) that allows
   L2TP Control Connection Endpoints (LCCEs) to advertise one or more
   Seamless Bidirectional Forwarding Detection (S-BFD) Discriminator
   values using the Layer Two Tunneling Protocol, Version Protocol version 3 (L2TPv3).

Requirements Language

   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 RFC 2119 [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 an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list  It represents the consensus of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid the IETF community.  It has
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   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of six months this document, any errata,
   and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any
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   This Internet-Draft will expire on October 17, 2016.
   http://www.rfc-editor.org/info/rfc7886.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  S-BFD Target Discriminator ID AVP . . . . . . . . . . . . . .   2
     2.1.  Encoding Format . . . . . . . . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  Acknowledgements  References  . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Contributing Authors . . .   4
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
   7.   4
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgements  . . . . . . . .   5
     7.1.  Normative References . . . . . . . . . . . . . . . .   5
   Contributors  . . . . . . . . .   5
     7.2.  Informative References . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6   5

1.  Introduction

   [I-D.ietf-bfd-seamless-base]

   [RFC7880] defines a simplified mechanism to use Bidirectional
   Forwarding Detection (BFD) [RFC5880], referred to as Seamless
   Bidirectional Forwarding Detection (S-BFD).  The S-BFD
   mechanisms depend mechanism
   depends on network nodes knowing the BFD discriminators
   which Discriminators that each
   node in the network has reserved for this purpose.  S-BFD requires
   the usage of unique discriminators within an administrative domain.
   The use of the Layer Two Tunneling Protocol, Version Protocol version 3 (L2TPv3)
   [RFC3931] is one possible means of advertising these discriminators.

   This document specifies the encoding to be used when S-BFD
   discriminators
   Discriminators are advertised using L2TPv3.

1.1.  Terminology

   The reader is expected to be very familiar with the terminology and
   protocol constructs defined in S-BFD (see Section 2 of
   [I-D.ietf-bfd-seamless-base]) [RFC7880]) and
   L2TPv3 (see Section 1.3 of [RFC3931]).

   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 RFC 2119 [RFC2119].

2.  S-BFD Target Discriminator ID AVP

   The "S-BFD S-BFD Target Discriminator ID" AVP Identifier (ID) Attribute Value Pair
   (AVP) is exchanged using the ICRQ (Incoming-Call-Request), ICRP
   (Incoming-Call-Reply), OCRQ (Outgoing-
   Call-Request), (Outgoing-Call-Request), and OCRP
   (Outgoing-Call-Reply) control messages during session negotiations. negotiation.

2.1.  Encoding Format

   The S-BFD Target Discriminator Identifier (ID) Attribute Value Pair
   (AVP), ID AVP, Attribute Type "TBA by IANA", 102, is an
   identifier used to advertise the S-BFD Target Discriminator(s) target discriminator(s)
   supported by an LCCE L2TP Control Connection Endpoint (LCCE) for the S-BFD Reflector
   reflector operation.  This AVP indicates that the advertiser
   implements an S-BFD reflector supporting the specified target
   discriminator(s) and is ready for S-BFD Reflector reflector operation.  The
   receiving LCCE MAY use this AVP if it wants to monitor connectivity
   to the advertising LCCE using S-BFD.

   The Attribute Value field for this AVP has the following format:

   S-BFD Target Discriminator ID (ICRQ, ICRP, OCRQ, OCRP):

                                          No. of octets
      +-----------------------------+
      | Discriminator Value(s)      |     4/Discriminator
      :                             :
      +-----------------------------+

   An LCCE MAY include the S-BFD Target Discriminator Advertisement ID AVP
   advertisement in a an L2TP Control Protocol control message (ICRQ, ICRP, OCRQ, OCRP)
   [RFC3931].  If the other LCCE does not wish to monitor connectivity
   using S-BFD, it MAY safely discard this AVP without affecting the
   rest of session negotiation.  While [I-D.ietf-bfd-seamless-base] [RFC7880] concerns itself with
   the advertisement of only one discriminator unless the mapping to of
   discriminators to entities is specified, the AVP encoding allows the
   specification of an arbitrary number of S-BFD Discriminators (at
   least one) for extensibility.

   When an LCCE uses the S-BFD Target Discriminator ID AVP, AVP
   advertisement, multiple S-BFD Discriminators MAY be included, and at
   least one S-BFD Discriminator MUST be included.  When one S-BFD
   Discriminator is advertised, such an S-BFD Discriminator is
   associated with the L2TPv3
   Session. session.  When multiple S-BFD discriminators
   Discriminators are advertised advertised, how a given discriminator is mapped to
   a specific use case is out of scope for this document.

   The S-BFD Target Discriminator ID AVP allows for advertising at least
   one S-BFD Discriminator value:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Discriminator 1                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Discriminator 2 (Optional)                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               ...                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Discriminator n (Optional)                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The M bit of the L2TP Control Protocol Message control message (ICRQ, ICRP, OCRQ, OCRP)
   [RFC3931] MUST NOT be set inside the S-BFD Target Discriminator
   ID AVP advertisement. AVP.

3.  IANA Considerations

   IANA maintains a sub-registry "Message Type AVP (Attribute Type 0)
   Values" in the "Control Message Attribute Value Pairs"
   sub-registry as per [RFC3438].  IANA is requested to assign has assigned the first free following value from
   this sub-registry as
   to the Message typ AVP for "S-BFD S-BFD Target Discriminator ID".

   A summary of the new AVPs requested for Attribute Type 0 follows: ID:

   Control Message Attribute Value Pairs

         Attribute
         Type          Description
         -----------   ------------------
         TBA by IANA
         102           S-BFD Target Discriminator ID

4.  Security Considerations

   Security concerns for L2TP are addressed in [RFC3931].  Introduction  The
   introduction of the S-BFD Target Discriminator Advertisement ID AVP advertisement
   introduces no new security risks for L2TP.

   Advertisement of

   Advertising the S-BFD discriminators does make Discriminators makes it possible for attackers
   to initiate S-BFD sessions using the advertised information.  The
   vulnerabilities this poses and how to mitigate them are discussed in
   the Security Considerations section of
   [I-D.ietf-bfd-seamless-base].

7. [RFC7880].

5.  References

7.1.

5.1.  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.

   [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>.

   [RFC3438]  Townsley, W., "Layer Two Tunneling Protocol (L2TP)
              Internet Assigned Numbers Authority (IANA) Considerations
              Update", BCP 68, RFC 3438, DOI 10.17487/RFC3438, December
              2002, <http://www.rfc-editor.org/info/rfc3438>.

   [RFC3931]  Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed.,
              "Layer Two Tunneling Protocol - Version 3 (L2TPv3)",
              RFC 3931, DOI 10.17487/RFC3931, March 2005,
              <http://www.rfc-editor.org/info/rfc3931>.

7.2.

   [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>.

5.2.  Informative References

   [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>.

5.

Acknowledgements

   Authors

   The authors would like to thank Nobo Akiya, Stewart Bryant Bryant, and Pawel
   Sowinski for providing core inputs for the document and for document, performing
   thorough reviews reviews, and providing a number of comments.
   Authors  The authors
   would also like to thank Nagendra Kumar for his reviews.

6.  Contributing Authors

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