Advertising S-BFD Discriminators in L2TPv3
draft-ietf-l2tpext-sbfd-discriminator-00

Networking Working Group                                     V. Govindan
Internet-Draft                                              C. Pignataro
Intended status: Standards Track                           Cisco Systems
Expires: January 24, 2016                                  July 23, 2015

               Advertising S-BFD Discriminators in L2TPv3
              draft-ietf-l2tpext-sbfd-discriminator-00.txt

Abstract

   This document defines a new AVP for advertising one or more S-BFD
   Discriminators using the L2TPv3 Control Protocol AVP.

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

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Table of Contents

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

1.  Introduction

   [I-D.ietf-bfd-seamless-base] defines a simplified mechanism to use
   Bidirectional Forwarding Detection (BFD)[RFC5880].  This mechanism
   depends on network nodes knowing the BFD discriminators which each
   node in the network has reserved for this purpose.  Use of the Layer2
   Tunneling protocol Version 3 (L2TPv3) [RFC3931] is one possible means
   of advertising these discriminators.  S-BFD requires the usage of
   unique discriminators within an administrative domain.

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

2.  S-BFD Target Discriminator ID AVP

   This AVP is exchanged during session negotiation (ICRQ, ICRP, OCRQ,
   OCRP).

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2.1.  Encoding Format

   The S-BFD Target Discriminator ID AVP, Attribute Type TBD, is an
   identifier used to advertise the S-BFD target discriminators
   supported by an LCCE for S-BFD Reflector operation.  This AVP
   indicates that the advertiser implements a S-BFD reflector supporting
   the specified target discriminators and is ready for S-BFD Reflector
   operation.  The receiving LCCE MAY use this AVP if it wants to
   monitor connectivity to the advertising LCCE using S-BFD or BFD.

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

   S-BFD Discriminator Advertisement (ICRQ, ICRP, ICCN, OCRQ, OCRP,
   OCCN):

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

   An LCCE MAY include the S-BFD Discriminator Advertisement AVP in a
   L2TP Control Protocol message (ICRQ, ICRP, OCRQ, OCRP) [RFC3931].
   Multiple S-BFD Discriminators AVPs MAY be advertised by a LCCE.  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 current use-cases
   [I-D.ietf-bfd-seamless-use-case] of S-BFD require advertisement of
   only one discriminator, the AVP encoding allows specification an
   arbitrary number of discrminators for extensibility.  When multiple
   S-BFD discriminators are advertised, the mechanism to choose a subset
   of specific discriminator(s) is out of scope for this document.

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

3.  IANA Considerations

   This number space is managed by IANA as per [RFC3438].

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

   Control Message Attribute Value Pairs

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         Attribute
         Type        Description
         ---------   ------------------
         TBD         S-BFD Discriminators

4.  Security Considerations

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

   Advertisement of the S-BFD discriminators does make 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].

5.  Acknowledgements

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

6.  Contributing Authors

   Mallik Mudigonda
   Cisco Systems
   Email: mmudigon@cisco.com

7.  References

7.1.  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-05 (work in
              progress), June 2015.

   [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>.

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   [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>.

   [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>.

7.2.  Informative References

   [I-D.ietf-bfd-seamless-use-case]
              Bhatia, M., Matsushima, S., Mirsky, G., and N. Kumar,
              "Seamless Bidirectional Forwarding Detection (BFD) Use
              Case", draft-ietf-bfd-seamless-use-case-02 (work in
              progress), April 2015.

Authors' Addresses

   Vengada Prasad Govindan
   Cisco Systems

   Email: venggovi@cisco.com

   Carlos Pignataro
   Cisco Systems

   Email: cpignata@cisco.com

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