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 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 material or to cite them other than as "work in progress." This Internet-Draft will expire on January 24, 2016. Copyright Notice Copyright (c) 2015 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 Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must Govindan & Pignataro Expires January 24, 2016 [Page 1] Internet-Draft l2tpext-sbfd-discriminator July 2015 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. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. 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). Govindan & Pignataro Expires January 24, 2016 [Page 2] Internet-Draft l2tpext-sbfd-discriminator July 2015 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 Govindan & Pignataro Expires January 24, 2016 [Page 3] Internet-Draft l2tpext-sbfd-discriminator July 2015 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, . Govindan & Pignataro Expires January 24, 2016 [Page 4] Internet-Draft l2tpext-sbfd-discriminator July 2015 [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, . [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, . [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, . 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 Govindan & Pignataro Expires January 24, 2016 [Page 5]