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diff --git a/doc/rfc/rfc7886.txt b/doc/rfc/rfc7886.txt new file mode 100644 index 0000000..ed169b6 --- /dev/null +++ b/doc/rfc/rfc7886.txt @@ -0,0 +1,339 @@ + + + + + + +Internet Engineering Task Force (IETF) V. Govindan +Request for Comments: 7886 C. Pignataro +Category: Standards Track Cisco +ISSN: 2070-1721 July 2016 + + + Advertising Seamless Bidirectional Forwarding Detection (S-BFD) + Discriminators in the Layer Two Tunneling Protocol Version 3 (L2TPv3) + +Abstract + + This document defines a new 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 3 (L2TPv3). + +Status of This Memo + + This is an Internet Standards Track document. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Further information on + Internet Standards is available in Section 2 of RFC 7841. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + 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. + + 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 + 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. + + + + + + + +Govindan & Pignataro Standards Track [Page 1] + +RFC 7886 S-BFD Discriminators in L2TPv3 July 2016 + + +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. References ......................................................5 + 5.1. Normative References .......................................5 + 5.2. Informative References .....................................5 + Acknowledgements ...................................................6 + Contributors .......................................................6 + Authors' Addresses .................................................6 + +1. Introduction + + [RFC7880] defines a simplified mechanism to use Bidirectional + Forwarding Detection (BFD) [RFC5880], referred to as Seamless + Bidirectional Forwarding Detection (S-BFD). The S-BFD mechanism + depends on network nodes knowing the BFD 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 3 (L2TPv3) + [RFC3931] is one possible means of advertising these discriminators. + + This document specifies the encoding to be used when S-BFD + 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 [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 Target Discriminator Identifier (ID) Attribute Value Pair + (AVP) is exchanged using the ICRQ (Incoming-Call-Request), ICRP + (Incoming-Call-Reply), OCRQ (Outgoing-Call-Request), and OCRP + (Outgoing-Call-Reply) control messages during session negotiation. + + + + + + +Govindan & Pignataro Standards Track [Page 2] + +RFC 7886 S-BFD Discriminators in L2TPv3 July 2016 + + +2.1. Encoding Format + + The S-BFD Target Discriminator ID AVP, Attribute Type 102, is an + identifier used to advertise the S-BFD target discriminator(s) + supported by an L2TP Control Connection Endpoint (LCCE) for the S-BFD + 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 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 ID AVP + advertisement in an L2TP 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 [RFC7880] concerns itself with + the advertisement of only one discriminator unless the mapping 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 + 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. When multiple S-BFD + Discriminators are advertised, how a given discriminator is mapped to + a specific use case is out of scope for this document. + + + + + + + + + + + + + +Govindan & Pignataro Standards Track [Page 3] + +RFC 7886 S-BFD Discriminators in L2TPv3 July 2016 + + + 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 message (ICRQ, ICRP, OCRQ, OCRP) + [RFC3931] MUST NOT be set inside the S-BFD Target Discriminator + ID AVP. + +3. IANA Considerations + + IANA maintains the "Control Message Attribute Value Pairs" + sub-registry as per [RFC3438]. IANA has assigned the following value + to the S-BFD Target Discriminator ID: + + Control Message Attribute Value Pairs + + Attribute + Type Description + ----------- ------------------ + 102 S-BFD Target Discriminator ID + +4. Security Considerations + + Security concerns for L2TP are addressed in [RFC3931]. The + introduction of the S-BFD Target Discriminator ID AVP advertisement + introduces no new security risks for L2TP. + + Advertising the S-BFD 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 [RFC7880]. + + + + + + + + + +Govindan & Pignataro Standards Track [Page 4] + +RFC 7886 S-BFD Discriminators in L2TPv3 July 2016 + + +5. References + +5.1. Normative References + + [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>. + + [RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S. + Pallagatti, "Seamless Bidirectional Forwarding Detection + (S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 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>. + + + + + + + + + + + + + + + + + + + + + + +Govindan & Pignataro Standards Track [Page 5] + +RFC 7886 S-BFD Discriminators in L2TPv3 July 2016 + + +Acknowledgements + + The authors would like to thank Nobo Akiya, Stewart Bryant, and Pawel + Sowinski for providing core inputs for the document, performing + thorough reviews, and providing a number of comments. The authors + would also like to thank Nagendra Kumar for his reviews. + +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 + + + + + + + + + + + + + + + + + + + + + + + + + +Govindan & Pignataro Standards Track [Page 6] + |