RFC 7883

Advertising Seamless Bidirectional Forwarding Detection (S-BFD) Discriminators in IS-IS

📅 published July 2016, from ietf

Advertising Seamless BFD Discriminators in IS-IS 🦋

Okay bestie, here's the title block first so you know what you're looking at ✨

  • RFC number: 7883
  • Title: Advertising Seamless Bidirectional Forwarding Detection (S-BFD) Discriminators in IS-IS
  • Stream: Internet Engineering Task Force (IETF)
  • Authors: L. Ginsberg (Cisco Systems), N. Akiya (Big Switch Networks), M. Chen (Huawei)
  • Category: Standards Track
  • ISSN: 2070-1721
  • Date: July 2016
  • Obsoletes / Updates: the title block doesn't list anything this one obsoletes or updates 🌈

Abstract ✨

Okay so this doc is all about giving S-BFD Discriminators a ride through IS-IS. It defines a way to advertise one or more Seamless Bidirectional Forwarding Detection (S-BFD) Discriminators using the IS-IS Router CAPABILITY TLV 💖

Status of This Memo 📝

This is an Internet Standards Track document, so it's a real standard, not just vibes 💅

It's a product of the Internet Engineering Task Force (IETF), and it represents the consensus of the IETF community. It got public review and was approved for publication by the Internet Engineering Steering Group (IESG). If you want more on Internet Standards, check out Section 2 of RFC 7841.

For the current status, any errata, and how to give feedback, go to http://www.rfc-editor.org/info/rfc7883 🫶

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) as in effect on the date of publication. Please actually read these, because they spell out your rights and restrictions. Code Components pulled out of this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions, and they come 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 people controlling the copyright in some of that material may not have granted the IETF Trust the right to allow modifications outside the IETF Standards Process. Without an adequate license from those copyright holders, 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. The exceptions are formatting it for publication as an RFC or translating it into languages other than English 🌸

Table of Contents 🗂️

   1. Introduction ....................................................3
   2. Encoding Format .................................................3
   3. IANA Considerations .............................................4
   4. Security Considerations .........................................4
   5. Normative References ............................................4
   Acknowledgements ...................................................5
   Authors' Addresses .................................................5

1. Introduction 🌸

Okay so [RFC7880] defines a simplified way to use Bidirectional Forwarding Detection (BFD) [RFC5880]. The catch is that this mechanism depends on network nodes knowing the BFD Discriminators that each node has reserved for it. Using the Intermediate System to Intermediate System (IS-IS) [IS-IS] protocol is one possible way to advertise those discriminators 🧠

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. Encoding Format 🎀

So the IS-IS Router CAPABILITY TLV from [RFC4971] is what gets used to advertise Seamless BFD (S-BFD) Discriminators. A new sub-TLV is defined below, and the S-BFD Discriminators sub-TLVs are formatted as specified in [RFC5305] 🦋

                                                  No. of octets
                 +-----------------------------+
                 | Type (20)                   |     1
                 +-----------------------------+
                 | Length (multiple of 4)      |     1
                 +-----------------------------+
                 | Discriminator Value(s)      |     4/Discriminator
                 :                             :
                 +-----------------------------+

Including an S-BFD Discriminators sub-TLV in a Router CAPABILITY TLV is optional. Multiple S-BFD Discriminators sub-TLVs MAY be advertised by an IS. How a given discriminator maps to a specific use case when several are advertised is out of scope for this document 🫧

S-BFD Discriminator advertisements MAY be flooded within an area or throughout the domain, using the procedures in [RFC4971]. The right flooding scope depends on what S-BFD is being used for. If S-BFD usage stays entirely within a Level-1 area, then area scope is the way to go. If S-BFD usage spans different Level-1 areas, then domain scope is the move 🌈

3. IANA Considerations 🧚

IANA added a new sub-TLV to the "Sub-TLVs for TLV 242" registry. Here's the registration 📋

   Value  Description
   -----  --------------------
   20     S-BFD Discriminators

4. Security Considerations 💀

Okay this part is serious. Security concerns for IS-IS are covered in [IS-IS], [RFC5304], and [RFC5310]. The new S-BFD Discriminators sub-TLV does not introduce any new security risks for IS-IS 🔐

Advertising the S-BFD Discriminators makes it possible for attackers to initiate S-BFD sessions using the advertised information. The vulnerabilities this creates, and how to mitigate them, are discussed in [RFC7880]. Do not skip that one 😭

5. Normative References 📚

Here are all the references, copied exactly as they appear 🫶

   [IS-IS]    International Organization for Standardization,
              "Intermediate System to Intermediate System intra-domain
              routeing information exchange protocol for use in
              conjunction with the protocol for providing the
              connectionless-mode network service (ISO 8473)",
              ISO Standard 10589, 2002.

   [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>.

   [RFC4971]  Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed.,
              "Intermediate System to Intermediate System (IS-IS)
              Extensions for Advertising Router Information", RFC 4971,
              DOI 10.17487/RFC4971, July 2007,
              <http://www.rfc-editor.org/info/rfc4971>.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304,
              October 2008, <http://www.rfc-editor.org/info/rfc5304>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305,
              October 2008, <http://www.rfc-editor.org/info/rfc5305>.

   [RFC5310]  Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
              and M. Fanto, "IS-IS Generic Cryptographic
              Authentication", RFC 5310, DOI 10.17487/RFC5310,
              February 2009, <http://www.rfc-editor.org/info/rfc5310>.

   [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>.

   [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>.

Acknowledgements 🙏

The authors thank Sam Aldrin, Manav Bhatia, and Carlos Pignataro for input that was essential to defining the needed functionality 💖

Authors' Addresses 💌

   Les Ginsberg
   Cisco Systems
   510 McCarthy Blvd.
   Milpitas, CA  95035
   United States of America

   Email: ginsberg@cisco.com


   Nobo Akiya
   Big Switch Networks

   Email: nobo.akiya.dev@gmail.com


   Mach(Guoyi) Chen
   Huawei

   Email: mach.chen@huawei.com
📦 where this page comes from