RFC 6233

IS-IS Registry Extension for Purges

📅 published May 2011, from ietf

RFC 6233: IS-IS Registry Extension for Purges 🎀

  • RFC number: 6233
  • Title: IS-IS Registry Extension for Purges
  • Authors: T. Li and L. Ginsberg, both from Cisco Systems, Inc. (Tony Li and Les Ginsberg, bestie!)
  • Category: Standards Track
  • Date: May 2011
  • ISSN: 2070-1721
  • Updates: RFC 3563, RFC 5304, RFC 5310
  • Obsoletes: not listed in the title block

It's an IETF (Internet Engineering Task Force) document, so it's basically official Internet homework 📚✨

Abstract 🦋

okay so IANA keeps the "IS-IS TLV Codepoints" registry, which tells you which TLVs can show up in which kinds of IS-IS PDUs. What it doesn't tell you is which TLVs are allowed in zero Remaining Lifetime LSPs, a.k.a. purges 🙈 This doc adds that info to the registry, listing the TLVs that are allowed in purges, and it updates the rules for making and processing purges when authentication is involved. It also updates RFC 3563, RFC 5304, and RFC 5310. main character energy 💅

Status of This Memo 📜

This is an Internet Standards Track document. ✨

It's a product of the Internet Engineering Task Force (IETF), so it represents the consensus of the IETF community. It got public review and was approved for publication by the Internet Engineering Steering Group (IESG). For more on Internet Standards, check Section 2 of RFC 5741.

Want the current status, any errata, or a way to send feedback? Head to http://www.rfc-editor.org/info/rfc6233 🌸

Copyright (c) 2011 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 they stand on the publication date. Please actually read these, because they spell out your rights and restrictions for this document. 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 the Simplified BSD License describes.

Table of Contents 🧚

   1. Introduction ....................................................2
      1.1. Requirements Language ......................................2
   2. Registry Changes ................................................2
   3. Purges and Authentication .......................................3
   4. IANA Considerations .............................................3
   5. Security Considerations .........................................3
   6. Normative References ............................................4

1. Introduction 🌈

The IS-IS [ISO-10589] routing protocol keeps a link state database of its routing domain's topology by flooding a set of Link State Protocol Data Units (LSPs). When the protocol doesn't need the info in an LSP anymore, it uses the purge mechanism to make the Intermediate Systems (ISs) in its domain throw that info away 🗑️ The process for generating purges is in Section 7.3.16.4 of [ISO-10589]. It keeps only the LSP header and drops any TLVs that were carried in the LSP.

Later IS-IS upgrades, like [RFC5304] and [RFC5310], change how purges get generated and let certain TLVs ride along in them. 🔥

1.1. 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 [RFC2119]. Yes, we're doing this properly 💅

2. Registry Changes 🍓

This document extends the current "IS-IS TLV Codepoints" registry, which [RFC3563] defines, so it records the set of TLVs that MAY be found in purges. All other TLVs MUST NOT appear in purges. Later docs can point to this registry as the definitive list of TLVs allowed in purges, and implementers get an easy-to-find cheat sheet of allowable TLVs ✨

The purge status for a given TLV also applies to all of its sub-TLVs. 🦋

3. Purges and Authentication 🔐

Earlier authentication docs, [RFC5304] and [RFC5310], said an IS could only accept a purge if the purge contained nothing but the Authentication TLV 🙃

This document updates and generalizes that behavior like so: an implementation that does authentication MUST NOT accept a purge containing any TLV that the registry lists as not acceptable in a purge. An implementation MUST NOT accept a purge containing a TLV that isn't listed in the registry, unless the purge also contains the Purge Originator Identification (POI) TLV [RFC6232]. Accepted purges MUST be propagated with no TLVs removed. If several purges arrive for the same LSP, the implementation MAY propagate any one of them 🎀

If an implementation that does authentication accepts a purge without the POI TLV and then decides to insert the POI TLV, it MUST also recompute authentication. 🫶

ISs MUST NOT accept LSPs that have a non-zero Remaining Lifetime and contain the POI TLV. 🙈

Purge generation is updated as follows: an implementation that does authentication generates a purge by first removing any TLVs that the registry doesn't list as acceptable in purges. The POI TLV MUST be added. Then any other TLVs that MAY be in purges, as the registry shows, MAY be added. Last of all, authentication, if any, gets added ✨

4. IANA Considerations 🌸

IANA has changed the "IS-IS TLV Codepoints" registry by adding a column for 'Purge'. A 'y' in this column means the TLV in that row MAY be found in a purge. An 'n' means the TLV in that row MUST NOT be found in a purge. 💖

The 'Purge' column should start out with a 'y' for TLV type 10 (Authentication) and for TLV type 137 (Dynamic hostname). Every other entry in this column gets an 'n'. Any other additions to this registry should explicitly specify their value for this column. 🧚

5. Security Considerations 💀

This document introduces no new security issues. Phew 😭🫶

6. Normative References 📚

   [ISO-10589]  ISO, "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/IEC 10589:2002.

   [RFC2119]    Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3563]    Zinin, A., "Cooperative Agreement Between the ISOC/IETF
                and ISO/IEC Joint Technical Committee 1/Sub Committee 6
                (JTC1/SC6) on IS-IS Routing Protocol Development",
                RFC 3563, July 2003.

   [RFC5304]    Li, T. and R. Atkinson, "IS-IS Cryptographic
                Authentication", RFC 5304, October 2008.

   [RFC5310]    Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
                and M. Fanto, "IS-IS Generic Cryptographic
                Authentication", RFC 5310, February 2009.

   [RFC6232]    Wei, F., Qin, Y., Li, Z., Li, T., and J. Dong, "Purge
                Originator Identification TLV for IS-IS", RFC 6232,
                May 2011.

Authors' Addresses 💌

   Tony Li
   Cisco Systems, Inc.
   170 W. Tasman Dr.
   San Jose, CA  95134
   USA

   EMail: tony.li@tony.li


   Les Ginsberg
   Cisco Systems, Inc.
   170 W. Tasman Dr.
   San Jose, CA  95134
   USA

   EMail: ginsberg@cisco.com

That's the whole RFC, bestie! 🌈👑

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