Updates to IS-IS TLV Codepoints Registry

The IS-IS TLV Codepoints registry was created by [RFC3563] and extended by [RFC6233]. The assignment policy for the registry is "Expert Review" as defined in [RFC5226]. As IS-IS related documents are developed, the codepoints required for the protocol extensions are reviewed by the Designated Experts and added to the IANA managed registry. As these documents are published as RFCs, the registries are updated to reference the relevant RFC. In the case of TLVs supporting prefix advertisement, currently separate sub-TLV registries are maintained for each TLV. These registries need to be combined into a common sub-TLV registry similar to what has been done for neighbor advertisement TLVs. In some cases there is a need to allocate codepoints defined in Internet-Drafts which seem likely to eventually gain WG approval without waiting for those drafts to be published as RFCs. This can be achieved using Expert Review, and this document sets out guidance for the Designated Experts to apply when reviewing allocations from the registry.

There is an existing common sub-TLV registry for Sub-TLVs for TLV 22, 141, and 222. [RFC5311] defines the IS Neighbor Attribute TLV (23) and the MT IS Neighbor Attribute TLV (223). Format of these TLVs is identical to TLVs 22 and 222 respectively. The IS Neighbor sub-TLV Registry needs to be extended to include these two TLVs. Settings for inclusion of each sub-TLV are identical to the settings for TLVs 22 and 222 respectively.

Currently there exist separate sub-TLV registries for TLVs (135, 235, 236, 237). As in the case of the IS Neighbor TLVs discussed in the previous section, assignment of sub-TLVs applicable to one or more of these TLVs is intended to be common. Therefore the existing separate sub-TLV registries need to be combined into a single registry entitled "Sub-TLVs for TLVs 135, 235, 236, and 237". As existing sub-TLV assignments are common to all the TLVs this represents no change to the protocol - only a clearer representation of the intended sub-TLV allocation strategy. Format of the registry would be as shown below:

When new drafts are introduced requiring new codepoints, it is advantageous to be able to allocate codepoints without waiting for them to progress to RFC. The reasons this is advantageous are described in [RFC7120]. However, [RFC7120] procedures for early allocation do not apply to registries such as the IS-IS TLV Codepoints Registry which utilize "Expert Review" allocation policy. In such cases what is required is that a request be made to the Designated Experts who MAY approve the assignments according to the guidance that has been established for the registry concerned. The following guidance applies specifically to the IS-IS TLV Codepoints registry. Application for a codepoint allocation MAY be made to the Designated Experts at any time. The Designated Experts SHOULD only consider requests that arise from Internet-Drafts that have already been accepted as Working Group documents or that are planned for progression as AD Sponsored documents in the absence of a suitably chartered Working Group. In the case of Working Group documents, the Designated Experts SHOULD check with the Working Group chairs that there is consensus within the Working Group to make the allocation at this time. In the case of AD Sponsored documents, the Designated Experts SHOULD check with the AD for approval to make the allocation at this time. The Designated Experts SHOULD then review the assignment requests on their technical merit. The Designated Experts SHOULD NOT seek to overrule IETF consensus, but MAY raise issues for further consideration before the assignments are made. Once the Designated Experts have granted approval IANA will update the registry marking the allocated codepoints with a reference to the associated document as normal. In the event that the document fails to progress to RFC the Expiry and deallocation process defined in [RFC7120] MUST be followed for the relevant code points - noting that the Designated Experts perform the role assigned to Working Group chairs.

This document requires the addition of TLVs 23 and 223 to the existing Sub-TLVs for TLV 22, 141, and 222 registry as described in Section 2. This document requires the existing sub-TLV registries for TLVs (135, 235, 236, 237) be combined into a single registry as described in Section 3.

This document introduces no new security issues.

The author wishes to thank Alia Atlas and Amanda Baber for their input in defining the correct process to follow to get these changes implemented. Special thanks to Adrian Farrel for crafting the text in Section 4.