Reviewer: David Black Review result: Not Ready This document has been reviewed as part of the transport area review team's ongoing effort to review key IETF documents. These comments were written primarily for the transport area directors, but are copied to the document's authors and WG to allow them to address any issues raised and also to the IETF discussion list for information. When done at the time of IETF Last Call, the authors should consider this review as part of the last-call comments they receive. Please always CC tsv-art@xxxxxxxx if you reply to or forward this review. This draft defines a YANG module for tunnel types based on the MIB-2 tunnel type registry maintained by IANA. My fundamental concern with this draft is that the MIB-2 tunnel type registry is seriously incomplete and out of date, as there are a large number of tunnel types that aren't included in that registry, e.g., IPsec tunnel-mode AMT tunneling. In its current form, that registry does not appear to be a good starting point for specifying YANG management of tunnels. A limited justification that I could envision for defining this YANG module would be to use it for mechanical translations to YANG of existing MIBs that use MIB-2 tunnel types - if that's the justification, then it would need to be clearly stated in an applicability statement within this draft, and the discussion of extension of this YANG module would need to be aligned with that limited applicability. The proverbial "right thing to do" would be to update both the MIB-2 tunnel type registry and this draft with all of the currently known tunnel types. The references section of draft-ietf-tsvwg-rfc6040update-shim (https://datatracker.ietf.org/doc/draft-ietf-tsvwg-rfc6040update-shim/) may help in identifying tunnel protocols that should be included. A minor concern involves the use of RFC 8085 as the reference for UDP tunnels; while that's certainly better than the existing use of RFC 4087, due to the extensive design guidance in RFC 8085, designers of UDP-encapsulated tunnel protocols ought to be encouraged to register their protocols as separate tunnel types (e.g., so the network operator has some idea of what the UDP tunnel is actually being used for). This draft ought to encourage tunnel protocol designers to register their own tunnel types in preference to reuse of the UDP tunnel type, including placing text in the IANA tunnel type registry and this YANG module to encourage that course of action.
