Eric – I will let the draft authors respond to the bulk of your comments. But in regards to your question/comment:
“I assume (but do not actually know) that a similar situation exists for the new ISIS FAD Sub-TLV of the existing TLV Type 242 - i.e. - ISIS presumably has well defined handling for sub-TLVs (of at least type 242) that are not recognized. If so, than the new Sub-TLV types defined are also not an issue.” Indeed, base behavior for the IS-IS protocol as defined in ISO 10589 is to ignore unrecognized TLVs - and this extends to unrecognized sub-TLVs as well. This is key to the ability to introduce the many extensions that have been defined by the plethora of IS-IS RFCs over the last 20+ years. This point is further discussed in the recently published: https://www.rfc-editor.org/rfc/rfc8918.html#name-handling-of-disallowed-tlvs So I think your concerns about backwards compatibility are unwarranted. In particular the statement: “[backwards compatibility] apparently relies on configuration of those routers that _do_ support the extensions to address this” Is not correct. Les From: rtg-dir <rtg-dir-boun...@ietf.org> On Behalf Of Eric Gray Sent: Friday, October 16, 2020 11:49 AM To: rtg-...@ietf.org; lsr-cha...@ietf.org Cc: rtg-...@ietf.org; lsr@ietf.org Subject: [RTG-DIR] Rtg-Dir Last Call review of draft-ietf-lsr-flex-algo Hello, I have been selected as the Routing Directorate reviewer for this draft. The Routing Directorate seeks to review all routing or routing-related drafts as they pass through IETF last call and IESG review, and sometimes on special request. The purpose of the review is to provide assistance to the Routing ADs. For more information about the Routing Directorate, please see https://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir. Although these comments are primarily for the use of the Routing ADs, it would be helpful if you could consider them along with any other IETF Last Call comments that you receive, and strive to resolve them through discussion or by updating the draft. Document: draft-ietf-lsr-flex-algo-12.txt Reviewer: Eric Gray Review Date: 16 October, 2020 IETF LC End Date: Unknown Intended Status: Standards Track Summary: This document is well organized, relatively easy to read, and probably ready for publication, but has one potential minor issue and a very small number of NITs that might be considered prior to publication. Major Issues: None Minor Issues: The statement in section 15 (Backward Compatibility) - "This extension brings no new backward compatibility issues" - seems somewhat flip. I suspect that a tiny bit of analysis would not hurt. The extensions in this draft are clearly intended to work in an environment where routers that _do_not_ support these extensions are also deployed, but apparently relies on configuration of those routers that _do_ support the extensions to address this. That seems correct. From my reading of the draft (which I have not closely followed for its entire development), while it introduces at least one new TLV, the OSPF routing protocol has well defined handling for TLVs that are not understood - hence the introduction of one or more new TLVs should not present a problem in OSPF. Obviously Sub-TLVs of the new OSPF TLV type will not introduce compatibility issues. I assume (but do not actually know) that a similar situation exists for the new ISIS FAD Sub-TLV of the existing TLV Type 242 - i.e. - ISIS presumably has well defined handling for sub-TLVs (of at least type 242) that are not recognized. If so, than the new Sub-TLV types defined are also not an issue. Shouldn't this section say something along these lines? I suspect that it would be more helpful if verifying the content of the "considerations" sections were not left as an exercise for the reader. 😊 NITs: In the Introduction, the phrase "must often be replaced" seems very slightly problematic (especially given this is a standards track RFC wanna-be). Would it be better to say "is often replaced" instead? In section 17.1.2 and 17.2 - '... a "Interior Gateway ...' should probably be '... an "Interior Gateway ..." in both cases. -- Eric
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