Folks – Here is the relevant paragraph from the Appendix - some emphasis added.
“As a means of interoperating with implementations which do not conform to the corrections defined in this document, implementers may wish to consider temporarily supporting sending and/or receiving the form of the sub-TLVs using a length of 5 and including the RESERVED field. However, the intent of this revision is to specify one and only one normative behavior. Any existing implementations which encode the sub-TLVs using a length of 5 are expected to be revised to conform to the normative behavior specified in this document.” Several things of note regarding this paragraph: 1)It was put in in response to a review comment from the Document shepherd: <snip> Hi All, I was reviewing this draft as the Shepherd. It is a fairly simple and straightforward bis update to RFC7810 to fix an encoding error. There is one point that I would like the authors and WG to consider. The draft in the appendix talks about two interpretations of the erroneous sub-TLVs and from the conversation on the list I get the impression that there are at least two implementations out there which did different interpretations. Do we want to consider putting in a suggestion (i.e. not normative perhaps) that implementations updated to this specifications accept the sub-TLV with the Reserved field included and size 5? So they don't consider such an encoding as error or malformed on reception? Thanks, Ketan <end snip> I agreed with Ketan’s comment and so the text was added. 2)The text is very careful to comply with RFC 8174. It uses lowercase “may” – therefore clearly non-normative. It also unambiguously states that implementations written using a length of 5 “are expected to be revised”. 3)If you read this from the POV of someone who implements the protocol extensions, I think this text is useful in providing context for what interoperability issues might be encountered in the field. Even though the implementation we know of that used a length of 5 has been fixed – there are still older versions of that code deployed. It suggests – but clearly does NOT require - what could be done (at the implementer’s discretion) to deal with the non-conformant implementations. I fail to see how this is in any way confusing. I think the document is better off as is – but if you folks insist I will remove the text – though clearly I disagree with this choice. Les From: Alvaro Retana <aretana.i...@gmail.com> Sent: Thursday, December 20, 2018 4:01 AM To: Acee Lindem (acee) <a...@cisco.com>; Les Ginsberg (ginsberg) <ginsb...@cisco.com>; Suresh Krishnan <sur...@kaloom.com> Cc: lsr-cha...@ietf.org; lsr@ietf.org; The IESG <i...@ietf.org>; Ketan Talaulikar (ketant) <ket...@cisco.com>; draft-ietf-lsr-isis-rfc7810...@ietf.org Subject: Re: Suresh Krishnan's No Objection on draft-ietf-lsr-isis-rfc7810bis-04: (with COMMENT) On December 20, 2018 at 5:38:51 AM, Acee Lindem (acee) (a...@cisco.com<mailto:a...@cisco.com>) wrote: We only know of one implementation that has the wrong encoding and we have fixed that one. I then see no harm in removing the “generosity” paragraph. As Suresh suggests, it will make the document even clearer. Thanks! Alvaro.
_______________________________________________ Lsr mailing list Lsr@ietf.org https://www.ietf.org/mailman/listinfo/lsr