Last Call Review of draft-ietf-sipcore-multiple-reasons-01
review-ietf-sipcore-multiple-reasons-01-opsdir-lc-zhou-2022-10-28-00

I have reviewed this document as part of the Operational directorate's ongoing
effort to review all IETF documents being processed by the IESG.  These
comments were written with the intent of improving the operational aspects of
the IETF drafts. Comments that are not addressed in last call may be included
in AD reviews during the IESG review.  Document editors and WG chairs should
treat these comments just like any other last call comments.

Ready with nits.

From the operational point of view, I am not sure how an exisitng/old
application will behave when it receive this message with multiple value. Yes,
RFC3326 has this text "An implementation is free to ignore Reason values that
it does not understand." However, there is "MUST" in the old text "all of them
MUST have different protocol values". I am not clear about existing
implemenations. But posibly an application may check this rule and return
error, since this is a "MUST". I am also interested why old text need a very
hard rule "all of them MUST have different protocol values", but now relex.

Cheers,
Tianran