I am the assigned Gen-ART reviewer for this draft. The General Area Review Team (Gen-ART) reviews all IETF documents being processed by the IESG for the IETF Chair.  Please treat these comments just like any other last call comments. For more information, please see the FAQ at . Document: draft-ietf-insipid-session-id-24.txt Reviewer: Elwyn Davies Review Date: 2016/08/04 IETF LC End Date: 2016/08/04 IESG Telechat date: (if known) - Summary: Almost ready.  I think it would be worth emphasising the interoperability with H.323 more than is done at present.  I am also not sure if Version 4 UUIDs are actually allowed - there was a previous query on UUID types and I am not sure if the Version 4 mention was intended to be removed.  Caveat: I haven't checked the fine details of the examples but have looked them over.  Major issues: None Minor issues: Interoperability with H.323 The requirements for the Session Identifier [RFC7206] Section 4.2 stresses interoperability with H.323.  This is mentioned in passing in s1 and in a bit more detail in s3.  I think it would be worth mentioning this somewhat more prominently and  that the relevant interoperability will potentially be achieved since the format of the Session-ID in H.460.27 appears to match the one defined in this draft. To this end, I suggest: - Mentioning the interoperability in the abstract and stating the ITU rec number - this effectively indicates its 'use' in H.323 per the end of para 1 in the abstract. - Say a bit more about about interoperability in s1, mention H.460.27 and give it as a reference there also. GIven that H.323 now supports the use of Session Identifiers, it might be useful to indicate how Session-IDs need to be handled at SBCs [Caveat: I am not a SIP expert and this may be trivial, but I think something probably needs to be mentioned.] s4.1: Para 2 mentions the possible use of Version 4 or Version 5 UUIDs.  The last para constrains stateless intermediaries to using Version 5 UUIDs 'to ensure consistent generation'.    I am confused about whether this consistency would be maintained if endpoints and/or stateful intermediaries generated Version 4 UUIDs, or whether in fact all UUIDs should be Version 5? s8, bullet 5, s6 , s7 and s9:  If an endpoint is involved in a multi-point conference has to send a CANCEL message, which remote UUID should it be using?  The one that came back with the original INVITE response or the one used to identify the conference that is sent in the re-INVITEs from the conference focus? (e.g., in s10.4, for Alice M1 or M'). [Note lack of SIP expertise:  I am not sure if there are circumstances in which this would arise.] Nits/editorial comments: s1, paras 1 and 3; s2, last para : s/like/such as/ (total of 3 places) s2:  There is no definition of the term 'communication session' in the draft.  A definition is given in s3.2 of RFC 7206 and H.460.27 has: 3.2.1 communication session: A communication session, or simply ''session'', refers to a call or series of calls initiated or received by an endpoint for which the endpoint utilizes the same universally unique identifier (UUID) value in call signalling messages. From a calling user's perspective, this would be all call signalling messages from the time the user initiates a call until the time the call is terminated. From the called user's perspective, this would be all call signalling messages from first message received by the user's terminal until the call is terminated. In the light of the interoperability question, should the definition say something about SBCs? And how the session identifier is generated/interpreted in a 'session' that extends across an interconnected SIP/H.323 network?  Would SBC be an 'intermediary' within the meaning of the definition in s2? s2, last para:  The expansion of the B2BUA acronym occurs on the second instance rather than the first that is a couple of lines earlier. s4.2, end of para 2 and in many places thereafter:  The 'null UUID' is known as the 'nil UUID' in s4.1.7 of RFC 4122.  For consistency s/null/nil/g.  A reference to s4.1.7 of RFC 4122 should be added to the first instance in s4.2. s5: Given that RFC 7329 will be obsoleted by this document, it would be desirable to copy the gist of the  statements in the first para of s7 of RFC 7329: This document adds the "Session-ID" token to the definition of the element "message-header" in the SIP message grammar. The Session-ID header is a single-instance header. Something like an additional para at the beginning of s5:    This document replaces the definition of the "Session-ID" token that was added to the definition of the    element "message-header" in the SIP message grammar by [RFC7329].  The Session-ID    header is a single-instance header. s5, para 3: OLD: The UUID values for each endpoint are inserted into the "Session-ID"    header field of all transmitted SIP messages. This is potentially confusing when it comes to conference calls as there may be more than two endpoints involved in a communication session if it is a multi-point conference.  Maybe NEW: Any SIP message associated with a communication session has the UUIDs for the session created by the message source and destination endpoints inserted into the "Session-ID header field of the transmitted SIP message. END s5, last para: The Session-ID header field value is technically case-INSENSITIVE, but only lowercase characters are allowed in the sess-uuid components. Receiving entities MUST treat sess-uuid components as case-insensitive and not produce an error if an uppercase hexadecimal character is received. I know this is partly carried over from RFC 7329, but, as currently drafted, it seems pointless.  Can we not just have:      sess-uuid = 32(DIGIT / %x41-46 / %x61-66) ;32 chars of [0-9A-Fa-f] If the reasoning is that sending upper case to 'old' implementations will break them, then it would be better to be explicit about it. Perhaps, replace the para with:      To allow interoperation with implementations conforming to the    pre-standard specification in [RFC7329], implementations SHOULD use    only lower case letters ("a" - "f") in the sess-uuid field. s6, para 2: There could be some minor confusion as to whether the 'no change of UUID' rule is broken when a conference focus (per s9 and the examples in s10) changes its UUID after processing the initial INVITE and issuing a re-INVITE with a different UUID associated with the conference.  Some words covering (I guess) the idea that the conference itself is a different communication session from the setup request(s) would be useful.  See also the comments on s10.4 in Minor Issues above. s6 and s7, next to last paras:  These are near duplicates.  They could be replaced by a single instance at the end of s5, but no big deal. s7, para 12: Expand 3PCC on first use. s7, para 12: s/locally-frabricated/locally-fabricated/ s8, bullet 5: s/487/Request Terminated (487 - see Section 15.1.2 of [RFC3261]) s10.1, start of expansion of SIP messages: I think there is a missing 'example.'... OLD:    INVITE sip:bob at biloxi.com SIP/2.0 NEW:    INVITE sip:bob at biloxi.example.com SIP/2.0 END s11: Effectively there is another new/old requirement: the sess-uuid field has to use lower case letters (probably). s12, para 3: I think 'inherit' is not what you mean here... OLD: Because of the inherit property that Session Identifiers are conveyed    end-to-end NEW Because of the inherent property that Session Identifiers are conveyed    end-to-end END s13.2: As of this moment, no header parameters have been registered for the old RFC 7329 Session-ID header.  I don't know if any proprietary, non-documented parameters are around given the status of RFC 7329, but would it be worth explicitly banning the registration of any new parameters under the old scheme - and maybe explicitly not allowing any other parameters than 'remote'  for the new version, to avoid issues of privacy etc. If not it might be necessary to copy over some of the words about the nature of parameters in Session-ID headers and what B2BUAs might have to do from the security considerations of RFC 7329.