Hi.
Thanks for the very rapid response.
Most of this looks just fine.
Couple of points:- On the conference CANCEL issue: My SIP knowledge is severely
lacking... could the CANCEL ever apply to the original INVITE? If not it is
probably sufficient just to remind people that the M' UUID would be used once
the conference was joined. I guess you might want to use M1 etc if the
conferece joining failed in some way. In any case I'd add a few words to
clarify which UUID they should be using - I'm not sure it is totally obvious.
- On the s11 nit.. whether you need to do something here depends on what the
decision on the spec of sess-uuid settles as.
I'd be happy to scan a pre-release of the updated draft before publishing if
you send it along.
Cheers,Elwyn
Sent from Samsung tablet.
-------- Original message --------From: "Paul Giralt (pgiralt)"
<[email protected]> Date: 04/08/2016 21:40 (GMT+00:00) To: Elwyn Davies
<[email protected]> Cc: General area reviewing team <[email protected]>,
[email protected] Subject: Re: Gen-art LC review of
draft-ietf-insipid-session-id-24
Elwyn,
Thank you for the review. We should be able to address these issues. See my
comments inline..
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.
ok - sounds reasonable.
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.]
An SBC interworking between H.323 and SIP should still follow the rules of an
intermediary. This draft will define its behavior for the SIP call leg and
H.460.27 will define its behavior for the H.323 call leg. I can put some
verbiage to this effect.
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?
Both Version 4 and Version 5 UUIDs would be maintained for endpoints / stateful
intermediaries because they can retain the value of the generated Version 4
UUID as part of that state. The reason stateless intermediaries must use
Version 5 is they need a way to generate the same UUID for the session without
storing the UUID between messages and a Version 4 UUID would not provide this
consistency.
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.]
CANCELling a re-INVITE would be unusual and unlikely to happen in the scenario
you describe, but is technically possible. As mentioned in s8, bullet 5, the
Session-ID header field value in the CANCEL request MUST be identical to the
Session-ID header field value in the corresponding INVITE. In this case,
because the CANCEL corresponds to the re-INVITE, the Session-ID header field
value would be that of the re-INVITE, as that is the transaction being
cancelled. I think the draft as it stands is clear enough on the expected
behavior but can modify if you feel strongly that this should be clarified.
Nits/editorial comments:
s1, paras 1 and 3; s2, last para : s/like/such as/ (total of 3
places)
Will change. Thanks.
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.
I’m good with copying this text from 7206 into Section 2.
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?
Yes, it would be considered an intermediary except Section 2 specifically calls
out intermediaries as being “any SIP entity”. It might be softening the
language there to include any intermediaries that are interworking between SIP
and another protocol that also supports the Session Identifier defined in this
draft.
Section 7, which discusses the behavior of intermediaries, already notes that
SBC’s are a type of intermediary, so don’t think we need to make that callout.
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.
Good catch. Thanks.
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.
Thanks for this. I wasn’t aware of this and makes sense to use consistent
naming from 4122.
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.
Sounds reasonable. I can add something along those lines for clarity.
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
Let me see how I might be able to clarify this for the multipoint use case
where there are more than two endpoints in the session. I don’t think your new
version is as clear as it could be either.
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.
To be honest I’m not sure why this was written this way originally and, like
you say, it was just carried over from 7329. Will look into whether we should
make a change here.
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.
Section 6 describes Endpoint behavior so don’t think a change is needed there,
but could possibly add some text in Section 9 that describes what is shown in
the example in section 10.4.
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.
I’m not totally sure if it makes sense as-is in section 5, but could probably
modify slightly to make it fit into section 5.
s7, para 12: Expand 3PCC on first use.
Will do. Thanks.
s7, para 12: s/locally-frabricated/locally-fabricated/
Thanks.
s8, bullet 5: s/487/Request Terminated (487 - see Section 15.1.2 of
[RFC3261])
Ok. Thanks.
s10.1, start of expansion of SIP messages:
I think there is a missing 'example.'...
OLD:
INVITE sip:[email protected] SIP/2.0
NEW:
INVITE sip:[email protected] SIP/2.0
END
Nice catch. Thanks!
s11: Effectively there is another new/old requirement: the sess-uuid
field has to use lower case letters (probably).
The old and the new both specify the identifier is lowercase, so not sure what
needs to change here.
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
Yes, thanks for the correction.
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.
I’d actually prefer to leave generic-param as allowed so that this version
could interoperate with any potential future version that might add additional
parameters. Explicitly banning such additional parameters could cause issues if
we decide to extend the capabilities in a future draft. That said, some mention
along the same lines as specified in 7329 are worth considering so that
arbitrary additional parameters are not added which could then lead to privacy
issues. Let me chew on this one…
-Paul
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