Subject: Re: [sipcore] draft-holmberg-sipcore-proxy-feature- why notjust use Supported

From: <[email-masked]>
Date: Wed, 1 Dec 2010 16:17:05 +0100

Hi,

indeed some Rel-10 CRs were agreed that would add a reference to this draft and also the use of it in earlier releases has been considered. 

CRs that introduce the dependency towards this draft are coming for approval in TSG CT plenary next week, so it would be useful to understand the level of interest to work on this in IETF, and any possible opposition that might risk timely completion.

(Rel-10 is foreseen to freeze in March 2011).

BR,
Hannu Hietalahti
3GPP TSG CT Chairman
tel: +358 40 5021724

>-----Original Message-----
>From: [email-masked] 
>[mailto:[email-masked]] On Behalf Of ext Christer Holmberg
>Sent: 30 November, 2010 20:16
>To: Leis, Peter (NSN - DE/Munich); [email-masked]
>Subject: Re: [sipcore] draft-holmberg-sipcore-proxy-feature- 
>why notjust use Supported
>
>Hi,
>
>At the previous 3GPP CT1 meeting, the group indicated 
>willingness to use the mechanism in the draft in the work on 
>session continuity.
>
>There has been some comments on that we need text regarding 
>"directionality", ie if an indicated capability is only valid 
>in one direction, and I agree to that we need to address that.
>
>But, in general I would like to know what to do in order to 
>move the draft forward and adopt it as a working group item.
>
>Regards,
>
>Christer
>
>________________________________________
>From: Leis, Peter (NSN - DE/Munich) [[email-masked]]
>Sent: Tuesday, November 30, 2010 10:51 AM
>To: [email-masked]
>Cc: Christer Holmberg; Andrew Allen; [email-masked]
>Subject: RE: [sipcore] draft-holmberg-sipcore-proxy-feature- 
>why notjust        use     Supported
>
>hello,
>
>I support solving the 3GPP use case that Christer was refering 
>to in the
>draft, using the draft as the basis for the work.
>
>regards
>Peter
>
>> -----Original Message-----
>> From: [email-masked] [mailto:[email-masked]] On
>> Behalf Of ext Christer Holmberg
>> Sent: Wednesday, November 10, 2010 4:01 AM
>> To: Andrew Allen; [email-masked]; [email-masked]
>> Subject: Re: [sipcore] draft-holmberg-sipcore-proxy-feature- why
>> notjust use Supported
>>
>>
>> Hi,
>>
>> Andrew is correct: just because something isn't a "pure" proxy, it
>> doesn't mean it is going to modify the Contact header, Supported
>header
>> etc.
>>
>> Also, I think the use-case (which I have presented on the list) where
>a
>> proxy indicates that the Path address information can be used for
>> routing requests in both direction is an example of a "pure" proxy
>use-
>> case. That is also an old problem, that we have discussed earlier
>every
>> now and then.
>>
>> Regards,
>>
>> Christer
>>
>>
>>
>>
>> > -----Original Message-----
>> > From: [email-masked]
>> > [mailto:[email-masked]] On Behalf Of Andrew Allen
>> > Sent: 10. marraskuuta 2010 3:20
>> > To: [email-masked]; [email-masked]
>> > Subject: Re: [sipcore] draft-holmberg-sipcore-proxy-feature-
>> > why not just use Supported
>> >
>> >
>> > I think the second case Paul describes is what in 3GPP is
>> > called a Routing B2BUA which sometimes behaves like a proxy
>> > and sometimes like a UA. IMHO these entities should use
>> > Record-Route to keep themselves on the path and not write
>> > their own URI in the Contact but pass the Contact header
>> > transparently. To do otherwise breaks things like GRUU and
>> > callee caps.
>> >
>> > I support the solving in a general way of how an intermediary
>> > that provides some kind of funtionality on behalf of a UA can
>> > indicate its presence to other entities.
>> >
>> > Another use case for this is helping to solve service
>> > interaction problems where multiple application servers are
>> > involved and the service logic performed by one may need to
>> > be taken into account by the other.
>> >
>> > I also think it is necessary that UAs can detect the presence
>> > of intermediaries such as IP-PBXs and application servers in
>> > the path of a session and obtain a URI to which they can send
>> > requests to invoke service logic at those servers without
>> > them having to overwrite the contact URI for the reasons stated
>above.
>> >
>> > Andrew.
>> >
>> > ----- Original Message -----
>> > From: Paul Kyzivat [mailto:[email-masked]]
>> > Sent: Tuesday, November 09, 2010 07:04 PM
>> > To: [email-masked] <[email-masked]>
>> > Subject: Re: [sipcore] draft-holmberg-sipcore-proxy-feature-
>> > why not just use    Supported
>> >
>> > I'm tempted to agree with Cullen on this.
>> > But I think it "depends".
>> >
>> > If the B2BUA is a "proper" UA, and inserts its own Contact
>> > address in the call, then I think Cullen's description is right.
>> >
>> > If its a B2BUA because it messes with things a proxy cannot, but
>> > *doesn't* modify the Contact address, then just manipulating
>> > Supported isn't enough. Then the features that *it* supports
>> > are obtainable directly only by sending a request to *it*,
>> > using the Route header, etc.
>> > to identify that address.
>> >
>> > Its always seemed to me that a UA should always supply its
>> > own Contact address, but I've looked for verification of that
>> > in 3261 and not found it.
>> >
>> >     Thanks,
>> >     Paul
>> >
>> > On 11/10/2010 4:42 AM, Cullen Jennings wrote:
>> > >
>> > > So, in my week of agreeing with Hadriel, I think he got it
>> > exactly right when he said there is pretty much no feature a
>> > "plain" proxy would need for this. If we are talking about
>> > things that would be a strict technical read be considered
>> > B2BUA even if they are implemented a lot like a proxy, then I
>> > can why something provided something like this functionality
>> > would be needed.
>> > >
>> > > But given this would be used by a B2BUA, I don't see why
>> > you need anything more than just normal option tags. Say a
>> > SIP message comes from A to B to C and now the response is
>> > coming back. C says it supports feature c1, c2, and c3. B
>> > knows that it can transparently forward on whatever is needed
>> > for c1, c2, but not c3 and it knows that in additional to
>> > this it can do features b4 and b5. It modifies the Supported
>> > header to have c1,c2,b4, and b5. and sends that back to A.
>> > >
>> > > If the real uses cases have to do with caller pref
>> > features, then B can modify those in the same way.
>> > >
>> > > Anyways, I think we are way way ahead of ourselves
>> > discussing mechanism before we even understand what the use
>> > cases are we are trying to solve. I'd like to see some
>> > specific real world use cases and so we can work out the real
>> > requirements. I'm expect the uses cases will contain B2BUA in
>> > the call flows - that's reality.
>> > >
>> > >
>> > > On Sep 24, 2010, at 5:04 AM, Christer Holmberg wrote:
>> > >
>> > >>
>> > >>
>> > >> Hi,
>> > >>
>> > >> I've submitted a draft, which extends the rr-param rule,
>> > allowing proxies to indicate supported features using feature
>> > tags in Path, Record-Route etc.
>> > >>
>> > >> The draft can also be found at:
>> > >>
>> >
>http://users.piuha.net/cholmber/drafts/draft-holmberg-sipcore-proxy-f
>> > >> eature-00.txt
>> > >>
>> > >> As I indicated earlier on the list, and as you can read in
>> > the draft, there is a 3GPP use-case where we believe the
>> > mechanism could be used. But, there is nothing 3GPP specific
>> > about the mechanism as such.
>> > >>
>> > >> Regards,
>> > >>
>> > >> Christer
>> > >> _______________________________________________
>> > >> sipcore mailing list
>> > >> [email-masked]
>> > >> https://www.ietf.org/mailman/listinfo/sipcore
>> > >
>> > > _______________________________________________
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>> >
>> >
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