AW: AW: AW: AW: [Sip] Extension of conference procedures

["Huelsemann, Martin" <[e-mail]>]

Yes, that is of course the prefered solution and this are the normal procedure how this ad-hoc conference will be activated.. 
But like in the other thread we discuss in also here is the problem with a dumb phone, in the worst case only compliant to RFC 3261 and only able to handle 1 dialog at the same time. And for this our proposal is, to develop a fallback basing on sending a re-INVITE in the original dialog. That minimizes the requirements on the invited user and maximizes the chance the conference will be established.
Of course the normal case is that there are smart phones compliant to all RFCs needed for the service. But I think it's useful to have at least a fallback for the case that B does not fulfil all the requirements needed for a service you're providing to A. Or simply doesn't want to accept a 2nd INVITE.

BR, Martin



> -----Ursprüngliche Nachricht-----
> Von: Paul Kyzivat [mailto:[e-mail]] 
> Gesendet: Donnerstag, 13. September 2007 16:00
> An: Hülsemann, Martin
> Cc: [e-mail]; [e-mail]; [e-mail]; 
> [e-mail]; [e-mail]
> Betreff: Re: AW: AW: AW: [Sip] Extension of conference procedures
> 
> 
> Why not simply REFER the focus to send an INVITE/Replaces to 
> the calls 
> with existing dialogs?
> 
> 	Paul
> 
> 
> Huelsemann, Martin wrote:
> > Hi all,
> >  
> > thanks for your interest in this, but I think my question 
> pointed in a 
> > littlebit different direction.
> >  
> > I think the procedures to start a centralized ad-hoc 
> dial-out conference 
> > are fine, you send an INVITE to the conference factory to start the 
> > conference, and then you send REFERS to the focus referring 
> INVITEs to 
> > the other participants. Even better is an INVITE to the 
> confernce with a 
> > URI list of the participants who shall be invited to the 
> conference, 
> > because this needs lees messages.
> >  
> > The problem is the INVITE from the focus to the 
> participants. As this is 
> > an ad-hoc conference, it's clear that the invited user is 
> already in a 
> > dialog with the inviting user, and because of this it 
> depends on the 
> > invited user if he accepts the invitation to the 
> conference, or if he 
> > e.g. just answers with a 486. The proposal is to trigger a 
> re-INVITE in 
> > the original dialog by using the "?" mechanism to transfer 
> the dialog ID 
> > of the original dialog to the focus, as this wouldn't cause 
> a 2nd dialog 
> > at the invited UE and therefore means the fewest 
> requirements on the 
> > invited user.
> 
> 
> > To mee it seems that the Join header cannot solve this 
> problem. If you 
> > include the Join header in the INVITE to the focus, that 
> means you want 
> > to join some dialog at the focus which doesn't exist.
> > If you include the Join header also using "?" in the header 
> portion in 
> > the Refer-to header of a REFER or in the header protions in the URI 
> > list, this means the focus shall generate an INVITE 
> including a Join 
> > header and sends this to the invited user. The invited user 
> then would 
> > have to start the procedures to include the focus in the original 
> > dialog. If he accepts the 2nd INVITE and is compatible to RFC3911.
> > Triggering a re-INVITE because of the Join header part in 
> the Refer-to 
> > header to me seems to be not in accordance with RFC3911.
> > Because of this I don't think the usage of the Join header 
> can solve the 
> > problem of 2 dialogs at the invited user in case of an 
> ad-hoc dial-out 
> > conference.
> >  
> > BR, Martin
> >  
> >  
> >  
> > 
> >     -----Ursprüngliche Nachricht-----
> >     *Von:* Jerry Yin [mailto:[e-mail]]
> >     *Gesendet:* Mittwoch, 12. September 2007 22:14
> >     *An:* Alan Johnston
> >     *Cc:* [e-mail]; DRAGE, Keith (Keith); Mary Barnes
> >     *Betreff:* Re: AW: AW: [Sip] Extension of conference procedures
> > 
> >     Hi Alan and Peili,
> >      
> >     Thanks for your responses. I saw Alan's RFC before. I 
> revisited it
> >     today briefly. But I still can't find the solution I am 
> looking for.
> >     Basically in your RFC, even for the ad-hoc conference, the user
> >     always starts with calling the conference server first. 
> What I am
> >     looking for is that the user puts two (or more) lines 
> on hold, then
> >     he decides to conference them together in a conference room.
> >      
> >     The solution I proposed will allow user to have a 
> smooth experience
> >     to conduct a conference in a conference room, if the 
> server supports
> >     this feature. If server does not support it then it 
> will be a local
> >     3way conference on the phone that most SIP phones 
> support. The UI
> >     design and user experience will be exactly the same in 
> both the cases.
> >      
> >     As to the RFC3911, I agree that it didn't say 
> explicitly that the
> >     Join header can be used in a re-Invite. I also admit that my
> >     proposal does not interpret the Join header as the RFC 
> defines. But
> >     if it works, then we might want to re-interpret the defintion of
> >     Join header? Or we might want to consider introducing a 
> new header
> >     for this purpose!
> >      
> >     To answer your question, if the join does not match an existing
> >     dialog, then according to the RFC 3911, it will be ignored.
> >      
> >     BTW, I saw the RFC 4579 depends on out-dialog REFER. 
> Would it be a
> >     security concern?
> >      
> >     thanks,
> >     Jerry
> > 
> > 
> >     */Alan Johnston <[e-mail]>/* wrote:
> > 
> >         Hi Jerry,
> > 
> >         The use of a Join header field in a re-INVITE in 
> your system is
> >         problematic. RFC 3911 does not seem to specifically 
> rule it out but
> >         implies that it can only be used in a initial 
> (dialog creating)
> >         INVITE.
> >         Also, the error response generation described in 
> RFC 3911 can
> >         not be
> >         applied to a re-INVITE scenario, so I'm curious 
> what you do if
> >         the Join
> >         does not match an existing one.
> > 
> >         There are solutions in RFC 4579 for transitioning 
> conferences to
> >         and
> >         from point to point sessions that may be of use to you.
> > 
> >         Thanks,
> >         Alan
> > 
> > 
> >         Jerry Yin wrote:
> >          > I think there are two ways to invoke a 
> conference. One is to
> >         invoke
> >          > the conference by the conference server. The 
> other is ad-hoc
> >          > conference invoked by the participants. The
> >          > draft-ietf-sip-uri-list-conferencing was trying 
> to solve the
> >         problem
> >          > by initiating a conference from the server.
> >          > Here's what I think for the ad-hoc conference.
> >          > Participants: A calls B (a UA or a conference 
> room) and put B
> >         on-hold,
> >          > and then A calls C. Now A presses the conf button.
> >          > 1. If B has a conference room url, A will 
> transfer C to B (by
> >         REFER),
> >          > as some of you discussed already. It actually is 
> supported by
> >         some
> >          > companies already as I know.
> >          > 2. But if B is a UA, when the conf button is pressed, the
> >         only SIP
> >          > messages send out by A is the re-Invite 
> (off-hold) to B since
> >         most SIP
> >          > phones support 3-way conference locally. Then A 
> will do the
> >         audio
> >          > mixing locally. So far I didn't find any 
> solution to transfer
> >         the
> >          > local 3-way conference to a centralized conference yet.
> >         Currently in
> >          > our system, we adopted the "Join" header 
> (RFC3911). When A
> >         sends the
> >          > re-Invite to B, it also includes a Join header 
> contains the
> >         C's dialog
> >          > info. The B2B server will translate the Join to 
> a centralized
> >          > conference. It will Invite C with a Replace 
> header to replace
> >         the
> >          > session between A and C. C will sends a BYE to 
> A. The server
> >         will
> >          > update the media to A and B (reInvite). Then all three
> >         parties are in
> >          > the centralized conference room.
> >          > I hope the new RFC for conference also capture 
> the behavior
> >         described
> >          > in 2. Whether it's Join header or something 
> else. The user
> >         should be
> >          > able to call someone first and then decided to setup a
> >         conference.
> >          > Jerry
> >          >
> >          > */Jeroen van Bemmel /* wrote:
> >          >
> >          > Concretely, would we be looking at something like
> >          >
> >          >
> >         
> sip:[e-mail]?From=[e-mail];tag=x
> &To=sip:[e-mail];tag=y&Call-ID=i&CSeq=1234&Route=rrr&body=
> >          > with proper session versions etc>
> >          >
> >          > in order to help the conference server fake a 
> reINVITE towards B?
> >          >
> >          > RFC3261 provides some guidance on the types of 
> headers that
> >         elements
> >          > might accept as part of a URI. Specifically, it 
> states in 19.1.5:
> >          > "An implementation SHOULD NOT honor these 
> obviously dangerous
> >         header
> >          > fields: From, Call-ID, CSeq, Via, and Record-Route."
> >          >
> >          > I believe the usage that was foreseen for this 
> mechanism (as
> >          > illustrated
> >          > by some of the examples in RFC3261) was to 
> provide some context
> >          > for the
> >          > request, such as Subject and Priority fields. In 
> other words,
> >          > optional
> >          > information that might help the receiver 
> understand the context.
> >          >
> >          > The above are not different semantics for 
> headers in a URI
> >         (concept
> >          > remains: form a new request based on the URI, 
> inserting the
> >         headers),
> >          > but it does imply a deviation from the basic SIP 
> call model
> >          > (basically a
> >          > way of encoding dialog state in a SIP URI, and 
> sending that to
> >          > another
> >          > element such that it can reconstruct that state 
> and assume the
> >          > role of
> >          > the party which shared the state).
> >          >
> >          > Apart from the fact that this approach will fall 
> short for SDP
> >          > related
> >          > state: is this desirable?
> >          >
> >          > Regards,
> >          > Jeroen
> >          >
> >          > Mary Barnes wrote:
> >          > > RFC 4244 (History-Info) also uses this 
> mechanism to capture the
> >          > Reason
> >          > > and Privacy associated with the URIs that are 
> included as part
> >          > of the
> >          > > History-Info header. My understanding is that 
> it's really
> >         just a
> >          > nifty
> >          > > way to compactly reuse existing headers (i.e., 
> it makes the
> >          > History-Info
> >          > > much more compact as I didn't need to define additional
> >          > parameters for
> >          > > the header, but could rather reuse the 
> existing ones, whose
> >         existing
> >          > > semantics perfectly applicable). I do think 
> that the use of the
> >          > headers
> >          > > that might be escaped using this mechanism 
> should be explained,
> >          > > particularly in cases where you might be 
> extending the use of
> >          > existing
> >          > > headers as I did for the Privacy header.
> >          > >
> >          > > Mary.
> >          > >
> >          > > -----Original Message-----
> >          > > From: Peili Xu [mailto:[e-mail]]
> >          > > Sent: Wednesday, September 05, 2007 10:41 AM
> >          > > To: DRAGE, Keith (Keith)
> >          > > Cc: [e-mail]
> >          > > Subject: Re: AW: AW: [Sip] Extension of 
> conference procedures
> >          > >
> >          > > Yes, It's vague in RFC3261. I'm only aware of 
> the usage in
> >         REFER
> >          > now.
> >          > > It'll be good to clarify the semantics in the usage in
> >         url-list.
> >          > >
> >          > > 2007/9/5, DRAGE, Keith (Keith) :
> >          > >
> >          > >> So this is a convenient way to bring us back 
> to the other half
> >          > of the
> >          > >>
> >          > > issue which we do not seem to have discussed 
> yet. When the
> >          > syntax was
> >          > > defined that allowed ?headers:
> >          > >
> >          > >> Headers: Header fields to be included in a 
> request constructed
> >          > >> from the URI.
> >          > >>
> >          > >> Headers fields in the SIP request can be 
> specified with the
> >          > >>
> >          > > "?"
> >          > >
> >          > >> mechanism within a URI. The header names and 
> values are
> >          > >> encoded in ampersand separated hname = hvalue 
> pairs. The
> >          > >> special hname "body" indicates that the 
> associated hvalue is
> >          > >> the message-body of the SIP request.
> >          > >>
> >          > >> What usage did the SIP WG envisage for this, 
> and thus what
> >          > semantics
> >          > >>
> >          > > did they define for that usage.
> >          > >
> >          > >> Is it appropriate to assign new semantics to 
> such usage?
> >          > >>
> >          > >> Regards
> >          > >>
> >          > >> Keith
> >          > >>
> >          > >>
> >          > > Note: I snipped the rest of this thread as it 
> was getting
> >         really
> >          > LONG.
> >          > >
> >          > >
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