[SIPForum-discussion] Calls vs sessions vs dialogs vs transactions

[Barry Demchak]

Thanks, Deepanshu ... the draft-ietf-sipping-dialogusage-04 was very 
informative.

 From RFC3261 and from the example in 
http://www.tech-invite.com/Ti-sip-service-11.html, this is what it 
looks like to me:

(Anyone: feel free to jump in)

A dialog (1 usage) is used to set up and maintain a session.

A session is an exchange of data, including voice or video. The point 
of the dialog is to set up the session and then stay out of the way. 
So, the real feed is the session, and the dialog amounts to 
out-of-band signalling.

A dialog can contain multiple transactions, staged serially. A 
transaction can affect the dialog and/or the session.

There isn't a formal definition of the term "call", though a call-id 
is part of a dialog identifier. The sense of "call" I get from 
http://www.tech-invite.com/Ti-sip-service-11.html is that it can 
contain multiple dialogs (as in the case of a dialog between Alice 
and Bob, and another between Bob and Carol).

As for the relationship between dialogs and usages, a dialog can 
contain one or more usages, and when the last usage closes, the 
dialog closes, too.

Comments?? Deepanshu?? Anyone else??

Thanks.

At 02:29 AM 10/23/2007, Deepanshu wrote:
>calls and session are same.
>
>session can have numerous dialogs in the following case:
>
>A -----INVITE---------->B
>A<-----200OK------------B
>-------session established---------
>-------INVITE Dialog established --------
>A---------REFER--------->B
>A<---------202 Accepted--------B
>--------REFER Dialog established with in current session----------
>A <------------BYE------------B
>--------------session/refer dialog/invite dialog ends-----------------
>
>refer to draft-ietf-sipping-dialogusage-04 for more
>
>BR
>Deepanshu Gautam
>Huawei Technologies Co. Ltd.
>
>
>
>----- Original Message -----
>From: "Barry Demchak" <vendors at tpsoft.com>
>To: <discussion at sipforum.org>
>Sent: Monday, October 22, 2007 10:24 AM
>Subject: [SIPForum-discussion] Calls vs sessions vs dialogs vs transactions
>
>
> > Hi, all --
> >
> > Sorry for such an elementary question. I'm trying to model some
> > aspects of SIP, and I'm not quite sure how calls, sessions, and
> > dialogs relate. (Dialogs are easy ... they're the context for
> > transactions ... and can support a number of them over time.)
> >
> > I have definitely read RFP3261, but it's not quite helpful here. I
> > have also visited the (excellent) tech-info site.
> >
> > Here's what I'm having trouble with:
> >
> > Is a call the same as a session??
> >
> > Apparently a session can have numerous dialogs ... when can that
> > happen, and what does it mean?
> >
> > Clearly, setting up a dialog has a formal process. Is there a process
> > for constructing a session or a call ... separate from setting up a
>dialog??
> >
> > Thanks.
> >
> >
> >
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