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

[Barry Demchak]

Thanks, Deepanshu ...

A big help!


At 06:58 PM 10/23/2007, Deepanshu wrote:
>inine line staring in [DG]
>----- Original Message -----
>From: "Barry Demchak" <vendors at tpsoft.com>
>To: "Deepanshu" <deepanshu at huawei.com>
>Sent: Wednesday, October 24, 2007 4:06 AM
>Subject: Re: [SIPForum-discussion] Calls vs sessions vs dialogs vs
>transactions
>
>
> > 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).
>[DG] as you said there 'call' is not a formal term in SIP, so anyone can put
>that in his/her own way. According to me 'call' is neither a session nor a
>dialog rather it is just a user action.
> >
> > 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.
>[DG] that true. I would like to add one point. This type of behaviour is
>being criticized because of its complex nature. In
>draft-ietf-sipping-dialogusage-04 it is said to aviod using dialog with
>multiple usage. The possible solution is to use Target-Dialog header filed
>(RFC4538)
> >
> > 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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