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

[Deepanshu]

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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