Hi, Lincoln thanks for your instructions.
I know that dialog can exist without session since SUBSCRIBE/REFER can create dialog and without any media between communication peers. What I want to know is the relationship of dialog and session when they both exist in one communication activity. Take a example, when there are 2 person participating talks with voice, we say there is a dialog and a session. But when one caller invites another callee and gets five 200 final responses from 5 UA every of which has its own session description. We can say that there are 5 dialogs between caller and the other 5 callees, right? And then what is the exact number of session in this scenario? One session or five session? That is what I want to know. Dialog is determined by dialogID (call-id, from/to tag) and session id is determined by session id given in the SDP message. My answer is there are 5 dialog and one session now, right? Thanks for your further instructions Zongjun 2008/4/24, Lincoln Y. Lavoie <[EMAIL PROTECTED]>: > Hello BR, > > In the strictest context, the dialog exists only in SIP and can exist > without the establishment of a media session (setup through SDP). To define > a dialog, the SIP specification RFC-3261 defines several qualifiers, which > all must be present in the SIP messages, off the top of my head, they are > tag parameters in the TO/FROM headers, and a CALLID header. You should > check our RFC-3261 to look for the others. > For a simple example of a dialog without SDP, think of the presence > subscription case. In this case, the SUBSCRIBE request message and 200OK > response establish the SIP dialog. After that, all the NOTIFY messages use > the same dialog to transmit the requested information. The actual > information is usually carried directly in the same packet, encoded as DSL > or something. > > Cheers, > Lincoln > > > 孙宗君 wrote: > > > Thanks for all your kindly explanation. > > > > Do you mean that dialog and session is one-2-one relationship and only > > for different scenario and different context? > > > > Thanks > > BR > > Zongjun > > > > 2008/4/24, James M. Polk <[EMAIL PROTECTED]>: > > > > > > > At 01:28 PM 4/23/2008, [EMAIL PROTECTED] wrote: > > > > From: "=?GB2312?B?y+/X2r79?=" <[EMAIL PROTECTED]> > > > > > > > > I am confused about the conception of session and dialog in RFC > 3261. > > > > Although someone pointed out the dialog is a relationship between > > > > peer-2-peer and session is a multimedia relative relation, I am > still > > > > not clear about that. > > > > > > > >As I understand the terms, a "session" is the set of media > > > >transmisstions described/controlled by a series of SDP offer/answer > > > >exchanges. These exchanges are usually carried by the messages in one > > > >SIP dialog. > > > > > > > > > To this too, these terms are often meant to be interchangeable - even > > > though technically they are separate terms with subtlety different > > > actual meanings (SDP "sessions", and SIP "dialogs"). Sessions and > > > Dialogs can, sometimes mean the same thing. Thus it requires a bit of > > > understanding the context in which either is stated in to understand > > > if they are meaning one or the other, or were misused for the same > meaning. > > > > > > > > > > > > >Dale > > > >_______________________________________________ > > > >Sip mailing list > https://www.ietf.org/mailman/listinfo/sip > > > >This list is for NEW development of the core SIP Protocol > > > >Use [EMAIL PROTECTED] for questions on > current sip > > > >Use [EMAIL PROTECTED] for new developments on the application of sip > > > > > > _______________________________________________ > > > Sip mailing list > https://www.ietf.org/mailman/listinfo/sip > > > This list is for NEW development of the core SIP Protocol > > > Use [EMAIL PROTECTED] for questions on > current sip > > > Use [EMAIL PROTECTED] for new developments on the application of sip > > > > > > > > > > > _______________________________________________ > > Sip mailing list > https://www.ietf.org/mailman/listinfo/sip > > This list is for NEW development of the core SIP Protocol > > Use [EMAIL PROTECTED] for questions on > current sip > > Use [EMAIL PROTECTED] for new developments on the application of sip > > > > > > -- > ********************************************************************** > Lincoln Lavoie > Senior Engineer > UNH InterOperability Laboratory > 121 Technology Drive, Suite 2, Durham, NH 03824 > +1-603-862-4809 > Email: [EMAIL PROTECTED] > AIM: LincolnAtIOL > > Ars sine scientia nihil est! -- Art without science is nothing. > Scientia sine ars est vacua! -- Science without art is empty. > ********************************************************************** > > _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
