Hello Nick Hollinghurst,
In the sip scenario, it is not compulsory to have both signaling and media exchange for a user to be from the same place. A user can have its signaling handled from one location, while media exchanged from another. An example, There is a website sip.xyz.com providing sip service. There are a number of users subscribing to this site for sip service. Now the website uses some proprietary mechanism to know when and where those user want to place calls. To the outside world, it is the the sip.xyz.com site doing the sip signaling and not the user at sip.xyz.com. Now, to allow the sip.xyz.com user to actually talk, sip.xyz.com provides that user's actual location in the sdp description. Thus here, signaling is handled at sip.xyz.com, while media exchange is from actual user's site. Now, about your problem. It can happen, that the sip.xyz.com sip server becomes loaded and hence wants to transfer the siganling load of the current user to another sip.xyz.com server. Hence, sends in a re-invite with new contact for further signaling exchange. This invite may also contain modifications for the media exchange. The media exchange changes may not be acceptable. Its possible. But there should be no problem in updating the signaling endpoint information. Media and signaling are handled by separate entities. SIP only tells who can handle media. It does not itself handle media. Hence, one can safely update contact info, even when the media parameters are unacceptable. Media problems should not cause worries to the sip entity. Now, about your second query: when a declining re-invitation cause terminating of a dialog. Well, if the decline is based on media problems, termination will depend on what action the initiator takes when it receives the decline rsponse. It may then re-invite with new set of media capabilities. Or may terminate. Hope it helps, -Manish S. Jalan On Tue, 11 Dec 2001 Nick Hollinghurst wrote : > Could somebody please explain what happens when a > itation is received > with a new" Contact:" field but is otherwise > unacceptable? > > According to bis-05, the act of receiving a > reinvitation from the server > transaction layer updates the UAS's stored > Contact/Route-set; but if the > UAS declines the reinvitation (e.g. if the session > media are unacceptable), > must it still update its Route-set? It seems strange to > act on a request > which is refused... > > And in what cases if any (481?) does declining a > reinvitation constitute > terminating the dialog? > > Regards, > > Nick Hollinghurst > [EMAIL PROTECTED] > Research Engineer > AT&T Laboratories, Cambridge, England > _______________________________________________ > Sip-implementors mailing list > [EMAIL PROTECTED] > http://lists.cs.columbia.edu/mailman/listinfo/sip-implem- > entors _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
