Dale, Dale.Worley@xxxxxxxxxxx wrote:
People have been discussing alternatives to the concept of correlating separate dialogs in order to present them as parts of one (user-centered) communication session. The ideal solution seems to be to use one dialog containing SDP that describes all the associated media streams. SDP allows this, as each stream can have a separate c= line. But in some cases, this won't work. E.g., if an IM conversation has been progressing using MESSAGE requests. (And MESSAGE seems to be how SIP-enabled IM clients send IM.) In that case, there's no SDP to be revised to include an audio or video session.
Well, since the draft only talks about correlating dialogs, the issue with MESSAGE only comes when using MESSAGE in-dialog.
While it isn't *forbidden* to use MESSAGE in a dialog, that technique was rejected by the WG for session mode IM. Also, the last I knew, at least Microsoft's use of MESSAGE in-dialog also used a special m-line in SDP to negotiate doing so.
Establishing a dialog without media, to be used for exchanging MESSAGE hasn't been formally defined. It would be problematic - some kind of signaling would be needed to indicate that the intent is to exchange MESSAGEs. If you have that, then it could probably be used to combine the media. Certainly if you have a dialog with no media you can make another offer to add voice or video.
Thanks, Paul _______________________________________________ Sipping mailing list https://www.ietf.org/mailman/listinfo/sipping This list is for NEW development of the application of SIP Use sip-implementors@xxxxxxxxxxxxxxx for questions on current sip Use sip@xxxxxxxx for new developments of core SIP
