Thank you so much for the detailed explanation. On Sat, Mar 20, 2010 at 1:41 AM, WORLEY, DALE R (DALE) <[email protected]>wrote:
> ________________________________________ > From: [email protected] [ > [email protected]] On Behalf Of Premalatha > Kuppan [[email protected]] > Thanks for the valuable comments. > > Then during outgoing call, how can both devices participate such that > audio > should be from/to one device and video from/to other device ? > ________________________________________ > > As you know, there is no completely standardized way to do this. It is an > area of active research in the SIPCORE working group. Generally speaking, > GRUU is not centrally significant to solving the problem. > > Of course, an incoming call can be forked to several UAs at the same time, > and several UAs may send 200 responses. But the calling UA will (in all > ordinary circumstances) select one of the 200 responses to continue the call > and will immediately terminate the dialogs created by the other 200s. > > One technique is to use a B2BUA, such as a conference server, to maintain > dialogs to all of the UAs that you want to participate in the call, and to > route the media appropriately. > > Another technique is to have one UA answer the call and pretend to the > calling UA that it has all the media facilities needed. The answering UA > can then place a call to the "secondary" UA (e.g., the laptop that displays > the video), configuring that dialog to only have video media. After that, > the answering UA can either relay the media arriving from the remote UA to > the secondary UA, or it can use 3rd party call control techniques to get the > remote UA to send the correct media (e.g., video) directly to the secondary > UA. > > Some complication arises when the answering UA attempts to contact the > secondary UA. One technique is for the answering UA to know the secondary > UA's contact URI. A better solution is for it to know its GRUU, which > generally stays the same over time, even if the secondary UA's network > location changes. Another possibility is for the answering UA to place a > call to its own AOR, specifying caller preferences and SDP for the media > that it needs displayed on its behalf (e.g., video). The call will only > ring on UAs capable of handling the specified media, and you can cause the > one you desire to use to answer. > > Dale > _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
