Residential line emulation (RLE) is tough. (a.k.a. POTS emulation or keyed system) There have been some suggestions to have SIP full mesh signaling, but audio which does otherwise. I would like to discuss this. Forgive me, but how does the audio gets plumbed if the SIP signaling is full mesh? I am interested in the audio using unicast. I don't see how the clients agree on who mixes. Actually, maybe I do know. Some "smart" call controller sends out a bunch of REFER messages, which the phones hide from the user. This, I will argue, is worse than B2BUA. I have many issues. Agreed, that SIP full mesh does appear to spread the state, such that if any participant dies, the others may have enough knowledge to recover. This is at great expense of UA complexity. I question whether implementations will be strong enough to handle it. The unsuspecting far end may not be capable. More importantly, the fault condition may not be noticed because senders can arbitrarily stop sending audio. Recovery detection would be tough to write and harder to test. Ultimately, I expect the smart controller to have essential state. Is there some rule of thumb I am missing? ...like, "All two-party call legs utilizing the same call-id should be presented as the same line light to a PSTN acquainted human." I am NOT yet ready to accept this. Would someone please clue me in? Does anyone care to discuss this? Maybe we are not yet ready for this can of worms. Sadly, I do not yet have an elegant solution to this problem. Using a B2BUA doesn't yet solve the problem of shared line light presentation. My current drafts rely on phonectl: A B2BUA device (which maybe inside one of the phones, the primary phone) owns the call state. It manages the audio. One or more secondary phones is a phonectl master and presents the line statuses as his own to the human. The phonectl syntax would need modification. Specifically the primary phone would need to support multiple call-legs/media-streams per line light, and the phonectl syntax reflect this. I am still undecided whether phonectl sent down an established call-leg should refer to the call-leg as a device or a line. Pardon the alpha nomenclature (argot? :-). Cheers, Rick 3Com _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
