> From: Jan Fricke [[email protected]] > > I know that there are some end-devices that support CCBS (call > completion on busy subscriber). E.g. we used it some time ago with > snom phones. If I’m not wrong the feature is implemented on phone side > with some kind of event-package (Subscribe/notify etc.). This seems > complex to me and also has some implications on using voicemail. Also > it is not available if you use some phone types that does not support > CCBS (e.g. mix of wired and wireless devices).
In SIP, as far as I know, most CCBS implementations are along the lines of section 2.17 of RFC 5359, viz., the caller subscribes to the dialog events for the callee, and when the dialog events report that the callee is not busy, the caller calls again. Of course, the PSTN has supported CCBS for a long time, with a more complex implementation architecture, and better features (e.g., if 10 callers are waiting for the same callee, when the callee hangs up, only one caller is selected to re-call). There is a recent IETF specification (http://datatracker.ietf.org/doc/draft-ietf-bliss-call-completion/) for implementing CCBS and CCNR services in a way that interoperates with the PSTN services. That spec describes how an agent process in the caller's "switch" and an agent process in the callee's "switch" coordinate to perform CCBS/CCNR. It is left up to the local systems to define exactly how the caller invokes CCBS, etc. The only implementation of draft-ietf-bliss-call-completion that I know of is in Asterisk. But I am sure that the Asterisk implementation places no special demands on the phones, and it might be straightforward to reimplement it on sipX. Dale _______________________________________________ sipx-users mailing list [email protected] List Archive: http://list.sipfoundry.org/archive/sipx-users/
