Hi everyone, welcome to the this years call-completion discussion.
As I understood from the results of Vancouver people prefer a solution using a cookie. In the case there is a queue at the callee the callee's monitor adds a cookie to the 486, this cookie is a specific call-completion reference and indicates that call completion is possible in general. The caller's agent then can subscribe to his call-completion state at the callee's monitor, but only if he sends the cookie with the SUBSCRIBE. Also when the caller starts the call-completion call after he has received the notification that he is on top of the queue he has to add the cookie in the INVITE in order to prioritize the call-completion call. Is this correct so far? It would basically look like the flow available under http://www.bliss-ietf.org/drafts/misc/ccbs_flow1.gif. If this is in principal correct, the question then is how does this cookie look like. Probably there will be something specific for a particular call-completion case, e.g. CCBS ID, a callee ID and a caller ID. As the concept of a CCBS cookie doesn't exist in the PSTN, this causes problems at the interworking, especially when a PSTN caller wants to activate CCBS on an Internet callee. The problem is that for this interworking with the PSTN it is possible that the 3 dialogs (busy call, supscription and call-completion call) are handled by 3 different MGCs, but only the MGC which interworked the busy call dialog knows about this cookie. So in many cases neither the subscription for the call-completion event package nor the call-completion call will work. http://www.bliss-ietf.org/drafts/misc/ccbs_flow2.gif illustrates this problem. Are there any suggestions from you how this problem can be solved? I was thinking of some kind of default cookie when it can be detected that a call came in from the PSTN. BR, Martin
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