On Mon, 2009-08-10 at 17:52 +0530, Aryan wrote: > Actually i am having an issue when 183 is not unreliable , but 180 is > reliable. But i have read somewhere that 183 is more preferred over 180, > right?
No... In general, the answerer may send the answer in some or all of the provisional responses, but it must ultimately send the answer in a "reliable" response, either a reliable provisional response or a 2xx response. *All of these answers must be the same.* So if you are seeing a conflict between the 183's answer and the 180's answer, the device generating them is malfunctioning. (Unless I've made a mistake.) > However if both the 183 and 180 are having different TO tags and different > codec lists then its again an issue. > then we cannot come to know whether to reject the 180 which is reliable or > not? If two provisional responses have different to-tags, then they are part of two different dialogs, and the rules apply to each dialog separately. In this case, the 180 and 183 answers can be different. This does present the UAC with the problem of how to render the two dialogs, for which there is no standard. A common tactic is to check to see if any dialog(s) are providing the media described in the answer(s). If so, all of those media streams are mixed together and presented to the user. If no dialogs are providing media, and if a 180 (Ringing) has been received, then a ring tone is presented to the user. Dale _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
