On Wed, 2009-02-25 at 08:46 +0000, Andrew Wood wrote: > What is the recommended way to identify a dialog at a proxy given that > the To tag will initially be absent and the Call-ID may not be unique > if the caller is behind NAT?
If all you're looking at is the initial out-of-dialog request, then there isn't a dialog. Indeed, there will be zero or more responses from different destinations, each of which may create a separate dialog. (And each of which will have a different to-tag, which is used to identify the various dialogs.) Call-Ids will be unique regardless of the location of the device that generates them. See RFC 3261 section 8.1.1.4: In a new request created by a UAC outside of any dialog, the Call-ID header field MUST be selected by the UAC as a globally unique identifier over space and time unless overridden by method-specific behavior. All SIP UAs must have a means to guarantee that the Call- ID header fields they produce will not be inadvertently generated by any other UA. On Wed, 2009-02-25 at 15:27 +0000, Andrew Wood wrote: > Because if the caller was behibnd NAT surely is perfectly possible for > the Call-ID to be something like [email protected] > which could easily be chosen by 2 different clients on different > networks but whose request is forwarded to the same proxy Because such a scheme for generating Call-Ids violates section 8.1.1.4, it may not be used. Dale _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
