[SIPForum-discussion] Regarding Call-ID in REGISTER method

[Dale R. Worley]

Sam Kirubakaran L <samkirubakaranl at outlook.com> writes:
> But if the same UA is registering to diff Registrars, should the call
> id be same or different?
>
> If same, then how come the UA will differentiate the responses?

The question is whether the registrations are for the same AOR or for
different AORs.  If the UA maintains registrations for two different
AORs, then the two sequences of REGISTER messages, the two
quasi-dialogs, are "different registrations", and each has its own
Call-ID.

If the registrations are for the same AOR, then the fact that one
REGISTER request goes to one registrar and one REGISTER request goes to
a different registrar (due to the operations of RFC 3263) is
accidental.  All of the registrations are considered to be to the same
logical registrar and have one Call-ID.

Dale