Finally, I figured out how our SBC does matches invites to registrations with the Contact header, but now I face another issue: how do I set the contact header of an invite different to the From header?
INVITE sip:called-id@URI SIP/2.0
Via: SIP/2.0/UDP IP:5060;branch=z9hG4bK495c70cc Max-Forwards: 70
From: "SBC TEST" <sip:callerID@IP>;tag=as2c330ac5
;username=user-from-reg secret=hidden host=URI
outboundproxy=IP of Proxy
As soon as I set either fromuser or username, this also overwrites the callerID and then of course the CallerID which should be sent over the trunk is not correct anymore.
And of course because the CallerID can be different for each call (it’s a trunk) I cannot set it with CallerID= in the peer definition.
Am I missing something?