Olle E. Johansson wrote:
...and I've seen implementation who refuse to accept the registered contact as a request URI...
There's some vague security thinking behind a device who doesn't accept any r-URI from, but only the registered contact. Is some cases, the contact indicates a line or something in the device, so it needs the full contact to be able to provide the user with the proper interface reaction for the incoming call.
Yep. It's not stupid; the logic is quite clear, and the behaviour is as intended. It just poses a problem for trunking and/or multiple DIDs where the device is expected to potentially route a call differently based on the number used to reach it.