I wonder if you could help me, I've been asked by an interviewer to do some research on UDP. Apparently their is a vendor advising that you can block all inbound UDP ports on their firewall and still operate a SIP/VoIP cloud based system through it. I've had a look online and cant see any vendors listing this as a feature. I've asked a colleague who mentioned that Palo Alto networks has mentioned having something like this feature, but again after having a good look around their website I have drawn a blank.
As far as I'm aware unless their is a UDP session already established the UDP ports would have to be open to accept incoming calls, if the source server cant establish the session through UDP then the call will fail. Part of me is wondering if this is a trick question.
Thanks in advance for any help.