The IP gateway implements SIP as defined in RFC 3261.
Any product wishing to establish SIP calls with the IP gateway should implement INVITE,
ACK, BYE, and CANCEL messages along with responses from 1xx to 6xx. The
IP gateway acts as a client and does not return 5xx and 6xx responses itself;
however, proxies and other intermediaries may do so.
To use a SIP registrar in conjunction with the IP gateway, you must register
an ID for the IP gateway with the SIP registrar.
For video Fast
Update Requests, the IP gateway uses a type that involves
sending an INFO message with an XML body. This only applies to video endpoints,
but these endpoints should be able to correctly reply to INFO requests whether
or not they understand them as Fast Update Requests.
