________________________________________ From: Roman Shpount [[email protected]]
UA opens a new TCP connection to the SIP proxy. This TCP connection will use a new source port (this is normal for TCP). It will go through NAT again, which will probably assign different public port to this connection. This means connection to proxy will come from a different source port and potentially IP. ___________________________ Well, I'm no expert on "SIP outbound", but it seems to me that it can only work if the UA can reliably connect from the same IP/port. The reason is that there is no other way for the proxy to recognize the UA involved. Without NAT, etc., the proxy can always achieve communication with the UA by opening a new connection to the Contact URI that the UA has provided. But under the "outbound" conditions, the proxy has to see a TCP connection established by the UA whose origin address is that of the Contact URI. If the UA cannot consistently create such connections, the proxy has no way of establishing a connection and no way of recognizing if the UA has established such a connection. But I may well be wrong about this. E.g., perhaps the "instance id" can be used to avoid this problem. Perhaps you can look at the archived discussions of this document in the IETF SIP mailing list. Dale _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
