Hello list, I have a NAT issue, this is the case:
Client A has an ip-address 192.168.0.2. User of this clients wants to call B, B has an uri sip:[EMAIL PROTECTED] which is the only uri that A knows of. B has recently registered into his registrar that he is located at sip:123.123.123.123:123 (the external address of A and Bs NAT). B has an ip-address 192.168.0.3, which is at the same network as A. When A contacts b.com, b.com reacts as a proxy and contacts 123.123.123.123:123 (which is all fine). The SIP session advances to the stage where A is to send an ACK (directly to 123.123.123.123:123). 123.123.123.123 is the external address of A and Bs NAT. This is the point where things can collapse. At least some NATs doesn't have proper (from my point of view) loopback-functions (a connection from an internal ip-address to the external address of the NAT is in my eyes the same as a connection coming from the external interface of the NAT or at least the internal interface). The network administrator has probably only thought of connections to services coming from the outside (otherwise one would use the internal address), actually some NATs doesn't even support this kind of loopback-functionality. It is fully possible for A to "call" B with sip:192.168.0.3, but then one would miss the beauty of registrars and personal mobility. Another solution would be to have a proxy on the internal network, the clients will have it as an outbound proxy (so that all connections goes through it) depending on the address of the caller the proxy will use different addresses (i.e. sip:[EMAIL PROTECTED] will resolve to sip:192.168.0.3 for callers with internal addresses and sip:123.123.123.123 for callers with external addresses). The proxy might also need to modify SDP, and set the contact information to be the localnet addresses. Is there any "standard way" to do this? _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
