> The UA sends a Register request with source UDP port Y and > SIP contact header port X, including the rport parameter:
<snip> > The proxy server handles the registration request by > replying to UA with destination UDP port Y, as suggested > in RFC 3851: <snip> > So the UA is registered in the network with 2 different > ports, as a kind of NAT. I don't have a reply concerning the questions; however the UAC skipped "additional registration" step. RFC 3581: Using this specification, a client behind a NAT can learn its address and port as seen by the proxy which receives a REGISTER request. The client can then perform an additional registration, using this address in a Contact header. This would allow a client to receive incoming requests, such as INVITE, on the IP address and port it used to populate the source IP address and port of the registration it sent. This approach will only work when servers send requests to a UA from the same address and port on which the REGISTER itself was received. RFC 5626: Note: If the UAC wants a UDP flow to work through NATs or firewalls, it still needs to put the 'rport' parameter [RFC3581] in its Via header field value, and send from the port it is prepared to receive on. More general information about NAT traversal in SIP is described in [NAT-SCEN]. _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
