Hi I have been using fix_nated_register/fix_nated_contact for NAT traversal and all worked fine. I've come across add_contact_alias and handle_ruri_alias: http://sip-router.org/wiki/tutorials/alias-example where it says: "The benefits of using add_contact_alias() and handle_ruri_alias() functions instead of conventional NAT traversal solutions are: * Request-URI in requests to UAs behind NATs is always what UAs expect * Re-use of tcp/tls sessions between proxy and UAs " I assumed the 'conventional NAT traversal solution' here means fix_nated_contact? I understand the first point, in that the R-URI always contains what the client puts in the contact hf. But for the second point, about tcp/tls reuse, does fix_nated_contact do the same trick, or does add_contact_alias and handle_ruri_alias give you more benefit over fix_nated_contact? So far I feel they achieve the same thing but would like this confirmed/corrected. Thank you very much! Yufei