Klaus Darilion writes:
They achieve both the same. I don't remember the problems anymore which caused add_contact_alias() to be implemented. IIRC I think it was that some clients did not put "transport=tcp" into the Contact header and thus the fix_anted_contact missed the transport - add_contact_alias always adds the transport protocol. But that is just a guess, I may be wrong.
the main reason why i implemented those two functions was to assure that request uri in in-dialog requests is always correct. regarding tcp connection reuse, i don't remember why i wrote about that in the tutorial. perhaps i was just mislead by the name of fix_nated_contact() function that is incorrect. i just checked and the function has nothing to do with nated contacts.
-- juha