Dear All Now I want to try UAC module to solve the proxy authentication to Asterisk. Until now it still fail even the username/password and realm are already correct 100% Then I found this statement "For sending authentication credentials to the termination provider openser has the "uac" module. But be aware that this module does not always works as it does not increase the cseq when sending the INVITE with credentials (search the archive for details). E.g. the uac module wont work if the termination providers uses Asterisk (as Asterisk checks the cseq)" Actually why UAC module has this limitation and why this does not get solved until now? Thanks Regards Halomoan Zhou