Sorry... found my answer....
While guessing a SIPS AOR from a known SIP AOR and using it to initiate a request is a valid thing to do, doing the opposite (i.e., guessing a SIP AOR from a SIPS AOR and using it) is not a valid thing to do as it would be a security downgrade. Although "downgrading" from SIPS to SIP is disallowed, it is possible that a redirect server or UAS sends a 3XX response to a request to a Audet Expires October 15, 2007 [Page 8] Internet-Draft SIPS April 2007 SIPS URI with a contact header field containing a SIP URI. [RFC3261]/8.1.3.4 states that if the UAC decide to recurse to the SIP URI, it "SHOULD inform the user". When a proxy is handling the 3XX, it can obviously not indicate anything to the user that it is being redirected from SIPS to SIP: therefore, proxies would not be able recurse on the contact header field, and instead would either forward the 3XX to the UAC or reject the request. -----Original Message----- From: Attila Sipos Sent: 17 May 2007 09:52 To: [email protected] Subject: [Sip] sips if possible,sip if not. - a question on sip-sips-03 draft What if you want to use sips where possible but don't mind a fallback to sip? So, if someone makes a call using sips in request URI and the called person doesn't have a sips URI registered, I guess the proxy will return 404 not found. So then then caller might say, ok, there isn't a sips URI, I will now try a sip URI and see if that works. The problem is that the called person might not have registered anything at all. So in such cases, the 2nd call attempt using sip is a waste. Is there a requirement for some kind of new SIP response code which says something like "no SIPS URI registered but there is a SIP one"? What are the potential problems with this idea? Regards, Attila _______________________________________________ Sip mailing list https://www1.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip _______________________________________________ Sip mailing list https://www1.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
