Hi Lei, Questions like this should be posted to the SIP-Implementors list: [EMAIL PROTECTED]
The SIP list is for issues related to the ongoing development of the protocol. The Contact header in the INVITE and the response are used for subsequent requests (like BYE) during the session. These identify the location of the User Agents for the session. These can be different than the To and From addresses. The To & From addresses identify the users. The Contacts identify the current device/computer they are communicating on for the session. You only need to know the URI of the user to initiate a session. You don't need to know which device(s) they are currently using. These are learned from the INVITE and the response. cheers, (-:bob Robert F. Penfield Chief Software Architect Acme Packet, Inc. 130 New Boston Street Woburn, MA 01801 [EMAIL PROTECTED] ----- Original Message ----- From: "Lei Liang" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, October 04, 2001 7:28 AM Subject: [Sip] greener question for "contact" header field > hello, everyone, > I see the "contact" header is used to specify the sender's addr. does the > caller and callee always use this addr to communicate after they get > it? looks it's more efficient to use the addr in "contact" header but not > the one in "To" as the destination addr, doesn't it? > another question is the RFC said using the "contact" addr can avoid the > proxies. but it's impossible for me because it has to pass firewall, a > kind of proxy, if the caller or callee is behind it. am I right? > thanks a lot for ur reading. > cheers. > lei > > > > _______________________________________________ > Sip mailing list http://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-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
