It is possible to have two instances of a UA (for example) on one unit. So using the port is theoretically one way to differentiate between instances. It's not useless. If you get a Contact header with a port then you have to send to that port (discounting NAT traversal scenarios) otherwise everything will break. >>Or is the port number is which the UAS is listening to? How the UAC knows it is 5555 if so? A UAC might not know but a proxy/registrar might - for example if a user was registered with the Contact as port 5555, then requests to that user will get forwarded to port 5555. Another user using, for example, port 5556 will register using a Contact with 5556 and so will receive requests to that port. Regards,
Attila ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Yuantao Zhang Sent: 04 June 2008 11:10 To: [email protected]; [EMAIL PROTECTED] Subject: [Sip] What is the port number in "Invite" request-line? Thanks Dear all INVITE sip:[EMAIL PROTECTED] SIP/2.0:5555 INVITE sip:[EMAIL PROTECTED] SIP/2.0 Above are 2 "Invite" request-line examples. In example one, it indicates a port number, 5555. What does the port number mean? Is it the port number of SIP proxy? Why we include port number here? The SIP proxy(biloxi.com) application layer who receives this "Invite" should receive this via port 5555 from lowe layer(UDP). Therefore, The SIP proxy(biloxi.com) application layer already know the port is 5555. Actualy, the SIP proxy application layer keeps listening port 5555. The second "Invite" request-line example is from RFC3261 and does not include port number. Can I say the port number is useless? So why example one includes a useless part in "Invite" request-line URL? Or is the port number is which the UAS is listening to? How the UAC knows it is 5555 if so? Any standard on this port number issue? Thanks. Best regards Steven
_______________________________________________ Sip mailing list https://www.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
