From: "Rick Whitesel \(rwhitese\)" <[EMAIL PROTECTED]>

   I certainly understand that when one uses UDP the port numbers make
   sense in all the standard places. I just do not understand why one
   would include port numbers when using TCP or TLS over TCP since the
   port number is set up by TCP and carried at the TCP level.

That is true for a single TCP connection.  But assume that a request
is carried through two proxies:  UAC -> A -> B -> UAS.  Then when UAS
sends a reply, it can (but need not) send the response on the same TCP
connection through which it received the request from B.

But what does B do with the response?  The Via header tells B the
address/port (of A) to which the response must be send.  If B has a
TCP connection to that address/port, it can use it, or it can set up a
new TCP connection.

Etc.

Without having correct port number information, B could not
distinguish A from the proxy A' (which is on the same host but listens
on a different port).

Dale
_______________________________________________
Sip-implementors mailing list
[email protected]
https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors

Reply via email to