Also, it can resolve the NAT issues also though it might not be the intention.
Rport/received/sent-by was mainly introduced in a UAC/UAS or proxy server that is multi homed (Multiple IP Addresses for the SIP communication), when responding to a message, it is recommended to use the same IP address as the original request was received from and sent to the same address where the message is sent from and hence the sent-by and received helps in identifying the same. It also helps NAT due to the fact that if the UAC is behind a NAT, the address in VIA might not be the same as the address that is received by a Proxy Server and remembering the address is needed to use the NAT pipe that UAC has used. Let me know if you have further questions. Dutt Kalapatapu Senior Architect | tel:+1.408.533.3315 | sip:[EMAIL PROTECTED] -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Vikram Chhibber Sent: Wednesday, April 09, 2008 9:46 AM To: Iñaki Baz Castillo Cc: [email protected] Subject: Re: [Sip-implementors] Why "rport" is not defined in RFC3261 as"received" parameter? I think "received" was introduced so that response reach the sip-node that sent the request. It has nothing to do with NAT as 3261 never considered and address this problem. So, if the top most Via contains non-ip sent-by, the UAS is supposed to replace it with the IP address from where it has received the request so that while sending response, it need not perform dns procedures which may resolve sent-by to some other IP address which is different from the UAC one. On Wed, Apr 9, 2008 at 4:14 AM, Iñaki Baz Castillo <[EMAIL PROTECTED]> wrote: > Hi, I can't imagine why "rport" is an extension (RFC 3581) to SIP instead of > being included directly in RFC 3261. > > Ok, I know that in RFC 3261 NAT doesn't exist (I imagine IETF meetings using > a > private LAN with IPv6 XDDD) but even if NAT wasn't exist I can't imagine an > scenario where the source IP changes but not the port. Any example please? > > Thanks a lot. > > -- > Iñaki Baz Castillo > > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
