[SIPForum-discussion] What agent inserts the record-route? Beginner questions.

[Rodrigo Pimenta Carvalho]

Hi.


I have a network with softphones (SIP user agents) and one SIP Proxy. Callee is in the local network (same hardware as SIP Proxy) and Callers are in a remote network.


When a callee answers a SIP INVITE with SIP OK, some agent is adding a record-route field in the header. I think is the SIP Proxy that adds the record-route. So, I have some basic questions:


1 - What is the general utility of the record-route field in the header of a SIP OK message?

2 - Does the UAS (from callee) use to add a record-route in some situation?

3 - Is the SIP Proxy the only one that can add record-routes?

4 - The SIP OK from callee has 2 records-route. Is it due to the fact that callee and SIP Proxy is in the same hardware? (The callee is registered with IP 127.0.0.1. There is a loopback and my SIP Proxy listen to loopback too.)

5 - Is the newest inserted record-route the top most?

6 - When UAC has to send SIP ACK for the SIP OK. does it read the top most record-route to figure out where to send the message?


Any hint will very helpful!

Best regards.


RODRIGO PIMENTA CARVALHO
Inatel Competence Center
Software
Ph: +55 35 3471 9200 RAMAL 979
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