Let me explain this issue, step by step.
What is Record-Route?
A SIP proxy is a SIP application/server that proxies the SIP messages to another SIP client or Server. If such a proxy want to receive subsequent requests, it is supposed to add a Record-Route header to the SIP Message. Record-Route header contains the SIP URI representing the proxy.
Eg:
Record-Route: <sip:server10.biloxi....
