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- Register
The phone has ability to register to a failover server when the Primary SIP Server has no response to a REGISTER request.
1) The phone sends a REGISTER request to the Primary SIP Server.
2) The phone retries to send REGISTER requests to the Primary SIP server (three times by default).
3) After no response from the Primary SIP server, the phone sends a REGISTER request to the failover server.
4) The phone retries to send REGISTER requests to the Failover SIP server (three times by default).
5) After no response from the Failover SIP server, the phone sends a REGISTER request to the Second Failover server.
6) The Failover server responds with 200 OK to the REGISTER request. - Invite
The phone has ability to register to a failover server when the Primary SIP Server has no response to a INVITE request.
Phone A places a call to Phone B, Then Phone B answers the call.
1) The phone sends a INVITE request to the Primary SIP Server.
2) The phone retries to send INVITE requests to the Primary SIP server (three times by default).
3) After no response from the Primary SIP server, the phone sends a REGISTER request to the failover server.
4) The Failover server responds with 200 OK to the REGISTER request.
5) The phone sends a INVITE request to the Failover server.
Phone A sends REGISTER requests to the working server to detect whether the server is available. When the working server recovers, the phone has ability to fail back the INVITE request to the working server.
FSUSN Scenario
The following introduces a REGISTER FSUSN scenario. The SIP server 1 is configured with the domain name of the working server. The working server is resolved to two SIP servers (primary server and secondary server) using the DNS mechanism. The parameter DNS-mode set to DNS-SRV or DNS-NAPTR
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