SIP intercom registration methods
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SIP Intercom Registration methods
This article describes the different methods for SIP registration on Zenitel IP stations.
Parallel
In Parallel mode the IP station will try to be registered to all configured SIP servers at the same time. The station will use primary SIP server for outgoing calls if available, otherwise it will use the next available backup server. In this mode the station can receive calls from multiple SIP servers at the same time.
This mode is not recommended in a Cisco Unified Callmanager cluster with multiple publishers and subscribers.
Serial
Serial registrations means that the station will always register to the next available SIP server. The station starts with registering to primary SIP server, then if the station loses contact with the primary SIP server it will register on the backup server. If the station loses contact with the backup server, then it will register on the secondary backup server. If the station loses contact with the secondary backup server it will register to the primary SIP server.
Top-Down
Top-Down registration means that the station will try to be registered to the primary SIP server, but periodically (every 60 seconds) poll the backup servers to check that they are up without registering. If primary SIP server shuts down, then the station will register to the next backup server which is up. If the primary SIP server starts up the station will unregister at the backup server and switch back to the primary server. The station will not cancel any active call during this operation, but there is a chance that the IPBX will because of the station unregisters.
Cisco
Cisco registration is the same as Top-Down for primary and backup server, while the second backup server will register to its configured server in parallell.