SIP Entity Monitoring provides background detection for monitored connections to improve alternative routing and to minimize the call setup time due to SIP link failures. The SIP Monitor periodically tests the status of the SIP proxy servers. If a proxy fails to reply, SIP messages are no longer routed to that proxy. As a result, call delays are reduced since calls are not routed to the failed servers. The SIP Monitor continues to monitor the failed SIP entity. When the proxy replies, SIP messages are again routed over that link.

SIP monitoring sends OPTIONS requests to SIP entities to determine whether these are in up, partially up, down or deny new service state. An entity is considered up if all of the addresses associated with it are up. An entity is down if all of its addresses are down. An entity is partially up if some, but not all, of its addresses are up. An address is considered down if the response of address to OPTIONS is:

• 408 Request Timeout

• 500 Server Internal Error: Destination Unreachable

• 503 Service Unavailable (with no parenthetical text)

• 503 Service Unavailable (no media resources)

• 504 Server Timeout

All other responses (including "503 Service Unavailable") with other parenthetical text, such as "503 Service Unavailable (Signaling Resources Unavailable)" results in the address to be considered up.

You can turn the monitoring on or off for a given SIP entity. If monitoring is turned off, the SIP entity is not monitored by any instance.

You can also turn monitoring on or off for an entire Session Manager instance. If monitoring is turned off, none of the SIP entities are monitored by that Session Manager instance. If monitoring for the Session Manager instance is turned on, only those SIP entities for which monitoring is turned on are monitored.

SIP Monitoring can only report problems if the Security Module is functional.

SIP Monitoring setup is administered using the SIP Entity and the Session Manager Administration pages.