SIP Session Agent Continuous Ping

You can configure the Oracle® Enterprise Session Border Controller to use either a keep-alive or continuous method for pinging SIP session agents to determine their health—i.e., whether or not the Oracle® Enterprise Session Border Controller should route requests to them. To summarize the two methods:

keep-alive— Oracle® Enterprise Session Border Controller sends a ping message of a type you configure to the session agent in the absence of regular traffic. Available in Release C5.1.0 and in earlier releases.
continuous—The Oracle® Enterprise Session Border Controller sends a ping message regardless of traffic state (regular or irregular); the Oracle® Enterprise Session Border Controller regularly sends a ping sent based on the configured ping interval timer. Available in Release C5.1.1p6 and in later releases.

By sending ping messages, the Oracle® Enterprise Session Border Controller monitors session agents’ health and can determine whether or not to take a session out of service (OOS), leave it in service, or bring it back into service after being OOS.

When you set it to use the keep-alive mode of pinging (available in Release C5.1.0 and before), the Oracle® Enterprise Session Border Controller starts sending a configured ping message to a session agent when traffic for that session agent has become irregular. The Oracle® Enterprise Session Border Controller only sends the ping if there are no SIP transactions with a session agent over a configurable period of time, to which the session agent’s response can have one of the following results:

Successful response—A successful response is either any SIP response code or any response code not found in the out-service-response-codes parameter; these leave the session agent in service. In addition, any successful response or any response in the ping-in-service-response-codes parameter can bring a session agent from OOS to in-service status.
Unsuccessful response—An unsuccessful response is any SIP response code configured in the out-service-response-codes parameter and takes the session agent sending it OOS. Because this parameter is blank by default, the Oracle® Enterprise Session Border Controller considers any SIP response code successful.
Transaction timeout—A transaction timeout happens when the session agent fails to send a response to the Oracle® Enterprise Session Border Controller’s request, resulting in the session agent’s being taken OOS.

Despite the fact that the keep-alive ping mode is a powerful tool for monitoring session agents’ health, you might want to use the continuous ping method if you are concerned about the Oracle® Enterprise Session Border Controller not distinguishing between unsuccessful responses from next-hop session agents and ones from devices downstream from the next-hop session agent. For example, if a SIP hop beyond the session agent responds with a 503 Service Unavailable, the Oracle® Enterprise Session Border Controller does not detect whether a session agent or the device beyond it generated the response.

When you use the continuous ping method, only the next-hop session agent responds—preventing the request from being sent to downstream devices. The Oracle® Enterprise Session Border Controller also sends the ping in regular traffic conditions when in continuous ping mode, so it is certain the response comes from the next hop associated with the session agent. And in continuous ping mode, only entries for the ping-out-service-response-codes parameter and transaction timeouts bring session agents OOS.