SIP Session Agent Continuous Ping

You can configure the Oracle Communications 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 SBC should route requests to them.

To summarize the two methods:

• keep-alive— SBC sends a ping message of a type you configure to the session agent in the absence of regular traffic.
• continuous—The SBC sends a ping message regardless of traffic state (regular or irregular); the SBC regularly sends a ping sent based on the configured ping interval timer.

By sending ping messages, the SBC 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, the SBC starts sending a configured ping message to a session agent when traffic for that session agent has become irregular. The SBC 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 SBC considers any SIP response code successful.
• Transaction timeout—A transaction timeout happens when the session agent fails to send a response to the SBC’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 SBC 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 SBC 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 SBC 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.

By default, if the SBC does not receive a response to the ping from the session-agent, it marks it as out-of-service. You can configure the number of ping failures that the SBC can receive before it marks the session-agent as out-of-service. This is achieved by configuring the OPTIONS parameter in the session-agent with a ping-failure value, where value is the number of ping response failures. This is true for both the keep-alive and continuous-ping modes.

For example, set the Options parameter by typing options, followed by a Space, the option name: ping-failure-count=N (where N is the number of ping response failures before the SA is set to OOS) and press Enter. You may prepend the option parameter with a plus sign to add and not replace this option to the existing realm-config option list.

ORACLE (session-agent) #options +ping-failure-count=3

The session-agent is set out of service after the third ping response failure.

To remove the ping-failure-count option configuration, enter options -ping

ORACLE (session-agent) #options –ping

SIP SA Continuous Ping Configuration

You can set the ping mode in the session agent or session constraints configuration. The default for the ping-send-mode parameter is keep-alive.

Configure Ping Mode for Session Agents

1. Access the session-agent configuration element.

   ORACLE# configure terminal
   ORACLE(configure)# session-router
   ORACLE(session-router)# session-agent
   ORACLE(session-agent)

2. If you are adding to an existing configuration, then you will need to select the configuration you want to edit.
3. ping-send-mode—If to want to use continuous ping mode to send ping messages to session agents in regular traffic conditions, set this parameter to continuous. If you want to use the keep-alive mode, leave this parameter set to keep-alive (default).
4. Save and activate your configuration.

Configure Ping Mode for Session Constraints

1. Access the session-constraints configuration element.

   ORACLE# configure terminal
   ORACLE(configure)# session-router
   ORACLE(session-router)# session-constraints
   ORACLE(session-agent)

2. If you are adding to an existing configuration, then you will need to select the configuration you want to edit.
3. ping-send-mode—If to want to use continuous ping mode to send ping messages to session agents in regular traffic conditions, set this parameter to continuous. If you want to use the keep-alive mode, leave this parameter set to keep-alive (default).
4. Save and activate your configuration.