Managing Overload Control with Priority Handling for Emergency Calls
You can enable the virtual BGF to notify a gateway controller when it experiences processing overload that might prevent the timely execution of H.248 transactions. The gateway controller can then adjust how H.248 transactions are passed to the virtual BGF. The configurable overload control options provide priority handling for emergency calls.
The gateway controller activates the overload control feature by setting the overload control event. Incoming H.248 transactions are pushed into a work queue. Overload control actions are based on the following user-defined threshold levels:
- queue-limit-percentage—When the pending transactions in the work queue occupy this percentage of the maximum queue size, the virtual BGF sends an overload notification for each received ADD command in incoming H.248 transactions. The gateway controller lowers the rate used to admit calls to the virtual BGF (the admitted rate). The actions to be initiated for each overload threshold are configured on the gateway controller.
- reject-new-calls-threshold—When this threshold is reached, the virtual BGF rejects all non-emergency ADD transactions. Emergency ADD transactions, SUBTRACT, MODIFY, and AUDIT transactions are admitted. This percentage must be greater than or equal to the percentage specified for queue-limit-percentage.
- reject-all-commands-threshold—When this threshold is reached, all non-emergency transactions except for SUBTRACT transactions are rejected. This percentage must be greater than or equal to the percentage specified for reject-new-calls-threshold.
When transactions in the work queue occupy 100 percent of the work queue's maximum size, the virtual BGF drops received transactions and sends error code #511 (Temporarily Busy). When transactions in the work queue occupy less than the queue-limit-percentage, overload notifications are no longer sent.
