Adaptive Overload is the recommended mode for congestion controls with the SBC. In adaptive mode, a trigger MC level is defined. When this level is reached, based on the configured CPU utilization for that level, the SBC adjusts the system call and registration acceptance rate up or down to maintain the target CPU usage configured for that level. This maximizes the system throughput without exceeding the desired CPU bounds.

This adaptive targeting is independent of hardware configuration, call scenario mix, signaling types, and user retry behavior. The current CPU usage is sampled at various intervals, and the call acceptance rate is adjusted by an amount that is likely to increase/decrease the CPU usage to the desired interval.

The following parameters must be configured for adaptive overload controls:

  • Adaptive MC level—The MC level at which adaptive overload controls start.
  • MC level overload profile—The overload profile that defines the parameters for that level. This should be configured for all levels up to, and including, the adaptive MC level.

During adaptive throttling, the SBC can assign different preferences (priorities) to normal calls, emergency calls, and initial SIP registrations. This is configured by the policer preference values assigned to each request type. Additionally, the maximum burst size is configurable.

For details of configuring system congestion controls, refer to:

 

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