Cisco CAC CUBE
Configures the Call Spike Call Admission Control feature at the device level to reject SIP calls when the call spike is detected as per the configuration (10 incoming call requests per 300 milliseconds)
Device(config)# call spike 10 steps 3 size 100
Configures the Call Admission Control feature based on the total calls, cpu, and memory usage at the interface level to reject SIP calls when the bandwidth that is required for the calls exceed the aggregate bandwidth threshold. Note:
By default, the system rejects incoming calls if the 5-second CPU utilization on the gateway exceeds 95%, and if the in-use process memory on the gateway exceeds 98%.
Device(config)# call threshold global total-calls low 1 high 1
or
Device(config)# call threshold global cupu-avg low 75 high 85
or
Device(config)# call threshold global toal-mem low 75 high 85
ref:https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/voice/cube/configuration/cube-book/voi-cube-call-admission-control.html