The SBC Core detects congestion by monitoring a time-decaying average of the CPU utilization. It also monitors the Internal Round-Trip Time (IRTT) during call setup for determining whether the SBC is in congestion. When congestion (for either reason) is detected and the congestion level reaches MC2, the SBC activates a control algorithm which adaptively throttles calls to eliminate the congestion while still maximizing the call throughput.

This object displays the system Congestion Status.

On SBC main screen, go to Monitoring > System > Category: System Status and Statistics > System Congestion Status. The System Congestion Status window is displayed.

Figure 1: System - System Congestion Status


By default only ten entries are displayed in a view. You can choose the number of entries to be displayed under the Show entries drop down box. 

The following fields are displayed:

Table 1: System Congestion Status Parameters

ParameterDescription
NameThe name of the CE Node.
System Congestion MCLevel System congestion level.
System Congestion CPULevel The current System Machine Congestion (MC) Level at the time this command is executed.

  • 0 – No Congestion

  • 1 – Level one congestion

  • 2 – Level two congestion

  • 3 – Level three congestion

System Congestion Call Rate Level Call rate congestion level.
System Congestion IRTTLevel Internal RoundTrip Time (IRTT) congestion level.
System Congestion MCDurationNumber of seconds the system has been at this congestion level.
System Congestion Call Arrival Rate A snapshot of the number of call arrivals in the last second.
System Congestion Call Accept Rate Current rate at which calls are being accepted by the system.
System Congestion Call Accept Count Current number of calls being accepted by the system measured in calls/second. A value of "65535" represents all calls. During MC2 congestion, SBC calculates the CallAcceptRate peridocially (each second), and uses the value to compute a new CallAcceptCount.
System Congestion Call Eq Arrival RateThe weighted sum of the number of SIP calls, registrations, SUBSCRIBEs and any other SIP traffic that arrived at the SBC in the last second. For purposes of calculating the weighted sum, 4 units of any SIP non-INVITE traffic is considered equivalent to a call.
System Congestion Register Arrival RateA snapshot of the number of SIP registration arrivals in the last second.
System Congestion Subscriptions Arrival Rate The number of SIP SUBSCRIBEs that arrived in the last second.
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