Cisco Cisco ASR 5000 Technical Manual

The congestion service policies are configurable for each service, such as Packet Data Serving Node (PDSN),
Gateway GPRS Support Node (GGSN), and Serving GPRS Support Node (SGSN). These policies dictate the
manner in which the services respond when congestion is detected on the system due to a congestion
threshold breach.

This section describes the configurations that are required in order to enable the congestion control and the
basic tuning of congestion control.

The congestion control is disabled by default on the chassis. Enter the congestion−control command in global
configuration mode in order to enable it:

The congestion control overload disconnect enables or disables the policy for disconnection of the
chassis−wide passive calls during an overload situation. This is disabled by default. It allows disconnection of
the passive calls in stages and in iterations from the chassis until congestion control is cleared. The threshold
for the license−utilization and max−sessions−per−service−utilization, along with the threshold value, can be
configured.

For example, if the threshold is configured with at value of 90% and a tolerance of 5%, then the system stops
the passive call disconnect when the number of calls drops below 85% of the total allowed calls for that
service.

Here is the CLI syntax that can be used in order to enable the congestion control overload disconnect, which is
always configured in global configuration mode:

congestion−control overload−disconnect [ iterations−per−stage <integer> | percent

 <percentage_value> | threshold { license−utilization <percentage_value> |

 max−sessions−per−service−utilization <percentage_value> | tolerance <number> } ]

Here are some notes about this syntax:

Iterations−per−stage: This parameter defines the number of calls to be disconnected during the
defined number of seconds. This value can range between two and eight.

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Percent: This parameter specifies the percentage of calls to be disconnected in stages during an
overload situation. This value can range between zero and one hundred, with five as the default value.

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Threshold: This parameter defines the threshold values for the license and the maximum session
utilization. It also allows for a definition of the tolerance value.

License−utilization: This specifies the license utilization percentage threshold for overload
situations. In case of a trigger, the passive calls are disconnected. This value ranges between
one and one hundred, with 80 as the default value.

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