Congestion Control


Congestion Control
 
 
This chapter describes the Congestion Control feature.
The following topics are covered in this chapter:
 
 
Overview
This section provides an overview of the Congestion Control feature.
Congestion Control monitors the system for conditions that could potentially degrade performance when the system is under heavy load. Typically, these conditions are temporary (for example, high CPU or memory utilization) and are quickly resolved. However, continuous or large numbers of these conditions within a specific time interval may have an impact the system’s ability to service subscriber sessions. Congestion control helps identify such conditions and invokes policies for addressing the situation.
Congestion control operation is based on configuring the following:
 
Congestion Condition Thresholds: Thresholds dictate the conditions for which congestion control is enabled and establishes limits for defining the state of the system (congested or clear). These thresholds function in a way similar to operation thresholds that are configured for the system as described in the Thresholding Configuration Guide. The primary difference is that when congestion thresholds are reached, a service congestion policy and an SNMP trap, starCongestion, are generated.
A threshold tolerance dictates the percentage under the configured threshold that must be reached in order for the condition to be cleared. An SNMP trap, starCongestionClear, is then triggered.
Port Utilization Thresholds: If you set a port utilization threshold, when the average utilization of all ports in the system reaches the specified threshold, congestion control is enabled.
Port-specific Thresholds: If you set port-specific thresholds, when any individual port-specific threshold is reached, congestion control is enabled system-wide.
Service Congestion Policies: Congestion policies are configurable for each service. These policies dictate how services respond when the system detects that a congestion condition threshold has been crossed.
Important: This section provides the minimum instruction set for configuring congestion control. Commands that configure additional interface or port properties are provided in the Subscriber Configuration Mode chapters of the Command Line Interface Reference.
 
Configuring Congestion Control
To configure Congestion Control functionality:
Step 1
Step 2
Step 3
Step 4
Step 5
Save your configuration as described in the Saving and Verifying Your Configuration chapter.
 
Configuring the Congestion Control Threshold
To configure congestion control threshold, apply the following example configuration:
configure
  congestion-control threshold max-sessions-per-service-utilization <percent>
  congestion-control threshold tolerance <percent>
  end
Notes:
 
 
Configuring Service Congestion Policies
To create a congestion control policy, apply the following example configuration:
configure
  congestion-control policy <service> action { drop | none | redirect | reject }
  end
Notes:
 
For the MME redirect is not available.
 
Enabling Congestion Control Redirect Overload Policy
To create a congestion control policy and configure a redirect overload policy for the service, apply the following example configuration:
Important: Redirect is not available on PDIF for this release.
configure
  congestion-control
  context <context_name>
      {service_configuration_mode}
         policy overload redirect address
         end
Notes:
 
Optional: If the congestion control policy action was configured to redirect, then a redirect overload policy must be configured for the service(s) that are affected.
You can set various options for redirection. See the Command Line Interface Reference for more information.
 
Verify the Service Overload Policies
To verify that the service overload policies were properly configured, in the Exec Mode, enter the following command:
show <service_type> name service_name
This command lists the entire service configuration. Ensure that the information displayed for the “Overload Policy” is accurate.
Repeat this configuration example to configure additional services in other contexts.
 
Verify the Congestion Control Configuration
To verify Congestion Control Configuration, in the Exec Mode, enter the following command:
show congestion-control configuration
The following output is a concise listing of all threshold and policy configurations:
Congestion-control: enabled
Congestion-control threshold parameters
system cpu utilization: 80%
service control cpu utilization: 80%
system memory utilization: 80%
message queue utilization: 80%
message queue wait time: 10 seconds
port rx utilization: 80%
port tx utilization: 80%
license utilization: 100%
max-session-per-service utilization: 100%
tolerence limit: 10%
Congestion-control Policy
   pdsn-service: none
   hsgw-service: none
   ha-service: none
   lma-service: none
   ggsn-service: none
 
   lns-service: none
   cscf-service: reject
   pdif-service: none
 
   sgsn-service: none
   mme-service: drop
   asngw-service: none
   asnpc-service: none
   phsgw-service: none
   phspc-service: none
   mipv6ha-service: none
   sgw-service: none
   pgw-service: none
 
Disconnecting Subscribers Based on Call or Inactivity Time
During periods of heavy system load, it may be necessary to disconnect subscribers in order to maintain an acceptable level of system performance. You can establish thresholds to select subscribers to disconnect based on the length of time that a call has been connected or inactive.
To enable overload disconnect for the currently selected subscriber, use the following configuration example:
configure
   context <context_name>
      subscriber name <subscriber_name>
         default overload-disconnect threshold inactivity-time <dur_thresh>
         default overload-disconnect threshhold connect-time <dur_thresh>
         end
To disable the overload disconnect feature for this subscriber, use the following configuration example:
configure
   context <context_name>
      subscriber <subscriber_name>
      no overload-disconnect {[ threshold inactivity-time] | [ threshhold connect-time]}
      end
Notes:
 
overload-disconnect is not supported for the CSCF service.
 

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