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PDN Gateway Overview
Important:
Statistics chapter in the System Administration Guide.
Congestion Control
The congestion control feature allows you to set policies and thresholds and specify how the system reacts when faced
with a heavy load condition.
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
Service Congestion Policies: Congestion policies are configurable for each service. These policies
Important:
Administration Guide.
Default and Dedicated EPC Bearers
Provides a foundation for contributing towards improved Quality of User Experience (QoE) by enabling deterministic
end-to-end forwarding and scheduling treatments for different services or classes of applications pursuant to their
requirements for committed bandwidth resources, jitter and delay. In this way, each application receives the service
treatment that users expect.
In the StarOS 9.0 release and later, the Cisco EPC core platforms support one or more EPS bearers (default plus
dedicated). An EPS bearer is a logical aggregate of one or more Service Data Flows (SDFs), running between a UE and
a P-GW in the case of a GTP-based S5/S8 interface, and between a UE and HSGW (HRPD Serving Gateway) in case of
a PMIP-based S2a interface. In networks where GTP is used as the S5/S8 protocol, the EPS bearer constitutes a
concatenation of a radio bearer, S1-U bearer and an S5/S8 bearer anchored on the P-GW. In cases where PMIPv6 is
used the EPS bearer is concatenated between the UE and HSGW with IP connectivity between the HSGW and P-GW.
For more information on bulk statistic configuration, refer to the Configuring and Maintaining Bulk
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.
dictate how services respond when the system detects that a congestion condition threshold has been
crossed.
For more information on congestion control, refer to the Congestion Control chapter in the System
Cisco ASR 5x00 Packet Data Network Gateway Administration Guide ▄
Features and Functionality - Base Software ▀
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