3Com S7902E, Configuration Manual

Page: 1758 / 2621

5-1
5
Congestion Management Configuration
When configuring hardware congestion management, go to these sections for information you are
interested in:
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Congestion Management Overview
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Congestion Management Configuration Approaches
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Per-Queue Hardware Congestion Management
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Displaying and Maintaining Congestion Management
Congestion Management Overview
Causes, Impacts, and Countermeasures of Congestion
Network congestion is a major factor contributed to service quality degrading on a traditional network.
Congestion is a situation where the forwarding rate decreases due to insufficient resources, resulting in
extra delay.
Congestion easily occurs in complex packet switching circumstances in the Internet. The following
figure shows two common cases:
Figure 5-1 Traffic congestion causes
100M>10M
（
100M+10M+50M
）
>100M
100M
100M
100M
50M
10M
10M
（
1
） （
2
）
Congestion may bring these negative results:
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Increased delay and jitter during packet transmission
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Decreased network throughput and resource use efficiency
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Network resource (memory in particular) exhaustion and even system breakdown
Congestion is unavoidable in switched networks and multi-user application environments. To improve
the service performance of your network, you must take some proper measures to address the
congestion issues.
The key to congestion management is how to define a dispatching policy for resources to decide the
order of forwarding packets when congestion occurs.
Congestion Management Policies
In general, congestion management uses queuing technology. The system uses a certain queuing
algorithm for traffic classification, and then uses a certain precedence algorithm to send the traffic.