H3C Technologies H3C S10500 Series Switches - Manual (Page 51)

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Congestion management configuration
Congestion management overview
Causes, impacts, and countermeasures
Network congestion degrades service quality on a traditional network. Congestion is a situation where
the forwarding rate decreases due to insufficient resources, resulting in extra delay.
Congestion is more likely to occur in complex packet switching circumstances.
Figure 14 shows two
common cases:
Figure 14 Traffic congestion causes
Congestion can bring the following negative results:
• Increased delay and jitter during packet transmission
• Decreased network throughput and resource use efficiency
• Network resource (memory, in particular) exhaustion and system breakdown
Congestion is unavoidable in switched networks and multi-user application environments. To improve the
service performance of your network, you must take proper measures to address the congestion issues.
The key to congestion management is defining a dispatching policy for resources to decide the order of
forwarding packets when congestion occurs.
Congestion management techniques
Congestion management uses queuing and scheduling algorithms to classify and sort traffic leaving a
port. Each queuing algorithm addresses a particular network traffic problem, and has a different impact
on bandwidth resource assignment, delay, and jitter.
Queue scheduling processes packets by their priorities, preferentially forwarding high-priority packets.
The following section describes Strict Priority (SP) queuing, Weighted Fair Queuing (WFQ), Weighted
Round Robin (WRR) queuing, SP+WRR queuing, and SP+WFQ queuing.
SP queuing
SP queuing is designed for mission-critical applications that require preferential service to reduce the
response delay when congestion occurs.