R3303-HP HSR6800 Routers ACL and QoS Configuration Guide

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Configuring hardware congestion
management
This feature is supported only on SAP modules operating in bridge mode.
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 24 sh
ows two
common cases.
Figure 24 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 even system breakdown
Congestion is unavoidable in switched networks and multi-user application environments. To improve the
service performance of your network, take 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 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 in detail Strict Priority (SP) queuing, Weighted Fair Queuing (WFQ),
Weighted Round Robin (WRR) queuing, and Class-Based Queuing (CBQ).