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Configuring congestion management
Overview
Causes, impacts, and countermeasures of congestion
Congestion occurs on a link or node when traffic size exceeds the processing capability of the link or
node. It is typical of a statistical multiplexing network and can be caused by link failures, insufficient
resources, and various other causes.
shows some common congestion scenarios.
Figure 15 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 or multiuser application environments. To improve
the service performance of your network, take measures to manage and control it.
One major issue that congestion management deals with is defining a resource dispatching policy to
prioritize packets for forwarding when congestion occurs.
Congestion management policies
Queuing is a common congestion management technique. It classifies traffic into queues and picks
out packets from each queue by using a certain algorithm. Various queuing algorithms are available,
and each addresses a particular network traffic problem. Your choice of algorithm significantly affects
bandwidth assignment, delay, and jitter.
Queue scheduling treats packets with different priorities differently to transmit high-priority packets
preferentially.
This section briefly describes several common queue-scheduling mechanisms.