Impact; Countermeasure; Traffic Management Technologies - 3Com MSR 50 Series Configuration Manual

Impact

Countermeasure

Traffic Management
Technologies
When traffic arrives at wire speed, congestion may occur for network resource
bottleneck.
Besides the bottleneck of link bandwidth, congestion will also be caused by
resources deficiency in normal packet forwarding, such as the deficiency of
assignable processor time, buffer and memory. In addition, congestion may occur
if the arrival traffic is not managed efficiently and the assignable network
resources are inadequate.
Congestion may cause the following negative effects:
Increase the delay and jitter of packet transmission, and an excessive delay
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leads to packet re-transmission.
Decrease the efficient throughput of network and lower the utilization of
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network resources.
Intensified congestion can occupy too many network resources (especially in
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memory), and the irrational assignment of resources even can lead to resource
block and breakdown for the system.
It is obvious that congestion will make the traffics unable to obtain the resources
in time and degrade the service performance accordingly. No one wants
congestion, but it occurs frequently in complex environments where packet
switching and multi-users applications coexist. So it needs to be treated cautiously.
A direct way to solve resources deficiency problem is to increase the bandwidth of
network; however, it cannot resolve all the problems caused by congestion.
A more effective method to solve the problem of QoS is to enhance the functions
of traffic control and resource allocation in the network, and to provide
differentiated services for applications with different service requirement in order
to allocate and use resources rightly. During the process of resources allocation
and traffic control, the direct or indirect factors that might cause network
congestion should be controlled with best effort to reduce the probability of
congestion. As congestion occurs, resource allocation should be balanced
according to features and demands of applications, to minimize the effects on
QoS by congestion.
Traffic classification, traffic policing, traffic shaping, congestion management, and
congestion avoidance are the foundations for a network to provide differentiated
services. Mainly they implement the following functions:
Traffic classification: It is a prerequisite for differentiated service, to identify the
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interested objects based on a certain matching rule.
Traffic policing: polices the specification of particular traffics entering the
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router. When the traffics exceed the specification, then some restriction or
punishment measures can be taken to protect the commercial benefits of
carriers and to prevent network resources from being damaged.
Traffic shaping: A traffic control measure of actively adjusting the output speed
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of traffics, generally it can enable the traffic to adapt to the network resources
supplied by the downstream router, to prevent the unwanted packet dropping

Traffic Management Technologies

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