Qos Overview; Introduction To Qos; Introduction To Qos Service Models - 3Com S7906E Configuration Manual

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QoS Overview

The S7900E Series Ethernet Switches are distributed devices supporting Intelligent Resilient
Framework (IRF). Two S7900E series can be connected together to form a distributed IRF device. If an
S7900E series is not in any IRF, it operates as a distributed device; if the S7900E series is in an IRF, it
operates as a distributed IRF device. For introduction of IRF, refer to IRF Configuration in the System
Volume.
This chapter covers the following topics:

Introduction to QoS

Introduction to QoS Service Models

QoS Techniques Overview
Introduction to QoS
For network traffic, the Quality of Service (QoS) involves bandwidth, delay, and packet loss rate during
traffic forwarding process. In a network, you can improve the QoS by guaranteeing the bandwidth, and
reducing the delay, jitter, and packet loss rate.
The network resources are always scarce. QoS requirements exist on any occasion where traffic flows
contend for network resources. QoS is a relative concept for traffic flows, that is, guaranteeing QoS for
a certain traffic flow may damage QoS of other traffic flows. For example, in the case of fixed bandwidth,
if a traffic flow gets more bandwidth, the other traffic flows will get less bandwidth and may be affected.
Therefore, the network administrator should reasonably plan and allocate network resources based on
the characteristics of various traffic flows, thus utilizing the network resources effectively.
The following part introduces the QoS service models, and some mature QoS techniques used most
widely. Using these techniques reasonably in the specific environments, you can improve the QoS
effectively.
Introduction to QoS Service Models
This section covers three typical QoS service models:
Best-effort service
Integrated service (IntServ)
Differentiated service (DiffServ)
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