Quality Of Service - Allied Telesis SwitchBlade x908 Series Software Reference Manual

Switching Introduction

Quality of Service

Quality of Service (QoS) enables you to both prioritize traffic and limit its available bandwidth.
The concept of QoS is a departure from the original networking protocols, in which all traffic
on the Internet or within a LAN had the same available bandwidth. Without QoS, all traffic
types are equally likely to be dropped if a link becomes oversubscribed. This approach is now
inadequate in many networks, because traffic levels have increased and networks often carry
time-critical applications such as streams of real-time video data. QoS also enables service
providers to easily supply different customers with different amounts of bandwidth.
Configuring Quality of Service involves two separate stages:
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2.
The switch's QoS functionality includes the following:
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For more information on QoS see
QoS
14.18
Classifying traffic into flows, according to a wide range of criteria. Classification is
performed by the switch's class maps.
Acting on these traffic flows.
policies, to provide a QoS configuration for a port or ports
traffic classes, for bandwidth limiting and user prioritization
maximum bandwidth limiting on a traffic class
flow groups within traffic classes, for user prioritization
control of the egress scheduling algorithm
priority relabelling of frames, at Layer 2, by replacing the VLAN tag User Priority field
class of service relabelling of frames, at Layer 3, by replacing the DSCP (DiffServ Code
Point) or the TOS precedence value in the IP header's Type of Service (TOS) field.
Commands.
Software Reference for SwitchBlade® x908, x900 and x600 Series Switches
TM
AlliedWare Plus Operating System - Software Version 5.3.1
Chapter 50, Quality of Service (QoS) and Chapter 51,
C613-50007-01 REV B