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4.8 QoS
4.8.1 Understand QOS
Quality of Service (QoS) is an advanced traffic prioritization feature that allows you to establish control
traffic, such as multi-media, video, protocol-specific, time critical, and file-backup traffic.
ces bandwidth limitations, delay, loss, and jitter. It also provides increased reliability for delivery
tly
h to treat selected applications and types of traffic.
You can use QoS on your system to:
。 Control a wide variety of network traffic by:
yi
。 Assigning priorities to traffic (for example, to set higher priorities to time-critical or business-critical
app
。 Applying security policy through traffic filtering.
。 Provide predictable throughput for multimedia applications such as video conferencing or voice
s the amount of traffic
。 the need to constantly add bandwidth to the network.
QoS Terminology
work. Traffic classifications are determined by protocol,
ices to indicate the level of service required by the packet across a
Service Level－defines the priority that will be given to a set of classified traffic. You can create and
mod
Policy－comprises a set of “rules” that are applied to a network so that a network meets the needs of the
business. That is, traffic can be prioritized across a network according to its importance to that particular
vel combinations). The QoS
Rule vel and a classifier to define how theSwitch will treat certain types of traffic.
over network traffic. QoS enables you to assign various grades of network service to different types of
QoS redu
of your data and allows you to prioritize certain applications across your network. You can define exac
how you want the switc
。 Classif ng traffic based on packet attributes.
lications).
over IP by minimizing delay and jitter.
。 Improve performance for specific types of traffic and preserve performance a
grows.
Reduce
。 Manage network congestion.
Classifier－classifies the traffic on the net
application, source, destination, and so on. You can create and modify classifications. The Switch then
groups classified traffic in order to schedule them with the appropriate service level.
DiffServ Code Point (DSCP) － is the traffic prioritization bits within an IP header that are encoded by
certain applications and/or dev
network.
ify service levels.
business type.
QoS Profile－consists of multiple sets of rules (classifier plus service le
profile is assigned to a port(s).
s－comprises a service le