GS-5220-Series User Manual

User’s Manual of GS-5220 Ultra PoE & PoE+ Series
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4.9 Quality of Service
4.9.1 Understanding QoS
Quality of Service (QoS) is an advanced traffic prioritization feature that allows you to establish control over network traffic. QoS
enables you to assign various grades of network service to different types of traffic, such as multi-media, video, protocol-specific,
time critical, and file-backup traffic.
QoS reduces bandwidth limitations, delay, loss, and jitter. It also provides increased reliability for delivery of your data and
allows you to prioritize certain applications across your network. You can define exactly how you want the switch to treat
selected applications and types of traffic. You can use QoS on your system to:
• Control a wide variety of network traffic by:
• Classifying traffic based on packet attributes.
• Assigning priorities to traffic (for example, to set higher priorities to time-critical or business-critical applications).
• Applying security policy through traffic filtering.
• Provide predictable throughput for multimedia applications such as video conferencing or voice over IP by minimizing
delay and jitter.
• Improve performance for specific types of traffic and preserve performance as the amount of traffic grows.
• Reduce the need to constantly add bandwidth to the network.
• Manage network congestion.
QoS Terminology
• Classifier－classifies the traffic on the network. Traffic classifications are determined by protocol, 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 devices to indicate the level of service required by the packet across a network.
• Service Level－defines the priority that will be given to a set of classified traffic. You can create and modify service
levels.
• 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 business type.
• QoS Profile－consists of multiple sets of rules (classifier plus service level combinations). The QoS profile is assigned
to a port(s).
• Rules－comprises a service level and a classifier to define how the Switch will treat certain types of traffic. Rules are
associated with a QoS Profile (see above).
To implement QoS on your network, you need to carry out the following actions:
1. Define a service level to determine the priority that will be applied to traffic.
2. Apply a classifier to determine how the incoming traffic will be classified and thus treated by the Switch.
3. Create a QoS profile which associates a service level and a classifier.
4. Apply a QoS profile to a port(s).