Configure Quality of Service
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XS708T, XS712Tv2, and XS716T Smart Managed Pro Switch User Manual
The allowed Per Hop Behavior (PHBs) values, apart from other DSCP experimental
values, are as follows:
• Class Selector (CS) PHB. These values are based on IP precedence.
• Assured Forwarding (AF) PHB. These values define four main levels to sort and
manipulate some flows within the network.
• Expedited Forwarding (EF) PHB. These values are used to prioritize traffic for
real-time applications. In many situations, if the network exceeded traffic and you
need some bandwidth guaranteed for an application, the EF traffic must receive this
rate independently of the intensity of any other traffic attempting to transit the node.
7. Click the Apply button.
The updated configuration is sent to the switch. Configuration changes take effect
immediately.
Manage Differentiated Services
The QoS feature contains Differentiated Services (DiffServ) support that allows traffic to be
classified into streams and given certain QoS treatment in accordance with defined per-hop
behaviors.
Standard IP-based networks are designed to provide best effort data delivery service. Best
effort service implies that the network delivers the data in a timely fashion, although there is
no guarantee. During times of congestion, packets might be delayed, sent sporadically, or
dropped. For typical Internet applications, such as email and file transfer, a slight degradation
in service is acceptable and in many cases unnoticeable. Conversely, any degradation of
service can negatively affect applications with strict timing requirements, such as voice or
multimedia.
Defining DiffServ
To use DiffServ for QoS, you must first define the following categories and their criteria:
1. Class. Create classes and define class criteria.
2. Policy. Create policies, associate classes with policies, and define policy statements.
3. Service. Add a policy to an inbound interface.
Packets are classified and processed based on defined criteria. The classification criteria are
defined by a class. The processing is defined by a policy’s attributes. Policy attributes can be
defined on a per-class instance basis, and it is these attributes that are applied when a match
occurs. A policy can contain multiples classes. When the policy is active, the actions taken
depend on which class matches the packet.
Packet processing begins by testing the class match criteria for a packet. A policy is applied
to a packet when a class match within that policy is found.
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