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GS752TP, GS728TP, and GS728TPP Gigabit Smart Switches
Differentiated Services
The QoS feature provides Differentiated Services (DiffServ) support that enables traffic to be
classified into streams and given certain QoS treatment in accordance with defined per-hop
behaviors. For more information, see DiffServ Traffic Classes .
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 that it will. 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 has undesirable effects on 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. A class defines the
classification criteria. A policy’s attributes define the processing. Policy attributes might 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 checking the class match criteria for a packet. A policy is
applied to a packet when a class match within that policy is found.
From the DiffServ menu under the QoS tab, you can access the following:
•Diffserv Configuration
•DSCP Violate Action Mapping
•Class Configuration
•IPv6 Class Configuration
•Policy Configuration
•Service Configuration
•Service Statistics