User Manual

Configure Quality of Service
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M4200 and M4300 Series ProSAFE Managed Switches Web Management User Manual
11. Use WRED Drop Probability Scale to determine the packet drop probability for the current
drop precedence level.
The range is 0 to 100. The default is 10.
12. Click the Apply button.
The updated configuration is sent to the switch. Configuration changes take effect
immediately.
The following table describes the nonconfigurable data that is displayed.
Differentiated Services Overview
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 e-mail 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.
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.
Table 180. CoS Interface Queue Drop Precedence Status
Field Description
Interface The CoS configurable interface.
Queue ID The queue ID.
Drop Precedence Level The drop precedence level.
WRED Minimum Threshold The weighted RED minimum queue threshold value.
WRED Maximum Threshold The weighted RED maximum queue threshold value.
WRED Drop Probability Scale The packet drop probability value.