Configuring Quality Of Service; Quality Of Service (Qos) Overview - Dell PowerConnect 2708 User Manual

Configuring Quality of Service

This section provides information for defining and configuring Quality of Service (QoS)
parameters.

Quality of Service (QoS) Overview

An implementation example that requires QoS includes certain types of traffic such as Voice,
Video, and real-time traffic, which can be assigned a high priority queue, while other traffic can be
assigned a lower priority queue. The result is an improved traffic flow for traffic with high demand.
The system supports four queues per port. After a packet is classified, it assigned to one of the
output queues. QoS Terms:
• Classification — Specifies which packet fields are matched to specific values. All packets
matching the user-defined specifications are classified together.
• Action — Defines traffic management where packets being forwarded are based on packet
information and packet field values, such as VLAN priority (VPT) and DSCP (DiffServ Code
Point).
VPT Tag Classification Information
VLAN Priority Tags are used to classify the packets by mapping packets to one of the egress queues.
VLAN Priority Tag to queue assignments are user-definable. The table below details the VPT to
queue default settings:
Table 7-1. VPT to Queue Default Settings
CoS Value
0
1
2
3
4
5
6
7
Forwarding Queue Values
q2 (Best Effort)
q1 (Lowest Priority)
q1 (Lowest Priority)
q2 (Best Effort)
q3
q3
q4 (Highest Priority)
q4 (Highest Priority)
7
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