3com 3CDSG10PWR Guia Do Utilizador

Quality of Service (QoS) provides the ability to implement QoS and priority 
queuing within a network. For example, certain types of traffic that 
require minimal delay, such as Voice, Video, and real-time traffic 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. QoS is defined by:

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Classification — Specifies which packet fields are matched to specific 
values. All packets matching the user-defined specifications are 
classified together.

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Action — Defines traffic management where packets are forwarded 
are based on packet information, and packet field values such as 
VLAN Priority Tag (VPT) and DiffServ Code Point (DSCP).

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VPT Classification Information — VLAN Priority Tags (VPT) are used 
to classify packets by mapping packets to one of the egress queues. 
VPT to Queue assignments are user-definable. Packets arriving 
untagged are assigned a default VPT value, which is set on a per-port 
basis. The assigned VPT is used to map the packet to the egress 
queue. 

This section contains information for configuring QoS, and includes the 
following topics: 

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