Quality of Service
QoS Features and Components
Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 490
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QoS Features and Components
The QoS feature is used to optimize network performance.
QoS provides the following:
•Classification of incoming traffic to traffic classes, based on attributes,
including:
-Device Configuration
-Ingress interface
-Packet content
-Combination of these attributes
QoS includes the following:
•Traffic Classification—Classifies each incoming packet as belonging to a
specific traffic flow, based on the packet contents and/or the port. The
classification is done by ACL (Access Control List), and only traffic that
meets the ACL criteria is subject to CoS or QoS classification.
•Assignment to Hardware Queues—Assigns incoming packets to
forwarding queues. Packets are sent to a particular queue for handling as a
function of the traffic class to which they belong. See Configuring QoS
Queues.
•Other Traffic Class-Handling Attribute—Applies QoS mechanisms to
various classes, including bandwidth management.

QoS Operation

The type of header field to be trusted is entered in the Global Settings page. For
every value of that field, an egress queue is assigned, indicating through which
queue the frame is sent, in the CoS/802.1p to Queue page or the DSCP to Queue
page (depending on whether the trust mode is CoS/802.1p or DSCP, respectively).