Allied Telesis AT-S63 - Manual (Page 171)

AT-S63 Management Software Features Guide
Section II: Advanced Operations 171
Traffic Classes
Traffic classes are the central component of the QoS solution. They
provide most of the QoS controls that allow a QoS solution to be deployed.
A traffic class can be assigned to only one policy. Traffic classes consist of
a set of QoS parameters and a group of QoS flow groups. Traffic can be
prioritized, marked (IP TOS or DSCP field set), and bandwidth limited.
Traffic is matched in the order of traffic class. For example, if a policy has
traffic classes 1, 3, 2 and 5, this is the order in which the packets are
matched.