Allied Telesis AT-S63 - Manual (Page 144)

Chapter 13: Quality of Service
144 Section II: Advanced Operations
Flow Groups
Flow groups group similar traffic flows together, and allow more specific
QoS controls to be used, in preference to those specified by the traffic
class. Flow groups consist of a small set of QoS parameters and a group
of classifiers. After a flow group has been added to a traffic class it cannot
be added to another traffic class. A traffic class may have many flow
groups. Traffic is matched in the order of the flow groups. For example, if a
traffic class has flow groups 1, 3, 2 and 5, this is the order in which the
packets are matched.
QoS controls at the flow group level provide a QoS hierarchy. Non-default
flow group settings are always used, but if no setting is specified for a flow
group, the flow group uses the settings for the traffic class to which it
belongs. For example, you can use a traffic class to limit the bandwidth
available to web and FTP traffic combined. Within that traffic class, you
can create two different flow groups with different priorities, to give web
traffic a higher priority than FTP. Web traffic would then be given
preferential access to bandwidth, but would be limited to the bandwidth
limit of the traffic class.