Allied Telesis AT-S63 - Manual (Page 329)

AT-S63 Management Software Menus Interface User’s Guide
Section II: Advanced Operations 329
The effects of this behavior become evident when using the maximum
bandwidth feature of QoS. Here is an example. Suppose you have a policy
that assigns 5 Mbps of maximum bandwidth to an egress port. Now
assume there are 10 ports on the switch where ingress traffic matches the
criteria specified in the classifier assigned to the policy of the egress port.
Since the policy considers each ingress flow separately, the result would
be a maximum bandwidth of 50 Mbps (10 x 5 Mbps) on the egress port,
because there are 10 flows, one from each ingress port, directed to the
egress port.
An additional factor to consider when specifying an egress port in a policy
is that if the destination MAC address of the traffic flow has not been
learned by the egress port or, alternatively, added as a static address to
the port, the policy remains inactive. This is because the ingress ports
consider the traffic as unknown traffic and flood the traffic to all the ports.
This applies equally to unknown unicast and unknown multicast traffic, as
well as broadcast traffic.
QoS Policy
Guidelines
Following is a list of QoS policy guidelines:
ˆ A classifier may be assigned to many flow groups. However, assigning
a classifier more than once within the same policy may lead to
undesirable results. A classifier may be used successfully in many
different policies.
ˆ A flow group must be assigned at least one classifier but may have
many classifiers.
ˆ A flow group may be assigned to only one traffic class.
ˆ A traffic class may have many flow groups.
ˆ A traffic class may only be assigned to one policy.
ˆ A policy may have many traffic classes.
ˆ A policy may be assigned to many ports.
ˆ A port may only have one policy.
ˆ You can create a policy without assigning it to a port, but the policy will
be inactive.
ˆ A policy must have at least one action defined in the flow group, traffic
class, or the policy itself. A policy without an action is invalid.
ˆ A Quality of Service policy and an access control list can coexist on the
same port only if they have different classifiers.
ˆ The switch can store up to 64 flow groups.
ˆ The switch can store up to 64 traffic classes.
ˆ The switch can store up to 64 policies.