Allied Telesis AT-S63 - Manual (Page 254)

Chapter 18: Quality of Service (QoS) Commands
254 Section I: Basic Features
if no value has been specified at the flow group
level. It will override any value set at the policy level.
maxbandwidth Specifies the maximum bandwidth available to the
traffic class. This parameter determines the
maximum rate at which the ingress port accepts
data belonging to this traffic class before either
dropping or remarking occurs, depending on option
3, Exceed Action. If the sum of the maximum
bandwidth for all traffic classes on a policy exceeds
the (ingress) bandwidth of the port to which the
policy is assigned, the bandwidth for the port takes
precedence and the port discards packets before
they can be classified. The range is 0 to 1016 Mbps.
The value for this parameter is rounded up to the
nearest Mbps value when this traffic class is
assigned to a policy on a 10/100 port, and up to the
nearest 8 Mbps value when assigned to a policy on
a gigabit port (for example, on a gigabit port, 1 Mbps
is rounded to 8 Mbps, and 9 is rounded to 16).
burstsize Specifies the size of a token bucket for the traffic
class. The token bucket is used in situations where
you have set a maximum bandwidth for a class, but
where traffic activity may periodically exceed the
maximum. A token bucket can provide a buffer for
those periods where the maximum bandwidth is
exceeded.
Tokens are added to the bucket at the same rate as
the traffic class’ maximum bandwidth, set with
option 6, Max Bandwidth. For example, a maximum
bandwidth of 50 Mbps adds tokens to the bucket at
that rate.
If the amount of the traffic flow matches the
maximum bandwidth, no traffic is dropped because
the number of tokens added to the bucket matches
the number being used by the traffic. However, no
unused tokens will accumulate in the bucket. If the
traffic increases, the excess traffic will be discarded
since no tokens are available for handling the
increase.
If the traffic is below the maximum bandwidth,
unused tokens will accumulate in the bucket since
the actual bandwidth falls below the specified
maximum. The unused tokens will be available for
handling excess traffic should the traffic exceed the