Allied Telesis AT-S63 - Manual (Page 173)

AT-S63 Management Software Web Browser User’s Guide
Section II: Advanced Operations 173
Burst Size
Specifies the size of a token bucket for the traffic class. The range is 4
to 512 Kbps. The default is 512 Kbps.
The token bucket is used in situations where you 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 the
same rate.
If the amount of 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 is 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 maximum bandwidth.
Should an increase in traffic continue to the point where all the unused
tokens are used up, packets will be discarded.
Unused tokens accumulate in the bucket until the bucket reaches
maximum capacity, set by this parameter. Once the maximum capacity
of the bucket is reached, no extra tokens are added.
Note
To use this parameter you must specify a maximum bandwidth using
the Max Bandwidth parameter. Specifying a token bucket size
without also specifying a maximum bandwidth serves no function.
Priority
Specifies the priority value in the IEEE 802.1p tag control field that
traffic belonging to this traffic class is assigned. Priority values range
from 0 to 7 with 0 being the lowest priority and 7 being the highest
priority. Incoming frames are mapped into one of four Class of Service
(CoS) queues based on the priority value.
If you want the packets to retain the new value when they exit the
switch, change the Remark Priority parameter to Yes.
If you specify a new user priority value here and in Flow Group, the
value in Flow Group overwrites the value here.