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Page 19 | AlliedWare Plus™ OS: Overview of QoS
Twin-rate policing
Both ordinary and aggregate policers can be twin-rate. Twin-rate policing uses four
parameters:
z minimum bandwidth (in kbps)
z maximum bandwidth (in kbps)
z maximum burst size (in bytes)
z minimum burst size (in bytes)
With this combination, the algorithm used to determine the temporary bandwidth class to
assign to a packet is:
If the data rate for the policer is below the minimum bandwidth, or is slightly above the
minimum bandwidth, but the accumulation of total bits that have exceeded the minimum
bandwidth has not yet reached the minimum burst size, then the bandwidth class is green.
If the data rate for the policer is above the minimum bandwidth, and the accumulation of
total bits that have exceeded the minimum bandwidth has exceeded the minimum burst
size, or if the data rate is above the maximum bandwidth, and the accumulation of total
bits that have exceeded the maximum bandwidth has not yet reached the maximum burst
size, then the bandwidth class is yellow.
If the data rate for the policer is above the maximum bandwidth, and the accumulation of
total bits that have exceeded the maximum bandwidth has exceeded the maximum burst
size, then the bandwidth class is red.
For a more detailed explanation of the algorithm, see the Advanced QoS White Paper in the
White Papers library at www.alliedtelesis.com/resources/literature/literature.aspx?id=3.
An example of configuring a policer to do twin-rate policing would be:
awplus(config-pmap-c)#police twin-rate <minimum-bandwidth>
<maximum-bandwidth> <minimum-burstsize> <maximum-burstsize>
exceed-action {drop|policed-dscp-transmit}