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Page 18 | AlliedWare Plus™ OS: Overview of QoS
Single-rate policing
Both ordinary and aggregate policers can be single-rate. Single-rate policing uses three
parameters:
z average bandwidth (in kbps)
z minimum burst size (in bytes)
z maximum 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 average bandwidth, or is slightly above the
average bandwidth, but the accumulation of total bits that have exceeded the average
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 average bandwidth, and the accumulation of
total bits that have exceeded the average bandwidth has exceeded the minimum burst size
but not yet reached the maximum burst size, then the bandwidth class is yellow.
If the data rate for the policer is above the average bandwidth, and the accumulation of
total bits that have exceeded the average 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 single-rate policing would be:
awplus(config-pmap-c)#police single-rate <average-bandwidth>
<minimum-burstsize> <maximum-burstsize>
exceed-action {drop|policed-dscp-transmit}
An exceed action of drop means that the switch simply drops red packets. An exceed action
of policed-dscp-transmit means that the switch remarks packets after policing.