Task 11: Configuring quality of
service
Chapter 2: Configuration and alignment
2-106
pmp-0050 (May 2012)
Task 11: Configuring quality of service
Maximum Information Rate (MIR) Parameters
Point-to-multipoint links use the following four MIR parameters for bandwidth management:
Sustained Uplink Data Rate
(kbps)
Uplink Burst Allocation
(kb)
Sustained Downlink Data Rate
(kbps)
Downlink Burst Allocation
(kb)
You can independently set each of these parameters per AP or per SM.
Token Bucket Algorithm
The software uses a
token bucket
algorithm that
stores credits (tokens) for the SM to spend on bandwidth for reception or transmission.
drains tokens during reception or transmission.
refills with tokens at the sustained rate set by the network operator.
For each token, the SM can send toward the network in the uplink (or the AP can send toward the SM in the
downlink) an equivalent number of kilobits. Two buckets determine the permitted throughput: one in the SM
for uplink and one in the AP for downlink.
The applicable set of
Uplink Burst Allocation
and
Downlink Burst Allocation
parameters determine the
number
of tokens that can fill each bucket. When the SM transmits (or the AP transmits) a packet, the equivalent
number of tokens is removed from the uplink (or downlink) bucket.
Except when full, the bucket is continuously being refilled with tokens at
rates
that the applicable set of
Sustained Uplink Data Rate
and
Sustained Downlink Data Rate
parameters specify. The bucket often drains at
a rate that is much faster than the sustained data rate but can refill at only the sustained data rate. Thus, the
effects of the allocation and rate parameters on packet delay are as follows:
the burst allocation affects how many kilobits are processed before packet delay is imposed.
the sustained data rate affects the packet delay that is imposed.
Which set of these MIR parameters are applicable depends on the interactions of other parameter values. Also,
where the
Configuration Source
parameter setting in the AP specifies that BAM values should be used, they are
used only if Prizm is configured to send the values that it stores for the MIR parameters.
Summary of Contents for PMP 450
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