User guide

Understanding Canopy Networks March 2005
Through Software Release 6.1
Issue 1 Page 63 of 425
Canopy System User Guide
For example, in the Canopy SM, if you set the Sustained Uplink Data Rate parameter to
2,000 kbps and the Sustained Downlink Data Rate parameter to 10,000 kbps, then the
uplink and downlink caps that will be enforced for the SM can be calculated as shown in
Figure 25.
uplink cap enforced =
2
,
000
kbps x 7,
000
kbps
2,000 kb
p
s + 10,000 kb
ps
= 1,167 kbps
downlink cap enforced =
1
0
,
000
kbps x 7,
000
kbps
2,000 kb
p
s + 10,000 kb
p
s
= 5,833 kbps
Figure 25: Uplink and downlink rate cap adjustment example
In this example case, the derived 1,167-kbps uplink and 5,833-kbps downlink caps sum
to the fixed 7,000-kbps aggregate cap of the Canopy SM.
The sustained data rate and burst allocation parameters can be set either
◦ in the AP to apply to all SMs in the sector.
◦ in the SM (in Canopy System Release 6.1 and later).
7.1.9 Committed Information Rate
The Committed Information Rate (CIR) capability feature enables the service provider to
guarantee to any subscriber that bandwidth will never decrease to below a specified
minimum, unless CIR is oversubscribed. Bandwidth can be, and typically will be, higher
than the minimum, but this guarantee helps the WISP to attract and retain subscribers.
In BAM Release 2.1 and later releases, BAM supports CIR capability as follows:
◦ Both the BAM GUI and the SSE command line interface allow you to view and
change CIR configuration parameters per SM.
◦ When an SM successfully registers and authenticates, if BAM has CIR
configuration data for the SM, then messages push the CIR configuration to the
SM.
◦ BAM allows the CIR feature to be disabled in the SM without deleting the CIR
configuration data.
7.1.10 Bandwidth from the SM Perspective
In the Canopy SM, normal web browsing, e-mail, small file transfers, and short streaming
video are rarely rate limited with practical bandwidth management (QoS) settings in the
AP or BAM. When the SM processes large downloads such as software upgrades and
long streaming video or a series of medium-size downloads, the bucket rapidly drains,
the burst limit is reached, and some packets are delayed. The subscriber experience is
more affected in cases where the traffic is more latency sensitive.