User guide

Canopy System User Guide Understanding Bandwidth Management

pmp-0229 (Mar 2013)

For example, in the 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 MIR that will be

enforced for the SM can be calculated as shown in Figure 26.

Figure 26: Uplink and downlink rate cap adjustment example

In this example case, the derived 1,167-kbps uplink and 5,833-kbps downlink MIR sum to the fixed 7,000-

kbps aggregate cap of the SM.

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.

CIR configuration is supported as follows:

• The GUI allows you to view and change CIR configuration parameters per SM.

• When an SM successfully registers and authenticates, if the authentication server has CIR

configuration data for the SM, then messages make the CIR configuration available to the

SM, depending on the Configuration Source setting. (See Setting the Configuration Source on

Page 324.)

• The operator can disable the CIR feature in the SM without deleting the CIR configuration

data.

Bandwidth from the SM Perspective

In the SM, normal web browsing, e-mail, small file transfers, and short streaming video are rarely

rate limited with practical bandwidth management (QoS) settings. 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.

uplink cap enforced =

2,000 kbps x 7,000 kbps

2,000 kbps + 10,000 kbps

= 1,167 kbps

downlink cap enforced =

10,000 kbps x 7,000 kbps

2,000 kbps + 10,000 kbps

= 5,833 kbps