User's Manual

Table Of Contents
PMP 450 Operations Guide
Interaction of Burst Allocation and
Sustained Data Rate Settings
pmp-0049 (September 2012)
2-3
Maximum Information Rate Data Entry Checking
Uplink and downlink MIR is enforced as shown in Figure 1.
In these figures, entry refers to the setting in the data rate parameter, not the burst allocation
parameter.
Figure 1 Uplink and downlink rate caps adjusted to apply aggregate cap
uplink cap enforced =
uplink entry x aggregate cap for the SM
uplink entry + downlink entry
downlink cap enforced =
downlink entry x aggregate cap for the SM
uplink entry + downlink entry
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.
Interaction of Burst Allocation and Sustained Data Rate
Settings
If the Burst Allocation is set to 1200 kb and the Sustained Data Rate is set to 128 kbps, a data burst of
1000 kb is transmitted at full speed because the Burst Allocation is set high enough. After the burst,
the bucket experiences a significant refill at the Sustained Data Rate. This configuration uses the
advantage of the settable Burst Allocation.
If both the Burst Allocation and the Sustained Data Rate are set to 128 kb, a burst is limited to the
Burst Allocation value. This configuration does not take advantage of the settable Burst Allocation.
If the Burst Allocation is set to 128 kb and the Sustained Data Rate is set to 256 kbps, the actual rate
will be the burst allocation (but in kbps). As above, this configuration does not take advantage of the
settable Burst Allocation.