User guide

March 2005 Understanding Canopy Networks
Through Software Release 6.1
Page 64 of 425 Issue 1
Canopy System User Guide
7.1.11 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.
A Burst Allocation value of zero prohibits all data transmission.
7.1.12 High-priority Bandwidth
To support low-latency traffic such as VoIP (Voice over IP) or video, the Canopy system
implements a high-priority channel. This channel does not affect the inherent latencies in
the Canopy system but allows high-priority traffic to be immediately served. The high-
priority pipe separates low-latency from traffic that is latency tolerant, such as standard
web traffic and file downloads.
The Canopy system separates this traffic by recognizing the IPv4 Type of Service (ToS)
Low Latency bit (Bit 3). Bit 3 is set by a device outside the Canopy system. In the uplink
frame, the SM monitors Bit 3. If this bit is set, then
◦ the SM prioritizes this traffic in its high-priority queue according to AP
configuration settings for the high-priority channel.
◦ the system sends the packet on the high-priority channel and services this
channel before any normal traffic.
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NOTE:
To enable the high-priority channel, you must configure all high-priority
parameters.
The high-priority channel is enabled by configuration of four parameters in the
Configuration web page of the AP. These parameters are
◦ High Priority Uplink Percentage
◦ UAcks Reserved High
◦ DAcks Reserved High
◦ NumCtrlSlots Reserved High