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The access point examines the ToS field in the headers of all packets that pass through the
AP. Based on the value in a packet's ToS field, the AP prioritizes the packet for transmission
by assigning it to one of the queues. This process occurs automatically, regardless of
whether you deliberately configure QoS or not.
A different type of data is associated with each queue. The queue and associated priorities
and parameters for transmission are as follows:
•
Data 0 (Voice). Highest priority queue, minimum delay. Time-sensitive data such as
Voice over IP (VoIP) is automatically sent to this queue.
•
Data 1 (Video). High priority queue, minimum delay. Time-sensitive data such as Video
and other streaming media are automatically sent to this queue.
•
Data 2 (Best Effort). Medium priority queue, medium throughput and delay. Most tradi-
tional IP data is sent to this queue.
•
Data 3 (Background). Lowest priority queue, high throughput. Bulk data that requires
maximum throughput and is not time-sensitive is sent to this queue (FTP data, for
example).
Packets in a higher priority queue will be transmitted before packets in a lower priority
queue. Interactive data in the queues labelled "Data 0" and "Data 1" is always sent first, best
effort data in "Data 2" is sent next, and Background (bulk) data in "Data 3" is sent last. Each
lower priority queue (class of traffic) gets bandwidth that is left over after the higher classes
of traffic have been sent. At an extreme end if you have enough interactive data to keep the
access point busy all the time, low priority traffic would never get sent.
Using the QoS settings on the Administration UI, you can configure Enhanced Distributed
Channel Access (EDCA) parameters that determine how each queue is treated when it is
sent by the access point to the client or by the client to the access point.
Note: Wireless traffic travels:
• Downstream from the access point to the client station.
• Upstream from client station to access point.
• Upstream from access point to network.
• Downstream from network to access point.
With WMM enabled, QoS settings on the 9160 G2 Wireless Gateway affect the first
two of these; downstream traffic flowing from the access point to client station (AP
EDCA parameters) and the upstream traffic flowing from the station to the access
point (station EDCA parameters).
With WMM disabled, you can still set parameters on the downstream traffic flowing
QoS Queues And Parameters To Coordinate Traffic Flow
Psion Teklogix 9160 G2 Wireless Gateway User Manual
Chapter 19: Quality Of Service (QoS)
189
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