D-Link DWL-3500AP - AirPremier Wireless Switching 108G Access Point Administrator's Manual page 71

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
traditional 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).
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.
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 Unified Access Point 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 some parameters on the downstream traffic flowing
from the access point to the client station (AP EDCA parameters).
The other phases of the traffic flow (to and from the network) are not under control of the QoS
settings on the AP.
EDCF Control of Data Frames and Arbitration Interframe Spaces
Data is transmitted over 802.11 wireless networks in frames. A Frame consists of a discrete
portion of data along with some descriptive meta-information packaged for transmission on a
wireless network.
Each frame includes a source and destination MAC address, a control field with protocol
version, frame type, frame sequence number, frame body (with the actual information to be
transmitted) and frame check sequence for error detection.
The 802.11 standard defines various frame types for management and control of the wireless
infrastructure, and for data transmission. 802.11 frame types are (1) management frames, (2)
control frames, and (3) data frames. Management and control frames (which manage and
control the availability of the wireless infrastructure) automatically have higher priority for
transmission.
802.11e uses interframe spaces to regulate which frames get access to available channels and
to coordinate wait times for transmission of different types of data.
6 Configuring Access Point Services
Configuring Quality of Service (QoS) 71