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AT-TQ2403 Management Software User's Guide 123
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.
Note: Wireless traffic travels:
Downstrea
m 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 AT-TQ2403 Management Software 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).
The other phases of the traffic flow (to and from the network) are not under control of the
QoS settings on the AP.
EDCA 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.
Note: A Frame is similar in concept to a Packet, the differe
nce being that a packet operates
on the Network layer (layer 3 in the OSI model) whereas a frame operates on the
Data-Link layer (layer 2 in the OSI model).
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.
Management and control frames wait a minimum amount of time for transmission; they wait a short
interframe space (SIF). These wait times are built-in to 802.11 as infrastructure support and are not
configurable.
The AT-TQ2403 Management Software supports the Enhanced Distribution Coordination Access
(EDCA) as defined by the 802.11e standard. EDCA, which is an enhancement to the DCF standard and