Configuring Quality of Service (QoS)

Quality of Service (QoS) provides you with the ability to specify parameters on multiple queues for increased throughput and better performance of differentiated wireless traffic like Voice-over-IP (VoIP), other types of audio, video, and streaming media as well as traditional IP data over the U.S. Robotics Professional Access Point.

Configuring QoS Queues

Configuring Quality of Service (QoS) on the U.S. Robotics Professional Access Point consists of setting parameters on existing queues for different types of wireless traffic, and effectively specifying minimum and maximum wait times (via Contention Windows) for transmission. The settings described here apply to data transmission behavior on the access point only, not to that of the client stations.


Notes	For the Guest interface, QoS queue settings apply to the access point load as a whole (both BSSes together). On a two-radio access point these settings apply to both radios but the traffic for each radio is queued independently. (The exception to this is guest traffic as noted below.) Internal and Guest network traffic is always queued together within each radio. This is the case on both one-radio and two-radio APs.

QoS on the access point leverages existing information in the IP packet header related to Type of Service (ToS). 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. A different type of data is associated with each queue. You can configure parameters that determine how each queue is treated when it is sent by the access point.

For more detailed explanation of QoS concepts, see Understanding QoS in the Administrators Guide.

Configuring Quality of Service includes:

Configuring AP EDCA Parameters

Enabling/Disabling Wi-Fi Multimedia

Updating Settings

Configuring AP EDCA Parameters

AP Enhanced Distributed Channel Access (EDCA) Parameters affect traffic flowing from the access point to the client station.


Field	Description
Queue	Queues are defined for different types of data transmitted from AP-to-station: Data 0 (Voice) High priority queue, minimum delay. Time-sensitive data such as VoIP and streaming media are automatically sent to this queue. Data 1(Video) High priority queue, minimum delay. Time-sensitive video data is 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). For more information, see QoS Queues and Parameters to Coordinate Traffic Flow in the Administators Guide.
AIFs (Inter-Frame Space)	The Arbitration Inter-Frame Spacing (AIFs) specifies a wait time (in milliseconds) for data frames. Valid values for AIFs are 1 through 255. For more information, see DCF Control of Data Frames and Interframe Spaces.
cwMin (Minimum Contention Window)	This parameter is input to the algorithm that determines the initial random backoff wait time ("window") for retry of a transmission. The value specified here in the Minimum Contention Window is the upper limit (in milliseconds) of a range from which the initial random backoff wait time is determined. The first random number generated will be a number between 0 and the number specified here. If the first random backoff wait time expires before the data frame is sent, a retry counter is incremented and the random backoff value (window) is doubled. Doubling will continue until the size of the random backoff value reaches the number defined in the Maximum Contention Window. Valid values for the "`cwmin`" are 1, 3, 7, 15, 31, 63, 127, 255, 511, or 1024. The value for "`cwmin`" must be lower than the value for "`cwmax`". For more information, see Random Backoff and Minimum / Maximum Contention Windows in the Administrators Guide.
cwMax (Maximum Contention Window)	The value specified here in the Maximum Contention Window is the upper limit (in milliseconds) for the doubling of the random backoff value. This doubling continues until either the data frame is sent or the Maximum Contention Window size is reached. Once the Maximum Contention Window size is reached, retries will continue until a maximum number of retries allowed is reached. Valid values for the "cwmax" are 1, 3, 7, 15, 31, 63, 127, 255, 511, or 1024. The value for "cwmax" must be higher than the value for "cwmin". For more information, see Random Backoff and Minimum / Maximum Contention Windows in the Administrators Guide.
Max. Burst Length	AP EDCA Parameter Only (The Max. Burst Length applies only to traffic flowing from the access point to the client station.) This value specifies (in milliseconds) the Maximum Burst Length allowed for packet bursts on the wireless network. A packet burst is a collection of multiple frames transmitted without header information. The decreased overhead results in higher throughput and better performance. Valid values for maximum burst length are 0.0 through 999.9. For more information, see Packet Bursting for Better Performance in the Administrators Guide.

Enabling/Disabling Wi-Fi Multimedia

By default, Wi-Fi MultiMedia (WMM) is enabled on the access point. With WMM enabled, QoS prioritization and coordination of wireless medium access is on. With WMM enabled, QoS settings on the U.S. Robotics Professional Access Point control 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).

Disabling WMM will deactivate QoS control of station EDCA parameters on upstream traffic flowing from the station to the access point

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).

To disable WMM exentsions, click Disabled.

To enable WMM extensions, click Enabled.

Configuring Station EDCA Parameters

Station Enhanced Distributed Channel Access (EDCA) Parameters affect traffic flowing from the client station to the access point.


Field	Description
Queue	Queues are defined for different types of data transmitted from station-to-AP: Data 0 (Voice) Highest priority queue, minimum delay. Time-sensitive data such as VoIP and streaming media are automatically sent to this queue. Data 1(Video) Highest priority queue, minimum delay. Time-sensitive video data is 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). For more information, see QoS Queues and Parameters to Coordinate Traffic Flow in the Administators Guide.
AIFs (Inter-Frame Space)	The Arbitration Inter-Frame Spacing (AIFs) specifies a wait time (in milliseconds) for data frames. For more information, see DCF Control of Data Frames and Interframe Spaces.
cwMin (Minimum Contention Window)	This parameter is input to the algorithm that determines the initial random backoff wait time ("window") for retry of a transmission. The value specified here in the Minimum Contention Window is the upper limit (in milliseconds) of a range from which the initial random backoff wait time is determined. The first random number generated will be a number between 0 and the number specified here. If the first random backoff wait time expires before the data frame is sent, a retry counter is incremented and the random backoff value (window) is doubled. Doubling will continue until the size of the random backoff value reaches the number defined in the Maximum Contention Window. For more information, see Random Backoff and Minimum / Maximum Contention Windows in the Administrators Guide.
cwMax (Maximum Contention Window)	The value specified here in the Maximum Contention Window is the upper limit (in milliseconds) for the doubling of the random backoff value. This doubling continues until either the data frame is sent or the Maximum Contention Window size is reached. Once the Maximum Contention Window size is reached, retries will continue until a maximum number of retries allowed is reached. For more information, see Random Backoff and Minimum / Maximum Contention Windows in the Administrators Guide.
TXOP Limit	Station EDCA Parameter Only (The TXOP Limit applies only to traffic flowing from the client station to the access point.) The Transmission Opportunity (TXOP) is an interval of time when a WME client station has the right to initiate transmissions onto the wireless medium (WM). This value specifies (in milliseconds) the Transmission Opportunity (TXOP) for client stations; that is, the interval of time when a WMM client station has the right to initiate transmissions on the wireless network.

Updating Settings

To apply your changes, click Update Settings.