This page enables you to define the parameters of Carrier Sense Multiple Access (CSMA) for each traffic access category. These parameters affect how packets are delivered for the different classes of service. See the QoS Policies page to determine the level of service you want.

These parameters should be modified with caution because radio behavior is affected. To revert to the default values, refer to the Installation and Configuration Guide.

Min Contention Window

For each access category, enter the minimum contention window value. Channel access is prioritized by assigning smaller contention window values to a higher priority traffic class. If a channel is busy or a transmission collides, a node chooses a random number between 0 and the current contention window minimum.

Max Contention Window

For each access category, enter the maximum contention window value. The minimum contention window value is doubled each time a collision occurs until the maximum is reached. A small contention window value decreases the access delay but increases the probability of a collision.

Fixed Slot Time

For each access category, enter the fixed slot time. Channel access can be strictly prioritized by assigning smaller contention window values to a higher priority traffic class. Traffic in the access category must wait this fixed number of slots after each packet received before resuming its random back-off.

Admission Control

Note: In this release, clients are blocked from using an access category when they select Enable for Admission Control.

The Admission Control check boxes control client use of the access categories. When you enable admission control for an access category, clients associated to the access point must complete the WMM admission control procedure before they can use that access category. However, access points do not support the admission control procedure in this release, so clients cannot use the access category when you enable Admission Control.

Transmit Opportunity Limit

Enter the number of microseconds that qualified transmitters can transmit through the normal backoff procedure with a set of pending packets. Larger values allow a client to control the channel for longer periods of time, allowing it to achieve higher throughput in this access category at the expense of longer access times for all access categories.

See Also: Services: QoS Policies, Services: QoS Policies - Advanced