340 CHAPTER 16: CONFIGURING QUALITY OF S ERVICEIn this example, the MAP places the packet in the Voice forwardingqueue. The Voice queue has statistically more access to the air thanthe other queues, so the user’s voice traffic receives priority treatment.SVP QoS ModeThe SVP QoS mode optimizes forwarding of SVP traffic by setting therandom wait time a MAP radio waits before transmitting the traffic to 0microseconds.Normally, a MAP radio waits an additional number of microsecondsfollowing the fixed wait time, before forwarding a queued packet orframe. Each forwarding queue has a different range of possible randomwait times. The Voice queue has the narrowest range, whereas theBackground and Best Effort queues have the widest range. The randomwait times ensure that the Voice queue gets statistically more access tothe air than the other queues.By setting the random wait time to 0 for SVP, the SVP QoS mode provides SVPtraffic the greatest possible access to the air, on a statistical basis. The QoSmode affects forwarding of SVP traffic only. The random wait times for othertypes of traffic are the same as those used when the QoS mode is WMM.Call AdmissionControlCall Admission Control (CAC) is an optional feature that helps ensure thathigh-priority clients have adequate bandwidth, by limiting the number ofactive sessions MAP radios can have for an SSID. For example, you canlimit the number of active sessions on a VoIP SSID to ensure that each callreceives the bandwidth required for quality voice service.You can use CAC with either QoS mode (WMM or SVP).CAC is disabled by default. You can enable session-based CAC on aservice-profile basis. When enabled, CAC limits the number of activesessions a radio can have to 14 by default. You can change the maximumnumber of sessions to a value from 0 to 100.CAC is configured on a service profile basis and limits association toradios only for the service profile’s SSID. Association to the radios byclients on other SSIDs is not limited. To ensure voice quality, do not mapother service profiles to the radio profile you plan to use for voice traffic.(To configure CAC, see “Configuring Call Admission Control” onpage 343.)
