Open as PDF
340 CHAPTER 16: CONFIGURING QUALITY OF SERVICE
In this example, the MAP places the packet in the Voice forwarding
queue. The Voice queue has statistically more access to the air than
the other queues, so the user’s voice traffic receives priority treatment.
SVP QoS Mode
The SVP QoS mode optimizes forwarding of SVP traffic by setting the
random wait time a MAP radio waits before transmitting the traffic to 0
Normally, a MAP radio waits an additional number of microseconds
following the fixed wait time, before forwarding a queued packet or
frame. Each forwarding queue has a different range of possible random
wait times. The Voice queue has the narrowest range, whereas the
Background and Best Effort queues have the widest range. The random
wait times ensure that the Voice queue gets statistically more access to
the air than the other queues.
By setting the random wait time to 0 for SVP, the SVP QoS mode provides SVP
traffic the greatest possible access to the air, on a statistical basis. The QoS
mode affects forwarding of SVP traffic only. The random wait times for other
types of traffic are the same as those used when the QoS mode is WMM.
Call Admission Control (CAC) is an optional feature that helps ensure that
high-priority clients have adequate bandwidth, by limiting the number of
active sessions MAP radios can have for an SSID. For example, you can
limit the number of active sessions on a VoIP SSID to ensure that each call
receives 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 a
service-profile basis. When enabled, CAC limits the number of active
sessions a radio can have to 14 by default. You can change the maximum
number of sessions to a value from 0 to 100.
CAC is configured on a service profile basis and limits association to
radios only for the service profile’s SSID. Association to the radios by
clients on other SSIDs is not limited. To ensure voice quality, do not map
other service profiles to the radio profile you plan to use for voice traffic.
(To configure CAC, see “Configuring Call Admission Control” on