Expedited Bandwidth Requests - Cisco 2100 Series Configuration Manual

Chapter 4 Configuring Controller SettingsWireless Device Access
In load-based CAC, the access point continuously measures and updates the utilization of the RF channel
(that is, the percentage of bandwidth that has been exhausted), channel interference, and the additional
calls that the access point can admit. The access point admits a new call only if the channel has enough
unused bandwidth to support that call. By doing so, load-based CAC prevents over-subscription of the
channel and maintains QoS under all conditions of WLAN loading and interference.
Load-based CAC is supported only on lightweight access points. If you disable load-based CAC, the
Note
access points start using bandwidth-based CAC.

Expedited Bandwidth Requests

The expedited bandwidth request feature enables CCXv5 clients to indicate the urgency of a WMM
traffic specifications (TSPEC) request (for example, an e911 call) to the WLAN. When the controller
receives this request, it attempts to facilitate the urgency of the call in any way possible without
potentially altering the quality of other TSPEC calls that are in progress.
You can apply expedited bandwidth requests to both bandwidth-based and load-based CAC. Expedited
bandwidth requests are disabled by default. When this feature is disabled, the controller ignores all
expedited requests and processes TSPEC requests as normal TSPEC requests.
See
bandwidth requests.
Table 4-2 TSPEC Request Handling Examples
Reserved bandwidth for
1
CAC Mode voice calls
Bandwidth- 75% (default setting)
based CAC
Load-based
CAC
1. For bandwidth-based CAC, the voice call bandwidth usage is per access point and does not take into account co-channel access points. For load-based
CAC, the voice call bandwidth usage is measured for the entire channel.
2. Bandwidth-based CAC (consumed voice and video bandwidth) or load-based CAC (channel utilization [Pb]).
When video ACM is enabled, the controller rejects a video TSPEC if the Nom-MSDU size in the TSPEC
Note
is greater than 149 or the mean data rate is greater than 1 Kb/s.
OL-17037-01
Table 4-2 for examples of TSPEC request handling for normal TSPEC requests and expedited
2
Usage
Less than 75%
Between 75% and 90%
(reserved bandwidth for voice
calls exhausted)
More than 90%
Less than 75%
Between 75% and 85%
(reserved bandwidth for voice
calls exhausted)
More than 85%
Configuring Voice and Video Parameters
Normal TSPEC TSPEC with Expedited
Request Bandwidth Request
Admitted Admitted
Rejected Admitted
Rejected Rejected
Admitted Admitted
Rejected Admitted
Rejected Rejected
Cisco Wireless LAN Controller Configuration Guide
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