Call Admission Control (Cac) - Cisco 8821 Manual

When multiple Cisco Wireless LAN Controllers are to be in the same mobility group, then the IP address and MAC address of
each Cisco Wireless LAN Controller should be added to the Static Mobility Group Members configuration.

Call Admission Control (CAC)

It is recommended to enable Admission Control Mandatory for Voice and configure the maximum bandwidth and reserved
roaming bandwidth percentages for either 5 or 2.4 GHz depending on which frequency band is to be utilized.
The maximum bandwidth default setting for voice is 75% where 6% of that bandwidth is reserved for roaming clients.
Roaming clients are not limited to using the reserved roaming bandwidth, but roaming bandwidth is to reserve some bandwidth
for roaming clients in case all other bandwidth is utilized.
If CAC is to be enabled, will want to ensure Load-based CAC is enabled.
Load-based CAC will account for all energy on the channel.
SIP CAC can help ensure that downstream voice frames are prioritized correctly when a client does not support TSPEC.
Load based CAC logic is utilized with SIP CAC, so all 802.11 traffic and energy on the channel is accounted for to determine
available bandwidth.
Cisco Wireless IP Phone 8821 and 8821-EX Wireless LAN Deployment Guide
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