Cisco 8821 Manual page 57

The WMM policy should be set to Required only if the Cisco Wireless IP Phone 8821 and 8821-EX or other WMM enabled
phones will be using this SSID.
If there are non-WMM clients existing in the WLAN, it is recommended to put those clients on another WLAN.
If non-other WMM clients must utilize the same SSID as the Cisco Wireless IP Phone 8821 and 8821-EX, then ensure the
WMM policy is set to Allowed.
Enabling WMM will enable the 802.11e version of QBSS. There are also the 7920 Client CAC and 7920 AP CAC options,
where 7920 Client CAC will enable Cisco version 1 and 7920 AP CAC enables Cisco version 2.
Cisco Wireless IP Phone 8821 and 8821-EX Wireless LAN Deployment Guide
57