How to enable:
http://www.cisco.com/c/en/us/support/docs/wireless/2500-series-wireless-controllers/113034-2500-deploy-guide-00.html#enable
Impact:
2500, WiSM2, WLC2—These platforms by default will not contain DTLS. To turn on data DTLS, you must install a license. These platforms will have a single image with data DTLS turned off. To use data DTLS you will need to have a license.
http://www.cisco.com/c/en/us/products/collateral/wireless/2500-series-wireless-controllers/data_sheet_c78-645111.html
AS per cisco: Encryption limits throughput at both the controller and the access point.
Regards
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