Broadcast/Multicast (BC/MC) traffic sends BC/MC frames on any Basic Service Set Identifier (BSSID) or wired network.
The BC/MC rate optimization determines the optimal rate to send BC/MC frames based on the lowest of the unicast rates across all associated or wired clients. BC/MC rate optimization only applies to BC/MC data frames. 802.11 management frames are transmitted at the lowest configured rate.
If BC/MC rate optimization is enabled, a controller scans the list of all associated stations in the Basic Service Set (BSS) and determines the lowest transmission rate as indicated by the rate adaptation station of each station.
The follwoing URL describes the troubleshooting best practice for excessive BC/MC traffic and provides guidance for initial debugging.