Wireless (802.11) Considerations
An 802.11 wireless network will handle multicast traffic differently, depending on the configuration of Delivery Traffic Indication Message (DTIM), and beacon interval settings. If no stations within the basic service set are in power save mode, multicast packets are sent immediately when they arrive. If there are one or more stations in power save mode, access points then only deliver multicast traffic after each DTIM interval, and transmit at one of the supported rates in the basic rate set. In most retail wireless access points/routers, this interval is 102.4 ms (DTIM=1 (beacon interval)) and the transmit rate is either 1 Mbit/s or 6 Mbit/s, depending on the operating band and protection mode. As a result, the DTIM and beacon interval settings should be adjusted for optimum performance when implementing multicast in wireless networks.
Read more about this topic: IP Multicast