Starting with Windows XP SP1 and Windows Server 2003, ICF examines and drops (blocks) unsolicited inbound unicast, multicast, and broadcast traffic.
Broadcast traffic is transmitted to all devices on the network.
Multicast traffic is transmitted to all devices on the network that request it (listening).
If you want to permit this traffic through the firewall, you must manually open the appropriate ports.
NOTE: If you open a port, inbound unicast, broadcast, and multicast traffic on that port and protocol are permitted.