Wavetronix Click 342 (lean managed ethernet switch) (CLK-342) - Managed Switches User Guide - Manual (Page 68)

Multicast Filtering
7
In this chapter
˽ Dynamic Multicast Groups
7
Multicast applications, other than Unicast applications using point-to-point communica-
tion, do not transmit their data using a MAC address of the target, but they use a multicast
group address that is target-independent. Always using wireless communication, a station
transmits one data packet that is received by one or more receiving stations.
Some of the advantages include:
˽ In case one data packet of a transmitter is to be transmitted to eight receivers, the same
packet must not be sent eight times to the addresses of all eight devices. Instead it only
needs to be sent once to the address of the multicast group that includes eight devices.
˽ When using multicast communication and filtering, the required bandwidth for data
transmission is reduced because every packet can only be transmitted once.
Dynamic Multicast Groups
The Internet Group Management Protocol (IGMP) describes a procedure for distributing
information via multicast applications between routers and termination devices on the IP
level (layer 3).
When starting a multicast application, a network device transmits a so-called IGMP mem-
bership report and thus publishes its membership of a specified multicast group. A router
collects these membership reports and thus maintains the multicast groups of its subnet-
works.