When sending the same data to multiple receivers, rather than send multiple copies all the way from sender to all the receivers, just send one copy and duplicate where paths diverge

  • Better bandwidth utilisation
  • Less host/router processing
  • Receivers’ addresses may be unknown
  • A possible thing to use for IPTV over WiMAX.

Multicast Advantages

  • Enhanced Efficiency: Controls network traffic and reduces server and CPU loads
  • Optimised Performance: Eliminates traffic redundancy
  • Distributed Applications: Makes multipoint applications possible

Multicast Disadvantages

  • Best Effort Delivery: Drops are to be expected. Multicast applications should not expect reliable delivery of data and should be designed accordingly. Reliable Multicast is still an area for much research.
  • No Congestion Avoidance: Lack of TCP windowing and “slowstart” mechanisms can result in network congestion. If possible, Multicast applications should attempt to detect and avoid congestion conditions.

Duplicates: Some multicast protocol mechanisms result in the occasional generation of duplicate packets. Multicast applications should be designed to expect occasional duplicate packets.