Multicast

Multicast is intended to keep the computing overhead on the source computer and network at a minimum by passing the data onto other hosts for duplication and distribution, where necessary, and implies that a data set only needs to be sent once from the host (potentially the system can have multiple data hosts contributing to the multicast) and it will reach multiple recipients who have specifically requested to receive the data in question. Deering & Cheriton (1990) stated that “an efficient multicast facility provides packet delivery to groups of hosts at a lower network and host overhead than broadcasting to all hosts or unicasting to each host in a group.” The minimalist Internet multicast service model is a two part network-layer process that utilises the Internet Group Management Protocol (IGMP) and “multicast routing protocols” Kurose & Ross (2010, p416) to achieve Deering & Cheriton’s objective.

The IGMP utilises edge routers where hosts can register a request to join, receive data from or leave the multicast group and the type of protocol used greatly depends on the application, the infrastructure available to the system and how the data flows. Kurose and Ross (2010) state that the current most widely used protocol is the Protocol-Independent Multicast (PIM) which has two modes of operation depending on the location of the routers in the area which effectively use different distribution trees to send traffic.

The minimalist Internet multicast service model is applicable to any application where the infrastructure available to the system is such that there are large and decentralised data contributors and/or receivers that will remain in existence for a period of time that is justified by the overhead of establishing and administrating the multicast system (i.e. time and cost). In addition, the data flows should be interactive, therefore “applications that would benefit from multicast, such as media streaming and interactive applications” according to Diot et al (2002), such as live updates for news, gaming, software distribution, etc. would be ideal candidates for multicast, whereas any form of one-to-many read only application would not present the reduced overhead benefit that multicast would present.

References

Deering, S. & Cheriton, D. (1990) Multicast Routing in Datagram Internetworks and Extended LANs [Online]. Available at http://www-cse.ucsd.edu/classes/wi01/cse222/papers/deering-multicast-tocs90.pdf (Accessed 1 May 2011).

Diot, C., Levine, B., Lyles, B., Kassem, H. & Balensiefen, D. (2002) Deployment Issues for the IP Multicast Service and Architecture [Online]. Available via EBSCOhost (Accessed 1 May 2011).

Kurose & Ross (2010) Computer Networking: A Top-Down Approach (Fifth Edition). Addison Wesley.