Streaming multimedia and peer to peer file sharing seem like ideally suited applications for IP multicasting. Multimedia is fairly bandwidth intensive and it would be a waste to use that bandwidth on subnets where it hadn't been asked for. Peer to peer protocols could pose a challenge to some multicast routing protocols because their connection topology may change frequently. But both classes of application are much better suited to multicasting than such session oriented apps as SSH and FTP or such client server apps as HTTP or databases.
Streaming audio and/or video may well be the most appropriate use for IP multicasting that we have today. Its similarity to a broadcasting paradigm isn't coincidental. One source is supplying data to many receivers and therefore multicasting's model is perfect. An efficient multicast routing protocol like PIM can ensure that not much traffic goes to segments where it isn't wanted while every client that asks for it receives it (Kurose, 2009).
Peer to peer protocols may be a good application for IP multicasting (Noh et al, 2009). While on the surface such connections are many to many, examining the actual traffic sequences often reveals a nearly clients-server usage pattern. Many file sharing sessions rely on one or a few 'seed' which possess the entire file so this often results in much of the same data passing from these few to a multitude of clients. This results in a single (or few) to many pattern that very much resembles a directed broadcast and which could be well suited to an adaptive multicast.
True client-server application usage patterns are not generally suited to multicasting. Even if many clients are connected to the same server at the same time it is unlikely that they will be requesting identical data at a similar enough time. Therefore there is little savings in having network equipment duplicate data on different ports, nor even for the server itself to retransmit from a buffer. Even less suited to multicasting are interactive sessions or single file transfers which are unique to the source and destination systems.
Kurose, J.F. Computer Networking – A Top Down Approach Featuring The Internet 4th Ed. Pearson International
Noh, J., Baccichet, P., Hatung, F., Mavlankar, A & Girod, B. Stanford Peer-to-Peer Multicast (SPPM) – Overview and Recent Extensions [Online]. Available from: http://www.stanford.edu/~jhnoh/resources/PCS2009_SPPM_OverviewAndExtensions.pdf (Accessed: 31 October, 2010)