A Carnegie Mellon University research group has developed a QuickTime-based, peer-to-peer streaming system called End System Multicast (ESM).
Traditional streaming is very expensive, because the broadcaster must have enough bandwidth to support the datarate of the bitstream multiplied by the number of viewers (plus some overhead). P2P streaming is important because the bandwidth burden is shared among the broadcaster and its viewers, and so it makes streaming broadcasts possible where it would’ve otherwise been cost-prohibitive.
ESM works by putting viewers into a distributed, self-organizing “tree” with the broadcaster as the roots. Viewers pass the content they receive to a small number of additional viewers, who then pass the content to a small number of additional viewers, and so on. ESM recently gained the ability to support NAT and firewalls, which means that most readers should be able to participate in upcoming broadcasts (see below).