Peercasting

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Peercasting is a way to send audio or video over the Internet using a network of peers. Instead of streaming from one central server to everyone, each viewer also forwards the stream to others. This makes it possible for commercial, independent, and hobby broadcasts to reach many people and even deliver content on demand, not just live.

Peers connect through a P2P overlay that helps them find relays for a given stream. If relays go offline or many peers switch relays (a situation called churn), the quality of the stream can drop.

One approach is minute swarming: the live stream is cut into one-minute pieces that are shared by peers using P2P software. But starting a new swarm every minute creates extra overhead.

Another approach is to stripe the live stream into several substreams, like RAID striping. Each substream has error correction and timing information so the original stream can be rebuilt from most of the substreams. Fountain codes can make this process efficient. The substreams are then relayed using the usual peercasting method.

Finally, a design lets a client switch to a new relay and continue where they left off. The relays keep a back buffer so users can resume within that buffer. This would be an extension to the Icecast protocol.