[mafintosh]

It's only between the peers in your subset of the swarm for now. They exchange a series of WANT and HAVE messages where they subscribe to the sections of each others logs they are interested in.

We are working on expanding this scheme so peers can help discover peers that have the section you are looking for.

Due to the compressed bitfields these section are quite large. In most cases using a few kilobytes you can share WANT/HAVE for millions of blocks

[rklaehn]

Yes, I saw the compressed bitfields. Most amount of bit twiddling I have ever seen in a pure javascript library...

Being able to identify a piece of content by an integer instead of a hash makes things more efficient compared to content-addressed storage a la IPFS.