List passing in a background file sharing network

A mechanism is provided for distributing file fragments in the background of a segmented peer-to-peer network using list passing between peers. Rather than trading actual content, peers may trade file names or file fragment identifiers. Upon receiving a new file name or identifier, a peer may request that file from the network, either in the background or the foreground. For example, once a client begins background file sharing in a swarm, the client may propagate file information for files it possesses to all or a portion of the peers in a swarm. Those clients then have the file information for a file without the user having to locate and specifically request that file. The file list may piggyback on a file fragment that is transferred as a result of a file sharing request.