A peer-to-peer communication system in which a peer communicating with a tracker node on a local torrent can locate and download files that are not currently available from other peers communicating on the local torrent. To enable this, the tracker node maintains collaboration information for a list of files. The collaboration information includes, for each file, a list of locations at which a full copy of the file may be located. The list of locations may include active peers, dormant peers and remote tracker nodes. The collaboration information may be obtained from each peer when it joins a local torrent. Upon joining the torrent, the peer may provide the local tracker node with a list of files that it is willing to serve.