BitTorrent or BitCrunch: Evidence of a Credit Squeeze in BitTorrent?

BitTorrent is a highly popular peer-to-peer file sharing protocol. Much BitTorrent activity takes place within private virtual communities called "private trackers" - a server that allows only community members to share files. Many private trackers implement "ratio enforcement" where the tracker monitors the upload and download behavior of peers. If a peer downloads substantially more than it uploads then service is terminated. Tracker policies related to credit effect the performance of the community as a whole. We identify the possibility of a "credit squeeze" in which performance is reduced due to lack of credit for some peers. We consider statistics from a popular private tracker and results from a simple model (called "BitCrunch").