Downloading a file in segments rather than all at once. PFS has been implemented in such protocols as BitTorrent, EDonkey2000, and Mike’s Protocol. Many gnutella applications will soon implement this protocol as well. It has a two-fold benefit:
First, it prevents file corruption that some poorly designed routers may induce, as data is transferred over the internet. Each segment has its own hash. When the individual segment has finished downloading, it is rehashed and checked against the reported hash value from the host. If the hashes differ, the downloaded segment is discarded – most likely corrupt – and the client redownloads that segment.
Second, one can share parts of files that have not yet finished downloading with this protocol. Instead of sharing the entire file, one shares segments that he or she has downloaded. In such a regard, PFS greatly enhances file sharing speed and availability.
TakeDown.NET -> “Partial-File-Sharing”