Tech Report: BitTorrent

Date Completed: July 2009

BitTorrent protocol has emerged as the most popular P2P protocol over the past years. The core BitTorrent protocol has been designed and implemented by Bram Cohen in 2001.

The protocol is especially useful for distributing large popular files (like open-source operating system distributions) as its performance improves as the number of interested connected peers increases. The way in which BitTorrent operates lessens the burden (hardware costs and bandwidth resources) of servers hosting the files and distributes that burden among all the peers currently connected, reducing costs significantly for original content distributors as a result. Connected peers share the task of serving the content to newly-connected peers and a “tit-for-tat” mechanism ensures fairness among all the peers. This method of content sharing also improves redundancy in the overlay network (formed around that specific content), as a probable malfunctioning of the original content provider does not render the content unavailable. In this Tech Report, we explain the functionality of the BitTorrent protocol and its various system components.