BitTorrent

How it applies to networking

What is BitTorrent

P2P file sharing protocol Allows users to distribute large amounts of data

without placing a heavy burden on their computer

Similar to packets, it breaks a file into small chunks, usually 512 K.

Done over TCP/IP, but several small requests are sent to different machines (the packets)

How it works

Seed- the provider of the file Publish it to the network- creates a torrent file

Contains metadata about files to be shared with tracker

-tracker- the computer that coordinates the communication between peers with the bit torrent protocol. Can be public or private

Each client is required to communicate with the tracker to initiate downloads, and those that have already begun downloading communicate periodically to negotiate with newer peers and provide statistics

How it Works Continued

Peers- those that connect and download the seed file.

The initial peer will connect directly to the seed and request chunks, then as more peers are added, chunks are requested from different peers

Once multiple peers have multiple pieces of the seed, they also become “seeds” of the file.

Health of the file Downloads in random or “rarest first approach”

The purpose of bit Torrent is to “swarm” so that the download has a good chance of success.

*.Torrent File Contents

Similar to GET/POST method Contains URL of tracker as well as info of files

SHA-1 hash code- verify integrity

-In trackerless systems

- every peer becomes its own tracker, done through DHT. Each chunk becomes a key and a value similar to a hash table. Requests are sent to receive each file chunk using the keys

Bit Torrent Public vs Private

Public- anyone can download- sometimes filled with viruses.

Private- only certain users are allowed to connect. Usually have tons of illegal files

Both offer Protocol Header Encryption ISP cant tell what kind of traffic it is

Both expose IP addresses in the tracker even when done downloading

Torrent In Action

Problems with Bit Torrent

Bandwidth Hog

Problems

Leeches Hard to get files if not popular Easy to track, risk of getting sued and attacked

How to Setup your own Torrent System

Your own private peer to peer torrent systemOneSwarm- developed at University of Washington

http://oneswarm.cs.washington.edu/screencasts/overview.mp4

One swarm in practice

First I linked two gmail accounts as friends

OneSwarm

OneSwarm

Other alternatives to Torrent

Pure Private Peer to Peer, over VPN

Gbridge from google

Other