bittorrent how it applies to networking. what is bittorrent p2p file sharing protocol allows users...
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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
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