BitTorrent
اعلانات
What is BitTorrent:
BitTorrent is a peer-to-peer file sharing protocol which enables us to
share a large amount of data over the internet. it allows an unlimited number
of users to connect to the site or download a file. it can replace the large
servers with home computers, by allowing the user to join the ‘swarm’ to
download and upload from each other.
History:
·
in 2001, American programmer
called Bram Cohen began to work on the protocol.
The peer-to-peer protocol
named BitTorrent
·
Bram Cohen, born in 1975 in New York he wrote his first BitTorrent client implementation in
python language and in 2004 the traffic of its protocol is 35% of the traffic of
the internet
·
He is also the organizer of the San
Francisco Bay Area P2P-hackers meeting, and the co-author of Codeville.
Terminology:
1.
Tracker: is a server that keeps track of which seeds and peers
in the swarm the clients report the data to it, the Tracker does not have
a copy of data (file) like the seeder it
only guide the peers to the seeders to start the download.
2.
Seeder: a peer which
completed downloading of the file it becomes a seeder and start to upload the
contents of the file to another peer.
3.
Leecher: refer to a peer that have a very poor share ratio,
which mean he is download more than upload. might closed the seed after
complete downloading or limit the upload speed
4.
Subpiece: its very small
size of bytes and it’s the unit of request
How it works?
To share any file first a peer,
create a file with extension name. Torrent
this file contains the metadata about the file. To be able to download a file
you should first have this file name. Torrent
to connect with specified
tracker which will guide
you to another peer which
contain the same file
and the pieces they should
download.
**The file is split into
pieces and a SHA-1 hash is calculated
for each piece
the peer which have the file split it to number of pieces
have the same size usually between 32kb and 16mb a peer
creates a hash for each piece and attach it in the name. Torrent file
Advantages:
·
Peer-to-peer in nature
·
It has a server called a tracker
·
The Tracker uses HTTP
·
You can download and upload at the same time
·
The more people download file the more speed of download
Download speed factors:
·
BitTorrent protocol detect the more you contribute with sharing file
the more speed you will gain to your downloads (seeder have more speed than
leecher).
·
The speed will increase when the file become trending (a lot of people
downloading it or seeding it).
File swarming
File swarming allows users
to download files with the maximum possible speed because it Enables
simultaneous downloads of pieces of the same file from multiple users.
Because the upload speed
is very low if you download your file from one peer you will download with this
low speed (the upload speed of the peer you connected to) then, to solve this
problem the swarm enables you to connect and download from multiple peer at the
same time while you can download different pieces of the same file from them.
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