Fri Nov 18, 2011 06:53
THIS IS HOW WE ARE SHARING FROM UR CLIENTS :
A user who wants to upload a file first creates a small torrent descriptor file that they distribute by conventional means (web, email, etc.). They then
make the file itself available through a BitTorrent node acting as a seed. Those with the torrent descriptor file can give it to their own BitTorrent nodes
which, acting as peers or leechers, download it by connecting to the seed and/or other peers.
The file being distributed is divided into segments called pieces. As each peer receives a new piece of the file it becomes a source of that piece to other
peers, relieving the original seed from having to send a copy to every computer or user wishing for a copy. With BitTorrent, the task of distributing the file
is shared by those who want it; it is entirely possible for the seed to send only a single copy of the file itself and eventually distribute to an unlimited
number of peers.
Each piece is protected by a cryptographic hash contained in the torrent descriptor.This ensures that any modification of the piece can be reliably
detected, and thus prevents both accidental and malicious modifications of any of the pieces received at other nodes. If a node starts with an authentic
copy of the torrent descriptor, it can verify the authenticity of the entire file it receives.
That's why we see authenticaltion in our client.
Also this is why the original peer[uploader] can edit his descripted file.
When a peer completely downloads a file, it becomes an additional seed. This eventual shift from peers to seeders determines the overall "health" of the
file (as determined by the number of times a file is available in its complete form).
That's why we judge torrent health n reliabilty with its seeds.
Torrent files are typically published on websites or elsewhere, and registered with at least one tracker. The tracker maintains lists of the clients currently
participating in the torrent.Alternatively, in a trackerless system (decentralized tracking) every peer acts as a tracker.
Users browse the web to find a torrent of interest, download it, and open it with a BitTorrent client. The client connects to the tracker(s) specified in the
torrent file, from which it receives a list of peers currently transferring pieces of the file(s) specified in the torrent. The client connects to those peers to
obtain the various pieces. If the swarm contains only the initial seeder, the client connects directly to it and begins to request pieces.
Clients incorporate mechanisms to optimize their download and upload rates; for example they download pieces in a random order to increase the
opportunity to exchange data, which is only possible if two peers have different pieces of the file.
The effectiveness of this data exchange depends largely on the policies that clients use to determine to whom to send data. Clients may prefer to send
data to peers that send data back to them (a tit for tat scheme), which encourages fair trading.
A technique called Broadcatching combines RSS with the BitTorrent protocol to create a content delivery system, further simplifying and automating