About bitTorrent
Posted On June 28, 2009 at 3:43 pm in BitTorrent, uTorrent information
BitTorrent (literally, pp. «Bitstream») – peer-to-peer (P2P) network protocol Cohen for the cooperative exchange of files over the Internet.
The files are transmitted in parts, each torrent-client, receiving (downloading) of these parts, at the same time preference (downloads) to other customers, which reduces the burden and dependence on the source of each client and provides data redundancy.
The first torrent-client «BitTorrent» Bram Cohen created the Python 4 April 2001, launching the first version was held on 2 July 2001.
There are many other programs customers to exchange files from BitTorrent.
The operating principle of the protocol
How it works BitTorrent: load on the distributor of the file is reduced due to the fact that customers are beginning to share data immediately, even if the file does not dokachan them to the end.
Before you start downloading the client connects to the tracker, he said his address and the hash sum of the requested file, which in response the customer receives the addresses of other clients to download or distributing the same file. The client periodically informs the tracker about the process and obtain an updated list of addresses.
Customers are connected with each other and exchange segments of files without the direct involvement of tracker, which is only regularly updates information on the contracts for the exchange of clients and other statistical information. An effective network BitTorrent necessary that as many customers have been able to accept incoming connections. Incorrect changes to the NAT or firewall can prevent this.
When connecting clients directly exchange information on their segments. Clients wishing to download segment, sends a request and if the second client is ready to give, receive the segment. The client then verifies the checksum for the segment and notifies all connected peers about having him in this segment.
Each client is able to temporarily block the return to another client (eng. choke). This is done to make better use of the channel output. In addition, if you choose – one to unlock preferred piram, which are transferred to this client a lot of segments. Thus, the feasts with good impact velocities encourage each other on the principle of «you – I, I – you».
Exchange of segments is on a «you – I, I – you» symmetrically in two directions and in random order. Clients periodically communicate with each other on their segments. Data transfer starts when both parties are interested in it, that is, each side has segments, which have no other. The number of transferred segments are calculated, and if one party discovers that sends on average more than taking it to block (engl. choke) returns. Thus, the protocol provided protection against licherov.
Upon receipt of the full file, the client goes into a special mode of operation, in which he pays only the data (becomes Sid).
Clients periodically inform the tracker on the changes in the status of the download and update the lists of IP-addresses.
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