69 lines
2.4 KiB
Markdown
69 lines
2.4 KiB
Markdown
---
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title: Torrenting
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tags: [question, networks]
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created: Saturday, August 03, 2024
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---
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# Torrenting
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**What is torrenting? Is this the same thing as a peer-to-peer network? How do
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these technologies fit within the client-server paradigm?**
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Torrenting is a specific application of
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[peer_to_peer_networking](Peer_to_peer_network.md) applied to file-sharing.
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Each peer on the network both consumes resources and makes resources available
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to others.
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## Procedure
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Large files are divided into small equal sized pieces and each piece is assigned
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a unique hash identifier. The `.torrent` file details the number of pieces,
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their sizes and hash values.
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Clients request different pieces from different peers simultaneously. As pieces
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are received, they are verified against their hash. Corrupted or incorrect
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pieces are discarded and re-downloaded.
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The client software reassembles the pieces in the correct order and the final
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file will be identical to the original which can be verified by comparing
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hashes.
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## Key terms
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- _tracker_
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- a server that coordinates communication between peers (so there is a server
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but its role is more lightweight than client-server, coordinating the peers
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rather than hosting or distributing file content)
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- _swarm_
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- a group of peers sharing the same file
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- _seeding_
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- uploading file pieces to other peers
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- _leeching_
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- downloading file pieces from other peers
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> An alternative to a tracker server is to use trackerless methods such as
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> distributed hash tables
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## Terminological clarification
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- _BitTorrent_ is the communications [protocols](Network_protocols.md) for P2P
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file sharing. It was also a client software developed by the company
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BitTorrent Inc.
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- _torrenting_ is the general terms for that act of sharing files using the
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BitTorrent protocol
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## Napster
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Napster pre-dated the emergence of the BitTorrent protocol. It did not segment
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files and files were downloaded directly from peers. It was a centralised P2P
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network because there was a central server that indexed all available files
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which kept a database of all connected users and their files.
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When you searched Napster you would be querying this DB on the server. The
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server would facilitate a direct connection between the consumer and provider
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peer for the data exchange.
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When users share with BitTorrent the `.torrent` file is the source of truth and
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a swarm is created around the users who have possess the file.
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