Arpit's Newsletter read by 90000+ engineers
Weekly essays on real-world system design, distributed systems, or a deep dive into some super-clever algorithm.
Overview of the BitTorrent architecture
The BitTorrent Architecture BitTorrent architecture consists of the following entities
- Torrent File
- Tracker
- Leecher
- Seeders
Each torrent is independent and it holds information about one or many files that need to be distributed. To download a specific file, we need to hunt its torrent file from any torrent search engine.
Pieces
The original file is split into equal size pieces and the SHA-1 of each piece is put into the .torrent file. The hash is then used by the peers to download the corresponding piece and once all the pieces are downloaded, they are merged to re-generate the file.
Tracker
Tracker is the only central entity and it holds the information about all the peers participating in the torrent network. It is a simple HTTP server that responds to the queries of the peers and stores status information coming in from the peers.
Each torrent file holds a Tracker URL that helps the peers locate and talk to the tracker to participate in the torrent. The tracker keeps track of
- peers who hold the pieces of the file
- peers who are downloading
- peers who need help to find other peers
Although the tracker keeps track of a lot of information, it does not download or participate in the download of the actual content of the file; it simply holds the meta information.
Leecher
Leecher is any peer in the network that is downloading the pieces and is awaiting the completion of the file. Leecher talks to the tracker to get the list of 50 peers and then talks to them to get the desired pieces.
The leechers also help other leechers by sharing the pieces they have, thus quickly distributing the file across the network.
Seeder
Seeder is a peer in the network that has all the pieces of the file and does not need to download anything. So, if any leecher needs any piece that is not available with any other leecher, it can obtain from the seeder.
A leecher, after completing the download of the entire file, becomes the seeder and continues to participate in the network.
Here's the video ⤵
Courses I teach
Alongside my daily work, I also teach some highly practical courses, with a no-fluff no-nonsense approach, that are designed to spark engineering curiosity and help you ace your career.
System Design Masterclass
A no-fluff masterclass that helps experienced engineers form the right intuition to design and implement highly scalable, fault-tolerant, extensible, and available systems.
System Design for Beginners
An in-depth and self-paced course for absolute beginners to become great at designing and implementing scalable, available, and extensible systems.
Redis Internals
A self-paced and hands-on course covering Redis internals - data structures, algorithms, and some core features by re-implementing them in Go.