Introduction #

In the meantime, there are several distributed systems. The blockchain technologies are only the newest ones. There are for example still:

• Distributed file system (e.g. Hadoop, NFS, CIFS, AFP).
• Peer to peer video platform (e.g. PeerTube).
• Federated short message service (e.g. Mastodon)
• Email
• Internet (web server)
• DNS
• Distributed Hash Tables (e.g. Kademlia, Chord, TomP2P, Paxos, Raft)
• BitTorrent
• Software updates in Windows 10 and some games
• Browser Peer to Peer via WebRTC (video telephony, chat etc.)
• Remote Procedure Call (RPC) (e.g. gRPC, Apache Avro)
• Peer to Peer Internet (e.g. Tor)
• Message Queue (e.g. RabbitMQ, ActiveMQ, Qpid, ZeroMQ, Kafka)
• Hierarchical key-value-store (e.g. Apache ZooKeeper)

I will describe some as exam preparation. Much material can be found on Maarten van Steen’s website.