CYCLADES was a ground-breaking, and extremely influential, early packet switching data network, done in France in the late 1970's. It was the key intermediate technical step between the ARPANET and the Internet.
CYCLADES was the first network to move reliability into the hosts attached to the network (using the now-standard mechanisms of sequence numbers, acknowledgements, timeouts, and retransmissions to achieve it), and out of the network.
In addition to making the packet switches in the network much simpler (a major gain, and one that would be crucial in the development of internets), it was also a step toward the end to end model of networking.
The actual physical network (links and switches) was named CIGALE; CYCLADES includes the whole ensemble, including the hosts and higher-level protocols and applications.
- Louis Pouzin (editor), The Cyclades Computer Network: Toward Layered Network Architectures (North-Holland, Amsterdam, 1982)