Internet Guide Logo


Last Edit: 12/06/17

bullet Introduction

CYCLADES was an early French packet switching computer network that influenced the design of later network models. CYCLADES featured a decentralised networking model that placed the responsibility for complex 'intelligent' functions at the edge of the network (hosts) rather than on a central authority. The best-effort datagram delivery method - for the central transport protocol of CYCLADES - was a first for packet switching networks and was later implemented in the design of TCP/IP; with the Internet Protocol (IP) being a best-effort connectionless protocol. CYCLADES was developed in 1972, the project was headed by Louis Pouzin and included Hubert Zimmermann:

Hubert Zimmermann, used his experience with CYCLADES to design the OSI model. Hubert Zimmermann Louis Pouzin, the chief designer of CYCLADES that connected over 20 nodes across the European continent. Louis Pouzin

Some other members of the team that designed/built CYCLADES included Jean-Louis Grangé and Lauriot Prévost.

CYCLADES is named after the Greek island group in the Aegean Sea. The Cyclades islands form a archipelago: a group of islands that are typically governed by a standard set of laws. Likewise, the architecture of the CYCLADES computer network was built upon a similar idea: a group of computer networks, who communicated using a standard protocol suite.

CYCLADES was an influential computer network: as it built and improved upon the network architecture of ARPANET. CYCLADES pioneered the development of end-to-end protocols: where hosts, instead of the network, took responsibility for complex functions. This was a revolutionarily idea (unreliable data transmission). CYCLADES spearheaded the development of packet switching networks that featured a simple and basic central transport methodology. The intelligent functions of the network were handled by the hosts: which made it far simpler, than previously, to interconnect new nodes and networks together.

CYCLADES was influential in the development of TCP/IP and the ISO-OSI (Open Systems Interconnection) model. Both of these protocol suites would copy CYCLADES layered model (Data Transmission Layer, a Transport Layer, and an Application Layer) and end-to-end protocol structure, where hosts were responsible for the delivery of data (packet assembly, packet disassembly, flow control, sequence number-ing, and virtual connection).

bullet History

It has been claimed that the inspiration to create CYCLADES began when a delegation of French computing scientists visited the United States in 1970 and came across the ARPANET computer network; one of the first packet switching networks. The team picked by Louis Pouzin to design and build CYCLADES had thoroughly studied the networking experiments conducted at the National Physical Lab in the UK and had a good understanding of the ARPA packet network. BBN, who built the router for ARPANET, provided the CYCLADES team with advice. The coordination team for CYCLADES was situated at the Institut de Recherche d'Informatique et d'Automatique (IRIA) and was sponsored by the French national government.

Designing CYCLADES began in 1972, and a working example of the network was displayed at a CIGALE Presentation in 1974. The network was fully deployed between 1974-1976, and included nodes across France and the European continent. CYCLADES was designed with a protocol suite that featured layers, and with a communication sub-network named CIGALE. CIGALE implemented an address architecture that featured a datagram (unreliable data packet) methodology with a simple header format and a maximum payload size.

CIGALE was basic, easily implemented, and enabled nodes to be more easily connected. CYCLADES would run interconnection experiments with the UK's NPL Mark.I packet switching network, and NPL would later connect to CYCLADES. The CYCLADES network was built with: nodes using routers (Mitra-15 mini-computers); hosts connected via communication lines which were point-to-point PTT leased lines and telephones lines; and hosts using V24 interfaces. The original CYCLADES network featured five nodes located at: Rennes, Paris (2), Toulouse, and Grenoble (four corners of France).

CYCLADES would run into funding problems in 1975, and the amount of nodes in the network shrank; although the network did connect to the European Space Agency (ESA) and European Informatics Network (EIN) by 1976. By the 1980's, European computer networking projects had switched it's focus from a datagram methodology to a virtual circuit approach. If CYCLADES had been fully financially and ideologically backed, then it may have rivaled the Internet as a global communications network.