The CYCLADES computer network (French pronunciation: [siklad] ) was a French research network created in the early 1970s. It was one of the pioneering networks experimenting with the concept of packet switching, and was developed to explore alternatives to the ARPANET design. The network supported general local network research.
A computer network is a digital telecommunications network which allows nodes to share resources. In computer networks, computing devices exchange data with each other using connections between nodes. These data links are established over cable media such as wires or optic cables, or wireless media such as Wi-Fi.
France, officially the French Republic, is a country whose territory consists of metropolitan France in Western Europe and several overseas regions and territories. The metropolitan area of France extends from the Mediterranean Sea to the English Channel and the North Sea, and from the Rhine to the Atlantic Ocean. It is bordered by Belgium, Luxembourg and Germany to the northeast, Switzerland and Italy to the east, and Andorra and Spain to the south. The overseas territories include French Guiana in South America and several islands in the Atlantic, Pacific and Indian oceans. The country's 18 integral regions span a combined area of 643,801 square kilometres (248,573 sq mi) and a total population of 67.3 million. France, a sovereign state, is a unitary semi-presidential republic with its capital in Paris, the country's largest city and main cultural and commercial centre. Other major urban areas include Lyon, Marseille, Toulouse, Bordeaux, Lille and Nice.
Packet switching is a method of grouping data that is transmitted over a digital network into packets. Packets are made of a header and a payload. Data in the header are used by networking hardware to direct the packet to its destination where the payload is extracted and used by application software. Packet switching is the primary basis for data communications in computer networks worldwide.
The CYCLADES network was the first to make the hosts responsible for the reliable delivery of data, rather than this being a centralized service of the network itself. Datagrams were exchanged on the network using transport protocols that do not guarantee reliable delivery, but only attempt best-effort. To empower the network leaves, the hosts, to perform error-correction, the network ensured end-to-end protocol transparency, a concept later to be known as the end-to-end principle. This simplified network design, reduced network latency, and reduced the opportunities for single point failures. The experience with these concepts led to the design of key features of the Internet protocol in the ARPANET project.
A network host is a computer or other device connected to a computer network. A network host may offer information resources, services, and applications to users or other nodes on the network. A network host is a network node that is assigned a network address.
The end-to-end principle is a design framework in computer networking. In networks designed according to this principle, application-specific features reside in the communicating end nodes of the network, rather than in intermediary nodes, such as gateways and routers, that exist to establish the network.
The network was sponsored by the French government, through the Institut de Recherche en lnformatique et en Automatique (IRIA), the national research laboratory for computer science in France, now known as INRIA, which served as the co-ordinating agency. Several French computer manufacturers, research institutes and universities contributed to the effort. CYCLADES was designed and directed by Louis Pouzin.
Louis Pouzin invented the datagram and designed an early packet communications network, CYCLADES.
Design and staffing started in 1972, and November 1973 saw the first demonstration, using three hosts and one packet switch. Deployment continued in 1974, with three packet switches installed by February, although at that point the network was only operational for three hours each day. By June the network was up to seven switches, and was available throughout the day for experimental use.
A terminal concentrator was also developed that year, since time-sharing was still a prevalent mode of computer use. In 1975, the network shrank slightly due to budgetary constraints, but the setback was only temporary. At that point, the network provided remote login, remote batch and file transfer user application services.
In computing, time-sharing is the sharing of a computing resource among many users by means of multiprogramming and multi-tasking at the same time.
File transfer is the transmission of a computer file through a communication channel from one computer system to another. Typically, file transfer is mediated by a communications protocol. In the history of computing, a large number of file transfer protocols have been designed for different contexts.
By 1976 the network was in full deployment, eventually numbering 20 nodes with connections to NPL in London, ESA in Rome, and to the European Informatics Network (EIN).
The European Space Agency is an intergovernmental organisation of 22 member states dedicated to the exploration of space. Established in 1975 and headquartered in Paris, France, ESA has a worldwide staff of about 2,200 in 2018 and an annual budget of about €5.72 billion in 2019.
CYCLADES used a layered architecture, as did the Internet. The basic packet transmission like function, named CIGALE, was novel; it provided an unreliable datagram service (the word was coined by Louis Pouzin by combining data and telegram). Since the packet switches no longer had to ensure correct delivery of data, this greatly simplified their design.
“The inspiration for datagrams had two sources. One was Donald Davies' studies. He had done some simulation of datagram networks, although he had not built any, and it looked technically viable. The second inspiration was I like things simple. I didn't see any real technical motivation to overlay two levels of end-to-end protocols. I thought one was enough.”
The CIGALE network featured a distance vector routing protocol, and allowed experimentation with various metrics. it also included a time synchronization protocol in all the packet switches. CIGALE included early attempts at performing congestion control by dropping excess packets.
The name CIGALE—(French pronunciation: [siɡal] ) which is French for cicada —originates from the fact that the developers installed a speaker at each computer, so that "it went 'chirp chirp chirp' like cicadas" when a packet passed a computer.
An end-to-end protocol built on top of that provided a reliable transport service, on top of which applications were built. It provided a reliable sequence of user-visible data units called letters, rather than the reliable byte stream of TCP. The transport protocol was able to deal with out-of-order and unreliable delivery of datagrams, using the now-standard mechanisms of end-end acknowledgments and timeouts; it also featured sliding windows and end-to-end flow control.
By 1976, the French PTT was developing Transpac, a packet network based on the emerging X.25 standard. The academic debates between datagram and virtual circuit networks continued for some time, but were eventually cut short by bureaucratic decisions.
Data transmission was a state monopoly in France at the time, and IRIA needed a special dispensation to run the CYCLADES network. The PTT did not agree to funding by the government of a competitor to their Transpac network, and insisted that the permission and funding be rescinded. By 1981, Cyclades was forced to shut down.
The most important legacy of CYCLADES was in showing that moving the responsibility for reliability into the hosts was workable, and produced a well-functioning service network. It also showed that it greatly reduced the complexity of the packet switches. The concept became a cornerstone in the design of the Internet.
The network was also a fertile ground for experimentation, and allowed a generation of French computer scientists to experiment with networking concepts.Louis Pouzin and the CYCLADES alumni initiated a number of follow-on projects at IRIA to experiment with local area networks, satellite networks, the Unix operating system, and the message passing operating system Chorus.
Hubert Zimmermann used his experience in CYCLADES to influence the design of the OSI model, which is still a common pedagogical tool.
CYCLADES alumni and researchers at IRIA/INRIA were also influential in spreading adoption of the Internet in France, eventually witnessing the success of the datagram-based Internet, and the demise of the X.25 and ATM virtual circuit networks.
Internetworking is "the concept of interconnecting different types of networks to build a large, global network" such that any pair of connected hosts can exchange packets. To build an internetwork, the following are needed: A standardized scheme to address packets to any host on any participating network; a standardized protocol defining format and handling of transmitted packets; components interconnecting the participating networks by routing packets to their destinations based on standardized addresses.
The Internet Protocol (IP) is the principal communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.
The Internet protocol suite is the conceptual model and set of communications protocols used in the Internet and similar computer networks. It is commonly known as TCP/IP because the foundational protocols in the suite are the Transmission Control Protocol (TCP) and the Internet Protocol (IP). It is occasionally known as the Department of Defense (DoD) model because the development of the networking method was funded by the United States Department of Defense through DARPA.
The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is commonly referred to as TCP/IP. TCP provides reliable, ordered, and error-checked delivery of a stream of octets (bytes) between applications running on hosts communicating via an IP network. Major internet applications such as the World Wide Web, email, remote administration, and file transfer rely on TCP. Applications that do not require reliable data stream service may use the User Datagram Protocol (UDP), which provides a connectionless datagram service that emphasizes reduced latency over reliability.
In computer networking, the User Datagram Protocol (UDP) is one of the core members of the Internet protocol suite. The protocol was designed by David P. Reed in 1980 and formally defined in RFC 768. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network. Prior communications are not required in order to set up communication channels or data paths.
A datagram is a basic transfer unit associated with a packet-switched network. Datagrams are typically structured in header and payload sections. Datagrams provide a connectionless communication service across a packet-switched network. The delivery, arrival time, and order of arrival of datagrams need not be guaranteed by the network.
In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet protocol suite and the OSI model. The protocols of this layer provide host-to-host communication services for applications. It provides services such as connection-oriented communication, reliability, flow control, and multiplexing.
Catenet is an obsolete term for a system of packet-switched communication networks interconnected via gateways.
The Advanced Research Projects Agency Network (ARPANET) was an early packet-switching network and the first network to implement the TCP/IP protocol suite. Both technologies became the technical foundation of the Internet. The ARPANET was initially funded by the Advanced Research Projects Agency (ARPA) of the United States Department of Defense.
Connection-oriented communication is a network communication mode in telecommunications and computer networking, where a communication session or a semi-permanent connection is established before any useful data can be transferred, and where a stream of data is delivered in the same order as it was sent. The alternative to connection-oriented transmission is connectionless communication, for example the datagram mode communication used by the IP and UDP protocols, where data may be delivered out of order, since different network packets are routed independently, and may be delivered over different paths.
Best-effort delivery describes a network service in which the network does not provide any guarantee that data is delivered or that delivery meets any quality of service. In a best-effort network, all users obtain best-effort service, meaning that they obtain unspecified variable bit rate and latency and packet loss, depending on the current traffic load. This can be contrasted with reliable delivery, which can be built on top of best-effort delivery, or with circuit switching schemes which maintain a defined, continuous quality of service.
In computer networking, a reliable protocol is a protocol which notifies the sender whether or not the delivery of data to intended recipients was successful. Reliability is a synonym for assurance, which is the term used by the ITU and ATM Forum.
The following outline is provided as an overview of and topical guide to the Internet.
The internet layer is a group of internetworking methods, protocols, and specifications in the Internet protocol suite that are used to transport network packets from the originating host across network boundaries, if necessary, to the destination host specified by an IP address. The internet layer derives its name from its function facilitating internetworking, which is the concept of connecting multiple networks with each other through gateways.
In telecommunication, a communication protocol is a system of rules that allow two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both.
The NPL Network or NPL Data Communications Network was a local area computer network operated by a team from the National Physical Laboratory in England that pioneered the concept of packet switching. Following a pilot experiment during 1967, elements of the first version of the network, Mark I, became operational during 1969 then fully operational in 1970, and the Mark II version operated from 1973 until 1986. The NPL network, followed by the wide area ARPANET in the United States, were the first two computer networks that implemented packet switching, and were interconnected in the early 1970s. The NPL network was designed and directed by Donald Davies.