CYCLADES
Encyclopedia
The CYCLADES packet switching
network
was a French
research network created in the early 1970s. It was developed to explore alternatives to the ARPANET
design and to support network research generally. It was extremely influential on the Internet's initial design.
The CYCLADES network was the first to make the hosts
responsible for the reliable delivery of data, rather than the network itself, using unreliable datagram
s and associated end-to-end protocol
mechanisms. These concepts were later used in TCP/IP
, the protocol of the Internet
; CYCLADES was one of the predecessor systems with the greatest technical influence on the Internet.
The network was sponsored by the French government, through the Institut de Recherche d'lnformatique et d'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
.
. 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.
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 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—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 (Gillies and Cailliau 2000:38).
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.
was developing Transpac, a packet network based on the emerging X.25
standard. The academic debates between datagram and virtual circuit
raged for some time, but were eventually cut short by bureaucratic maneuvering.
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 see why the French government would fund a competitor to their Transpac network, and insisted that the permission and funding be rescinded. By 1981, Cyclades was forced to shut down.
It 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 network
s, satellite networks, the Unix
operating system
, and the message passing operating system Chorus
.
Hubert Zimmerman
used his experience in CYCLADES to influence the design of the OSI 7 layer model
, which is still an extremely common pedagogical device.
CYCLADES alumni and researchers at IRIA/INRIA were also influential in spreading 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.
Packet switching
Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams over a shared network...
network
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
was a French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
research network created in the early 1970s. It was developed to explore alternatives to the ARPANET
ARPANET
The Advanced Research Projects Agency Network , was the world's first operational packet switching network and the core network of a set that came to compose the global Internet...
design and to support network research generally. It was extremely influential on the Internet's initial design.
The CYCLADES network was the first to make the hosts
Host (network)
A network host is a computer 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 layer host address....
responsible for the reliable delivery of data, rather than the network itself, using unreliable datagram
Datagram
A datagram is a basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order are not guaranteed....
s and associated end-to-end protocol
End-to-end principle
The end-to-end principle is a classic design principle of computer networking which states that application specific functions ought to reside in the end hosts of a network rather than in intermediary nodes, provided they can be implemented "completely and correctly" in the end hosts...
mechanisms. These concepts were later used in TCP/IP
Internet protocol suite
The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...
, the protocol of the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
; CYCLADES was one of the predecessor systems with the greatest technical influence on the Internet.
The network was sponsored by the French government, through the Institut de Recherche d'lnformatique et d'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
Louis Pouzin invented the datagram and designed an early packet communications network, CYCLADES...
.
Conception and deployment
Design and staffing started in 1972, and November 1973 saw the first demonstration, using three hosts and one packet switchPacket switch
A packet switch is a node in a network which uses the packet switching paradigm for data communication. Packet switches can operate at a number of different levels in a protocol suite; although the exact technical details differ, fundamentally they all perform the same function: they store and...
. 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
Time-sharing
Time-sharing is the sharing of a computing resource among many users by means of multiprogramming and multi-tasking. Its introduction in the 1960s, and emergence as the prominent model of computing in the 1970s, represents a major technological shift in the history of computing.By allowing a large...
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
File transfer
File transfer is a generic term for the act of transmitting files over a computer network or the Internet. There are numerous ways and protocols to transfer files over a network. Computers which provide a file transfer service are often called file servers. Depending on the client's perspective the...
user application services.
By 1976 the network was in full deployment, eventually numbering 20 nodes with connections to NPL
National Physical Laboratory, UK
The National Physical Laboratory is the national measurement standards laboratory for the United Kingdom, based at Bushy Park in Teddington, London, England. It is the largest applied physics organisation in the UK.-Description:...
in London, ESA
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...
in Rome, and to the European Informatics Network (EIN).
Technical details
CYCLADES used a layered architecture, as did the Internet. The basic packet transmission function, named CIGALE, was novel; however, 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 CIGALE network featured a distance vector routing protocol
Routing protocol
A routing protocol is a protocol that specifies how routers communicate with each other, disseminating information that enables them to select routes between any two nodes on a computer network, the choice of the route being done by routing algorithms. Each router has a priori knowledge only of...
, 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—which is French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
for cicada
Cicada
A cicada is an insect of the order Hemiptera, suborder Auchenorrhyncha , in the superfamily Cicadoidea, with large eyes wide apart on the head and usually transparent, well-veined wings. There are about 2,500 species of cicada around the world, and many of them remain unclassified...
—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 (Gillies and Cailliau 2000:38).
An end-to-end protocol built on top of that provided a reliable transport
Transport layer
In computer networking, the transport layer or layer 4 provides end-to-end communication services for applications within a layered architecture of network components and protocols...
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
Reliable byte stream
A reliable byte stream is a common service paradigm in computer networking; it refers to a byte stream in which the bytes which emerge from the communication channel at the recipient are exactly the same, and in exactly the same order, as they were when the sender inserted them into the channel.The...
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.
Demise
By 1976, the French PTTPostal Telegraph and Telephone
A postal, telegraph, and telephone service is a government agency responsible for postal mail, telegraph, and telephone services. Such monopolies existed in many countries, though not in North America or Japan. Many PTTs have been partially or completely privatized in recent years...
was developing Transpac, a packet network based on the emerging X.25
X.25
X.25 is an ITU-T standard protocol suite for packet switched wide area network communication. An X.25 WAN consists of packet-switching exchange nodes as the networking hardware, and leased lines, Plain old telephone service connections or ISDN connections as physical links...
standard. The academic debates between datagram and virtual circuit
Virtual circuit
In telecommunications and computer networks, a virtual circuit , synonymous with virtual connection and virtual channel, is a connection oriented communication service that is delivered by means of packet mode communication...
raged for some time, but were eventually cut short by bureaucratic maneuvering.
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 see why the French government would fund a competitor to their Transpac network, and insisted that the permission and funding be rescinded. By 1981, Cyclades was forced to shut down.
Legacy
As mentioned, 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. Today's Internet still uses these ideas.It 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 network
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
s, satellite networks, the Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
, and the message passing operating system Chorus
ChorusOS
ChorusOS is a microkernel real-time operating system designed for embedded systems. Sun Microsystems acquired Chorus Systèmes, the company which created ChorusOS, in 1997. Sun no longer supports ChorusOS. The founders of Chorus Systems started a new company called Jaluna in August 2002. Jaluna has...
.
Hubert Zimmerman
Hubert Zimmerman
In 1991, Hubert Zimmerman was awarded the SIGCOMM Award for "20 years of leadership in the development of computer networking and the advancement of international standardization".-References:...
used his experience in CYCLADES to influence the design of the OSI 7 layer model
OSI model
The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
, which is still an extremely common pedagogical device.
CYCLADES alumni and researchers at IRIA/INRIA were also influential in spreading the Internet in France, eventually witnessing the success of the datagram-based Internet, and the demise of the X.25 and ATM
Asynchronous Transfer Mode
Asynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
virtual circuit networks.
Further reading
- Louis Pouzin (editor), The Cyclades Computer Network: Toward Layered Network Architectures (North-Holland, Amsterdam, 1982)