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X.25
X.25 is an ITU-T standard protocol suite for Packet switched network, packet-switched data communication in wide area network, wide area networks (WAN). It was originally defined by the CCITT, International Telegraph and Telephone Consultative Committee (CCITT, now ITU-T) in a series of drafts and finalized in a publication known as ''The Orange Book'' in 1976.CCITT, Study Group VII, ''Draft Recommendation X-25'', March 1976 The protocol suite is designed as three conceptual layers, which correspond closely to the lower three layers of the seven-layer OSI model, OSI Reference Model, although it was developed several years before the OSI model (1984). It also supports functionality not found in the OSI network layer. An X.25 WAN consists of packet switching, packet-switching exchange (PSE) nodes as the networking hardware, and leased lines, plain old telephone service connections, or ISDN connections as physical links. X.25 was popular with telecommunications company, telecommun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Packet Switching
In telecommunications, packet switching is a method of grouping Data (computing), data into short messages in fixed format, i.e. ''network packet, packets,'' that are transmitted over a digital Telecommunications network, network. Packets consist of a header (computing), header and a payload (computing), payload. Data in the header is used by networking hardware to direct the packet to its destination, where the payload is extracted and used by an operating system, application software, or Protocol stack, higher layer protocols. Packet switching is the primary basis for data communications in computer networks worldwide. During the early 1960s, American engineer Paul Baran developed a concept he called ''distributed adaptive message block switching'', with the goal of providing a fault-tolerant, efficient routing method for telecommunication messages as part of a research program at the RAND Corporation, funded by the United States Department of Defense. His ideas contradicted t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Packet Switched Network
In telecommunications, packet switching is a method of grouping data into short messages in fixed format, i.e. '' packets,'' that are transmitted over a digital network. Packets consist of a header and a payload. Data in the header is used by networking hardware to direct the packet to its destination, where the payload is extracted and used by an operating system, application software, or higher layer protocols. Packet switching is the primary basis for data communications in computer networks worldwide. During the early 1960s, American engineer Paul Baran developed a concept he called ''distributed adaptive message block switching'', with the goal of providing a fault-tolerant, efficient routing method for telecommunication messages as part of a research program at the RAND Corporation, funded by the United States Department of Defense. His ideas contradicted then-established principles of pre-allocation of network bandwidth, exemplified by the development of telecommun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Packet Switching
In telecommunications, packet switching is a method of grouping Data (computing), data into short messages in fixed format, i.e. ''network packet, packets,'' that are transmitted over a digital Telecommunications network, network. Packets consist of a header (computing), header and a payload (computing), payload. Data in the header is used by networking hardware to direct the packet to its destination, where the payload is extracted and used by an operating system, application software, or Protocol stack, higher layer protocols. Packet switching is the primary basis for data communications in computer networks worldwide. During the early 1960s, American engineer Paul Baran developed a concept he called ''distributed adaptive message block switching'', with the goal of providing a fault-tolerant, efficient routing method for telecommunication messages as part of a research program at the RAND Corporation, funded by the United States Department of Defense. His ideas contradicted t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Public Data Network
A public data network (PDN) is a network established and operated by a telecommunications administration, or a recognized private operating agency, for the specific purpose of providing data transmission services for the public. The first public packet switching networks were RETD in Spain (1972), the experimental RCP network in France (1972) and Telenet in the United States (1975). "Public data network" was the common name given to the collection of X.25 providers, the first of which were Telenet in the U.S. and DATAPAC in Canada (both in 1976), and Transpac in France (in 1978). The International Packet Switched Service (IPSS) was the first commercial and international packet-switched network (1978). The networks were interconnected with gateways using X.75. These combined networks had large global coverage during the 1980s and into the 1990s. The networks later provided the infrastructure for the early Internet. Description In communications, a PDN is a circuit- or p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Packet Switch Stream
Packet Switch Stream (PSS) was a public data network in the United Kingdom, provided by British Telecommunications (BT). It operated from the late 1970s through to the mid-2000s. Research, development and implementation EPSS Roger Scantlebury was seconded from the National Physical Laboratory to the British Post Office Telecommunications division (BPO-T) in 1969. He had worked with Donald Davies in the late 1960s pioneering the implementation of packet switching and the associated communication protocols on the local-area NPL network. By 1973, BPO-T engineers had developed a packet-switching communication protocol from basic principles for an Experimental Packet Switched Service (EPSS) based on a virtual call capability. However, the protocols were complex and limited; Donald Davies described them as "esoteric". Ferranti supplied the hardware and software. The handling of link control messages (acknowledgements and flow control) was different from that of most other network ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ISDN
Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Work on the standard began in 1980 at Bell Labs and was formally standardized in 1988 in the CCITT "Red Book". By the time the standard was released, newer networking systems with much greater speeds were available, and ISDN saw relatively little uptake in the wider market. One estimate suggests ISDN use peaked at a worldwide total of 25 million subscribers at a time when 1.3 billion analog lines were in use. ISDN has largely been replaced with digital subscriber line (DSL) systems of much higher performance. Prior to ISDN, the telephone system consisted of digital links like T1/ E1 on the long-distance lines between telephone company offices and analog signals on copper telephone wires to the customers, the " last mile". At the time, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Circuit
A virtual circuit (VC) is a means of transporting data over a data network, based on packet switching and in which a connection is first established across the network between two endpoints. The network, rather than having a fixed data rate reservation per connection as in circuit switching, takes advantage of the statistical multiplexing on its transmission links, an intrinsic feature of packet switching. A 1978 standardization of virtual circuits by the CCITT imposes per-connection Flow control (data), flow controls at all user-to-network and network-to-network interfaces. This permits participation in congestion control and reduces the likelihood of packet loss in a heavily loaded network. Some circuit protocols provide Reliability (computer networking), reliable communication service through the use of data retransmissions invoked by error detection and automatic repeat request (ARQ). Before a virtual circuit may be used, it must be established between network nodes in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rémi Després
Rémi Després (born January 16, 1943) is a French engineer and entrepreneur known for his contributions on data networking. Education In 1961–1963, Rémi Després attended École Polytechnique of Paris, of which he holds an Engineer degree. At UC Berkeley, he received a master's degree in 1967, and a Ph.D degree in 1969, both in the EECS Department. Career From 1963 to 1971 at CNET and UC Berkeley, he specialized in programming languages and time-sharing operating systems. From 1971 to 1980, Rémi Després was in charge of R&D of the French PTT on packet switching. He was one of the leading "innovators who worked across the boundaries of computers and communications" in the 1970s. As such, he introduced the concept of "graceful saturated operation", which was referenced by Bob Kahn and Vint Cerf in their seminal 1974 paper on internetworking, ''"A Protocol for Packet Network Intercommunication".'' He named and formalized the concept of virtual circuits and, with his t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OSI Model
The Open Systems Interconnection (OSI) model is a reference model developed by the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems interconnection." In the OSI reference model, the components of a communication system are distinguished in seven abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. The model describes communications from the physical implementation of transmitting bits across a transmission medium to the highest-level representation of data of a distributed application. Each layer has well-defined functions and semantics and serves a class of functionality to the layer above it and is served by the layer below it. Established, well-known communication protocols are decomposed in software development into the model's hierarchy of function calls. The Internet protocol suite as defined in and is a model of net ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halvor Bothner-By
Halvor Bothner-By (August 20, 1938 - June 13, 2014) was a telecommunication engineer of the Norwegian Telecommunications Administration. He was a rapporteur on packet switching for the CCITT. As such, he chaired the group that, in March 1975, proposed to the CCITT Recommendation X.2x on virtual circuits to be offered by public networks. After its unanimous approval at the May 1976 CCITT plenary, it became the well-known protocol X.25. He was also renowned for having coined the term ''datagram 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 de ...'' in the early seventies on a train between Paris and Rennes on the way to attend a CEPT Rapporteur meeting. X.25 Virtual Circuits — Transpac in France — Pré-Internet Data Networking References 1938 births 2014 deaths Telecomm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CYCLADES
The CYCLADES computer network () 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, unlike the ARPANET, was explicitly designed to facilitate internetworking. 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. The network ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lawrence Roberts (scientist)
Larry Roberts (December 21, 1937 – December 26, 2018) was an American computer scientist and Internet pioneer. As a program manager and later office director at the Advanced Research Projects Agency, Roberts and his team created the ARPANET, the first wide-area computer network to implement packet switching techniques invented by British computer scientist Donald Davies and American engineer Paul Baran. The ARPANET's principal designer was Bob Kahn, alongside several other computer scientists from Bolt Beranek and Newman (BBN) who worked on the Interface Message Processors (IMPs) and their communication protocols. Roberts asked Leonard Kleinrock to apply mathematical methods to model and measure the performance of the network. In the 1970s, ARPA sponsored research on communication protocols for internetworking, using concepts pioneered by Louis Pouzin, that led to the development of the modern Internet. After his work at ARPA, Roberts became CEO of the commercial packet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
