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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 delivery, arrival time, and order of arrival of datagrams need not be guaranteed by the network. History In the early 1970s, the term ''datagram'' was created by combining the words ''data'' and ''telegram'' by the CCITT rapporteur on packet switching, Halvor Bothner-By. While the word was new, the concept had already a long history. In 1962, Paul Baran described, in a RAND Corporation report, a hypothetical military network having to resist a nuclear attack. Small standardized "message blocks", bearing source and destination addresses, were stored and forwarded in computer nodes of a highly redundant meshed computer network. "The network user who has called up a "virtual connection" to an end station and has transmitted messages ... ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internet Protocol
The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP has the task of delivering packets from the source host to the destination host solely based on the IP addresses in the packet headers. For this purpose, IP defines packet structures that encapsulate the data to be delivered. It also defines addressing methods that are used to label the datagram with source and destination information. IP was the connectionless datagram service in the original Transmission Control Program introduced by Vint Cerf and Bob Kahn in 1974, which was complemented by a connection-oriented service that became the basis for the Transmission Control Protocol (TCP). The Internet protocol suite is therefore often referred to as ''TCP/IP''. The first major version of IP, Internet Protocol Version 4 (IPv4), i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Packet-switched Network
In telecommunications, packet switching is a method of grouping data into '' packets'' that are transmitted over a digital network. Packets are made 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. In the early 1960s, American computer scientist Paul Baran developed the concept that 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 telecommunications in the Bell System. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Packet Switching
In telecommunications, packet switching is a method of grouping data into '' packets'' that are transmitted over a digital network. Packets are made 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. In the early 1960s, American computer scientist Paul Baran developed the concept that 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 telecommunications in the Bell S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission Control Protocol
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, which is part of the Transport Layer of the TCP/IP suite. SSL/TLS often runs on top of TCP. TCP is connection-oriented, and a connection between client and server is established before data can be sent. The server must be listening (passive open) for connection requests from clients before a connection is established. Three-way handshake (active open), retransmission, and error detection adds to reliability but lengthens latency. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Louis Pouzin
Louis Pouzin (April 20, 1931 in Chantenay-Saint-Imbert, Nièvre, France) is a French computer scientist. He designed an early packet communications network, CYCLADES. This network was the first actual implementation of the pure datagram model, initially conceived and described by Donald Davies, subsequently named by Halvor Bothner-By, and seen by Louis Pouzin as his personal invention. His work, and that of his colleagues Hubert Zimmerman and Gérard Le Lann, were acknowledged by Vinton Cerf as substantial contributions to the design of TCP/IP, the protocol suite used by the Internet. Biography He studied at the École Polytechnique from 1950 to 1952. Having participated in the design of the Compatible Time-Sharing System (CTSS) at MIT, Pouzin wrote a program for it called RUNCOM around 1963–64. RUNCOM permitted the execution of commands contained within a folder and can be considered the ancestor of the command-line interface and shell scripts. Pouzin was the one who ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
End-to-end Principle
The end-to-end principle is a design framework in computer networking. In networks designed according to this principle, guaranteeing certain application-specific features, such as reliability and security, requires that they reside in the communicating end nodes of the network. Intermediary nodes, such as gateways and routers, that exist to establish the network, may implement these to improve efficiency but cannot guarantee end-to-end correctness. The essence of what would later be called the end-to-end principle was contained in the work of Paul Baran and Donald Davies on packet-switched networks in the 1960s. Louis Pouzin pioneered the use of the end-to-end strategy in the CYCLADES network in the 1970s. The principle was first articulated explicitly in 1981 by Saltzer, Reed, and Clark. The meaning of the end-to-end principle has been continuously reinterpreted ever since its initial articulation. Also, noteworthy formulations of the end-to-end principle can be found ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Connection-oriented Communication
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. The established connection ensures that data is delivered in the correct order to the upper communication layer. The alternative to connection-oriented transmission is connectionless communication, for example the datagram mode communication used by Internet Protocol (IP) and User Datagram Protocol, where data may be delivered out of order, since different network packets are routed independently and may be delivered over different paths. Connection-oriented communication may be implemented with a circuit switched connection, or a packet-mode virtual circuit connection. In the latter case, it may use either a transport layer virtual circuit protocol such as the TCP protocol, allowing data to be delivered in order. Although the lower-layer switching is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IPv6
Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4 address exhaustion, and is intended to replace IPv4. In December 1998, IPv6 became a Draft Standard for the IETF, which subsequently ratified it as an Internet Standard on 14 July 2017. Devices on the Internet are assigned a unique IP address for identification and location definition. With the rapid growth of the Internet after commercialization in the 1990s, it became evident that far more addresses would be needed to connect devices than the IPv4 address space had available. By 1998, the IETF had formalized the successor protocol. IPv6 uses 128-bit addresses, theoretically allowing 2128, or approximately total addresses. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Donald Davies
Donald Watts Davies, (7 June 1924 – 28 May 2000) was a Welsh computer scientist who was employed at the UK National Physical Laboratory (NPL). In 1965 he conceived of packet switching, which is today the dominant basis for data communications in computer networks worldwide. Davies proposed a commercial national data network in the United Kingdom and designed and built the local-area NPL network to demonstrate the technology. Many of the wide-area packet-switched networks built in the 1970s were similar "in nearly all respects" to his original 1965 design. The ARPANET project credited Davies for his influence, which was key to the development of the Internet. Davies' work was independent of the work of Paul Baran in the United States who had a similar idea in the early 1960s, and who also provided input to the ARPANET project, after his work was highlighted by Davies' team. Early life Davies was born in Treorchy in the Rhondda Valley, Wales. His father, a clerk at a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ARPANET
The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first networks to implement the TCP/IP protocol suite. Both technologies became the technical foundation of the Internet. The ARPANET was established by the Advanced Research Projects Agency (ARPA) of the United States Department of Defense. Building on the ideas of J. C. R. Licklider, Bob Taylor initiated the ARPANET project in 1966 to enable access to remote computers. Taylor appointed Larry Roberts as program manager. Roberts made the key decisions about the network design. He incorporated Donald Davies' concepts and designs for packet switching, and sought input from Paul Baran. ARPA awarded the contract to build the network to Bolt Beranek & Newman who developed the first protocol for the network. Roberts engaged Leonard Kleinrock at UCLA to develop mathematical methods for analyzing the packet network technology. The first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Packet
In telecommunications and computer networking, a network packet is a formatted unit of data carried by a packet-switched network. A packet consists of control information and user data; the latter is also known as the ''payload''. Control information provides data for delivering the payload (e.g., source and destination network addresses, error detection codes, or sequencing information). Typically, control information is found in packet headers and trailers. In packet switching, the bandwidth of the transmission medium is shared between multiple communication sessions, in contrast to circuit switching, in which circuits are preallocated for the duration of one session and data is typically transmitted as a continuous bit stream. Terminology In the seven-layer OSI model of computer networking, ''packet'' strictly refers to a protocol data unit at layer 3, the network layer. A data unit at layer 2, the data link layer, is a '' frame''. In layer 4, the transport layer, the da ... [...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 del ... in the early seventies. X.25 Virtual Circuits — Transpac in France — Pré-Internet Data Networking References Norwegian engineers Telecommunications engineers 1938 births 2014 deaths {{Norway-engineer-stub X.25 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
