Internet protocol suite
The Internet protocol suite is the conceptual model and set of communications protocols used in the Internet and similar computer networks. It is known as TCP/IP because the foundational protocols in the suite are the Transmission Control Protocol and the Internet Protocol, it is known as the Department of Defense model because the development of the networking method was funded by the United States Department of Defense through DARPA. The Internet protocol suite provides end-to-end data communication specifying how data should be packetized, transmitted and received; this functionality is organized into four abstraction layers, which classify all related protocols according to the scope of networking involved. From lowest to highest, the layers are the link layer, containing communication methods for data that remains within a single network segment; the technical standards underlying the Internet protocol suite and its constituent protocols are maintained by the Internet Engineering Task Force.
The Internet protocol suite predates the OSI model, a more comprehensive reference framework for general networking systems. The Internet protocol suite resulted from research and development conducted by the Defense Advanced Research Projects Agency in the late 1960s. After initiating the pioneering ARPANET in 1969, DARPA started work on a number of other data transmission technologies. In 1972, Robert E. Kahn joined the DARPA Information Processing Technology Office, where he worked on both satellite packet networks and ground-based radio packet networks, recognized the value of being able to communicate across both. In the spring of 1973, Vinton Cerf, who helped develop the existing ARPANET Network Control Program protocol, joined Kahn to work on open-architecture interconnection models with the goal of designing the next protocol generation for the ARPANET. By the summer of 1973, Kahn and Cerf had worked out a fundamental reformulation, in which the differences between local network protocols were hidden by using a common internetwork protocol, instead of the network being responsible for reliability, as in the ARPANET, this function was delegated to the hosts.
Cerf credits Hubert Zimmermann and Louis Pouzin, designer of the CYCLADES network, with important influences on this design. The protocol was implemented as the Transmission Control Program, first published in 1974; the TCP managed both datagram transmissions and routing, but as the protocol grew, other researchers recommended a division of functionality into protocol layers. Advocates included Jonathan Postel of the University of Southern California's Information Sciences Institute, who edited the Request for Comments, the technical and strategic document series that has both documented and catalyzed Internet development. Postel stated, "We are screwing up in our design of Internet protocols by violating the principle of layering." Encapsulation of different mechanisms was intended to create an environment where the upper layers could access only what was needed from the lower layers. A monolithic design would lead to scalability issues; the Transmission Control Program was split into two distinct protocols, the Transmission Control Protocol and the Internet Protocol.
The design of the network included the recognition that it should provide only the functions of efficiently transmitting and routing traffic between end nodes and that all other intelligence should be located at the edge of the network, in the end nodes. This design is known as the end-to-end principle. Using this design, it became possible to connect any network to the ARPANET, irrespective of the local characteristics, thereby solving Kahn's initial internetworking problem. One popular expression is that TCP/IP, the eventual product of Cerf and Kahn's work, can run over "two tin cans and a string." Years as a joke, the IP over Avian Carriers formal protocol specification was created and tested. A computer called, it forwards network packets forth between them. A router was called gateway, but the term was changed to avoid confusion with other types of gateways. From 1973 to 1974, Cerf's networking research group at Stanford worked out details of the idea, resulting in the first TCP specification.
A significant technical influence was the early networking work at Xerox PARC, which produced the PARC Universal Packet protocol suite, much of which existed around that time. DARPA contracted with BBN Technologies, Stanford University, the University College London to develop operational versions of the protocol on different hardware platforms. Four versions were developed: TCP v1, TCP v2, TCP v3 and IP v3, TCP/IP v4; the last protocol is still in use today. In 1975, a two-network TCP/IP communications test was performed between Stanford and University College London. In November 1977, a three-network TCP/IP test was conducted between sites in the US, the UK, Norway. Several other TCP/IP prototypes were developed at multiple research centers between 1978 and 1983. In March 1982, the US Department of Defense declared TCP/IP as the standard for all military computer networking. In the same year, Peter T. Kirstein's research group at University College London adopted the protocol; the migration of the ARPANET to TCP/IP was completed on flag day January 1, 1983, when the new protocols were permanently activated.
In 1985, the Internet Advisory Board held a three-day TCP/
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. Network computer devices that originate and terminate the data are called network nodes. Nodes are identified by network addresses, can include hosts such as personal computers and servers, as well as networking hardware such as routers and switches. Two such devices can be said to be networked together when one device is able to exchange information with the other device, whether or not they have a direct connection to each other. In most cases, application-specific communications protocols are layered over other more general communications protocols; this formidable collection of information technology requires skilled network management to keep it all running reliably. Computer networks support an enormous number of applications and services such as access to the World Wide Web, digital video, digital audio, shared use of application and storage servers and fax machines, use of email and instant messaging applications as well as many others.
Computer networks differ in the transmission medium used to carry their signals, communications protocols to organize network traffic, the network's size, traffic control mechanism and organizational intent. The best-known computer network is the Internet; the chronology of significant computer-network developments includes: In the late 1950s, early networks of computers included the U. S. military radar system Semi-Automatic Ground Environment. In 1959, Anatolii Ivanovich Kitov proposed to the Central Committee of the Communist Party of the Soviet Union a detailed plan for the re-organisation of the control of the Soviet armed forces and of the Soviet economy on the basis of a network of computing centres, the OGAS. In 1960, the commercial airline reservation system semi-automatic business research environment went online with two connected mainframes. In 1963, J. C. R. Licklider sent a memorandum to office colleagues discussing the concept of the "Intergalactic Computer Network", a computer network intended to allow general communications among computer users.
In 1964, researchers at Dartmouth College developed the Dartmouth Time Sharing System for distributed users of large computer systems. The same year, at Massachusetts Institute of Technology, a research group supported by General Electric and Bell Labs used a computer to route and manage telephone connections. Throughout the 1960s, Paul Baran and Donald Davies independently developed the concept of packet switching to transfer information between computers over a network. Davies pioneered the implementation of the concept with the NPL network, a local area network at the National Physical Laboratory using a line speed of 768 kbit/s. In 1965, Western Electric introduced the first used telephone switch that implemented true computer control. In 1966, Thomas Marill and Lawrence G. Roberts published a paper on an experimental wide area network for computer time sharing. In 1969, the first four nodes of the ARPANET were connected using 50 kbit/s circuits between the University of California at Los Angeles, the Stanford Research Institute, the University of California at Santa Barbara, the University of Utah.
Leonard Kleinrock carried out theoretical work to model the performance of packet-switched networks, which underpinned the development of the ARPANET. His theoretical work on hierarchical routing in the late 1970s with student Farouk Kamoun remains critical to the operation of the Internet today. In 1972, commercial services using X.25 were deployed, used as an underlying infrastructure for expanding TCP/IP networks. In 1973, the French 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. In 1973, Robert Metcalfe wrote a formal memo at Xerox PARC describing Ethernet, a networking system, based on the Aloha network, developed in the 1960s by Norman Abramson and colleagues at the University of Hawaii. In July 1976, Robert Metcalfe and David Boggs published their paper "Ethernet: Distributed Packet Switching for Local Computer Networks" and collaborated on several patents received in 1977 and 1978.
In 1979, Robert Metcalfe pursued making Ethernet an open standard. In 1976, John Murphy of Datapoint Corporation created ARCNET, a token-passing network first used to share storage devices. In 1995, the transmission speed capacity for Ethernet increased from 10 Mbit/s to 100 Mbit/s. By 1998, Ethernet supported transmission speeds of a Gigabit. Subsequently, higher speeds of up to 400 Gbit/s were added; the ability of Ethernet to scale is a contributing factor to its continued use. Computer networking may be considered a branch of electrical engineering, electronics engineering, telecommunications, computer science, information technology or computer engineering, since it relies upon the theoretical and practical application of the related disciplines. A computer network facilitates interpersonal communications allowing users to communicate efficiently and via various means: email, instant messaging, online chat, video telephone calls, video conferencing. A network allows sharing of computing resources.
Users may access and use resources provided by devices on the network, such as printing a document on a shared network printer or use of a shared storage device. A network allows sharing of files, and
The Internet is the global system of interconnected computer networks that use the Internet protocol suite to link devices worldwide. It is a network of networks that consists of private, academic and government networks of local to global scope, linked by a broad array of electronic and optical networking technologies; the Internet carries a vast range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web, electronic mail and file sharing. Some publications no longer capitalize "internet"; the origins of the Internet date back to research commissioned by the federal government of the United States in the 1960s to build robust, fault-tolerant communication with computer networks. The primary precursor network, the ARPANET served as a backbone for interconnection of regional academic and military networks in the 1980s; the funding of the National Science Foundation Network as a new backbone in the 1980s, as well as private funding for other commercial extensions, led to worldwide participation in the development of new networking technologies, the merger of many networks.
The linking of commercial networks and enterprises by the early 1990s marked the beginning of the transition to the modern Internet, generated a sustained exponential growth as generations of institutional and mobile computers were connected to the network. Although the Internet was used by academia since the 1980s, commercialization incorporated its services and technologies into every aspect of modern life. Most traditional communication media, including telephony, television, paper mail and newspapers are reshaped, redefined, or bypassed by the Internet, giving birth to new services such as email, Internet telephony, Internet television, online music, digital newspapers, video streaming websites. Newspaper and other print publishing are adapting to website technology, or are reshaped into blogging, web feeds and online news aggregators; the Internet has enabled and accelerated new forms of personal interactions through instant messaging, Internet forums, social networking. Online shopping has grown exponentially both for major retailers and small businesses and entrepreneurs, as it enables firms to extend their "brick and mortar" presence to serve a larger market or sell goods and services online.
Business-to-business and financial services on the Internet affect supply chains across entire industries. The Internet has no single centralized governance in either technological implementation or policies for access and usage; the overreaching definitions of the two principal name spaces in the Internet, the Internet Protocol address space and the Domain Name System, are directed by a maintainer organization, the Internet Corporation for Assigned Names and Numbers. The technical underpinning and standardization of the core protocols is an activity of the Internet Engineering Task Force, a non-profit organization of loosely affiliated international participants that anyone may associate with by contributing technical expertise. In November 2006, the Internet was included on USA Today's list of New Seven Wonders; when the term Internet is used to refer to the specific global system of interconnected Internet Protocol networks, the word is a proper noun that should be written with an initial capital letter.
In common use and the media, it is erroneously not capitalized, viz. the internet. Some guides specify that the word should be capitalized when used as a noun, but not capitalized when used as an adjective; the Internet is often referred to as the Net, as a short form of network. As early as 1849, the word internetted was used uncapitalized as an adjective, meaning interconnected or interwoven; the designers of early computer networks used internet both as a noun and as a verb in shorthand form of internetwork or internetworking, meaning interconnecting computer networks. The terms Internet and World Wide Web are used interchangeably in everyday speech. However, the World Wide Web or the Web is only one of a large number of Internet services; the Web is a collection of interconnected documents and other web resources, linked by hyperlinks and URLs. As another point of comparison, Hypertext Transfer Protocol, or HTTP, is the language used on the Web for information transfer, yet it is just one of many languages or protocols that can be used for communication on the Internet.
The term Interweb is a portmanteau of Internet and World Wide Web used sarcastically to parody a technically unsavvy user. Research into packet switching, one of the fundamental Internet technologies, started in the early 1960s in the work of Paul Baran and Donald Davies. Packet-switched networks such as the NPL network, ARPANET, the Merit Network, CYCLADES, Telenet were developed in the late 1960s and early 1970s; the ARPANET project led to the development of protocols for internetworking, by which multiple separate networks could be joined into a network of networks. ARPANET development began with two network nodes which were interconnected between the Network Measurement Center at the University of California, Los Angeles Henry Samueli School of Engineering and Applied Science directed by Leonard Kleinrock, the NLS system at SRI International by Douglas Engelbart in Menlo Park, California, on 29 October 1969; the third site was the Culler-Fried Interactive Mathematics Center at the University of California, Santa Barbara, followed by the University of
Engineering is the application of knowledge in the form of science and empirical evidence, to the innovation, construction and maintenance of structures, materials, devices, systems and organizations. The discipline of engineering encompasses a broad range of more specialized fields of engineering, each with a more specific emphasis on particular areas of applied mathematics, applied science, types of application. See glossary of engineering; the term engineering is derived from the Latin ingenium, meaning "cleverness" and ingeniare, meaning "to contrive, devise". The American Engineers' Council for Professional Development has defined "engineering" as: The creative application of scientific principles to design or develop structures, apparatus, or manufacturing processes, or works utilizing them singly or in combination. Engineering has existed since ancient times, when humans devised inventions such as the wedge, lever and pulley; the term engineering is derived from the word engineer, which itself dates back to 1390 when an engine'er referred to "a constructor of military engines."
In this context, now obsolete, an "engine" referred to a military machine, i.e. a mechanical contraption used in war. Notable examples of the obsolete usage which have survived to the present day are military engineering corps, e.g. the U. S. Army Corps of Engineers; the word "engine" itself is of older origin deriving from the Latin ingenium, meaning "innate quality mental power, hence a clever invention."Later, as the design of civilian structures, such as bridges and buildings, matured as a technical discipline, the term civil engineering entered the lexicon as a way to distinguish between those specializing in the construction of such non-military projects and those involved in the discipline of military engineering. The pyramids in Egypt, the Acropolis and the Parthenon in Greece, the Roman aqueducts, Via Appia and the Colosseum, Teotihuacán, the Brihadeeswarar Temple of Thanjavur, among many others, stand as a testament to the ingenuity and skill of ancient civil and military engineers.
Other monuments, no longer standing, such as the Hanging Gardens of Babylon, the Pharos of Alexandria were important engineering achievements of their time and were considered among the Seven Wonders of the Ancient World. The earliest civil engineer known by name is Imhotep; as one of the officials of the Pharaoh, Djosèr, he designed and supervised the construction of the Pyramid of Djoser at Saqqara in Egypt around 2630–2611 BC. Ancient Greece developed machines in both military domains; the Antikythera mechanism, the first known mechanical computer, the mechanical inventions of Archimedes are examples of early mechanical engineering. Some of Archimedes' inventions as well as the Antikythera mechanism required sophisticated knowledge of differential gearing or epicyclic gearing, two key principles in machine theory that helped design the gear trains of the Industrial Revolution, are still used today in diverse fields such as robotics and automotive engineering. Ancient Chinese, Greek and Hungarian armies employed military machines and inventions such as artillery, developed by the Greeks around the 4th century BC, the trireme, the ballista and the catapult.
In the Middle Ages, the trebuchet was developed. Before the development of modern engineering, mathematics was used by artisans and craftsmen, such as millwrights, clock makers, instrument makers and surveyors. Aside from these professions, universities were not believed to have had much practical significance to technology. A standard reference for the state of mechanical arts during the Renaissance is given in the mining engineering treatise De re metallica, which contains sections on geology and chemistry. De re metallica was the standard chemistry reference for the next 180 years; the science of classical mechanics, sometimes called Newtonian mechanics, formed the scientific basis of much of modern engineering. With the rise of engineering as a profession in the 18th century, the term became more narrowly applied to fields in which mathematics and science were applied to these ends. In addition to military and civil engineering, the fields known as the mechanic arts became incorporated into engineering.
Canal building was an important engineering work during the early phases of the Industrial Revolution. John Smeaton was the first self-proclaimed civil engineer and is regarded as the "father" of civil engineering, he was an English civil engineer responsible for the design of bridges, canals and lighthouses. He was a capable mechanical engineer and an eminent physicist. Using a model water wheel, Smeaton conducted experiments for seven years, determining ways to increase efficiency. Smeaton introduced iron gears to water wheels. Smeaton made mechanical improvements to the Newcomen steam engine. Smeaton designed the third Eddystone Lighthouse where he pioneered the use of'hydraulic lime' and developed a technique involving dovetailed blocks of granite in the building of the lighthouse, he is important in the history, rediscovery of, development of modern cement, because he identified the compositional requirements needed to obtain "hydraulicity" in lime.