Internet
The
Internet is a global system of interconnected
computer networks that use the standard
Internet Protocol Suite (TCP/IP) to serve billions of users worldwide. It is a
network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless and optical networking technologies. The Internet carries a vast range of
information resources and services, such as the inter-linked
hypertext documents of the
World Wide Web (WWW) and the infrastructure to support
electronic mail.
Most traditional communications media including telephone, music, film, and television are reshaped or redefined by the Internet, giving birth to new services such as
Voice over Internet Protocol (VoIP) and
IPTV. Newspaper, book and other print publishing are adapting to
Web site technology, or are reshaped into
blogging and
web feeds. The Internet has enabled or accelerated new forms of human interactions through
instant messaging,
Internet forums, and
social networking.
Online shopping has boomed both for major retail outlets and small
artisans and traders.
Business-to-business and
financial services on the Internet affect
supply chains across entire industries.
The origins of the Internet reach back to research of the 1960s, commissioned by the United States government in collaboration with private commercial interests to build robust, fault-tolerant, and distributed computer networks. The funding of a new U.S.
backbone by the
National Science Foundation in the 1980s, as well as private funding for other commercial backbones, led to worldwide participation in the development of new networking technologies, and the merger of many networks. The
commercialization of what was by the 1990s an international network resulted in its popularization and incorporation into virtually every aspect of modern human life. As of 2009, an estimated quarter of Earth's population used the services of the Internet.
The Internet has no centralized governance in either technological implementation or policies for access and usage; each constituent network sets its own standards. Only 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 (ICANN). The technical underpinning and standardization of the core protocols (
IPv4 and
IPv6) is an activity of the
Internet Engineering Task Force (IETF), a non-profit organization of loosely affiliated international participants that anyone may associate with by contributing technical expertise.
Terminology
Internet is a short form of the technical term
internetwork,
[1] the result of interconnecting computer networks with special gateways or routers. The Internet is also often referred to as
the Net.
The term
the Internet, when referring to the entire global system of IP networks, has been treated as a
proper noun and written with an initial
capital letter. In the media and popular culture a trend has also developed to regard it as a generic term or common noun and thus write it as "the internet", without capitalization. Some guides specify that the word should be capitalized as a noun but not capitalized as an adjective.
Depiction of the Internet as a
cloud in network diagrams
The terms
Internet and
World Wide Web are often used in everyday speech without much distinction. However, the Internet and the
World Wide Web are not one and the same. The Internet is a global data communications system. It is a hardware and software
infrastructure that provides connectivity between computers. In contrast, the Web is one of the services communicated via the Internet. It is a collection of interconnected documents and other
resources, linked by
hyperlinks and
URLs.
[2]
In many technical illustrations when the precise location or interrelation of Internet resources is not important, extended networks such as the Internet are often depicted as a cloud.
[3] The verbal image has been formalized in the newer concept of
cloud computing.
History
The
USSR's launch of
Sputnik spurred the United States to create the
Advanced Research Projects Agency (ARPA or DARPA) in February
1958 to regain a technological lead.
[4][5] ARPA created the
Information Processing Technology Office (IPTO) to further the research of the
Semi Automatic Ground Environment (SAGE) program, which had networked country-wide
radar systems together for the first time. The IPTO's purpose was to find ways to address the US military's concern about survivability of their communications networks, and as a first step interconnect their computers at the
Pentagon,
Cheyenne Mountain, and
Strategic Air Command headquarters (SAC).
J. C. R. Licklider, a promoter of universal networking, was selected to head the IPTO. Licklider moved from the Psycho-Acoustic Laboratory at
Harvard University to
MIT in
1950, after becoming interested in
information technology. At MIT, he served on a committee that established
Lincoln Laboratory and worked on the SAGE project. In
1957 he became a Vice President at
BBN, where he bought the first production
PDP-1 computer and conducted the first public demonstration of
time-sharing.
At the IPTO, Licklider's successor
Ivan Sutherland in 1965 got
Lawrence Roberts to start a project to make a network, and Roberts based the technology on the work of
Paul Baran,
[6] who had written an exhaustive study for the
United States Air Force that recommended
packet switching (opposed to
circuit switching) to achieve better network robustness and disaster survivability. Roberts had worked at the
MIT Lincoln Laboratory originally established to work on the design of the SAGE system. UCLA professor
Leonard Kleinrock had provided the theoretical foundations for packet networks in 1962, and later, in the 1970s, for
hierarchical routing, concepts which have been the underpinning of the development towards today's Internet.
Sutherland's successor
Robert Taylor convinced Roberts to build on his early packet switching successes and come and be the IPTO Chief Scientist. Once there, Roberts prepared a report called
Resource Sharing Computer Networks which was approved by Taylor in June 1968 and laid the foundation for the launch of the working ARPANET the following year.
After much work, the first two nodes of what would become the
ARPANET were interconnected between Kleinrock's Network Measurement Center at the
UCLA's School of Engineering and Applied Science and
Douglas Engelbart's NLS system at
SRI International (SRI) in
Menlo Park, California, on 29 October 1969. The third site on the ARPANET was the Culler-Fried Interactive Mathematics center at the University of California at Santa Barbara, and the fourth was the
University of Utah Graphics Department. In an early sign of future growth, there were already fifteen sites connected to the young ARPANET by the end of 1971.
In an independent development,
Donald Davies at the
UK National Physical Laboratory developed the concept of packet switching in the early 1960s, first giving a talk on the subject in 1965, after which the teams in the new field from two sides of the Atlantic ocean first became acquainted. It was actually Davies' coinage of the wording
packet and
packet switching that was adopted as the standard terminology. Davies also built a packet-switched network in the UK, called the Mark I in 1970.
[7] Bolt, Beranek & Newman (BBN), the private contractors for ARPANET, set out to create a separate commercial version after establishing "value added carriers" was legalized in the U.S.
[8] The network they established was called
Telenet and began operation in 1975, installing free public
dial-up access in cities throughout the U.S. Telenet was the first packet-switching network open to the general public.
[9]
Following the demonstration that packet switching worked on the ARPANET, the
British Post Office,
Telenet,
DATAPAC and TRANSPAC collaborated to create the first international packet-switched network service. In the UK, this was referred to as the
International Packet Switched Service (IPSS), in
1978. The collection of
X.25-based networks grew from Europe and the US to cover Canada, Hong Kong and Australia by 1981. The X.25 packet switching standard was developed in the CCITT (now called
ITU-T) around 1976. X.25 was independent of the TCP/IP protocols that arose from the experimental work of DARPA on the ARPANET, Packet Radio Net, and Packet Satellite Net during the same time period.
The early ARPANET ran on the
Network Control Program (NCP), implementing the host-to-host connectivity and switching layers of the protocol stack, designed and first implemented in December 1970 by a team called the Network Working Group (NWG) led by
Steve Crocker. To respond to the network's rapid growth as more and more locations connected,
Vinton Cerf and
Robert Kahn developed the first description of the now widely used TCP protocols during 1973 and published a paper on the subject in May 1974. Use of the term "Internet" to describe a single global
TCP/IP network originated in December 1974 with the publication of
RFC 675, the first full specification of TCP that was written by Vinton Cerf, Yogen Dalal and Carl Sunshine, then at
Stanford University. During the next nine years, work proceeded to refine the protocols and to implement them on a wide range of operating systems. The first
TCP/IP-based wide-area network was operational by 1 January 1983 when all hosts on the ARPANET were switched over from the older NCP protocols.
T3 NSFNET Backbone, c. 1992
In 1985, the United States'
National Science Foundation (NSF) commissioned the construction of the
NSFNET, a university 56
kilobit/second network backbone using computers called "
fuzzballs" by their inventor,
David L. Mills. The following year, NSF sponsored the conversion to a higher-speed 1.5
megabit/second network that became operational in 1988. A key decision to use the DARPA
TCP/IP protocols was made by Dennis Jennings, then in charge of the Supercomputer program at NSF. The NSFNET backbone was upgraded to 45 Mbps in 1991 and decommissioned in 1995 when it was replaced by new backbone networks operated by commercial
Internet Service Providers.
The opening of the NSFNET to other networks began in 1988.
[10] The US Federal Networking Council approved the interconnection of the NSFNET to the commercial
MCI Mail system in that year and the link was made in the summer of 1989. Other commercial electronic mail services were soon connected, including OnTyme, Telemail and Compuserve. In that same year, three commercial Internet service providers (ISPs) began operations:
UUNET,
PSINet, and CERFNET. Important, separate networks that offered gateways into, then later merged with, the Internet include
Usenet and
BITNET. Various other commercial and educational networks, such as
Telenet (by that time renamed to Sprintnet),
Tymnet,
Compuserve and
JANET were interconnected with the growing Internet in the 1980s as the TCP/IP protocol became increasingly popular. The adaptability of TCP/IP to existing communication networks allowed for rapid growth. The open availability of the specifications and reference code permitted commercial vendors to build interoperable network components, such as routers, making standardized network gear available from many companies. This aided in the rapid growth of the Internet and the proliferation of local-area networking. It seeded the widespread implementation and rigorous standardization of TCP/IP on
UNIX and virtually every other common operating system.
Although the basic applications and guidelines that make the Internet possible had existed for almost two decades, the network did not gain a public face until the 1990s. On 6 August 1991,
CERN, a pan-European organization for particle research, publicized the new
World Wide Web project. The Web was invented by British scientist
Tim Berners-Lee in 1989. An early popular
web browser was
ViolaWWW, patterned after
HyperCard and built using the
X Window System. It was eventually replaced in popularity by the
Mosaic web browser. In 1993, the
National Center for Supercomputing Applications at the
University of Illinois released version 1.0 of Mosaic, and by late 1994 there was growing public interest in the previously academic, technical Internet. By 1996 usage of the word
Internet had become commonplace, and consequently, so had its use as a
synecdoche in reference to the World Wide Web.
Meanwhile, over the course of the decade, the Internet successfully accommodated the majority of previously existing public computer networks (although some networks, such as
FidoNet, have remained separate). During the late 1990s, it was estimated that traffic on the public Internet grew by 100 percent per year, while the mean annual growth in the number of Internet users was thought to be between 20% and 50%.
[11] This growth is often attributed to the lack of central administration, which allows organic growth of the network, as well as the non-proprietary open nature of the Internet protocols, which encourages vendor interoperability and prevents any one company from exerting too much control over the network.
[12] The estimated population of
Internet users is 1.97 billion as of 30 June 2010.
[13]
From 2009 onward, the Internet is expected to grow significantly in
Brazil,
Russia,
India,
China, and
Indonesia (BRICI countries). These countries have large
populations and moderate to high economic growth, but still low Internet penetration rates. In 2009, the BRICI countries represented about 45 percent of the world's population and had approximately 610 million Internet users, but by 2015, Internet users in BRICI countries will double to 1.2 billion, and will triple in Indonesia.
[14][15]
Technology
Protocols
The complex communications infrastructure of the Internet consists of its hardware components and a system of software layers that control various aspects of the architecture. While the hardware can often be used to support other software systems, it is the design and the rigorous standardization process of the software architecture that characterizes the Internet and provides the foundation for its scalability and success. The responsibility for the architectural design of the Internet software systems has been delegated to the
Internet Engineering Task Force (IETF).
[16] The IETF conducts standard-setting work groups, open to any individual, about the various aspects of Internet architecture. Resulting discussions and final standards are published in a series of publications, each called a
Request for Comments (RFC), freely available on the IETF web site. The principal methods of networking that enable the Internet are contained in specially designated RFCs that constitute the
Internet Standards. Other less rigorous documents are simply informative, experimental, or historical, or document the best current practices (BCP) when implementing Internet technologies.
The Internet Standards describe a framework known as the
Internet Protocol Suite. This is a model architecture that divides methods into a layered system of protocols (
RFC 1122,
RFC 1123). The layers correspond to the environment or scope in which their services operate. At the top is the
Application Layer, the space for the application-specific networking methods used in software applications, e.g., a web browser program. Below this top layer, the
Transport Layer connects applications on
different hosts via the network (e.g.,
client–server model) with appropriate data exchange methods. Underlying these layers are the core networking technologies, consisting of two layers. The
Internet Layer enables computers to identify and locate each other via
Internet Protocol (IP) addresses, and allows them to connect to one-another via intermediate (transit) networks. Lastly, at the bottom of the architecture, is a software layer, the
Link Layer, that provides connectivity between hosts on the same local network link, such as a local area network (
LAN) or a
dial-up connection. The model, also known as
TCP/IP, is designed to be independent of the underlying hardware which the model therefore does not concern itself with in any detail. Other models have been developed, such as the
Open Systems Interconnection (OSI) model, but they are not compatible in the details of description, nor implementation, but many similarities exist and the TCP/IP protocols are usually included in the discussion of OSI networking.
The most prominent component of the Internet model is the
Internet Protocol (IP) which provides addressing systems (
IP addresses) for computers on the Internet. IP enables
internetworking and essentially establishes the Internet itself. IP Version 4 (
IPv4) is the initial version used on the first generation of the today's Internet and is still in dominant use. It was designed to address up to ~4.3 billion (10
9) Internet hosts. However, the explosive growth of the Internet has led to
IPv4 address exhaustion which is estimated to enter its final stage in approximately 2011.
[17] A new protocol version,
IPv6, was developed in the mid 1990s which provides vastly larger addressing capabilities and more efficient routing of Internet traffic.
IPv6 is currently in commercial
deployment phase around the world and Internet address registries (
RIRs) have begun to urge all resource managers to plan rapid adoption and conversion.
[18]
IPv6 is not interoperable with IPv4. It essentially establishes a "parallel" version of the Internet not directly accessible with IPv4 software. This means software upgrades or translator facilities are necessary for every networking device that needs to communicate on the IPv6 Internet. Most modern computer operating systems are already converted to operate with both versions of the Internet Protocol. Network infrastructures, however, are still lagging in this development. Aside from the complex physical connections that make up its infrastructure, the Internet is facilitated by bi- or multi-lateral commercial contracts (e.g.,
peering agreements), and by technical specifications or
protocols that describe how to exchange
data over the network. Indeed, the Internet is defined by its interconnections and routing policies.
Structure
The Internet structure and its usage characteristics have been studied extensively. It has been determined that both the Internet IP routing structure and hypertext links of the World Wide Web are examples of
scale-free networks. Similar to the way the commercial Internet providers connect via
Internet exchange points, research networks tend to interconnect into large subnetworks such as
GEANT,
GLORIAD,
Internet2 (successor of the
Abilene Network), and the UK's
national research and education network JANET. These in turn are built around smaller networks (see also the list of
academic computer network organizations).
Many computer scientists describe the Internet as a "prime example of a large-scale, highly engineered, yet highly complex system".
[19] The Internet is extremely heterogeneous; for instance,
data transfer rates and physical characteristics of connections vary widely. The Internet exhibits "
emergent phenomena" that depend on its large-scale organization. For example, data transfer rates exhibit temporal
self-similarity. The principles of the routing and addressing methods for traffic in the Internet reach back to their origins the 1960s when the eventual scale and popularity of the network could not be anticipated. Thus, the possibility of developing alternative structures is investigated.
[20]
