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Brief History of the Internet

The original ARPANET grew into the Internet. Internet was based on the idea that there would be multiple independent networks of rather arbitrary design, beginning with the ARPANET as the pioneering packet switching network, but soon to include packet satellite networks, ground-based packet radio networks and other networks. The Internet as we now know it embodies a key underlying technical idea, namely that of open architecture networking. In this approach, the choice of any individual network technology was not dictated by a particular network architecture but rather could be selected freely by a provider and made to interwork with the other networks through a meta-level "Internetworking Architecture".

Thus, Kahn decided to develop a new version of the protocol which could meet the needs of an open-architecture network environment. This protocol would eventually be called the Transmission Control Protocol/Internet Protocol (TCP/IP). While NCP tended to act like a device driver, the new protocol would be more like a communications protocol.

Four ground rules were critical to Kahn's early thinking:


Each distinct network would have to stand on its own and no internal changes could be required to any such network to connect it to the Internet.

Communications would be on a best effort basis. If a packet didn't make it to the final destination, it would shortly be retransmitted from the source.

Black boxes would be used to connect the networks; these would later be called gateways and routers. There would be no information retained by the gateways about the individual flows of packets passing through them, thereby keeping them simple and avoiding complicated adaptation and recovery from various failure modes.

There would be no global control at the operations level.
Other key issues that needed to be addressed were:


Algorithms to prevent lost packets from permanently disabling communications and enabling them to be successfully retransmitted from the source.

Providing for host to host "pipelining" so that multiple packets could be enroute from source to destination at the discretion of the participating hosts, if the intermediate networks allowed it.

Gateway functions to allow it to forward packets appropriately. This included interpreting IP headers for routing, handling interfaces, breaking packets into smaller pieces if necessary, etc.

The need for end-end checksums, reassembly of packets from fragments and detection of duplicates, if any.

The need for global addressing

Techniques for host to host flow control.

Interfacing with the various operating systems

There were also other concerns, such as implementation efficiency, internetwork performance, but these were secondary considerations at first.

The internet is a grouping of private networks. The very protocol that allows this internetworking was made with the idea that there was no global control.

Widespread development of LANS, PCs and workstations in the 1980s allowed the nascent Internet to flourish. Ethernet technology, developed by Bob Metcalfe at Xerox PARC in 1973, is now probably the dominant network technology in the Internet and PCs and workstations the dominant computers. This change from having a few networks with a modest number of time-shared hosts (the original ARPANET model) to having many networks has resulted in a number of new concepts and changes to the underlying technology. First, it resulted in the definition of three network classes (A, B, and C) to accommodate the range of networks. Class A represented large national scale networks (small number of networks with large numbers of hosts); Class B represented regional scale networks; and Class C represented local area networks (large number of networks with relatively few hosts).

The shift to having a large number of independently managed networks (e.g., LANs) meant that having a single table of hosts was no longer feasible, and the Domain Name System (DNS) was invented by Paul Mockapetris of USC/ISI. The DNS permitted a scalable distributed mechanism for resolving hierarchical host names (e.g. www.acm.org) into an Internet address.

One of the more interesting challenges was the transition of the ARPANET host protocol from NCP to TCP/IP as of January 1, 1983. This was a "flag-day" style transition, requiring all hosts to convert simultaneously or be left having to communicate via rather ad-hoc mechanisms. This transition was carefully planned within the community over several years before it actually took place and went surprisingly smoothly (but resulted in a distribution of buttons saying "I survived the TCP/IP transition").

TCP/IP was adopted as a defense standard three years earlier in 1980. This enabled defense to begin sharing in the DARPA Internet technology base and led directly to the eventual partitioning of the military and non- military communities. By 1983, ARPANET was being used by a significant number of defense R&D and operational organizations. The transition of ARPANET from NCP to TCP/IP permitted it to be split into a MILNET supporting operational requirements and an ARPANET supporting research needs.

Thus, by 1985, Internet was already well established as a technology supporting a broad community of researchers and developers, and was beginning to be used by other communities for daily computer communications.

With the exception of BITNET and USENET, these early networks (including ARPANET) were purpose-built - i.e., they were intended for, and largely restricted to, closed communities of scholars; there was hence little pressure for the individual networks to be compatible and, indeed, they largely were not. In addition, alternate technologies were being pursued in the commercial sector, including XNS from Xerox, DECNet, and IBM's SNA. 8 It remained for the British JANET (1984) and U.S. NSFNET (1985) programs to explicitly announce their intent to serve the entire higher education community, regardless of discipline. Indeed, a condition for a U.S. university to receive NSF funding for an Internet connection was that "... the connection must be made available to ALL qualified users on campus."

A key to the rapid growth of the Internet has been the free and open access to the basic documents, especially the specifications of the protocols.

The beginnings of the ARPANET and the Internet in the university research community promoted the academic tradition of open publication of ideas and results. However, the normal cycle of traditional academic publication was too formal and too slow for the dynamic exchange of ideas essential to creating networks.

On October 24, 1995, the FNC unanimously passed a resolution defining the term Internet. This definition was developed in consultation with members of the internet and intellectual property rights communities. RESOLUTION: The Federal Networking Council (FNC) agrees that the following language reflects our definition of the term "Internet". "Internet" refers to the global information system that -- (i) is logically linked together by a globally unique address space based on the Internet Protocol (IP) or its subsequent extensions/follow-ons; (ii) is able to support communications using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite or its subsequent extensions/follow-ons, and/or other IP-compatible protocols; and (iii) provides, uses or makes accessible, either publicly or privately, high level services layered on the communications and related infrastructure described herein.