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A computer network is defined as: "two or more computing devices equipped with transceivers attached to a shared media." Similar to what you see in figure 1, computer networks that are physically confined geographically to a location like a room, a building, a campus, or a hotspot are called Local Area Networks (LANs). The computing devices that are connected (including wireless devices) to the local area network are referred to as nodes or hosts. In order to communicate on a network each node must have a properly configured device which is capable of transmitting and receiving messages, this device is known as a transceiver or a network interface card (NIC). Each transceiver will send and receive messages over some type of media, usually copper wire, fiber optic cable, or in the case of wireless transceivers, over airwaves. As was just illustrated, the media used by the transceivers can vary depending on the transceiver type and the needs of the network. Today, most LAN nodes are interconnected using unshielded twisted-pair (UTP) cabling. If the node is wireless, more than likely, it will be using an 802.11g wireless transceiver which uses the 2.45 - 2.5 GHz band of radio frequencies(RF) to carry the data.
Large companies that have computers in many different locations around a city can form their own Metropolitan Area Networks (MANs) as shown in figure 2 and if they are spread throughout a single country or worldwide across many countries, they can create their own Wide Area Network (WAN) as shown in figure 3. In both the case of the MAN and the WAN, usually, a telecommunications provider (AT&T, Verizon, etc.) is needed to provide leased phones lines that connect one location's LAN to another location's LAN. Privately leased lines are expensive, the advantage to businesses and universities is privacy and security. Since the organizations leasing the lines are the only ones having access to them they are considered safe and secure, mainly because they are not using a public network like the Internet to transfer data from one location to another.
So how do all these private networks get together to form the Internet? Some say the journey began in 1946 when a comic science-fiction writer using the pen-name of Murray Leinster (real name William F. Jenkins) wrote a story called A Logic Named Joe which described, to some degree, concepts that would be used by the Internet decades later. In 1958, for defense purposes spurred on by the Cold War and Russia's launch of Sputnik, a branch of the United States Department of Defense (DOD) was established and referred to as the DOD's Advanced Research Projects Agency (DARPA) which was later renamed ARPA by officials who felt that the "D" (which represented the Department of Defense) should be removed from the acronym in order to make the organization's name less ominous sounding. The organization has since been renamed again back to DARPA. At about that same time, during the late 1950's, a gentleman by the name of J. C. R. Licklider, known as JCR or "Lick" to his friends, colleagues, and acquintances, worked as a vice-president at a company called Bolt, Beranek, and Newman (BBN). Based on the projects that Lick and his co-workers worked on at BBN, in 1960 he began writing a series of three papers known as the Galactic Network memos which described his vision of a galactic network - a network of computers that allows users to gather data and access computer programs anywhere in the world. The first paper he wrote Man-Computer Symbioses, described Licklider's view of man's interaction with computers and the need for computer time sharing.
A year later another Internet visionary and Massachusetts Institute of Technology (MIT) professor, Leonard Kleinrock, wrote a paper on packet switching networks. In 1962, Licklider wrote his second paper titled, On-Line Man Computer Communication, describing the concept of social interaction through the networking of computers; later that same year Lick was appointed as the first director of the Information Processing Techniques Office (IPTO) for ARPA.
In 1965, MIT researcher Lawrence G. Roberts and Thomas Merrill made the first interstate connection of computers by telephone line; proving that computer network communication would have to use "packets" to exchange data instead of using single bits at the circuit level. In 1966, Roberts joined DARPA and in 1967 completed drawing up a plan for realizing Lick's dream, the ARPAnet. In 1968, Licklider and Robert W. Taylor wrote the third and final paper about Lick's Galactic Network which was titled The Computer as a Communication Device. Further work by Robert Kahn, Kleinrock, and others brought the ARPAnet closer to fruition until in 1969 it became a reality. The now UCLA computer science professor Kleinrock and U.S. DOD contractor BBN were instrumental in establishing communication between the first two nodes of the ARPAnet, UCLA and the Stanford Research Institute (SRI), on October 29, 1969 with the implementation of two Internet Message Processors (IMPs) installed at each site. Professor Kleinrock was supervising his student/programmer Charley Kline (CSK) and they set up a message transmission to go from the UCLA SDS Sigma 7 Host computer to another programmer, Bill Duvall, at the SRI SDS 940 Host computer. The transmission itself was simply to "login" to SRI from UCLA. They succeeded in transmitting the "l" and the "o" and then the system crashed! Hence, the first message on the Internet was "lo", as in "lo and behold! They were able to do the full login about an hour later.
The first communication protocol designed for use on the ARPAnet was called the Network Control Protocol (NCP). During the year 1970 the Arpanet is growing at the rate of one node added per month. In 1972, Ray Tomlinson of BBN writes the first email program to send messages across the ARPAnet, he uses the @ sign to test his program by sending a an email to himself. In 1973 Vint Cerf and Robert Kahn began writing a paper later published in May 1974 describing the Transmission Control Protocols (TCP). In December of 1974 the term "Internet" began to be used to describe a global TCP/IP-based network of the ARPAnet along with several other, mainly X.25-based, networks that were cropping up in the U.S. as well as Canada and Europe (Britain & France).
In the beginning there was a lot of resistance by large companies, research facilities, and places of higher learning to join the Arpanet; all of them had large, powerful computer networks of their own, and didn't really want to share them with others, so their acceptance of the idea of joining their networks together with others via a public, unsecured, network was not a vision embraced by many network administrators of the day. The Internet then got a little more prompting from the U.S. government. In 1988, Vice President Al Gore, heard a report titled Toward a National Research Network by UCLA's Kleinrock (view book on right) , which prompted Gore to introduce a bill into congress, the High Performance Computing and Communication Act of 1991 which led to the creation of a document called the National Information Infrastructure (NII) defining four Network Access Points (NAPs) to be located in Washington D.C., Pennsauken, N.J., Chicago, Il. and San Francisco, CA, for providing regional access to what was then emerging into the mother of all WANs, the Internet. The National Science Foundation (NSF) awarded contracts for operations and maintenance of the original four NAPs to MFS Datanet, Sprint, Ameritech, and Pacific Bell respectively.
As more and more people who had influence over the huge and previously private data networks realized the benefits of the Internet, one by one they began joining. The Internet began growing rapidly, by 1990 the ARPAnet was phased out. In 1991 the Gopher protocol was released by the University of Minnesota, and the World Wide Web (WWW) is developed by Tim Berners-Lee and released by the European Organization for Nuclear Research - CERN, and the rest as they say "is history."
Several telecommunications mergers have occurred since the formation of the original NAPs resulting in many of the NAPs being owned by Verizon, who subsequently bought MCI. MCI owned a trademark on Metropolitan Area Exchanges (MAE), so you'll hear many of the Internet's NAPs also referred to as MAEs, i.e. MAE-West or MAE-East. But, not all NAPs were MAEs! Today, NAP is a legacy term only found in the history books and the huge infrastructure of access points to the Internet are called Internet Exchange Points (IXPs).
Telecommunications providers, Verizon, AT&T, Sprint, and the like, are big players on the Internet because they provide the connectivity between all those LANs, MANs and WANS. Follow the three links below to learn more about the Internet backbone providers. The first link leads you to a page of more links, this is Russ Haynal's Internet Map Collection. With all of the mergers between telecommunications companies lately, many of Haynai's links are now broken. The next two links give you an example of how large these telecommunication networks are.
Attached to those IXPs are Internet Service Providers (ISPs). You, like most, connect to the Internet through an ISP. Now many times the ISP is also your local telephone company, but not always, in fact due to the Telecommunications Act of 1996 competition for your communications dollars is still quite robust although it's hard to tell how long that will last as huge telecomms continue to gobble up the littler ones.
An ISP provides you with "Internet Service," in other words they give you connectivity to the rest of the Internet through their network which is ultimately attached to a IXP. In a home environment ISPs pretty much do all of the work for you. They will install your Internet router, attach your home network to it, and configure all of the necessary settings to get the homeowner up and running with access to the Internet including an all important "IP address." In a business environment ISPs will provide any wiring necessary up to the Maximum Point of Entry (MPoE) or the company's Main Distribution Facility (MDF). It is up to the company's IT personnel to get their LAN configured to work with the ISP's Internet connection.