A. DARPA (Defense Advanced Research Projects Agency)
DARPA (Defense Advanced Research Projects Agency) is the independent research branch of the U.S. Department of Defense that funded a project that in time was to lead to the creation of the Internet.Originally called ARPA (the “D” was added to its name later), DARPA came into being in 1958 as a reaction to the success of Sputnik, Russia’s first manned satellite. DARPA’s explicit mission was (and still is) to think independently of the rest of the military and to respond quickly and innovatively to national defense challenges.
In the late 1960s, ARPA provided funds and oversight for a project aimed at interconnecting computers at four university research sites. By 1972, this initial network, now called the ARPANET, had grown to 37 computers. Because ARPA’s name was changed to Defense Advanced Research Projects Agency (DARPA) in 1971, some people refer to ARPANET as DARPANET. (DARPA was changed back to ARPA in 1993 and back to DARPA again in 1996.
B. ARPANET (Advanced Research Project Agency)
ARPANET (Advanced Research Projects Agency)was the network that became the basis for the Internet. Based on a concept first published in 1967, ARPANET was developed under the direction of the U.S. Advanced Research Projects Agency ARPA. In 1969, the idea became a modest reality with the interconnection of four university computers. The initial purpose was to communicate with and share computer resources among mainly scientific users at the connected institutions. ARPANET took advantage of the new idea of sending information in small units called packets that could be routed on different paths and reconstructed at their destination. The development of the TCO/IP protocol in the 1970s made it possible to expand the size of the network, which now had become a network of networks, in an orderly way.
In the 1980s, ARPANET was handed over to a separate new military network, the Defense Data Network, and NSFNET a network of scientific and academic computers funded by the National Science Foundation. In 1995, NSFNet in turn began a phased withdrawal to turn the backbone of the Internet (called vBNS) over to a consortium of commercial backbone providers (PSINet, UUNET,ANS/AOL, Sprint, MCI, and AGIS-Net99).
Because ARPA’s name was changed to Defense Advanced Research Projects Agency (DARPA) in 1971, ARPANET is sometimes referred to as DARPANET. (DARPA was changed back to ARPA in 1993 and back to DARPA again in 1996.) The history of ARPANET and developments leading up to today’s Internet can be found in Where Wizards Stay Up Late, by Katie Hafner and Matthew Lyon.
C.MILNET (Military Network)
MILNET (Military Network) was the name given to the part of the ARPANET internetwork designated for unclassified United States Department of Defens traffic.
MILNET was split off from the ARPANET in 1983: the ARPANET remained in service for the academic research community, but direct connectivity between the networks was severed for security reasons. Gateways relayed electronic mail between the two networks. BBN tecnologies built and managed both the MILNET and the ARPANET and the two networks used very similar technology. It is also known as “Military Net.”
During the 1980s the MILNET expanded to become the Defense Data Network a worldwide set of military networks running at different security levels. In the 1990s, MILNET became the NIPRNET.
D.National Science Foundation Network (NSFNET)
National Science Foundation Network (NSFNET)was a program of coordinated, evolving projects sponsored by the National Science Foundation beginning in 1985 to promote advanced research and education networking in the United States.
NSFNET was also the name given to several nationwide backbone networks that were constructed to support NSF’s networking initiatives from 1985-1995. Initially created to link researchers to the nation’s NSF-funded supercomputing centers, through further public funding and private industry partnerships it developed into a major part of the Internet backbone.
E. Internet Networking
- Local area networks (LANs)
Local area networks (LANs)are computer networks ranging in size from a few computers in a single office to hundreds or even thousands of devices spread across several buildings. They function to link computers together and provide shared access to printers, file servers, and other services. LANs in turn may be plugged into larger networks, such as larger LANs or wide area networks (WANs), connecting many computers within an organization to each other and/or to the Internet. Because the technologies used to build LANs are extremely diverse, it is impossible to describe them except in the most general way. Universal components consist of the physical media that connect devices, interfaces on the individual devices that connect to the media, protocols that transmit data across the network, and software that negotiates, interprets, and administers the network and its services. Many LANs also include signal repeaters and bridges or routers, especially if they are large or connect to other networks.The level of management required to run a LAN depends on the type, configuration, and number of devices involved, but in some cases it can be considerable.
- MAN (metropolitan area network)
MAN (metropolitan area network) is a larger network that usually spans several buildings in the same city or town. The IUB network is an example of a MAN.
- WAN (wide area network)
WAN (wide area networkin comparison to a MAN, is not restricted to a geographical location, although it might be confined within the bounds of a state or country. A WAN connects several LANs, and may be limited to an enterprise (a corporation or an organization) or accessible to the public. The technology is high speed and relatively expensive. The Internet is an example of a worldwide public WAN.