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Local area networks (LANs).

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DEFINITION The concept of local area networks (LANs) is not new. It represents a logical development of computer technology. With the advent of microcomputers in the 1980s many office workers began bringing their own disks into work, compromising data integrity. They also began keeping their own databases, which companies did not like. The answer was to create a computer network. A computer network is a group of computers connected together enabling users to share resources and communicate with each other. Resources can be hardware, software, or data. Without a network, each employee might require a dedicated printer connected to his workstation or individual copies of application software loaded on his workstation. A network will also allow dissimilar computers to communicate and share resources. This means that an IBM PC can communicate with an Apple Macintosh with ease. There are three general types of networks: Local Area Networks (LANs), Metropolitan Area Networks (MANs), and Wide Area Networks (WANs). They are described or classified by the area of coverage and by the method of information exchange. A LAN encompasses two or more computers connected by one or more types of medium (usually wire) located within close proximity of each other. This distance is generally limited to 2 kilometers. ...read more.


Servers are identified by the service they provide. A disk server might contain several CDs or Hard Drives with applications to be shared across the network. A file server usually stores files and folders and provides the core services of a network. In order for any workstation to be able to connect to a network it will need an access point. This is normally known as a Network Interface Card (NIC). NICs provide signal and protocol conversion between network adapters and the transmission media. Signal conversion is accomplished by the Media Attachment Unit (MAU), while protocol conversion is the job of the Host Access Unit (HAU). NICs can support a variety of modes, including Ethernet, Token Ring, fiber optics, and wireless networks. A workstation can also connect remotely via a public switched telephone network using a Modulator/Demodulator (Modem). These can be either internal or external, although they are more commonly found to be internal. Modems must always operate in pairs. A second modem must be connected to the distant end of the communications link to demodulate the signal. They must also operate under the same protocol. Repeaters allow a network to extend to distances not normally allowable by using cabling alone. Signals sent through cables are affected by noise and will degenerate in proportion to the length of the cable. ...read more.


Network software came along in 1984 with IBM's Network Basic Input/Output System (NETBIOS). This was the first rationalization of a PC networking software creating a point-to-point communication between computers. Of course, each computer needed it's own operating system. Enter MS-DOS. With the release of Microsoft's MS-DOS 3.1 in late 1984, the concept of accessing files on a remote server, simultaneously with other users became a possibility. This, of course, led to the creation of a network operating system, necessary to use any network. Novell Netware, one of the most portable network operating systems, was the first to take advantage of the new technology. What protocols are used in a network is very important in selecting a network operating system. The most commonly used protocols are TCP/IP and IPX/SPX. Microsoft, of course, has it's own protocol, NETBeui, but this is a non-routable protocol so it can only be used in LANs and not MANs or WANs. Today, the most commonly used network operating systems are Windows NT and 2000, as well as Sun Microsystems Solaris 8. There are advantages and disadvantages to each, but they are too extensive to go into detail. For the purpose of this paper we will consider them equal. Well, now we have all necessary hardware and software, so putting together a network should be easy as pie, right? Right... Fernando A. Castro 1 IS315 ...read more.

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