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Primary Function of Local Area Networks
To better understand the capabilities of local area networks, let’s examine their primary function and some typical activities and application areas. The majority of users expect a local area network to provide access to hardware and software resources that will allow them to perform one or more of the following activities in an office, academic, or manufactring environments: file serving, database and application serving, print serving, Internet accessing, e-mailing, video and music transfers, process control and monitoring, and distributed processing.
A local area network performs file serving when it’s connected to a workstation with a large storage disk drive that acts as a central storage repository, or file server. For example, when the local area network offers access to a high-level application such as a commercial project management application, the network stores the project management software (or a portion of it) on the file server and transfers a copy of it to the appropriate workstation on demand. By keeping all of the application on the server – or more likely, par of it on the server and part of it on the client workstation – the network can control access to the software and can reduce the amount of disk storage required on each user’s workstation for this application. For a second example, suppose two or more users wish to share a data set. In this case, the data set, like the application software, would be stored on the file server, while the network provided access to those users who had the appropriate permissions.
A local area network can also provide access to one or more high-quality printers. The local area network software called a print server provides workstations with the authorization to access a particular printer, accepts and queues prints jobs, prints cover sheets, and allows user access to the job queue for routine administrative functions.
Most local area networks provide the service of sending and receiving e-mail. This e-mail service can operate both within the local area network and between the local area network and other networks, such as the Internet. Stored somewhere on the network is a database of e-mail messages, both old and new. When users log in to access their e-mail, their messages are stored and retrieved from the e-mail server.
A local area network can interface with other local area networks, wide area networks (such as the Internet), and mainframe computers. Thus, a local area network is often the glue that holds together many different types of computer systems and networks. A company can use a local area network’s interfacing ability to enable its employees to interact with people external to the company, such as customers and suppliers. For example, if employees wished to send purchase orders to vendors, they could enter transactions on their workstations. These transactions would travel across the company’s local area network, which would be connected to a wide area network. The suppliers would eventually receive the orders by being connected to this wide area network through their own local area network.
Many higher-speed local area networks provide the capabilities of transferring video images and video streams. For example, a local area network could allow a user to transfer high-resolution graphic images, transfer video streams, and perform teleconferencing between two or more users.
In manufacturing and industrial environments, local area networks are often used to monitor manufacturing events and report and control their occurrence. The local area network provides process control and monitoring. An automobile assembly line that uses sensors to monitor partially completed automobiles and control robots for assembly is an excellent example of a local area network performing process control functions.
Depending on the type of network and the choice of network operation system, a local area network may support distributed processing in which a task is subdivided and sent to remote workstations on the network for execution. Often-times, these remote workstation are idle; thus, the distributed processing tasks amounts to the “stealing” of CPU time from other machines (and is often called grid computing). The results of these remote executions are then returned to the originating workstation for dissemination or further processing. By delegating tasks to those computers that are most capable of handling specific chores, the distribution of tasks or parts of tasks can lead to an increase in execution speed.
In addition to performing these common activities, a local area network can be an effective tool in many application areas. One of the most common application areas is an office environment. A local area network in an office can provide word processing, spreadsheet operations, database functions, electronic mail (e-mail) access, Internet access, electronic appointment scheduling, and graphic image creation capabilities over a wide variety of platforms and to a large number of workstations. Completed documents can be routed to high-quality printers to produce letterheads, graphically designed newsletters, and formal documents.
A second common application area for a local area network is an academics environment. In a laboratory setting, for example, a local area network can provide students with access to the tools necessary to complete homework assignments, send e-mail, and interact with the Internet. In a classroom setting, a local area network can enable professors to deliver tutorials and lessons with high-quality graphics and sound to students. Multiple workstations can be used to provide students with instruction at their own pace, while the instructor monitors and records each student’s progress at every workstation.
A third common application area for a local area network is manufacturing. In fact, modern assembly lines operate exclusively under the control of local area networks. As products move down the assembly line, sensors control position; robots perform mundane, exacting, or dangerous operations; and product subassemblies are inventoried and ordered. The modern automobile assembly line is a technological tour de force, incorporating numerous local area networks and mainframe computers.
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