Communications Networks

Communications channels and hardware may have different layouts or networks, varying in size from large to small: wide area networks (WANs), metropolitan area networks (MANs), and local networks.

Features of networks are hosts, nodes, downloading, and uploading.

Networks allow users to share peripheral devices, programs, and data; to have better communications; to have more secure information; and to have access to databases.

A network, or com­munications network, is a system of interconnected computers, telephones, or other communications devices that can communicate with one another and share applications and data. Here let us consider the following:

· Types of networks—wide area, metropolitan area, and local

· Some network features

· Advantages of networks

Types of Networks: Wide Area, Metropolitan Area, & Local

Networks are categorized principally in the following three sizes:

· Wide area networks: A wide area network (WAN) is a communications network that covers a wide geographical area, such as a state or a country. The international pathway Internet links together hundreds of computer WANs. Most telephone systems—long-distance and local—are WANs.

· Metropolitan area network: A metropolitan area network (MAN) is a communica-tions network covering a geographic area the size of a city or suburb. The purpose of a MAN is often to bypass local telephone compa­nies when accessing long-distance services. Cellular phone systems are often MANs.

· Local network: A local network is a privately owned communications network that serves users within a confined geographical area. The range is usually within a mile—perhaps one office, one building, or a group of buildings close together, as a college campus. Local networks are of two types: private branch exchanges (PBXs) and local area networks (LANs), as we discuss shortly.

All of these networks may consist of various combinations of computers, storage devices, and communications devices.

Some Features: Hosts & Nodes, Downloading & Uploading

Many computer networks, particularly large ones, are served by a host com­puter. A host computer, or simply a host, is the main computer—the cen­tral computer that controls the network. On a local area network, some or all of the functions of the host may be performed by a computer called a server. A server is a computer shared by several users in a network.

A node is simply a device that is attached to a network. A node may be a microcomputer, terminal, or some peripheral device (a peripheral device is any piece of hardware that is connected to a computer).

As a network user you can download and upload files. Download means that you retrieve files from another computer and store them in your com­puter. Upload means that you send files from your computer to another computer.

Дата добавления: 2015-11-14