On the other hand connecting directly by wire limits the distance over which

On the other hand connecting directly by wire limits

This preview shows page 60 - 61 out of 71 pages.

This is still one of the most popular ways to connect computers, as it provides very high rates of data transmission. On the other hand, connecting directly by wire limits the distance over which computers can be connected. Other common methods to connect computers are by using public communication networks like the telephone lines or the cable TV network. This requires using something called a “modem” to translate the signals coming out of your computer into something that can be transmitted along the telephone or cable network. At the other the modem converts signals received from the network into something that the recipient’s computer can understand. This process is called mo dulation/ dem odulation, thus the name modem. Today one of the most popular ways for the public at large to connect to a wide range of servcies is via wireless “wifi” connection. The transmission medium in this case is the air (or airwaves), not unlike the signals you receive when listening to the radio (assuming anyone still does that). One of the other key technologies is called a router. As its name suggests, the router’s job is to route the data traffic to and from the appropriate computers within a network. You may have heard of the company Cisco, whose main products are routers and other telecommunications networking products. If you have a computer network at home, the chances are pretty high that you have a router made by Cisco (or Linksys, which is owned by Cisco). Within larger networking contexts, such as an office building of users sharing printers, computer file storage, and application specific software, organizations will employ switches to allow many computer devices and peripherals to co-exist on the same network, switching the flow of data from one point to another. (Cisco makes a lot of these switching devices as well). Computer networks can be categorized in three ways that are of interest to us: geography, communication roles, and access. 1. Geography . This refers to the distance over which the network operates. Different technologies are required for communicating over longer distances than shorter ones. Wires and wifi work well with computers that are close to one another. Computers that are located at large distances from each other need to use long-distance technologies like the telephone system or satellite transmission. a. We call networks made up of computers that are in close proximity, on a contiguous piece of property (like a home, an office building, or a campus), and where the company owns the wiring Local Area Networks (LAN). b. We call networks made up of computers that are located at some distance from one another, separated by property owned by others, and where a third party owns the wiring (typically a teleco company) Wide Area Networks (WAN). c. We therefore typically observe groups of computers that are physically close and connected to one another as a LAN, and each local network connected to other local area networks using WAN technologies. So the LAN in your office building may be connected to the LAN in the Tokyo office and the LAN in the London office.
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