ks (LANs) The final section of this chapter describes a type of communication system known as a local area network, or LAN for short. As the name suggests, this is a network intended to allow a number of different users (usually computers) located close to one another to communicate together. It might be used in an office building, or in a university setting, to allow people's computers to talk to one another. Typically, LANs provide very high-bit-rate communications, enabling multiple users to communicate lots of information very quickly. Two types of LANs have become popular. The first is called Ethernet, and the second is known as Token ring. Ethernet is shown in Figure 2.23. Here, you see three computers connected together by a single coaxial cable. These users can communicate at 10 Mb/s (tradi- tional speed) or 100 Mb/s (high speed). Let's say that computer A wants to talk with computer B. Here's what happens: Chapter Two Computer Computer Looks Looks Sees it is not Sees data is for him. for him. Reads data. Figure 2.23 LAN using Ethernet 1. Computer A listens to the cable to see if there is a communication transmis- sion. If there is no transmission, then computer A sends its information on the cable. If there is a transmission, then computer A waits until the transmission is done, and then it begins to send its signal. 2. When computer A first sends out its information, it checks to see if another computer has sent a transmission at the same time. If not, Computer A continues to send its data. If computer A and another computer were trying to send data at the same time, a "collision" is detected. Computer A stops its transmission, waits a random amount of time, and then tries to send it again. 3. When computer A is able to send information on the line (and no "collision" is detected), it sends out the name of the destination computer, Computer B. All the computers look at the data, to see if it is for them. 4. Computer B sees its name and reads the information. That is, briefly, all there is to Ethernet co