Chapter 4 discusses the equipment commonly used to connect network resources and transmission media. The objectives important to this chapter are on page 4-1:
Concepts:Two terms should be defined on page 4-2, but they are not. To help you understand this chapter consider the following definitions:
It is important to know whether we are working with one network or several in the story problems that follow. The chapter concerns the different connection devices used in both networking and internetworking. It is important to know which kind of job a given device does. On page 4-2, the text states "network connectivity devices connect individual devices to a single network". Page 4-16 tells us that "internetwork connectivity devices connect multiple independent networks together to provide access to remote resources". The first list on page 4-2 is about connectivity devices needed by each
computer to connect to a network segment:
Remember, from Chapter 2, that each kind of medium used in networking has a maximum segment length. Multiple segments can be joined together, creating a larger network than a single segment can support. The second list on page 4-2 lists connectivity devices that do this:
Regarding the connectors on page 4-3, you should know that:
On page 4-6 you see three illustrations of how a network interface
board may be deployed. It may be an add on card, it may be a part
of the motherboard of the computer, or it may be an adapter to convert
signals. Three terms are given to us as rough equivalents:
Modems can be used to dial in to networks, instead of using a standard connection. This is most common for mobile or remote users. (Remote users dial in to use one network, mobile users dial in to use parts of several networks.) A repeater is discussed on page 4-9. It can be an amplifier, which will amplify static as well as signal, or a signal regenerating repeater, which repeats only the signal. Note that rules exist that limit the number of repeaters allowed on a network. (We will discuss the 5-4-3 rule and the 5-4 rule later.) Hubs are discussed on page 4-12. The term concentrator
is often used for a hub, since the hub is used to collect connections
at one point. Hubs come in four types:
Bridges connect network segments together and act as filters, to minimize traffic. Without such filters, all traffic on the net would go to all stations on the net, on all segments. In the graphic on page 4-13, the bridge would prevent traffic on segment A from reaching segment B, unless it was meant for a station on segment B. (In that case, all stations on both segments would get the traffic.) A multiplexer is a device for putting more than one signal on a medium. This is usually done one of three ways, which are discussed in Chapter 6: frequency division, time division or statistical time division. The idea is to make better use of the bandwidth on the medium. Interconnectivity hardware involves connecting one or more networks together. Three classes of such devices are listed on page 4-16:
|
