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Unit Contents
Overview 
This unit introduces the technologies used to connect two or more local area networks (LANs) over an extended distance. The resulting network is either a metropolitan area network (MAN) or wide area network (WAN). The difference between MANs and WANs is the distance between the connected LANs. A MAN covers a metropolitan area, using local public telecommunication services. A WAN spans multiple sites over a wider geographic area, typically using both local and long-distance carrier facilities. However, the same transmission technologies can be used to create both MANs and WANs. Thus, we will use the term "WAN" to include both types of network. This unit introduces the two main classes of technologies used for WAN connectivity: point-to-point services and switched services. We will also describe the devices needed to implement each type of service. In general, LANs are interconnected using routers. A router is installed between a LAN and point-to-point connection, or between a LAN and public-switched network. The router's job is to keep all data off the expensive WAN link except traffic destined for a distant site. This is why routers are often called "gateways." Each type of transmission service also requires hardware specific to that technology. As we will see, there is no single right way to establish a WAN. When choosing a WAN technology, or combination of technologies, a network professional must consider the cost and performance of each service, plus many other factors. The final lesson in this unit introduces some of the most important factors to consider when choosing products and services to build a WAN or MAN.
Terms You Should Know
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