The most basic concept that you’ll need to understand before going any further is the difference between LANs and WANs. A Local Area Network represents a group of connected computers, usually within a given office or building. For the most part, LANs are distinguished by their limited geographic distance and relatively high transmission speeds – anywhere from less than ten and up to hundreds of megabits (millions of bits) per second. Common LAN technologies include Ethernet, Token Ring, and FDDI, each of which we’ll look at in this chapter.
Wide Area Networks interconnect LANs over great geographic distances, sometimes spanning the globe. WAN technologies differ from those found on a LAN, and are mainly characterized based on their ability to span large distances and lower relative speeds. For the most part, WANs rely on the infrastructure of telecommunications service providers to deliver connectivity over these long distances. Common speeds found on WANs vary widely, ranging anywhere from a few kilobits (thousands of bits) per second, up to multiple megabits (millions of bits) per second and higher. Examples of WAN technologies include simple dial-up modem connections, Frame Relay, ISDN, ATM, and others. WAN technologies and protocols will be looked at in detail in Chapter 11.