t © 2005 Elsevier Inc. All rights reserved CHAPTER 5.1 Wireless local area networks kilometers. They are generally owned and operated by In the simplest view, there are small networks (PANs and the same folks who own the site: private companies, LANs) and big networks (MANs and WANs). Small individuals in their homes, government agencies, networks deliver best-effort services over short distances and SO on. They are generally used indoors and and are cost sensitive. Big networks deliver guaranteed- historically have been solely for the movement reliable services over long distances and are quality sen- of data, though the recent implementation of sitive and cost competitive. This book focuses on how voice-over-Internet-protocol technologies has small networks are converted from wires to wireless allowed LANs to provide voice service as well. links. Ethernet (see section 5.1.2) is by far the most All networks, big or small, have certain elements in prevalent LAN technology. common. A message (typically a packet in a data net- Metropolitan area networks (MANs): MANs connect work) must be addressed to the destination station. The different buildings and facilities within a city or message must have a format the destination station can populated region together. There is a significant understand. The message has to get access to some technological and historical discontinuity between physical medium to be sent. Errors in transmission must LANs and MANs: LANs were invented by the be corrected. These activities can be grouped into a hi- computer-using community for data transfer, erarchical arrangement that helps provide structure for whereas MANs descended primarily from the designing and operating the networks. Applications live telephone network, traditionally organized to move on the top of the hierarchy and use the networking ser- time-synchronous voice traffic. MANs are generally vices. Networks support applications and deal with owned by local telephone exchanges (incumbent routing messages to the destination st