tailieunhanh - Ebook Data and computer communications (5th edition): Part 2

(BQ) Part 2 book "Data and computer communications" has contents: Local area network overview, high speed lans, wreless lans, internetwork protocols, internetwork operation, internetwork operation, network security, internet applications—electronic mail and network management,. and other contents. | PART FOUR Local Area Networks T he trend in local area networks (LANs) involves the use of shared transmission media or shared switching capacity to achieve high data rates over relatively short distances. Several key issues present themselves. One is the choice of transmission medium. Whereas coaxial cable was commonly used in traditional LANs, contemporary LAN installations emphasize the use of twisted pair or optical fiber. In the case of twisted pair, efficient encoding schemes are needed to enable high data rates over the medium. Wireless LANs have also assumed increased importance. Another design issue is that of access control. ROAD MAP FOR PART FOUR Chapter 15 Local Area Network Overview The essential technology underlying all forms of LANs comprises topology, transmission medium, and medium access control technique. Chapter 15 examines the first two of these elements. Four topologies are in common use: bus, tree, ring, and star. The most common transmission media for local networking are twisted pair (unshielded and shielded), coaxial cable (baseband and broadband), optical fiber, and wireless (microwave and infrared). These topologies and transmission media are discussed, with the exception of wireless, which is covered in Chapter 17. The increasing deployment of LANs has led to an increased need to interconnect LANs with each other and with WANs. Chapter 15 also discusses a key device used in interconnecting LANs: the bridge. 444 Chapter 16 High-Speed LANs Chapter 16 looks in detail at the topologies, transmission media, and MAC protocols of the most important LAN systems in current use; all of these have been defined in standards documents. The most important of these is Ethernet, which has been deployed in versions at 10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps. Then the chapter looks at Fibre Channel. Chapter 17 Wireless LANs Wireless LANs use one of three transmission techniques: spread spectrum, narrowband microwave, and infrared. Chapter 17 .