无线通信与网络chap3.ppt

Communication Networks Chapter 3 Types of Communication Networks Traditional Traditional local area network (LAN) Traditional wide area network (WAN) Higher-speed High-speed local area network (LAN) Metropolitan area network (MAN) High-speed wide area network (WAN) Speed and Distance of Communications Networks Characteristics of WANs Covers large geographical areas Circuits provided by a common carrier Consists of interconnected switching nodes Traditional WANs provide modest capacity 64000 bps common Business subscribers using T-1 service – 1.544 Mbps common Higher-speed WANs use optical fiber and transmission technique known as asynchronous transfer mode (ATM) 10s and 100s of Mbps common Characteristics of LANs Like WAN, LAN interconnects a variety of devices and provides a means for information exchange among them Traditional LANs Provide data rates of 1 to 20 Mbps High-speed LANS Provide data rates of 100 Mbps to 1 Gbps Differences between LANs and WANs Scope of a LAN is smaller LAN interconnects devices within a single building or cluster of buildings LAN usually owned by organization that owns the attached devices For WANs, most of network assets are not owned by same organization Internal data rate of LAN is much greater The Need for MANs Traditional point-to-point and switched network techniques used in WANs are inadequate for growing needs of organizations Need for high capacity and low costs over large area MAN provides: Service to customers in metropolitan areas Required capacity Lower cost and greater efficiency than equivalent service from telephone company Switching Terms Switching Nodes: Intermediate switching device that moves data Not concerned with content of data Stations: End devices that wish to communicate Each station is connected to a switching node Communications Network: A collection of switching nodes Switched Network Observations of Figure 3.3 Some nodes connect only to other nodes (e.g., 5 and 7) Some nodes connect to one or more sta