lect21 - 1.264 Lecture 21 Telecom Local area networks Fiber...

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1.264 Lecture 21 Telecom: Local area networks Fiber optics, wireless
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Local area networks (LANs) Ethernet is dominant: Cheap, universal, good enough Token ring offers better utilization of capacity and better performance But its complexity and cost are not worth it in LANs Token ring ideas are dominant in WANs, though Ethernet topology is a star Individual devices are connected to an Ethernet switch It eliminates collisions, filters traffic Cabling is usually twisted pair Fiber optics also coming into use in LANs Fewer crosstalk and shielding problems but doesn’t provide power
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Ethernet standards Steady increase in speed from 10 Mbps to 10 Gbps in near future Most computers have Fast Ethernet (100 Mbps) cards Increase in range from 2 km to perhaps 10-40 km for certain kinds of links If carriers will provide ‘dark fiber’ to a company, it can run its corporate Ethernet these distances to other sites Traffic prioritization is possible though not yet often done (802.1p) Voice and video traffic need priority on congested LANs Power over Ethernet (PoE) for phones is possible
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Repeaters, Bridges, Routers, Gateways Figure by MIT OCW. Application Presentation Session Transport Network Data Link Physical (1) SIGNAL TO SIGNAL REPEATER (3) ETHERNET TO ETHERNET ROUTER (4) ETHERNET TO X.25 GATEWAY (2) FRAME TO FRAME BRIDGE Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Bridge Bridge Router Router X.25 Gateway Physical Physical Repeater Physical Physical Data Link Data Link PPSN Physical Physical Data Link Data Link Network Network
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Ethernet switches Ethernet switches are a
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