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Lecture Data communications and networks: Chapter 15 - Forouzan 

This chapter introduces you to wired LANs: Ethernet. This chapter introduces wired local area networks. A wired LAN, viewed as a link, is mostly involved in the physical and data link layers. We have devoted the chapter to the discussion of Ethernet and its evolution, a dominant technology today. | Chapter 15 Connecting LANs, Backbone Networks, and Virtual LANs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 15. 15-1 CONNECTING DEVICES In this section, we divide connecting devices into five different categories based on the layer in which they operate in a network. Passive Hubs Active Hubs Bridges Two-Layer Switches Routers Three-Layer Switches Gateways Topics discussed in this section: 15. Figure 15.1 Five categories of connecting devices 15. Figure 15.2 A repeater connecting two segments of a LAN 15. A repeater connects segments of a LAN. Note 15. A repeater forwards every frame; it has no filtering capability. Note 15. A repeater is a regenerator, not an amplifier. Note 15. Figure 15.3 Function of a repeater 15. Figure 15.4 A hierarchy of hubs 15. A bridge has a table used in filtering decisions. Note 15. Figure 15.5 A bridge connecting two LANs 15. A bridge does not change the physical (MAC) addresses in a frame. Note 15. Figure 15.6 A learning bridge and the process of learning 15. Figure 15.7 Loop problem in a learning bridge 15. Figure 15.8 A system of connected LANs and its graph representation 15. Figure 15.9 Finding the shortest paths and the spanning tree in a system of bridges 15. Figure 15.10 Forwarding and blocking ports after using spanning tree algorithm 15. Figure 15.11 Routers connecting independent LANs and WANs 15. 15-2 BACKBONE NETWORKS A backbone network allows several LANs to be connected. In a backbone network, no station is directly connected to the backbone; the stations are part of a LAN, and the backbone connects the LANs. Bus Backbone Star Backbone Connecting Remote LANs Topics discussed in this section: 15. In a bus backbone, the topology of the backbone is a bus. Note 15. Figure 15.12 Bus backbone 15. In a star backbone, the topology of the backbone is a star; the backbone is just one switch. | Chapter 15 Connecting LANs, Backbone Networks, and Virtual LANs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 15. 15-1 CONNECTING DEVICES In this section, we divide connecting devices into five different categories based on the layer in which they operate in a network. Passive Hubs Active Hubs Bridges Two-Layer Switches Routers Three-Layer Switches Gateways Topics discussed in this section: 15. Figure 15.1 Five categories of connecting devices 15. Figure 15.2 A repeater connecting two segments of a LAN 15. A repeater connects segments of a LAN. Note 15. A repeater forwards every frame; it has no filtering capability. Note 15. A repeater is a regenerator, not an amplifier. Note 15. Figure 15.3 Function of a repeater 15. Figure 15.4 A hierarchy of hubs 15. A bridge has a table used in filtering decisions. Note 15. Figure 15.5 A bridge connecting two LANs 15. A bridge does not change the .