Local Area Networks Part I: Basic Concepts and Wired Ethernet LANs

Chapter 9Local Area NetworksPart I:Basic Concepts andWired Ethernet LANsUnderstand the use of LANs in an organization.List the components of a LAN.Be familiar with the IEEE standards.Be familiar with traditional Ethernet technology and itsimplementations.After reading this chapter, the reader should be able to:OBJECTIVESBe familiar with Gigabit Ethernet technology and its implementations.Be familiar with Fast Ethernet technology and itsimplementations.BASICCONCEPTS9.1Figure 9-1A client-server model with dedicated serversFigure 9-2A client-server modelwith a general serverFigure 9-3Peer-to-peer modelFigure 9-4Physical bus topologyFigure 9-5Physical star topologyThe star topology is the dominant physical topology today.Note:Figure 9-6Logical bus topologyIn 1985, the Computer Society of the IEEE developed Project 802. It covers the first two layers of the Internet model.Note:Figure 9-7Logical star topologyTechnical Focus: Ring TopologyAnother physical topology common at the beginning of the LAN era was the ring topology. In a ring topology, each station isconnected to the next station as shown in the following figure:Project 802 has split the data link layer into two different sublayers: logical link control (LLC) and media access control (MAC). Note:Figure 9-8LAN compared with the Internet modelWIREDETHERNETLANs9.2Figure 9-9Collision in CSMA/CDTechnical Focus: Ethernet AddressingEach station on an Ethernet network (such as a PC, workstation, or printer) has its own network interface card (NIC). The NIC usually fits inside the station and provides the station with a 6-byte (48-bit) physical address.Technical Focus: SignalingTraditional Ethernet uses Manchester digital encoding (discussed in Chapter 6). In this type of signaling, the transition at the middle of each bit is used for synchronizationbetween the sender and receiver.Figure 9-10Implementations of EthernetFigure 9-11:aEthernet connection to the mediumFigure 9-11:bEthernet connection to the mediumFigure 9-11:cEthernet connection to the mediumFigure 9-11:dEthernet connection to the mediumTechnical Focus: Ethernet FrameTraditional Ethernet has a frame with the following format:Figure 9-12Switched EthernetFigure 9-13Fast Ethernet implementationsFigure 9-14:aFast Ethernet connection to the mediumFigure 9-14:bFast Ethernet connection to the mediumFigure 9-14:cFast Ethernet connection to the mediumFigure 9-15Gigabit Ethernet implementationsFigure 9-16:aGigabit Ethernet connection to the mediumFigure 9-16:bGigabit Ethernet connection to the mediumTechnical Focus: Token Ring NetworksAt the beginning of the LAN era, a LAN technology called Token Ring was developed that uses a token passing method. Whenever the network is unoccupied, a token circulates freely from one station to another. When a station has data to send, it captures the token and sends its frame.