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Chapter 9

Local Area NetworksPart I:

Basic Concepts andWired Ethernet LANs

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Understand the use of LANs in an organization.Understand the use of LANs in an organization.

List the components of a LAN.List the components of a LAN.

Be familiar with the IEEE standards.Be familiar with the IEEE standards.

Be familiar with traditional Ethernet technology and itsBe familiar with traditional Ethernet technology and itsimplementations.implementations.

After reading this chapter, the reader should After reading this chapter, the reader should be able to:be able to:

OOBJECTIVESBJECTIVES

Be familiar with Gigabit Ethernet technology and its Be familiar with Gigabit Ethernet technology and its implementations.implementations.

Be familiar with Fast Ethernet technology and itsBe familiar with Fast Ethernet technology and itsimplementations.implementations.

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BASICBASICCONCEPTSCONCEPTS

BASICBASICCONCEPTSCONCEPTS

9.19.1

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Figure 9-1

A client-server model with dedicated servers

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Figure 9-2

A client-server modelwith a general server

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Figure 9-3

Peer-to-peer model

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Figure 9-4

Physical bus topology

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Figure 9-5

Physical star topology

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The star topology is the dominant The star topology is the dominant physical topology today.physical topology today.

Note:Note:

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Figure 9-6 Logical bus topology

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In 1985, the Computer Society of the In 1985, the Computer Society of the IEEE developed Project 802. It covers IEEE developed Project 802. It covers

the first two layers of the Internet the first two layers of the Internet model.model.

Note:Note:

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Figure 9-7Logical star topology

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Technical Focus:Technical Focus: Ring TopologyRing Topology

Another 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:

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Project 802 has split the data link layer Project 802 has split the data link layer into two different sublayers: logical into two different sublayers: logical link control (LLC) and media access link control (LLC) and media access control (MAC). control (MAC).

Note:Note:

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Figure 9-8

LAN compared with the Internet model

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WIREDWIREDETHERNETETHERNET

LANsLANs

WIREDWIREDETHERNETETHERNET

LANsLANs

9.29.2

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Figure 9-9

Collision in CSMA/CD

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Technical Focus:Technical Focus: Ethernet AddressingEthernet Addressing

Each 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.

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Technical Focus:Technical Focus: SignalingSignaling

Traditional 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.

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Figure 9-10

Implementations of Ethernet

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Figure 9-11:a

Ethernet connection to the medium

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Figure 9-11:b

Ethernet connection to the medium

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Figure 9-11:c

Ethernet connection to the medium

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Figure 9-11:d

Ethernet connection to the medium

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Technical Focus:Technical Focus: Ethernet FrameEthernet Frame

Traditional Ethernet has a frame with the following format:

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Figure 9-12

Switched Ethernet

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Figure 9-13

Fast Ethernet implementations

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Figure 9-14:a

Fast Ethernet connection to the medium

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Figure 9-14:b

Fast Ethernet connection to the medium

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Figure 9-14:c

Fast Ethernet connection to the medium

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Figure 9-15

Gigabit Ethernet implementations

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Figure 9-16:a

Gigabit Ethernet connection to the medium

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Figure 9-16:b

Gigabit Ethernet connection to the medium

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Technical Focus:Technical Focus: Token Ring NetworksToken Ring Networks

At 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.