Business Data Communications, Fourth Edition

Chapter 9: Local Area Networks

Learning Objectives

• Describe the hardware and software used in a local area network

• List the topologies used in local area networks

• Specify the differences among CSMA/CD, token ring, token bus, ARCnet and AppleTalk

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Learning Objectives

• Describe and show the difference between peer-to-peer and server-based networks

• List the differences between wired and wireless LANs

• Differentiate between various network operating systems

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Learning Objectives

• Describe the advantage of using high-speed LANs

• Define a gateway, bridge, and router in the context of local area networks

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Introduction

• Local area networks are located in a limited geographic area

• Local area networks are privately owned

• Universities often use local area networks for lab environments

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LAN Hardware

• Three main components– Personal computer– Network interface card (NIC)– Transmission medium

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LAN Hardware

• Personal Computer– Must be compatible with LAN software

– Many different types can be combined on the same network

– Need open slot for network interface card

– Workstation or client on the network

– Diskless workstation

– Network computers (NCs)

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LAN Hardware

• Network Interface Card (NIC)– Link between physical network and PC– Type of card linked to specific type of LAN

• Transmission Medium– Guided media– Unguided media– Fiber optic often used for “backbone” network

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LAN Hardware

• LAN Standards– Institute of Electrical and Electronics

Engineers (IEEE)• IEEE 802.x standard

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LAN Topologies

• Topology– Physical arrangement of the network– LAN equipment is often moved

• Ring Topology– Creates a closed loop between the PCs– Data travels in one direction

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LAN Topologies

• Ring Topology– Active stations – send/receive messages– Inactive stations – cannot respond

• Bypassed by data on the network

– Fiber Distributed Data Interface (FDDI)• Double ring using fiber-optic cable• Used for backbone

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LAN Topologies

• Bus Topology– Single wire connecting all devices– Terminator used at ends of the cable– Inexpensive and easy to install– Ethernet standard uses bus topology

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LAN Topologies

• Star Topology– Central device connecting all other devices in

the network– Point-to-point links used– Private Branch Exchange (PBX)– Hub failure is the main problem– UPS can be used to avoid sudden loss of

power

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Protocols

• Ethernet– Based on bus topology– 10Base-T connector

• 10Mbps• Baseband transmission• 10BaseT (twisted pair)

– Thick Ethernet – regular coaxial cable– Thin Ethernet – smaller coaxial cable

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Protocols

• Ethernet– Fast Ethernet (100 Mbps)– Gigabit Ethernet (1 Gbps)– 10 Gigabit Ethernet (10 Gbps)– Carrier Sense Multiple Access with Collision

Detection (CSMA/CD)• MAC protocol• Contention method

– Originally used for small network, now expanded to larger networks.

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Protocols

• Token Passing– Token – string of bits– Token Ring Network

• Data is added to the token and transmitted• Free versus busy token• Uses a MAU, ring is within the MAU• 4 or 16 Mbps, 100 Mbps in the future• Fair protocol

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Protocols

• Token Passing– Token Bus Network

• Token is taken off the network • Designed like a ring• ARCnet uses it (2.5 or 20 Mbps)

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Protocols

• Apple Networks– Appletalk Network

• Original Macintosh network• CSMA/CA• 230,400 bps, up to 32 users

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Protocols

• Apple Networks– AppleShare IP

• Makes Macintosh network more compatible with other networks, including the Internet

• Speed depends on server used, up to 500 users• May be used as Web server

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Types of Networks

• Private Branch Exchange LANs– Central switch in telephone system– Failure of central node is greatest threat

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Types of Networks

• Peer-to-Peer LANs– All workstations are equal– Hard drives can be shared– Easy to set up and maintain– CSMA/CD used– Windows operating systems have built-in peer

networks

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Types of Networks

• Server-Based LANs– Central computer used to store files– File server

• Files shared among users on LAN• Files can be stored on server• Software stored on server, eases maintenance

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Types of Networks

• Server-Based LANs– Disk server

• Specific amount of disk space allocated to users

– Database server• Only actual data is returned, not entire file

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Types of Networks

• Wireless LANs– Rapidly growing technology– IEEE 802.11a, b, g standards– Cellular Digital Packet Data (CDPD)

• Cellular radio technology

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Types of Networks

• Wireless LANs– Spread Spectrum Radio (SSR)

• Modulated radio signal• Eliminates interference and eavesdropping• Frequency-hopping spread spectrum (FHSS)• Direct-sequence spread spectrum (DSSS)

– Infrared Transmission

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LAN Software

• Network Operating System– Does not always replace the operating system

• Novell NetWare– Dedicated server– Supports Ethernet or Token ring– Uses disk caching for file access

• Frequently access files stored in memory for quicker access

– NetWare Directory Services (NDS)

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LAN Software

• LANtastic– Peer network– Ethernet or Token ring– PCs defined as servers or workstations

• Windows NT/2000/2003– Does not need DOS– NT Server and NT Workstation– 2000 Server and 2000 Advanced Server– Server 2003

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LAN Software

• Linux– Similar to UNIX– Open source code– Alternative to high-end NOSs

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High-Speed LANs

• Fast Ethernet– 100 Mbps– Uses CSMA/CD, same as Ethernet– Used for links between servers

• Gigabit Ethernet– 1 Gbps– Backbone for high volume networks– 10 Gigabit Ethernet

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Connecting Networks

• Repeaters– Cable length without repeaters limited to

1,641 feet by IEEE 802.3 standard– LAN can be extended by four segments using

repeaters

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Connecting Networks

• Bridge– Connects two LANs using the same protocol– Operates at data link layer– Internal bridge

• Adapter card

– External bridge• Separate PC• Used on high-volume LANs

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Connecting Networks

• Routers– More sophisticated than a bridge– Operate at network layer– Can be used to isolate a portion of the LAN

• Gateways– Connect networks using different protocols– Can be used to connect a LAN to a WAN

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Summary

• LANs used for sharing hardware and software

• Personal computers, adapter cards, and cables make up the LAN

• LANs use ring, bus, and star topologies

• Unique protocols are used in LANs – CSMA/CD, token bus, token ring

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Summary

• Control of LANs are different in PBX, peer, and server-based networks

• Software is needed to run the network

• Connections between networks can be made using repeaters, bridges, routers, and gateways

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Chapter 9 Complete