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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