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 highspeed 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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Chapter 9: Local Area Networks
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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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Chapter 9: Local Area Networks
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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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Chapter 9: Local Area Networks
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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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Chapter 9: Local Area Networks
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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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Chapter 9: Local Area 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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Chapter 9: Local Area Networks
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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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Chapter 9: Local Area Networks
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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
Chapter 9: Local Area Networks
• 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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