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Chapter 8
Computer Networks
Networking and Communications Applications
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Wireless phones
 Cellular phones
 Satellite phones
Paging and messaging
Global positioning systems (GPSs)
Satellite radio
Online conferencing (online meetings)
 Videoconferencing
 Web conferencing
Collaborative computing
Telecommuting
Telemedicine
What Is a Network and How Does it Transmit Data?
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Computer network—a collection of computers and other hardware connected together to
share data, hardware, software, programs, and facilitate electronic communication.
Data Transmission Characteristics
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Analog (continuous wave) vs. digital (discreet 0s and 1s).
Bandwidth and speed (higher bandwidth allows more data to travel at the same time).
Serial vs. parallel transmission.
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Transmission directions
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Simplex transmission (one way only).
Half-duplex transmission (one way at a time).
Full-duplex transmission (both ways at the same time).
Transmission timing
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Synchronous transmission
Asynchronous transmission
Isochronous transmission
Wired vs. Wireless Connections
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With a wired network connection, the PC is physically cabled to the network.
 Common in schools, business, and government facilities.
Wireless network connections allow great freedom regarding where users can use their
PCs.
 Increasingly common in homes, businesses, and wireless public hot spots (e.g.
Starbucks).
Wired Network Transmission Media
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Twisted-pair cable
 Pairs of wires twisted together.
 Used for telephone and network connections.
Coaxial cable
 Thick center wire.
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 Used for cable TV and network connections.
Fiber-optic cable
 Glass or fiber strands through which light can pass.
 Used for high-speed communications.
Wireless Network Transmission Media
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Broadcast radio transmissions (FM and AM radio broadcasts, short-range networking and
wireless devices).
Microwave and satellite transmissions.
 Microwave stations
 Communications satellites
Cellular radio transmissions.
Network Topologies
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Star
Bus
Ring
Network Architectures
LANs, WANs, and Other Types of Networks
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Local area networks (LANs)
Wide area networks (WANs)
Metropolitan area networks (MANs)
Personal area networks (PANs)
LANs, WANs, and Other Types of Networks, Cont’d.
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Intranets and extranets
Virtual private networks (VPNs)
Storage area networks (SANs)
Networking Hardware
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Network adapters, also called network interface cards (NICs).
 Needed to connect PC to network.
 Come in a variety of formats (internal or external, wireless or wired, PC card, USB, etc.).
Modems (used to connect PC to the Internet)
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Conventional dial-up
ISDN
DSL
Cable
Satellite
Hubs, switches, and routers
Wireless access points
Gateways and bridges
Repeaters
Multiplexers and concentrators
Communications Protocols
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Communications protocol—an agreed-upon standard for transmitting data between two
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devices on a network.
Common wired protocols are Ethernet, Token Ring, and TCP/IP.
Common wireless protocols are 802.11 (Wi-Fi), Bluetooth, and WAP.
Ethernet
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Typically used with wired LANs.
Utilizes a set of procedures (CSMA/CD) to send data and make sure it arrives.
Traditional (10Base-T) Ethernet networks run at 10 Mbps; newer 100 Mbps and 1 Gbps
versions are now available.
Token Ring
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Usually used with a ring network topology and utilizes a token to send and retrieve data.
TCP/IP
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The protocol used with the Internet also increasingly being used with LANs.
Sends data in packets.
802.11 (Wi-Fi) and Bluetooth
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802.11 (Wi-Fi for wireless fidelity)—a family of wireless networking standards.
 802.11b is the original standard (11 Mbps).
 802.11g is faster (54 Mbps) and expected to eventually replace 802.11b.
 Newer versions are in development.
Bluetooth is a standard for low-cost, short-range, wireless connections between Bluetoothenabled devices.
Other Networking Protocols
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Wireless Application Protocol (WAP)—for Web content delivered to smart phones and other
mobile devices.
IrDA—used for short range infrared data transfers.
Phoneline (Home PNA)
Powerline
Ultra Wideband (UWB)—for home multimedia delivery.
Network Security Issues
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Unauthorized access and unauthorized use.
 Hacking
 War driving
Protecting against unauthorized access and use.
 Possessed knowledge systems (e.g. passwords).
 Possessed object systems (e.g. cards or badges).
 Biometric systems (e.g fingerprint scanners or face readers).
 Firewalls and other protective software.
Computer sabotage
 Computer viruses and other types of malware (e.g. computer worms and Trojan
horses).
 Denial of service (DoS) attacks.
 Malicious spamming.
 Data or program alteration.
Protecting against computer sabotage.
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Use up-to-date antivirus and firewall software.
Limit sharing disks and other removable storage media.
Only download programs from reputable Web sites.
Only open e-mail attachments that aren’t executable and are from people you know.
Regularly download and install the latest security patches available for your e-mail program and browser.
Key Terms
802. 11 (Wi-Fi)
Analog
Biometric device
Bluetooth
Bus network
Cellular radio
Client/server
Coaxial cable
Communications
Communications
satellite
Computer network
Computer worm
Computer virus
Denial of service
(DoS) attack
Digital
Ethernet
Extranet
Fiber-optic cable
Firewall
Global positioning
system (GPS)
Hacking
Hub
Intranet
Local area network
(LAN)
Malware
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Microwave station
Modem
Network adapter
Network interface card
(NIC)
Online conferencing
Parallel transmission
Password
Ring network
Router
Serial transmission
Star network
Switch
TCP/IP
Telecommuting
Telemedicine
Token ring
Trojan horse
Twisted-pair cable
Unauthorized access
Unauthorized use
Virtual private
network (VPN)
Wide area network
(WAN)
Wired network
Wireless access point
Wireless Application
Protocol (WAP)
Wireless network
Wireless phone
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