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Chapter 09: Communications and
Networks
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Computing Essentials 2012: Making IT Work for You
Introduction
• We live in a truly connected society.
• Increased connectivity potentially means
increased productivity, especially in business.
• You will learn more about the concept of
connectivity and the impact of the wireless
revolution in this chapter.
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Communications
• Computer communications is the process of
sharing data, programs, and information between
two or more computers
• Numerous applications depend on communication
systems, including
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E-mail
Instant messaging
Internet telephone
Electronic commerce
Global positioning
systems (GPS)
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Communications Today
• Connectivity uses computer networks to link
people and resources
• The Wireless Revolution
– Single most dramatic change in connectivity and
communications has been widespread use of mobile
telephones with wireless Internet connectivity
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Communication Systems
• Four basic elements
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Sending and receiving devices
Communication channel
Connection devices
Data transmission specifications
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Communication Channels
• Communication channels carry the data
from one computer to another
• Two categories of communication channels
– Physical connection
– Wireless connection
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Physical Connections
• Ethernet cable
(Twisted pair cable)
• Coaxial cable
• Fiber-optic cable
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Wireless Connections
• Radio frequency (RF)
– Wi-Fi (wireless fidelity)
– Bluetooth (short-range)
– WiMax (extends Wi-Fi)
• Microwave
• Satellite
– Global positioning system (GPS)
• Infrared
– Short distances and line of sight
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Computing Essentials 2012: Making IT Work for You
Communication Channels Summary
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Connection Device Signals
• Types of signals
– Analog
– Digital
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Computing Essentials 2012: Making IT Work for You
Connection Devices
• Types of modems
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Telephone modem
Broad Band-DSL (digital subscriber line)
Cable modem
Wireless modem
(WWAN)
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Computing Essentials 2012: Making IT Work for You
Connection Services
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Connection Costs and Speeds
• Typical user connection costs, bandwidth
speeds, and comparable time required to
download an image
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Computing Essentials 2012: Making IT Work for You
Bandwidth
• Measurement of the width or capacity of
the communication channel
• Categories
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Voice band (or low bandwidth)
Medium band
Broadband
Baseband
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Computing Essentials 2012: Making IT Work for You
Protocols
• Communication rules for exchanging data
between computers
• Internet standard: TCP/IP (Transmission control
protocol/Internet protocol)
– Identification – unique IP address
– Packetization – broken down and reassembled
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Computing Essentials 2012: Making IT Work for You
Networks
• A computer network is a communication system
that connects two or more computers
• Allows exchange of information and resources
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Computing Essentials 2012: Making IT Work for You
Computer Networks
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Node
Client
Server
Directory server
Host
Switch
Network interface
cards (NIC)
• Network operating
systems (NOS)
• Network administrator
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Computing Essentials 2012: Making IT Work for You
Network Types
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Local area network (LAN)
Home network
Wireless LAN (WLAN)
Personal area
network (PAN)
• Metropolitan area
network (MAN)
• Wide area network
(WAN)
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Computing Essentials 2012: Making IT Work for You
LAN-MAN-WAN
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Network Architecture
• Arrangement is called topology
• Types of network topology
– Legacy
• Bus
• Ring
– Current
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Star
Tree
Hybrid
Mesh
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Bus Network
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• Each device is connected to a common cable,
called a bus or backbone
• All communications travel along this bus
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Ring Network
• Each device is connected to two other devices
• No central file server or computer
• Useful in a decentralized environment
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Computing Essentials 2012: Making IT Work for You
Star Network
• Most widely used network topology for both
homes and large businesses
• Each device connects directly to a central network
switch
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Tree Network
• Each device is connected to a central node, either
directly or through subordinate nodes
• Also known as a hierarchical network
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Computing Essentials 2012: Making IT Work for You
Hybrid Network
• Combination of different topologies
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Computing Essentials 2012: Making IT Work for You
Mesh Network
• Does not use a specific physical layout, but
requires that each node have more than
one connection to other nodes
• Wireless technologies are frequently used
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Computing Essentials 2012: Making IT Work for You
Network Topologies
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Computing Essentials 2012: Making IT Work for You
Network Strategies
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Terminal server network
Client/server network
Peer-to-peer (P2P) network
Distributed processing network
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Terminal Server
Client/Server
Peer-to-Peer
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Computing Essentials 2012: Making IT Work for You
Organizational Networks
• Intranets
– Private network within an organization
– Works like the Internet, where employees use
browsers to access Web sites and Web pages
• Extranets
– Private network that connects organizations
– Works like the Internet, but provides suppliers and
other trusted partners with limited access to the
organization’s networks
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Computing Essentials 2012: Making IT Work for You
Network Security
• Firewalls
– Combination of hardware and software
– Proxy server provides pass-through access
– Protects against external threats
• Intrusion detection systems (NIDS)
• Virtual private networks (VPN)
– Creates a secure private network connection
between your computer and the organization
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Computing Essentials 2012: Making IT Work for You
Careers In IT
• Network Administrator
– Manages a company’s LAN and WAN networks
– Maintains networking hardware and software, diagnosing and
repairing problems that arise
– Candidates usually have a bachelor’s degree in computer science
and practical experience
– Annual salary is typically between $48,500 and $79,000
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A Look to the Future
• Telepresence Lets You Be There without
Actually Being There
– Seeks to create the illusion that you are
actually at a remote location
– Early implementations mainly focus on an
extension of video-conferencing
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Open-Ended Questions (1 of 2)
• Define and discuss connectivity, the
wireless revolution, and communications.
• Identify and describe the various physical
and wireless communication channels.
• Identify the standard Internet protocol and
discuss its essential features.
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Open-Ended Questions (2 of 2)
• Discuss past and present network
topologies.
• Define and discuss four common network
strategies.
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