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Chapter 6
Information System Networks
and
the Internet
© 2001 Business & Information Systems 2/e
2
Our Agenda
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Communications Concepts
Communications Hardware
Communications Software
© 2001 Business & Information Systems 2/e
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Our Agenda (cont’d.)
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Network Concepts
Local Area Networks
Wide Area Networks
Internetworks
The Internet
Electronic Commerce
© 2001 Business & Information Systems 2/e
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Learning Objectives
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Summarize the communications
hardware and software needed for
computers to communicate with other
computers.
Describe the main characteristics of
communications channels.
© 2001 Business & Information Systems 2/e
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Learning Objectives (cont’d.)
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Describe the main types of
communications processors and give
several examples.
Describe the main functions of
communications software.
Explain how local area networks are
organized and list the special hardware
and software used in them.
© 2001 Business & Information Systems 2/e
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Learning Objectives (cont’d.)
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Describe the structure of wide area
networks.
Explain how and why networks are
interconnected.
Explain what the Internet, intranets,
and extranets are.
Describe the special hardware and
software needed for E-Commerce.
© 2001 Business & Information Systems 2/e
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Communications Concepts
Information System Networks
and
the Internet
© 2001 Business & Information Systems 2/e
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Communications Concepts
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Two main types of communications
hardware
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Communications channel – the link over
which data is sent
Communications processors – provide
processing capabilities between the
computer and the communications channel
A modem is a communication processor
© 2001 Business & Information Systems 2/e
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Communications Hardware
Information System Networks
and
the Internet
© 2001 Business & Information Systems 2/e
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Communications Hardware
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Communications channel characteristics
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Data is transmitted over the channel as
bits.
Each bit is sent one after the other.
Bits are grouped to form bytes that
represent characters using ASCII, EBCDIC,
Unicode or some other code.
© 2001 Business & Information Systems 2/e
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Communications Hardware
(cont’d.)
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The way in which bits are sent
determines two main characteristics of
the channel
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Signal type
Data rate
© 2001 Business & Information Systems 2/e
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Signal Type
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Bits can be sent either as
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An Analog signal – data is transmitted by a
wave pattern that varies continuously
A Digital signal – data is transmitted as a
series of high and low pulses
The human voice is analog
Telephones are analog
Computers are digital
© 2001 Business & Information Systems 2/e
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Data Rate
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Data rate is measured as bits per
second (bps).
Each type of channel has a maximum
data rate.
Baud rate is used to express data rate
9,600 baud = 9,600 bps.
Bandwidth describes how much data
can be transmitted over a channel.
© 2001 Business & Information Systems 2/e
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Communications Channel
Media
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Wire cables – sometimes called
“copper” have been used since the
1800s.
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Two main forms
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Twisted-pair wiring
Coaxial cable
© 2001 Business & Information Systems 2/e
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Communications Channel
Media (cont’d.)
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Twisted-pair wiring
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Two wires twisted together
Most telephone lines are twisted-pair
Can also be used for data
Data transmission rate is slow compared to
other media
© 2001 Business & Information Systems 2/e
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Communications Channel
Media (cont’d.)
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Coaxial cable
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Copper wire insulated with rubber and
plastic.
Used with cable television systems.
Data transmission rate is faster than
twisted-pair, and more expensive, but
slower than other media.
© 2001 Business & Information Systems 2/e
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Communications Channel
Media (cont’d.)
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Fiber-optic cables
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Bundles of glass or plastic fibers.
Each fiber is 1/2000 inch thick – about the
size of a human hair.
Data is transmitted by a laser that pulses
light through the fiber.
Data transmission rate is very fast.
© 2001 Business & Information Systems 2/e
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Communications Channel
Media (cont’d.)
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Microwave
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Special types of radio signals sent from one
microwave antenna to another.
Transmission is line-of-sight, i.e, one
antenna must be able to “see” the other.
Two types
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Land based – antenna approximately 30 miles
apart.
Satellite – positioned 22,300 miles in space –
geosynchronous orbit.
© 2001 Business & Information Systems 2/e
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Communications Channel
Media (cont’d.)
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Other media
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Infrared spectrum
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Very short distances
Relatively slow
Wireless systems
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Used for mobile computing
Usually in small areas or hard to wire areas
© 2001 Business & Information Systems 2/e
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Communications Processors
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Channel interface devices
Communications control units
Communications protocols
Communications security
© 2001 Business & Information Systems 2/e
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Channel Interface Devices
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Modems – convert digital signals to
analog signals at the origin and reverse
the process at the destination of the
signal.
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Digital to analog is modulation.
Analog to digital is demodulation.
Modems may be either internal or
external to the computer.
© 2001 Business & Information Systems 2/e
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Channel Interface Devices
(cont’d.)
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Modem data rates are typically 33 Kbps
to 56 Kbps.
Cable modems – are devices to provide
the interface between a computer and a
cable system’s data transmission
capability.
For ISDN or DSL a terminal adapter is
required.
© 2001 Business & Information Systems 2/e
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Communication Control Units
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Multiplexer – combines signals from
several slow-speed devices to transmit
over a faster device.
Controller – stores and forwards signals
to improve the throughput of the
channel.
Front-End Processor – operates
between the channel and the main
computer.
© 2001 Business & Information Systems 2/e
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Communications Protocols
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Protocols are the rules computers must
follow when they communicate with
one another.
Computers that wish to communicate
and have different protocols must use a
protocol converter to standardize their
communication.
© 2001 Business & Information Systems 2/e
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Communications Security
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A problem with data communications is
the lack of security over a communications
channel. One way of solving this problem
is to use data encryption to convert the
data to an unintelligible form for
transmission and to return it to an
intelligible form at the destination.
Encryption requires a key.
© 2001 Business & Information Systems 2/e
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Communications Software
Information System Networks
and
the Internet
© 2001 Business & Information Systems 2/e
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Communications Software
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Communications software is required to
control communications between
computers. It receives data from
communications processors connected
to the channel and passes the data to
other software in the computer for
processing.
© 2001 Business & Information Systems 2/e
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Communications Software
(cont’d.)
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Types of communications software
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Terminal emulators
Client software – as used in client/server
computing
File transfer protocol (FTP) – software
Network Operating System software (NOS)
© 2001 Business & Information Systems 2/e
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Network Concepts
Information System Networks
and
the Internet
© 2001 Business & Information Systems 2/e
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Network Topologies
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Star network – each node is connected
to each other node.
Hierarchical network – organized like a
family tree.
Bus network – each node is connected
to a single, common communications
channel.
Ring network – each node is connected
to a common channel forming a loop.
© 2001 Business & Information Systems 2/e
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Types of Networks
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Local Area Network (LAN)
Wide Area Network (WAN)
Metropolitan Area Network (MAN)
Internetwork – connected networks
© 2001 Business & Information Systems 2/e
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Local Area Networks
Information System Networks
and
the Internet
© 2001 Business & Information Systems 2/e
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Local Area Networks
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Local Area Network Structure
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Connection Topology.
Media for communications channel.
Usually either Ethernet or Token Ring.
Require Network Interface Cards (NIC) in
each device on the network.
Permits sharing of resources.
© 2001 Business & Information Systems 2/e
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Wide Area Networks
Information System Networks
and
the Internet
© 2001 Business & Information Systems 2/e
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Wide Area Networks
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Connection Topology.
Media for communications channel.
Permits sharing of resources.
Can include a Virtual Private Network.
Often a combination or resources.
© 2001 Business & Information Systems 2/e
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Internetworks
Information System Networks
and
the Internet
© 2001 Business & Information Systems 2/e
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Internetworks
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Connecting two or more networks using
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Bridges
Gateways
Routers
© 2001 Business & Information Systems 2/e
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The Internet
Information System Networks
and
the Internet
© 2001 Business & Information Systems 2/e
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Internet
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Origins in ARPANET in 1969.
Grew slowly at first and “exploded” in 1993
with the adoption of the HTML standards for
the World Wide Web.
Two protocols
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Transmission Control Protocol (TCP)
Internet Protocol (IP)
Most users require a relationship with an
Internet Service Provider (ISP).
© 2001 Business & Information Systems 2/e
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Internet Services
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Electronic Mail – E-Mail
World Wide Web (WWW)
Telnet
File Transfer Protocol (FTP)
Gopher
Usenet or NetNews
Chat
© 2001 Business & Information Systems 2/e
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Intranets and Extranets
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An Intranet is an Internet like network
but access is restricted to within a
business or organization.
Firewalls are used to control access to
an Intranet.
An Extranet permits controlled outside
access to an Intranet like network.
© 2001 Business & Information Systems 2/e
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Electronic Commerce
Information System Networks
and
the Internet
© 2001 Business & Information Systems 2/e
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Hardware and Software
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Requires the business have a web site.
The web software runs on a web server
which has special e-commerce
software.
© 2001 Business & Information Systems 2/e
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Information System
Networks and the Internet
Key Terms
© 2001 Business & Information Systems 2/e
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Key Terms
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Analog Signal
Bandwidth
Baud Rate
Bus Network
Cable Modem
Channel Interface
Device
Client Software
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© 2001 Business & Information Systems 2/e
Communications
Channel
Communications Control
Unit
Communications
Processor
Database Server
Data Encryption
Digital Signal
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Key Terms (cont’d.)
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Downloading
DSL
Electronic Commerce
(E-commerce)
Electronic Mail (E-mail)
Extranet
File Server
File Transfer
Firewall
© 2001 Business & Information Systems 2/e
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Hierarchical Network
Hybrid Network
Information
Superhighway
Internet
Internet Service
Provider (ISP)
Internetwork
Intranet
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Key Terms (cont’d.)
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ISDN
Local Area Network
(LAN)
Modem
Network Computer
Network Interface Card
(NIC)
Print Server
Protocol
© 2001 Business & Information Systems 2/e
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Protocol Converter
Ring Network
Star Network
Terminal Adapter
Terminal Emulation
Software
Uniform Resource
Locator (URL)
Uploading
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Key Terms (cont’d.)
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Value Added Network
(VAN)
Virtual Private Network
(VPN)
Web Server
Web Site
Wide Area Network
(WAN)
Wireless LAN
© 2001 Business & Information Systems 2/e
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World Wide Web
(WWW)
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Summary
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Communications Concepts
Communications Hardware
Communications Software
© 2001 Business & Information Systems 2/e
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Summary
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Network Concepts
Local Area Networks
Wide Area Networks
Internetworks
The Internet
Electronic Commerce
© 2001 Business & Information Systems 2/e
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Final Black Slide