Transcript Chapter 4: Telecommunications and Networking - McGraw

Chapter 4
Telecommunications and Networking
Information Technology & Management
Thompson Cats-Baril
The McGraw-Hill Companies, Inc. 2002
Chapter Objectives
• To understand the basic performance characteristics of
telecommunications and networking technologies.
• To have an appreciation for the trends in
telecommunications technologies and how they
influence technology options and decisions.
• To understand how it is possible to view
telecommunications as an enabler of organizational
communications.
• To appreciate the potential for distortion in
organizational communications, and how information
and telecommunication technologies may help to
reduce distortion.
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Organizational Communication
• Communication is the sharing of information
between two or more entities.
• Organizational Communication is the sharing of
information related to an organization activity
between two or more individuals or organizational
units.
– Sharing of information implies, collection, analysis, and
transmission of information.
– Formal and Informal Communication
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Communication Dyads
• A communication network is made of a
series of communication dyads.
• A dyad consists of
–
–
–
–
–
Sender
Receiver
Message
Channel
Medium
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Distortion in Communication
• Communication Distortion is the transformation of
the meaning of a message by intentionally or
unintentionally altering its content.
– Lost
– Destroyed
– Modified or Altered
• Noise consists of disturbances in the
communication process that interferes with the
intended effect of the message.
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Types of Distortion
• Distortion
– Routing – the message gets routed to the wrong
receiver or not at all.
– Delaying the message
– Modifying it the content of the message
– Summarizing
• Intentional
• Unintentional
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Distortion
Type
Intentional
Unintentional
Routing
Sending a message to
wrong person; news
leaks
Delaying
Purposely waiting for a Not being able to send
deadline to go by
message due to overload
Modifying
Changing the message; Forgetting to include
destroying data
some material in message
Summarizing
Leaving negative data
out
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Not knowing where to
send message; sending to
wrong address
Not having time to
integrate all available
material
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Analog and Digital Data
• Analog signals are transmitted as sound waves
along a channel such as a copper telephone wire
• Digital signals are transmitted as a series of bits or
on/off signals
• A modem converts digital signals into analog
signals and another modem can be used to
convert analog signals back to digital signals.
• See Figure 4.6
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Telecommunications
•
Voice communications require:
1.
2.
3.
4.
•
•
A source device
A switching system
A data channel
A destination device
Data communications is used to refer to
telecommunications involving computerized
data.
Data traffic on the Internet doubles every 100
days.
Information Technology & Management
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The McGraw-Hill Companies, Inc. 2002
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Data Channels
• Bandwidth is used to describe the capacity of a
communications medium
• bps, bits per second
• kHz, kilohertz and MHz, megahertz
– Narrowband (transmission speeds of 64 kbps or less)
– Wideband (transmission speeds between 64 kbps and
1.544 Mbps)
– Broadband (transmission rates of 1.544 Mbps or
higher)
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Data Channels
• Wireline
– Twisted pair copper
– Coaxial cable (cable television)
– Fiber-optic cable
• Wireless
–
–
–
–
Infrared light
Cellular telephone (analog or digital)
Microwave
Satellite (geostationary or low-earth)
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Communication Protocol
• A communication protocol is essentially a set of
codes or conventions used for facilitating
communications between hardware and software.
– IP or Internet Protocol directs packets on the Internet.
– TCP or Transmission control protocol puts the packets
in their correct sequence.
– HTTP or hyper text transfer protocol is used to transmit
web pages over the Internet.
– Mobile IP provides IP routing for mobile devices.
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The McGraw-Hill Companies, Inc. 2002
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Telecommunications
• ISDN or Integrated Services Digital Network is a
set of standards that provide additional capabilities
for copper wire.
• DSL or digital subscriber line technology refers to
a a group of methods for transmitting at speeds up
to 8 Mbps over copper wire.
• Cable Modems allow transmission of Internet
traffic through the cable TV network.
Information Technology & Management
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The McGraw-Hill Companies, Inc. 2002
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Telecommunications
• T-carrier systems are digital transmission systems
that take analog voice circuits and converts them
to digital form for transmission. Companies
typically lease T lines.
• Frame relay carries data packets over the system
that vary in length and are referred to as frames.
• Fast Ethernet is a protocol that was designed
originally local area networks.
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Thompson Cats-Baril
The McGraw-Hill Companies, Inc. 2002
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Networks
• A computer network is used to connect multiple
uses and computing devices together, using
telecommunications technologies.
• Three classes of networks
– Local Area Network (LAN)
– Metropolitan Area Network (MAN)
– Wide Area Network (WAN)
• Two types of networks
– Server-based networks
– Peer-to-peer networks
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LAN Components
• LANs employ both wireline and wireless
communications
– Wireline
• Twisted pair cable, Coaxial cable, & Fiber optical cable
– Wireless
• Infrared light, & Radio waves
• A bridge connects two networks of the same type
• A router connects several networks
• A gateway is used to connect different types of
networks.
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The McGraw-Hill Companies, Inc. 2002
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Music Industry
• Napster and Gnutella
– Allow users to swap files using file sharing software.
– Napster allowed a users machine to become a client in a
server-based network.
– Gnutella allows users to share files via a peer-to-peer
network.
• Morpheus and KaZaA
– Tried peer-to-peer but still needed a central web server
to provide service.
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LAN Protocols
• Network communications are facilitated by
some type of protocol.
– Ethernet
• Data are moved at 10 Mbps
– Fast Ethernet
• Data are moved at 100 Mbps
– Giga Ethernet
• Data are moved at 1 Gbps
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LAN Protocols
• Other Network Protocols
– Token ring protocol
• Used in wired LANs
– IEEE 802.11 (WI-FI)
• Several variations designed for used in medium range, higher
data rate applications.
• Range less than 150 yards and 22 Mbps are possible.
– Bluetooth is a radio frequency technology designed to
provide wireless connectivity to a broad range of
devices.
• Uses less power than most wireless LAN technologies
• Named for Danish King
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LAN Topologies
• Topology is the configuration of the LAN (See
Figure 4.15)
– Star, Ring, Bus
• Performance can be measured by the mode of the
connection.
– Simplex transmission, messages can be carried in only
one direction.
– Half-duplex, messages can be carried in both directions
just not simultaneously.
– Full-duplex, messages can be carried in both directions
simultaneously.
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The McGraw-Hill Companies, Inc. 2002
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Intranets and Extranets
• An Intranet is a controlled, self contained
grouping of information resources that can
be accessed using Web browsers.
• An Extranet is similar to an Intranet but is
designed to facilitate communications
between two or more business partners.
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The McGraw-Hill Companies, Inc. 2002
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