Transcript 11. Building Information Systems

CHAPTER 8
TELECOMMUNICATIONS
AND
NETWORKS
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TELECOMMUNICATIONS
Telecommunications: Communication
of all types of information, including
digital data, voice, fax, sound, and video
from one location to another over some
type of network
Network: A group of computers and
associated peripheral devices connected
by a communication channel of sharing
information and other resources among
users
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Types of Data
Text
Voice
Image
Video
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Basic Communications Model
SENDER
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MEDIUM
RECEIVER
COMPONENTS OF
A TELECOMMUNICATIONS SYSTEM
Computers to process information
Terminals or any input/output devices
that send or receive data
Communications processors
Communications software
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COMPONENTS OF
A TELECOMMUNICATIONS SYSTEM
Figure 8-1
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Basic components of a data communications system
Data communications processors
PC
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Data communications
Medium
PC
FUNCTIONS OF
A TELECOMMUNICATIONS SYSTEM
Transmit information
Establish interface between sender and
the receiver
Route messages along most efficient
paths
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FUNCTIONS OF
A TELECOMMUNICATIONS SYSTEM
Perform elementary processing of
information
Perform editorial tasks on data
Convert message speed or format
Control flow of information
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Analog and digital signals
Analogue signal: a
continuous wave
Digital: a discrete set of
on (1) and off (0)
electronic bursts rather
than a continuous wave.
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+1
0
1
1
0
0
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Communication
Media/Channels
Guided Media:
Twisted Pair
Coaxial Cable
Optical Fiber
Unguided Media:
Microwave
Satellite
Broadcast Radio
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Guided Media
Twisted Pair
Coaxial Cable
Optical Fiber
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Unguided Media: Microwave
Microwave- “Line of sight” media:
antennas need to see each other
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Unguided Media: Satellite
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COMMUNICATIONS CHANNELS
Transmission Speed
Total amount of info that can be transmitted
through any channel is measured in bits per
second
Baud: change in signal from + to – or vice
versa that is used as a measure of
transmission speed
Frequency: the number of cycles per second
that can be sent through that medium (in
hertz)
Bandwidth: the range of frequencies that can
be accommodated on a particular
communication channel
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COMMUNICATIONS PROCESSORS AND SOFTWARE
Front-end processor: Manages
communications for the host computer
Concentrator: Collects and temporarily
stores messages
Controller: Supervises communication
traffic between CPU and peripheral
devices
Multiplexer: Enables single
communication channel to carry data
transmissions from multiple sources
simultaneously
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Computer Networks
 By geographic span
Local Area Network (LAN)
Wide Area Network (WAN)
 By topology (physical)
Star
Bus
Ring
Mesh
 By architecture (logical)
Peer to peer versus client-server
Centralized versus distributed versus hybrid
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Network Topology: STAR
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Network Topology: Bus
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Network Topology: Ring
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Network Topology: Mesh
Each node is
connected to
each other
node in the
network
Global
Storage
Medium
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Shared Printer
Network Architecture: e.g., Client-Server
Server
• provides global information and software,
• manages the use of shared printers,
• provides communication within and external
to the network.
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Network Architecture: e.g., Centralized Network
The host computer handles
all information processing,
manages communication,
and stores all software and
information.
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COMMUNICATIONS NETWORKS
Private Branch Exchanges
Central switching system
Handle firm’s voice and digital
communications
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COMMUNICATIONS NETWORKS
Local Area Networks
Encompass a limited distance
Require its own communication channels
Support high volumes of data and
functions requiring high transmission
speed
Gateway, router, Network Operating
System (NOS)
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COMMUNICATIONS NETWORKS
A Local Area Network (LAN)
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Figure 8-8
COMMUNICATIONS NETWORKS
Wide Area Networks (WANs)
Span large geographical distance
Consist of variety of switched and
dedicated lines, satellite, and microwave
technologies
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COMMUNICATIONS NETWORKS
Network Services
Value Added Networks: private, multipath,
data only, third party managed networks
Packet switching technology
Frame Relay
Asynchronous transfer mode (ATM)
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Standards and Connectivity for Digital Integration
Models of Connectivity for Networks
Transmission Control Protocol/Internet
Protocol (TCP/IP)
Open Systems Interconnect (OSI)
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Standards and Connectivity for Digital Integration
(TCP/IP) Reference Model
Figure 9-2
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PC to PC Communication using TCP/IP
PC-1
PC-2
Application
Application protocol
HTTP Request
TCP
TCP
HTTP Request
HTTP Request
Transport protocol
TCP
HTTP Request
IP
TCP
HTTP Request
IP
TCP
HTTP Request
IP protocol
IP
IP
TCP
HTTP Request
Data Link
protocol
Data Link
Ethernet
IP
TCP
HTTP Request
Ethernet
Physical layer
Physical medium: e.g., Ethernet cable
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COMMUNICATIONS NETWORKS
Packed-Switched Networks and Packet Communications
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Figure 8-9
Packet Switching
Packet switching breaks transmissions into packets
When a packet arrives at a switch, the switch must decide
where to send the packet next
D
E
Switch
A
Switch
Trunk Line
B
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C
Circuit Switching
End-to-end connection between phones
May pass through multiple switches and trunk lines
Reserved (guaranteed) capacity during call
Reserved circuit capacity is expensive
Good for voice/bad for data
Capacity is wasted between bursts, but still must pay for capacity
D
E
Switch
Trunk Line
A
Switch
B
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C
ELECTRONIC DATA INTERCHANGE
EDI
Direct computer to computer exchange
between two organizations of standard
business transaction documents
Lower transaction cost
Provide strategic benefits by increasing
switching cost
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