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CHAPTER 6
Telecommunications and Networks
Learning Objectives
1.
2.
3.
4.
Understand the concept of a network.
Apply Metcalfe’s law in understanding the value of
a network.
Identify several major developments and trends in
the industries, technologies, and business
applications of telecommunications and Internet
technologies.
Provide examples of the business value of Internet,
intranet, and extranet applications.
Learning Objectives
5.
6.
7.
8.
9.
Identify the basic components, functions, and types of
telecommunications networks used in business.
Explain the functions of major components of
telecommunications network hardware, software,
media, and services.
Explain the concept of client/server networking.
Understand the two forms of peer-to-peer networking.
Explain the difference between digital and analog
signals.
Learning Objectives
10.
11.
12.
13.
Identify the various transmission media and
topologies used in telecommunications networks.
Understand the fundamentals of wireless network
technologies.
Explain the concepts behind TCP/IP.
Understand the seven layers of the OSI network
model.
Network Concept

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Network: A connected system of objects or people
Computer network: A collection of computers and other
hardware devices connected together so users can share
hardware, software, and data, and electronically
communicate
Networks range from small private networks to the
Internet (largest network in the world)
Network Concepts

Number of possible connections on a network is N *
(N-1)
 Where
N = number of nodes (points of connections on
the network)
 Example, if there are 10 computers on a network, there
are 10 * 9 = 90 possible connections
Bob Metcalfe’s Law



The usefulness (value) of a network equals the
square of the number of users
If there are only 2 users on the network, it’s not very
useful; if there are 200 it’s much more useful.
So the Internet with millions of computers is
incredibly useful.
Telecommunications

Telecommunications
 Exchange
of information in any form (voice, data, text,
images, audio, video) over networks
Telecommunications

When we communicate, we are sharing information. This sharing
can be local or remote.
Local ( usually occurs face to face) or
remote ( take place over distance)

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
Data Communications

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
The movement of computer information from one point to another by
means of electrical or optical transmission systems.
Such systems are often called data communications networks.
Telecommunication (which Includes telephony, telegraphy and
television ) (tele is Greek for "far“)


means communication at a distance
Exchange of information in any form (voice, data, text, images,
audio, video) over networks
Components of data communication
1. Message: data  text, number, audio …
2. Sender: device that sends the data – computer, telephone, camera
3. Receiver: device that receives the data – computer, telephone,
camera
4. Transmission medium: physical path by which message travels.
5. Rules or Protocols: Set of rules that govern data communications/
an agreement between the communicating devices
components of data communication
Simple model of communication
Simple model of Communication

The key elements of this model are:
 Source

generates data to be transmitted
 Transmitter

converts data into transmittable signals
 Transmission

System
carries data from source to destination
 Receiver

converts received signal into data
 Destination

takes incoming data
Open Systems


Information systems that use common standards for
hardware, software, applications and networks
Open systems provide:

Connectivity:
 Ability of networked computers to easily access and communicate with
each other and share information
Interoperability:
 The ability of an open system to enable end user applications to be
accomplished using different varieties of computer systems, software
packages, and databases provided by a variety of interconnected
networks
Middleware

Any programming that serves to “glue together” two
separate programs
Middleware
Programming that mediates between
two separate programs
Allows a particular database to access other
databases without custom programming
Data Transmission Characteristics



There are two fundamentally different types of data:
Digital data –
 Computer produced signals that are binary, either
on or off.
 Digital data have discrete states and take discrete
values.
Analog –
 Electrical signals which are shaped like the sound
waves they transfer.
 Analog data are continuous and take continuous
values
15
Data Transmission Characteristics
Signals: Electric representations of information. Can be Analog or
Digital

An analog signal refers to something that is continuous- a
type of signal represented by continuous waves.


Analog signals can have an infinite number of values
in a range
A digital signal refers to something that is discrete –a type of
signal where data represented by 0s and 1s

digital signals can have only a limited number of
values.
Transmission can also be Analog or Digital

Analog transmission system: continuous signals

Digital transmission system: discrete signals
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encoder/decoder
modulator/demodulator
Digital Network Technologies
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Rapid change from analog to digital network
technologies
Analog: voice-oriented transmission, sound waves
Digital: discrete pulse transmission
Digital allows:
 Higher
transmission speed
 Larger amounts of information
 Lower error rates
…
Internet2
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Next generation of the Internet
High-performance network
In use at 200 universities, scientific institutions,
communications corporations
Internet2 may never replace the Internet. May
remain a scientific and government network.
Business Value of Telecommunication Networks
The Internet
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Over 46 million servers (2004)
710 – 945 million users (2004)
No central computer system
No governing body
No one owns it
Internet Service Provider

ISP
A
company that specializes in providing easy access to
the Internet
 For a monthly fee, you get software, user name,
password and access

ISPs are connect to one another through network
access points
Popular uses of the Internet
An Intranet

A network inside an organization
 That
uses Internet technologies (such as Web browsers
and servers, TCP/IP protocols, HTML, etc.)
 To provide an Internet-like environment within the
organization
 For information sharing, communications, collaboration
and support of business processes
 Can be accessed by authorized users through the
Internet
Enterprise Information Portal
Intranets provide an enterprise information portal.
Extranet

Network links that use Internet technologies
 To
connect the Intranet of a business With the Intranets
of its customers, suppliers or other business partners
 Intranet
that is at least partially accessible to authorized
outsiders
Types of Communications Networks
Wide Area
Local Area
Communication
Networks
Peer-to-Peer
Virtual Private
Client/Server
Wide Area Network (WAN)

Telecommunications network that covers a large
geographic area
Source: Courtesy of Cisco Systems Inc.
Local Area Network (LAN)

Connect computers within a limited physical area
such as an office, classroom, or building
Virtual Private Networks (VPN)
A secure network that uses the Internet as its
backbone but relies on firewalls, encryption
and other security
 A pipe traveling through the Internet

VPN
Client/Server networks
Clients: End user personal computers or
networked computers
 Interconnected by LANs
 Servers: manage networks
 Processing shared between clients and servers

Network Computing
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Thin client means that very little processing is done
on the client. Most the processing is done on the
server.
Three-tier model includes thin clients, application
servers and database servers
Two tiered client server includes just client and
server
Peer-to-Peer Networks
Central Server Architecture
P2P file-sharing software connects all PCs
to a central server that contains a directory of all online users
The server sends the requesting PC a list of
links to all active peers who have the file
Clicking a link connects the two PCs and
automatically transfers the file to the
requesting PC
Peer-to-Peer Networks
Pure Peer-to-Peer Architecture
No central directory or server
File-sharing software connects
one PC to another online user
When you request a file, the software
searches every online user, then sends
you a list of active file names
Clicking a link automatically transfers the file
from that user’s hard drive to yours
Peer-to-Peer Network Diagrams
Telecommunications Media
Source: Phil Degginger/Getty Images.
Wireless Technologies

microwave
 Earthbound
microwave systems that transmit high-speed
radio signals in a line-of-sight path
 Between relay systems spaced approximately 30-miles
apart

Communications satellites
 Satellite
serves as relay stations for communications
signals
 Uses microwave radio signals
Wireless Technologies

Cellular and PCS telephone and pager systems
 Divide
the geographic area into small areas or cells
 Each cell has transmitter or radio relay antenna to send
message from one cell to another

Wireless LANs
 Radio
signals within an office or building
 Connect PCs to networks

Bluetooth
 Short-range
wireless technology
 To connect PC to peripherals such as printer
Wireless Web

Connect portable communications devices to the
Internet
Telecommunications Processors

Modems
 Convert
digital signals from a computer into
 Analog frequencies that can be transmitted over
ordinary telephone lines
Comparing modem and other
technologies
Internetwork Processors
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Switch – makes connections between
telecommunications circuits in a network
Router – intelligent communications processor that
interconnects networks based on different protocols
Hub – a port switching communications processor
Gateway – connects networks using different
communications architectures
Telecommunications Processors

Multiplexer… allows a single communications
channel to carry simultaneous data transmissions
from many terminals
Telecommunications Software
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
Used by servers and other computers to manage
network performance
Network Operating Systems
Middleware
Network management functions

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Traffic Management – manage network resources and traffic to
avoid congestion and optimize service levels to users
Security – provide authentication, encryption, firewall, auditing
and enforcement
Network Monitoring – troubleshoot and watch over the network,
informing network administrators of potential problems before
they occur
Capacity Planning – survey network resources and traffic
patterns and users’ needs to determine how best to
accommodate the needs of the network as it grows and changes
Network Topologies
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Topology: structure of a network
Star: ties end user computers to a central computer
Ring: ties local computer processors together in a ring
on a relatively equal basis
Bus: local processors share the same communications
channel
Network Topologies
OSI & TCP/IP Models

Open Systems Interconnection (OSI) Model
A
seven-layer model that serves as a standard model
for network architectures
 Model for how messages should be transmitted between
two points in a network
 Each layer adds functions

Transmission Control Protocol / Internet Protocol
(TCP/IP)
A
five layer telecommunications protocol used by the
Internet
OSI & TCP/IP Models
Internet Telephony
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Using an Internet connection to pass voice data using
IP
Voice over IP (VoIP)
Skips standard long-distance phone charges
Bandwidth

Bandwidth
 Frequency
range of a telecommunications channel
 Determines transmission rate
 Classified in bits per second (bps)

Transmission Rates:
 Narrow-band
– low-speed
 Broadband – high-speed
Transmission Speeds
Switching Alternatives

Circuit Switching
 Switch
opens a circuit to establish a link between a
sender and receiver
 it remains open until the communication session is
completed

Packet Switching
 Break
messages into groups called packets
 Transmit packets separately