Communications and Networks

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Copyright © 2012 The McGraw
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McGraw
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Chapter 09: Communications and
Networks

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Competencies

(Page 1 of 2)


Discuss
connectivity
, the
wireless revolution, and
communication
systems.


Describe physical and wireless
communications channels.


Discuss connection devices and
services, including dial
-
up, DSL,
cable, satellite, and cellular.


Describe data transmission
factors, including
bandwidths
and
protocols
.

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Competencies

(Page 2 of 2)


Discuss networks and key network terminology
including
network interface cards

and
network
operating systems
.


Describe different types of networks, including
local
,

home
,

wireless
,

personal
,

metropolitan
,

and

wide area
networks.


Describe
network architectures
,

including

topologies

and
strategies
.


Describe the organization issues related to
Internet technologies and network security.

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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


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


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

Return

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Wireless Connections

Return


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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Communication Channels Summary

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Connection Device Signals


Types of signals


Analog


Digital

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Connection Devices


Types of modems


Telephone modem


DSL (digital subscriber line)


Cable modem


Wireless modem

(WWAN)

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Connection Services


Dial
-
Up services


Uses phone lines


Leased lines


T1


Faster
T3

and
DS3


Replaced by
optical
carrier (OC)

lines


Digital subscriber line
(DSL)


Uses phone lines


ADSL
is most widely
used
type of DSL


Cable


Uses existing TV cable


Speeds
as fast as
DSL


Satellite connection
services


Use almost anywhere


Slower than DSL
and
cable modem


Cellular
Services


Use
3G and 4G cellular
network
to provide wireless
connectivity

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Typical user connection costs, bandwidth
speeds, and comparable time required to
download an image

Connection Costs and Speeds

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Bandwidth


Measurement of the width or capacity of
the communication channel


Categories


Voice band
(or
low bandwidth
)


Medium band


Broadband


Baseband

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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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Networks


A computer network is a communication system
that connects two or more computers


Allows exchange of information and resources

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Computer Networks


Node


Client


Server


Directory server


Host


Switch


Network interface

cards (NIC)


Network operating

systems (NOS)


Network administrator


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Network Types


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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Network Architecture


Arrangement is called
topology


Types of network topology


Legacy


Bus


Ring


Current


Star


Tree


Hybrid


Mesh


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Bus Network


Each device is connected to a common cable,
called a
bus

or backbone


All communications travel along this bus


There is no host; messages are passed device
-
to
-
device in a sequence

Return

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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

Return

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Star Network


Most widely used network topology for both
homes and large businesses


Each device connects directly to a central
network
switch

Return

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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

Return

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Hybrid Network


Combination of different topologies


Large organizations have a complex
network of smaller networks


These smaller networks use a variety of
configurations


When connected together,
they form a
hybrid

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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

Return

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Network Topologies


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Network Strategies


Terminal server network


Client/server network


Peer
-
to
-
peer (P2P) network


Distributed processing network

Terminal Server

Peer
-
to
-
Peer

Client/Server

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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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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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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.

Copyright © 2012 The McGraw
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Hill Companies, Inc. All rights reserved.

Computing Essentials 2012:
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Open
-
Ended Questions
(2 of 2)



Discuss past and present network
topologies.



Define and discuss four common network
strategies.