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Lecture 13
NETWORK BASICS
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STUDENT LEARNING
OUTCOMES
1. Identify and describe the four basic concepts
on which networks are built and describe
what is needed to set up a small peer-topeer network at home.
2. Describe the components used to build large
business networks and define and compare
local area networks (LANs), wide area
networks (WANs), and metropolitan area
networks (MANs).
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STUDENT LEARNING
OUTCOMES
3. Compare and contrast the various Internet
connection possibilities.
4. Compare and contrast the types of
communications media.
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STUDENT LEARNING
OUTCOMES
5. State the four principles of computer security
and describe how different network security
devices reflect those principles.
6. Describe client/server business networks
from a business and physical point of view.
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INTRODUCTION
o Computer network – two or more computers
connected so that they can communicate with
each other and share information, software,
peripheral devices, and/or processing power
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INTRODUCTION
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Basic Principles of Networks
Four main principles
1. Each computer must have a network
interface to provide a doorway for
information
2. The network usually has at least one
connecting device
3. The network must have communications
media to transport information
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Basic Principles of Networks
4. Each computer must have software to move
information in and out of the computer
These four principles apply to all networks,
large and small
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HOME NETWORKS
A typical home network setup has
1. An Ethernet network card in each computer or a
wireless card in each laptop
2. Network cables to transmit signals, or no cables
for wireless
3. A DSL or cable modem connection and a
broadband/home router
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Network Cards
Network interface card (NIC) – an expansion
card or PC card that connects your computer
to a network
– Ethernet card – the most common type of network
interface card
– Built into the motherboards of many new computers
– looks like a telephone jack, but wider
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Wired Transmission Media
Cat 5 (Category 5) cable – better-constructed
version of phone twisted-pair cable
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Wireless Transmission Media
o Wireless Access Point (WAP) – device that
allows a computer to use radio waves to access
a network
o Connects to hub or switch with a cable like a
wired computer
o May be built into broadband router and not
require separate cabling
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Home Internet Service
o Broadband router or home router – a device to
connect computers together to share DSL or
cable Internet service in a home or small office
– One port to plug into DSL or cable connection to connect
to the Internet
– Usually several ports to build a network for home
computers or printers and share Internet connection
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Network Software
o Makes each computer's hardware work
o Can use Windows
o Turn on file sharing to make files available to
other computers on the network
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NETWORK COMPONENTS
o Hub – a device that connects computers into
a network and repeats all transmissions to
every connected computer
– Only one computer can transmit at a time
– All computers see every message
– Can have collisions when two computers try to
transmit at the same time
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NETWORK COMPONENTS
o Switch – a device that connects computers
and repeats transmissions only to intended
recipient
– Multiple conversations can occur simultaneously
between different sets of computers
– Only recipient computer sees each message
– Computers can still broadcast messages to all
other computers on the network
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NETWORK COMPONENTS
o Router – a device that connects subnetworks
(subnets) of a larger network
– Can connect different buildings at same or different
locations
– Passes transmissions from one network to another
– May pass through multiple routers on the way from
source to destination
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NETWORK COMPONENTS
o More on routers
– Home/broadband routers often have built-in
switches or hubs
– Corporate routers generally require separate
switches or hubs
– Routers must be configured with information about
the networks they connect
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NETWORKS BY DISTANCE
o Large networks can be classified by the
proximity of the area(s) they serve:
– Local Area Network (LAN) – network that serves
a building or buildings in a contiguous area
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NETWORKS BY DISTANCE
o More networks by distance
– Wide Area Network (WAN) – a set of connected
networks serving areas not immediately contiguous
– Metropolitan Area Network (MAN) – a set of
connected networks within the same city or
metropolitan area but not in immediate proximity to
each other
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THE INTERNET
o A vast network of computers that connects
people all over the world
o Computers pass messages through routers to
their ultimate destinations
o Each router determines whether it has a
direct path to the recipient or whether to send
the message on to another router
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Bandwidth
o The amount of information that can be
transferred in a given amount of time
o Usually expressed as bits per second (bps)
o Higher bandwidths expressed as
– kilobits per second (Kbps) – thousands of bits per
second
– megabits per second (Mbps) – millions of bits per
second
– gigabits per second (Gbps) – billions of bits per
second
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Internet Connection Types
o
o
o
o
o
Phone line and dialup modem
Phone line and DSL modem
Cable TV line and cable modem
Satellite modem
Dedicated high-speed business lines
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Broadband Internet Connection
o Broadband – high-capacity
telecommunications line capable of providing
high-speed Internet service
o All Internet access methods on the previous
slide are broadband except the dialup modem
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Dialup Connection
o Modem – connects a computer to a phone line
to access another computer or network
o Modulates outgoing signal from digital to analog
form
o Demodulates incoming signal from analog to
digital form
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Digital Subscriber Line (DSL)
o Digital Subscriber Line (DSL) – highspeed Internet connection using phone
lines, which allows you to use your phone
for voice communications at the same
time
o Runs at a higher frequency than voice
conversations, so not supported on some
older phone lines
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Cable Modem
o Cable modem – uses your TV cable to deliver
an Internet connection
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Satellite Modem
o Satellite modem – delivers Internet access
from satellite dish
o Satellite TV and modem may share same
dish or may be separate
o Connects to computer or broadband router
like cable modem
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T1 and DS3 Business Lines
o T1 and DS3 developed by phone companies
to carry many long-distance voice
conversations
o T1 runs up to about 1.5 Mbps
o DS3 runs up to about 45 Mbps
o Can carry both voice and network over the
same lines
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Frame Relay and ATM Business
Services
o Frame Relay and ATM are used to
connect many branch offices to the
main office
o Use virtual circuits to simulate
having a line from every office to
every other office
Virtual Circuits
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Comparison of Connection Types
o Telephone modem
– + Inexpensive and available anywhere there's a
phone line
– - Slow, and ties up the line for voice calls too
o DSL
– + Higher-speed connection, doesn't tie up the
phone line for voice calls, and can be left on all the
time
– - Not available in all areas or on all lines
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Comparison of Connection Types
o Cable modem
– + Higher-speed connection, doesn't use the phone
line at all, and always-on
– - Connection shared with the neighborhood, so
speed may vary
o Satellite modem
– + Available in remote locations where DSL and
cable aren't
– - High cost
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Comparison of Connection Types
o T1 and DS3
– + High-speed to very-high-speed connections, can
transmit both voice and data
– - High cost that may be mileage-dependent
o Frame relay and ATM
– + Use virtual circuits to simulate more inter-office
connections than are physically present
– - High cost normally affordable only by mid- to
large-scale enterprises
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Voice Over IP
o Voice over IP – allows you to send voice
communications over the Internet and avoid
long-distance toll charges
o No long-distance calling cost
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NETWORK COMMUNICATIONS
MEDIA
o Communications media – the paths in a
network over which information travels
o Wired communications media – transmit
information over a closed, connected path
o Wireless communications media – transmit
information through the air
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Wired Communications Media
o Twisted-pair cable – a bundle of copper wires
for transmitting voice or data
o Cat 5 and Cat 5e are common for modern
networks
o Coaxial cable (coax) – one central wire
surrounded by insulation, a metallic shield, and
a covering of insulation
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Wired Communications Media
o Optical fiber – uses a very thin glass or plastic
fiber through which pulses of light travel
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Wireless Communications Media
o Infrared – uses red light to send and
receive information
o Bluetooth – a standard for transmitting
information in the form of short-range radio
waves over distances of up to 30 feet and
is used for purposes such as wirelessly
connecting a cell phone or PDA to a
computer
o Microwave – a type of radio transmission
– Repeater – receives a radio signal, strengthens
it, and sends it on
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Wireless Communications Media
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Wireless Communications Media
o Communications Satellite – microwave
repeater in space
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NETWORK SECURITY
The four principles of network security are:
1.
2.
3.
4.
Confidentiality
Authenticity
Integrity
Availability
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NETWORK SECURITY
o Confidentiality – information can be obtained
only by those authorized to access it
– Bank statements, credit reports, employee
evaluations
– Threatened by capture of network transmissions
and easily-guessed passwords
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NETWORK SECURITY
o Authenticity – information really comes from
the source it claims to come from
– Military orders, medical diagnoses, stockbroker
directions
– Threatened by fraudulent e-mails and misspellings
of popular Web site names
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NETWORK SECURITY
o Integrity – information has not been altered
– Bank balance, corporate Web site, prescriptions,
credit card charges
– Threatened by forged network transmissions and
faulty server software
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NETWORK SECURITY
o Availability – a service or resource is
available when it's supposed to be
– Mail-order Web site, corporate e-mail server
– Threatened by network failures, faulty server
software, and high volumes of malicious network
traffic
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Firewalls & Intrusion Detection
Systems
o Firewall – protects a computer from intruders
o Intrusion detection system (IDS) – watches
for and reports intrusion attempts
o Intrusion prevention system (IPS) – type of
IDS that also takes action against intrusion
attempts
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Encryption
o Encryption – scrambles data so you can't
read it without having the decryption key
o Virtual Private Network (VPN) – encrypts all
network transmissions between two
endpoints to protect confidentiality and
integrity of data
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Firewalls & Intrusion
Detection Systems
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Malware
o Malware – software designed to harm your
computer or security
1. Virus – software written with malicious intent to
cause annoyance or damage
2. Worm – spreads itself from computer to computer
via e-mail and other network traffic
3. Spyware – collects information about you and
reports it to someone else without your permission
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CLIENT/SERVER SOFTWARE
MODEL
o Client/server network – a network in which
one or more computers are servers and
provide services to the other computers,
called clients
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Client/Server: A Business View
Client/server networks differ according to
1. Where the processing for the presentation of
information occurs
2. Where the processing of logic or business rules
occurs
3. Where the data management component (DBMS)
and information (database) are located
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Client/Server: Model 5
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Five Models of Client/Server
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Five Models of Client/Server
1. Distributed Presentation
–
The server handles almost all functions, including
a major portion of the presentation
2. Remote Presentation
–
The client handles all presentation functions
3. Distributed Logic
–
The server handles all data management, the
client handles all presentation formatting, and the
logic processing is shared
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Five Models of Client/Server
4. Remote Data Management
–
The server handles data management only, and
the client processes business rules and formats
the presentation of results
5. Distributed Data Management
–
The client handles all presentation formatting and
business rule processing, and both the server and
client share data management duties
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