module e: network basics. introduction computer network – two or more computers connected so that...
TRANSCRIPT
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Module E: Network BASICS
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INTRODUCTION
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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Number of connections
For n nodes, you would need n(n-1)/2 connections
For examples to connect 5 nodes we would need 5 (5-1)/2=10
connections
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Basic Principles of Networks
Four main principles1. 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 has1. 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
Wireless Access Point (WAP) – device that allows a computer to use radio waves to access a network
Connects to hub or switch with a cable like a wired computer
May be built into broadband router and not require separate cabling
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Home Internet Service
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
Makes each computer's hardware work Can use Windows Turn on filesharing to make files
available to other computers on the network
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NETWORK COMPONENTS
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
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
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
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
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
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
A vast network of computers that connects people all over the world
Computers pass messages through routers to their ultimate destinations
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
The amount of information that can be transferred in a given amount of time
Usually expressed as bits per second (bps)
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
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
Broadband – high-capacity telecommunications line capable of providing high-speed Internet service
All Internet access methods on the previous slide are broadband except the dialup modem
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Dialup Connection
Modem – connects a computer to a phone line to access another computer or network
Modulates outgoing signal from digital to analog form
Demodulates incoming signal from analog to digital form
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Digital Subscriber Line (DSL)
Digital Subscriber Line (DSL) – high-speed Internet connection using phone lines, which allows you to use your phone for voice communications at the same time
Runs at a higher frequency than voice conversations, so not supported on some older phone lines
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Cable Modem
Cable modem – uses your TV cable to deliver an Internet connection
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Satellite Modem
Satellite modem – delivers Internet access from satellite dish
Satellite TV and modem may share same dish or may be separate
Connects to computer or broadband router like cable modem
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T1 and DS3 Business Lines
T1 and DS3 developed by phone companies to carry many long-distance voice conversations
T1 runs up to about 1.5 Mbps DS3 runs up to about 45 Mbps Can carry both voice and network
over the same lines
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Frame Relay and ATM Business Services
Frame Relay and ATM are used to connect many branch offices to the main office
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
Telephone modem + Inexpensive and available anywhere
there's a phone line - Slow, and ties up the line for voice
calls too 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
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
Satellite modem + Available in remote locations where
DSL and cable aren't - High cost
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Comparison of Connection Types T1 and DS3
+ High-speed to very-high-speed connections, can transmit both voice and data
- High cost that may be mileage-dependent
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
Voice over IP – allows you to send voice communications over the Internet and avoid long-distance toll charges
No long-distance calling cost
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NETWORK COMMUNICATIONS MEDIA
Communications media – the paths in a network over which information travels
Wired communications media – transmit information over a closed, connected path
Wireless communications media – transmit information through the air
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Wired Communications Media
Twisted-pair cable – a bundle of copper wires for transmitting voice or data
Cat 5 and Cat 5e are common for modern networks
Coaxial cable (coax) – one central wire surrounded by insulation, a metallic shield, and a covering of insulation
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Wired Communications Media
Optical fiber – uses a very thin glass or plastic fiber through which pulses of light travel
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Wireless Communications Media Infrared – uses red light to send and
receive information 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
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
Communications Satellite – microwave repeater in space
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NETWORK SECURITY
The four principles of network security are:1. Confidentiality2. Authenticity3. Integrity4. Availability
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NETWORK SECURITY
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
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
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
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
Firewall – protects a computer from intruders
Intrusion detection system (IDS) – watches for and reports intrusion attempts
Intrusion prevention system (IPS) – type of IDS that also takes action against intrusion attempts
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Encryption
Encryption – scrambles data so you can't read it without having the decryption key
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
Malware – software designed to harm your computer or security1. 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
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 to1. Where the processing for the
presentation of information occurs2. Where the processing of logic or
business rules occurs3. 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