james tam computer networks concepts covered what is a computer network benefits and issues of...
TRANSCRIPT
James Tam
Computer Networks
Concepts covered
•What is a computer network
•Benefits and issues of networks
•Types of networks
James Tam
Benefits Of Networks (Business View)1
1) Resource sharing• Programs, hardware, data etc.
2) Reliability• Multiple copies of files, multiple processors
3) Reducing costs• Initial cost of network and future upgrades
4) Communication• The network provides yet another means of communicating
1 From “Computer Networks” by Tanebaum
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4) Communication (Instant Messaging Continued)
AIM (American online/Netscape)
ICQ (I seek you)
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Benefits Of Networks (Business View - Continued)
4) Communication - groupware
e.g. The TeamWave Workplace (Sonexis Inc.)
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Benefits of networks (person-based view)1
1) Access to remote information• E.g., access to information
2) Person-person communication• E.g., Instant messenger services, ICQ, email etc
3) Entertainment• Fun and games
1 From “Computer Networks” by Tanebaum
Diablo (Blizzard) Black Knight(Microsoft)
Ghost Recon (Red Storm)
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Social Issues Of Networks1
1) Determining what is acceptable
2) Privacy• Employers. Employees• The need for the storage of access to information vs. individual rights
3) Anonymity• Costs and benefits
1 From “Computer Networks” by Tanebaum
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What You Need For A Two Computer Network
Two computers (obvious)
A network interface card (NIC) for each computer
Ethernet connection
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A Picture Of A Two Computer Network
Computer name = “Fred”
Computer name = “Freda”
Network name = “Fland”
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What You Need For A Multi (3+) Computer Network
The computers
A network interface card for each computer
Ethernet connection
Network hub
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Connecting A Network To Other Networks
Router
• Avoids clogging computers with irrelevant data• Ensures that information reaches the proper destination
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Protecting Your Network From The Outside
Firewall
• Filters information- Offensive web sites
• Protects network- Hackers
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Types Of Networks
Local Area Network (LAN)• May be located within a single building or campus
Metropolitan Area Network (MAN)• A larger version of a LAN• May span several corporate offices or an entire city
•Wide Area Network (WAN)• May span a country or even a continent
LANMAN
LAN LAN
WAN
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Bandwidth
Determines the amount of information that can be transmitted by a network connection• Finite amount• Measured in bits per second (bps)
Transmission rate analogous to a road• Number of “lanes”• Speed
Categories• Narrow band: 40 – 100 bits/second (telegraph line)• Voice band: 110 – 9600 bits/second (phone line)• Broad band: several Megabits/second (next slides)
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Types Of Network Connections
Physical • Twisted pair• Coaxial cable• Fiber optic
Wireless• Microwave• Infrared• Light• Radio
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Twisted Pair Networks (Physical)
Twisting eliminates electrical interference from nearby pairs
Increased twisting increases the transmission rate
Category 1 Less than 1 Megabit/second (phone lines)
Category 2 Up to 4 Megabits/second
Category 3 10 Megabits/second (U of C)
Category 4 20 Megabits/second (Token Ring)
Category 5 100 Megabits/second (Fast Ethernet)
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Twisted Pair Networks (Physical - Continued)
Twisted pair can be:
•Unshielded – cheaper and takes up less space
•Shielded – protects against interference
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Coaxial Cable Networks (Physical)
Speed range• 10 – 100 Megabits per second
Copper core
Insulation
Braided outer conductor
Protective plastic covering
Metal connector
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Twisted pair vs. Coaxial cables
Both• Transmit signals through a metal cable
Coaxial cables can be longer• 100 meters (twisted pair) vs. 500 meters (coaxial cable)
Coaxial cables are linear (one break takes down an entire part of the network)
Hub
Twisted pair Coaxial cable
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Fiber Optic Networks (Physical)
Light is transmitted through a clear plastic tube
Fast with few errors• 100 Megabits per second
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Pros And Cons of Fiber (Physical Continued)
Advantages over copper wires (twisted pair and coax)• Long range• Not affected by electrical problems• Not effected by air borne corrosives • Thin and light• Secure
Disadvantages of fiber over copper• New and unfamiliar technology• Unidirectional – light travels in one direction
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Microwave-based Networks (Wireless)
No physical link required• May increase flexibility in location
Lower costs
Low error rate
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Microwave-based Networks (Wireless continued)
Slow transmission rate• 8 Megabits per second
Linear• Microwaves travel in a straight line
May be effected by atmospheric conditions• Transmissions called on account of rain…
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Infrared Networks (Wireless)
No physical link required
Cheap and easy to build
Need a clear line of sight• IR beams don’t pass well through solid objects
Slow transmission rate• 4 Megabits per second
Doesn’t work outside
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Light-based Networks (Wireless)
No physical link required
Unidirectional and limited range• ~ Several hundred meters
Highly dependent on the weather
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Radio-wave Networks (Wireless)
No physical link required
Works outdoors and indoors
Omni directional
Slow transmission• 1 Megabit per second
Subject to interference
Direct Indirect
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Radio-wave Networks: Bluetooth (Wireless)
No physical link required
Short range radio• 10 m (100 with antenna)
Works with any electronic device• Keyboard, computer, mouse, cell phone, head phone etc.
Slow• 1 Megabit per second