networks chapters 15 and 16. physical networks
TRANSCRIPT
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Networks
Chapters 15 and 16
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Physical Networks
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How Far Fetched?
http://www.youtube.com/watch?feature=player_embedded&v=5WCTn4FljUQ
1981
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The Ubiquitous Web
“When I took office, only high energy physicists had ever heard of what is called the Worldwide Web…. Now even my cat has its own page.”
- President Bill Clinton, 1996
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World Wide Web
2005
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How Many?
This is a topic that is important to us at Cisco. We believe the number of internet connected devices reached:
8.7 billion
in 2012.
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How Many?
Country Population
USA 315,718,000
Canada 35,056,064
France 65,619,000
Japan 127,360,000
India 1,354,040,000
China 1,354,040,000
The world 6,952,794,452
The Internet 8,700,000,000
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Internet All Over the World
• Africa
• Asia
• Europe
• Latin America/Carribean
• Middle East
• North America
• Oceania/Australia
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Internet All Over the World
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Internet All Over the World
By country: http://www.internetworldstats.com/top25.htm
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Languages of the Internet• Arabic
• Chinese
• English
• French
• German
• Japanese
• Korean
• Portugese
• Russian
• Spanish
• Everything else
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Languages of the Internet
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Basic Connectivity
• Circuit switching
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Basic Connectivity
• Circuit switching
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Basic Connectivity
• Packet switching
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Basic Connectivity
• Packet switching
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Basic Connectivity
• Packet switching
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LAN Topologies
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LAN Topologies
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LAN Topologies
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WANs
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When Do You Notice Packets?
When transmitting MPEGs, if the reference frame packet is lost, it isn’t possible to resolve the relative descriptions.
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Bandwidth
• Rate at which data are transmitted across a network.
• Usually measured in bits/sec.
• “Goodput” will be less than physical throughput.
• Is limited by the weakest link in the chain.
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Bandwidth
http://www.internetfrog.com/mypc/speedtest/
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Protocols
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The Restaurant Protocol
• Enter the restaurant. • Wait until greeted and taken to table.• Sit. Wait for menus.• Order drinks.• Order food.• Wait for food to come, then eat.• Ask for bill.• Pay bill.• Leave
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English Is a Communication Protocol
• Put the children’s cereal on the bottom shelves.
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Ambiguity
• You can have potatoes or rice and beans.
or
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Ambiguity
• You can have potatoes or rice and beans.
andor
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Ambiguity• You can have potatoes or rice and salad.
andor
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Robustness
The audio speaker is so construction that a sound of volume will come out of it when a key is depressed due to the finger. This is due to an electricity of alternate flowing in the coil in it.
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Robustness
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Network Protocols
• Efficient
• Unambiguous
• Robust
We need a protocol that is:
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Communication Protocols You May Have Heard Of
• tcp• ip• http• https
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The Internet Protocol Stack
TLS/SSL
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IP Addresses
232 = 4,294,967,296 different ip addresses
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Human Friendly Domain Names
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Domain Name Servers
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TCP/IP
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Watching It Work
http://www.wimp.com/internetworks/
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The Internet Protocol Stack
TLS/SSL
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World Wide Web
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Memex
Vannevar Bush’s Memex machine, described in the essay, “As We May Think” in 1945.
http://en.wikipedia.org/wiki/Vannevar_Bush
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Memex
Vannevar Bush’s Memex machine, described in the essay, “As We May Think” in 1945.
http://en.wikipedia.org/wiki/Vannevar_Bush
“Bush’s great insight was realizing that there’s more value in the connections between data than in the data itself.” - Brewster Kayle (Wired)
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Hypertext
http://www.cs.utexas.edu/~ear/
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Hypertext Transfer Protocol (HTTP)
Client Server
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HTML
Our project:
http://www.cs.utexas.edu/~ear/cs302/Homeworks/WebpageProject.html
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Building and Publishing a Site
Site Builder Server
FTP
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Secure Communication
• http://www.statesman.com
• https://www.bankofamerica.com
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