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Behind the Plug

Behind the Plug. 0110: In the Dirt, Under the Sea. In the Dirt, Under the Sea. Remember these?. In the Dirt, Under the Sea. But what does the road actually look like? Where are these links? What about these routers? What does a router look like? Where do you keep a router?

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Behind the Plug

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  1. Behind the Plug 0110: In the Dirt, Under the Sea

  2. In the Dirt, Under the Sea Remember these?

  3. In the Dirt, Under the Sea • But what does the road actually look like? • Where are these links? • What about these routers? • What does a router look like? • Where do you keep a router? • If a server that sends me a web page is just another computer, then where are all those kept?

  4. Bending Light • But why does light stay in a fiber? • If you’ve ever looked at an aquarium from the inside… • It looks like you’re surrounded by mirrors if you’re seeing the glass at an angle • Light inside a glass fiber is the same way • As long as the angle at which the light strikes the outside of the fiber is low, the light reflects off • The light “bounces” down the fiber, reflecting from side to side • Special coatings are used to enhance this mirror effect (mcgyver light mp4)

  5. Bending Light (aquarium) (bending light in water)

  6. Bending Light • Electrical signals stay inside a wire for the same reason… • The electrons “reflect” off the higher resistance air or plastic around the wire • Physically signals are either changes in light waves or changes in electrical waves • Signaling works on the “edge,” or the change in the signal • Not on the level • It’s not whether the light is on or off • It’s whether the light was off and is now on, or was on and is now off

  7. Bending Light • How far can such a signal travel? • It depends on the bandwidth you’re trying to transmit • The longest ones are around 7000km • Around 4300 miles! • Where do all these cables actually run? (ditch witch) (laying cable)

  8. Routers • These cables always terminate in some form of networking device • Either a switch or a router • The interfaces on switches and routers convert these light or electrical signals into 0’s and 1’s • Based on the protocol in use on that particular cable • The 0’s and 1’s are converted into packets • Which carry the data through protocols…

  9. Routers

  10. Reading 0’s & 1’s • We know how to convert an IP address into the binary and back • But how do we convert a letter into a number and back? • Through two different “codes” • ASCII • Unicode • Both of these are just “substitution codes”

  11. Reading 0’s & 1’s

  12. Reading 0’s & 1’s • But how do I know these numbers should be interpreted as ASCII code? • In other words, how do I know to convert these into letters, instead of something else? • 01000011 could represent a “C,” or the number 67, or… • To answer this, we have to go back to the protocol… • We came at protocols from the top down last time, we’re coming from the bottom up now 0100001101101111011011000110111101101110011010010110000101101100 C o l o n i a l

  13. Reading 0’s and 1’s Data

  14. Network Operation Review • So, let’s begin at the beginning and look at how you get that web page you were after…

  15. Network Review The web browser asks the DNS server, “what is this server’s address?” You type in “colonial.org”

  16. Network Review And your computer tells your web browser the address of the place you’re trying to go… The DNS server then responds to your computer…

  17. Network Review • The IP address tells your computer where the server is that has the information you want… • But it doesn’t tell your computer how to get there

  18. Network Review Your computer sends the packet to a nearby router, which knows how to get there because of the routing protocol The packet travels along roads of fiber and copper buried in the dirt and under the sea

  19. Network Review • At the other end of these routers and cables sits a server, just another computer • It has the information you’re looking for • The information is stored in a file • The file is formatted in a specific way to make it possible for your web browser to understand it (google data center mp4)

  20. Network Review The file the server returns looks something like this…

  21. Network Review HTML Markup (Web Page) Java Applet Flash SWF Web Browser Operating System Processor Memory Monitor Printer … Network Card Your web browser converts this mishmash of 0’s and 1’s into something you can read and understand on your screen…

  22. Network Review

  23. Network Review • Next week… • We’ll also think through a couple of network models that might help more sense out of this • We’ll figure out how the Internet is put together from a different angle… • Who owns and operates all this stuff? • How are they connected together? • Who makes all this stuff up?

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