Delay X Throughput Product

(From page 175)


Tips:

- Break it into pieces

- Draw a diagram

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- 1 MB file needs to be sent.

  Related question:  What is the relationship of different data sizes?

  
































  Common measurements:  

  Bit - smallest unit. 0 or 1

  Byte - 8 bits (An IP address is written as four "octets", 4 bytes)

  Kb - kilobyte - 1,000 bytes (Actually 2 to the tenth power = 1,024)

  Mb - megabyte - 1,000 kilobytes

  Gb - gigabyte - 1,000 megabytes

  Tb - terabyte - 1,000 gigabytes  

  (These are rarely used:)

  Pb - petabyte - 1,000 terabytes

  Eb - exabyte	- 1,000 petabytes
 

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Data link operates at 64 kbps.

So how long does it take for the data link to process 1 MB?














































1 MB = 1,000 KB

1,000 / 64 =   15.625 seconds.

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We are using a fiber optic link with a propogation rate which is the speed of light
(3 X 10 to the eighth power meters/second)

Distance = 4,800 kilometers.

How long does it take for data to get from source to destination?


































(4,800,000 meters) / (300,000,000 meters/second) = .016 seconds

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How long would it take for a signal to go all the way around the globe?

Circumfrence of earth = 4,087 KM = 40,087,000 meters







































40,087,000 meters / (300,000,000 meters/second) = .13 seconds


Fiber optic cable is really fast!


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What was the total transmission time?

(Transmission delay + propogation delay)



































15.625 +
  .016
--------

15.641 seconds


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With 1 Gbps data link?











































GB = 1000 MB

1 MB / 1000 MB per second = .001 seconds

Transmission delay .001 seconds + propogation delay .016 seconds.

.001
.016
-----

.017 seconds total transmission time.







What conclusions should we draw?