Animation of a Transmission Link

• Note that the packets have variable length. We often model the packet lengths by an exponential distribution.
• If you look carefully, you can see that the arrivals of packets to the system are random in time.
  • Such a sequence of random events can be modeled by a Poisson arrival process.
• The model for a link transmission system which has a Poisson arrival process and an exponential service distribution is called an M/M/1 queue.
• If you watch the animation of the M/M/1 queue for a while, you will see that sometimes the buffer can get very full. Hence the time that packet can spend waiting for transmission can be very large.
• We can show USING THE MATHEMATICS OF PROBABILITY, that this waiting time is due to the randomness inhernent in the system.
  • If you would like to find out more about the exciting subject of probability, click here to see the inside story.

If you are not yet sufficiently motivated to follow any of the mathematics links above, think about what this system would be like without random arrivals and random packet lengths.

• Would packets have to spend time waiting while packets ahead are transmitted?

• Click here to see an animation of a nonrandom (``deterministic") link transmission system.

POP QUIZ

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