![](/icons/Lines/rainline.gif)
Animation of a Transmission Link
|
As you watch the animation . . .
- 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.
- 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.
![](/icons/Rulers/look.gif)
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.
Randomness is an important cause of delay for packets in a computer network.
![](/~vastola/icons/lrainline.gif)
next
Ken Vastola
Fri Mar 15 14:12:07 EST 1996