From johnh@ISI.EDU  Mon Aug 11 19:30:01 2003
From: johnh@ISI.EDU (John Heidemann)
Date: Mon Aug 11 18:30:01 2003
Subject: [Ns-edu] comments about some of the ns/nam animations
Message-ID: <200308120125.h7C1PIEC006058@dash.isi.edu>

As the summer draws to a close, folks are starting to think about fall
networking classes.  I wanted to post some comments about some of the
animations in the current ns-edu animation database.

These comments are based on my notes about which animations I used
last year in class (a graduate level networking class).

My goal is to highlight a few of the animations that I know work
well, and how they fit in.

If other folks have comments about animations THEY used, please let us
know.

   -John

Some comments:

- all of the animations can be gotten from
http://www.isi.edu/cgi-bin/ns-edu/view_db.pl

- you can also browse through
http://www.isi.edu/nsnam/repository/topics.html
for a topical list (you have to be a little careful, though.  Some of
the animations have suffered bit rot and don't show what they claim.
We need to do some pruning.)

- you should download a current nam for best results.
There should be a windows binary on the nam web page.

- all of the scripts produce lots of warnings, even when run with the
  current nam.  This is a bug we should fix, but haven't done so yet. :-(

- You can link them in to powerpoint if you want; for details see
http://www.isi.edu/nsnam/ns/edu/powerpoint.html
(I just show them on a linux laptop.)

- finally, I hope to have a couple of wireless animations in a  week
  or two.  I'll post to ns-edu again when they're up.



NoSlowStart.nam:

shows the concept of dumping a large window into a bandwidth limited
link, and that causing loss.

No annotations at all, so you need to spell out what the point is for
sudents.

Good to contrast with SlowStart.nam (next).

I didn't show this one last year, but in an undergrad class it might
be nice, and could be presented quickly.


SlowStart.nam

Same setup as NoSlowStart.nam, but shows opening the window slowly,
and shows getting to a reasonable operating point (with packets spaced
and such better.

Has annotations that try to tell the story, but there are probably too
many details for it to be used alone... it has a some retransmits and
such, so not a clean story.

I didn't show this one last year, but in an undergrad class it might
be nice, and could be presented quickly, if coupled with NoSlowStart.
Otherwise 1_A4-slow-start is better (but less flashy).



1_A4-slow-start.nam

Very simple concept, but it has a good animation of slow-start.
(exponential increase in pkts/round.)  Very good for an undergrad
class.  Mabye to simple for a grad class, except that showing
time/sequence plots is IMHO important and this might be a good vehicle
for that.

Also good to show correlation between packets in flight and TCP
time/event graphs.
Pop it up in nam, then do "Analaysis > Active sessions" and click on
the button "TCP session between node 0.0 and node 1.0" to bring up the
namgraph.

By comparions ot SlowStart.nam, this one tells a much, much simpler
story, and has a nam graph.



fast-retransmit-out.nam

Reasonable job of showing fast retransmit.
Again, good to show with packets and namgraph.

Good for a grad class.  Mabye too much TCP detail for an undergrad
class or maybe not, depending on how much TCP you do.



fast-recovery-out.nam

A more complex concept.  Probably too much for an undergrad class.  I
go over it in my grad class some, but fast recovery is getting pretty
detailed wrt TCP algorithms.

As an animation, it does a reasonable job, although no annotations (text
in at the bottom of nam window).  But the dupack_ count and cwnd_ and
such is all in the monitor.