Re: Melting the Internet?

Sean Foderaro (jkf@frisky.Franz.COM)
Thu, 04 May 95 08:13:56 -0700


>> I have been watching this Internet "battle" from the side line for
>> several days now and would like to know what is your goal is?

I see it more as a discussion than a battle. My comments were
made because I didn't hear anyone seriously address Barre Ludvigsen's comments
(about CU-SeeMe filling up the trans-Atlantic internet pipe).
You are correct that CU-SeeMe was not designed to be used over 14.4k
modems, however I would guess that for most of us, if you took
the bandwidth of your connection to the internet backbone divided by the number
of people you with whom you share that connection you'll find that
you don't have much more than 14.4k allocated to you. CU-SeeMe works
now by making use of the portion of the bandwidth not used by
your co-workers or fellow students. This has the implication that
the more popular CU-SeeMe becomes the worse it is for everyone
(thus the anti-Usenet newsgroup messages).

My message was that the current version of CU-SeeMe is internet-unfriendly
because it uses UDP and doesn't do adequate flow control, and
that it unnecessarly retransmits parts of pictures that haven't
changed. The folks at CU didn't agree or disagree with this statement, they
just said that the next version (due out within a few weeks) won't
have these problems.

I agree that in theory using UDP is better, as real-time data has
different properties than static data. Whether it is better in
practice will depend on how well CU layers flow control and
eliminates unneeded retransmission. Also there are many different ways of
implementing the TCP/IP protcol suite and often the only way to
find out how well something performs is to experiment [see "TCP/IP
Illustrated, Volume 1" by Stevens]. I've started some experiments
and if anything interesting comes from it I'll publish the information
here.

I also wanted to gently chastise CU for releasing CU-SeeMe in its
current form to the masses. Its default behavior is to be a
bandwidth hog. It didn't have to be that way: it could have come up
in 'demo' mode (1fps cap) and one could set it higher for
a only a certain amount of time. So if you walked away from your
terminal it would eventually slow down again. Maybe a meter
showing total packets transfered would give the person an idea
of how much of the net they were using (one advantage of using
CU-SeeMe over a modem line is that you really understand how
much retransmission goes on for those still pictures people
often send to reflectors).

When you put something out on the net for general use you
really have to think about how it will be used and safeguard against
abuse. It's a different engineering problem than designing something
for your own use.

And one final reason for my message: I'd like to seen this
mailing list used for some technical discussion.