Re: thoughts

Tim_Dorcey@cornell.edu
Sat, 22 Oct 1994 16:23:20 -0400


Per Gregers Bilse <bilse@EU.net> says:

>On Oct 17, 21:38, Tim_Dorcey@cornell.edu wrote:
>> >> anybody have time to help us out with some quick experiments? Try running
>> >> CU-SeeMe point-to-point along with some big ftp's over some low capacity
>> >> link and measure the throughputs. Does CU-SeeMe's rate cap stabilize?
>>How
>> >> does it compare to the ftp throughput?].
>> >
....
>
>> >remote office, we added one cu-seeme point-to-point connection, limited
>> >to a fairly low rate maximum transmission. The effect was to destroy the
>> >performance for users of TCP terminal sessions.
>
>.. CU-SeeMe session prevents low bandwidth, well-behaved traffic
>like terminal sessions from getting through, how will higher-volume,
>well-behaved traffic fare? Why don't you stage the experiment
>yourself, if you believe an experiment is necessary? You do know how
>TCP works and deals with network congestion, don't you? A non-TCP
>application doesn't need particularly pointed elbows to cause TCP,
>which is very polite, to slow down to a crawl.

Per is right to take me to task if there was a hint in my suggested
experiment that CU-SeeMe might be as polite as TCP. CU-SeeMe is surely
going to use more of the bandwidth than an ftp (experiments could tell us
by how much). I also regret suggesting that there might be a simple
technological solution just around the corner. It is true that the
situation will be improved tremendously when reflectors have the ability to
send different rate video to different recipients, but that won't get us to
the point where you can fire up CU-SeeMe on any network without concern for
the resources it may consume. And, to put those resources into
perspective, if you are transmitting video at the default rate of 80 kbps
(kilobits per second), that's roughly equivalent to sending this mail file
3 times per second, or, put another way, 5000 people sending a mail file
like this once every half hour. Now, if you are receiving 8 such
streams...well, you can do the arithmetic.

>
>Like anybody else doing what we do, we have a bag of network test
>tools. Some of these are clearly labeled "Dangerous", like eg wping
>from Matt Mathis:
>
>"
>Due to windowed ping's potential danger to the Internet, we are taking
>measures to limit its distribution. At this time we are only releasing the
>code to people who support some aspect of the global Internet, including
>network researchers, router vendors, and network service providers. We are
>not releasing windowed ping to people who have no use for it except to harass
>their network providers.
>"

If someone is interested in harassing their network provider, there is
nothing difficult in writing an application that will transmit UDP packets
at a far higher rate than CU-SeeMe. I don't believe Internet usage can be
effectively regulated by limiting the distribution of software or of the
knowlege to create it. It is our objective to make it easy for CU-SeeMe
users to be responsible bandwidth consumers, but ultimate responsibility
must lie with the user. There will soon be a number of improvements along
those lines, and we always welcome additional suggestions. Also, we need
to do more in the way of education. The perspective of a network service
provider is especially valuable and I hope everyone has been listening to
what Per has to say.

-Tim
__________________________________________________________________
Tim Dorcey T.Dorcey@cornell.edu
Sr. Programmer/Analyst (607) 255-5715
Advanced Technologies & Planning
CIT Network Resources
Cornell University
Ithaca, NY 14850
__________________________________________________________________