Re: CuSeeme overloading the net?

John D. Lauer (johnlaue@umich.edu)
Tue, 30 May 1995 19:18:41 -0400


Well, there have been many heated debates going on about CU-SeeMe's
implementation of UDP and no flow control. What happened to you happens all
the time actually. It just usually doesn't turn into such a big deal.

Taken from the Berkley Sockets Help file:
TCP stands for Transmission Control Protocol. It provides for the
bi-directional, reliable, sequenced, and unduplicated flow of data without
record boundaries.

UDP stands for User Datagram Protocol. It supports bi-directional flow of
data which is not promised to be sequenced, reliable, or unduplicated. That
is, a process receiving messages on a datagram socket may find messages
duplicated, and, possibly, in an order different from the order in which it
was sent. An important characteristic of a datagram socket is that record
boundaries in
data are preserved. Datagram sockets closely model the facilities found in
many contemporary packet switched networks such as Ethernet.

UDP is essentially a subset of TCP. To totally support TCP/IP you have to
support UDP. The name says it all. TCP uses controlled transmission. If
you can only receive 14.4 kbps it will only send that much. UDP is sort of
blind and just sends it out onto the net in hopes it will get to where its
going. So it can easily send packets too quickly which ends up flooding the
net.

There's really nothing you can do except get more bandwidth.

At 11:13 PM 5/30/95 +0200, Luk Van de Heyning wrote:
>Hi,
>
>me again....
>
>My provider checked things out after I caused a major panic over here in
>Europe (by using CuSeeme it seems I overloaded the net).
>
>He claims CuSeeme (or the reflectors) are NOT TCP/IP, but UDP/IP.
>
>And in the "small print" of the providers contract it says they will provide
>total TCP/IP access. So they legally can cut this UDP/IP - thing...
>preventing us from using CuSeeme!
>
>Does anyone know what UDP means? And what the difference is compared to
TCP/IP ?
>
>My provider claims CuSeeme (or the reflector) do NO CHECKING wether the
>packets sent are all received. So they send 128 kbytes/sec (for example),
>not knowing if I (on a dial-up PPP modem-connection) can receive them. And
>with this 128 kbytes/sec, the whole system reaches it's maximum over here!
>
>Perhaps the people at Cornell can give me some answers to this one?
>
>I wan't to keep using CuSeeme (I love it), but I don't want to cause more
>trouble to the rest of Europe!
>
>
>Greatings / groetjes
>
>Luk Van de Heyning
>
>(-: PhD Internet-Addictions :-)
>
>mailto:Luk.VandeHeyning@ping.be