Re: where'd my typed text go???... a sample TraceRoute

Ron Elkayam (relkay01@fiu.edu)
Sat, 13 Jul 1996 16:54:25 -0400 (EDT)


On Sat, 13 Jul 1996, Dennis J. Streveler wrote:

> >I'm not really sure where the problem is... Why can't CU-SeeMe do the
> >serialization and verification and automatically resend lost text packets?
> >I mean, nobody cares about a part of a video frame being lost (and the
> >packet authentication process will be a massive overhead which will
> >severely hamper image quality anyways), but for text messages, I really
> >think a built-in mechanism should be used to guarrantee all packets
> >are received. Since text is cheap compared to video, why not send 10
> >copies of the packet and have the receiver discard the duplicates it
> >receives?

> Your suggestion of redundant broadcast of chat packets makes some sense,
> although, in times of network conjestion, there is still a chance, although
> a diminishing chance of even the tenth packet not getting thru (using the
> UDP protocol).
>
> As for a "builtin mechanism" to assure packet delivery, well, that is the
> very essence of what the TCP/IP protocol is. If you use it however, it means
> you would have long delays. A "message" is composed of many packets (in the
> worst case) and thus the receivor will wait until all packets arrive and are
> reassembled before they are sent to the client (your computer). Thus, the
> delays would be very long for "real time" applications like voice.

Thank you for the detailed explanation and the example. But in my
argument, I suggested that video (and implied audio as well) should not be
part of this "verification" process since you'll always be kept behind
(and progressivly more and more behind) due to the fact that while you're
trying to resend and receive lost packets, a massive number of new ones
are born (coming in). What I suggested is that I guess TCP/IP will be
used for the text comminucator part. Whatever they use in IRC, in other
words. There will be lag at times (when having a multi-conference,
meaning, not the 1-on-1 DCC chat thingie in IRC), but it's still better
than not receiving the text at all! Since, as it is, the text chat is
useless if it misses even 5% of the typed text when the net is congested.

And instead of 10 copies, why not send 50? I seriously doubt anyone had a
case where 50 lines of his text disappeared in a consecutive order. That
would be the simplest way to rectify the problem without using a whole new
protocol for the text chat.

Thanks again for the educating material,
Ron