Re: transmission rate cap

Jan Engvald LDC (Jan.Engvald@LDC.lu.se)
Fri, 16 Sep 1994 16:17:22 -0400


> Should I be looking for a reason for the very slow data rate (< 1 fps) and
> high packet loss (95%) I experience off the NASA Select feed at my site or is
> this something everyone is experiencing. My previous experience has been
> pretty good audio fidelity but recent performance is unintelligable ... Gav

I often also get high packet loss, when it is more than 30 % it is rare
to hear any complete sentence. Investigations tell that most of the time
this is due to an overload of the link between t1.gwnasa.oar.net
(199.18.113.74) and csp2-e0.cleveland.oar.net (199.18.112.2).

If you have a MS-DOS PC you can easily find the bottlenecks of a path
using the trace route function of PDTSTNET, just call

pdtstnet hopcheck=<name or IP nr>

and the path will be traced 3 times in a few seconds (10 seconds
actually). Where you see a jump in delay times is where the bottleneck is.
I have often seen a 1000 ms increase at the abovementioned link,
other links add less than some tens of milliseconds per link.

PDTSTNET is available from oak.oakland.edu:pub/msdos/pktdrvr/pdtst217.zip
and other simtel mirrors.

You can also use other trace route routines, but they often take a minute
or more to complete when the packet loss rate is high.


Jan Engvald, Lund University Computing Center
________________________________________________________________________
Address: Box 783 E-mail: Jan.Engvald@ldc.lu.se
S-220 07 LUND Earn/Bitnet: XJELDC@SELUND
SWEDEN Span/Hepnet: Sweden::Gemini::xjeldc
Office: Soelvegatan 18 VAXPSI: psi%2403732202020::xjeldc
Telephone: +46 46 107458 X.400: S=Engvald/G=Jan/O=ldc/
Telefax: +46 46 138225 PRMD=lu/ADMD=sunet/C=se
Telex: 33533 LUNIVER S