LAT drops info

[Bill Daniels]

Hardware: DECstation 5000, DECserver 300, Xyplex 5500
Software: Ultrix 3.1D

We are running a test application on a DECstation 5000 using the built-in
Thinwire port and terminal servers for serial output.  Our test application
involves writing data to 32 terminal server ports which have their serial
ports looped directly to another 32 terminal server ports which are read
into a file.  There is a process for each of the write tasks and a process
for each of the read tasks for a total of 64 processing writing and reading
as fast as possible.  Things begin to slow considerably on the DS5000 during
the test.  The read processes put the correct number of bytes into the data
files when running to the DECservers MOST OF THE TIME BUT NOT ALL OF THE
TIME.  The read processes never put the correct number of bytes into the
data files when running to the Xyplex servers (8-port cards in a rack).  This
data loss seems to be load related because running fewer ports (32, 16, 8)
provides NO data loss.  During the 64 port test to the DECserver 300, the
DS5000 reports approx. 9000 frames received and 9000 frames transmitted over
the course of 150 seconds or so using "lcp -c".  The same command run after
a test of the 8-port cards in the Xyplex rack reports approximately 17,000
frames.

Is there a buffer associated with "lta" that may be getting overrun?  This
seems to be implied by the Xyplex servers with lower port density using
more frames and more data loss.  If there is a buffer that is getting
overrun, what can be done about it?  What is a reasonable number of bytes
and packets to expect LAT to handle correctly under Ultrix?

HELP ME PLEASE!!!

bd
-- 
bill daniels
federal express, memphis, tn
{hplabs!csun,mit-eddie!premise}!fedeva!bill