need help with TCP/IP (socket) performance problem

[Mark C. Henderson]

I don't know if there is any way around this, but here is our problem...

We have an application which opens a socket to a Xyplex terminal server
in an HP terminal emulator window. HP terminals use (of course) ENQ/ACK
flow control and the serial line we are connected to via the Xyplex is
9600 bps. Unfortunately, we're getting absolutely miserable performance
with this set up (screen update...&c. is extremely slow). Typical
sessions run almost twice as slowly (in terms of screen update) as they
do with an HP terminal hooked directly to the serial line.

A small diagram follows.
              
Workstation| 		     
running	   |  TCP/IP socket  |      |	Serial line    | Host which 
HP terminal|-----------------|Xyplex| -----------------| requires an HP
emulator   |    ethernet     |      |		       | terminal

I figure the problem is being caused by the use of ENQ/ACK flow control
(no choice) perhaps combined with some of the other peculiarities of
the HP terminal protocol, as it doesn't show up with this setup if we
replace the HP terminal emulator with a VT100 emulator (say xterm) and
the serial connection with one to a Unix host.

One thing we've tried is the TCP_NODELAY option, which doesn't seem to
give us any significant performance improvement (it seemed reasonable that
it might...) Are there are some other options that we should try?

Any help would be greatly appreciated.

Mark
-- 
Mark C. Henderson, Special Service Networks, MPR Teltech Ltd.
8999 Nelson Way, Burnaby, BC V5A 4B5 CANADA	
Email: 		henderso at mpr.ca, uunet!ubc-cs!mprgate!henderso
Telephone: 	+1 604 293 5474