Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!ncar!csn!boulder!daemon
From: MAP@lcs.mit.edu (Michael A. Patton)
Newsgroups: comp.dcom.sys.cisco
Subject: Terminal server hangs
Message-ID: <35141@boulder.Colorado.EDU>
Date: 16 May 91 23:15:43 GMT
Sender: daemon@boulder.Colorado.EDU
Lines: 34


   From: evan@is.rice.edu (Evan R. Wetstone)
   Date: Wed, 15 May 91 10:05:56 CDT

   We have experienced delays as well.  ... between our TS and our Sun 4/490.
	...
   Terminal server acks with window size of 870,
   Sun responds immediately with 7 bytes
   Terminal server acks with window size of 863,
   Sun responds 5 seconds later with 863 bytes......

This isn't what we're seeing.  We see it on connections to at least
half a dozen different systems and the symptomology is very different
from what you describe.  The pauses are substantially longer than 5
seconds (I timed one at a minute and a half) and are most noticed
during interactive echoing as delays in the echo time.

In our case the symptoms seem to have gone away again.  This coincided
pretty closely with end of classes, so I'm getting more convinced that
it's a total box load issue.  I wonder if BillW could comment on how
the system degrades when the total output rate approaches the box's
limit.  Could this affect other lines without as much output?  Might
it cause lost interrupts on the Ethernet interface?  What affect would
THAT have?  Would it just drop an incoming packet or two (which would
cause short delays awaiting retransmit timers) because you didn't pick
them up from the interface in time?  Might it cause packet output to
stop (this was one symptom we thought we noticed last time but didn't
have sufficient data to prove) because you missed an interrupt that
said you could send now.

            __
  /|  /|  /|  \         Michael A. Patton, Network Manager
 / | / | /_|__/         Laboratory for Computer Science
/  |/  |/  |atton       Massachusetts Institute of Technology