randomly dropping terminal lines

[Ed Flint]

   this is an appeal for help on the chance that someone else may have
   come across a similar problem...

   we are running 4.2BSD on a VAX 780 with Emulex CS21/F DMF lookalikes
   connected through a Gandalf PACX front end.

   over the last several weeks, logged in lines will mysteriously 'drop'
   forcing the user to log in again.  there is no consistent pattern as to
   specific lines, specific users, whether the line is idle or in the middle
   of activity.  we have been able to trap the symptoms on a datascope
   and it appears that the dmf is dropping dtr which causes the PACX to then
   drop dsr, cts and dcd, effectively logging the user off (in fact a record
   will appear in the /usr/adm/wtmp file).  the line does not appear to be 
   'hung' since a subsequent logon will work.

   a cursory look at the dmf driver says that dtr is only dropped when a tty
   line is closed or an stty 0 is received.  if this is the case why would
   a line with no activity suddenly be 'closed' ??  i haven't been able to 
   come up with a suitable explantation for the problem either from the 
   hardware or software side. 

   two other points which tend to confuse the issue:
	- the emulex board runs diagnostics like a trooper
	- a similar hardware setup running VMS has not experienced the same 
	  problems

   any assistance or potential clues would be greatly appreciated....

	ed flint
	Xerox
				{allegra|seismo}!rochester!rocksanne!ed
				flint.wbst at xerox.arpa