lost characters in serial I/O

[Jeffrey W Percival]

We have an 11/70 running 2.8BSD, and are trying to send in data from
a remote site that supports only a crude protocol.  The remote person
logs into the 11/70, and types "cat > filename".  Then the remote person
causes the remote computer to send data down the line (2400 baud), and cat
stuffs the bytes into the file.  The remote site ends with a cntl/d.  The
remote computer uses XON/XOFF in the transfer.  Here's the problem:
if only the remote person is logged in, everything's fine.  If just
one other person logs in, then data dropouts appear in the file being
built by cat.  That is, just one additional login interferes with the
data transfer.  Can anybody suggest what the problem is?  If you want
or need more info, let me know by e-mail.

Oh yeah...  we also see something like this in another context.  When
the system is *extremely* busy, sometimes characters from users'
keyboards get dropped.  A user might type "abcdefg" and see only "abg"
on the terminal screen.  Are these problems related?  Why does very
light use cause problem #1, but problem #2 appears only with heavy use?

We will appreciate any hints you can give on this...

-- 
	Jeff Percival ...!uwvax!uwmacc!jwp