From: utzoo!decvax!cca!dpk@BRL@sri-unix
Newsgroups: net.unix-wizards
Title: Re:  Very Distant Host support under 4.1bsd Unix.
Article-I.D.: sri-unix.3191
Posted: Thu Sep  9 17:10:53 1982
Received: Fri Sep 10 06:34:20 1982

From:     Doug Kingston 
Date:     8 Sep 82 4:44:12-EDT (Wed)
I can't speak to the condition of the VDH (or HDH) code
in 4.1, but even if it worked, you would not want to use it,
the system load of doing all the VDH (HDH) protocol on top of
TCP/IP is prohibitively expensive.  A better solution to your
problem of being distant from the IMP, is to buy a pair of ECU's
(error correction units) which are manufactured by the same people
who bring you the LHDH-11 ArpaNet Interface (ACC, Associated Computer
Consultants).  These wonderful boxes are designed to be placed between
the IMP host port and your CPU interface.  The ECU at the IMP end looks
like a host, and the ECU at the HOST end looks like an IMP.  In the
you hook up the best phone line you can get (the one you would be
running VDH on) and the ECU do the error correction in hardware to
provide an error free link from HOST to IMP.  The ECU can look like
a DISTANT or LOCAL host on either end, and the ECU is good for all the
bandwidth you can give it.  Its also a lot cheaper than getting another
IMP.
					Don't let VDH get you down,
							-Doug-