SUPDUP protocol


William Westfield (BILLW@MATHOM.CISCO.COM)
Mon 28 Sep 87 15:31:31-PDT


Although the SUPDUP protocol has a lot of advantages over the TELNET
protocol for modern computers systems, it does not provide for any
local echoing capability at all, nor does it provide for local "break
characters" (what it does provide is a standard way of negotiating
terminal capabilities (now somewhat dated in scope), and terminal
independent display capabilities).

TOPS20 has the concept of a break character bitmap, but not for an
echoing bitmap, and it required monitor modifications to get the
break character implementation to be at all useful to the popular
display editor emacs. (I originally implemented these changes back
at SRI, to (hopefully) lessen the impact of emacs on system performance.

I believe that VMS has a similar scheme.

DEC's CTERM protocol provides the means of transmitting such info over
a network connection, but DEC engineers I have talked with said that
even within DEC, the standard is rather abused (eg, most of VMS
terminal IO is done via system-extension-code XYZZY, and such).

Unix, one of the worlds most popular operating systems, doesn't have
either concept. The Annex boxes implement some local editing
functionality, but this requires both a custom version of the editor,
and custom software on the Annex, and is not a published standard.
(nor does it help outside of the editor...)

A good protocol would permit some local intelligence (eg echoing,
bunching of characters) without the local server having to know
specifics about the type of terminal being used.

What it amounts to is that most operating systems are STILL dealing
with the terminal as if it were a printer, and that this probably has
to change before a smarter virtual terminal protocol can be defined.

Bill Westfield
cisco Systems
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