1. RFC 0734
NWG/RFC# 734				        MRC 07-OCT-77 08:46  41953
SUPDUP Display Protocol						    Page 1

Network Working Group					      Mark Crispin
Request for Comments 734					     SU-AI
NIC 41953						    7 October 1977

			  SUPDUP Protocol


This document describes  the SUPDUP protocol,  a highly efficient  display
telnet protocol.  It originally started as a private protocol between  the
ITS systems at MIT to allow a user at any one of these systems to use  one
of the others as a display.  At the current writing, SUPDUP user  programs
also exist  for  Data  Disc  and  Datamedia  displays  at  SU-AI  and  for
Datamedias at SRI-KL.  The author is not aware of any SUPDUP servers other
than at the four MIT ITS sites.

The advantage  of  the  SUPDUP  protocol  over  an  individual  terminal's
protocol is that SUPDUP defines a "virtual" or "software" display terminal
that implements relevant  cursor motion operations.   The protocol is  not
built on  any  particular  display  terminal but  rather  on  the  set  of
functions common to all display terminals; hence it is completely  device-
independent.  In addition, the protocol also provides for terminals  which
cannot handle certain operations, such as line or character insert/delete.
In fact,  it is  more than  this.   It provides  for terminals  which  are
missing any set of features, all the way down to model 33 Teletypes.

The advantage over the TELNET protocol  is that SUPDUP takes advantage  of
the full  capabilities of  display  terminals, although  it also  has  the
ability to run printing terminals.

It is to be  noted that SUPDUP operates  independently from TELNET; it  is
not an option to  the TELNET protocol.   In addition, certain  assumptions
are made about the  server and the user  programs and their  capabilities.
Specifically, it is  assumed that the  operating system on  a server  host
provides all the display-oriented features of ITS.  However, a server  may
elect not to do certain display operations available in SUPDUP; the SUPDUP
protocol is far-reaching enough so  that the protocol allows terminals  to
be handled  as well  as that  host can  handle terminals  in general.   Of
course, if a host does not  support display terminals in any special  way,
there is no point in bothering  to implement a SUPDUP server since  TELNET
will work just as well.

A more complete description  of the display facilities  of SUPDUP and  ITS
can be found by FTP'ing the  online file .INFO.;ITS TTY from ARPAnet  host
MIT-AI (host 206 octal, 134. decimal).  For more information, the  mailing
address for SUPDUP is "(BUG SUPDUP) at MIT-AI".  If your mail system won't
allow you to use parentheses, use Bug-SUPDUP@MIT-AI.