Telnet SUPDUP-Output option
RFC 749

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NWG/RFC  749                                  BSG 26-Sep-78 13:13  45499
Network Working Group                                  Bernard Greenberg
Request for Comments 749                                     MIT-Multics
NIC 45499                                              18 September 1978

                      Telnet SUPDUP-OUTPUT Option

1.  Command name and code.

   SUPDUP-OUTPUT   22

2.  Command meanings.

   IAC WILL SUPDUP-OUTPUT

   The  sender   of  this  command   REQUESTS   permission  to  transmit
   SUPDUP-OUTPUT format messages over the TELNET connection.

   IAC WON'T SUPDUP-OUTPUT

   The sender  of this command  STATES  that  he  will  no  longer  send
   SUPDUP-OUTPUT format messages over the TELNET connection.

   IAC DO SUPDUP-OUTPUT

   The sender  of this command  grants  the receiver  permission to send
   SUPDUP-OUTPUT format messages over the TELNET connection.

   IAC DON'T SUPDUP-OUTPUT

   The sender  of this  command  DEMANDS  that  the  receiver  not  send
   SUPDUP-OUTPUT format messages over the TELNET connection.

   IAC SB SUPDUP-OUTPUT 1 <terminal-parameters> IAC SE

   The sender of this command (which must be the TELNET user process) is
   supplying   information  describing  the  capabilities  of  the  user
   process' terminal.

   IAC SB SUPDUP-OUTPUT 2 n TD1 TD2 ..  TDn SCx SCy IAC SE

   The sender  of this command, which must be the TELNET server process,
   is sending  explicit  screen control information to be carried out by
   the user TELNET process.

3.  Default.

   WON'T SUPDUP-OUTPUT

   DON'T SUPDUP-OUTPUT

   i.e., the SUPDUP-OUTPUT format messages may not be transmitted.

Greenberg                                                       [page 1]


NWG/RFC  749                                  BSG 26-Sep-78 13:13  45499
Telnet SUPDUP-OUTPUT Option

4.  Motivation for the option.

   The SUPDUP-OUTPUT  protocol  provides  a means to access  the virtual
   display  support provided by the SUPDUP protocol (see RFC 734) within
   the context  of a standard  TELNET connection. This allows occasional
   display-oriented  programs  at non-display-oriented  servers  to take
   advantage  of the standardized  display  support  provided by SUPDUP.
   This cannot  be done with the standard  SUPDUP protocol or the TELNET
   SUPDUP option (RFC 736), for they both require that all communication
   after the negotiation  to  use  SUPDUP  has  been  completed  proceed
   according  to the protocol  of RFC 734.   This places upon the server
   total responsibility  for screen  management  for the duration of the
   connection,  which, by hypothesis, the non-display oriented server is
   not willing to accept.

   User TELNET  programs  at display-oriented  user hosts provide  local
   screen  management  by mapping  the NVT commands of TELNET into local
   screen   management   commands;   often,   this  involves  scrolling,
   end-of-page  processing, line clearing etc.  The SUPDUP-OUTPUT option
   allows  a display-oriented  application program at the server side to
   take over  screen  management  explicitly,  via  the  SUPDUP  display
   control repertoire.  TELNET remains in effect throughout.  The IAC IP
   and other TELNET commands are still valid.

   By means of the SUPDUP-OUTPUT  option,  display-oriented programs can
   run  on  the  server   host,  and  control  the  user  host's  screen
   explicitly.   The user TELNET process sends a description of the user
   terminal  (as specified in RFC 734) to the server TELNET process as a
   subnegiotiation  block when the SUPDUP-OUTPUT  negotiation  has  been
   successfully  completed.   The server  TELNET  process sends explicit
   screen  control commands via subnegotiation blocks to the user TELNET
   process.

5.  Description of the option.

   The SUPDUP-OUTPUT protocol may only be initiated by the server TELNET
   process.   A server  TELNET  process wishing to take advantage of the
   SUPDUP-OUTPUT  protocol will initiate a negotiation for it by sending
   IAC WILL SUPDUP-OUTPUT.   The user  TELNET  process  must  accept  or
   refuse  the offer by  sending  IAC  DO  SUPDUP-OUTPUT  or  IAC  DON'T
   SUPDUP-OUTPUT.

   If the user  TELNET  process  agrees  to  support  the  SUPDUP-OUTPUT
   option,   it  must  follow   the  sending  of  IAC  DO  SUPDUP-OUTPUT
   immediately   with  a  description  of  the  user's  terminal.   This
   information  is described in RFC 734 as the "terminal parameters." It
   is to be sent as a series  of six-bit  bytes,  one byte per eight-bit

Greenberg                                                       [page 2]


NWG/RFC  749                                  BSG 26-Sep-78 13:13  45499
Telnet SUPDUP-OUTPUT Option

   TELNET  data byte.   These  words may or may not contain the optional
   line speed and graphics capabilities parameters described by RFC 747;
   the first  six bytes  specify  the count of 36-bit words to follow as
   described by RFC 734.

   The terminal  parameter block will be sent as a subnegotiation of the