Remote Controlled Transmission and Echoing Telnet option
RFC 560

Document Type RFC - Unknown (August 1973; No errata)
Updated by RFC 581
Last updated 2013-03-02
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Network Working Group                                         D. Crocker
Request for Comments: 560                                      J. Postel
Category: Protocols, TELNET                               20 August 1973
NIC: 18492

         Remote Controlled Transmission & Echoing TELNET Option

   Currently, a terminal in character-at-a-time transmission and
   foreign-host echo causes four Network Messages for each character
   struck.  (The character sent from local to foreign host; its RFNM;
   the echoed character sent from the foreign to the local host; and its
   RFNM.)

   By eliminating most echoing (1/2 as many messages) and packaging the
   characters into useful units (assuming an average of five character
   per unit; therefore another 80 per cent reduction), it is believed
   that almost a 90 per cent reduction in character-mode interactive
   Network terminal traffic can be attained.

   The packaging of characters and elimination of foreign echoing should
   also lessen the load placed on the foreign hosts.

1. Command name and code:

   RCTE

2. Command meanings:

   IAC WILL RCTE

      The sender of this command REQUESTS or AGREES to use the RCTE
      option, and will send instructions for controlling the other
      side's terminal printer.

   IAC WON'T RCTE

      The sender of this option REFUSES to send instructions for
      controlling the other side's terminal printer.

   IAC DO RCTE

      The sender REQUEST or AGREES to have the other side (sender of
      WILL RCTE) issue commands which will control his (sender of the
      DO) output to the terminal printer.

Crocker, et. al.                                                [Page 1]
RFC 560               RCT & Echoing TELNET Option            August 1973

   IAC DON'T RCTE

      The sender of this command REFUSES to allow the other side to
      control his (sender of DON'T) terminal printer.

   IAC SB RCTE <cmd> [BC1 BC2] [TC1 TC2]

      where:

         <cmd> is one 8-bit byte having the following flags (bits are
         counted from the right):

         Bit   Meaning

         0      0 = Ignore all other bits in this byte and repeat the
                    last <cmd> that was sent.  Equals a 'continue what
                    you have been doing'.
                1 = Perform actions as indicated by other bits in this
                    byte.

         1      0 = Print (echo) Break character
                1 = Skip (don't echo) Break character

         2      0 = Print (echo) text up to Break character
                1 = Skip (don't echo) text up to Break character

         3      0 = Continue using same classes of Break characters.
                1 = The two 8-bit bytes following this byte contain
                    flags for the new Break classes.

         4      0 = Continue using same classes of Transmit characters.
                1 = Reset Transmit classes according to the two bytes
                    following 1) the Break classes bytes, if the Break
                    classes are also being reset, or 2) this byte, if
                    the Break classes are NOT also being reset.

      Value (decimal) of the <cmd> byte and its meaning:

                0 = Continue what you have been doing

                1 = Print (echo) up to AND INCLUDING Break character

                3 = Print up to Break character and SKIP (don't echo)
                    Break character

                5 = Skip text (don't echo) up to Break character, but
                    PRINT Break character

Crocker, et. al.                                                [Page 2]
RFC 560               RCT & Echoing TELNET Option            August 1973

                7 = Skip up to and including Break character

                Add one of the previous non-zero values to one of the
                    following values, to get the total decimal value for
                    the byte (Note that Classes may not be reset without
                    also resetting the printing action; so an odd number
                    is guaranteed):

                8 = Set Break classes (using the next two bytes [BC1
                    BC2])

                16 = Set Transmission classes (using the next two bytes
                    [TC1 TC2])

                24 = Set Break classes (using the next two bytes [BC1
                    BC2]) and the Transmission classes (using the two
                    bytes after that [TC1 TC2]).

      Sub-commands (IAC SB RCTE...) are only sent by the Controlling
      Host and, in addition to other functions, functionally replace the
      Go-Ahead (IAC GA) Telnet Command.

3. Default:

   WON'T RCTE -- DON'T RCTE

      Neither host asserts special control over the other host's
      terminal printer.

4. Motivation for the option:

   RFC's 1, 5 and 51 discuss Network and process efficiency and
   smoothness.

   RFC 357, by John Davidson, introduces the problem of echoing delay
   that occurs when a remote user accesses a full-duplex host, thru a
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