
Network Working Group                                          J. Postel
Request for Comments: 858                                    J. Reynolds
                                                                     ISI
Obsoletes: NIC 15392                                            May 1983

                    TELNET SUPPRESS GO AHEAD OPTION


This RFC specifies a standard for the ARPA Internet community.  Hosts on
the ARPA Internet are expected to adopt and implement this standard.

1.  Command Name and Code

   SUPPRESS-GO-AHEAD     3

2.  Command Meanings

   IAC WILL SUPPRESS-GO-AHEAD

      The sender of this command requests permission to begin
      suppressing transmission of the TELNET GO AHEAD (GA) character
      when transmitting data characters, or the sender of this command
      confirms it will now begin suppressing transmission of GAs with
      transmitted data characters.

   IAC WON'T SUPPRESS-GO-AHEAD

      The sender of this command demands to begin transmitting, or to
      continue transmitting, the GA character when transmitting data
      characters.

   IAC DO SUPPRESS-GO-AHEAD

      The sender of this commannd requests that the sender of data start
      suppressing GA when transmitting data, or the sender of this
      command confirms that the sender of data is expected to suppress
      transmission of GAs.

   IAC DON'T SUPPRESSS-GO-AHEAD

      The sender of this command demands that the receiver of the
      command start or continue transmitting GAs when transmitting data.

3.  Default

   WON'T SUPPRESS-GO-AHEAD

   DON'T SUPPRESS-GO-AHEAD

      Go aheads are transmitted.



Postel & Reynolds                                               [Page 1]



RFC 858                                                         May 1983


4. Motivation for the Option

   While the NVT nominally follows a half duplex protocol complete with
   a GO AHEAD signal, there is no reason why a full duplex connection
   between a full duplex terminal and a host optimized to handle full
   duplex terminals should be burdened with the GO AHEAD signal.
   Therefore, it is desirable to have a TELNET option with which parties
   involved can agree that one or the other or both should suppress
   transmission of GO AHEADS.

5.  Description of the Option

   When the SUPPRESS-GO-AHEAD option is in effect on the connection
   between a sender of data and the receiver of the data, the sender
   need not transmit GAs.

   It seems probable that the parties to the TELNET connection will
   suppress GO AHEAD in both directions of the TELNET connection if GO
   AHEAD is suppressed at all;  but, nonetheless, it must be suppressed
   in both directions independently.

   With the SUPPRESS-GO-AHEAD option in effect, the IAC GA command
   should be treated as a NOP if received, although IAC GA should not
   normally be sent in this mode.

6.  Implementation Considerations

   As the SUPRESS-GO-AHEAD option is sort of the opposite of a line at a
   time mode, the sender of data which is suppressing GO AHEADs should
   attempt to actually transmit characters as soon as possible (i.e.,
   with minimal buffering) consistent with any other agreements which
   are in effect.

   In many TELNET implementations it will be desirable to couple the
   SUPPRESS-GO-AHEAD option to the echo option so that when the echo
   option is in effect, the SUPPRESS-GO-AHEAD option is in effect
   simultaneously:  both of these options will normally have to be in
   effect simultaneously to effect what is commonly understood to be
   character at a time echoing by the remote computer.











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