RFC 933 (rfc933) - Page 2 of 4


Output marking Telnet option



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RFC 933                                                     January 1985
Output Marking Telnet Option


   IAC SB OUTMRK ACK IAC SE

      The sender acknowledges the data and agrees to use it to perform
      output marking (see below).

   IAC SB OUTMRK NAK IAC SE

      The sender objects to using the data to perform output marking
      (see below).

3.  Default

   WON'T OUTMRK

      Output marking information will not be exchanged.

   DON'T OUTMRK

      Output marking information will not be exchanged.

4.  Motivation for the Option

   The security architecture of some military systems identifies a
   security level with each Telnet connection.  There is a corresponding
   need to display a security banner on visual display devices.
   (Reference: Department of Defense Trusted Computer System Evaluation
   Criteria, Section 3.1.1.3.2.3, Labeling Human-Readable Output.)

   The output marking is currently done by transmitting the banner as
   data within each screen of data.  It would be more efficient to
   transmit the data once with instructions and have User-Telnet
   maintain the banner automatically without any additional
   Server-Telnet action.  This frees Server-Telnet from needing to know
   the output device page size.

   Under this proposal Server-Telnet would send an option sequence with
   the command, a control flag, and the banner to be used.  While
   current systems use the top of the screen, it is conceivable other
   systems would want to put the banner at the bottom or perhaps even
   the side of the screen.  This is the reason for the control flag.

5.  Description of the Option

   Either side of the session can initiate the option; however, normally
   it will be the server side that initiates the request to perform
   output marking.  Either the Server-Telnet sends "WILL OUTMRK" or the
   User-Telnet sends a "DO OUTMRK".  The party receiving the initial


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