Telnet output vertical tab disposition option

D. Crocker (UCLA-NMC)
RFC 657, NIC 31160 (Oct. 25, 1974)
Online file: [ISI]<DCROCKER>NAOVTD.TXT

TELNET OUTPUT VERTICAL TAB DISPOSITION OPTION

Command name and code NAOVTD 15 (Negotiate About Output Vertcial Tab Disposition)

Command meanings In the following, we are discussing a simplex connection, as described in the NAOL and NAOP Telnet Options specifications. IAC DO NAOVTD The data sender requests or agrees to negotiate about output vertical tab character disposition with the data receiver. In the case where agreement has been reached and in the absence of further subnegotiations, the data receiver is assumed to be handling output vertical tab character considerations. IAC DON'T NAOVTD The data sender refuses to negotiate about output vertical tab character disposition with the data receiver, or demands a return to the unnegotiated default mode. IAC WILL NAOVTD The data receiver requests or agrees to negotiate about output vertical tab character disposition with the sender. In the case where agreement has been reached and in the absence of further subnegotiations, the data receiver alone is assumed to be handling output vertical tab character considerations. IAC WON'T NAOVTD The data receiver refuses to negotiate about output vertical tab character disposition, or demands a return to the unnegotiated default mode. IAC SB NAOVTD DS <8-bit value> IAC SE The data sender specifies, with the 8-bit value, which party should handle output vertical tab characters and what their disposition should be. The code for DS is 1. IAC SB NAOVTD DR <8-bit value> IAC SE The data receiver specifies, with the 8-bit value, which party should handle output vertical tab characters and what their disposition should be. The code for DR is 0.

Default DON'T NAOVTD/WON'T NAOVTD In the default absence of negotiations concerning which party, data sender or data receiver, is handling output vertical tab character considerations, neither party is required to handle vertical tab characters and neither party is prohibited from handling them; but it is appropriate if at least the data receiver handles vertical tab character considerations, albeit primitively.

      8 bit value   Meaning
      
      0             Command sender suggests that he alone will handle
                    vertical tab characters, for the connection.
      1 to 250      Command sender suggests that the other party alone
                    should handle tab characters, but suggests that a 
            delay of the indicated value be used. The value is 
            the number of character-times to wait or number of
                   NULs to insert in the data stream before sending the 
            next data character.
      251           Command sender suggests that the other party alone
                    handle vertical tabs, but suggests that each 
            occurrence of the character be replaced by 
            carriage-return/linefeed.
      252           Command sender suggests that the other party alone
                    handle vertical tabs, but suggests that they be discarded.
      253           Command sender suggests that the other party alone
                    should handle tab characters, but suggests that 
            tabbing be simulated.
      254           Command sender suggests that the other party alone
                    should handle the output disposition but suggests 
            waiting for a character to be transmitted (on the 
            other simplex connection) before sending more data.
                   Note that, due to the assynchrony of the two 
            simplex connections, phase problems can occur with 
            this option.
      255           Command sender suggests that the other party alone
                    should handle the output disposition and suggests 
            nothing about how it should be done.

The guiding rules are that:

      1. if neither data receiver nor data sender wants to handle the 
      output vertical tab characters, the data receiver must do it, and
      2. if both data receiver and data sender want to handle the output
      vertical tab characters, the data sender gets to do it.
   
   The reasoning for the former rule is that if neither want to do it, then
   the default in the NAOVTD option dominates.  If both want to do it, the
   sender, who is presumed to have special knowledge about the data, should
   be allowed to do it, taking into account any suggestions the receiver may
   make.  Simulation is defined as the replacement of the character by
   enough line-feeds (only) to advance the paper (or line-pointer) to the
   next vertical tab stop.  
   Note that delays, controlled by the data sender, must consist of NUL
   characters, inserted immediately after the line-feed character.  This is
   necessary due to the assynchrony of network transmissions.  As with all
   option negotiations, neither party should suggest a state already in
   effect except to refuse to negotiate; changes should be acknowledged; and
   once refused, an option should not be resuggested until "something
   changes" (e.g., another process starts).  At any time, either party can
   disable further negotiation by giving the appropriate WON'T NAOVTD or
   DON'T NAOVTD command.