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

           TELNET OUTPUT VERTICAL TAB DISPOSITION OPTION

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

2. 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.

3. 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.

4. Motivation for the Option
  Please refer to section 4 of the NAOL and of the NAOVTD Telnet option
  descriptions.

5. Description of the Option
  The data sender and the data receiver use the 8-bit value along with
  the DS and DR SB commands as follows:

     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.

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