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HISTORIC

TELNET OUTPUT VERTICAL TABSTOPS OPTION
RFC 656, NIC 31159 (Oct. 25, 1974)"
D. Crocker (UCLA-NMC)
Online file: [ISI]<DCROCKER>NAOVTS.TXT

                TELNET OUTPUT VERTICAL TABSTOPS OPTION

1. Command name and code
   NAOVTS 14
      (Negotiate About Vertcial Tabstops)

2. Command meanings
   In the following, we are discussing a simplex connection, as described in
   the NAOL and NAOP Telnet Options specifications.
      IAC DO NAOVTS
         The data sender requests or agrees to negotiate about output
         vertical tabstops 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 tabstop considerations.
      IAC DON'T NAOVTS
         The data sender refuses to negotiate about output vertical tabstops
         with the data receiver, or demands a return to the unnegotiated
         default mode.
      IAC WILL NAOVTS
         The data receiver requests or agrees to negotiate about output
         vertical tabstops 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 tabstop
         considerations.
      IAC WON'T NAOVTS
         The data receiver refuses to negotiate about output vertical
         tabstops, or demands a return to the unnegotiated default mode.
      IAC SB NAOVTS DS <8-bit value> ... <8-bit value> IAC SE
         The data sender specifies, with the 8-bit value(s), which party
         should handle output vertical tabstop considerations and what the
         stops should be.  The code for DS is 1.
      IAC SB NAOVTS DR <8-bit value> ... <8-bit value> IAC SE
         The data receiver specifies, with the 8-bit value(s), which party
         should handle output vertical tabstop considerations and what the
         stops should be.  The code for DR is 0.

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

4. Motivation for the Option
   Please refer to section 4 of the NAOL and of the NAOVTS Telnet option
   descriptions.
5. Description of the Option
   The data sender and the data receiver use the 8-bit value(s) along with
   the DS and DR SB commands as follows (multiple 8-bit values are allowed
   only if each is greater than zero and less than 251):

      8-bit value                      Meaning

      0            Command sender suggests that he alone will handle
                   the vertical tabstops, for the connection.
      1 to 250     Command sender suggests that the other party alone
                   should handle the stops, but suggests that the
                   indicated value(s) be used.  Each value is the line
                   number, relative to the top of the printer page or
                   terminal screen, that is to be set as a vertical
                   tabstop.
      251 to 254   Not allowed, in order to be compatible with
                   related Telnet options.
      255          Command sender suggests that the other party alone
                   should handle output vertical tabstops 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 output
      vertical tabstops, the data receiver must do it, and
      2) if both data receiver and data sender want to handle output vertical
      tabstops, the data sender gets to do it.

The reasoning for the former rule is that if neither wants to do it, then
the default in the NAOVTS 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.
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 NAOVTS or DON'T NAOVTS command.


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