RFC656

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

Command name and code

NAOVTS 14

  (Negotiate About Vertcial Tabstops)

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.

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.

Motivation for the Option

Please refer to section 4 of the NAOL and of the NAOVTS Telnet option descriptions.

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.