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D. Crocker (UCLA-NMC)RFC 657, NIC 31160 (Oct. 25, 1974)Online file: [ISI]<DCROCKER>NAOVTD.TXT            TELNET OUTPUT VERTICAL TAB DISPOSITION OPTION1. 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 tosection 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.