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TELNET OUTPUT HORIZONTAL TAB DISPOSITION OPTIONRFC 654, NIC 31157 (Oct. 25, 1974)D. Crocker (UCLA-NMC)Online file: [ISI]<DCROCKER>NAOHTD.TXT           TELNET OUTPUT HORIZONTAL TAB DISPOSITION OPTION1. Command name and code   NAOHTD 12      (Negotiate About Output Horizontal Tab Disposition)2. Command meanings   In the following, we are discussing a simplex connection, as described in   the NAOL and NAOP Telnet options.      IAC DO NAOHTD         The data sender requests or agrees to negotiate about output         horizontal 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         horizontal tab character considerations.      IAC DON'T NAOHTD         The data sender refuses to negotiate about output horizontal tab         characters with the data receiver, or demands a return to the         unnegotiated default mode.      IAC WILL NAOHTD         The data receiver requests or agrees to negotiate about output         horizontal tab characters 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 horizontal tab character considerations.      IAC WON'T NAOHTD         The data receiver refuses to negotiate about output horizontal tab         characters, or demands a return to the unnegotiated default mode.      IAC SB NAOHTD DS <8-bit value> IAC SE         The data sender specifies, with the 8-bit value, which party should         handle output horizontal tab characters and what their disposition         should be.  The code for DS is 1.      IAC SB NAOHTD DR <8-bit value> IAC SE         The data receiver specifies, with the 8-bit value, which party         should handle output horizontal tab characters and what their         disposition should be.  The code for DR is 0.3. Default   DON'T NAOHTD/WON'T NAOHTD.      In the default absence of negotiations concerning which party, data      sender or data receiver, is handling output horizontal tab character      considerations, neither party is required to handle horizontal tab      characters and neither party is prohibited from handling them; but it      is appropriate if at least the data receiver handles horizontal tab      character considerations, albeit primitively.4. Motivation for the Option   Please refer tosection 4 of the NAOL and of the NAOP 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                   horizontal tab characters, for the connection.      1 to 250     Command sender suggests that the other party alone                   should handle horizontal 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 horizontal tabs, but suggests that each                   occurrence of the character be replaced by a space.      252          Command sender suggests that the other party alone                   handle horizontal tabs, but suggests that they be                   discarded.      253          Command sender suggests that the other party alone                   should handle horizontal tab characters, but                   suggests that tabbing be simulated.      254          Command sender suggests that the other party alone                   should handle horizontal tab characters, but                   suggests that 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 output horizontal tabs 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      horizontal tab characters, the data receiver must do it, and      2) if both data receiver and data sender wants to handle output      horizontal tab characters, 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 NAOHTD 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 horizontal tab   character by enough spaces to move the printer head (or line-pointer) to   the next horizontal tab stop.   Note that delays, controlled by the data sender, must consist of NUL   characters inserted immediately after the horizontal tab 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 NAOHTD or   DON'T NAOHTD command.