RFC 657: Telnet output vertical tab disposition option

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.

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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.

RFC 657: Telnet output vertical tab disposition option