Telnet output linefeed disposition

　　D. Crocker (UCLA-NMC)

　　RFC658, NIC 31161 (Oct. 25, 1974)

　　Online file: [ISI]NAOLFD.TXT

　　TELNET OUTPUT LINEFEED DISPOSITION

　　1. Command name and code

　　NAOLFD 16

　　(Negotiate About Output Linefeed Disposition)

　　2. Command meanings

　　In the following, we are discussing a simplex connection, as described in 　the NAOL and NAOP Telnet Options.

　　IAC DO NAOLFD

　　The data sender requests or agrees to negotiate about output　linefeed 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　linefeed considerations.

　　IAC DON'T NAOLFD

　　The data sender refuses to negotiate about output linefeed　disposition with the data receiver, or demands a return to the　unnegotiated default mode.

　　IAC WILL NAOLFD

　　The data receiver requests or agrees to negotiate about output　linefeed 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 linefeed　considerations.

　　IAC WON'T NAOLFD

　　The data receiver refuses to negotiate about output linefeed 　disposition, or demands a return to the unnegotiated default mode.

　　IAC SB NAOLFD DS <8-bit value> IAC SE

　　The data sender specifies, with the 8-bit value, which party should　handle output linefeeds and what their disposition should be. The 　code for DS is 1.

　　IAC SB NAOLFD DR <8-bit value> IAC SE

　　The data receiver specifies, with the 8-bit value, which party　should handle output linefeeds and what their disposition should　be. The code for DR is 0.

　　3. Default

　　DON'T NAOLFD/WON'T NAOLFD.

　　In the default absence of negotiations concerning which party, data　under or data receiver, is handling output linefeed considerations,　neither party is required nor prohibited from handling linefeeds; but　it is appropriate if at least the data receiver handles them, albeit　primitively.

　　4. Motivation for the Option

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

　　5. Description of the Option

　　The data sender and the data receiver use the 8-bit value along with DS　and DR SB commands as follows:

　　8-bit value Meaning

　　0 Command sender suggests that he alone will handle　linefeeds, for the connection.

　　1 to 250 Command sender suggests that the other party alone　should handle linefeeds, 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. (See qualifications, below.)

　　251 Not allowed, in order to be compatible with　related Telnet options.

　　252 Command sender suggests that the other party alone　handle linefeeds, but suggests that they be discarded.

　　253 Command sender suggests that the other party alone should handle linefeeds, but suggests that　linefeeds be simulated.

　　254 Command sender suggests that the other party alone should handle output linefeeds but suggests waiting for a character to be transmitted (on the other simplex connection) before sending more data. (See qualifications, below.) 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 linefeeds 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 linefeeds, the data receiver must do it, and

        2) if both data receiver and data sender want to handle output linefeed disposition, 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 NAOLFD 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 linefeed character　by new-line (see following) and enough blanks to move the print head (or　line pointer) to the same lateral position it occupied just prior to　receiving the linefeed. To avoid infinite recursion, such simulation is　allowed only for linefeed characters that are not immediately preceded by　carriage-returns (that is, part of a Telnet new-line combination). It is　assumed that linefeed simulation will be necessary for printers that do　not have a separate linefeed (like the IBM 2741); in this case,　end-of-line character padding can be specified through NAOCRD. Any　padding (0 <<8-bit-value> <251) of linefeed characters is to be done　for ALL linefeed characters.

　　NOTE: Delays, controlled by the data sender, must consist of NUL　characters inserted immediately after the character. This is necessary　due to the assynchrony of network transmissions. Additionally, due to　the presence of the Telnet end-of-line convention, it may be necessary to　add carriage-return padding or delay after the associated linefeed (see　NAOCRD Telnet option). 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 NAOLFD or DON'T NAOLFD command.