RFC658

D. Crocker (UCLA-NMC) RFC 658, NIC 31161 (Oct. 25, 1974) Online file: [ISI]<DCROCKER>NAOLFD.TXT

              TELNET OUTPUT LINEFEED DISPOSITION

Command name and code

NAOLFD 16

  (Negotiate About Output Linefeed Disposition)

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.

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.

Motivation for the Option

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

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.