D. Crocker (UCLA-NMC)
RFC 658, 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.
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