RFC652
From RFC-Wiki
Request for Comments: 652 D. Crocker (UCLA-NMC)
25 Oct. 74
NIC #31155 Online file: [ISI]<DCROCKER>NAOCRD.TXT
Telnet Output Carriage-Return Disposition Option
Contents
Command name and code
NAOCRD 10 (Negotiate About Output Carriage-Return Disposition)
Command meanings
In the following, we are discussing a simplex connection, as described in the NAOL and NAOP Telnet options.
IAC DO NAOCRD The data sender requests or agrees to negotiate
about output carriage-return 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
carriage-returns.
IAC DON'T NAOCRD The data sender refuses to negotiate about
output carriage-return disposition with the
data receiver, or demands a return to the
unnegotiated default mode.
IAC WILL NAOCRD The data receiver requests or agrees to
negotiate about output carriage-return
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
carriage-returns.
IAC WON'T NAOCRD The data receiver refuses to negotiate about
output carriage-return disposition, or demands
a return to the unnegotiated default mode.
IAC SB NAOCRD DS <8-bit value> IAC SE
The data sender specifies, with the 8-bit
value, which party should handle
carriage-returns and what their disposition
should be. The code for DS is 1.
Telnet NAOCRD Option Page 2
IAC SB NAOCRD DR <8-bit value> IAC SE The data receiver
specifies, with the 8-bit value, which party
should handle carriage-returns and what their
disposition should be. The code for DR is 0.
Default
DON'T NAOCRD/WON'T NAOCRD. In the default absence of negotiations concerning which party, data sender or data receiver, is handling output carriage-returns, neither party is required to handle carriage-returns and neither party is prohibited from handling them; but it is appropriate if at least the data receiver handles carriage-returns, albeit primitively.
Motivation for the Option
Please refer to section 4 of the NAOL and of the NAOP Telnet option descriptions.
Description of the Option
The data sender and the data receiver use the 8-bit value along with the NAOCRD SB commands as follows:
8-bit value Meaning
0 Command sender suggests that he alone will
handle carriage-returns, for the connection.
1 to 250 Command sender suggests that the other party
alone should handle carriage-returns, 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 qualification,
below.)
251 Not allowed, in order to be compatible with
related Telnet options.
252 Command sender suggests that the other party
alone handle carriage-returns, but suggests
that they be discarded.
253 Not allowed, in order to be compatible with
related Telnet options.
Telnet NAOCRD Option Page 3
254 Command sender suggests that the other party
alone should handle carriage-returns but
suggests waiting for a character to be
transmitted (on the other simplex connection)
before sending more data. (See qualification,
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 carriage-returns 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
carriage-returns, the data receiver must do it, and
(2) if both data receiver and data sender want to handle
carriage-returns, 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 NAOCRD 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.
Note that carriage-return delays, controlled by the data sender, must consist of NUL characters inserted immediately after the character in question. This is necessary due to the assynchrony of network transmissions. Due to the Telnet end-of-line convention, with carriage-returns followed by a linefeed, any NULs that would otherwise be placed after the carriage-return must be placed after the linefeed, regardless of any modifications that may additionally be made to the line feed (see NAOLFD 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 NAOCRD or DON'T NAOCRD command.
