RFC652 - Telnet output carriage-return disposition option

王朝other·作者佚名  2008-05-31
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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

1. Command name and code

NAOCRD 10 (Negotiate About Output Carriage-Return Disposition)

2. 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.

3. 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.

4. Motivation for the Option

Please refer to section 4 of the NAOL and of the NAOP Telnet

option descriptions.

5. 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.

 
 
 
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