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rfc:rfc652

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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