RFC 1053 (rfc1053) - Page 2 of 21

Telnet X

RFC 1053                 Telnet X.3 PAD Option                April 1988


   ("DO") or the user ("WILL") side.

      Once DO and WILL have been exchanged, the host ("DO") telnet may
      send the following messages:

   IAC SB  X.3-PAD  SET            ...  IAC SE
   IAC SB  X.3-PAD  RESPONSE-SET   ...  IAC SE
   IAC SB  X.3-PAD  SEND          IAC SE

      while the user ("WILL") telnet may send the following messages:

   IAC SB  X.3-PAD  IS             ...  IAC SE
   IAC SB  X.3-PAD  RESPONSE-IS    ...  IAC SE

   The code for SET          is 0
   The code for RESPONSE-SET is 1
   The code for IS           is 2
   The code for RESPONSE-IS  is 3
   The code for SEND         is 4

      Messages listing parameter-value pairs may contain any number of
      such pairs, including zero.  Each parameter and each value
      occupies one octet, except that 255 (IAC) is doubled wherever it
      appears.

3.  Default conditions

   The initial state is DON'T X.3-PAD, WON'T X.3-PAD.  This RFC does not
   specify default values for most X.3 parameters.  If the host telnet
   wishes a particular initial state (as it normally will), it should
   negotiate for it after exchange of DO/WILL messages.

   X.3-PAD parameter values need not be preserved except when DO/WILL
   X.3-PAD is in effect.  Thus if a host enables ("DO") X.3-PAD,
   negotiates about some parameters, then for some reason disables
   ("DONT") and later re-enables X.3-PAD, it must renegotiate any
   parameters it cares about.

   Keeping in mind that the host telnet may not recognize all the
   parameters known to the user telnet, it is suggested that the user
   telnet's initial parameters allow a reasonable level of service even
   if they are never changed (e.g., it would be unwise to begin with all
   data forwarding conditions disabled).  Extensions to X.3 should
   default to states resembling normal X.3 service where possible.







Levy & Jacobson