Network Working Group J. Postel
Request for Comments: 861
Obsoletes: NIC 16239 May 1983
TELNET EXTENDED OPTIONS - LIST OPTION
This RFC specifies a standard for the ARPA Internet community. Hosts on
the ARPA Internet are expected to adopt and implement this standard.
1. Command Name and Code
EXTENDED-OPTIONS-LIST (EXOPL) 255
2. Command Meanings
IAC DO EXOPL
The sender of this command REQUESTS that the receiver of this
command begin negotiating, or confirms that the receiver of this
command is expected to begin negotiating, TELNET options which are
on the "Extended Options List".
IAC WILL EXOPL
The sender of this command requests permission to begin
negotiating, or confirms that it will begin negotiating, TELNET
options which are on the "Extended Options List".
IAC WON'T EXOPL
The sender of this command REFUSES to negotiate, or to continue
negotiating, options on the "Extended Options List".
IAC DON'T EXOPL
The sender of this command DEMANDS that the receiver conduct no
further negotiation of options on the "Extended Options List".
IAC SB EXOPL <subcommand>
The subcommand contains information required for the negotiation
of an option of the "Extended Options List". The format of the
subcommand is discussed in section 5
WON'T EXOPL, DON'T EXOPL
Negotiation of options on the "Extended Options List" is not
4. Motivation for the Option
Eventually, a 257th TELNET option will be needed. This option will
extend the option list for another 256 options in a manner which is
easy to implement. The option is proposed now, rather than later
(probably much later), in order to reserve the option number (255).
5. An Abstract Description of the Option
The EXOPL option has five subcommand codes: WILL, WON'T, DO, DON'T,
and SB. They have exactly the same meanings as the TELNET commands
with the same names, and are used in exactly the same way. For
consistency, these subcommand codes will have the same values as the
TELNET command codes (250-254). Thus, the format for negotiating a
specific option on the "Extended Options List" (once both parties
have agreed to use it) is:
IAC SB EXOPL DO/DON'T/WILL/WON'T/<option code> IAC SE
Once both sides have agreed to use the specific option specified by
<option code>, subnegotiation may be required. In this case the
format to be used is:
IAC SB EXOPL SB <option code> <parameters> SE IAC SE