Telnet Extended Options: List Option

　　Network Working Group J. Postel

　　Request for Comments: 861 J. Reynolds　ISI

　　Obsoletes: NIC 16239 May 1983

　　TELNETEXTENDED OPTIONS - LIST OPTION

　　This RFCspecifies 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

　　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 below.

　　3. Default

　　WON'T EXOPL, DON'T EXOPL

　　RFC861May 1983

　　Negotiation of options on the "Extended Options List" is not　permitted.

　　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/ IAC SE

　　Once both sides have agreed to use the specific option specified by　, subnegotiation may be required. In this case the　format to be used is:

　　IAC SB EXOPL SB SE IAC SE