Telnet terminal type option
RFC 884

Document Type RFC - Unknown (December 1983; No errata)
Obsoleted by RFC 930
Last updated 2013-03-02
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Network Working Group                                     Marvin Solomon
Request for Comments: 884                                 Edward Wimmers
                                       University of Wisconsin - Madison
                                                           December 1983

                      TELNET TERMINAL TYPE OPTION

This RFC specifies a standard for the ARPA Internet community.  Hosts on
the ARPA Internet that exchange terminal type information within the
Telnet protocol are expected to adopt and implement this standard.

1. Command Name and Code

   TERMINAL-TYPE    24

2. Command Meanings

   IAC WILL TERMINAL-TYPE

      Sender is willing to send terminal type information in a
      subsequent sub-negotiation

   IAC DO TERMINAL-TYPE

      Sender is willing to receive terminal type information in a
      subsequent sub-negotiation

   IAC DON'T TERMINAL-TYPE

      Sender refuses to accept terminal type information

   IAC WON'T TERMINAL-TYPE

      Sender refuses to send terminal type information

   IAC SB TERMINAL-TYPE SEND IAC SE

      Sender requests receiver to transmit his (the receiver's) terminal
      type. The code for SEND is 1. (See below.)

   IAC SB TERMINAL-TYPE IS ... IAC SE

      Sender is stating the name of his terminal type. The code for IS
      is 0. (See below.)

Solomon & Wimmers                                               [Page 1]



RFC 884                                                    December 1983

3. Default

   DON'T TERMINAL-TYPE

   WON'T TERMINAL-TYPE

   Terminal type information will not be exchanged.

4. Motivation for the Option

   This option allows a telnet server to determine the type of terminal
   connected to a user telnet program.  The transmission of such
   information does not immediately imply any change of processing.
   However, the information may be passed to a process, which may alter
   the data it sends to suit the particular characteristics of the
   terminal. For example, some operating systems have a terminal driver
   that accepts a code indicating the type of terminal being driven.
   Using the TERMINAL TYPE and BINARY options, a telnet server program
   on such a system could arrange to have terminals driven as if they
   were directly connected, including such special functions as cursor
   addressing, multiple colors, etc., not included in the Network
   Virtual Terminal specification.  This option fits into the normal
   structure of TELNET options by deferring the actual transfer of
   status information to the SB command.

5. Description of the Option

   WILL and DO are used only to obtain and grant permission for future
   discussion. The actual exchange of status information occurs within
   option subcommands (IAC SB TERMINAL-TYPE...).

   Once the two hosts have exchanged a WILL and a DO, the sender of the
   WILL TERMINAL-TYPE is free to transmit type information, spontan-
   eously or in response to a request from the sender of the DO.  At
   worst, this may lead to transmitting the information twice. Only the
   sender of the DO may send requests (IAC SB TERMINAL-TYPE SEND IAC SE)
   and only the sender of the WILL may transmit actual type information
   (within an IAC SB TERMINAL-TYPE IS ... IAC SE command).

   The terminal type information is an NVT ASCII string.  Within this
   string, upper and lower case are considered equivalent.  A few
   terminal type names useful in the context of IBM systems are listed
   below.  It is anticipated that additional names will be added in the
   future.  The complete list of valid terminal types will be found in
   the latest "Assigned Numbers" RFC.

Solomon & Wimmers                                               [Page 2]



RFC 884                                                    December 1983

   The following is an example of use of the option:

      Host1: IAC DO TERMINAL-TYPE

      Host2: IAC WILL TERMINAL-TYPE

         (Host2 is now free to send status information at any time.
         Solicitations from Host1 are NOT necessary. This should not
         produce any dangerous race conditions. At worst, two IS's will
         be sent.)

      Host1 (perhaps): IAC SB TERMINAL-TYPE SEND IAC SE

      Host2:

         IAC SB TERMINAL-TYPE IS IBM-3278-2 IAC SE

6.  Implementation Suggestions

   The "terminal type" information may be any NVT ASCII string meaning-
   ful to both ends of the negotiation.  The list of suggestions below
   is intended to minimize confusion caused by alternative "spellings"
   of the terminal type.  For example, confusion would arise if one
   party were to call a terminal "IBM3278-2" while the other called it
   "IBM-3278/2".  There is no negative acknowledgement for a terminal
   type that is not understood, but certain other options (such as
   switching to BINARY mode) may be refused if a valid terminal type
   name has not been specified.  In some cases, a particular terminal
   may be known by more than one name, for example a specific type and a
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