RFC884
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.
Contents
Command Name and Code
TERMINAL-TYPE 24
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.)
Default
DON'T TERMINAL-TYPE
WON'T TERMINAL-TYPE
Terminal type information will not be exchanged.
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.
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.
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
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 more generic type. In such cases, the sender of the TERMINAL-TYPE IS command should reply to successive TERMINAL-TYPE SEND commands with the various names, from most to least specific. In this way, a telnet server that does not understand the first response can prompt for alternatives. However, it should cease sending TERMINAL-TYPE SEND commands after receiving the same response two consecutive times. Similarly, a sender should indicate it has sent all available names by repeating the last one sent.
Here are a few terminal types useful in the IBM environment:
IBM-3275-2 IBM-3276-2 IBM-3276-3 IBM-3276-4 IBM-3277-2 IBM-3278-2 IBM-3278-3 IBM-3278-4
IBM-3278-5 IBM-3279-2 IBM-3279-3
Here are a few terminal types useful in the TOPS20 environment:
ANN-ARBOR-AMBASSADOR CONCEPT-100 DATAMEDIA-2500 DEC-LA30 DEC-VT100 DEC-VT52 EXECUPORT-4000 HAZELTINE-1500 HP-2621 HP-2640 HP-2645A HP-2649 NETWORK-VIRTUAL-TERMINAL TEKTRONIX-4025 TELERAY-1061 TELETYPE-33 TELETYPE-37 TELEVIDEO-950 TERMINET-300 TI-700 ZENITH-H19
Here are a few terminal types used in the Unix environment:
ADDS-CONSUL-980 ADDS-REGENT-200 ANDERSON-JACOBSON-832 ANN-ARBOR-AMBASSADOR BITGRAPH CDI-1203 COMPUCOLOR-II CONCEPT-100 DATA-GENERAL-6053 DATAGRAPHIX-132A DATAMEDIA-3045A DATAPOINT-3360 DEC-DECWRITER-II DEC-GT40 DEC-VT52 DELTA-DATA-5000 DIABLO-1620 EXECUPORT-4000
GENERAL-TERMINAL-100A HAZELTINE-1500 HAZELTINE-2000 HP-2621 HP-2640A HP-2645 HP-2649A IBM-3101 INFOTON-100 LSI-ADM-3 MICROTERM-ACT-V MICROTERM-MIME-2 NETWORK-VIRTUAL-TERMINAL PERKIN-ELMER-1100 PLASMA-PANEL SUPERBEE-III-M TEKTRONIX-4014 TELERAY-3700 TELETYPE-33 TELETYPE-37 TELEVIDEO-912 TERMINET-300 TI-700 TI-733 TI-745 VISUAL-200 XEROX-1720 ZENITH-H19 ZENTEC-30
The type "UNKNOWN" should be used if the type of the terminal is unknown or unlikely to be recognized by the other party.
The complete and up-to-date list will be maintained in the "Assigned Numbers".
