Telnet extended ASCII option (RFC0698)
Original Publication Date: 1975-Jul-23
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
Request for Comments: 698 Jul 1975
TELNET EXTENDED ASCII OPTION
1. Command Name and Code.
2. Command Meanings.
IAC WILL EXTEND-ASCII
The sender of this command requests Permission to begin
transmitting, or confirms that it may now begin transmitting
extended ASCII, where additional 'control' bits are added to
normal ASCII, which are treated sPecially by certain programs on
the host computer.
IAC WON'T EXTEND-ASCII
If the connection is already being operated in extended ASCII
mode, the sender of this command demands that the receiver begin
transmitting data characters in standard NVT ASCII. If the
connection is not already being operated in extended ASCII mode,
The sender of this command refuses to begin transmitting extended
IAC DO EXTEND-ASCII
The sender of this command requests that the receiver begin
transmitting,or confirms that the receiver of this command is
allowed to begin transmitting extended ASCII.
IAC DON'T EXTEND-ASCII
The sender of this command demands that the receiver of this
command stop or not start transmitting data in extended ASCII
IAC SB EXTASC
This command transmits an extended ASCII character in the form of
two 8-bit bytes. Each 8-bit byte contains 8 data bits.
TELNET EXTENDED ASCII OPTION
RFC 698, NIC 32964 (July 23 1975)
i.e., only use standard NVT ASCII
Several sites on the net, for example, SU-AI and MIT-AI, use
keyboards which use almost all 128 characters as printable
characters, and use one or more additional bits as "control' bits as
command modifiers or to separate textual input from command input to
programs. Without these additional bits, several characters cannot
be entered as text because they are used for control purposes, such
as the greek letter "beta' which on a TELNET connection is CONTROL-C
and is used for stopping ones job. In addition there are several
commonly used programs at these sites which require these additional
bits to be run effectively. Hence it is necessary to provide some
means of sending characters larger than 8 bits wide.
5. Description of the option.
This option is to allow the transmission of extended ASCII.
Experience has shown that most of the time, 7-bit ASCII is typed,
with an occasional "control' character used. Hence, it is expected
normal NVT ASCII would be used for 7-bit ASCII and that
extended-ASCII be sent as an escape character sequence.
The exact meaning of these additional bits depends on the user
program. At SU-AI and at MIT-AI, the first two bits beyond the
normal 7-bit ASCII are passed on to the user program and are denoted
Bit 8 (or 200 octal) is the CONTROL bit
Bit 9 (or 400 octal) is the META bit
(NOTE: "CONTROL' is used in a non-standard way here; that is, it
usually refers to codes 0-37 in NVT ASCII. CONTROL and META are
echoed by prefixing the nor...