Telnet subliminal-message option (RFC1097)
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2019-Feb-15
Internet Society Requests For Comment (RFCs)
This RFC specifies a standard for the Internet community. Hosts on the Internet that display subliminal messages within the Telnet protocol are expected to adopt and implement this standard.
Network Working Group B. Miller Request for Comments: 1097 CMU-NetDev 1 April 1989
TELNET SUBLIMINAL-MESSAGE Option
Status of this Memo
This RFC specifies a standard for the Internet community. Hosts on the Internet that display subliminal messages within the Telnet protocol are expected to adopt and implement this standard. Distribution of this memo is unlimited.
1. Command name and code.
2. Command meanings.
IAC WILL SUBLIMINAL-MESSAGE
The sender of this command REQUESTS permission to, or confirms that it will, display subliminal messages.
IAC WONT SUBLIMINAL-MESSAGE
The sender of this command REFUSES to display subliminal messages.
IAC DO SUBLIMINAL-MESSAGE
The sender of this command REQUESTS that the receiver, or grants the receiver permission to, display subliminal messages.
IAC DONT SUBLIMINAL-MESSAGE
The sender of this command DEMANDS that the receiver not display subliminal messages.
IAC SB SUBLIMINAL-MESSAGE <16-bit value> <16-bit value> <string> IAC SE
The sender specifies a message to be subliminaly displayed by the remote host. If the client has agreed (via the standard WILL WONT DO DONT mechanism) to display subliminal messages, it must accept this subnegotiation and attempt to display the message string on the users console for the specified duration and continue to do so at fixed intervals until another SUBLIMINAL-MESSAGE subnegotiation is received. The position and rendering of the message of
Miller [Page 1]
RFC 1097 SUBLIMINAL 1 April 1989
The first 16-bit value specifies the duration of the message in milliseconds. It is sent MSB first. The second 16-bit value specifies the frequency with which the message is displayed. It represents the number of seconds between displays and is also sent MSB first. The final parameter is the message itself.
The syntax for this subnegotiation is:
IAC SB SUBLIMINAL-MESSAGE DURATION DURATION FREQUENCY FREQUENCY MESSAGE_STRING IAC SE
As required by the Telnet protocol, any occurence of 255 in the subnegotiation must be doubled to destinguish it from the IAC character (which has a value of 255).
i.e., subliminal messages will not be displayed.
4. Motivation for the option
Frequently the use of "Message of the day" banners and newsletters is insufficient to convince stubborn users to upgrade to the latest version of telnet. Some users will use the same outdated version for years. I ran across this problem trying to convince people to use the REMOTE-FLOW-CONTROL Telnet option. These users need to be gently "persuaded".
5. Description and implementation notes.
The quality of the client implementation will depend o...