Telnet remote flow control option (RFC1080)
Original Publication Date: 1988-Nov-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 do remote flow control within the Telnet protocol are expected to adopt and implement this standard.
Network Working Group C. Hedrick Request for Comments: 1080 Rutgers University November 1988
Telnet Remote Flow Control Option
Status of This Memo
This RFC specifies a standard for the Internet community. Hosts on the Internet that do remote flow control within the Telnet protocol are expected to adopt and implement this standard. Distribution of this memo is unlimited.
This memo describes a method of remotely toggling flow control between a user telnet process and the attached terminal. Only flow control of data being transmitted from the telnet process to the terminal is considered. Many systems will also allow flow control of data from the terminal to the telnet process. However there is seldom need to change this behavior repeatedly during the session.
There are two common ways of doing flow control: hardware and software. Hardware flow control uses signals on wires dedicated for this purpose. Software flow control uses one or two specific characters sent along the same path as normal input data. Most commonly, XOFF (control-S) and XON (control-Q) are used to stop and start output, respectively. The option described herein is useful primarily where software flow control is being used. (Since hardware flow control does not preempt any characters, there is normally no need to disable it.)
The primary difficulty with software flow control is that it preempts one or two characters. Host software often requires the user to be able to input every possible ASCII character. (Certain editors are notorious for having XOFF and XON as commonly-used commands.) For this reason, operating systems often allow programs to disable flow control. While it is disabled, the characters that normally signal flow control may be read as normal input. In a telnet environment, flow control is normally done by the user telnet process, not by the host computer. Thus this RFC defines a way to propagate flow control status from the host computer to the user telnet process.
Hedrick [Page 1]
RFC 1080 Telnet Remote Flow Control Option December 1988
1. Command Name and Code
Code = 33
2. Command Meanings
IAC WILL TOGGLE-FLOW-CONTROL
Sender is willing to enable and disable flow control upon command.
IAC WON’T TOGGLE-FLOW-CONTROL
Sender refuses to enable and disable flow control. Nothing is implied about whether sender does or does not use flow control. It is simply unwilling to enable and disable it using this protocol.
IAC DO TOGGLE-FLOW-CONTROL
Sender is willing to send commands to enable and disable flow control.
IAC DON’T TOGGLE-FLOW-CONTROL
Sender refuses to send command to enable and disable flow control.
IAC SB TOGGLE-FLOW-CONTROL OFF IAC SE
Sender requests receiver to disable flow control. The code for OFF is 0.
IAC SB TOGGLE-FLOW-CONTROL ON IAC SE
Sender requests receiver to enable flow control. The code for ON is 1.
Flow control information will not be exchanged.
Hedrick [Page 2]
RFC 1080 Telnet Rem...