Telnet Remote Flow Control Option (RFC1372)
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2019-Feb-11
Internet Society Requests For Comment (RFCs)
C. Hedrick: AUTHOR [+1]
This document specifies an extended version of the Telnet Remote Flow Control Option, RFC 1080, with the addition of the RESTART-ANY and RESTART-XON suboptions. [STANDARDS-TRACK]
Network Working Group C. Hedrick Request for Comments: 1372 Rutgers University Obsoletes: RFC 1080 D. Borman Cray Research, Inc. October 1992
Telnet Remote Flow Control Option
Status of This Memo
This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited.
This document specifies an extended version of the Telnet Remote Flow Control Option, RFC 1080, with the addition of the RESTART-ANY and RESTART-XON suboptions.
1. Command Names and Codes
TOGGLE-FLOW-CONTROL 33 OFF 0 ON 1 RESTART-ANY 2 RESTART-XON 3
2. Command Meanings
IAC WILL TOGGLE-FLOW-CONTROL
Sender is willing to enable and disable flow control upon command.
IAC WONT 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.
Hedrick & Borman [Page 1]
RFC 1372 Telnet Remote Flow Control Option October 1992
IAC DONT 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.
IAC SB TOGGLE-FLOW-CONTROL ON IAC SE
Sender requests receiver to enable flow control.
IAC SB TOGGLE-FLOW-CONTROL RESTART-ANY IAC SE
Sender requests that when flow control is enabled, the receiver allow any character (except another XOFF) to restart output.
IAC SB TOGGLE-FLOW-CONTROL RESTART-XON IAC SE
Sender requests that when flow control is enabled, the receiver allows only the XON character to restart output.
3. Default Specification
The default specification for this option is
WONT TOGGLE-FLOW-CONTROL DONT TOGGLE-FLOW-CONTROL
meaning flow control information will not be exchanged in either direction.
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 character...