Telnet terminal speed option

Network Working Group                                         C. Hedrick
Request for Comments: 1079                            Rutgers University
                                                           December 1988


                      Telnet Terminal Speed Option

Status of This Memo

   This RFC specifies a standard for the Internet community.  Hosts on
   the Internet that exchange terminal speed information within the
   Telnet protocol are expected to adopt and implement this standard.
   Distribution of this memo is unlimited.

   This standard is modelled on RFC 930 [1], the telnet terminal type
   option.  Much of the text of this document is copied from that RFC.

Motivation

   Most operating systems have provisions to keep track of the speed
   (bit rate) of directly attached terminals and modems.  This
   information is used to control various timing-dependent display
   processes, e.g., the number of padding characters used for delay.
   Some software also has user interfaces that are tuned differently for
   fast and slow terminals.  The purpose of this option is to provide
   similar information for telnet connections.

1. Command Name and Code

      TERMINAL-SPEED

      Code = 32

2. Command Meanings

      IAC WILL TERMINAL-SPEED

         Sender is willing to send terminal speed information in a
         subsequent sub-negotiation.

      IAC WON'T TERMINAL-SPEED

         Sender refuses to send terminal speed information.

      IAC DO TERMINAL-SPEED

         Sender is willing to receive terminal speed information in a
         subsequent sub-negotiation.

      IAC DON'T TERMINAL-SPEED

         Sender refuses to accept terminal speed information.

      IAC SB TERMINAL-SPEED SEND IAC SE

         Sender requests receiver to transmit his (the receiver's)
         terminal speed. The code for SEND is 1. (See below.)

      IAC SB TERMINAL-SPEED IS ... IAC SE

         Sender is stating his terminal speed. The code for IS is 0.
         (See below.)

3. Default

      WON'T TERMINAL-SPEED

         Terminal speed information will not be exchanged.

      DON'T TERMINAL-SPEED

         Terminal speed information will not be exchanged.

4. 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-SPEED...).

   Once the two hosts have exchanged a WILL and a DO, the sender of the
   DO TERMINAL-SPEED is free to request speed information.  Only the
   sender of the DO may send requests (IAC SB TERMINAL-SPEED SEND IAC
   SE) and only the sender of the WILL may transmit actual speed
   information (within an IAC SB TERMINAL-SPEED IS ... IAC SE command).
   Terminal speed information may not be sent spontaneously, but only in
   response to a request.

   The terminal speed information is an NVT ASCII string.  This string
   contains the decimal representation of the transmit and receive
   speeds of the terminal, separated by a comma, e.g.,

         9600,100

   No leading zeros may be included.  No extraneous characters such as
   spaces may be included.

      The following is an example of use of the option:

         Host1: IAC DO TERMINAL-SPEED

         Host2: IAC WILL TERMINAL-SPEED

      (Host1 is now free to request status information at any time.)

         Host1: IAC SB TERMINAL-SPEED SEND IAC SE

         Host2: IAC SB TERMINAL-SPEED IS "1200,1200" IAC SE

      (This command is 15 octets.)

5. Implementation Suggestions

   Many systems allow only certain discrete terminal speeds.  In such
   cases it is possible that a speed may be received that does not match
   one of the allowed values.  We suggest that you pick the nearest
   speed that is allowed, rounding in a "safe" direction.  Safety will
   depend upon the use of the speed information.  If it is being used
   for padding, it is best to round up, since too much padding is better
   than too little.

Reference

   [1]  Solomon, M., and Wimmers, E., "Telnet Terminal Type Option",
        RFC 930, January, 1985

[AAuthor's Address:

   Charles Hedrick
   Rutgers University
   Center for Computer and Information Services
   Hill Center, Busch Campus
   P.O. Box 879
   Piscataway, NJ 08855-0879

   Phone: (201) 932-3088

   Email: HEDRICK@ARAMIS.RUTGERS.EDU