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Network Working Group R. Nedved Request for Comments: 946 Carnegie-Mellon University

                                                              May 1985

               TELNET TERMINAL LOCATION NUMBER OPTION

Status of this Memo

 This RFC proposes a new option for Telnet for the ARPA-Internet
 community, and requests discussion and suggestions for improvements.
 Distribution of this memo is unlimited.

Overview

 In a community of users that share a large degree of common
 facilities, it is often advantageous to use some common feature to
 improve software performance and reduce initial implementation costs.

 In March of 1982, CMU designed and implemented based on the growing
 CMU PUP-based network a terminal location database and modified
 existing network software to handle a 64-bit number which some call
 the Terminal Location Number or TTYLOC for short.  The number can be
 efficiently stored in operating systems tables and can be passed
 between various levels of operating system and network layering with
 minimum modifications to existing software.  An initial evaluation of
 changing software to communicate an unfixed or reasonable length
 terminal location string indicated it would be expensive.

 CMU now wishes to extend this mechanism into the TCP-based networking
 support that is replacing the existing PUP-based software.  The
 mechanism is not viewed as a replacement for the Telnet Terminal
 Location (SEND-LOCATION) Option but as a shorthand mechansim for
 communicating hosts in the same community.

TTYLOC Number

 The TTYLOC number is a 64-bit number composed of two (2) 32-bit
 numbers: The 32-bit official ARPA Internet host address (may be any
 one of the addresses for multi-homed hosts) and a 32-bit number
 representing the terminal on the specified host.  The host address of
 [0.0.0.0] is defined to be "unknown", the terminal number of FFFFFFFF
 (hex, r or-1 in decimal) is defined to be "unknown" and the terminal
 number of FFFFFFFE (hex, or -2 in decimal) is defined to be
 "detached" for processes that are not attached to a terminal.

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RFC 946 May 1985 Telnet Terminal Location Number Option

1. Command Name and Option Code

 TTYLOC  28

2. Command Meanings

 IAC WILL TTYLOC

    The sender offers to send the TTYLOC information or confirms that
    it can send the TTYLOC information.

 IAC WON'T TTYLOC

    The sender refuses to send the TTYLOC information.

 IAC DO TTYLOC

    The sender requests to receive the TTYLOC information or confirms
    that it will receive the TTYLOC information.

 IAC DON'T TTYLOC

    The sender refuses to receive the TTYLOC information.

 IAC SB TTYLOC <format> <TTYLOC number with IAC doubling> IAC SE

    The sender is transmitting the TTYLOC information. The 64-bit
    TTYLOC number has format 0. The first 32-bits is the Internet host
    number and the second 32-bits is the line on the specified
    Internet host. The bytes are in most significant 8-bit byte to
    least significant byte order.

3. Default Specification

 WON'T TTYLOC

    TTYLOC information will not be sent.

 DON'T TTYLOC

    TTYLOC information will not be received.

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RFC 946 May 1985 Telnet Terminal Location Number Option

4. Motivation

 Many systems provide a mechanism for finding out where a user is
 logged in from usually including information about telephone
 extension and office occupants names. The information is useful for
 physically locating people and/or calling them on the phone.

 For incoming network connections to a host, only the remote host's
 name is available. This option and the Telnet Terminal Location
 option (RFC-779) provide the information to the system so it in turn
 can provide the information to the various mechanisms (FINGER, WHOIS,
 etc.).

5. Description of the Option

 When the user Telnet connects to a remote host, it can attempt to
 send the terminal location number information by doing a
 IAC WILL TTYLOC command. If the Telnet server can use the
 information, it replies with a IAC DO TTYLOC command. The user Telnet
 then sends the TTYLOC number in the subnegotiation.

 It is recommended that if sending the TTYLOC number is refused then
 the Telnet Terminal Location (SEND-LOCATION in RFC-779) should be
 attempted.

 The following are two example usage scenarios:

    User Side First:

       (User) Host1: IAC WILL TTYLOC

          Host1 is asking if it can send the 64-bit terminal location
          number (I will send...).

       (Server) Host2: IAC DO TTYLOC

          Host2 indicates to Host1 that it will accept the 64-bit
          terminal location number in a subnegotiation (You please do
          ...).

       (User) Host1: IAC SB TTYLOC 0 <64-bit number> IAC SE

          Host1 is sending the location number to Host2 which can
          communicate the number to the operating system or other
          system components.

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RFC 946 May 1985 Telnet Terminal Location Number Option

    Server Side First:

       (Server) HostA: IAC DO TTYLOC

          HostA indicates to HostB that it would like to know the
          64-bit terminal location number (You please do ...).

       (User) HostB: IAC WILL TTYLOC

          HostB agrees to send the 64-bit terminal location number to
          HostA in a subnegotiation (I will send...).

       (User) HostB: IAC SB TTYLOC 0 <64-bit number> IAC SE

          HostB is sending the location number to HostA which can
          communicate the number to the operating system or other
          system components.

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