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Network Working Group                                          R. NedvedRequest for Comments: 946                     Carnegie-Mellon University                                                                May 1985TELNET TERMINAL LOCATION NUMBER OPTIONStatus 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.Nedved                                                          [Page 1]

RFC 946                                                         May 1985Telnet Terminal Location Number Option1. Command Name and Option Code   TTYLOC  282. 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.Nedved                                                          [Page 2]

RFC 946                                                         May 1985Telnet Terminal Location Number Option4. 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 inRFC-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.Nedved                                                          [Page 3]

RFC 946                                                         May 1985Telnet 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.Nedved                                                          [Page 4]