Telnet terminal location number option

　　Network Working Group R. Nedved

　　Request for Comments: 946 Carnegie-Mellon University

　　May 1985

　　TELNETTERMINAL LOCATION NUMBER OPTION

　　Status of this Memo

　　This RFCproposes 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.

　　RFC946May 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 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.

　　RFC946May 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 officeoccupants 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.

　　RFC946May 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.