INTERNET DRAFT EXPIRES MAY 1998 INTERNET DRAFT Network Working Group A. S. Beals Internet Draft Cisco Systems 4 November 1997 The TPING option for the Telnet protocol Status of This Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet- Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Distribution of this document is unlimited. Overview and Rational When using the telnet protocol to talk to a remote device, as one would with RFC 2217, it would be useful to be able to determine if the remote server is active or not. In contrast with the ''Are You There'' sub-option, the return message is not mixed into the data stream presented to the user or client program, it is simply passed between the telnet client/server pair. 1. Command names and codes TPING.................45 Beals [Page 1] Internet Draft Telnet TPING Option 4 November 1997 As a convenience, standard TELNET text and codes for commands used in this document are reproduced here (excerpted from [1]): All TELNET commands consist of at least a two byte sequence: the "Interpret as Command" (IAC) escape character followed by the code for the command. The commands dealing with option negotiation are three byte sequences, the third byte being the code for the option referenced. ... [O]nly the IAC need be doubled to be sent as data, and the other 255 codes may be passed transparently. The following are [some of] the defined TELNET commands. Note that these codes and code sequences have the indicated meaning only when immediately preceded by an IAC. NAME CODE MEANING WILL 251 Indicates the desire to begin performing, or confirmation that you are now performing, the indicated option. WON'T 252 Indicates the refusal to perform, or continue performing, the indicated option. DO 253 Indicates the request that the other party perform, or confirmation that you are expecting the other party to perform, the indicated option. DON'T 254 Indicates the demand that the other party stop performing, or confirmation that you are no longer expecting the other party to perform, the indicated option. IAC 255 Data Byte 255. 2. Command Meanings A very simple meta-syntax is used, where most tokens represent previously defined items (such as IAC); angle-brackets ("<>") are used for items to be further defined; curly-braces ("{}") are used around optional items; ellipses represent repeated sequences of items; and quotes are used for literal strings. IAC DO TPING The sender REQUESTS the remote server to respond with a Beals [Page 2] Internet Draft Telnet TPING Option 4 November 1997 WILL TPING. IAC WILL TPING Sent in response to a DO TPING packet. If unsolicited, it should be ignored. IAC WON'T TPING No meaning. Should be ignored by the recipient. IAC DON'T TPING No meaning. Should be ignored by the recipient. Discussion This option is most useful in the case where telnet is a hidden intermediary service. The user only knows that he is using a remote resource that appears to be local and does not want to know about the infrastructure imbetween. The telnet ping option allows the hidden client/server pair ascertain if its peer is active. References [1] Postel, J. and J. Reynolds, "Telnet Protocol Specification", STD 8, RFC 854, ISI, May 1983. Author's Address Andrew S. Beals Cisco Systems 170 West Tasman Drive San Jose, CA 95134-1706 Phone: (408) 526-8838 EMail: asb@cisco.com INTERNET DRAFT EXPIRES MAY 1998 INTERNET DRAFT