tjs@UF.MSC.UMN.EDU ("Tim Salo") (07/17/89)
Effective X.3/Telnet Gateway for Unix Desired --------------------------------------------- Overview -------- This note describes the need for a gateway which would enable asynchronous devices attached to X.25 networks to communicate effectively with Unix hosts using Telnet. The gateway should translate between X.3/X.25 and Telnet/TCP/IP protocols. Furthermore, the gateway should use one-character X.25 packets when required and one-line X.25 packets with local echoing when possible. This note assumes that Line Mode Telnet is available. I am looking for people with experience with or opinions about such a gateway. Additionally, I would like to know whether anyone has or plans to develop, or has interest in working on, an RFC for or prototype implementation of such a gateway. I will summarize the responses. X.3/Telnet Gateway Requirement ------------------------------ The configuration of the desired X.3/Telnet Gateway is shown below. The X.3 PAD, X.25 Packet-Switched Data Network and Telnet Host are existing products. The X.3/Telnet Gateway is the product which is desired. ........ ______ . . ______________ _______ | | . . | | | Telnet| TTY ___| X.3 |___. X.25 .___| X.3/Telnet | | (Unix)| ^ | PAD | ^ . PSDN . ^ | Gateway | | Host | ^ |______| ^ . . ^ |______________| |_______| ^ ^ ........ ^ | | async X.25 X.25 | | | | Telnet/TCP/IP (ethernet) | | ============================================= X.3/Telnet Gateway Configuration The X.3/Telnet Gateway should map between telnet connections and X.3 connections, including X.3 SET PAD PARAMETERS and telnet option negotiations. The X.3/Telnet Gateway must work well with Unix hosts. 1. Efficient use should be made of the X.25 network; local echoing at the X.3 PAD and large packets should be used when possible. 2. Effective support for Unix software which relies upon one- character-at-a-time communications and echoing by the Unix user program should be provided. Programs such as "vi", "less", and "more" should operate, from the perspective of the terminal user, the same as if the terminal were directly attached to the Unix host. 3. The gateway should automatically switch the X.3 PAD between line-at-a-time and character-at-a-time communications. It is assumed that Line Mode Telnet is available on the Unix host to signal the gateway, through the telnet protocol, when the user software moves into and out of character-at- a-time communications. The gateway, upon receipt of an indication that the user software in entering character-at- a-time communications, should issue SET PAD PARAMETER packets to the remote X.3 PAD to prepare it for one- character X.25 packets. Upon receipt of an indication of line-at-a-time communications, the gateway should issue SET PAD PARAMETERS to prepare the remote PAD forward at the end of a line and to echo locally. Proposed X.3/Telnet Gateway Architecture ---------------------------------------- The X.3/Telnet Gateway should be a combined X.3 PAD and telnet client. The telnet client and Unix host must implement the Line Mode Telnet option to provide signalling of the movement of the Unix user software in and out of character-at-a-time mode. X.3/Telnet Gateway Unix Host ___________________ _______________ | | | G | | | | | | | U | _____ | | | a | T | T | | T | T | K | s | | | | X | X | t | e | C | | C | e | e | e | TTY ___| X.3 |_____| . | . | e | l | P | | P | l | r | r | ^ | PAD | ^ | 2 | 3 | w | n | / | | / | n | n | | ^ |_____| ^ | 5 | | a | e | I | | I | e | e | S | ^ | ^ | | | y | t | P | | P | t | l | W | async | X.25 |___|___|___|___|___| |___|___|___|___| |______________| ^ | |_______| | X.3/X.28 ^ | TCP/IP | ^ |_______________| ^ Telnet (line mode) ^ X.3/Telnet Gateway Functionality ------------------ Feel free to send comments to: Tim Salo Minnesota Supercomputer Center tjs@msc.umn.edu (612) 626-0347