INTERNET-DRAFT draft-clark-telnet-control-00.txt Expire in six months Network Working Group Glen Clark Internet-Draft ESDL, Inc. March 1996 Telnet Comport Control Option Preamble: 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 containing 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). Status Section: This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Introduction Section: This memo proposes a protocol to allow greater use of modems attached to a network. Increased needs for "off network" communications has increased the need for modems. Increasing the functionality of Telnet increases the functionality of network attached modems. For example, the ability to send a FAX via a network attached modem. This memo addresses configuration of the comport to which the modem is attached. It does not address the internal configuration of the modem itself. Clark Page [1] INTERNET-DRAFT Telnet Comport Control Option March 1996 Table of Contents 1. Negotiation of the Comport Control Option Protocol .................. 2 2. Comport Configuration Commands .................. 3 Version Baud Rate Data Bit Size Parity Stop Bit size 3. Special Comport Control Commands .................. 6 XON/XOFF Flow Control HARDWARE Flow Control BREAK Signal DTR Signal RTS Signal 4. Notification of Comport and .................. 7 Modem Line Changes 5. Flow Control .................. 7 Command Names and Codes: COMPORT-OPTION 40 QUERY-VERSION 0 SET-BAUDRATE 1 SET-DATASIZE 2 SET-PARITY 3 SET-STOPSIZE 4 SET-CONTROL 5 NOTIFY-LINESTATE 6 NOTIFY-MODEMSTATE 7 1. Negotiation of the Comport Control Option Protocol The negotiation of the comport control option protocol uses the standard Telnet negotiation protocol mechanism. IAC WILL COMPORT-OPTION The sender of this command is willing to send comport control option commands. IAC WONT COMPORT-OPTION The sender refuses to send comport control option commands. IAC DO COMPORT-OPTION The sender of this command is willing to accept comport control option commands. IAC DONT COMPORT-OPTION The sender of this command refuses to accept comport control options commands. Typically a client will use WILL and WONT, while a host will use DO and DONT. Clark Page [2] INTERNET-DRAFT Telnet Comport Control Option March 1996 2. Comport Configuration Commands Once DO and WILL have been negotiated, the client may send any of the following commands. The client can send these commands at any time and multiple times throughout the Telnet session. Each command transmitted from the client to the host is acknowledged with a confirmation of the command and the actual value set. The client should expect a response within a reasonable time (such as twice the delay acknowledgment timer). The client may wish to resend any command which is not acknowledged, however the client may also ignore the failure to receive an acknowledgment. Though the commands may be sent from the client to the host in any sequence, there are sequences which may result in invalid configurations for the comport (for example: EVEN parity is only valid if the data size is set to less than 8 bits). Thus it is recommended that commands be issued in the following sequence: 1. SET-BAUDRATE 2. SET-DATASIZE 3. SET-PARITY 4. SET-STOPSIZE Discussion: As initially proposed, comport configuration commands are only sent from the client to the host. There is no current vision that the host would initiate the use a comport configuration command. Host initiated comport configuration commands could easily be included in the protocol. It would require that a response command have a different value than an initiate command. For example: Command Initiate Value Response Value SET-BAUDRATE 1 101 SET-DATASIZE 2 102 SET-PARITY 3 103 SET-STOPSIZE 4 104 SET-CONTROL 5 105 Discussion: The prompt response mechanism suggested here allows the protocol to be used to query the values at the host as well as set the values. The use of this mechanism provides more functionality than a simple ACK/NAK protocol. Clark Page [3] INTERNET-DRAFT Telnet Comport Control Option March 1996 IAC SB COMPORT-OPTION QUERY-VERSION <value> IAC SE This command is sent by the client to the host to query the version of the COMPORT-OPTION protocol supported by the host. The value is one octect (byte). When sent by the client the value indicates the version supported by the client. When returned by the host, the value indicates the version supported by the host. This exchange allows both parties to know the capabilities supported by the other and make appropriate modifications in the commands and responses. The value is an index into the following value table: Value Version 0 Draft Version 1 Initial Approved Version 2-127 Available for Future Use IAC SB COMPORT-OPTION SET-BAUD <value> IAC SE This command is sent by the client to the host to set the baud rate of the comport. The command can also be sent to query the current baud rate as well as receive the maximum baud rate supported by the comport. The value is one octet (byte). The value is an index into the following value table: Value Baud Rate (bits per second) 0 Request Current Baud Rate 1 110 2 150 3 300 4 600 5 1200 6 2400 7 4800 8 9600 9 14400 10 19200 11 28800 12 38400 13 57600 14 115200 15-126 Available for Future Use 127 Query Maximum Baud Supported Discussion: Baud rates use today form a very sparse value space. Representing these by their actual value requires four octets. In additional to the extra data transmitted this representation requires the negotiation of the byte order for the longer data representation. The value table mechanism provides ample room for future expansion as well as avoids the need for byte order negotiation. Clark Page [4] INTERNET-DRAFT Telnet Comport Control Option March 1996 IAC SB COMPORT-OPTION SET-DATASIZE <value> IAC SE This command is sent by the client to the host to set the data bit size. The command can also be sent to query the current data bit size. The value is one octet (byte). The value is an index into the following value table: Value Data Bit Size 0 Request Current Data Bit Size 1 Available for Future Use 2 Available for Future Use 3 Available for Future Use 4 Available for Future Use 5 5 6 6 7 7 8 8 9-127 Available for Future Use Discussion: There are only eight possible values for the data bit size, only four have ever been used historically and only two are commonly used today. The use of the command-value format is recommended to preserve consistency with other commands. It also reduces the number of commands defined in the protocol, and allows for future expansion. IAC SB COMPORT-OPTION SET-PARITY <value> IAC SE This command is sent by the client to the host to set the parity. The command can also be sent to query the current parity. The value is one octet (byte). The value is an index into the following value table: Value Parity [1] 0 Request Current Data Size 1 NONE 2 ODD 3 EVEN 4 MARK 5 SPACE 6-127 Available for Future Use Discussion: There are only five possible values for parity commonly used today. The use of the command-value format is recommended to preserve consistency with other commands. Clark Page [5] INTERNET-DRAFT Telnet Comport Control Option March 1996 IAC SB COMPORT-OPTION SET-STOPSIZE <value> IAC SE This command is sent by the client to the host to set the number of stop bits. The command can also be sent to query the current stop bit size. The value is one octet (byte). The value is an index into the following value table: Value Stop Bit Size 0 Request Current Data Size 1 1 2 2 3 1.5 4-127 Available for Future Use Discussion: Stop bit 1.5 is supported by most comport hardware only if data size is set to 5 bits. It is not commonly used. 3. Special Comport Control Commands The client can send this command to the host at any time and multiple times throughout the Telnet session. Each command transmitted from the client to the host is acknowledged with a confirmation of the command and the actual value set. The client should expect a response within a reasonable time (such as twice the delay acknowledgment timer). The client may wish to resend any command which is not acknowledged, however the client may also ignore the failure to receive an acknowledgment. IAC SB COMPORT-OPTION SET-CONTROL <value> IAC SE This command is sent by the client to the host to set special comport options. The command can also be sent to query the current option value. The value is one octet (byte). The value is an index into the following value table: Value Control Commands 0 Request Comport Flow Control Setting 1 Use No Flow Control 2 Use XON/XOFF Flow Control 3 Use HARDWARE Flow Control 4 Request BREAK State 5 Set BREAK State ON 6 Set BREAK State OFF 7 Request DTR Signal State 8 Set DTR Signal State ON 9 Set DTR Signal State OFF 10 Request RTS Signal State 11 Set RTS Signal State ON 12 Set RTS Signal State OFF 13-127 Available for Future Use Clark Page [6] INTERNET-DRAFT Telnet Comport Control Option March 1996 4. Notification of Comport and Modem Line Changes The host can send these commands to the client any time and multiple times throughout the Telnet session. The host should send the appropriate command to the client as soon as the comport or modem line changes occurs. The client does not issue a response to these commands. IAC SB COMPORT-OPTION NOTIFY-LINESTATE <value> IAC SE The value is one octet (byte). The value is a bit level composition made up from the value table below. Multiple bit values may be set in a single transmission. The values are based on the most popular UART (comport control chip) in use. [1] Bit Position Value Meaning 7 128 Time-out Error 6 64 Transfer Shift Register Empty 5 32 Transfer Holding Register Empty 4 16 Break-detect Error 3 8 Framing Error 2 4 Parity Error 1 2 Overrun Error 0 1 Data Ready IAC SB COMPORT-OPTION NOTIFY-MODEMSTATE <value> IAC SE The value is one octet (byte). The value is a bit level composition made up from the value table below. Multiple bit values may be set in a single transmission. The values are based on the most popular UART (comport control chip) in use. [1] Bit Position Value Meaning 7 128 Receive Line Signal Detect 6 64 Ring Indicator 5 32 Data-Set-Ready Signal State 4 16 Clear-To-Send Signal State 3 8 Delta Receive Line Signal Detect 2 4 Trailing-edge Ring Detector 1 2 Delta Data-Set-Ready 0 1 Delta Clear-To-Send 5. Flow Control Flow control will follow the protocol established in RFC 1372: Telnet Remote Flow Control Option. [2] Security Consideration Section: Security issues are not discussed in this memo. Clark Page [7] INTERNET-DRAFT Telnet Comport Control Option March 1996 Author Address: Glen Clark, Chief Architect Enterprise Solutions Development Laboratories, Inc. 15127 NE 24th Street, Suite 157 Redmond, WA 98052 Internet: glenc@esdl.com WEB: www.esdl.com CompuServe: 73750,1607 Reference Section: [1] Joe Campbell. C Programmer's Guide to Serial Communications, Second Edition. Indianapolis: SAMS Publishing, 1993. 213-224. [2] Internet Engineering Task Force, Telnet Working Group, C. Hedrick and D. Borman, "Telnet Remote Flow Control Option", RFC 1372, Cray Research, Inc., October 1992. Clark Page [8]