libssh/doc/draft-ietf-secsh-break-00.txt

Secure Shell Working Group                                  J. Galbraith
Internet-Draft                                          VanDyke Software
Expires: September 17, 2003                                   P. Remaker
                                                      Cisco Systems, Inc
                                                          March 19, 2003


                    Session Channel Break Extension
                     draft-ietf-secsh-break-00.txt

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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   This Internet-Draft will expire on September 17, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   The Break Extension provides a way to send a break signal during a
   SSH terminal session.












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Table of Contents

   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2. The Break Request  . . . . . . . . . . . . . . . . . . . . . . . 4
      References . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
      Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
      Intellectual Property and Copyright Statements . . . . . . . . . 6












































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1. Introduction

   The SSH session channel provides a mechanism for the client-user to
   interactively enter commands and receive output from a remote host
   while taking advantage of the SSH transport's privacy and integrity
   features.

   A common application of the telnet protocol is the "Console Server"
   whereby a telnet NVT can be connected to a physical RS-232/V.24
   asynchronous port, allowing the telnet NVT to appear as a locally
   attached terminal to that port, and allowing that port to appear as a
   network addressable device.  A number of major computer equipment
   vendors provide high level administrative functions through an
   asynchronous serial port and generally expect the attached terminal
   to be capable of send a BREAK signal, which is defined as the TxD
   signal being held in a SPACE state for a time greater than a whole
   character time, typically interpreted as 250 to 500 ms.

   The telnet protocolprovides a means to send a "BREAK" signal, which
   is defined as a "a signal outside the USASCII set which is currently
   given local meaning within many systems." [1]  Console Server vendors
   interpret the TELNET break signal as a physical break signal, which
   can then allow access to the full range of administartive functions
   available on an asynchronous serial console port.

   The lack of a similar facility in the SSH session channel has forced
   users to continue the use of telnet for the "Console Server"
   function.























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2. The Break Request

   The following following channel specific request can be sent to
   request that the remote host perform a break operation.

           byte               SSH_MSG_CHANNEL_REQUEST
           uint32             recipient channel
           string             "break"
           boolean            want_reply
           uint32             break-length in milliseconds

   If the break length cannot be controlled by the application receiving
   this request, the break length parameter SHOULD be ignored and the
   default break signal length of the chipset or underlying chipset
   driver SHOULD be sent.

   If the application can control the break-length, the following
   suggestions are made reagarding break duration. If a break duration
   request of greater than 3000ms is received, it SHOULD be processed as
   a 3000ms break, in order to an unreasonably long break request
   causing the port to become unavailable for as long as 47 days while
   executing the break.  Applications that require a longer break may
   choose to ignore this requirement.  If  break duration request of
   less than 500ms, is requested a break of 500ms SHOULD be sent since
   most devices will recognize a break of that length.  In the event
   that an application needs a shorter break, this can be ignored.  If
   the break-length parameter is 0, the break SHOULD be sent as 500ms or
   the default break signal length of the chipset or underlying chipset
   driver .

   If the want_reply boolean is set, the server MUST reply using
   SSH_MSG_CHANNEL_SUCCESS or SSH_MSG_CHANNEL_FAILURE [4] messages.  If
   a break of any kind was preformed, SSH_MSG_CHANNEL_SUCCESS MUST be
   sent.  If no break was preformed, SSH_MSG_CHANNEL_FAILURE MUST be
   sent.

   This operation SHOULD be support by most general purpose SSH clients.














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References

   [1]  Postel, J. and J. Reynolds, "Telnet Protocol Specification", STD
        8, RFC 854, May 1983.

   [2]  Rinne, T., Ylonen, T., Kivinen, T. and S. Lehtinen, "SSH
        Protocol Architecture", draft-ietf-secsh-architecture-13 (work
        in progress), September 2002.

   [3]  Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S.
        Lehtinen, "SSH Transport Layer Protocol",
        draft-ietf-secsh-transport-15 (work in progress), September
        2002.

   [4]  Rinne, T., Ylonen, T., Kivinen, T. and S. Lehtinen, "SSH
        Connection Protocol", draft-ietf-secsh-connect-16 (work in
        progress), September 2002.


Authors' Addresses

   Joseph Galbraith
   VanDyke Software
   4848 Tramway Ridge Blvd
   Suite 101
   Albuquerque, NM  87111
   US

   Phone: +1 505 332 5700
   EMail: galb-list@vandyke.com


   Phillip Remaker
   Cisco Systems, Inc
   170 West Tasman Drive
   San Jose, CA  95120
   US

   EMail: remaker@cisco.com












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Intellectual Property Statement

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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.











































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