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Re: Automatic Reinitialization of connections

Greg A. Woods woods@weird.com
Tue, 28 May 2002 09:28:29 -0700 (PDT)

[ On Tuesday, May 28, 2002 at 12:20:07 (+1200), Malcolm Gibbs wrote: ]
> Subject: Automatic Reinitialization of connections
> My preference would be to have failed console connections stay in a down
> state to be rectified and manually restarted at a later date.

If you're talking about telnet connections to terminal servers then I
should warn you that it's quite possible the terminal server will freeze
console output if there is no telnet client connected to accept its

Often this effect can be avoided by careful configuration of both the
terminal server and the server's console port.  However even with the
most careful control of these configurations the very cause of the
disconnect may result in an inability to restore the proper
configuration parameters at the most critical time.  For example if you
have a catastrophic power failure on a Friday night and both your
terminal server and the servers it manages consoles for are reset, the
terminal server may send an XOFF character to the booting servers.  This
might prevent them from completing their boot procedures, or it might
cause kernel output to be permanently frozen while syslog output isn't
which will lead to the impression that everything's OK until suddenly
your server freezes entirely when the kernel gets stuck at some later
date as it trys to print a message on the console.

This is in fact one of the reasons I've been working on the chat
solution (since my terminal servers require an access password to be
sent before they'll complete the connection).

I.e. You really do want automatic re-initialisation of telnet
connections.  Appropriately placed pauses can alleviate resource
starvation caused by failed retries.

								Greg A. Woods

+1 416 218-0098;  <gwoods@acm.org>;  <g.a.woods@ieee.org>;  <woods@robohack.ca>
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