Re: telnet hanging intermittenly

From: Ben K. Li (benl_at_ben-li.com)
Date: 10/07/03 

Date: Tue, 7 Oct 2003 17:14:21 +0800
To: Leon The Peon <noemail@nowhere.com>

So, finally, after loosing sleep for a few days, I figured out what the
problem was.

I might have failed to mention that I was accessing my machine that was
connected through DSL broadband service running over PPPoe. So, the
problem was the MTU was being recognized as 1500, whereas 1492 would be
the correct value due to the 8 byte overhead for pppoe.

Thanks to all who replied.

On Tue, 7 Oct 2003, Leon The Peon wrote:

>
> "Ben K. Li" <benl@ben-li.com> wrote in message
> news:Pine.LNX.4.44.0310031139540.6437-100000@ben-li.com...
> >
> > Hi,
> >
> > Here's my problem. I have redhat 9 installed. Every once in awhile (more
> > often than not), I will telnet into my machine from work and it will hang.
> > It doesn't hang on the login. I actually login and get a prompt.
> > However, when I do something else like ls or pine, the connection will
> > freeze. Using send ayt from telnet prompt returns a YES. The only way to
> > get out of it is to do a ctrl-] and then quit. I can immediately login
> > again, but same problem exists.
> >
> > I'm telneting out of a firewall-telnet gateway from work and I don't seem
> > to have any problems when I go to cyberspace.org (for example).
> >
> > Strangely, sometimes this problem does not occur at all.
> >
> > Could someone begin to give me a hand as to what is causing this?
>
> maybe the firewall NAT has a very short timeout on it.
> The NAT firewall assumes that a TCP/IP session that has been idle for X
> seconds is now defunct and should be forgotten.
> (if this timeout is too long, the NAT tables fill up and it cant allow any
> new TCP/IP sessions to be created, or it slows down too much)
>
> Also some Telnet programs do not like lost packets, there may be a problem
> with the network reliability, such as it being flooded.
>
> Perhaps the use of putty and ssh will fix the problem.
> Perhaps the firewall needs to be configured to have a longer time out for
> tcp
>
>
>
>
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