RE: [masq] MTU/MRU, always-defrag, diald, masq not working for some URLs

Cy (ib@digicron.com)
Sat, 26 Dec 1998 18:16:09 -0600


Just wanted to say thanks for this thread. I've been puzzling over tcpdump,
masq debugging, and ppp debugging for the last week or so trying to figure
out why I would have timeouts when collecting mail through my linux box. I
would NEVER have guessed the MTU/MRU sizes. Changing to 1500 fixed the
problem. I prefer 576, but can definitely live with 1500.

Cy

> -----Original Message-----
> From: Fuzzy Fox [mailto:fox@dallas.net]
> Sent: Saturday, December 26, 1998 1:11 AM
> To: masq@tori.indyramp.com; linux-kernel@vger.rutgers.edu;
> masq-dev@tori.indyramp.com
> Subject: Re: [masq] MTU/MRU, always-defrag, diald, masq not working for
> some URLs
>
>
> Thanks for using NetForward!
> http://www.netforward.com
> v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v
>
> Tom Oehser <tom@toms.net> wrote:
> >
> > The mtu/mru 1500 causes the problem to go away.
>
> Many people find that to be the case.
>
> > Given that this is a bad wrong problematic kludge, where should I be
> > looking to fix this *without* changing my mtu/mru from 296 to 1500?
>
> It seems that most folks are able to live with the larger MTU. The fast
> speed of today's modems means that the time difference to transfer a
> 296-byte packet, vs. a 1500-byte packet is somewhere near 300 ms.
> Certainly measurable, but not like it was in the 2400-baud days.
>
> > Is there a problem with the defrag, where an interaction with diald
> > between the sl0 and ppp0 causes the always-defrag to not defrag?
>
> Many people see this without diald in the equation, so I believe it is a
> problem in the IP refragmentation code, but I don't think anyone is
> actively trying to solve this problem.
>
> > Changing my MTU/MRU from 296 to 1500 causes many other problems, I
> > have to find another approach to this...
>
> Performance might be degraded, but is it that much? Is there some way
> to work around it using TOS settings of ipchains?
>
> --
> fox@dallas.net (Fuzzy Fox) || "Nothing takes the taste
> out of peanut
> sometimes known as David DeSimone || butter quite like unrequited love."
> http://www.dallas.net/~fox/ || --
> Charlie Brown
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