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Date:      Thu, 18 Jan 2001 10:20:30 -0500
From:      Bill Moran <wmoran@mail.iowna.com>
To:        Darren Henderson <darren@bmv.state.me.us>
Cc:        Ted Mittelstaedt <tedm@toybox.placo.com>, freebsd-questions@FreeBSD.ORG
Subject:   Re: pppd, modem, app oddity
Message-ID:  <3A6709BD.C2C6BD4C@mail.iowna.com>
References:  <Pine.A41.4.21.0101180957420.19416-100000@katahdin.bmv.state.me.us>

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Darren Henderson wrote:

> Thanks, I'll give that a look this evening. Currently the modem is doing the
> compression I believe, I've not given pppd any instructions regarding
> compression so I really can't say if it is doing its thing as well (I can
> see where two levels of compression would not be a good thing).

I'd be surprised if this were the problem. (but you should probably
check it out anyway) It reminds me of my youth when we asked the Idiotic
Question "What happens if you compress a compressed file?"
All that happens is that you get another layer of compression
abstraction. The data doesn't get any more compressed - you actually
increase the size of the file due to header stuff. The upshot of the
silly experiment, however, was that you could zip within zip within zip
(I think we tested to 6 layers or something) and get absolutely no data
corruption.

Your mention of MTUs got me thinking, though, especially since changing
them changed the situation (a sure sign that you're on the right track)
NFS apparently has problems on some machines that are caused by MTUs
being too small. I'm wondering if your problem is similar. It's
described here: http://www.freebsd.org/handbook/nfs.html at the bottom
of the page. Perhaps the solution is to raise the MTU/MRU on the ppp
line?? (I'm going out on a limb here, but I thought I'd share it on the
outside chance that I was right)

Hope this helps,
Bill


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