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Date:      Thu, 22 Nov 2012 14:20:06 +0100
From:      Ingo Flaschberger <if@xip.at>
To:        freebsd-net@freebsd.org
Subject:   Re: Low Bandwidth on intercontinental connections
Message-ID:  <50AE2686.8070007@xip.at>
In-Reply-To: <50AE1CCC.7080706@mpeters.org>
References:  <50ACF62C.8000408@mpeters.org> <CAOgwaMuUuJ2%2BmKqsFVp=DyVFkfm8Et%2Brnt2iEGDO8i1Kt_kDVA@mail.gmail.com> <50ad087d.1892cc0a.2cce.3bf2@mx.google.com> <50AD1012.7020209@mpeters.org> <50AD14F8.8050001@xip.at> <50ADE5E4.9090708@mpeters.org> <50AE0B12.8000309@xip.at> <50AE1CCC.7080706@mpeters.org>

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Am 22.11.2012 13:38, schrieb Marc Peters:
> interesting, the MTU is way lower, than i expected. Through the VPN 
> tunnel, only 1322 bytes are possible without fragmentation. ScreenOS 
> adds 42 additional bytes per paket and the FreeBSD box is receiving 
> 1364 bytes, according to tcpdump. From the outside (only one Netscreen 
> on the way), 1472 is the maximum possible size to send pakets without 
> fragmentation (-D). Which MTU would you suggest to use? Shouldn't the 
> MTU discovery of FreeBSD handle this correct?

do you see fragmented tcp packets on the receiving site in tcpdump?

When you load the tcpdump data (tcpdump -s 1500 -w filename ...) into 
wireshark, you can graph the speed (bit/sec, packets/sec) and do some 
more tcp analysis.

Kind regards,
     Ingo Flaschberger



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