[Vpn-help] MTU packet problems on Linux ...

Rodrigo Ferroni rferroni at gmail.com
Fri Dec 14 15:55:14 CST 2007


Matthew, thanks for the explain my doubts,

now i'm using 1396 for the mtu, like u said to probe,
and work well, the maximum of the esp packet is 1364 and then fragment.
using winscp i transfer around 7gb download and 500mg upload without
problem.

well i will keep whit this kind of test.

thanks, rodrigo.

2007/12/12, Matthew Grooms <mgrooms at shrew.net>:
>
> Matthew Grooms wrote:
> >
> > I have been toying with the idea of making the virtual private network
> > adapter use an MTU of 1480 bytes. This could potentially make most of
> > these problems go away for the average user. Let me do some testing here
> > locally and if things look good, I will post a build. Would you be able
> > to test this for me with your adapter reset to the full 1500 byte MTU?
> >
>
> I guess the adapter MTU would need to decrease to around 1396 bytes.
>
> 1500
> -  8    PPPOE Header
> - 20    IP Header
> -  8    UDP Header
> - 16    ESP Header
> - 32    ESP IV Data ( estimated max )
> - 16    ESP Padding ( estimated max )
> -  1    ESP Pad Bytes
> -  1    Next Protocol
> -  2    Round to nearest 4 bytes
> ----
> 1396
>
> Some trial and error would probably be in order.
>
> -Matthew
>
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