>In some mail from Fernando Gont, sie said:
> > The IPv4 minimum MTU is 68, and not 576. If you blindly send packets
> larger
> > than 68 with the DF bit set, in the case there's an intermmediate with an
> > MTU lower that 576, the connection will stall.
>
>And I think you can safely say that if you see any packets trying to
>indicate that the MTU of a link is "68" then you should ignore it.
Yes. But what about 296?
>Ignoring quenches as a problem, if you try to send 10K of data to a
>box that has an MTU of 68, 1200+ packets are required vs less than 10
>for an ethernet MTU. The problem is 1200 packets require a lot more
>system time to send than 6 or 7. A different kind of DoS attack.
?
That of "more system time" required was listed as one of the effects of the
PMTUD attack in one of the e-mails I sent today.
Not sure what you are saying about ICMP Source Quenches....
>I think it is reasonable to say anyone trying to advertise an MTU less
>than 576 has nefarious purposes in mind.
There are still some radio links with MTUs of 296 bytes.
>In some mail from Fernando Gont, sie said:
> > The IPv4 minimum MTU is 68, and not 576. If you blindly send packets
> larger
> > than 68 with the DF bit set, in the case there's an intermmediate with an
> > MTU lower that 576, the connection will stall.
>
>And I think you can safely say that if you see any packets trying to
>indicate that the MTU of a link is "68" then you should ignore it.
Yes. But what about 296?
>Ignoring quenches as a problem, if you try to send 10K of data to a
>box that has an MTU of 68, 1200+ packets are required vs less than 10
>for an ethernet MTU. The problem is 1200 packets require a lot more
>system time to send than 6 or 7. A different kind of DoS attack.
?
That of "more system time" required was listed as one of the effects of the
PMTUD attack in one of the e-mails I sent today.
Not sure what you are saying about ICMP Source Quenches....
>I think it is reasonable to say anyone trying to advertise an MTU less
>than 576 has nefarious purposes in mind.
There are still some radio links with MTUs of 296 bytes.
[ reply ]