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. This came up some years ago in discussion about ... hmm... I think it was what made a good (or sensible) "fragmentation required" ICMP message. 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. I think it is reasonable to say anyone trying to advertise an MTU less than 576 has nefarious purposes in mind. oh, IPv6 guarantees a min. MTU of 1280. Lets just stop using IPv4 already. Darren
