>An MTU of less than 576 violates the IPv4 standard, and will cause
>all kinds of obscure (and some not-so-obscure!) problems, even in
>the presence of Path MTU discovery.

	incorrect, 576 is the minimum supported size for the packet
	size after reassembly.  minimum MTU requirement is 68 octets.

RFC791:
>>    impractical for most hosts and networks.  All hosts must be prepared
>>    to accept datagrams of up to 576 octets (whether they arrive whole
>>    or in fragments).  It is recommended that hosts only send datagrams
>>    larger than 576 octets if they have assurance that the destination
>>    is prepared to accept the larger datagrams.

>>    Every internet module must be able to forward a datagram of 68
>>    octets without further fragmentation.  This is because an internet
>>    header may be up to 60 octets, and the minimum fragment is 8 octets.

itojun