On 29 Dec 2011, at 13:46 , Masataka Ohta wrote: > we must assume MTU of 1280B. But, as IPv6 extension headers can > be as lengthy as 1000B or 2000B, no applications are guaranteed > to work over IPv6. As IP is an unreliable datagram service, there are no guarantees, period. The presence of firewalls also removes any guarantees left in place after the previous point.