Branimir,

>> "When an lwB4 receives an IPv4 packet from its connected host that is
>>    larger than the MTU size after encapsulation, the lwB4 MUST fragment
>>    the IPv4 packet before encapsulation."
>> 
>> If the DF flag is set, the packet shouldn't be fragmented, instead PMTUD
>> mechanism should be honored. Right? Fragmenting an IPv4 packet with DF bit
>> set sounds like a bad thing.
> 
> One more thing I find puzzling - RFCs 2473 and 6333 state that you have to 
> encapsulate the packet first into IPv6 and if it exceeds the IPv4-in-IPv6 
> tunnel MTU, fragment the IPv6 packet. This draft states the opposite thing, 
> if the encapsulated packet is larger than the tunnel MTU, you have to 
> fragment IPv4 and then encapsulate it into IPv6. In my opinion, the simpler 
> thing to do would be to encapsulate first and fragment afterwards.

RFC4459 gives a good analysis of the problem.

> I think this is also a problem because RFC 6333 describes fragmentation only 
> from the AFTR's viewpoint and this draft describes it from the B4's 
> viewpoint. Since this draft refers to RFC6333 for fragmentation, it would 
> mean that the lwAFTR and lwB4 would have different fragmentation logic.

cheers,
Ole

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