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If you're fragmenting and drop one packet of a 4-packet-sequence you waste the other 3 packets anyway as its gotta send the whole oversize packet as multiple fragments all over again. My guess is that is his reasoning - and seems fair...

Sending a 9600byte packet in one frame, or fragmented into seven frames isn't really a meaningful test if you're trying to prove that jumbo frames are better when there is packet loss. In the real world, the non-jumbo frame setup would only send 1500 byte packets...