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I know that the frames having size greater than the MTU size should be dropped . i.e, The Ethernet frame having size more than 1522 should be dropped .

But my doubt here is what is Jumbo Frame ?

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Jumbo means any frame with an MTU greater than the 802.3 spec of 1500. There is no set, specified number. It is a generally accepted spec to support "9000", but each manufacturer is free to call "jumbo" whatever they wish. (I've seen some as low as 5k (realtek) and others as high as 16k (broadcom))

IEEE refuses to add it because it breaks backwards compatibility.

And there's no "should" about it. A frame larger than the set max will be dropped by the NIC -- it's an error, and the OS will never know about it. (an oversized frame counter will click up, but that's all.)

  • Hi , Before OS reads the packet , it needs to pass via NIC , then NIC will check for the size right ? If the size is more than it's MTU size it should be dropped right ? – user2720323 Dec 1 '13 at 0:13
  • @user2720323 you seem to be developing a bad habit of defaulting to posting a question here instead of making at least a minimal effort to finding the answer via google first. If you read Ricky Beam's answer, the OS doesn't see the packet due to the NIC dropping it because the frame size is too large. The OS will register this as an error counter increment, and that's all. – John Jensen Dec 1 '13 at 17:09

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