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Re: Thoughts on increasing MTUs on the internet

  • From: Iljitsch van Beijnum
  • Date: Thu Apr 12 11:43:51 2007


On 12-apr-2007, at 15:26, Steven M. Bellovin wrote:


Last I heard, the IEEE won't go along, and they're the ones who
standardize 802.3.

I knew there was a reason we use ethernet II rather than IEEE 802.3 for IP. :-)


A few years ago, the IETF was considering various jumbogram options.
As best I recall, that was the official response from the relevant
IEEE folks: "no". They're concerned with backward compatibility.

Obviously keeping the same maximum packet size when moving from 10 to 100 to 1000 to 10000 Mbps is suboptimal. However, if the newer standards were to mandate a larger maximum packet size, a station connected to a 10/100/1000 switch at 1000 Mbps would be able to send packets that a 10 Mbps station wouldn't be able to receive. (And the 802.3 length field starts clashing with ethernet II type codes.)


However, to a large degree this ship has sailed because many vendors implement jumboframes. If we can fix the interoperability issue at layer 3 for IP that the IEEE can't fix at layer 2 for 802.3, then I don't see how anyone could have a problem with that. Also, such a mechanism would obviously be layer 2 agnostic, so in theory, it doesn't step on the IEEE's turf at all.