Thoughts on increasing MTUs on the internet

Thu Apr 12 15:32:35 UTC 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.