Thoughts on increasing MTUs on the internet

Thu Apr 12 15:42:06 UTC 2007

* Steven M. Bellovin:

> On Thu, 12 Apr 2007 16:12:43 +0200
> Florian Weimer <fw at deneb.enyo.de> wrote:
>
>> * Steven M. Bellovin:
>> 
>> > 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.  
>> 
>> Gigabit ethernet has already broken backwards compatibility and is
>> essentially point-to-point, so the old compatibility concerns no
>> longer apply.  Jumbo frame opt-in could even be controlled with a
>> protocol above layer 2.

> I'm neither attacking nor defending the idea; I'm merely reporting.

I just wanted to point out that the main reason why this couldn't be
done without breaking backwards compatibility is gone (shared physical
medium with unknown and unforeseeable receiver capabilities).

> I'll also note that the IETF is very unlikely to challenge IEEE on
> this.

It's certainly unwise to do so before PMTUD works without ICMP
support. 8-)