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Re: The IPv4 Internet MTU
On 12-okt-2007, at 21:06, Doug Barton wrote:
There are basically two types of UDP protocols: the old / low
volume ones such as the DNS, where a 512 / 576 limit is explicitly
or implicitly understood,
And of course this assumption is no longer valid in the EDNS0 world
where UDP packets can be as large as 6k.
I should do some checking to see how many implementations advertise
an EDNS0 size larger than 1500 and set the DF bit.
A while back there was at least one root server that set the DF bit
which causes breakage with an MTU lower than 450 bytes because
obviously they don't retry with smaller packets when a "too big" is
returned.