[dns-operations] PMTUD of .org servers

Michael Graff mgraff at isc.org
Sat Jun 20 16:05:20 UTC 2009

Right but I personally suspect that few recursive resolvers live on a  
network with less than Ethernet mtu. I do think many live behind  
fragment dropping firewalls. Spending time on pmtu for udp thus seems  
like a net loss to me.

If only we could examine the broken side of any brokenness better.


On Jun 20, 2009, at 9:52, Florian Weimer <fw at deneb.enyo.de> wrote:

> * Michael Graff:
>> Without and feedback on pmtu the local interface Mtu would be used I
>> think. That would normally result in a maximum sized packet per
>> fragment.
> It doesn't if the link MTU is lower.  The oversized fragments will be
> split further.  That's where the 5 (well, I wrote 7, but it should be
> 5) fragments come from.
> There is no reassembly in transit, unless you use stock Linux for
> forwarding, which you probably shouldn't (unless you know what your
> doing, usual disclaimers apply etc.).

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