Internet Exchanges supporting jumbo frames?

Saku Ytti saku at
Wed Mar 9 16:20:05 UTC 2016

On 9 March 2016 at 16:34, Job Snijders <job at> wrote:

IXP can verify if MTU is too large or too small with active poller.

Poller in the IXP has too large MTU, it tries to send ping packets
with max_size+1, if they work, customer has too large MTU. Also it
tries to send max_size, if it does not work, customer has too small
MTU. As icing on top, it tries to send max_size+1 but fragments it to
max_size and 1, and sees what comes back.

IXP is only interface in whole of Internet which collapses MTU to
1500B, private peers regularly have higher MTU, ~everyone runs core at
higher MTU.

I think it's crucial that we stop thinking MTU as single thing, we
should separate edge MTU and core MTU, that is how we already think
and provision when we think about our own network. Then question
becomes, is IXP edge or core? I would say run core MTU in IXP, so edge
MTU can be tunneled without fragmentation over it.
IXP can offer edgeMTU and coreMTU VLANs, so that people who are
religiously against it, can only peer in edgeMTU VLAN.


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