[address-policy-wg] IXP pool lower boundary of assignments

* Matthias Wichtlhuber

> While I think a /29 would be too radical (renumbering peering LANs
> can be a real headache, you don't want to do that more often than
> needed), a /26 as a default might be a good compromise. 62 usable
> addresses are still enough for ~70% of all IXes including 100% over
> provisioning. This would likely stretch the pool well into the 2030s.

The IXP pool was created in 2012 (2011-05).

In 2019 (2019-05) we went «whoops, we're burning through it too fast,
more is needed», and doubled its size.

In 2022, today, we're again going «whoops, we're burning through it too
fast», proposing to only slightly change the default assignment value
to /25 (or /26).

I see a pattern here…

How long before the next «whoops, we're burning through it too fast»?
Will we at that point change the default by another bit, going to /26
(or /27)?

Renumbering is a headache, but it is doable (it has been done many
times before), and the IXP community could certainly create a BCP
document on how to best do it – if one does not exist already.

Conditioning new IXPs already from their very infancy that they will
need to renumber every time they double in size already (when
renumbering is the least painful) is not unreasonable, in my opinion.
This requirement is balanced against the preservation of the IXP pool
for future and growing IXPs, after all.

If a new IXP with three founding members and a small/unrealistic
prospect of future growth applies for an IXP assignment, I think the
radical approach is to give that IXP something larger than the /29 it
actually requires. Doing so will inevitably mean that some other IXP
will be told «sorry, fresh out, no assignment for you» at some point in
the future.

Tore