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

* Aleksi Suhonen

> I feel that /26 is the smallest reasonable subnet size for an IXP, no
> matter how small the IXP is initially. If it starts growing, it will 
> quickly grow past /27, but might just stay inside the /26. This is
> based on empirical experience over the decades.

Could you please share the actual data on which your «empirical
experience» is founded with the list?

Reason I am asking is that the only actual data that has been shared
with the list so far is https://github.com/mwichtlh/address-policy-wg/,
which appears to disagree with you. Looking at Figure 2 here, it would
appear that «~55% of all IXPs would fit into a /27 including 100%
overprovisioning».

In other words, a majority of all IX-es would fit into a subnet smaller
than your claimed «smallest reasonable size» while having ample elbow
room – enough to at least double their current member count.

> PS. I don't think Tore appreciates how much more difficult it is to 
> renumber an IXP compared to a data centre or an access provider.

Actually, I do have some real-life experience here as I/AS39029 was
part of the NIX renumbering process back in 2017. The whole operation
was rather straight-forward and went very smoothly. NIX staff simply
informed all members of their new IPs by e-mail and told to migrate
within a certain date (different dates for NIX1 and NIX2).

Most members opted to have both addresses simultaneously active during
the migration period to facilitate hitless migration of traffic to the
new addresses without needing to coordinate with each individual peer.

NIX is (and was) a mid-sized IX, currently around 60 participants.
Based on that experience I have honestly a very hard time believing
that renumbering a small IX is «much more difficult [than renumbering
a] data centre or an access provider».

Tore