/25 is too small, even for smaller IXPs.
~400-500 of the entries in the PCH IXP directory are defunct. For the remainder, the participant numbers are inaccurate, mostly on the low side. A figure of about 500 active IXPs is largely corroborated by the IXP DB (650 entries, with some effectively defunct). Hmm.. why shouldn't defunct IXPs not be taken in consideration though? To me that sounds like ~400-500 IXPs requesting an allocation at some
Nick Hilliard wrote on 04/06/2019 20:17: point in time, and probably most of them not needing anything more than a /24 (or maybe less), assuming they failed in their mission. As much as I'd love to assume that all IXPs requesting allocations onwards will succeed (and thus needing more than /25 or /24), I don't think that's realistic. So I still believe averaging participants across all of the IXP entries, be it Euro-IX (probably more accurate), or even PCH, is an acceptable metric.
The central question of this policy update is not the assignment size for IXPs, but whether it's worth investing 4 days out of 30 years worth of allocations in order to provide important flexibility for the internet core in the future. I'm inclined to think it is. Agreed, and: Marco's email mentions "This proposal aims to increase the reserved IPv4 pool for IXPs to a /15 and finetune assignment criteria."
IMO fine tuning the initial allocation to a /25 makes sense, if only to further the mission of the policy and extend the life of the pool. If anything, IXPs could always provide evidence as to why they need more IP space, even initially, regardless of whether it's a /24 or a /22. To summarize my point of view, having more stringent controls as to who gets what seems only reasonable, given the scarcity of the resource, but allow for flexibility, if the application is well justified. Kind regards, Aris