[address-policy-wg] 2019-07 New Policy Proposal (Default assignment size for IXPs)

* Marco Schmidt

> A new RIPE Policy proposal, 2019-07, "Default assignment size for IXPs"
> is now available for discussion.
> 
> This proposal aims to change the default IXP assignment size from a /24
> to a needs-based model, with a /27 as a minimum.

While I do support the proposal's aim of reducing the default assignment size, I would suggest that we make the default a /29 instead of a /27:

- The reserved IXP pool currently contains prefixes sized /29 and /28. These can not be delegated under neither the current nor the proposed policy. However, small IXPs could make use of these just fine. I see why reason why we should «lock them up and throw away the key».

- Looking at figure 2 at https://github.com/mwichtlh/address-policy-wg/ it would appear that ~43% of all IXPs would fit into a /28 including 100% overprovisioning (or into a /29 with no overprovisioning). This suggests that /29s and /28s would be useful and sufficient to a significant number of IXPs.

- Lowering the default assignment size to a /29 does obviously not mean that IXPs that do require a /27 or larger should not receive it. They simply have to justify it, exactly the same as an IXP requesting a /{26..22} would have to under the proposed policy. This is not a unreasonable thing to ask, in my opinion - IPv4 is a very scarce resource, after all.

- This might require growing IXPs to renumber from /29->/28->/27, which they would not have to do under the currently proposed policy. However, I do not think that is an unreasonable thing to ask. The smaller the IXP is, the easier it is to coordinate a renumbering process. Renumbering is in any case a process they will to go through as they grow out of the /27 currently proposed as the new default assignment size.

Tore