Default assignment size for IXPs

Summary of proposal:

This proposal changes the default IXP assignment size from a /24 to a needs-based model, with a /27 as a minimum.

Policy text:

a) Current policy text

6.1. Assignments to Internet Exchange Points

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4. New IXPs will be assigned a /24 by default. Once they require a larger assignment, they must return their current one (or existing PI used as an IXP peering LAN) and receive a replacement up to maximum of a /22. After one year, utilisation of the new assignment must be at least 50%, unless special circumstances are defined. On request or once there are no more assignments of /24 (or larger) available, assignments can be made down to /27.

[...]

b) New policy text

6.1. Assignments to Internet Exchange Points

[...]

4. New IXPs will be assigned a /27 as a minimum. If an IXP requires a larger assignment, they must return their current assignment, if they have one (or existing PI used as an IXP peering LAN), and receive an assignment with a /22 being the maximum assignment size. For this, they must demonstrate need for at least 50% of the new assignment within two years.

[...]

Rationale:

a. Arguments Supporting the Proposal

Changing the default assignment size from a /24 to a fully needs-based policy with a minimum of a /27 (giving 28 customer assignable addresses after network, broadcast, BGP collector and route server) drastically reduces the consumption of the IXP pool – ensuring it will last for a longer time. Research here indicates that over 50% of IXPs wouldn’t need more than a /27 including 100% overprovisioning.
RIPE NCC will not re-evaluate current assignments other than when a request comes in to get a larger assignment.

b. Arguments Opposing the Proposal

IXPs themselves can operate just fine in prefixes smaller than a /24. The problem lies on the side of the ISPs and other parties connecting to them, who routinely filter any prefixes smaller than a /24 in BGP, as a part of their globally-deployed filtering policy. This means that any prefix longer than a /24 that gets announced by an IXP will get filtered, including well-known communities like ‘NO EXPORT’.