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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- 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
[...]
- 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’.