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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

[...]

  1. 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

[...]

  1. 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’.

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The Address Policy Working Group develops policies relating to the allocation and registration of Internet number resources (IPv4 and IPv6 addresses and ASNs) by the RIPE NCC and its members. Anyone with an interest in Internet numbering issues is welcome to observe, participate and contribute to the WG. To post a message to the list, send an email to address-policy-wg@ripe.net. Please note that only subscribers can post messages.

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