[ppml] Policy Proposal 2005-8: Proposal to amend ARIN IPv6 assignment and, utilisation requirement

Member Services memsvcs at arin.net
Thu Sep 1 15:56:28 EDT 2005

On August 31, 2005, the ARIN Advisory Council (AC) concluded its review 
of proposed policy "Proposal to amend ARIN IPv6 assignment and 
utilisation requirement" and agreed to forward it as a formal proposal 
for discussion by the community. This proposal is designated 2005-8: 
Proposal to amend ARIN IPv6 assignment and utilisation requirement 
(Section 6 of ARIN Number Resource Policy Manual). The policy proposal 
text is below and can be found at: 

All persons in the community are encouraged to discuss Policy Proposal
2005-8 in the weeks leading to the ARIN Public Policy Meeting in Los
Angeles, CA, scheduled for October 26-27. Both the discussion on the
PPML and at the public policy meeting will be used to determine the
community consensus regarding this policy proposal.

The ARIN Internet Resource Policy Evaluation Process can be found at:

ARIN's Policy Proposal Archive can be found at:


Member Services
American Registry for Internet Numbers (ARIN)

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Policy Proposal 2005-8: Proposal to amend ARIN IPv6 assignment and
utilisation requirement

Author: Thomas Narten and Lea Roberts

Policy statement:

It is proposed to make the following changes to the existing ARIN IPv6

1. Define an additional end site assignment size of /56. This /56
assignment should be considered the general case, intended for small
office, household, and personal networks, and other small and
medium-sized deployments where the number of potential subnets exceeds
1, but is not expected to exceed 256.

2. Amend the existing policy regarding /48 end-site assignments to refer
specifically to assignments to large enterprise and corporate end-site
environments where there is a requirement for more than 255 subnets at
the end site.

3. Amend the evaluation threshold calculation to be based on a default
end site assignment size of a /56. Further end-site assignment
information should be provided to ARIN in order to use a different
average end-site assignment size for HD-ratio calculation purposes.


The key benefit of IPv6 is its large address space, and a fundamental
assumption motivating its adoption is that with IPv6, sufficient address
space will always be available to ensure that users can obtain sufficent
public address space for their needs.  Projections for IPv6 address
consumption over the next 50-100 years indicate that there are scenarios
(depending on one's assumptions) in which a signficant percentage of the
total IPv6 address space could be handed out, raising the possibility
that address allocation policies will then need to be revised to become
significantly more conservative to ensure that the IPv6 address space
does not become exhausted. Given the IPv4 experience, in which early
adopters were able to acquire large amounts of address space easily, but
later adopters were not, and the resultant problems this has caused, it
would be preferable to take steps now to signficantly reduce the
likelyhood of ever needing to make such a change, especially if changes
can be made with minimal impact.

The RIR communities adopted address allocation policies in 2002 in which
the default assignment to end sites was assumed to be a /48 in many
cases. For SOHO users (e.g., home users and small businesses), being
given enough address space to number 65,536 subnets seems excessive
given their anticipated needs. Changing the default assignment size to a
/56 allows for numbering 256 subnets, still a large number. Making such
a change would save roughly two orders of magnitude of address space.
That is, for any projection made assuming a /48 assignment, assigning
/56s instead would result in roughly 100 times less total consumption.

The goal of this policy proposal is not to make it impossible for end
sites to obtain a /48. Rather, it is intended to make the default
assignment size a /56 in the vast number of cases where a /48 seems
profligate. In those cases where the end site can argue that it has a
need for more than 256 subnets, a /48 should be given out.

Background information:

"Issues Related to the Management of IPv6 Address Space", by Thomas Narten.

Similar policy proposal submitted to APNIC (includes detailed background
and pointers to more background information than is included here).

State of related discussion in other RIRs: See section "Situation in
other RIRs" in

IETF revisitation of RFC 3177 "IAB/IESG Recommendations on IPv6 Address
Allocations to Sites", the document in which the case for assigning /48s
was made.
(note: this document was adopted as a WG item by the IPv6 WG at IETF
63 in August.)

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