The following version was archived on 25 November 2008.
Policy Proposal 2008-5
Dedicated IPv4 block to facilitate IPv6 deployment
Author: Alain Durand
Date: 6 June 2008
Proposal type: New
Policy term: Permanent
When ARIN receives its last /8 IPv4 allocation from IANA, a contiguous /10 IPv4 block will be set aside and dedicated to facilitate IPv6 deployment. Allocations and assignments from this block must be justified by immediate IPv6 deployment requirements. Examples of such needs include: IPv4 addresses for key dual stack DNS servers, and NAT-PT or NAT464 translators. ARIN staff will use their discretion when evaluating justifications.
This block will be subject to a minimum size allocation of /28 and a maximum size allocation of /24. ARIN should use sparse allocation when possible within that /10 block.
In order to receive an allocation or assignment under this policy:
- the applicant may not have received resources under this policy in the preceding six months;
- previous allocations/assignments under this policy must continue to meet the justification requirements of this policy;
- previous allocations/assignments under this policy must meet the utilization requirements of end user assignments;
- the applicant must demonstrate that no other allocations or assignments will meet this need;
- on subsequent allocation under this policy, ARIN staff may require applicants to renumber out of previously allocated / assigned space under this policy in order to minimize non-contiguous allocations;
- recipient organizations must be members in good standing of ARIN.
Rationale for reserving IPv4 space:
This policy provides predictability on how the end game of IPv4 is going to be played after IANA completion. It will facilitate IPv6 deployment by ensuring that some small chunks of IPv4 space will remain available for a long time to ease the co-existence of IPv4 & IPv6.
Rationale for reserving a contiguous /10
This is a balance between setting aside too much space and not having enough to facilitate IPv6 deployment for many years. Out of the last /8, that would leave the equivalent of 3 /10 to ARIN either for business as usual or for other policies in the spirit of this one.
A /10 represents 4,194,304 IP addresses, If all of them were to be used in NAT-PT or NAT464 type devices with a consolidation factor of 100 users behind each IP address, that would represent about 400 million users.
Most networks today filter IPv4 announcements more specific than /24.
This policy creates allocations & assignment prefixes as long as /28.
Allocating out of a contiguous block will mitigate the impact of this policy on filter lists.
Rationale for minimum size allocation of /28
This minimum size allocation will put a cap at 250k additional entries in the global IPv4 routing table.
Rationale for maximum size allocation of /24 and for the 6 month delay between allocations
This maximum allocation size coupled with the requirement of a 6 months delay between allocations will prevent hoarding and make sure this pool will last several years.
Rationale for forced renumbering for further allocation
The minimum allocation size of /28 may create a huge increase in the
IPv4 routing table size. Forcing renumbering for subsequent allocations under this policy will somehow limit the growth of the routing table size by enabling the announcement of aggregated space. It is expected that the savings in routing table entries will outweigh the pain of forced renumbering.
However, renumbering is never an easy task, so it should only be considered as last resort. it is expected that sparse allocation techniques will prevent the need of force renumbering for a fairly long time.
Note: This policy proposal hints that the /10 should come out of the last /8 received by ARIN from IANA. However, it does not say so explicitly, leaving the final decision up to the ARIN staff.
Timetable for implementation:
As soon as ARIN gets its last /8 allocation from IANA.