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

Member Services memsvcs at arin.net
Fri Apr 14 15:55:53 EDT 2006

The ARIN Advisory Council (AC), acting under the provisions of the ARIN 
Internet Resource Policy Evaluation Process (IRPEP), has reviewed policy 
proposal 2005-8: Proposal to amend ARIN IPv6 assignment and utilisation 
requirement  and has determined that there is community consensus in 
favor of the proposal to move it to last call. The AC made this 
determination at their meeting at the conclusion of the ARIN Public 
Policy meeting on April 11, 2006. The results of the AC meeting were 
reported by the Chair of the AC at the member meeting. This report can 
be found at http://www.arin.net/meetings/minutes/ARIN_XVII/mem.html

The policy proposal text is provided below and is also available at 

Comments are encouraged. All comments should be provided to 
ppml at arin.net. This last call will expire at 12:00 Noon, Eastern Time, 
April 28, 2006.

The ARIN Internet Resource Policy Evaluation Process can be found at 


Member Services
American Registry for Internet Numbers (ARIN)

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

This proposal would amend the IPv6 address allocation policies (ARIN's 
NRPM, section 6) regarding the definition of the default size of End 
Site assignments and the threshold value for End Site allocation 
efficiency, no longer assuming the fixed values for End Site assignments 
established by RFC3177. Many references to "/48" will need to be 
replaced by "End Site assignment".

for example, section should be replaced as follows: Assignment address space size

End Users are assigned an End Site assignment from their LIR or ISP. The 
exact size of the assignment is a local decision for the LIR or ISP to 
make, using a minimum value of a /64 (when only one subnet is 
anticipated for the End Site) up to the normal maximum of /48, except in 
cases of extra large end sites where a larger assignment can be justified.

The following guidelines may be useful (but they are only guidelines):

- /64 when it is known that one and only one subnet is needed

- /56 for small sites, those expected to need only a few subnets over 
the next 5 years.

- /48 for larger sites

For end sites to whom reverse DNS will be delegated, the LIR/ISP should 
consider making an assignment on a nibble (4-bit) boundary to simplify 
reverse lookup delegation.

RIRs/NIRs are not concerned about which address size an LIR/ISP actually 
assigns. Accordingly, RIRs/NIRs will not request the detailed information on
IPv6 user networks as they did in IPv4, except for the cases described 
in Section 6.4.4 and for the purposes of measuring utilization as 
defined in this document.

also, section 6.9 will need to be replaced:

6.9. IPv6 Reassignments policy

The size of IPv6 address assignments to End Sites is to be determined by 
the ISP/LIR.

ISPs and LIRs may choose whether to make changes to their procedures for 
assigning address blocks to End Sites. The threshold End Site allocation 
efficiency level is between 20% to 50% for most ISPs and LIRs when based 
on a 0.94 HD Ratio. ISPs and LIRs will need to operate address plans 
according to this target level of End Site allocation efficiency.

there's a need to change ARIN NRPM IPv6 Utilization:

The ARIN NRPM Section 6.7 will be amended so its IPv6 allocation 
utilization criteria will reflect the use of a /56 as the unit quantity 
in the calculation of the ISP or LIR's end site allocation efficiency.

Policy Rationale

The current IPv6 Address Allocation and Assignment Policy (section 6 of 
ARIN's NRPM) indicates that end sites should be allocated a /48 as a 
uniform allocation unit if using more than one host or one subnet.

This proposal alters the existing policy regarding LIR and ISP 
assignments to End Sites to allow the unit of assignment to be an LIR or 
ISP decision.

In assessing the address utilization efficiency for ISPs or LIRs, the 
definition of an End Site for the purposes of the calculation of ISP or 
LIR End Site allocation efficiency, is to be made according to a /56 size.

This measure, if undertaken generally by all RIRs, in conjunction with 
the further measures undertaken by the addressing community regarding 
increasing the HD ratio to 0.94, would increase the anticipated useful 
lifetime of IPv6 to encompass a period in excess of 100 years, in which 
case no further allocation policy changes would be anticipated.

A more detailed rationale is available in Geoff Huston's presentation on 
the subject, at RIPE 50, which can be found at:

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