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

Member Services memsvcs at arin.net
Mon Mar 13 13:54:29 EST 2006

Policy Proposal 2005-8: Proposal to amend ARIN IPv6 assignment and
utilisation requirement has been revised by the authors. This proposal
is open for discussion on this mailing list and will be on the agenda at
the upcoming ARIN Public Policy Meeting.

The current policy proposal text is provided below and is also available
at: http://www.arin.net/policy/proposals/2005_8.html


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

Authors: Lea Roberts and Thomas Narten

Proposal Version: 2 (10-Mar-2006)

Proposal type: modify

Policy term: permanent

Policy statement:

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

    8. 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:


Appendix A. References
This material is not formally part of the Policy Proposal. It is
included here for informational purposes.

1. The IPv6 Address Plan - Geoff Huston

2. Internet Draft: Issues Related to the Management of IPv6 Address
Space - Thomas Narten

[unfortunately, the ID expired, so use the URL:


3. Internet Draft: IPv6 Address Allocation to End Sites - Thomas Narten,
Geoff Huston & Lea Roberts

Timetable for implementation: upon adoption

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