[ppml] a modified proposal 2005-8

Lea Roberts lea.roberts at stanford.edu
Sat Mar 11 03:34:09 EST 2006

was just sent in to ARIN...  for your additional reading pleasure. /Lea

		Policy Proposal 2005-8, version 2:

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 DNS will be delegated, the LIR/ISP should
   consider making an assignment on a nibble (4-bit) boundary to allow
   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


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

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

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