Policy Proposal 2001-4
memsvcs at arin.net
Wed Sep 26 11:24:08 EDT 2001
ARIN welcomes feedback and discussion about the following policy
proposal in the weeks leading to the ARIN Public Policy and Members
meetings in Miami, scheduled for October 28 - 31, 2001. All feedback
received on the mailing lists about this policy proposal will be
included in the discussions that will take place in Miami.
The three RIRs have compiled the proposal document provided below
using feedback received from the RIR communities since the publishing
of the provisional IPv6 document in 1999. In the interest of
maintaining global IPv6 policies, the IPv6 policy discussion in the
ARIN region will be held in conjunction with discussions taking place
in the APNIC and RIPE NCC regions.
When formulating this framework document, the RIRs took the following
feedback into account:
* The allocation criteria should be such that it is easy to obtain
IPv6 address space.
* The size of the initial allocation should be large enough to allow
flexibility in addressing infrastructure and customer sites.
This results in the following proposed IPv6 allocation criteria
1. recognize existing infrastructure (both IPv4 and IPv6) where it
exists and calculate IPv6 address needs based on existing networks.
2. apply the slow start mechanism only for 'IPv6 only' networks
without existing IPv4 infrastructure
3. reduce the minimum allocation size for those IPv6 only networks
(unless larger requirements are shown)
4. measure the utilization rate with the HD ratio rather than
5. make subsequent allocations when the HD ratio is reached
The full text of the proposal document is provided below.
This policy proposal discussion will take place on the IPv6 working group
mailing list (v6wg at arin.net). Subscription information is available at
Director of Operations
American Registry for Internet Numbers
*** Proposal Document ***
This document provides a set of proposed policies for the management
of IPv6 address space, specifically concerning the allocation of
address space allocated by Regional Internet Registries (RIRs) to
organisations operating IPv6 networks.
Under the current system of management of global IP address space,
Regional Internet Registries (RIRs) are responsible for allocation of
address space to organisations within their respective geographic
In 1999, the RIRs APNIC, ARIN and RIPE NCC published a provisional policy
document for IPv6, which has been in operation since then. Since 2000,
this document has been under review and discussion, and through this
process many issues have been raised.
It is the aim of this document to propose a new policy framework for
IPv6 address space management which takes into account the operational
experience of the past 3 years, and addresses most if not all of the
major issues raised through the open review process.
This document does not attempt to provide details of policy
implementation, procedures or documentation; nor does it document requirements
for management of address space which is allocated. These policies can be
established globally or regionally as appropriate, based on global
consensus regarding the fundamental principles described here.
3. Address Space Requirement for Initial Allocation
It is proposed to recognise existing network infrastructure and
address utilisation (both IPv4 and IPv6). New IPv6 address needs are
then based on these existing networks.
In assessing a request for an initial allocation, there are 3 possible
cases to consider:
3.1. the requesting organisation has an existing IPv4 network which
will be addressed by the new IPv6 allocation
3.2. the requesting organisation has an existing IPv6 network
3.3. the requesting organisation has no network at all
3.1. Case 1 - Existing IPv4 services
Where IPv6 address space is requested for addressing an existing IPv4
network, the address requirement is determined according to the
structure and customer base of the existing IPv4 network. This only
relates to the part of the network that will be migrated to IPv6.
Additional policies may require the return of IPv4 address space to
the RIR or upstream ISP, in the case the existing network is
renumbered to the new IPv6 space in future.
3.2. Case 2 - Existing IPv6 services
Where an IPv6 allocation is requested by an organisation to address
infrastructure which is already addressed by IPv6 addresses from an
upstream provider (or from the 6BONE), the address requirement is
determined from the number of site addresses assigned by the
organisation (as registered in the appropriate whois database).
Where existing address space is no longer used, it must be returned.
3.3. Case 3 - No existing IPv4 or IPv6 services
Where IPv6 address space is required by an organisation which has no
existing infrastructure, the address requirement will be assessed
according to network architecture plans and other documentation
provided to the RIR within the request process. Such documentation be
thorough enough to satisfy the RIR that the network deployment is
genuine, however the specific details of documentation requirements
will be defined separately.
4. Size of Initial Allocation
The amount of addresses allocated to an existing network, will be
determined based on the existing infrastructure and address
utilisation of that network.
For new networks without existing infrastructure, it is proposed to
establish a minimum allocation for IPv6 address space. It is suggested
to keep the size of the initial allocation relatively small (a /35 or
smaller) and to determine the size of subsequent allocations based on
the utilisation rate of the initial allocation (this is called slow
start mechanism). This will allow easy access to IPv6 allocations for
newcomers. At the same time possible wastage of address space and
routing table growth will be limited.
5. Qualification for Subsequent Allocation
An organisation which has already received address space from an RIR may
receive a subsequent allocation providing that its existing address space
is utilised in accordance with these policies. As explained below, the
HD-Ratio will be used to measure utilisation of the existing address
An organisation which is deploying substantial new network infrastructure
may receive a subsequent allocation before it has reached the required
utilisation threshold, providing that the address requirement would
immediate cause the organisation to exceed the utilisation threshold. In
such cases, the new network infrastructure will be examined by the RIR as
if it is a request for a new network, and the RIR may require the same
level of documentation detail, in order to approve the allocation.
6. Address Space Requirement for Subsequent Allocation
For subsequent allocations, the RIR should assess the address requirement
according to the organisation's history of IP address usage, as well as
stated requirements for future development.
In general, the RIR should provide address space for a fixed time
period of 2 years.
The above recommendation should be followed in cases where the
organisation concerned has complied with all relevant address management policies. In
other cases, the RIR may allocate for a shorter future timeframe, and
require that identified problems be rectified before larger allocations
7. IPv6 Utilisation Metric: the HD-Ratio
In IPv4, currently, a "utilisation threshold" of 80% is applied
consistently in determining whether an IPv4 address pool is to be
considered utilised, regardless of the size of that block.
Consequently, an organisation which holds IP address space may
not receive additional addresses until it has utilised at least 80% of
the address space held.
For IPv6 is it proposed to assess utilisation according to the "HD-Ratio"
rather than by a simple percentage. The HD-Ratio was proposed by Durand
"draft-durand-huitema-h-density-ratio-01.txt" (an adaptation of the
original H-Ratio defined by Huitema in RFC-1715).
Using the HD-ratio we can establish a utilisation metric which allows
percentage utilisation to decrease as the address space grows large. This
is appropriate for management of the much larger blocks of address space
under IPv6, and the likelihood of complex routing and allocation
hierarchies within those address blocks.
More details about the HD ratio can be found in Appendix A.
In the general case, where individual objects are allocated out of an
arbitrary address space, the HD-Ratio is calculated as follows:
log(number of allocated objects)
HD = --------------------------------------------
log(maximum number of allocatable objects)
Where the objects being allocated are IPv6 site addresses (/48s) assigned
from an IPv6 prefix of length P, we can restate this formula as follows
(where A is the number of /48 prefixes actually assigned):
In other words, the utilisation threshold T, expressed as a number of
individual /48 prefixes to be allocated from IPv6 prefix P, can be
T = 2
In accordance with the recommendations of
draft-durand-huitema-h-density-ratio-01.txt, it is proposed in this draft
to adopt an HD-Ratio of 0.8 as the utilisation threshold for IPv6 address
The following table provides equivalent absolute and percentage
address utilisation figures for IPv6 prefixes, corresponding to an
HD-Ratio of 0.8
P 48-P Total /48s Threshold Util%
48 0 1 1 100.0%
47 1 2 2 87.1%
46 2 4 3 75.8%
45 3 8 5 66.0%
44 4 16 9 57.4%
43 5 32 16 50.0%
42 6 64 28 43.5%
41 7 128 49 37.9%
40 8 256 84 33.0%
39 9 512 147 28.7%
38 10 1024 256 25.0%
37 11 2048 446 21.8%
36 12 4096 776 18.9%
35 13 8192 1351 16.5%
34 14 16384 2353 14.4%
33 15 32768 4096 12.5%
32 16 65536 7132 10.9%
31 17 131072 12417 9.5%
30 18 262144 21619 8.2%
29 19 524288 37641 7.2%
28 20 1048576 65536 6.3%
27 21 2097152 114105 5.4%
26 22 4194304 198668 4.7%
25 23 8388608 345901 4.1%
24 24 16777216 602249 3.6%
23 25 33554432 1048576 3.1%
22 26 67108864 1825677 2.7%
21 27 134217728 3178688 2.4%
20 28 268435456 5534417 2.1%
19 29 536870912 9635980 1.8%
18 30 1073741824 16777216 1.6%
17 31 2147483648 29210830 1.4%
16 32 4294967296 50859008 1.2%
15 33 8589934592 88550677 1.0%
14 34 17179869184 154175683 0.9%
13 35 34359738368 268435456 0.8%
12 36 68719476736 467373275 0.7%
11 37 137438953472 813744135 0.6%
10 38 274877906944 1416810831 0.5%
9 39 549755813888 2466810934 0.4%
8 40 1099511627776 4294967296 0.4%
7 41 2199023255552 7477972398 0.3%
6 42 4398046511104 13019906166 0.3%
5 43 8796093022208 22668973294 0.3%
4 44 17592186044416 39468974941 0.2%
3 45 35184372088832 68719476736 0.2%
2 46 70368744177664 119647558364 0.2%
1 47 140737488355328 208318498661 0.1%
0 48 281474976710656 362703572709 0.1%
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