[address-policy-wg] 2005-01 - Last Call for Comments (HD-ratio Proposal)

Here is the promised report on the address consumption implications of the 
policy proposal 2005-1 (HD-Ratio Proposal) If there is any other aspect 
of implications of adoption of this proposal that folk may want investigated 
I'd be happy to see what I can do. Also if any part of this report is unclear 
I'd be happy to attempt to clarify further the process I've used here.

I trust that this report is helpful in terms of assessing some of the impacts 
of the proposal.

regards,

  Geoff Huston
 



An Analysis of the Sensitivity of using the HD Ratio for IPv4 Address
Allocations


Geoff Huston
V1.0 22 February 2005


This document describes the outcomes of an analytical process intended to
describe the sensitivity of the use of HD Ratio metrics as the means of
assessing address utilization efficiency, and the relation between the use
of HD Ratio values and projected lifetimes of the unallocated IPv4 address
pool. This document is a commentary on RIPE Policy Proposal 2005-1

1. Methodology
--------------

The methodology used here uses only published RIR allocation data. The
primary data source for RIPE NCC data is the delegated file:
  ftp://ftp.ripe.net/pub/stats/ripencc/delegated-ripencc-latest

All IPv4 allocation records with an allocation date on or after 1-Jan-2000
are collected. The allocation sizes are rounded up to the next largest
power of 2, or 256, which is the greatest. The relative proportion of each
allocation size is also calculated. This is shown in the table below (Table
1).

----------------------------------------------------------------
Table 1 - RIPE NCC IPV4 Address Allocations (since 1-Jan-2000)

Size    Number  Relative        Cumulative
                Frequency       Relative
                                Frequency

/24     2637     23.04           23.04
/23     1383     12.09           35.13
/22      934      8.16           43.29
/21      545      4.76           48.06
/20     2247     19.64           67.69
/19     1713     14.97           82.66
/18      784      6.85           89.51
/17      407      3.56           93.07
/16      499      4.36           97.43
/15      135      1.18           98.61
/14       75      0.66           99.27
/13       44      0.38           99.65
/12       21      0.18           99.83
/11       15      0.13           99.97
/10        4      0.03          100.00
----------------------------------------------------------------

The assumption made here is that these allocations are made under a policy
of a uniform 80% utilization efficiency. From this can be calculated the
inferred maximum end use count for each prefix size (Table 2).

----------------------------------------------------------------
Table 2 - Inferred Maximum End Population Count for each Prefix Size
           under the uniform 80% efficiency policy

/24          205
/23          410
/22          819
/21         1638
/20         3277
/19         6554
/18        13107
/17        26214
/16        52429
/15       104858
/14       209715
/13       419430
/12       838861
/11      1677722
/10      3355443
/9       6710886
/8      13421773
----------------------------------------------------------------

The HD ratio is calculated by the function: HD = log(used)/log(addresses).
This implies that the population can be inferred for any given prefix size
using the equation: used = 10**(HD x log_base_10(addresses). The inferred
maximum end use count for each prefix size using an HD Ratio value of 0.96
is shown below (Table 3).

----------------------------------------------------------------
Table 3 - Inferred Maximum End Population Count for each Prefix Size
           under an HD = 0.96 allocation policy

/24         205
/23         399
/22         776
/21        1510
/20        2937
/19        5713
/18       11113
/17       21619
/16       42055
/15       81811
/14      159147
/13      309590
/12      602249
/11     1171560
/10     2279048
/9      4433455
/8      8624444
----------------------------------------------------------------

The next step is to determine the relative impact on address consumption by
changing from a uniform 80% utilization efficiency metric to one determined
by an HD Ratio setting of 0.96.

To do this a sequence of 10,000 allocations are simulated. with each
allocation being in the range of a /24 to a /10 prefix. with a probability
of any particular prefix being selected based on the relatively frequency
distribution of Table 1. The inferred population lies between the maximum
population of this prefix and that of the population of the next smaller
prefix in Table 2. A random value is drawn from this population range (this
is a uniform probability selection between the two extreme population
values, so that any population value is equally likely to be selected).
This population value is used as a lookup key into Table 3, and the next
highest population count is used to determine the equivalent HD Ratio
allocated prefix. In effect, this approach generates a series of demand
populations that would generate the existing RIR allocation prefix
distribution, and then uses this population set to generate a HD-Ratio-
based set of allocations that would correspond to this population
distribution. The total amount of allocated address space is calculated in
each case, and the ratio of the two address pool sizes is recorded.

This experiment has been repeated 1,000 times in order to determine a
stable average value for the relative increase in address consumption
corresponding to a change in the address allocation policies from uniform
80% to an HD Ratio of 0.96, assuming constant demand for addresses.

This relative change in address demands can then be added into the IPv4
address consumption projection (see http://ipv4.potaroo.net). The change
here is in the simulation of the address consumption model, where in the
base model all RIR's are assumed to be operating a uniform address
efficiency metric of a uniform 80% utilization target. The same
exponential growth model in advertised address growth is used, but this
model is augmented by the relative increase in address consumption as
contributed by the HD Ratio allocation metric. The unadvertised address
ratio is then derived from this higher advertised address count, and this,
in turn, generates a more rapid overall address consumption model. The
measure under investigation in this case is the change in predicted date of
the exhaustion of the IANA unallocated address pool



2. Results
---------

The relative distribution of allocated prefixes by the RIPE NCC using an HD
Ratio of 0.96 as an allocation efficiency metric would be as shown in Table
4.

----------------------------------------------------------------
Table 4 - RIPE NCC IPV4 Address Allocations

Size  2000-2006         HD Ratio
       Relative         Relative
       Frequency        Frequency

/24     23.04           23.23
/23     12.09           11.37
/22      8.16            7.87
/21      4.76            4.85
/20     19.64           16.33
/19     14.97           15.21
/18      6.85            8.58
/17      3.56            4.39
/16      4.36            3.88
/15      1.18            2.39
/14      0.66            0.86
/13      0.38            0.50
/12      0.18            0.28
/11      0.13            0.15
/10      0.03            0.09
/9       0.00            0.02
/8       0.00            0.00
----------------------------------------------------------------

 From the simulations of registry allocations, the use of an HD Ratio of
0.96 for IPv4 address allocations made by the RIPE NCC is predicted to
increase total address consumption by 46% over the existing flat 80%
utilization allocation policy framework.

The current prediction for the data of exhaustion of the IANA unallocated
address pool is 12 January 2012, assuming, among other factors, a continued
application of the constant 80% address utilization metric. If the RIPE NCC
were to adopt an allocation policy of using an HD Ratio of 0.96 to access
IPv4 address allocations, and no other changes were made to the mode, and
no other RIRs were to adopt such a policy to use the HS Ratio as a
utilization metric, then the impact on the predicted exhaustion date is an
overall change in address consumption rates by approximately 17% (as the
RIPE NCC is responsible for some 38% of all allocated IPv4 addresses), and
a predicted unallocated IANA pool exhaustion date of 9 December 2010 under
these conditions (or approximately 1 year earlier than the predictions
using the current address allocation policy framework

A related consideration is that of the adoption of such a policy proposal
by all 5 RIRs. If this were the case, and the adoption of this policy was
to be effective immediately, then the relative increase in overall address
consumption for each RIR would be: Afrinic 39%, APNIC 47%, ARIN 46%, LACNIC
47%. The simulation of IPv4 address consumption under these conditions
predicts that the IANA pool of unallocated addresses would be exhausted by
22 March 2010 (or approximately 2 years earlier than the predictions using
the current address allocation policy framework).



--------------------------------------------------

At 05:34 PM 21/02/2006, Geoff Huston wrote:
>Hi,
> 
>I was wondering if it would help to look at the potential impact of this policy on IPv4 address consumption predictions. I have built a model of projection IPv4 address consumption based on continuity of current address allocation policies <http://ipv4.potaroo.net>http://ipv4.potaroo.net, and it may be useful to look at the impact of using the HD ratio on this model. I'll try and get some results posted by the end of this week on a simulation of the effects of adoption of this policy proposal 
> 
>thanks,
> 
>  Geoff
> 
>
>
> 
>On 2/7/06, RIPE NCC Policy Coordinator <<mailto:adrian at ripe.net>adrian at ripe.net> wrote: 
>PDP Number: 2005-01
>HD-ratio Proposal
>
>Dear Colleagues
>
>The proposal to change to RIPE Document ripe-324 is now at its final stage. 
>
>You can find the full proposal at:
>
>   <http://www.ripe.net/ripe/policies/proposals/2005-1.html>http://www.ripe.net/ripe/policies/proposals/2005-1.html
>
>Please e-mail any final comments about this proposal to <mailto:address-policy-wg at ripe.net>address-policy-wg at ripe.net before 7 March 2006.
>
>We will publish the new policy after this date if we receive no objections.
>
>Regards
>
>Adrian Bedford
>RIPE NCC 
>