Re: [sig-policy] Final call for comments prop-020-v001 Application of th

  • To: Save Vocea <save at apnic dot net>, sig-policy at apnic dot net
  • Subject: Re: [sig-policy] Final call for comments prop-020-v001 Application of the HD ratio to IPv4
  • From: Geoff Huston <gih at apnic dot net>
  • Date: Sat, 18 Mar 2006 05:35:09 +1100
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  • In-reply-to: <7A5D57F1-E02B-4B79-992C-F94519662D63 at apnic dot net>
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    • At 12:13 PM 17/03/2006, Save Vocea wrote:
      Dear colleagues
      APNIC welcomes comments and suggestions on the following policy
      Status of [prop-020-v001] "Application of the HD ratio to IPv4"
      I would like to request that the following analysis be considered in relation to this policy proposal
        Geoff Huston
      An Analysis of the Sensitivity of using the HD Ratio for IPv4 Address
      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
      This study uses RIPE allocation data as the base of the analysis. As noted
      in this document a similar analysis relating to APNIC IPv4 address allocations
      indicates that the total address consumption by APNIC is this proposal
      were to be adopted would be an increase of 47%. As noted this has some
      significant implications for IPv4 lifetime projections for the remaining unallocated
      address pools. I also note that the major change here is the address allocation
      sizes for larger allocations under this policy, while allocations for smaller
      blocks would be substantially similar to the current 80% utilization policy.
      1. Methodology
      The methodology used here uses only published RIR allocation data. The
      primary data source for RIPE NCC data is the delegated file:
      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
      Table 1 - RIPE NCC IPV4 Address Allocations (since 1-Jan-2000)
      Size    Number  Relative        Cumulative
                      Frequency       Relative
      /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 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
      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 HD 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).