IPv4 Address Lifetime ExpectancyRevisited - Revisited

Geoff HustonNovember 2003

Presentation to the IEPG

Research activitysupported by APNIC

The Regional Internet Registries s do not make forecasts or predictions about number resource lifetimes. The RIRs provide statistics of what has been allocated. The following presentation is a personal contribution based on extrapolation of RIR allocation data.

IPv4 Address Lifetime Expectancy

In July the IEPG presentation on address lifetime expectancy used the rate of growth of BGP advertised address space as the overall address consumption driver

The presentation analysed the roles of the IANA and the RIRs and created an overall model of address consumption

IPv4 Model

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IANA

RIR

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RIR-P

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LIR

Modelling the Process – July 2003

Projections

IANA Pool Exhaustion 2022

RIR Pool Exhaustion 2024

Address Consumption Models The basic assumption was that continued

growth will remain at a constant proportion of the total advertised address space (compound growth), and that as a consequence address exhaustion was predicted to occur sometime around 2025

Does the advertised address data support this view of the address growth model?

The Advertised Address Space

Notes It’s noisy data

There are 3 /8 prefixes that flap on a multi-day cycle

There are shorter term flaps of smaller prefixes

Reduce the noise by: Removing large steps Applying gradient filter Apply averaging to smooth the data

Smoothed Data (1)Filter to 18 /8 advertisements

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Smoothed Data (2)Gradient Filtered

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Model MatchingApplying Models to the Data

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Data

Linear

Polynomial

But Which Model?

A number of models can be applied to this data: Linear model, assuming a constant

rate of growth Polynomial model, assuming a

constant rate of change of growth Exponential model, assuming a

geometric growth with a constant doubling period

First Order Differential of the data

First Order Differential

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Linear Best Fit to Differential

Least Squares Best Fit

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Growth Rate The growth rate of 4 – 5 /8 blocks

per year in 99-00 is now appoximately half that, at 2 – 3 /8 blocks per year

A constant growth model has a best fit of 3.5 /8 blocks per year

The change in growth over the period is a decline in growth rate by 0.4 /8 blocks per year

Log of DataLog of smoothed data

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Best Fit to LogBest Fit to Log Data

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Exponential Model

The exponential model assumes a liner best fit to the log of the data series

This linear fit is evident across 2000

More recent data shows a negative declining rate in growth of the log of the data.

ProjectionsProjections

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Linear

X**2 Polynomial

Exponential

Average Data

Observations Polynomial best fit sees a continuing

decline in growth until growth reaches zero in 2010 Matches a model of market saturation

Exponential best fit sees continuing increase in growth until exhaustion occurs in 2021 Matches a model of uniform continued growth

in all parts of the network Linear best fit sees constant growth until

exhaustion occurs in 2042 Matches a model of progressive saturation in

existing markets offset by demands in new markets

Modelling the Process Assume that the RIR efficiency in allocation

slowly declines, then the amount of RIR-held space increases over time

Assume that the Unannounced space shrinks at the same rate as shown over the past3 years

Assume linear best fit model to the announced address space projections and base RIR and IANA pools from the announced address space projections

Modelling the ProcessIPv4 Model

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Jan-00 Jan-05 Jan-10 Jan-15 Jan-20 Jan-25 Jan-30 Jan-35 Jan-40 Jan-45

IANA

RIR

BGP

IANA-P

RIR-P

BGP-P

RIR

LIR

Projections

IANA Pool Exhaustion 2030

RIR Pool Exhaustion 2037

Unadvertised Address Pool

RIR Holding Pool

Observations Extrapolation of current allocation practices and current

demand models using an exponential growth model derived from a 2000 – 2003 data would see RIR IPv4 space allocations being made for the next 2 decades, with the unallocated draw pool lasting until 2018 - 2020

The use linear growth model sees RIR IPv4 space allocations being made for the next 3 decades, with the unallocated draw pool lasting until 2030 – 2037

Re-introducing the held unannounced space into the routing system over the coming years would extend this point by a further decade, prolonging the useable lifetime of the unallocated draw pool until 2038 – 2045

This is just a model

Questions

Externalities: What are the underlying growth drivers

and how are these best modeled? What forms of disruptive events would

alter this model? What would be the extent of the

disruption (order of size of the disruptive address demand)?