Encouraging return of legacy space WAS Re: [ppml] ARIN Policy Proposal 2002-9

J. Scott Marcus scott at scottmarcus.com
Wed Oct 2 17:32:48 EDT 2002

Speaking only for myself...

I agree with David Conrad on this.  People have 
voluntarily returned large blocks in the past, 
notably including Stanford University and my 
former employer, BBN/GTE.

ARIN's ability to recover legacy address space 
from unwilling holders is unclear, and the attempt 
might well be both painful and expensive.

ARIN's ability to recover space _voluntarily_, 
however, is largely untested.  It may be that 
folks have not returned IPv4 space because they 
have not persuasively been asked.

In any case, it seems to me that the cost of 
making a preliminary experiment is not great.  
Nearly a quarter of all IPv4 space, and nearly a 
half of all allocated IPv4 space, is tied up in 
blocks 003/8 to 057/8.  These seem to me to 
represent low hanging fruit - if memory serves, 
the CAIDA data presented a few meetings ago 
showed that a significant fraction of that space 
is "dark", which seems to suggest (but not prove) 
that much of it might be underutilized.  And only 
about fifty organizations hold that low hanging 

My understanding is that, at the time of the ALE 
work, it was felt that reclamation was not 
warranted.  The exponential growth of address 
consumption would quickly overcome any possible 

That does not seem to me to be the case today.  
The last data I know of showed the annual growth 
of IPv4 address consumption to be in the range 
between 3% and 7% per year, and declining over 
time.  Relative to that rate of growth, address 
reclamation could perhaps extend the life of the 
IPv4 space by some years.  I think that that would 
be a good thing, although some might legitimately 
argue otherwise...

In any case, it seems to me that a targeted and 
prioritized pilot program for voluntary 
reclamation of IPv4 addresses would be worth 
attempting, would not need to be very expensive, 
and if done with sensitivity need not generate ill 
will between ARIN and the holders of these address 


Does this make sense?

Do people see either positive or negative 
incentives that ARIN could use to encourage the 
return of large, low utilization IPv4 address 

Best regards,
- Scott

---- Original message ----
>Date: Wed, 2 Oct 2002 15:27:41 -0500 
>From: Bill Darte <billd at cait.wustl.edu>  
>Subject: RE: Encouraging return of legacy space 
WAS Re: [ppml] ARIN Policy Proposal 2002-9  
>To: "'David Conrad'" <david.conrad at nominum.com>, 
Trevor Paquette <Trevor.Paquette at TeraGo.ca>, 
"'Mury'" <mury at goldengate.net>, sigma at smx.pair.com
>Cc: ARIN PPML <ppml at arin.net>
>FYI on this issue, there is RFC 1917 which 
specifically requests the return
>of unused networks...
>RFC 1917
>An Appeal to the Internet Community to Return
>Unused IP Networks (Prefixes) to the IANA
>Network Working Group
>Request for Comments: 1917
>BCP: 4
>Category: Best Current Practice
>P. Nesser II
>Nesser & Nesser Consulting
>February 1996
>Bill Darte
>ARIN Advisory Council
>314 935-7575
>> -----Original Message-----
>> From: David Conrad 
[mailto:david.conrad at nominum.com]
>> Sent: Wednesday, October 02, 2002 2:46 PM
>> To: Trevor Paquette; 'Mury'; sigma at smx.pair.com
>> Subject: Re: Encouraging return of legacy space 
WAS Re: [ppml] ARIN
>> Policy Proposal 2002-9
>> I think you'd be surprised.  Two data points: 
>> University returned a
>> /8.  BBN returned a couple of /8s I believe.
>> The last time an effort was undertaken to 
encourage people to 
>> return address
>> space, it was fairly successful.
>> Rgds,
>> -drc
>>    <... snip ... >

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