[arin-ppml] IPv4 is depleted today

David Farmer farmer at umn.edu
Fri Aug 29 12:33:51 EDT 2008

When will IPv4 be depleted?  Well I realized yesterday that for me and many 
other Legacy holders it already is.

Let's step back a minute, from discussion on the list its become obvious to 
me that IPv4 depletion isn't a singe event like when the IANA or ARIN Free 
Pools are depleted, it is not a magic date.  It is a series of events or dates 
that occurs when each organization can't easily get any more addresses.  
For some networks, that date will come before others, and for some that 
date could be a long ways away.  Then, I realized for some of us that day 
already came a long time ago, especially for many Legacy holders.  

Actually, for UMN that day was 8 or 10 years ago, when I realized we will 
never ever justify another IPv4 address assignment, nor should we for that 
matter.  I'm not complaining or bragging, but stating a fact.  You could argue 
that we don't deserve the resources we have and should return some.  I'll 
grant you the right to your opinion.  I have arguments why I believe your 
wrong.  However, both are irrelevant to this line of thought.  

The discussion about what IP addresses cost got me thinking about this.  
Because, IP address have been quite expensive for us for sometime, not in 
hard currency, but in remembering and reorganizing within the IPv4 address 
space we have.  This is no where as easy as some on the list try to make it 
sound, NATs don't scale for us in bandwidth, number of flows, or cost.   

There are a few places we use RFC1918 addresses, mostly for things that 
don't ever need to talk to the Public Internet, but DNS issues both for 
reverse and the leaking of forward DNS out to the Internet make this very 
ugly and just as much of a Hack as NAT.  We are considering very limited 
uses of NAT, like for visitor wireless access.  

Personally, I can't compare these costs to the costs associated with 
justifying more address space through ARIN.  Realistically we can't do that, 
at least not until very long after IANA free pool exhaustion.  It is possible that 
they are comparable, I don't know.

You might say we (UMN) really have not and probably will not completely 
exhaust our IPv4 address, that is use it to 100%, well that is probably true.  
But, this is probably going to be true for all networks.  There are very few if 
any networks that use each and every address they have.  There will always 
be little unused bits within subnets and small subnets sitting around in all 
networks.  The difference is only a matter of degree and the rate of growth 
for each network.  Eventually, each network will get into a dead-lock state 
where they don't have enough resources to maneuver to free up old 
resource, or a pseudo-dead-lock where it is more costly than it is worth to 
free up old resources.

So what will we (UMN) do when the IANA and ARIN IPv4 free pools are 
gone?  Well, much the same as we are doing now, try to make use of our 
current resources more efficiently.  We probably will never sell or return our 
current IPv4 address space it is to valuable internally.  We might share it 
with other less directly associated customers or projects, but always public 

What about IPv6 you ask, well we have been working on it for sometime, the 
GigaPOP (think of it as an Internet2 regional ISP) we operate has been 
doing IPv6 for over 5 years.  I my opinion, IPv6 transport is very easy, and 
been that way for a while.  Where things get much harder is the local subnet 
and with the host.  We have had IPv6 operating in our lab off and on over 
the last 5 years, for about the past year we have had it in Beta on the 
network engineers and security folks subnets.  I hope to enable it on our 
whole backbone and make it available anywhere anyone wants it yet this 
year or early next, then in 2010 or 2011 turn it on by default everywhere on 

Personally I think, increased use IPv4 NAT, some kind of transfer policy, or 
forced return of unused resources, will be necessary to extend the life of 
IPv4 long enough for us to get IPv6 ramped up.  I think a transfer policy will 
be cleaner than trying to force people to return resources.

But please don't take that as saying I like those options or that it is an 
alternative to deploying IPv6, it is just necessary.  We have to do BOTH, we 
have to keep the IPv4 elephants dancing until we get all the IPv6 elephants 
dancing.  I loved that pice of metaphoric imagery.:)  So, if you haven't 
started tuning up the IPv6 band for the IPv6 elephants get started now, the 
IPv4 elephants are starting to get tired. 

David Farmer				     Email:	farmer at umn.edu
Office of Information Technology
Networking & Telecomunication Services
University of Minnesota			     Phone:	612-626-0815
2218 University Ave SE			     Cell:		612-812-9952
Minneapolis, MN 55414-3029		     FAX:	612-626-1818

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