[AusNOG] Less than 10% of IPv4 Addresses Remain Unallocated

[Geoff Huston]

On 20/01/2010, at 9:47 PM, Noel Butler wrote:

> On Tue, 2010-01-19 at 23:16 -0800, Scott Howard wrote:
>> Not that I disagree with what they are trying to achieve here, but the math here is a bit iffy, depending on what you consider as "available".
>> 
>> Personally I'd consider the "available" address to be 1/8 through 223/8, probably excluding 127/8, and possibly even excluding the various RFC1918 blocks.
>> 
>> At most that gives 223 /8's, probably closer to 221.
>> 
>> Based on http://www.iana.org/assignments/ipv4-address-space/ipv4-address-space.xhtml, there are a total of 24 /8's still unallocated by IANA.  Even then it's a matter of who's perspective you look at - 1/8 and 27/8 are "allocated" from IANA's perspective, but I'm presuming they are completely unallocated from APNIC's perspective.
>> 
>> So IMHO we're not down to 10% yet, but of course to a certain extent the difference between 10% and even 15% isn't that significant...
>> 
> 
> Yep, and I still stand by at _LEAST_ 2015 before we seriously get close to looking like running out of ipv4, maybe longer than that.
> There's around 400 million IP's stilll up for grabs.

Thats an interesting opinion, but unfortunately it appears to be one that is not well backed up by any currently observable data. So lets try a basic definitions and then some numbers to see what is a credible projection.

What is "run out"? A definition I've been using is "when the current distribution system for IPv4 addresses ceases. That implies that when your local Regional Internet Registry has no more addresses to allocate or assign under the prevailing policies then we've "run out". Note that "run out" does not imply "unobtainable for any price and under any condition". Doubtless, if you want to pay and someone wants to sell you might well be able to secure some addresses. And under the current "last /8 policies" that have been adopted by all the RIRs each RIR will have one last /8 to allocate under _different_ policies and circumstances than today. So under the terms of "run out" these 5 /8s are not part of the pool of addresses that allocated and assigned under the prevailing system.

So how many addresses for part of the pool of addresses that are allocated or assigned under the current system? IPv4 has 4294967296, or 2**32 addresses, of 256 8s. But a number of /8s are reserved: 0/8, 10/8, 127/8, 224/8 through to 255/8. That's 35/8s, leaving 221 /8s in the pool. But there are also a number of smaller blocks that are reserved - go read RFC5735 for the details, but here's the summary

0.0.0.0/8           "This" Network             RFC 1122, Section 3.2.1.3
10.0.0.0/8          Private-Use Networks       RFC 1918
127.0.0.0/8         Loopback                   RFC 1122, Section 3.2.1.3
169.254.0.0/16      Link Local                 RFC 3927
172.16.0.0/12       Private-Use Networks       RFC 1918
192.0.0.0/24        IETF Protocol Assignments  RFC 5736
192.0.2.0/24        TEST-NET-1                 RFC 5737
192.88.99.0/24      6to4 Relay Anycast         RFC 3068
192.168.0.0/16      Private-Use Networks       RFC 1918
198.18.0.0/15       Network Interconnect
                    Device Benchmark Testing   RFC 2544
198.51.100.0/24     TEST-NET-2                 RFC 5737
203.0.113.0/24      TEST-NET-3                 RFC 5737
224.0.0.0/4         Multicast                  RFC 3171
240.0.0.0/4         Reserved for Future Use    RFC 1112, Section 4
255.255.255.255/32  Limited Broadcast          RFC 919, Section 7
                                               RFC 922, Section 7


In total 35.078 /8s are reserved, leaving 220.9218 /8s. But 5 /8s are gojng to be used as the "last /8s", and will be allocated using a more constrained policy structure than the current setup. So the current allocation system has a total pool size of 215.921 /8s.

IANA currently has 24 /8s left in its pool - here's its list.

iana|ZZ|ipv4|5.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|14.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|23.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|31.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|36.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|37.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|39.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|42.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|49.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|50.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|100.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|101.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|102.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|103.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|104.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|105.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|106.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|107.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|176.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|177.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|179.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|181.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|185.0.0.0|16777216|20100120|unallocated
iana|ZZ|ipv4|223.0.0.0|16777216|20100120|unallocated

But 5 of these /8s are going to be used for the "last /8" policy, so there are 19 /8s left to use for the current allocation framework.

when will these 19/8s that are going to be used for general allocations run out? We've been getting through an average of a little over 11 /8s a year since 2007. There are seasonal variations in this rate and in 2009 the rate peaked at a little over the equivalent of 12 /8s and had a low point in the middle of the northern hemisphere summer of 10 /8s. (http://www.potaroo.net/tools/ipv4/fig25.png). 


This implies that in a little over 20 months from now, or at the start of September 2011 IANA will hand out its last "general use" /8 and at the same time will also hand out its remaining 5 /8s to be used as the last /8s.

Assuming that the RIRs continue to allocate  IPv4 addresses at much the same rate as they are doing now, then the first RIR til run through its generall allocation pools of IPv4 will be APNIC and this is projected to occur 11 months later, in August 2012. (APNIC is getting through some 5 /8s per year) After that the "last /8 policy will take over, and the current allocation system will have come to its conclusion. See http://ipv4.potaroo.net for details.

Have we reached 10% today? Well IANA is down to 19 /8 blocks, out of a total of 215.92 /8s, so by that reckoning IANA has just 8.7% remaining. Thats less than 10%.

When will we get seriously close to exhaustion? "Today" looks like a seriously "close" kind of date, not 2015. 

When will the current framework of IPv4 address allocation in the Asia Pacific region draw to a conclusion? August 2012 looks like the best prediction based on recent address consumption data, but this assumes that there is no last minute panic or sudden last chance run on the remaining address pool. 

And after that? Well you had better be prepared to pay dearly for any ongoing addiction to more IPv4 addresses after that date, or maybe have your IPv6 deployment plans well and truly underway by then. 


   Geoff Huston

    Usual pro-forma disclaimer: No - I am not speaking for APNIC here, and the data is all public data.