So where is IPv6 deployment most evident? It?s a very difficult thing to measure. It is difficult to measure the amount of IPv6 traffic as so much of it is tunneled inside of IPv4. And anyway, tunneled traffic is probably from end users rather than ISPs, but we need ISPs to deploy IPv6 to allow the Internet to grow. So how can we see where ISPs are deploying IPv6 in their networks?

One possible measure of IPv6 deployment in ISPs is the number of IPv6 address blocks (prefixes) seen in the routing table in comparison with the the number of autonomous systems (ASs – roughly equivalent to ISPs) in a region. Geoff Huston has a regional breakdown of advertised ASs on his web site and the SixXS project has a regional breakdown of the IPv6 address blocks visible per region on its web site.

AfriNIC, the Regional Internet Registry for Africa and parts of the Indian Ocean, has a higher proportion of networks in its region announcing IPv6 addresses than the others. Africa also has a smaller deployed base but IPv6’s size is designed to support exactly the kind of network growth that highly populated areas, like Africa and Asia will see as their deployed base grows in the next few years.

Proportion of ASs in RIPE NCC service region announcing IPv6 prefixes

Proportion of ASs in APNIC service region announcing IPv6 prefixes

Proportion of ASs in ARIN service region announcing IPv6 prefixes

Proportion of ASs in LACNIC service region announcing IPv6 prefixes

Proportion of ASs in AfriNIC service region announcing IPv6 prefixes

With help from the Regional Internet Registries, three /8s were returned in 2007 and last month we recovered one more. We now have 43 unallocated /8s. Here’s a table showing the details of the returned blocks.

/8	Year	Help from
46 – BBN	2007	BBN and ARIN
49 – US DoD	2007	ARIN
50 – US DoD	2007	ARIN
14 – Public Data Net	2008	Network Operators

Despite this windfall we are unlikely to see any more whole /8s returned to the IANA free pool. Our investigations indicate that the other legacy “Class A” assignments are all at least partially used. Recovering the space in those blocks would require large companies to engage in expensive renumbering exercises.

But more importantly, it would not buy us very much time. We allocated more than one /8 per month in 2007, so to gain even one year would require a huge amount of renumbering by the users of more than a dozen legacy assignments.

Geoff Huston’s mathematical projection suggests the IANA free pool will be empty before the second half of 2011 and the RIRs’ pools will run out barely a year later. Of course, whatever mathematical models he uses, he cannot account for the very human possibility of a run on the bank.

Address recovery cannot extend the life of the IANA free pool by more than a few months.

It is possible that unused portions of the legacy “Class A” and “Class B” will be returned to the RIRs free pools. Alternatively, it is possible people with partially used legacy assignments will wait for a variant on the policy proposals in the RIPE and APNIC communities to emerge and then engage in remunerated renumbering and address transfer programs.

Whatever actually happens in the next few years, we can be sure that anyone needing large amounts of address space for a rapidly growing network will have to deploy IPv6. IPv6 deployment in the Internet’s core infrastructure is continuing and network operators at ISPs and enterprises need to plan for a world where their users will need to communicate with systems on both IPv4 and IPv6.