[Last month, I remotely attended the second meeting of the FCC’s current Technical Advisory Committee (TAC), where chairs of several working groups set up at the first meeting (in November) reported on their progress and plans. I’m a member of the FCC TAC’s IPv6 working group, (more on this soon), and so far have been asked to answer two questions I’ve been thinking about for a couple of years: what data do we have to gauge IPv6 deployment by Internet service providers, and what data do we need? Last November I addressed the first question in a (still pending) NSF proposal to measure IPv6 deployment, with the following text. I’ll post some updates shortly.]
IANA allocated the first IPv6 address in 1999. Today, estimates of IPv6 penetration span at least three orders of magnitude across different sources, which is arguably consistent with the wide range of interest (or lack of interest) in this new protocol. The U.S. federal government is again requiring IPv6 deployment within .gov networks . Although most agencies have thus far only done the bare minimum in response to such regulations, it is still a sign that the U.S. is willing to regulate into existence a critical information technology . Yet the economic crisis has further lowered the chance that any ISPs will voluntarily invest capital in creating and operating the parallel networks that will be required while the world transitions to IPv6.
Many attempts have been made to evaluate the status of IPv6 adoption and penetration . None have found significant activity, even though IPv6 has been implemented on all major network and host operating systems. Current levels of observable IPv6 activity are well below 1% , although up to 7% of global Autonomous Systems announce at least one IPv6 prefix . By some accounts, IPv6 development is progressing faster in Asian countries: Japan, South Korea, China  . Notably, the 2008 Summer Olympics was the first major world event with a presence on the IPv6 Internet .
Traffic data is the most accurate way to measure actual IPv6 usage, but also has the most difficult policy obstacles to access, and does not reveal preparatory activity. Arbor Networks  reported that observable IPv6 (6to4) traffic remained less than one twentieth of one percent (<0.05%) of traffic they observed at their sensors in October 2010, though they point out this is two orders of magnitude larger than in 2008, and is admittedly a lower bound on IPv6 traffic due to observation capability limitations. CAIDA measurements of an OC-192 commercial backbone link in April 2010 showed a similarly low IPv6 traffic level of 0.005% of packets .
Given the difficulty of measuring IPv6 directly, Huston and Michaelson  studied a range of types of data collected over four years (January 2004 to April 2008) that might reflect IPv6 activity. They analyzed inter-domain routing announcement data, access logs from www.apnic.net, and data captured from queries of reverse DNS zones that map IPv4 and IPv6 addresses back to domain names. All of their metrics show some increase in IPv6 deployment activity starting in the second half of 2006, but they emphasize that their metrics are limited in scientific integrity; most only measure some interest in IPv6 rather than usable IPv6 support.
Hurricane Electric maintains daily statistics  on IPv6 metrics such as domains registered with AAAA DNS records (which provide a mapping from hostnames to IPv6 addresses). Mark Prior  posts weekly results of testing IPv6 reachability to web, email, DNS, NTP, and jabber ports for Internet2 sites and partners. None of these sites show aggregated long term trends.
Not only do we lack data that would provide a complete picture of IPv6 deployment ; we do not even have consensus on the definition of IPv6 usage, much less growth. Even more challenging to policymakers, researchers, and operators are the tremendous counter-incentives to sharing data to establish empirically grounded consensus, including the time and money it takes to obtain measurements. Internet2 is an eye-opening example — it operates the U.S. national research and education backbone, which supports IPv6, but their routers have not thus far supported IPv6 flow statistics, so we have not even been able to obtain regular data on IPv6 usage on our own national research backbone . (Internet2 is working on it.)
-  R. Mohan, “Will U.S. Government Directives Spur IPv6 Adoption?,”, September 2010.
-  T. Wheeler, “Launching the TAC Blog Series”, November 2010.
-  R. Broesma, DREN IPv6 implementation update, July 2008.
-  J. Baird, The DoD HPC Modernization Program Helps Make The Transition To IPv6, 2008.
-  H. Ringberg, C. Labovitz, D. McPherson and S. Iekel-Johnson, “A One Year Study of Internet IPv6 Traffic”, 2008.
-  L. Colitti, “Global IPv6 Statistics – Measuring the current state of IPv6 for ordinary users”, 2008.
-  G. Huston and G. Michaelson, “Measuring IPv6 Deployment”, 2008.
-  E. Karpilovsky, A. Gerber, D. Pei, J. Rexford, and A. Shaikh, “Quantifying the Extent of IPv6 Deployment”, in PAM 2009, (Seoul, Korea), Apr 2009.
-  M. Leber, Global IPv6 Deployment Progress Report, 2006.
-  T. Kuehne, Examining Actual State of IPv6 Deployment, 2008.
-  M. Prior, IPv6 survey, 2009.
-  M. Abrahamsson, some real life data, 2008.
-  E. Aben, IPv4/IPv6 measurements for: RIPE-NCC, November 2010.
-  E. Aben, “Interesting Graph – Networks with IPv6 over Time,”, November 2010.
-  E. Aben, “Measuring IPv6 at Web Clients and Caching Resolvers,”, Mar. 2010.
-  Craig Labovitz, “IPv6 Momentum?”
-  Roch Guerin, “IPv6 Adoption Monitor”.
-  Ma Yan, “Construction of CNGI-CERNET IPv6 CPN”, 2009.
-  Olympic Games 2008, 2008.
-  E. Aben, M. Dusi, and kc claffy, “Packet size distribution comparison between Internet links in 1998 and 2008”, 2008.
-  J. S. Sauver, “IPv6 and The Security of Your Network and Systems”, 2009. presented at April 2009 I2 member meeting,