IPv6 ASNs - Network Size Matters

Emile Aben — Aug 12, 2013 09:50 AM
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This article provides statistics about how much IPv4 address space is being announced by networks (ASNs) that are also announcing IPv6 address space. Currently this is about 70% of IPv4 address space.

Prompted by an interesting question on the ipv6-ops mailing list by Martin Millnert, I carried out a short analysis looking at how the IPv4 size of a network (ASN) relates to it announcing IPv6 address space.

Announcing IPv6 address space is a necessary step a network needs to take for its users to be able to communicate with the rest of the IPv6 Internet. However, many more steps are needed to make a network fully IPv6 enabled. Looking at announced IPv6 address space tells us something about networks that have taken steps towards IPv6 deployment, but not necessarily the networks that have fully deployed IPv6.

The specific question Martin asked was:

"What is the total amount of IPv4 address space announced by ASNs that also announce IPv6?"

At 1 August 2013, the answer was that 69.6% of IPv4 address space is announced by networks that also announce IPv6. If you just look at the number of networks that announce IPv6 address space, regardless of their size, IPv6 deployment is at 16.6% (this is what the RIPE NCC's IPv6-ASN graph shows you over time, broken up by country). Another way to look at the 69.6% number is that it is the percentage of networks that announce IPv6, normalised by IPv4 address space size. 

From these numbers, it is clear that networks with more IPv4 address space are more likely to also announce IPv6 space. A breakdown by IPv4 network size confirms this:

IPv4 network size

%IPv6

Number of networksTotal IPv4 address space announced by networks this size
< 1k 5.2 17987 6690776
1k - 10k 16.0 18594 61829496
10k - 100k 34.9 6674 251408867
100k - 1M 50.7 1562 426352473
1M - 10M 72.7 300 842592302
> 10M 75.5 40 1045486168

Table 1: IPv6 deployment broken up by IPv4 network size

The larger a network is in terms of announced IPv4 space, the more likely it will have already taken the important step of announcing IPv6 address space to the rest of the Internet. Of the largest 40 networks, only 9 do not announce IPv6 address space. Upon closer inspection, at least two of these (AT&T and CERNET) are cases of organisations that hold multiple ASNs, and at least one of the other ASNs does announce IPv6 address space.

This breakdown by IPv4 network size also confirms some of our earlier findings where larger networks scored higher on IPv6 deployment then smaller networks.

Something to keep in mind is that IPv4 network size is not always a good indicator for true network size. For instance, some of the legacy Class A network blocks may be announced by a network that in reality only uses a very small fraction of this block. Another thing to keep in mind is that organisations don't always match up 1:1 to ASNs and the links between organisations and ASNs can be different between IPv4 and IPv6.

At 70%, the percentage of IPv4 address space announced by ASNs that also announce IPv6 is in stark contrast with the fact that only around 1.5% of end users can actually use the IPv6 Internet, according to Google's statistics. The difference between these two numbers tells us something about the number of networks that have taken a step towards deployment versus those that have fully deployed IPv6.

Another way of looking at it is that for 30% of IPv4 address space, the step of announcing IPv6 address space appears to not have been made yet. This can be partially explained by organisations using their ASNs differently for IPv4 and IPv6. And while the smaller networks score the lowest for IPv6 deployment at the ASN-level, even at the bigger networks the work on this essential step for IPv6 deployment is not finished.

If people find this normalisation by IPv4 address space a useful way to show IPv6 deployment at the network level - please let us know! A potential next step we can take is to show these statistics by country.

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