Where in the world is IPv6?

How big is the address space? Undecillion means a billion billion billion billion. So, around 340 of those. That’s a lot.

There are approximately 62 million IPv4 addresses left to be allocated, and estimates put exhaustion somewhere around August, 2011.  That means time is running out for the bulk of the Internet to begin rolling out IPv6.

What does all of that mean?

IPv4 is the current majority protocol that the Internet runs on.  The device you use to read these words almost undoubtedly used it to get them.  It defines the underlying behavior for the little packets of data that are sent and received to make the Internet work.  Part of that behavior is a way to say who the data is from and who it is for.

IPv4 addresses fill that role by having four parts of eight bits each.  That means that each portion of the address is a number from 0 to 255.  A full address might look like  That representation is referred to as “dotted decimal” because the delimiters are dots (periods) and the numbers are in base 10 (decimal).

But there’s a catch: The maximum number of addresses in a 32-bit address space is 232, or just beyond four billion addresses. The actual number is smaller, as there are several blocks of addresses that are reserved for various purposes, which are not part of the general allocation pool.

And the number of addresses that aren’t allocated is quickly approaching zero.  Wikipedia: IPv4 address exhaustion: Predictions of exhaustion dates has a couple of graphics worth examining.  One shows the exhaustion curves, while the other shows the allocations.

To continue the growth of the Internet beyond IPv4 address exhaustion, more addresses will be needed.  That means moving to IPv6, with its 128-bit addresses.  With 128-bit addresses there are not just four times as many addresses, but 296 as many. In total, the IPv6 address space holds around 340 undecillion addresses.

Undecillion means a billion billion billion billion. So, around 340 of those.  Again, minus some of the space for reserved and private uses, but a small enough amount to not worry about that.

The problem is that the world needs IPv6, but it’s been slow to roll out and a long time coming.  Many of the major web properties will be holding a test day in June, but it will probably be once the switch is flipped that a bulk of the Internet actually starts moving in the right direction, and there will probably be a bit of breakage along the way as people find hard-coded addresses from decades past and other such bitrot.

Anyway, I’ll leave you with a fun song that was sung back in 2007 at the RIPE conference, The Day the Router Died:



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