IPv6 comes with 128-bit addressing. The huge number of all theoretically possible IPv6 addresses is something human beings can not imagine.

The unthinkable number 2128, which is the number of all possible combinations of 128 bits that form an IPv6 address, is so huge that we can not scope with. For example, a precise answer to a question “How many IP addresses are available in IPv6 compared to IPv4” is:

There are 79228162514264337593543950336 times more IP addresses in v6 compared to v4.

You, as myself, might find that information pretty much useless. Let us find some down-to-earth comparisons.

The clouds.
First, let us compare the number of all air molecules in a typical cloud with the number of all possible IPv6 addresses.
Putting it all together, a number of molecules in the cloud (n), the molecular mass of air(1) (M = 29 g/mol), Avogadro’s number (A = 6 x 1023/mol), gravitational constant (g = 10 m/s2) and a typical cloud surface pressure into an equation, we can calculate the number of air molecules in the cloud. Our equations basically rely on the observation that the cloud is not accelerating, therefore an overall force acting on the cloud is zero:


Here m is the mass of the cloud, Δp the pressure difference and S the surface(2). We come out with n = 1034 molecules in a small sunny Cumulus and 1038 in a huge stormy Cumulonimbus.

Comparing these numbers to 2128 = 3.4 x 1038, we can conclude that IPv6 could be used to address all the air molecules in a gigantic cloud.


(1) Note that water vapor in air will replace other gases and reduce the total density of the mixture. Therefore, dry air is more dense than humid air.
(2) We approximate the pressure difference Δp from 104 (light cloud) to 7 times 104 Pa (stormy cloud) and we use S between 1 (small cloud) and 3000 square kilometers (huge cloud).


Coming soon:
IPv6 subnets and the barley.
IPv6 in the beer.

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