This is a bit of a thought experiment, so it may be not entirely correct (especially the maths – my probability theory is very rusty).

One of the lesser reasons for using the DNS rather than IP4 addresses is that typing mistakes are more easily caught – if you intend to type 192.168.67.52, but accidentally enter 192.168.67.53 instead, you still have a valid IPv4 address. Whereas entering the domain name *wombar.example.com* instead of *wombat.example.com* will most likely get you an error instead of sending your secrets off to an unknown location on your network – unless you have a rather silly server naming convention of course!

But how likely are you to make a mistake typing in an IPv4 address? According to a random web site “out there”, the average accuracy of a typist is 92%, or an *average* of 8 typos per 100 characters. If we convert this into a probability, we get a probability of typing each character correctly as 0.92.

Given that typing IPv4 addresses is something that some of us have a lot of practice at, and in many cases we will notice typos before they become a problem, I’m going to arbitrarily declare that the probability of getting any character within an IPv4 address *correct* is 0.999. But to type in an IPv4 address correctly we have to get a maximum of 15 characters correct :-

1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |

1 | 9 | 2 | . | 1 | 6 | 8 | . | 1 | 2 | 8 | . | 1 | 2 | 8 |

So the probability of getting all those characters right is 0.999 (first character) x 0.999 (second character) … Or *0.999^15*.

And once you work that out, subtract it from 1 (to get the probability of making a mistake) and convert it into a percentage, there is an 11% chance of making a typo in an IPv4 address.

For an IPv6 address such as *2001:db8:ca2c:dead:44f0:c3e9:28be:c903, *which has 38 characters (no I’m not doing that silly table for IPv6) – *100 * (1 – 0.999 ^ 38)* – 32%.

Now whilst my calculations may be a bit off, the likelihood of entering an IPv6 address incorrectly is nearly three times higher than the risk of entering an IPv4 address incorrectly.

In other words, with IPv6 you *really* need a good working DNS solution just to keep the errors to manageable levels.