IPv4 is 32 bits address and IPv6 is 128bit address sufficient to address each single molecule on the surface of the earth.
But what happened to IPv1 .. 2..3..and IPv5?
As far as I know none of them existed but why?
Is it that IPv4 was drafted in 1984?
Do you hear about windows 99, windos 2001, windows 2002, windows 2006?
The version number is not strict number indexed. It is not always inreament by 1, or start from 1.
It is a instance where the version was not sufficiently ready, modified or upgraded to be released.
Have you ever played a video game where it went from 1.0 to 1.5? It is because when they make small revisions, they may not feel it suitable to release to the public at large.
So keep in mind that what is in IPv6 contains whatever changes were in IPv6, but with the newer enhancements of IPv6.
Your replies were very helpful but do check the following link to find out more about this issue
I have heard that the version number is related to the number of parts.
IPv4: 4 parts 0-255
IPv6: 6 parts 0-255 (but in hexadecimal notation)
Of course this may be just a myth.
Where did you find that every molecule on earth can be indexed? I have trouble believing this.
Well remember that those pieces of data have to be read they are an identification number.
Why 0 and 15 were set aside, I have no idea. My guess is they could mean something like. Maybe 0 means extended header and 15 means even-more-extended header allowing for more than 4bits(16 possibilites).