Actually -- dark matter is there because we cannot explain the gravitational effects observed (the observable universe weighs less than it should - dark energu is the driving force of the never-ending expansion.
My source of info ("Universe" by Heather Cooper and Nigel Henbest 1998) says darkmatter is responsible for the expansion, though perhaps the book is somewhat outdated now. Can you recommend anything more recent? The Universe does fascinate me
Re IPv6:
I read somewhere that it is still in its testing form, which is why it's not being widely deployed. Any truth in that?
