If one has to go through the pain of changing everything why not make sure one doesn't have to do it again any time soon?
Also having 64-bit for the network address (and 64-bit for the device) does have certain benefits that make it easier to use than shorter addresses in practice for a single entity, since one can hierarchically model the network and do things like <my_network>:<site-id>:<vlan>.
So even in absence of DNS one doesn't quite have to remember 128-bit of information for every device.
> why not make sure one doesn't have to do it again any time soon?
the pyramids in egypt took over a lifetime to build; a marvel of engineering, as theyve lasted thousands of years and noones had to build replacement pyramids. the problem, though, is noone in todays culture needs pyramids.
But ever since privacy extensions, that's not how IPv6 is allocated, right? Each individual system is supposed to get a /64. Your household should actually have a /56 or something crazy like that, which few ISPs actually do. SLAAC doesn't even work if it doesn't have it's own /64 per host, I believe.
It is.
A typical enterprise might get allocated a /32, which gives them 32-bit to nicely design their network and give 64-bit to each individual network where devices are connected.
A typical ISP will get allocated a much larger allocation like a /20, which allows them to allocate a /56 for each of their customers while still having a few bits to play with.
But all starting with the same <isp_network> prefix.
With IPv4 you will have many separate fragmented networks that have no numbers in common. And this will only get worse over time.
Your initial claim was that a IPv6 address consists of a 64-bit network address, then a 64-bit device address that could be separated into <site-id>:<vlan> as an example.
However, SLAAC demands that each device is given a 64-bit prefix that it then chooses many random 64-bit host addresses from, without any other rhyme or reason. So, if you want to know the IP of a host you want to connect to, you have to remember at least a 64-bit number that changes every day by design. Add to that some extra bits for the particular part of the network you are in.
So your IPv6 is more like <isp-assigned-prefix, 32-56 bits>:<internal-net-prefix, 8-32 bits>:<random-host-address, 64 bits>. Human friendly this is not.
That's OK if you're directly trying to access the machine, but it's not enough if you're looking through logs to try to understand which of your machines is contacting you.
Also having 64-bit for the network address (and 64-bit for the device) does have certain benefits that make it easier to use than shorter addresses in practice for a single entity, since one can hierarchically model the network and do things like <my_network>:<site-id>:<vlan>. So even in absence of DNS one doesn't quite have to remember 128-bit of information for every device.