CGNat adds a layer of privacy that a public /32 (ipv4) or /64 (ipv6) doesn’t give.
SLAAC? Literally a hack that accidentally caught on because some vendor implemented it sooner than DHCPv6 for some reason. It was intended that everyone would use DHCP just like before. And that's the biggest difference from v4 other than the address format.
They might sound minor but in practice they violate assumptions that are really crucial for implementations. Everyone who deals with addresses must make decisions about how and what to do in face of these quirks.
Another example is the zone identifier string. So how do you store them efficiently in memory or a db? Golang did a really clever thing with netip but the implementation was not easy. Oh well maybe we can always ignore and strip it? Maybe, depends on the use case.
The point is going from exactly 32 bit to 128 bit + sometimes maybe a variable length string (max length, encoding, allowed chars?) is not a small change for something so important and ubiquitous as ip.
The history I recall is very much a academics designing theoretical standards vs operators who actually implement the damn things.
The academics designed the standards around the use of SLAAC deliberately and intentionally. DHCPv6 was the ‘hack’ that operators implemented after the fact.
I’m sure there’s an RFC somewhere that’ll prove this one way or another, if anyone else reading this cares enough to determine for sure (Duty Calls).
With ipv6 you can match IPs realistically to a single household across multiple sites.
Access porn.com from 12.34.56.78 and you are one of dozens of households. Just because Bob Bobson who logged into Netflix is on the same IP it doesn’t mean that house was on porn.com.
Access from 2100:1234:5678:abcd:: and you are accessing from one specific household, even if the lower 64 bits differ. You’ll likely keep the same ip for longer than in cgnat anyway (and by design you keep it until your isp changes)
