They don't need to be really long. Adding one more octet to v4 makes it 1 trillion addresses. Sure the header should support longer than that, but it doesn't mean everyone needs to use all of it.
1 trillion addresses isn't anywhere near enough[1]. Remember that we're not talking about L2 here. (...I don't think 1 trillion MACs would even be enough if we want to ensure they're unique, and it seems the IEEE agree with me since they expanded MACs to 64 bits, but that's a different conversation.)
And you already don't have to use all 128 bits in v6. You're forced to use about 48 of them, but the rest is your choice. You can just... not use some of them. It's fine.
The world is already managing with 32 bits of addresses plus NAT, and NAT most likely gives you less than 256 concurrent users per address. But sure, if some cheap ISP only owns a few /32s and needs to use more octets, let them do that, doesn't mean my 4-octet address needs to be super long too.
You're kinda forced to use 128 bits in v6 if you're an end user, cause that's the lowest common denominator. SLAAC is default, DHCP6 is widely unsupported. Most ISPs also only give out a /64 per spec minimum.
[–] mahboi 3 hours ago
[–] Dagger2 2 hours ago
And you already don't have to use all 128 bits in v6. You're forced to use about 48 of them, but the rest is your choice. You can just... not use some of them. It's fine.
[1] https://www.rfc-editor.org/info/rfc1715/
[–] mahboi 1 hour ago
You're kinda forced to use 128 bits in v6 if you're an end user, cause that's the lowest common denominator. SLAAC is default, DHCP6 is widely unsupported. Most ISPs also only give out a /64 per spec minimum.