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Comment by tardedmeme | Hacker News Reader

We have that, it's called ipv6. A section of the v6 address space is sectioned off to hold all v4 addresses

The embedding I believe you are referring to is not a part of the global routing model. (maybe I am wrong?) What I am describing is making that kind of declaration central to the system in a deterministic, network wide mapping of ipv4 to the larger ipv6 space. The translation in ipv6 ended up being handled by a mix of mechanisms after the fact, rather than a single, uniform mapping model that tied directly to the address structure. I think part of the problem is they did not put that front and center, at the beginning, when doing the initial specification.

How would an embedding handle the other 99.999999999999% of addresses not embedded?

At least at first, you wouldn't, you'd embed all of them. Cloudflare has 1.1.1.1, so they get 1.1.1.1:: too.

Not doing that was one of the key points of starting fresh with IPv6. Doing that would mean that you could end up with billions of routes to consider.

One reason for large address space is that those with networks could be placed sparsely and left room to grow. Thus allowing less routes in general.

Indeed doing it this way would keep the fragmentation, or at least delay fixing it. That's what these articles always overlook, the goal of ipv6 wasn't to just add more bits, it was also to defrag the routes.

I think instead of 1.1.1.1::, you could do 4:1.1.1.1::, wait for v4 to be gone, then start building new topologies in the other /8s. Not sure how hard that is, but it seems easier than what they're trying to do now.

Would it help at all? You can't just send IPv6 packets down the equivalent IPv4 path because that bext-hop router probably xoesn't understand IPv6 packets. In fact there could be no IPv6 path at all between you and the destination, so knowing where they are still wouldn't help you forward packets. If it understood them, it would have given you an IPv6 route anyway. Updating BGP to support IPv6 routes wasn't an actual problem.

There are lots of services I can't send v6 to, not because some router in the middle only understands v4 but because the service operator decided not to deal with v6.

So the idea is to surreptitiously install software on the service operator's machines that they can't disable?

It's already a bit like that, but they can and do disable it. You can see the other comments in this thread: many people disable IPv6 upon any sign of a networking problem.

No, the idea is you can turn v6 on/off, but doing so only changes the packet format and nothing else at first. There's no separate place to configure v6-specific settings because there are none. You use the same address, routes, DHCP, NAT, DNS, etc as v4, but you're limited to 32-bit addrs at first. The point is to just get people off v4.

Once v6 has reached enough adoption, you can turn off v4. Those who want to keep the addrs from v4 can, except now they get way more addresses under those too. Others can start building a clean new topology under the other prefixes without worrying about compatibility.

I don't see why anyone would change all the bits you actually need to change for some nebulous future gains. Still have to deal with new sockets and new routing decisions at least. To not really gain much from new features.

To me it looks like something that would have gained nearly no actual adoption outside some toy examples. Later you will need to anyway get new DNS, DHCP(or alternative) and so on.

That's a legit concern. If that's not interesting enough to the kind of user that wants all-new v6, instead start from today where some users are on the new v6 network, and say they added the 4:: prefix as a way to pick up the kind of user that doesn't want to change much. They'd still be compatible eventually. Though the reason I was thinking 4:: from the start would've been attractive enough is, a lot of people did use 6to4 and other halfway measures despite having no immediate gain.

Today's DNS6 DHCP6 etc are totally incompatible with v4. 4:: buys backwards-compatibility. Each can be updated to support longer addrs without caring whether you use it with v4 or v6.

> At least at first, you wouldn't, you'd embed all of them. Cloudflare has 1.1.1.1, so they get 1.1.1.1:: too.

Everyone with an IPv4 address automatically got an IPv6 allocation:

> For any 32-bit global IPv4 address that is assigned to a host, a 48-bit 6to4 IPv6 prefix can be constructed for use by that host (and if applicable the network behind it) by appending the IPv4 address to 2002::/16.

> For example, the global IPv4 address 192.0.2.4 has the corresponding 6to4 prefix 2002:c000:0204::/48. This gives a prefix length of 48 bits, which leaves room for a 16-bit subnet field and 64 bit host addresses within the subnets.

* https://en.wikipedia.org/wiki/6to4

What does it mean to have an /48? Well, a IPv6 subnet is /64, so that's 16 bits for subnets. In IPv4 land, if you take a subnet to be /24, an allocation with 16 bits worth of subnets would be a /8.

So basically, with 6to4, every person with an IPv4 address got the equilvalent of a Class A in IPv6.

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