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Having partial deployment of IPv4x is no different than having partial deployment of IPv6: you have islands of it and have to fall back to the 'legacy' IPv4-pla

Having partial deployment of IPv4x is no different than having partial deployment of IPv6: you have islands of it and have to fall back to the 'legacy' IPv4-plain protocol when the new protocol fails to connect: * https://en.wikipedia.org/wiki/Happy_Eyeballs https://en.wikipedia.org/wiki/Happy_Eyeballs Getting "free" new-protocol addresses is also nothing new: > 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 https://en.wikipedia.org/wiki/6to4 Translation boxes and tunnels are still needed for both IPv4x and IPv6.

zadikian 7mo ago
Ok, I see what you mean then by 6to4 already supporting what v4x proposed, but that path wasn't taken either. It's a special feature with rare usage rather than the minimum default way of doing v6.
- Dagger2 7mo ago
  We did take that path. If you zoom in on the start of https://www.google.co.uk/intl/en/ipv6/statistics.html https://www.google.co.uk/intl/en/ipv6/statistics.html you can see that 6to4+Teredo was more common than native until 2010. (Okay, that's combined with Teredo, but I think probably 6to4 is the majority of it because Windows will use 6to4 without needing a registry change or custom application behavior.) You see it as a special feature with rare usage because it competed with native and lost. People overwhelmingly preferred deploying v6 natively instead of deploying 6to4. Obviously more people would be using it if it was the only option, but if you're trying to come up with an alternative to the way v6 went then "an approach that v6 took but which nobody wanted to use when native v6 was the alternative" might not be a very promising place to start.
  - zadikian 7mo ago
    It's not like the v6 spec said, here are two options on equal footing, go figure out which is better. 6to4 was a temp bolt-on. I had to look up what things were actually like in 2010 because I really don't remember getting a 2002:, which brought me to rfc6343 that explained why exactly 6to4 suffered. A big part of it is that even a v6-enabled ISP didn't give you a 2002:, rather you were relying on anycast to reach a relay server. Why would an ISP or user ever want that mess? Either they do v6, or more likely they don't care and focus on v4. So actually I take it back, 6to4 was pretty different from this ipv4x idea. I misunderstood and thought a v6-enabled ISP would give you a 2002: under 6to4, which you could later subdivide. Ignoring that, say 6to4 were like v4x... The idea that those 2 years showed that native was preferable, that was among a small minority who even cared about v6 to begin with (0.25% at the time). This was a primary, not a final.
    - Dagger2 7mo ago
      It doesn't rely on anycast. The ISP gives you a v4 address from which you generate the 2002:: prefix, and when talking to another 6to4 network you send the packets directly from your v4 address to their v4 address. Inside those packets is an extra 80 bits of addressing that the source and destination networks can use. Or, ISPs that want to do so can use one of their own v4 addresses to get the corresponding /48 6to4 prefix, split it up and hand that out to customers while handling the v4 packets themselves. Looking at the 15 or so years afterwards shows native v6 deployment at 50% of the Internet, and approximately nobody interested in deploying 6to4 outside of these posts where people keep reinventing it but with different names and an assertion that if only the IETF had thought of this, everybody would have loved it. I think that's decent evidence that they wouldn't.
      - zadikian 7mo ago
        What you're describing is what rfc6343 called "router 6to4" as opposed to the anycast variant, but anycast was what got used. "In practice, there are few if any deployments of Router 6to4 following these recommendations. Mostly, Anycast 6to4 has been deployed." But even router 6to4 isn't easy like the v4x-like ideas: "not designed to be an unmanaged solution." To whoever wishes the IETF had thought of ipv4x, I'll bet the IETF thought of it and decided they wanted to start with a clean slate in v6. I can understand why, big part because of v4's fragmented routes, and also /8 haves&have-nots. But v4x at least had a way to gradually defrag things once it was fully adopted. If you're suggesting staying on 6to4 forever, that would've meant continuing to use vanilla ipv4 between subnets. Also, all those compromise ideas had NAT staying at least on day 1. Many v6 proponents seem to think your device on any random guest network should be able to receive inbound connections, enabling true P2P everywhere, which implies having no router firewall. Others recommend a router firewall. Not sure what IETF's initial position was on this, but they later recommended that residential routers give the user a clear choice between closed vs open. v4x with its NAT would just default to closed. In reality, I've never seen a consumer router clearly say what it does with inbound v6 traffic.

zadikian 7mo ago

Ok, I see what you mean then by 6to4 already supporting what v4x proposed, but that path wasn't taken either. It's a special feature with rare usage rather than the minimum default way of doing v6.

Dagger2 7mo ago
We did take that path. If you zoom in on the start of https://www.google.co.uk/intl/en/ipv6/statistics.html https://www.google.co.uk/intl/en/ipv6/statistics.html you can see that 6to4+Teredo was more common than native until 2010. (Okay, that's combined with Teredo, but I think probably 6to4 is the majority of it because Windows will use 6to4 without needing a registry change or custom application behavior.) You see it as a special feature with rare usage because it competed with native and lost. People overwhelmingly preferred deploying v6 natively instead of deploying 6to4. Obviously more people would be using it if it was the only option, but if you're trying to come up with an alternative to the way v6 went then "an approach that v6 took but which nobody wanted to use when native v6 was the alternative" might not be a very promising place to start.
- zadikian 7mo ago
  It's not like the v6 spec said, here are two options on equal footing, go figure out which is better. 6to4 was a temp bolt-on. I had to look up what things were actually like in 2010 because I really don't remember getting a 2002:, which brought me to rfc6343 that explained why exactly 6to4 suffered. A big part of it is that even a v6-enabled ISP didn't give you a 2002:, rather you were relying on anycast to reach a relay server. Why would an ISP or user ever want that mess? Either they do v6, or more likely they don't care and focus on v4. So actually I take it back, 6to4 was pretty different from this ipv4x idea. I misunderstood and thought a v6-enabled ISP would give you a 2002: under 6to4, which you could later subdivide. Ignoring that, say 6to4 were like v4x... The idea that those 2 years showed that native was preferable, that was among a small minority who even cared about v6 to begin with (0.25% at the time). This was a primary, not a final.
  - Dagger2 7mo ago
    It doesn't rely on anycast. The ISP gives you a v4 address from which you generate the 2002:: prefix, and when talking to another 6to4 network you send the packets directly from your v4 address to their v4 address. Inside those packets is an extra 80 bits of addressing that the source and destination networks can use. Or, ISPs that want to do so can use one of their own v4 addresses to get the corresponding /48 6to4 prefix, split it up and hand that out to customers while handling the v4 packets themselves. Looking at the 15 or so years afterwards shows native v6 deployment at 50% of the Internet, and approximately nobody interested in deploying 6to4 outside of these posts where people keep reinventing it but with different names and an assertion that if only the IETF had thought of this, everybody would have loved it. I think that's decent evidence that they wouldn't.
    - zadikian 7mo ago
      What you're describing is what rfc6343 called "router 6to4" as opposed to the anycast variant, but anycast was what got used. "In practice, there are few if any deployments of Router 6to4 following these recommendations. Mostly, Anycast 6to4 has been deployed." But even router 6to4 isn't easy like the v4x-like ideas: "not designed to be an unmanaged solution." To whoever wishes the IETF had thought of ipv4x, I'll bet the IETF thought of it and decided they wanted to start with a clean slate in v6. I can understand why, big part because of v4's fragmented routes, and also /8 haves&have-nots. But v4x at least had a way to gradually defrag things once it was fully adopted. If you're suggesting staying on 6to4 forever, that would've meant continuing to use vanilla ipv4 between subnets. Also, all those compromise ideas had NAT staying at least on day 1. Many v6 proponents seem to think your device on any random guest network should be able to receive inbound connections, enabling true P2P everywhere, which implies having no router firewall. Others recommend a router firewall. Not sure what IETF's initial position was on this, but they later recommended that residential routers give the user a clear choice between closed vs open. v4x with its NAT would just default to closed. In reality, I've never seen a consumer router clearly say what it does with inbound v6 traffic.