4 ms·

There’s probably a good reason for it, but I’ve never understood why IPv6 couldn’t be fully backwards compatible. Then there would be no need to migrate - every

by lovecg 5y ago

There’s probably a good reason for it, but I’ve never understood why IPv6 couldn’t be fully backwards compatible. Then there would be no need to migrate - everyone would be already on IPv6 by definition.

bejelentkezni 5y ago
If I recall correctly, ipv6 addresses beginning with 0::0:ffff are mapped 1-to-1 with ipv4 addresses.
- lovecg 5y ago
  I’m mostly still annoyed about the colon. Come on, ip:port is a pretty widely used convention people! The number of parsing bugs I had to fix with the migration…
  - fulafel 5y ago
    On the plus side the schedule was reasonable, you had time since the 1990s :)
    - lovecg 5y ago
      The flip side is job security so it’s not all bad :)
  - Dagger2 5y ago
    It is today, but what about at the time it was picked? Software from that era (e.g. telnet) take their hostname/service arguments as two strings (e.g. `telnet 127.1 ssh`). I believe ip:port comes from URLs, the RFC for which was published at the end of 1994, which is about the same time that v6 was being developed. So it's not clear that the fault isn't on the URL side, or on the side of software using URL conventions when they're not using URLs. Note that staying with "." wasn't an option, due to ambiguity with DNS. (Consider something like "2001.db8.3.4.5.6.7.be": is that an IP or a hostname under .be?)
duskwuff 5y ago
How does an IPv4-only host send a packet to an IPv6-only host?
- whoknowswhat11 5y ago
  They could have at least let ipv6 only folks talk to ipv4 more easily. Something like 464XLAT maybe built in out the gate more? You go ipv6 until next hop is IPv4. If you are in IPv4 mapped address space translate to IPv4 there and continue.
  - duskwuff 5y ago
    > They could have at least let ipv6 only folks talk to ipv4 more easily. And how do the IPv4 hosts talk back? 464XLAT is one solution, but it requires infrastructure to be in place to perform the protocol translation. The protocol alone isn't enough to allow interoperation.
  - p1mrx 5y ago
    NAT64/464XLAT exists and it works. It can't really be "part of the protocol" because it depends on stateful IPv4 devices in the middle of the network. Ultimately it's up to the ISPs which IPv4-as-a-service mechanism they want to deploy.
  - maccolgan 5y ago
    Do you mean Teredo?
- hansel_der 5y ago
  it doesn't
fulafel 5y ago
You can't fit the bigger address into the v4 address field, on the wire or in API/ABI. Also, conflating them would bring massive confusiin when v6 and v4 hosts can't reach the same addresses.

by lovecg 5y ago

bejelentkezni 5y ago

If I recall correctly, ipv6 addresses beginning with 0::0:ffff are mapped 1-to-1 with ipv4 addresses.

lovecg 5y ago
I’m mostly still annoyed about the colon. Come on, ip:port is a pretty widely used convention people! The number of parsing bugs I had to fix with the migration…
- fulafel 5y ago
  On the plus side the schedule was reasonable, you had time since the 1990s :)
  - lovecg 5y ago
    The flip side is job security so it’s not all bad :)
- Dagger2 5y ago
  It is today, but what about at the time it was picked? Software from that era (e.g. telnet) take their hostname/service arguments as two strings (e.g. `telnet 127.1 ssh`). I believe ip:port comes from URLs, the RFC for which was published at the end of 1994, which is about the same time that v6 was being developed. So it's not clear that the fault isn't on the URL side, or on the side of software using URL conventions when they're not using URLs. Note that staying with "." wasn't an option, due to ambiguity with DNS. (Consider something like "2001.db8.3.4.5.6.7.be": is that an IP or a hostname under .be?)

duskwuff 5y ago

How does an IPv4-only host send a packet to an IPv6-only host?

whoknowswhat11 5y ago
They could have at least let ipv6 only folks talk to ipv4 more easily. Something like 464XLAT maybe built in out the gate more? You go ipv6 until next hop is IPv4. If you are in IPv4 mapped address space translate to IPv4 there and continue.
- duskwuff 5y ago
  > They could have at least let ipv6 only folks talk to ipv4 more easily. And how do the IPv4 hosts talk back? 464XLAT is one solution, but it requires infrastructure to be in place to perform the protocol translation. The protocol alone isn't enough to allow interoperation.
- p1mrx 5y ago
  NAT64/464XLAT exists and it works. It can't really be "part of the protocol" because it depends on stateful IPv4 devices in the middle of the network. Ultimately it's up to the ISPs which IPv4-as-a-service mechanism they want to deploy.
- maccolgan 5y ago
  Do you mean Teredo?
hansel_der 5y ago
it doesn't

fulafel 5y ago

You can't fit the bigger address into the v4 address field, on the wire or in API/ABI. Also, conflating them would bring massive confusiin when v6 and v4 hosts can't reach the same addresses.