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In my experience, the IPv6 protocol is much simpler than the IPv4 protocol. However, the IPv6 tooling and documentation is still worse than it is with IPv4, and

In my experience, the IPv6 protocol is much simpler than the IPv4 protocol. However, the IPv6 tooling and documentation is still worse than it is with IPv4, and dual-stack is inherently going to be more complicated than implementing any single protocol, so I do have some sympathy towards "IPv6 is hard". For example, the IPv6 packet structure [0] is much simpler than the IPv4 packet structure [1]; SLAAC [2] is much simpler than DHCPv4 [3]; IPv6 multicast [4] is much simpler than IGMP [5]; IPv6's lack of NAT simplifies peer-to-peer networking compared to IPv4; ULAs [6] prevent the annoying address conflicts you get with IPv4 [7]; etc. [0]: https://en.wikipedia.org/wiki/IPv6_packet#Fixed_header https://en.wikipedia.org/wiki/IPv6_packet#Fixed_header [1]: https://en.wikipedia.org/wiki/IPv4#Packet_structure https://en.wikipedia.org/wiki/IPv4#Packet_structure [2]: https://en.wikipedia.org/wiki/IPv6_address#Stateless_address_autoconfiguration_(SLAAC) https://en.wikipedia.org/wiki/IPv6_address#Stateless_address... [3]: https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Pro... [4]: https://en.wikipedia.org/wiki/IPv6#Multicasting https://en.wikipedia.org/wiki/IPv6#Multicasting [5]: https://en.wikipedia.org/wiki/Internet_Group_Management_Protocol https://en.wikipedia.org/wiki/Internet_Group_Management_Prot... [6]: https://en.wikipedia.org/wiki/Unique_local_address https://en.wikipedia.org/wiki/Unique_local_address [7]: https://stackoverflow.com/a/52374482/30512871 https://stackoverflow.com/a/52374482/30512871

j16sdiz 6mo ago
ULA give more trouble than what it solves. Almost all computer have multiple interface (virtual or not). Application now need to know which interface the destination is on, and there is no easy data structure to store the interface
- eqvinox 6mo ago
  You're confusing ULAs (Unique Local Addresses) with LLAs (Link-Local Addresses). (ULAs don't need the interface specified.) ULA: fc..:… and fd..:… LLA: fe80:… [ed.: By the way, sin6_scope_id is where the interface identifier is stored in struct sockaddr_in6. So, basically every single IPv6 address object you're handling has the field for it.]
- gucci-on-fleek 6mo ago
  > ULA give more trouble than what it solves. How? They're essentially the same as IPv4 addresses; the only difference is that there are way more of them, so address conflicts are much less likely. > Almost all computer have multiple interface (virtual or not) Sure, but that's the case with IPv4 too: my cell phone has one IPv4 address over WiFi and another over cellular, and my laptop has one IPv4 address over WiFi and another over Ethernet. Edit: Ah, I think that eqvinox's comment [0] is what you were getting at here. And yeah, I agree that LLAs are kinda confusing and annoying. The difference is that LLAs aren't routable [1] and don't have an IPv4 analog, while ULAs are routable and are mostly equivalent to IPv4 addresses [2]. [0]: https://news.ycombinator.com/item?id=47814154 https://news.ycombinator.com/item?id=47814154 [1]: https://en.wikipedia.org/wiki/Link-local_address https://en.wikipedia.org/wiki/Link-local_address [2]: https://en.wikipedia.org/wiki/Unique_local_address https://en.wikipedia.org/wiki/Unique_local_address
  - seba_dos1 6mo ago
    > LLAs (...) and don't have an IPv4 analog They do. You don't really see them on Linux unless configured manually, but Windows defaults (or at least defaulted in the past, my Windows-foo is very outdated by now) to a IPv4 LLA when DHCP fails. The difference is that IPv6 requires it on every interface regardless of whether it has a different address already.

j16sdiz 6mo ago

ULA give more trouble than what it solves. Almost all computer have multiple interface (virtual or not). Application now need to know which interface the destination is on, and there is no easy data structure to store the interface

eqvinox 6mo ago
You're confusing ULAs (Unique Local Addresses) with LLAs (Link-Local Addresses). (ULAs don't need the interface specified.) ULA: fc..:… and fd..:… LLA: fe80:… [ed.: By the way, sin6_scope_id is where the interface identifier is stored in struct sockaddr_in6. So, basically every single IPv6 address object you're handling has the field for it.]
gucci-on-fleek 6mo ago
> ULA give more trouble than what it solves. How? They're essentially the same as IPv4 addresses; the only difference is that there are way more of them, so address conflicts are much less likely. > Almost all computer have multiple interface (virtual or not) Sure, but that's the case with IPv4 too: my cell phone has one IPv4 address over WiFi and another over cellular, and my laptop has one IPv4 address over WiFi and another over Ethernet. Edit: Ah, I think that eqvinox's comment [0] is what you were getting at here. And yeah, I agree that LLAs are kinda confusing and annoying. The difference is that LLAs aren't routable [1] and don't have an IPv4 analog, while ULAs are routable and are mostly equivalent to IPv4 addresses [2]. [0]: https://news.ycombinator.com/item?id=47814154 https://news.ycombinator.com/item?id=47814154 [1]: https://en.wikipedia.org/wiki/Link-local_address https://en.wikipedia.org/wiki/Link-local_address [2]: https://en.wikipedia.org/wiki/Unique_local_address https://en.wikipedia.org/wiki/Unique_local_address
- seba_dos1 6mo ago
  > LLAs (...) and don't have an IPv4 analog They do. You don't really see them on Linux unless configured manually, but Windows defaults (or at least defaulted in the past, my Windows-foo is very outdated by now) to a IPv4 LLA when DHCP fails. The difference is that IPv6 requires it on every interface regardless of whether it has a different address already.