i will admittedly say i have no idea what sixxs is
SixXS was a free IPv6 tunneling service, so that people with only IPv4 provider can still get access to IPv6 addresses through a 3rd party.
(But more reliably than 6in4 which is dependent on the dynamic IPv4 address, and relies on volunteer servers reached though anycast).
The idea was to break the chicken-and-egg problem faced by IPv6 migration :
- content provider don't care about moving to IPv6 because nobody is using it and most people are still on IPv4
- and ISP not spending the effort to provide IPv6 to their clients, because there's no IPv6 content to justify the move.
SixXS provided a 3rd party with a very reliable way to get onto IPv6, so at least the "there are no users" excuse isn't valid anymore.
Now fast forward a decade and a half later and nowadays a lot of content providers *ARE* on IPv6 (e.g.: Google, most universities, etc.), but there are still ISP not providing IPv6 on their network (e.g.: using something like 6rd, which basically works like 6in4 but relies on official servers with fixed address that is owned and operated by the ISP),
Instead of that ISPs let the users go use SixXS, for the users who want IPv6. So rely on a free 3rd party service, instead of putting the efforts themselves to enable IPv6 for their own users as they should be doing.
So SixXS is shutting down to force ISPs to setup and listen to their users and provide IPv6, instead of deferring it to SixXS.
its sad to see them go since it was a free service, providing a service for people without means.
The thing is, SixXS was providing a service that should in theory be provided by the ISPs themselves, but some are too lazy to implement IPv6 even after almost 2 decades.
(and it's not for people without means. Technically, it's for people who have the means to pay an ISP for a connection, but said ISP is damn shit lazy and doesn't care to provide something more modern than last century's IPv4)