It may be built on top of IP, but TCP / UDP levels are important for NAT and such. Too few people use DMZ and other features of routers / firewalls. Its way easier to just put up with TCP / UDP issues to stay compatible with most home setups.
Firewalls -- whose firewalls are we talking about here? If a client (say, home user) tries to initiate an SCTP connection to a server somewhere, what step will fail?
Because they have to do NAT, at least on IPv4.
> Firewalls -- whose firewalls are we talking about here? If a client (say, home user) tries to initiate an SCTP connection to a server somewhere, what step will fail?
Because the connection tracking that's needed to even recognize whether a packets belongs to an outbound or an inbound connection needs to understand the protocol.
https://www.ietf.org/proceedings/48/I-D/sigtran-sctptunnel-0...
Home routers is another matter, home users don't make conscious decision about it, but in my experience UDP works just fine (because a lot of games use it) and it should be good enough for any protocol.
You might say that they're clueless and shouldn't be allowed near networking equipment (and you might even be right) but it's not going to change a thing. For the foreseeable future, working around broken environments is all we can do.
("Getting through broken routers" is certainly a significant advantage; I'm just asking if that's the only good reason to not build directly on IP.)
What allocating a new IP protocol says is pretty close to "all bets are off, and we're carefully taking responsibility for how every system that interacts with TCP/IP headers will handle these packets". Since SCTP doesn't need that, there's no upside. It's vanity and bloody-mindedness.
However, the high turnover for mobile phones has allowed more aggressive changes to the networking stack. Perhaps this, in addition to IPv6, would make something like SCTP easier to adopt widely?
I dove into the world of curve fitting (wee!) and my prediction[1] for 95% IPv6 adoption is around the year 2025: https://imgur.com/a/LyBJn (fitted to the logistic curve[2], x=0 is basically 2010, y is percent adoption)
[1] Which you should completely trust because I've been doing this for all of 20 minutes!
[2] https://en.wikipedia.org/wiki/Logistic_function#In_economics...
Lets say 20% adoption means we're 40% of the way through the transition. The slope for IPv6 looks better and better every day, but overall it's not a great adoption story for tech that inevitably has to happen. (not to discourage or minimize the all the hard work done in getting IPv6 this far)
I assume workplaces have a lower adoption rate due to enterprise inertia. Or is there another explanation?
The last dogleg was January 2015. And since then it’s been linear (with a little stall this month) at about 5% of the Internet converting per year. That’s another 15 years to convert the rest, unless there’s a new dog leg up.
Also percentages don’t work the way humans think they do. Especially when the number of devices is constantly climbing. That may just indicate that some fraction of new hardware is ipv6 but little old hardware is being updated.
We may well have ~2 billion machines on ipv4 pretty much indefinitely, slowly being diluted by addition of new hardware.
The economics going forward will be interesting. I've seen some low-end VPSes charge a lower rate for machines that are IPv6-only.
So you end up with a chicken-and-egg problem: router manufacturers aren't going to add support for it unless there's sufficient demand, and there can't be sufficient demand because very few people can use and rely on it.