>Sctp only breaks if the ISP or user has turned on NAT.
This describes 95%+ of home users. NAT may do bad things to IP, but if you are an app developer that depends on no NAT, you're product is going to have a very limited market of people that can use it.
They are tunneling IPv6 over Teredo if native IPv6 is unavailable. They provide their own relay servers for people who have NAT traversal incapable connectivity.
Teredo is a Microsoft-developed (but IETF-standadized) NAT-traversing IPv6-over-IPv4 tunneling method.
An ISP employee here. We did nothing particular to support SCTP, so I got curious whenever it works. Just ran a pair of socat's (sctp-listen:12345 and sctp:example.org:12345) and it worked perfectly.
In our setup, NAT's done on a GNU/Linux machines in a simplest possible way, almost like `iptables -t nat -A POSTROUTING -s 10.0.0.0/8 -o eth1 -j MASQUERADE` (we offer dynamic globally-routeable IPv4 addresses first, but when our pools are drained, we have no choice but do NAT for v4). So, it seems, almost every ISP who uses software routers (they're stable, performant and cheap) should be SCTP-friendly.
No idea about Ciscos and alikes, though. None we have does NAT, and given I'm not a Cisco guy I'm not going to reconfigure one just to test things.
