Another method is to either use AYIYA or TSP, both of which send IPv6 inside UDP packets, which is able to cross most NAT setups and even firewalls.
This can be done using the tunnel broker's web site or using an automated protocol like TSP or Heartbeat, as used by AICCU.
It was started as a project of Viagenie and then Hexago was spun off as a commercial company selling Gateway6, which powered Freenet6, as their flagship product.
In June 2009, Hexago became gogo6 through a management buyout and the Freenet6 service became part of gogoNET, a social network for IPv6 professionals.
It is custom built software for the purpose of tunneling at high performance with low latency.
[4][failed verification] Due to scalability issues and other problems sixxsd was designed and developed.
CITC Tunnel Broker, run by the Saudi Arabia IPv6 Task Force, uses their own implementation of the TSP RFC named 'ddtb'.