6Bone
6Bone was the name of an IPv6 test network.
Since Version 6 of the Internet Protocol was developed in 1995 , many universities, companies and private individuals have been testing IPv6 in their networks. Since most routers in the Internet did not yet forward IPv6 packets, the functionality was limited to the own network and IPv6 islands emerged in the Internet.
In order to still be able to send IPv6 packets from network A to network B, a tunnel was created between a computer on both networks. Every IPv6 packet that is to be sent to the other network was packed into an IPv4 packet by the tunnel mechanism and transported to the destination via IPv4. There it was unpacked again and passed on as an IPv6 packet.
The 6Bone was created by networking many such IPv6 islands.
According to RFC 3701 , the address prefix used by the 6Bone was returned to the IANA on June 6, 2006 (06/06/06), officially ending the operation of the 6bone.