Two IPv6 Hosts Communicating over IPv4 network

Dear all,

I would like to have two hosts, which run IPv6 application on Linux,
communicate each other across a commercial network. But there is no IPv6
support in the commercial network.

I guess IPv6/ICMPv6 packets must be converted to IPv4/ICMPv4 packets in host
b4 they enter the IPv4 network. Likewise, IPv4/ICMPv4 shall be converted
back to IPv6/ICMPv6 once they reach the destination IPv6 host. I have a few
questions as follows.

1) Has such work been implemented in Linux or other OS?
2) If no, which RFC or draft addressing this issue?
3) Does my scenario need to touch 6Bone, since only two IPv6 hosts are
involved?
4) Anything else need to be done apart from conversion of IP/ICMP?

Any suggestion and comment are highly appreciated.

Best regards,
Zhigao