Why are sit and tunnel4 modules loaded?

[Steve Snyder]

I recently starting using IPv6 networking on my Fedora8 machine.  This 
is native, not 6over4 tunneled, networking.  So why then am I getting 
the sit and tunnel4 kernel modules loaded?

I've got "NETWORKING_IPV6=yes" in /etc/sysconfig/network  
and "IPV6INIT=yes" in ifcfg-eth0.  No references to tunneling at all.

The only interfaces shown by ifconfig are lo and eth0 (which has both 
IPv4 and IPv6 addresses).  No sit[n] interfaces.

So why do I need to have these kernel modules loaded?

Thanks.