How to use two WAN connections at once?

[Frank Wille <frank%phoenix.owl.de@localhost>]

Hi,

I have two WAN connections (e.g. ADSL), which I both want to use transparently
from my LAN. A kind of load-balancing would be nice, because the first WAN
port is slower than the second, but more stable.

Is that possible with ipfilter or pf? How would I do that?

Can I give the two connections a different weight, e.g. use the first WAN
port for 20% of all packets and the second for the remaining 80%?

Or is it even possible to route the packets always to the WAN port which
has more bandwidth left?

Regards,

-- 
Frank Wille