How to aggregate bandwidth from 2 DSL modems?

[Steve Westerhouse]

I have two DSL modems (each has same bandwidth) connected to my RedHat 7.1 Linux gateway.  There are 3 NICs in the system (1 LAN, 2 WAN).  How can I combine the bandwidth of both of these modems?  I have a feeling this can be accomplished using iptables in some way.  I understand that any given file transfer will not be able to exceed the bandwidth of an individual DSL modem.  The real advantage comes in when there are > 1 concurrent connections. I appreciate the help. Thanks!