I have a private internal network with two seperate internet connections and i want to setup a server that would act as a gateway/firewall with NAT&PAT and enable NIC bonding on it.

Now I need your much appriciated help on three questions.

What would be the perfect distro for this problem? Some network/security oriented one please.

Is there any open source solution which I could implement on that gateway server that would monitor user bandwidth consumption from the internal network and slow their speed if they reach a certain limit?

The two internet connections are ADSL and cable, ADSL has a max limit of 9GB and cable has a limit of 12GB. Is it possible with or without NIC bonding to setup the server so it has load balancing but doesn`t use each connection over its limit?

Any suggestions are welcome, ty

NIC bonding is the feature given by driver not OS.so any OS wud be fine..