W2K router to divide bandwith?

I have a Windows 2000 Router with a 256K signal to the internet and sharing it with several networks, each with its own NIC.
I want to set how much bandwith each of the networks can use from that original 256k Link to the internet….

Subnet 1 -Max 64 K
Subnet 2 – Max 128 K

Etc…

How can I do this? Do I have to use QoS or this is not that complicated?