Connect a CSU/DSU Modem to a Cisco2600

I have a CSU/DSU modem from Tainet and would like to connect one end of it to a Cisco 2600 Router and controll available bandwidth to the Modem.

I currently run a mission critical ervice on the LAN network and would thus prefer to limit bandwidthto the Serial network. My uplink is via a frame-relay network.