You can also use ATM in Frame mode on the edge routers. In that case, a PVC is configured between the edge routers. The configuration on the router consists of an ATM subinterface with PVC. LDP is enabled on the subinterface with the command mpls ip. The ATM switches in this case are not MPLS-aware. The routers on the edge peer with each other—both for OSPF and LDP—instead of with the ATM switches. This is the overlay model. The label space used on the ATM subinterface is the platform-wide label space instead of the per-interface label space used on the LC-ATM interface. The configuration needed on the edge routers is shown in Example 5-26. A PVC is created between the edge ATM routers washington and brussels.