What is a major drawback of using traditional IP routing over an ATM network when connecting multiple sites?

What is a major drawback of using traditional IP routing over an ATM network when connecting multiple sites?

A.
Each ATM switch in the path has to perform Layer 3 routing lookup.

B.
ATM virtual circuits have to be established between the different sites.

C.
There is high ATM management overhead between the ATM switch and the router at each site.

D.
Each ATM switch has to be manually configured to participate in Layer 3 routing.

E.
There is high PNNI overhead.-

Explanation:

Drawbacks of Traditional IP Forwarding IP over ATM
1) Layer 2 devices have no knowledge of Layer 3 routing information – virtual circuits must be manually established.
2) Layer 2 topology may be different from Layer 3 topology, resulting in suboprtimal paths and link use.
3) Even if the two topologies overlap, the hub-and-spoke topology is usually used because of easier management.