Network Topology with the Iu-BC Interface

The external CBC supports only Iu-BC over IP. Therefore, switching from TCP/IP to IP over ATM (IPoA) must be  performed if the ATM transmission mode is used on the Iu-BC interface.
Networking solutions are different in Iu-BC over IP mode and in Iu-BC over ATM mode.

The below fig describes the networking solution in Iu-BC over IP mode: