Final answer:
NETCONF is the southbound API that uses XML and RPCs to configure network devices, allowing for the management of network configuration data.
Step-by-step explanation:
The southbound API that uses XML and RPCs (Remote Procedure Calls) to configure network devices is NETCONF (Network Configuration Protocol). NETCONF provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses XML as the data encoding format for the configuration data as well as the protocol messages. The protocol allows for a network management system to interact with the configuration data of network devices.