Which two header components are used in ATM virtual circuits (VC) to switch cells across networks?

The Virtual Path Identifier (VPI) and Virtual Channel Identifier (VCI) are essential components in the header of cells used in Asynchronous Transfer Mode (ATM) networks. The VPI and VCI work together to identify and route the information across the network.

The VPI is used to identify a specific virtual path, which is essentially a bundle of virtual channels sharing the same physical path. This allows multiple streams of data to be effectively managed over a single connection. On the other hand, the VCI identifies individual virtual channels within that virtual path, ensuring that the ATM cell reaches its intended specific endpoint.

By utilizing both the VPI and the VCI, ATM is able to effectively manage and switch cells in a scalable manner, ensuring that data flows efficiently across the network and that cells are delivered to the correct destination without confusion.

The other choices do not provide the necessary mechanisms for switching cells in ATM. Addresses and other components mentioned are not specific to virtual circuit management as required in ATM technology, thus demonstrating why the selection of VPI and VCI as header components is critical for ATM operations.