What does the Internet Layer primarily do?

The Internet Layer primarily focuses on the delivery of packets from the source to the destination across various networks. Its main functions include adding IP addresses to packets, which is essential for identifying the source and destination of the data being transmitted. By utilizing these IP addresses, the Internet Layer can determine the most efficient routing path for the packets as they travel through interconnected networks.

This layer operates independently of the data link layer, which handles physical data transmission, and the transport layer, which manages end-to-end communication and data integrity. The Internet Layer's ability to route packets across different networks is crucial for the functioning of the Internet, as it allows multiple devices with potentially different underlying network technologies to communicate seamlessly.

Other options do not accurately describe the primary functions of the Internet Layer. For instance, handling physical data transmission pertains to lower layers of the network stack, such as the Physical and Data Link Layers. Encrypting data for secure transmission is generally the responsibility of higher-level protocols like TLS (Transport Layer Security) and not the Internet Layer. Lastly, providing a user interface for network access typically involves application layer protocols and not the Internet Layer.