What does Internet Protocol Security (IPsec) primarily ensure during data transmission?

Internet Protocol Security (IPsec) primarily focuses on securing Internet Protocol communications by authenticating and encrypting each IP packet in a communication session. The primary goals of IPsec are to provide confidentiality, ensuring that data remains private during transmission, and integrity, ensuring that the data is not tampered with.

Packet authentication, which is given as the chosen answer, is a fundamental aspect of IPsec. It ensures that the data can be verified for authenticity, confirming that it comes from a trusted source and has not been altered in transit. This function helps prevent attacks such as man-in-the-middle, where an unauthorized entity could intercept and change data packets.

While data encryption is also a significant feature of IPsec, the emphasis on authentication in this context reflects the primary function of IPsec in assuring the identity of the data source and maintaining data integrity rather than just keeping data secret. User authorization and network device tracking are not inherent functions of IPsec but relate more to access control and network management strategies. Thus, the focus on packet authentication aligns closely with the core capabilities of IPsec in enhancing secure data transmission.