What is an "IPsec" tunnel?

An IPsec tunnel is a protocol suite specifically designed for securing Internet Protocol (IP) communications. It achieves this by encrypting and authenticating each IP packet within a communication session. The two main protocols that make up IPsec are the Authentication Header (AH) and the Encapsulating Security Payload (ESP), which provide various features such as data integrity, data confidentiality, and data origin authentication.

IPsec operates at the network layer and can be utilized for creating Virtual Private Networks (VPNs) in which data traffic is securely transmitted over potentially untrusted networks, such as the internet. By doing so, it ensures that sensitive information remains private and cannot be intercepted or altered during transmission. This makes IPsec a critical component for enterprises needing to maintain secure communications, particularly in scenarios involving remote access or connecting multiple sites securely.

The other options describe different concepts but do not correctly capture the essence of what an IPsec tunnel is focused on. Hence, the selection of the correct answer highlights the fundamental role of IPsec in securing communications over IP networks.