Encapsulating Security Payload (ESP) is used to provide confidentiality by encrypting the IP payload, as well as integrity, and authentication of the IP packet. This is essential for secure VPN tunnels. Authentication Header (AH) only provides integrity and authentication of the IP packet but does not encrypt the data payload, thus it is not sufficient when confidentiality is required. RSA and ECC are cryptographic algorithms that are used for encryption or digital signatures but they are not protocols that would encapsulate IPv4 packets to provide the described functionality.