What is a VPN and differentiate between IPsec tunnel mode, IPsec transport mode, and TLS VPN.

• A. TLS VPN uses TLS over SSH for remote access.
• B. VPN creates encrypted tunnel for remote access or site-to-site; IPsec tunnel mode encrypts entire IP packet; IPsec transport mode encrypts only the payload; TLS VPN uses TLS over TCP.
• C. IPsec tunnel mode encrypts only the payload; TLS VPN uses UDP.
• D. VPN is only for site-to-site connections and not remote access.

Answer: (B)

A VPN serves to create a secure, encrypted connection over an untrusted network so you can connect remotely or link separate networks as if they were directly connected. When you look at how different VPN technologies protect traffic, you see important differences in what they encrypt and where they operate.

IPsec in tunnel mode protects the entire IP packet. That means both the payload and the original IP header are wrapped and carried through the VPN tunnel, which is ideal for network-to-network links or remote access where you want to shield every bit of the original packet as it traverses the public network.

IPsec in transport mode, on the other hand, protects only the payload, leaving the IP header unencrypted. The header remains visible to routing devices along the path, making this mode suitable for end-to-end protection between two hosts on a shared trusted network rather than for gateway-to-gateway VPNs.

TLS VPN (often called SSL VPN) uses the TLS protocol over TCP to secure the connection. This approach is typically application-oriented, enabling remote access to specific applications or networks through a browser or TLS-enabled client, and benefits from the reliability and firewall/NAT traversal characteristics of TCP.

Putting these together, the description that a VPN creates an encrypted tunnel for remote access or site-to-site, that IPsec tunnel mode encrypts the entire IP packet, that IPsec transport mode encrypts only the payload, and that TLS VPN uses TLS over TCP, captures the distinct roles and protections of these technologies.