A network engineer must connect two sites across a public network using a secure tunneling technology that supports multicast traffic. Which technology must be chosen?

IPsec provides encryption and authentication but does not inherently support the encapsulation of multicast traffic.

GRE tunnels can encapsulate multicast traffic but lack native encryption and strong authentication, making them insecure for public network deployments without additional security layers.

PPTP (Point-to-Point Tunneling Protocol) is an older VPN protocol with known security vulnerabilities and is not recommended for secure site-to-site connections, nor does it robustly support multicast traffic.

GRE over IPsec combines the capabilities of both protocols: GRE encapsulates multicast traffic, which IPsec alone cannot do, and then IPsec provides secure encryption and authentication for the GRE tunnel. This ensures both the secure transmission of data over a public network and the proper handling of multicast traffic between sites.