A cloud administrator wants to make a web application on the company's private cloud available to multiple remote sites. Which of the following protocols BEST provides IP packet encapsulation?

L2TP (Layer 2 Tunneling Protocol) primarily encapsulates Layer 2 frames (like PPP) rather than directly encapsulating IP packets as its main function for routing, and it typically requires IPsec for encryption.

Generic Routing Encapsulation (GRE) is a tunneling protocol that encapsulates a variety of network layer protocols, including IP, within IP packets. This makes it an effective solution for creating direct connections between remote sites and a private cloud, enabling IP packet transmission over a public network.

PPTP (Point-to-Point Tunneling Protocol) is an older and less secure VPN protocol, primarily encapsulating PPP frames, and is generally not recommended for modern secure connectivity due to known vulnerabilities.

SIP (Session Initiation Protocol) is a signaling protocol used for establishing, managing, and terminating real-time communication sessions (e.g., VoIP), and it does not provide IP packet encapsulation for network connectivity.