A. Internet protocol (IP)
B. UDP (User Datagram Protocol)
C. SMTP (Simple Mail Transfer Protocol)
D. HTTP (Hyper Text Transfer Protocol)

Solution

A. Internet protocol (IP)

Explanation

<p><span style="font-size: 14px;">Protocols that work on the Network Layer include:</span></p><ul><li><span style="font-size: 14px; background-color: rgb(255, 255, 0);">IP (Internet Protocol) → IPv4 and IPv6 (main protocol for logical addressing &amp; routing).</span></li><li><span style="letter-spacing: 0.01rem;">ICMP (Internet Control Message Protocol) → used for error reporting and diagnostics (e.g., ping, traceroute).</span></li><li><span style="letter-spacing: 0.01rem;">IGMP (Internet Group Management Protocol) → manages multicast group memberships.</span></li><li><span style="letter-spacing: 0.01rem;">IPsec (Internet Protocol Security) → provides authentication and encryption at the network layer.</span></li></ul>