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

Protocols that work on the Network Layer include:

• IP (Internet Protocol) → IPv4 and IPv6 (main protocol for logical addressing & routing).
• ICMP (Internet Control Message Protocol) → used for error reporting and diagnostics (e.g., ping, traceroute).
• IGMP (Internet Group Management Protocol) → manages multicast group memberships.
• IPsec (Internet Protocol Security) → provides authentication and encryption at the network layer.