Which of the following is a common Application Layer protocol?

• A. HTTP
• B. IP
• C. TCP
• D. ICMP

Answer: (A)

At the Application Layer, protocols define how software applications exchange meaningful data. HTTP is a standard Application Layer protocol used for web client–server communication, describing how a browser requests resources and how a server returns them. It focuses on the semantics of web messages and relies on a transport protocol to actually move the data. Typically, HTTP runs over TCP, which provides reliable delivery and connection management, though HTTP/3 uses QUIC over UDP. The other options aren’t at the Application Layer: IP handles addressing and routing at the Network layer, TCP is a Transport Layer protocol that ensures reliable transfer, and ICMP is used for network diagnostics and error messages at the Network Layer. Because HTTP directly enables typical application-level data exchange between software entities over the network, it’s the common Application Layer protocol.