Hypertext Transfer Protocol (HTTP) is the application-layer protocol that forms the foundation of data communication for the World Wide Web. It defines the specific rules and formats for how messages are exchanged between a client, such as a web browser, and a web server. When a user enters a URL, the browser sends an HTTP request (e.g., GET) to the server, which then responds with the requested resource (e.g., an HTML page). While HTTP relies on TCP for reliable transport, HTTP itself is the protocol that governs the web communication logic.

A. ICMP: Used for network-layer diagnostics and error reporting (e.g., ping), not for transferring application data like web pages.

B. TCP: A transport-layer protocol that provides reliable, connection-oriented data delivery. HTTP uses TCP, but TCP is not the application protocol for web requests.

C. UDP: A transport-layer protocol providing connectionless, unreliable data delivery, unsuitable for the reliable transfer of web content required by standard browsing.

1. Odom, W. (2019). CCNA 200-301 Official Cert Guide, Volume 1. Cisco Press. Chapter 2, "Fundamentals of TCP/IP Transport and Applications," section "Common TCP/IP Applications," Table 2-3 lists HTTP as the primary protocol for web browsing.

2. Fielding, R., et al. (2014). RFC 7230: Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing. Internet Engineering Task Force (IETF). Section 2.1, "Client/Server Messaging," states, "The Hypertext Transfer Protocol (HTTP) is a stateless request/response protocol... for distributed, collaborative, hypermedia information systems."

3. Kurose, J. F., & Ross, K. W. (2017). Computer Networking: A Top-Down Approach (7th ed.). Pearson. Chapter 2, "Application Layer," Section 2.2, "The Web and HTTP," provides a detailed overview of HTTP as the Web's application-layer protocol.