Which statement best describes the function of the application layer?

• A. Deals with encryption and data formatting
• B. Provides access to network resources
• C. Transmits raw bit streams
• D. Routes data between networks

Answer: (B)

The application layer is about giving end-user programs access to network services and resources. It provides the interfaces and protocols that applications use to request data, transfer files, send email, or look up names—think HTTP, FTP, SMTP, and DNS. The actual movement of raw bits, and the decisions about how to route those bits across networks, are handled by lower layers: transmitting raw bit streams is not the job of the application layer, and routing data between networks is handled by the network (routing) layer and routers. While some encryption or data formatting can involve higher-level protocols, the primary function of the application layer is to enable applications to access and use network resources. For example, a web browser uses HTTP at this layer to fetch web content, illustrating how applications gain access to remote resources.