Which two layers of the OSI reference model are combined in the TCP/IP model's Network Access Layer?

The TCP/IP model's Network Access Layer encompasses both the Data Link Layer and the Physical Layer from the OSI reference model. This layer is responsible for the physical transmission of data over the network medium as well as providing the necessary layered functionalities to manage how data packets are prepared for the transmission, which includes framing, addressing, and error detection.

The Data Link Layer in the OSI model handles protocols for data transfer between adjacent network nodes, ensuring that data is packaged into frames and manages node-to-node connections. The Physical Layer takes care of the actual hardware transmission of raw bits over the physical medium, which could be electrical signals, light pulses, or radio waves.

In the TCP/IP model, these two layers are combined to streamline the model by focusing on the practical implementation of networking, which includes both framing the data for transmission and the actual transmission itself over the selected physical medium. This combination reflects a more simplified approach compared to the OSI model, embodying the essential functionalities needed to establish network communication effectively.