In which layer of the OSI model does routing primarily occur?

Routing primarily occurs in the Network Layer of the OSI model. This layer is responsible for determining the best path for data packets to travel from the source to the destination across multiple networks. It handles logical addressing (such as IP addresses) and routing protocols, which facilitate the movement of data between different networks. The Network Layer encapsulates packets and makes forwarding decisions based on the addresses in the packet headers, ensuring that data is routed through the most efficient paths in the interconnected network.

Other layers serve different functions: the Application Layer deals with end-user software interactions, the Transport Layer ensures reliable communication and data flow control between hosts, and the Data Link Layer manages node-to-node data transfer and physical addressing. While these layers support the overall process of data communication, it is specifically within the Network Layer where routing is fundamentally managed.