Which layer is responsible for routing packets across networks in the OSI model?

The Network layer is responsible for routing packets across networks in the OSI model. This layer manages the delivery of packets between devices across different networks and is crucial for establishing logical addressing, which allows devices to communicate with each other regardless of their physical location.

At this layer, routing protocols like IP (Internet Protocol) function to determine the best path for data to travel from the source to the destination through various interconnected networks. The Network layer encapsulates data received from the Transport layer into packets, adding necessary headers that include source and destination IP addresses.

In contrast, the other layers have distinct responsibilities: the Physical layer deals with the physical transmission of raw bit streams over a medium, the Data Link layer provides node-to-node data transfer and handles error correction, and the Transport layer is focused on end-to-end communication and flow control of data, ensuring complete data transfer without errors. Thus, the crucial role of routing is uniquely fulfilled by the Network layer.