Which layer of the OSI model is responsible for routing?

The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven distinct layers. Each layer has specific responsibilities. Routing, the process of selecting a path for data packets across different networks, is the primary responsibility of the Network Layer (Layer 3).

• The Physical Layer (A) (Layer 1) deals with the physical transmission of raw bit streams over a physical medium, such as cables or wireless signals. It is concerned with hardware specifications and electrical signals, not routing decisions.
• The Data Link Layer (B) (Layer 2) handles frame transmission between adjacent network nodes and error detection/correction within a single network segment. Devices like switches operate at this layer.
• The Transport Layer (D) (Layer 4) provides end-to-end communication between applications, managing segmentation, reassembly, and flow control (e.g., TCP, UDP). It ensures reliable data delivery but does not handle inter-network routing.

Thus, the Network Layer is correctly identified as responsible for routing.