At what Open System Interconnect layer do network switches and bridges operate?

Network switches and bridges operate at the Data Link layer of the Open Systems Interconnection (OSI) model. The Data Link layer is responsible for node-to-node data transfer and error detection and correction. It ensures that data frames are properly delivered to the correct devices on a local area network (LAN).

Bridges are used to divide larger networks into smaller segments, reducing collision domains and improving performance. They function at the Data Link layer by analyzing the MAC (Media Access Control) addresses within the data frames to determine if they should be forwarded or filtered.

Switches enhance this functionality by allowing multiple devices to connect to a LAN and by creating point-to-point connections between device pairs, which further minimizes collisions. They operate similarly to bridges but with more advanced capabilities, enabling them to manage more data traffic efficiently.

The other layers mentioned have different functions: the Physical layer deals with the physical connections and transmission of raw bit streams over a medium; the Network layer is responsible for routing packets across different networks; and the Transport layer facilitates end-to-end communication, managing the delivery and error recovery of messages between devices. These roles clearly differentiate their operation from that of switches and bridges at the Data Link layer.