What is the primary function of Layer 3 in the OSI model?

Layer 3 of the OSI model, known as the Network Layer, is responsible for logical addressing. This means that it provides a way to identify devices on a network uniquely using IP addresses. The use of logical addressing enables routers to make decisions about where to forward packets across different networks based on these addresses.

In practical terms, when a device needs to communicate with another device that is not on the same local network, it relies on Layer 3 routing. Here, the IP address indicates both the network to which the device belongs and the specific device within that network. This logical addressing is a key part of how devices on the internet find each other and communicate effectively, facilitating the routing process across multiple networks.

The other options focus on functions that are attributed to different layers of the OSI model. For instance, physical connectivity refers to Layer 1 (Physical Layer), which deals with the transmission and reception of raw bitstreams over a physical medium. Data correctness deals with error detection and correction mechanisms, which fall under Layer 2 (Data Link Layer). Session management is a function of Layer 5 (Session Layer), which is responsible for establishing, managing, and terminating connections between applications.