Which layer of the OSI model uses port numbers for communication?

The Transport Layer is responsible for end-to-end communication and data flow management in the OSI model. One of its key functions is to facilitate the establishment of connections between different applications running on devices across a network. Port numbers play a crucial role in this process, as they allow multiple applications on a single device to communicate over the same network connection.

When data is sent from one application to another, the Transport Layer uses these port numbers to ensure that the data is directed to the correct application process. For instance, when a web server communicates with a web browser, it typically uses port 80 for HTTP or port 443 for HTTPS. The Transport Layer protocols, such as TCP (Transmission Control Protocol) and UDP (User Datagram Protocol), utilize these port numbers to manage the transmission of data streams, ensuring that messages are delivered to the appropriate application.

In contrast, other layers of the OSI model have different responsibilities. The Application Layer deals with the end-user interface and application-specific functions, while the Network Layer handles routing and packet forwarding without focusing on application specifics. The Data Link Layer is concerned with the physical transmission of data over a medium and does not involve port numbers. Thus, the Transport Layer distinctly utilizes port numbers for communication, solidifying its essential