Which term refers to the use of unique identifiers that distinguish processes on a system in the Transport Layer?

The correct term that refers to the use of unique identifiers distinguishing processes on a system in the Transport Layer is port numbering. In the Transport Layer of the OSI model, port numbers are crucial because they allow multiple applications to communicate over the same network interface. Each process or application running on a device is assigned a specific port number, which acts as a communication endpoint.

Port numbering facilitates various services to run simultaneously without interference. For instance, when a web browser requests a webpage, it typically uses port 80 for HTTP, while secure web traffic often uses port 443 for HTTPS. This way, the Transport Layer can direct incoming data to the appropriate application based on the specified port number, ensuring that each process receives the correct data packets.

The other choices refer to different aspects of networking. IP addressing pertains to identifying devices on a network layer, socket addressing combines an IP address with a port number but is not used explicitly to refer to unique identifiers for processes, and domain naming relates to human-readable addresses used for locating resources on the internet. Hence, port numbering is the most accurate term for the unique identifiers in the Transport Layer context.