Which of the following protocols is commonly used in the Session Layer?

The Session Layer, which is the fifth layer of the OSI model, is responsible for establishing, managing, and terminating sessions between applications. Advanced Program-to-Program Communications (APPC) is specifically designed for communication between programs in different computers. It operates at the Session Layer and facilitates the management of sessions, ensuring proper dialog control, synchronization, and data exchange.

APPC allows different systems to communicate by establishing a session between them, making it suitable for managing connections and maintaining communication sessions as required in a multi-user environment. This characteristic is essential in many enterprise contexts where multiple applications need to coordinate communication reliably and efficiently.

The other protocols listed serve different purposes: Internet Protocol (IP) operates at the Network Layer, enabling routing of packets across networks; Transmission Control Protocol (TCP) functions at the Transport Layer, providing reliable data transmission and ensuring ordered delivery; and File Transfer Protocol (FTP), while it does operate at a higher level to facilitate file transfers, primarily functions at the Application Layer.