What does the Transport Layer do in the OSI model?

The Transport Layer of the OSI model is primarily responsible for the reliable delivery of data across a network and plays a crucial role in ensuring that data packets are sent to the correct application on a host device. One of the key functionalities of the Transport Layer is the use of port numbers, which act as identifiers for specific processes or applications that are running on a device. When a packet arrives, the Transport Layer examines the destination port number included in the packet header to determine which application should receive the data, ensuring that it is delivered accurately to the intended service, such as a web server or an email client. This capability facilitates communication between different applications and services over the network, establishing connections and managing data flow effectively.

This understanding of how the Transport Layer utilizes port numbers to route packets is essential for comprehending network communication and application networking protocols, which play a significant role in cybersecurity and network management, central themes in the GSEC certification curriculum.