Transport layer

There are two transport protocols in Layer 4 of the OSI layer model: TCP and UDP. The TCP Protocol represents a connection-oriented transmission while the UDP Protocol implements a connectionless transmission. Both protocols divide the data that are to be transmitted into smaller parts. These divided-up data are called segments in TCP and datagrams in UDP.

Because the transport protocols use either connection-oriented transmission or connectionless transmission, they are suitable for different uses. TCP-only, UDP-only, or a combination of the two protocols may be used, depending on the requirements for security and transmission speed.

Addressing

To reach the desired destination node, data are transmitted via the Internet Protocol (IP) on the underlying layer (Layer 3). Ports that allow addressing of functions and applications are used to connect to the higher layers. If a port is opened, data can be exchanged with the associated function or application.