Transport layer, focuses on delivering messages to the host. The Transport layer allows applications and services to run faster because upstream processes do not have to take into account the unique characteristics of each device's communications network. This layer is the basis for the UDP and TCP protocols, which we'll get to shortly.
Session level
The transport layer doesn't care whether two computers have already established a connection - it just focuses on sending packets back and forth. The session layer organizes traffic into a logical beginning and end.
Presentation level
The volume of these data packets can be very large. The presentation greece telegram data layer mainly focuses on encoding and compressing these packets to reduce bandwidth requirements before they leave the sender's device.
Application layer
Finally, this received data (or data to be sent) must be transmitted to the user. While OSI is a useful model, keep in mind that no modern protocol follows its exact outlines at all seven layers. For example, TCP and UDP protocols focus only on the network and transport layers.
What is TCP
The Transport Control Protocol was essentially the first network protocol. Invented shortly after the Internet was born in 1981, its first form focused on segmenting data into packets. Over the decades, it has grown to become the TCPIP stack that is today's standard. Packets in TCP are divided into four layers: data link, network, transport, and application.