NetworkModels

• The OSI model uses seven different layers, which are hierarchically based on each other to achieve this goal.
• The TCP/IP model is also a layered reference model, often referred to as the Internet Protocol Suite.

In a layered system, devices in a layer exchange data in a different format called a protocol data unit (PDU).
When an application sends a packet to the other system, the system works the layers shown above from layer 7 down to layer 1, and the receiving system unpacks the received packet from layer 1 up to layer 7.

During the transmission, each layer adds a header to the PDU from the upper layer, which controls and identifies the packet. This process is called encapsulation. The header and the data together form the PDU for the next layer. The process continues to the Physical Layer or Network Layer, where the data is transmitted to the receiver. The receiver reverses the process and unpacks the data on each layer with the header information.

It is useful to understand and familiarize with both reference models.