partitioned into seven layers :

1. The Application Layer – responsible for interacting with the application software
2. The Presentation Layer – responsible for compression, encryption, and formatting of data being presented
3. The Session Layer – responsible for creating, managing, and ending a session’s communication
4. The Transport Layer – responsible for sequencing and delivery of data
5. The Network Layer – responsible for the addressing and routing of the network packets
6. The Data Link Layer – responsible for formatting the packet as per the medium of transmission of packets
7. The Physical Layer – responsible for defining the actual media and characteristics of the transmitted data

When we type a URL in the address bar of a browser, the data typically flows through the OSI protocol stack in the following way:

1. We type the URL in the browser’s address bar. The Application Layer interacts with the corresponding software application, the web browser. The browser makes an HTTP request to access the webpage from the web server. The data is passed through the next layer of the OSI model, the Presentation Layer.
2. The Presentation Layer is concerned with the actual format of data being presented. When the browser receives the data from the web server, the Presentation Layer presents it in a proper format, such as JPEG, MPEG, MOV, HTML, etc. This layer can also encrypt and compress the data.
3. The next layer of the OSI model is the Session Layer. This layer is responsible for creating, managing, and ending the session’s communication between the data sender and receiver. The Session Layer, the Presentation Layer, and the Application Layer are mainly responsible for composing the payload of a packet.
4. The Transport Layer deals with the sequencing and delivery of the data. It breaks the data into segments, sequences the segments, establishes a connection between the source and destination of the segments, and then sends those through the next layer of the OSI model. Please note that the Transport Layer is not concerned with managing and ending sessions. It only processes the connection between the sender and the receiver of the data.
5. The Network Layer is responsible for addressing and routing network packets. It deals with how the packets travel from one part of the network to the other. However, it is not concerned with whether the packets received are error-free. The Transport Layer takes care of that.
6. The Data Link Layer formats the packets according to the medium used for transmitting them—e.g., wireless medium, Ethernet connection, etc.
7. The Physical Layer does not change the actual data of the frames. It defines the actual media and characteristics of the transmitted data. The Physical Layer, the Data Link Layer, the Network Layer, and the Transport Layer are mainly responsible for composing the data headers.

The lineage of Packet Inspection