OSI Model | Networking for Hacking

 In this article, we gonna learn about the OSI Model. It is an important part of networking. Everything in our globe is based on the concept of the OSI Model. Hence, it is very necessary to understand it.

Let's start...

#OSI Model: OSI model stands for Open System Interconnections. This model is established by the ISO(International Organization for Standardization).

Now, let's understand why this model came into this field?, why we need it? But before that let's understand, what is an Open System??

OSI Model

    An open system is a system in which you can exchange data. For example, You have a laptop or computer and you wanna change some data from the other laptop or computer. If the data exchanges then the system is open system means you are capable of exchanging the data from outside the environment.

#Why do we need Communication Architecture??

    Let's understand via a Scenario, You are sending some data to another computer, At this time, you knew that you are sending data but how actually the data is going from one device to another at the physical level, we don't know at that time. To understand it we need communication architecture.

• Strategy for connecting host computers and other communication tools.
• Specifies the features required for data communication between devices.
• The structure of communication, therefore, defines the standard of communicating hosts.
• The editor formats the data in the manner defined by the communication structure and transfers it to the communication software program.
• Separating communication functions may add flexibility, for example, we do not need to modify all host software to include additional communication resources.

#OSI Reference Model

• The OSI Model is now regarded as the main Architectural Model for computer-aided communication.
• We say reference model because it was not actually used. But we refer to it to understand how networks work.
• The OSI model describes how information or data flows from application editors (such as spreadsheets) through a network (such as a phone) to another application program on another computer.
• The OSI reference model separates the problem of moving data from one device to another network location into SEVEN small and controllable Layers.
• This division of small manageable tasks is known as Layering.
• Every Layer has its own work that we gonna understand. 

Let's see the diagram of the OSI Model:

Let's understand each layer one by one...

#Application Layer:

• It is the top-most layer of the OSI Model.
• It provides the interface between users to communicate, for sending and receiving files, and to use network services like message handling, database query, etc.
• This layer is responsible for providing services to the users so that users can do their work.
• Examples of application layers are file transfer, electronic mail, etc.
• Protocols used in the application layer are FTP, DNS, DHCP, HTTP, HTTPS, TELNET, etc.

#Presentation Layer:

• In the current scenario, the application layer and the presentation layer is now mixed. This means we are using functions of both layers simultaneously.
• This layer manages the data format that has been shared between users for network communication.
• For outgoing messages, this layer converts the data into a generic format for network transmission. 
• For incoming messages, it converts the generic data format into the given format that the user can understand.
• This layer is responsible for certain process modification, data encryption / encryption or compression / compression data.
• A special software center called "redirect" works on this layer to determine if a request is network-related or not and to transfer network-related applications to the appropriate network device.

#Session Layer: 

• Allows two network applications to hold continuous communication (called a session) across the network (chat session).
• An application at any end of the session can exchange data during the session.
• This layer is responsible for initiating, maintaining, and finishing times.
• You are also responsible for the security and control of access to session information (by identifying the session participant).
• Responsible for synchronization services, as well as testing services.

Now, in the next article, we will understand the next 4 layers of the OSI Model. These 4 layers are very important so don't miss the article.

Previous Articles:

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1. Introduction to Networking 

2. Networking Devices

3. Transmission Media(Guided and Unguided)

4. Switching in Networking

5. OSI Model

6. OSI Model - Part 2

7. Functions of OSI Layers

8. TCP/IP Model

9. OSI vs TCP/IP

10. Internet Protocol(IP)

11. Internet Protocol Versions | Internet Versions Explained

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