7 Layers Of Network – OSI Model Explained

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Today we will talk about Network Layers in a very simple language. These seven layers are logical representations of a network, which basically designed for troubleshooting network problems. After reading this article, you will have a clear idea of these layers. Let’s Begin…

7. Application Layer


The application layer directly interacts with User. You can think about your Internet Browsers or any application which takes data from the user and send it over the network. It can be your Email clients also (e.g. Outlook). Suppose that your browser is corrupted and you are not able to connect to a web app, then we can say that the problem is at Application Layer aka User Level.

6. Presentation Layer

Operating Systems
Operating Systems

Yes, you got it. It is clear from the picture that this layer is related to the Operating System. This includes all the network configurations at the OS level. It is generally taken care of by OS only. Just suppose you are able to access a web application in one OS e.g. Windows Server 2012 but the same is not working in another OS e.g. Windows Server 2008, then there might be a problem at OS configuration level aka at Presentation Layer.

5. Session Layer

session layer picture
Session Timed Out Scenario

As demonstrated by the picture itself. This layer is related to your sessions when you log into a website. Just imagine you are logged in to your banking website, due to being idle for few minutes, you are redirected to login page due to session timed out issue. So in this case, you have to login again to create the new session with the banking server. So this logical layer helps us to troubleshoot session related problems in a network.

4. Transport Layer

Transport Layer
Transport Layer Representation

The Transport Layer collects message segments from applications and transmits them into the network (Layer 3). This layer ensures the delivery of messages from one endpoint to another through popular TCP and UDP protocol, which we will cover in a separate topic.

3. Network Layer

network layer routers
Network Layer

The Network Layer is related to our routers. A Router is a networking device that forwards data packets between computer networks. So basically routers operate at the Network layer. It means all your IP addresses are at the network layer. If your router has some problem then we can say that the problem is at the third layer the Network Layer.

2. Data Link Layer

network switches
Network Switches

Data Link Layer is the layer that switches operates on. As you know that all the computers in a network are connected to each other with a switch so that they can talk to each other, which happens on the Data Link Layer.

1. Physical Layer

network cable
network cable

The Physical layer is all the physical stuff that connects a computer to the network. This includes all the cabling etc. If your cable is not connected to your computer or damaged, then we can say that it is Layer 1 problem the Physical Layer problem.

Reference Video is here.

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