How the OSI Model is Used in Creating a Network Connection

Do you ever wonder what is driving the magical force behind your phone or computer that allows it to connect to the internet or communicate with other devices? All of the devices used today are constantly sending and receiving information. But how do these devices translate the sequence of taps by your fingertips to send and receive this information through thin air without getting it all jumbled up?

Luckily, a tool was developed in 1984 to internationally standardize the way humans send and receive information through our networks. This allows different softwares, devices and applications to securely and systematically communicate by following the same protocols. This protocol is called the Open Systems Interconnection Model (OSI) and is categorized into 7 layers. The majority of network vendors use this model and as new standards emerge they are placed into one of the seven layers. To explain this model, I am going to use a simple example almost everyone has performed: visiting a website on their personal computer.

Beginning with the highest layer of the OSI model is layer 7, the application layer. An example of one of these applications would be the http application, which is the protocol websites such as Facebook use to connect the software your computer is running, to the server or computer a website stores their files in. These file transfers create the text, graphics, image, audio, multimedia, or video you see when you open up your browser and connect to a website on your personal computer.

Next is layer 6, the presentation layer. The data these files contain are translated to a format that both computers can read. At the presentation layer, both your computer and the website’s server computer send and receive data to one another. As your mouse clicks on a link, your computer software sends a specific code which is translated in the presentation layer so the website server can load the requested information. All of this happens behind your screen without you having to understand how the data is structured or stored.

Layer 5, the session layer, is responsible for establishing, terminating, and monitoring communication sessions between applications. An example would be when you log onto or exit your web page by clicking the X in the upper right hand corner. You might notice certain websites like your bank’s website will log you out if your session has been inactive longer than a certain time period.

Layer 4, the transport layer, verifies that the application transmitting the data is actually allowed to access the network. Some websites also have tools that encrypt your messages in the transport layer to protect its privacy through a secure connection.

Layer 3, the network layer is operated by network routers. This also includes the modem you have in your home such usually installed by your service provider. With an IP address you can decide which traffic goes through your network. Your router indicates which devices can receive and process this data when you choose who can have your wifi password.

Layer 2, The Data-link layer receives packets from the network layer and structures these packets into frames. The frames are then moved to the Physical layer for sending. This is the format used to encapsulate the data. Here your modem and router are decoding the wifi signals from your computer into a form that can be transmitted to the physical layer.

Layer 1 is the physical layer by which the data travels through the physical medium. In this example, it would be the ethernet cable. Here the data is transmitted as 0s and 1s by light pulses powered through electricity.

Basically, each of these layers can both send and receive data. The website you visit sends and receives data through its server that is connected the internet and physical layer the same way your computer is. When you are in range of your router and are connected to your wifi, these messages are transported through the air as radio waves.

It’s important to understand how your device and the websites or apps you visit handle, store, and transport your data. Millions of people trust their messages or other sensitive information being sent across this network. Thankfully websites and other applications are always trying to stay up to date and advance their security protocols as technology continues to evolve and advance. Some websites have added security protocols to ensure your information stays confidential. However, it’s also important that you are extra careful with which sites you visit while using a public wifi service such as the kind offered at certain coffee shops. When you visit a website that isn’t secured, a hacker using the same wifi could steal your information.

 

References:

http://www.tech-faq.com/osi-model.html

https://www.lifewire.com/open-systems-interconnection-model-816290

 

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