The seven layers that power the internet


Date: 1 October 2012

Computer networks are complex things. But if you want to get beyond the ‘I plug it in and it works’ stage, it’s worth knowing a little about the Seven Layer OSI Model. It’s always good to have a bit of basic knowledge when dealing with IT suppliers too.

The Seven Layer OSI Model was created in the 1970s as an open standard for all networks and applications that exchange data. Since then, technology has changed a lot, so you will find that many books and articles on the subject contradict each other to some extent.

These days, it’s common for some of the layers to be blended together, but the principles of the Seven Layer Model do still stand.

How the Seven Layer OSI Model works

You can think of the seven layers in the Model as different stages of a production line. At each stage, something is done to the data passing through the network that gets it ready for the next. The seven layers are:

  • Application layer: interacts with your software to send or receive data.
  • Presentation layer: converts data into a standard format.
  • Session layer: starts, maintains and stops network communication.
  • Transport layer: makes sure all data reaches the right destination.
  • Network layer: routes data to the correct place.
  • Data layer: defines which how the data will be transmitted.
  • Physical layer: the network cables and signals that pass down them.

Why do we need the OSI Model?

The OSI model is one of those important things that sits behind everything on any network. It provides a structure so the internet can function. Without the OSI model it would have been nearly impossible to connect networks together. We just wouldn’t have the internet as we know it today.

It aims to break down all network communications into smaller elements that are easier to create standards around. With these standards in place any IT developer - especially those involved in networking – can work to the same framework.

This means that a developer working for Facebook doesn’t need to know how the physical network cabling is laid, nor how an ISP routes its data. As long as everything sticks to the OSI Model’s standards, it’ll work fine.

David Barker is technical director and founder of 4D Data Centres, the green colocation and connectivity supplier.

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