When it comes to networking, it can be helpful to have a conceptual understanding of the different types of connections required for data transfers. In order to troubleshoot network problems, promote interoperability among devices, and simplify the task of writing network protocols, a model was developed which provides an overall framework for understanding networking complexities. This model is known as the Open Systems Interconnection (OSI) model, and it is comprised of seven layers, each describing a different type of connectivity.
The seven layers of the OSI model are as follows:
1. Physical Layer: This includes the cable and wireless connections among devices, as well as specifications of the jacks, plugs, and voltages.
2. Data Link Layer: This layer provides the direct protocol connection between two nodes on a network and handles error connection from the physical layer.
3. Network Layer: This is the routing layer at which packets are forwarded from their source to their destination.
4. Transport Layer: This layer coordinates the transfer of data between systems and hosts by specifying such things as how much data to send and at what rate.
5. Session Layer: For two devices to transact specific functions between each other, a session is required, and this layer handles setting up sessions and coordinating the rules for communication.
6. Presentation Layer: At this layer, data is prepared for presentation between layers. For example, data that is encrypted across a network would be decrypted at this layer for presentation to an application at the destination device.
7. Application Layer: This is the layer at which applications are displayed to the end user.
While the OSI model can be quite complicated to remember, there are some memory tricks that can help. Here are a few examples:
– For remembering the layers from layer 1 to layer 7: Please Do Not Throw Sausage Pizza Away, Pew Dead Ninja Turtles Smell Particularly Awful, People Don’t Need to See Paula Abdul, Pete Doesn’t Need to Sell Pickles Anymore.
– For remembering the layers from layer 7 down to layer 1: Anchovy Pizza Should Tempt Nobody’s Delicate Palette, All Pros Search Top-Notch Donut Places, A Penguin Said That Nobody Drinks Pepsi, A Priest Saw Two Nuns Doing Push-Ups.
By understanding the seven layers of the OSI model and the different types of connectivity they describe, you can gain a deeper appreciation for the complexities of networking. And with a few helpful memory tricks, you can make sure you never forget the order of the layers again.