The Open Systems Interconnection model or OSI model is that standardizes each of the functions of data transformation by breaking it down into layers. Well why is the OSI model important in order to better understand packet analysis.
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Explore the OSI model
You must understand the way the data is prepared for transit the OSI model is a seven layer representation of how data changes in form as each layer provides services to the next layer and in particular how data is encapsulated as it is prepared for transit. The OSI model was proposed by the International Organisation for Standardization or ISO. It’s a common framework for developers and networking students for better understanding reference models and standards. Both enable interoperability among layers and communicating devices.
Now we can look at the seven layer OSI model starting at the top end Layer 7 is the application layer where we initiate contact with the network layer 6 the presentation layer, layer 5 the session layer layer for the transport layer, layer 3 the network layer layer to the datalink layer, and layer one the physical layer. There are two phrases that you can use to remember the first letter of each of the layers from Layer 7 to layer 1. The phrase is All people seem to need data processing. From layer 1 to Layer 7. PLEASE DO NOT THROW sausage pizza away.
How the encapsulation process
Now that we know the layers. Let’s take a look at them and how the encapsulation process works together. We’ll take a look at the layer itself. The PDU or protocol data unit. And then we’ll look at the header information in form of what address is used and the top three layers. The application presentation and session layers. The protocol data unit is simply data. Nothing has changed. It’s just in data format. There is no address but then it readies itself so that it can communicate to the next layer. The transport layer at the transport layer.
The protocol data unit is a segment. Now with this layer does is add a transport layer header which could include the source and destination port address the court address associates us with an application for example port 80 is associated with HTTP at the network layer. The protocol data unit is a packet and the network layer header is an IP address which includes the source and destination IP address of the host. The datalink layer at the datalink layer. The protocol data unit is a frame. At this layer source and destination MAC address is added and the physical layer the protocol data unit is simply bits. There is no address and the physical layer is the way the data is transmitted across the media.
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