Data Flow and Encapsulation in OSI Layer
OSI (Open Systems Interconnection) is reference model for how applications can communicate over a network. A reference model is a conceptual framework for understanding relationships. The purpose of the OSI reference model is to guide vendors and developers so the digital communication products and software programs they create will interoperate, and to facilitate clear comparisons among communications tools.
Layer-7: Application Layer
Data flow occurs when two devices are connected in a network with some kind of shared transmission medium. An application running on the source device creates some kind of data. This happens at the Application layer.
Layer-6: Presentation Layer
In our case the application needs to add encryption to that data. This will be done at the Presentation layer.
Layer-5: Session Layer
At the Session layer it appends the Session ID. At this point the information is still one block of data.
Layer-4 : Transport Layer
Next, data goes down to the Transport layer. The Transport layer breaks the data into blocks of data which we call Segments. Every Segment also gets the Port number to identify which upper layer application needs to receive the data on the destination device
Layer-3: Netowrk Layer
The Segment is then passed to the Network layer. The Network layer takes the Segment, which includes the Port number, and appends the source and destination IP address. At that point the Segment becomes a Packet.
Layer-2: Data Link Layer
The Packet is then passed to the Data Link layer where the source and destination MAC address and the CRC is added. At this point we have a Frame.
Layer-1: Physical Layer
The Frame then is sent to the physical device where it is translated into some kind of a signal, whether it's electrical, radio wave, light or other signal. This Frame then becomes some kind of a signal that represents a series of zeros and ones. This is why at the Physical layer we often call it Bits. The Network Interface Card (NIC) prepares those signals and sends it out on the transmission medium.
OSI Encapsulation and Layers :
One important piece of information to keep in mind is that data flows 2 ways in the OSI model, DOWN (data encapsulation) and UP (data decapsulation).
The picture below is an example of a simple data transfer between 2 computers and shows how the data is encapsulated and decapsulated.
OSI (Open Systems Interconnection) is reference model for how applications can communicate over a network. A reference model is a conceptual framework for understanding relationships. The purpose of the OSI reference model is to guide vendors and developers so the digital communication products and software programs they create will interoperate, and to facilitate clear comparisons among communications tools.
Layer-7: Application Layer Data flow occurs when two devices are connected in a network with some kind of shared transmission medium. An application running on the source device creates some kind of data. This happens at the Application layer.
Layer-6: Presentation Layer
In our case the application needs to add encryption to that data. This will be done at the Presentation layer.
At the Session layer it appends the Session ID. At this point the information is still one block of data.
Next, data goes down to the Transport layer. The Transport layer breaks the data into blocks of data which we call Segments. Every Segment also gets the Port number to identify which upper layer application needs to receive the data on the destination device
The Segment is then passed to the Network layer. The Network layer takes the Segment, which includes the Port number, and appends the source and destination IP address. At that point the Segment becomes a Packet.
The Packet is then passed to the Data Link layer where the source and destination MAC address and the CRC is added. At this point we have a Frame.
The Frame then is sent to the physical device where it is translated into some kind of a signal, whether it's electrical, radio wave, light or other signal. This Frame then becomes some kind of a signal that represents a series of zeros and ones. This is why at the Physical layer we often call it Bits. The Network Interface Card (NIC) prepares those signals and sends it out on the transmission medium.
OSI Encapsulation and Layers :
One important piece of information to keep in mind is that data flows 2 ways in the OSI model, DOWN (data encapsulation) and UP (data decapsulation).
The picture below is an example of a simple data transfer between 2 computers and shows how the data is encapsulated and decapsulated.
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