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This is how I understand Data Encapsulation

I tried to understand Data Encapsulation but failed to find stuff that easy to understand, maybe because I am a slow learner.
So, I have written this to gain understanding on this topic. Please help me correct this material in case there is error. Also pardon my shit english, it is my second language.
If you gain benefit from this, I am glad, thank you for reading.

Fundamental - OSI layer and PDU

OSI - 7 Layer (Physical, Data Link, Network, Transport, Session, Presentation, Application)

PDU - Protocol Data Unit, the model/control of the information on each layer. PSU are encapsulated by attaching them to the data at each layer.

Per OSI, 5th, 6th and 7th layer is considered application layer or upper layer.

1st, 2nd, 3rd and 4th layer are considered data flow layer.

For encapsulation, we want to look more at tne Data Flow layer. PDU on each layer are defines as follows:

  • Transport layer - Segment
  • Network layer - Packet
  • Data link layer - Frame
  • Physical layer- Bit


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Transport layer - TCP Encapsulation

When data come from the upper layer, it is then encapsulated in a "segment" with a segment header. The segment is then sequenced so that when it reach the destination, it can be put again in original state.

Network layer - IP header Encapsulation

Once the data is broken and segmented to be routed, it will again encapsulated in a "packet" with dedicated header. This header contains the address of the source and destination of host.
However, do note that in this layer, there are multiple protocol operating with different function.

Data Link layer - Mac header Encapsulation

Packet is now received and ready to be transferred over the wire/cable/wireless. It is then encapsulated in "frame" with MAC header of source and destination host address.

Physical Layer Encapsulation

Frame is now ready to go to the other end. Frame will be converted into digital signal. By OSI standard, Physical layer is responsible to encapsulate/digital encoding these frame in form of "bit" into digital signal.

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My Reference:
  1. http://www.idc-online.com/technical_references/pdfs/information_technology/Understanding_Data_Encapsulation.pdf
  2. https://en.wikipedia.org/wiki/OSI_model
  3. https://www.cs.clemson.edu/course/cpsc424/material/TCP-IP%20Networks/Packets%20and%20Encapsulation.pdf

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