Definition and usages of OSI 7 Models

참고 링크
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Open Systems Interconnection Model

• Standardized 7 stages of communication functions of a telecommunication or computing system

What for?

1. To track the flow of data transmission Encapsulation : Each time data passes through each layer, a header is added. It makes the data transmitted in a set order regardless of the data type.
2. To find the source of a problem faster (e.g. Ping)
3. To enhance compatibility between networking hardwares

Let's dive into the each layer

1. Physical Layer

• Transfers binary data using physical cable. (e.g. cabels and hubs)
• Electrical on/off
• Forwards data without any involvement in what the data is, what errors are present, etc.

2. Data Link Layer

• Divided as Media Access Control sub-layer and Logical Link Control sub-layer.
• MAC sub-layer controls authorization of data access and transmission. (MAC address)
• LLC sub-layer cheks physical data transmission errors.

3. Network Layer

• addresses using IP, the logical address.
• selects the safest and fastest path selection to the destination.
• forwards data packet.

⇒ Routing

4. Transport Layer

• delivers data across network connections by transport protocols. (TCP, UDP)
• Transport protocols support error recovery, flow control, and support for re-transmission.

References

• https://iebmedia.com/technology/looking-behind-the-automation-protocols/
• https://www.electronicdesign.com/unused/article/21800810/whats-the-difference-between-the-osi-sevenlayer-network-model-and-tcpip
• https://www.lifewire.com/layers-of-the-osi-model-illustrated-818017