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OSI & TCP/IP Models

OSI Model

OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a telecommunications or networking system into seven distinct layers:

  1. Physical Layer: This layer deals with the physical medium and hardware aspects of data transmission, such as cables, switches, and electrical signals.

  2. Data Link Layer: Responsible for the reliable transmission of data over a physical medium, it handles tasks like addressing, error detection, and framing.

  3. Network Layer: Focuses on routing and forwarding data packets between different networks, often using logical addressing (like IP addresses).

  4. Transport Layer: Ensures end-to-end data transfer reliability and provides services like flow control, error detection and correction, and data segmentation.

  5. Session Layer: Manages the establishment, maintenance, and termination of communication sessions between devices, allowing for synchronization and organization of data exchange.

  6. Presentation Layer: Responsible for data translation, encryption, and compression, making sure data is in a format that can be understood by both sender and receiver.

  7. Application Layer: This is the topmost layer that interacts with end-user applications and provides network services like email, web browsing, and file transfer.

TCP/IP

TCP/IP (Transmission Control Protocol/Internet Protocol) is a generic term for many network protocols, which is not only refer to these two protocols but is usually used as a generic term for an entire protocol family. These protocols are responsible for the switching and transport of data packets on the Internet.

  1. Link: Places and retrieves packets on/from the network medium, regardless of format or method.

  2. Internet: Handles addressing, packaging, and routing of data packets.

  3. Transport : Manages sessions (TCP) and datagrams (UDP) for reliable communication.

  4. Application: Enables applications to use network services and defines data exchange protocols.

Packet Encapsulation

Packet encapsulation refers to the process of adding headers to data as it moves through different layers of a network protocol stack. In both the OSI model and TCP/IP model, data is progressively encapsulated as it moves from the top to the bottom layers for transmission and then decapsulated at the receiving end.

Images

But besides all explanations I think in this topic pictures are better explainers:

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