Explain the OSI 7 Layer of Networking Architecture with examples?

The Open Systems Interconnection (OSI) model is a categorical representation of how different network protocols interact and work with each other. It is divided into seven different layers. Here is a brief explanation of each:

  1. Physical Layer (Layer 1): This layer is responsible for the physical connection between devices. It defines the electrical/optical, mechanical, and functional interfaces to the physical medium, and carries the digital bit stream over a network. Include protocols like Ethernet, DSL, ISDN etc. Essentially, it's about the cables and hardware.

  2. Data Link Layer (Layer 2): This layer ensures reliable transit of data across a physical network link. It handles error detection and correction, provides framing, and allows control over the physical layer by deciding when transmission over the medium is possible. Examples include IEEE 802.3 (Ethernet), 802.11 (Wireless LAN) etc.

  3. Network Layer (Layer 3): This layer is in charge of network routing, transferring data from node to node, providing Quality of Service (QoS), and recognizing and forwarding to the transport layer. Protocols include IP (Internet Protocol), ICMP (Internet Control Message Protocol) etc.

  4. Transport Layer (Layer 4): Key responsibilities include end-to-end communication services for applications, provide services like connection-oriented communication, reliability, flow control, and multiplexing. Protocols such as TCP (Transmission Control Protocol) or UDP (User Datagram Protocol) reside in this layer.

  5. Session Layer (Layer 5): This layer is responsible for maintaining, managing and ending connections between applications. It coordinates conversation between systems, and manages the exchange of information. Protocols include NFS, NetBIOS, SQL.

  6. Presentation Layer (Layer 6): It ensures data is in a usable format and is where data is converted and encoded. It presents data and controls how data is sent and received. Protocols like SSL, TLS, JPEG, GIF, TIFF, etc. operate at this layer.

  7. Application Layer (Layer 7): The top of the hierarchy, the application layer provides an interface for the end user operating a device connected to a network. This layer interacts with software applications that implement a communicating component. Protocols like HTTP, POP3, SMTP, FTP, Telnet, SNMP work on this layer.

Each layer communicates with its counterpart on the other side, sending data downwards through the layers on one side and upwards on the other.

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