The OSI (Open Systems Interconnection) reference model is a conceptual framework used to understand and implement network communications between different systems. It divides the networking process into seven distinct layers, each with its specific functions. The OSI model is crucial for guiding the design and development of network protocols and services, ensuring that different systems can communicate effectively, even if they use different hardware or software.
- Physical Layer : Deals with the physical connection between devices, including the transmission of raw data bits over a physical medium (like cables, switches, and network interfaces).Examples: Ethernet cables, fiber optics, hubs, repeaters.
- Data Link Layer : Ensures reliable data transfer across the physical link, managing errors in the physical layer, and controlling how data is placed on the medium. It also handles MAC (Media Access Control) addressing.Examples: Switches, bridges, MAC addresses, ARP (Address Resolution Protocol).
- Network Layer : Manages the routing of data between devices on different networks, handling logical addressing, path determination, and packet forwarding.Examples: Routers, IP addresses, ICMP (Internet Control Message Protocol), IP (Internet Protocol).
- Transport Layer : Ensures complete data transfer by providing end-to-end communication services, including error recovery, flow control, and segmentation of data.Examples: TCP (Transmission Control Protocol), UDP (User Datagram Protocol).
- Session Layer : Manages sessions or connections between applications, controlling dialogues (connections) between computers, establishing, maintaining, and terminating the connections.Examples: NetBIOS, RPC (Remote Procedure Call), session management protocols.
- Presentation Layer : Translates data between the application layer and the network format, handling data encryption, decryption, compression, and translation.Examples: SSL/TLS (Secure Sockets Layer/Transport Layer Security), encryption, JPEG, ASCII, EBCDIC.
- Application Layer : Provides network services directly to the user's applications, facilitating user interface and interaction with the network.Examples: HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), DNS (Domain Name System).
