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OSI Model Layers - Markdown

The OSI Reference Model (Open Systems Interconnection Reference Model) is a 7-layer reference model for computer network communication defined by ISO/IEC 7498-1, originally established by the International Organization for Standardization (ISO) in 1984 and revised in 1994. It provides a common framework for ensuring interoperability between different systems, defining communication protocols across seven hierarchical layers from the Physical Layer to the Application Layer. It is widely used as a foundation for network design, troubleshooting, and education.

OSI Model ISO Standard Networking Protocol Communication Model ISO/IEC 7498-1

| code | slug | name | description | dataUnit | keyProtocols |
| --- | --- | --- | --- | --- | --- |
| 7 | application-layer | Application Layer | The layer that provides network services to end-user applications. | Data | ["HTTP","HTTPS","FTP","SMTP","POP3","IMAP","DNS","SNMP","Telnet","SSH"] |
| 6 | presentation-layer | Presentation Layer | The layer that translates data between the application layer and the network. | Data | ["SSL","TLS","JPEG","GIF","MPEG","ASCII","EBCDIC","MIME"] |
| 5 | session-layer | Session Layer | The layer that establishes, manages, and terminates sessions between applications. | Data | ["NetBIOS","RPC","PPTP","SIP","SAP"] |
| 4 | transport-layer | Transport Layer | The layer that provides end-to-end communication and error recovery. | Segments | ["TCP","UDP","SCTP","DCCP","SPX"] |
| 3 | network-layer | Network Layer | The layer that handles data routing, forwarding, and addressing. | Packets | ["IP","IPv4","IPv6","ICMP","IGMP","OSPF","BGP","RIP","IPsec"] |
| 2 | data-link-layer | Data Link Layer | The layer that provides reliable data transmission across a single network segment. | Frames | ["Ethernet","Wi-Fi","PPP","HDLC","ATM","Frame Relay","ARP","L2TP"] |
| 1 | physical-layer | Physical Layer | The layer that transmits raw bit streams over a physical medium. | Bits | ["Ethernet Cable","Fiber Optic","Coaxial Cable","Twisted Pair","USB","Bluetooth","RS-232"] |