OSI model

The OSI model is a means of grouping protocols by the layer at which they operate.

LayerNameDescriptionExamples
7ApplicationPrimary interface for working with a communication systemFTP, [[HTTPnet.http]], SSH
6PresentationFormatting and presentation of data; e.g. encoding, data compression, encryption/decryptionASCII, PNG
5SessionManaging communication sessions (continuous transmissions between two nodes)SYN, ACK, source and destination ports
4TransportReliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing[[TCPnet.tcp]], [[UDPnet.udp]], [[port numbersnet#common-port-numbers (Private)]]
3NetworkStructuring and managing a multi-node network, including addressing, routing and traffic controlIP ([[v4net.ipv4]] and [[v6net.ipv6]]), routers
2Data linkReliable transmission of data frames between two nodes connected by a physical layer[[Ethernetnet.ethernet]], MAC, switches
1PhysicalTransmission and reception of raw bit streams over a physical medium[[Ethernetnet.ethernet]], Twisted pair, optical fiber, RJ45

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