OSI-Model defines Communication Layers within the Open Systems Interconnection (OSI)

OSI Model

#LayerLevelProtocol Data Unit (PDU)Function
7Application LayerHost layerDataHigh-level APIs, including resource sharing, remote file access
6Presentation LayerHost layerDataTranslation of data between a networking service and an application; including character encoding, data compression and encryption/decryption
5Session LayerHost layerDataManaging communication sessions, i.e. continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes
4Transport LayerHost layerSegment TCP/ Datagram (UDP)Reliable protocol transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing
3Network LayerMedia layerPacketStructuring and managing a multi-node network, including addressing, routing and traffic control
2Data-link LayerMedia layerFrameReliable protocol transmission of data frames between two nodes connected by a Physical Layer
1Physical LayerMedia layerBitTransmission and reception of raw bit streams over a physical medium

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