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Open Systems Interconnection model (OSI) 
The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes the communication functions of computing systems.
High-level APIs, including resource sharing, remote file access
Translation of data between a networking service and an application; including character encoding, data compression and encryption/decryption
Managing communication sessions, i.e. continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes.
Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing
Structuring and managing a multi-node network, including addressing, routing and traffic control
Reliable transmission of data frames between two nodes connected by a physical layer
Transmission and reception of raw bit streams over a physical medium