OSI reference model

ISO developed the Open Systems Interconnection model (OSI model). It is a conceptual model that standardizes the communication functions of a telecommunications or computing system, without regard to its internal structure and technology.

The purpose of the OSI reference model is to provide guidance to vendors and developers so that products they develop can communicate with one another.

The OSI reference model is a seven-layer model, and each layer provides specific services. The CompTIA Security + exam focuses mainly on layers 2, 3, and 7:




Packet structure




The applications are windows sockets, such as HTTP for web browsers or SMTP for email.

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