Summary

Chapter 8: Fundamental Networks 39Explain the OSI and TCP/IP Data ModelsAn architectural model is a common frame of reference for explaining Internet communicationsand developing communication protocols. It separates the functions of protocols intomanageable layers. Each layer performs a specific function in the process of communicatingover a network.The TCP/IP model was created by researchers in the U.S. Department of Defense (DoD).The TCP/IP model is a tool used to help explain the TCP/IP suite of protocols, which is thedominant standard for transporting data across networks. This model has four layers, asshown in Table 8-5.Table 8-5TCP/IP Model Versus the OSI ModelTCP/IP ModelApplicationPresentationSessionTransportInternetNetwork accessPhysicalOSI ModelApplicationTransportNetworkData linkIn the early 1980s, the ISO developed the Open Systems Interconnection (OSI) model,which was defined in ISO standard 7498-1, to standardize how devices communicate on anetwork. This model has seven layers, as shown in Table 8-5. This model was a major steptoward ensuring that network devices could interoperate.After completing this section, you will meet these objectives:■■■Define the TCP/IP model.Define the OSI model.Compare the OSI and TCP/IP models.Define the TCP/IP ModelThe TCP/IP reference model provides a common frame of reference for developing the protocolsused on the Internet. It consists of layers that perform functions necessary to preparedata for transmission over a network. Table 8-6 describes the four layers of the TCP/IPmodel.