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Lecture-3 ISO Model, Network Security, and Protocols

Lecture-3 ISO Model, Network Security, and Protocols -...

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Information Systems Security ISO Model, Network Security, and Protocols Mohammad Qasim Khan
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OSI Model Communications between computers over networks is made possible by the use of protocols. A protocol is a set of rules and restrictions that define how data is transmitted over a network medium (e.g., twisted-pair cable, wireless transmission, and so on). Protocols make computer-to computer communications possible. In the early days of network development, many companies had their own proprietary protocols, which meant interaction between 2 Lecture-3
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History of the OSI Model OSI model wasn’t the first or only movement to streamline networking protocols or establish a common communications standard. Most widely used protocol today, the TCP/IP protocol (which was based upon the DARPA model, also known now as the TCP/IP model), was developed in the early 1970s. The Open Systems Interconnection (OSI) protocol was developed to 3 Lecture-3
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OSI Functionality Networking tasks into seven distinct layers. Each layer is responsible for performing specific tasks or operations toward the ultimate goal of supporting data exchange (i.e., network communication) between two computers. Always numbered from bottom to top They are referred to by either their name or their layer number. For example, layer 3 is also known as the Network layer. Ordered specifically to indicate how information flows through the various levels of communication. Layers are said to communicate with three other layers. Each layer communicates directly with the layer above it as well as the layer below it plus the peer layer on a communication partner system. This standard, or guide, provides a common foundation for the development of new protocols, networking services, and even hardware devices. By working from the OSI model, vendors are able to ensure that their products will integrate with products from other companies and be supported by a wide range of operating systems. 4 Lecture-3
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OSI Functionality …cont. If vendors developed their own networking framework, interoperability between products from different vendors would be next to impossible. The real benefit of the OSI model is found in its expression of how networking actually functions. Network communications occur over a physical connection. This is true even if wireless networking devices are employed. Physical devices establish channels through which electronic signals can pass from one computer to another. Physical device channels are only one type of the seven logical channel types defined by the OSI model. Each layer of the OSI model communicates via a logical channel with its peer layer on another computer.
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