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‫The TCP IP model is a model with four layers, which is for both modeling current internet architecture,

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‫as well as providing a set of rules that govern all forms of transmission over a network.

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‫DARPA, an agency of the United States Department of Defense, created it in the 1970s.

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‫This model was being made at the same time the Osai model was created.

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‫The TCP IP model is not the same as high model, however, it was influenced by the model, which is

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‫why many of the names of the different layers are the same.

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‫So we can simply say that the TCP IP reference model represents reality in the real world, whereas

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‫the OSAI reference model represents an ideal.

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‫OK.

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‫So these are the main differences of the TCP IP reference model.

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‫The three top players in the U.S. model that is the application layer, the presentation layer and the

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‫session layer are not distinguished separately in the TCP IP model, which only has an application layer

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‫above the transport layer.

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‫TCP corresponds to Osai layer for the transport layer.

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‫IP corresponds to a subset of Osai layer three, the network layer.

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‫TCP IP makes no prescriptions as to the link layers below IP, while OCI specifies two layers.

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‫The physical address, commonly the Mac address, which is located in a special field in the data link

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‫layer header changes as the packet passes from one device to another.

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‫For example, from the source PC to a switch to a router to another switch and then finally to the destination

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‫PC.

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‫However, the original IP source and destination addresses do not change when transiting the network

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‫because the packet is stripped of its layer three header only when it goes beyond a router.

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‫When it stays within the same land, it only passes through switches, which de capsule8 it at the layer

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‫to header containing the Mac address.

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‫So as a result, the header changes as the packet is re encapsulated, as does the Mac address fields.