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#REDIRECT [[Internet protocol suite]]
{{IPstack}}
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The '''[[TCP/IP]] reference model''' or '''TCP/IP model''', sometimes called the '''DoD model''' (DoD, [[United States Department of Defense|Department of Defense]]), [[ARPANET]] reference model or the [[Internet]] reference model, is a layered abstract description for communications and computer [[network protocol]] design. It was created in the [[1970s]] by [[DARPA]] for use in developing the [[Internet]]'s [[Internet protocol suite | protocols]], and the structure of the Internet is still closely reflected by the TCP/IP model. It has fewer, less rigidly defined layers than the commonly referenced [[OSI model]], and thus provides an easier fit for real-world protocols.
No document officially specifies the model; different names are given to the layers by different documents, and different numbers of layers are shown by different documents. There are versions of this model with four layers and with five layers. The four-layer version of the model has
*Layer 4 - '''Process Layer or Application Layer''' - This is where the "higher level" protocols such as [[SMTP]], [[File Transfer Protocol|FTP]], [[SSH]], [[HTTP]], etc. operate.
*Layer 3 - '''Host-To-Host (Transport) Layer''' - This is where flow-control and connection protocols exist, such as [[Transmission Control Protocol|TCP]]. This layer deals with opening and maintaining connections, ensuring that packets are in fact received.
*Layer 2 - '''Internet or Internetworking Layer''' - This layer defines [[IP number]]s, with many routing schemes for navigating packets from one IP address to another.
*Layer 1 - '''Network Access Layer''' - This layer describes the physical equipment necessary for communications, such as [[twisted pair]] cables, the signalling used on that equipment, and the low-level protocols using that signalling.
The five-layer version of the model splits Layer 1 into a Physical layer and a Network Access layer, corresponding to the [[physical layer]] and [[data link layer]] of the OSI model.
==See also==
*[[OSI model]]
[[Category:Network architecture]]
[[de:DoD-Schichtenmodell]]
[[pl:Model DoD]]
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