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#REDIRECT [[Internet protocol suite]]
The '''DoD model''' (DoD, Department of Defense) 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 protocols, and the structure of the Internet is still closely reflected by the DoD model.
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The DoD model has four layers:
*Layer 1 - network access. This layer describes the physical equipment necessary for communications, for example the [[MAC address]]es of the network cards in an [[Ethernet]].
*Layer 2 - internet protocol. This layer defines [[IP number]]s, with many routing schemes for navigating packets from one IP address to another.
*Layer 3 - the host-to-host 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 4 - the process layer. This is where the "higher level" protocols such as [[SMTP]], [[FTP]], [[SSH]], [[HTTP]], etc. operate.
