The DoD model (DoD, Department of Defense), sometimes called the 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 protocols, and the structure of the Internet is still closely reflected by the DoD 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. The model has four or five layers; the four-layer model has

• Layer 4 - Process Layer or Application Layer - This is where the "higher level" protocols such as SMTP, FTP, SSH, HTTP, etc. operate.
• Layer 3 - Host-To-Host (Transport) Layer - This is where flow-control and connection protocols exist, such as 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 numbers, 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.

while the five-layer 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

DoD-Schichtenmodell | Model DoD