TCP/IP and the DoD Model By Networking Hub

The Transmission Control Protocol/Internet Protocol (TCP/IP) model was created by the Department of Defense to ensure and preserve data integrity as well as maintain communications in the event of catastrophic war.

Introducing TCP/IP

TCP/IP is central to working with the Internet and intranets, it is essential for you to understand it in detail. We will begin by giving you some background on TCP/IP and how it came about and then move on to describing the important technical terms defined by the original designers. After that, you will find out how TCP/IP compares to an Open Systems Interconnection (OSI) model.

The DoD (TCP/IP) model is basically a condensed version of the OSI model it’s composed of four layers, instead of seven, layers:

  1. Application layer
  2. Transport Layer
  3. Internet layer
  4. Network Access layer


A vast array of protocols combine at the TCP/IP model’s Application layer to integrate the various activities and duties. Its focus on the OSI’s corresponding top three layers (Application, Presentation, and Session). The Application layer defines protocols for node-to-node application response and also controls user-interface specifications.

Transport Layer

The TRansport Layer parallels the functions of the OSI’s Transport layer, defining protocols for setting up the level of transmission service for applications. It takes care of issues such as creating reliable end-to-end communication and ensuring the error-free delivery of data.

Provides packet sequencing and maintains data integrity. The Internet layer in TCP/IP corresponds to the OSI’s Network layer, designating the protocols relating to the logical transmission of packets over the entire network. It handles the addressing of hosts by giving them an IP  address, and it handles the routing of packets among multiple networks.

At the bottom of the TCP/IP  model, the Network Access layer implements the data exchange between the host and the network. The TCP/IP and OSI models are alike in design and concept and have similar functions in similar layers. 

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