A Comparison of Network Models
There are two network models that describe how networks 'work'. The OSI Model, the older model, was designed for the OSI protocol stack. While different organizations were battling over standards, Vint Cerf and Bob Khan worked out the TCP/IP software from which the TCP/IP Model was co-designed. The diagram below shows how the two networking models compare, and how the logical and physical networking protocols relate to the layers in each of the two models.
There are seven layers in the OSI Model, only four in the TCP/IP model. This is because TCP/IP assumes that applications will take care of everything beyond the Transport layer. The TCP/IP model also squashes the OSI's Physical and Data Link layers together into the Network Access Layer. Internet Protocol really doesn't (and shouldn't) care about the hardware underneath, so long as the computer can run the network device and send IP packets over the connection.