Similar to the OSI networking model, the TCP/IP networking model divides
networking architecture into modular layers. Figure
shows how the
TCP/IP networking model maps to the layers of the OSI networking model. It is
this close mapping that allows the TCP/IP suite of protocols to successfully
communicate with so many networking technologies.
The TCP/IP network
access layer corresponds to the OSI physical and data-link layers. The network
access layer communicates directly with the network media and provides an
interface between the architecture of the network and the Internet layer.
TCP/IP Internet layer relates to the OSI Network layer. The Internet layer
of the TCP/IP protocol model is responsible for placing messages in a fixed
format that allows devices to handle them.
The transport layers of TCP/IP
and OSI directly correspond in function. The transport layer is responsible for
exchanging packets between devices on a TCP/IP network.
The application
layer in the TCP/IP suite actually combines the functions of the three OSI
model layers which are session, presentation, and application. The application
layer provides communication between applications such as FTP, HTTP, and SMTP
on separate hosts.