This illustration depicts the path of information as a blue arrow that travels up and down various protocol stacks as it goes from source to destination. The source computer is shown with its five-layer protocol stack as well as its transport layer segment, which appears this way:

Data begins by travelling down the protocol stack and through a communications link, where it arrives at a link-layer switch. The link-layer switch, includes two parts of the protocol stack, receives the transport layer segment, and is depicted this way:

The data travels up through the protocol stack and back down through the protocol stack. It travels by communications link to a router. The router, which includes three parts of the protocol stack, receives the transport layer segment, and is depicted this way:

The data travels up through the protocol stack and back down through the protocol stack. It travels by communications link to the destination computer, where it travels up through the five-layer protocol stack (which is identical to the source computer's protocol stack) from bottom to top and the data is delivered.