Table I-1. Summary: Same-Layer and Adjacent-Layer Interactions
Same-layer interaction on different computers
The two computers use a protocol to communicate with the same layer on another computer. The protocol defined by each layer uses a header that is transmitted between the computers, to communicate what each computer wants to do.
Adjacent-layer interaction on the same computer
On a single computer, one layer provides a service to a higher layer. The software or hardware that implements the higher layer requests that the next lower layer perform the needed function.