Page 738 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

the OSI protocol, the OSI model, was readily accepted. The OSI model
serves as an abstract framework, or theoretical model, for how

protocols should function in an ideal world on ideal hardware. Thus,
the OSI model has become a common reference point against which all
protocols can be compared and contrasted.

OSI Functionality

The OSI model divides networking tasks into seven distinct layers.

Each layer is responsible for performing specific tasks or operations
for the ultimate goal of supporting data exchange (in other words,
network communication) between two computers. The layers are
always numbered from bottom to top (see Figure 11.1). They are
referred to by either their name or their layer number. For example,
layer 3 is also known as the Network layer. The layers are ordered
specifically to indicate how information flows through the various

levels of communication. Each layer communicates directly with the
layer above it as well as the layer below it, plus the peer layer on a
communication partner system.