DLPI Programmer's Guide

Chapter 1 17
Introduction to DLPI
The Data Link Layer
The Data Link Layer
The data link layer (layer 2 in the OSI Reference Model) is responsible
for the transmission and error-free delivery of bits of information over a
physical communications medium. The model defines networking
functionality at several layers and service providers between the layers.
A model of the data link layer is presented here to describe concepts that
are used throughout this guide. It is described in terms of an interface
architecture, as well as addressing concepts needed to identify different
components of that architecture. The description of the model assumes
familiarity with the OSI Reference Model.
The Service Interface
Each layer of the OSI Reference Model has two standards:
• one that defines the services provided by the layer.
• one that defines the protocol through which layer services are
provided.
DLPI is an implementation of the first type of standard. It specifies an
interface to the services of the data link layer. Figure 1-1 illustrates how
DLPI performs this function.