ABSTRACT
The key to understanding local area network (LAN) performance issues is a detailed level of knowledge concerning the flow of data on a network. To understand how data flows on a LAN we must examine the method by which information is carried within a frame or cell and how different fields are used to provide such functions as routing, error detection, and other network functions. Thus, the purpose of this chapter is to obtain a detailed understanding of the composition of Ethernet and Token Ring frames and ATM cells, including their frame and cell fields and the function of each field within a frame or cell. This information will provide us with the ability to understand the overhead associated with different network frames and cells with respect to the field actually used to transport information. In addition, this information provides a review concerning how network access occurs, network addressing considerations, and similar information we must consider in attempting to determine problems that may occur when establishing or expanding a network or attempting to connect two previously independent networks. In examining LAN frame operations, we first focus attention on the frame format used on an Ethernet network and then examine the three types of transmission formats supported by a Token Ring network. Once the preceding is accomplished, we turn our attention to ATM, examining the composition of the ATM cell, obtaining an overview of ATM connectivity, and computing the overhead associated with the use of a cell-based technology.
