1.2 Ethernet, Token Ring and ATM Frame and Cell Operations

Material in Chapter 2 is presented to provide readers with a review of LAN dataflow operations. The key to understanding many performance- related issues is a detailed knowledge of the frame and cell format used on different types of LANs ” material that is presented in Chapter 2.

Chapter 2 focuses attention on the fields of Ethernet and Token Ring frames , to include a discussion of Fast and Gigabit Ethernet. This will provide us with information necessary to understand the relationship between the overhead of a frame and the length of its information field. Doing so will assist us in understanding the effect of the frame length upon the efficiency of transmission on different types of LANs. Once the preceding is accomplished, we turn our attention to ATM and examine the overhead of the ATM cell and its effect on the transmission efficiency of ATM-based networks. Thus, the primary focus of Chapter 2 is to provide readers with information that can be used in later chapters to answer many LAN performance-related questions. Answers to such questions will allow us to note techniques that can be used to adjust the length of LAN frames and enhance their information transfer capability, which can result in an improvement in the efficiency of transmission over the network. Other questions we will tackle in later chapters that are related to the material presented in Chapter 2 include how to determine the effect of the frame length on bridge and router operations, as well as on their buffer memory requirements.