Gigabit Ethernet: Technology and Applications for High-Speed LANs

• Authors: Rich Seifert
• Venue: Gigabit Ethernet: Technology and Applications for High-Speed LANs
• Year: 1998

From the Book:PREFACE: During the 1980s and 1990s, the growth in the use of computer networks has been nothing short of phenomenal. No longer do organizations consider whether they need a network, but only what type of network should be employed. The parallel growth in the capabilities of the devices connecting to the networks (personal computers, workstations, servers, and so on) and the applications using those networks have combined to transform yesterday's network technologies into a performance roadblock. Like our freeways, we constantly add lanes only to find that the traffic demand simply increases to keep the road as congested as always. Gigabit Ethernet, conceived in 1995, is the most recent addition to the world's most popular family of local area network (LAN) technologies. The lure of riding yet another wave of successful Ethernet systems has attracted enormous interest from vendors eager to provide new products to feed bandwidth-hungry network applications. In that year, the Institute for Electronics and Electrical Engineers (IEEE) LAN/MAN Standards Committee began the process of developing an industry standard for Gigabit Ethernet. While the gestation period of an IEEE standard may exceed even that of an elephant, the IEEE 802.3z Gigabit Ethernet standard is expected to be formally approved by IEEE in mid-1998 and is already endorsed by dozens of equipment manufacturers. Even more important, products are becoming available for users to deploy in their networks. This book guides both users and developers through the complex issues involved in designing and deploying high-speed networks. Who Should Read this Book This book is aimed at theneedsof both: Network Technologists: This includes engineers working in companies involved in the design and manufacture of computers and communications products, academics (both instructors and students), network product marketing and sales personnel, independent consultants, and anyone else interested in understanding at a detailed level how Gigabit Ethernet works. In this context, the book is a reference work, providing technical detail without the terseness and formality of the IEEE standard. Network Users: This includes network planners, designers, installers and administrators, Management Information Services (MIS) management, Value-Added Resellers (VARs), and operations staff in any organization that selects, installs, or uses network products. This book will help these users to understand and become more comfortable with this new technology, as well as to make rational decisions in the selection and purchase of products. In many cases, these users depend primarily on equipment suppliers as their main source of information. Such information is always suspect, as suppliers have a strong motivation to sell their technology regardless of whether it is appropriate. The reader is assumed to be at least casually familiar with LANs and Ethernet in particular. No attempt is made to provide a complete, from-the-ground-up tutorial suitable for novices. Indeed, such a work would require an encyclopedia and make it impossible to focus on Gigabit Ethernet and the related technologies on which it builds and relies. Network technologists and users grounded in the fundamentals of Ethernet will find everything they need to understand completely the workings of the new Gigabit Ethernet system. In the process, they will gain enormous insight into why things are done the way they are at 10, 100, and 1000 Mb/s, and not just the cold facts. This book is not intended as a "standards companion." While a summary of the standard itself is provided (Chapter 13), the bulk of the book is concerned with helping the reader to understand Gigabit Ethernet technology and the ways in which it may best serve the needs of real applications. A conscious effort has been made to use practical, everyday terminology, rather than the Arcane Architectural Abstractions and Acronyms (AAAAAs) typical of standards documents. Organization of the Book The book is organized into three main sections: Part I: Foundations of Gigabit Ethernet Chapter 1 provides a historical context for Gigabit Ethernet, looks at why Ethernet is as popular as it is, and identifies the key enabling technologies that aided its development. Chapter 2 discusses the shift from shared media (coaxial cable) to dedicated media (twisted-pair and optical fiber). Chapter 3 introduces the principles of bridging and switching and the move from shared-bandwidth LANs to dedicated LANs with central switches. Chapter 4 shows how full-duplex operation became possible through the use of switches, and the implications of its use. Chapter 5 describes the subtle variations in Ethernet frame formats (and their ultimate unification) that have developed over the years. Chapter 6 provides detailed information about the operation and use of Ethernet flow control. Chapter 7 shows how the controller-to-transceiver interface has evolved from the original 10 Mb/s transceiver cable to the medium-independent interface used in 100 Mb/s and Gigabit Ethernet. Chapter 8 explains the operation of the automatic link configuration mechanism (Auto-Negotiation). Part II: Gigabit Ethernet Technology Chapter 9 provides an overview of Gigabit Ethernet. For knowledgeable readers and experienced networkers looking for a quick summary of what's new in Gigabit Ethernet relative to its slower-speed cousins, this chapter is the place to start. (But be sure to go back and read Part I. It contains a lot of useful information and provides insights that you have never seen before!) Chapter 10 explains the modifications made to the Ethernet Medium Access Control (MAC) algorithms to support 1000 Mb/s operation. Both half- and full-duplex operation are discussed. Chapter 11 discusses options for the design and selection of hubs for Gigabit Ethernet use. Repeaters, switches, routers, and the concept of a "Buffered Distributor" are fully explained. Chapter 12 delves into the details of the low-level physical signaling used with Gigabit Ethernet. Comprehensive information on encoding methods, interfaces, media specifications, and topology rules are provided, both for optical fiber and twisted-pair media. The principles of Auto-Negotiation for Gigabit Ethernet are also explained. This chapter is useful for network installers and facilities planners. Chapter 13 is your Sherpa guide to the IEEE 802.3z Gigabit Ethernet standard itself. Part III: Applying Gigabit Ethernet Chapter 14 discusses the different network requirements imposed by different application environments and shows which technologies are best suited to each. It emphasizes a "top-down," application-centric approach to network design, rather than a technology-driven model. Chapter 15 looks at the performance implications of complex networks and considers the real causes of poor network performance. Some insight is provided into the best way to measure network performance and get the most out of the network you have paid for. Chapter 16 considers technology alternatives to Gigabit Ethernet, including switched Fast Ethernet and FDDI, Fibre Channel, HIPPI, and ATM. My Thanks It's a daunting task to write a book of this depth and magnitude. Fortunately, I had the help of numerous experts who reviewed material, corrected my errors, and gave excellent advice on the content and organization of this work. Thanks to: Carsten Bormann, Bob Fink, Howard Frazier, Andy Hacker, Frank Kastenholz, Dennis Miller, Rex Naden, Thomas Skibo, Joel Snyder, Rich Taborek, and Geoff Thompson, and especially to Greg Hersh, Bert Manfredi, and Mart Molle for their time and advice. Thanks also to Mary Harrington and Genevieve Rajewski for all of their help with the nuts and bolts of publishing and to Carol Long for navigating the winding roads of the Santa Cruz Mountains and getting me started on this project in the first place. I also would like to thank all of my consulting clients, whose interesting projects continually force me to stay on top of current technologies, and my students at the University of California at Berkeley, who (unbeknownst to them) provided a testing ground for most of the figures, tables, and material in the book. Thanks also to my colleagues in the IEEE 802.3 Working Group and IEEE 802.3z Gigabit Ethernet Task Force, who consistently develop the highest-quality and most widely adopted standards in the LAN industry. Of course, any errors contained in this work are my responsibility alone. Technology Updates Network technology changes quickly, especially in relation to the time required to write and publish a book such as this one. This book was written contemporaneously with the development of the Gigabit Ethernet standard; at the time of publication, the standard had not yet been formally approved. As a result, there may be minor differences between some operational parameters presented here and those of the final approved standard. Also, work on Gigabit Ethernet will not come to a halt when the first revision of the standard is approved. There are ongoing projects both to expand the usefulness of the technology, and to correct and maintain the standard. To keep you informed with the most up-to-date information, including any corrections to this book, I will be maintaining a World Wide Web site for this purpose, at: ...