Routing and Switching: Time of Convergence
Rita Pužmanová · Addison-Wesley eBooks · 2001
From the Book: Why this book came into existence What follows is a personal note on the reasons that brought me to develop the idea for a book and how it came to be. I have been acquainted with networking for more than a decade, a decade in which major breakthroughs in internetworking development and deployment have been made. I first got involved in network management during my PhD studies, having had a wonderful opportunity to complete my degree in Spain at the University of Vallodolid and the Politecnica de Madrid. It was here I met knowledgeable teams dedicated to IP networking and network management and it was then that, for the first time, I could appreciate the fascinating resource that was the Internet. But it was also a time when OSI was being intensively promoted and also a time when the IETF made a number of moves towards eventual convergence with OSI. (CMOT was not to become a historic protocol for a number of years.) As I delved deeper into network management I had to make sure I understood the operation of all the various layers. Moving from the top down, I began to be fascinated by the relaying (routing) concept in building internets, and the introduction of LAN switches to the market added to my interest. However, what fascinates me most about network interconnections is the routing technology, the algorithms and the diverse routing protocols which handle the ever-changing topology and determine the proper path through the wild network jungle. (We may not actually see them as they are transparent to us but we are all familiar with the tangible black, or white, or blue boxes which perform the routingfunctions.) As time went by I kept a close eye on developments in internetworking and made my first contribution to the topic in 1996 (although it was then too early to draw any, even interim, conclusions or recommendations about the merging of routing and switching). However, the move towards integration has now reached a point where it is necessary to make some clear distinctions between the options available and their viability. As an unbiased, lifelong, independent networking specialist I try to keep an objective viewpoint about both open and proprietary proposals. I hope the reader who has not as yet been gripped by internetworking technology will share my enthusiasm after getting through this book. Although we will be discussing the technology running through the programs based on man-made algorithms there are still a number of mysteries in the background (which we sometimes call bugs). Trying to get to the bottom of these mysteries, the hidden issues, the black holes, requires a deal of hard work, intuition, and luck, but the result is very satisfying. Although this book is not essentially about troubleshooting per se, it will be prerequisite reading for any sensible person intending to troubleshoot on an internet. The same may be said about internet design while this book is not about designing internets, it does cover design issues related to individual technologies and protocols. The need for bandwidth, speed, and performance are the major drivers of developments in the internetworking arena. New features and new proposed technologies both in hardware and software seem to appear almost every day. Not all will succeed in today's highly competitive networking market, but all contribute to a solid global understanding of what is happening at network interconnect points now, and what needs to be happening there tomorrow. It is still a vendor-driven field today, but it is much less so than it was ten years ago, and everyone can benefit from the current multivendor proposals which have resulted from the Internet community itself. Note for readers This book has been written in precise and technical language with the intention of eliminating marketing hype and other inappropriate descriptions. (Indeed the book is no light read as the topics covered are taken most seriously by myself.) The terminology used is derived from standard use (i.e. internationally approved through the standardization process), and new terms are defined to avoid any confusion. However, occasionally, even among the creators of the technology, the terminology is not consistent so I have chosen those terms which seem most appropriate for consistency throughout the text. Although I personally do not always feel comfortable with the terms that have been endorsed, I do believe that the developers always try to advance the most appropriate terminology and so should not be castigated unduly afterwards. Routing and Switching: Time of Convergence? provides a global and complex overview of the issues surrounding internetworking, together with sufficient detail to satisfy the internet professional as well as provide a proper understanding of the underlying principles. The primary aim of the text is to show what is behind the evolution in network interconnection, and give some clue as to where industry developments and standardization efforts are heading: to gain performance by avoiding unnecessary processing in the internetworking device, whether router or switch. To make the book easier to use I have broken the text into sections of reasonable length and included a wealth of illustrations and tables to complement the individual topics. More importantly, I have included highlighted Snapshots and Hints to summarize the important concepts in a nutshell to aid comprehension, while the Quick Tips will help the reader to get to the bottom of ideas that may not be quite so obvious. Also included throughout are highlighted references to the appropriate standards and RFCs Standards and RFC Watches with additional details of the organizations from which they originate. The chapters or major sections also conclude with a complete list of all standards and RFCs mentioned throughout the text. A word of caution should be added here. Due to the speed of developments in the areas on which this book concentrates it has not been possible to avoid mentioning enhancements which are only at the proposal stage (usually in the form of Internet Drafts). New drafts appear every day and a great many of them will directly or partially relate to the topics of interest here. I have tried to concentrate on those proposals which have already gathered significant attention and seem viable for future development. However, readers should consider sections where work in progress is mentioned with care and check how far any proposals have been taken by the time the book is read. For similar reasons I have not included the links to or names of such drafts as they may well be renamed, their current versions become obsolete, or their status may have changed by the time the section is read. Let me conclude with a motto to bear in mind before you start to read the text which follows: Read not to contradict and confute, nor to believe and take for granted, nor to find talk or discourse, but to weigh and consider. (Francis Bacon)