Preface

In the developed parts of the world virtually all information-based organizations are underpinned by some form of communications infrastructure, and for many companies the communications network is intimately bound with core business operations. For large, multinational companies the annual cost of running such an infrastructure may run into millions of dollars, and the unexpected cost of service outages may be equally as large. Good network design and attention to detail are fundamental to providing cost-effective and reliable data networks. It is surprising, therefore, that there are very few books that deal with the subject of network design from the ground up, combining the theoretical, practical, and financial issues associated with real design networks.

Designing modern enterprise networks is now so complex that it cannot be achieved without the use of specialist software tools, and, as with any large problem, it is also beneficial to break down the problem into manageable components. There is, fortunately, a natural split in the design process between the delivery of the physical topology (be it a local or wide area network) and the routing and higher-layer services. This split mirrors what we find in the field today. There seem to be two broad classes of network designer: those who know much about routing and little about topology analysis, and vice versa. Unfortunately, knowledge of both is critical in planning and implementing an efficient data network. Network design must be approached holistically, from the ground up; otherwise, the result is typically a suboptimal network, with substantial reengineering costs due to inappropriate assumptions made during the design phase.

Since this is such a huge topic, I have divided my treatment into two books. In this book we discover how to deliver an optimized logical topology—covering the addressing, routing, and security issues required for delivering enterprise services, and how such networks should be tuned for performance, availability, and maintainability. The first book (High-Performance Data Network Design) deals with the design techniques required to deliver an optimized physical topology. The book covers the design process from initiation, capacity planning, backbone and access design, and performance modeling, to the various LAN, MAN, and WAN switching technologies required to deliver a basic network infrastructure.

My objective in starting this project was to unite a number of apparently disparate areas of network design and to provide a balance of theoretical and practical information that practicing engineers would find useful in their day-to-day job. Since network design often receives very fragmented coverage, this book is an attempt to bring together those pieces so that they may be seen in context. In particular, the key issues in designing network addressing schemes are discussed, including how to design using the latest routing protocols, how to optimize performance using the latest technologies, how to build fault-tolerant and resilient networks within budget, how to assess and quantify risk in order to deploy security technologies appropriate for each network, how to deploy Virtual Private Networks (VPNs), understanding the latest developments in Quality of Service (QoS), and, finally, how to manage and maintain networks.

I started this project in an environment where the goalposts are far from static. The speed of change in information technology is simply staggering: Within the last 20 years we have seen a massive shift from large, centralized, host-centric networks to a situation where most of today's computing power reside on desktops. With processing power growing exponentially, and memory prices declining every year, we are now witnessing another paradigm shift toward an era of mobile personal computing. We have seen the emergence of distributed architectures, multimedia, and the explosive growth of the Internet and the World Wide Web (WWW), each forcing the development of new protocols and new applications. Network security has become a real force for change in recent years, with massive growth in the firewall market and completely new models of secure networking, such as the Public Key Infrastructure (PKI) and VPNs. Businesses are now demanding quality-of-service guarantees and information privacy, and there is increasing emphasis on Service-Level Agreements (SLAs). With overall improvements in the communications infrastructure we have also seen a significant increase in voice communications, new applications for packetized Voice over IP (VoIP), and the unification of both text and audio messaging systems. Finally, there are radical changes afoot in the field of user interfaces, including the take-up of voice recognition, text to audio translation, and the use of biometrics.

In all areas of technology the boundaries are blurring between local and wide area networks, data and voice, wired and wireless. All of these technologies are now being provisioned via a new breed of highly integrated hybrid devices with built-in routing, switching, bandwidth management, and security services. In a very short space of time every home will have Internet access via smart, integrated digital terminals. There has already been a massive shift in the adoption of mobile wireless computing and Internet access via a new generation of data-aware mobile phones. Over the next few years we will see the adoption of Java-enabled telephony, with high-resolution color displays capable of running more powerful applications. This, together with the use of more intuitive user interfaces and voice recognition, will truly mobilize the face of personal computing. We can only guess what changes the next two decades will bring.

About this book

This book is written for practicing engineers and project managers involved in planning, designing, and maintaining data networks. It is also appropriate for undergraduate students who have taken basic courses in data communications. The content reflects much of my experience in the industry, having worked for several leading network manufacturers in the areas of network design, network security, network modeling, and simulation.

This book represents the second of two complementary books on network design and optimization. This book covers addressing and naming schemes, routing protocols and router design, security techniques, virtual private networks, network optimization, designing high-availability and fault-tolerant networks, quality of service, and the management and maintenance of networks. The book deals with network design systematically, assuming that the core LAN, MAN or WAN infrastructure is in place, as described in the first book.

Since this book is concerned primarily with large-scale network design, it focuses heavily on the IP protocol suite, rather than attempting exhaustive coverage of other protocol stacks. Because my primary focus is on the design and performance characteristics of data networks, the approach taken throughout this book is to document technologies in sufficient depth only where they are relevant; for exhaustive information the book cites numerous good references, including TCP/IP Explained, by Phil Miller, from Digital Press.

Although the book does include occasional material where numerical techniques are presented, it is not heavily mathematical. The book also makes occasional use of programming code, although the reader may skip these sections. Unfortunately, the use of design algorithms and numerical modeling is an important part of network design. Where appropriate, suitable references are provided.