Five years have elapsed between the original publishing of this book and this second edition, and it is unquestionably interesting to analyze what has changed. The original baseline was that Quality of Service, or QOS, was in the spotlight. Five years have elapsed and QOS prominence has just kept on growing. It has entered in new realms like the Data Center and also spread into new devices. It is no longer just switches and routers—now even servers have at their disposal a complete QOS toolkit to deal, for example, with supporting multiple virtual machines.

This book’s focus remains in the roots and foundations of the QOS realm. Knowledge of the foundations of QOS is the key to understanding what benefits it offers and what can be built on top of it. This knowledge will help the reader engage in both the conceptual and actual tasks of designing or implementing QOS systems, thinking in terms of the concepts, rather than thinking of QOS simply as a series of commands that should be pasted into the configuration of the devices. It will also help the reader to troubleshoot a QOS network, to decide whether the undesired results being seen are a result of misconfigured tools that require some fine-tuning or the wrong tools. As Galileo Galilei once said, “Doubt is the father of all invention.”

A particular attention is also dedicated to special traffic types and networks, and three case studies are provided where the authors share their experience in terms of practical deployments of QOS.

Although the authors work for two specific vendors, this book is completely vendor agnostic, and we have shied away from showing any CLI output or discussing hardware-specific implementations.

History of This Project

The idea behind this book started to take shape in 2007, when Miguel engaged with British Telecom (BT) in several workshops about QOS. Several other workshops and training initiatives followed, and the material presented matured and stabilized over time. In July 2009, Miguel and Peter, who had also developed various QOS workshop and training guides, joined together to work on this project which led to the creation of the first edition.

In December 2014, both authors agreed that the book needed a revamp to cover the new challenges posed in the Data Center realm, which originated this second edition.

Who Should Read This Book?

The target audience for this book are network professionals from both the enterprise and the service provider space who deal with networks in which QOS is present or in which a QOS deployment is planned. Very little knowledge of other areas of networking is necessary to benefit from this book, because as the reader will soon realize, QOS is indeed a world of its own.

Structure of the Book

This book is split into three different parts following the Julius Caesar approach (“Gallia est omnis divisa in partes tres”):

Part One provides a high-level overview of the QOS tools. It also discusses the challenges within the QOS realm and certain types of special traffic and networks.

Part Two dives more deeply into the internal mechanisms of the important QOS tools. It is here that we analyze the stars of the QOS realm.

Part Three glues back together all the earlier material in the book. We present three case studies consisting of end-to-end deployments: the first focused on VPLS, the second focused on Data Center, and the third one focused on the mobile space.

Have fun.