 study the legal aspects of network industries. The result is an outline of a theory of telecommunications networks that generates insights into important public policy debates, including mandatory access and network neutrality. The book is organized as follows: The first part introduces the economics of networks. Chapter 1 considers the structure and functions of networks and introduces some basic ideas from graph theory. Chapter 2 examines the design and costs of networks and includes some basic concepts from engineering and economics. Chapter 3 studies the pricing of network services and efficient choice of capacity. It is not possible to give a complete overview of the vast fields of network mathematics, network engineering, and network economics. This book thus seeks Preface simply to provide an introduction to networks and then to apply some of the basic concepts to the design of public policy. The second part of the book presents a comprehensive overview of regulatory and antitrust approaches to network access. Chapter 4 examines the rationales traditionally invoked to justify regulation of communications networks, as well as the policy instruments used to implement these rationales. Chapter 5 looks at the transaction costs of providing access to networks. Chapter 6 examines market- based pricing of access to networks. Chapter 7 examines constitutional limits on the pricing of access to networks. The third and final part of the book presents a set of four key policy appli- cations. Chapter 8 analyzes the access to local telephone networks mandated by the Telecommunications Act of 1996. Chapter 9 examines how antitrust policy has addressed access to networks. Chapter 10 then studies access to local broadband networks, such as digital subscriber line (DSL) and cable modem systems, an issue that has been the focus of recent Supreme Court decisions and FCC proceedings. Chapters 11 and 12 address an issue known as "network neutrality," which has emerged as the most controversial issue in Internet policy, applyi