[...]... for Multimedia Applications 688 9.4 Overlay Networks 693 9.4.1 Routing Overlays 695 9.4.2 Peer-to-Peer Networks (Gnutella, BitTorrent) 702 9.4.3 Content Distribution Networks 714 9.5 Summary Open Issue: New Network Architecture 719 720 Further Reading 721 Exercises 722 Solutions to Select Exercises 729 Glossary 743 Bibliography 769 Index 785 EDITION COMPUTER NETWORKS A S Y S T E M S A P P R O A C H 4... video) and they typically connect to special-purpose devices (terminals, hand receivers, and television sets) What distinguishes a computer network from these other types of networks? Probably the most important characteristic of a computer network is its generality Computer networks are built primarily from general-purpose programmable hardware, and they are not optimized for a particular application... market, we have developed a perspective— which we call the systems approach that forms the soul of this book The systems approach has several implications: ■ Rather than accept existing artifacts as gospel, we start first with principles and walk you through the thought process that led to today’s networks This allows us to explain why networks look like they do It is our experience that once you understand... understand how to design a computer network, we should first agree on exactly what a computer network is At one time, the term network meant the set of serial lines used to attach dumb terminals to mainframe computers To some, the term implies the voice telephone network To others, the only interesting network is the cable network used to disseminate video signals The main thing these networks have in common... from the TCP/IP Internet—to illustrate how networks work in practice This allows us to include real-world experiences in the discussion ■ Although at the lowest levels networks are constructed from commodity hardware that can be bought from computer vendors and communication services that can be leased from the phone company, it is the software that allows networks to provide new services and adapt... a network architecture, which lays the foundation for the rest of the book Third, it introduces some of the key elements in the implementation of computer networks Finally, it identifies the key metrics that are used to evaluate the performance of computer networks 1 4 1.1 1 Foundation Applications Most people know the Internet through its applications: the World Wide Web, email, streaming audio and... failed to thrive over the long run The goal of these sidebars is to make the material relevant by showing how technologies have fared in the competitive world of networking Approach For an area that’s as dynamic and changing as computer networks, the most important thing a textbook can offer is perspective—to distinguish between what’s important and what’s not, and between what’s lasting and what’s superficial... all the way from the application to the hardware ■ The systems approach implies doing experimental performance studies, and then using the data you gather both to quantitatively analyze various design options and to guide you in optimizing the implementation This emphasis on empirical analysis pervades the book ■ Networks are like other computer systems—for example, operating systems, processor architectures,... the obvious, a network must provide connectivity among a set of computers Sometimes it is enough to build a limited network that connects only a few select machines In fact, for reasons of privacy and security, many private (corporate) networks have the explicit goal of limiting the set of machines that are connected In contrast, other networks (of which the Internet is the prime example) are designed... topics we have selected cover the core of computer networking, and so we recommend that the book be read sequentially, from front to back In addition, we have included a liberal supply of references to help you locate supplementary material that is relevant to your specific areas of interest, and we have included solutions to select exercises The book takes a unique approach to the topic of congestion control