Book Preface

PREFACE Objective Communication networks are in a period of transition from networks that are based on telephone architecture and standards to networks based on the Internet Protocol (IP) architecture. The main reason for this change is that new services and applications can be deployed with unprecedented speed over an Internet that has attained the global reach of the telephone network. Many of these new applications and services are quite visible to the student. For example, in addition to e-mail and web surfing, there is buying/selling over the Internet (eBay), MP3 and other file exchange (Napster, KaZaA, and many others), interactive games (Counterstrike), video streaming (CNN), and voice over IP (NetMeeting, ICQ). Many other applications and services are having profound impact on business, manufacturing, international commerce, medicine, and government. The infrastructure of communication networks is undergoing dramatic change under pressure from the new services and enabled by technology innovation. A new generation of wireless devices combines aspects of cellular phones, personal digital assistants, and even digital cameras and is enabling new modes of mobile communication such as short text messaging, event notification, e-mail, and web browsing. These wireless services are blazing a trail away from traditional telephony to new modes of IP-based multimedia communications. Inevitably the signaling system that enables all of the functionality of the cellular and telephone network will be replaced by more versatile signaling based on Internet protocols. A new generation of IP-based protocols will control and manage the resources in the next generation of networks. It is in this exciting context of new services and emerging next-generation network architecture that we offer this second edition of our textbook. The purpose of this book is to provide an introduction to fundamental network architecture concepts and their application in existing and emerging networks. We emphasize the pivotal role of Internet protocols in future network architecture and at the same time provide a broad coverage of fundamental network concepts. Our view is that the student will be best prepared for a future of constant change through exposure to network design alternatives. Target Courses The book is designed for introductory courses in computer networks and in communication networks at the upper level undergraduate and first year graduate programs in electrical engineering, computer engineering, and computer science. The book contains all the basic material covered in typical one-semester first courses in computer networks and in communication networks. The book also provides additional material in each chapter as well as advanced topics in the later chapters so that the book can be used in a two-semester course sequence. The book is up-to-date in its coverage of emerging network architecture and can also be used by engineering and computer professionals. As prerequisites the book assumes a general knowledge of computer systems. In certain optional parts of the text, knowledge of programming, elementary probability or elementary calculus is required. These sections are clearly indicated and can be skipped. Approach and Content The book is organized into three parts. Part I presents the big picture of networks. We trace the evolution of networks and identify the key concepts and functions which form the basis for layered architectures. We introduce examples of services and applications that are familiar to the student (web browsing, email, and telephone) and we explain how these services are supported by networks. This big picture view helps the student to see how the various parts of a network architecture fit into one whole. Part I. Big Picture First. (Chapters 1-2) • Evolution of network concepts in telegraph, telephone, and computer networks • How services and applications drive network architecture evolution • How layers work together to deliver services • Application layer, transport layer, and sockets • Preparation for Experimentation: Network protocol analyzer, IP utilities, and socket programming The second part presents fundamental concepts of network architecture and focuses on the lower four layers of the protocol stack. Our approach is to develop the fundamental concepts first and then to show their application in concrete examples. For example, we develop ARQ in detail as an example of a peer-to-peer protocol and then we discuss its application in TCP reliable stream service and flow control. We cover the essential computer network topics, but we also have extensive discussion of access and transport networks, telephone and cellular services and signaling. This additional material is organized so that it is optional, but we include it because we believe that much of network architecture evolution in the near future will involve the extension Internet protocols to traditional networks and services. Part II. Fundamental concepts in network architecture (Chapters 3-7) • Digital transmission; copper, cable, radio, and optical media • SONET and optical networking • Circuit switching, signaling, telephone services, mobility • Peer-to-peer protocol design; PPP, HDLC, POS and GFP • Medium-access control; Ethernet and 802.11 wireless LANs • Voice and data cellular networks • Packet switching, routing, congestion control and QoS The third and final part deals with key network architectures, advanced topics, and next generation networks. We present the protocols and standards that are likely to shape the next generation networks. Part III. Key architectures, advanced topics, and next generation networks (Chapters 8-12 and Appendices) • IPv4 and IPv6; TCP, UDP; RIP, OSPF, BGP; DHCP and mobile IP • ATM networks • New Architectures: IntServ, RSVP, DiffServ, Peer vs. Overlay Interconnection, MPLS and GMPLS, RTP, SIP, H.323, and WAP • Network Security: DES and AES, RSA, IPSec, SSL and TLS, 802.11 • Multimedia standards: JPEG, MPEG, Audio, MP3, Voice-over-IP • Network management and performance modeling The book attempts to provide a balanced view of all important elements of networking. This is a very big challenge in the typical one-semester introductory course that has limited time available. We have organized the book so that all the relevant topics can be covered at some minimum essential level of detail. Additional material is provided that allows the instructor to cover certain topics in greater depth. Dependencies between sections are discussed later in the Preface. Changes from the First Edition The most important change in the second edition is the extensive use of the open-source Ethereal network protocol analyzer in the teaching of network protocols. Ethereal allows any PC to capture live network traffic and to analyze the headers and payloads of the stream of captured traffic at layers 2 and above at any level of detail. We use Ethereal in the following ways: • Examples of Ethereal packet captures demonstrate the operation of protocols such as HTTP, SMTP, Telnet, SIP, RSVP, RTP, DNS, TCP, UDP, OSPF, IP, ARP, Ethernet, 802.11, PPP, LCP, IPCP, SSL and TLS. • We provide instructors with Ethereal packet capture files that allow the instructor to interactively demonstrate the operation of protocols in class. • Exercises in the problem section require the students to carry out their own packet captures to examine and analyze the operation of protocols using real traffic. • The book web site contains experiments that involve the use of Ethereal in Linux-based router networks. The second edition also contains various organizational and content changes. The following lists the key content and organizational changes from the first edition: • The material in the book has been rearranged so that optional sections can be skipped without a disruption in the topic flow. The sections that contain optional material are indicated by a diamond in the heading. The optional sections that contain detailed mathematics are now indicated by a sidebar. • Chapter 1 has been shortened and the discussion of network evolution has been simplified. The functions associated with each layer are introduced along with the discussion on network evolution. • In Chapter 2 the discussion on how all the layers work together has been improved by introducing examples using Ethereal packet captures. The section on application layer protocols has been expanded and a new section provides an introduction to network protocol analyzers. • PCM speech coding has been moved from Chapter 12 to Chapter 3. • Chapter 4 provides more detail on SONET and optical transport networks. Satellite cellular networks have been dropped. • Chapter 5 now consists of two parts. The first part deals with peer-to-peer protocols using reliable data transfer protocols as an example. The first part also includes TCP reliable byte stream service. The second part focuses on data link layer protocols and now includes a section on framing. • Chapter 6 has also been divided into the principles of medium access control protocols (Part 1) and LANs (Part 2). We have simplified the mathematical discussion of medium access controls and provide details in a separate section. • In Chapter 7 we have streamlined the discussion of packet networks, and we have separated clearly the more advanced discussion of traffic management. • Chapter 8 makes extensive use of packet capture examples to illustrate the operation of TCP/IP protocols. • Chapter 10 on advanced network architectures has been revised extensively. The discussion of ATM over IP has been replaced by a discussion of the overlay and peer models to network interconnection. The chapter now contains discussion on virtual networks and GMPLS. The material on RTP and SIP has been updated and moved from Chapter 12 to this chapter. • Chapter 11 has been updated with brief discussions of the Advanced Encryption Standard and 802.11 security. Chapter Dependencies The book was designed to support a variety of introductory courses on computer and communication networks. By appropriate choice of sections, the instructor can provide a desired focus or make adjustments to account for the background of the students. Figure 1 contains a flow chart of the dependencies between sections in the book. The solid black line indicates the sequence of topics that forms the core of most introductory courses. The dashed lines show sections that can be added to provide greater depth in various topic areas. Section numbers in parentheses indicate dependencies that involve only subsections. After Chapter 8, the chapters are less interdependent. Chapter 11 depends on Chapter 8 only in regards to the header structure of IPv4 and IPv6. Chapter 12 depends only on sections 3.1 and 3.2. Appendix A on queueing models provides supporting material for sections 4.7, 5.7, and 6.5, which deal with performance modeling. Pedagogical Elements We have improved the pedagogical elements of the first edition and offer several new elements. • Ethereal Virtual Lab. Lab experiments are the most effective means for reinforcing the concepts taught in lectures. At the physical layer a rich set of instruments (for example, oscilloscopes, spectrum analyzers, bit error rate sets) is available in the field to troubleshoot systems and can be used in the lab to teach and demonstrate the application of concepts in real systems. The tcpdump program written by Jacobson, Leres, and McCanne has formed the basis for many network protocol analyzers that are now used to troubleshoot protocols in network systems in the field and in the lab. The Ethereal open-source tool is one such network protocol analyzer that supports a very broad array of protocols and that is continuously updated by a large community of developers. We have used Ethereal to teach protocols in lectures and in experiments and have found it to be very effective in bringing the protocol concepts to life. <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/007246352x/103135/chart.jpg','popWin', 'width=440,height=370,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (47.0K)</a> Figure 1. Chapter dependencies (solid arrows show sequence of core topics). Figure 2 shows an Ethereal screenshot of a packet capture that a student can readily capture from a PC at home. The top pane shows the sequence of packets that transpire after the student clicks on a web link: A DNS query and response; A TCP three-way connection setup; an HTTP request, followed by a TCP acknowledgment, and then the beginning of the HTTP response. The sequence of packets exchanged for various types of protocols can be analyzed in this fashion. The middle pane allows the user to delve into the details in the headers of any of the protocol data units at layer 2 and above. The middle pane in the figure below shows some of the details of the IP, UDP, and DNS headers. The bottom pane allows the user to zoom into the bits and bytes of the header as well as the payload. This rich set of capabilities was developed within Ethereal for use in troubleshooting protocols in development labs as well as in the field. These same capabilities make Ethereal an extremely powerful teaching tool. We use Ethereal to examine PPP, HDLC, Ethernet, MPLS, IP, IPv6, OSPF, UDP, TCP, DNS, HTTP, RTP, SIP, H.323, SSL and TLS. We provide the instructor with packet capture files that allow the instructor to demonstrate protocols interactively in the classroom. Most of the examples can be readily reproduced and examined in greater detail by the student. We also introduce networks utilities such as PING, IPconfig, netstat, and traceroute, which can be used in exercises that involve Ethereal packet captures. <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/007246352x/103135/sampleethereal.jpg','popWin', 'width=328,height=420,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (42.0K)</a> Figure 2. Sample Ethereal display. • Numerous figures. Network diagrams, time diagrams, performance graphs, state transition diagrams are essential to effectively convey concepts in networking. • Lecture charts. We have prepared approximately 500 MS PowerPoint® charts for use in lecture presentations. We have also prepared approximately 50 presentation charts that use animation to demonstrate certain key concepts more effectively. All of these charts are available to instructors in the book web site. • Numerous examples. The discussion of fundamental concepts is accompanied with examples illustrating the use of the concept in practice. Numerical examples are included in the text wherever possible. • Text boxes. Commentaries in text boxes are used to discuss network trends and interesting developments, to speculate about future developments, and to motivate new topics. • Problems. The authors firmly believe that learning must involve problem solving. The book contains ### problems. Each chapter includes problems with a range of difficulties from simple application of concepts to exploring, developing or elaborating various concepts and issues. Quantitative problems range from simple calculations to brief case studies exploring various aspects of certain algorithms, techniques or networks. Simple programming exercises involving sockets and TCP/IP utilities are included where appropriate. • Chapter introductions. Each chapter includes an introduction previewing the material covered in the chapter and in the context of the “big picture.” • Chapter summaries and checklist of important terms. Each chapter includes a summary that reiterates the most important concepts. A checklist of important terms aids the student in reviewing the material. • Mathematical sections. In general key mathematical results are summarized in the main text. A sidebar indicates (optional) mathematical sections that contain more detailed mathematical discussion of these results. • References. Each chapter includes a list of references. Given the introductory nature of the text, references concentrate on pointing to more advanced materials. Reference to appropriate Internet Engineering Taskforce (IETF) RFCs and research papers is made where appropriate, especially with more recent topics. • A web site. This website contains links to the following teaching resources: • An Instructor’s Solutions Manual • Additional problems, exercises and experiments for instructors • Answers to selected problems for students • Animated PowerPoint lectures and presentations • Chapter pointers to useful and interesting websites Acknowledgments The material in the book was developed over many years in introductory as well as advanced courses in networking, both in regular undergraduate and graduate programs as well as in programs with an orientation towards professional practice. We acknowledge the feedback from the many students who participated in these courses and who used various versions of the manuscript. For their help on the first edition, we acknowledge the input of the graduate students who served as teaching assistants in these courses, especially Dennis Chan, Yasser Rasheed, Mohamed Arad, Masoud Hashemi, Hasan Naser, and Andrew Jun. We thank Anindo Banerjea, Raouf Boutaba, Michael Kaplan and Gillian Woodruff for many exciting conversations on networking. Anindo and Raouf graciously provided some of the material that is presented in Chapter 2. We would also like to thank Anwar Elwalid and Debasis Mitra for their continued encouragement and interest in the book. We thank Yau-Ren Jenq for reviewing the fair queueing discussions in detail. We are especially grateful to Irene Katzela for testing the manuscript in her courses. We also thank Ray Pickholtz for testing various versions of the text, including the beta version, and for his many valuable suggestions and his continued encouragement. We thank the reviewers for their many useful comments on the various versions of the first edition manuscript: Subrata Banerjee (Stevens Institute of Technology), John A. Copeland, (Georgia Institute of Technology), Mario Gerla (UCLA), Rohit Goyal (Ohio State University), Gary Harkin (Montana State University), Melody Moh (San Jose State University), Kihong Park (Purdue University - West Lafayette), Raymond L. Pickholtz (The George Washington University), Chunming Qiao (SUNY Buffalo), Arunabha Sen (Arizona State University), Stuart Tewksbury (West Virginia University), and Zhi-li Zhang (University of Minnesota). We would like to acknowledge the many friends from Nortel Networks for showing us the many facets of networking. We thank Sidney Yip for opening the door to many years of interaction. We also thank Richard Vickers, Marek Wernik, and Jim Yan for many illuminating conversations over the years. We especially thank Tony Yuen for sharing his vast knowledge of the networking industry and for continuously showing how the big picture is actually bigger! For their help with the preparation of the second edition we would like to thank the following reviewers: Maurice F. Aburdene (Bucknell University), John Anderson (University of Lund), LeRoy W. Bearnson (Brigham Young University), Michael J. Donahoo (Baylor University), Yuguang Fang (University of Florida), Jeff Fedor (University of Southern California), Jeremiah F. Hayes (Concordia University), Mike Kain (Drexel University/Unisys Corporation), W. David Laverell (Calvin College), Ching-Cheng Lee (San Jose State University), Derong Liu (University of Illinois – Chicago), T.N.Nagabhushan (Sri Jayacharajendra College of Engineering), Juan Pimentel (Kettering University), Arunabha Sen (Arizona State University), Vassilis Tsaoussidis (Northeastern University), and Bryan Usevitch (Univ. of Texas at El Paso). We also thank many friends at AcceLight Networks who shared their experience of networks with us: Hyong Kim, Leigh Chang, Louis Zhang, Masoud Hashemi, Paul Chow, Debashis Basak, Denny Lee, Safa Almalki, Tom McGill, Hasan Naser, Srini Ramaswami, Stanko Vuleta, Rick Murphy, Stephane Gagnon, Ryan Moore, Mark Milinkovic, Jingyun Zhang, and Mark Fredericks. We thank Paul Bertels and Muhamed Durani for sharing their knowledge of Ethereal with us. We are also grateful for various technical interactions we had with colleagues at Fujitsu: Yau-Ren Jenq, Edmund Cher, Amalendu Chatterjee, Anna Chui, Steven Wright, and Masafumi Katoh; and at Bell Labs: Iraj Saniee, Yikai Su, Debasis Mitra, Anwar Elwalid, Carl Nuzman, Krishnan Kumaran, Randy Giles and Lijun Qian. We thank Eric Munson from McGraw-Hill for persuading us to take the plunge with this project, and Betsy Jones, Executive Editor, for providing decisive support at key times. In addition we thank the production team at McGraw-Hill for their patience, ideas, and continued support, especially John Griffin and Jill Peter. IW would like to thank his wife Liesye for her constant encouragement and continued support while he was working on the second edition of the book. Finally, ALG would like to thank his partner and best friend, Karen Carlyle, who made this second edition happen. ALG can finally think about renovating the house. With the help of the many reviewers, professors, and students who have used previous versions of this book we have tried to make the complex and fluid topic of network architecture as approachable, up-to-date and error-free as possible. We welcome all comments and suggestions on how to improve the text. Please contact us via the text's website with any ideas you may have.