(特价书)计算机网络系统方法（英文版·第3版）

1.5.2 Delay x Bandwidth Product
1.5.3 High-Speed Networks
1.5.4 Application Performance Needs
1.6 Summery
Open Issue: Ubiquitous Networking
Further Reading
Exercises
2 Direct Link Networks
Problem: Physically Connecting Hosts
2.1 Hardware Building Blocks
2.1.1 Nodes
2.1.2 Links
2.2 Encoding (NRZ, NRZI, Manchester, 4B/5B)
2.3 Framing
2.3.1 Byte-Oriented Protocols (BISYNC, PPP, DDCMP)
2.3.2 Bit-Oriented Protocols (HDLC)
2.3.3 Clock-Based Framing (SONET)
2.4 Error Detection
2.4.1 Two-Dimensional Parity
2.4.2 Internet Checksum Algorithm
2.4.3 Cyclic Redundancy Check
2.5 Reliable Transmission
2.5.1 Stop-dad-Wait
2.5.2 Sliding Window
2.6.3 Concurrent Logical Channels
2.6 Ethernet (802.3)
2.6.1 Physical Properties
2.0.2 Access Protocol
2.8.3 Experience with Ethernet
2.7 Token Rings (802.5, FDDI)
2.7.1 Physical Properties
2.7.2 Token Ring Media Access Control
2.7.3 Token Ring Maintenance
2.7.4 Frame Format
2.7.5 FDDI
2.8 Wireless (802.11)
2.8.1 Physical Properties
2.8.2 Collision Avoidance
2.8.3 Distribution System
2.8.4 Frame Format
2.9 Network Adaptors
2.9.1 Components
2.9.2 View from the Host
2.9.3 Memory Bottleneck
2.10 Summary
Open Issue: Does It Belong in Hardware?
Further Reading
Exercises
3 Packet Switching
Problem: Not All Networks Are Directly Connected
3.1 Switching and Forwarding
3.1.1 Datagrams
3.1.2 Virtual Circuit Switching
3.1.3 Source Routing
3.2 Bridges and LAN Switches
3.2.1 Learning Bridges
3.2.2 Spanning Tree Algorithm
3.2.3 Broadcast and Multicast
3.2.4 Limitations of Bridges
3.3 Cell Switching (ATM)
3.3.1 Cells
3.3.2 Segmentation and Reassembly
3.3.3 Virtual Paths
3.3.4 Physical Layers for ATM
3.3.5 ATM in the LAN
3.4 Implementation and Performance
3.4.1 Ports
3.4.2 Fabrics
3.5 Summary
Open Issue: The Future of ATM
Further Reading
Exercises
4 Internetworking
Problem: There Is More Than One Network
4.1 Simple Intarnotworking (IP)
4.1.1 What Is an Internetwork?
4.1.2 Service Model
4.1.3 Global Addresses
4.1.4 Dctagrem Forwarding in IP
4.1.5 Address Translation (ARP)
4.1.6 Host Configuration (DHCP)
4.1.7 Error Reporting (ICMP)
4.1.8 Virtual Networks and Tunnels
4.2 Routing
4.2.1 Network as c Graph
4.2.2 Distance Vector (RIP)
4.2.3 Link State (OSPF)
4.2.4 Metrics
4.2.5 Routing for Mobile Hosts
4.3 Global Intemet
4.3.1 Subnetting
4.3.2 Classless Routing (CIDR)
4.3.3 Intardomein Routing (BGP)
4.3.4 Routing Areas
4.3.6 IP Version 6 (IPv6)
4.4 Multicast
4.4.1 Link-Stata Multiceat
4.4.2 Distance-Vector Multicast
4.4.3 Protocol Independent Multicast (PIM)
4.6 Multiprotocol Label Switching (MPLS)
4.6.1 Destinetion-Baead Forwarding
4.5.2 Explicit Routing
4.5.3 Virtual Private Networks and Tunnels
4.6 Summary
Open Issue: Deployment of IPV6
Further Reading
Exereieas
5 End-to-End Protocols
Problem: Getting Processess to Communicate
5.1 Simple Demultiplexer (UDP)
5.2 Reliable Byte Stream (TCP)
5.2.1 End-to-End Issues
5.2.2 Segment Format
5.2.3 Connection Establishment and Termination
5.2.4 Sliding Window Revisited
5.2.5 Triggering Transmission
5.2.6 Adaptive Retrensmission
5.2.7 Record Boundaries
5.2.8 TCP Extensions
5.2.9 Alternative Design Choices
g.3 Remote Procedure Call
5.3.1 Bulk Transfer (BLAST)
5.3.2 Request/Reply (CHAN)
5.3.3 Dispatcher (SELECT)
5.3.4 Putting It All Together (SunRPC, DCE)
5.4 Performance
5.5 Summary
Open Issue: Applicstion-Specific Protocols
Further Reading
Exercises
6 Congestion Control and Resource Allocation
Problem: Allocating Resources
6.1 lssuec in Resource Allocation
6.1.1 Network Model
6.1.2 Taxonomy
8.1.3 Evaluation Criteria
6.2 Queuing Disciplines
6.2.1 FIFO
6.2.2 Fair Queuing
6.3 TCP Congestion Control
6.3.1 Additive Incrense/Multiplicstive Decrease
6.3.2 Slow Start
6.3.3 Fast Rctrensmit and Fast Recovery
6.4 Congestion-Avoidance Mechanisms
6.4.1 DECbit
6.4.2 Random Early Detection (RED)
6.4.3 Source-Based Congestion Avoidance
6.5 Quality of Service
6.5.1 Application Requirements
6.5.2 Integrated Services (RSVP)
6.5.3 Differentiated Services (EF, AF)
6.5.4 ATM Quality of Service
6.5.5 Equation-Based Congestion Control
6.6 Summary
Open Issue: Inside versus Outside the Network
Further Reading
Exercises
7 End-to-End Data
Problem: What Do We Do with the Data?
7,1 Presentation Formatting
7.1.1 Taxonomy
7.1.2 Examoles (XDR, ASN. 1, NDR)
7.1.3 Markup Languages (XMl)
7.2 Data Compression.
7.2.1 Lossless Compression Algorithms
7.2.2 Image Compression (JPEG)
7.2.3 Video Compression (MPEG)
7.2.4 Transmitting MPEG over a Network
7.2.5 Audio Compression (MP3)
7.3 Summary
Open lssue:Computer Networks Meet Consumer Electronice
Further Reading
Exercises
8 Network Security
Problem: Securing the Data
8.1 Cryptographic Algorithms
8.1.1 Requirementu
8.1.2 Secret Key Encryption (DES)
8.1.3 Public Key Encryption (RSA)
8.1.4 Message Digest Algorithms (MDS)
8.1.5 Implementation and Performance
8.2 Security Mechanisms
8.2.1 Authentication Protocols
8.2.2 Message Integrity Protocols
8.2.3 Public Key Distribution (X.509)
8.3 Example Systems
8.3.1 Pretty Good Privacy (PGP)
8.3.2 Secure Shell (SSH)
8.3.3 Transport Layer Security (TLS, SSL, HTTPS)
8.3.4 IP Security (IPSEC)
8.4 Firewalls
8.4.1 Filter-Based Firewalls
8.4.2 Proxy-Based Firewells
8.4.3 Limitations
8.5 Summery
Open Issue: Denial-of-Service Attacks
Further Reading
Exercises
9 Applications
Problem: Applications Need Their Own Protocols
9.1 Name Service (DNS)
9.1.1 Domain Hierarchy
9.1.2 Name Servers
9.1.3 Name Resolution
9.2 Traditional Applications
9.2.1 Electronic Mail (SMTP, MIME, IMAP)
9.2.2 World Wide Web (HTrP)
9.2.3 Network Management (SNMP)
9.3 Multimedia Applications
9.3.1 Real-time Transport Protocol (RTP)
9.3.2 Session Control and Call Control (SDP, SIP, H.323)
9.4 Overlay Networks
9.4.1 Routing Overlays
9.4.2 Peer-to-Peer Networks
9.4.3 Content Distribution Networks
9.5 Summary
Open Issue: New Network Artichitecture
Further Reading
Exercises
Glossary
Bibliography
Solutions to Selected Exercises
Index
About the Authors

.　　 ~ Although the material is loosely organized around the traditional network layers, starting at the bottom and moving up the protocol stack, we do not adopt a rigid layered approach. Many topics--congestion control and security are good examples--have implications up and down the hierarchy, and so we discuss them outside the traditional layered model. In short, we believe layering makes a good servant but a poor master; it's more often useful to take an end-to-end perspective.
　　 ~ Rather than explain how protocols work in the abstract, we use the most important protocols in use today--many of them from the TCP/IP Internet-to illustrate how networks work in practice. This allows us to include realworld 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 tSe leased from the phone company, it is the software that allows networks to provide new services and adapt quickly to changing circumstances. It is for this reason that we emphasize how network software is implemented, rather than stopping with a description of the abstract algorithms involved. We also include code segments taken from a working protocol stack to illustrate how you might implement certain protocols and algorithms.
　　 ~ Networks are constructed from many building-block pieces, and while it is necessary to be able to abstract away uninteresting elements when solving a particular problem, it is essential to understand how all the pieces fit together to form a functioning network. We therefore spend considerable time explaining the overall end-to-end behavior of networks, not just the individual components, so that it is possible to understand how a complete network operates, 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, distributed and parallel systems, and so on. They are all large and complex. To help manage this complexity, system builders often draw on a collection of design principles. We highlight these design principles as they are introduced throughout the book, illustrated, of course, with examples from computer networks.
　　Pedagogy and Features
　　The third edition retains several features that we encourage you to take advantage of:
　　 ~ Problem statements. At the start of each chapter, we describe a problem that identifies the next set of issues that must be addressed in the design of a network. This statement introduces and motivates the issues to be explored in the chapter.
　　 ~ Shaded sidebars. Throughout the text, shaded sidebars elaborate on the topic being discussed or introduce a related advanced topic. In many cases, these sidebars relate real-world anecdotes about networking.
　　 ~Highligbted paragraphs. These paragraphs summarize an important nugget of information that we want you to take away from the discussion, such as a widely applicable system design principle.
　　 ~ Real protocols. Even though the book's focus is on core concepts rather than existing protocol specifications, real protocols are used to illustrate most of the important ideas. As a result, the book can be used as a source of reference for many protocols. To help you find the descriptions of the protocols, each applicable section heading parenthetically identifies the protocols described in that section. For example, Section 5.2, which describes the principles of reliable end-to-end protocols, provides a detailed description of TCP, the canonical example of such a protocol.
　　 ~ Open issues. We conclude the main body of each chapter with an important issue that is currently being debated in the research community, the commercial world, or society as a whole. We have found that discussing these issues helps to make the subject of networking more relevant and exciting.
　　 ~Furtber reading. These highly selective lists appear at the end of each chapter. Each list generally contains the seminal papers on the topics just discussed. We strongly recommend that advanced readers (e.g., graduate students) study the papers in this reading list to supplement the material covered in the chapter.
　　Road Map and Course Use
　　The book is organized as follows:
　　 ~ Chapter 1 introduces the set of core ideas that are used throughout the rest of the text. Motivated by widespread applications, it discusses what goes into network architecture, and it defines the quantitative performance metrics that often drive network design.
　　 ~ Chapter 2 surveys a wide range of low-level network technologies, ranging from Ethernet to token ring to wireless. It also describes many of the issues that all data link protocols must address, including encoding, framing, and error detection.
　　 ~ Chapter 3 introduces the basic models of switched networks (datagrams versus virtual circuits) and describes one prevalent switching technology (ATM) in some detail. It also discusses the design of hardware-based switches.
　　 ~ Chapter 4 introduces internetworking and describes the key elements of the Internet Protocol (IP). A central question addressed in this chapter is how networks that scale to the size of the Internet are able to route packets.
　　 ~ Chapter 5 moves up to the transport level, describing both the Internet's Transmission Control Protocol (TCP) and Remote Procedure Call (RPC) used to build client/server applications in detail.
　　 ~ Chapter 6 discusses congestion control and resource allocation. The issues in this chapter cut across both the network level (Chapters 3 and 4) and the transport level (Chapter 5). Of particular note, this chapter describes how congestion control works in TCP, and it introduces the mechanisms used by both the Internet and ATM to provide quality of service.
　　 ~ Chapter 7 considers the data sent through a network. This includes the problems of both presentation formatting and data compression. The discussion of compression includes explanations of how MPEG video compression and MP3 audio compression work.
　　 ~ Chapter 8 discusses network security, ranging from an overview of cryptography protocols (DES, RSA, MD5), to protocols for security services (authentication, digital signature, message integrity), to complete security systems (privacy enhanced email, IPSEC). The chapter also discusses pragmatic issues like firewalls.
　　 ~ Chapter 9 describes a representative sample of network applications and the protocols they use, including traditional applications like email and the Web, multimedia applications such as IP telephony and video streaming, and overlay networks like peer-to-peer file sharing and content distribution networks.
　　 For an undergraduate course, extra class time will most likely be needed to help students digest the introductory material in the first chapter, probably at the expense of the more advanced topics covered in Chapters 6 through 8. Chapter 9 then returns to the popular topic of network applications. In contrast, the instructor for a graduate course should be able to cover the first chapter in only a lecture or two--with students studying the material more carefully on their own-thereby freeing up additional class time to cover the last four chapters in depth. Both graduate and undergraduate classes will want to cover the core material contained in the middle four chapters (Chapters 2-5), although an undergraduate class might choose to skim the more advanced sections (e.g., Sections 2.2, 2.9, 3.4, and 4.4).
　　 For those of you using the book in self-study, we believe that the 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 selected exercises.
　　 The book takes a unique approach to the topic of congestion control by pulling all topics related to congestion control and resource allocation together in a single place--Chapter 6. We do this because the problem of congestion control cannot be solved at any one level, and we want you to consider the various design options at the same time. (This is consistent with our view that strict layering often obscures important design trade-offs.) A more traditional treatment of congestion control is possible, however, by studying Section 6.2 in the context of Chapter 3 and Section 6.3 in the context of Chapter 5.
　　Exercises Significant effort has gone into improving the exercises in both the second and third editions. In the second edition we greatly increased the number of problems and, based on class testing, dramatically improved their quality. In this edition, we added a few more exercises, but made two other important changes:
　　 ~ For those exercises that we feel are particularly challenging or require special knowledge not provided in the book (e.g., probability expertise), we have added an icon ★ to indicate the extra level of difficulty.
　　 ~ In each chapter we added some extra representative exercises for which worked solutions are provided in the back of the book. These exercises, marked √, are intended to provide some help in tackling the other exercises in the book.
　　 The current sets of exercises are of several different styles:
　　 ~ Analytical exercises that ask the student to do simple algebraic calculations that demonstrate their understanding of fundamental relationships
　　 ~ Design questions that ask the student to propose and evaluate protocols for various circumstances
　　 ~ Hands-on questions that ask the student to write a few lines of code to test an idea or to experiment with an existing network utility
　　 ~ Library research questions that ask the student to learn more about a partic-ular topic
　　 Also, as described in more detail below, socket-based programming assignments, as well as simulation labs, are available online. Supplemental Materials and Online Resources To assist instructors, we have prepared an instructor's manual that contains solutions to selected exercises. The manual is available from the publisher.
　　 Additional support materials, including lecture slides, figures from the text, socket-based programming assignments, and sample exams and programming assignments are available through the Morgan Kaufmann Web site at http://www, mkp.oom (search for Computer Networks). We suggest that you visit the page for this book every few weeks, as we will be adding support materials and establishing links to networking-related sites on a regular basis.
　　And finally, new with the third edition, a set of laboratory experiments supple-ments the book. These labs, developed by Professor Emad Aboelela from the University of Massachusetts Dartmouth, use simulation to explore the behavior, scalability, and performance of protocols covered in the book. The simulations use the OPNET simu-lation tooiset, which is available for free to anyone using Computer Networks in their course. Call outs in the form of a test beaker icon (shown on this page) appear in the mar-gins throughout the text to draw attention to experiments found in the online lab manual. Acknowledgments This book would not have been possible without the help of many people. We would like to thank them for their efforts in improving the end result. Before we do so, however, we should mention that we have done our best to correct the mistakes that the reviewers have pointed out and to accurately describe the protocols and mechanisms that our colleagues have explained to us. We alone are responsible for any remaining errors. If you should find any of these, please send email to our publisher, Morgan Kaufmann, at netbugs@mkp.com, and we will endeavor to correct them in future printings of this book.
　　 First, we would like to thank the many people who reviewed drafts of all or parts of the manuscript. In addition to those who reviewed prior editions, we wish to thank Carl Emberger, Isaac Ghansah, and Bobby Bhattacharjee for their thorough reviews. Thanks also to Peter Druschel, Limin Wang, Aki Nakao, Dave Oran, George Swallow, Peter Lei, and Michael Ramalho for their reviews of various sections. We also wish to thank all those who provided feedback and input to help us decide what to do in this edition: Chedley Aouriri, Peter Steenkiste, Esther A. Hughes, Ping-Tsai Chung, Doug Szajda, Mark Andersland, Leo Tam, C. P. Watkins, Brian L. Mark, Miguel A. Labrador, Gene Chase, Harry W. Tyrer, Robert Siegfried, Harlan B. Russell, John R. Black, Robert Y. Ling, Julia Johnson, Karen Collins, Clark Verbrugge, Monjy Rabemanantsoa, Kerry D. LaViolette, William Honig, Kevin Mills, Murat Demirer, J Rufinus, Manton Matthews, Errin W. Fulp, Wayne Daniel, Luiz DaSilva, Don Yates, Raouf Boules, Nick McKeown, Neil T. Spring, Kris Verma, Szuecs Laszlo, Ted Herman, Mark Sternhagen, Zongming Fei, Dulal C. Kar, Mingyan Liu, Ken Surendran, Rakesh Arya, Marlo J. Gonzalez, Annie Stanton, Tim Batten, and Paul Francis. Second, several members of the Network Systems Group at Princeton contributed ideas, examples, corrections, data, and code to this book. In particular, we would like to thank Andy Bavier, Tammo Spalink, Mike Wawrzoniak, Zuki Gottlieb, George Tzanetakis, and Chad Mynhier. As before, we want to thank the Defense Advanced Research Projects Agency, the National Science Foundation, Intel Corporation, and Cisco Systems, Inc. for supporting our networking research over the past several years.
　　 Third, we would like to thank our series editor, David Clark, as well as all the people at Morgan Kaufmann who helped shepherd us through the book-writing process. A special thanks is due to our original sponsoring editor, Jennifer Mann; our editor for the third edition, Rick Adams; our developmental editor, Karyn Johnson; and our production manager, Simon Crump. The whole crew at MKP has been a delight to work with.