《经典原版书库：计算机网络（英文版·第5版）》是国内外使用广泛的计算机网络经典教材。全书自下而上系统地介绍了计算机网络的基本原理，并给出了大量实例。

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　 PREFACE

　 This book is now in its fifth edition. Each edition has corresponded to a different phase in the way computer networks were used. When the first edition appearedin 1980 networks were an academic curiosity. When the second edition appeared in 1988 networks were used by universities and large businesses. When the third edition appeared in 1996 computer networks especially the Internet had become a daily reality for millions of people. By the fourth edition in 2003 wireless networks and mobile computers had become commonplace for accessing the Web and the Internet. Now in the fifth edition networks are about content distribution(especially videos using CDNs and peer-to-peer networks) and mobile phones are small computers on the Internet.

　 Among the many changes in this book the most important one is the addition f Prof. David J. Wetheall as a co-author. David brings a rich background in networkinghaving cut his teeth designing metropolitan-area networks more than 20years ago. He has worked with the Internet and wireless networks ever since and is a professor at the University of Washington where he has been teaching and doing research on computer networks and related topics for the past decade.

　 Of course the book also has many changes to keep up with the: ever-changing world of computer networks. Among these are revised and new material on Wireless networks (802.12 and 802.16)

　 The 3G networks used by smart phones

　 RFID and sensor networks

　 Content distribution using CDNs

　 Peer-to-peer networks

　 Real-time media (from stored streaming and live sources)

　 Internet telephony (voice over IP)

　 Delay-tolerant networks

　 A more detailed chapter-by-chapter list follows.

　 Chapter 1 has the same introductory function as in the fourth edition but the contents have been revised and brought up to date. The Internet mobile phone networks 802.11 and RFID and sensor networks are discussed as examples of computer networks. Material on the original Ethernet—with its vampire taps—has been removed along with the material on ATM.

　 Chapter 2 which covers the physical layer has expanded coverage of digital modulation (including OFDM as widely used in wireless networks) and 3G networks (based on CDMA). New technologies are discussed including Fiber to the Home and power-line networking.

　 Chapter 3 on point-to-point links has been improved in two ways. The material on codes for error detection and correction has been updated and also includes a brief description of the modern codes that are important in practice (e.g. convolutional and LDPC codes). The examples of protocols now use Packet over SONET and ADSL. Sadly the material on protocol verification has been removed as it is little used.

　 In Chapter 4 on the MAC sublayer the principles are timeless but the technologies have changed. Sections on the example networks have been redone accordingly including gigabit Ethernet 802.11 802.16 Bluetooth and RFID.

　 Also updated is the coverage of LAN switching including VLANs.

　 Chapter 5 on the network layer covers the same ground as in the fourth edition.

　 .　　The revisions have been to update material and add depth particularly for quality of service (relevant for real-time media) and internetworking. The sections on BGP OSPF and CIDR have been expanded as has the treatment of multicast routing. Anycast routing is now included.

　 Chapter 6 on the transport layer has had material added revised and removed.

　 New material describes delay-tolerant networking and congestion control in general. The revised material updates and expands the coverage of TCP congestion control. The material removed described connection-oriented network layers something rarely seen any more.

　 Chapter 7 on applications has also been updated and enlarged. While material on DNS and email is similar to that in the fourth edition in the past few years there have been many developments in the use of the Web streaming media and content delivery. Accordingly sections on the Web and streaming media have been brought up to date. A new section covers content distribution including CDNs and peer-to-peer networks.

　 Chapter 8 on security still covers both symmetric and public-key cryptography for confidentiality and authenticity. Material on the techniques used in practice including firewalls and VPNs has been updated with new material on 802.11 security and Kerberos V5 added.

　 Chapter 9 contains a renewed list of suggested readings and a comprehensive bibliography of over 300 citations to the current literature. More than half of these are to papers and books written in 2000 or later and the rest are citations to classic papers.

　 Computer books are full of acronyms. This one is no exception. By the time you are finished reading this one the following should ring a bell: ADSL AES AJAX AODV AP ARP ARQ AS BGP BOC CDMA CDN CGI CIDR CRL CSMA CSS DCT DES DHCP DHT DIFS DMCA DMT DMZ DNSDOCSIS DOM DSLAM DTN FCFS FDD FDDI FDM FEC FIFO FSKFTP GPRS GSM HDTV HFC HMAC HTTP IAB ICANN ICMP IDEAIETF IMAP IMP IP IPTV IRTF ISO ISP ITU JPEG JSP JVM LANLATA LEC LEO LLC LSR LTE MAN MFJ MIME MPEG MPLS MSCMTSO MTU NAP NAT NRZ NSAP OFDM OSI OSPF PAWS PCM PGPPIM PKI POP POTS PPP PSTN QAM QPSK RED RFC RFID RPC RSARTSP SHA SIP SMTP SNR SOAP SONET SPE SSL TCP TDD TDMTSAP UDP UMTS URL VLAN VSAT WAN WDM and XML. But don’t worry. Each will appear in and be carefully defined before it is used. As a fun test see how many you can identify before reading the book write the number in the margin then try again after reading the book.

　 To help instructors use this book as a text for courses ranging in length from quarters to semesters we have structured the chapters into core and optional material.

　 The sections marked with a ‘‘*’’ in the table of contents are the optional ones. If a major section (e.g. 2.7) is so marked all of its subsections are optional.

　 They provide material on network technologies that is useful but can be omitted from a short course without loss of continuity. Of course students should be encouraged to read those sections as well to the extent they have time as all the material is up to date and of value.

　 The following protected instructors’ resource materials are available on the publisher’s Web site at www.pearsonhighered.com/tanenbaum. For a username and password please contact your local Pearson representative.

　 Solutions manual

　 PowerPoint lecture slides

　 Resources for students are available through the open-access Companion Web site link on www.pearsonhighered.com/tanenbaum including Web resources links to tutorials organizations FAQs and more Figures tables and programs from the book Steganography demo Protocol simulators

　 Many people helped us during the course of the fifth edition. We would especially like to thank Emmanuel Agu (Worcester Polytechnic Institute) Yoris Au (University of Texas at Antonio) Nikhil Bhargava (Aircom International Inc.)Michael Buettner (University of Washington) John Day (Boston University)Kevin Fall (Intel Labs) Ronald Fulle (Rochester Institute of Technology) Ben Greenstein (Intel Labs) Daniel Halperin (University of Washington) Bob Kinicki (Worcester Polytechnic Institute) Tadayoshi Kohno (University of Washington)Sarvish Kulkarni (Villanova University) Hank Levy (University of Washington)Ratul Mahajan (Microsoft Research) Craig Partridge (BBN) Michael Piatek (University of Washington) Joshua Smith (Intel Labs) Neil Spring (University of Maryland) David Teneyuca (University of Texas at Antonio) Tammy VanDegrift (University of Portland) and Bo Yuan (Rochester Institute of Technology)for providing ideas and feedback. Melody Kadenko and Julie Svendsen provided administrative support to David.

　 Shivakant Mishra (University of Colorado at Boulder) and Paul Nagin (Chimborazo

　 Publishing Inc.) thought of many new and challenging end-of-chapter problems. Our editor at Pearson Tracy Dunkelberger was her usual helpful self in many ways large and small. Melinda Haggerty and Jeff Holcomb did a good job of keeping things running smoothly. Steve Armstrong (LeTourneau University) prepared the PowerPoint slides. Stephen Turner (University of Michigan at Flint) artfully revised the Web resources and the simulators that accompany the text. Our copyeditor Rachel Head is an odd hybrid: she has the eye of an eagle and the memory of an elephant. After reading all her corrections both of us wondered how we ever made it past third grade.

　 Finally we come to the most important people. Suzanne has been through this 19 times now and still has endless patience and love. Barbara and Marvin now know the difference between good textbooks and bad ones and are always an inspiration to produce good ones. Daniel and Matilde are welcome additions to our family. Aron is unlikely to read this book soon but he likes the nice pictures on page 884 (AST). Katrin and Lucy provided endless support and always managed to keep a smile on my face.

　 Thank you (DJW).

　 ANDREW S. TANENBAUM

　 DAVID J.WETHERALL