TCP/IP Illustrated is a complete and detailed guide to the entire TCP/IP protocol suite-with an important difference from other books on the subject. Rather than just describing what the RFCs say the protocol suite should do, this unique book uses a popular diagnostic tool so you may actually watch the protocols in action.By forcing various conditions to occur-such as connection establishment, timeout and retransmission, and fragmentation-and then displaying the results, TCP/IP Illustrated gives you a much greater understanding of these concepts than words alone could provide. Whether you are new to TCP/IP or you have read other books on the subject, you will come away with an increased understanding of how and why TCP/IP works the way it does, as well as enhanced skill at developing applications that run over TCP/IP.
With this unique approach, TCP/IP Illustrated presents the structure and function of TCP/IP from the link layer up through the network, transport, and application layers. You will learn about the protocols that belong to each of these layers and how they operate under numerous implementations, including Sun OS 4.1.3, Solaris 2.2, System V Release 4, BSD/386TM, AIX 3.2.2, and 4.4BSD.In TCP/IP Illustrated you will find the most thorough coverage of TCP available - 8 entire chapters. You will also find coverage of the newest TCP/IP features, including multicasting, path MTU discovery, and long fat pipes.
"While all of Stevens' books are excellent, this new opus (TCP/IP Illustrated, Volume 1) is awesome. Although many books describe the TCP/IP protocols, the author provides a level of depth and real-world detail lacking from the competition."
- Unix Review
"This book (TCP/IP Illustrated, Volume 1) is a stone jewel...Written by W. Richard Stevens, this book probably provides the most comprehensive view of TCP/IP available today in print."
"The diagrams he uses are excellent and his writing style is clear and readable. Please read it (TCP/IP Illustrated, Volume 1) and keep it on your bookshelf."
- Sys Admin
"The word 'illustrated' distinguishes this book (TCP/IP Illustrated, Volume 1) from its many rivals. Stevens uses the Lawrence Berkeley Laboratories tcdump program to capture packets in promiscuous mode under a variety of OS and TCP/IP implementations. Studying tcdump output helps you understand how the various protocols work."
- Unix Review
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The Domain Name System.
Standard, Simple Services.
Application Programming Interfaces.
Ethernet and IEEE 802 Encapsulation.
SLIP: Serial Line IP.
PPP: Point-to-Point Protocol.
Serial Line Throughput Calculations.
Special Case IP Addresses.
A Subnet Example.
ARP Packet Format.
RARP Packet Format.
RARP Server Design.
ICMP Message Types.
ICMP Address Mask Request and Reply.
ICMP Timestamp Request and Reply.
ICMP Port Unreachable Error.
4.4BSD Processing of ICMP Messages.
IP Record Route Option.
IP Timestamp Option.
Traceroute Program Operation.
IP Source Routing Option.
ICMP Host and Network Unreachable Errors.
To Forward or Not to Forward.
ICMP Redirect Errors.
ICMP Router Discovery Messages.
Unix Routing Daemons.
RIP: Routing Information Protocol.
RIP Version 2.
OSPF: Open Shortest Path First.
BGP: Border Gateway Protocol.
CIDR: Classless Interdomain Routing.
A Simple Example.
ICMP Unreachable Error (Fragmentation Required).
Determining the Path MTU Using Traceroute.
Path MTU Discovery with UDP.
Interaction Between UDP and ARP.
Maximum UDP Datagram Size.
ICMP Source Quench Error.
UDP Server Design.
DNS Message Format.
A Simple Example.
UDP or TCP.
BOOTP Packet Format.
BOOTP Server Design.
BOOTP Through a Router.
Connection Establishment and Termination.
Timeout of Connection Establishment.
Maximum Segment Size.
TCP State Transition Diagram.
TCP Server Design.
Window Size Advertisements.
Normal Data Flow.
Bulk Data Throughput.
Simple Timeout and Retransmission Example.
Round-Trip Time Measurement.
An RTT Example.
Congestion Avoidance Algorithm.
Fast Retransmit and Fast Recovery Algorithms.
Congestion Example (Continued).
Silly Window Syndrome.
Path MTU Discovery.
Long Fat Pipes.
Window Scale Option.
PAWS: Protection Against Wrapped Sequence Numbers.
T/TCP: A TCP Extension for Transactions.
Structure of Management Information.
Introduction to the Management Information Base.
Management Information Base (Continued).
ASN.1 and BER.
SNMP Version 2.
Sun Remote Procedure Call.
XDR: External Data Representation.
NFS Version 3.
Archie, WAIS, Gopher, Veronica, and WWW.
X Window System.
BSD Packet Filter.
SunOS Network Interface Tap.
SVR4 Data Link Provider Interface.
Socket Debug Option.
BSD/386 Version 1.0.
System V Release 4.
When networking protocols were being developed in the 1960s through the 1980s, expensive, dedicated hardware was required to see the packets going "across the wire." Extreme familiarity with the protocols was also required to comprehend the packets displayed by the hardware. Functionality of the hardware analyzers was limited to that built in by the hardware designers.
Today this has changed dramatically with the ability of the ubiquitous workstation to monitor a local area network Mogul 1990. Just attach a workstation to your network, run some publicly available software (described in Appendix A), and watch what goes by on the wire. While many people consider this a tool to be used for diagnosing network problems, it is also a powerful tool for understanding how the network protocols operate, which is the goal of this book.
This book is intended for anyone wishing to understand how the TCP/IP protocols operate: programmers writing network applications, system administrators responsible for maintaining computer systems and networks utilizing TCP/IP, and users who deal with TCP/IP applications on a daily basis.
This book also uses a functional approach instead of following a strict bottom-to-top order. For example, Chapter 3 describes the IP layer and the IP header. But there are numerous fields in the IP header that are best described in the context of an application that uses or is affected by a particular field. Fragmentation, for example, is best understood in terms of UDP (Chapter 11), the protocol often affected by it. The time-to-live field is fully described when we look at the Traceroute program in Chapter 8, because this field is the basis for the operation of the program. Similarly, many features of ICMP are described in the later chapters, in terms of how a particular ICMP message is used by a protocol or an application.
We also don't want to save all the good stuff until the end, so we describe TCP/IP applications as soon as we have the foundation to understand them. Ping and Traceroute are described after IP and ICMP have been discussed. The applications built on UDP (multicasting, the DNS, TFTP, and BOOTP) are described after UDP has been examined. The TCP applications, however, along with network management, must be saved until the end, after we've thoroughly described TCP. This text focuses on how these applications use the TCP/IP protocols. We do not provide all the details on running these applications.
This book can be used in many ways. It can be used as a self-study reference and covered from start to finish by someone interested in all the details on the TCP/IP protocol suite. Readers with some TCP/IP background might want to skip ahead and start with Chapter 7, and then focus on the specific chapters in which they're interested. Exercises are provided at the end of the chapters, and most solutions are in Appendix D. This is to maximize the usefulness of the text as a self-study reference.
When used as part of a one- or two-semester course in computer networking, the focus should be on IP (Chapters 3 and 9), UDP (Chapter 11), and TCP (Chapters 17-24), along with some of the application chapters.
Many forward and backward references are provided throughout the text, along with a thorough index, to allow individual chapters to be studied by themselves. A list of all the acronyms used throughout the text, along with the compound term for the acronym, appears on the inside back covers.
If you have access to a network you are encouraged to obtain the software used in this book (Appendix F) and experiment on your own. Hands-on experimentation with the protocols will provide the greatest knowledge (and make it more fun).
Most of the systems have a name that indicates the type of software being used: bsdi, svr4, sun, solaris, aix, slip, and so on. In this way we can identify the type of software that we're dealing with by looking at the system name in the printed output.
A wide range of different operating systems and TCP/IP implementations are used:
Also, we always include the name of the system as part of the shell prompt (bsdi in this example) to show on which host the command was run.
Throughout the text we'll use indented, parenthetical notes such as this to describe historical points or implementation details.We sometimes refer to the complete description of a command in the Unix manual as in ifconfig(8). This notation, the name of the command followed by a number in parentheses, is the normal way of referring to Unix commands. The number in parentheses is the section number in the Unix manual of the "manual page" for the command, where additional information can be located. Unfortunately not all Unix systems organize their manuals the same, with regard to the section numbers used for various groupings of commands. We'll use the BSD-style section numbers (which is the same for BSD-derived systems such as SunOS 4.1.3), but your manuals may be organized differently.
The consulting editor, Brian Kernighan, is undoubtedly the best in the business. He was the first one to read various drafts of the manuscript and mark it up with his infinite supply of red pens. His attention to detail, his continual prodding for readable prose, and his thorough reviews of the manuscript are an immense resource to a writer.
Technical reviewers provide a different point of view and keep the author honest by catching technical mistakes. Their comments, suggestions, and (most importantly) criticisms add greatly to the final product. My thanks to Steve Bellovin, Jon Crowcroft, Pete Haverlock, and Doug Schmidt for comments on the entire manuscript. Equally valuable comments were provided on portions of the manuscript by Dave Borman, Tony DeSimone, Bob Gilligan, Jeff Gitlin, John Gulbenkian, Tom Herbert, Mukesh Kacker, Barry Margolin, Paul Mockapetris, Burr Nelson, Steve Rago, James Risner, Chris Walquist, Phil Winterbottom, and Gary Wright. A special thanks to Dave Borman for his thorough review of all the TCP chapters, and to Bob Gilligan who should be listed as a coauthor for Appendix E.
An author cannot work in isolation, so I would like to thank the following persons for lots of small favors, especially by answering my numerous e-mail questions: Joe Godsil, Jim Hogue, Mike Karels, Paul Lucchina, Craig Partridge, Thomas Skibo, and Jerry Toporek.
This book is the result of my being asked lots of questions on TCP/IP for which I could find no quick, immediate answer. It was then that I realized that the easiest way to obtain the answers was to run small tests, forcing certain conditions to occur, and just watch what happens. I thank Pete Haverlock for asking the probing questions and Van Jacobson for providing so much of the publicly available software that is used in this book to answer the questions.
A book on networking needs a real network to work with along with access to the Internet. My thanks to the National Optical Astronomy Observatories (NOAO), especially Sidney Wolff, Richard Wolff, and Steve Grandi, for providing access to their networks and hosts. A special thanks to Steve Grandi for answering lots of questions and providing accounts on various hosts. My thanks also to Keith Bostic and Kirk McKusick at the U.C. Berkeley CSRG for access to the latest 4.4BSD system.
Finally, it is the publisher that pulls everything together and does whatever is required to deliver the final product to the readers. This all revolves around the editor, and John Wait is simply the best there is. Working with John and the rest of the professionals at Addison-Wesley is a pleasure. Their professionalism and attention to detail show in the end result.
Camera-ready copy of the book was produced by the author, a Troff die-hard, using the Groff package written by James Clark. I welcome electronic mail from any readers with comments, suggestions, or bug fixes.
W. Richard Stevens