The protocol wars are over and TCP/IP won. TCP/IP is now universally recognized as the pre-eminent communications protocol for linking together diverse computer systems. The importance of interoperable data communications and global computer networks is no longer debated. But that was not always the case. When I wrote the first edition of this book, IPX was far and away the leading PC communications protocol. Microsoft did not bundle communications protocols in their operating system. Corporate networks were so dependent on SNA that many corporate network administrators had not even heard of TCP/IP. Even UNIX, the mother of TCP/IP, nursed a large number of pure UUCP networks. Back then I felt compelled to tout the importance of TCP/IP by pointing out that it was used on thousands of networks and hundreds of thousands of computers. How times have changed! Today we count the hosts and users connected to the Internet in the tens of millions. And the Internet is only the tip of the TCP/IP iceberg. The largest market for TCP/IP is in the corporate "intranet." An intranet is a private TCP/IP network used to disseminate information within the enterprise. The competing network technologies have shrunk to niche markets where they fill special needs - while TCP/IP has grown to be the communications software that links the world.
The acceptance of TCP/IP as a worldwide standard and the size of its global user base are not the only things that have changed. In 1991 I lamented the lack of adequate documentation. At the time it was difficult for a network administrator to find the information he or she needed to do the job. Since that time there has been an explosion of books about TCP/IP and the Internet. However, there are still too few books that concentrate on what a system administrator really needs to know about TCP/IP administration and too many books that try to tell you how to surf the Web. In this book I strive to focus on TCP/IP and UNIX, and not to be distracted by the phenomenon of the Internet.
I am very proud of the first edition of TCP/IP Network Administration . In the second edition, I have done everything I can to maintain the essential character of the book while making it better. The Domain Name Service material has been updated to cover the latest version of the BIND 4 software. The email configuration is now based on sendmail version 8, and the operating system examples are from the current versions of Solaris and Linux. The routing protocol coverage has been expanded to include Open Shortest Path First (OSPF) and Border Gateway Protocol (BGP). I have also added new topics such as one-time passwords and configuration servers based on Dynamic Host Configuration Protocol (DHCP) and Bootstrap Protocol (BOOTP). Despite the additional topics, the book has been kept to a reasonable length.
The bulk of this edition is derived directly from the first edition of the book. To emphasize both that times have changed and that my focus on practical information has not, I have left the introductory paragraphs from the first edition intact.
The Internet, the world's largest network, grew from fewer than 6,000 computers at the end of 1986 to more than 600,000 computers five years later.  This explosive growth demonstrates the incredible demand for network services. This growth has taken place despite a lack of practical information for network administrators. Most administrators have been forced to content themselves with man pages, or protocol documents and scholarly texts written from the point of view of the protocol designer. For practical information, most of us have relied on the advice of friends who had already networked their computers. This book addresses the lack of information by providing practical, detailed network information for the UNIX system administrator.
Networks have grown so extravagantly because they provide an important service. It is in the nature of computers to generate and process information, but this information is frequently useless unless it can be shared with the people who need it. The network is the vehicle that enables data to be easily shared. Once you network your computer, you'll never want to be stuck on an isolated system again.
The common thread that ties the enormous Internet together is TCP/IP network software. TCP/IP is a set of communications protocols that define how different types of computers talk to each other. This is a book about building your own network based on TCP/IP. It is both a tutorial covering the "why" and "how" of TCP/IP networking, and a reference manual for the details about specific network programs.