Preface
Recently, while driving to my work, I listened to radio as usual. Because of the establishment of the new EU (European Union) domain, there was an interview with a representative of one of the Internet Service Providers. For some time the interview went on, boringly similar to other common radio interviews, but suddenly the presswoman started to improvise and she asked, "But isn’t the DNS too vulnerable? Is it prepared for terrorist attacks?" The ISP representative enthusiastically answered, "The whole Internet arose more than 30 years ago, initiated by the American Department of Defense. From the very beginning, the Internet architecture took into account that it should be able to keep the communication functional even if a part of the infrastructure of the USA were destroyed, i.e., it must be able to do without a destroyed area."
He went on enthusiastically, "We have 13 root name servers in total. Theoretically, only one is enough to provide the complete DNS function." At this point, we must stop for a moment our radio interview to remind you that a role and principle of usage of root name servers are described in the first chapter of this book. Now, let’s go back to our interview again. The presswoman, not satisfied with the answer, asked, "All these root name servers are in the USA, aren’t they? What will happen if someone or something cuts off the international connectivity, and I am not be able to reach any root name server?" The specialist, caught by the presswoman’s questions, replied, "This would be a catastrophe. In such a case, the whole Internet would be out of order."
That time I did not immediately came upon the solution that an area cut off this way is by nature similar to an Intranet. In such a case, it would be enough to create national (or continental) recovery plan and put into work a fake national (or continental) name server, exactly according to the description in Chapter 9, describing closed company networks. The result would be that the Internet would be limited only to our national (or continental) network; however, it would be at least partially functional.
In fact at that time, the specialist’s answer made me angry. "So what?", I thought, "Only DNS would be out of order; i.e., names could not be translated to IP addresses. If we do not use names but use IP addresses instead, we could still communicate. The whole network infrastructure would be intact in that case!"
But working according to my way would be lengthy, and I thought about it over and over. After some time I realized that the present Internet is not the same as it was in the early 1990s. At that time the handful of academics involved with the Internet would have remembered those few IP addresses. But in the present scenario, the number of IP addresses is in the millions, and the number of people using the Internet is much higher still. Most of them are not IT experts and know nothing about IP addresses and DNS. For such people, the Internet is either functional or not—similar to, for example, an automatic washing machine. From this point of view, the Internet without functional DNS would be really out of order (in fact it would still be functional, but only IT experts would be able to use it).
But working according to my way would be lengthy, and I thought about it over and over. After some time I realized that the present Internet is not the same as it was in the early 1990s. At that time the handful of academics involved with the Internet would have remembered those few IP addresses. But in the present scenario, the number of IP addresses is in the millions, and the number of people using the Internet is much higher still. Most of them are not IT experts and know nothing about IP addresses and DNS. For such people, the Internet is either functional or not—similar to, for example, an automatic washing machine. From this point of view, the Internet without functional DNS would be really out of order (in fact it would still be functional, but only IT experts would be able to use it).
The goal of this publiction is to illustrate to readers the principles on which the DNS is based. This publication is generously filled with examples. Some are from a UNIX environment, some from Microsoft. The concrete examples mostly illustrate some described problem. The publication is not a text book of a DNS implementation for a concrete operating system, but it always tries to find out the base of the problem. The reader is led to create similar examples according to his or her concrete needs by him- or herself.
The goal of this book is to give the reader a deep understanding of DNS, independent of any concrete DNS implementation. After studying this book, the reader should be able to study DNS standards directly from the countless Requests for Comments (RFC). Links to particular RFCs are listed in the text. In fact, it is quite demanding to study the unfriendly RFCs directly without any preliminary training. For a beginner, only to find out the right RFC could be a problem.
Before studying this book, the reader should know the IP principles covered in the Understanding TCP/IP book published by Packt Publishing (ISBN: 1-904811-71-X) because this publication is a logical follow-on from that book.
The authors wish you good luck and hope that you get a lot of useful information by reading this publication.