The first step to dealing with a problem is recognizing that you have one. So, I have to come clean with you, my reader. I have a problem: an addiction to… detail. J Every time I set out to write about a particular protocol, technology or concept, I start with a modest goal regarding how much I want to write. I always begin knowing that I really need to control myself, to prevent my project from going on forever. But as I explore each subject, I learn more and more, and I start to say to myself things like…“this is important, I simply must include coverage for it” and… “if I am going to cover subject #1, I also should cover subject #2, because they are related”. This is how I turned a six-month project into a multi-year ordeal. J

However, even though self-control in this area is a weakness for me, even I realized I could not possibly cover everything related to TCP/IP in this Guide. Consider that the TCP/IP suite contains dozens of protocols and technologies that have each had thick books written about them. I was willing to spend years on this project but not decades. J Thus, I had to limit the scope of this Guide somewhat, both to preserve what remains of my sanity and to spare you from having to wade through a ridiculously large document.

Here are a few different points that will help explain decisions that I made to limit the scope of The TCP/IP Guide:

• Theory versus Practice: This is primarily a reference resource on the TCP/IP protocol suite. The material here is designed to allow a student to learn the nuts and bolts of how TCP/IP works. I do discuss quite a number of “real-world” practical issues related to how TCP/IP internetworks operate, but this is not my primary focus here. If you want to really understand what TCP/IP is and what makes it work, you’ve come to the right place. If all you want is simple instructions on how to connect a few PCs together in your home using TCP/IP, this probably isn’t the Guide for you. J
  
  
• Current versus Future Protocols: Most of the emphasis in this Guide is on the present state of the art in TCP/IP. The suite is always changing, and there are constantly new protocols being written and revisions to existing protocols being published. I have not provided extensive coverage of technologies still in development, to try to keep the size of the Guide manageable, and to reduce the number of changes I will have to make to keep the material up-to-date.
  
  The one exception to this general rule of thumb is version 6 of the Internet Protocol. IPv6 represents a significant change to the core of how most of TCP/IP operates. While not universally deployed yet, IPv6 is sufficiently far along in its development that I feel any student of TCP/IP needs to know what it is and how it works, and understand its significance. Thus, I have included a detailed section describing it, and also mentioned how it impacts the operation of several other key protocols such as ICMP, DNS and DHCP.
  
  
• Application Coverage: There are many thousands of different applications that run on TCP/IP internetworks, and I could not possibly hope to describe all of them. The scope of this Guide is limited to the most important, “classical” TCP/IP applications and application protocols, such as electronic mail, general file transfer and the World Wide Web.
  
  
• TCP/IP versus The Internet: The TCP/IP protocol suite and the Internet are very closely related in many ways, as you will discover as you read this Guide. In fact, they are often tied together so much that it is hard to discuss one without the other. However, the Internet as a whole is an enormous subject, and trying to describe it in general terms would have substantially increased the size of this Guide. Thus, I describe Internet issues only within the context of explanations of TCP/IP technologies.
  
  For example, while I cover the World Wide Web in this Guide, I discuss its generalities only briefly. I focus my technical discussions on how the Hypertext Transfer Protocol (HTTP) that implements it works. I don’t talk all about how to set up a Web site, or how to choose a Web browser, or any of those sorts of details. These are covered in a dazzling array of different books, papers and of course, Web sites. J
  
  
• Limited TCP/IP Security Coverage: Security is a very important and very large topic, especially in modern networking. This Guide does include a fairly detailed section on the operation of the IP Security protocols (IPSec), and also touches upon security issues in describing several other protocols and technologies. However, it is not specifically geared towards detailed discussions of security considerations. It is possible that in the future I will add more security-related information, but for now, if your primary interest is TCP/IP security matters, you will want to supplement this Guide with other materials.
  
  
• Small Computer Orientation: In general terms, TCP/IP technologies can be used to connect together any types of devices that have the appropriate hardware and software. There are some issues, however, where explanations require me to focus on how specific types of underlying networks and devices work; this is especially true of some of my diagrams. In these cases, my preference has generally been to show how TCP/IP is used to connect together typical small computers such as PCs, Macintoshes and UNIX workstations, which are what most people use.