DNS - It's Critical!
If someone were to ask me what is my favorite part of the Internet architecture, though it is a tough choice, I might very well name the Domain Name System, known more commonly as DNS. It is an amazing distributed, decentralized system, though not free of politics, without which the Internet could barely function. Theoretically, we could use IP addresses and no logical names, which is what DNS provides. So, to get to this site, you'd have to enter 199.203.70.93. But, aside from that being harder to remember and easier to make mistakes (and don't even think about it for an IPv6 address, such as that of www.kame.net, which is 2001:200:0:8002:203:47ff:fea5:3085), what would happen if RAD Data Communications, Ltd., the sponsor of RAD University, decided to relocate the server to another location (or migrated to IPv6), causing a change in IP address? How would you learn about the change of address? Think about how you let all your friends and contacts know when you change your address, or phone number, or email address - what a pain! But if based on your logical name, say "Debby Koren", people could find your address or phone number and you had access to update the data base containing this information, you'd only need to make a change in the data base, and everyone would automatically get the new information. What a concept!
And how does anyone find your phone number the first time around? Some kind of phone book or directory service. But that directory service needs to be able to be updated any time an organization (or individual) wants to. And that directory service needs to be always available. And that diretory service should not become a single point of failure. And that directory service has to provide information about hundreds of millions of hosts. Wait! One server with all that information would be insane! Even if we replicated it to avoid the sinlge-point-of-failure-problem, the data base would be huge, and searching for a record would take too much time. And, it is extremely important that the data base be secure. You don't want someone else touching your directory information.
When Jon Postel first proposed domain names in his "Computer Mail Meeting Notes" of February, 1982 (RFC 805), there was no way he could ever have imagined the scope of the name space today, nor did he have any idea of the types of applications that we take for granted and that rely on DNS. DNS may not be a perfect system - in fact, the Internet's operation is at risk from attacks on the root servers, and security isn't bullet-proof, but it is an amazing system, nevertheless, and has a lot more that is terrific about it than is faulty.
In this portal, I present a detailed tutorial on DNS, including material on IPv6, a terrific Flash movie (which the developers - a group of my former students - have humbly called the best ever), a tutorial on (Secure) Dynamic DNS, and some useful references, and I've included some links along the way to various sites and tools, so as to provide you with an interactive, hands-on experience. If you are reading this tutorial, you have access to the Internet, in which case there is no better laboratory for understanding how DNS works, what it can do for you, and no better playground to appreciate the immensity of the task that DNS performs and the huge success that DNS is.
Thank you for visiting RAD University. We hope that this portal will be helpful and fun, and we
welcome your comments.
Debby Koren, "Dean" RAD University
