Internet Domain Names
Technology with Integrity
By Tim Torian, Torian Group, Inc.
You probably have a web site for your business. This article is a brief introduction to what goes on “under the hood” with internet domain names, and how to get the most from yours. Why do you care? By understanding a little bit about domain names, you can talk intelligently to your Internet Service Provider and Web hosting service. You can also understand better how your customers get to your domain, and what can go wrong.
As you may know, the internet was formed originally as a research tool for universities and the military. It has evolved into a business tool only in the last decade or so. In the early days, there was not as much money involved, and things were a lot less formal. Domain names were handed out freely, as were public IP addresses.
An IP address is a number which is assigned to a connection on the computer. It is public if the connection is available on the internet. It is private if it is on a network not directly connected to the internet. Because Public IP addresses must be reachable by everyone, they must be unique. They are assigned to individuals or companies, somewhat like getting a phone number. There are a limited number of addresses available, again like there are a finite number of possible phone numbers. It is much more difficult to get them than it used to be. An IP address is a requirement for being reachable on the internet. Every web server and every email server must be reachable on a public address. Large blocks of addresses are owned by Internet Service Providers (ISP’s) and sold in small groups (typically either one address, or a group of 6 addresses) to businesses.
IP addresses are not that convenient as a way to reach information. They are hard to remember. Early on, someone got the idea of assigning names to the numbers, similar to a phone directory. This was the origin of the domain naming system (DNS). So, instead of typing 126.96.36.199 you type www.toriangroup.com. To make the names more useful, they were designed to have suffixes, similar to first and last names. Unlike most people’s names, a domain name can have any number of parts, with the most general part to the right. Each part to the left further defines the domain as a part of the parent domain. For example, .edu is divided into k12.edu and cc.edu. tcoe.k12.edu is a 3rd level domain which is part of k12.edu, which is part of .edu. Translating the domain name to a number is called “resolving the domain name”.
Until a few years ago, domain names and IP address assignment was managed by Internic (now Verisign). When the internet started to take on financial importance, the Internet Corporation for Assigned Names and Numbers (ICANN www.icann.org) was founded, and they now manage the process of creating and assigning domain names and IP addresses. The Internet Assigned Name Authority (IANA www.iana.org) works with ICANN on managing IP address assignment.
ICANN is the global, non-profit, private-sector coordinating body acting in the public interest. Among its other responsibilities, ICANN oversees the processes and systems that ensure that each domain name maps to the correct IP address. They also authorize domain name registrars. The domain name registrar is a company which assigns a domain name to an entity – Company, person, or organization – for their use. When they assign the name, they also require that the domain name be associated with at least two name servers. These servers act as translators, matching the name to an IP address. They also require an Administrative, Technical, and Billing Contact for the domain. There are now lots of companies who will reserve a domain name for you for a fee, typically $10 to $15 per year. Reserving a name is just the first step. You then need to have an IP address, and associate that address with your domain name. In many cases your ISP takes care of all of this for you for a monthly fee. The point here is that they are separate steps, and reserving a domain does not automatically make it reachable.
Behind the scenes, the story becomes a little more complicated. In an Internet address – such as toriangroup.com – the .com part is known as a Top Level Domain, or TLD. So-called "TLD registry" organizations house online databases that contain information about the domain names in that TLD. The .com registry database, for example, contains the Internet whereabouts – or IP address – of toriangroup.com. So in trying to find the Internet address of toriangroup.com your computer must first find the .com registry database. At the heart of the DNS are 13 special computers, called root servers. They are coordinated by ICANN and are distributed around the world. All 13 contain the same vital information – this is to spread the workload and back each other up. The root servers contain the IP addresses of all the TLD registries – both the global registries such as .com, .org, etc. and the 244 country-specific registries such as .fr (France), .cn (China), etc. This is critical information. These registries are used to refer requests to the DNS name server which has the IP address of the domain in question. This is why you need to provide the Name Server information when you register your domain. Each registered DNS server is “Authoritative” for one or more domains, and must be present for the system to resolve names to IP addresses. Again, typically your ISP provides this service for you. It is important to know that the DNS service is completely separate from your Web and Email servers, and without them, nothing else works.
If you are still with the story, you are already wondering about more complicated names with more parts such as www.toriangroup.com. Well, the DNS is a hierarchical system. First, the resolver on the requesting computer finds the IP address for the DNS server for the .com registry, queries that registry to find the IP address for the DNS server for toriangroup.com, then queries again for either an address or another authoritative server matching www. The left most name must match an individual IP address, which is returned to the requesting computer. The computer then uses this IP address to actually connect to the requested resource which the name refers to.
All that work goes on every time you open your web browser, in fractions of a second. It’s the miracle of modern computing.
Tim Torian has taught computer networking at the College of Sequoias and Cal Poly Extension. He has a BS in Computer Science, and has been consulting on computer networks for the past 18 Years. His industry certifications include: Cisco CCNA and CCNI, Microsoft MCSE, and Novell CNE. He is president of Torian Group, Inc. which provides a full range of Technology Consulting services to local business, including computer services, networking, and custom software development. They can be reached at (559) 733-1940 or on the web at http://www.toriangroup.com