What is DNS? DNS stands for Domain Name System. It is also often referred to as a DNS server or name server.
Computers and other network devices on the Internet use an IP address to send your request to the site you're trying to reach. This is like dialing a phone number to connect to the person that you want to speak to.
Remembering a set of IP addresses (or phone numbers) is a not easy. DNS allow you to use user friendly domain names. Now instead of keying in 18.104.22.168 to reach this site, you simply key in the domainnameprimer.com (which is much easier to remember).
DNS works in the background, using a massive database to map these user friendly domain names to IP addresses. When you access a web site or send an email, your computer uses a DNS server to look up the domain name you're trying to access. The proper term for this process is DNS name resolution, and you would say that the DNS server resolves the domain name to the IP address.
DNS Root Servers and Hierarchy
DNS servers are organized in a hierarchy. At the top level of the hierarchy, are root servers that store the complete database of domain names and their corresponding IP addresses. The Internet employs 13 such root servers that resides in several countries such as the United States, Japan, UK and Sweden. They are maintained by independent agencies.
Only the 13 root servers contain the complete database of domain names and IP addresses. All other DNS servers are installed at lower levels of the hierarchy and maintain only parts of the database. Lower level DNS servers are mostly owned by Internet Service Providers (ISP) or large businesses.
For example, Google maintains various DNS servers around the world that manage the google.com, google.co.uk, and other domains. Your ISP also maintains DNS servers as part of your Internet connection setup.
When you enter a domain name into your browser, it issues a request to your ISP's DNS server for its corresponding IP address. If your ISP's DNS server does not have the IP address, it automatically passes that request to another DNS server higher up the hierarchy. Eventually the request arrives at a server that has the matching domain name and IP address in its database. The information is then relayed back to you.
The IP address of your web site is like a house address. It changes when you move from one hosting provider to another (or when there is a network reconfiguration). Most registrars provide services to update your records on the DNS servers. Your domain name is mapped to the new IP address and people can still find you as long as they remember your domain name.
By far the most widely used DNS software is called BIND. It is an implementation of the Domain Name System (DNS) protocols. The name BIND stands for "Berkeley Internet Name Domain", because the software originated in the early 1980s at the University of California at Berkeley.
The BIND software distribution contains three parts, the domain name server itself, the resolver library and testing tools. The domain name server answers questions and give correct information about your domain name. The resolver library is a collection of software components that a programmer can add to software being developed to give the software the ability to resolve names. This save the developer time and ensure that the new software correctly follows the DNS standards. Finally the distribution also includes testing tools to do your own testing and ensure that the server is working properly.
Bind is by far the most widely used DNS software on the Internet. It is robust and stable and is fully compliant with published DNS standards.
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