The proper functioning of the DNS servers is crucial for the accessibility of the domain names on the Internet. That is why companies should be very careful about the DNS software versions they use to map alpha-numeric Internet domains to numeric IP addresses (the real names of the websites). The use of outdated or unstable DNS software may result in a company's DNS servers going down, which will lead to interruption in the company's online availability and the incoming mail will bounce back.
In order to create a machine, which is capable of handling the DNS queries, you will not only have to think about the hardware, you will also have to equip it with the right DNS server software. This software is what will handle all the work, keeping the DNS zone files for your domain names or acting as a DNS forwarder for your own queries, translating domain names to their respective IP addresses and vice versa. If you want to have a website online, keeping your domain name live, the machine where you are going to host the files for your site must have a DNS software running.
Free DNS Software
Most of the recommended DNS server software solutions are distributed under the GNU license, i.e. free of charge. The most widely used DNS software on the Internet today is BIND for Unix based platforms. Currently, the BIND DNS server software is the industry standard and also ranks in the top 3 of the most used DNS software platforms with its 3 different versions BIND 9, BIND 8 and BIND 4, taking first, second and third place, respectively. The second popular open-source DNS server application is Djbdns, boasting fast modular components and high security levels. Other open-source DNS software solutions also worth mentioning are NSD - an authoritative server, the easy-to-use MaraDNS server, the C++ written Posadis, Unbound - a high-performance, validating, recursive and caching DNS server, and many more.
Commercial DNS Software
There are also commercial alternatives to the free DNS software solutions. The most popular commercial DNS server software is Microsoft's DNS Server, embedded in the Microsoft Server OS. It ranks fourth among the most used DNS servers, providing an easy-to-use GUI. This DNS software is perfect for die-hard Windows users, since it has the same user interface and approach to server control.
Another commercial DNS software solution is Simple DNS, which ranks right behind Microsoft's DNS Server when speaking about commercial DNS software. It is compatible with all versions of Windows since Windows 2000, including the not-yet-released Windows 7. It has a very simple and user-oriented interface, which makes getting used to it a really simple task. Another popular commercial DNS software alternative is ASN, which stands for Authoritative Name Server. It is designed by Nominum, a company founded by Paul Mockapetris, the inventor of the DNS system, and is quickly gaining popularity.