A Quick Look At DNS

DNS, also known as domain name system, is how domain names, like Nusuni.com, are turned into IP addresses when you visit the site. A DNS server is a server that contains entries which describe where a domain name points to and where to send data for certain services (like e-mail).

When you first set up a domain for web hosting you may have to set up nameserver addresses. These are nothing more than pointers to DNS servers that will tell everyone on the ‘net where your domain lives. The ISPs across the Internet cache this nameserver data to help speed up the process of turning a domain into an IP address, which is why it can take up to 72 hours for DNS changes to occur for everyone across the world.

Well, they say it takes 72 hours to propagate across the ‘net, personally I’ve never had it take longer than a day.

When you open say Nusuni.com in your web browser your computer will go and talk to your ISP and try to figure out where to send the data to. The ISP will return an IP address for the domain, and the request is sent off to that server.

The ISP figures out where to send the data by looking at several entries on the DNS server that cover a wide range of services:

• A - The A record is what maps the hostname (domain name) to an IPv4 address. This is the meat of the ‘net.
• AAAA - This is the same as above, except it maps the domain to an IPv6 address (which is the new standard, and is being rolled out currently).
• CNAME - If you run multiple servers on one machine, you may need to set up aliases for a domain name to access the other servers. For example, the FTP alias for most domains is ftp.example.com. That is an alias of example.com, and it has it’s own DNS records.
• MX - The MX entry simply tells you where a mail exchange server is. This is how e-mail gets routed.
• PTR - The PTR entry is kind of the opposite of the A record. If your DNS server implements it for your domain, then a reverse DNS lookup can be performed (finding a domain based on its IP address, instead of the other way around).
• NS - This is a list of the nameservers (DNS servers) for the domain.

Well, that is about it. You can learn a whole lot more about DNS at sites like Wikipedia.

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