Every computer on the Internet has a physical address associated with it which uniquely identifies it to other computers or devices on the network. This physical address is known as an IP Address. An IP Address consists of 4 digits separated by dots such as "201.29.13.1". This IP Address is convenient for computers but very difficult for humans to remember.

In order to make this easier for end users, each IP address can be assigned a FQDN (Fully Qualified Domain Name). These are the names you are used to seeing such as "www.cnn.com", "www.yahoo.com", etc. When you use a FQDN, or domain name for short, your computer will translate it to a physical IP address to be able to connect to the desired computer or device.

Traditionally, a domain name has been assigned to a fixed IP Address or set of addresses that never change. However, as the Internet exploded and available IP Addresses became fewer and fewer, people realized that they had to start rationing the IP addresses or otherwise they would quickly run out.

One solution that resulted was DHCP (Dynamic Host Control Protocol) which dynamically provided an IP address to a device from a fixed pool of IP Addresses. This greatly reduced the number of IP addresses that needed to be given out. Your internet provider uses DHCP to assign you an IP address whenever you want to connect to the Internet. If you do not use it for a period of time (set by a configurable lease time), the IP address will be assigned to another user. This way IP Addresses only need to be assigned to active devices instead of every possible device on the Internet.

What is DNS?

DNS (Domain Name Service) is the Internet service/protocol which provides the translation between a FQDN, or domain name, and its associated IP address. A DNS server is a computer that is running the DNS service/protocol. Every internet domains must be assigned a DNS server or set of DNS servers to be able to resolve names for that domain.

For example, if you were to type in "mail.mycompany.com", your computer would lookup who the DNS servers were for the domain mycompany.com. It would then query that DNS server for the IP address of the name mail.mycompany.com. At that point, the DNS server would return the IP Address associated with mail.mycompany.com and then your computer would connect to that IP Address.

But what happens if your IP address changes periodically such as if your machine is connected to your internet service provider who is providing you a dynamic IP Address via DHCP?

DDNS (Dynamic Domain Name Service) was created to solve this problem of giving a name to devices whose IP addresses change continually. So who is most likely to use Dynamic DNS? Well, static IP Addresses or web hosting accounts are relatively expensive. And there were alot of people who had a perfectly good computers at home behind their dedicated internet connection (cable or DSL). They wanted to use that machine as a server, for example, a web server.

But if someone typed "www.mycompany.com", there needed to be a service that could keep track of what the latest IP Address assigned to your computer was so that it could return the correct IP Address of your computer to a requesting computer. In a nutshell, that is what Dynamic DNS does.

How Does Dynamic DNS Work?

There are two components that are needed for Dynamic DNS to work. One is a client side component that will send the latest IP Address of the computer or device whenever it changes. And the second component is a server side DNS service which will receive the IP Address update from the client side component and also service DNS requests.

Setting Up Dynamic DNS