Dynamic DNS (DDNS) is a method of automatically updating a name server in the Domain Name System (DNS), often in real time, with the active DDNS configuration of its configured hostnames, addresses or other information.
The term DDNS is used to describe two different concepts. The first is “dynamic DNS updating” which refers to systems that are used to update traditional DNS records without manual editing.
The second kind of dynamic DNS permits lightweight and immediate updates often using an update clients. These clients provide a persistent addressing method for devices that change their location, configuration or IP address frequently.
Dynamic DNS is a system that addresses the problem of rapid updates. The term is used in two ways, which, while technically similar, have very different purposes and user populations.
The first is “standards-based DNS updates”, which uses an extension of the DNS protocol to ask for an update. This is often used for company laptops to register their address.
The second is usually a web-based protocol, normally a single HTTP fetch with username and password which then updates some DNS records (by some unspecified method). This is commonly used for a domestic computer to register itself by a publicly-known name in order to be found by a wider group, for example as a game server or webcam.
End users of Internet access receive an allocation of IP addresses, often only a single address, by their Internet service provider (ISP). The assigned addresses may either be fixed (i.e. static), or may change from time to time, a situation called dynamic. Dynamic addresses are generally given only to residential customers and small businesses, as most enterprises specifically require static addresses.
Dynamic IP addresses present a problem if the customer wants to provide a service to other users on the Internet, such as a web service. As the IP address may change frequently, corresponding domain names must be quickly re-mapped in the DNS, to maintain accessibility using a well-known URL.
Many providers offer commercial or free Dynamic DNS service for this scenario. The automatic reconfiguration is generally implemented in the user’s router or computer, which runs software to update the DDNS service. The communication between the user’s equipment and the provider is not standardized, although a few standard web-based methods of updating have emerged over time.