dynamic domain name system (DNS) (DDNS)
Normally, IP addresses are permanently assigned to a computer. With dynamic address assignment, however, the IP address changes with each new session. DynDNS is a DNS network service where IP addresses change in real time.
When a computer connects to the Internet, the IP address of the other side must be known so that it can establish a connection to the target computer. However, if IP addresses change as they do with the Dynamic Domain NameSystem (DDNS), then the name server of the DDNS provider must be informed about the constantly changing IP addresses and manage them. The changing IP addresses for the local computer are generated by a client program and communicated to the name server of the DDNS provider, which can then establish a connection to the new IP address.
Dynamic address change has the advantage of being very flexible and making better use of network resources. It is useful when the connection is made through different networks and components or when the computers are disconnected from the network. The DynDNS method is used in DSL routers and Internet telephony, among other things.