 The first is "standards-based DDNS", 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 "proprietary DDNS", 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 games server or webcam.End users of Internet access receive an allocation of IP addresses, often only a single address, by their Internet service provider.