This scheme[23] separates the Element ID component of the URN into two pieces, the Authority ID and the Request ID. A full URN based on the x-dns-2 scheme would look like this:
x-dns-2:shells.unix.computing.subjects.int:zsh
The host listed in the Authority ID field is to be contacted using the HTTP protocol, and information on the resource listed in the Element ID (e.g. zsh) requested. In this case shells.unix.computing.subjects.int is the host to contact.