Use the reserved internet domain names for examples

Created by: philarcher

This issue affects many sections.

The IETF reserves a number of top level and second level domain names for use in documentation. See https://www.ietf.org/archive/id/draft-jabley-reserved-domain-names-00.html#iana. Most useful are the second level domain names of example.com, example.org and example.net. Next most useful, IMO, is the top level domain name of example. That is, you can write something like resolver.example which makes it clear what you're saying without having to create such a service. I've seen standards that refer to example.example!

The alternative, which is seen commonly within UNTP and elsewhere, is to create a domain name that is already, or could be, an actual one in use. Currently, for example, sample-service.com is available. Whereas sample-service.example will never be available.

I think it is safer to use the reserved domain names throughout our documentation.