Thank you those are very useful articles!
Because the DNS names of all the nodes that require name resolution include the Internet DNS domain name for the organization, choose an Internet DNS domain name that is short and easy to remember. Because DNS is hierarchical, DNS domain names grow when you add subdomains to your organization. Short domain names make the computer names easy to remember.
If the organization has an Internet presence, use names that are relative to the registered Internet DNS domain name. For example, if you have registered the Internet DNS domain name contoso.com, use a DNS domain name such as corp.contoso.com for the intranet domain name.come
For your Active Directory Domain Name, use a subdomain of your public domain.