Network Solutions Advanced DNS Manager
This took a Google search to find. Network Solutions web site is pretty bad.
The traditional approach to moving a domain to a new provider is:
1. Give new provider domain name
1. go to network solutions (for example)
2. change where DNS server address from old provider to new provider.
The alternative approach is documented on this page. In this case Network Solutions takes over the DNS functions and one tells Network Solutions which machine to point to.
It feels like it comes down to who one trusts more, and to whom should one give power over a domain.