We pick a.root-servers.net, one of the 13 root servers (1), and ask it about dispendik.surabaya.go.id and learn that id is delegated to four name servers (2), so we ask sec3.apnic.net where we learn that surabaya.go.id is delegated to four name servers, including ns2.rad.net.id (3), so we ask that one and get the following answer: