We pick h.root-servers.net, one of the 13 root servers (1), and ask it about ntop.org and learn that org is delegated to six name servers (2), so we ask a0.org.afilias-nst.info where we learn that ntop.org is delegated to two name servers, including nameserver.cnr.it (3), so we ask that one and get the following answer:
Ntop.org is a domain controlled by two domain name servers at cnr.it and ntop.org having a total of three IP numbers. All three of them are on different IP networks. Incoming mail for ntop.org is handled by one mail server at ntop.org themselves. Ntop.org has one IP number (131.114.21.22), but the reverse is jake.unipi.it.