While troubleshooting, a technician notices that some clients using FTP still work and that pings to the local router and servers are working. The technician tries to ping all known nodes on the network and they reply positively, except for one of the servers. The technician notices that ping works only when the host name is used but not when FQDN is used. Which of the following servers is MOST likely down?
A. WINS server
B. Domain controller
C. DHCP server
D. DNS server