Web HTTP testing performs several steps while validating browser response starting with DNS resolution. After that the test checks establishment of a 3 way TCP handshake to Connect, potentially negotiation of SSL, Sending the HTTP request, Receiving the HTTP Response and Verify and Validating the received response. During HTTP testing, Enterprise Agents will query the DNS server specified in the "/etc/resolv.conf" file. The DNS resolution test result is based on the local maps of each agent you have in a test so the resulting errors may vary from source to source shown in the Table view of your HTTP Server test result View. Comparatively, DNS Server tests will directly query a server specified in the test target (See the "DNS Servers" Field). DNS Trace tests query authoritative nameservers for each zone of the domain space starting at the root then at the Top-Level Domain (TLD) and so on until an authoritative answer is received. Common TLDs are familiar domains like .com, .net, .org, and so on.