The Internet Domain Name System (DNS) is an essential part of the Internet infrastructure. Each web site or email lookup involves traversing a tree-structure distributed database to complete the mapping from a hostname to an IP address. The root and top level domain (TLD) nameservers form the highest level of authority over the Internet naming hierarchy, and are thus potentially involved in reaching any and every URL or email address we seek. We use passive measurements to analyze performance of these critical nameservers from a client network's viewpoint.

We use NeTraMet meters on a university campus to take passive measurements of DNS response time, request loss rate and request load to the root and gTLD (generic top level domain, e.g., .com, .net, .org) servers.

From these measurements we produce strip charts that are useful for day-to-day monitoring of one's Internet connectivity, since they reveal changes in network behaviour on paths between one's local network and the global servers without the need to actively inject traffic into the network. We are developing a monitoring tool to produce such plots in near real time.