Studying DNS Server Characteristics
If you're reading this, then you probably control/monitor a DNS server that has been scanned by our research project.
The main thrust of this study is to examine the characteristics of publicly available recursive DNS servers. We are
examining several aspects such as cache lifetime, TTL behavior, and some others.
For this study, we are utilizing the PlanetLab Network to perform the
measurements. While there are a little over a hundred nodes (computers) in the PlanetLab network currently running this
experiment, the number of nodes that contacts any given DNS server should only be two or three.
A typical "run" of this experiment involves approximately 170 DNS queries to the server, with approximately 120 of those
happening within the first 100 seconds of contact. Afer that, 30-50 extra queries (total) will be sent distributed over
the course of hours and days. Also, one other planetlab node may attempt to connect to the DNS server on port 80 to
determine if a web server is running.
If our study is disrupting your network in any way, please email Tom Callahan (contact info below) with the IP addresses
of any DNS servers you want removed from the experiment and they will be removed from the list immediately.
FAQ:
Q: My DNS servers aren't published anywhere! How did you find them?
A: We randomly scanned approximately 200 million IP addresses (roughly 5% of the Internet) simply issuing recursive DNS
queries and include hosts that do in our list.
Q: I'm getting some DNS packets to IPs in my netblock that don't even have DNS Servers!
A: We're probably working on refreshing our list of recursive DNS servers. If there is no server operating at an IP,
you in general shouldn't get more than a packet or two to it. If it is a hardship, we can add your netblocks to a
blacklist.
People
Tom Callahan
PhD Student, Case Western Reserve University
Tom's Web Page
Email: trc36@case.edu
Misha Rabinovich
Professor, Case Western Reserve University
Misha's Web Page
Email: misha@eecs.case.edu
Mark Allman
Senior Research Scientist, International Computer Science Institute
Mark's Web Page
Email: mallman@icir.org