CAIDA : research : dns : roottraffic

Recommendations for future large scale simultaneous DNS data collections

2007 Analysis of DNS root server traffic

In collaboration with ISC and OARC, we held the second large-scale simultaneous data collection event on January 9-10, 2007. We captured tcpdump traces at multiple anycast instances of the C, E, F, K, and M root servers.

This collection of the DNS root server traffic was part of a larger measurement effort, "The Day in the life of the Internet". CAIDA organized an unprecedented scientific measurement experiment on the worldwide Internet, in which during 48 hours we coordinated global measurements of Internet traffic and relevant parameters at many participating locations and links. A summary describes acquired data in more detail.

With ISC/OARC permission, we indexed these traces into the Internet Measurement Data Catalog (DatCat). Researchers will need to contact the OARC directly in order to access the data.

We are in the process of analyzing the data obtained from the top of the DNS hierarchy. We presented preliminary analysis results at the 8th CAIDA-WIDE workshop (July 2007, Chicago). The paper is in preparation. A report comparing 2006 and 2007 observations of root server traffic is available.

2006 Analysis of DNS root server traffic

We studied DNS traffic collected over a two-day period on January 10-11, 2006 at anycast instances of the C, F and K root nameservers. Our goal was to investigate how anycast DNS service affects the worldwide population of Internet users.

First, for each root instance, we examined client locations and the geographic distances between a server and its clients to determine whether clients actually use the instance closest to them. We found that frequently the choice, which is entirely determined by BGP routing, is not the geographically closest one. Next, we considered specific AS paths and investigated some cases where local instances had a higher than usual proportion of non-local clients. Finally, we found that instance selection by BGP is highly stable: over a two-day period less than 2% of both C-root and F-root clients and <5% of K-root clients experienced an instance change. We concluded that overall, anycast roots significantly localize DNS traffic, thereby improving DNS service to clients worldwide.

We presented our results at the IEPG meeting (July 2006, Montreal) and published a paper at PAM 2007. We indexed the data used for the PAM paper into the Internet Measurement Data Catalog (DatCat). Interested researchers should contact the OARC directly in order to access the data.

2002 Analysis of DNS root server traffic

In 2002 (prior to anycast deployment), Ken Keys analyzed clients and queries reaching the A, E, F, I, K and M DNS root servers.