A Root with a view…

26 November 2007

John CrainJohn Crain, Chief Security, Stability, and Resiliency Officer

Running a DNS server that serves the root gives an interesting view into the world of the DNS. With the ongoing improvements to the ICANN operated L-ROOT we've been fortunate enough to be able to make use of the "DNS Statistics Collector" tool.


"DSC" allows us to generate different views of the DNS queries we have been seeing at the L-ROOT systems. Both to the current IP address ( and to the old address (

The above graph shows the commonly queried Top Level Domains for a single day and the type of queries being asked. These are queries seen across l.root-servers.net. The TLDs change from day to day but some are persistent.No surprises in there really although some of the TLDs being queried should raise a few eyebrows.Seeing mainly addresses record queries (A and AAAA) for .com or .net, or a lot of requests for reverse delegation informations (PTR) in .arpa are logical things to see.However, ".local" is constantly in the top five of queries which is likely an indication of misconfiguration somewhere. Regular appearances are also made by ".localhost", ".belkin", ".home", ".invalid", ".localdomain" and ".domain".I leave it to the reader to decide why this is and at whom to point fingers…

Clearly one thing is certain, a large portion of the queries we are seeing are for non existing domains and hence get answered with "NXDOMAIN" (See above).Oh and one last snippet of information. I know that sometimes people do not allow DNS queries over TCP. This is actually not a good idea. According to the RFCs it is OK to query over TCP and in the case of a large enough answer (over 512 bytes) then TCP is typically the way to get that. So although the number of TCP queries is small compared to those using UDP, they can be valid queries.

Special thanks have to go to the folks who produced DSC . If only for making my life easier.If people want to see more data or would like to hear more about what we are doing in L-ROOT operations then speak up and I will do my best to inform. After all we run this for the community.Also see http://l.root-servers.org for information on L-ROOT operations.

John Crain
John Crain
Chief Security, Stability, and Resiliency Officer

John Crain

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