Is Your Caching Resolver Polluting the Internet?
Presented at SIGCOMM NetTS in 2004

Duane Wessels
The Measurement Factory, Inc.
and the Cooperative Association for Internet Data Analysis - CAIDA
San Diego Supercomputer Center,
University of California, San Diego

Previous research has shown that most of the DNS queries reaching the root of the hierarchy are bogus . This behavior derives from two constraints on the system: (1) queries that cannot be satisfied locally percolate up to the root of the DNS; (2) some caching nameservers are behind packet filters or firewalls that allow outgoing queries but block incoming replies. These resolvers assume the network failure is temporary and retransmit their queries, often aggressively.

DNS pollution may not be causing any perceivable performance problems. The root servers seem well equipped to handle the load. Since DNS messages are small, the pollution does not contribute significantly to the total traffic generated by most organizations. Nonetheless, this paper provides a few reasons why network operators should take the time to investigate and fix these problems.