Impact of Configuration Errors on DNS Robustness

IBM Res., Hawthorne, NY
IEEE Journal on Selected Areas in Communications (Impact Factor: 3.45). 05/2009; 27(3):275 - 290. DOI: 10.1109/JSAC.2009.090404
Source: DBLP


During the past twenty years the Domain Name System (DNS) has sustained phenomenal growth while maintaining satisfactory user-level performance. However, the original design focused mainly on system robustness against physical failures, and neglected the impact of operational errors such as mis-configurations. Our measurement efforts have revealed a number of mis-configurations in DNS today: delegation inconsistency, lame delegation, diminished server redundancy, and cyclic zone dependency. Zones with configuration errors suffer from reduced availability and increased query delays up to an order of magnitude. The original DNS design assumed that redundant DNS servers fail independently, but our measurements show that operational choices create dependencies between servers. We found that, left unchecked, DNS configuration errors are widespread. Specifically, lame delegation affects 15% of the measured DNS zones, delegation inconsistency appears in 21% of the zones, diminished server redundancy is even more prevalent, and cyclic dependency appears in 2% of the zones. We also noted that the degrees of mis-configuration vary from zone to zone, with the most popular zones having the lowest percentage of errors. Our results indicate that DNS, as well as any other truly robust large-scale system, must include systematic checking mechanisms to cope with operational errors.

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    • "A DNS query failure often signifies that the requested resource does not exist in the system when the query is issued. While such a failure may be caused by a mis-typed host name or URL by a human user or occasionally due to DNS misconfigurations by human operators [1], a large portion of DNS query failures can be attributed to other causes — as pointed out in several recent studies [2], [3], [4]. For instance, several anti-spam and anti-virus services employ DNS " overloading " to notify a querying host whether the requested domain name belongs to the blacklists they maintain (e.g., of email spam servers or reported attack sites). "
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    • "We also consider the role of glue records and caching. Pappas, et al. [2] surveyed the DNS infrastructure for configuration errors that negatively impact DNS robustness. The authors examined subtle misconfigurations that could bring about behaviors such as diminished server redundancy, lame delegation, and cyclic dependency. "
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