DNS Search List Processing

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Last updated 2014-10-13 (latest revision 2014-04-11)
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Domain Names can be Qualified or Unqualified Domain Names. Qualified Domain Names are resolved over the public DNS infrastructure, whereas Unqualified Domain Names are resolved using search lists. How search lists are generated and interpreted varies from one application to another and from one operating system to another. This makes Unqualified Domain Name resolution unpredictable, non deterministic, and as such neither reliable nor stable. In addition, there is neither clear rules to define whether a name is a Qualified or an Unqualified Domain Name. This also contributes in making the naming resolution unreliable, as the resolution of a given name can result in different responses. As a consequence, most resolution systems currently end with a "try and error" strategy. More specifically, according to some system dependent heuristics, a resolver initiates an Unqualified (resp. Qualified) Domain Name resolution, and, in case of a NXDOMAIN response, fails back in a Qualified (resp. Unqualified) Domain Name resolution. Such strategies were acceptable as the probability of collision between domains within search list and those published in the public DNS infrastructure remains low. In the context of the generalization of Top Level Domain, this assumption is not acceptable anymore, resulting in an unreliable and unstable naming resolution. This document describes how search list should be generated and interpreted. Then, it describes how resolvers distinguish between Qualified and Unqualified Domain Names as well as how to resolve them.


Daniel Migault (daniel.migault@orange.com)

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)