Greetings. The definition of "recursive resolver" has been problematic both in RFC 7719 and in draft-ietf-dnsop-terminology-bis. Section 6 of draft-ietf-dnsop-terminology-bis defines a bunch of terms about servers, including "recursive mode" and "recursive resolver". The current text gives:

   Recursive mode:  A resolution mode of a server that receives DNS
queries and either responds to those queries from a local cache or
      sends queries to other servers in order to get the final answers
      to the original queries.  Section 2.3 of [RFC1034] describes this
      as "The first server pursues the query for the client at another
      server".  A server operating in recursive mode may be thought of
as having a name server side (which is what answers the query) and a resolver side (which performs the resolution function). Systems
      operating in this mode are commonly called "recursive servers".
      Sometimes they are called "recursive resolvers".  While strictly
      the difference between these is that one of them sends queries to
another recursive server and the other does not, in practice it is
      not possible to know in advance whether the server that one is
      querying will also perform recursion; both terms can be observed
      in use interchangeably.

   Recursive resolver:  A resolver that acts in recursive mode.  In
      general, a recursive resolver is expected to cache the answers it
      receives (which would make it a full-service resolver), but some
      recursive resolvers might not cache.

That is, "recursive mode" is only barely defined in RFC 1034, and "recursive resolver" is defined almost trivially.

Can these be improved on? This is one of the core ideas in the DNS protocol and it seems a bit weird that we don't have a crisp set of definitions. If there is more text from RFCs to quote, that would possibly be a big help.

--Paul Hoffman

DNSOP mailing list

Reply via email to