[DNSOP] Please review the definitions around "recursive" in terminology-bis

"Paul Hoffman" <paul.hoffman@vpnc.org> Mon, 12 March 2018 15:09 UTC

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From: "Paul Hoffman" <paul.hoffman@vpnc.org>
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Date: Mon, 12 Mar 2018 08:09:27 -0700
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Subject: [DNSOP] Please review the definitions around "recursive" in terminology-bis
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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 

    Recursive mode:  A resolution mode of a server that receives DNS
       queries and either responds to those queries from a local cache 
       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) 
       a resolver side (which performs the resolution function).  
       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 
       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