DNS/RFC/8109について、ここに記述してください。

https://tools.ietf.org/html/rfc8109 

{{{                                                                        
                                                   BEST CURRENT PRACTICE
                                                                        

Internet Engineering Task Force (IETF)                           P. Koch
Request for Comments: 8109                                      DENIC eG
BCP: 209                                                       M. Larson
Category: Best Current Practice                               P. Hoffman
ISSN: 2070-1721                                                    ICANN
                                                              March 2017


            Initializing a DNS Resolver with Priming Queries

Abstract

   This document describes the queries that a DNS resolver should emit
   to initialize its cache.  The result is that the resolver gets both a
   current NS Resource Record Set (RRset) for the root zone and the
   necessary address information for reaching the root servers.
}}}


3.1.  Repeating Priming Queries

   The recursive resolver SHOULD send a priming query only when it is
   needed, such as when the resolver starts with an empty cache and when
   the NS RRset for the root zone has expired.  Because the NS records
   for the root are not special, the recursive resolver expires those NS
   records according to their TTL values.  (Note that a recursive
   resolver MAY pre-fetch the NS RRset before it expires.)