Initializing a DNS Resolver with Priming Queries
draft-klh-dnsop-rfc8109bis-00

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Network Working Group                                            P. Koch
Internet-Draft                                                  DENIC eG
Obsoletes: 8109 (if approved)                                  M. Larson
Intended status: Best Current Practice                        P. Hoffman
Expires: January 1, 2021                                           ICANN
                                                           June 30, 2020

            Initializing a DNS Resolver with Priming Queries
                      draft-klh-dnsop-rfc8109bis-00

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.

   This document, when published, obsoletes RFC 8109.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on January 1, 2021.

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   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must

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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

1.  Introduction

   Recursive DNS resolvers need a starting point to resolve queries.
   [RFC1034] describes a common scenario for recursive resolvers: they
   begin with an empty cache and some configuration for finding the
   names and addresses of the DNS root servers.  [RFC1034] describes
   that configuration as a list of servers that will give authoritative
   answers to queries about the root.  This has become a common
   implementation choice for recursive resolvers, and is the topic of
   this document.

   This document describes the steps needed for this common
   implementation choice.  Note that this is not the only way to start a
   recursive name server with an empty cache, but it is the only one
   described in [RFC1034].  Some implementers have chosen other
   directions, some of which work well and others of which fail
   (sometimes disastrously) under different conditions.  For example, an
   implementation that only gets the addresses of the root name servers
   from configuration, not from the DNS as described in this document,
   will have stale data that could cause slower resolution.

   This document only deals with recursive name servers (recursive
   resolvers, resolvers) for the IN class.

1.1.  Changes from RFC 8109

   This document obsoletes [RFC8109].  The significant changes from RFC
   8109 are:

   o  Added section on the content of priming information.

   o  Added paragraph about no expectation that the TC bit in responses
      will be set.

   o  Clarified language for root server domain names as "root server
      identifiers".

   o  Added informative references to RSSAC documents.

   o  Added short discussion about this document and private DNS.

   o  Future changes noted in the current text with [[ text like this
      ]].

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1.2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   See [RSSAC026v2] for terminology that relates to the root server
   system.

2.  Description of Priming

   Priming is the act of finding the list of root servers from a
   configuration that lists some or all of the purported IP addresses of
   some or all of those root servers.  A recursive resolver starts with
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