Child-to-Parent Synchronization in DNS
RFC 7477

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Internet Engineering Task Force (IETF)                       W. Hardaker
Request for Comments: 7477                                 Parsons, Inc.
Category: Standards Track                                     March 2015
ISSN: 2070-1721

                 Child-to-Parent Synchronization in DNS

Abstract

   This document specifies how a child zone in the DNS can publish a
   record to indicate to a parental agent that the parental agent may
   copy and process certain records from the child zone.  The existence
   of the record and any change in its value can be monitored by a
   parental agent and acted on depending on local policy.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7477.

Copyright Notice

   Copyright (c) 2015 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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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.

Hardaker                     Standards Track                    [Page 1]
RFC 7477         Child-to-Parent Synchronization in DNS       March 2015

Table of Contents

   1. Introduction ....................................................2
      1.1. Terminology Used in This Document ..........................3
   2. Definition of the CSYNC RRType ..................................3
      2.1. The CSYNC Resource Record Format ...........................4
           2.1.1. The CSYNC Resource Record Wire Format ...............4
           2.1.2. The CSYNC Presentation Format .......................6
           2.1.3. CSYNC RR Example ....................................6
   3. CSYNC Data Processing ...........................................6
      3.1. Processing Procedure .......................................7
      3.2. CSYNC Record Types .........................................8
           3.2.1. The NS type .........................................8
           3.2.2. The A and AAAA Types ................................9
   4. Operational Considerations ......................................9
      4.1. Error Reporting ...........................................10
      4.2. Child Nameserver Selection ................................10
      4.3. Out-of-Bailiwick NS Records ...............................10
      4.4. Documented Parental Agent Type Support ....................11
      4.5. Removal of the CSYNC Records ..............................11
      4.6. Parent/Child/Grandchild Glue Synchronization ..............12
   5. Security Considerations ........................................12
   6. IANA Considerations ............................................12
   7. References .....................................................13
      7.1. Normative References ......................................13
      7.2. Informative References ....................................14
   Acknowledgments ...................................................15
   Author's Address ..................................................15

1.  Introduction

   This document specifies how a child zone in the DNS ([RFC1034]
   [RFC1035]) can publish a record to indicate to a parental agent (see
   Section 1.1 for a definition of "parental agent") that it can copy
   and process certain records from the child zone.  The existence of
   the record and any change in its value can be monitored by a parental
   agent and acted on depending on local policy.

   Currently, some resource records (RRs) in a parent zone are typically
   expected to be in sync with the source data in the child's zone.  The
   most common records that should match are the nameserver (NS) records
   and any necessary associated address records (A and AAAA), also known
   as "glue records".  These records are referred to as "delegation
   records".

   It has been challenging for operators of child DNS zones to update
   their delegation records within the parent's set in a timely fashion.
   These difficulties may stem from operator laziness as well as from