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844 lines
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Internet Engineering Task Force (IETF) W. Hardaker
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Request for Comments: 7477 Parsons, Inc.
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Category: Standards Track March 2015
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ISSN: 2070-1721
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Child-to-Parent Synchronization in DNS
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Abstract
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This document specifies how a child zone in the DNS can publish a
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record to indicate to a parental agent that the parental agent may
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copy and process certain records from the child zone. The existence
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of the record and any change in its value can be monitored by a
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parental agent and acted on depending on local policy.
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Status of This Memo
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This is an Internet Standards Track document.
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This document is a product of the Internet Engineering Task Force
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(IETF). It represents the consensus of the IETF community. It has
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received public review and has been approved for publication by the
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Internet Engineering Steering Group (IESG). Further information on
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Internet Standards is available in Section 2 of RFC 5741.
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Information about the current status of this document, any errata,
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and how to provide feedback on it may be obtained at
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http://www.rfc-editor.org/info/rfc7477.
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Copyright Notice
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Copyright (c) 2015 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
|
||
Provisions Relating to IETF Documents
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||
(http://trustee.ietf.org/license-info) in effect on the date of
|
||
publication of this document. Please review these documents
|
||
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
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the Trust Legal Provisions and are provided without warranty as
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||
described in the Simplified BSD License.
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Hardaker Standards Track [Page 1]
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RFC 7477 Child-to-Parent Synchronization in DNS March 2015
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Table of Contents
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1. Introduction ....................................................2
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1.1. Terminology Used in This Document ..........................3
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2. Definition of the CSYNC RRType ..................................3
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2.1. The CSYNC Resource Record Format ...........................4
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2.1.1. The CSYNC Resource Record Wire Format ...............4
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2.1.2. The CSYNC Presentation Format .......................6
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2.1.3. CSYNC RR Example ....................................6
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3. CSYNC Data Processing ...........................................6
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3.1. Processing Procedure .......................................7
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3.2. CSYNC Record Types .........................................8
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3.2.1. The NS type .........................................8
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3.2.2. The A and AAAA Types ................................9
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4. Operational Considerations ......................................9
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4.1. Error Reporting ...........................................10
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4.2. Child Nameserver Selection ................................10
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4.3. Out-of-Bailiwick NS Records ...............................10
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4.4. Documented Parental Agent Type Support ....................11
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4.5. Removal of the CSYNC Records ..............................11
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4.6. Parent/Child/Grandchild Glue Synchronization ..............12
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5. Security Considerations ........................................12
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6. IANA Considerations ............................................12
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7. References .....................................................13
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7.1. Normative References ......................................13
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7.2. Informative References ....................................14
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Acknowledgments ...................................................15
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Author's Address ..................................................15
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1. Introduction
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This document specifies how a child zone in the DNS ([RFC1034]
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[RFC1035]) can publish a record to indicate to a parental agent (see
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Section 1.1 for a definition of "parental agent") that it can copy
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and process certain records from the child zone. The existence of
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the record and any change in its value can be monitored by a parental
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agent and acted on depending on local policy.
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Currently, some resource records (RRs) in a parent zone are typically
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expected to be in sync with the source data in the child's zone. The
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most common records that should match are the nameserver (NS) records
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and any necessary associated address records (A and AAAA), also known
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as "glue records". These records are referred to as "delegation
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records".
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It has been challenging for operators of child DNS zones to update
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their delegation records within the parent's set in a timely fashion.
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These difficulties may stem from operator laziness as well as from
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Hardaker Standards Track [Page 2]
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RFC 7477 Child-to-Parent Synchronization in DNS March 2015
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the complexities of maintaining a large number of DNS zones. Having
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an automated mechanism for signaling updates will greatly ease the
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child zone operator's maintenance burden and improve the robustness
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of the DNS as a whole.
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This document introduces a new Resource Record Type (RRType) named
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"CSYNC" that indicates which delegation records published by a child
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DNS operator should be processed by a parental agent and used to
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update the parent zone's DNS data.
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This specification was not designed to synchronize DNSSEC security
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records, such as DS RRsets. For a solution to this problem, see the
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complementary solution [RFC7344], which is designed to maintain
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security delegation information. In addition, this specification
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does not address how to perform bootstrapping operations, including
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to get the required initial DNSSEC-secured operating environment in
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place.
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1.1. Terminology Used in This Document
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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document are to be interpreted as described in [RFC2119].
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Terminology describing relationships between the interacting roles
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involved in this document are defined in the following list:
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Child: The entity on record that has the delegation of the domain
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from the parent
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Parent: The domain in which the child is registered
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Child DNS operator: The entity that maintains and publishes the zone
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information for the child DNS
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Parental agent: The entity that the child has relationship with, to
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change its delegation information
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2. Definition of the CSYNC RRType
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The CSYNC RRType contains, in its RDATA component, these parts: an
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SOA serial number, a set of flags, and a simple bit-list indicating
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the DNS RRTypes in the child that should be processed by the parental
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agent in order to modify the DNS delegation records within the
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parent's zone for the child DNS operator. Child DNS operators
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wanting a parental agent to perform the synchronization steps
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outlined in this document MUST publish a CSYNC record at the apex of
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the child zone. Parental agent implementations MAY choose to query
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Hardaker Standards Track [Page 3]
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RFC 7477 Child-to-Parent Synchronization in DNS March 2015
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child zones for this record and process DNS record data as indicated
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by the Type Bit Map field in the RDATA of the CSYNC record. How the
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data is processed is described in Section 3.
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Parental agents MUST process the entire set of child data indicated
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by the Type Bit Map field (i.e., all record types indicated along
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with all of the necessary records to support processing of that type)
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or else parental agents MUST NOT make any changes to parental records
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at all. Errors due to unsupported Type Bit Map bits, or otherwise
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nonpunishable data, SHALL result in no change to the parent zone's
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delegation information for the child. Parental agents MUST ignore a
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child's CSYNC RDATA set if multiple CSYNC resource records are found;
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only a single CSYNC record should ever be present.
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The parental agent MUST perform DNSSEC validation ([RFC4033]
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[RFC4034] [RFC4035]), of the CSYNC RRType data and MUST perform
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DNSSEC validation of any data to be copied from the child to the
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parent. Parents MUST NOT process any data from any of these records
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if any of the validation results indicate anything other than
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"Secure" [RFC4034] or if any the required data cannot be successfully
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retrieved.
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2.1. The CSYNC Resource Record Format
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2.1.1. The CSYNC Resource Record Wire Format
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The CSYNC RDATA consists of the following fields:
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1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| SOA Serial |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Flags | Type Bit Map /
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/ Type Bit Map (continued) /
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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2.1.1.1. The SOA Serial Field
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The SOA Serial field contains a copy of the 32-bit SOA serial number
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from the child zone. If the soaminimum flag is set, parental agents
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querying children's authoritative servers MUST NOT act on data from
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zones advertising an SOA serial number less than this value. See
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[RFC1982] for properly implementing "less than" logic. If the
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soaminimum flag is not set, parental agents MUST ignore the value in
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the SOA Serial field. Clients can set the field to any value if the
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soaminimum flag is unset, such as the number zero.
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Hardaker Standards Track [Page 4]
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RFC 7477 Child-to-Parent Synchronization in DNS March 2015
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Note that a child zone's current SOA serial number may be greater
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than the number indicated by the CSYNC record. A child SHOULD update
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the SOA Serial field in the CSYNC record every time the data being
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referenced by the CSYNC record is changed (e.g., an NS record or
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associated address record is changed). A child MAY choose to update
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the SOA Serial field to always match the current SOA Serial field.
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Parental agents MAY cache SOA serial numbers from data they use and
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refuse to process data from zones older than the last instance from
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which they pulled data.
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Although Section 3.2 of [RFC1982] describes how to properly implement
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a less-than comparison operation with SOA serial numbers that may
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wrap beyond the 32-bit value in both the SOA record and the CSYNC
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record, it is important that a child using the soaminimum flag must
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not increment its SOA serial number value more than 2^16 within the
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period of time that a parent might wait between polling the child for
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the CSYNC record.
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2.1.1.2. The Flags Field
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The Flags field contains 16 bits of boolean flags that define
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operations that affect the processing of the CSYNC record. The flags
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defined in this document are as follows:
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0x00 0x01: "immediate"
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0x00 0x02: "soaminimum"
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The definitions for how the flags are to be used can be found in
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Section 3.
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The remaining flags are reserved for use by future specifications.
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Undefined flags MUST be set to 0 by CSYNC publishers. Parental
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agents MUST NOT process a CSYNC record if it contains a 1 value for a
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flag that is unknown to or unsupported by the parental agent.
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2.1.1.2.1. The Type Bit Map Field
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The Type Bit Map field indicates the record types to be processed by
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the parental agent, according to the procedures in Section 3. The
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Type Bit Map field is encoded in the same way as the Type Bit Map
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field of the NSEC record, described in [RFC4034], Section 4.1.2. If
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||
a bit has been set that a parental agent implementation does not
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understand, the parental agent MUST NOT act upon the record.
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Specifically, a parental agent must not simply copy the data, and it
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must understand the semantics associated with a bit in the Type Bit
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Map field that has been set to 1.
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Hardaker Standards Track [Page 5]
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RFC 7477 Child-to-Parent Synchronization in DNS March 2015
|
||
|
||
|
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2.1.2. The CSYNC Presentation Format
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The CSYNC presentation format is as follows:
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The SOA Serial field is represented as an integer.
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The Flags field is represented as an integer.
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The Type Bit Map field is represented as a sequence of RRType
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mnemonics. When the mnemonic is not known, the TYPE
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representation described in [RFC3597], Section 5, MUST be used.
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Implementations that support parsing of presentation format
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records SHOULD be able to read and understand these TYPE
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representations as well.
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2.1.3. CSYNC RR Example
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The following CSYNC RR shows an example entry for "example.com" that
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indicates the NS, A, and AAAA bits are set and should be processed by
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the parental agent for example.com. The parental agent should pull
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data only from a zone using a minimum SOA serial number of 66 (0x42
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in hexadecimal).
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example.com. 3600 IN CSYNC 66 3 A NS AAAA
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The RDATA component of the example CSYNC RR would be encoded on the
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wire as follows:
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0x00 0x00 0x00 0x42 (SOA Serial)
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0x00 0x03 (Flags = immediate | soaminimum)
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0x00 0x04 0x60 0x00 0x00 0x08 (Type Bit Map)
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3. CSYNC Data Processing
|
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The CSYNC record and associated data must be processed as an "all or
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nothing" operation set. If a parental agent fails to successfully
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query for any of the required records, the whole operation MUST be
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aborted. (Note that a query resulting in "no records exist" as
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proven by NSEC or NSEC3 is to be considered successful).
|
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Parental agents MAY:
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Process the CSYNC record immediately if the "immediate" flag is
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set. If the "immediate" flag is not set, the parental agent MUST
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NOT act until the zone administrator approves the operation
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through an out-of-band mechanism (such as through pushing a button
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via a web interface).
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|
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Hardaker Standards Track [Page 6]
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|
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RFC 7477 Child-to-Parent Synchronization in DNS March 2015
|
||
|
||
|
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Choose not to process the CSYNC record immediately, even if the
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"immediate" flag is set. That is, a parental agent might require
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the child zone administrator approve the operation through an out-
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of-band mechanism (such as through pushing a button via a web
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interface).
|
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|
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Note: how the approval is done out of band is outside the scope of
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this document and is implementation specific to parental agents.
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3.1. Processing Procedure
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The following shows a sequence of steps that SHOULD be used when
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collecting and processing CSYNC records from a child zone. Because
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DNS queries are not allowed to contain more than one "question" at a
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time, a sequence of requests is needed. When processing a CSYNC
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transaction request, all DNS queries should be sent to a single
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authoritative name server for the child zone. To ensure a single
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host is being addressed, DNS over TCP SHOULD be used to avoid
|
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conversing with multiple nodes at an anycast address.
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1. Query for the child zone's SOA record
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2. Query for the child zone's CSYNC record
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3. Query for the child zone's data records, as required by the CSYNC
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record's Type Bit Map field
|
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* Note: if any of the resulting records being queried are not
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authoritative within the child zone but rather in a grandchild
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or deeper, SOA record queries must be made for the
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grandchildren. This will require the parental agent to
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determine where the child/grandchild zone cuts occur. Because
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of the additional operational complexity, parental agents MAY
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choose not to support this protocol with children making use
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of records that are authoritative in the grandchildren.
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4. Query for the collected SOA records again, starting with the
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deepest and ending with the SOA of the child's.
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If the SOA records from the first, middle, and last steps for a given
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zone have different serial numbers (for example, because the zone was
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edited and republished during the interval between steps 1 and 4),
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then the CSYNC record obtained in the second set SHOULD NOT be
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processed (rapidly changing child zones may need special
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consideration or processing). The operation MAY be restarted or
|
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retried in the future.
|
||
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Hardaker Standards Track [Page 7]
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||
RFC 7477 Child-to-Parent Synchronization in DNS March 2015
|
||
|
||
|
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If the soaminimum flag is set and the SOA serial numbers are equal
|
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but less than the CSYNC record's SOA Serial field [RFC1982], the
|
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record MUST NOT be processed. If state is being kept by the parental
|
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agent and the SOA serial number is less than the last time a CSYNC
|
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record was processed, this CSYNC record SHOULD NOT be processed.
|
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Similarly, if state is being kept by the parental agent and the SOA
|
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Serial field of the CSYNC record is less than the SOA Serial field of
|
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the CSYNC record from last time, then this CSYNC record SHOULD NOT be
|
||
processed.
|
||
|
||
If a failure of any kind occurs while trying to obtain any of the
|
||
required data, or if DNSSEC fails to validate all of the data
|
||
returned for these queries as "secure", then this CSYNC record MUST
|
||
NOT be processed.
|
||
|
||
See the "Operational Consideration" section (Section 4) for
|
||
additional guidance about processing.
|
||
|
||
3.2. CSYNC Record Types
|
||
|
||
This document defines how the following record types may be processed
|
||
if the CSYNC Type Bit Map field indicates they are to be processed.
|
||
|
||
3.2.1. The NS type
|
||
|
||
The NS type flag indicates that the NS records from the child zone
|
||
should be copied into the parent's delegation information records for
|
||
the child.
|
||
|
||
NS records found within the child's zone should be copied verbatim
|
||
(with the exception of the Time to Live (TTL) field, for which the
|
||
parent MAY want to select a different value) and the result published
|
||
within the parent zone should be a set of NS records that match
|
||
exactly. If the child has published a new NS record within their
|
||
set, this record should be added to the parent zone. Similarly, if
|
||
NS records in the parent's delegation records for the child contain
|
||
records that have been removed in the child's NS set, then they
|
||
should be removed in the parent's set as well.
|
||
|
||
Parental agents MAY refuse to perform NS updates if the replacement
|
||
records fail to meet NS record policies required by the parent zone
|
||
(e.g., "every child zone must have at least two NS records").
|
||
Parental agents MUST NOT perform NS updates if there are no NS
|
||
records returned in a query, as verified by DNSSEC denial-of-
|
||
existence protection. This situation should never happen unless the
|
||
child nameservers are misconfigured.
|
||
|
||
|
||
|
||
|
||
|
||
Hardaker Standards Track [Page 8]
|
||
|
||
RFC 7477 Child-to-Parent Synchronization in DNS March 2015
|
||
|
||
|
||
Note that it is permissible for a child's nameserver to return a
|
||
CSYNC record that removes the queried nameserver itself from the
|
||
future NS or address set.
|
||
|
||
3.2.2. The A and AAAA Types
|
||
|
||
The A and AAAA type flags indicates that the A and AAAA address glue
|
||
records for in-bailiwick NS records within the child zone should be
|
||
copied verbatim (with the exception of the TTL field, for which the
|
||
parent MAY want to select a different value) into the parent's
|
||
delegation information.
|
||
|
||
Queries should be sent by the parental agent to determine the A and
|
||
AAAA record addresses for each NS record within a NS set for the
|
||
child that are in bailiwick.
|
||
|
||
Note: only the matching types should be queried. For example, if the
|
||
AAAA bit has not been set, then the AAAA records (if any) in the
|
||
parent's delegation should remain as is. If a given address type is
|
||
set and the child's zone contains no data for that type (as proven by
|
||
appropriate NSEC or NSEC3 records), then the result in the parent's
|
||
delegation records for the child should be an empty set. However, if
|
||
the end result of processing would leave no glue records present in
|
||
the parent zone for any of the of the in-bailiwick NS records, then
|
||
the parent MUST NOT update the glue address records. That is, if the
|
||
result of the processing would leave no in-bailiwick A or AAAA
|
||
records when there are in-bailiwick NS records, then processing of
|
||
the address records cannot happen as it would leave the parent/child
|
||
relationship without any address linkage.
|
||
|
||
The procedure for querying for A and AAAA records MUST occur after
|
||
the procedure, if required, for querying for NS records as defined in
|
||
Section 3.2.1. This ensures that the right set of NS records is used
|
||
as provided by the current NS set of the child. That is, for CSYNC
|
||
records that have the NS bit set, the NS set used should be the one
|
||
pulled from the child while processing the CSYNC record. For CSYNC
|
||
records without the NS bit set, the existing NS records within the
|
||
parent should be used to determine which A and/or AAAA records to
|
||
update.
|
||
|
||
4. Operational Considerations
|
||
|
||
There are a number of important operational aspects to consider when
|
||
deploying a CSYNC RRType.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Hardaker Standards Track [Page 9]
|
||
|
||
RFC 7477 Child-to-Parent Synchronization in DNS March 2015
|
||
|
||
|
||
4.1. Error Reporting
|
||
|
||
There is no inline mechanism for a parental agent to report errors to
|
||
operators of child zones. Thus, the only error reporting mechanisms
|
||
must be out of band, such as through a web console or over email.
|
||
Parental agents should, at a minimum, at least log errors encountered
|
||
when processing CSYNC records. Child operators utilizing the
|
||
"immediate" flag that fail to see an update within the parental
|
||
agent's specified operational window should access the parental
|
||
agent's error logging interface to determine why an update failed to
|
||
be processed.
|
||
|
||
4.2. Child Nameserver Selection
|
||
|
||
Parental agents will need to poll child nameservers in search of
|
||
CSYNC records and related data records.
|
||
|
||
Parental agents MAY perform best-possible verification by querying
|
||
all NS records for available data to determine which has the most
|
||
recent SOA and CSYNC version (in an ideal world, they would all be
|
||
equal, but this is not possible in practice due to synchronization
|
||
delays and transfer failures).
|
||
|
||
Parental agents may offer a configuration interface to allow child
|
||
operators to specify which nameserver should be considered the master
|
||
to send data queries, too. Note that this master could be a
|
||
different nameserver than the publicly listed nameservers in the NS
|
||
set (i.e., it may be a "hidden master").
|
||
|
||
Parental agents with a large number of clients may choose to offer a
|
||
programmatic interface to let their children indicate that new CSYNC
|
||
records and data are available for polling rather than polling every
|
||
child on a frequent basis.
|
||
|
||
Children that wish to phase out a nameserver will need to publish the
|
||
CSYNC record to remove the nameserver and then wait for the parental
|
||
agent to process the published record before turning off the service.
|
||
This is required because the child cannot control which nameserver in
|
||
the existing NS set the parental agent may choose to query when
|
||
performing CSYNC processing.
|
||
|
||
4.3. Out-of-Bailiwick NS Records
|
||
|
||
When a zone contains NS records where the domain name pointed at does
|
||
not fall within the zone itself, there is no way for the parent to
|
||
safely update the associated glue records. Thus, the child DNS
|
||
operator MAY indicate that the NS records should be synchronized, and
|
||
|
||
|
||
|
||
|
||
Hardaker Standards Track [Page 10]
|
||
|
||
RFC 7477 Child-to-Parent Synchronization in DNS March 2015
|
||
|
||
|
||
MAY set any glue record flags (A, AAAA) as well, but the parent will
|
||
only update those glue records that are below the child's delegation
|
||
point.
|
||
|
||
Children deploying NS records pointing to domain names within their
|
||
own children (the "grandchildren") SHOULD ensure the grandchildren's
|
||
associated glue records are properly set before publishing the CSYNC
|
||
record. That is, it is imperative that proper communication and
|
||
synchronization exist between the child and the grandchild.
|
||
|
||
4.4. Documented Parental Agent Type Support
|
||
|
||
Parental agents that support processing CSYNC records SHOULD publicly
|
||
document the following minimum processing characteristics:
|
||
|
||
The fact that they support CSYNC processing
|
||
|
||
The Type Bit Map bits they support
|
||
|
||
The frequency with which they poll clients (which may also be
|
||
configurable by the client)
|
||
|
||
If they support the "immediate" flag
|
||
|
||
If they poll a child's single nameserver, a configured list of
|
||
nameservers, or all of the advertised nameservers when querying
|
||
records
|
||
|
||
If they support SOA serial number caching to avoid issues with
|
||
regression and/or replay
|
||
|
||
Where errors for CSYNC processing are published
|
||
|
||
If they support sending queries to a "hidden master"
|
||
|
||
4.5. Removal of the CSYNC Records
|
||
|
||
Children MAY remove the CSYNC record upon noticing that the parent
|
||
zone has published the required records, thus eliminating the need
|
||
for the parent to continually query for the CSYNC record and all
|
||
corresponding records. By removing the CSYNC record from the child
|
||
zone, the parental agent will only need to perform the query for the
|
||
CSYNC record and can stop processing when it finds it missing. This
|
||
will reduce resource usage by both the child and the parental agent.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Hardaker Standards Track [Page 11]
|
||
|
||
RFC 7477 Child-to-Parent Synchronization in DNS March 2015
|
||
|
||
|
||
4.6. Parent/Child/Grandchild Glue Synchronization
|
||
|
||
When a child needs to publish a CSYNC record that synchronizes NS and
|
||
A/AAAA glue records and the NS record is actually pointing to a child
|
||
of the child (a grandchild of the parent), then it is critical that
|
||
the glue records in the child point to the proper real addresses
|
||
records published by the grandchild. It is assumed that if a child
|
||
is using a grandchild's nameserver that they must be in careful
|
||
synchronization. Specifically, this specification requires this to
|
||
be the case.
|
||
|
||
5. Security Considerations
|
||
|
||
This specification requires the use of DNSSEC in order to determine
|
||
that the data being updated was unmodified by third parties.
|
||
Parental agents implementing CSYNC processing MUST ensure all DNS
|
||
transactions are validated by DNSSEC as "secure". Clients deploying
|
||
CSYNC MUST ensure their zones are signed, current and properly linked
|
||
to the parent zone with a DS record that points to an appropriate
|
||
DNSKEY of the child's zone.
|
||
|
||
This specification does not address how to perform bootstrapping
|
||
operations to get the required initial DNSSEC-secured operating
|
||
environment in place. Additionally, this specification was not
|
||
designed to synchronize DNSSEC security records, such as DS pointers,
|
||
or the CSYNC record itself. Thus, implementations of this protocol
|
||
MUST NOT use it to synchronize DS records, DNSKEY materials, CDS
|
||
records, CDNSKEY records, or CSYNC records. Similarly, future
|
||
documents extending this protocol MUST NOT offer the ability to
|
||
synchronize DS, DNSKEY materials, CDS records, CDNSKEY records, or
|
||
CSYNC records. For such a solution, please see the complimentary
|
||
solution [RFC7344] for maintaining security delegation information.
|
||
|
||
To ensure that an older CSYNC record making use of the soaminimum
|
||
flag cannot be replayed to revert values, the SOA serial number MUST
|
||
NOT be incremented by more than 2^16 during the lifetime of the
|
||
signature window of the associated RRSIGs signing the SOA and CSYNC
|
||
records. Note that this is independent of whether or not the
|
||
increment causes the 2^32 bit serial number field to wrap.
|
||
|
||
6. IANA Considerations
|
||
|
||
This document defines a new DNS Resource Record Type, named "CSYNC".
|
||
The IANA has assigned a code point from the "Resource Record (RR)
|
||
TYPEs" sub-registry of the "Domain Name System (DNS) Parameters"
|
||
registry (http://www.iana.org/assignments/dns-parameters) for this
|
||
record.
|
||
|
||
|
||
|
||
|
||
Hardaker Standards Track [Page 12]
|
||
|
||
RFC 7477 Child-to-Parent Synchronization in DNS March 2015
|
||
|
||
|
||
TYPE Value Meaning Reference
|
||
----- ------ -------------------------- -----------
|
||
CSYNC 62 Child-to-Parent Synchronization [RFC7477]
|
||
|
||
The IANA has created and maintains a sub-registry (the "Child
|
||
Synchronization (CSYNC) Flags" registry) of the "Domain Name System
|
||
(DNS) Parameters" registry. The initial values for this registry are
|
||
below.
|
||
|
||
A "Standards Action" [RFC5226] is required for the assignment of new
|
||
flag value.
|
||
|
||
This registry holds a set of single-bit "Flags" for use in the CSYNC
|
||
record within the 16-bit Flags field. Thus, a maximum of 16 flags
|
||
may be defined.
|
||
|
||
The initial assignments in this registry are:
|
||
|
||
Bit Flag Description Reference
|
||
---- ------ ------------- -----------
|
||
Bit 0 immediate Immediately process this [RFC7477],
|
||
CSYNC record. Section 3
|
||
|
||
Bit 1 soaminimum Require a SOA serial [RFC7477],
|
||
number greater than the Section 2.1.1.1
|
||
one specified.
|
||
|
||
7. References
|
||
|
||
7.1. Normative References
|
||
|
||
[RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
|
||
August 1996, <http://www.rfc-editor.org/info/rfc1982>.
|
||
|
||
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
|
||
Requirement Levels", BCP 14, RFC 2119, March 1997,
|
||
<http://www.rfc-editor.org/info/rfc2119>.
|
||
|
||
[RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record
|
||
(RR) Types", RFC 3597, September 2003,
|
||
<http://www.rfc-editor.org/info/rfc3597>.
|
||
|
||
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
|
||
Rose, "Resource Records for the DNS Security Extensions",
|
||
RFC 4034, March 2005,
|
||
<http://www.rfc-editor.org/info/rfc4034>.
|
||
|
||
|
||
|
||
|
||
|
||
Hardaker Standards Track [Page 13]
|
||
|
||
RFC 7477 Child-to-Parent Synchronization in DNS March 2015
|
||
|
||
|
||
7.2. Informative References
|
||
|
||
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
|
||
STD 13, RFC 1034, November 1987,
|
||
<http://www.rfc-editor.org/info/rfc1034>.
|
||
|
||
[RFC1035] Mockapetris, P., "Domain names - implementation and
|
||
specification", STD 13, RFC 1035, November 1987,
|
||
<http://www.rfc-editor.org/info/rfc1035>.
|
||
|
||
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
|
||
Rose, "DNS Security Introduction and Requirements", RFC
|
||
4033, March 2005,
|
||
<http://www.rfc-editor.org/info/rfc4033>.
|
||
|
||
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
|
||
Rose, "Protocol Modifications for the DNS Security
|
||
Extensions", RFC 4035, March 2005,
|
||
<http://www.rfc-editor.org/info/rfc4035>.
|
||
|
||
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
|
||
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
|
||
May 2008, <http://www.rfc-editor.org/info/rfc5226>.
|
||
|
||
[RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating
|
||
DNSSEC Delegation Trust Maintenance", RFC 7344, September
|
||
2014, <http://www.rfc-editor.org/info/rfc7344>.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Hardaker Standards Track [Page 14]
|
||
|
||
RFC 7477 Child-to-Parent Synchronization in DNS March 2015
|
||
|
||
|
||
Acknowledgments
|
||
|
||
A thank you goes out to Warren Kumari and Olafur Gudmundsson, whose
|
||
work on the CDS record type helped inspire the work in this document,
|
||
as well as the definition for the "parental agent" definition and
|
||
significant contributions to the text. A thank you also goes out to
|
||
Ed Lewis, with whom the author held many conversations about the
|
||
issues surrounding parent/child relationships and synchronization.
|
||
Much of the work in this document is derived from the careful
|
||
existing analysis of these three esteemed colleagues. Thank you to
|
||
the following people who have contributed text or detailed reviews to
|
||
the document (in no particular order): Matthijs Mekking, Petr Spacek,
|
||
JINMEI Tatuya, Pete Resnick, Joel Jaeggli, Brian Haberman, Warren
|
||
Kumari, Adrian Farrel, Alia Atlas, Barry Leiba, Richard Barnes,
|
||
Stephen Farrell, and Ted Lemon. Lastly, the DNSOP WG chairs Tim
|
||
Wicinski and Suzanne Woolf have been a tremendous help in getting
|
||
this document moving forward to publication.
|
||
|
||
A special thanks goes to Roy Arends, for taking the "bite out of that
|
||
hamburger" challenge while discussing this document.
|
||
|
||
A similar project, independently designed and developed, was
|
||
conducted by ep.net called "Child Activated DNS Refresh".
|
||
|
||
Author's Address
|
||
|
||
Wes Hardaker
|
||
Parsons, Inc.
|
||
P.O. Box 382
|
||
Davis, CA 95617
|
||
US
|
||
|
||
Phone: +1 530 792 1913
|
||
EMail: ietf@hardakers.net
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Hardaker Standards Track [Page 15]
|
||
|