Internet DRAFT - draft-ietf-dnsop-generalized-notify
draft-ietf-dnsop-generalized-notify
DNSOP Working Group J. Stenstam
Internet-Draft The Swedish Internet Foundation
Intended status: Standards Track P. Thomassen
Expires: 5 September 2024 deSEC, Secure Systems Engineering
J. Levine
Standcore LLC
4 March 2024
Generalized DNS Notifications
draft-ietf-dnsop-generalized-notify-01
Abstract
This document extends the use of DNS NOTIFY ([RFC1996] beyond
conventional zone transfer hints, bringing the benefits of ad-hoc
notifications to DNS delegation maintenance in general. Use cases
include DNSSEC key rollovers hints, and quicker changes to a
delegation's NS record set.
To enable this functionality, a method for discovering the receiver
endpoint for such notification message is introduced, via the new
NOTIFY record type.
TO BE REMOVED: This document is being collaborated on in Github at:
https://github.com/peterthomassen/draft-ietf-dnsop-generalized-notify
(https://github.com/peterthomassen/draft-ietf-dnsop-generalized-
notify). The most recent working version of the document, open
issues, etc. should all be available there. The authors (gratefully)
accept pull requests.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 5 September 2024.
Stenstam, et al. Expires 5 September 2024 [Page 1]
Internet-Draft Generalized Notifications March 2024
Copyright Notice
Copyright (c) 2024 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 (https://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 include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Publication of Notification Targets . . . . . . . . . . . . . 4
2.1. Design Requirements . . . . . . . . . . . . . . . . . . . 4
2.2. Signaling Method . . . . . . . . . . . . . . . . . . . . 5
3. The DSYNC Record . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Wire Format . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Semantics . . . . . . . . . . . . . . . . . . . . . . . . 6
3.3. Rationale . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Delegation Maintenance: CDS/CDNSKEY and CSYNC
Notifications . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Endpoint Discovery . . . . . . . . . . . . . . . . . . . 8
4.2. Sending Notifications . . . . . . . . . . . . . . . . . . 8
4.2.1. Timing . . . . . . . . . . . . . . . . . . . . . . . 9
4.2.2. Rationale for Using the DNS Message Format . . . . . 9
4.3. Processing of NOTIFY Messages . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
8. Normative References . . . . . . . . . . . . . . . . . . . . 12
Appendix A. Efficiency and Convergence Issues in DNS Scanning . 14
A.1. Original NOTIFY for Zone Transfer Nudging . . . . . . . . 14
A.2. Similar Issues for DS Maintenance and Beyond . . . . . . 14
Appendix B. Change History (to be removed before publication) . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
Stenstam, et al. Expires 5 September 2024 [Page 2]
Internet-Draft Generalized Notifications March 2024
1. Introduction
Traditional DNS notifications [RFC1996], which are here referred to
as "NOTIFY(SOA)", are sent from a primary server to a secondary
server to minimize the latter's convergence time to a new version of
the zone. This mechanism successfully addresses a significant
inefficiency in the original protocol.
Today similar inefficiencies occur in new use cases, in particular
delegation maintenance (DS and NS record updates). Just as in the
NOTIFY(SOA) case, a new set of notification types will have a major
positive benefit by allowing the DNS infrastructure to completely
sidestep these inefficiencies. For additional context, see
Appendix A.
No DNS protocol changes are introduced by this document. The
mechanism instead makes use of a wider range of DNS messages allowed
by the protocol. Future extension for further use cases (such as
multi-signer key exchange) is possible.
Readers are expected to be familiar with DNSSEC, including [RFC4033],
[RFC4034], [RFC4035], [RFC6781], [RFC7344], [RFC7477], [RFC7583], and
[RFC8901].
1.1. Requirements Notation
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.
1.2. Terminology
In the text below there are two different uses of the term "NOTIFY".
One refers to the NOTIFY message, sent from a DNSSEC signer or name
server to a notification target (for subsequent processing). We
refer to this message as NOTIFY(RRtype) where the RRtype indicates
the type of NOTIFY message (CDS or CSYNC).
The second is a proposed new DNS record type, with the suggested
mnemonic "NOTIFY". This record is used to publish the location of
the notification target. We refer to this as the "NOTIFY record".
Stenstam, et al. Expires 5 September 2024 [Page 3]
Internet-Draft Generalized Notifications March 2024
2. Publication of Notification Targets
To use generalized notifications, it is necessary for the sender to
know where to direct each NOTIFY message. This section describes the
procedure for discovering that notification target.
Note that generalized NOTIFY messages are but one mechanism for
improving the efficiency of automated delegation maintenance. Other
alternatives alternatives, such as contacting the parent via an API
or DNS Update ([RFC2136]), may (or may not) be more suitable in
individual cases. Like generalized notifications, they similarly
require a means for discovering where to send the API or DNS Update
requets.
The scope for the publication mechanism is therefore wider than only
to support generalized notifications, and a unified approach that
works independently of the notification method is specified in this
section.
2.1. Design Requirements
When the parent is interested in notifications for delegation
maintenance (such as for DS or NS updates), a service will need to be
made available for accepting these notifications. Depending on the
context, this service may be run by the parent zone operator
themselves, or by a designated entity who is in charge of handling
the domain's delegation data (such as a domain registrar).
The simplest solution enabling straightforward discovery is for the
parent to publish the address where it prefers to have notifications
sent. Potential notification senders, knowing the name of the parent
zone, can then simply look up that information.
It is strongly desirable that the notification sender is able to
figure out where to send the NOTIFY via a single lookup, even when
ignorant of the details of the parent-side business relationships
(e.g., whether there is a registrar or not). The mechanism should
thus enable the parent to (optionally) announce the notification
endpoint in a delegation-specific way. (If the delegation is several
labels deep, an extra query may be needed for identifying the
parent.)
These requirements suggest making the endpoint discoverable at a
child-specific name. The record there is expected to live at a
wildcard name, unless the parent intends to publish a child-specific
endpoint.
Stenstam, et al. Expires 5 September 2024 [Page 4]
Internet-Draft Generalized Notifications March 2024
2.2. Signaling Method
Parents participating in the discovery scheme for the purpose of
delegation maintenance notifications MUST publish endpoint
information using the record type defined in Section 3, as described
in this section.
The suggested mnemonic for the new record type is "DSYNC" and it is
further described below.
If the parent itself performs CDS/CDNSKEY and CSYNC processing, or if
the parent forwards the notifications internally to the designated
party (such as as registrar), the following scheme is used:
*._signal.se. IN DSYNC CDS scheme port endpoint.registry.se.
*._signal.se. IN DSYNC CSYNC scheme port endpoint.registry.se.
It is also possible to publish child-specific records, where the
wildcard label is replaced by the child's FQDN with the parent zone's
labels stripped.
As an example, consider a registrar offering domains like example.se,
delegated from se zone. If the registrar provides the notification
endpoint, the parent may publish this information using the following
scheme:
example._signal.se. IN DSYNC CDS scheme port endpoint.registrar.com.
(Note that this is a generic method, allowing the parent to securely
publish other sorts of information about a child that currently is
not easily represented in DNS, such as the registrar's identity.)
The parent MAY synthesize records under the _signal domain. The
_signal domain may be delegated to another nameserver dedicated for
this purpose.
To accommodate indirect delegation management models (such as ICANN's
RRR model), the parent's designated notification target may relay
notifications to the registrar, e.g. via an EPP call, or by
forwarding the NOTIFY(CDS) message directly. The same is true also
for NOTIFY(CSYNC).
3. The DSYNC Record
3.1. Wire Format
The DSYNC RDATA wire format is encoded as follows:
Stenstam, et al. Expires 5 September 2024 [Page 5]
Internet-Draft Generalized Notifications March 2024
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RRtype | Scheme | Port
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target ... /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-/
RRtype The type of generalized NOTIFY that this DSYNC RR defines the
desired target address for. For now, only CDS and CSYNC are
supported values.
Scheme The scheme for locating the desired notification address.
The range is 0-255. This is an 8 bit unsigned integer. The value
0 is an error, and values 128-255 are reserved for private use.
The value 1 is described in this document, and all other values
are currently unspecified.
Port The port on the target host of the notification service. The
range is 0-65535. This is a 16 bit unsigned integer in network
byte order.
Target The domain name of the target host providing the service of
listening for generalized notifications of the specified type.
This name MUST resolve to one or more address records.
3.2. Semantics
For now, the only scheme defined is scheme=1 with the interpretation
that when a new CDS (or CDNSKEY or CSYNC) is published, a NOTIFY(CDS)
or NOTIFY(CSYNC) should be sent to the address and port listed in the
corresponding NOTIFY RRset.
Other schemes are possible, but are out of scope for this document.
Example:
parent. IN DSYNC CDS 1 5359 cds-scanner.parent.
parent. IN DSYNC CSYNC 1 5360 csync-scanner.parent.
From the perspective of this protocol, the NOTIFY(CDS) packet is
simply sent to the parent's published notification address. However,
should this turn out not to be sufficient, it is possible to define a
new "scheme" that specifies alternative logic for dealing with such
requirements. Description of internal processing in the recipient
end or for locating the recipient are out of scope of this document.
Stenstam, et al. Expires 5 September 2024 [Page 6]
Internet-Draft Generalized Notifications March 2024
3.3. Rationale
(RFC Editor: This subsection is to be removed before publication)
It may look like it's possible to store the same information in an
SRV record. However, this would require indicating the RRtype via a
label in the owner name, leading to name space pollution. It would
also require changing the semantics of one of the integer fields of
the SRV record.
Such overloading has not been a good idea in the past. Furthermore,
as the generalized notifications are a new proposal with no prior
deployments, there is an opportunity to avoid repeating mistakes.
The DSYNC record type also provides a cleaner solution for bundling
all the new types of notification signaling in an RRset, like:
parent. IN DSYNC CDS 1 59 scanner.parent.
parent. IN DSYNC CSYNC 1 59 scanner.parent.
For DSYNC records indicating CDS/CDNSKEY/CSYNC notification targets,
no special processing needs to be applied by the authoritative
nameserver upon insertion of a DSYNC record. The nameserver can thus
be "unaware".
Future use cases (such as for multi-signer key exchange) may require
the nameserver to trigger special operations, for example when a
DSYNC record is inserted during onboarding of a new signer. It seems
cleaner and easier that such processing be associated with the
insertion of a record of a new type, not an existing type like SRV.
4. Delegation Maintenance: CDS/CDNSKEY and CSYNC Notifications
Delegation maintenance notifications address the inefficiencies
related to scanning child zones for CDS/CDNSKEY records [RFC7344].
(For an overview of the issues, see Appendix A.)
Delegation maintenance NOTIFY messages MUST be formatted as described
in [RFC1996], with the qtype field replaced as appropriate.
To address the CDS/CDNSKEY dichotomy, the NOTIFY(CDS) message (with
qtype=CDS) is defined to indicate any child-side changes pertaining
to an upcoming update of DS records. Upon receipt of NOTIFY(CDS),
the recipient (the parent registry or a registrar) SHOULD initiate
the same DNS lookups and verifications that would otherwise be
triggered based on a timer.
Stenstam, et al. Expires 5 September 2024 [Page 7]
Internet-Draft Generalized Notifications March 2024
The CSYNC [RFC7477] inefficiency may be similarly treated, with the
child sending a NOTIFY(CSYNC) message (with qtype=CSYNC) to an
address where the parent (or a registrar) is listening to CSYNC
notifications.
In both cases the notification will speed up processing times by
providing the recipient with a hint that a particular child zone has
published new CDS, CDNSKEY and/or CSYNC records.
4.1. Endpoint Discovery
To locate the target for outgoing delegation maintenance
notifications, the notification sender MUST perform the following
procedure:
1. Construct the lookup name, by injecting the _signal label after
the first label of the delegation owner name.
2. Perform a lookup of type DSYNC for the lookup name, and validate
the response if DNSSEC is enabled. If a DSYNC RRset results,
return it.
3. When the query resulted in a negative response:
* If the negative response indicates that the parent is more
than one label away from the _signal label, construct a new
lookup name by inserting the _signal label into the delegation
owner name just before the parent zone labels inferred from
the negative response, and go to step 2.
For example, city.ise.mie.jp is delegated from jp (and not
from ise.mie.jp or mie.jp!). The initial DSYNC query relating
to it is thus directed at city._signal.ise.mie.jp. This is
expected to result in a negative response from jp, and another
query for city.ise.mie._signal.jp is then required;
* Otherwise, if the lookup name has any labels in front of the
_signal label, remove them to construct a new lookup name
(such as _signal.jp), and go to step 2. (This is to enable
zone structures without wildcards.)
* Otherwise, return null (no notification target available).
4.2. Sending Notifications
When changing a CDS/CDNSKEY/CSYNC RRset in the child zone, the DNS
operator SHOULD send a suitable NOTIFY message to the endpoint
located as described in the previous section.
Stenstam, et al. Expires 5 September 2024 [Page 8]
Internet-Draft Generalized Notifications March 2024
A NOTIFY message can only carry information about changes concerning
one child zone. When there are changes to several child zones, the
sender MUST send a separate notification for each one.
Because of the security model where a notification by itself never
causes a change (it can only speed up the time until the next check
for the same thing), the sender's identity is not crucial. This
opens up the possibility of having an arbitrary party (e.g., a side-
car service) send the notifications to the parent, thereby enabling
this functionality even before the emergence of native support in
nameserver software.
While the receiving side will often be a scanning service provided by
the registry itself, it is expected that in the ICANN RRR model, some
registries will prefer registrars to conduct CDS/CDNSKEY processing.
In such cases, the registrar notification endpoint should be
published in the parent zone, enabling the child to direct their
notifications to the appropriate target. From the perspective of the
child, it is inconsequential who's in charge of processing the
notification: the NOTIFY message is simply sent to the published
address.
4.2.1. Timing
When a primary name server publishes a new RRset in the child, there
will be a time delay until all publicly visible copies of the zone
will have been updated. If the primary sends a NOTIFY at the exact
time of publication of the new zone, there is a potential for the
parent to attempt CDS/CDNSKEY/CSYNC processing before the updated
zone is visible. In this case the parent may draw the wrong
conclusion (“the CDS RRset has not been updated”).
Having a delay between the publication of the new data and the check
for the new data would alleviate this issue. However, as the parent
has no way of knowing how quickly the child zone propagates, the
appropriate amount of delay is uncertain.
It is therefore RECOMMENDED that the child delays sending NOTIFY
messages to the recipient until a consistent public view of the
pertinent records is ensured.
4.2.2. Rationale for Using the DNS Message Format
(RFC Editor: This subsection is to be removed before publication)
In the most common cases of using generalized notifications the
recipient is expected to not be a nameserver, but rather some other
type of service, like a CDS/CSYNC scanner.
Stenstam, et al. Expires 5 September 2024 [Page 9]
Internet-Draft Generalized Notifications March 2024
However, this will likely not always be true. In particular it seems
likely that in cases where the parent is not a large delegation-
centric zone like a TLD, but rather a smaller zone with a small
number of delegations there will not be separate services for
everything and the recipient of the NOTIFY(CDS) or NOTIFY(CSYNC) will
be an authoritative nameserver for the parent zone.
For this reason it seems most reasonable to stay within the the well
documented and already supported message format specified in RFC 1996
and delivered over normal DNS transport, although not necessarily to
port 53.
4.3. Processing of NOTIFY Messages
NOTIFY(CDS) messages carrying notification payloads (records) for
several child zones MUST be discarded, as sending them is an error.
Upon receipt of a (potentially forwarded) valid NOTIFY(CDS) message
for a particular child zone at the published address for CDS
notifications, the receiving side (parent registry or registrar) has
two options:
1. Schedule an immediate check of the CDS and CDNSKEY RRsets as
published by that particular child zone.
If the check finds that the CDS/CDNSKEY RRset has indeed changed,
the parent MAY reset the scanning timer for children for which
NOTIFY(CDS) is received, or reduce the periodic scanning
frequency accordingly (e.g. to every two weeks). This will
decrease the scanning effort for the parent. If a CDS/CDNSKEY
change is then detected (without having received a notification),
the parent SHOULD clear that state and revert to the default
scanning schedule.
Parents introducing CDS/CDNSKEY scanning support at the same time
as NOTIFY(CDS) support are not in danger of breaking children's
scanning assumption, and MAY therefore use a low-frequency
scanning schedule in default mode.
2. Ignore the notification, in which case the system works exactly
as before. (One reason to do this may be a rate limit, see
Section 5.)
If the parent implements the first option, the convergence time (time
between publication of a new CDS/CDNSKEY record in the child and
propagation of the resulting DS) will decrease significantly, thereby
providing improved service to the child zone.
Stenstam, et al. Expires 5 September 2024 [Page 10]
Internet-Draft Generalized Notifications March 2024
If the parent, in addition to scheduling an immediate check for the
child zone of the notification, also choses to modify the scanning
schedule (to be less frequent), the cost of providing the scanning
service will be reduced.
Upon receipt of a NOTIFY(CSYNC) to the published address for CSYNC
notifications, the same options and considerations apply as for the
NOTIFY(CDS).
5. Security Considerations
The original NOTIFY specification sidesteps most security issues by
not relying on the information in the NOTIFY message in any way, and
instead only using it to "enter the state it would if the zone's
refresh timer had expired" (Section 4.7 of [RFC1996]).
This security model is reused for generalized NOTIFY messages. It
therefore seems impossible to affect the behaviour of the recipient
of the NOTIFY other than by hastening the timing for when different
checks are initiated.
The receipt of a notification message will, in general, cause the
receiving party to perform one or more outbound queries for the
records of interest (for example, NOTIFY(CDS) will cause CDS/CDNSKEY
queries). When done via port 53, the size of these queries is
comparable to that of the NOTIFY messages themselves, rendering any
amplification attempts futile. The number of queries triggered per
notification is also limited by the requirement that a NOTIFY message
can refer to one child only.
However, when the outgoing query occurs via encrypted transport, some
amplification is possible, both with respect to bandwidth and
computational burden. In this case, the usual principle of bounding
the work, even under unreasonable events, applies.
Receivers therefore MUST implement rate limiting for notification
processing. It is RECOMMENDED to configure rate limiting
independently for both the notification's source IP address and the
name of the zone that is conveyed in the NOTIFY message. Rate
limiting also mitigates processing load from garbage notifications.
Alternative solutions (such as signing notifications and validating
their signatures) appear significantly more expensive without
tangible benefit.
Stenstam, et al. Expires 5 September 2024 [Page 11]
Internet-Draft Generalized Notifications March 2024
6. IANA Considerations
Per [RFC8552], IANA is requested to create a new registry on the
"Domain Name System (DNS) Parameters" IANA web page as follows:
Name: DSYNC: Location of Synchronization Endpoints
Assignment Policy: Expert Review
Reference: (this document)
+============+=========+========================+=================+
| DSYNC type | Scheme | Purpose | Reference |
+============+=========+========================+=================+
| CDS | 1 | Delegation management | (this document) |
+------------+---------+------------------------+-----------------+
| CSYNC | 1 | Delegation management | (this document) |
+------------+---------+------------------------+-----------------+
| | 128-255 | Reserved (private use) | (this document) |
+------------+---------+------------------------+-----------------+
Table 1
7. Acknowledgements
Joe Abley, Mark Andrews, Christian Elmerot, Ólafur Guðmundsson, Paul
Wouters, Brian Dickson
8. Normative References
[I-D.wisser-dnssec-automation]
Wisser, U. and S. Huque, "DNSSEC automation", Work in
Progress, Internet-Draft, draft-wisser-dnssec-automation-
03, 6 March 2022, <https://datatracker.ietf.org/doc/html/
draft-wisser-dnssec-automation-03>.
[RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone
Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996,
August 1996, <https://www.rfc-editor.org/rfc/rfc1996>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
Stenstam, et al. Expires 5 September 2024 [Page 12]
Internet-Draft Generalized Notifications March 2024
[RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, DOI 10.17487/RFC2136, April 1997,
<https://www.rfc-editor.org/rfc/rfc2136>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, DOI 10.17487/RFC4033, March 2005,
<https://www.rfc-editor.org/rfc/rfc4033>.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005,
<https://www.rfc-editor.org/rfc/rfc4034>.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
<https://www.rfc-editor.org/rfc/rfc4035>.
[RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC
Operational Practices, Version 2", RFC 6781,
DOI 10.17487/RFC6781, December 2012,
<https://www.rfc-editor.org/rfc/rfc6781>.
[RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating
DNSSEC Delegation Trust Maintenance", RFC 7344,
DOI 10.17487/RFC7344, September 2014,
<https://www.rfc-editor.org/rfc/rfc7344>.
[RFC7477] Hardaker, W., "Child-to-Parent Synchronization in DNS",
RFC 7477, DOI 10.17487/RFC7477, March 2015,
<https://www.rfc-editor.org/rfc/rfc7477>.
[RFC7583] Morris, S., Ihren, J., Dickinson, J., and W. Mekking,
"DNSSEC Key Rollover Timing Considerations", RFC 7583,
DOI 10.17487/RFC7583, October 2015,
<https://www.rfc-editor.org/rfc/rfc7583>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8552] Crocker, D., "Scoped Interpretation of DNS Resource
Records through "Underscored" Naming of Attribute Leaves",
BCP 222, RFC 8552, DOI 10.17487/RFC8552, March 2019,
<https://www.rfc-editor.org/rfc/rfc8552>.
Stenstam, et al. Expires 5 September 2024 [Page 13]
Internet-Draft Generalized Notifications March 2024
[RFC8901] Huque, S., Aras, P., Dickinson, J., Vcelak, J., and D.
Blacka, "Multi-Signer DNSSEC Models", RFC 8901,
DOI 10.17487/RFC8901, September 2020,
<https://www.rfc-editor.org/rfc/rfc8901>.
Appendix A. Efficiency and Convergence Issues in DNS Scanning
A.1. Original NOTIFY for Zone Transfer Nudging
[RFC1996] introduced the concept of a DNS Notify message which was
used to improve the convergence time for secondary servers when a DNS
zone had been updated in the primary. The basic idea was to augment
the traditional "pull" mechanism (a periodic SOA query) with a "push"
mechanism (a Notify) for a common case that was otherwise very
inefficient (due to either slow convergence or wasteful overly
frequent scanning of the primary for changes).
While it is possible to indicate how frequently checks should occur
(via the SOA Refresh parameter), these checks did not allow catching
zone changes that fall between checkpoints. [RFC1996] addressed the
optimization of the time-and-cost trade-off between a seceondary
checking frequently for new versions of a zone, and infrequent
checking, by replacing scheduled scanning with the more efficient
NOTIFY mechanism.
A.2. Similar Issues for DS Maintenance and Beyond
Today, we have similar issues with slow updates of DNS data in spite
of the data having been published. The two most obvious cases are
CDS and CSYNC scanners deployed in a growing number of TLD
registries. Because of the large number of child delegations,
scanning for CDS and CSYNC records is rather slow (as in infrequent).
It is only a very small number of the delegations that will have
updated CDS or CDNSKEY record in between two scanning runs. However,
frequent scanning for CDS and CDNSKEY records is costly, and
infrequent scanning causes slower convergence (i.e., delay until the
DS RRset is updated).
Unlike in the original case, where the primary is able to suggest the
scanning interval via the SOA Refresh parameter, an equivalent
mechanism does not exist for DS-related scanning.
Stenstam, et al. Expires 5 September 2024 [Page 14]
Internet-Draft Generalized Notifications March 2024
All of this above also applies to parents that offer automated NS and
glue record maintenance via CSYNC scanning [RFC7477]. Again, given
that CSYNC records change only rarely, frequent scanning of a large
number of delegations seems disproportionately costly, while
infrequent scanning causes slower convergence (delay until the
delegation is updated).
While use of the NOTIFY mechanism for coordinating the key exchange
in multi-signer setups [I-D.wisser-dnssec-automation] is conceivable,
the detailed specification is left for future work.
Appendix B. Change History (to be removed before publication)
* draft-ietf-dnsop-generalized-notify-01
Reserve scheme values 128-255
Rename NOTIFY rrtype to DSYNC (to distinguish from NOTIFY message)
Describe endpoint discovery
Discussion on garbage notifications
More discussion on amplification risks
Clean-up, editorial changes
* draft-ietf-dnsop-generalized-notify-00
Revision after adoption.
* draft-thomassen-dnsop-generalized-dns-notify-02
Add rationale for staying in band
Add John as an author
* draft-thomassen-dnsop-generalized-dns-notify-01
Mention Ry-to-Rr forwarding to accommodate RRR model
Add port number flexiblity
Add scheme parameter
Drop SRV-based alternative in favour of new NOTIFY RR
Editorial improvements
Stenstam, et al. Expires 5 September 2024 [Page 15]
Internet-Draft Generalized Notifications March 2024
* draft-thomassen-dnsop-generalized-dns-notify-00
Initial public draft.
Authors' Addresses
Johan Stenstam
The Swedish Internet Foundation
Email: johan.stenstam@internetstiftelsen.se
Peter Thomassen
deSEC, Secure Systems Engineering
Email: peter@desec.io
John Levine
Standcore LLC
Email: standards@standcore.com
Stenstam, et al. Expires 5 September 2024 [Page 16]