Diff: rfc9471.original

	rfc9471.original	rfc9471.txt


	DNSOP M. Andrews	Internet Engineering Task Force (IETF) M. Andrews
	Internet-Draft ISC	Request for Comments: 9471 ISC
	Updates: 1034 (if approved) S. Huque	Updates: 1034 S. Huque
	Intended status: Standards Track Salesforce	Category: Standards Track Salesforce
	Expires: 16 December 2023 P. Wouters	ISSN: 2070-1721 P. Wouters
	Aiven	Aiven
	D. Wessels	D. Wessels
	Verisign	Verisign

	14 June 2023	September 2023

	DNS Glue Requirements in Referral Responses	DNS Glue Requirements in Referral Responses

	draft-ietf-dnsop-glue-is-not-optional-09

	Abstract	Abstract

	The DNS uses glue records to allow iterative clients to find the	The DNS uses glue records to allow iterative clients to find the
	addresses of name servers that are contained within a delegated zone.	addresses of name servers that are contained within a delegated zone.

	Authoritative Servers are expected to return all available glue	Authoritative servers are expected to return all available glue
	records for in-domain name servers in a referral response. If	records for in-domain name servers in a referral response. If
	message size constraints prevent the inclusion of all glue records	message size constraints prevent the inclusion of all glue records

	for in-domain name servers, the server must set the TC flag to inform	for in-domain name servers, the server must set the TC (Truncated)
	the client that the response is incomplete, and that the client	flag to inform the client that the response is incomplete and that
	should use another transport to retrieve the full response. This	the client should use another transport to retrieve the full
	document updates RFC 1034 to clarify correct server behavior.	response. This document updates RFC 1034 to clarify correct server
		behavior.

	Status of This Memo	Status of This Memo


	This Internet-Draft is submitted in full conformance with the	This is an Internet Standards Track document.
	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	This document is a product of the Internet Engineering Task Force
	and may be updated, replaced, or obsoleted by other documents at any	(IETF). It represents the consensus of the IETF community. It has
	time. It is inappropriate to use Internet-Drafts as reference	received public review and has been approved for publication by the
	material or to cite them other than as "work in progress."	Internet Engineering Steering Group (IESG). Further information on
		Internet Standards is available in Section 2 of RFC 7841.


	This Internet-Draft will expire on 16 December 2023.	Information about the current status of this document, any errata,
		and how to provide feedback on it may be obtained at
		https://www.rfc-editor.org/info/rfc9471.

	Copyright Notice	Copyright Notice

	Copyright (c) 2023 IETF Trust and the persons identified as the	Copyright (c) 2023 IETF Trust and the persons identified as the
	document authors. All rights reserved.	document authors. All rights reserved.

	This document is subject to BCP 78 and the IETF Trust's Legal	This document is subject to BCP 78 and the IETF Trust's Legal

	Provisions Relating to IETF Documents (https://trustee.ietf.org/	Provisions Relating to IETF Documents
	license-info) in effect on the date of publication of this document.	(https://trustee.ietf.org/license-info) in effect on the date of
	Please review these documents carefully, as they describe your rights	publication of this document. Please review these documents
	and restrictions with respect to this document. Code Components	carefully, as they describe your rights and restrictions with respect
	extracted from this document must include Revised BSD License text as	to this document. Code Components extracted from this document must
	described in Section 4.e of the Trust Legal Provisions and are	include Revised BSD License text as described in Section 4.e of the
	provided without warranty as described in the Revised BSD License.	Trust Legal Provisions and are provided without warranty as described
		in the Revised BSD License.

	Table of Contents	Table of Contents


	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2	1. Introduction
	1.1. Reserved Words . . . . . . . . . . . . . . . . . . . . . 3	1.1. Requirements Language
	2. Types of Glue in Referral Responses . . . . . . . . . . . . . 3	2. Types of Glue in Referral Responses
	2.1. Glue for In-Domain Name Servers . . . . . . . . . . . . . 3	2.1. Glue for In-Domain Name Servers
	2.2. Glue for Sibling Domain Name Servers . . . . . . . . . . 4	2.2. Glue for Sibling Domain Name Servers
	2.3. Glue for Cyclic Sibling Domain Name Servers . . . . . . . 5	2.3. Glue for Cyclic Sibling Domain Name Servers
	2.4. Missing Glue . . . . . . . . . . . . . . . . . . . . . . 6	2.4. Missing Glue
	3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7	3. Requirements
	3.1. Glue for In-Domain Name Servers . . . . . . . . . . . . . 7	3.1. Glue for In-Domain Name Servers
	3.2. Glue for Sibling Domain Name Servers . . . . . . . . . . 8	3.2. Glue for Sibling Domain Name Servers
	3.3. Updates to RFC 1034 . . . . . . . . . . . . . . . . . . . 8	3.3. Update to RFC 1034
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 8	4. Security Considerations
	5. Operational Considerations . . . . . . . . . . . . . . . . . 8	5. Operational Considerations
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9	6. IANA Considerations
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9	7. References
	8. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 9	7.1. Normative References
	9. Normative References . . . . . . . . . . . . . . . . . . . . 10	7.2. Informative References
	10. Informative References . . . . . . . . . . . . . . . . . . . 11	Acknowledgements
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12	Authors' Addresses

	1. Introduction	1. Introduction


	The Domain Name System (DNS) [RFC1034], [RFC1035] uses glue records	The Domain Name System (DNS) [RFC1034] [RFC1035] uses glue records to
	to allow iterative clients to find the addresses of name servers that	allow iterative clients to find the addresses of name servers that
	are contained within a delegated zone. Glue records are added to the	are contained within a delegated zone. Glue records are added to the
	parent zone as part of the delegation process and returned in	parent zone as part of the delegation process and returned in

	referral responses, otherwise a resolver following the referral has	referral responses; otherwise, a resolver following the referral has
	no way of finding these addresses. Authoritative servers are	no way of finding these addresses. Authoritative servers are
	expected to return all available glue records for in-domain name	expected to return all available glue records for in-domain name
	servers in a referral response. If message size constraints prevent	servers in a referral response. If message size constraints prevent
	the inclusion of all glue records for in-domain name servers over the	the inclusion of all glue records for in-domain name servers over the
	chosen transport, the server MUST set the TC (Truncated) flag to	chosen transport, the server MUST set the TC (Truncated) flag to

	inform the client that the response is incomplete, and that the	inform the client that the response is incomplete and that the client
	client SHOULD use another transport to retrieve the full response.	SHOULD use another transport to retrieve the full response. This
	This document clarifies that expectation.	document clarifies that expectation.

	DNS responses sometimes contain optional data in the additional	DNS responses sometimes contain optional data in the additional
	section. In-domain glue records, however, are not optional. Several	section. In-domain glue records, however, are not optional. Several
	other protocol extensions, when used, are also not optional. This	other protocol extensions, when used, are also not optional. This
	includes TSIG [RFC8945], OPT [RFC6891], and SIG(0) [RFC2931].	includes TSIG [RFC8945], OPT [RFC6891], and SIG(0) [RFC2931].

	At the time of this writing, addresses (A or AAAA records) for a	At the time of this writing, addresses (A or AAAA records) for a
	delegation's authoritative name servers are the only type of glue	delegation's authoritative name servers are the only type of glue
	defined for the DNS.	defined for the DNS.


	Note that this document only clarifies requirements of name server	Note that this document only clarifies requirements for name server
	software implementations. It does not introduce or change any	software implementations. It does not introduce or change any

	requirements on data placed in DNS zones or registries. In other	requirements regarding data placed in DNS zones or registries. In
	words, this document only makes requirements on "available glue	other words, this document only makes requirements regarding
	records" (i.e., those given in a zone), but does not make	"available glue records" (i.e., those given in a zone) but does not
	requirements regarding their presence in a zone. If some glue	make requirements regarding their presence in a zone. If some glue
	records are absent from a given zone, an authoritative name server	records are absent from a given zone, an authoritative name server
	may be unable to return a useful referral response for the	may be unable to return a useful referral response for the
	corresponding domain. The IETF may want to consider a separate	corresponding domain. The IETF may want to consider a separate
	update to the requirements for including glue in zone data, beyond	update to the requirements for including glue in zone data, beyond
	those given in [RFC1034] and [RFC1035].	those given in [RFC1034] and [RFC1035].

	This document assumes a reasonable level of familiarity with DNS	This document assumes a reasonable level of familiarity with DNS
	operations and protocol terms. Much of the terminology is explained	operations and protocol terms. Much of the terminology is explained
	in further detail in "DNS Terminology" [RFC8499].	in further detail in "DNS Terminology" [RFC8499].


	1.1. Reserved Words	1.1. Requirements Language

	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and

	"OPTIONAL" in this document are to be interpreted as described in BCP	"OPTIONAL" in this document are to be interpreted as described in
	14 [RFC2119] [RFC8174] when, and only when, they appear in all	BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.	capitals, as shown here.

	2. Types of Glue in Referral Responses	2. Types of Glue in Referral Responses

	This section describes different types of glue that may be found in	This section describes different types of glue that may be found in
	DNS referral responses. Note that the type of glue depends on the	DNS referral responses. Note that the type of glue depends on the
	QNAME. A particular name server (and its corresponding glue record)	QNAME. A particular name server (and its corresponding glue record)
	can be in-domain for one response and in a sibling domain for	can be in-domain for one response and in a sibling domain for
	another.	another.


	skipping to change at page 4, line 27 ¶	skipping to change at line 165 ¶
	foo.test. 86400 IN NS ns1.foo.test.	foo.test. 86400 IN NS ns1.foo.test.
	foo.test. 86400 IN NS ns2.foo.test.	foo.test. 86400 IN NS ns2.foo.test.

	;; ADDITIONAL SECTION:	;; ADDITIONAL SECTION:
	ns1.foo.test. 86400 IN A 192.0.2.1	ns1.foo.test. 86400 IN A 192.0.2.1
	ns2.foo.test. 86400 IN AAAA 2001:db8::2:2	ns2.foo.test. 86400 IN AAAA 2001:db8::2:2

	2.2. Glue for Sibling Domain Name Servers	2.2. Glue for Sibling Domain Name Servers

	Sibling domain name servers are NS records that are not contained in	Sibling domain name servers are NS records that are not contained in

	the delegated zone itself, but in another zone delegated from the	the delegated zone itself but rather are contained in another zone
	same parent. In many cases, glue for sibling domain name servers are	delegated from the same parent. In many cases, glue for sibling
	not strictly required for resolution, since the resolver can make	domain name servers is not strictly required for resolution, since
	follow-on queries to the sibling zone to resolve the name server	the resolver can make follow-on queries to the sibling zone to
	addresses (after following the referral to the sibling zone).	resolve the name server addresses (after following the referral to
	However, most name server implementations today provide them as an	the sibling zone). However, most name server implementations today
	optimization to obviate the need for extra traffic from iterative	provide them as an optimization to obviate the need for extra traffic
	resolvers.	from iterative resolvers.


	Here the delegating zone "test" contains two delegations for the	Here, the delegating zone "test" contains two delegations for the
	child zones "bar.test" and "foo.test":	child zones "bar.test" and "foo.test":

	bar.test. 86400 IN NS ns1.bar.test.	bar.test. 86400 IN NS ns1.bar.test.
	bar.test. 86400 IN NS ns2.bar.test.	bar.test. 86400 IN NS ns2.bar.test.
	ns1.bar.test. 86400 IN A 192.0.2.1	ns1.bar.test. 86400 IN A 192.0.2.1
	ns2.bar.test. 86400 IN AAAA 2001:db8::2:2	ns2.bar.test. 86400 IN AAAA 2001:db8::2:2

	foo.test. 86400 IN NS ns1.bar.test.	foo.test. 86400 IN NS ns1.bar.test.
	foo.test. 86400 IN NS ns2.bar.test.	foo.test. 86400 IN NS ns2.bar.test.


	skipping to change at page 5, line 24 ¶	skipping to change at line 207 ¶
	ns2.bar.test. 86400 IN AAAA 2001:db8::2:2	ns2.bar.test. 86400 IN AAAA 2001:db8::2:2

	2.3. Glue for Cyclic Sibling Domain Name Servers	2.3. Glue for Cyclic Sibling Domain Name Servers

	The use of sibling domain name servers can introduce cyclic	The use of sibling domain name servers can introduce cyclic
	dependencies. This happens when one domain specifies name servers	dependencies. This happens when one domain specifies name servers
	from a sibling domain, and vice versa. This type of cyclic	from a sibling domain, and vice versa. This type of cyclic
	dependency can only be broken when the delegating name server	dependency can only be broken when the delegating name server
	includes glue for the sibling domain in a referral response.	includes glue for the sibling domain in a referral response.


	Here the delegating zone "test" contains two delegations for the	Here, the delegating zone "test" contains two delegations for the
	child zones "bar.test" and "foo.test", and each use name servers	child zones "bar.test" and "foo.test", and each uses name servers
	under the other:	under the other:

	bar.test. 86400 IN NS ns1.foo.test.	bar.test. 86400 IN NS ns1.foo.test.
	bar.test. 86400 IN NS ns2.foo.test.	bar.test. 86400 IN NS ns2.foo.test.
	ns1.bar.test. 86400 IN A 192.0.2.1	ns1.bar.test. 86400 IN A 192.0.2.1
	ns2.bar.test. 86400 IN AAAA 2001:db8::2:2	ns2.bar.test. 86400 IN AAAA 2001:db8::2:2

	foo.test. 86400 IN NS ns1.bar.test.	foo.test. 86400 IN NS ns1.bar.test.
	foo.test. 86400 IN NS ns2.bar.test.	foo.test. 86400 IN NS ns2.bar.test.
	ns1.foo.test. 86400 IN A 192.0.2.3	ns1.foo.test. 86400 IN A 192.0.2.3

	skipping to change at page 6, line 5 ¶	skipping to change at line 235 ¶
	;www.bar.test. IN A	;www.bar.test. IN A

	;; AUTHORITY SECTION:	;; AUTHORITY SECTION:
	bar.test. 86400 IN NS ns1.foo.test.	bar.test. 86400 IN NS ns1.foo.test.
	bar.test. 86400 IN NS ns2.foo.test.	bar.test. 86400 IN NS ns2.foo.test.

	;; ADDITIONAL SECTION:	;; ADDITIONAL SECTION:
	ns1.foo.test. 86400 IN A 192.0.2.3	ns1.foo.test. 86400 IN A 192.0.2.3
	ns2.foo.test. 86400 IN AAAA 2001:db8::2:4	ns2.foo.test. 86400 IN AAAA 2001:db8::2:4


	In late 2021 the authors analyzed zone file data available from	In late 2021, the authors analyzed zone file data available from
	ICANN's Centralized Zone Data Service [CZDS] and found 222 out of	ICANN's Centralized Zone Data Service [CZDS] and found 222 out of
	approximately 209,000,000 total delegations that had only sibling	approximately 209,000,000 total delegations that had only sibling

	domain NS RRs in a cyclic dependency as above.	domain NS Resource Records (RRs) in a cyclic dependency as above.

	2.4. Missing Glue	2.4. Missing Glue


	An example of missing glue is included here, even though it can not	An example of missing glue is included here, even though it cannot be
	be considered as a type of glue. While not common, real examples of	considered as a type of glue. While not common, real examples of
	responses that lack required glue, and with TC=0, have been shown to	responses that lack required glue, and with TC=0, have been shown to
	occur and cause resolution failures.	occur and cause resolution failures.

	The example below, from the dig command [DIG], is based on a response	The example below, from the dig command [DIG], is based on a response
	observed in June 2020. The names have been altered to fall under	observed in June 2020. The names have been altered to fall under
	documentation domains. It shows a case where none of the glue	documentation domains. It shows a case where none of the glue
	records present in the zone fit into the available space of the UDP	records present in the zone fit into the available space of the UDP
	response, and the TC flag was not set. While this example shows a	response, and the TC flag was not set. While this example shows a

	referral with DNSSEC records [RFC4033], [RFC4034], [RFC4035], this	referral with DNSSEC records [RFC4033] [RFC4034] [RFC4035], this
	behavior has been seen with plain DNS responses as well. Some	behavior has been seen with plain DNS responses as well. Some
	records have been truncated for display purposes. Note that at the	records have been truncated for display purposes. Note that at the
	time of this writing, the servers originally responsible for this	time of this writing, the servers originally responsible for this
	example have been updated and now correctly set the TC flag.	example have been updated and now correctly set the TC flag.

	% dig +norec +dnssec +bufsize=512 +ignore @ns.example.net \	% dig +norec +dnssec +bufsize=512 +ignore @ns.example.net \
	rh202ns2.355.foo.example	rh202ns2.355.foo.example

	; <<>> DiG 9.15.4 <<>> +norec +dnssec +bufsize +ignore \	; <<>> DiG 9.15.4 <<>> +norec +dnssec +bufsize +ignore \
	@ns.example.net rh202ns2.355.foo.example	@ns.example.net rh202ns2.355.foo.example

	skipping to change at page 7, line 41 ¶	skipping to change at line 294 ¶

	3. Requirements	3. Requirements

	This section describes updated requirements for including glue in DNS	This section describes updated requirements for including glue in DNS
	referral responses.	referral responses.

	3.1. Glue for In-Domain Name Servers	3.1. Glue for In-Domain Name Servers

	This document clarifies that when a name server generates a referral	This document clarifies that when a name server generates a referral
	response, it MUST include all available glue records for in-domain	response, it MUST include all available glue records for in-domain

	name servers in the additional section, or MUST set TC=1 if	name servers in the additional section or MUST set TC=1 if
	constrained by message size.	constrained by message size.


	At the time of writing, most iterative clients send initial queries	At the time of this writing, most iterative clients send initial
	over UDP and retry over TCP upon receiving a response with the TC	queries over UDP and retry over TCP upon receiving a response with
	flag set. UDP responses are generally limited to between 1232 and	the TC flag set. UDP responses are generally limited to between 1232
	4096 bytes, due to values commonly used for the EDNS0 UDP Message	and 4096 bytes, due to values commonly used for the EDNS0 UDP Message
	Size field [RFC6891], [FLAGDAY2020]. TCP responses are limited to	Size field [RFC6891] [FLAGDAY2020]. TCP responses are limited to
	65,535 bytes.	65,535 bytes.

	3.2. Glue for Sibling Domain Name Servers	3.2. Glue for Sibling Domain Name Servers

	This document clarifies that when a name server generates a referral	This document clarifies that when a name server generates a referral
	response, it SHOULD include all available glue records in the	response, it SHOULD include all available glue records in the
	additional section. If, after adding glue for all in-domain name	additional section. If, after adding glue for all in-domain name
	servers, the glue for all sibling domain name servers does not fit	servers, the glue for all sibling domain name servers does not fit
	due to message size constraints, the name server MAY set TC=1 but is	due to message size constraints, the name server MAY set TC=1 but is
	not obligated to do so.	not obligated to do so.

	Note that users may experience resolution failures for domains with	Note that users may experience resolution failures for domains with

	cyclically-dependent sibling name servers when the delegating name	cyclically dependent sibling name servers when the delegating name
	server chooses to omit the corresponding glue in a referral response.	server chooses to omit the corresponding glue in a referral response.
	As described in Section 2.3, such domains are rare.	As described in Section 2.3, such domains are rare.


	3.3. Updates to RFC 1034	3.3. Update to RFC 1034


	Replace	OLD:


	"Copy the NS RRs for the subzone into the authority section of the	\| Copy the NS RRs for the subzone into the authority section of the
	reply. Put whatever addresses are available into the additional	\| reply. Put whatever addresses are available into the additional
	section, using glue RRs if the addresses are not available from	\| section, using glue RRs if the addresses are not available from
	authoritative data or the cache. Go to step 4."	\| authoritative data or the cache. Go to step 4.


	with	NEW:


	"Copy the NS RRs for the subzone into the authority section of the	\| Copy the NS RRs for the subzone into the authority section of the
	reply. Put whatever NS addresses are available into the additional	\| reply. Put whatever NS addresses are available into the
	section, using glue RRs if the addresses are not available from	\| additional section, using glue RRs if the addresses are not
	authoritative data or the cache. If all glue RRs for in-domain name	\| available from authoritative data or the cache. If all glue RRs
	servers do not fit, set TC=1 in the header. Go to step 4."	\| for in-domain name servers do not fit, set TC=1 in the header. Go
		\| to step 4.

	4. Security Considerations	4. Security Considerations

	This document clarifies correct DNS server behavior and does not	This document clarifies correct DNS server behavior and does not
	introduce any changes or new security considerations.	introduce any changes or new security considerations.

	5. Operational Considerations	5. Operational Considerations

	At the time of this writing, the behavior of most DNS server	At the time of this writing, the behavior of most DNS server
	implementations is to set the TC flag only if none of the available	implementations is to set the TC flag only if none of the available
	glue records fit in a response over UDP transport. The updated	glue records fit in a response over UDP transport. The updated
	requirements in this document might lead to an increase in the	requirements in this document might lead to an increase in the

	fraction of UDP responses with the TC flag set, and consequently an	fraction of UDP responses with the TC flag set and, consequently, an
	increase in the number of queries received over TCP transport.	increase in the number of queries received over TCP transport.

	6. IANA Considerations	6. IANA Considerations


	There are no actions for IANA.	This document has no IANA actions.

	7. Acknowledgements

	The authors wish to thank Joe Abley, David Blacka, Brian Dickson,
	Kazunori Fujiwara, Paul Hoffman, Geoff Huston, Jared Mauch, George
	Michaelson, Yasuhiro Orange Morishita, Benno Overeinder, John R
	Levine, Hugo Salgado, Shinta Sato, Puneet Sood, Petr Spacek, Ralf
	Weber, Tim Wicinski, Suzanne Woolf, and other members of the DNSOP
	working group for their input.

	8. Changes

	RFC Editor: Please remove this section before publication.

	This section lists substantial changes to the document as it is being
	worked on.

	From -01 to -02:

	* Clarified that "servers" means "authoritative servers".

	* Clarified that "available glue" means "all available glue".

	* Updated examples and placed before RFC 1034 update.

	From -02 to -03:

	* Clarified scope to focus only on name server responses, and not
	zone/registry data.

	* Reorganized with section 2 as Types of Glue and section 3 as
	Requirements.

	* Removed any discussion of promoted / orphan glue.

	* Use appropriate documentation addresses and domain names.

	* Added Sibling Cyclic Glue example.

	From -03 to -04:

	* Use "referral glue" on the assumption that other types of glue may
	be defined in the future.

	* Added Operational Considerations section.

	* Note many current implementations set TC=1 only when no glue RRs
	fit. New requirements may lead to more truncation and TCP.

	* Sibling glue can be optional. Only require TC=1 when all in-
	domain glue RRs don't fit.

	* Avoid talking about requirements for UDP/TCP specifically, and
	talk more generically about message size constraints regardless of
	transport.

	From -04 to -05:

	* Reverting the -04 change to use the phrase "referral glue".

	* Rephrase "in-domain glue" as "glue for in-domain name servers".

	* Rephrase "sibling glue" as "glue for sibling domain name servers".

	* Expand paragraph noting this document does not make requirements
	about presence of glue in zones.

	From -05 to -06:

	* More instances of rephrasing "in-domain glue" as "glue for in-
	domain name servers" (and for sibling glue).

	From -06 to -07:

	* Change "NOT REQUIRED to set TC=1" to "MAY set TC=1 but is not
	obligated to do so."

	From -07 to -08:

	* Update TSIG reference to RFC8945.

	From -08 to -09:

	* Lowercase RFC2119 keywords in abstract

	* Add informative reference to DNS terminology RFC


	* Add informative reference to dig	7. References


	9. Normative References	7.1. Normative References

	[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",	[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
	STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,	STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
	<https://www.rfc-editor.org/info/rfc1034>.	<https://www.rfc-editor.org/info/rfc1034>.

	[RFC1035] Mockapetris, P., "Domain names - implementation and	[RFC1035] Mockapetris, P., "Domain names - implementation and
	specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,	specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
	November 1987, <https://www.rfc-editor.org/info/rfc1035>.	November 1987, <https://www.rfc-editor.org/info/rfc1035>.

	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,	Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,	DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.	<https://www.rfc-editor.org/info/rfc2119>.

	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.	May 2017, <https://www.rfc-editor.org/info/rfc8174>.


	10. Informative References	7.2. Informative References


	[CZDS] ICANN, "Centralized Zone Data Service", January 2022,	[CZDS] ICANN, "Centralized Zone Data Service",
	<https://czds.icann.org/>.	<https://czds.icann.org/>.


	[DIG] Wikipedia, "dig (command)", June 2023,	[DIG] Wikipedia, "dig (command)", September 2023,
	<https://en.wikipedia.org/wiki/Dig_(command)>.	<https://en.wikipedia.org/wiki/Dig_(command)>.

	[FLAGDAY2020]	[FLAGDAY2020]
	Various DNS software and service providers, "DNS Flag Day	Various DNS software and service providers, "DNS Flag Day
	2020", October 2020, <https://dnsflagday.net/2020/>.	2020", October 2020, <https://dnsflagday.net/2020/>.

	[RFC2931] Eastlake 3rd, D., "DNS Request and Transaction Signatures	[RFC2931] Eastlake 3rd, D., "DNS Request and Transaction Signatures
	( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September	( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September
	2000, <https://www.rfc-editor.org/info/rfc2931>.	2000, <https://www.rfc-editor.org/info/rfc2931>.


	skipping to change at page 12, line 15 ¶	skipping to change at line 421 ¶
	[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS	[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
	Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,	Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
	January 2019, <https://www.rfc-editor.org/info/rfc8499>.	January 2019, <https://www.rfc-editor.org/info/rfc8499>.

	[RFC8945] Dupont, F., Morris, S., Vixie, P., Eastlake 3rd, D.,	[RFC8945] Dupont, F., Morris, S., Vixie, P., Eastlake 3rd, D.,
	Gudmundsson, O., and B. Wellington, "Secret Key	Gudmundsson, O., and B. Wellington, "Secret Key
	Transaction Authentication for DNS (TSIG)", STD 93,	Transaction Authentication for DNS (TSIG)", STD 93,
	RFC 8945, DOI 10.17487/RFC8945, November 2020,	RFC 8945, DOI 10.17487/RFC8945, November 2020,
	<https://www.rfc-editor.org/info/rfc8945>.	<https://www.rfc-editor.org/info/rfc8945>.


		Acknowledgements

		The authors wish to thank Joe Abley, David Blacka, Brian Dickson,
		Kazunori Fujiwara, Paul Hoffman, Geoff Huston, John R. Levine, Jared
		Mauch, George Michaelson, Yasuhiro Orange Morishita, Benno
		Overeinder, Hugo Salgado, Shinta Sato, Puneet Sood, Petr Spacek, Ralf
		Weber, Tim Wicinski, Suzanne Woolf, and other members of the DNSOP
		Working Group for their input.

	Authors' Addresses	Authors' Addresses

	M. Andrews	M. Andrews
	ISC	ISC
	Email: marka@isc.org	Email: marka@isc.org

	Shumon Huque	Shumon Huque
	Salesforce	Salesforce
	Email: shuque@gmail.com	Email: shuque@gmail.com


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