draft-ietf-dnsop-nxdomain-cut-00.txt		draft-ietf-dnsop-nxdomain-cut-01.txt
	Domain Name System Operations (dnsop) Working Group S. Bortzmeyer		Domain Name System Operations (dnsop) Working Group S. Bortzmeyer
	Internet-Draft AFNIC		Internet-Draft AFNIC
	Updates: 1034,2308 (if approved) S. Huque		Updates: 1034,2308 (if approved) S. Huque
	Intended status: Standards Track Verisign labs		Intended status: Standards Track Verisign Labs
	Expires: June 29, 2016 December 27, 2015		Expires: September 11, 2016 March 10, 2016
	NXDOMAIN really means there is nothing underneath		NXDOMAIN really means there is nothing underneath
	draft-ietf-dnsop-nxdomain-cut-00		draft-ietf-dnsop-nxdomain-cut-01
	Abstract		Abstract
	This document states clearly that when a DNS resolver receives a		This document states clearly that when a DNS resolver receives a
	response with response code of NXDOMAIN, it means that the domain		response with response code of NXDOMAIN, it means that the domain
	name which is thus denied AND ALL THE NAMES UNDER IT do not exist.		name which is thus denied AND ALL THE NAMES UNDER IT do not exist.
	REMOVE BEFORE PUBLICATION: this document should be discussed in the		REMOVE BEFORE PUBLICATION: this document should be discussed in the
	IETF DNSOP (DNS Operations) group, through its mailing list. The		IETF DNSOP (DNS Operations) group, through its mailing list. The
	source of the document, as well as a list of open issues, is		source of the document, as well as a list of open issues, is
	skipping to change at page 1, line 41 ¶		skipping to change at page 1, line 41 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on June 29, 2016.		This Internet-Draft will expire on September 11, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2016 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		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction and background . . . . . . . . . . . . . . . . . 2		1. Introduction and background . . . . . . . . . . . . . . . . . 2
	1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3		1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 4		3. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 4
	4. Possible issues . . . . . . . . . . . . . . . . . . . . . . . 5		4. Possible issues . . . . . . . . . . . . . . . . . . . . . . . 5
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5		5. Implementation considerations . . . . . . . . . . . . . . . . 5
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 5		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	7. Implementation status - RFC EDITOR: REMOVE BEFORE PUBLICATION 5		7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6		8. Implementation status - RFC EDITOR: REMOVE BEFORE PUBLICATION 6
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6		9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
	9.1. Normative References . . . . . . . . . . . . . . . . . . 7		10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	9.2. Informative References . . . . . . . . . . . . . . . . . 7		10.1. Normative References . . . . . . . . . . . . . . . . . . 7
	9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 8		10.2. Informative References . . . . . . . . . . . . . . . . . 8
			10.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	Appendix A. Why can't we just use the owner name of the returned		Appendix A. Why can't we just use the owner name of the returned
	SOA? . . . . . . . . . . . . . . . . . . . . . . . . 8		SOA? . . . . . . . . . . . . . . . . . . . . . . . . 9
	Appendix B. Related approaches . . . . . . . . . . . . . . . . . 9		Appendix B. Related approaches . . . . . . . . . . . . . . . . . 9
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
	1. Introduction and background		1. Introduction and background
	The DNS protocol [RFC1035] defines response code 3 as "Name Error",		The DNS protocol [RFC1035] defines response code 3 as "Name Error",
	or "NXDOMAIN", i.e. the queried domain name does not exist in the		or "NXDOMAIN" [RFC2308], which means that the queried domain name
	DNS. Since domain names are represented as a tree of labels		does not exist in the DNS. Since domain names are represented as a
	([RFC1034], Section 3.1), non-existence of a node implies non-		tree of labels ([RFC1034], Section 3.1), non-existence of a node
	existence of the entire sub-tree rooted at this node.		implies non-existence of the entire sub-tree rooted at this node.
	The DNS iterative resolution algorithm precisely interprets the		The DNS iterative resolution algorithm precisely interprets the
	NXDOMAIN signal in this manner. If it encounters an NXDOMAIN		NXDOMAIN signal in this manner. If it encounters an NXDOMAIN
	response code from an authoritative server, it immediately stops		response code from an authoritative server, it immediately stops
	iteration and returns the NXDOMAIN response to the querier.		iteration and returns the NXDOMAIN response to the querier.
	However, in virtually all existing resolvers, a cached NXDOMAIN is		However, in most known existing resolvers today, a cached non-
	not considered "proof" that there can be no child domains underneath.		existence for a domain is not considered "proof" that there can be no
	This is due to an ambiguity in [RFC1034] that failed to distinguish		child domains underneath. This is due to an ambiguity in [RFC1034]
	Empty Non-Terminal names (ENT) ([RFC7719]) from nonexistent names.		that failed to distinguish Empty Non-Terminal names (ENT) ([RFC7719])
	For DNSSEC, the IETF had to distinguish this case ([RFC4035], section		from nonexistent names. The distinction became especially important
	3.1.3.2), but the implication on non-DNSSEC resolvers wasn't fully		for the development of DNSSEC, which provides proof of non-existence.
	realized.
			[RFC4035], section 3.1.3.2, describes how security-aware
			authoritative name servers make the distinction, but no existing RFCs
			describe the behavior for recursive name servers.
	This document specifies that an NXDOMAIN response for a domain name		This document specifies that an NXDOMAIN response for a domain name
	means that no child domains underneath the queried name exist either.		means that no child domains underneath the queried name exist either.
	And furthermore, that DNS resolvers should interpret cached NXDOMAIN		And furthermore, that DNS resolvers should interpret cached non-
	responses in this manner. Since the domain names are organized in a		existence in this manner. Since the domain names are organized in a
	tree, it is a simple consequence of the tree structure: non-existence		tree, it is a simple consequence of the tree structure: non-existence
	of a node implies non-existence of the entire sub-tree rooted at this		of a node implies non-existence of the entire sub-tree rooted at this
	node.		node.
	1.1. Terminology		1.1. Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	"Denied name": the domain name whose existence has been denied by a		"Denied name": the domain name whose existence has been denied by a
	response of rcode NXDOMAIN. In most cases, it is the QNAME but,		response of rcode NXDOMAIN. In most cases, it is the QNAME but,
	because of [RFC6604], it is not always the case.		because of [RFC6604], it is not always the case.
			Other terms are defined in [RFC1034] or [RFC1035] or (like NXDOMAIN
			itself) in the more recent [RFC7719].
	2. Rules		2. Rules
	When searching downward in its cache, an iterative caching DNS		When an iterative caching DNS resolver receives a response NXDOMAIN,
	resolver SHOULD stop searching if it encounters a cached NXDOMAIN.		it SHOULD store it in its cache and all names and RRsets at or below
	The response to the triggering query should be NXDOMAIN.		that node SHOULD then be considered to be unreachable. Subsequent
			queries for such names SHOULD elicit an NXDOMAIN response.
	When an iterative caching DNS resolver stores an NXDOMAIN in its		[TODO: currently under discussion, some people find it dangerous.
	cache, all names and RRsets at or below that node SHOULD be		Only if the NXDOMAIN is DNSSEC-validated? Perhaps the resolver could
	considered to be unreachable, and subsequent queries for such names		be configured to not apply this rule to TLDs (or root). See
	SHOULD elicit an NXDOMAIN response. A resolver, depending on its		Section 7.]
	implementation, MAY prune the subtree of positive cache entries at
	that node, or delete all individual cache entries for names below
	that node. [TODO: currently under discussion, some people find it
	dangerous. Only if the NXDOMAIN is DNSSEC-validated? Perhaps the
	resolver could be configured to not "bulk delete" TLDs (or root).
	See Section 6.]
	By implication, a stream of queries foo.example, then		For example, consider two successive queries to a resolver, with a
	bar.foo.example, where foo.example does not exist would normally		non-existing domain 'foo.example': the first is for 'foo.example'
	cause both queries to be forwarded to example's nameservers.		(which results in an NXDOMAIN) and the second for 'bar.foo.example'
	Following this recommended practice of "NXDOMAIN cut", the second		(which also results in an NXDOMAIN). Many resolvers today will
	query and indeed any other query for names at or below foo.example		forward both queries, as noticed in Section 8. However, following
	would not be forwarded.		the rules in this document ("NXDOMAIN cut"), a resolver would cache
			the first NXDOMAIN response, as a sign of non-existence, and then
			immediately return an NXDOMAIN response for the second query, without
			transmitting it to an authoritative server.
			If the first request is for 'bar.foo.example' and the second for
			'baz.foo.example', the first NXDOMAIN response won't tell anything
			about 'baz.foo.example' and therefore the second query will be
			transmitted as it was before "NXDOMAIN cut" (see Appendix A).
	These rules replace the second paragraph of section 5 of [RFC2308].		These rules replace the second paragraph of section 5 of [RFC2308].
	Otherwise, [RFC2308] applies unchanged, and the fact that a subtree		Otherwise, this document does not update any other parts of
	does not exist is not forever: the NXDOMAIN is cached only for the		[RFC2308]. The fact that a subtree does not exist is not forever:
	duration of the "negative TTL" (section 3 of [RFC2308]).		[RFC2308], section 3, already describes the amount of time that an
			NXDOMAIN response may be cached (the "negative TTL").
	If the cached NXDOMAIN response is from a DNSSEC signed zone, then it		If the NXDOMAIN response due to a cached non-existence is from a
	will have accompanying NSEC or NSEC3 records that authenticate the		DNSSEC signed zone, then it will have accompanying NSEC or NSEC3
	non-existence of the name. For a descendant name of the original		records that authenticate the non-existence of the name. For a
	NXDOMAIN name, the same set of NSEC or NSEC3 records proves the non-		descendant name of the original NXDOMAIN name, the same set of NSEC
	existence of the descendant name. The iterative, caching resolver		or NSEC3 records proves the non-existence of the descendant name.
	MUST return these NSEC or NSEC3 records in the response to the		The iterative, caching resolver MUST return these NSEC or NSEC3
	triggering query.		records in the response to the triggering query if the query had the
			DNSSEC OK (DO) bit set.
	Warning: if there is a chain of CNAME (or DNAME), the name which does		Warning: if there is a chain of CNAME (or DNAME), the name which does
	not exist is the last of the chain ([RFC6604]) and not the QNAME.		not exist is the last of the chain ([RFC6604]) and not the QNAME.
	The NXDOMAIN stored in the cache is for the denied name, not always		The NXDOMAIN stored in the cache is for the denied name, not always
	for the QNAME.		for the QNAME.
	3. Benefits		3. Benefits
	The main benefit is a better efficiency of the caches. In the		The main benefit is a better efficiency of the caches. In the
	example above, we send only one query instead of two, the second one		example above, the resolver send only one query instead of two, the
	being answered from the cache.		second one being answered from the cache.
	The correct behavior (in [RFC1034] and made clearer in this document)		The correct behavior (in [RFC1034] and made clearer in this document)
	is specially useful when combined with QNAME minimisation		is specially useful when combined with QNAME minimisation
	[I-D.ietf-dnsop-qname-minimisation] since it will allow a resolver to		[I-D.ietf-dnsop-qname-minimisation] since it will allow a resolver to
	stop searching as soon as an NXDOMAIN is encountered.		stop searching as soon as an NXDOMAIN is encountered.
	NXDOMAIN cut may also help mitigate certain types of random QNAME		NXDOMAIN cut may also help mitigate certain types of random QNAME
	attacks [joost-dnsterror] [balakrichenan-dafa888], where there is a		attacks [joost-dnsterror] [balakrichenan-dafa888], where there is a
	fixed suffix which does not exist. In these attacks against the		fixed suffix which does not exist. In these attacks against the
	authoritative name server, queries are sent to resolvers for a QNAME		authoritative name server, queries are sent to resolvers for a QNAME
	composed of a fixed suffix ("dafa888.wf" in one of the articles		composed of a fixed suffix ("dafa888.wf" in one of the articles
	above), which is typically nonexistent, and a random prefix,		above), which is typically nonexistent, and a random prefix,
	different for each request. A resolver receiving these requests have		different for each request. A resolver receiving these requests have
	to forward them to the authoritative servers. With NXDOMAIN cut, we		to forward them to the authoritative servers. With NXDOMAIN cut, a
	would just have to send to the resolver a query for the fixed suffix,		system administrator would just have to send to the resolver a query
	the resolver would get a NXDOMAIN and then would stop forwarding the		for the fixed suffix, the resolver would get a NXDOMAIN and then
	queries. (It would be better if the SOA record in the NXDOMAIN		would stop forwarding the queries. (It would be better if the SOA
	response were sufficient to find the non-existing domain but it is		record in the NXDOMAIN response were sufficient to find the non-
	not the case, see Appendix A.)		existing domain but it is not the case, see Appendix A.)
	Since the principles set in this document are so great, why are the
	rules of Section 2 SHOULD and not MUST? This is because some
	resolver may have a cache which is NOT organized as a tree (but, for
	instance, as a dictionary) and therefore have a good reason to ignore
	this.
	4. Possible issues		4. Possible issues
	Let's assume the TLD example exists but foobar.example is not		Let's assume the TLD example exists but foobar.example is not
	delegated (so the example's name servers will reply NXDOMAIN for a		delegated (so the example's name servers will reply NXDOMAIN for a
	query about anything.foobar.example). A system administrator decides		query about anything.foobar.example). A system administrator decides
	to name the internal machines of his organization under		to name the internal machines of his organization under
	office.foobar.example and use a trick of his resolver to forward		office.foobar.example and uses a trick of his resolver to forward
	requests about this zone to his local authoritative name servers.		requests about this zone to his local authoritative name servers.
	NXDOMAIN cut would create problems here, since, depending on the		NXDOMAIN cut would create problems here, since, depending on the
	order of requests to the resolver, it may have cached the NXDOMAIN		order of requests to the resolver, it may have cached the non-
	from example and therefore "deleted" everything under. This document		existence from example and therefore "deleted" everything under.
	assumes that such setup is rare and does not need to be supported.		This document assumes that such setup is rare and does not need to be
			supported.
	Another issue that may happen: today, we see broken authoritative		Another issue that may happen: today, we see broken authoritative
	name servers which reply to ENT ([RFC7719], section 6) with NXDOMAIN		name servers which reply to ENT ([RFC7719], section 6) with NXDOMAIN
	instead of the normal NODATA ([RFC7719], section 3).		instead of the normal NODATA ([RFC7719], section 3).
	RFC-EDITOR: REMOVE THE PARAGRAPH BEFORE PUBLICATION. An example		RFC-EDITOR: REMOVE THE PARAGRAPH BEFORE PUBLICATION. An example
	today is mta2._domainkey.cbs.nl (which exists) where querying		today is mta2._domainkey.cbs.nl (which exists) where querying
	_domainkey.cbs.nl yields NXDOMAIN. Another example is www.upenn.edu,		_domainkey.cbs.nl yields NXDOMAIN. Another example is www.upenn.edu,
	redirected to www.upenn.edu-dscg.edgesuite.net while a query for edu-		redirected to www.upenn.edu-dscg.edgesuite.net while a query for edu-
	dscg.edgesuite.net returns NXDOMAIN.		dscg.edgesuite.net returns NXDOMAIN.
	Such name servers are definitely wrong and have always been. Given		Such name servers are definitely wrong and have always been. Their
	the advantages of NXDOMAIN cuts, there is little reason to support		behaviour is incompatible with DNSSEC. Given the advantages of
	this behavior.		NXDOMAIN cuts, there is little reason to support this behavior.
	5. IANA Considerations		5. Implementation considerations
			This section is non-normative, and is composed only of various things
			which may be useful for implementors. A recursive resolver may
			implement its cache in many ways. The most obvious one is a tree
			data structure, because it fits the data model of domain names. But,
			in practice, other implementations are possible, as well as various
			optimisations (such as a tree, augmented by an index of some common
			domain names).
			If a resolver implements its cache as a tree (without any
			optimisation), one way to follow the rules of Section 2 is, when
			receiving the NXDOMAIN, to prune the subtree of positive cache
			entries at that node, or to delete all individual cache entries for
			names below that node. Then, when searching downward in its cache,
			this iterative caching DNS resolver stop searching if it encounters a
			cached non-existence.
			Some resolver may have a cache which is NOT organized as a tree (but,
			for instance, as a dictionary) and therefore have a reason to ignore
			the rules of Section 2. So these rules are a SHOULD and not a MUST.
			6. IANA Considerations
	This document has no actions for IANA.		This document has no actions for IANA.
	6. Security Considerations		7. Security Considerations
	The technique described here may help against a denial-of-service		The technique described here may help against a denial-of-service
	attack named "random qnames" and described in Section 3. Apart from		attack named "random qnames" and described in Section 3. Apart from
	that, it is believed to have no security consequences.		that, it is believed to have no security consequences.
	If a resolver does not validate the answers with DNSSEC, it can of		If a resolver does not validate the answers with DNSSEC, or if the
	course be poisoned with a false NXDOMAIN, thus "deleting" a part of		zone is not signed, the resolver can of course be poisoned with a
	the domain name tree. This denial-of-service attack is already		false NXDOMAIN, thus "deleting" a part of the domain name tree. This
	possible without the rules of this document (but "NXDOMAIN cut" may		denial-of-service attack is already possible without the rules of
	increase its effects). The only solution is to use DNSSEC.		this document (but "NXDOMAIN cut" may increase its effects). The
			only solution is to use DNSSEC.
	7. Implementation status - RFC EDITOR: REMOVE BEFORE PUBLICATION		8. Implementation status - RFC EDITOR: REMOVE BEFORE PUBLICATION
	This section records the status of known implementations of the		This section records the status of known implementations of the
	protocol defined by this specification at the time of posting of this		protocol defined by this specification at the time of posting of this
	Internet-Draft, and is based on a proposal described in [RFC6982].		Internet-Draft, and is based on a proposal described in [RFC6982].
	The description of implementations in this section is intended to		The description of implementations in this section is intended to
	assist the IETF in its decision processes in progressing drafts to		assist the IETF in its decision processes in progressing drafts to
	RFCs. Please note that the listing of any individual implementation		RFCs. Please note that the listing of any individual implementation
	here does not imply endorsement by the IETF. Furthermore, no effort		here does not imply endorsement by the IETF. Furthermore, no effort
	has been spent to verify the information presented here that was		has been spent to verify the information presented here that was
	supplied by IETF contributors. This is not intended as, and must not		supplied by IETF contributors. This is not intended as, and must not
	be construed to be, a catalog of available implementations or their		be construed to be, a catalog of available implementations or their
	features. Readers are advised to note that other implementations may		features. Readers are advised to note that other implementations may
	exist.		exist.
	skipping to change at page 6, line 22 ¶		skipping to change at page 6, line 48 ¶
	features. Readers are advised to note that other implementations may		features. Readers are advised to note that other implementations may
	exist.		exist.
	According to [RFC6982], "this will allow reviewers and working groups		According to [RFC6982], "this will allow reviewers and working groups
	to assign due consideration to documents that have the benefit of		to assign due consideration to documents that have the benefit of
	running code, which may serve as evidence of valuable experimentation		running code, which may serve as evidence of valuable experimentation
	and feedback that have made the implemented protocols more mature.		and feedback that have made the implemented protocols more mature.
	It is up to the individual working groups to use this information as		It is up to the individual working groups to use this information as
	they see fit".		they see fit".
	As of today, practically all existing DNS resolvers are conservative:		As of today, practically all existing DNS resolvers are conservative
	they consider a NXDOMAIN as only significant for the name itself, not		by default: they consider a NXDOMAIN as only significant for the name
	for the names under. Almost all the current recursive servers will		itself, not for the names under. Almost all the current recursive
	send upstream a query for out-of-cache sub.example.com even if their		servers will send upstream a query for out-of-cache sub.example.com
	cache contains an NXDOMAIN for example.com.		even if their cache contains an NXDOMAIN for example.com.
	There are a few exceptions. The Unbound resolver has a configuration		There are a few exceptions. The Unbound resolver has a configuration
	parameter called "harden-below-nxdomain" [2], which if set to "yes"		parameter called "harden-below-nxdomain" [2], which if set to "yes"
	turns on NXDOMAIN cut behavior ("only DNSSEC-secure nxdomains are		turns on NXDOMAIN cut behavior ("only DNSSEC-secure nxdomains are
	used", see Section 6). The PowerDNS recursor has optional partial		used", see Section 7). The PowerDNS recursor has optional partial
	support for NXDOMAIN cut, for the root domain only, with its "root-		support for NXDOMAIN cut, for the root domain only, with its "root-
	nx-trust" setting, described as [3] "If set, an NXDOMAIN from the		nx-trust" setting, described as [3] "If set, an NXDOMAIN from the
	root-servers will serve as a blanket NXDOMAIN for the entire TLD the		root-servers will serve as a blanket NXDOMAIN for the entire TLD the
	query belonged to. The effect of this is far fewer queries to the		query belonged to. The effect of this is far fewer queries to the
	root-servers.".		root-servers.".
	8. Acknowledgments		9. Acknowledgments
	The main idea is in this document is taken from		The main idea is in this document is taken from
	[I-D.vixie-dnsext-resimprove], section 3, "Stopping Downward Cache		[I-D.vixie-dnsext-resimprove], section 3, "Stopping Downward Cache
	Search on NXDOMAIN". Thanks to its authors, Paul Vixie, Rodney		Search on NXDOMAIN". Thanks to its authors, Paul Vixie, Rodney
	Joffe, and Frederico Neves. Additionally Tony Finch, John Levine,		Joffe, and Frederico Neves. Additionally Tony Finch, John Levine,
	Jinmei Tatuya, and Duane Wessels provided valuable feedback and		Jinmei Tatuya, and Duane Wessels provided valuable feedback and
	suggestions.		suggestions.
	9. References		10. References
	9.1. Normative References
			10.1. 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,
	<http://www.rfc-editor.org/info/rfc1034>.		<http://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, <http://www.rfc-editor.org/info/rfc1035>.		November 1987, <http://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/
	DOI 10.17487/RFC2119, March 1997,		RFC2119, March 1997,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
	[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS		[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
	NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,		NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,
	<http://www.rfc-editor.org/info/rfc2308>.		<http://www.rfc-editor.org/info/rfc2308>.
	[RFC6604] Eastlake 3rd, D., "xNAME RCODE and Status Bits		[RFC6604] Eastlake 3rd, D., "xNAME RCODE and Status Bits
	Clarification", RFC 6604, DOI 10.17487/RFC6604, April		Clarification", RFC 6604, DOI 10.17487/RFC6604, April
	2012, <http://www.rfc-editor.org/info/rfc6604>.		2012, <http://www.rfc-editor.org/info/rfc6604>.
	9.2. Informative References		10.2. Informative References
	[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.		[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
	Rose, "Protocol Modifications for the DNS Security		Rose, "Protocol Modifications for the DNS Security
	Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,		Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
	<http://www.rfc-editor.org/info/rfc4035>.		<http://www.rfc-editor.org/info/rfc4035>.
	[RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running		[RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
	Code: The Implementation Status Section", RFC 6982,		Code: The Implementation Status Section", RFC 6982, DOI
	DOI 10.17487/RFC6982, July 2013,		10.17487/RFC6982, July 2013,
	<http://www.rfc-editor.org/info/rfc6982>.		<http://www.rfc-editor.org/info/rfc6982>.
	[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS		[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
	Terminology", RFC 7719, DOI 10.17487/RFC7719, December		Terminology", RFC 7719, DOI 10.17487/RFC7719, December
	2015, <http://www.rfc-editor.org/info/rfc7719>.		2015, <http://www.rfc-editor.org/info/rfc7719>.
	[I-D.vixie-dnsext-resimprove]		[I-D.vixie-dnsext-resimprove]
	Vixie, P., Joffe, R., and F. Neves, "Improvements to DNS		Vixie, P., Joffe, R., and F. Neves, "Improvements to DNS
	Resolvers for Resiliency, Robustness, and Responsiveness",		Resolvers for Resiliency, Robustness, and Responsiveness",
	draft-vixie-dnsext-resimprove-00 (work in progress), June		draft-vixie-dnsext-resimprove-00 (work in progress), June
	2010.		2010.
	[I-D.ietf-dnsop-qname-minimisation]		[I-D.ietf-dnsop-qname-minimisation]
	Bortzmeyer, S., "DNS query name minimisation to improve		Bortzmeyer, S., "DNS query name minimisation to improve
	privacy", draft-ietf-dnsop-qname-minimisation-08 (work in		privacy", draft-ietf-dnsop-qname-minimisation-09 (work in
	progress), November 2015.		progress), January 2016.
	[I-D.fujiwara-dnsop-nsec-aggressiveuse]		[I-D.fujiwara-dnsop-nsec-aggressiveuse]
	Fujiwara, K. and A. Kato, "Aggressive use of NSEC/NSEC3",		Fujiwara, K. and A. Kato, "Aggressive use of NSEC/NSEC3",
	draft-fujiwara-dnsop-nsec-aggressiveuse-02 (work in		draft-fujiwara-dnsop-nsec-aggressiveuse-02 (work in
	progress), October 2015.		progress), October 2015.
	[joost-dnsterror]		[joost-dnsterror]
	Joost, M., "About DNS Attacks and ICMP Destination		Joost, M., "About DNS Attacks and ICMP Destination
	Unreachable Reports", December 2014,		Unreachable Reports", December 2014,
	<http://www.michael-joost.de/dnsterror.html>.		<http://www.michael-joost.de/dnsterror.html>.
	[balakrichenan-dafa888]		[balakrichenan-dafa888]
	Balakrichenan, S., "Disturbance in the DNS - "Random		Balakrichenan, S., "Disturbance in the DNS - "Random
	qnames", the dafa888 DoS attack"", October 2014,		qnames", the dafa888 DoS attack"", October 2014,
	<https://indico.dns-oarc.net/event/20/session/3/		<https://indico.dns-oarc.net/event/20/session/3/
	contribution/37>.		contribution/37>.
	9.3. URIs		10.3. URIs
	[1] https://github.com/bortzmeyer/ietf-dnsop-nxdomain
	[2] https://www.unbound.net/documentation/unbound.conf.html		[1] https://www.unbound.net/documentation/unbound.conf.html
	[3] https://doc.powerdns.com/md/recursor/settings/#root-nx-trust		[2] https://doc.powerdns.com/md/recursor/settings/#root-nx-trust
	Appendix A. Why can't we just use the owner name of the returned SOA?		Appendix A. Why can't we just use the owner name of the returned SOA?
	In this document, we deduce the non-existence of a domain only for		In this document, we deduce the non-existence of a domain only for
	NXDOMAIN answers where the denied name was this exact domain. If a		NXDOMAIN answers where the denied name was this exact domain. If a
	resolver sends a query to the name servers of the TLD example, and		resolver sends a query to the name servers of the TLD example, and
	asks the MX record for www.foobar.example, and receives a NXDOMAIN,		asks the MX record for www.foobar.example, and receives a NXDOMAIN,
	it can only register the fact that www.foobar.example (and everything		it can only register the fact that www.foobar.example (and everything
	underneath) does not exist. Even if the accompanying SOA record is		underneath) does not exist. Even if the accompanying SOA record is
	for example only, one cannot infer that foobar.example is		for example only, one cannot infer that foobar.example is
	skipping to change at page 9, line 34 ¶		skipping to change at page 10, line 4 ¶
	Stephane Bortzmeyer		Stephane Bortzmeyer
	AFNIC		AFNIC
	1, rue Stephenson		1, rue Stephenson
	Montigny-le-Bretonneux 78180		Montigny-le-Bretonneux 78180
	France		France
	Phone: +33 1 39 30 83 46		Phone: +33 1 39 30 83 46
	Email: bortzmeyer+ietf@nic.fr		Email: bortzmeyer+ietf@nic.fr
	URI: http://www.afnic.fr/		URI: http://www.afnic.fr/
	Shumon Huque		Shumon Huque
	Verisign labs		Verisign Labs
	12061 Bluemont Way		12061 Bluemont Way
	Reston 20190		Reston 20190
	USA		USA
	Email: shuque@verisign.com		Email: shuque@verisign.com
	URI: http://www.verisignlabs.com/		URI: http://www.verisignlabs.com/
End of changes. 38 change blocks.
	109 lines changed or deleted		136 lines changed or added
This html diff was produced by rfcdiff 1.44. The latest version is available from http://tools.ietf.org/tools/rfcdiff/