draft-ietf-dnsop-qname-minimisation-01.txt		draft-ietf-dnsop-qname-minimisation-02.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
	Intended status: Experimental February 15, 2015		Intended status: Experimental March 4, 2015
	Expires: August 19, 2015		Expires: September 5, 2015
	DNS query name minimisation to improve privacy		DNS query name minimisation to improve privacy
	draft-ietf-dnsop-qname-minimisation-01		draft-ietf-dnsop-qname-minimisation-02
	Abstract		Abstract
	This document describes one of the techniques that could be used to		This document describes one of the techniques that could be used to
	improve DNS privacy (see [I-D.ietf-dprive-problem-statement]), a		improve DNS privacy (see [I-D.ietf-dprive-problem-statement]), a
	technique called "qname minimisation".		technique called "qname minimisation".
	Discussions of the document should take place on the DNSOP working		REMOVE BEFORE PUBLICATION Discussions of the document should take
	group mailing list [dnsop].		place on the DNSOP working group mailing list [dnsop].
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	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 August 19, 2015.		This Internet-Draft will expire on September 5, 2015.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2015 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
	skipping to change at page 2, line 13		skipping to change at page 2, line 13
	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
	2. Qname minimisation . . . . . . . . . . . . . . . . . . . . . 2		2. Qname minimisation . . . . . . . . . . . . . . . . . . . . . 2
	3. Operational considerations . . . . . . . . . . . . . . . . . 3		3. Operational considerations . . . . . . . . . . . . . . . . . 3
	4. Performance implications . . . . . . . . . . . . . . . . . . 5		4. Performance implications . . . . . . . . . . . . . . . . . . 5
	5. Security considerations . . . . . . . . . . . . . . . . . . . 5		5. Security considerations . . . . . . . . . . . . . . . . . . . 6
	6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6		6. Implementation status - REMOVE BEFORE PUBLICATION . . . . . . 6
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6		7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
	7.1. Normative References . . . . . . . . . . . . . . . . . . 6		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	7.2. Informative References . . . . . . . . . . . . . . . . . 6		8.1. Normative References . . . . . . . . . . . . . . . . . . 7
	7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 7		8.2. Informative References . . . . . . . . . . . . . . . . . 7
	Appendix A. An algorithm to find the zone cut . . . . . . . . . 7		8.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8		Appendix A. An algorithm to find the zone cut . . . . . . . . . 8
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
	1. Introduction and background		1. Introduction and background
	The problem statement is exposed in		The problem statement is exposed in
	[I-D.ietf-dprive-problem-statement] TODO: add a reference to the		[I-D.ietf-dprive-problem-statement] TODO: add a reference to the
	specific section when ietf-dprive-problem-statement will be published		specific section when ietf-dprive-problem-statement will be published
	as RFC. The terminology ("qname", "resolver", etc) is also defined		as RFC. The terminology ("qname", "resolver", etc) is also defined
	in this companion document. This specific solution is not intended		in this companion document. This specific solution is not intended
	to fully solve the DNS privacy problem; instead, it should be viewed		to fully solve the DNS privacy problem; instead, it should be viewed
	as one tool amongst many.		as one tool amongst many.
	It follows the principle explained in section 6.1 of [RFC6973]: the		It follows the principle explained in section 6.1 of [RFC6973]: the
	less data you send out, the less privacy problems you'll get.		less data you send out, the fewer privacy problems you'll get.
	2. Qname minimisation		2. Qname minimisation
	The idea is to minimise the amount of data sent from the DNS		The idea is to minimise the amount of data sent from the DNS
	resolver. When a resolver receives the query "What is the AAAA		resolver. Under current practice, when a resolver receives the query
	record for www.example.com?", it sends to the root (assuming a cold		"What is the AAAA record for www.example.com?", it sends to the root
	resolver, whose cache is empty) the very same question. Sending		(assuming a cold resolver, whose cache is empty) the very same
	"What are the NS records for .com?" would be sufficient (since it		question. Sending "What are the NS records for .com?" would be
	will be the answer from the root anyway). To do so would be		sufficient (since it will be the answer from the root anyway). This
	compatible with the current DNS system and therefore could be easily		is compatible with the current DNS system and therefore can easily be
	deployable, since it is an unilateral change to the resolvers, it		deployed; since it is a unilateral change to the resolver, it does
	does not change the protocol. Because of that, resolver implementers		not change the protocol. Because of that, resolver implementers may
	may do qname minmisation in slightly different ways.		do qname minmisation in slightly different ways.
	If "minimisation" is too long, you can write it "m10n".
	To do such minimisation, the resolver needs to know the zone cut		To do such minimisation, the resolver needs to know the zone cut
	[RFC2181]. Zone cuts do not necessarily exist at every label		[RFC2181]. Zone cuts do not necessarily exist at every label
	boundary. If we take the name www.foo.bar.example, it is possible		boundary. If we take the name www.foo.bar.example, it is possible
	that there is a zone cut between "foo" and "bar" but not between		that there is a zone cut between "foo" and "bar" but not between
	"bar" and "example". So, assuming the resolver already knows the		"bar" and "example". So, assuming the resolver already knows the
	name servers of .example, when it receives the query "What is the		name servers of .example, when it receives the query "What is the
	AAAA record of www.foo.bar.example", it does not always know if the		AAAA record of www.foo.bar.example", it does not always know whether
	request should be sent to the name servers of bar.example or to those		the request should be sent to the name servers of bar.example or to
	of example. [RFC2181] suggests a method to find the zone cut		those of example. [RFC2181] suggests a method to find the zone cut
	(section 6), so resolvers may try it.		(section 6), so resolvers may try it.
	Note that DNSSEC-validating resolvers already have access to this		Note that DNSSEC-validating resolvers already have access to this
	information, since they have to find the zone cut (the DNSKEY record		information, since they have to find the zone cut (the DNSKEY record
	set is just below, the DS record set just above).		set is just below, the DS record set just above).
	Minimising the amount of data sent also, in part, addresses the case
	of a wire sniffer as well the case of privacy invasion by the
	servers.
	One should note that the behaviour suggested here (minimising the		One should note that the behaviour suggested here (minimising the
	amount of data sent in qnames) is NOT forbidden by the [RFC1034]		amount of data sent in qnames from the resolver) is NOT forbidden by
	(section 5.3.3) or [RFC1035] (section 7.2). Sending the full qname		the [RFC1034] (section 5.3.3) or [RFC1035] (section 7.2). Sending
	to the authoritative name server is a tradition, not a protocol		the full qname to the authoritative name server is a tradition, not a
	requirment. This tradition comes[mockapetris-history] from a desire		protocol requirement. This tradition comes[mockapetris-history] from
	to optimize the number of requests, when the same name server is		a desire to optimize the number of requests, when the same name
	authoritative for many zones in a given name (something which was		server is authoritative for many zones in a given name (something
	more common in the old days, where the same name servers served .com		which was more common in the old days, where the same name servers
	and the root) or when the same name server is both recursive and		served .com and the root) or when the same name server is both
	authoritative (something which is strongly discouraged now).		recursive and authoritative (something which is strongly discouraged
	Whatever the merits of this choice at this time, the DNS is quite		now). Whatever the merits of this choice at this time, the DNS is
	different now.		quite different now.
			It may be noticed that many documents explaining the DNS and intended
			for a wide audience, incorrectly describe the resolution process as
			using qname minimisation, for instance by showing a request going to
			the root, with just the TLD in the query. As a result, these
			documents may confuse the privacy analysis of the users who see them.
	As mentioned before, there are several ways to implement qname		As mentioned before, there are several ways to implement qname
	minimisation. Two main strategies are the aggressive one and the		minimisation. Two main strategies are the aggressive one and the
	lazy one. In the aggressive one, the resolver only sends NS queries		lazy one. In the aggressive one, the resolver only sends NS queries
	as long as it does not know the zone cuts. This is the safest, from		as long as it does not know the zone cuts. This is the safest, from
	a privacy point of view. The lazy way "piggybacks" on the		a privacy point of view. The lazy way "piggybacks" on the
	traditional resolution code. It sends traditional full qnames and		traditional resolution code. It sends traditional full qnames and
	learn the zone cuts from the referrals received, then switching to NS		learns the zone cuts from the referrals received, then switches to NS
	queries. This leaks more data but probably requires less changes in		queries asking only for the minimum domain name. This leaks more
	the existing resolver codebase.		data but probably requires fewer changes in the existing resolver
			codebase.
	3. Operational considerations		3. Operational considerations
	The administrators of the forwarders, and of the authoritative name		The administrators of the forwarders, and of the authoritative name
	servers, will get less data, which will reduce the utility of the		servers, will get less data, which will reduce the utility of the
	statistics they can produce (such as the percentage of the various		statistics they can produce (such as the percentage of the various
	qtypes). On the other hand, it may decrease their legal		qtypes). On the other hand, it may decrease their legal
	responsibility.		responsibility in some jurisdictions. (TODO: do we keep any mention
			of legal issues? We're not lawyers.)
	Some broken name servers do not react properly to qtype=NS requests.		Some broken name servers do not react properly to qtype=NS requests.
	For instance, some authoritative name servers embedded in load		For instance, some authoritative name servers embedded in load
	balancers reply properly to A queries but send REFUSED to NS queries.		balancers reply properly to A queries but send REFUSED to NS queries.
	REMOVE THIS SENTENCE BEFORE PUBLICATION: As an example of today, look		REMOVE THIS SENTENCE BEFORE PUBLICATION: As an example of today, look
	at www.ratp.fr (not ratp.fr). This behaviour is a gross protocol		at www.ratp.fr (not ratp.fr). This behaviour is a gross protocol
	violation, and there is no need to stop improving the DNS because of		violation, and there is no need to stop improving the DNS because of
	such brokenness. However, qname minimisation may still work with		such brokenness. However, qname minimisation may still work with
	such domains since they are only leaf domains (no need to send them		such domains since they are only leaf domains (no need to send them
	NS requests). Such setup breaks more than just qname minimisation.		NS requests). Such setup breaks more than just qname minimisation.
	skipping to change at page 4, line 38		skipping to change at page 4, line 40
	See also section 3 of [I-D.vixie-dnsext-resimprove] for the other bad		See also section 3 of [I-D.vixie-dnsext-resimprove] for the other bad
	consequences of this brokenness.		consequences of this brokenness.
	Another way to deal with such broken name servers would be to try		Another way to deal with such broken name servers would be to try
	with A requests (A being chosen because it is the most common and		with A requests (A being chosen because it is the most common and
	hence a qtype which will be always accepted, while a qtype NS may		hence a qtype which will be always accepted, while a qtype NS may
	ruffle the feathers of some middleboxes). Instead of querying name		ruffle the feathers of some middleboxes). Instead of querying name
	servers with a query "NS example.com", we could use "A _.example.com"		servers with a query "NS example.com", we could use "A _.example.com"
	and see if we get a referral.		and see if we get a referral.
	Other strange and illegal practices may pose a problem: for instance,		Other strange and illegal practices may pose a problem: there is a
	there is a common DNS anti-pattern used by low-end web hosters that		common DNS anti-pattern used by low-end web hosters that also do DNS
	also do DNS hosting that exploits the fact that the DNS protocol		hosting that exploits the fact that the DNS protocol (pre-DNSSEC)
	(pre-DNSSEC) allows certain serious misconfigurations, such as parent		allows certain serious misconfigurations, such as parent and child
	and child zones disagreeing on the location of a zone cut.		zones disagreeing on the location of a zone cut. Basically, they
	Basically, they have a single zone with wildcards like:		have a single zone with wildcards for each TLD like:
	*.example. 60 IN A 192.0.2.6		*.example. 60 IN A 192.0.2.6
	(It is not known why they don't just wildcard all of "*." and be done		(It is not known why they don't just wildcard all of "*." and be done
	with it.)		with it.)
			This lets them turn up many web hosting customers without having to
	This lets them turn up tons of web hosting customers without having		configure thousands of individual zones on their nameservers. They
	to configure thousands of individual zones on their nameservers.		just tell the prospective customer to point their NS records at the
	They just tell the prospective customer to point their NS records at		hoster's nameservers, and the Web hoster doesn't have to provision
	their nameservers, and the Web hoster doesn't have to provision		anything in order to make the customer's domain resolve. NS queries
	anything in order to make the customer's domain resolve.		to the hoster will therefore do not give the right result, which may
			endanger qname minimisation (it will be a problem for DNSSEC, too).
	Qname minimisation can decrease performance in some cases, for		Qname minimisation can decrease performance in some cases, for
	instance for a deep domain name (like		instance for a deep domain name (like
	www.host.group.department.example.com where		www.host.group.department.example.com where
	host.group.department.example.com is hosted on example.com's name		host.group.department.example.com is hosted on example.com's name
	servers). For such a name, a cold resolver will, depending how qname		servers). For such a name, a cold resolver will, depending how qname
	minimisation is implemented, send more queries. Once warm, there		minimisation is implemented, send more queries. Once the cache is
	will be no difference with a traditional resolver. A possible		warm, there will be no difference with a traditional resolver. A
	solution is to always use the traditional algorithm when the cache is		possible solution is to always use the traditional algorithm when the
	cold and then to move to qname minimisation. This will decrease the		cache is cold and then to move to qname minimisation. This will
	privacy a bit but will guarantee no degradation of performance.		decrease the privacy a bit but will guarantee no degradation of
			performance.
	Another useful optimisation may be, in the spirit of the HAMMER idea		Another useful optimisation may be, in the spirit of the HAMMER idea
	[I-D.wkumari-dnsop-hammer] to probe in advance for the introduction		[I-D.wkumari-dnsop-hammer] to probe in advance for the introduction
	of zone cuts where none previously existed (i.e. confirm their		of zone cuts where none previously existed (i.e. confirm their
	continued absence, or discover them.)		continued absence, or discover them.)
	4. Performance implications		4. Performance implications
	The main goal of qname minimisation is to improve privacy by sending		The main goal of qname minimisation is to improve privacy by sending
	less data. However, it may have other advantages. For instance, if		less data. However, it may have other advantages. For instance, if
	a root name server receives a query from some resolver for A.CORP		a root name server receives a query from some resolver for A.CORP
	followed by B.CORP followed by C.CORP, the result will be three		followed by B.CORP followed by C.CORP, the result will be three
	NXDOMAINs, since .CORP does not exist in the root zone. Under query		NXDOMAINs, since .CORP does not exist in the root zone. Under query
	name minimisation, the root name servers would hear only one question		name minimisation, the root name servers would hear only one question
	(for .CORP itself) to which they could answer NXDOMAIN, thus opening		(for .CORP itself) to which they could answer NXDOMAIN, thus opening
	up a negative caching opportunity in which the full resolver could		up a negative caching opportunity in which the full resolver could
	know a priori that neither B.CORP or C.CORP could exist. Thus in		know a priori that neither B.CORP or C.CORP could exist. Thus in
	this common case the total number of upstream queries under qname		this common case the total number of upstream queries under qname
	minimisation would be counter-intuitively less than the number of		minimisation would be counter-intuitively inferior to the number of
	queries under the traditional iteration (as described in the DNS		queries under the traditional iteration (as described in the DNS
	standard).		standard).
	Qname minimisation may also improve look-up performance for TLD		Qname minimisation may also improve look-up performance for TLD
	operators. For a typical TLD, delegation-only, and with delegations		operators. For a typical TLD, delegation-only, and with delegations
	just under the TLD, a 2-label QNAME query is optimal for finding the		just under the TLD, a 2-label QNAME query is optimal for finding the
	delegation owner name.		delegation owner name.
	5. Security considerations		5. Security considerations
			Qname minimisation's benefits are clear in the case where you want to
			decrease exposure to the authoritative name server. But minimising
			the amount of data sent also, in part, addresses the case of a wire
			sniffer as well the case of privacy invasion by the servers.
			(Encryption is of course a better defense against wire sniffers but,
			unlike qname minimisation, it changes the protocol and cannot be
			deployed unilaterally.)
			Qname minimisation offers zero protection against the recursive
			resolver, which still sees the full request coming from the stub
			resolver.
			At this stage, this document does not recommend one of the two qname
			minimisation approaches (aggressive or lazy) against the other.
	No security consequence (besides privacy improvment) is known at this		No security consequence (besides privacy improvment) is known at this
	time.		time.
	6. Acknowledgments		6. Implementation status - REMOVE BEFORE PUBLICATION
			This section records the status of known implementations of the
			protocol defined by this specification at the time of posting of this
			Internet-Draft, and is based on a proposal described in [RFC6982].
			The description of implementations in this section is intended to
			assist the IETF in its decision processes in progressing drafts to
			RFCs. Please note that the listing of any individual implementation
			here does not imply endorsement by the IETF. Furthermore, no effort
			has been spent to verify the information presented here that was
			supplied by IETF contributors. This is not intended as, and must not
			be construed to be, a catalog of available implementations or their
			features. Readers are advised to note that other implementations may
			exist.
			According to [RFC6982], "this will allow reviewers and working groups
			to assign due consideration to documents that have the benefit of
			running code, which may serve as evidence of valuable experimentation
			and feedback that have made the implemented protocols more mature.
			It is up to the individual working groups to use this information as
			they see fit".
			As of today, no production resolver implements qname minimisation.
			For Unbound, see ticket 648 [1].
			The algorithm to find the zone cuts described in Appendix A is
			implemented with qname minimisation in the sample code zonecut.go
			[2]. It is also implemented, for a much longer time, in an option of
			dig, "dig +trace", but without qname minimisation.
			7. Acknowledgments
	Thanks to Olaf Kolkman for the original idea although the concept is		Thanks to Olaf Kolkman for the original idea although the concept is
	probably much older [1]. Thanks to Mark Andrews and Francis Dupont		probably much older [3]. Thanks to Mark Andrews and Francis Dupont
	for the interesting discussions. Thanks to Brian Dickson, Warren		for the interesting discussions. Thanks to Brian Dickson, Warren
	Kumari and David Conrad for remarks and suggestions. Thanks to		Kumari, Evan Hunt and David Conrad for remarks and suggestions.
	Mohsen Souissi for proofreading. Thanks to Tony Finch for the zone		Thanks to Mohsen Souissi for proofreading. Thanks to Tony Finch for
	cut algorithm in Appendix A. Thanks to Paul Vixie for pointing out		the zone cut algorithm in Appendix A. Thanks to Paul Vixie for
	that there are practical advantages (besides privacy) to qname m10n.		pointing out that there are practical advantages (besides privacy) to
	Thanks to Phillip Hallam-Baker for the fallback on A queries, to deal		qname minimisation. Thanks to Phillip Hallam-Baker for the fallback
	with broken servers. Thanks to Robert Edmonds for an interesting		on A queries, to deal with broken servers. Thanks to Robert Edmonds
	anti-pattern.		for an interesting anti-pattern.
	7. References		8. References
	7.1. Normative References		8.1. Normative References
	[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",		[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
	STD 13, RFC 1034, November 1987.		STD 13, RFC 1034, November 1987.
	[RFC1035] Mockapetris, P., "Domain names - implementation and		[RFC1035] Mockapetris, P., "Domain names - implementation and
	specification", STD 13, RFC 1035, November 1987.		specification", STD 13, RFC 1035, November 1987.
	[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,		[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
	Morris, J., Hansen, M., and R. Smith, "Privacy		Morris, J., Hansen, M., and R. Smith, "Privacy
	Considerations for Internet Protocols", RFC 6973, July		Considerations for Internet Protocols", RFC 6973, July
	2013.		2013.
	[I-D.ietf-dprive-problem-statement]		[I-D.ietf-dprive-problem-statement]
	Bortzmeyer, S., "DNS privacy considerations", draft-ietf-		Bortzmeyer, S., "DNS privacy considerations", draft-ietf-
	dprive-problem-statement-01 (work in progress), January		dprive-problem-statement-01 (work in progress), January
	2015.		2015.
	7.2. Informative References		8.2. Informative References
	[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS		[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
	Specification", RFC 2181, July 1997.		Specification", RFC 2181, July 1997.
			[RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
			Code: The Implementation Status Section", RFC 6982, July
			2013.
	[I-D.wkumari-dnsop-hammer]		[I-D.wkumari-dnsop-hammer]
	Kumari, W., Arends, R., Woolf, S., and D. Migault, "Highly		Kumari, W., Arends, R., Woolf, S., and D. Migault, "Highly
	Automated Method for Maintaining Expiring Records", draft-		Automated Method for Maintaining Expiring Records", draft-
	wkumari-dnsop-hammer-01 (work in progress), July 2014.		wkumari-dnsop-hammer-01 (work in progress), July 2014.
	[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.
	[dnsop] IETF, , "The DNSOP working group of IETF", March 2014,		[dnsop] IETF, , "The DNSOP working group of IETF", March 2014,
	<https://datatracker.ietf.org/wg/dnsop/charter/>.		<https://datatracker.ietf.org/wg/dnsop/charter/>.
	[mockapetris-history]		[mockapetris-history]
	Mockapetris, P., "Private discussion", January 2015.		Mockapetris, P., "Private discussion", January 2015.
	7.3. URIs		[kaliski-minimum]
			Kaliski, B., "Minimum Disclosure: What Information Does a
			Name Server Need to Do Its Job?", March 2015,
			<http://blogs.verisigninc.com/blog/entry/
			minimum_disclosure_what_information_does>.
	[1] https://lists.dns-oarc.net/pipermail/dns-		8.3. URIs
			[1] https://www.nlnetlabs.nl/bugs-script/show_bug.cgi?id=648
			[2] https://github.com/bortzmeyer/my-IETF-work/blob/master/draft-
			ietf-dnsop-qname-minimisation/zonecut.go
			[3] https://lists.dns-oarc.net/pipermail/dns-
	operations/2010-February/005003.html		operations/2010-February/005003.html
	Appendix A. An algorithm to find the zone cut		Appendix A. An algorithm to find the zone cut
	Although a validating resolver already has the logic to find the zone		Although a validating resolver already has the logic to find the zone
	cut, other resolvers may be interested by this algorithm to follow in		cut, other resolvers may be interested by this algorithm to follow in
	order to locate this cut:		order to locate this cut:
	(0) If the query can be answered from the cache, do so, otherwise		(0) If the query can be answered from the cache, do so, otherwise
	iterate as follows:		iterate as follows:
End of changes. 26 change blocks.
	80 lines changed or deleted		146 lines changed or added
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