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	<rfc ipr="trust200902" category="bcp" docName="draft-ietf-dnsop-no-response-issu		<rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902"
	e-23">		submissionType="IETF" category="bcp" consensus="true"
			docName="draft-ietf-dnsop-no-response-issue-23" number="8906"
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			<!-- xml2rfc v2v3 conversion 2.44.0 -->
	<front>		<front>
	<title abbrev="Failure To Communicate">		<title abbrev="Failure to Communicate">
	A Common Operational Problem in DNS Servers - Failure To Communicate		A Common Operational Problem in DNS Servers: Failure to Communicate
	</title>		</title>
			<seriesInfo name="RFC" value="8906"/>
			<seriesInfo name="BCP" value="231"/>
	<author initials="M." surname="Andrews" fullname="M. Andrews">		<author initials="M." surname="Andrews" fullname="M. Andrews">
	<organization abbrev="ISC">Internet Systems Consortium</organization>		<organization abbrev="ISC">Internet Systems Consortium</organization>
	<address>		<address>
	<postal>		<postal>
	<street>PO Box 360</street>		<street>PO Box 360</street>
	<city>Newmarket</city>		<city>Newmarket</city>
	<region>NH</region>		<region>NH</region>
	<code>03857</code>		<code>03857</code>
	<country>US</country>		<country>United States of America</country>
	</postal>		</postal>
	<email>marka@isc.org</email>		<email>marka@isc.org</email>
	</address>		</address>
	</author>		</author>
	<author initials="R." surname="Bellis" fullname="Ray Bellis">		<author initials="R." surname="Bellis" fullname="Ray Bellis">
	<organization abbrev="ISC">Internet Systems Consortium</organization>		<organization abbrev="ISC">Internet Systems Consortium</organization>
	<address>		<address>
	<postal>		<postal>
	<street>PO Box 360</street>		<street>PO Box 360</street>
	<city>Newmarket</city>		<city>Newmarket</city>
	<region>NH</region>		<region>NH</region>
	<code>03857</code>		<code>03857</code>
	<country>US</country>		<country>United States of America</country>
	</postal>		</postal>
	<email>ray@isc.org</email>		<email>ray@isc.org</email>
	</address>		</address>
	</author>		</author>
	<date/>		<date year="2020" month="September"/>
	<abstract>		<abstract>
	<t>		<t>
	The DNS is a query / response protocol. Failing to respond		The DNS is a query/response protocol. Failing to respond
	to queries, or responding incorrectly, causes both immediate		to queries, or responding incorrectly, causes both immediate
	operational problems and long term problems with protocol		operational problems and long-term problems with protocol
	development.		development.
	</t>		</t>
	<t>		<t>
	This document identifies a number of common kinds of queries		This document identifies a number of common kinds of queries
	to which some servers either fail to respond or else respond		to which some servers either fail to respond or respond
	incorrectly. This document also suggests procedures for		incorrectly. This document also suggests procedures for
	zone operators to apply to identify and remediate the problem.		zone operators to apply to identify and remediate the problem.
	</t>		</t>
	<t>		<t>
	The document does not look at the DNS data itself, just the		The document does not look at the DNS data itself, just the
	structure of the responses.		structure of the responses.
	</t>		</t>
	</abstract>		</abstract>
	</front>		</front>
	<middle>		<middle>
	<section anchor="intro" title="Introduction">		<section anchor="intro" numbered="true" toc="default">
	<t>		<name>Introduction</name>
	The DNS <xref target="RFC1034"/>, <xref target="RFC1035"/>		<t>The DNS <xref target="RFC1034" format="default"/> <xref
	is a query / response protocol. Failing to respond to		target="RFC1035" format="default"/> is a query/response protocol.
	queries, or responding incorrectly, causes both immediate		Failing to respond to queries or responding incorrectly causes both
	operational problems and long term problems with protocol		immediate operational problems and long-term problems with protocol
	development.		development.</t>
	</t>
	<t>		<t>
	Failure to respond to a query is indistinguishable from		Failure to respond to a query is indistinguishable from
	packet loss without doing an analysis of query-response		packet loss without doing an analysis of query-response
	patterns. Additionally failure to respond results in		patterns. Additionally, failure to respond results in
	unnecessary queries being made by DNS clients, and		unnecessary queries being made by DNS clients and
	introduces delays to the resolution process.		introduces delays to the resolution process.
	</t>		</t>
	<t>		<t>
	Due to the inability to distinguish between packet loss and		Due to the inability to distinguish between packet loss and
	nameservers or middle boxes dropping EDNS <xref target="RFC6891"/>		nameservers or middleboxes dropping Extension Mechanisms for DNS
			(EDNS) <xref target="RFC6891" format="default"/>
	queries, packet loss is sometimes misclassified as lack of EDNS		queries, packet loss is sometimes misclassified as lack of EDNS
	support which can lead to DNSSEC validation failures.		support, which can lead to DNSSEC validation failures.
	</t>		</t>
	<t>		<t>
	The existence of servers which fail to respond to queries		The existence of servers that fail to respond to queries
	results in developers being hesitant to deploy new standards.		results in developers being hesitant to deploy new standards.
	Such servers need to be identified and remediated.		Such servers need to be identified and remediated.
	</t>		</t>
	<t>		<t>
	The DNS has response codes that cover almost any conceivable		The DNS has response codes that cover almost any conceivable
	query response. A nameserver should be able to respond to		query response. A nameserver should be able to respond to
	any conceivable query using them. There should be no need		any conceivable query using them. There should be no need
	to drop queries because a nameserver does not understand		to drop queries because a nameserver does not understand
	them.		them.
	</t>		</t>
	<t>		<t>
	Unless a nameserver is under attack, it should respond to		Unless a nameserver is under attack, it should respond to
	all DNS requests directed to it. When a nameserver is under		all DNS requests directed to it. When a nameserver is under
	attack it may wish to drop packets. A common attack is to		attack, it may wish to drop packets. A common attack is to
	use a nameserver as an amplifier by sending spoofed packets.		use a nameserver as an amplifier by sending spoofed packets.
	This is done because response packets are bigger than the		This is done because response packets are bigger than the
	queries and large amplification factors are available especially		queries and large amplification factors are available, especially
	if EDNS is supported. Limiting the rate of responses is		if EDNS is supported. Limiting the rate of responses is
	reasonable when this is occurring and the client should		reasonable when this is occurring, and the client should
	retry. This however only works if legitimate clients are		retry. However, this only works if legitimate clients are
	not being forced to guess whether EDNS queries are accepted		not being forced to guess whether or not EDNS queries are accepted. As
	or not. As long as there are still a pool of servers that don't		long as there is still a pool of servers that don't
	respond to EDNS requests, clients have no way to know if		respond to EDNS requests, clients have no way to know if
	the lack of response is due to packet loss, or EDNS packets		the lack of response is due to packet loss, EDNS packets
	not being supported, or rate limiting due to the server being		not being supported, or rate limiting due to the server being
	under attack. Misclassification of server behaviour is		under attack. Misclassification of server behaviour is
	unavoidable when rate limiting is used until the population		unavoidable when rate limiting is used until the population
	of servers which fail to respond to well-formed queries		of servers that fail to respond to well-formed queries
	drops to near zero.		drops to near zero.
	</t>		</t>
	<t>		<t>
	Nameservers should respond to queries even if the queried		Nameservers should respond to queries even if the queried
	name is not for any name the server is configured to answer		name is not for any name the server is configured to answer
	for. Misconfigured nameservers are a common occurrence in the		for. Misconfigured nameservers are a common occurrence in the
	DNS and receiving queries for zones that the server is not		DNS, and receiving queries for zones that the server is not
	configured for is not necessarily an indication that the		configured for is not necessarily an indication that the
	server is under attack. Parent zone operators are advised		server is under attack. Parent zone operators are advised
	to regularly check that the delegating NS records are		to regularly check that the delegating NS records are
	consistent with those of the delegated zone and to correct		consistent with those of the delegated zone and to correct
	them when they are not <xref target="RFC1034"/>, Section 4.4.2,		them when they are not (<xref target="RFC1034" sectionFormat="of" sectio
	Paragraph 3. Doing this regularly should reduce the instances		n="4.2.2"/>,
			Paragraph 3).
			Doing this regularly should reduce the instances
	of broken delegations.		of broken delegations.
	</t>		</t>
	<t>		<t>
	This document does not try to identify all possible errors		This document does not try to identify all possible errors
	nor does it supply an exhaustive list of tests.		nor does it supply an exhaustive list of tests.
	</t>		</t>
	</section>		</section>
	<section anchor="consequences" title="Consequences">		<section anchor="consequences" numbered="true" toc="default">
			<name>Consequences</name>
	<t>		<t>
	Failure to follow the relevant DNS RFCs has multiple adverse		Failure to follow the guidance in relevant DNS RFCs has multiple adverse
	consequences. Some are caused directly by the non-compliant		consequences. Some are caused directly by the non-compliant
	behaviour and others as a result of work-arounds forced on		behaviour and others as a result of workarounds forced on
	recursive servers. Addressing known issues now will reduce		recursive servers. Addressing known issues now will reduce
	future interoperability issues as the DNS protocol continues		future interoperability issues as the DNS protocol continues
	to evolve and clients make use of newly-introduced DNS		to evolve and clients make use of newly introduced DNS
	features. In particular the base DNS specification		features. In particular, the base DNS specification
	<xref target="RFC1034"/>, <xref target="RFC1035"/> and the		<xref target="RFC1034" format="default"/> <xref target="RFC1035" format=
	EDNS specification <xref target="RFC6891"/>, when implemented,		"default"/> and the
			EDNS specification <xref target="RFC6891" format="default"/>, when imple
			mented,
	need to be followed.		need to be followed.
	</t>		</t>
	<t>		<t>
	Some examples of known consequences include:		Some examples of known consequences include the following:
	<list style="symbols">		</t>
	<t>		<ul spacing="normal">
			<li>
	The AD (Authenticated Data) bit in a response		The AD (Authenticated Data) bit in a response
	cannot be trusted to mean anything as some servers		cannot be trusted to mean anything, as some servers
	incorrectly copy the flag bit from the request to the		incorrectly copy the flag bit from the request to the
	response <xref target="RFC1035"/>, <xref target="RFC4035"/>.		response <xref target="RFC1035" format="default"/> <xref
			target="RFC4035" format="default"/>.
	The use of the AD bit in requests is defined in		The use of the AD bit in requests is defined in
	<xref target="RFC6840"/>.		<xref target="RFC6840" format="default"/>.
	</t>		</li>
	<t>		<li>
	Widespread non-response to EDNS queries has led to		Widespread non-response to EDNS queries has led to
	recursive servers having to assume that EDNS is not		recursive servers having to assume that EDNS is not
	supported and that fallback to plain DNS is required,		supported and that fallback to plain DNS is required,
	potentially causing DNSSEC validation failures.		potentially causing DNSSEC validation failures.
	</t>		</li>
	<t>		<li>
	Widespread non-response to EDNS options requires		Widespread non-response to EDNS options requires
	recursive servers to decide whether to probe		recursive servers to decide whether to probe
	to see if it is the specific EDNS option or the use of		to see if it is the specific EDNS option or the use of
	EDNS in general that is causing the non response. In		EDNS in general that is causing the non-response. In
	the limited amount of time required to resolve a query		the limited amount of time required to resolve a query
	before the client times out this is not possible.		before the client times out, this is not possible.
	</t>		</li>
	<t>		<li>
	Incorrectly returning FORMERR to an EDNS option being		Incorrectly returning FORMERR to an EDNS option being
	present leads to the recursive server not being able		present leads to the recursive server not being able
	to determine if the server is just broken in the handling		to determine if the server is just broken in the handling
	of the EDNS option or doesn't support EDNS at all.		of the EDNS option or if it doesn't support EDNS at all.
	</t>		</li>
	<t>		<li>
	Mishandling of unknown query types has contributed		Mishandling of unknown query types has contributed
	to the abandonment of the transition of the SPF type.		to the abandonment of the transition of the SPF type.
	</t>		</li>
	<t>		<li>
	Mishandling of unknown query types has slowed up the		Mishandling of unknown query types has slowed up the
	development of DANE and resulted in additional rules		development of DNS-Based Authentication of Named Entities (DANE)
			and resulted in additional rules
	being specified to reduce the probability of interacting		being specified to reduce the probability of interacting
	with a broken server when making TLSA queries.		with a broken server when making TLSA queries.
	</t>		</li>
	</list>		</ul>
	</t>
	<t>		<t>
	The consequences of servers not following the RFCs will		The consequences of servers not following the RFCs will
	only grow if measures are not put in place to remove non		only grow if measures are not put in place to remove non-compliant
	compliant servers from the ecosystem. Working around issues		servers from the ecosystem. Working around issues
	due to non-compliance with RFCs is not sustainable.		due to non-compliance with RFCs is not sustainable.
	</t>		</t>
	<t>		<t>
	Most (if not all) of these consequences could have been		Most (if not all) of these consequences could have been
	avoided if action had been taken to remove non-compliant		avoided if action had been taken to remove non-compliant
	servers as soon as people were aware of them, i.e. to actively		servers as soon as people were aware of them, i.e., to actively
	seek out broken implementations and servers and inform their		seek out broken implementations and servers and inform their
	developers and operators that they need to fix their servers.		developers and operators that they need to fix their servers.
	</t>		</t>
	</section>		</section>
	<section anchor="query-kinds" title="Common kinds of queries that result in		<section anchor="query-kinds" numbered="true" toc="default">
	no or bad responses.">		<name>Common Kinds of Queries That Result in No or Bad Responses</name>
	<t>		<t>
	This section is broken down into Basic DNS requests and EDNS requests.		This section is broken down into Basic DNS requests and EDNS requests.
	</t>		</t>
	<section title="Basic DNS Queries">		<section numbered="true" toc="default">
	<section anchor="existence" title="Zone Existence">		<name>Basic DNS Queries</name>
			<section anchor="existence" numbered="true" toc="default">
			<name>Zone Existence</name>
	<t>		<t>
	If a zone is delegated to a server, that server should		If a zone is delegated to a server, that server should
	respond to an SOA query for that zone with an SOA record.		respond to a SOA query for that zone with an SOA record.
	Failing to respond at all is always incorrect, regardless		Failing to respond at all is always incorrect, regardless
	of the configuration of the server. Responding with		of the configuration of the server. Responding with
	anything other than an SOA record in the Answer section		anything other than an SOA record in the answer section
	indicates a bad delegation.		indicates a bad delegation.
	</t>		</t>
	</section>		</section>
	<section anchor="unknown" title="Unknown / Unsupported Type Queries">		<section anchor="unknown" numbered="true" toc="default">
			<name>Unknown/Unsupported Type Queries</name>
	<t>		<t>
	Some servers fail to respond to unknown or unsupported		Some servers fail to respond to unknown or unsupported
	types. If a server receives a query for a type that		types. If a server receives a query for a type that
	it doesn't recognise, or doesn't implement, it is		it doesn't recognise, or doesn't implement, it is
	expected to return the appropriate response as if it		expected to return the appropriate response as if it
	did recognise the type but does not have any data for		did recognise the type but does not have any data for
	that type: either NOERROR, or NXDOMAIN. The exceptions		that type, i.e., either NOERROR or NXDOMAIN. The exceptions
	to this are queries for Meta-RR types which may return		to this are queries for Meta-RR types, which may return
	NOTIMP.		NOTIMP.
	</t>		</t>
	</section>		</section>
	<section anchor="dns-flags" title="DNS Flags">		<section anchor="dns-flags" numbered="true" toc="default">
			<name>DNS Flags</name>
	<t>		<t>
	Some servers fail to respond to DNS queries with various		Some servers fail to respond to DNS queries with various
	DNS flags set, regardless of whether they are defined or		DNS flags set, regardless of whether they are defined or
	still reserved. At the time of writing there are servers		still reserved. At the time of writing, there are servers
	that fail to respond to queries with the AD flag set to 1		that fail to respond to queries with the AD flag set to 1
	and servers that fail to respond to queries with the last		and servers that fail to respond to queries with the last
	reserved flag set.		reserved flag set.
	</t>		</t>
	<t>		<t>Servers should respond to such queries. If the server does not
	Servers should respond to such queries. If the server does		know the meaning of a flag, it must not copy it to the response
	not know the meaning of a flag it must not copy it to the		(<xref target="RFC1035" sectionFormat="of" section="4.1.1"/>). If
	response <xref target="RFC1035"/> Section 4.1.1. If the server		the server does not understand the meaning of a request, it should
	does not understand the meaning of a request it should reply		reply with a FORMERR response with unknown flags set to zero.</t>
	with a FORMERR response with unknown flags set to zero.		<section anchor="recursion" numbered="true" toc="default">
	</t>		<name>Recursive Queries</name>
	<section anchor="recursion" title="Recursive Queries">
	<t>		<t>
	A non-recursive server is supposed to respond to recursive		A non-recursive server is supposed to respond to recursive
	queries as if the RD bit is not set <xref target="RFC1034"/>.		queries as if the Recursion Desired (RD) bit is not set <xref
			target="RFC1034" format="default"/>.
	</t>		</t>
	</section>		</section>
	</section>		</section>
	<section anchor="opcode" title="Unknown DNS opcodes">		<section anchor="opcode" numbered="true" toc="default">
			<name>Unknown DNS Opcodes</name>
	<t>		<t>
	The use of previously undefined opcodes is to be expected.		The use of previously undefined opcodes is to be expected.
	Since the DNS was first defined two new opcodes have been		Since the DNS was first defined, two new opcodes have been
	added, UPDATE and NOTIFY.		added, UPDATE and NOTIFY.
	</t>		</t>
	<t>		<t>
	NOTIMP is the expected rcode to an unknown or unimplemented		NOTIMP is the expected rcode to an unknown or unimplemented
	opcode.		opcode.
	</t>		</t><aside>
	<t>		<t>
	Note: while new opcodes will most probably use the current		NOTE: while new opcodes will most probably use the current
	layout structure for the rest of the message there is no		layout structure for the rest of the message, there is no
	requirement that anything other than the DNS header match.		requirement that anything other than the DNS header match.
	</t>		</t></aside>
	</section>		</section>
	<section anchor="tcp" title="TCP Queries">		<section anchor="tcp" numbered="true" toc="default">
			<name>TCP Queries</name>
	<t>		<t>
	All DNS servers are supposed to respond to queries over		All DNS servers are supposed to respond to queries over
	TCP <xref target="RFC7766"/>. While firewalls should not		TCP <xref target="RFC7766" format="default"/>. While firewalls shou
	block TCP connection attempts, those that do they should		ld not
			block TCP connection attempts, those that do should
	cleanly terminate the connection by sending TCP RESET		cleanly terminate the connection by sending TCP RESET
	or sending ICMP/ICMPv6 Administratively Prohibited		or sending ICMP/ICMPv6 Administratively Prohibited
	messages. Dropping TCP connections introduces excessive		messages. Dropping TCP connections introduces excessive
	delays to the resolution process.		delays to the resolution process.
	</t>		</t>
	</section>		</section>
	</section>		</section>
	<section title="EDNS Queries">		<section numbered="true" toc="default">
			<name>EDNS Queries</name>
	<t>		<t>
	EDNS queries are specified in <xref target="RFC6891"/>.		EDNS queries are specified in <xref target="RFC6891" format="default" />.
	</t>		</t>
	<section anchor="edns-independent" title="EDNS Queries - Version Indepen		<section anchor="edns-independent" numbered="true" toc="default">
	dent">		<name>EDNS Queries: Version Independent</name>
	<t>		<t>
	Identifying servers that fail to respond to EDNS queries		Identifying servers that fail to respond to EDNS queries
	can be done by first confirming that the server responds		can be done by first confirming that the server responds
	to regular DNS queries, followed by a series of otherwise		to regular DNS queries, followed by a series of otherwise
	identical queries using EDNS, then making the original		identical queries using EDNS, then making the original
	query again. A series of EDNS queries is needed as at		query again. A series of EDNS queries is needed, as at
	least one DNS implementation responds to the first EDNS		least one DNS implementation responds to the first EDNS
	query with FORMERR but fails to respond to subsequent		query with FORMERR but fails to respond to subsequent
	queries from the same address for a period until a		queries from the same address for a period until a
	regular DNS query is made. The EDNS query should specify		regular DNS query is made. The EDNS query should specify
	a UDP buffer size of 512 bytes to avoid false classification		a UDP buffer size of 512 bytes to avoid false classification
	of not supporting EDNS due to response packet size.		of not supporting EDNS due to response packet size.
	</t>		</t>
	<t>		<t>
	If the server responds to the first and last queries		If the server responds to the first and last queries
	but fails to respond to most or all of the EDNS queries,		but fails to respond to most or all of the EDNS queries,
	it is probably faulty. The test should be repeated a		it is probably faulty. The test should be repeated a
	number of times to eliminate the likelihood of a false		number of times to eliminate the likelihood of a false
	positive due to packet loss.		positive due to packet loss.
	</t>		</t>
	<t>		<t>
	Firewalls may also block larger EDNS responses but there		Firewalls may also block larger EDNS responses, but there
	is no easy way to check authoritative servers to see		is no easy way to check authoritative servers to see
	if the firewall is mis-configured.		if the firewall is misconfigured.
	</t>		</t>
	</section>		</section>
	<section anchor="edns-specific" title="EDNS Queries - Version Specific">		<section anchor="edns-specific" numbered="true" toc="default">
			<name>EDNS Queries: Version Specific</name>
	<t>		<t>
	Some servers respond correctly to EDNS version 0 queries		Some servers respond correctly to EDNS version 0 queries
	but fail to respond to EDNS queries with version numbers		but fail to respond to EDNS queries with version numbers
	that are higher than zero. Servers should respond with		that are higher than zero. Servers should respond with
	BADVERS to EDNS queries with version numbers that they		BADVERS to EDNS queries with version numbers that they
	do not support.		do not support.
	</t>		</t>
	<t>		<t>
	Some servers respond correctly to EDNS version 0 queries		Some servers respond correctly to EDNS version 0 queries
	but fail to set QR=1 when responding to EDNS versions		but fail to set QR=1 when responding to EDNS versions
	they do not support. Such responses may be discarded		they do not support. Such responses may be discarded
	as invalid (as QR is not 1) or treated as requests (when the		as invalid (as QR is not 1) or treated as requests (when the
	source port of the original request was port 53).		source port of the original request was port 53).
	</t>		</t>
	</section>		</section>
	<section anchor="edns-options" title="EDNS Options">		<section anchor="edns-options" numbered="true" toc="default">
			<name>EDNS Options</name>
	<t>		<t>
	Some servers fail to respond to EDNS queries with EDNS		Some servers fail to respond to EDNS queries with EDNS
	options set. The original EDNS specification left this		options set. The original EDNS specification left this
	behaviour undefined <xref target="RFC2671"/>, but the		behaviour undefined <xref target="RFC2671" format="default"/>, but t
	correct behaviour was clarified in <xref target="RFC6891"/>.		he
			correct behaviour was clarified in <xref target="RFC6891" format="de
			fault"/>.
	Unknown EDNS options are supposed to be ignored by the server.		Unknown EDNS options are supposed to be ignored by the server.
	</t>		</t>
	</section>		</section>
	<section anchor="edns-flags" title="EDNS Flags">		<section anchor="edns-flags" numbered="true" toc="default">
			<name>EDNS Flags</name>
	<t>		<t>
	Some servers fail to respond to EDNS queries with EDNS		Some servers fail to respond to EDNS queries with EDNS
	flags set. Servers should ignore EDNS flags they do not		flags set. Servers should ignore EDNS flags they do not
	understand and must not add them to the response <xref		understand and must not add them to the response <xref target="RFC68
	target="RFC6891"/>.		91" format="default"/>.
	</t>		</t>
	</section>		</section>
	<section anchor="truncated-edns" title="Truncated EDNS Responses">		<section anchor="truncated-edns" numbered="true" toc="default">
			<name>Truncated EDNS Responses</name>
	<t>		<t>
	Some EDNS aware servers fail to include an OPT record when a		Some EDNS-aware servers fail to include an OPT record when a
	truncated response is sent. An OPT record is supposed to be		truncated response is sent. An OPT record is supposed to be
	included in a truncated response <xref target="RFC6891"/>.		included in a truncated response <xref target="RFC6891" format="defa ult"/>.
	</t>		</t>
	<t>		<t>
	Some EDNS aware servers fail to honour the advertised EDNS		Some EDNS-aware servers fail to honour the advertised EDNS
	UDP buffer size and send over-sized responses		UDP buffer size and send oversized responses
	<xref target="RFC6891"/>. Servers must send UDP responses		<xref target="RFC6891" format="default"/>. Servers must send UDP re
			sponses
	no larger than the advertised EDNS UDP buffer size.		no larger than the advertised EDNS UDP buffer size.
	</t>		</t>
	</section>		</section>
	<section anchor="dobit" title="DO=1 Handling">		<section anchor="dobit" numbered="true" toc="default">
			<name>DO=1 Handling</name>
	<t>		<t>
	Some nameservers incorrectly only return an EDNS response		Some nameservers incorrectly only return an EDNS response
	when the DO bit <xref target="RFC3225"/> is 1 in the		when the DNSSEC OK (DO) bit <xref target="RFC3225" format="default"/ > is 1 in the
	query. Servers that support EDNS should always respond to		query. Servers that support EDNS should always respond to
	EDNS requests with EDNS responses.		EDNS requests with EDNS responses.
	</t>		</t>
	<t>		<t>
	Some nameservers fail to copy the DO bit to the response		Some nameservers fail to copy the DO bit to the response
	despite clearly supporting DNSSEC by returning an RRSIG		despite clearly supporting DNSSEC by returning an RRSIG
	records to EDNS queries with DO=1. Nameservers that support		records to EDNS queries with DO=1. Nameservers that support
	DNSSEC are expected to copy the DO bit from the request to		DNSSEC are expected to copy the DO bit from the request to
	the response.		the response.
	</t>		</t>
	</section>		</section>
	<section anchor="tcp-edns" title="EDNS over TCP">		<section anchor="tcp-edns" numbered="true" toc="default">
			<name>EDNS over TCP</name>
	<t>		<t>
	Some EDNS aware servers incorrectly limit the TCP response		Some EDNS-aware servers incorrectly limit the TCP response
	sizes to the advertised UDP response size. This breaks DNS		sizes to the advertised UDP response size. This breaks DNS
	resolution to clients where the response sizes exceed the		resolution to clients where the response sizes exceed the
	advertised UDP response size despite the server and the client		advertised UDP response size despite the server and the client
	being capable of sending and receiving larger TCP responses		being capable of sending and receiving larger TCP responses,
	respectively. It effectively defeats setting TC=1 in UDP		respectively. It effectively defeats setting TC=1 in UDP
	responses.		responses.
	</t>		</t>
	</section>		</section>
	</section>		</section>
	</section>		</section>
	<section title="Firewalls and Load Balancers">		<section numbered="true" toc="default">
			<name>Firewalls and Load Balancers</name>
	<t>		<t>
	Firewalls and load balancers can affect the externally		Firewalls and load balancers can affect the externally
	visible behaviour of a nameserver. Tests for conformance		visible behaviour of a nameserver. Tests for conformance
	should to be done from outside of any firewall so that the		should to be done from outside of any firewall so that the
	system is tested as a whole.		system is tested as a whole.
	</t>		</t>
	<t>		<t>
	Firewalls and load balancers should not drop DNS packets		Firewalls and load balancers should not drop DNS packets
	that they don't understand. They should either pass		that they don't understand. They should either pass
	the packets or generate an appropriate error response.		the packets or generate an appropriate error response.
	skipping to change at line 427 ¶		skipping to change at line 434 ¶
	<t>		<t>
	Requests for unknown query classes are normal client behaviour		Requests for unknown query classes are normal client behaviour
	and should not be construed as an attack. Nameservers have		and should not be construed as an attack. Nameservers have
	always been expected to be able to handle such queries.		always been expected to be able to handle such queries.
	</t>		</t>
	<t>		<t>
	Requests with unknown opcodes are normal client behaviour		Requests with unknown opcodes are normal client behaviour
	and should not be construed as an attack. Nameservers have		and should not be construed as an attack. Nameservers have
	always been expected to be able to handle such queries.		always been expected to be able to handle such queries.
	</t>		</t>
	<t>		<t>Requests with unassigned flags set (DNS or EDNS) are expected client
	Requests with unassigned flags set (DNS or EDNS) are expected		behaviour and should not be construed as an attack. The behaviour for
	client behaviour and should not be construed as an attack.		unassigned flags is to ignore them in the request and to not set them in
	The behaviour for unassigned flags is to ignore them in the		the response. Dropping DNS/EDNS packets with unassigned flags makes it
	request and to not set them in the response. Dropping DNS		difficult to deploy extensions that make use of them due to the need to
	/ EDNS packets with unassigned flags makes it difficult to		reconfigure and update firewalls.</t>
	deploy extensions that make use of them due to the need to
	reconfigure and update firewalls.
	</t>
	<t>		<t>
	Requests with unknown EDNS options are expected client		Requests with unknown EDNS options are expected client
	behaviour and should not be construed as an attack. The		behaviour and should not be construed as an attack. The
	correct behaviour for unknown EDNS options is to ignore		correct behaviour for unknown EDNS options is to ignore
	their presence when constructing a reply.		their presence when constructing a reply.
	</t>		</t>
	<t>		<t>
	Requests with unknown EDNS versions are expected client		Requests with unknown EDNS versions are expected client
	behaviour and should not be construed as an attack. The		behaviour and should not be construed as an attack. The
	correct behaviour for unknown EDNS versions is to return		correct behaviour for unknown EDNS versions is to return
	skipping to change at line 466 ¶		skipping to change at line 470 ¶
	</t>		</t>
	<t>		<t>
	DNS, and EDNS in particular, are designed to allow clients to		DNS, and EDNS in particular, are designed to allow clients to
	be able to use new features against older servers without		be able to use new features against older servers without
	having to validate every option. Indiscriminate blocking		having to validate every option. Indiscriminate blocking
	of messages breaks that design.		of messages breaks that design.
	</t>		</t>
	<t>		<t>
	However, there may be times when a nameserver mishandles		However, there may be times when a nameserver mishandles
	messages with a particular flag, EDNS option, EDNS version		messages with a particular flag, EDNS option, EDNS version
	field, opcode, type or class field or combination thereof		field, opcode, type or class field, or combination thereof
	to the point where the integrity of the nameserver is		to the point where the integrity of the nameserver is
	compromised. Firewalls should offer the ability to selectively		compromised. Firewalls should offer the ability to selectively
	reject messages using an appropriately constructed response		reject messages using an appropriately constructed response
	based on all these fields while awaiting a fix from the		based on all these fields while awaiting a fix from the
	nameserver vendor. Returning FORMERR or REFUSED are two		nameserver vendor. Returning FORMERR or REFUSED are two
	potential error codes to return.		potential error codes to return.
	</t>		</t>
	</section>		</section>
	<section anchor="scrubbing" title="Packet Scrubbing Services">		<section anchor="scrubbing" numbered="true" toc="default">
			<name>Packet Scrubbing Services</name>
	<t>		<t>
	Packet scrubbing services are used to filter out undesired traffic,		Packet scrubbing services are used to filter out undesired traffic,
	including but not limited to, denial of service traffic. This is		including but not limited to denial-of-service traffic. This is
	often done using heuristic analysis of the traffic.		often done using heuristic analysis of the traffic.
	</t>		</t>
	<t>		<t>
	Packet scrubbing services can affect the externally visible behaviour		Packet scrubbing services can affect the externally visible behaviour
	of a nameserver in a similar way to firewalls. If an operator		of a nameserver in a similar way to firewalls. If an operator
	uses a packet scrubbing service, they should check that legitimate		uses a packet scrubbing service, they should check that legitimate
	queries are not being blocked.		queries are not being blocked.
	</t>		</t>
	<t>		<t>
	Packet scrubbing services, unlike firewalls, are also turned on		Packet scrubbing services, unlike firewalls, are also turned on
	and off in response to denial of service attacks. One needs		and off in response to denial-of-service attacks. One needs
	to take care when choosing a scrubbing service.		to take care when choosing a scrubbing service.
	</t>		</t>
	<t>		<t>
	Ideally, Operators should run these tests against a packet scrubbing		Ideally, operators should run these tests against a packet scrubbing
	service to ensure that these tests are not seen as attack		service to ensure that these tests are not seen as attack
	vectors.		vectors.
	</t>		</t>
	</section>		</section>
	<section title="Whole Answer Caches">		<section numbered="true" toc="default">
			<name>Whole Answer Caches</name>
	<t>		<t>
	Whole answer caches take a previously constructed answer		Whole answer caches take a previously constructed answer
	and return it to a subsequent query for the same question.		and return it to a subsequent query for the same question.
	However, they can return the wrong response if they do not		However, they can return the wrong response if they do not
	take all of the relevant attributes of the query into account.		take all of the relevant attributes of the query into account.
	</t>		</t>
	<t>		<t>
	In addition to the standard tuple of &lt;qname,qtype,qclass&gt;		In addition to the standard tuple of &lt;qname,qtype,qclass&gt;,
	a non-exhaustive set of attributes that must be considered		a non-exhaustive set of attributes that must be considered
	include: RD, AD, CD, OPT record, DO, EDNS buffer size, EDNS		include: RD, AD, CD, OPT record, DO, EDNS buffer size, EDNS
	version, EDNS options, and transport.		version, EDNS options, and transport.
	</t>		</t>
	</section>		</section>
	<section anchor="response" title="Response Code Selection">		<section anchor="response" numbered="true" toc="default">
			<name>Response Code Selection</name>
	<t>		<t>
	Choosing the correct response code when responding to DNS		Choosing the correct response code when responding to DNS
	queries is important. Response codes should be chosen		queries is important. Response codes should be chosen
	considering how clients will handle them.		considering how clients will handle them.
	</t>		</t>
	<t>		<t>
	For unimplemented opcodes NOTIMP is the expected response code.		For unimplemented opcodes, NOTIMP is the expected response code.
	Note: Newly implemented opcodes may change the message format by		Note: newly implemented opcodes may change the message format by
	extending the header, changing the structure of the records,		extending the header, changing the structure of the records,
	etc. Servers are not expected to be able to parse these,		etc. Servers are not expected to be able to parse these
	and should respond with a response code of NOTIMP rather		and should respond with a response code of NOTIMP rather
	than FORMERR (which would be expected if there was a parse error		than FORMERR (which would be expected if there was a parse error
	with an known opcode).		with a known opcode).
	</t>		</t>
	<t>		<t>
	For unimplemented type codes, and in the absence of other		For unimplemented type codes, and in the absence of other
	errors, the only valid response is NoError if the qname		errors, the only valid response is NOERROR if the qname
	exists, and NameError (NXDOMAIN) otherwise. For Meta-RRs		exists and NXDOMAIN otherwise.
	NOTIMP may be returned instead.
	</t>		For Meta-RRs, NOTIMP may be returned instead.
	<t>
	If a zone cannot be loaded because it contains unimplemented
	type codes that are not encoded as unknown record types
	according to <xref target="RFC3597"/> then the expected
	response is SERVFAIL as the whole zone should be rejected
	<xref target="RFC1035"> Section 5.2</xref>. If a zone loads then
	<xref target="RFC1034"> Section 4.3.2</xref> applies.
	</t>		</t>
			<t>If a zone cannot be loaded because it contains unimplemented type
			codes that are not encoded as unknown record types according to <xref
			target="RFC3597" format="default"/>, then the expected response is
			SERVFAIL, as the whole zone should be rejected (<xref target="RFC1035"
			sectionFormat="of" section="5.2"></xref>). If a zone loads, then <xref
			target="RFC1034" sectionFormat="of" section="4.3.2"></xref> applies.</t>
	<t>		<t>
	If the server supports EDNS and receives a query with an		If the server supports EDNS and receives a query with an
	unsupported EDNS version, the correct response is BADVERS		unsupported EDNS version, the correct response is BADVERS
	<xref target="RFC6891"/>.		<xref target="RFC6891" format="default"/>.
	</t>		</t>
	<t>		<t>
	If the server does not support EDNS at all, FORMERR is		If the server does not support EDNS at all, FORMERR is
	the expected error code. That said a minimal EDNS		the expected error code. That said, a minimal EDNS
	server implementation requires parsing the OPT records		server implementation requires parsing the OPT records
	and responding with an empty OPT record in the additional		and responding with an empty OPT record in the additional
	section in most cases. There is no need to interpret any		section in most cases. There is no need to interpret any
	EDNS options present in the request as unsupported EDNS		EDNS options present in the request, as unsupported EDNS
	options are expected to be ignored <xref target="RFC6891"/>.		options are expected to be ignored <xref target="RFC6891" format="defaul
	Additionally EDNS flags can be ignored. The only part of the		t"/>.
			Additionally, EDNS flags can be ignored. The only part of the
	OPT record that needs to be examined is the version field		OPT record that needs to be examined is the version field
	to determine if BADVERS needs to be sent or not.		to determine if BADVERS needs to be sent or not.
	</t>		</t>
	</section>		</section>
	<section anchor="testing" title="Testing">		<section anchor="testing" numbered="true" toc="default">
			<name>Testing</name>
	<t>		<t>
	Testing is divided into two sections: "Basic DNS", which all		Testing is divided into two sections: "Basic DNS", which all
	servers should meet, and "Extended DNS", which should be met		servers should meet, and "Extended DNS", which should be met
	by all servers that support EDNS (a server is deemed to		by all servers that support EDNS (a server is deemed to
	support EDNS if it gives a valid EDNS response to any EDNS		support EDNS if it gives a valid EDNS response to any EDNS
	query). If a server does not support EDNS it should still		query). If a server does not support EDNS, it should still
	respond to all the tests, albeit with error responses.		respond to all the tests, albeit with error responses.
	</t>		</t>
	<t>		<t>
	These tests query for records at the apex of a zone that the		These tests query for records at the apex of a zone that the
	server is nominally configured to serve. All tests should		server is nominally configured to serve. All tests should
	use the same zone.		use the same zone.
	</t>		</t>
	<t>		<t>
	It is advisable to run all of the tests below in parallel		It is advisable to run all of the tests below in parallel
	so as to minimise the delays due to multiple timeouts when		so as to minimise the delays due to multiple timeouts when
	the servers do not respond. There are 16 queries directed		the servers do not respond. There are 16 queries directed
	to each nameserver (assuming no packet loss) testing different		to each nameserver (assuming no packet loss) testing different
	aspects of Basic DNS and Extended DNS.		aspects of Basic DNS and Extended DNS.
	</t>		</t>
	<t>		<t>
	The tests below use dig from BIND 9.11.0 <xref target="ISC"/>.		The tests below use dig from BIND 9.11.0 <xref target="ISC" format="defa ult"/>.
	Replace $zone with the name of the zone being used for testing.		Replace $zone with the name of the zone being used for testing.
	Replace $server with the name or address of the server being tested.		Replace $server with the name or address of the server being tested.
	</t>		</t>
	<t>		<t>
	When testing recursive servers set RD=1 and choose a zone		When testing, recursive servers set RD=1 and choose a zone
	name that is known to exist and is not being served by the		name that is known to exist and is not being served by the
	recursive server. The root zone (".") is often a good		recursive server. The root zone (".") is often a good
	candidate as it is DNSSEC signed. RD=1, rather than RD=0,		candidate, as it is DNSSEC signed. RD=1, rather than RD=0,
	should be present in the responses for all test involving		should be present in the responses for all test involving
	the opcode QUERY. Non-authoritative answers (AA=0) are		the opcode QUERY. Non-authoritative answers (AA=0) are
	expected when talking to a recursive server. AD=1 is only		expected when talking to a recursive server. AD=1 is only
	expected if the server is validating responses and		expected if the server is validating responses and
	one or both AD=1 or DO=1 is set in the request otherwise		one or both AD=1 or DO=1 is set in the request, otherwise
	AD=0 is expected.		AD=0 is expected.
	</t>		</t>
	<section anchor="testing-basic" title="Testing - Basic DNS">		<section anchor="testing-basic" numbered="true" toc="default">
			<name>Testing: Basic DNS</name>
	<t>		<t>
	This first set of tests cover basic DNS server behaviour		This first set of tests cover Basic DNS server behaviour
	and all servers should pass these tests.		and all servers should pass these tests.
	</t>		</t>
	<section title="Is The Server Configured For The Zone?">		<section numbered="true" toc="default">
			<name>Is the server configured for the zone?</name>
	<t>		<t>
	Ask for the SOA record of the configured zone. This		Ask for the SOA record of the configured zone. This
	query is made with no DNS flag bits set and without		query is made with no DNS flag bits set and without
	EDNS.		EDNS.
	</t>		</t>
	<t>		<t>
	We expect the SOA record for the zone to be returned		We expect the SOA record for the zone to be returned
	in the answer section, the rcode to be set to NOERROR, and		in the answer section, the rcode to be set to NOERROR, and
	the AA and QR bits to be set in the header; RA may		the Authoritative Answer (AA) and Query/Response (QR) bits to be
	also be set <xref target="RFC1034"/>. We do not expect		set in the header; the Recursion Available (RA) bits may also be
	an OPT record to be returned <xref target="RFC6891"/>.		set <xref target="RFC1034" format="default"/>. We
	</t>		do not expect an OPT record to be returned <xref target="RFC6891"
	<t>		format="default"/>.</t>
	<figure>		<t keepWithNext="true">
	<preamble>
	Verify the server is configured for the zone:		Verify the server is configured for the zone:
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +noedns +noad +norec soa $zone @$server		dig +noedns +noad +norec soa $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: the SOA record to be present in the answer section		expect: the SOA record to be present in the answer section
	expect: flag: aa to be present		expect: flag: aa to be present
	expect: flag: rd to NOT be present		expect: flag: rd to NOT be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	expect: the OPT record to NOT be present		expect: the OPT record to NOT be present
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	<section title="Testing Unknown Types">		<section numbered="true" toc="default">
			<name>Testing Unknown Types</name>
	<t>		<t>
	Identifying servers that fail to respond to unknown or		Identifying servers that fail to respond to unknown or
	unsupported types can be done by making an initial DNS		unsupported types can be done by making an initial DNS
	query for an A record, making a number of queries for an		query for an A record, making a number of queries for an
	unallocated type, then making a query for an A record		unallocated type, then making a query for an A record
	again. IANA maintains a registry of allocated types.		again. IANA maintains a registry of allocated types <xref
			target="IANA-DNS"/>.
	</t>		</t>
	<t>		<t>
	If the server responds to the first and last queries but		If the server responds to the first and last queries but
	fails to respond to the queries for the unallocated type,		fails to respond to the queries for the unallocated type,
	it is probably faulty. The test should be repeated a		it is probably faulty. The test should be repeated a
	number of times to eliminate the likelihood of a false		number of times to eliminate the likelihood of a false
	positive due to packet loss.		positive due to packet loss.
	</t>		</t>
	<t>		<t>
	Ask for the TYPE1000 RRset at the configured zone's		Ask for the TYPE1000 RRset at the configured zone's
	name. This query is made with no DNS flag bits set and		name. This query is made with no DNS flag bits set and
	without EDNS. TYPE1000 has been chosen for this purpose		without EDNS. TYPE1000 has been chosen for this purpose,
	as IANA is unlikely to allocate this type in the near		as IANA is unlikely to allocate this type in the near
	future and it is not in a range reserved for private		future and it is not in a range reserved for private
	use <xref target="RFC6895"/>. Any unallocated type code		use <xref target="RFC6895" format="default"/>. Any unallocated type code
	could be chosen for this test.		could be chosen for this test.
	</t>		</t>
	<t>		<t>
	We expect no records to be returned in the answer		We expect no records to be returned in the answer
	section, the rcode to be set to NOERROR, and the AA and		section, the rcode to be set to NOERROR, and the AA and
	QR bits to be set in the header; RA may also be set		QR bits to be set in the header; RA may also be set
	<xref target="RFC1034"/>. We do not expect an OPT record		<xref target="RFC1034" format="default"/>. We do not expect an OPT
	to be returned <xref target="RFC6891"/>.		record
			to be returned <xref target="RFC6891" format="default"/>.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that queries for an unknown type work:		Check that queries for an unknown type work:
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +noedns +noad +norec type1000 $zone @$server		dig +noedns +noad +norec type1000 $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: an empty answer section.		expect: an empty answer section.
	expect: flag: aa to be present		expect: flag: aa to be present
	expect: flag: rd to NOT be present		expect: flag: rd to NOT be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	expect: the OPT record to NOT be present		expect: the OPT record to NOT be present
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	<section title="Testing Header Bits">		<section numbered="true" toc="default">
	<section title="Testing CD=1 Queries">		<name>Testing Header Bits</name>
			<section numbered="true" toc="default">
			<name>Testing CD=1 Queries</name>
	<t>		<t>
	Ask for the SOA record of the configured zone.		Ask for the SOA record of the configured zone.
	This query is made with only the CD DNS flag bit set,		This query is made with only the CD DNS flag bit set,
	all other DNS bits clear, and without EDNS.		with all other DNS bits clear, and without EDNS.
	</t>		</t>
	<t>		<t>
	We expect the SOA record for the zone to be returned		We expect the SOA record for the zone to be returned
	in the answer section, the rcode to be set to NOERROR,		in the answer section, the rcode to be set to NOERROR,
	and the AA and QR bits to be set in the header. We		and the AA and QR bits to be set in the header. We
	do not expect an OPT record to be returned.		do not expect an OPT record to be returned.
	</t>		</t>
	<t>		<t>
	If the server supports DNSSEC, CD should be set in		If the server supports DNSSEC, CD should be set in
	the response <xref target="RFC4035"/> otherwise CD		the response <xref target="RFC4035" format="default"/>; otherwise,
	should be clear <xref target="RFC1034"/>.		CD
			should be clear <xref target="RFC1034" format="default"/>.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that queries with CD=1 work:		Check that queries with CD=1 work:
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +noedns +noad +norec +cd soa $zone @$server		dig +noedns +noad +norec +cd soa $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: the SOA record to be present in the answer section		expect: the SOA record to be present in the answer section
	expect: flag: aa to be present		expect: flag: aa to be present
	expect: flag: rd to NOT be present		expect: flag: rd to NOT be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	expect: the OPT record to NOT be present		expect: the OPT record to NOT be present
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	<section title="Testing AD=1 Queries">		<section numbered="true" toc="default">
	<t>		<name>Testing AD=1 Queries</name>
	Ask for the SOA record of the configured zone. This		<t>Ask for the SOA record of the configured zone. This query is
	query is made with only the AD DNS flag bit set and		made with only the AD DNS flag bit set, with all other DNS bits clear
	all other DNS bits clear and without EDNS.		,
	</t>		and without EDNS.</t>
	<t>		<t>
	We expect the SOA record for the zone to be returned		We expect the SOA record for the zone to be returned
	in the answer section, the rcode to be set to NOERROR,		in the answer section, the rcode to be set to NOERROR,
	and the AA and QR bits to be set in the header. We		and the AA and QR bits to be set in the header. We
	do not expect an OPT record to be returned. The		do not expect an OPT record to be returned. The
	purpose of this query is to detect blocking of queries		purpose of this query is to detect blocking of queries
	with the AD bit present, not the specific value of		with the AD bit present, not the specific value of
	AD in the response.		AD in the response.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that queries with AD=1 work:		Check that queries with AD=1 work:
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +noedns +norec +ad soa $zone @$server		dig +noedns +norec +ad soa $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: the SOA record to be present in the answer section		expect: the SOA record to be present in the answer section
	expect: flag: aa to be present		expect: flag: aa to be present
	expect: flag: rd to NOT be present		expect: flag: rd to NOT be present
	expect: the OPT record to NOT be present		expect: the OPT record to NOT be present
	</artwork>		]]></sourcecode>
	<postamble>		<t keepWithPrevious="true">
	AD use in queries is defined in <xref target="RFC6840"/>.		AD use in queries is defined in <xref target="RFC6840" format=
	</postamble>		"default"/>.
	</figure>
	</t>		</t>
	</section>		</section>
	<section title="Testing Reserved Bit">		<section numbered="true" toc="default">
			<name>Testing Reserved Bit</name>
	<t>		<t>
	Ask for the SOA record of the configured zone. This		Ask for the SOA record of the configured zone. This
	query is made with only the final reserved DNS flag		query is made with only the final reserved DNS flag
	bit set and all other DNS bits clear and without EDNS.		bit set, with all other DNS bits clear, and without EDNS.
	</t>		</t>
	<t>		<t>
	We expect the SOA record for the zone to be returned		We expect the SOA record for the zone to be returned
	in the answer section, the rcode to be set to NOERROR,		in the answer section, the rcode to be set to NOERROR,
	and the AA and QR bits to be set in the header; RA		and the AA and QR bits to be set in the header; RA
	may be set. The final reserved bit must not be set		may be set. The final reserved bit must not be set
	<xref target="RFC1034"/>. We do not expect an OPT		<xref target="RFC1034" format="default"/>. We do not expect an OP
	record to be returned <xref target="RFC6891"/>.		T
			record to be returned <xref target="RFC6891" format="default"/>.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that queries with the last unassigned DNS		Check that queries with the last unassigned DNS
	header flag work and that the flag bit is not		header flag work and that the flag bit is not
	copied to the response:		copied to the response:
	</preamble>		</t>
	<artwork>		<sourcecode name="" type="" ><![CDATA[
	dig +noedns +noad +norec +zflag soa $zone @$server		dig +noedns +noad +norec +zflag soa $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: the SOA record to be present in the answer section		expect: the SOA record to be present in the answer section
	expect: MBZ to NOT be in the response (see below)		expect: MBZ to NOT be in the response (see below)
	expect: flag: aa to be present		expect: flag: aa to be present
	expect: flag: rd to NOT be present		expect: flag: rd to NOT be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	expect: the OPT record to NOT be present		expect: the OPT record to NOT be present
	</artwork>		]]></sourcecode>
	<postamble>		<t keepWithPrevious="true"> MBZ (Must Be Zero) is a dig-specific
	MBZ (Must Be Zero) is a dig-specific indication that		indication that the flag bit has been incorrectly copied. See
	the flag bit has been incorrectly copied. See Section		<xref target="RFC1035" sectionFormat="of" section="4.1.1"/>:</t>
	4.1.1, <xref target="RFC1035"/> "Z Reserved for		<dl newline="false">
	future use. Must be zero in all queries and		<dt>"Z</dt>
	responses."		<dd>Reserved for future use. Must be zero in all queries and responses."</dd>
	</postamble>		</dl>
	</figure>
	</t>
	</section>		</section>
	<section title="Testing Recursive Queries">		<section numbered="true" toc="default">
			<name>Testing Recursive Queries</name>
	<t>		<t>
	Ask for the SOA record of the configured zone. This		Ask for the SOA record of the configured zone. This
	query is made with only the RD DNS flag bit set and		query is made with only the RD DNS flag bit set and
	without EDNS.		without EDNS.
	</t>		</t>
	<t>		<t>
	We expect the SOA record for the zone to be returned		We expect the SOA record for the zone to be returned
	in the answer section, the rcode to be set to NOERROR, and		in the answer section, the rcode to be set to NOERROR, and
	the AA, QR and RD bits to be set in the header; RA		the AA, QR and RD bits to be set in the header; RA
	may also be set <xref target="RFC1034"/>. We do not		may also be set <xref target="RFC1034" format="default"/>. We do
	expect an OPT record to be returned <xref target="RFC6891"/>.		not
			expect an OPT record to be returned <xref target="RFC6891" format=
			"default"/>.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that recursive queries work:		Check that recursive queries work:
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +noedns +noad +rec soa $zone @$server		dig +noedns +noad +rec soa $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: the SOA record to be present in the answer section		expect: the SOA record to be present in the answer section
	expect: flag: aa to be present		expect: flag: aa to be present
	expect: flag: rd to be present		expect: flag: rd to be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	expect: the OPT record to NOT be present		expect: the OPT record to NOT be present
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	</section>		</section>
	<section title="Testing Unknown Opcodes">		<section numbered="true" toc="default">
			<name>Testing Unknown Opcodes</name>
	<t>		<t>
	Construct a DNS message that consists of only a DNS		Construct a DNS message that consists of only a DNS
	header with opcode set to 15 (currently not allocated),		header with opcode set to 15 (currently not allocated),
	no DNS header bits set and empty question, answer,		no DNS header bits set, and empty question, answer,
	authority and additional sections.		authority, and additional sections. </t>
	</t>		<t keepWithNext="true">
	<t>
	<figure>
	<preamble>
	Check that new opcodes are handled:		Check that new opcodes are handled:
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +noedns +noad +opcode=15 +norec +header-only @$server		dig +noedns +noad +opcode=15 +norec +header-only @$server
	expect: status: NOTIMP		expect: status: NOTIMP
	expect: opcode: 15		expect: opcode: 15
	expect: all sections to be empty		expect: all sections to be empty
	expect: flag: aa to NOT be present		expect: flag: aa to NOT be present
	expect: flag: rd to NOT be present		expect: flag: rd to NOT be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	expect: the OPT record to NOT be present		expect: the OPT record to NOT be present
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	<section title="Testing TCP">		<section numbered="true" toc="default">
			<name>Testing TCP</name>
	<t>		<t>
	Whether a server accepts TCP connections can be tested		Whether a server accepts TCP connections can be tested
	by first checking that it responds to UDP queries to		by first checking that it responds to UDP queries to
	confirm that it is up and operating, then attempting the		confirm that it is up and operating, then attempting the
	same query over TCP. An additional query should be made		same query over TCP. An additional query should be made
	over UDP if the TCP connection attempt fails to confirm		over UDP if the TCP connection attempt fails to confirm
	that the server under test is still operating.		that the server under test is still operating.
	</t>		</t>
	<t>		<t>
	Ask for the SOA record of the configured zone. This		Ask for the SOA record of the configured zone. This
	query is made with no DNS flag bits set and without		query is made with no DNS flag bits set and without
	EDNS. This query is to be sent using TCP.		EDNS. This query is to be sent using TCP.
	</t>		</t>
	<t>		<t>
	We expect the SOA record for the zone to be returned		We expect the SOA record for the zone to be returned
	in the answer section, the rcode to be set to NOERROR, and		in the answer section, the rcode to be set to NOERROR, and
	the AA and QR bits to be set in the header; RA may		the AA and QR bits to be set in the header; RA may
	also be set <xref target="RFC1034"/>. We do not expect		also be set <xref target="RFC1034" format="default"/>. We do not ex
	an OPT record to be returned <xref target="RFC6891"/>.		pect
			an OPT record to be returned <xref target="RFC6891" format="default"
			/>.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that TCP queries work:		Check that TCP queries work:
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +noedns +noad +norec +tcp soa $zone @$server		dig +noedns +noad +norec +tcp soa $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: the SOA record to be present in the answer section		expect: the SOA record to be present in the answer section
	expect: flag: aa to be present		expect: flag: aa to be present
	expect: flag: rd to NOT be present		expect: flag: rd to NOT be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	expect: the OPT record to NOT be present		expect: the OPT record to NOT be present
	</artwork>		]]></sourcecode>
	<postamble>		<t keepWithPrevious="true">
	The requirement that TCP be supported is defined		The requirement that TCP be supported is defined
	in <xref target="RFC7766"/>.		in <xref target="RFC7766" format="default"/>.
	</postamble>
	</figure>
	</t>		</t>
	</section>		</section>
	</section>		</section>
	<section anchor="testing-edns" title="Testing - Extended DNS">		<section anchor="testing-edns" numbered="true" toc="default">
			<name>Testing: Extended DNS</name>
	<t>		<t>
	The next set of tests cover various aspects of EDNS		The next set of tests cover various aspects of EDNS
	behaviour. If any of these tests succeed (indicating		behaviour. If any of these tests succeed (indicating
	at least some EDNS support) then all of them should		at least some EDNS support), then all of them should
	succeed. There are servers that support EDNS but fail		succeed. There are servers that support EDNS but fail
	to handle plain EDNS queries correctly so a plain EDNS		to handle plain EDNS queries correctly, so a plain EDNS
	query is not a good indicator of lack of EDNS support.		query is not a good indicator of lack of EDNS support.
	</t>		</t>
	<section title="Testing Minimal EDNS">		<section numbered="true" toc="default">
			<name>Testing Minimal EDNS</name>
	<t>		<t>
	Ask for the SOA record of the configured zone. This		Ask for the SOA record of the configured zone. This
	query is made with no DNS flag bits set. EDNS version		query is made with no DNS flag bits set. EDNS version
	0 is used without any EDNS options or EDNS flags set.		0 is used without any EDNS options or EDNS flags set.
	</t>		</t>
	<t>		<t>
	We expect the SOA record for the zone to be returned		We expect the SOA record for the zone to be returned
	in the answer section, the rcode to be set to NOERROR, and		in the answer section, the rcode to be set to NOERROR, and
	the AA and QR bits to be set in the header; RA may		the AA and QR bits to be set in the header; RA may
	also be set <xref target="RFC1034"/>. We expect		also be set <xref target="RFC1034" format="default"/>. We expect
	an OPT record to be returned. There should be no EDNS		an OPT record to be returned. There should be no EDNS
	flags present in the response. The EDNS version field		flags present in the response. The EDNS version field
	should be 0 and there should be no EDNS options present		should be 0, and there should be no EDNS options present
	<xref target="RFC6891"/>.		<xref target="RFC6891" format="default"/>.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that plain EDNS queries work:		Check that plain EDNS queries work:
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +nocookie +edns=0 +noad +norec soa $zone @$server		dig +nocookie +edns=0 +noad +norec soa $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: the SOA record to be present in the answer section		expect: the SOA record to be present in the answer section
	expect: an OPT record to be present in the additional section		expect: an OPT record to be present in the additional section
	expect: EDNS Version 0 in response		expect: EDNS Version 0 in response
	expect: flag: aa to be present		expect: flag: aa to be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	</artwork>		]]></sourcecode>
	<postamble>		<t keepWithPrevious="true">
	+nocookie disables sending a EDNS COOKIE option which		+nocookie disables sending an EDNS COOKIE option, which
	is otherwise enabled by default in BIND 9.11.0 (and		is otherwise enabled by default in BIND 9.11.0 (and
	later).		later).
	</postamble>
	</figure>
	</t>		</t>
	</section>		</section>
	<section title="Testing EDNS Version Negotiation">		<section numbered="true" toc="default">
			<name>Testing EDNS Version Negotiation</name>
	<t>		<t>
	Ask for the SOA record of a zone the server is nominally		Ask for the SOA record of a zone the server is nominally
	configured to serve. This query is made with no DNS flag		configured to serve. This query is made with no DNS flag
	bits set. EDNS version 1 is used without any EDNS options		bits set. EDNS version 1 is used without any EDNS options
	or EDNS flags set.		or EDNS flags set.
	</t>		</t>
	<t>		<t>
	We expect the SOA record for the zone to NOT be returned		We expect the SOA record for the zone to NOT be returned
	in the answer section with the extended rcode set to		in the answer section with the extended rcode set to
	BADVERS and the QR bit to be set in the header; RA		BADVERS and the QR bit to be set in the header; RA
	may also be set <xref target="RFC1034"/>. We expect		may also be set <xref target="RFC1034" format="default"/>. We expec t
	an OPT record to be returned. There should be no EDNS		an OPT record to be returned. There should be no EDNS
	flags present in the response. The EDNS version field		flags present in the response. The EDNS version field
	should be 0 in the response as no other EDNS version		should be 0 in the response, as no other EDNS version
	has as yet been specified <xref target="RFC6891"/>.		has as yet been specified <xref target="RFC6891" format="default"/>.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that EDNS version 1 queries work (EDNS supported):		Check that EDNS version 1 queries work (EDNS supported):
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +nocookie +edns=1 +noednsneg +noad +norec soa $zone @$server		dig +nocookie +edns=1 +noednsneg +noad +norec soa $zone @$server
	expect: status: BADVERS		expect: status: BADVERS
	expect: the SOA record to NOT be present in the answer section		expect: the SOA record to NOT be present in the answer section
	expect: an OPT record to be present in the additional section		expect: an OPT record to be present in the additional section
	expect: EDNS Version 0 in response		expect: EDNS Version 0 in response
	expect: flag: aa to NOT be present		expect: flag: aa to NOT be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	</artwork>		]]></sourcecode>
	<postamble>		<t keepWithPrevious="true">
	+noednsneg has been set as dig supports EDNS version		+noednsneg has been set, as dig supports EDNS version
	negotiation and we want to see only the response to the		negotiation, and we want to see only the response to the
	initial EDNS version 1 query.		initial EDNS version 1 query.
	</postamble>
	</figure>
	</t>		</t>
	</section>		</section>
	<section title="Testing Unknown EDNS Options">		<section numbered="true" toc="default">
			<name>Testing Unknown EDNS Options</name>
	<t>		<t>
	Ask for the SOA record of the configured zone. This		Ask for the SOA record of the configured zone. This
	query is made with no DNS flag bits set. EDNS version		query is made with no DNS flag bits set. EDNS version
	0 is used without any EDNS flags. An EDNS option is		0 is used without any EDNS flags. An EDNS option is
	present with a value that has not yet been assigned by		present with a value that has not yet been assigned by
	IANA. We have picked an unassigned code of 100 for		IANA. We have picked an unassigned code of 100 for
	the example below. Any unassigned EDNS option code		the example below. Any unassigned EDNS option code
	could have been choosen for this test.		could have been chosen for this test.
	</t>		</t>
	<t>		<t>
	We expect the SOA record for the zone to be returned		We expect the SOA record for the zone to be returned
	in the answer section, the rcode to be set to NOERROR, and		in the answer section, the rcode to be set to NOERROR, and
	the AA and QR bits to be set in the header; RA may		the AA and QR bits to be set in the header; RA may
	also be set <xref target="RFC1034"/>. We expect		also be set <xref target="RFC1034" format="default"/>. We expect
	an OPT record to be returned. There should be no EDNS		an OPT record to be returned. There should be no EDNS
	flags present in the response. The EDNS version field		flags present in the response. The EDNS version field
	should be 0 as EDNS versions other than 0 are yet to		should be 0, as EDNS versions other than 0 are yet to
	be specified and there should be no EDNS options present		be specified, and there should be no EDNS options present,
	as unknown EDNS options are supposed to be ignored by the		as unknown EDNS options are supposed to be ignored by the
	server <xref target="RFC6891"/> Section 6.1.2.		server (<xref target="RFC6891" sectionFormat="of" section="6.1.1"/>) .
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that EDNS queries with an unknown option work (EDNS suppor ted):		Check that EDNS queries with an unknown option work (EDNS suppor ted):
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +nocookie +edns=0 +noad +norec +ednsopt=100 soa $zone @$server		dig +nocookie +edns=0 +noad +norec +ednsopt=100 soa $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: the SOA record to be present in the answer section		expect: the SOA record to be present in the answer section
	expect: an OPT record to be present in the additional section		expect: an OPT record to be present in the additional section
	expect: OPT=100 to NOT be present		expect: OPT=100 to NOT be present
	expect: EDNS Version 0 in response		expect: EDNS Version 0 in response
	expect: flag: aa to be present		expect: flag: aa to be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	<section title="Testing Unknown EDNS Flags">		<section numbered="true" toc="default">
			<name>Testing Unknown EDNS Flags</name>
	<t>		<t>
	Ask for the SOA record of the configured zone. This		Ask for the SOA record of the configured zone. This
	query is made with no DNS flag bits set. EDNS version		query is made with no DNS flag bits set. EDNS version
	0 is used without any EDNS options. An unassigned EDNS		0 is used without any EDNS options. An unassigned EDNS
	flag bit is set (0x40 in this case).		flag bit is set (0x40 in this case).
	</t>		</t>
	<t>		<t>
	We expect the SOA record for the zone to be returned		We expect the SOA record for the zone to be returned
	in the answer section, the rcode to be set to NOERROR, and		in the answer section, the rcode to be set to NOERROR, and
	the AA and QR bits to be set in the header; RA may		the AA and QR bits to be set in the header; RA may
	also be set <xref target="RFC1034"/>. We expect		also be set <xref target="RFC1034" format="default"/>. We expect
	an OPT record to be returned. There should be no EDNS		an OPT record to be returned. There should be no EDNS
	flags present in the response as unknown EDNS flags are		flags present in the response, as unknown EDNS flags are
	supposed to be ignored. The EDNS version field		supposed to be ignored. The EDNS version field
	should be 0 and there should be no EDNS options present		should be 0, and there should be no EDNS options present
	<xref target="RFC6891"/>.		<xref target="RFC6891" format="default"/>.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that EDNS queries with unknown flags work (EDNS supported) :		Check that EDNS queries with unknown flags work (EDNS supported) :
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +nocookie +edns=0 +noad +norec +ednsflags=0x40 soa $zone @$server		dig +nocookie +edns=0 +noad +norec +ednsflags=0x40 soa $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: the SOA record to be present in the answer section		expect: the SOA record to be present in the answer section
	expect: an OPT record to be present in the additional section		expect: an OPT record to be present in the additional section
	expect: MBZ not to be present		expect: MBZ not to be present
	expect: EDNS Version 0 in response		expect: EDNS Version 0 in response
	expect: flag: aa to be present		expect: flag: aa to be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	</artwork>		]]></sourcecode>
	<postamble>		<t keepWithPrevious="true">
	MBZ (Must Be Zero) is a dig-specific indication that		MBZ (Must Be Zero) is a dig-specific indication that
	a flag bit has been incorrectly copied as per		a flag bit has been incorrectly copied, as per
	Section 6.1.4, <xref target="RFC6891"/>.		<xref target="RFC6891" sectionFormat="of" section="6.1.4"/>.
	</postamble>
	</figure>
	</t>		</t>
	</section>		</section>
	<section title="Testing EDNS Version Negotiation With Unknown EDNS Flags		<section numbered="true" toc="default">
	">		<name>Testing EDNS Version Negotiation with Unknown EDNS Flags</name>
	<t>		<t>
	Ask for the SOA record of the configured zone. This		Ask for the SOA record of the configured zone. This
	query is made with no DNS flag bits set. EDNS version		query is made with no DNS flag bits set. EDNS version
	1 is used without any EDNS options. An unassigned EDNS		1 is used without any EDNS options. An unassigned EDNS
	flag bit is set (0x40 in this case).		flag bit is set (0x40 in this case).
	</t>		</t>
	<t>		<t>
	We expect the SOA record for the zone to NOT be returned		We expect the SOA record for the zone to NOT be returned
	in the answer section with the extended rcode set to		in the answer section with the extended rcode set to
	BADVERS and the QR bit to be set in the header; RA		BADVERS and the QR bit to be set in the header; RA
	may also be set <xref target="RFC1034"/>. We expect		may also be set <xref target="RFC1034" format="default"/>. We expec t
	an OPT record to be returned. There should be no EDNS		an OPT record to be returned. There should be no EDNS
	flags present in the response as unknown EDNS flags are		flags present in the response, as unknown EDNS flags are
	supposed to be ignored. The EDNS version field should		supposed to be ignored. The EDNS version field should
	be 0 as EDNS versions other than 0 are yet to be		be 0, as EDNS versions other than 0 are yet to be
	specified and there should be no EDNS options present		specified, and there should be no EDNS options present
	<xref target="RFC6891"/>.		<xref target="RFC6891" format="default"/>.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that EDNS version 1 queries with unknown flags work (EDNS supported):		Check that EDNS version 1 queries with unknown flags work (EDNS supported):
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +nocookie +edns=1 +noednsneg +noad +norec +ednsflags=0x40 soa \		dig +nocookie +edns=1 +noednsneg +noad +norec +ednsflags=0x40 soa \
	$zone @$server		$zone @$server
	expect: status: BADVERS		expect: status: BADVERS
	expect: SOA record to NOT be present		expect: SOA record to NOT be present
	expect: an OPT record to be present in the additional section		expect: an OPT record to be present in the additional section
	expect: MBZ not to be present		expect: MBZ not to be present
	expect: EDNS Version 0 in response		expect: EDNS Version 0 in response
	expect: flag: aa to NOT be present		expect: flag: aa to NOT be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	<section title="Testing EDNS Version Negotiation With Unknown EDNS Optio		<section numbered="true" toc="default">
	ns">		<name>Testing EDNS Version Negotiation with Unknown EDNS Options</name
			>
	<t>		<t>
	Ask for the SOA record of the configured zone. This		Ask for the SOA record of the configured zone. This
	query is made with no DNS flag bits set. EDNS version		query is made with no DNS flag bits set. EDNS version
	1 is used. An unknown EDNS option is present. We have		1 is used. An unknown EDNS option is present. We have
	picked an unassigned code of 100 for the example below.		picked an unassigned code of 100 for the example below.
	Any unassigned EDNS option code could have been chosen for		Any unassigned EDNS option code could have been chosen for
	this test.		this test.
	</t>		</t>
	<t>		<t>
	We expect the SOA record for the zone to NOT be returned		We expect the SOA record for the zone to NOT be returned
	in the answer section with the extended rcode set to		in the answer section with the extended rcode set to
	BADVERS and the QR bit to be set in the header; RA		BADVERS and the QR bit to be set in the header; RA
	may also be set <xref target="RFC1034"/>. We expect		may also be set <xref target="RFC1034" format="default"/>. We expec t
	an OPT record to be returned. There should be no EDNS		an OPT record to be returned. There should be no EDNS
	flags present in the response. The EDNS version field		flags present in the response. The EDNS version field
	should be 0 as EDNS versions other than 0 are yet		should be 0, as EDNS versions other than 0 are yet
	to be specified and there should be no EDNS options		to be specified, and there should be no EDNS options
	present <xref target="RFC6891"/>.		present <xref target="RFC6891" format="default"/>.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that EDNS version 1 queries with unknown options work (EDN S supported):		Check that EDNS version 1 queries with unknown options work (EDN S supported):
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +nocookie +edns=1 +noednsneg +noad +norec +ednsopt=100 soa \		dig +nocookie +edns=1 +noednsneg +noad +norec +ednsopt=100 soa \
	$zone @$server		$zone @$server
	expect: status: BADVERS		expect: status: BADVERS
	expect: SOA record to NOT be present		expect: SOA record to NOT be present
	expect: an OPT record to be present in the additional section		expect: an OPT record to be present in the additional section
	expect: OPT=100 to NOT be present		expect: OPT=100 to NOT be present
	expect: EDNS Version 0 in response		expect: EDNS Version 0 in response
	expect: flag: aa to NOT be present		expect: flag: aa to NOT be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	<section title="Testing Truncated Responses">		<section numbered="true" toc="default">
			<name>Testing Truncated Responses</name>
	<t>		<t>
	Ask for the DNSKEY records of the configured zone, which		Ask for the DNSKEY records of the configured zone, which
	must be a DNSSEC signed zone. This query is made with		must be a DNSSEC signed zone. This query is made with
	no DNS flag bits set. EDNS version 0 is used without		no DNS flag bits set. EDNS version 0 is used without
	any EDNS options. The only EDNS flag set is DO. The		any EDNS options. The only EDNS flag set is DO. The
	EDNS UDP buffer size is set to 512. The intention of		EDNS UDP buffer size is set to 512. The intention of
	this query is to elicit a truncated response from the		this query is to elicit a truncated response from the
	server. Most signed DNSKEY responses are bigger than		server. Most signed DNSKEY responses are bigger than
	512 bytes. This test will not give a valid result if		512 bytes. This test will not give a valid result if
	the zone is not signed.		the zone is not signed.
	</t>		</t>
			<t>We expect a response, the rcode to be set to NOERROR, and the AA
			and QR bits to be set. AD may be set in the response if the server
			supports DNSSEC; otherwise it should be clear; TC and RA may also be
			set <xref target="RFC1035" format="default"/> <xref target="RFC4035"
			format="default"/>. We expect an OPT record to be present in the
			response. There should be no EDNS flags other than DO present in
			the response. The EDNS version field should be 0, and there should
			be no EDNS options present <xref target="RFC6891"
			format="default"/>.</t>
	<t>		<t>
	We expect a response, the rcode to be set to NOERROR, and		If TC is not set, it is not possible to confirm that the
	the AA and QR bits to be set, AD may be set in the
	response if the server supports DNSSEC otherwise it
	should be clear; TC and RA may also be set <xref
	target="RFC1035"/> <xref target="RFC4035"/>. We expect
	an OPT record to be present in the response. There
	should be no EDNS flags other than DO present in the
	response. The EDNS version field should be 0 and
	there should be no EDNS options present <xref
	target="RFC6891"/>.
	</t>
	<t>
	If TC is not set it is not possible to confirm that the
	server correctly adds the OPT record to the truncated		server correctly adds the OPT record to the truncated
	responses or not.		responses or not.
	</t>		</t>
	<t>		<sourcecode name="" type=""><![CDATA[
	<figure>
	<artwork>
	dig +norec +dnssec +bufsize=512 +ignore dnskey $zone @$server		dig +norec +dnssec +bufsize=512 +ignore dnskey $zone @$server
	expect: NOERROR		expect: NOERROR
	expect: OPT record with version set to 0		expect: OPT record with version set to 0
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	<section title="Testing DO=1 Handling">		<section numbered="true" toc="default">
			<name>Testing DO=1 Handling</name>
	<t>		<t>
	Ask for the SOA record of the configured zone, which		Ask for the SOA record of the configured zone, which
	does not need to be DNSSEC signed. This query is made		does not need to be DNSSEC signed. This query is made
	with no DNS flag bits set. EDNS version 0 is used		with no DNS flag bits set. EDNS version 0 is used
	without any EDNS options. The only EDNS flag set is		without any EDNS options. The only EDNS flag set is
	DO.		DO.
	</t>		</t>
	<t>		<t>We expect the SOA record for the zone to be returned in the
	We expect the SOA record for the zone to be returned		answer section, the rcode to be set to NOERROR, and the AA and QR
	in the answer section, the rcode to be set to NOERROR, and		bits to be set in the response. AD may be set in the response if the
	the AA and QR bits to be set in the response, AD may		server supports DNSSEC, otherwise it should be clear; RA may also be
	be set in the response if the server supports DNSSEC		set <xref target="RFC1034" format="default"/>. We expect an OPT
	otherwise it should be clear; RA may also be set <xref		record to be returned. There should be no EDNS flags other than DO
	target="RFC1034"/>. We expect an OPT record to be		present in the response, which should be present if the server
	returned. There should be no EDNS flags other than DO		supports DNSSEC. The EDNS version field should be 0, and there
	present in the response which should be present if the		should be no EDNS options present <xref target="RFC6891"
	server supports DNSSEC. The EDNS version field should		format="default"/>.</t>
	be 0 and there should be no EDNS options present		<t keepWithNext="true">
	<xref target="RFC6891"/>.
	</t>
	<t>
	<figure>
	<preamble>
	Check that DO=1 queries work (EDNS supported):		Check that DO=1 queries work (EDNS supported):
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +nocookie +edns=0 +noad +norec +dnssec soa $zone @$server		dig +nocookie +edns=0 +noad +norec +dnssec soa $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: the SOA record to be present in the answer section		expect: the SOA record to be present in the answer section
	expect: an OPT record to be present in the additional section		expect: an OPT record to be present in the additional section
	expect: DO=1 to be present if an RRSIG is in the response		expect: DO=1 to be present if an RRSIG is in the response
	expect: EDNS Version 0 in response		expect: EDNS Version 0 in response
	expect: flag: aa to be present		expect: flag: aa to be present
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	<section title="Testing EDNS Version Negotiation With DO=1">		<section numbered="true" toc="default">
			<name>Testing EDNS Version Negotiation with DO=1</name>
	<t>		<t>
	Ask for the SOA record of the configured zone, which does		Ask for the SOA record of the configured zone, which does
	not need to be DNSSEC signed. This query is made with no		not need to be DNSSEC signed. This query is made with no
	DNS flag bits set. EDNS version 1 is used without any EDNS		DNS flag bits set. EDNS version 1 is used without any EDNS
	options. The only EDNS flag set is DO.		options. The only EDNS flag set is DO.
	</t>		</t>
	<t>		<t>We expect the SOA record for the zone NOT to be returned in the ans
	We expect the SOA record for the zone to NOT be returned		wer
	in the answer section, the rcode to be set to NOERROR, ;		section, the extended rcode to be set to BADVERS, and the QR bit to be set in
	the QR bit and possibly the RA bit to be set <xref		the header; RA may also be set <xref target="RFC1034"
	target="RFC1034"/>. We expect an OPT record to		format="default"/>.
	be returned. There should be no EDNS flags other than
	DO present in the response which should be there if		We expect an OPT record to be returned. There
	the server supports DNSSEC. The EDNS version field		should be no EDNS flags other than DO present in the response, which
	should be 0 and there should be no EDNS options		should be there if the server supports DNSSEC. The EDNS version
	present <xref target="RFC6891"/>.		field should be 0, and there should be no EDNS options present <xref
	</t>		target="RFC6891" format="default"/>.</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that EDNS version 1, DO=1 queries work (EDNS supported):		Check that EDNS version 1, DO=1 queries work (EDNS supported):
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +nocookie +edns=1 +noednsneg +noad +norec +dnssec soa \		dig +nocookie +edns=1 +noednsneg +noad +norec +dnssec soa \
	$zone @$server		$zone @$server
	expect: status: BADVERS		expect: status: BADVERS
	expect: SOA record to NOT be present		expect: SOA record to NOT be present
	expect: an OPT record to be present in the additional section		expect: an OPT record to be present in the additional section
	expect: DO=1 to be present if the EDNS version 0 DNSSEC query test		expect: DO=1 to be present if the EDNS version 0 DNSSEC query test
	returned DO=1		returned DO=1
	expect: EDNS Version 0 in response		expect: EDNS Version 0 in response
	expect: flag: aa to NOT be present		expect: flag: aa to NOT be present
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	<section title="Testing With Multiple Defined EDNS Options">		<section numbered="true" toc="default">
	<t>		<name>Testing with Multiple Defined EDNS Options</name>
	Ask for the SOA record of the configured zone. This		<t>Ask for the SOA record of the configured zone. This query is
	query is made with no DNS flag bits set. EDNS version		made with no DNS flag bits set. EDNS version 0 is used. A number
	0 is used. A number of defined EDNS options are present		of defined EDNS options are present (NSID <xref target="RFC5001"
	(NSID <xref target="RFC5001"/>, DNS COOKIE <xref		format="default"/>, DNS COOKIE <xref target="RFC7873"
	target="RFC7873"/>, EDNS Client Subnet <xref		format="default"/>, EDNS Client Subnet <xref target="RFC7871"
	target="RFC7871"/> and EDNS Expire <xref target="RFC7314"/>).		format="default"/>, and EDNS Expire <xref target="RFC7314"
	</t>		format="default"/>).</t>
	<t>		<t>
	We expect the SOA record for the zone to be returned		We expect the SOA record for the zone to be returned
	in the answer section, the rcode to be set to NOERROR, and		in the answer section, the rcode to be set to NOERROR, and
	the AA and QR bits to be set in the header; RA may		the AA and QR bits to be set in the header; RA may
	also be set <xref target="RFC1034"/>. We expect an OPT		also be set <xref target="RFC1034" format="default"/>. We expect an OPT
	record to be returned. There should be no EDNS flags		record to be returned. There should be no EDNS flags
	present in the response. The EDNS version field should		present in the response. The EDNS version field should
	be 0. Any of the requested EDNS options supported		be 0. Any of the requested EDNS options supported
	by the server and permitted server configuration may		by the server and permitted server configuration may
	be returned <xref target="RFC6891"/>.		be returned <xref target="RFC6891" format="default"/>.
	</t>		</t>
	<t>		<t keepWithNext="true">
	<figure>
	<preamble>
	Check that EDNS queries with multiple defined EDNS options work:		Check that EDNS queries with multiple defined EDNS options work:
	</preamble>		</t>
	<artwork>		<sourcecode name="" type=""><![CDATA[
	dig +edns=0 +noad +norec +cookie +nsid +expire +subnet=0.0.0.0/0 \		dig +edns=0 +noad +norec +cookie +nsid +expire +subnet=0.0.0.0/0 \
	soa $zone @$server		soa $zone @$server
	expect: status: NOERROR		expect: status: NOERROR
	expect: the SOA record to be present in the answer section		expect: the SOA record to be present in the answer section
	expect: an OPT record to be present in the additional section		expect: an OPT record to be present in the additional section
	expect: EDNS Version 0 in response		expect: EDNS Version 0 in response
	expect: flag: aa to be present		expect: flag: aa to be present
	expect: flag: ad to NOT be present		expect: flag: ad to NOT be present
	</artwork>		]]></sourcecode>
	</figure>
	</t>
	</section>		</section>
	</section>		</section>
	<section title="When EDNS Is Not Supported">		<section numbered="true" toc="default">
			<name>When EDNS Is Not Supported</name>
	<t>		<t>
	If EDNS is not supported by the nameserver, we expect a		If EDNS is not supported by the nameserver, we expect a
	response to each of the above queries. That response may		response to each of the above queries. That response may
	be a FORMERR error response or the OPT record may just		be a FORMERR error response, or the OPT record may just
	be ignored.		be ignored.
	</t>		</t>
	<t>		<t>
	Some nameservers only return a EDNS response when a		Some nameservers only return an EDNS response when a
	particular EDNS option or flag (e.g. DO=1) is present in		particular EDNS option or flag (e.g., DO=1) is present in
	the request. This behaviour is not compliant behaviour		the request. This behaviour is not compliant behaviour
	and may hide other incorrect behaviour from the above		and may hide other incorrect behaviour from the above
	tests. Re-testing with the triggering option / flag		tests. Retesting with the triggering option/flag
	present will expose this misbehaviour.		present will expose this misbehaviour.
	</t>		</t>
	</section>		</section>
	</section>		</section>
	<section anchor="remediation" title="Remediation">		<section anchor="remediation" numbered="true" toc="default">
			<name>Remediation</name>
	<t>		<t>
	Nameserver operators are generally expected to test their		Nameserver operators are generally expected to test their
	own infrastructure for compliance to standards. The above		own infrastructure for compliance to standards. The above
	tests should be run when new systems are brought online,		tests should be run when new systems are brought online
	and should be repeated periodically to ensure continued		and should be repeated periodically to ensure continued
	interoperability.		interoperability.
	</t>		</t>
	<t>		<t>
	Domain registrants who do not maintain their own DNS		Domain registrants who do not maintain their own DNS
	infrastructure are entitled to a DNS service that conforms		infrastructure are entitled to a DNS service that conforms
	to standards and interoperates well. Registrants who become		to standards and interoperates well. Registrants who become
	aware that their DNS operator does not have a well maintained		aware that their DNS operator does not have a well-maintained
	or compliant infrastructure should insist that their service		or compliant infrastructure should insist that their service
	provider correct issues, and switch providers if they do		provider correct issues and switch providers if they do
	not.		not.
	</t>		</t>
	<t>		<t>
	In the event that an operator experiences problems due to		In the event that an operator experiences problems due to
	the behaviour of nameservers outside their control, the		the behaviour of nameservers outside their control, the
	above tests will help in narrowing down the precise issue(s)		above tests will help in narrowing down the precise issue(s),
	which can then be reported to the relevant party.		which can then be reported to the relevant party.
	</t>		</t>
	<t>		<t>
	If contact information for the operator of a misbehaving		If contact information for the operator of a misbehaving
	nameserver is not already known, the following methods of		nameserver is not already known, the following methods of
	communication could be considered:		communication could be considered:
	<list style="symbols">		</t>
	<t>		<ul spacing="normal">
			<li>
	the RNAME of the zone authoritative for the name of the		the RNAME of the zone authoritative for the name of the
	misbehaving server		misbehaving server
	</t>		</li>
			<li>
	<t>
	the RNAME of zones for which the offending server is		the RNAME of zones for which the offending server is
	authoritative		authoritative
	</t>		</li>
			<li>
	<t>
	administrative or technical contacts listed in the		administrative or technical contacts listed in the
	registration information for the parent domain of the		registration information for the parent domain of the
	name of the misbehaving server, or for zones for which		name of the misbehaving server or for zones for which
	the nameserver is authoritative		the nameserver is authoritative
	</t>		</li>
			<li>
	<t>
	the registrar or registry for such zones		the registrar or registry for such zones
	</t>		</li>
			<li>
	<t>		DNS-specific, operational fora (e.g., mailing lists)
	DNS-specific operational fora (e.g. mailing lists)		</li>
	</t>		</ul>
	</list>
	</t>
	<t>		<t>
	Operators of parent zones may wish to regularly test the		Operators of parent zones may wish to regularly test the
	authoritative nameservers of their child zones.   However,		authoritative nameservers of their child zones. However,
	parent operators can have widely varying capabilities in		parent operators can have widely varying capabilities in
	terms of notification or remediation depending on whether		terms of notification or remediation depending on whether
	they have a direct relationship with the child operator.		they have a direct relationship with the child operator.
	Many TLD registries, for example, cannot directly contact		Many Top-Level Domain (TLD) registries, for example, cannot directly con
			tact
	their registrants and may instead need to communicate through		their registrants and may instead need to communicate through
	the relevant registrar.   In such cases it may be most		the relevant registrar. In such cases, it may be most
	efficient for registrars to take on the responsibility for		efficient for registrars to take on the responsibility for
	testing the name ervers of their registrants, since they		testing the nameservers of their registrants, since they
	have a direct relationship.		have a direct relationship.
	</t>		</t>
	<t>		<t>
	When notification is not effective at correcting problems		When notification is not effective at correcting problems
	with a misbehaving nameserver, parent operators can choose		with a misbehaving nameserver, parent operators can choose
	to remove NS record sets (and glue records below) that refer		to remove NS record sets (and glue records below) that refer
	to the faulty server until the servers are fixed. This should		to the faulty server until the servers are fixed. This should
	only be done as a last resort and with due consideration, as		only be done as a last resort and with due consideration, as
	removal of a delegation can have unanticipated side effects.		removal of a delegation can have unanticipated side effects.
	For example, other parts of the DNS tree may depend on names		For example, other parts of the DNS tree may depend on names
	below the removed zone cut, and the parent operator may find		below the removed zone cut, and the parent operator may find
	themselves responsible for causing new DNS failures to occur.		themselves responsible for causing new DNS failures to occur.
	skipping to change at line 1404 ¶		skipping to change at line 1346 ¶
	When notification is not effective at correcting problems		When notification is not effective at correcting problems
	with a misbehaving nameserver, parent operators can choose		with a misbehaving nameserver, parent operators can choose
	to remove NS record sets (and glue records below) that refer		to remove NS record sets (and glue records below) that refer
	to the faulty server until the servers are fixed. This should		to the faulty server until the servers are fixed. This should
	only be done as a last resort and with due consideration, as		only be done as a last resort and with due consideration, as
	removal of a delegation can have unanticipated side effects.		removal of a delegation can have unanticipated side effects.
	For example, other parts of the DNS tree may depend on names		For example, other parts of the DNS tree may depend on names
	below the removed zone cut, and the parent operator may find		below the removed zone cut, and the parent operator may find
	themselves responsible for causing new DNS failures to occur.		themselves responsible for causing new DNS failures to occur.
	</t>		</t>
	</section>		</section>
			<section anchor="seccon" numbered="true" toc="default">
	<section anchor="seccon" title="Security Considerations">		<name>Security Considerations</name>
	<t>		<t>
	Testing protocol compliance can potentially result in false		Testing protocol compliance can potentially result in false
	reports of attempts to attack services from Intrusion Detection		reports of attempts to attack services from Intrusion Detection
	Services and firewalls. All of the tests are well-formed		Services and firewalls. All of the tests are well-formed
	(though not necessarily common) DNS queries. None of the tests		(though not necessarily common) DNS queries. None of the tests
	listed above should cause any harm to a protocol-compliant		listed above should cause any harm to a protocol-compliant
	server.		server.
	</t>		</t>
	<t>		<t>
	Relaxing firewall settings to ensure EDNS compliance could		Relaxing firewall settings to ensure EDNS compliance could
	potentially expose a critical implementation flaw in the		potentially expose a critical implementation flaw in the
	nameserver. Nameservers should be tested for conformance		nameserver. Nameservers should be tested for conformance
	before relaxing firewall settings.		before relaxing firewall settings.
	</t>		</t>
	<t>		<t>
	When removing delegations for non-compliant servers there		When removing delegations for non-compliant servers, there
	can be a knock on effect on other zones that require these		can be a knock-on effect on other zones that require these
	zones to be operational for the nameservers addresses to be		zones to be operational for the nameservers addresses to be
	resolved.		resolved.
	</t>		</t>
	</section>		</section>
	<section anchor="iana" title="IANA Considerations">		<section anchor="iana" numbered="true" toc="default">
	<t>		<name>IANA Considerations</name>
	There are no actions for IANA.		<t>This document has no IANA actions.</t>
	</t>
	</section>
	<section title="Acknowledgements">
	<t>
	The contributions of the following are gratefully acknowledged:
	</t>
	<t>
	Matthew Pounsett, Tim Wicinski.
	</t>
	</section>		</section>
	</middle>		</middle>
	<back>		<back>
	<references title="Normative References">		<references>
	&rfc1034; &rfc1035; &rfc3225; &rfc4035;		<name>References</name>
	&rfc6840; &rfc6895; &rfc6891; &rfc7766;		<references>
	</references>		<name>Normative References</name>
	<references title="Informative References">		<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
	&rfc2671; &rfc3597;		ence.RFC.1034.xml"/>
	&rfc5001; &rfc7314; &rfc7871; &rfc7873;		<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
	<reference anchor="ISC" target="https://www.isc.org/">		ence.RFC.1035.xml"/>
	<front>		<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
	<title>Internet Systems Consortuim</title>		ence.RFC.3225.xml"/>
	<author/>		<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
	<date/>		ence.RFC.4035.xml"/>
	</front>		<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
	</reference>		ence.RFC.6840.xml"/>
			<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
			ence.RFC.6895.xml"/>
			<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
			ence.RFC.6891.xml"/>
			<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
			ence.RFC.7766.xml"/>
			</references>
			<references>
			<name>Informative References</name>
			<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
			ence.RFC.2671.xml"/>
			<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
			ence.RFC.3597.xml"/>
			<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
			ence.RFC.5001.xml"/>
			<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
			ence.RFC.7314.xml"/>
			<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
			ence.RFC.7871.xml"/>
			<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer
			ence.RFC.7873.xml"/>
			<reference anchor="ISC" target="https://www.isc.org/">
			<front>
			<title>Internet Systems Consortuim</title>
			<author/>
			<date/>
			</front>
			</reference>
			<reference anchor="IANA-DNS"
			target="https://www.iana.org/assignments/dns-parameters/">
			<front>
			<title>Domain Name System (DNS) Parameters</title>
			<author><organization>IANA</organization></author>
			</front>
			</reference>
			</references>
	</references>		</references>
			<section numbered="false" toc="default">
			<name>Acknowledgements</name>
			<t>The contributions of <contact fullname="Matthew Pounsett"/> and
			<contact fullname="Tim Wicinski"/> are gratefully acknowledged.</t>
			</section>
	</back>		</back>
	</rfc>		</rfc>
End of changes. 240 change blocks.
	557 lines changed or deleted		535 lines changed or added
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