draft-ietf-dnsop-no-response-issue-23.txt		rfc8906.txt
	Network Working Group M. Andrews		Internet Engineering Task Force (IETF) M. Andrews
	Internet-Draft R. Bellis		Request for Comments: 8906 R. Bellis
	Intended status: Best Current Practice ISC		BCP: 231 ISC
	Expires: October 18, 2020 April 16, 2020		Category: Best Current Practice September 2020
			ISSN: 2070-1721
	A Common Operational Problem in DNS Servers - Failure To Communicate		A Common Operational Problem in DNS Servers: Failure to Communicate
	draft-ietf-dnsop-no-response-issue-23
	Abstract		Abstract
	The DNS is a query / response protocol. Failing to respond to		The DNS is a query/response protocol. Failing to respond to queries,
	queries, or responding incorrectly, causes both immediate operational		or responding incorrectly, causes both immediate operational problems
	problems and long term problems with protocol development.		and long-term problems with protocol development.
	This document identifies a number of common kinds of queries to which		This document identifies a number of common kinds of queries to which
	some servers either fail to respond or else respond incorrectly.		some servers either fail to respond or respond incorrectly. This
	This document also suggests procedures for zone operators to apply to		document also suggests procedures for zone operators to apply to
	identify and remediate the problem.		identify and remediate the problem.
	The document does not look at the DNS data itself, just the structure		The document does not look at the DNS data itself, just the structure
	of the responses.		of the responses.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This memo documents an Internet Best Current Practice.
	provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		This document is a product of the Internet Engineering Task Force
	and may be updated, replaced, or obsoleted by other documents at any		(IETF). It represents the consensus of the IETF community. It has
	time. It is inappropriate to use Internet-Drafts as reference		received public review and has been approved for publication by the
	material or to cite them other than as "work in progress."		Internet Engineering Steering Group (IESG). Further information on
			BCPs is available in Section 2 of RFC 7841.
	This Internet-Draft will expire on October 18, 2020.		Information about the current status of this document, any errata,
			and how to provide feedback on it may be obtained at
			https://www.rfc-editor.org/info/rfc8906.
	Copyright Notice		Copyright Notice
	Copyright (c) 2020 IETF Trust and the persons identified as the		Copyright (c) 2020 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction
	2. Consequences . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Consequences
	3. Common kinds of queries that result in no or bad responses. . 5		3. Common Kinds of Queries That Result in No or Bad Responses
	3.1. Basic DNS Queries . . . . . . . . . . . . . . . . . . . . 5		3.1. Basic DNS Queries
	3.1.1. Zone Existence . . . . . . . . . . . . . . . . . . . 5		3.1.1. Zone Existence
	3.1.2. Unknown / Unsupported Type Queries . . . . . . . . . 5		3.1.2. Unknown/Unsupported Type Queries
	3.1.3. DNS Flags . . . . . . . . . . . . . . . . . . . . . . 6		3.1.3. DNS Flags
	3.1.4. Unknown DNS opcodes . . . . . . . . . . . . . . . . . 6		3.1.4. Unknown DNS Opcodes
	3.1.5. TCP Queries . . . . . . . . . . . . . . . . . . . . . 6		3.1.5. TCP Queries
	3.2. EDNS Queries . . . . . . . . . . . . . . . . . . . . . . 6		3.2. EDNS Queries
	3.2.1. EDNS Queries - Version Independent . . . . . . . . . 7		3.2.1. EDNS Queries: Version Independent
	3.2.2. EDNS Queries - Version Specific . . . . . . . . . . . 7		3.2.2. EDNS Queries: Version Specific
	3.2.3. EDNS Options . . . . . . . . . . . . . . . . . . . . 7		3.2.3. EDNS Options
	3.2.4. EDNS Flags . . . . . . . . . . . . . . . . . . . . . 7		3.2.4. EDNS Flags
	3.2.5. Truncated EDNS Responses . . . . . . . . . . . . . . 8		3.2.5. Truncated EDNS Responses
	3.2.6. DO=1 Handling . . . . . . . . . . . . . . . . . . . . 8		3.2.6. DO=1 Handling
	3.2.7. EDNS over TCP . . . . . . . . . . . . . . . . . . . . 8		3.2.7. EDNS over TCP
	4. Firewalls and Load Balancers . . . . . . . . . . . . . . . . 8		4. Firewalls and Load Balancers
	5. Packet Scrubbing Services . . . . . . . . . . . . . . . . . . 9		5. Packet Scrubbing Services
	6. Whole Answer Caches . . . . . . . . . . . . . . . . . . . . . 10		6. Whole Answer Caches
	7. Response Code Selection . . . . . . . . . . . . . . . . . . . 10		7. Response Code Selection
	8. Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . 11		8. Testing
	8.1. Testing - Basic DNS . . . . . . . . . . . . . . . . . . . 12		8.1. Testing: Basic DNS
	8.1.1. Is The Server Configured For The Zone? . . . . . . . 12		8.1.1. Is the server configured for the zone?
	8.1.2. Testing Unknown Types . . . . . . . . . . . . . . . . 12		8.1.2. Testing Unknown Types
	8.1.3. Testing Header Bits . . . . . . . . . . . . . . . . . 13		8.1.3. Testing Header Bits
	8.1.4. Testing Unknown Opcodes . . . . . . . . . . . . . . . 15		8.1.4. Testing Unknown Opcodes
	8.1.5. Testing TCP . . . . . . . . . . . . . . . . . . . . . 15		8.1.5. Testing TCP
	8.2. Testing - Extended DNS . . . . . . . . . . . . . . . . . 16		8.2. Testing: Extended DNS
	8.2.1. Testing Minimal EDNS . . . . . . . . . . . . . . . . 16		8.2.1. Testing Minimal EDNS
	8.2.2. Testing EDNS Version Negotiation . . . . . . . . . . 17		8.2.2. Testing EDNS Version Negotiation
	8.2.3. Testing Unknown EDNS Options . . . . . . . . . . . . 17		8.2.3. Testing Unknown EDNS Options
	8.2.4. Testing Unknown EDNS Flags . . . . . . . . . . . . . 18		8.2.4. Testing Unknown EDNS Flags
	8.2.5. Testing EDNS Version Negotiation With Unknown EDNS		8.2.5. Testing EDNS Version Negotiation with Unknown EDNS
	Flags . . . . . . . . . . . . . . . . . . . . . . . . 19		Flags
	8.2.6. Testing EDNS Version Negotiation With Unknown EDNS		8.2.6. Testing EDNS Version Negotiation with Unknown EDNS
	Options . . . . . . . . . . . . . . . . . . . . . . . 20		Options
	8.2.7. Testing Truncated Responses . . . . . . . . . . . . . 20		8.2.7. Testing Truncated Responses
	8.2.8. Testing DO=1 Handling . . . . . . . . . . . . . . . . 21		8.2.8. Testing DO=1 Handling
	8.2.9. Testing EDNS Version Negotiation With DO=1 . . . . . 21		8.2.9. Testing EDNS Version Negotiation with DO=1
	8.2.10. Testing With Multiple Defined EDNS Options . . . . . 22		8.2.10. Testing with Multiple Defined EDNS Options
	8.3. When EDNS Is Not Supported . . . . . . . . . . . . . . . 22		8.3. When EDNS Is Not Supported
	9. Remediation . . . . . . . . . . . . . . . . . . . . . . . . . 23		9. Remediation
	10. Security Considerations . . . . . . . . . . . . . . . . . . . 24		10. Security Considerations
	11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24		11. IANA Considerations
	12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24		12. References
	13. References . . . . . . . . . . . . . . . . . . . . . . . . . 24		12.1. Normative References
	13.1. Normative References . . . . . . . . . . . . . . . . . . 24		12.2. Informative References
	13.2. Informative References . . . . . . . . . . . . . . . . . 25		Acknowledgements
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26		Authors' Addresses
	1. Introduction		1. Introduction
	The DNS [RFC1034], [RFC1035] is a query / response protocol. Failing		The DNS [RFC1034] [RFC1035] is a query/response protocol. Failing to
	to respond to queries, or responding incorrectly, causes both		respond to queries or responding incorrectly causes both immediate
	immediate operational problems and long term problems with protocol		operational problems and long-term problems with protocol
	development.		development.
	Failure to respond to a query is indistinguishable from packet loss		Failure to respond to a query is indistinguishable from packet loss
	without doing an analysis of query-response patterns. Additionally		without doing an analysis of query-response patterns. Additionally,
	failure to respond results in unnecessary queries being made by DNS		failure to respond results in unnecessary queries being made by DNS
	clients, and introduces delays to the resolution process.		clients and introduces delays to the resolution process.
	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 [RFC6891] queries, packet		nameservers or middleboxes dropping Extension Mechanisms for DNS
	loss is sometimes misclassified as lack of EDNS support which can		(EDNS) [RFC6891] queries, packet loss is sometimes misclassified as
	lead to DNSSEC validation failures.		lack of EDNS support, which can lead to DNSSEC validation failures.
	The existence of servers which fail to respond to queries results in		The existence of servers that fail to respond to queries results in
	developers being hesitant to deploy new standards. Such servers need		developers being hesitant to deploy new standards. Such servers need
	to be identified and remediated.		to be identified and remediated.
	The DNS has response codes that cover almost any conceivable query		The DNS has response codes that cover almost any conceivable query
	response. A nameserver should be able to respond to any conceivable		response. A nameserver should be able to respond to any conceivable
	query using them. There should be no need to drop queries because a		query using them. There should be no need to drop queries because a
	nameserver does not understand them.		nameserver does not understand them.
	Unless a nameserver is under attack, it should respond to all DNS		Unless a nameserver is under attack, it should respond to all DNS
	requests directed to it. When a nameserver is under attack it may		requests directed to it. When a nameserver is under attack, it may
	wish to drop packets. A common attack is to use a nameserver as an		wish to drop packets. A common attack is to use a nameserver as an
	amplifier by sending spoofed packets. This is done because response		amplifier by sending spoofed packets. This is done because response
	packets are bigger than the queries and large amplification factors		packets are bigger than the queries and large amplification factors
	are available especially if EDNS is supported. Limiting the rate of		are available, especially if EDNS is supported. Limiting the rate of
	responses is reasonable when this is occurring and the client should		responses is reasonable when this is occurring, and the client should
	retry. This however only works if legitimate clients are not being		retry. However, this only works if legitimate clients are not being
	forced to guess whether EDNS queries are accepted or not. As long as		forced to guess whether or not EDNS queries are accepted. As long as
	there are still a pool of servers that don't respond to EDNS		there is still a pool of servers that don't respond to EDNS requests,
	requests, clients have no way to know if the lack of response is due		clients have no way to know if the lack of response is due to packet
	to packet loss, or EDNS packets not being supported, or rate limiting		loss, EDNS packets not being supported, or rate limiting due to the
	due to the server being under attack. Misclassification of server		server being under attack. Misclassification of server behaviour is
	behaviour is unavoidable when rate limiting is used until the		unavoidable when rate limiting is used until the population of
	population of servers which fail to respond to well-formed queries		servers that fail to respond to well-formed queries drops to near
	drops to near zero.		zero.
	Nameservers should respond to queries even if the queried name is not		Nameservers should respond to queries even if the queried name is not
	for any name the server is configured to answer for. Misconfigured		for any name the server is configured to answer for. Misconfigured
	nameservers are a common occurrence in the DNS and receiving queries		nameservers are a common occurrence in the DNS, and receiving queries
	for zones that the server is not configured for is not necessarily an		for zones that the server is not configured for is not necessarily an
	indication that the server is under attack. Parent zone operators		indication that the server is under attack. Parent zone operators
	are advised to regularly check that the delegating NS records are		are advised to regularly check that the delegating NS records are
	consistent with those of the delegated zone and to correct them when		consistent with those of the delegated zone and to correct them when
	they are not [RFC1034], Section 4.4.2, Paragraph 3. Doing this		they are not (Section 4.2.2 of [RFC1034], Paragraph 3). Doing this
	regularly should reduce the instances of broken delegations.		regularly should reduce the instances of broken delegations.
	This document does not try to identify all possible errors nor does		This document does not try to identify all possible errors nor does
	it supply an exhaustive list of tests.		it supply an exhaustive list of tests.
	2. Consequences		2. Consequences
	Failure to follow the relevant DNS RFCs has multiple adverse		Failure to follow the guidance in relevant DNS RFCs has multiple
	consequences. Some are caused directly by the non-compliant		adverse consequences. Some are caused directly by the non-compliant
	behaviour and others as a result of work-arounds forced on recursive		behaviour and others as a result of workarounds forced on recursive
	servers. Addressing known issues now will reduce future		servers. Addressing known issues now will reduce future
	interoperability issues as the DNS protocol continues to evolve and		interoperability issues as the DNS protocol continues to evolve and
	clients make use of newly-introduced DNS features. In particular the		clients make use of newly introduced DNS features. In particular,
	base DNS specification [RFC1034], [RFC1035] and the EDNS		the base DNS specification [RFC1034] [RFC1035] and the EDNS
	specification [RFC6891], when implemented, need to be followed.		specification [RFC6891], when implemented, need to be followed.
	Some examples of known consequences include:		Some examples of known consequences include the following:
	o The AD (Authenticated Data) bit in a response cannot be trusted to		* The AD (Authenticated Data) bit in a response cannot be trusted to
	mean anything as some servers incorrectly copy the flag bit from		mean anything, as some servers incorrectly copy the flag bit from
	the request to the response [RFC1035], [RFC4035]. The use of the		the request to the response [RFC1035] [RFC4035]. The use of the
	AD bit in requests is defined in [RFC6840].		AD bit in requests is defined in [RFC6840].
	o Widespread non-response to EDNS queries has led to recursive		* Widespread non-response to EDNS queries has led to recursive
	servers having to assume that EDNS is not supported and that		servers having to assume that EDNS is not supported and that
	fallback to plain DNS is required, potentially causing DNSSEC		fallback to plain DNS is required, potentially causing DNSSEC
	validation failures.		validation failures.
	o Widespread non-response to EDNS options requires recursive servers		* Widespread non-response to EDNS options requires recursive servers
	to decide whether to probe to see if it is the specific EDNS		to decide whether to probe to see if it is the specific EDNS
	option or the use of EDNS in general that is causing the non		option or the use of EDNS in general that is causing the non-
	response. In the limited amount of time required to resolve a		response. In the limited amount of time required to resolve a
	query before the client times out this is not possible.		query before the client times out, this is not possible.
	o Incorrectly returning FORMERR to an EDNS option being present		* Incorrectly returning FORMERR to an EDNS option being present
	leads to the recursive server not being able to determine if the		leads to the recursive server not being able to determine if the
	server is just broken in the handling of the EDNS option or		server is just broken in the handling of the EDNS option or if it
	doesn't support EDNS at all.		doesn't support EDNS at all.
	o Mishandling of unknown query types has contributed to the		* Mishandling of unknown query types has contributed to the
	abandonment of the transition of the SPF type.		abandonment of the transition of the SPF type.
	o Mishandling of unknown query types has slowed up the development		* Mishandling of unknown query types has slowed up the development
	of DANE and resulted in additional rules being specified to reduce		of DNS-Based Authentication of Named Entities (DANE) and resulted
	the probability of interacting with a broken server when making		in additional rules being specified to reduce the probability of
	TLSA queries.		interacting with a broken server when making TLSA queries.
	The consequences of servers not following the RFCs will only grow if		The consequences of servers not following the RFCs will only grow if
	measures are not put in place to remove non compliant servers from		measures are not put in place to remove non-compliant servers from
	the ecosystem. Working around issues due to non-compliance with RFCs		the ecosystem. Working around issues due to non-compliance with RFCs
	is not sustainable.		is not sustainable.
	Most (if not all) of these consequences could have been avoided if		Most (if not all) of these consequences could have been avoided if
	action had been taken to remove non-compliant servers as soon as		action had been taken to remove non-compliant servers as soon as
	people were aware of them, i.e. to actively seek out broken		people were aware of them, i.e., to actively seek out broken
	implementations and servers and inform their developers and operators		implementations and servers and inform their developers and operators
	that they need to fix their servers.		that they need to fix their servers.
	3. Common kinds of queries that result in no or bad responses.		3. Common Kinds of Queries That Result in No or Bad Responses
	This section is broken down into Basic DNS requests and EDNS		This section is broken down into Basic DNS requests and EDNS
	requests.		requests.
	3.1. Basic DNS Queries		3.1. Basic DNS Queries
	3.1.1. Zone Existence		3.1.1. Zone Existence
	If a zone is delegated to a server, that server should respond to an		If a zone is delegated to a server, that server should respond to a
	SOA query for that zone with an SOA record. Failing to respond at		SOA query for that zone with an SOA record. Failing to respond at
	all is always incorrect, regardless of the configuration of the		all is always incorrect, regardless of the configuration of the
	server. Responding with anything other than an SOA record in the		server. Responding with anything other than an SOA record in the
	Answer section indicates a bad delegation.		answer section indicates a bad delegation.
	3.1.2. Unknown / Unsupported Type Queries		3.1.2. Unknown/Unsupported Type Queries
	Some servers fail to respond to unknown or unsupported types. If a		Some servers fail to respond to unknown or unsupported types. If a
	server receives a query for a type that it doesn't recognise, or		server receives a query for a type that it doesn't recognise, or
	doesn't implement, it is expected to return the appropriate response		doesn't implement, it is expected to return the appropriate response
	as if it did recognise the type but does not have any data for that		as if it did recognise the type but does not have any data for that
	type: either NOERROR, or NXDOMAIN. The exceptions to this are		type, i.e., either NOERROR or NXDOMAIN. The exceptions to this are
	queries for Meta-RR types which may return NOTIMP.		queries for Meta-RR types, which may return NOTIMP.
	3.1.3. DNS Flags		3.1.3. DNS Flags
	Some servers fail to respond to DNS queries with various DNS flags		Some servers fail to respond to DNS queries with various DNS flags
	set, regardless of whether they are defined or still reserved. At		set, regardless of whether they are defined or still reserved. At
	the time of writing there are servers that fail to respond to queries		the time of writing, there are servers that fail to respond to
	with the AD flag set to 1 and servers that fail to respond to queries		queries with the AD flag set to 1 and servers that fail to respond to
	with the last reserved flag set.		queries with the last reserved flag set.
	Servers should respond to such queries. If the server does not know		Servers should respond to such queries. If the server does not know
	the meaning of a flag it must not copy it to the response [RFC1035]		the meaning of a flag, it must not copy it to the response
	Section 4.1.1. If the server does not understand the meaning of a		(Section 4.1.1 of [RFC1035]). If the server does not understand the
	request it should reply with a FORMERR response with unknown flags		meaning of a request, it should reply with a FORMERR response with
	set to zero.		unknown flags set to zero.
	3.1.3.1. Recursive Queries		3.1.3.1. Recursive Queries
	A non-recursive server is supposed to respond to recursive queries as		A non-recursive server is supposed to respond to recursive queries as
	if the RD bit is not set [RFC1034].		if the Recursion Desired (RD) bit is not set [RFC1034].
	3.1.4. Unknown DNS opcodes		3.1.4. Unknown DNS Opcodes
	The use of previously undefined opcodes is to be expected. Since the		The use of previously undefined opcodes is to be expected. Since the
	DNS was first defined two new opcodes have been added, UPDATE and		DNS was first defined, two new opcodes have been added, UPDATE and
	NOTIFY.		NOTIFY.
	NOTIMP is the expected rcode to an unknown or unimplemented opcode.		NOTIMP is the expected rcode to an unknown or unimplemented opcode.
	Note: while new opcodes will most probably use the current layout		| NOTE: while new opcodes will most probably use the current
	structure for the rest of the message there is no requirement that		| layout structure for the rest of the message, there is no
	anything other than the DNS header match.		| requirement that anything other than the DNS header match.
	3.1.5. TCP Queries		3.1.5. TCP Queries
	All DNS servers are supposed to respond to queries over TCP		All DNS servers are supposed to respond to queries over TCP
	[RFC7766]. While firewalls should not block TCP connection attempts,		[RFC7766]. While firewalls should not block TCP connection attempts,
	those that do they should cleanly terminate the connection by sending		those that do should cleanly terminate the connection by sending TCP
	TCP RESET or sending ICMP/ICMPv6 Administratively Prohibited		RESET or sending ICMP/ICMPv6 Administratively Prohibited messages.
	messages. Dropping TCP connections introduces excessive delays to		Dropping TCP connections introduces excessive delays to the
	the resolution process.		resolution process.
	3.2. EDNS Queries		3.2. EDNS Queries
	EDNS queries are specified in [RFC6891].		EDNS queries are specified in [RFC6891].
	3.2.1. EDNS Queries - Version Independent		3.2.1. EDNS Queries: Version Independent
	Identifying servers that fail to respond to EDNS queries can be done		Identifying servers that fail to respond to EDNS queries can be done
	by first confirming that the server responds to regular DNS queries,		by first confirming that the server responds to regular DNS queries,
	followed by a series of otherwise identical queries using EDNS, then		followed by a series of otherwise identical queries using EDNS, then
	making the original query again. A series of EDNS queries is needed		making the original query again. A series of EDNS queries is needed,
	as at least one DNS implementation responds to the first EDNS query		as at least one DNS implementation responds to the first EDNS query
	with FORMERR but fails to respond to subsequent queries from the same		with FORMERR but fails to respond to subsequent queries from the same
	address for a period until a regular DNS query is made. The EDNS		address for a period until a regular DNS query is made. The EDNS
	query should specify a UDP buffer size of 512 bytes to avoid false		query should specify a UDP buffer size of 512 bytes to avoid false
	classification of not supporting EDNS due to response packet size.		classification of not supporting EDNS due to response packet size.
	If the server responds to the first and last queries but fails to		If the server responds to the first and last queries but fails to
	respond to most or all of the EDNS queries, it is probably faulty.		respond to most or all of the EDNS queries, it is probably faulty.
	The test should be repeated a number of times to eliminate the		The test should be repeated a number of times to eliminate the
	likelihood of a false positive due to packet loss.		likelihood of a false positive due to packet loss.
	Firewalls may also block larger EDNS responses but there is no easy		Firewalls may also block larger EDNS responses, but there is no easy
	way to check authoritative servers to see if the firewall is mis-		way to check authoritative servers to see if the firewall is
	configured.		misconfigured.
	3.2.2. EDNS Queries - Version Specific		3.2.2. EDNS Queries: Version Specific
	Some servers respond correctly to EDNS version 0 queries but fail to		Some servers respond correctly to EDNS version 0 queries but fail to
	respond to EDNS queries with version numbers that are higher than		respond to EDNS queries with version numbers that are higher than
	zero. Servers should respond with BADVERS to EDNS queries with		zero. Servers should respond with BADVERS to EDNS queries with
	version numbers that they do not support.		version numbers that they do not support.
	Some servers respond correctly to EDNS version 0 queries but fail to		Some servers respond correctly to EDNS version 0 queries but fail to
	set QR=1 when responding to EDNS versions they do not support. Such		set QR=1 when responding to EDNS versions they do not support. Such
	responses may be discarded as invalid (as QR is not 1) or treated as		responses may be discarded as invalid (as QR is not 1) or treated as
	requests (when the source port of the original request was port 53).		requests (when the source port of the original request was port 53).
	skipping to change at page 8, line 7 ¶		skipping to change at line 331 ¶
	Unknown EDNS options are supposed to be ignored by the server.		Unknown EDNS options are supposed to be ignored by the server.
	3.2.4. EDNS Flags		3.2.4. EDNS Flags
	Some servers fail to respond to EDNS queries with EDNS flags set.		Some servers fail to respond to EDNS queries with EDNS flags set.
	Servers should ignore EDNS flags they do not understand and must not		Servers should ignore EDNS flags they do not understand and must not
	add them to the response [RFC6891].		add them to the response [RFC6891].
	3.2.5. Truncated EDNS Responses		3.2.5. Truncated EDNS Responses
	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 included		truncated response is sent. An OPT record is supposed to be included
	in a truncated response [RFC6891].		in a truncated response [RFC6891].
	Some EDNS aware servers fail to honour the advertised EDNS UDP buffer		Some EDNS-aware servers fail to honour the advertised EDNS UDP buffer
	size and send over-sized responses [RFC6891]. Servers must send UDP		size and send oversized responses [RFC6891]. Servers must send UDP
	responses no larger than the advertised EDNS UDP buffer size.		responses no larger than the advertised EDNS UDP buffer size.
	3.2.6. DO=1 Handling		3.2.6. DO=1 Handling
	Some nameservers incorrectly only return an EDNS response when the DO		Some nameservers incorrectly only return an EDNS response when the
	bit [RFC3225] is 1 in the query. Servers that support EDNS should		DNSSEC OK (DO) bit [RFC3225] is 1 in the query. Servers that support
	always respond to EDNS requests with EDNS responses.		EDNS should always respond to EDNS requests with EDNS responses.
	Some nameservers fail to copy the DO bit to the response despite		Some nameservers fail to copy the DO bit to the response despite
	clearly supporting DNSSEC by returning an RRSIG records to EDNS		clearly supporting DNSSEC by returning an RRSIG records to EDNS
	queries with DO=1. Nameservers that support DNSSEC are expected to		queries with DO=1. Nameservers that support DNSSEC are expected to
	copy the DO bit from the request to the response.		copy the DO bit from the request to the response.
	3.2.7. EDNS over TCP		3.2.7. EDNS over TCP
	Some EDNS aware servers incorrectly limit the TCP response sizes to		Some EDNS-aware servers incorrectly limit the TCP response sizes to
	the advertised UDP response size. This breaks DNS resolution to		the advertised UDP response size. This breaks DNS resolution to
	clients where the response sizes exceed the advertised UDP response		clients where the response sizes exceed the advertised UDP response
	size despite the server and the client being capable of sending and		size despite the server and the client being capable of sending and
	receiving larger TCP responses respectively. It effectively defeats		receiving larger TCP responses, respectively. It effectively defeats
	setting TC=1 in UDP responses.		setting TC=1 in UDP responses.
	4. Firewalls and Load Balancers		4. Firewalls and Load Balancers
	Firewalls and load balancers can affect the externally visible		Firewalls and load balancers can affect the externally visible
	behaviour of a nameserver. Tests for conformance should to be done		behaviour of a nameserver. Tests for conformance should to be done
	from outside of any firewall so that the system is tested as a whole.		from outside of any firewall so that the system is tested as a whole.
	Firewalls and load balancers should not drop DNS packets that they		Firewalls and load balancers should not drop DNS packets that they
	don't understand. They should either pass the packets or generate an		don't understand. They should either pass the packets or generate an
	skipping to change at page 9, line 12 ¶		skipping to change at line 384 ¶
	should not be construed as an attack. Nameservers have always been		should not be construed as an attack. Nameservers have always been
	expected to be able to handle such queries.		expected to be able to handle such queries.
	Requests with unknown opcodes are normal client behaviour and should		Requests with unknown opcodes are normal client behaviour and should
	not be construed as an attack. Nameservers have always been expected		not be construed as an attack. Nameservers have always been expected
	to be able to handle such queries.		to be able to handle such queries.
	Requests with unassigned flags set (DNS or EDNS) are expected client		Requests with unassigned flags set (DNS or EDNS) are expected client
	behaviour and should not be construed as an attack. The behaviour		behaviour and should not be construed as an attack. The behaviour
	for unassigned flags is to ignore them in the request and to not set		for unassigned flags is to ignore them in the request and to not set
	them in the response. Dropping DNS / EDNS packets with unassigned		them in the response. Dropping DNS/EDNS packets with unassigned
	flags makes it difficult to deploy extensions that make use of them		flags makes it difficult to deploy extensions that make use of them
	due to the need to reconfigure and update firewalls.		due to the need to reconfigure and update firewalls.
	Requests with unknown EDNS options are expected client behaviour and		Requests with unknown EDNS options are expected client behaviour and
	should not be construed as an attack. The correct behaviour for		should not be construed as an attack. The correct behaviour for
	unknown EDNS options is to ignore their presence when constructing a		unknown EDNS options is to ignore their presence when constructing a
	reply.		reply.
	Requests with unknown EDNS versions are expected client behaviour and		Requests with unknown EDNS versions are expected client behaviour and
	should not be construed as an attack. The correct behaviour for		should not be construed as an attack. The correct behaviour for
	skipping to change at page 9, line 39 ¶		skipping to change at line 411 ¶
	signal that multiple DNS messages be returned rather than a single		signal that multiple DNS messages be returned rather than a single
	UDP message that is fragmented at the IP layer.		UDP message that is fragmented at the IP layer.
	DNS, and EDNS in particular, are designed to allow clients to be able		DNS, and EDNS in particular, are designed to allow clients to be able
	to use new features against older servers without having to validate		to use new features against older servers without having to validate
	every option. Indiscriminate blocking of messages breaks that		every option. Indiscriminate blocking of messages breaks that
	design.		design.
	However, there may be times when a nameserver mishandles messages		However, there may be times when a nameserver mishandles messages
	with a particular flag, EDNS option, EDNS version field, opcode, type		with a particular flag, EDNS option, EDNS version field, opcode, type
	or class field or combination thereof to the point where the		or class field, or combination thereof to the point where the
	integrity of the nameserver is compromised. Firewalls should offer		integrity of the nameserver is compromised. Firewalls should offer
	the ability to selectively reject messages using an appropriately		the ability to selectively reject messages using an appropriately
	constructed response based on all these fields while awaiting a fix		constructed response based on all these fields while awaiting a fix
	from the nameserver vendor. Returning FORMERR or REFUSED are two		from the nameserver vendor. Returning FORMERR or REFUSED are two
	potential error codes to return.		potential error codes to return.
	5. Packet Scrubbing Services		5. Packet Scrubbing Services
	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.
	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 uses a		of a nameserver in a similar way to firewalls. If an operator uses a
	packet scrubbing service, they should check that legitimate queries		packet scrubbing service, they should check that legitimate queries
	are not being blocked.		are not being blocked.
	Packet scrubbing services, unlike firewalls, are also turned on and		Packet scrubbing services, unlike firewalls, are also turned on and
	off in response to denial of service attacks. One needs to take care		off in response to denial-of-service attacks. One needs to take care
	when choosing a scrubbing service.		when choosing a scrubbing service.
	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 vectors.		service to ensure that these tests are not seen as attack vectors.
	6. Whole Answer Caches		6. Whole Answer Caches
	Whole answer caches take a previously constructed answer and return		Whole answer caches take a previously constructed answer and return
	it to a subsequent query for the same question. However, they can		it to a subsequent query for the same question. However, they can
	return the wrong response if they do not take all of the relevant		return the wrong response if they do not take all of the relevant
	attributes of the query into account.		attributes of the query into account.
	In addition to the standard tuple of <qname,qtype,qclass> a non-		In addition to the standard tuple of <qname,qtype,qclass>, a non-
	exhaustive set of attributes that must be considered include: RD, AD,		exhaustive set of attributes that must be considered include: RD, AD,
	CD, OPT record, DO, EDNS buffer size, EDNS version, EDNS options, and		CD, OPT record, DO, EDNS buffer size, EDNS version, EDNS options, and
	transport.		transport.
	7. Response Code Selection		7. Response Code Selection
	Choosing the correct response code when responding to DNS queries is		Choosing the correct response code when responding to DNS queries is
	important. Response codes should be chosen considering how clients		important. Response codes should be chosen considering how clients
	will handle them.		will handle them.
	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, etc.		extending the header, changing the structure of the records, etc.
	Servers are not expected to be able to parse these, and should		Servers are not expected to be able to parse these and should respond
	respond with a response code of NOTIMP rather than FORMERR (which		with a response code of NOTIMP rather than FORMERR (which would be
	would be expected if there was a parse error with an known opcode).		expected if there was a parse error with a known opcode).
	For unimplemented type codes, and in the absence of other errors, the		For unimplemented type codes, and in the absence of other errors, the
	only valid response is NoError if the qname exists, and NameError		only valid response is NOERROR if the qname exists and NXDOMAIN
	(NXDOMAIN) otherwise. For Meta-RRs NOTIMP may be returned instead.		otherwise. For Meta-RRs, NOTIMP may be returned instead.
	If a zone cannot be loaded because it contains unimplemented type		If a zone cannot be loaded because it contains unimplemented type
	codes that are not encoded as unknown record types according to		codes that are not encoded as unknown record types according to
	[RFC3597] then the expected response is SERVFAIL as the whole zone		[RFC3597], then the expected response is SERVFAIL, as the whole zone
	should be rejected Section 5.2 [RFC1035]. If a zone loads then		should be rejected (Section 5.2 of [RFC1035]). If a zone loads, then
	Section 4.3.2 [RFC1034] applies.		Section 4.3.2 of [RFC1034] applies.
	If the server supports EDNS and receives a query with an unsupported		If the server supports EDNS and receives a query with an unsupported
	EDNS version, the correct response is BADVERS [RFC6891].		EDNS version, the correct response is BADVERS [RFC6891].
	If the server does not support EDNS at all, FORMERR is the expected		If the server does not support EDNS at all, FORMERR is the expected
	error code. That said a minimal EDNS server implementation requires		error code. That said, a minimal EDNS server implementation requires
	parsing the OPT records and responding with an empty OPT record in		parsing the OPT records and responding with an empty OPT record in
	the additional section in most cases. There is no need to interpret		the additional section in most cases. There is no need to interpret
	any EDNS options present in the request as unsupported EDNS options		any EDNS options present in the request, as unsupported EDNS options
	are expected to be ignored [RFC6891]. Additionally EDNS flags can be		are expected to be ignored [RFC6891]. Additionally, EDNS flags can
	ignored. The only part of the OPT record that needs to be examined		be ignored. The only part of the OPT record that needs to be
	is the version field to determine if BADVERS needs to be sent or not.		examined is the version field to determine if BADVERS needs to be
			sent or not.
	8. Testing		8. Testing
	Testing is divided into two sections: "Basic DNS", which all servers		Testing is divided into two sections: "Basic DNS", which all servers
	should meet, and "Extended DNS", which should be met by all servers		should meet, and "Extended DNS", which should be met by all servers
	that support EDNS (a server is deemed to support EDNS if it gives a		that support EDNS (a server is deemed to support EDNS if it gives a
	valid EDNS response to any EDNS query). If a server does not support		valid EDNS response to any EDNS query). If a server does not support
	EDNS it should still respond to all the tests, albeit with error		EDNS, it should still respond to all the tests, albeit with error
	responses.		responses.
	These tests query for records at the apex of a zone that the server		These tests query for records at the apex of a zone that the server
	is nominally configured to serve. All tests should use the same		is nominally configured to serve. All tests should use the same
	zone.		zone.
	It is advisable to run all of the tests below in parallel so as to		It is advisable to run all of the tests below in parallel so as to
	minimise the delays due to multiple timeouts when the servers do not		minimise the delays due to multiple timeouts when the servers do not
	respond. There are 16 queries directed to each nameserver (assuming		respond. There are 16 queries directed to each nameserver (assuming
	no packet loss) testing different aspects of Basic DNS and Extended		no packet loss) testing different aspects of Basic DNS and Extended
	DNS.		DNS.
	The tests below use dig from BIND 9.11.0 [ISC]. Replace $zone with		The tests below use dig from BIND 9.11.0 [ISC]. Replace $zone with
	the name of the zone being used for testing. Replace $server with		the name of the zone being used for testing. Replace $server with
	the name or address of the server being tested.		the name or address of the server being tested.
	When testing recursive servers set RD=1 and choose a zone name that		When testing, recursive servers set RD=1 and choose a zone name that
	is known to exist and is not being served by the recursive server.		is known to exist and is not being served by the recursive server.
	The root zone (".") is often a good candidate as it is DNSSEC signed.		The root zone (".") is often a good candidate, as it is DNSSEC
	RD=1, rather than RD=0, should be present in the responses for all		signed. RD=1, rather than RD=0, should be present in the responses
	test involving the opcode QUERY. Non-authoritative answers (AA=0)		for all test involving the opcode QUERY. Non-authoritative answers
	are expected when talking to a recursive server. AD=1 is only		(AA=0) are expected when talking to a recursive server. AD=1 is only
	expected if the server is validating responses and one or both AD=1		expected if the server is validating responses and one or both AD=1
	or DO=1 is set in the request otherwise AD=0 is expected.		or DO=1 is set in the request, otherwise AD=0 is expected.
	8.1. Testing - Basic DNS		8.1. Testing: Basic DNS
	This first set of tests cover basic DNS server behaviour and all		This first set of tests cover Basic DNS server behaviour and all
	servers should pass these tests.		servers should pass these tests.
	8.1.1. Is The Server Configured For The Zone?		8.1.1. Is the server configured for the zone?
	Ask for the SOA record of the configured zone. This query is made		Ask for the SOA record of the configured zone. This query is made
	with no DNS flag bits set and without EDNS.		with no DNS flag bits set and without EDNS.
	We expect the SOA record for the zone to be returned in the answer		We expect the SOA record for the zone to be returned in the answer
	section, the rcode to be set to NOERROR, and the AA and QR bits to be		section, the rcode to be set to NOERROR, and the Authoritative Answer
	set in the header; RA may also be set [RFC1034]. We do not expect an		(AA) and Query/Response (QR) bits to be set in the header; the
	OPT record to be returned [RFC6891].		Recursion Available (RA) bits may also be set [RFC1034]. We do not
			expect an OPT record to be returned [RFC6891].
	Verify the server is configured for the zone:		Verify the server is configured for the zone:
	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
	8.1.2. Testing Unknown Types		8.1.2. Testing Unknown Types
	Identifying servers that fail to respond to unknown or unsupported		Identifying servers that fail to respond to unknown or unsupported
	types can be done by making an initial DNS query for an A record,		types can be done by making an initial DNS query for an A record,
	making a number of queries for an unallocated type, then making a		making a number of queries for an unallocated type, then making a
	query for an A record again. IANA maintains a registry of allocated		query for an A record again. IANA maintains a registry of allocated
	types.		types [IANA-DNS].
	If the server responds to the first and last queries but fails to		If the server responds to the first and last queries but fails to
	respond to the queries for the unallocated type, it is probably		respond to the queries for the unallocated type, it is probably
	faulty. The test should be repeated a number of times to eliminate		faulty. The test should be repeated a number of times to eliminate
	the likelihood of a false positive due to packet loss.		the likelihood of a false positive due to packet loss.
	Ask for the TYPE1000 RRset at the configured zone's name. This query		Ask for the TYPE1000 RRset at the configured zone's name. This query
	is made with no DNS flag bits set and without EDNS. TYPE1000 has		is made with no DNS flag bits set and without EDNS. TYPE1000 has
	been chosen for this purpose as IANA is unlikely to allocate this		been chosen for this purpose, as IANA is unlikely to allocate this
	type in the near future and it is not in a range reserved for private		type in the near future and it is not in a range reserved for private
	use [RFC6895]. Any unallocated type code could be chosen for this		use [RFC6895]. Any unallocated type code could be chosen for this
	test.		test.
	We expect no records to be returned in the answer section, the rcode		We expect no records to be returned in the answer section, the rcode
	to be set to NOERROR, and the AA and QR bits to be set in the header;		to be set to NOERROR, and the AA and QR bits to be set in the header;
	RA may also be set [RFC1034]. We do not expect an OPT record to be		RA may also be set [RFC1034]. We do not expect an OPT record to be
	returned [RFC6891].		returned [RFC6891].
	Check that queries for an unknown type work:		Check that queries for an unknown type work:
	skipping to change at page 13, line 23 ¶		skipping to change at line 584 ¶
	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
	8.1.3. Testing Header Bits		8.1.3. Testing Header Bits
	8.1.3.1. Testing CD=1 Queries		8.1.3.1. Testing CD=1 Queries
	Ask for the SOA record of the configured zone. This query is made		Ask for the SOA record of the configured zone. This query is made
	with only the CD DNS flag bit set, all other DNS bits clear, and		with only the CD DNS flag bit set, with all other DNS bits clear, and
	without EDNS.		without EDNS.
	We expect the SOA record for the zone to be returned in the answer		We expect the SOA record for the zone to be returned in the answer
	section, the rcode to be set to NOERROR, and the AA and QR bits to be		section, the rcode to be set to NOERROR, and the AA and QR bits to be
	set in the header. We do not expect an OPT record to be returned.		set in the header. We do not expect an OPT record to be returned.
	If the server supports DNSSEC, CD should be set in the response		If the server supports DNSSEC, CD should be set in the response
	[RFC4035] otherwise CD should be clear [RFC1034].		[RFC4035]; otherwise, CD should be clear [RFC1034].
	Check that queries with CD=1 work:		Check that queries with CD=1 work:
	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
	8.1.3.2. Testing AD=1 Queries		8.1.3.2. Testing AD=1 Queries
	Ask for the SOA record of the configured zone. This query is made		Ask for the SOA record of the configured zone. This query is made
	with only the AD DNS flag bit set and all other DNS bits clear and		with only the AD DNS flag bit set, with all other DNS bits clear, and
	without EDNS.		without EDNS.
	We expect the SOA record for the zone to be returned in the answer		We expect the SOA record for the zone to be returned in the answer
	section, the rcode to be set to NOERROR, and the AA and QR bits to be		section, the rcode to be set to NOERROR, and the AA and QR bits to be
	set in the header. We do not expect an OPT record to be returned.		set in the header. We do not expect an OPT record to be returned.
	The purpose of this query is to detect blocking of queries with the		The purpose of this query is to detect blocking of queries with the
	AD bit present, not the specific value of AD in the response.		AD bit present, not the specific value of AD in the response.
	Check that queries with AD=1 work:		Check that queries with AD=1 work:
	skipping to change at page 14, line 23 ¶		skipping to change at line 632 ¶
	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
	AD use in queries is defined in [RFC6840].		AD use in queries is defined in [RFC6840].
	8.1.3.3. Testing Reserved Bit		8.1.3.3. Testing Reserved Bit
	Ask for the SOA record of the configured zone. This query is made		Ask for the SOA record of the configured zone. This query is made
	with only the final reserved DNS flag bit set and all other DNS bits		with only the final reserved DNS flag bit set, with all other DNS
	clear and without EDNS.		bits clear, and without EDNS.
	We expect the SOA record for the zone to be returned in the answer		We expect the SOA record for the zone to be returned in the answer
	section, the rcode to be set to NOERROR, and the AA and QR bits to be		section, the rcode to be set to NOERROR, and the AA and QR bits to be
	set in the header; RA may be set. The final reserved bit must not be		set in the header; RA may be set. The final reserved bit must not be
	set [RFC1034]. We do not expect an OPT record to be returned		set [RFC1034]. We do not expect an OPT record to be returned
	[RFC6891].		[RFC6891].
	Check that queries with the last unassigned DNS header flag work and		Check that queries with the last unassigned DNS header flag work and
	that the flag bit is not copied to the response:		that the flag bit is not copied to the response:
	skipping to change at page 14, line 46 ¶		skipping to change at line 655 ¶
	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
	MBZ (Must Be Zero) is a dig-specific indication that the flag bit has		MBZ (Must Be Zero) is a dig-specific indication that the flag bit has
	been incorrectly copied. See Section 4.1.1, [RFC1035] "Z Reserved		been incorrectly copied. See Section 4.1.1 of [RFC1035]:
	for future use. Must be zero in all queries and responses."
			"Z Reserved for future use. Must be zero in all queries and
			responses."
	8.1.3.4. Testing Recursive Queries		8.1.3.4. Testing Recursive Queries
	Ask for the SOA record of the configured zone. This query is made		Ask for the SOA record of the configured zone. This query is made
	with only the RD DNS flag bit set and without EDNS.		with only the RD DNS flag bit set and without EDNS.
	We expect the SOA record for the zone to be returned in the answer		We expect the SOA record for the zone to be returned in the answer
	section, the rcode to be set to NOERROR, and the AA, QR and RD bits		section, the rcode to be set to NOERROR, and the AA, QR and RD bits
	to be set in the header; RA may also be set [RFC1034]. We do not		to be set in the header; RA may also be set [RFC1034]. We do not
	expect an OPT record to be returned [RFC6891].		expect an OPT record to be returned [RFC6891].
	skipping to change at page 15, line 29 ¶		skipping to change at line 684 ¶
	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
	8.1.4. Testing Unknown Opcodes		8.1.4. Testing Unknown Opcodes
	Construct a DNS message that consists of only a DNS header with		Construct a DNS message that consists of only a DNS header with
	opcode set to 15 (currently not allocated), no DNS header bits set		opcode set to 15 (currently not allocated), no DNS header bits set,
	and empty question, answer, authority and additional sections.		and empty question, answer, authority, and additional sections.
	Check that new opcodes are handled:		Check that new opcodes are handled:
	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
	skipping to change at page 16, line 27 ¶		skipping to change at line 729 ¶
	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
	The requirement that TCP be supported is defined in [RFC7766].		The requirement that TCP be supported is defined in [RFC7766].
	8.2. Testing - Extended DNS		8.2. Testing: Extended DNS
	The next set of tests cover various aspects of EDNS behaviour. If		The next set of tests cover various aspects of EDNS behaviour. If
	any of these tests succeed (indicating at least some EDNS support)		any of these tests succeed (indicating at least some EDNS support),
	then all of them should succeed. There are servers that support EDNS		then all of them should succeed. There are servers that support EDNS
	but fail to handle plain EDNS queries correctly so a plain EDNS query		but fail to handle plain EDNS queries correctly, so a plain EDNS
	is not a good indicator of lack of EDNS support.		query is not a good indicator of lack of EDNS support.
	8.2.1. Testing Minimal EDNS		8.2.1. Testing Minimal EDNS
	Ask for the SOA record of the configured zone. This query is made		Ask for the SOA record of the configured zone. This query is made
	with no DNS flag bits set. EDNS version 0 is used without any EDNS		with no DNS flag bits set. EDNS version 0 is used without any EDNS
	options or EDNS flags set.		options or EDNS flags set.
	We expect the SOA record for the zone to be returned in the answer		We expect the SOA record for the zone to be returned in the answer
	section, the rcode to be set to NOERROR, and the AA and QR bits to be		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 [RFC1034]. We expect an OPT		set in the header; RA may also be set [RFC1034]. We expect an OPT
	record to be returned. There should be no EDNS flags present in the		record to be returned. There should be no EDNS flags present in the
	response. The EDNS version field should be 0 and there should be no		response. The EDNS version field should be 0, and there should be no
	EDNS options present [RFC6891].		EDNS options present [RFC6891].
	Check that plain EDNS queries work:		Check that plain EDNS queries work:
	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
	+nocookie disables sending a EDNS COOKIE option which is otherwise		+nocookie disables sending an EDNS COOKIE option, which is otherwise
	enabled by default in BIND 9.11.0 (and later).		enabled by default in BIND 9.11.0 (and later).
	8.2.2. Testing EDNS Version Negotiation		8.2.2. Testing EDNS Version Negotiation
	Ask for the SOA record of a zone the server is nominally configured		Ask for the SOA record of a zone the server is nominally configured
	to serve. This query is made with no DNS flag bits set. EDNS		to serve. This query is made with no DNS flag bits set. EDNS
	version 1 is used without any EDNS options or EDNS flags set.		version 1 is used without any EDNS options or EDNS flags set.
	We expect the SOA record for the zone to NOT be returned in the		We expect the SOA record for the zone to NOT be returned in the
	answer section with the extended rcode set to BADVERS and the QR bit		answer section with the extended rcode set to BADVERS and the QR bit
	to be set in the header; RA may also be set [RFC1034]. We expect an		to be set in the header; RA may also be set [RFC1034]. We expect an
	OPT record to be returned. There should be no EDNS flags present in		OPT record to be returned. There should be no EDNS flags present in
	the response. The EDNS version field should be 0 in the response as		the response. The EDNS version field should be 0 in the response, as
	no other EDNS version has as yet been specified [RFC6891].		no other EDNS version has as yet been specified [RFC6891].
	Check that EDNS version 1 queries work (EDNS supported):		Check that EDNS version 1 queries work (EDNS supported):
	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
	+noednsneg has been set as dig supports EDNS version negotiation and		+noednsneg has been set, as dig supports EDNS version negotiation,
	we want to see only the response to the initial EDNS version 1 query.		and we want to see only the response to the initial EDNS version 1
			query.
	8.2.3. Testing Unknown EDNS Options		8.2.3. Testing Unknown EDNS Options
	Ask for the SOA record of the configured zone. This query is made		Ask for the SOA record of the configured zone. This query is made
	with no DNS flag bits set. EDNS version 0 is used without any EDNS		with no DNS flag bits set. EDNS version 0 is used without any EDNS
	flags. An EDNS option is present with a value that has not yet been		flags. An EDNS option is present with a value that has not yet been
	assigned by IANA. We have picked an unassigned code of 100 for the		assigned by IANA. We have picked an unassigned code of 100 for the
	example below. Any unassigned EDNS option code could have been		example below. Any unassigned EDNS option code could have been
	choosen for this test.		chosen for this test.
	We expect the SOA record for the zone to be returned in the answer		We expect the SOA record for the zone to be returned in the answer
	section, the rcode to be set to NOERROR, and the AA and QR bits to be		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 [RFC1034]. We expect an OPT		set in the header; RA may also be set [RFC1034]. We expect an OPT
	record to be returned. There should be no EDNS flags present in the		record to be returned. There should be no EDNS flags present in the
	response. The EDNS version field should be 0 as EDNS versions other		response. The EDNS version field should be 0, as EDNS versions other
	than 0 are yet to be specified and there should be no EDNS options		than 0 are yet to be specified, and there should be no EDNS options
	present as unknown EDNS options are supposed to be ignored by the		present, as unknown EDNS options are supposed to be ignored by the
	server [RFC6891] Section 6.1.2.		server (Section 6.1.1 of [RFC6891]).
	Check that EDNS queries with an unknown option work (EDNS supported):		Check that EDNS queries with an unknown option work (EDNS supported):
	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
	skipping to change at page 18, line 38 ¶		skipping to change at line 832 ¶
	8.2.4. Testing Unknown EDNS Flags		8.2.4. Testing Unknown EDNS Flags
	Ask for the SOA record of the configured zone. This query is made		Ask for the SOA record of the configured zone. This query is made
	with no DNS flag bits set. EDNS version 0 is used without any EDNS		with no DNS flag bits set. EDNS version 0 is used without any EDNS
	options. An unassigned EDNS flag bit is set (0x40 in this case).		options. An unassigned EDNS flag bit is set (0x40 in this case).
	We expect the SOA record for the zone to be returned in the answer		We expect the SOA record for the zone to be returned in the answer
	section, the rcode to be set to NOERROR, and the AA and QR bits to be		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 [RFC1034]. We expect an OPT		set in the header; RA may also be set [RFC1034]. We expect an OPT
	record to be returned. There should be no EDNS flags present in the		record to be returned. There should be no EDNS flags present in the
	response as unknown EDNS flags are supposed to be ignored. The EDNS		response, as unknown EDNS flags are supposed to be ignored. The EDNS
	version field should be 0 and there should be no EDNS options present		version field should be 0, and there should be no EDNS options
	[RFC6891].		present [RFC6891].
	Check that EDNS queries with unknown flags work (EDNS supported):		Check that EDNS queries with unknown flags work (EDNS supported):
	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
	MBZ (Must Be Zero) is a dig-specific indication that a flag bit has		MBZ (Must Be Zero) is a dig-specific indication that a flag bit has
	been incorrectly copied as per Section 6.1.4, [RFC6891].		been incorrectly copied, as per Section 6.1.4 of [RFC6891].
	8.2.5. Testing EDNS Version Negotiation With Unknown EDNS Flags		8.2.5. Testing EDNS Version Negotiation with Unknown EDNS Flags
	Ask for the SOA record of the configured zone. This query is made		Ask for the SOA record of the configured zone. This query is made
	with no DNS flag bits set. EDNS version 1 is used without any EDNS		with no DNS flag bits set. EDNS version 1 is used without any EDNS
	options. An unassigned EDNS flag bit is set (0x40 in this case).		options. An unassigned EDNS flag bit is set (0x40 in this case).
	We expect the SOA record for the zone to NOT be returned in the		We expect the SOA record for the zone to NOT be returned in the
	answer section with the extended rcode set to BADVERS and the QR bit		answer section with the extended rcode set to BADVERS and the QR bit
	to be set in the header; RA may also be set [RFC1034]. We expect an		to be set in the header; RA may also be set [RFC1034]. We expect an
	OPT record to be returned. There should be no EDNS flags present in		OPT record to be returned. There should be no EDNS flags present in
	the response as unknown EDNS flags are supposed to be ignored. The		the response, as unknown EDNS flags are supposed to be ignored. The
	EDNS version field should be 0 as EDNS versions other than 0 are yet		EDNS version field should be 0, as EDNS versions other than 0 are yet
	to be specified and there should be no EDNS options present		to be specified, and there should be no EDNS options present
	[RFC6891].		[RFC6891].
	Check that EDNS version 1 queries with unknown flags work (EDNS		Check that EDNS version 1 queries with unknown flags work (EDNS
	supported):		supported):
	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
	8.2.6. Testing EDNS Version Negotiation With Unknown EDNS Options		8.2.6. Testing EDNS Version Negotiation with Unknown EDNS Options
	Ask for the SOA record of the configured zone. This query is made		Ask for the SOA record of the configured zone. This query is made
	with no DNS flag bits set. EDNS version 1 is used. An unknown EDNS		with no DNS flag bits set. EDNS version 1 is used. An unknown EDNS
	option is present. We have picked an unassigned code of 100 for the		option is present. We have picked an unassigned code of 100 for the
	example below. Any unassigned EDNS option code could have been		example below. Any unassigned EDNS option code could have been
	chosen for this test.		chosen for this test.
	We expect the SOA record for the zone to NOT be returned in the		We expect the SOA record for the zone to NOT be returned in the
	answer section with the extended rcode set to BADVERS and the QR bit		answer section with the extended rcode set to BADVERS and the QR bit
	to be set in the header; RA may also be set [RFC1034]. We expect an		to be set in the header; RA may also be set [RFC1034]. We expect an
	OPT record to be returned. There should be no EDNS flags present in		OPT record to be returned. There should be no EDNS flags present in
	the response. The EDNS version field should be 0 as EDNS versions		the response. The EDNS version field should be 0, as EDNS versions
	other than 0 are yet to be specified and there should be no EDNS		other than 0 are yet to be specified, and there should be no EDNS
	options present [RFC6891].		options present [RFC6891].
	Check that EDNS version 1 queries with unknown options work (EDNS		Check that EDNS version 1 queries with unknown options work (EDNS
	supported):		supported):
	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
	skipping to change at page 20, line 46 ¶		skipping to change at line 921 ¶
	Ask for the DNSKEY records of the configured zone, which must be a		Ask for the DNSKEY records of the configured zone, which must be a
	DNSSEC signed zone. This query is made with no DNS flag bits set.		DNSSEC signed zone. This query is made with no DNS flag bits set.
	EDNS version 0 is used without any EDNS options. The only EDNS flag		EDNS version 0 is used without any EDNS options. The only EDNS flag
	set is DO. The EDNS UDP buffer size is set to 512. The intention of		set is DO. The EDNS UDP buffer size is set to 512. The intention of
	this query is to elicit a truncated response from the server. Most		this query is to elicit a truncated response from the server. Most
	signed DNSKEY responses are bigger than 512 bytes. This test will		signed DNSKEY responses are bigger than 512 bytes. This test will
	not give a valid result if the zone is not signed.		not give a valid result if the zone is not signed.
	We expect a response, the rcode to be set to NOERROR, and the AA and		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		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		supports DNSSEC; otherwise it should be clear; TC and RA may also be
	set [RFC1035] [RFC4035]. We expect an OPT record to be present in		set [RFC1035] [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. There should be no EDNS flags other than DO present in
	the response. The EDNS version field should be 0 and there should be		the response. The EDNS version field should be 0, and there should
	no EDNS options present [RFC6891].		be no EDNS options present [RFC6891].
	If TC is not set it is not possible to confirm that the server		If TC is not set, it is not possible to confirm that the server
	correctly adds the OPT record to the truncated responses or not.		correctly adds the OPT record to the truncated responses or not.
	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
	8.2.8. Testing DO=1 Handling		8.2.8. Testing DO=1 Handling
	Ask for the SOA record of the configured zone, which does not need to		Ask for the SOA record of the configured zone, which does not need to
	be DNSSEC signed. This query is made with no DNS flag bits set.		be DNSSEC signed. This query is made with no DNS flag bits set.
	EDNS version 0 is used without any EDNS options. The only EDNS flag		EDNS version 0 is used without any EDNS options. The only EDNS flag
	set is DO.		set is DO.
	We expect the SOA record for the zone to be returned in the answer		We expect the SOA record for the zone to be returned in the answer
	section, the rcode to be set to NOERROR, and the AA and QR bits to be		section, the rcode to be set to NOERROR, and the AA and QR bits to be
	set in the response, AD may be set in the response if the server		set in the response. AD may be set in the response if the server
	supports DNSSEC otherwise it should be clear; RA may also be set		supports DNSSEC, otherwise it should be clear; RA may also be set
	[RFC1034]. We expect an OPT record to be returned. There should be		[RFC1034]. We expect an OPT record to be returned. There should be
	no EDNS flags other than DO present in the response which should be		no EDNS flags other than DO present in the response, which should be
	present if the server supports DNSSEC. The EDNS version field should		present if the server supports DNSSEC. The EDNS version field should
	be 0 and there should be no EDNS options present [RFC6891].		be 0, and there should be no EDNS options present [RFC6891].
	Check that DO=1 queries work (EDNS supported):		Check that DO=1 queries work (EDNS supported):
	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
	8.2.9. Testing EDNS Version Negotiation With DO=1		8.2.9. Testing EDNS Version Negotiation with DO=1
	Ask for the SOA record of the configured zone, which does not need to		Ask for the SOA record of the configured zone, which does not need to
	be DNSSEC signed. This query is made with no DNS flag bits set.		be DNSSEC signed. This query is made with no DNS flag bits set.
	EDNS version 1 is used without any EDNS options. The only EDNS flag		EDNS version 1 is used without any EDNS options. The only EDNS flag
	set is DO.		set is DO.
	We expect the SOA record for the zone to NOT be returned in the		We expect the SOA record for the zone NOT to be returned in the
	answer section, the rcode to be set to NOERROR, ; the QR bit and		answer section, the extended rcode to be set to BADVERS, and the QR
	possibly the RA bit to be set [RFC1034]. We expect an OPT record to		bit to be set in the header; RA may also be set [RFC1034]. We expect
	be returned. There should be no EDNS flags other than DO present in		an OPT record to be returned. There should be no EDNS flags other
	the response which should be there if the server supports DNSSEC.		than DO present in the response, which should be there if the server
	The EDNS version field should be 0 and there should be no EDNS		supports DNSSEC. The EDNS version field should be 0, and there
	options present [RFC6891].		should be no EDNS options present [RFC6891].
	Check that EDNS version 1, DO=1 queries work (EDNS supported):		Check that EDNS version 1, DO=1 queries work (EDNS supported):
	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
	8.2.10. Testing With Multiple Defined EDNS Options		8.2.10. Testing with Multiple Defined EDNS Options
	Ask for the SOA record of the configured zone. This query is made		Ask for the SOA record of the configured zone. This query is made
	with no DNS flag bits set. EDNS version 0 is used. A number of		with no DNS flag bits set. EDNS version 0 is used. A number of
	defined EDNS options are present (NSID [RFC5001], DNS COOKIE		defined EDNS options are present (NSID [RFC5001], DNS COOKIE
	[RFC7873], EDNS Client Subnet [RFC7871] and EDNS Expire [RFC7314]).		[RFC7873], EDNS Client Subnet [RFC7871], and EDNS Expire [RFC7314]).
	We expect the SOA record for the zone to be returned in the answer		We expect the SOA record for the zone to be returned in the answer
	section, the rcode to be set to NOERROR, and the AA and QR bits to be		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 [RFC1034]. We expect an OPT		set in the header; RA may also be set [RFC1034]. We expect an OPT
	record to be returned. There should be no EDNS flags present in the		record to be returned. There should be no EDNS flags present in the
	response. The EDNS version field should be 0. Any of the requested		response. The EDNS version field should be 0. Any of the requested
	EDNS options supported by the server and permitted server		EDNS options supported by the server and permitted server
	configuration may be returned [RFC6891].		configuration may be returned [RFC6891].
	Check that EDNS queries with multiple defined EDNS options work:		Check that EDNS queries with multiple defined EDNS options work:
	skipping to change at page 22, line 49 ¶		skipping to change at line 1021 ¶
	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
	8.3. When EDNS Is Not Supported		8.3. When EDNS Is Not Supported
	If EDNS is not supported by the nameserver, we expect a response to		If EDNS is not supported by the nameserver, we expect a response to
	each of the above queries. That response may be a FORMERR error		each of the above queries. That response may be a FORMERR error
	response or the OPT record may just be ignored.		response, or the OPT record may just be ignored.
	Some nameservers only return a EDNS response when a particular EDNS		Some nameservers only return an EDNS response when a particular EDNS
	option or flag (e.g. DO=1) is present in the request. This		option or flag (e.g., DO=1) is present in the request. This
	behaviour is not compliant behaviour and may hide other incorrect		behaviour is not compliant behaviour and may hide other incorrect
	behaviour from the above tests. Re-testing with the triggering		behaviour from the above tests. Retesting with the triggering
	option / flag present will expose this misbehaviour.		option/flag present will expose this misbehaviour.
	9. Remediation		9. Remediation
	Nameserver operators are generally expected to test their own		Nameserver operators are generally expected to test their own
	infrastructure for compliance to standards. The above tests should		infrastructure for compliance to standards. The above tests should
	be run when new systems are brought online, and should be repeated		be run when new systems are brought online and should be repeated
	periodically to ensure continued interoperability.		periodically to ensure continued interoperability.
	Domain registrants who do not maintain their own DNS infrastructure		Domain registrants who do not maintain their own DNS infrastructure
	are entitled to a DNS service that conforms to standards and		are entitled to a DNS service that conforms to standards and
	interoperates well. Registrants who become aware that their DNS		interoperates well. Registrants who become aware that their DNS
	operator does not have a well maintained or compliant infrastructure		operator does not have a well-maintained or compliant infrastructure
	should insist that their service provider correct issues, and switch		should insist that their service provider correct issues and switch
	providers if they do not.		providers if they do not.
	In the event that an operator experiences problems due to the		In the event that an operator experiences problems due to the
	behaviour of nameservers outside their control, the above tests will		behaviour of nameservers outside their control, the above tests will
	help in narrowing down the precise issue(s) which can then be		help in narrowing down the precise issue(s), which can then be
	reported to the relevant party.		reported to the relevant party.
	If contact information for the operator of a misbehaving nameserver		If contact information for the operator of a misbehaving nameserver
	is not already known, the following methods of communication could be		is not already known, the following methods of communication could be
	considered:		considered:
	o 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
	o the RNAME of zones for which the offending server is authoritative		* the RNAME of zones for which the offending server is authoritative
	o administrative or technical contacts listed in the registration		* administrative or technical contacts listed in the registration
	information for the parent domain of the name of the misbehaving		information for the parent domain of the name of the misbehaving
	server, or for zones for which the nameserver is authoritative		server or for zones for which the nameserver is authoritative
	o the registrar or registry for such zones		* the registrar or registry for such zones
	o DNS-specific operational fora (e.g. mailing lists)		* DNS-specific, operational fora (e.g., mailing lists)
	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, parent		authoritative nameservers of their child zones. However, parent
	operators can have widely varying capabilities in terms of		operators can have widely varying capabilities in terms of
	notification or remediation depending on whether they have a direct		notification or remediation depending on whether they have a direct
	relationship with the child operator. Many TLD registries, for		relationship with the child operator. Many Top-Level Domain (TLD)
	example, cannot directly contact their registrants and may instead		registries, for example, cannot directly contact their registrants
	need to communicate through the relevant registrar. In such cases		and may instead need to communicate through the relevant registrar.
	it may be most efficient for registrars to take on the responsibility		In such cases, it may be most efficient for registrars to take on the
	for testing the name ervers of their registrants, since they have a		responsibility for testing the nameservers of their registrants,
	direct relationship.		since they have a direct relationship.
	When notification is not effective at correcting problems with a		When notification is not effective at correcting problems with a
	misbehaving nameserver, parent operators can choose to remove NS		misbehaving nameserver, parent operators can choose to remove NS
	record sets (and glue records below) that refer to the faulty server		record sets (and glue records below) that refer to the faulty server
	until the servers are fixed. This should only be done as a last		until the servers are fixed. This should only be done as a last
	resort and with due consideration, as removal of a delegation can		resort and with due consideration, as removal of a delegation can
	have unanticipated side effects. For example, other parts of the DNS		have unanticipated side effects. For example, other parts of the DNS
	tree may depend on names below the removed zone cut, and the parent		tree may depend on names below the removed zone cut, and the parent
	operator may find themselves responsible for causing new DNS failures		operator may find themselves responsible for causing new DNS failures
	to occur.		to occur.
	skipping to change at page 24, line 30 ¶		skipping to change at line 1099 ¶
	of attempts to attack services from Intrusion Detection Services and		of attempts to attack services from Intrusion Detection Services and
	firewalls. All of the tests are well-formed (though not necessarily		firewalls. All of the tests are well-formed (though not necessarily
	common) DNS queries. None of the tests listed above should cause any		common) DNS queries. None of the tests listed above should cause any
	harm to a protocol-compliant server.		harm to a protocol-compliant server.
	Relaxing firewall settings to ensure EDNS compliance could		Relaxing firewall settings to ensure EDNS compliance could
	potentially expose a critical implementation flaw in the nameserver.		potentially expose a critical implementation flaw in the nameserver.
	Nameservers should be tested for conformance before relaxing firewall		Nameservers should be tested for conformance before relaxing firewall
	settings.		settings.
	When removing delegations for non-compliant servers there can be a		When removing delegations for non-compliant servers, there can be a
	knock on effect on other zones that require these zones to be		knock-on effect on other zones that require these zones to be
	operational for the nameservers addresses to be resolved.		operational for the nameservers addresses to be resolved.
	11. IANA Considerations		11. IANA Considerations
	There are no actions for IANA.		This document has no IANA actions.
	12. Acknowledgements
	The contributions of the following are gratefully acknowledged:
	Matthew Pounsett, Tim Wicinski.
	13. References		12. References
	13.1. Normative References		12.1. Normative References
	[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",		[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
	STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,		STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
	<https://www.rfc-editor.org/info/rfc1034>.		<https://www.rfc-editor.org/info/rfc1034>.
	[RFC1035] Mockapetris, P., "Domain names - implementation and		[RFC1035] Mockapetris, P., "Domain names - implementation and
	specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,		specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
	November 1987, <https://www.rfc-editor.org/info/rfc1035>.		November 1987, <https://www.rfc-editor.org/info/rfc1035>.
	[RFC3225] Conrad, D., "Indicating Resolver Support of DNSSEC",		[RFC3225] Conrad, D., "Indicating Resolver Support of DNSSEC",
	skipping to change at page 25, line 37 ¶		skipping to change at line 1147 ¶
	[RFC6895] Eastlake 3rd, D., "Domain Name System (DNS) IANA		[RFC6895] Eastlake 3rd, D., "Domain Name System (DNS) IANA
	Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895,		Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895,
	April 2013, <https://www.rfc-editor.org/info/rfc6895>.		April 2013, <https://www.rfc-editor.org/info/rfc6895>.
	[RFC7766] Dickinson, J., Dickinson, S., Bellis, R., Mankin, A., and		[RFC7766] Dickinson, J., Dickinson, S., Bellis, R., Mankin, A., and
	D. Wessels, "DNS Transport over TCP - Implementation		D. Wessels, "DNS Transport over TCP - Implementation
	Requirements", RFC 7766, DOI 10.17487/RFC7766, March 2016,		Requirements", RFC 7766, DOI 10.17487/RFC7766, March 2016,
	<https://www.rfc-editor.org/info/rfc7766>.		<https://www.rfc-editor.org/info/rfc7766>.
	13.2. Informative References		12.2. Informative References
			[IANA-DNS] IANA, "Domain Name System (DNS) Parameters",
			<https://www.iana.org/assignments/dns-parameters/>.
	[ISC] "Internet Systems Consortuim", <https://www.isc.org/>.		[ISC] "Internet Systems Consortuim", <https://www.isc.org/>.
	[RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)",		[RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
	RFC 2671, DOI 10.17487/RFC2671, August 1999,		RFC 2671, DOI 10.17487/RFC2671, August 1999,
	<https://www.rfc-editor.org/info/rfc2671>.		<https://www.rfc-editor.org/info/rfc2671>.
	[RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record		[RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record
	(RR) Types", RFC 3597, DOI 10.17487/RFC3597, September		(RR) Types", RFC 3597, DOI 10.17487/RFC3597, September
	2003, <https://www.rfc-editor.org/info/rfc3597>.		2003, <https://www.rfc-editor.org/info/rfc3597>.
	skipping to change at page 26, line 18 ¶		skipping to change at line 1179 ¶
	[RFC7871] Contavalli, C., van der Gaast, W., Lawrence, D., and W.		[RFC7871] Contavalli, C., van der Gaast, W., Lawrence, D., and W.
	Kumari, "Client Subnet in DNS Queries", RFC 7871,		Kumari, "Client Subnet in DNS Queries", RFC 7871,
	DOI 10.17487/RFC7871, May 2016,		DOI 10.17487/RFC7871, May 2016,
	<https://www.rfc-editor.org/info/rfc7871>.		<https://www.rfc-editor.org/info/rfc7871>.
	[RFC7873] Eastlake 3rd, D. and M. Andrews, "Domain Name System (DNS)		[RFC7873] Eastlake 3rd, D. and M. Andrews, "Domain Name System (DNS)
	Cookies", RFC 7873, DOI 10.17487/RFC7873, May 2016,		Cookies", RFC 7873, DOI 10.17487/RFC7873, May 2016,
	<https://www.rfc-editor.org/info/rfc7873>.		<https://www.rfc-editor.org/info/rfc7873>.
			Acknowledgements
			The contributions of Matthew Pounsett and Tim Wicinski are gratefully
			acknowledged.
	Authors' Addresses		Authors' Addresses
	M. Andrews		M. Andrews
	Internet Systems Consortium		Internet Systems Consortium
	PO Box 360		PO Box 360
	Newmarket, NH 03857		Newmarket, NH 03857
	US		United States of America
	Email: marka@isc.org		Email: marka@isc.org
	Ray Bellis		Ray Bellis
	Internet Systems Consortium		Internet Systems Consortium
	PO Box 360		PO Box 360
	Newmarket, NH 03857		Newmarket, NH 03857
	US		United States of America
	Email: ray@isc.org		Email: ray@isc.org
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