< draft-ietf-dnsext-delegation-signer-14.txt		draft-ietf-dnsext-delegation-signer-15.txt >
	DNSEXT Working Group Olafur Gudmundsson		DNSEXT Working Group Olafur Gudmundsson
	INTERNET-DRAFT May 2003		INTERNET-DRAFT June 2003
	<draft-ietf-dnsext-delegation-signer-14.txt>		<draft-ietf-dnsext-delegation-signer-15.txt>
	Updates: RFC 1035, RFC 2535, RFC 3008, RFC 3090.		Updates: RFC 1035, RFC 2535, RFC 3008, RFC 3090.
	Delegation Signer Resource Record		Delegation Signer Resource Record
	Status of this Memo		Status of this Memo
	This document is an Internet-Draft and is in full conformance with		This document is an Internet-Draft and is in full conformance with
	all provisions of Section 10 of RFC2026.		all provisions of Section 10 of RFC2026.
	skipping to change at page 1, line 32 ¶		skipping to change at page 1, line 32 ¶
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as ``work in progress.''		material or to cite them other than as ``work in progress.''
	The list of current Internet-Drafts can be accessed at		The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt		http://www.ietf.org/ietf/1id-abstracts.txt
	The list of Internet-Draft Shadow Directories can be accessed at		The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html		http://www.ietf.org/shadow.html
	Comments should be sent to the authors or the DNSEXT WG mailing list		This draft expires on January 19, 2004.
	namedroppers@ops.ietf.org
	This draft expires on December 6, 2003.
	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2003). All rights reserved.		Copyright (C) The Internet Society (2003). All rights reserved.
	Abstract		Abstract
	The delegation signer (DS) resource record is inserted at a zone cut		The delegation signer (DS) resource record is inserted at a zone cut
	(i.e., a delegation point) to indicate that the delegated zone is		(i.e., a delegation point) to indicate that the delegated zone is
	digitally signed and that the delegated zone recognizes the indicated		digitally signed and that the delegated zone recognizes the indicated
	key as a valid zone key for the delegated zone. The DS RR is a		key as a valid zone key for the delegated zone. The DS RR is a
	modification to the DNS Security Extensions definition, motivated by		modification to the DNS Security Extensions definition, motivated by
	operational considerations. The intent is to use this resource record		operational considerations. The intent is to use this resource record
	as an explicit statement about the delegation, rather than relying on		as an explicit statement about the delegation, rather than relying on
	inference.		inference.
	This document defines the DS RR, gives examples of how it is used and		This document defines the DS RR, gives examples of how it is used and
	the implications of this record on resolvers. This change is not		describes the implications on resolvers. This change is not backwards
	backwards compatible with RFC 2535.		compatible with RFC 2535.
	This document updates RFC1035, RFC2535, RFC3008 and RFC3090.		This document updates RFC1035, RFC2535, RFC3008 and RFC3090.
	1 Introduction		Table of contents
	Familiarity with the DNS system [RFC1035], DNS security extensions		Status of this Memo . . . . . . . . . . . . . . . . . . . . . . . . 1
	[RFC2535] and DNSSEC terminology [RFC3090] is important.		Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
			Table of contents . . . . . . . . . . . . . . . . . . . . . . . . . 2
			1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
			1.2 Reserved Words" . . . . . . . . . . . . . . . . . . . . . . . . 4
			2 Specification of the Delegation key Signer" . . . . . . . . . . . 4
			2.1 Delegation Signer Record Model" . . . . . . . . . . . . . . . . 4
			2.2 Protocol Change" . . . . . . . . . . . . . . . . . . . . . . . . 5
			2.2.1 RFC2535 2.3.4 and 3.4: Special Considerations at
			Delegation Points" . . . . . . . . . . . . . . . . . . . . . . . . . 6
			2.2.1.1 Special processing for DS queries" . . . . . . . . . . . . 6
			2.2.1.2 Special processing when child and an ancestor share
			server" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
			2.2.1.3 Modification on use of KEY RR in the construction of
			Responses" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
			2.2.2 Signer's Name (replaces RFC3008 section 2.7)" . . . . . . . . 9
			2.2.3 Changes to RFC3090" . . . . . . . . . . . . . . . . . . . . . 9
			2.2.3.1 RFC3090: Updates to section 1: Introduction" . . . . . . . . 9
			2.2.3.2 RFC3090 section 2.1: Globally Secured" . . . . . . . . . . . 9
			2.2.3.3 RFC3090 section 3: Experimental Status." . . . . . . . . . 10
			2.2.4 NULL KEY elimination" . . . . . . . . . . . . . . . . . . . . 10
			2.3 Comments on Protocol Changes" . . . . . . . . . . . . . . . . . 10
			2.4 Wire Format of the DS record" . . . . . . . . . . . . . . . . . 11
			2.4.1 Justifications for Fields" . . . . . . . . . . . . . . . . . . 12
			2.5 Presentation Format of the DS Record" . . . . . . . . . . . . . 12
			2.6 Transition Issues for Installed Base" . . . . . . . . . . . . . 12
			2.6.1 Backwards compatibility with RFC2535 and RFC1035" . . . . . . 12
			2.7 KEY and corresponding DS record example" . . . . . . . . . . . . 13
			3 Resolver" . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
			3.1 DS Example" . . . . . . . . . . . . . . . . . . . . . . . . . . 14
			3.2 Resolver Cost Estimates for DS Records" . . . . . . . . . . . . 15
			4 Security Considerations: " . . . . . . . . . . . . . . . . . . . . 15
			5 IANA Considerations: " . . . . . . . . . . . . . . . . . . . . . . 16
			6 Acknowledgments" . . . . . . . . . . . . . . . . . . . . . . . . . 16
			Normative References: " . . . . . . . . . . . . . . . . . . . . . . 16
			Informational References" " . . . . . . . . . . . . . . . . . . . . 17
			Author Address" . . . . . . . . . . . . . . . . . . . . . . . . . . 17
			Full Copyright Statement" . . . . . . . . . . . . . . . . . . . . . 17
			1 Introduction
	Experience shows that when the same data can reside in two		Familiarity with the DNS system [RFC1035], DNS security extensions
	administratively different DNS zones, the data frequently gets out of		[RFC2535] and DNSSEC terminology [RFC3090] is important.
	sync. The presence of an NS RRset in a zone anywhere other than at
	the apex indicates a zone cut or delegation. The RDATA of the NS
	RRset specifies the authoritative servers for the delegated or
	"child" zone. Based on actual measurements, 10-30% of all delegations
	on the Internet have differing NS RRsets at parent and child. There
	are a number of reasons for this, including a lack of communication
	between parent and child and bogus name servers being listed to meet
	registry requirements.
	DNSSEC [RFC2535,RFC3008,RFC3090] specifies that a child zone needs to		Experience shows that when the same data can reside in two
	have its KEY RRset signed by its parent to create a verifiable chain		administratively different DNS zones, the data frequently gets out of
	of KEYs. There has been some debate on where the signed KEY RRset		sync. The presence of an NS RRset in a zone anywhere other than at
	should reside, whether at the child [RFC2535] or at the parent. If		the apex indicates a zone cut or delegation. The RDATA of the NS
	the KEY RRset resides at the child, maintaining the signed KEY RRset		RRset specifies the authoritative servers for the delegated or
	in the child requires frequent two-way communication between the two		"child" zone. Based on actual measurements, 10-30% of all delegations
	parties. First the child transmits the KEY RRset to the parent and		on the Internet have differing NS RRsets at parent and child. There
	then the parent sends the signature(s) to the child. Storing the KEY		are a number of reasons for this, including a lack of communication
	RRset at the parent was thought to simplify the communication.		between parent and child and bogus name servers being listed to meet
			registry requirements.
	DNSSEC [RFC2535] requires that the parent store a NULL KEY record for		DNSSEC [RFC2535,RFC3008,RFC3090] specifies that a child zone needs to
	an unsecure child zone to indicate that the child is unsecure. A NULL		have its KEY RRset signed by its parent to create a verifiable chain
	KEY record is a waste: an entire signed RRset is used to communicate		of KEYs. There has been some debate on where the signed KEY RRset
	effectively one bit of information--that the child is unsecure.		should reside, whether at the child [RFC2535] or at the parent. If
	Chasing down NULL KEY RRsets complicates the resolution process in		the KEY RRset resides at the child, maintaining the signed KEY RRset
	many cases, because servers for both parent and child need to be		in the child requires frequent two-way communication between the two
	queried for the KEY RRset if the child server does not return it.		parties. First the child transmits the KEY RRset to the parent and
	Storing the KEY RRset only in the parent zone simplifies this and		then the parent sends the signature(s) to the child. Storing the KEY
	would allow the elimination of the NULL KEY RRsets entirely. For		RRset at the parent was thought to simplify the communication.
	large delegation zones the cost of NULL keys is a significant barrier
	to deployment.
	Another complication of the DNSSEC key model is that the KEY record		DNSSEC [RFC2535] requires that the parent store a NULL KEY record for
	can be used to store public keys for other protocols in addition to		an unsecure child zone to indicate that the child is unsecure. A NULL
	DNSSEC keys. There are number of potential problems with this,		KEY record is a waste: an entire signed RRset is used to communicate
	including:		effectively one bit of information--that the child is unsecure.
	1. The KEY RRset can become quite large if many applications and		Chasing down NULL KEY RRsets complicates the resolution process in
	protocols store their keys at the zone apex. Possible protocols		many cases, because servers for both parent and child need to be
	are IPSEC, HTTP, SMTP, SSH and others that use public key		queried for the KEY RRset if the child server does not return it.
	cryptography.		Storing the KEY RRset only in the parent zone simplifies this and
	2. The KEY RRset may require frequent updates.		would allow the elimination of the NULL KEY RRsets entirely. For
	3. The probability of compromised or lost keys, which trigger		large delegation zones the cost of NULL keys is a significant barrier
	emergency key rollover procedures, increases.		to deployment.
	4. The parent may refuse sign KEY RRsets with non-DNSSEC zone keys.
	5. The parent may not meet the child's expectations in turnaround
	time for resigning the KEY RRset.
	Given these reasons, SIG@parent isn't any better than SIG/KEY@Child.		Prior to the restrictions imposed by RFC3445[RFC3445], another
			implication of the DNSSEC key model is that the KEY record could be
			used to store public keys for other protocols in addition to DNSSEC
			keys. There are number of potential problems with this, including:
			1. The KEY RRset can become quite large if many applications and
			protocols store their keys at the zone apex. Possible protocols
			are IPSEC, HTTP, SMTP, SSH and others that use public key
			cryptography.
			2. The KEY RRset may require frequent updates.
			3. The probability of compromised or lost keys, which trigger
			emergency key rollover procedures, increases.
	1.2 Reserved Words		4. The parent may refuse to sign KEY RRsets with non-DNSSEC zone
			keys.
			5. The parent may not meet the child's expectations of turnaround
			time for resigning the KEY RRset.
	The key words "MAY","MAY NOT", "MUST", "MUST NOT", "REQUIRED",		Given these reasons, SIG@parent isn't any better than SIG/KEY@Child.
	"RECOMMENDED", "SHOULD", and "SHOULD NOT" in this document are to be
	interpreted as described in RFC2119.
	2 Specification of the Delegation key Signer		1.2 Reserved Words
	This section defines the Delegation Signer (DS) RR type (type code		The key words "MAY","MAY NOT", "MUST", "MUST NOT", "REQUIRED",
	TBD) and the changes to DNS to accommodate it.		"RECOMMENDED", "SHOULD", and "SHOULD NOT" in this document are to be
			interpreted as described in RFC2119.
	2.1 Delegation Signer Record Model		2 Specification of the Delegation key Signer
	This document presents a replacement for the DNSSEC KEY record chain		This section defines the Delegation Signer (DS) RR type (type code
	of trust [RFC2535] that uses a new RR that resides only at the		TBD) and the changes to DNS to accommodate it.
	parent. This record identifies the key(s) that the child uses to
	self-sign its own KEY RRset.
	The chain of trust is now established by verifying the parent KEY		2.1 Delegation Signer Record Model
	RRset, the DS RRset from the parent and the KEY RRset at the child.
	This is cryptographically equivalent to using just KEY records.
	Communication between the parent and child is greatly reduced, since		This document presents a replacement for the DNSSEC KEY record chain
	the child only needs to notify the parent about changes in keys that		of trust [RFC2535] that uses a new RR that resides only at the
	sign its apex KEY RRset. The parent is ignorant of all other keys in		parent. This record identifies the key(s) that the child uses to
	the child's apex KEY RRset. Furthermore, the child maintains full		self-sign its own KEY RRset.
	control over the apex KEY RRset and its content. The child can
	maintain any policies regarding its KEY usage for DNSSEC with minimal
	impact on the parent. Thus if the child wants to have frequent key
	rollover for its DNS zone keys, the parent does not need to be aware
	of it. The child can use one key to sign only its apex KEY RRset and
	a different key to sign the other RRsets in the zone.
	This model fits well with a slow roll out of DNSSEC and the islands		Even though DS identifies two roles for KEYs, Key Signing Key (KSK)
	of security model. In this model, someone who trusts "good.example."		and Zone Signing Key (ZSK), there is no requirement that zone use two
	can preconfigure a key from "good.example." as a trusted key, and		different keys for these roles. It is expected that many small zones
	from then on trusts any data signed by that key or that has a chain		will only use one key, while larger zones will be more likely to use
	of trust to that key. If "example." starts advertising DS records,		multiple keys.
	"good.example." does not have to change operations by suspending
	self-signing. DS records can also be used to identify trusted keys
	instead of KEY records. Another significant advantage is that the
	amount of information stored in large delegation zones is reduced:
	rather than the NULL KEY record at every unsecure delegation required
	by RFC 2535, only secure delegations require additional information
	in the form of a signed DS RRset.
	The main disadvantage of this approach is that verifying a zone's KEY		The chain of trust is now established by verifying the parent KEY
	RRset requires two signature verification operations instead of the		RRset, the DS RRset from the parent and the KEY RRset at the child.
	one required by RFC 2535. There is no impact on the number of		This is cryptographically equivalent to using just KEY records.
	signatures verified for other types of RRsets.
	Even though DS identifies two roles for KEY's, Key Signing Key (KSK)		Communication between the parent and child is greatly reduced, since
	and Zone Signing Key (ZSK), there is no requirement that zone use two		the child only needs to notify the parent about changes in keys that
	different keys for these roles. It is expected that many small zones		sign its apex KEY RRset. The parent is ignorant of all other keys in
	will only use one key, while larger organizations will be more likely		the child's apex KEY RRset. Furthermore, the child maintains full
	to use multiple keys.		control over the apex KEY RRset and its content. The child can
			maintain any policies regarding its KEY usage for DNSSEC with minimal
			impact on the parent. Thus if the child wants to have frequent key
			rollover for its DNS zone keys, the parent does not need to be aware
			of it. The child can use one key to sign only its apex KEY RRset and
			a different key to sign the other RRsets in the zone.
	2.2 Protocol Change		This model fits well with a slow roll out of DNSSEC and the islands
			of security model. In this model, someone who trusts "good.example."
			can preconfigure a key from "good.example." as a trusted key, and
			from then on trusts any data signed by that key or that has a chain
			of trust to that key. If "example." starts advertising DS records,
			"good.example." does not have to change operations by suspending
			self-signing. DS records can be used in configuration files to
			identify trusted keys instead of KEY records. Another significant
			advantage is that the amount of information stored in large
			delegation zones is reduced: rather than the NULL KEY record at every
			unsecure delegation demanded by RFC 2535, only secure delegations
			require additional information in the form of a signed DS RRset.
	All DNS servers and resolvers that support DS MUST support the OK bit		The main disadvantage of this approach is that verifying a zone's KEY
	[RFC3225] and a larger message size [RFC3226]. In order for a		RRset requires two signature verification operations instead of the
	delegation to be considered secure the delegation MUST contain a DS		one in RFC 2535 chain of trust. There is no impact on the number of
	RRset. If a query contains the OK bit, a server returning a referral		signatures verified for other types of RRsets.
	for the delegation MUST include the following RRsets in the authority
	section in this order:
	If DS RRset is present:
	parents copy of childs NS RRset
	DS and SIG(DS)
	If no DS RRset is present:
	parents copy of childs NS RRset
	parents zone NXT and SIG(NXT)
	This increases the size of referral messages and possilbly causing		2.2 Protocol Change
	some or all glue to be omitted. If the DS or NXT RRsets with
	signatures do not fit in the DNS message, the TC bit MUST be set.
	Additional section processing is not changed.
	A DS RRset accompanying a NS RRset indicates that the child zone is		All DNS servers and resolvers that support DS MUST support the OK bit
	secure. If a NS RRset exists without a DS RRset, the child zone is		[RFC3225] and a larger message size [RFC3226]. In order for a
	unsecure (from the parents point of view). DS RRsets MUST NOT appear		delegation to be considered secure the delegation MUST contain a DS
	at non-delegation points or at a zone's apex.		RRset. If a query contains the OK bit, a server returning a referral
			for the delegation MUST include the following RRsets in the authority
			section in this order:
			If DS RRset is present:
			parent's copy of child's NS RRset
			DS and SIG(DS)
			If no DS RRset is present:
			parent's copy of child's NS RRset
			parent's zone NXT and SIG(NXT)
	Section 2.2.1 defines special considerations related to authoritative		This increases the size of referral messages, possibly causing some
	servers responding to DS queries and replaces RFC2535 sections 2.3.4		or all glue to be omitted. If the DS or NXT RRsets with signatures do
	and 3.4. Section 2.2.2 replaces RFC3008 section 2.7, and section		not fit in the DNS message, the TC bit MUST be set. Additional
	2.2.3 updates RFC3090.		section processing is not changed.
	2.2.1 RFC2535 2.3.4 and 3.4: Special Considerations at Delegation Points		A DS RRset accompanying a NS RRset indicates that the child zone is
			secure. If a NS RRset exists without a DS RRset, the child zone is
			unsecure (from the parents point of view). DS RRsets MUST NOT appear
			at non-delegation points or at a zone's apex.
	DNS security views each zone as a unit of data completely under the		Section 2.2.1 defines special considerations related to authoritative
	control of the zone owner with each entry (RRset) signed by a special		servers responding to DS queries and replaces RFC2535 sections 2.3.4
	private key held by the zone manager. But the DNS protocol views the		and 3.4. Section 2.2.2 replaces RFC3008 section 2.7, and section
	leaf nodes in a zone that are also the apex nodes of a child zone		2.2.3 updates RFC3090.
	(i.e., delegation points) as "really" belonging to the child zone.
	The corresponding domain names appear in two master files and might
	have RRsets signed by both the parent and child zones' keys. A
	retrieval could get a mixture of these RRsets and SIGs, especially
	since one server could be serving both the zone above and below a
	delegation point [RFC 2181].
	Each DS RRset stored in the parent zone MUST be signed by at least		2.2.1 RFC2535 2.3.4 and 3.4: Special Considerations at Delegation Points
	one of the parent zone's private key. The parent zone MUST NOT
	contain a KEY RRset at any delegation point. Delegations in the
	parent MAY contain only the following RR types: NS, DS, NXT and SIG.
	The NS RRset MUST NOT be signed. The NXT RRset is the exceptional
	case: it will always appear differently and authoritatively in both
	the parent and child zones if both are secure.
	A secure zone MUST contain a self-signed KEY RRset at its apex. Upon		DNS security views each zone as a unit of data completely under the
	verifying the DS RRset from the parent, a resolver MAY trust any KEY		control of the zone owner with each entry (RRset) signed by a special
	identified in the DS RRset as a valid signer of the child's apex KEY		private key held by the zone manager. But the DNS protocol views the
	RRset. Resolvers configured to trust one of the keys signing the KEY		leaf nodes in a zone that are also the apex nodes of a child zone
	RRset MAY now treat any data signed by the zone keys in the KEY RRset		(i.e., delegation points) as "really" belonging to the child zone.
	as secure. In all other cases resolvers MUST consider the zone		The corresponding domain names appear in two master files and might
	unsecure. A DS RRset MUST NOT appear at a zone's apex.		have RRsets signed by both the parent and child zones' keys. A
			retrieval could get a mixture of these RRsets and SIGs, especially
			since one server could be serving both the zone above and below a
			delegation point [RFC 2181].
	An authoritative server queried for type DS MUST return the DS RRset		Each DS RRset stored in the parent zone MUST be signed by at least
	in the answer section.		one of the parent zone's private keys. The parent zone MUST NOT
			contain a KEY RRset at any delegation point. Delegations in the
			parent MAY contain only the following RR types: NS, DS, NXT and SIG.
			The NS RRset MUST NOT be signed. The NXT RRset is the exceptional
			case: it will always appear differently and authoritatively in both
			the parent and child zones if both are secure.
	2.2.1.1 Special processing for DS queries		A secure zone MUST contain a self-signed KEY RRset at its apex. Upon
			verifying the DS RRset from the parent, a resolver MAY trust any KEY
			identified in the DS RRset as a valid signer of the child's apex KEY
			RRset. Resolvers configured to trust one of the keys signing the KEY
			RRset MAY now treat any data signed by the zone keys in the KEY RRset
			as secure. In all other cases resolvers MUST consider the zone
			unsecure. A DS RRset MUST NOT appear at a zone's apex.
	When a server is authoritative for the parent zone at a delegation		An authoritative server queried for type DS MUST return the DS RRset
	point and receives a query for the DS record at that name, it will		in the answer section.
	return the DS from the parent zone. This is true whether or not it
	is also authoritative for the child zone.
	When the server is authoritative for the child zone at a delegation		2.2.1.1 Special processing for DS queries
	point but not the parent zone, there is no natural response, since
	the child zone is not authoritative for the DS record at the zone's
	apex. As these queries are only expected to originate from recursive
	servers which are not DS-aware, the authoritative server MUST answer
	with:
	RCODE: NOERROR
	AA bit: set
	Answer Section: Empty
	Authority Section: SOA [+ SIG(SOA) + NXT + SIG(NXT)]
	That is, it answers as if it is authoritative and the DS record does		When a server is authoritative for the parent zone at a delegation
	not exist. DS-aware recursive servers will query the parent zone at		point and receives a query for the DS record at that name, it MUST
	delegation points, so will not be affected by this.		answer based on data in the parent zone, return DS or negative
			answer. This is true whether or not it is also authoritative for the
			child zone.
	A server authoritative for only the child zone at a delegation point		When the server is authoritative for the child zone at a delegation
	that is also a caching server MAY (if the RD bit is set in the query)		point but not the parent zone, there is no natural response, since
	perform recursion to find the DS record at the delegation point, and		the child zone is not authoritative for the DS record at the zone's
	may return the DS record from its cache. In this case, the AA bit		apex. As these queries are only expected to originate from recursive
	MUST not be set in the response.		servers which are not DS-aware, the authoritative server MUST answer
			with:
			RCODE: NOERROR
			AA bit: set
			Answer Section: Empty
			Authority Section: SOA [+ SIG(SOA) + NXT + SIG(NXT)]
	2.2.1.2 Special processing when child and an ancestor share server"		That is, it answers as if it is authoritative and the DS record does
			not exist. DS-aware recursive servers will query the parent zone at
			delegation points, so will not be affected by this.
	Special rules are needed to permit DS RR aware servers to gracefully		A server authoritative for only the child zone, that is also a
	interact with older caches which otherwise might falsely label a		caching server MAY (if the RD bit is set in the query) perform
	server as lame because of the new placement of the DS RR set.		recursion to find the DS record at the delegation point, or MAY
			return the DS record from its cache. In this case, the AA bit MUST
			not be set in the response.
	Such a situation might arise when a server is authoritative for both		2.2.1.2 Special processing when child and an ancestor share server
	a zone and it's grandparent, but not the parent. This sounds like an
	obscure example, but it is very real. The root zone is currently
	served on 13 machines, and "root-servers.net." is served on 4 of the
	same 13, but "net." is served elsewhere.
	When a server receives a query for (<QNAME>, DS, IN), the response		Special rules are needed to permit DS RR aware servers to gracefully
	MUST be determined from reading these rules in order:		interact with older caches which otherwise might falsely label a
			server as lame because of the placement of the DS RR set.
	1) If the server is authoritative for the zone that holds the DS RR		Such a situation might arise when a server is authoritative for both
	set (i.e., the zone that delegates <QNAME> away, aka the "parent"		a zone and it's grandparent, but not the parent. This sounds like an
	zone), the response contains the DS RR set as an authoritative		obscure example, but it is very real. The root zone is currently
	answer.		served on 13 machines, and "root-servers.net." is served on 4 of the
			same 13, but "net." is served elsewhere.
	2) If the server is offering recursive service and the RD bit is set		When a server receives a query for (<QNAME>, DS, <QCLASS>), the
	in the query, the server performs the query itself (according to the		response MUST be determined from reading these rules in order:
	rules for resolvers described below) and returns it's findings.
	3) If the server is authoritative for the zone that holds the		1) If the server is authoritative for the zone that holds the DS RR
	<QNAME>'s SOA RR set, the response is an authoritative negative		set (i.e., the zone that delegates <QNAME>, aka the "parent" zone),
	answer as described in 2.2.1.1.		the response contains the DS RR set as an authoritative answer.
	4) If the server is authoritative for a zone or zones above the		2) If the server is offering recursive service and the RD bit is set
	QNAME, a referral to the most enclosing zone's servers is made.		in the query, the server performs the query itself (according to the
			rules for resolvers described below) and returns its findings.
	5) If the server is not authoritative for any part of the QNAME, a		3) If the server is authoritative for the zone that holds the
	response indicating a lame server for QNAME is given.		<QNAME>'s SOA RR set, the response is an authoritative negative
			answer as described in 2.2.1.1.
	Using these rules will require some special processing on the part of		4) If the server is authoritative for a zone or zones above the
	a DS RR aware resolver. To illustrate this, an example is used.		QNAME, a referral to the most enclosing zone's servers is made.
	Assuming a server is authoritative for roots.example.net. and for the		5) If the server is not authoritative for any part of the QNAME, a
	root zone but not the intervening two zones (or the intervening two		response indicating a lame server for QNAME is given.
	label deep zone). Assume that QNAME=roots.example.net., QTYPE=DS,
	and QCLASS=IN.
	The resolver will issue this request (assuming no cached data)		Using these rules will require some special processing on the part of
	expecting a referral to a net. server. Instead, rule number 3 above		a DS RR aware resolver. To illustrate this, an example is used.
	applies and a negative answer is returned by the server. The
	reaction by the resolver is not to accept this answer as final as it
	can determine from the SOA RR in the negative answer the context
	within which the server has answered.
	A solution to this is to instruct the resolver to hunt for the		Assuming a server is authoritative for roots.example.net. and for the
	authoritative zone of the data in a brute force manner.		root zone but not the intervening two zones (or the intervening two
			label deep zone). Assume that QNAME=roots.example.net., QTYPE=DS,
			and QCLASS=IN.
	This can be accomplished by taking the owner name of the returned SOA		The resolver will issue this request (assuming no cached data)
	RR and strip off enough left-hand labels until a successful NS		expecting a referral to a net. server. Instead, rule number 3 above
	response is obtained. A successful response here means that the		applies and a negative answer is returned by the server. The
	answer has NS records in it. (Entertaining the possibility that a		reaction by the resolver is not to accept this answer as final as it
	cut point may be two labels down in a zone.)		can determine from the SOA RR in the negative answer the context
			within which the server has answered.
	Returning to the example, the response will include a negative answer		A solution to this is to instruct the resolver to hunt for the
	with either the SOA RR for "roots.example.net." or "example.net."		authoritative zone of the data in a brute force manner.
	depending on whether roots.example.net is a delegated domain. In
	either case, removing the least significant label of the SOA owner
	name will lead to the location of the desired data.
	2.2.1.3 Modification on KEY RR in the construction of Responses		This can be accomplished by taking the owner name of the returned SOA
			RR and striping off enough left-hand labels until a successful NS
			response is obtained. A successful response here means that the
			answer has NS records in it. (Entertaining the possibility that a
			cut point can be two labels down in a zone.)
	This section updates RFC2535 section 3.5 by replacing it with the		Returning to the example, the response will include a negative answer
	following:		with either the SOA RR for "roots.example.net." or "example.net."
			depending on whether roots.example.net is a delegated domain. In
			either case, removing the left most label of the SOA owner name will
			lead to the location of the desired data.
	An query for KEY RR MUST NOT trigger any additional section		2.2.1.3 Modification on use of KEY RR in the construction of Responses
	processing. Security aware resolver will include corresponding SIG
	records in the answer section.
	KEY records SHOULD NOT be added to additional records section in		This section updates RFC2535 section 3.5 by replacing it with the
	response to any query.		following:
	RFC2535 included rules to in add KEY records to additional section		A query for KEY RR MUST NOT trigger any additional section
	when SOA or NS records where included in an answer. The is was done		processing. Security aware resolvers will include corresponding SIG
	to reduce round trips (in the case of SOA) and to force out NULL		records in the answer section.
	KEY's (in the NS case), as this document obsoletes NULL keys there is
	no need for the second case, the first case causes redundant
	transfers of KEY RRset as SOA is included in the authority section of
	negative answers.
	RFC2535 section 3.5 also included rule for adding KEY RRset to query		KEY records SHOULD NOT be added to the additional records section in
	for A and AAAA, as Restrict KEY[RFC3445] eliminated use of KEY RR by		response to any query.
	all applications therfore the rule is not needed anymore.
	2.2.2 Signer's Name (replaces RFC3008 section 2.7)		RFC2535 specified that KEY records be added to the additional section
			when SOA or NS records where included in an answer. This was done to
			reduce round trips (in the case of SOA) and to force out NULL KEYs
			(in the NS case). As this document obsoletes NULL keys there is no
			need for the inclusion of KEYs with NSs. Furthermore as SOAs are
			included in the authority section of negative answers, including the
			KEYs each time will cause redundant transfers of KEYs.
	The signer's name field of a SIG RR MUST contain the name of the zone		RFC2535 section 3.5 also included rule for adding the KEY RRset to
	to which the data and signature belong. The combination of signer's		the response for a query for A and AAAA types. As Restrict
	name, key tag, and algorithm MUST identify a zone key if the SIG is		KEY[RFC3445] eliminated use of KEY RR by all applications this rule
	to be considered material. This document defines a standard policy		is no longer needed.
	for DNSSEC validation; local policy may override the standard policy.
	There are no restrictions on the signer field of a SIG(0) record.		2.2.2 Signer's Name (replaces RFC3008 section 2.7)
	The combination of signer's name, key tag, and algorithm MUST
	identify a key if this SIG(0) is to be processed.
	2.2.3 Changes to RFC3090		The signer's name field of a SIG RR MUST contain the name of the zone
			to which the data and signature belong. The combination of signer's
			name, key tag, and algorithm MUST identify a zone key if the SIG is
			to be considered material. This document defines a standard policy
			for DNSSEC validation; local policy MAY override the standard policy.
	A number of sections of RFC3090 need to be updated to reflect the DS		There are no restrictions on the signer field of a SIG(0) record.
	record.		The combination of signer's name, key tag, and algorithm MUST
			identify a key if this SIG(0) is to be processed.
	2.2.3.1 RFC3090: Updates to section 1: Introduction		2.2.3 Changes to RFC3090
	Most of the text is still relevant but the words ``NULL key'' are to		A number of sections of RFC3090 need to be updated to reflect the DS
	be replaced with ``missing DS RRset''. In section 1.3 the last three		record.
	paragraphs discuss the confusion in sections of RFC 2535 that are
	replaced in section 2.2.1 above. Therefore, these paragraphs are now
	obsolete.
	2.2.3.2 RFC3090 section 2.1: Globally Secured		2.2.3.1 RFC3090: Updates to section 1: Introduction
	Rule 2.1.b is replaced by the following rule:		Most of the text is still relevant but the words ``NULL key'' are to
			be replaced with ``missing DS RRset''. In section 1.3 the last three
			paragraphs discuss the confusion in sections of RFC 2535 that are
			replaced in section 2.2.1 above. Therefore, these paragraphs are now
			obsolete.
	2.1.b. The KEY RRset at a zone's apex MUST be self-signed by a		2.2.3.2 RFC3090 section 2.1: Globally Secured
	private key whose public counterpart MUST appear in a zone signing
	KEY RR (2.a) owned by the zone's apex and specifying a mandatory-to-
	implement algorithm. This KEY RR MUST be identified by a DS RR in a
	signed DS RRset in the parent zone.
	If a zone cannot get its parent to advertise a DS record for it, the		Rule 2.1.b is replaced by the following rule:
	child zone cannot be considered globally secured. The only exception
	to this is the root zone, for which there is no parent zone.
	2.2.3.3 RFC3090 section 3: Experimental Status.		2.1.b. The KEY RRset at a zone's apex MUST be self-signed by a
			private key whose public counterpart MUST appear in a zone signing
			KEY RR (2.a) owned by the zone's apex and specifying a mandatory-to-
			implement algorithm. This KEY RR MUST be identified by a DS RR in a
			signed DS RRset in the parent zone.
	The only difference between experimental status and globally secured		If a zone cannot get its parent to advertise a DS record for it, the
	is the missing DS RRset in the parent zone. All locally secured zones		child zone cannot be considered globally secured. The only exception
	are experimental.		to this is the root zone, for which there is no parent zone.
	2.2.4 NULL KEY elimination		2.2.3.3 RFC3090 section 3: Experimental Status.
	RFC3445 section 3 elminates the top two bits in the flags field of		The only difference between experimental status and globally secured
	KEY RR. These two bits where used to indicate NULL KEY or NO KEY.		is the missing DS RRset in the parent zone. All locally secured zones
	RFC3090 defines that zone that defines that zone is either secure or		are experimental.
	not, eliminates the possible need to put NULL keys in the zone apex
	to indicate that the zone is not secured for a algorithm. Along with
	this document these other two elminate all uses for the NULL KEY,
	Thus this document obsoletes NULL KEY.
	2.3 Comments on Protocol Changes		2.2.4 NULL KEY elimination
	Over the years there have been various discussions surrounding the		RFC3445 section 3 eliminates the top two bits in the flags field of
	DNS delegation model, declaring it to be broken because there is no		KEY RR. These two bits were used to indicate NULL KEY or NO KEY.
	good way to assert if a delegation exists. In the RFC2535 version of		RFC3090 defines that zone is either secure or not, these rules
	DNSSEC, the presence of the NS bit in the NXT bit map proves there is		eliminates the possible need to put NULL keys in the zone apex to
	a delegation at this name. Something more explicit is needed and the		indicate that the zone is not secured for a algorithm. Along with
	DS record addresses this need for secure delegations.		this document these other two eliminate all uses for the NULL KEY,
			This document obsoletes NULL KEY.
	The DS record is a major change to DNS: it is the first resource		2.3 Comments on Protocol Changes
	record that can appear only on the upper side of a delegation. Adding
	it will cause interoperabilty problems and requires a flag day for
	DNSSEC. Many old servers and resolvers MUST be upgraded to take
	advantage of DS. Some old servers will be able to be authoritative
	for zones with DS records but will not add the NXT or DS records to
	the authority section. The same is true for caching servers; in
	fact, some may even refuse to pass on the DS or NXT records.
	2.4 Wire Format of the DS record		Over the years there have been various discussions surrounding the
			DNS delegation model, declaring it to be broken because there is no
			good way to assert if a delegation exists. In the RFC2535 version of
			DNSSEC, the presence of the NS bit in the NXT bit map proves there is
			a delegation at this name. Something more explicit is needed and the
			DS record addresses this need for secure delegations.
	The DS (type=TDB) record contains these fields: key tag, algorithm,		The DS record is a major change to DNS: it is the first resource
	digest type, and the digest of a public key KEY record that is		record that can appear only on the upper side of a delegation. Adding
	allowed and/or used to sign the child's apex KEY RRset. Other keys		it will cause interoperabilty problems and requires a flag day for
	MAY sign the child's apex KEY RRset.		DNSSEC. Many old servers and resolvers MUST be upgraded to take
			advantage of DS. Some old servers will be able to be authoritative
			for zones with DS records but will not add the NXT or DS records to
			the authority section. The same is true for caching servers; in
			fact, some might even refuse to pass on the DS or NXT records.
	1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3		2.4 Wire Format of the DS record
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| key tag | algorithm | Digest type |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| digest (length depends on type) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| (SHA-1 digest is 20 bytes) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The key tag is calculated as specified in RFC2535. Algorithm MUST be		The DS (type=TDB) record contains these fields: key tag, algorithm,
	an algorithm number assigned in the range 1..251 and the algorithm		digest type, and the digest of a public key KEY record that is
	MUST be allowed to sign DNS data. The digest type is an identifier		allowed and/or used to sign the child's apex KEY RRset. Other keys
	for the digest algorithm used. The digest is calculated over the		MAY sign the child's apex KEY RRset.
	canonical name of the delegated domain name followed by the whole
	RDATA of the KEY record (all four fields).
	digest = hash( canonical FQDN on KEY RR | KEY_RR_rdata)		1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| key tag | algorithm | Digest type |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| digest (length depends on type) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| (SHA-1 digest is 20 bytes) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	KEY_RR_rdata = Flags | Protocol | Algorithm | Public Key		The key tag is calculated as specified in RFC2535. Algorithm MUST be
			an algorithm number assigned in the range 1..251 and the algorithm
			MUST be allowed to sign DNS data. The digest type is an identifier
			for the digest algorithm used. The digest is calculated over the
			canonical name of the delegated domain name followed by the whole
			RDATA of the KEY record (all four fields).
	Digest type value 0 is reserved, value 1 is SHA-1, and reserving		digest = hash( canonical FQDN on KEY RR | KEY_RR_rdata)
	other types requires IETF standards action. For interoperabilty
	reasons, as few digest algorithms as possible should be reserved. The
	only reason to reserve additional digest types is to increase
	security.
	DS records MUST point to zone KEY records that are allowed to		KEY_RR_rdata = Flags | Protocol | Algorithm | Public Key
	authenticate DNS data. The indicated KEY record's protocol field
	MUST be set to 3; flag field bit 7 MUST be set to 1. The value of
	other flag bits is not significant for the purposes of this document.
	The size of the DS RDATA for type 1 (SHA-1) is 24 bytes, regardless		Digest type value 0 is reserved, value 1 is SHA-1, and reserving
	of key size, new digest types probably will have larger digests.		other types requires IETF standards action. For interoperabilty
			reasons, keeping number of digest algorithms low is strongly
			RECOMMENDED. The only reason to reserve additional digest types is
			to increase security.
	2.4.1 Justifications for Fields		DS records MUST point to zone KEY records that are allowed to
			authenticate DNS data. The indicated KEY records protocol field MUST
			be set to 3; flag field bit 7 MUST be set to 1. The value of other
			flag bits is not significant for the purposes of this document.
	The algorithm and key tag fields are present to allow resolvers to		The size of the DS RDATA for type 1 (SHA-1) is 24 bytes, regardless
	quickly identify the candidate KEY records to examine. SHA-1 is a		of key size. New digest types probably will have larger digests.
	strong cryptographic checksum: it is computationally infeasible for
	an attacker to generate a KEY record that has the same SHA-1 digest.
	Combining the name of the key and the key rdata as input to the
	digest provides stronger assurance of the binding. Having the key
	tag in the DS record adds greater assurance than the SHA-1 digest
	alone, as there are now two different mapping functions that a KEY RR
	must match.
	This format allows concise representation of the keys that the child		2.4.1 Justifications for Fields
	will use, thus keeping down the size of the answer for the
	delegation, reducing the probability of DNS message overflow. The
	SHA-1 hash is strong enough to uniquely identify the key and is
	similar to the PGP key footprint. The digest type field is present
	for possible future expansion.
	The DS record is well suited to listing trusted keys for islands of		The algorithm and key tag fields are present to allow resolvers to
	security in configuration files.		quickly identify the candidate KEY records to examine. SHA-1 is a
			strong cryptographic checksum: it is computationally infeasible for
			an attacker to generate a KEY record that has the same SHA-1 digest.
			Combining the name of the key and the key rdata as input to the
			digest provides stronger assurance of the binding. Having the key
			tag in the DS record adds greater assurance than the SHA-1 digest
			alone, as there are now two different mapping functions.
	2.5 Presentation Format of the DS Record		This format allows concise representation of the keys that the child
			will use, thus keeping down the size of the answer for the
			delegation, reducing the probability of DNS message overflow. The
			SHA-1 hash is strong enough to uniquely identify the key and is
			similar to the PGP key footprint. The digest type field is present
			for possible future expansion.
	The presentation format of the DS record consists of three numbers		The DS record is well suited to listing trusted keys for islands of
	(key tag, algorithm and digest type) followed by the digest itself		security in configuration files.
	presented in hex:
	example. DS 12345 3 1 123456789abcdef67890123456789abcdef67890
	2.6 Transition Issues for Installed Base		2.5 Presentation Format of the DS Record
	No backwards compatibility with RFC2535 is provided.		The presentation format of the DS record consists of three numbers
			(key tag, algorithm and digest type) followed by the digest itself
			presented in hex:
			example. DS 12345 3 1 123456789abcdef67890123456789abcdef67890
	RFC2535-compliant resolvers will assume that all DS-secured		2.6 Transition Issues for Installed Base
	delegations are locally secure. This is bad, but the DNSEXT Working
	Group has determined that rather than dealing with both
	RFC2535-secured zones and DS-secured zones, a rapid adoption of DS is
	preferable. Thus the only option for early adopters is to upgrade to
	DS as soon as possible.
	2.6.1 Backwards compatibility with RFC2535 and RFC1035		No backwards compatibility with RFC2535 is provided.
	This section documents how a resolver determines the type of		RFC2535-compliant resolvers will assume that all DS-secured
	delegation.		delegations are locally secure. This is bad, but the DNSEXT Working
	RFC1035 delegation (in parent) has:		Group has determined that rather than dealing with both
			RFC2535-secured zones and DS-secured zones, a rapid adoption of DS is
			preferable. Thus the only option for early adopters is to upgrade to
			DS as soon as possible.
	RFC1035 NS		2.6.1 Backwards compatibility with RFC2535 and RFC1035
	RFC2535 adds the following two cases:		This section documents how a resolver determines the type of
			delegation.
			RFC1035 delegation (in parent) has:
	Secure RFC2535: NS + NXT + SIG(NXT)		RFC1035 NS
	NXT bit map contains: NS SIG NXT
	Unsecure RFC2535: NS + KEY + SIG(KEY) + NXT + SIG(NXT)
	NXT bit map contains: NS SIG KEY NXT
	KEY must be a NULL key.
	DNSSEC with DS has the following two states:		RFC2535 adds the following two cases:
	Secure DS: NS + DS + SIG(DS)		Secure RFC2535: NS + NXT + SIG(NXT)
	NXT bit map contains: NS SIG NXT DS		NXT bit map contains: NS SIG NXT
	Unsecure DS: NS + NXT + SIG(NXT)		Unsecure RFC2535: NS + KEY + SIG(KEY) + NXT + SIG(NXT)
	NXT bit map contains: NS SIG NXT		NXT bit map contains: NS SIG KEY NXT
			KEY must be a NULL key.
	It is difficult for a resolver to determine if a delegation is secure		DNSSEC with DS has the following two states:
	RFC 2535 or unsecure DS. This could be overcome by adding a flag to
	the NXT bit map, but only upgraded resolvers would understand this
	flag, anyway. Having both parent and child signatures for a KEY RRset
	might allow old resolvers to accept a zone as secure, but the cost of
	doing this for a long time is much higher than just prohibiting RFC
	2535-style signatures at child zone apexes and forcing rapid
	deployment of DS-enabled servers and resolvers.
	RFC 2535 and DS can in theory be deployed in parallel, but this would		Secure DS: NS + DS + SIG(DS)
	require resolvers to deal with RFC 2535 configurations forever. This		NXT bit map contains: NS SIG NXT DS
	document obsoletes the NULL KEY in parent zones, which is a difficult		Unsecure DS: NS + NXT + SIG(NXT)
	enough change that a flag day is required.		NXT bit map contains: NS SIG NXT
	2.7 KEY and corresponding DS record example		It is difficult for a resolver to determine if a delegation is secure
			RFC 2535 or unsecure DS. This could be overcome by adding a flag to
			the NXT bit map, but only upgraded resolvers would understand this
			flag, anyway. Having both parent and child signatures for a KEY RRset
			might allow old resolvers to accept a zone as secure, but the cost of
			doing this for a long time is much higher than just prohibiting RFC
			2535-style signatures at child zone apexes and forcing rapid
			deployment of DS-enabled servers and resolvers.
	This is an example of a KEY record and the corresponding DS record.		RFC 2535 and DS can in theory be deployed in parallel, but this would
			require resolvers to deal with RFC 2535 configurations forever. This
			document obsoletes the NULL KEY in parent zones, which is a difficult
			enough change that to cause a flag day.
	dskey.example. KEY 256 3 1 (		2.7 KEY and corresponding DS record example
	AQPwHb4UL1U9RHaU8qP+Ts5bVOU1s7fYbj2b3CCbzNdj
	4+/ECd18yKiyUQqKqQFWW5T3iVc8SJOKnueJHt/Jb/wt
	) ; key id = 28668
	DS 28668 1 1 49FD46E6C4B45C55D4AC69CBD3CD34AC1AFE51DE
	3 Resolver		This is an example of a KEY record and the corresponding DS record.
	3.1 DS Example		dskey.example. KEY 256 3 1 (
			AQPwHb4UL1U9RHaU8qP+Ts5bVOU1s7fYbj2b3CCbzNdj
			4+/ECd18yKiyUQqKqQFWW5T3iVc8SJOKnueJHt/Jb/wt
			) ; key id = 28668
			DS 28668 1 1 49FD46E6C4B45C55D4AC69CBD3CD34AC1AFE51DE
	To create a chain of trust, a resolver goes from trusted KEY to DS to		3 Resolver
	KEY.
	Assume the key for domain "example." is trusted. Zone "example."		3.1 DS Example
	contains at least the following records:
	example. SOA <soa stuff>
	example. NS ns.example.
	example. KEY <stuff>
	example. NXT NS SOA KEY SIG NXT secure.example.
	example. SIG(SOA)
	example. SIG(NS)
	example. SIG(NXT)
	example. SIG(KEY)
	secure.example. NS ns1.secure.example.
	secure.example. DS tag=12345 alg=3 digest_type=1 <foofoo>
	secure.example. NXT NS SIG NXT DS unsecure.example.
	secure.example. SIG(NXT)
	secure.example. SIG(DS)
	unsecure.example NS ns1.unsecure.example.
	unsecure.example. NXT NS SIG NXT example.
	unsecure.example. SIG(NXT)
	In zone "secure.example." following records exist:		To create a chain of trust, a resolver goes from trusted KEY to DS to
	secure.example. SOA <soa stuff>		KEY.
	secure.example. NS ns1.secure.example.
	secure.example. KEY <tag=12345 alg=3>
	secure.example. KEY <tag=54321 alg=5>
	secure.example. NXT <nxt stuff>
	secure.example. SIG(KEY) <key-tag=12345 alg=3>
	secure.example. SIG(SOA) <key-tag=54321 alg=5>
	secure.example. SIG(NS) <key-tag=54321 alg=5>
	secure.example. SIG(NXT) <key-tag=54321 alg=5>
	In this example the private key for "example." signs the DS record		Assume the key for domain "example." is trusted. Zone "example."
	for "secure.example.", making that a secure delegation. The DS record		contains at least the following records:
	states which key is expected to sign the KEY RRset at		example. SOA <soa stuff>
	"secure.example.". Here "secure.example." signs its KEY RRset with		example. NS ns.example.
	the KEY identified in the DS RRset, thus the KEY RRset is validated		example. KEY <stuff>
	and trusted.		example. NXT NS SOA KEY SIG NXT secure.example.
			example. SIG(SOA)
			example. SIG(NS)
			example. SIG(NXT)
			example. SIG(KEY)
			secure.example. NS ns1.secure.example.
			secure.example. DS tag=12345 alg=3 digest_type=1 <foofoo>
			secure.example. NXT NS SIG NXT DS unsecure.example.
			secure.example. SIG(NXT)
			secure.example. SIG(DS)
			unsecure.example NS ns1.unsecure.example.
			unsecure.example. NXT NS SIG NXT example.
			unsecure.example. SIG(NXT)
	This example has only one DS record for the child, but parents MUST		In zone "secure.example." following records exist:
	allow multiple DS records to facilitate key rollover and multiple KEY		secure.example. SOA <soa stuff>
	algorithms.		secure.example. NS ns1.secure.example.
			secure.example. KEY <tag=12345 alg=3>
			secure.example. KEY <tag=54321 alg=5>
			secure.example. NXT <nxt stuff>
			secure.example. SIG(KEY) <key-tag=12345 alg=3>
			secure.example. SIG(SOA) <key-tag=54321 alg=5>
			secure.example. SIG(NS) <key-tag=54321 alg=5>
			secure.example. SIG(NXT) <key-tag=54321 alg=5>
	The resolver determines the security status of "unsecure.example." by		In this example the private key for "example." signs the DS record
	examining the parent zone's NXT record for this name. The absence of		for "secure.example.", making that a secure delegation. The DS record
	the DS bit indicates an unsecure delegation. Note the NXT record		states which key is expected to sign the KEY RRset at
	SHOULD only be examined after verifying the corresponding signature.		"secure.example.". Here "secure.example." signs its KEY RRset with
			the KEY identified in the DS RRset, thus the KEY RRset is validated
			and trusted.
	3.1 Resolver Cost Estimates for DS Records		This example has only one DS record for the child, but parents MUST
			allow multiple DS records to facilitate key rollover and multiple KEY
			algorithms.
	From a RFC2535 resolver point of view, for each delegation followed		The resolver determines the security status of "unsecure.example." by
	to chase down an answer, one KEY RRset has to be verified.		examining the parent zone's NXT record for this name. The absence of
	Additional RRsets might also need to be verified based on local		the DS bit indicates an unsecure delegation. Note the NXT record
	policy (e.g., the contents of the NS RRset). Once the resolver gets		SHOULD only be examined after verifying the corresponding signature.
	to the appropriate delegation, validating the answer might require
	verifying one or more signatures. A simple A record lookup requires
	at least N delegations to be verified and one RRset. For a DS-enabled
	resolver, the cost is 2N+1. For an MX record, where the target of
	the MX record is in the same zone as the MX record, the costs are N+2
	and 2N+2, for RFC 2535 and DS, respectively. In the case of negatives
	answer the same ratios hold true.
	The resolver may require an extra query to get the DS record and this		3.2 Resolver Cost Estimates for DS Records
	may add to the overall cost of the query, but this is never worse
	than chasing down NULL KEY records from the parent in RFC2535 DNSSEC.
	DS adds processing overhead on resolvers and increases the size of		From a RFC2535 resolver point of view, for each delegation followed
	delegation answers, but much less than storing signatures in the		to chase down an answer, one KEY RRset has to be verified.
	parent zone.		Additional RRsets might also need to be verified based on local
			policy (e.g., the contents of the NS RRset). Once the resolver gets
			to the appropriate delegation, validating the answer might require
			verifying one or more signatures. A simple A record lookup requires
			at least N delegations to be verified and one RRset. For a DS-enabled
			resolver, the cost is 2N+1. For an MX record, where the target of
			the MX record is in the same zone as the MX record, the costs are N+2
			and 2N+2, for RFC 2535 and DS, respectively. In the case of negatives
			answer the same ratios hold true.
	4 Security Considerations:		The resolver have to do an extra query to get the DS record and this
			increases the overall cost of resolving this question, but this is
			never worse than chasing down NULL KEY records from the parent in
			RFC2535 DNSSEC.
	This document proposes a change to the validation chain of KEY		DS adds processing overhead on resolvers and increases the size of
	records in DNSSEC. The change is not believed to reduce security in		delegation answers, but much less than storing signatures in the
	the overall system. In RFC2535 DNSSEC, the child zone has to		parent zone.
	communicate keys to its parent and prudent parents will require some
	authentication with that transaction. The modified protocol will
	require the same authentication, but allows the child to exert more
	local control over its own KEY RRset.
	There is a remote possibility that an attacker could generate a valid		4 Security Considerations:
	KEY that matches all the DS fields, of a specific DS set, and thus
	forge data from the child. This possibility is considered
	impractical, as on average more than
	2 ^ (160 - <Number of keys in DS set>)
	keys would have to be generated before a match would be found.
	An attacker that wants to match any DS record will have to generate		This document proposes a change to the validation chain of KEY
	on average at least 2^80 keys.		records in DNSSEC. The change is not believed to reduce security in
			the overall system. In RFC2535 DNSSEC, the child zone has to
			communicate keys to its parent and prudent parents will require some
			authentication with that transaction. The modified protocol will
			require the same authentication, but allows the child to exert more
			local control over its own KEY RRset.
	The DS record represents a change to the DNSSEC protocol and there is		There is a remote possibility that an attacker could generate a valid
	an installed base of implementations, as well as textbooks on how to		KEY that matches all the DS fields, of a specific DS set, and thus
	set up secure delegations. Implementations that do not understand the		forge data from the child. This possibility is considered
	DS record will not be able to follow the KEY to DS to KEY chain and		impractical, as on average more than
	will consider all zones secured that way as unsecure.		2 ^ (160 - <Number of keys in DS set>)
			keys would have to be generated before a match would be found.
	5 IANA Considerations:		An attacker that wants to match any DS record will have to generate
			on average at least 2^80 keys.
	IANA needs to allocate an RR type code for DS from the standard RR		The DS record represents a change to the DNSSEC protocol and there is
	type space (type 43 requested).		an installed base of implementations, as well as textbooks on how to
			set up secure delegations. Implementations that do not understand the
			DS record will not be able to follow the KEY to DS to KEY chain and
			will consider all zones secured that way as unsecure.
	IANA needs to open a new registry for the DS RR type for digest		5 IANA Considerations:
	algorithms. Defined types are:
	0 is Reserved,
	1 is SHA-1.
	Adding new reservations requires IETF standards action.
	6 Acknowledgments		IANA needs to allocate an RR type code for DS from the standard RR
			type space (type 43 requested).
	Over the last few years a number of people have contributed ideas		IANA needs to open a new registry for the DS RR type for digest
	that are captured in this document. The core idea of using one key to		algorithms. Defined types are:
	sign only the KEY RRset comes from discussions with Bill Manning and		0 is Reserved,
	Perry Metzger on how to put in a single root key in all resolvers.		1 is SHA-1.
	Alexis Yushin, Brian Wellington, Sam Weiler, Paul Vixie, Jakob		Adding new reservations requires IETF standards action.
	Schlyter, Scott Rose, Edward Lewis, Lars-Johan Liman, Matt Larson,
	Mark Kosters, Dan Massey, Olaf Kolman, Phillip Hallam-Baker, Miek
	Gieben, Havard Eidnes, Donald Eastlake 3rd., Randy Bush, David
	Blacka, Steve Bellovin, Rob Austein, Derek Atkins, Roy Arends, Mark
	Andrews, Harald Alvestrand, and others have provided useful comments.
	Normative References:		6 Acknowledgments
	[RFC1035] P. Mockapetris, ``Domain Names - Implementation and		Over the last few years a number of people have contributed ideas
	Specification'', STD 13, RFC 1035, November 1987.		that are captured in this document. The core idea of using one key to
			sign only the KEY RRset comes from discussions with Bill Manning and
			Perry Metzger on how to put in a single root key in all resolvers.
			Alexis Yushin, Brian Wellington, Sam Weiler, Paul Vixie, Jakob
			Schlyter, Scott Rose, Edward Lewis, Lars-Johan Liman, Matt Larson,
			Mark Kosters, Dan Massey, Olaf Kolman, Phillip Hallam-Baker, Miek
			Gieben, Havard Eidnes, Donald Eastlake 3rd., Randy Bush, David
			Blacka, Steve Bellovin, Rob Austein, Derek Atkins, Roy Arends, Mark
			Andrews, Harald Alvestrand, and others have provided useful comments.
	[RFC2535] D. Eastlake, ``Domain Name System Security Extensions'', RFC		Normative References:
	2535, March 1999.
	[RFC3008] B. Wellington, ``Domain Name System Security (DNSSEC) Signing		[RFC1035] P. Mockapetris, ``Domain Names - Implementation and
	Authority'', RFC 3008, November 2000.		Specification'', STD 13, RFC 1035, November 1987.
	[RFC3090] E. Lewis `` DNS Security Extension Clarification on Zone		[RFC2535] D. Eastlake, ``Domain Name System Security Extensions'', RFC
	Status'', RFC 3090, March 2001.		2535, March 1999.
	[RFC3225] D. Conrad, ``Indicating Resolver Support of DNSSEC'', RFC		[RFC3008] B. Wellington, ``Domain Name System Security (DNSSEC) Signing
	3225, December 2001.		Authority'', RFC 3008, November 2000.
	[RFC3445] D. Massey, S. Rose ``Limiting the scope of the KEY Resource		[RFC3090] E. Lewis `` DNS Security Extension Clarification on Zone
	Record (RR)``, RFC 3445, December 2002.		Status'', RFC 3090, March 2001.
	Informational References		[RFC3225] D. Conrad, ``Indicating Resolver Support of DNSSEC'', RFC
			3225, December 2001.
	[RFC2181] R. Elz, R. Bush, ``Clarifications to the DNS Specification'',		[RFC3445] D. Massey, S. Rose ``Limiting the scope of the KEY Resource
	RFC 2181, July 1997.		Record (RR)``, RFC 3445, December 2002.
	[RFC3226] O. Gudmundsson, ``DNSSEC and IPv6 A6 aware server/resolver		Informational References
	message size requirements'', RFC 3226, December 2001.
	Author Address		[RFC2181] R. Elz, R. Bush, ``Clarifications to the DNS Specification'',
			RFC 2181, July 1997.
	Olafur Gudmundsson		[RFC3226] O. Gudmundsson, ``DNSSEC and IPv6 A6 aware server/resolver
	3821 Village Park Drive		message size requirements'', RFC 3226, December 2001.
	Chevy Chase, MD, 20815
	USA
	<ogud@ogud.com>
	Full Copyright Statement		Author Address
	Copyright (C) The Internet Society (2003). All Rights Reserved.		Olafur Gudmundsson
			3821 Village Park Drive
			Chevy Chase, MD, 20815
			USA
			<ogud@ogud.com>
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	The limited permissions granted above are perpetual and will not be		Copyright (C) The Internet Society (2003). All Rights Reserved.
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	This document and the information contained herein is provided on an		This document and translations of it may be copied and furnished to
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	TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING		or assist in its implementation may be prepared, copied, published
	BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION		and distributed, in whole or in part, without restriction of any
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			Internet organizations, except as needed for the purpose of
			developing Internet standards in which case the procedures for
			copyrights defined in the Internet Standards process must be
			followed, or as required to translate it into languages other than
			English.
			The limited permissions granted above are perpetual and will not be
			revoked by the Internet Society or its successors or assigns.
			This document and the information contained herein is provided on an
			"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
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