draft-josefsson-dns-url-13.txt		draft-josefsson-dns-url.txt
	Network Working Group S. Josefsson		Network Working Group S. Josefsson
	Expires: February 6, 2006		Expires: February 2, 2006
	Domain Name System Uniform Resource Identifiers		Domain Name System Uniform Resource Identifiers
	draft-josefsson-dns-url-13		draft-josefsson-dns-url-14
	Status of this Memo		Status of this Memo
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	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2005).		Copyright (C) The Internet Society (2005).
	Abstract		Abstract
	This document define Uniform Resource Identifiers for Domain Name		This document defines Uniform Resource Identifiers for Domain Name
	System resources.		System resources.
	See <http://josefsson.org/dns-url/> for more information.		See <http://josefsson.org/dns-url/> for more information.
	Table of Contents		Table of Contents
	1. Introduction and Background . . . . . . . . . . . . . . . . . 3		1. Introduction and Background . . . . . . . . . . . . . . . . . 3
	2. Usage Model . . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Usage Model . . . . . . . . . . . . . . . . . . . . . . . . . 4
	3. DNS URI Registration . . . . . . . . . . . . . . . . . . . . . 5		3. DNS URI Registration . . . . . . . . . . . . . . . . . . . . . 5
	4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 8		4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9		5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 9		6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
	8. Copying conditions . . . . . . . . . . . . . . . . . . . . . . 10		8. Copying conditions . . . . . . . . . . . . . . . . . . . . . . 10
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10		9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
	9.1 Normative References . . . . . . . . . . . . . . . . . . . 10		9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
	9.2 Informative References . . . . . . . . . . . . . . . . . . 10		9.2. Informative References . . . . . . . . . . . . . . . . . . 10
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . 11		Appendix A. Revision Changes . . . . . . . . . . . . . . . . . . 11
	A. Revision Changes . . . . . . . . . . . . . . . . . . . . . . . 11		A.1. Changes since -06 . . . . . . . . . . . . . . . . . . . . 11
	A.1 Changes since -06 . . . . . . . . . . . . . . . . . . . . 11		A.2. Changes since -07 . . . . . . . . . . . . . . . . . . . . 11
	A.2 Changes since -07 . . . . . . . . . . . . . . . . . . . . 12		A.3. Changes since -08 . . . . . . . . . . . . . . . . . . . . 12
	A.3 Changes since -08 . . . . . . . . . . . . . . . . . . . . 12		A.4. Changes since -09 . . . . . . . . . . . . . . . . . . . . 12
	A.4 Changes since -09 . . . . . . . . . . . . . . . . . . . . 12		A.5. Changes since -10 . . . . . . . . . . . . . . . . . . . . 12
	A.5 Changes since -10 . . . . . . . . . . . . . . . . . . . . 12		A.6. Changes since -11 . . . . . . . . . . . . . . . . . . . . 12
	A.6 Changes since -11 . . . . . . . . . . . . . . . . . . . . 12		A.7. Changes since -12 . . . . . . . . . . . . . . . . . . . . 12
	A.7 Changes since -12 . . . . . . . . . . . . . . . . . . . . 13		A.8. Changes since -13 . . . . . . . . . . . . . . . . . . . . 12
	Intellectual Property and Copyright Statements . . . . . . . . 14		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
			Intellectual Property and Copyright Statements . . . . . . . . . . 14
	1. Introduction and Background		1. Introduction and Background
	The Domain Name System (DNS) [1] [2] is a widely deployed system used		The Domain Name System (DNS) [1] [2] is a widely deployed system used
	to, among other things, translate host names into IP addresses.		to, among other things, translate host names into IP addresses.
	Several protocols are using Uniform Resource Identifier (URI) to		Several protocols are using Uniform Resource Identifier (URI) to
	refer to data. By defining a URI scheme for DNS data, the gap		refer to data. By defining a URI scheme for DNS data, the gap
	between these two worlds are bridged. The DNS URI scheme defined		between these two worlds are bridged. The DNS URI scheme defined
	here can be used to reference any data stored in the DNS.		here can be used to reference any data stored in the DNS.
	Data browsers may support DNS URIs by forming DNS queries and render		Data browsers may support DNS URIs by forming DNS queries and
	DNS responses using HTML [14], similar to what is commonly done for		rendering DNS responses using HTML [12], similar to what is commonly
	FTP [6] resources. Applications that are Multipurpose Internet Mail		done for FTP [6] resources. Applications that are Multipurpose
	Extension (MIME) [7] aware may tag DNS data retrieve using this		Internet Mail Extensions (MIME) [7] aware may tag DNS data retrieved
	scheme with the text/dns or application/dns types as specified in		using this scheme with the text/dns or application/dns types as
	[18].		specified in [15].
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in RFC 2119 [3].		document are to be interpreted as described in RFC 2119 [3].
	2. Usage Model		2. Usage Model
	The reader is referred to section 1 of [5] for an in-depth discussion		The reader is referred to section 1 of [5] for an in-depth discussion
	of URI classifications. In particular, the reader is assumed to be		of URI classifications. In particular, the reader is assumed to be
	familiar with the "name" vs "locator" distinction. This section		familiar with the disction between "name" and "locator". This
	describe how the DNS URI scheme is intended to be used, and outline		section describes how the DNS URI scheme is intended to be used, and
	future work that may be required to use URIs with the DNS for some		outlines future work that may be required to use URIs with the DNS
	applications.		for some applications.
	The URI scheme described in this document focus on the data stored in		The URI scheme described in this document focuses on the data stored
	the DNS. As such, there is no provision to specify any of the fields		in the DNS. As such, there is no provision to specify any of the
	in the actual DNS protocol. This is intentional, so that the URI may		fields in the actual DNS protocol. This is intentional, so that the
	be used even in situations where the DNS protocol is not used		URI may be used even in situations where the DNS protocol is not used
	directly. Two examples for this is zone file editors and DNS-related		directly. Two examples for this are zone file editors and DNS-
	configuration files, which may use this URI scheme to identify data.		related configuration files, which may use this URI scheme to
	The application would not use the DNS protocol to resolve the URIs.		identify data. The application would not use the DNS protocol to
			resolve the URIs.
	A limitation of this design is that it do not accommodate all		A limitation of this design is that it does not accommodate all
	protocol parameters within the DNS protocol. It is expected that for		protocol parameters within the DNS protocol. It is expected that,
	certain applications, a more detailed URI syntax that map more		for certain applications, a more detailed URI syntax that maps more
	closely to the DNS protocol may be required. However, such an URI		closely to the DNS protocol may be required. However, such a URI
	definition is not included in this document. This document specify a		definition is not included in this document. This document specifies
	URI that is primarily intended to name DNS resources, but it can also		a URI that is primarily intended to name DNS resources, but it can
	be used to locate said resources for simple (but common)		also be used to locate said resources for simple, yet common,
	applications.		applications.
	3. DNS URI Registration		3. DNS URI Registration
	The section contain the registration template for the DNS URI scheme		The section contains the registration template for the DNS URI scheme
	in accordance with [13].		in accordance with [11].
	URL scheme name: "dns".		URL scheme name: "dns".
	URL scheme syntax: A DNS URI designate a DNS resource record set,		URL scheme syntax: A DNS URI designates a DNS resource record set,
	referenced by domain name, class, type and optionally the authority.		referenced by domain name, class, type and, optionally, the
	The DNS URI follows the generic syntax from RFC 3986 [5], and is		authority. The DNS URI follows the generic syntax from RFC 3986 [5],
	described using ABNF [4]. Strings are not case sensitive and free		and is described using ABNF [4]. Strings are not case-sensitive and
	insertion of linear-white-space is not permitted.		free insertion of linear-white-space is not permitted.
	dnsurl = "dns:" [ "//" dnsauthority "/" ]		dnsurl = "dns:" [ "//" dnsauthority "/" ]
	dnsname ["?" dnsquery]		dnsname ["?" dnsquery]
	dnsauthority = host [ ":" port ]		dnsauthority = host [ ":" port ]
	; See RFC 3986 for the		; See RFC 3986 for the
	; definition of "host" and "port".		; definition of "host" and "port".
	dnsname = *pchar		dnsname = *pchar
	; See RFC 3986 for the		; See RFC 3986 for the
	; definition of "pchar".		; definition of "pchar".
	; The "dnsname" field may be a		; The "dnsname" field may be a
	; "relative" or "absolute" name,		; "relative" or "absolute" name,
	; as per RFC 1034 section 3.1.		; as per RFC 1034 section 3.1.
	; Note further that an empty		; Note further that an empty
	; "dnsname" value is to be		; "dnsname" value is to be
	; interpreted as the root itself.		; interpreted as the root itself.
	; See below on relative dnsname's.		; See below on relative dnsnames.
	dnsquery = dnsqueryelement [";" dnsquery]		dnsquery = dnsqueryelement [";" dnsquery]
	dnsqueryelement = ( "CLASS=" dnsclassval ) / ( "TYPE=" dnstypeval )		dnsqueryelement = ( "CLASS=" dnsclassval ) / ( "TYPE=" dnstypeval )
	; Each clause MUST NOT be used more		; Each clause MUST NOT be used more
	; than once.		; than once.
	dnsclassval = 1*digit / "IN" / "CH" /		dnsclassval = 1*digit / "IN" / "CH" /
	<Any IANA registered DNS class mnemonic>		<Any IANA registered DNS class mnemonic>
	dnstypeval = 1*digit / "A" / "NS" / "MD" /		dnstypeval = 1*digit / "A" / "NS" / "MD" /
	<Any IANA registered DNS type mnemonic>		<Any IANA registered DNS type mnemonic>
	Unless specified in the URI, the authority ("dnsauthority") is		Unless specified in the URI, the authority ("dnsauthority") is
	assumed to be locally known, the class ("dnsclassval") to be the		assumed to be locally known, the class ("dnsclassval") to be the
	Internet class ("IN"), and the type ("dnstypeval") to be the Address		Internet class ("IN"), and the type ("dnstypeval") to be the Address
	type ("A"). These default values match the typical use of DNS; to		type ("A"). These default values match the typical use of DNS: to
	look up addresses for host names.		look up addresses for host names.
	A dnsquery element MUST NOT contain more than one occurance of the		A dnsquery element MUST NOT contain more than one occurrence of the
	"CLASS" and "TYPE" fields. For example, both "dns:		"CLASS" and "TYPE" fields. For example, both "dns:
	example?TYPE=A;TYPE=TXT" and "dns:example?TYPE=A;TYPE=A" are invalid.		example?TYPE=A;TYPE=TXT" and "dns:example?TYPE=A;TYPE=A" are invalid.
	However, the fields may occur in any order, so that both "dns:		However, the fields may occur in any order, so that both "dns:
	example?TYPE=A;CLASS=IN" and "dns:example?CLASS=IN;TYPE=A" are valid.		example?TYPE=A;CLASS=IN" and "dns:example?CLASS=IN;TYPE=A" are valid.
	The digit representation of types and classes MAY be used when a		The digit representation of types and classes MAY be used when a
	mnemonic for the corresponding value is not well known (e.g., for		mnemonic for the corresponding value is not well known (e.g., for
	newly introduced types or classes), but SHOULD NOT be used for the		newly introduced types or classes), but SHOULD NOT be used for the
	types or classes defined in the DNS specification [2]. All		types or classes defined in the DNS specification [2]. All
	implementations MUST recognize the mnemonics defined in [2].		implementations MUST recognize the mnemonics defined in [2].
	To avoid ambiguity, relative "dnsname" values (i.e., those not ending		To avoid ambiguity, relative "dnsname" values (i.e., those not ending
	with ".") are assumed to be relative to the root. For example, "dns:		with ".") are assumed to be relative to the root. For example, "dns:
	host.example" and "dns:host.example." both refer to the same owner		host.example" and "dns:host.example." both refer to the same owner
	name, namely "host.example.". Further, an empty "dnsname" value is		name, namely "host.example.". Further, an empty "dnsname" value is
	considered to be a degenerative form of a relative name, which refer		considered to be a degenerative form of a relative name, which refers
	to the root (".").		to the root (".").
	To resolve a DNS URI using the DNS protocol [2] a query is created,		To resolve a DNS URI using the DNS protocol, [2] a query is created,
	using as input the dnsname, dnsclassval and dnstypeval from the URI		using as input the dnsname, dnsclassval and dnstypeval from the URI
	string (or the appropriate default values). If an authority		string (or the appropriate default values). If an authority
	("dnsauthority") is given in the URI string, this indicate the server		("dnsauthority") is given in the URI string, this indicates the
	that should receive the DNS query, otherwise the default DNS server		server that should receive the DNS query. Otherwise, the default DNS
	should receive it.		server should receive it.
	Note that DNS URIs could be resolved by other protocols than the DNS		Note that DNS URIs could be resolved by other protocols than the DNS
	protocol, or by using the DNS protocol in some other way than as		protocol, or by using the DNS protocol in some other way than as
	described above (e.g., multicast DNS). DNS URIs do not require the		described above (e.g., multicast DNS). DNS URIs do not require the
	use of the DNS protocol, although it is expected to be the typical		use of the DNS protocol, although it is expected to be the typical
	usage. The previous paragraph only illustrate how DNS URIs are		usage. The previous paragraph only illustrates how DNS URIs are
	resolved using the DNS protocol.		resolved using the DNS protocol.
	A client MAY want to check that it understands the dnsclassval and		A client MAY want to check that it understands the dnsclassval and
	dnstypeval before sending a query, so that it will be able to		dnstypeval before sending a query, so that it will be able to
	understand the response. However, a typical example of a client that		understand the response. However, a typical example of a client that
	would not need to check dnsclassval and dnstypeval would be a proxy,		would not need to check dnsclassval and dnstypeval would be a proxy
	that would just treat the received answer as opaque data.		that would just treat the received answer as opaque data.
	Character encoding considerations: The characters are encoded as per		Character encoding considerations: Characters are encoded as per RFC
	RFC 3986 [5]. The DNS protocol do not consider character sets, it		3986 [5]. The DNS protocol does not consider character sets, it
	simply transports opaque data. In particular, the "dnsname" field of		simply transports opaque data. In particular, the "dnsname" field of
	the DNS URI is to be considered an internationalized domain name		the DNS URI is to be considered an internationalized domain name
	(IDN) unaware domain name slot, in the terminology of [16]. The		(IDN) unaware domain name slot, in the terminology of RFC3940 [14].
	considerations for "host" and "port" are discussed in [5]		The considerations for "host" and "port" are discussed in [5]
	Because "." is used as the DNS label separator, an escaping mechanism		Because "." is used as the DNS label separator, an escaping mechanism
	is required to encode a "." that is part of a DNS label. The		is required to encode a "." that is part of a DNS label. The
	escaping mechanism is described in section 5.1 of RFC 1035. For		escaping mechanism is described in section 5.1 of RFC 1035 [2]. For
	example, a DNS label of "exa.mple" can be escaped as "exa\.mple" or		example, a DNS label of "exa.mple" can be escaped as "exa\.mple" or
	"exa\046mple". However, the URI specification disallow the "\"		"exa\046mple". However, the URI specification disallows the "\"
	character from occuring directly in URIs, so it must be escaped as		character from occurring directly in URIs, so it must be escaped as
	"%5c". The single DNS label "exa.mple" is thus encoded as "exa%		"%5c". The single DNS label "exa.mple" is thus encoded as "exa%
	5c.mple". The same mechanism can be used to encode other characters,		5c.mple". The same mechanism can be used to encode other characters,
	for example "?" and ";". Note that "." and "%2e" are equivalent		for example "?" and ";". Note that "." and "%2e" are equivalent
	within dnsname, and are interchangable.		within dnsname, and are interchangeable.
	This URI specification allows all possible domain names to be encoded		This URI specification allows all possible domain names to be
	(of course following the encoding rules of [5]), however certain		encoded, provided the encoding rules are observed per [5]), however
	applications may restrict the set of valid characters. Care should		certain applications may restrict the set of valid characters. Care
	be taken so that invalid characters in these contexts does not cause		should be taken so that invalid characters in these contexts does not
	harm. In particular, host names in the DNS have certain		cause harm. In particular, host names in the DNS have certain
	restrictions. It is up to these application to limit this subset,		restrictions. It is up to these application to limit this subset;
	this URI scheme places no restrictions.		this URI scheme places no restrictions.
	Intended usage: Whenever DNS resources are useful to reference by		Intended usage: Whenever it is useful for DNS resources to be
	protocol independent identifiers, often when the data is more		referenced by protocol-independent identifiers, this URI
	important than the access method. Since software in general has		specification is applicable. Often, this occurs when the data is
			more important than the access method. Since software in general has
	coped without this so far, it is not anticipated to be implemented		coped without this so far, it is not anticipated to be implemented
	widely, nor migrated to by existing systems, but specific solutions		widely, nor migrated to by existing systems, but specific solutions
	(especially security related) may find this appropriate.		(especially security-related) may find this appropriate.
	Applications and/or protocols which use this scheme: Security related		Applications and/or protocols which use this scheme: Security-
	software. DNS administration tools. Network programming packages.		related software, DNS administration tools, and network programming
			packages.
	Interoperability considerations: The data referenced by this URI		Interoperability considerations: The data referenced by this URI
	scheme might be transferred by protocols that are not URI aware (such		scheme might be transferred by protocols that are not URI aware (such
	as the DNS protocol). This is not anticipated to have any serious		as the DNS protocol). This is not anticipated to have any serious
	interoperability impact though.		interoperability impact.
	Interoperability problems may occur if one entity understands a new		Interoperability problems may occur if one entity understands a new
	DNS class/type mnemonic and another entity do not understand it.		DNS class/type mnemonic that another entity does not. This is an
	This is an interoperability problem for DNS software in general,		interoperability problem for DNS software in general, although it is
	although it is not a major practical problem as the DNS types and		not a major practical problem for current DNS deployments as the DNS
	classes are fairly static. To guarantee interoperability		types and classes are fairly static. To guarantee interoperability,
	implementations can use integers for all mnemonics not defined in		implementations can use integers for all mnemonics not defined in
	[2].		[2].
	Interaction with Binary Labels [12], or other extended label types,		Interaction with Binary Labels [10] or other extended label types has
	has not been analyzed. However, they appear to be infrequently used		not been analyzed. However, they appear to be infrequently used in
	in practice.		practice.
	Contact: simon@josefsson.org		Contact: simon@josefsson.org
	Author/Change Controller: simon@josefsson.org		Author/Change Controller: simon@josefsson.org
	4. Examples		4. Examples
	A DNS URI is of the following general form. This is intended to		A DNS URI is of the following general form. This is intended to
	illustrate, not define, the scheme.		illustrate, not define, the scheme:
	dns:[//authority/]domain[?CLASS=class;TYPE=type]		dns:[//authority/]domain[?CLASS=class;TYPE=type]
	The following illustrate a URI for a resource with the absolute name		The following illustrates a URI for a resource with the absolute name
	"www.example.org.", the Internet (IN) class and the Address (A) type:		"www.example.org.", the Internet (IN) class and the Address (A) type:
	dns:www.example.org.?clAsS=IN;tYpE=A		dns:www.example.org.?clAsS=IN;tYpE=A
	Since the default class is IN, and the default type is A, the same		Since the default class is IN, and the default type is A, the same
	resource can be identified by a shorter URI, using a relative name:		resource can be identified by a shorter URI using a relative name:
	dns:www.example.org		dns:www.example.org
	The following illustrate a URI for a resource with the name		The following illustrate a URI for a resource with the name
	"simon.example.org", for the CERT type, in the Internet (IN) class:		"simon.example.org" for the CERT type in the Internet (IN) class:
	dns:simon.example.org?type=CERT		dns:simon.example.org?type=CERT
	The following illustrate a URI for a resource with the name		The following illustrate a URI for a resource with the name
	"ftp.example.org", in the Internet (IN) class and the address (A)		"ftp.example.org", in the Internet (IN) class and the address (A)
	type, but from the DNS authority 192.168.1.1 instead of the default		type, but from the DNS authority 192.168.1.1 instead of the default
	authority:		authority:
	dns://192.168.1.1/ftp.example.org?type=A		dns://192.168.1.1/ftp.example.org?type=A
	The following illustrate various escaping techniques. The owner name		The following illustrates various escaping techniques. The owner
	would be "world wide web.example\.domain.org" where "\." denote the		name would be "world wide web.example\.domain.example" where "\."
	character "." as part of a label, and "." denote the label separator:		denotes the character "." as part of a label, and "." denotes the
			label separator:
	dns:world%20wide%20web.example%5c.domain.example?TYPE=TXT		dns:world%20wide%20web.example%5c.domain.example?TYPE=TXT
	The following illustrate a strange, but valid, DNS resource:		The following illustrates a strange, but valid, DNS resource:
	dns://fw.example.org/*.%20%00.example?type=TXT		dns://fw.example.org/*.%20%00.example?type=TXT
	5. Acknowledgments		5. Acknowledgments
	Thanks to Stuart Cheshire, Donald Eastlake, Pasi Eronen, Bill Fenner,		Thanks to Stuart Cheshire, Donald Eastlake, Pasi Eronen, Bill Fenner,
	Ted Hardie, Russ Housley, Peter Koch, Andrew Main, Larry Masinter,		Ted Hardie, Russ Housley, Peter Koch, Andrew Main, Larry Masinter,
	Michael Mealling, Steve Mattson, Paul Vixie, Sam Weiler, and Bert		Michael Mealling, Steve Mattson, Marcos Sanz, Jason Sloderbeck, Paul
	Wijnen for comments and suggestions. The author acknowledges the RSA		Vixie, Sam Weiler, and Bert Wijnen for comments and suggestions. The
	Laboratories for supporting the work that led to this document.		author acknowledges RSA Laboratories for supporting the work that led
			to this document.
	6. Security Considerations		6. Security Considerations
	If a DNS URI references domains in the Internet DNS environment, both		If a DNS URI references domains in the Internet DNS environment, both
	the URI itself and the information referenced by the URI is public		the URI itself and the information referenced by the URI is public
	information. If a DNS URI is used within an "internal" DNS		information. If a DNS URI is used within an "internal" DNS
	environment, both the DNS URI and the data is referenced should be		environment, both the DNS URI and the data is referenced should be
	handled using the same considerations that apply to DNS data in the		handled using the same considerations that apply to DNS data in the
	environment.		"internal" environment.
	If information referenced by DNS URIs are used to make security		If information referenced by DNS URIs are used to make security
	decisions (examples of such data include, but is not limited to,		decisions (examples of such data include, but is not limited to,
	certificates stored in the DNS [10]), implementations may need to		certificates stored in the DNS [9]), implementations may need to
	employ security techniques such as Secure DNS [9], or even CMS [15]		employ security techniques such as Secure DNS [16], CMS [13], or
	or OpenPGP [8], to protect the data during transport. How to		OpenPGP [8], to protect the data during transport. How to implement
	implement this will depend on the usage scenario, and it is not up to		this will depend on the usage scenario, and it is not up to this URI
	this URI scheme to define how the data referenced by DNS URIs should		scheme to define how the data referenced by DNS URIs should be
	be protected.		protected.
	If applications accept unknown dnsqueryelement values (e.g., accepts		If applications accept unknown dnsqueryelement values in a URI (e.g.,
	the URI "dns:www.example.org?secret=value" without knowing what the		URI "dns:www.example.org?secret=value") without knowing what the
	"secret=value" dnsqueryelement means), a covert channel used to		"secret=value" dnsqueryelement means, a covert channel used to "leak"
	"leak" information may be enabled. The implications of covert		information may be enabled. The implications of covert channels
	channels should be understood by applications that accepts unknown		should be understood by applications that accept unknown
	dnsqueryelement values.		dnsqueryelement values.
	Slight variations, such as difference between upper and lower case in		Slight variations, such as difference between upper and lower case in
	the dnsname field, can be used as a covert channel to leak		the dnsname field, can be used as a covert channel to leak
	information.		information.
	7. IANA Considerations		7. IANA Considerations
	The IANA is asked to register the DNS URI scheme, using the template		The IANA is asked to register the DNS URI scheme, using the template
	in section 3, in accordance with RFC 2717 [13].		in section 3, in accordance with RFC 2717 [11].
	8. Copying conditions		8. Copying conditions
	Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005 Simon Josefsson		Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005 Simon Josefsson
	Regarding this entire document or any portion of it, the author makes		Regarding this entire document or any portion of it, the author makes
	no guarantees and is not responsible for any damage resulting from		no guarantees and is not responsible for any damage resulting from
	its use. The author grants irrevocable permission to anyone to use,		its use. The author grants irrevocable permission to anyone to use,
	modify, and distribute it in any way that does not diminish the		modify, and distribute it in any way that does not diminish the
	rights of anyone else to use, modify, and distribute it, provided		rights of anyone else to use, modify, and distribute it, provided
	that redistributed derivative works do not contain misleading author		that redistributed derivative works do not contain misleading author
	or version information. Derivative works need not be licensed under		or version information. Derivative works need not be licensed under
	similar terms.		similar terms.
	9. References		9. References
	9.1 Normative References		9.1. Normative References
	[1] Mockapetris, P., "Domain names - concepts and facilities",		[1] Mockapetris, P., "Domain names - concepts and facilities",
	STD 13, RFC 1034, November 1987.		STD 13, RFC 1034, November 1987.
	[2] Mockapetris, P., "Domain names - implementation and		[2] Mockapetris, P., "Domain names - implementation and
	specification", STD 13, RFC 1035, November 1987.		specification", STD 13, RFC 1035, November 1987.
	[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement		[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
	Levels", BCP 14, RFC 2119, March 1997.		Levels", BCP 14, RFC 2119, March 1997.
	[4] Crocker, D. and P. Overell, "Augmented BNF for Syntax		[4] Crocker, D. and P. Overell, "Augmented BNF for Syntax
	Specifications: ABNF", RFC 2234, November 1997.		Specifications: ABNF", RFC 2234, November 1997.
	[5] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform		[5] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
	Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,		Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
	January 2005.		January 2005.
	9.2 Informative References		9.2. Informative References
	[6] Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9,		[6] Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9,
	RFC 959, October 1985.		RFC 959, October 1985.
	[7] Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet		[7] Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet
	Mail Extensions (MIME) Part Four: Registration Procedures",		Mail Extensions (MIME) Part Four: Registration Procedures",
	BCP 13, RFC 2048, November 1996.		BCP 13, RFC 2048, November 1996.
	[8] Callas, J., Donnerhacke, L., Finney, H., and R. Thayer,		[8] Callas, J., Donnerhacke, L., Finney, H., and R. Thayer,
	"OpenPGP Message Format", RFC 2440, November 1998.		"OpenPGP Message Format", RFC 2440, November 1998.
	[9] Eastlake, D., "Domain Name System Security Extensions",		[9] Eastlake, D. and O. Gudmundsson, "Storing Certificates in the
	RFC 2535, March 1999.
	[10] Eastlake, D. and O. Gudmundsson, "Storing Certificates in the
	Domain Name System (DNS)", RFC 2538, March 1999.		Domain Name System (DNS)", RFC 2538, March 1999.
	[11] Myers, M., Ankney, R., Malpani, A., Galperin, S., and C. Adams,		[10] Crawford, M., "Binary Labels in the Domain Name System",
	"X.509 Internet Public Key Infrastructure Online Certificate
	Status Protocol - OCSP", RFC 2560, June 1999.
	[12] Crawford, M., "Binary Labels in the Domain Name System",
	RFC 2673, August 1999.		RFC 2673, August 1999.
	[13] Petke, R. and I. King, "Registration Procedures for URL Scheme		[11] Petke, R. and I. King, "Registration Procedures for URL Scheme
	Names", BCP 35, RFC 2717, November 1999.		Names", BCP 35, RFC 2717, November 1999.
	[14] Connolly, D. and L. Masinter, "The 'text/html' Media Type",		[12] Connolly, D. and L. Masinter, "The 'text/html' Media Type",
	RFC 2854, June 2000.		RFC 2854, June 2000.
	[15] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 3369,		[13] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 3369,
	August 2002.		August 2002.
	[16] Faltstrom, P., Hoffman, P., and A. Costello,		[14] Faltstrom, P., Hoffman, P., and A. Costello,
	"Internationalizing Domain Names in Applications (IDNA)",		"Internationalizing Domain Names in Applications (IDNA)",
	RFC 3490, March 2003.		RFC 3490, March 2003.
	[17] Yergeau, F., "UTF-8, a transformation format of ISO 10646",		[15] Josefsson, S., "Domain Name System Media Types", RFC 4027,
	STD 63, RFC 3629, November 2003.
	[18] Josefsson, S., "Domain Name System Media Types", RFC 4027,
	April 2005.		April 2005.
	Author's Address		[16] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
			"DNS Security Introduction and Requirements", RFC 4033,
	Simon Josefsson		March 2005.
	Email: simon@josefsson.org
	Appendix A. Revision Changes		Appendix A. Revision Changes
	Note to RFC editor: Remove this appendix before publication.		Note to RFC editor: Remove this appendix before publication.
	A.1 Changes since -06		A.1. Changes since -06
	The MIME registration templates for text/dns and application/dns was		The MIME registration templates for text/dns and application/dns was
	removed, and will be defined in separate documents.		removed, and will be defined in separate documents.
	Improved discussion related to which mnemonics that must be		Improved discussion related to which mnemonics that must be
	supported. The interoperability problem that provoked the		supported. The interoperability problem that provoked the
	clarification is also mentioned.		clarification is also mentioned.
	Security consideration improvements.		Security consideration improvements.
	A.2 Changes since -07		A.2. Changes since -07
	Author/Change Controller changed to author of this document, not		Author/Change Controller changed to author of this document, not
	IESG. Terminology section collapsed into introduction. The second		IESG. Terminology section collapsed into introduction. The second
	paragraph of the introduction rewritten and gives explicit examples.		paragraph of the introduction rewritten and gives explicit examples.
	Intended usage and applications fields fixed. Moved this revision		Intended usage and applications fields fixed. Moved this revision
	tracking information to an appendix. Mention IDN in charset section.		tracking information to an appendix. Mention IDN in charset section.
	All previous thanks to suggestions by Larry Masinter.		All previous thanks to suggestions by Larry Masinter.
	A.3 Changes since -08		A.3. Changes since -08
	Modifications derived from Last-Call comments: Made more clear that		Modifications derived from Last-Call comments: Made more clear that
	DNS URIs does not imply use of the DNS protocol, but the issue is not		DNS URIs does not imply use of the DNS protocol, but the issue is not
	stressed because of the apparent inflamatory state of affairs. Added		stressed because of the apparent inflamatory state of affairs. Added
	informative references to HTML and FTP. Clarified that dnsname can		informative references to HTML and FTP. Clarified that dnsname can
	be empty. Clarified that first dnsqueryelement "win" in case of		be empty. Clarified that first dnsqueryelement "win" in case of
	ambiguity. Clarified security consideration with respect to unknown		ambiguity. Clarified security consideration with respect to unknown
	dnsqueryelements. Use "authority" instead of "server". Say "IANA		dnsqueryelements. Use "authority" instead of "server". Say "IANA
	registered" instead of "standard". Interoperability note about		registered" instead of "standard". Interoperability note about
	binary DNS labels. Typos.		binary DNS labels. Typos.
	A.4 Changes since -09		A.4. Changes since -09
	Use legal texts from RFC 3667. Update UTF-8 reference to RFC 3629.		Use legal texts from RFC 3667. Update UTF-8 reference to RFC 3629.
	Simplified introduction. Discuss relative and absolute dnsname's.		Simplified introduction. Discuss relative and absolute dnsname's.
	Clarify that empty dnsname correspond to the root. Change so that		Clarify that empty dnsname correspond to the root. Change so that
	dns:foo?TYPE=A;TYPE=TXT is invalid, instead of meaning TYPE=A. The		dns:foo?TYPE=A;TYPE=TXT is invalid, instead of meaning TYPE=A. The
	underspecified extension mechanism was dropped; now only TYPE= and		underspecified extension mechanism was dropped; now only TYPE= and
	CLASS= are permitted. Remove background discussion of why the		CLASS= are permitted. Remove background discussion of why the
	dnsname field is made a IDN unaware domain name slot. Use standard		dnsname field is made a IDN unaware domain name slot. Use standard
	DNS escaping (i.e, "\." for ".") instead of broken approach that		DNS escaping (i.e, "\." for ".") instead of broken approach that
	violated the URI specification. Improve examples. Add security		violated the URI specification. Improve examples. Add security
	considerations.		considerations.
	A.5 Changes since -10		A.5. Changes since -10
	Add section "Usage Model". Move acknowledgements, as per rfc2223bis.		Add section "Usage Model". Move acknowledgements, as per rfc2223bis.
	Add permissive copying condition. Updates to align with RFC 3986.		Add permissive copying condition. Updates to align with RFC 3986.
	A.6 Changes since -11		A.6. Changes since -11
	Fix typos. IESG feedback: Move RFC2119 reference to normative		Fix typos. IESG feedback: Move RFC2119 reference to normative
	section. Replace OCSP example with X.509 CRL Distribution Point		section. Replace OCSP example with X.509 CRL Distribution Point
	extension. Fix ABNF not to use "...".		extension. Fix ABNF not to use "...".
	A.7 Changes since -12		A.7. Changes since -12
	Reference MIME and RFC 4027. IESG feedback: Do not mention OpenPGP/		Reference MIME and RFC 4027. IESG feedback: Do not mention OpenPGP/
	X.509 as illustrative examples in the introduction section.		X.509 as illustrative examples in the introduction section.
			A.8. Changes since -13
			Fix typos.
			Author's Address
			Simon Josefsson
			Email: simon@josefsson.org
	Intellectual Property Statement		Intellectual Property Statement
	The IETF takes no position regarding the validity or scope of any		The IETF takes no position regarding the validity or scope of any
	Intellectual Property Rights or other rights that might be claimed to		Intellectual Property Rights or other rights that might be claimed to
	pertain to the implementation or use of the technology described in		pertain to the implementation or use of the technology described in
	this document or the extent to which any license under such rights		this document or the extent to which any license under such rights
	might or might not be available; nor does it represent that it has		might or might not be available; nor does it represent that it has
	made any independent effort to identify any such rights. Information		made any independent effort to identify any such rights. Information
	on the procedures with respect to rights in RFC documents can be		on the procedures with respect to rights in RFC documents can be
	found in BCP 78 and BCP 79.		found in BCP 78 and BCP 79.
End of changes.
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