draft-ietf-uta-email-tls-certs-07.txt		draft-ietf-uta-email-tls-certs-08.txt
	Network Working Group A. Melnikov		Network Working Group A. Melnikov
	Internet-Draft Isode Ltd		Internet-Draft Isode Ltd
	Updates: 2595, 3207, 3501, 5804 (if December 9, 2015		Updates: 2595, 3207, 3501, 5804 (if December 17, 2015
	approved)		approved)
	Intended status: Standards Track		Intended status: Standards Track
	Expires: June 11, 2016		Expires: June 19, 2016
	Updated TLS Server Identity Check Procedure for Email Related Protocols		Updated TLS Server Identity Check Procedure for Email Related Protocols
	draft-ietf-uta-email-tls-certs-07		draft-ietf-uta-email-tls-certs-08
	Abstract		Abstract
	This document describes TLS server identity verification procedure		This document describes TLS server identity verification procedure
	for SMTP Submission, IMAP, POP and ManageSieve clients. It replaces		for SMTP Submission, IMAP, POP and ManageSieve clients. It replaces
	Section 2.4 of RFC 2595, updates Section 4.1 of RFC 3207, updates		Section 2.4 of RFC 2595, updates Section 4.1 of RFC 3207, updates
	Section 11.1 of RFC 3501, updates Section 2.2.1 of RFC 5804.		Section 11.1 of RFC 3501, updates Section 2.2.1 of RFC 5804.
	Status of This Memo		Status of This Memo
	skipping to change at page 1, line 35		skipping to change at page 1, line 35
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on June 11, 2016.		This Internet-Draft will expire on June 19, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2015 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 18		skipping to change at page 2, line 18
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Conventions Used in This Document . . . . . . . . . . . . . . 3		2. Conventions Used in This Document . . . . . . . . . . . . . . 3
	3. Email Server Certificate Verification Rules . . . . . . . . . 3		3. Email Server Certificate Verification Rules . . . . . . . . . 3
	4. Compliance Checklist for Certification Authorities . . . . . 5		4. Compliance Checklist for Certification Authorities . . . . . 5
	4.1. Notes on handling of SRV-ID by Certification Authorities 5		4.1. Notes on handling of SRV-ID by Certification Authorities 5
	5. Compliance Checklist for Mail Service Providers and		5. Compliance Checklist for Mail Service Providers and
	Certificate Signing Request generation tools . . . . . . . . 6		Certificate Signing Request generation tools . . . . . . . . 6
	5.1. Notes on hosting multiple domains . . . . . . . . . . . . 6		5.1. Notes on hosting multiple domains . . . . . . . . . . . . 6
	6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 7		6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 7
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8		7. Operational Considerations . . . . . . . . . . . . . . . . . 8
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 8		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9		9. Security Considerations . . . . . . . . . . . . . . . . . . . 9
	9.1. Normative References . . . . . . . . . . . . . . . . . . 9		10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
	9.2. Informative References . . . . . . . . . . . . . . . . . 10		10.1. Normative References . . . . . . . . . . . . . . . . . . 9
	Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 11		10.2. Informative References . . . . . . . . . . . . . . . . . 10
	Appendix B. Changes since draft-ietf-uta-email-tls-certs-00 . . 11		Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 12
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11		Appendix B. Changes since draft-ietf-uta-email-tls-certs-00 . . 12
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
	1. Introduction		1. Introduction
	Use of TLS by SMTP Submission, IMAP, POP and ManageSieve clients is		Use of TLS by SMTP Submission, IMAP, POP and ManageSieve clients is
	described in [RFC3207], [RFC3501], [RFC2595] and [RFC5804]		described in [RFC3207], [RFC3501], [RFC2595] and [RFC5804]
	respectively. Each of the documents describes slightly different		respectively. Each of the documents describes slightly different
	rules for server certificate identity verification (or doesn't define		rules for server certificate identity verification (or doesn't define
	any rules at all). In reality, email client and server developers		any rules at all). In reality, email client and server developers
	implement many of these protocols at the same time, so it would be		implement many of these protocols at the same time, so it would be
	good to define modern and consistent rules for verifying email server		good to define modern and consistent rules for verifying email server
	identities using TLS.		identities using TLS.
	This document describes the updated TLS server identity verification		This document describes the updated TLS server identity verification
	procedure for SMTP Submission [RFC6409] [RFC3207], IMAP [RFC3501],		procedure for SMTP Submission [RFC6409] [RFC3207], IMAP [RFC3501],
	POP [RFC1939] and ManageSieve [RFC5804] clients. It replaces		POP [RFC1939] and ManageSieve [RFC5804] clients. Section 3 of this
	Section 2.4 of RFC 2595.		document replaces Section 2.4 of [RFC2595].
	Note that this document doesn't apply to use of TLS in MTA-to-MTA		Note that this document doesn't apply to use of TLS in MTA-to-MTA
	SMTP.		SMTP.
	This document provides a consistent TLS server identity verification		This document provides a consistent TLS server identity verification
	procedure across multiple email related protocols. This should make		procedure across multiple email related protocols. This should make
	it easier for Certification Authorities and ISPs to deploy TLS for		it easier for Certification Authorities and ISPs to deploy TLS for
	email use, and would enable email client developers to write more		email use, and would enable email client developers to write more
	secure code.		secure code.
	2. Conventions Used in This Document		2. Conventions Used in This Document
	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 [RFC2119].		document are to be interpreted as described in [RFC2119].
	The following terms or concepts are used through the document:		The following terms or concepts are used through the document:
	reference identifier: (as defined in [RFC6125]) One of the domain		reference identifier: (formally defined in [RFC6125]) One of the
	names associated by the email (i.e., an SMTP, IMAP, POP3 or		domain names that the email client (an SMTP, IMAP, POP3 or
	ManageSieve) client with the target email server and optionally an		ManageSieve client) associates with the target email server. For
			some identifier types, the identifier can also include an
	application service type for performing name checks on the server		application service type for performing name checks on the server
	certificate. When name checks are applicable, at least one of the		certificate. When name checks are applicable, at least one of the
	reference identifiers MUST match an [RFC6125] DNS-ID or SRV-ID (or		reference identifiers MUST match an [RFC6125] DNS-ID or SRV-ID (or
	if none are present the [RFC6125] CN-ID) of the server		if none are present the [RFC6125] CN-ID) of the server
	certificate.		certificate.
	CN-ID, DNS-ID, SRV-ID and URI-ID are identifier types (see [RFC6125]		CN-ID, DNS-ID, SRV-ID and URI-ID are identifier types (see [RFC6125]
	for details). For convenience, their short definitions from		for details). For convenience, their short definitions from
	[RFC6125] are listed below:		[RFC6125] are listed below:
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	3. URI-ID identifier type (subjectAltName of		3. URI-ID identifier type (subjectAltName of
	uniformResourceIdentifier type [RFC5280]) MUST NOT be used by		uniformResourceIdentifier type [RFC5280]) MUST NOT be used by
	clients for server verification, as URI-ID were not historically		clients for server verification, as URI-ID were not historically
	used for email.		used for email.
	4. For backward compatibility with deployed software CN-ID		4. For backward compatibility with deployed software CN-ID
	identifier type (CN attribute from the subject name, see		identifier type (CN attribute from the subject name, see
	[RFC6125]) MAY be used for server identity verification.		[RFC6125]) MAY be used for server identity verification.
	5. Email protocols allow use of certain wilcards in identifiers		5. Email protocols allow use of certain wildcards in identifiers
	presented by email servers. The "*" wildcard character MAY be		presented by email servers. The "*" wildcard character MAY be
	used as the left-most name component of DNS-ID or CN-ID in the		used as the left-most name component of DNS-ID or CN-ID in the
	certificate. For example, a DNS-ID of *.example.com would match		certificate. For example, a DNS-ID of *.example.com would match
	a.example.com, foo.example.com, etc. but would not match		a.example.com, foo.example.com, etc. but would not match
	example.com. Note that the wildcard character MUST NOT be used		example.com. Note that the wildcard character MUST NOT be used
	as a fragment of the left-most name component (e.g.,		as a fragment of the left-most name component (e.g.,
	*oo.example.com, f*o.example.com, or foo*.example.com).		*oo.example.com, f*o.example.com, or foo*.example.com).
	4. Compliance Checklist for Certification Authorities		4. Compliance Checklist for Certification Authorities
	skipping to change at page 5, line 31		skipping to change at page 5, line 31
	4.1. Notes on handling of SRV-ID by Certification Authorities		4.1. Notes on handling of SRV-ID by Certification Authorities
	[RFC6186] provides an easy way for organizations to autoconfigure		[RFC6186] provides an easy way for organizations to autoconfigure
	email clients. It also allows for delegation of email services to an		email clients. It also allows for delegation of email services to an
	email hosting provider. When connecting to such delegated hosting		email hosting provider. When connecting to such delegated hosting
	service an email client that attempts to verify TLS server identity		service an email client that attempts to verify TLS server identity
	needs to know that if it connects to imap.hosting.example.net that		needs to know that if it connects to imap.hosting.example.net that
	such server is authorized to provide email access for an email such		such server is authorized to provide email access for an email such
	as alice@example.org. In absence of SRV-IDs, users of compliant		as alice@example.org. In absence of SRV-IDs, users of compliant
	email clients would be forced to manual confirm exception, because		email clients would be forced to manually confirm exception, because
	TLS server certificate verification procedures specified in this		the TLS server certificate verification procedures specified in this
	document would result in failure to match TLS server certificate		document would result in failure to match the TLS server certificate
	against the expected domains. One way to provide such authorization		against the expected domain(s). One way to provide such
	is for the TLS certificate for imap.hosting.example.net to include		authorization is for the TLS certificate for imap.hosting.example.net
	SRV-ID(s) (or DNS-ID) for example.org domain. (Another way is for		to include SRV-ID(s) (or DNS-ID) for the example.org domain.
	SRV lookups to be protected by DNSSEC, but this solution depends		(Another way is for SRV lookups to be protected by DNSSEC, but this
	reliance of DNSSEC and thus is not discussed in this document. A		solution depends on DNSSEC and thus is not discussed in this
	future update to this document might rectify this.)		document. A future update to this document might rectify this.)
	The ability of issuing certificates that contain SRV-ID implies the		The ability to issue certificates that contain SRV-ID implies the
	ability to verify that entities requesting them are authorized to run		ability to verify that entities requesting them are authorized to run
	email service for these SRV-IDs. In particular, certification		email service for these SRV-IDs. In particular, certification
	authorities that can't verify such authorization MUST NOT include		authorities that can't verify such authorization MUST NOT include
	email SRV-IDs in certificates they issue. This document doesn't		email SRV-IDs in certificates they issue. This document doesn't
	specify exact mechanism(s) that can be used to achieve this.		specify exact mechanism(s) that can be used to achieve this.
	However, a few special case recommendations are listed below.		However, a few special case recommendations are listed below.
	A certification authority willing to sign a certificate containing a		A certification authority willing to sign a certificate containing a
	particular DNS-ID SHOULD also support signing a certificate		particular DNS-ID SHOULD also support signing a certificate
	containing one or more of email SRV-IDs for the same domain, because		containing one or more of email SRV-IDs for the same domain, because
	the SRV-ID effectively provides more restricted access to an email		the SRV-ID effectively provides more restricted access to an email
	service for the domain (as opposed to unrestricted use of any		service for the domain (as opposed to unrestricted use of any
	services for the same domain, as specified by DNS-ID).		services for the same domain, as specified by DNS-ID).
	A certification authority which also provides DNS service for a		A certification authority which also provides DNS service for a
	domain can use DNS information to validate SRV-IDs for the domain.		domain can use DNS information to validate SRV-IDs for the domain.
	A certification authority MAY treat a certificate for a subdomain of
	example.com (e.g. imap.sub1.example.com or imap.example.com) that
	contains one or more SRV-ID for example.com as validated.
	5. Compliance Checklist for Mail Service Providers and Certificate		5. Compliance Checklist for Mail Service Providers and Certificate
	Signing Request generation tools		Signing Request generation tools
	1. MUST include the DNS-ID identifier type in Certificate Signing		1. MUST include the DNS-ID identifier type in Certificate Signing
	Requests for the host name(s) where the email server(s) are		Requests for the host name(s) where the email server(s) are
	running. SHOULD include the DNS-ID identifier type in		running. SHOULD include the DNS-ID identifier type in
	Certificate Signing Requests for the domain portion of served		Certificate Signing Requests for the domain portion of served
	email addresses.		email addresses.
	2. If the email services provided are discoverable using DNS SRV as		2. If the email services provided are discoverable using DNS SRV as
	skipping to change at page 6, line 45		skipping to change at page 6, line 41
	CN-ID can be used).		CN-ID can be used).
	4. MAY include "*" (wildcard) as the left-most name component of		4. MAY include "*" (wildcard) as the left-most name component of
	DNS-ID or CN-ID in Certificate Signing Requests.		DNS-ID or CN-ID in Certificate Signing Requests.
	5.1. Notes on hosting multiple domains		5.1. Notes on hosting multiple domains
	A server that hosts multiple domains needs to do one of the following		A server that hosts multiple domains needs to do one of the following
	(or some combination thereof):		(or some combination thereof):
	1. Use a single TLS certificate that includes a complete list of all		1. Use DNS SRV records to redirect each hosted email service to a
			fixed domain, deploy TLS certificate(s) for that single domain,
			and instruct users to configure their clients with appropriate
			pinning (unless the SRV records can always be obtained via
			DNSSEC). Some email clients come with preloaded list of pinned
			certificates for some popular domains, which can avoid the need
			for manual confirmation.
			2. Use a single TLS certificate that includes a complete list of all
	the domains it is serving.		the domains it is serving.
	2. Serve each domain on its own IP/port, using separate TLS		3. Serve each domain on its own IP/port, using separate TLS
	certificates on each IP/port.		certificates on each IP/port.
	3. Use Server Name Indication (SNI) TLS extension [RFC6066] to		4. Use Server Name Indication (SNI) TLS extension [RFC6066] to
	select the right certificate to return during TLS negotiation.		select the right certificate to return during TLS negotiation.
	Each domain has its own TLS certificate in this case.		Each domain has its own TLS certificate in this case.
	Each of these deployment choices have their scaling disadvantages		Each of these deployment choices have their scaling disadvantages
	when the list of domains changes. A single certificate (the first		when the list of domains changes. Use of DNS SRV without SRV-ID
	choice) requires that when a domain is added, then a new Certificate		requires manual confirmation from users. While preloading pinned
	Signing Request that includes a complete list of all the domains		certificates avoids the need for manual confirmation, this
	needs to be issued and passed to a CA in order to generate a new		information can get stale quickly or would require support for a new
	certificate. Separate IP/port can avoid regenerating the		mechanism for distributing preloaded pinned certificates. A single
	certificate, but requires more transport layer resources. Use of TLS		certificate (the second choice) requires that when a domain is added,
	SNI requires each email client to support it.		then a new Certificate Signing Request that includes a complete list
			of all the domains needs to be issued and passed to a CA in order to
			generate a new certificate. Separate IP/port can avoid regenerating
			the certificate, but requires more transport layer resources. Use of
			TLS SNI requires each email client to support it.
	Several Mail Service Providers host hundreds and even thousands of		Several Mail Service Providers host hundreds and even thousands of
	domain. This document, as well as its predecessors RFC 2595, RFC		domains. This document, as well as its predecessors RFC 2595, RFC
	3207, RFC 3501 and RFC 5804 don't address scaling issues caused by		3207, RFC 3501 and RFC 5804 don't address scaling issues caused by
	use of TLS in multi-tenanted environments. Further work is needed to		use of TLS in multi-tenanted environments. Further work is needed to
	address this issue, possibly using DNSSEC or something like POSH		address this issue, possibly using DNSSEC or something like POSH
	[RFC7711].		[RFC7711].
	6. Examples		6. Examples
	Consider an IMAP-accessible email server which supports both IMAP and		Consider an IMAP-accessible email server which supports both IMAP and
	IMAPS (IMAP-over-TLS) at the host "mail.example.net" servicing email		IMAPS (IMAP-over-TLS) at the host "mail.example.net" servicing email
	addresses of the form "user@example.net". A certificate for this		addresses of the form "user@example.net". A certificate for this
	skipping to change at page 8, line 29		skipping to change at page 8, line 37
	domain "example.net", which runs SMTP Submission, IMAPS and POP3S		domain "example.net", which runs SMTP Submission, IMAPS and POP3S
	(POP3-over-TLS) and ManageSieve services. Each of the servers can		(POP3-over-TLS) and ManageSieve services. Each of the servers can
	use their own certificate specific to their service (see examples		use their own certificate specific to their service (see examples
	above). Alternatively they can all share a single certificate that		above). Alternatively they can all share a single certificate that
	would include SRV-IDs of "_submission.example.net",		would include SRV-IDs of "_submission.example.net",
	"_imaps.example.net", "_pop3s.example.net" and "_sieve.example.net"		"_imaps.example.net", "_pop3s.example.net" and "_sieve.example.net"
	along with DNS-IDs of "example.net" and "mail.example.net". It might		along with DNS-IDs of "example.net" and "mail.example.net". It might
	also include CN-ID of "mail.example.net" for backward compatibility		also include CN-ID of "mail.example.net" for backward compatibility
	with deployed infrastructure.		with deployed infrastructure.
	7. IANA Considerations		7. Operational Considerations
			Section 5 covers operational considerations (in particular use of DNS
			SRV for autoconfiguration) related to generating TLS certificiates
			for email servers so that they can be successfully verified by email
			clients. Additionally, Section 5.1 talks about operational
			considerations related to hosting multiple domains.
			8. IANA Considerations
	This document doesn't require any action from IANA.		This document doesn't require any action from IANA.
	8. Security Considerations		9. Security Considerations
	The goal of this document is to improve interoperability and thus		The goal of this document is to improve interoperability and thus
	security of email clients wishing to access email servers over TLS		security of email clients wishing to access email servers over TLS
	protected email protocols, by specifying a consistent set of rules		protected email protocols, by specifying a consistent set of rules
	that email service providers, email client writers and Certification		that email service providers, email client writers and Certification
	Authorities can use when creating server certificates.		Authorities can use when creating server certificates.
	TLS Server Identity Check for Email relies on use of trustworthy DNS		TLS Server Identity Check for Email relies on use of trustworthy DNS
	hostnames when constructing "reference identifiers" that are checked		hostnames when constructing "reference identifiers" that are checked
	against an email server certificate. Such trustworthy names are		against an email server certificate. Such trustworthy names are
	either entered manually (for example if they are advertised on a Mail		either entered manually (for example if they are advertised on a Mail
	Service Provider's website), explicitly confirmed by the user (e.g.		Service Provider's website), explicitly confirmed by the user (e.g.
	if they are a target of a DNS SRV lookup) or derived using a secure		if they are a target of a DNS SRV lookup) or derived using a secure
	third party service (e.g. DNSSEC-protected SRV records which are		third party service (e.g. DNSSEC-protected SRV records which are
	verified by the client or trusted local resolver). Future work in		verified by the client or trusted local resolver). Future work in
	this area might benefit from integration with DANE [RFC6698], but it		this area might benefit from integration with DANE [RFC6698], but it
	is not covered by this document.		is not covered by this document.
	9. References		10. References
	9.1. Normative References		10.1. Normative References
	[RFC1939] Myers, J. and M. Rose, "Post Office Protocol - Version 3",		[RFC1939] Myers, J. and M. Rose, "Post Office Protocol - Version 3",
	STD 53, RFC 1939, DOI 10.17487/RFC1939, May 1996,		STD 53, RFC 1939, DOI 10.17487/RFC1939, May 1996,
	<http://www.rfc-editor.org/info/rfc1939>.		<http://www.rfc-editor.org/info/rfc1939>.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
	skipping to change at page 10, line 9		skipping to change at page 10, line 27
	[RFC6186] Daboo, C., "Use of SRV Records for Locating Email		[RFC6186] Daboo, C., "Use of SRV Records for Locating Email
	Submission/Access Services", RFC 6186,		Submission/Access Services", RFC 6186,
	DOI 10.17487/RFC6186, March 2011,		DOI 10.17487/RFC6186, March 2011,
	<http://www.rfc-editor.org/info/rfc6186>.		<http://www.rfc-editor.org/info/rfc6186>.
	[RFC6409] Gellens, R. and J. Klensin, "Message Submission for Mail",		[RFC6409] Gellens, R. and J. Klensin, "Message Submission for Mail",
	STD 72, RFC 6409, DOI 10.17487/RFC6409, November 2011,		STD 72, RFC 6409, DOI 10.17487/RFC6409, November 2011,
	<http://www.rfc-editor.org/info/rfc6409>.		<http://www.rfc-editor.org/info/rfc6409>.
	9.2. Informative References		10.2. Informative References
	[RFC2595] Newman, C., "Using TLS with IMAP, POP3 and ACAP",		[RFC2595] Newman, C., "Using TLS with IMAP, POP3 and ACAP",
	RFC 2595, DOI 10.17487/RFC2595, June 1999,		RFC 2595, DOI 10.17487/RFC2595, June 1999,
	<http://www.rfc-editor.org/info/rfc2595>.		<http://www.rfc-editor.org/info/rfc2595>.
	[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform		[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
	Resource Identifier (URI): Generic Syntax", STD 66,		Resource Identifier (URI): Generic Syntax", STD 66,
	RFC 3986, DOI 10.17487/RFC3986, January 2005,		RFC 3986, DOI 10.17487/RFC3986, January 2005,
	<http://www.rfc-editor.org/info/rfc3986>.		<http://www.rfc-editor.org/info/rfc3986>.
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