< draft-ietf-idnabis-mappings-01.txt		draft-ietf-idnabis-mappings-02.txt >
	IDNABIS P. Resnick, Ed.		IDNABIS P. Resnick
	Internet-Draft Qualcomm Incorporated		Internet-Draft Qualcomm Incorporated
	Intended status: Standards Track P. Hoffman		Intended status: Standards Track P. Hoffman
	Expires: January 4, 2010 VPN Consortium		Expires: February 11, 2010 VPN Consortium
	July 3, 2009		August 10, 2009
	Mapping Characters in IDNA		Mapping Characters in IDNA
	draft-ietf-idnabis-mappings-01		draft-ietf-idnabis-mappings-02
	Status of this Memo		Status of this Memo
	This Internet-Draft is submitted to IETF in full conformance with the		This Internet-Draft is submitted to IETF in full conformance with the
	provisions of BCP 78 and BCP 79. This document may contain material		provisions of BCP 78 and BCP 79. This document may contain material
	from IETF Documents or IETF Contributions published or made publicly		from IETF Documents or IETF Contributions published or made publicly
	available before November 10, 2008. The person(s) controlling the		available before November 10, 2008. The person(s) controlling the
	copyright in some of this material may not have granted the IETF		copyright in some of this material may not have granted the IETF
	Trust the right to allow modifications of such material outside the		Trust the right to allow modifications of such material outside the
	IETF Standards Process. Without obtaining an adequate license from		IETF Standards Process. Without obtaining an adequate license from
	skipping to change at page 1, line 43 ¶		skipping to change at page 1, line 43 ¶
	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.
	This Internet-Draft will expire on January 4, 2010.		This Internet-Draft will expire on February 11, 2010.
	Copyright Notice		Copyright Notice
	Copyright (c) 2009 IETF Trust and the persons identified as the		Copyright (c) 2009 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 in effect on the date of		Provisions Relating to IETF Documents in effect on the date of
	publication of this document (http://trustee.ietf.org/license-info).		publication of this document (http://trustee.ietf.org/license-info).
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 2, line 29 ¶		skipping to change at page 2, line 29 ¶
	encodes and passes to the DNS, but does not specify what to do with		encodes and passes to the DNS, but does not specify what to do with
	the result of user input. This document describes the actions taken		the result of user input. This document describes the actions taken
	by an implementation between user input and passing permitted code		by an implementation between user input and passing permitted code
	points to the new IDNA protocol.		points to the new IDNA protocol.
	1. Introduction		1. Introduction
	This document describes the operations that can be applied to user		This document describes the operations that can be applied to user
	input in order to get it into a form acceptable by the		input in order to get it into a form acceptable by the
	Internationalized Domain Names in Applications (IDNA) protocol		Internationalized Domain Names in Applications (IDNA) protocol
	[I-D.ietf-idnabis-protocol]. The document describes the underlying		[I-D.ietf-idnabis-protocol]. The document describes a general
	architectural principles (in section 2 and the general implementation		implementation procedure for mapping in section 2.
	procedure (in section 3).
	It should be noted that this document does not specify the behavior		It should be noted that this document does not specify the behavior
	of a protocol that appears "on the wire". It describes an operation		of a protocol that appears "on the wire". It describes an operation
	that is to be applied to user input in order to prepare that user		that is to be applied to user input in order to prepare that user
	input for use in an "on the network" protocol. As unusual as this		input for use in an "on the network" protocol. As unusual as this
	may be for an IETF protocol document, it is a necessary operation to		may be for an IETF protocol document, it is a necessary operation to
	maintain interoperability.		maintain interoperability.
	2. Architectural Principles		2. The General Procedure
	An application that implements the IDNA protocol
	[I-D.ietf-idnabis-protocol] will always take any user input and
	convert it to a set of Unicode code points. That user input may be
	acquired by any of several different input methods, all with
	differing conversion processes to be taken into consideration (e.g.,
	typed on a keyboard, written by hand onto some sort of digitizer,
	spoken into a microphone and interpreted by a speech-to-text engine,
	etc.). The process of taking any particular user input and mapping
	it into a Unicode code point may be a simple one: If a user strikes
	the "A" key on a US English keyboard, without any modifiers such as
	the "Shift" key held down, in order to draw a Latin small letter A
	("a"), many (perhaps most) modern operating system input methods will
	produce to the calling application the code point U+0061, encoded in
	a single octet.
	Sometimes the process is somewhat more complicated: a user might
	strike a particular set of keys to represent a combining macron
	followed by striking the "A" key in order to draw a Latin small
	letter A with a macron above it. Depending on the operating system,
	the input method chosen by the user, and even the parameters with
	which the application communicates with the input method, the result
	might be the code point U+0101 (encoded as two octets in UTF-8 or
	UTF-16, four octets in UTF-32, etc.), the code point U+0061 followed
	by the code point U+0304 (again, encoded in three or more octets,
	depending upon the encoding used) or even the code point U+FF41
	followed by the code point U+0304 (and encoded in some form). And
	these examples leave aside the issue of operating systems and input
	methods that do not use Unicode code points for their character set.
	In every case, applications (with the help of the operating systems
	on which they run and the input methods used) need to perform a
	mapping from user input into Unicode code points.
	The original version of the IDNA protocol [RFC3490] used a model
	whereby input was taken from the user, mapped (via whatever input
	method mechanisms were used) to a set of Unicode code points, and
	then further mapped to a set of Unicode code points using the
	Nameprep profile specified in [RFC3491]. In this procedure, there
	are two separate mapping steps: First, a mapping done by the input
	method (which might be controlled by the operating system, the
	application, or some combination) and then a second mapping performed
	by the Nameprep portion of the IDNA protocol. The mapping done in
	Nameprep includes a particular mapping table to re-map some
	characters to other characters, a particular normalization, and a set
	of prohibited characters.
	Note that the result of the two step mapping process means that the
	mapping chosen by the operating system or application in the first
	step might differ significantly from the mapping supplied by the
	Nameprep profile in the second step. This has advantages and
	disadvantages. Of course, the second mapping regularizes what gets
	looked up in the DNS, making for better interoperability between
	implementations which use the Nameprep mapping. However, the
	application or operating system may choose mappings in their input
	methods, which when passed through the second (Nameprep) mapping
	result in characters that are "surprising" to the end user.
	The other important feature of the original version of the IDNA
	protocol is that, with very few exceptions, it assumes that any set
	of Unicode code points provided to the Nameprep mapping can be mapped
	into a string of Unicode code points that are "sensible", even if
	that means mapping some code points to nothing (that is, removing the
	code points from the string). This allowed maximum flexibility in
	input strings.
	The present version of IDNA differs significantly in approach from
	the original version. First and foremost, it does not provide
	explicit mapping instructions. Instead, it assumes that the
	application (perhaps via an operating system input method) will do
	whatever mapping it requires to convert input into Unicode code
	points. This has the advantage of giving flexibility to the
	application to choose a mapping that is suitable for its user given
	specific user requirements, and avoids the two-step mapping of the
	original protocol. Instead of a mapping, the current version of IDNA
	provides a set of categories that can be used to specify the valid
	code points allowed in a domain name.
	In principle, an application ought to take user input of a domain
	name and convert it to the set of Unicode code points that represent
	the domain name the user intends. As a practical matter, of course,
	determining user intent is a tricky business, so an application needs
	to choose a reasonable mapping from user input. That may differ
	based on the particular circumstances of a user, depending on locale,
	language, type of input method, etc. It is up to the application to
	make a reasonable choice.
	3. The General Procedure
	This section defines a general algorithm that applications ought to		This section defines a general algorithm that applications ought to
	implement in order to produce Unicode code points that will be valid		implement in order to produce Unicode code points that will be valid
	under the IDNA protocol. An application might implement the full		under the IDNA protocol. An application might implement the full
	mapping as described below, or can choose a different mapping. In		mapping as described below, or can choose a different mapping. In
	fact, an appliction might want to implement a full mapping that is		fact, an application might want to implement a full mapping that is
	substantially compatible with the original IDNA protocol instead of		substantially compatible with the original IDNA protocol instead of
	the algorithm given here.		the algorithm given here.
	The general algorithm that an application (or the input method		The general algorithm that an application (or the input method
	provided by an operating system) ought to use is relatively		provided by an operating system) ought to use is relatively
	straightforward and generally follows section 5 of		straightforward:
	[I-D.ietf-idnabis-protocol]:
	1. All characters are mapped using Unicode Normalization Form C
	(NFC).
	2. Upper case characters are mapped to their lower case equivalents		1. Upper case characters are mapped to their lower case equivalents
	by using the algorithm for mapping Unicode characters.		by using the algorithm for mapping Unicode characters.
	3. Full-width and half-width characters (those defined with		2. Full-width and half-width characters (those defined with
	Decomposition Types <wide> and <narrow>) are mapped to their		Decomposition Types <wide> and <narrow>) are mapped to their
	decomposition mappings as shown in the Unicode character		decomposition mappings as shown in the Unicode character
	database.		database.
			3. All characters are mapped using Unicode Normalization Form C
			(NFC).
	Definitions for the rules in this algorithm can be found in		Definitions for the rules in this algorithm can be found in
	[Unicode51]. Specifically:		[Unicode51]. Specifically:
	o Unicode Normalization Form C can be found in Annex #15 of		o Unicode Normalization Form C can be found in Annex #15 of
	[Unicode51].		[Unicode51].
	o In order to map upper case characters to their lower case		o In order to map upper case characters to their lower case
	equivalents (defined in section 3.13 of [Unicode51]), first map		equivalents (defined in section 3.13 of [Unicode51]), first map
	characters to the "Lowercase_Mapping" property (the "<lower>"		characters to the "Lowercase_Mapping" property (the "<lower>"
	entry in the second column) in		entry in the second column) in
	skipping to change at page 5, line 47 ¶		skipping to change at page 4, line 5 ¶
	useful descriptions of the contents of these files.		useful descriptions of the contents of these files.
	If this mappings in this document are applied to versions of Unicode		If this mappings in this document are applied to versions of Unicode
	later than Unicode 5.1, the later versions of the Unicode Standard		later than Unicode 5.1, the later versions of the Unicode Standard
	should be consulted.		should be consulted.
	These are a minimal set of mappings that an application should		These are a minimal set of mappings that an application should
	strongly consider doing. Of course, there are many others that might		strongly consider doing. Of course, there are many others that might
	be done.		be done.
	4. IANA Considerations		3. IANA Considerations
	This memo includes no request to IANA.		This memo includes no request to IANA.
	5. Security Considerations		4. Security Considerations
	This document suggests creating mappings that might cause confusion		This document suggests creating mappings that might cause confusion
	for some users while alleviating confusion in other users. Such		for some users while alleviating confusion in other users. Such
	confusion is not covered in any depth in this document (nor in the		confusion is not covered in any depth in this document (nor in the
	other IDNA-related documents).		other IDNA-related documents).
	6. Normative References		5. Normative References
	[I-D.ietf-idnabis-protocol]		[I-D.ietf-idnabis-protocol]
	Klensin, J., "Internationalized Domain Names in		Klensin, J., "Internationalized Domain Names in
	Applications (IDNA): Protocol",		Applications (IDNA): Protocol",
	draft-ietf-idnabis-protocol-12 (work in progress),		draft-ietf-idnabis-protocol-14 (work in progress),
	May 2009.		August 2009.
	[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,		[RFC3490] 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.
	[RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep		[RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
	Profile for Internationalized Domain Names (IDN)",		Profile for Internationalized Domain Names (IDN)",
	RFC 3491, March 2003.		RFC 3491, March 2003.
	[Unicode51]		[Unicode51]
	The Unicode Consortium, "The Unicode Standard, Version		The Unicode Consortium, "The Unicode Standard, Version
	5.1.0", 2008.		5.1.0", 2008.
	defined by: The Unicode Standard, Version 5.0, Boston, MA,		defined by: The Unicode Standard, Version 5.0, Boston, MA,
	Addison-Wesley, 2007, ISBN 0-321-48091-0, as amended by		Addison-Wesley, 2007, ISBN 0-321-48091-0, as amended by
	Unicode 5.1.0		Unicode 5.1.0
	(<http://www.unicode.org/versions/Unicode5.1.0/>).		(<http://www.unicode.org/versions/Unicode5.1.0/>).
	Authors' Addresses		Authors' Addresses
	Peter W. Resnick (editor)		Peter W. Resnick
	Qualcomm Incorporated		Qualcomm Incorporated
	5775 Morehouse Drive		5775 Morehouse Drive
	San Diego, CA 92121-1714		San Diego, CA 92121-1714
	US		US
	Phone: +1 858 651 4478		Phone: +1 858 651 4478
	Email: presnick@qualcomm.com		Email: presnick@qualcomm.com
	URI: http://www.qualcomm.com/~presnick/		URI: http://www.qualcomm.com/~presnick/
	Paul Hoffman		Paul Hoffman
	VPN Consortium		VPN Consortium
	127 Segre Place		127 Segre Place
	Santa Cruz, CA 95060		Santa Cruz, CA 95060
	US		US
	Phone: 1-831-426-9827		Phone: 1-831-426-9827
	Email: paul.hoffman@vpnc.org		Email: paul.hoffman@vpnc.org
End of changes. 17 change blocks.
	111 lines changed or deleted		22 lines changed or added
This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/