Lines Matching +full:resolver +full:- +full:to +full:- +full:digital
22 improvements. Please refer to the current edition of the "Internet
32 Until now, there has been no standard method for domain names to use
37 repertoire (Unicode), but IDNA allows the non-ASCII characters to be
38 represented using only the ASCII characters already allowed in so-
39 called host names today. This backward-compatible representation is
41 introduced with no changes to the existing infrastructure. IDNA is
63 3.2.2. Non-domain-name data types stored in domain names... 9
70 6.2 Applications and resolver libraries....................... 15
72 6.4 Avoiding exposing users to the raw ACE encoding........... 16
86 IDNA works by allowing applications to use certain ASCII name labels
87 (beginning with a special prefix) to represent non-ASCII name labels.
88 Lower-layer protocols need not be aware of this; therefore IDNA does
89 not depend on changes to any infrastructure. In particular, IDNA
90 does not depend on any changes to DNS servers, resolvers, or protocol
94 This document does not require any applications to conform to IDNA,
95 but applications can elect to use IDNA in order to support IDN while
97 application wants to use non-ASCII characters in domain names, IDNA
98 is the only currently-defined option. Adding IDNA support to an
99 existing application entails changes to the application only, and
106 and DNS servers being updated in order for a user to use an
108 updating of all components, IDNA depends on updates to user
109 applications only; no changes are needed to the DNS protocol or any
122 of characters that can be used in domain names to include the Unicode
125 IDNA does not extend the service offered by DNS to the applications.
127 to see an exact-match lookup service. Either there is a single
128 exactly-matching name or there is no match. This model has served
139 upgrades to existing infrastructure (such as DNS servers and mail
141 in applications by using the ASCII representation of the non-ASCII
142 name labels. While such names are very user-unfriendly to read and
144 instance) replying to email and clicking on URLs even though the
145 domain name displayed is incomprehensible to the user. In order to
146 allow user-friendly input and output of the IDNs, the applications
147 need to be modified to conform to this specification.
157 inputting names in different scripts. Many important language-based
158 and script-based mappings are not covered in IDNA and need to be
161 mapped to a single canonical name. Another example is Scandinavian
163 DIAERESIS) will not be mapped to U+00F8 (LATIN SMALL LETTER O WITH
176 IDNA is how to provide a high probability that a user who is entering
184 issue relating to languages, input methods on computers, and so on.
191 Applications can use IDNA to support internationalized domain names
193 master files and resolver interfaces. (Applications can also define
194 protocols and interfaces that support IDNs directly using non-ASCII
200 not a client-server or peer-to-peer protocol: everything is done
201 inside the application itself. When used with a DNS resolver
203 resolver library. When used for writing names into a DNS zone, IDNA
204 is used just before the name is committed to the zone.
208 - The ToASCII operation is used before sending an IDN to something
209 that expects ASCII names (such as a resolver) or writing an IDN
212 - The ToUnicode operation is used when displaying names to users,
215 It is important to note that the ToASCII operation can fail. If it
217 as an internationalized domain name and the application has to have
237 and "MAY" in this document are to be interpreted as described in BCP
245 "U+" followed by four to six hexadecimal digits, while a range of
249 ASCII means US-ASCII [USASCII], a coded character set containing 128
254 The term "LDH code points" is defined in this document to mean the
255 code points associated with ASCII letters, digits, and the hyphen-
264 document explicitly cites [STD3] whenever referring to the host name
270 "com". (The zero-length root label described in [STD13], which can
287 An "internationalized label" is a label to which the ToASCII
292 generalization, embracing both old ASCII labels and new non-ASCII
300 name to be an IDN without it containing any non-ASCII characters).
301 This document does not attempt to define an "internationalized host
309 interpreting responses cannot be assumed to have any knowledge of
310 zone-specific restrictions or conventions.
314 or not the label was already an ASCII label. Labels are defined to
316 match using a case-insensitive ASCII comparison. ASCII labels
323 To allow internationalized labels to be handled by existing
326 that can be rendered in ASCII and is equivalent to an
329 operation will convert it to an equivalent ACE label (whereas an
331 unsuitable for display to users. The ToUnicode operation will
332 convert any label to an equivalent non-ACE label. In fact, an ACE
333 label is formally defined to be any label that the ToUnicode
334 operation would alter (whereas non-ACE labels are left unaltered by
347 The "ACE prefix" is defined in this document to be a string of ASCII
351 A "domain name slot" is defined in this document to be a protocol
356 following the at-sign (@) in the From: field of an email message
358 HTML <IMG> tag. General text that just happens to contain a domain
363 An "IDN-aware domain name slot" is defined in this document to be a
370 An "IDN-unaware domain name slot" is defined in this document to be
371 any domain name slot that is not an IDN-aware domain name slot.
379 IDNA conformance means adherence to the following four requirements:
386 2) Whenever a domain name is put into an IDN-unaware domain name slot
399 ToASCII operation (see section 4) to each label and, if dots are
400 used as label separators, changing all the label separators to
404 users when it is known that the environment can handle the non-ACE
406 is not known whether or not the environment can handle the non-ACE
407 form, the application MAY use the non-ACE form (which might fail,
409 form (which will look unintelligle to the user). Given an
412 operation (see section 4) to each label. When requirements 2 and
415 4) Whenever two labels are compared, they MUST be considered to match
417 (obtained by applying ToASCII) match using a case-insensitive
419 considered to match if and only if their corresponding labels
425 IDNA is applicable to all domain names in all domain name slots
428 This implies that IDNA is applicable to many protocols that predate
434 IDNA does not apply to domain names in the NAME and RDATA fields of
436 to every non-IN class, present and future, except where future
441 to DNS resource records; it depends entirely on the CLASS, and not on
443 unless there is a compelling reason for a new type to complicate
444 matters by imposing type-specific rules.
455 3.2.2. Non-domain-name data types stored in domain names
457 Although IDNA enables the representation of non-ASCII characters in
459 representation of non-ASCII characters in other data types that are
465 email standards are revised to invite the use of IDNA for local
467 SHOULD NOT begin with the ACE prefix, and even if it does, it is to
468 be interpreted literally as a local part that happens to begin with
473 An application converts a domain name put into an IDN-unaware slot or
474 displayed to a user. This section specifies the steps to perform in
477 The input to ToASCII or ToUnicode is a single label that is a
480 a character set other than Unicode or US-ASCII, it will first need to
481 be transcoded to Unicode.
484 takes to do the conversions are:
494 3) For each label, decide whether or not to enforce the restrictions
497 continue to make the decision the same way they always have; IDNA
499 restrictions are to be enforced, set the flag called
513 operation if you are about to put the name into an IDN-unaware
515 the name to a user; section 3.1 gives greater detail on the
519 separators, change all the label separators to U+002E (full stop).
525 of flags, and so on, in order to facilitate the specification of the
529 this document conforms to this specification.
538 It is important to note that the ToASCII operation can fail. ToASCII
542 with this failure is application-specific.
544 The inputs to ToASCII are a sequence of code points, the
550 ASCII range to begin with (although it could fail). Applying the
557 (0..7F) then proceed to step 2, otherwise skip to step 3.
572 (a) Verify the absence of non-LDH ASCII code points; that is, the
575 (b) Verify the absence of leading and trailing hyphen-minus; that
580 (0..7F) then proceed to step 5, otherwise skip to step 8.
589 8. Verify that the number of code points is in the range 1 to 63
604 Note that the number of octets needed to represent a sequence of code
607 The inputs to ToUnicode are a sequence of code points, the
612 then skip to step 3.
640 3, using a case-insensitive ASCII comparison.
647 alphanumeric ASCII characters followed by two hyphen-minuses. It
649 which includes the following: "bl--", "bq--", "dq--", "lq--", "mq--",
650 "ra--", "wq--" and "zq--". The ToASCII and ToUnicode operations MUST
651 recognize the ACE prefix in a case-insensitive manner.
653 The ACE prefix for IDNA is "xn--" or any capitalization thereof.
655 This means that an ACE label might be "xn--de-jg4avhby1noc0d", where
656 "de-jg4avhby1noc0d" is the part of the ACE label that is generated by
660 beginning with the ACE prefix are necessarily ACE labels. Non-ACE
681 In IDNA, applications perform the processing needed to input
683 domain names to users, and process the inputs and outputs from DNS
689 +------+
691 +------+
695 +-------------------|-------------------------------+
697 | +-----------------------------+ |
702 | +-----------------------------+ |
705 | Call to resolver: | | Application-specific |
708 | +----------+ | protocol is updated |
709 | | Resolver | | to handle other |
710 | +----------+ | encodings |
712 +-----------------|----------|----------------------+
716 +-------------+ +---------------------+
718 +-------------+ +---------------------+
742 An IDNA-aware application can accept and display internationalized
747 encouraged to do so except as an interface for special purposes,
748 possibly for debugging, or to cope with display limitations as
750 should thus only be exposed to users who absolutely need it. Because
753 application MAY have an option for the user to select the preferred
761 the headers and the body content in HTTP. It is important to
765 In protocols and document formats that define how to handle
791 6.2 Applications and resolver libraries
795 often called "the resolver library", and the applications communicate
796 with the resolver libraries through a programming interface (API).
798 Because these resolver libraries today expect only domain names in
799 ASCII, applications MUST prepare labels that are passed to the
800 resolver library using the ToASCII operation. Labels received from
801 the resolver library contain only ASCII characters; internationalized
806 ToASCII operation. The input to such a library might be in one or
807 more charsets that are used in applications (UTF-8 and UTF-16 are
808 likely candidates for almost any operating system, and script-
811 IDNA-aware applications MUST be able to work with both non-
812 internationalized labels (those that conform to [STD13] and [STD3])
815 It is expected that new versions of the resolver libraries in the
816 future will be able to accept domain names in other charsets than
818 names in Unicode, but also in local script to a new API for the
819 resolver libraries in the operating system. Thus the ToASCII and
821 the resolver libraries.
823 Domain names passed to resolvers or put into the question section of
847 ACE to something else, such as UTF-8. The question whether or not
851 6.4 Avoiding exposing users to the raw ACE encoding
855 header, will need to be updated if it is to prevent users from seeing
863 character (U+FFFD). This is to make it easier for the user to
864 transfer the name correctly to other programs. Programs that by
866 a name label SHOULD also have a mechanism to show the name that is
874 not a valid ACE label, and is not equivalent to any of the
881 Cryptography is used in conjunction with digital signatures to
882 provide a means for a requester of domain information to authenticate
883 the source of the data. This ensures that it can be traced back to a
885 source of the information to the top of the DNS hierarchy.
890 performed prior to a zone being signed by the private key for that
891 zone. Because of this ordering, it is important to recognize that
908 DNSSEC is that any special purpose proxies or forwarders used to
910 than DNSSEC authenticating nameservers for DNSSEC to work.
914 Existing DNS servers do not know the IDNA rules for handling non-
915 ASCII forms of IDNs, and therefore need to be shielded from them.
918 [RFC2136]) are IDN-unaware because they predate IDNA, and therefore
922 converted to their equivalent ASCII forms.
926 ToUnicode operations, there are no ACE labels that decode to ASCII
930 [RFC2181] explicitly allows domain labels to contain octets beyond
934 to applications, unpredictable behavior could result. The ASCII form
940 IDNs are likely to be somewhat longer than current domain names, so
941 the bandwidth needed by the root servers is likely to go up by a
944 responses may be forced to go to TCP instead of UDP.
963 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
978 [STD3] Braden, R., "Requirements for Internet Hosts --
980 "Requirements for Internet Hosts -- Application and
983 [STD13] Mockapetris, P., "Domain names - concepts and
984 facilities", STD 13, RFC 1034 and "Domain names -
993 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
1001 (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-61633-5),
1021 to the characteristics of the DNS can change the security of much of
1025 not valid according to STD3 and STD13 into octet values that are
1031 Domain names are used by users to identify and connect to Internet
1033 entering a single internationalized name is connected to different
1039 local character set and Unicode up to the application. If different
1046 Because this document normatively refers to [NAMEPREP], [PUNYCODE],
1050 If or when this specification is updated to use a more recent Unicode
1051 normalization table, the new normalization table will need to be
1052 compared with the old to spot backwards incompatible changes. If
1053 there are such changes, they will need to be handled somehow, or
1055 to handle the conflicts could include keeping the old normalization,
1071 system, the application needs to include the normalization tables
1076 To help prevent confusion between characters that are visually
1079 mechanisms can also be used to show when a name contains a mixture of
1080 simplified and traditional Chinese characters, or to distinguish zero
1082 (subject to the limitations in section 2) that try to minimize
1086 set of privileged or anti-privileged domains. In such situations it
1089 form, the proper comparison reduces to the same case-insensitive
1094 automatically be ACE labels, and will be considered equivalent to
1095 non-ASCII labels, whether or not that was the intent of the zone
1132 S-117 43 Stockholm Sweden
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1207 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION