idnits 2.17.1 draft-ietf-idnabis-protocol-13.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** The document seems to lack a License Notice according IETF Trust Provisions of 28 Dec 2009, Section 6.b.i or Provisions of 12 Sep 2009 Section 6.b -- however, there's a paragraph with a matching beginning. Boilerplate error? (You're using the IETF Trust Provisions' Section 6.b License Notice from 12 Feb 2009 rather than one of the newer Notices. See https://trustee.ietf.org/license-info/.) Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The draft header indicates that this document obsoletes RFC3490, but the abstract doesn't seem to mention this, which it should. -- The draft header indicates that this document updates RFC3492, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year (Using the creation date from RFC3492, updated by this document, for RFC5378 checks: 2002-01-10) -- The document seems to contain a disclaimer for pre-RFC5378 work, and may have content which was first submitted before 10 November 2008. The disclaimer is necessary when there are original authors that you have been unable to contact, or if some do not wish to grant the BCP78 rights to the IETF Trust. If you are able to get all authors (current and original) to grant those rights, you can and should remove the disclaimer; otherwise, the disclaimer is needed and you can ignore this comment. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (July 12, 2009) is 5373 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC1123' is defined on line 691, but no explicit reference was found in the text == Unused Reference: 'Unicode-PropertyValueAliases' is defined on line 701, but no explicit reference was found in the text == Unused Reference: 'Unicode-RegEx' is defined on line 706, but no explicit reference was found in the text == Unused Reference: 'Unicode-Scripts' is defined on line 711, but no explicit reference was found in the text == Unused Reference: 'ASCII' is defined on line 723, but no explicit reference was found in the text == Unused Reference: 'RFC2136' is defined on line 742, but no explicit reference was found in the text == Unused Reference: 'RFC2181' is defined on line 746, but no explicit reference was found in the text == Unused Reference: 'RFC2535' is defined on line 749, but no explicit reference was found in the text -- Possible downref: Non-RFC (?) normative reference: ref. 'IDNA2008-BIDI' -- Possible downref: Non-RFC (?) normative reference: ref. 'Unicode-PropertyValueAliases' -- Possible downref: Non-RFC (?) normative reference: ref. 'Unicode-RegEx' -- Possible downref: Non-RFC (?) normative reference: ref. 'Unicode-Scripts' -- Possible downref: Non-RFC (?) normative reference: ref. 'Unicode-UAX15' -- No information found for draft-ietf-idnabis-mapping - is the name correct? -- Obsolete informational reference (is this intentional?): RFC 2535 (Obsoleted by RFC 4033, RFC 4034, RFC 4035) -- Obsolete informational reference (is this intentional?): RFC 2671 (Obsoleted by RFC 6891) -- Obsolete informational reference (is this intentional?): RFC 3490 (Obsoleted by RFC 5890, RFC 5891) -- Obsolete informational reference (is this intentional?): RFC 3491 (Obsoleted by RFC 5891) -- Obsolete informational reference (is this intentional?): RFC 4952 (Obsoleted by RFC 6530) Summary: 1 error (**), 0 flaws (~~), 9 warnings (==), 15 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Klensin 3 Internet-Draft July 12, 2009 4 Obsoletes: 3490, 3491 5 (if approved) 6 Updates: 3492 (if approved) 7 Intended status: Standards Track 8 Expires: January 13, 2010 10 Internationalized Domain Names in Applications (IDNA): Protocol 11 draft-ietf-idnabis-protocol-13.txt 13 Status of this Memo 15 This Internet-Draft is submitted to IETF in full conformance with the 16 provisions of BCP 78 and BCP 79. This document may contain material 17 from IETF Documents or IETF Contributions published or made publicly 18 available before November 10, 2008. The person(s) controlling the 19 copyright in some of this material may not have granted the IETF 20 Trust the right to allow modifications of such material outside the 21 IETF Standards Process. Without obtaining an adequate license from 22 the person(s) controlling the copyright in such materials, this 23 document may not be modified outside the IETF Standards Process, and 24 derivative works of it may not be created outside the IETF Standards 25 Process, except to format it for publication as an RFC or to 26 translate it into languages other than English. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF), its areas, and its working groups. Note that 30 other groups may also distribute working documents as Internet- 31 Drafts. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 The list of current Internet-Drafts can be accessed at 39 http://www.ietf.org/ietf/1id-abstracts.txt. 41 The list of Internet-Draft Shadow Directories can be accessed at 42 http://www.ietf.org/shadow.html. 44 This Internet-Draft will expire on January 13, 2010. 46 Copyright Notice 48 Copyright (c) 2009 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents in effect on the date of 53 publication of this document (http://trustee.ietf.org/license-info). 54 Please review these documents carefully, as they describe your rights 55 and restrictions with respect to this document. 57 Abstract 59 This document is the revised protocol definition for 60 internationalized domain names (IDNs). The rationale for changes, 61 the relationship to the older specification, and important 62 terminology are provided in other documents. This document specifies 63 the protocol mechanism, called Internationalizing Domain Names in 64 Applications (IDNA), for registering and looking up IDNs in a way 65 that does not require changes to the DNS itself. IDNA is only meant 66 for processing domain names, not free text. 68 Table of Contents 70 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 71 1.1. Discussion Forum . . . . . . . . . . . . . . . . . . . . . 5 72 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 73 3. Requirements and Applicability . . . . . . . . . . . . . . . . 6 74 3.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 6 75 3.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 6 76 3.2.1. DNS Resource Records . . . . . . . . . . . . . . . . . 7 77 3.2.2. Non-domain-name Data Types Stored in the DNS . . . . . 7 78 4. Registration Protocol . . . . . . . . . . . . . . . . . . . . 7 79 4.1. Input to IDNA Registration Process . . . . . . . . . . . . 8 80 4.2. Permitted Character and Label Validation . . . . . . . . . 8 81 4.2.1. Input Format . . . . . . . . . . . . . . . . . . . . . 8 82 4.2.2. Rejection of Characters that are not Permitted . . . . 8 83 4.2.3. Label Validation . . . . . . . . . . . . . . . . . . . 8 84 4.2.4. Registration Validation Summary . . . . . . . . . . . 9 85 4.3. Registry Restrictions . . . . . . . . . . . . . . . . . . 10 86 4.4. Punycode Conversion . . . . . . . . . . . . . . . . . . . 10 87 4.5. Insertion in the Zone . . . . . . . . . . . . . . . . . . 10 88 5. Domain Name Lookup Protocol . . . . . . . . . . . . . . . . . 10 89 5.1. Label String Input . . . . . . . . . . . . . . . . . . . . 11 90 5.2. Conversion to Unicode . . . . . . . . . . . . . . . . . . 11 91 5.3. Character Changes in Preprocessing or the User 92 Interface . . . . . . . . . . . . . . . . . . . . . . . . 11 93 5.4. A-label Input . . . . . . . . . . . . . . . . . . . . . . 12 94 5.5. Validation and Character List Testing . . . . . . . . . . 13 95 5.6. Punycode Conversion . . . . . . . . . . . . . . . . . . . 14 96 5.7. DNS Name Resolution . . . . . . . . . . . . . . . . . . . 15 97 6. Security Considerations . . . . . . . . . . . . . . . . . . . 15 98 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 99 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 15 100 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 101 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 102 10.1. Normative References . . . . . . . . . . . . . . . . . . . 16 103 10.2. Informative References . . . . . . . . . . . . . . . . . . 17 104 Appendix A. Local Mapping Alternatives . . . . . . . . . . . . . 18 105 A.1. Transitional Mapping Model . . . . . . . . . . . . . . . . 19 106 A.1.1. Fallback Lookup . . . . . . . . . . . . . . . . . . . 19 107 A.1.2. Two-step Lookup . . . . . . . . . . . . . . . . . . . 20 108 A.2. Internationalized Resource Identifier (IRI) Mapping 109 Model . . . . . . . . . . . . . . . . . . . . . . . . . . 20 110 Appendix B. Summary of Major Changes from IDNA2003 . . . . . . . 21 111 Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 22 112 C.1. Changes between Version -00 and -01 of 113 draft-ietf-idnabis-protocol . . . . . . . . . . . . . . . 22 114 C.2. Version -02 . . . . . . . . . . . . . . . . . . . . . . . 22 115 C.3. Version -03 . . . . . . . . . . . . . . . . . . . . . . . 22 116 C.4. Version -04 . . . . . . . . . . . . . . . . . . . . . . . 23 117 C.5. Version -05 . . . . . . . . . . . . . . . . . . . . . . . 23 118 C.6. Version -06 . . . . . . . . . . . . . . . . . . . . . . . 23 119 C.7. Version -07 . . . . . . . . . . . . . . . . . . . . . . . 23 120 C.8. Version -08 . . . . . . . . . . . . . . . . . . . . . . . 24 121 C.9. Version -09 . . . . . . . . . . . . . . . . . . . . . . . 24 122 C.10. Version -10 . . . . . . . . . . . . . . . . . . . . . . . 24 123 C.11. Version -11 . . . . . . . . . . . . . . . . . . . . . . . 25 124 C.12. Version -12 . . . . . . . . . . . . . . . . . . . . . . . 25 125 C.13. Version -13 . . . . . . . . . . . . . . . . . . . . . . . 25 126 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 26 128 1. Introduction 130 This document supplies the protocol definition for internationalized 131 domain names. Essential definitions and terminology for 132 understanding this document and a road map of the collection of 133 documents that make up IDNA2008 appear in [IDNA2008-Defs]. 134 Appendix B discusses the relationship between this specification and 135 the earlier version of IDNA (referred to here as "IDNA2003") and the 136 rationale for these changes, along with considerable explanatory 137 material and advice to zone administrators who support IDNs is 138 provided in another documents, notably [IDNA2008-Rationale]. 140 IDNA works by allowing applications to use certain ASCII string 141 labels (beginning with a special prefix) to represent non-ASCII name 142 labels. Lower-layer protocols need not be aware of this; therefore 143 IDNA does not changes any infrastructure. In particular, IDNA does 144 not depend on any changes to DNS servers, resolvers, or protocol 145 elements, because the ASCII name service provided by the existing DNS 146 can be used for IDNA. 148 IDNA applies only to DNS labels. The base DNS standards [RFC1034] 149 [RFC1035] and their various updates specify how to combine labels 150 into fully-qualified domain names and parse labels out of those 151 names. 153 This document describes two separate protocols, one for IDN 154 registration (Section 4) and one for IDN lookup (Section 5), that 155 share some terminology, reference data and operations. [[anchor2: 156 Note in draft: See the note in the introduction to.]]Section 5 158 1.1. Discussion Forum 160 [[anchor4: RFC Editor: please remove this section.]] 162 This work is being discussed in the IETF IDNABIS WG and on the 163 mailing list idna-update@alvestrand.no 165 2. Terminology 167 Terminology used in IDNA, but also in Unicode or other character set 168 standards and the DNS, appears in [IDNA2008-Defs]. Terminology that 169 is required as part of the IDNA definition, including the definitions 170 of "ACE", appears in that document as well. Readers of this document 171 are assumed to be familiar with [IDNA2008-Defs] and with the DNS- 172 specific terminology in RFC 1034 [RFC1034]. 174 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 175 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 176 document are to be interpreted as described in BCP 14, RFC 2119 177 [RFC2119]. 179 3. Requirements and Applicability 181 3.1. Requirements 183 IDNA makes the following requirements: 185 1. Whenever a domain name is put into an IDN-unaware domain name 186 slot (see Section 2 and [IDNA2008-Defs]), it MUST contain only 187 ASCII characters (i.e., must be either an A-label or an NR-LDH- 188 label), unless the DNS application is not subject to historical 189 recommendations for "hostname"-style names (see [RFC1034] and 190 Section 3.2.1). 192 2. Labels MUST be compared using equivalent forms: either both 193 A-Label forms or both U-Label forms. Because A-labels and 194 U-labels can be transformed into each other without loss of 195 information, these comparisons are equivalent. A pair of 196 A-labels MUST be compared as case-insensitive ASCII (as with all 197 comparisons of ASCII DNS labels). U-labels must be compared 198 as-is, without case-folding or other intermediate steps. Note 199 that it is not necessary to validate labels in order to compare 200 them. In many cases, validation may be important for other 201 reasons and SHOULD be performed. 203 3. Labels being registered MUST conform to the requirements of 204 Section 4. Labels being looked up and the lookup process MUST 205 conform to the requirements of Section 5. 207 3.2. Applicability 209 IDNA applies to all domain names in all domain name slots in 210 protocols except where it is explicitly excluded. It does not apply 211 to domain name slots which do not use the Letter/Digit/Hyphen (LDH) 212 syntax rules. 214 Because it uses the DNS, IDNA applies to many protocols that were 215 specified before it was designed. IDNs occupying domain name slots 216 in those older protocols MUST be in A-label form until and unless 217 those protocols and implementations of them are explicitly upgraded 218 to be aware of IDNs in Unicode. IDNs actually appearing in DNS 219 queries or responses MUST be A-labels. 221 IDNA is not defined for extended label types (see RFC 2671, Section 3 223 [RFC2671]). 225 3.2.1. DNS Resource Records 227 IDNA applies only to domain names in the NAME and RDATA fields of DNS 228 resource records whose CLASS is IN. See RFC 1034 [RFC1034] for 229 precise definitions of these terms. 231 The application of IDNA to DNS resource records depends entirely on 232 the CLASS of the record, and not on the TYPE except as noted below. 233 This will remain true, even as new types are defined, unless a new 234 type defines type-specific rules. Special naming conventions for SRV 235 records (and "underscore names" more generally) are incompatible with 236 IDNA coding. The first two labels on a SRV type record (the ones 237 required to start in "_") MUST NOT be A-labels or U-labels, because 238 conversion to an A-label would lose information (since the underscore 239 is not a letter, digit, or hyphen and is consequently DISALLOWED in 240 IDNs). Of course, those labels may be part of a domain that uses IDN 241 labels at higher levels in the tree. 243 3.2.2. Non-domain-name Data Types Stored in the DNS 245 Although IDNA enables the representation of non-ASCII characters in 246 domain names, that does not imply that IDNA enables the 247 representation of non-ASCII characters in other data types that are 248 stored in domain names, specifically in the RDATA field for types 249 that have structured RDATA format. For example, an email address 250 local part is stored in a domain name in the RNAME field as part of 251 the RDATA of an SOA record (hostmaster@example.com would be 252 represented as hostmaster.example.com). IDNA does not update the 253 existing email standards, which allow only ASCII characters in local 254 parts. Even though work is in progress to define 255 internationalization for email addresses [RFC4952], changes to the 256 email address part of the SOA RDATA would require action in, or 257 updates to, other standards, specifically those that specify the 258 format of the SOA RR. 260 4. Registration Protocol 262 This section defines the procedure for registering an IDN. The 263 procedure is implementation independent; any sequence of steps that 264 produces exactly the same result for all labels is considered a valid 265 implementation. 267 Note that, while the registration and lookup protocols (Section 5) 268 are very similar in most respects, they are different and 269 implementers should carefully follow the appropriate steps. 271 4.1. Input to IDNA Registration Process 273 Registration processes, especially processing by entities, such as 274 "registrars" who deal with registrants before the request actually 275 reaches the zone manager ("registry") are outside the scope of these 276 protocols and may differ significantly depending on local needs. By 277 the time a string enters the IDNA registration process as described 278 in this specification, it is expected to be in Unicode and MUST be in 279 Unicode Normalization Form C (NFC [Unicode-UAX15]). Entities 280 responsible for zone files ("registries") are expected to accept only 281 the exact string for which registration is requested, free of any 282 mappings or local adjustments. They SHOULD avoid any possible 283 ambiguity by accepting registrations only for A-labels, possibly 284 paired with the relevant U-labels so that they can verify the 285 correspondence. 287 4.2. Permitted Character and Label Validation 289 4.2.1. Input Format 291 The registry SHOULD permit submission of labels in A-label form and 292 is encouraged to accept both the A-label form and the U-label one. 293 If it does so, it MUST perform a conversion to a U-label, perform the 294 steps and tests described below, and verify that the A-label produced 295 by the step in Section 4.4 matches the one provided as input. In 296 addition, if a U-label was provided, that U-label and the one 297 obtained by conversion of the A-label MUST match exactly. If, for 298 some reason, these tests fail, the registration MUST be rejected. If 299 the conversion to a U-label is not performed, the registry MUST still 300 verify that the A-label is superficially valid, i.e., that it does 301 not violate any of the rules of Punycode [RFC3492] encoding such as 302 the prohibition on trailing hyphen-minus, appearance of non-basic 303 characters before the delimiter, and so on. Fake A-labels, i.e., 304 invalid strings that appear to be A-labels but are not, MUST NOT be 305 placed in DNS zones that support IDNA. 307 4.2.2. Rejection of Characters that are not Permitted 309 The candidate Unicode string MUST NOT contain characters in the 310 "DISALLOWED" and "UNASSIGNED" lists specified in [IDNA2008-Tables]. 312 4.2.3. Label Validation 314 The proposed label (in the form of a Unicode string, i.e., a string 315 that at least superficially appears to be a U-label) is then 316 examined, performing tests that require examination of more than one 317 character. Character order is considered to be the on-the-wire 318 order, not the display order. 320 4.2.3.1. Consecutive Hyphens 322 The Unicode string MUST NOT contain "--" (two consecutive hyphens) in 323 the third and fourth character positions. 325 4.2.3.2. Leading Combining Marks 327 The Unicode string MUST NOT begin with a combining mark or combining 328 character (see The Unicode Standard, Section 2.11 [Unicode] for an 329 exact definition). 331 4.2.3.3. Contextual Rules 333 The Unicode string MUST NOT contain any characters whose validity is 334 context-dependent, unless the validity is positively confirmed by a 335 contextual rule. To check this, each code-point marked as CONTEXTJ 336 and CONTEXTO in [IDNA2008-Tables] MUST have a non-null rule. If such 337 a code-point is missing a rule, it is invalid. If the rule exists 338 but the result of applying the rule is negative or inconclusive, the 339 proposed label is invalid. 341 NOTE: These contextual rules are required to support characters that 342 could be used, under some conditions, to produce misleading labels or 343 to cause unacceptable ambiguity in label matching and interpretation. 344 For example, labels containing zero-width characters may be permitted 345 in context with characters whose presentation forms are significantly 346 changed by the zero-width characters, while other labels in which 347 zero-width characters appear may be rejected. 348 [[anchor11: Note in draft: Should this note be moved to Rationale??? 349 It has no normative consequences here.]] 351 4.2.3.4. Labels Containing Characters Written Right to Left 353 If the proposed label contains any characters that are written from 354 right to left it MUST meet the "bidi" criteria [IDNA2008-BIDI]. 356 4.2.4. Registration Validation Summary 358 Strings that contain at least one non-ASCII character, have been 359 produced by the steps above, whose contents pass all of the tests in 360 Section 4.2, and are 63 or fewer characters long in ACE form (see 361 Section 4.4), are U-labels. 363 To summarize, tests are made in Section 4.2 for invalid characters, 364 invalid combinations of characters, for labels that are invalid even 365 if the characters they contain are valid individually, and for labels 366 that do not conform to the restrictions for strings containing right 367 to left characters. 369 4.3. Registry Restrictions 371 In addition to the rules and tests above, there are many reasons why 372 a registry could reject a label. Registries at all levels of the 373 DNS, not just the top level, establish policies about label 374 registrations. Policies are likely to be informed by the local 375 languages and may depend on many factors including what characters 376 are in the label (for example, a label may be rejected based on other 377 labels already registered). See [IDNA2008-Rationale] for a 378 discussion and recommendations about registry policies. 380 The string produced by the above steps is checked and processed as 381 appropriate to local registry restrictions. Application of those 382 registry restrictions may result in the rejection of some labels or 383 the application of special restrictions to others. 385 4.4. Punycode Conversion 387 The resulting U-label is converted to an A-label. The A-label, more 388 precisely defined elsewhere, is the encoding of the U-label according 389 to the Punycode algorithm [RFC3492] with the ACE prefix "xn--" added 390 at the beginning of the string. The resulting string must, of 391 course, conform to the length limits imposed by the DNS. This 392 document updates RFC 3492 only to the extent of replacing the 393 reference to the discussion of the ACE prefix. The ACE prefix is now 394 specified in this document rather than as part of RFC 3490 or 395 Nameprep [RFC3491] but is the same in both sets of documents. 397 The failure conditions identified in the Punycode encoding procedure 398 cannot occur if the input is a U-label as determined by the steps 399 above. 401 4.5. Insertion in the Zone 403 The A-label is registered in the DNS by insertion into a zone. 405 5. Domain Name Lookup Protocol 407 Lookup is different from registration and different tests are applied 408 on the client. Although some validity checks are necessary to avoid 409 serious problems with the protocol, the lookup-side tests are more 410 permissive and rely on the assumption that names that are present in 411 the DNS are valid. That assumption is, however, a weak one because 412 the presence of wild cards in the DNS might cause a string that is 413 not actually registered in the DNS to be successfully looked up. 415 The two steps in Section 5.2 and Section 5.3 are required. 417 [[anchor14: Note in Draft: Try to reorganize and renumber Section 5 418 (Lookup) so that it exactly parallels Section 4 (Registration). This 419 has not been done in drafts -10 through -13 because the task will be 420 much easier if the local mapping material is pulled from here (and 421 there is no point trying to align the section numbers twice).]] 423 5.1. Label String Input 425 The user supplies a string in the local character set, typically by 426 typing it or clicking on, or copying and pasting, a resource 427 identifier, e.g., a URI [RFC3986] or IRI [RFC3987] from which the 428 domain name is extracted. Alternately, some process not directly 429 involving the user may read the string from a file or obtain it in 430 some other way. Processing in this step and the next two are local 431 matters, to be accomplished prior to actual invocation of IDNA. 433 5.2. Conversion to Unicode 435 The string is converted from the local character set into Unicode, if 436 it is not already Unicode. A Unicode string may require 437 normalization as discussed in Section 4.1. The result MUST be a 438 Unicode string in NFC form. 440 5.3. Character Changes in Preprocessing or the User Interface 442 [[anchor15: Note in Draft -13. This entire section is likely to need 443 significant revision when we make final decisions about mapping. The 444 changes from -12 are intended simply to illustrate one of the ways in 445 which the mapping material might be incorporated if we keep it... and 446 to fix a possible ambiguity about the NFC requirement for mapping 447 output.]] 449 The Unicode string MAY then be processed to prevent confounding of 450 user expectations. For instance, it might be reasonable, at this 451 step, to convert all upper case characters to lower case, if this 452 makes sense in the user's environment, but even this should be 453 approached with caution due to some edge cases: in the long term, it 454 is probably better for users to understand IDNs strictly in lower- 455 case, U-label, form. More generally, preprocessing may be useful to 456 smooth the transition from IDNA2003, especially for direct user 457 input, but with similar cautions. In general, IDNs appearing in 458 files and those transmitted across the network as part of protocols 459 are expected to be in either ASCII form (including A-labels) or to 460 contain U-labels, rather than being in forms requiring mapping or 461 other conversions. 463 The mapping issue and some suggestions and tradeoffs are discussed in 464 [IDNA2008-Mapping]. Note that this specification does not require 465 that the processing into Unicode (See Section 5.2 above) be applied 466 as a separate step if it incorporated into some mapping process as 467 described in [IDNA2008-Mapping]. 469 Other examples of processing for localization might be applied, 470 especially to direct user input, at this point. They include 471 interpreting various characters as separating domain name components 472 from each other (label separators) because they either look like 473 periods or are used to separate sentences, mapping halfwidth or 474 fullwidth East Asian characters to the common form permitted in 475 labels, or giving special treatment to characters whose presentation 476 forms are dependent only on placement in the label. Such 477 localization changes are also outside the scope of this 478 specification. 480 Recommendations for preprocessing for global contexts (i.e., when 481 local considerations do not apply or cannot be used) and for maximum 482 interoperability with labels that might have been specified under 483 liberal readings of IDNA2003 are given in [IDNA2008-Rationale]. It 484 is important to note that the intent of these specifications is that 485 labels in application protocols, files, or links are intended to be 486 in U-label or A-label form. Preprocessing MUST NOT map a character 487 that is valid in a label as specified elsewhere in this document or 488 in [IDNA2008-Tables] into another character. Excessively liberal use 489 of preprocessing, especially to strings stored in files, poses a 490 threat to consistent and predictable behavior for the user even if 491 not to actual interoperability. 493 Because these transformations are local, it is important that domain 494 names that might be passed between systems (e.g., in IRIs) be 495 U-labels or A-labels and not forms that might be accepted locally as 496 a consequence of this step. This step is not standardized as part of 497 IDNA, and is not further specified here. 499 If this step is applied, the results still MUST be in NFC form as 500 above. The step must not denormalize the characters. 502 5.4. A-label Input 504 If the input to this procedure appears to be an A-label (i.e., it 505 starts in "xn--"), the lookup application MAY attempt to convert it 506 to a U-label and apply the tests of Section 5.5 and the conversion of 507 Section 5.6 to that form. If the label is converted to Unicode 508 (i.e., to U-label form) using the Punycode decoding algorithm, then 509 the processing specified in those two sections MUST be performed, and 510 the label MUST be rejected if the resulting label is not identical to 511 the original. See the Name Server Considerations section of 512 [IDNA2008-Rationale] for additional discussion on this topic. 514 That conversion and testing SHOULD be performed if the domain name 515 will later be presented to the user in native character form (this 516 requires that the lookup application be IDNA-aware). If those steps 517 are not performed, the lookup process SHOULD at least make tests to 518 determine that the string is actually an A-label, examining it for 519 the invalid formats specified in the Punycode decoding specification. 520 Applications that are not IDNA-aware will obviously omit that 521 testing; others MAY treat the string as opaque to avoid the 522 additional processing at the expense of providing less protection and 523 information to users. 525 5.5. Validation and Character List Testing 527 As with the registration procedure described in Section 4, the 528 Unicode string is checked to verify that all characters that appear 529 in it are valid as input to IDNA lookup processing. As discussed 530 above and in [IDNA2008-Rationale], the lookup check is more liberal 531 than the registration one. Labels that have not been fully evaluated 532 for conformance to the applicable rules are referred to as "putative" 533 labels as discussed in [IDNA2008-Defs][[anchor16: ??? Insert section 534 number -- 2.2.3 as of Defs-09]]. Putative labels with any of the 535 following characteristics MUST BE rejected prior to DNS lookup: 537 o Labels containing code points that are unassigned in the version 538 of Unicode being used by the application, i.e.,in the UNASSIGNED 539 category of [IDNA2008-Tables]. 541 o Labels that are not in NFC form as defined in [Unicode-UAX15]. 543 o Labels containing prohibited code points, i.e., those that are 544 assigned to the "DISALLOWED" category in the permitted character 545 table [IDNA2008-Tables]. 547 o Labels containing code points that are identified in 548 [IDNA2008-Tables] as "CONTEXTJ", i.e., requiring exceptional 549 contextual rule processing on lookup, but that do not conform to 550 that rule. Note that this implies that a rule much be defined, 551 not null: a character that requires a contextual rule but for 552 which the rule is null is treated in this step as having failed to 553 conform to the rule. 555 o Labels containing code points that are identified in 556 [IDNA2008-Tables] as "CONTEXTO", but for which no such rule 557 appears in the table of rules. Applications resolving DNS names 558 or carrying out equivalent operations are not required to test 559 contextual rules for "CONTEXTO" characters, only to verify that a 560 rule is defined (although they MAY make such tests to provide 561 better protection or give better information to the user). 563 o Labels whose first character is a combining mark (see 564 Section 4.2.3.2). 566 In addition, the application SHOULD apply the following test. The 567 test may be omitted in special circumstances, such as when the lookup 568 application knows that the conditions are enforced elsewhere, because 569 an attempt to look up and resolve such strings will almost certainly 570 lead to a DNS lookup failure except when wildcards are present in the 571 zone. However, applying the test is likely to give much better 572 information about the reason for a lookup failure -- information that 573 may be usefully passed to the user when that is feasible -- than DNS 574 resolution failure information alone. In any event, lookup 575 applications should avoid attempting to resolve labels that are 576 invalid under that test. 578 o Verification that the string is compliant with the requirements 579 for right to left characters, specified in [IDNA2008-BIDI]. 581 For all other strings, the lookup application MUST rely on the 582 presence or absence of labels in the DNS to determine the validity of 583 those labels and the validity of the characters they contain. If 584 they are registered, they are presumed to be valid; if they are not, 585 their possible validity is not relevant. While a lookup application 586 may reasonably issue warnings about strings it believes may be 587 problematic, applications that decline to process a string that 588 conforms to the rules above (i.e., does not look it up in the DNS) 589 are not in conformance with this protocol. 591 5.6. Punycode Conversion 593 The string that has now been validated for lookup is converted to ACE 594 form using the Punycode algorithm (with the ACE prefix added). With 595 the understanding that this summary is not normative (the steps above 596 are), the string is either 598 o in Unicode NFC form that contains no leading combining marks, 599 contains no DISALLOWED or UNASSIGNED code points, has rules 600 associated with any code points in CONTEXTJ or CONTEXTO, and, for 601 those in CONTEXTJ, to satisfies the conditions of the rules; or 603 o in A-label form, was supplied under circumstances in which the 604 U-label conversions and tests have not been performed (see 605 Section 5.4). 607 5.7. DNS Name Resolution 609 That resulting validated string is looked up in the DNS, using normal 610 DNS resolver procedures. That lookup can obviously either succeed 611 (returning information) or fail. 613 6. Security Considerations 615 Security Considerations for this version of IDNA, except for the 616 special issues associated with right to left scripts and characters, 617 are described in [IDNA2008-Defs]. Specific issues for labels 618 containing characters associated with scripts written right to left 619 appear in [IDNA2008-BIDI]. 621 7. IANA Considerations 623 IANA actions for this version of IDNA are specified in 624 [IDNA2008-Tables] and discussed informally in [IDNA2008-Rationale]. 625 The components of IDNA described in this document do not require any 626 IANA actions. 628 8. Contributors 630 While the listed editor held the pen, the original versions of this 631 document represent the joint work and conclusions of an ad hoc design 632 team consisting of the editor and, in alphabetic order, Harald 633 Alvestrand, Tina Dam, Patrik Faltstrom, and Cary Karp. This document 634 draws significantly on the original version of IDNA [RFC3490] both 635 conceptually and for specific text. This second-generation version 636 would not have been possible without the work that went into that 637 first version and its authors, Patrik Faltstrom, Paul Hoffman, and 638 Adam Costello. While Faltstrom was actively involved in the creation 639 of this version, Hoffman and Costello were not and should not be held 640 responsible for any errors or omissions. 642 9. Acknowledgments 644 This revision to IDNA would have been impossible without the 645 accumulated experience since RFC 3490 was published and resulting 646 comments and complaints of many people in the IETF, ICANN, and other 647 communities, too many people to list here. Nor would it have been 648 possible without RFC 3490 itself and the efforts of the Working Group 649 that defined it. Those people whose contributions are acknowledged 650 in RFC 3490, [RFC4690], and [IDNA2008-Rationale] were particularly 651 important. 653 Specific textual changes were incorporated into this document after 654 suggestions from the other contributors, Stephane Bortzmeyer, Vint 655 Cerf, Lisa Dusseault, Mark Davis, Paul Hoffman, Kent Karlsson, Erik 656 van der Poel, Marcos Sanz, Andrew Sullivan, Ken Whistler, and other 657 WG participants. Special thanks are due to Paul Hoffman for 658 permission to extract material from his Internet-Draft to form the 659 basis for Appendix B. 661 10. References 663 10.1. Normative References 665 [IDNA2008-BIDI] 666 Alvestrand, H. and C. Karp, "An updated IDNA criterion for 667 right-to-left scripts", July 2008, . 670 [IDNA2008-Defs] 671 Klensin, J., "Internationalized Domain Names for 672 Applications (IDNA): Definitions and Document Framework", 673 February 2009, . 676 [IDNA2008-Tables] 677 Faltstrom, P., "The Unicode Codepoints and IDNA", 678 July 2008, . 681 A version of this document is available in HTML format at 682 http://stupid.domain.name/idnabis/ 683 draft-ietf-idnabis-tables-02.html 685 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 686 STD 13, RFC 1034, November 1987. 688 [RFC1035] Mockapetris, P., "Domain names - implementation and 689 specification", STD 13, RFC 1035, November 1987. 691 [RFC1123] Braden, R., "Requirements for Internet Hosts - Application 692 and Support", STD 3, RFC 1123, October 1989. 694 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 695 Requirement Levels", BCP 14, RFC 2119, March 1997. 697 [RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode 698 for Internationalized Domain Names in Applications 699 (IDNA)", RFC 3492, March 2003. 701 [Unicode-PropertyValueAliases] 702 The Unicode Consortium, "Unicode Character Database: 703 PropertyValueAliases", March 2008, . 706 [Unicode-RegEx] 707 The Unicode Consortium, "Unicode Technical Standard #18: 708 Unicode Regular Expressions", May 2005, 709 . 711 [Unicode-Scripts] 712 The Unicode Consortium, "Unicode Standard Annex #24: 713 Unicode Script Property", February 2008, 714 . 716 [Unicode-UAX15] 717 The Unicode Consortium, "Unicode Standard Annex #15: 718 Unicode Normalization Forms", 2006, 719 . 721 10.2. Informative References 723 [ASCII] American National Standards Institute (formerly United 724 States of America Standards Institute), "USA Code for 725 Information Interchange", ANSI X3.4-1968, 1968. 727 ANSI X3.4-1968 has been replaced by newer versions with 728 slight modifications, but the 1968 version remains 729 definitive for the Internet. 731 [IDNA2008-Mapping] 732 Resnick, P., "Mapping Characters in IDNA", July 2009, . 736 [IDNA2008-Rationale] 737 Klensin, J., Ed., "Internationalizing Domain Names for 738 Applications (IDNA): Issues, Explanation, and Rationale", 739 February 2009, . 742 [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, 743 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 744 RFC 2136, April 1997. 746 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS 747 Specification", RFC 2181, July 1997. 749 [RFC2535] Eastlake, D., "Domain Name System Security Extensions", 750 RFC 2535, March 1999. 752 [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", 753 RFC 2671, August 1999. 755 [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, 756 "Internationalizing Domain Names in Applications (IDNA)", 757 RFC 3490, March 2003. 759 [RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep 760 Profile for Internationalized Domain Names (IDN)", 761 RFC 3491, March 2003. 763 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 764 Resource Identifier (URI): Generic Syntax", STD 66, 765 RFC 3986, January 2005. 767 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource 768 Identifiers (IRIs)", RFC 3987, January 2005. 770 [RFC4690] Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and 771 Recommendations for Internationalized Domain Names 772 (IDNs)", RFC 4690, September 2006. 774 [RFC4952] Klensin, J. and Y. Ko, "Overview and Framework for 775 Internationalized Email", RFC 4952, July 2007. 777 [Unicode] The Unicode Consortium, "The Unicode Standard, Version 778 5.0", 2007. 780 Boston, MA, USA: Addison-Wesley. ISBN 0-321-48091-0 782 Appendix A. Local Mapping Alternatives 784 The subsections of this appendix are temporary and represent 785 different sketches of possible replacements for Section 5.3. They do 786 not represent an assertion of WG consensus or any assertion about the 787 possibility of including one of them as part of the WG's work 788 program. Instead, they are supplied only for purposes of comparison, 789 discussion, and, should it be relevant, refinement. 791 The first paragraph of each subsection describes how the material 792 would be placed relative to the existing main document text. 794 Subsequent paragraphs are the actual suggestions, although in 795 incomplete sketch form. 797 A.1. Transitional Mapping Model 799 If this subsection were adopted, Section 5.3 would be deleted and 800 this one would be inserted after, or integrated with, Section 5.7. 802 This specification does not support the extensive mappings from one 803 character to another, including Unicode Case Folding and 804 Compatibility Character mapping, of IDNA2003. It also changes the 805 interpretations of a small number of characters relative to IDNA2003. 806 Most applications, especially those with which IDNs have been used 807 for some time, will need to maintain reasonable compatibility with 808 files created under IDNA2003 and user interfaces designed for it. 809 This section specifies additional steps to be taken to provide 810 maximum IDNA2003 compatibility. 812 If an application requires IDNA2003 backward compatibility, it MUST 813 execute the steps in one of the two subsections that immediately 814 follow. 816 A.1.1. Fallback Lookup 818 If the string validates and the resolution attempt in Section 5.7 819 successfully returns a result, the lookup process terminates with 820 that result. If validation succeeds but resolution fails, the 821 validated string is proceeded through the ToASCII operation specified 822 in IDNA2003 [RFC3490]. Assuming it produces a valid result, the 823 resulting string is compared to the previous validated one. If they 824 are not identical, a resolution attempt is made with the ToASCII 825 output and the result of that attempt is returned as the result of 826 the lookup operation. 828 Should IDNA2008 validation fail, the string is processed through 829 ToASCII and, assuming the result is valid, the resulting string is 830 resolved and the result of that attempt returned as the result of the 831 lookup operation. 833 If ToASCII (IDNA2003) conversion is attempted and fails, the lookup 834 operation behaves as if no name was found in the DNS. 836 Note that this procedure involves, at most, one DNS lookup 837 (resolution attempt). If IDNA2008 string validation, conversion, and 838 resolution succeed, no attempt is made to use IDNA2003 mechanisms. 839 The procedure does, however, require that lookup applications fully 840 support both IDNA2008 and IDNA2003 lookup operations so that the 841 fallback can occur. 843 A.1.2. Two-step Lookup 845 Prior to the resolution attempt in Section 5.7, ACE strings are 846 computed using both IDNA2003 (ToASCII) and IDNA2008 methods (as 847 specified here). Assuming both validate, those strings are compared. 848 If they are identical, or only one was valid, then a single DNS 849 resolution is performed and its result is the result of the lookup 850 operation. If both are valid but they are not identical, one 851 resolution attempt is made with each of the two ACE strings. 853 If neither string is valid as an IDN, then the lookup operation 854 fails. 856 When two resolutions are attempted, if one of the two is successful 857 and the other is not, the successful value is used as the result of 858 the lookup. If both are successful, the user or calling application 859 must be presented with a choice in some way. 861 This procedure will require two DNS lookups (resolution attempts) in 862 all cases except those in which the label string fails IDNA2008 863 validation, neither IDNA2003 or IDNA2008 can validate the string and 864 translate it to ACE form, or the strings obtained from the two 865 conversions are identical. As with the prior option, IDNA 866 implementations will need to support both the IDNA2003 algorithm and 867 tables and the IDNA2008 one. The question of how multiple results 868 from different interpretations of the same input string should be 869 handled by applications is a difficult one, with potential false 870 positive and security attack vector implications as well as the 871 possibility of general confusion. 873 In particular, if both interpretations of the name return values, the 874 lookup application has no practical way to tell whether the relevant 875 registry has applied "variant" or "bundling" techniques to ensure 876 that both domain names are under the same control or not. From that 877 perspective, the approach in the previous subsection assumes that has 878 been done (if the IDNA2003-interpretation label is present at all) 879 while this one assumes that such bundling is unlikely to have 880 occurred. 882 [[anchor26: Note in Draft: If this appendix is used, RFC3490 must be 883 moved from Informative to Normative.]] 885 A.2. Internationalized Resource Identifier (IRI) Mapping Model 887 This subsection is intended to be descriptive of an approach that 888 lies outside IDNA, rather than a normative component of it. If it 889 were adopted, Section 5.3 would be deleted and the material below 890 would be referenced, either as a non-normative Appendix in Protocol 891 or, more reasonably, as a section of Rationale. 893 IDNA2003 supported extensive mappings from one character to another, 894 including Unicode Case Folding and Compatibility Character mapping. 895 Those mappings are no longer supported on registration and are 896 inconsistent with the "exact match" lookups that people expect from 897 the DNS. Some mapping should still be supported, both for 898 compatibility with applications that assume IDNA2003 and to avoid 899 confounding user expectations. The specific mappings involved are 900 not part of IDNA, but are expected to be specified as part of a 901 revision to the IRI specification [RFC3987] and the conversion from 902 IRI form to URI form. That change leaves mapping unspecified and 903 prohibited for actual domain names, however, in practice, most domain 904 names, especially in the web applications that appear to have been 905 most important for IDNs between the publication of IDNA2003 and the 906 release of this specification, are not interpreted as themselves but 907 as abbreviated form of URIs or IRIs and hence subject to the 908 transformation rules of the latter. 910 Appendix B. Summary of Major Changes from IDNA2003 912 1. Update base character set from Unicode 3.2 to Unicode version- 913 agnostic. 915 2. Separate the definitions for the "registration" and "lookup" 916 activities. 918 3. Disallow symbol and punctuation characters except where special 919 exceptions are necessary. 921 4. Remove the mapping and normalization steps from the protocol and 922 have them instead done by the applications themselves, possibly 923 in a local fashion, before invoking the protocol. 925 5. Change the way that the protocol specifies which characters are 926 allowed in labels from "humans decide what the table of 927 codepoints contains" to "decision about codepoints are based on 928 Unicode properties plus a small exclusion list created by 929 humans". 931 6. Introduce the new concept of characters that can be used only in 932 specific contexts. 934 7. Allow typical words and names in languages such as Dhivehi and 935 Yiddish to be expressed. 937 8. Make bidirectional domain names (delimited strings of labels, 938 not just labels standing on their own) display in a less 939 surprising fashion whether they appear in obvious domain name 940 contexts or as part of running text in paragraphs. 942 9. Remove the dot separator from the mandatory part of the 943 protocol. 945 10. Make some currently-valid labels that are not actually IDNA 946 labels invalid. 948 Appendix C. Change Log 950 [[anchor29: RFC Editor: Please remove this appendix.]] 952 C.1. Changes between Version -00 and -01 of draft-ietf-idnabis-protocol 954 o Corrected discussion of SRV records. 956 o Several small corrections for clarity. 958 o Inserted more "open issue" placeholders. 960 C.2. Version -02 962 o Rewrote the "conversion to Unicode" text in Section 5.2 as 963 requested on-list. 965 o Added a comment (and reference) about EDNS0 to the "DNS Server 966 Conventions" section, which was also retitled. 968 o Made several editorial corrections and improvements in response to 969 various comments. 971 o Added several new discussion placeholder anchors and updated some 972 older ones. 974 C.3. Version -03 976 o Trimmed change log, removing information about pre-WG drafts. 978 o Incorporated a number of changes suggested by Marcos Sanz in his 979 note of 2008.07.17 and added several more placeholder anchors. 981 o Several minor editorial corrections and improvements. 983 o "Editor" designation temporarily removed because the automatic 984 posting machinery does not accept it. 986 C.4. Version -04 988 o Removed Contextual Rule appendices for transfer to Tables. 990 o Several changes, including removal of discussion anchors, based on 991 discussions at IETF 72 (Dublin) 993 o Rewrote the preprocessing material (Section 5.3) somewhat. 995 C.5. Version -05 997 o Updated part of the A-label input explanation (Section 5.4) per 998 note from Erik van der Poel. 1000 C.6. Version -06 1002 o Corrected a few typographical errors. 1004 o Incorporated the material (formerly in Rationale) on the 1005 relationship between IDNA2003 and IDNA2008 as an appendix and 1006 pointed to the new definitions document. 1008 o Text modified in several places to recognize the dangers of 1009 interaction between DNS wildcards and IDNs. 1011 o Text added to be explicit about the handling of edge and failure 1012 cases in Punycode encoding and decoding. 1014 o Revised for consistency with the new Definitions document and to 1015 make the text read more smoothly. 1017 C.7. Version -07 1019 o Multiple small textual and editorial changes and clarifications. 1021 o Requirement for normalization clarified to apply to all cases and 1022 conditions for preprocessing further clarified. 1024 o Substantive change to Section 4.2.1, turning a SHOULD to a MUST 1025 (see note from Mark Davis, 19 November, 2008 18:14 -0800). 1027 C.8. Version -08 1029 o Added some references and altered text to improve clarity. 1031 o Changed the description of CONTEXTJ/CONTEXTO to conform to that in 1032 Tables. In other words, these are now treated as distinction 1033 categories (again), rather than as specially-flagged subsets of 1034 PROTOCOL VALID. 1036 o The discussion of label comparisons has been rewritten to make it 1037 more precise and to clarify that one does not need to verify that 1038 a string is a [valid] A-label or U-label in order to test it for 1039 equality with another string. The WG should verify that the 1040 current text is what is desired. 1042 o Other changes to reflect post-IETF discussions or editorial 1043 improvements. 1045 C.9. Version -09 1047 o Removed Security Considerations material to Defs document. 1049 o Removed the Name Server Considerations material to Rationale. 1050 That material is not normative and not needed to implement the 1051 protocol itself. 1053 o Adjusted terminology to match new version of Defs. 1055 o Removed all discussion of local mapping and option for it from 1056 registration protocol. Such mapping is now completely prohibited 1057 on Registration. 1059 o Removed some old placeholders and inquiries because no comments 1060 have been received. 1062 o Small editorial corrections. 1064 C.10. Version -10 1066 o Rewrote the registration input material slightly to further 1067 clarify the "no mapping on registration" principle. 1069 o Added placeholder notes about several tasks, notably reorganizing 1070 Section 4 and Section 5 so that subsection numbers are parallel. 1072 o Cleaned up an incorrect use of the terms "A-label" and "U-label" 1073 in the lookup phase that was spotted by Mark Davis. Inserted a 1074 note there about alternate ways to deal with the resulting 1075 terminology problem. 1077 o Added a temporarily appendix (above) to document alternate 1078 strategies for possible replacements for Section 5.3. 1080 C.11. Version -11 1082 o Removed dangling reference to "C-label" (editing error in prior 1083 draft). 1085 o Recast the last steps of the Lookup description to eliminate 1086 "apparent" (previously "putative") terminology. 1088 o Rewrote major portions of the temporary appendix that describes 1089 transitional mappings to improve clarity and add context. 1091 o Did some fine-tuning of terminology, notably in Section 3.2.1. 1093 C.12. Version -12 1095 o Extensive editorial improvements, mostly due to suggestions from 1096 Lisa Dusseault. 1098 o Conformance statements have been made consistent, especially in 1099 Section 4.2.1 and subsequent text, which said "SHOULD" in one 1100 place and then said "MAY" as the result of incomplete removal of 1101 registration-time mapping. Also clarified the definition of 1102 "registration processes" in Section 4.1 -- the previous text had 1103 confused several people. 1105 o A few new "question to the WG notes have been added about 1106 appropriateness or placement of text. If there are no comments on 1107 the mailing list, the editor will apply his own judgment. 1109 o Several of the usual small typos and other editorial errors have 1110 been corrected. 1112 o Section 5 has still not been reorganized to match Section 4 in 1113 structure and subsection numbering -- will be done as soon as the 1114 mapping decisions and references are final. 1116 C.13. Version -13 1118 o Modified the "putative label" text to better explain the term and 1119 explicitly point back to Defs. 1121 o Slight rewrite of Section 5.3 to clarify the NFC requirement and 1122 to start the transition toward having some of the explanation in 1123 the Mapping document. The latter might need to be undone as WG 1124 consensus evolves. 1126 Author's Address 1128 John C Klensin 1129 1770 Massachusetts Ave, Ste 322 1130 Cambridge, MA 02140 1131 USA 1133 Phone: +1 617 245 1457 1134 Email: john+ietf@jck.com