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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Reference: 'I-D.iab-identifier-comparison' is defined on line 295, but no explicit reference was found in the text == Outdated reference: A later version (-09) exists of draft-iab-identifier-comparison-03 -- Obsolete informational reference (is this intentional?): RFC 2629 (Obsoleted by RFC 7749) Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6MAN B. Carpenter 3 Internet-Draft Univ. of Auckland 4 Updates: 3986 (if approved) S. Cheshire 5 Intended status: Standards Track Apple Inc. 6 Expires: May 10, 2013 R. Hinden 7 Check Point 8 November 6, 2012 10 Representing IPv6 Zone Identifiers in Address Literals and Uniform 11 Resource Identifiers 12 draft-ietf-6man-uri-zoneid-05 14 Abstract 16 This document describes how the Zone Identifier of an IPv6 scoped 17 address can be represented in a literal IPv6 address and in a Uniform 18 Resource Identifier that includes such a literal address. It updates 19 RFC 3986 accordingly. 21 Status of this Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on May 10, 2013. 38 Copyright Notice 40 Copyright (c) 2012 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 2. Specification . . . . . . . . . . . . . . . . . . . . . . . . . 4 57 3. Web Browsers . . . . . . . . . . . . . . . . . . . . . . . . . 5 58 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 59 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 60 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 61 7. Change log [RFC Editor: Please remove] . . . . . . . . . . . . 6 62 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 63 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7 64 8.2. Informative References . . . . . . . . . . . . . . . . . . 7 65 Appendix A. Alternatives Considered . . . . . . . . . . . . . . . 8 66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 68 1. Introduction 70 The Uniform Resource Identifier (URI) syntax [RFC3986] defined how a 71 literal IPv6 address can be represented in the "host" part of a URI. 72 A subsequent specification [RFC4007] extended the text representation 73 of limited-scope IPv6 addresses such that a zone identifier may be 74 concatenated to a literal address, for purposes described in that 75 RFC. Zone identifiers are especially useful in contexts where 76 literal addresses are typically used, for example during fault 77 diagnosis, when it may be essential to specify which interface is 78 used for sending to a link local address. It should be noted that 79 zone identifiers have purely local meaning within the host where they 80 are defined, and they are completely meaningless for any other host. 81 Today, they are only meaningful when attached to addresses with less 82 than global scope, but it is possible that other uses might be 83 defined in the future. 85 RFC 4007 does not specify how zone identifiers are to be represented 86 in URIs. Practical experience has shown that this feature is useful, 87 in particular when using a web browser for debugging with link local 88 addresses, but as it is undefined, it is not implemented consistently 89 in URI parsers or in browsers. 91 Some versions of some browsers accept the RFC 4007 syntax for scoped 92 IPv6 addresses embedded in URIs, i.e., they have been coded to 93 interpret the "%" sign according to RFC 4007 instead of RFC 3986. 94 Clearly this approach is very convenient for users, although it 95 formally breaches the syntax rules of RFC 3986. The present document 96 defines an alternative approach that respects and extends the rules 97 of URI syntax, and IPv6 literals in general, to be consistent. 99 Thus, this document updates [RFC3986] by adding syntax to allow a 100 zone identifier to be included in a literal IPv6 address within a 101 URI. 103 It should be noted that in other contexts than a user interface, a 104 zone identifier is mapped into a numeric zone index or interface 105 number. The MIB textual convention [RFC4001] and the socket 106 interface [RFC3493] define this as a 32 bit unsigned integer. The 107 mapping between the human-readable zone identifier string and the 108 numeric value is a host-specific function that varies between 109 operating systems. The present document is concerned only with the 110 human-readable string. 112 Several alternative solutions were considered while this document was 113 developed. The Appendix briefly describes the alternatives and their 114 advantages and disadvantages. 116 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 117 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 118 document are to be interpreted as described in [RFC2119]. 120 2. Specification 122 According to RFC 4007, a zone identifier is attached to the textual 123 representation of an IPv6 address by concatenating "%" followed by 124 , where is a string identifying the zone of the 125 address. However, RFC 4007 gives no precise definition of the 126 character set allowed in . There are no rules or de facto 127 standards for this. For example, the first Ethernet interface in a 128 host might be called %0, %1, %en1, %eth0, or whatever the implementer 129 happened to choose. 131 In a URI, a literal IPv6 address is always embedded between "[" and 132 "]". This document specifies how a can be appended to the 133 address. A SHOULD contain only ASCII characters classified 134 in RFC 3986 as "unreserved", which conveniently excludes "]" in order 135 to simplify parsing. 137 Unfortunately "%" is always treated as an escape character in a URI, 138 and according to RFC 3986 it MUST therefore itself be escaped in a 139 URI, in the form "%25". Thus, the scoped address fe80::a%en1 would 140 appear in a URI as http://[fe80::a%25en1]. 142 If an operating system uses any other characters in zone or interface 143 identifiers that are not in the "unreserved" character set, they MUST 144 be escaped with a "%" sign according to RFC 3986. 146 We now present the necessary formal syntax. 148 In RFC 3986, the IPv6 literal format is formally defined in ABNF 149 [RFC5234] by the following rule: 151 IP-literal = "[" ( IPv6address / IPvFuture ) "]" 153 To provide support for a zone identifier, the existing syntax of 154 IPv6address is retained, and a zone identifier may be added 155 optionally to any literal address. This allows flexibility for 156 unknown future uses. The rule quoted above from RFC 3986 is replaced 157 by three rules: 159 IP-literal = "[" ( IPv6address / IPv6addrz / IPvFuture ) "]" 161 ZoneID = 1*( unreserved / pct-encoded ) 162 IPv6addrz = IPv6address "%25" ZoneID 164 This syntax fills the gap that is described at the end of Section 165 11.7 of RFC 4007. 167 The rules in [RFC5952] SHOULD be applied in producing URIs. 169 RFC 3986 states that URIs have a global scope, but that in some cases 170 their interpretation depends on the end-user's context. URIs 171 including a ZoneID are to be interpreted only in the context of the 172 host where they originate, since the ZoneID is of local signifance 173 only. 175 The 6man WG discussed and rejected an alternative in which the 176 existing syntax of IPv6address would be extended by an option to add 177 the ZoneID only for the case of link-local addresses. It was felt 178 that the present solution offers more flexibility for future uses and 179 is more straightforward to implement. 181 RFC 4007 offers guidance on how the ZoneID affects interface/address 182 selection inside the IPv6 stack. Note that the behaviour of an IPv6 183 stack if passed a non-zero zone index for an address other than link- 184 local is undefined. 186 3. Web Browsers 188 Due to the lack of a standard in this area, web browsers have been 189 inconsistent in providing for ZoneIDs. Many have no support, but 190 there are examples of ad hoc support. For example, older versions of 191 Firefox allowed the use of a ZoneID preceded by an unescaped "%" 192 character, but this was removed for consistency with RFC 3986. As 193 another example, recent versions of Internet Explorer allow use of a 194 ZoneID preceded by a "%" character escaped as "%25", still beyond the 195 syntax allowed by RFC 3986. This syntax extension is in fact used 196 internally in the Windows operating system and some of its APIs. 198 This document implies that all browsers should recognise a ZoneID 199 preceded by an escaped "%". In the spirit of "be liberal with what 200 you accept", we also recommend that URI parsers accept bare "%" signs 201 (i.e., a "%" not followed by two valid hexadecimal characters). This 202 makes it easy for a user to copy and paste a string such as 203 "fe80::a%en1" from the output of a "ping" command and have it work. 205 4. Security Considerations 207 The security considerations of [RFC3986] and [RFC4007] apply. In 208 particular, this URI format creates a specific pathway by which a 209 deceitful zone index might be communicated, as mentioned in the final 210 security consideration of RFC 4007. It is emphasised that the format 211 is intended only for debugging purposes, but of course this intention 212 does not prevent misuse. 214 To limit this risk, implementations SHOULD NOT allow use of this 215 format except for well-defined usages such as sending to link local 216 addresses under prefix fe80::/10. 218 An HTTP server or proxy MUST ignore any ZoneID attached to an 219 incoming URI, as it only has local significance at the sending host. 221 5. IANA Considerations 223 This document requests no action by IANA. 225 6. Acknowledgements 227 The lack of this format was first pointed out by Margaret Wasserman 228 some years ago, and more recently by Kerry Lynn. A previous draft 229 document by Martin Duerst and Bill Fenner [I-D.fenner-literal-zone] 230 discussed this topic but was not finalised. 232 Valuable comments and contributions were made by Karl Auer, Carsten 233 Bormann, Brian Haberman, Ted Hardie, Tatuya Jinmei, Tom Petch, 234 Tomoyuki Sahara, Juergen Schoenwaelder, Dave Thaler, and Ole Troan. 236 Brian Carpenter was a visitor at the Computer Laboratory, Cambridge 237 University during part of this work. 239 This document was produced using the xml2rfc tool [RFC2629]. 241 7. Change log [RFC Editor: Please remove] 243 draft-ietf-6man-uri-zoneid-05: tuned ABNF, clarified RFC 4007 text, 244 2012-11-06. 246 draft-ietf-6man-uri-zoneid-04: additional author, 2012-09-21. 248 draft-ietf-6man-uri-zoneid-03: reverted to percent-encoded model 249 following WGLC, 2012-09-10. 251 draft-ietf-6man-uri-zoneid-02: additional WG comments, 2012-07-11. 253 draft-ietf-6man-uri-zoneid-01: use "-" instead of %25, listed 254 alternatives in Appendix, according to WG debate, added suggestion 255 for browser developers, 2012-05-29. 257 draft-ietf-6man-uri-zoneid-00: adopted by WG, fixed syntax to allow 258 for % encoded characters, 2012-02-17. 260 draft-carpenter-6man-uri-zoneid-01: chose Option 2, removed 15 261 character limit, added explanation of ID/number mapping and other 262 clarifications, 2012-02-08. 264 draft-carpenter-6man-uri-zoneid-00: original version, 2011-12-07. 266 8. References 268 8.1. Normative References 270 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 271 Requirement Levels", BCP 14, RFC 2119, March 1997. 273 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 274 Resource Identifier (URI): Generic Syntax", STD 66, 275 RFC 3986, January 2005. 277 [RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and 278 B. Zill, "IPv6 Scoped Address Architecture", RFC 4007, 279 March 2005. 281 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 282 Specifications: ABNF", STD 68, RFC 5234, January 2008. 284 [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 285 Address Text Representation", RFC 5952, August 2010. 287 8.2. Informative References 289 [I-D.fenner-literal-zone] 290 Fenner, B. and M. Duerst, "Formats for IPv6 Scope Zone 291 Identifiers in Literal Address Formats", 292 draft-fenner-literal-zone-02 (work in progress), 293 October 2005. 295 [I-D.iab-identifier-comparison] 296 Thaler, D., "Issues in Identifier Comparison for Security 297 Purposes", draft-iab-identifier-comparison-03 (work in 298 progress), July 2012. 300 [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, 301 June 1999. 303 [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. 304 Stevens, "Basic Socket Interface Extensions for IPv6", 305 RFC 3493, February 2003. 307 [RFC4001] Daniele, M., Haberman, B., Routhier, S., and J. 308 Schoenwaelder, "Textual Conventions for Internet Network 309 Addresses", RFC 4001, February 2005. 311 [chrome] Google, "Use the address bar (omnibox)", 2012, . 314 Appendix A. Alternatives Considered 316 1. Leave the problem unsolved. 318 This would mean that per-interface diagnostics would still have 319 to be performed using ping or ping6: 321 ping fe80::a%en1 323 Advantage: works today. 325 Disadvantage: less convenient than using a browser. 327 2. Simply using the percent character. 329 http://[fe80::a%en1] 331 Advantage: allows use of browser, allows cut and paste. 333 Disadvantage: invalid syntax under RFC 3986; not acceptable to 334 URI community. 336 3. Escaping the escape character as allowed by RFC 3986: 338 http://[fe80::a%25en1] 340 Advantage: allows use of browser, consistent with general URI 341 syntax. 343 Disadvantage: somewhat ugly and confusing, doesn't allow simple 344 cut and paste. 346 4. Alternative separator 348 http://[fe80::a-en1] 350 Advantage: allows use of browser, simple syntax 352 Disadvantage: Requires all IPv6 address literal parsers and 353 generators to be updated in order to allow simple cut and paste; 354 inconsistent with existing tools and practice. 356 Note: the initial proposal for this choice was to use an 357 underscore as the separator, but it was noted that this becomes 358 effectively invisible when a user interface automatically 359 underlines URLs. 361 5. With the "IPvFuture" syntax left open in RFC 3986: 363 http://[v6.fe80::a_en1] 365 Advantage: allows use of browser. 367 Disadvantage: ugly and redundant, doesn't allow simple cut and 368 paste. 370 Authors' Addresses 372 Brian Carpenter 373 Department of Computer Science 374 University of Auckland 375 PB 92019 376 Auckland, 1142 377 New Zealand 379 Email: brian.e.carpenter@gmail.com 381 Stuart Cheshire 382 Apple Inc. 383 1 Infinite Loop 384 Cupertino, CA 95014 385 US 387 Email: cheshire@apple.com 388 Robert M. Hinden 389 Check Point Software Technologies, Inc. 390 800 Bridge Parkway 391 Redwood City, CA 94065 392 US 394 Email: bob.hinden@gmail.com