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Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 dnsop W. Kumari 3 Internet-Draft Google 4 Intended status: Informational A. Sullivan 5 Expires: March 16, 2016 Dyn 6 September 13, 2015 8 The ALT Special Use Top Level Domain 9 draft-ietf-dnsop-alt-tld-02 11 Abstract 13 This document reserves a string (ALT) to be used as a TLD label in 14 non-DNS contexts or for names that have no meaning in a global 15 context. It also provides advice and guidance to developers 16 developing alternate namespaces. 18 [ Ed note: This document lives in GitHub at: 19 https://github.com/wkumari/draft-wkumari-dnsop-alt-tld . Issues and 20 pull requests happily accepted. ] 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on March 16, 2016. 39 Copyright Notice 41 Copyright (c) 2015 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 1.1. Requirements notation . . . . . . . . . . . . . . . . . . 2 58 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 59 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 3. The ALT namespace . . . . . . . . . . . . . . . . . . . . . . 4 61 3.1. Choice of the ALT Name . . . . . . . . . . . . . . . . . 5 62 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 63 4.1. Domain Name Reservation Considerations . . . . . . . . . 6 64 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 65 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 66 7. Normative References . . . . . . . . . . . . . . . . . . . . 8 67 Appendix A. Changes / Author Notes. . . . . . . . . . . . . . . 8 68 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 70 1. Introduction 72 Many protocols and systems need to name entities. Names that look 73 like DNS names (a series of labels separated with dots) have become 74 common, even in systems that are not part of the global DNS 75 administered by IANA. 77 This document provides a solution that may be more appropriate than 78 [RFC6761] in many cases. 80 This document reserves the label "ALT" (short for "Alternate") as a 81 Special Use Domain ([RFC6761]). This label is intended to be used as 82 the final label to signify that the name is not rooted in the DNS, 83 and that normal registration and lookup rules do not apply. 85 1.1. Requirements notation 87 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 88 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 89 document are to be interpreted as described in [RFC2119]. 91 1.2. Terminology 93 This document assumes familiarity with DNS terms and concepts. 94 Please see [RFC1034] for background and concepts. 96 o DNS context: The namespace anchored at the globally-unique DNS 97 root. This is the namespace or context that "normal" DNS uses. 99 o non-DNS context: Any other (alternate) namespace. 101 o pseudo-TLD: A label that appears in a fully-qualified domain name 102 in the position of a TLD, but which is not registered in the 103 global DNS. 105 o TLD: The last visible label in either a fully-qualified domain 106 name or a name that is qualified relative to the root. See the 107 discussion in Section 2. 109 2. Background 111 The DNS data model is based on a tree structure, and has a single 112 root. Conventionally, a name immediately beneath the root is called 113 a "Top Level Domain" or "TLD". TLDs usually delegate portions of 114 their namespace to others, who may then delegate further. The 115 hierarchical, distributed and caching nature of the DNS has made it 116 the primary resolution system on the Internet. 118 Domain names are terminated by a zero-length label, so the root label 119 is normally invisible. Truly fully-qualified names indicate the root 120 label explicitly, thus: "an.example.tld.". Most of the time, names 121 are written implicitly relative to the root, thus: "an.example.tld". 122 In both of these cases, the TLD is the last label that is visible in 123 presentation format -- in this example, the string "tld". (This 124 little bit of pedantry is here because, in different contexts, people 125 can use the term "fully-qualified domain name" to refer to either of 126 these uses.) It is worth noting that the root label is present in 127 the on-wire format of fully-qualified domain names, even if not 128 displayed in the presentation form. 130 The success of the DNS makes it a natural starting point for systems 131 that need to name entities in a non-DNS context, or that have no 132 unique meaning in a global context. These name resolutions, 133 therefore, occur in a namespace distinct from the DNS. 135 In many cases, these systems build a DNS-style tree parallel to, but 136 separate from, the global DNS. They often use a pseudo-TLD to cause 137 resolution in the alternate namespace, using browser plugins, shims 138 in the name resolution process, or simply applications that perform 139 special handling of this particular alternate namespace. 141 In many cases, the creators of these alternate namespaces have chosen 142 a convenient or descriptive string and started using it. These new 143 strings are "alternate" strings and are not registered anywhere or 144 part of the DNS. However they appear to users and to some 145 applications to be TLDs. Issues may arise if they are looked up in 146 the DNS. These include: 148 o User confusion: If someone emails a link of the form 149 foo.bar.pseudo-TLD to someone who does not have the necessary 150 software to resolve names in the pseudo-TLD namespace, the name 151 will not resolve and the user may become confused. 153 o Excess traffic hitting the DNS root: Lookups leak out of the 154 pseudo-TLD namespace and end up hitting the DNS root nameservers. 156 o Collisions: If the pseudo-TLD is eventually delegated from the 157 root zone, the lookup behavior will change in a non-deterministic 158 fashion. 160 o Lack of success for the user's original goal. 162 An alternate name resolution system might be specifically designed to 163 provide confidentiality of the looked up name, and to provide a 164 distributed and censorship-resistant namespace. This goal would 165 necessarily be defeated if the queries leak into the DNS, because the 166 attempt to look up the name would be visible at least to the 167 operators of root name servers and to any entity viewing the DNS 168 lookups going to the root nameservers. 170 3. The ALT namespace 172 In order to avoid the above issues, we reserve the ALT label. Unless 173 the name desired is globally unique, has meaning on the global 174 context and is delegated in the DNS, it should be considered an 175 alternate namespace, and follow the ALT label scheme outlined below. 176 The ALT label MAY be used in any domain name as a pseudo-TLD to 177 signify that this is an alternate (non-DNS) namespace. 179 Alternate namespaces should differentiate themselves from other 180 alternate namespaces by choosing a name and using it in the label 181 position just before the pseudo-TLD (ALT). For example, a group 182 wishing to create a namespace for Friends Of Olaf might choose the 183 string "foo" and use any set of labels under foo.alt. 185 As they are in an alternate namespace, they have no significance in 186 the regular DNS context and so should not be looked up in the DNS 187 context. Some of these requests will inevitably leak into the DNS 188 context (for example, because clicks on a link in a browser that does 189 not have a extension installed that implements the alternate 190 namespace resolution), and so the ALT TLD has been added to the 191 "Locally Served DNS Zones" ( [RFC6303]) registry to limit how far 192 these flow. 194 Groups wishing to create new alternate namespaces SHOULD create their 195 alternate namespace under a label that names their namespace, and 196 under the ALT label. They SHOULD choose a label that they expect to 197 be unique and, ideally, descriptive. There is no IANA controlled 198 registry for names under the ALT TLD - it is an unmanaged namespace, 199 and developers are responsible for dealing with any collisions that 200 may occur under .alt. Informal lists of namespaces under .alt may 201 appear to assist the developer community. 203 [Editor note (to be removed before publication): There was 204 significant discussion on an IANA registry for the ALT namespace - 205 please consult the lists for full thread, but the consensus seems to 206 be that it would be better for the IETF / IANA to not administer a 207 registry for this. It is expected one or more unofficial lists will 208 be created where people can list the strings that they are using. ] 210 Currently deployed projects and protocols that are using pseudo-TLDs 211 may decide to move under the ALT TLD, but this is not a requirement. 212 Rather, the ALT TLD is being reserved so that current and future 213 projects of a similar nature have a designated place to create 214 alternate resolution namespaces that will not conflict with the 215 regular DNS context. 217 3.1. Choice of the ALT Name 219 A number of names other than "ALT" were considered and discarded. In 220 order for this technique to be effective the names need to continue 221 to follow both the DNS format and conventions (a prime consideration 222 for alternate name formats is that they can be entered in places that 223 normally take DNS context names); this rules out using suffixes that 224 do not follow the usual letter, digit, and hyphen label convention. 226 Another proposal was that the ALT TLD instead be a reservation under 227 .arpa. This was considered, but rejected for several reasons, 228 including: 230 1. We wished this to make it clear that this is not in the DNS 231 context, and .arpa clearly is. 233 2. The use of the string .alt is intended to evoke the alt.* 234 hierarchy in Usenet. 236 3. We wanted the string to be short and easily used. 238 4. A name underneath .arpa would consume at least five additional 239 octets of the total 255 octets available in domain names, which 240 could put pressure on applications that need long machine- 241 generated names. 243 5. We are suggesting that the string "ALT" get special treatment in 244 resolvers, and shim software. We are concerned that using 245 subdomains of an existing TLD (like .arpa) might end up with bad 246 implementations misconfiguring / overriding the TLD itself and 247 breaking .arpa. 249 There is a concern that if there were placed under .arpa, 250 inexperienced nameserver operators may inadvertently cover .arpa. A 251 more significant concern is that the scope of the issue if the query 252 does leak, and the fact that this would then make the root of the 253 alternate naming namespace a third level domain, and not a second 254 one. A project may be willing to have a name of the form 255 example.alt, but example.alt.arpa may be not look as good. 257 4. IANA Considerations 259 The IANA is requested to add the ALT string to the "Special-Use 260 Domain Name" registry ([RFC6761], and reference this document. In 261 addition, the "Locally Served DNS Zones" ([RFC6303]) registry should 262 be updated to reference this document. 264 4.1. Domain Name Reservation Considerations 266 This section is to satisfy the requirement in Section 5 of RFC6761. 268 The domain "alt.", and any names falling within ".alt.", are special 269 in the following ways: 271 1. Human users are expected to know that strings that end in .alt 272 behave differently to normal DNS names. Users are expected to 273 have applications running on their machines that intercept 274 strings of the form .alt and perform special handing 275 of them. If the user tries to resolve a name of the form 276 .alt without the plugin installed, the 277 request will leak into the DNS, and receive a negative response. 279 2. Writers of application software that implement a non-DNS 280 namespace are expected to intercept names of the form 281 .alt and perform application specific handing with 282 them. Other applications are not intended to perform any special 283 handing. 285 3. In general, writers of name resolution APIs and libraries do not 286 need to perform special handing of these names. If developers of 287 other namespaces implement their namespace through a "shim" or 288 library, they will need to intercept and perform their own 289 handling. 291 4. Caching DNS servers SHOULD recognize these names as special and 292 SHOULD NOT, by default, attempt to look up NS records for them, 293 or otherwise query authoritative DNS servers in an attempt to 294 resolve these names. Instead, caching DNS servers SHOULD 295 generate immediate negative responses for all such queries. 297 5. Authoritative DNS servers SHOULD recognize these names as special 298 and SHOULD, by default, generate immediate negative responses for 299 all such queries, unless explicitly configured by the 300 administrator to give positive answers for private-address 301 reverse-mapping names. 303 6. DNS server operators SHOULD be aware that queries for names 304 ending in .alt are not DNS names, and were leaked into the DNS 305 context (for example, by a missing browser plugin). This 306 information may be useful for support or debuggung purposes. 308 7. DNS Registries/Registrars MUST NOT grant requests to register 309 "alt" names in the normal way to any person or entity. These 310 "alt" names are defined by protocol specification to be 311 nonexistent, and they fall outside the set of names available for 312 allocation by registries/registrars. 314 5. Security Considerations 316 One of the motivations for the creation of the alt pseudo-TLD is that 317 unmanaged labels in the managed root name space are subject to 318 unexpected takeover if the manager of the root name space decides to 319 delegate the unmanaged label. 321 The unmanaged and "registration not required" nature of labels 322 beneath .alt provides the opportunity for an attacker to re-use the 323 chosen label and thereby possibly compromise applications dependent 324 on the special host name. 326 6. Acknowledgements 328 The authors understand that there is much politics surrounding the 329 delegation of a new TLD and thank the ICANN liaison in advance. 331 We would also like to thank Joe Abley, Mark Andrews, Marc Blanchet, 332 John Bond, Stephane Bortzmeyer, David Cake, David Conrad, Patrik 333 Faltstrom, Olafur Gudmundsson, Paul Hoffman, Joel Jaeggli, Ted Lemon, 334 Edward Lewis, George Michaelson, Ed Pascoe, Arturo Servin, and Paul 335 Vixie for feedback. 337 7. Normative References 339 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 340 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 341 . 343 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 344 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 345 RFC2119, March 1997, 346 . 348 [RFC6303] Andrews, M., "Locally Served DNS Zones", BCP 163, RFC 349 6303, DOI 10.17487/RFC6303, July 2011, 350 . 352 [RFC6761] Cheshire, S. and M. Krochmal, "Special-Use Domain Names", 353 RFC 6761, DOI 10.17487/RFC6761, February 2013, 354 . 356 Appendix A. Changes / Author Notes. 358 [RFC Editor: Please remove this section before publication ] 360 From -01 to -02: 362 o Merged a bunch of changes from Paul Hoffman. Thanks for sending a 363 git pull. 365 From -00 to 01: 367 o Removed the "delegated to new style AS112 servers" text -this was 368 legacy from the omnicient AS112 days. (Joe Abley) 370 o Removed the "Advice to implemntors" section. This used to 371 recommend that people used a subdomain of a domain in the DNS. It 372 was pointed out that this breaks things badly if the domain 373 expires. 375 o Added text about why we don't want to adminster a registry for 376 ALT. 378 From Individual-06 to DNSOP-00 379 o Nothing changed, simply renamed draft-wkumari-dnsop-alt-tld to 380 draft-ietf-dnsop-alt-tld 382 From -05 to -06 384 o Incorporated comments from a number of people, including a number 385 of suggestion heard at the IETF meeting in Dallas, and the DNSOP 386 Interim meeting in May, 2015. 388 o Removed the "Let's have an (optional) IANA registry for people to 389 (opportinistically) register their string, if they want that 390 option" stuff. It was, um, optional.... 392 From -04 to -05 394 o Went through and made sure that I'd captured the feedback 395 received. 397 o Comments from Ed Lewis. 399 o Filled in the "Domain Name Reservation Considerations" section of 400 RFC6761. 402 o Removed examples from .Onion. 404 From -03 to -04 406 o Incorporated some comments from Paul Hoffman 408 From -02 to -03 410 o After discussions with chairs, made this much more generic (not 411 purely non-DNS), and some cleanup. 413 From -01 to -02 415 o Removed some fluffy wording, tightened up the language some. 417 From -00 to -01. 419 o Fixed the abstract. 421 o Recommended that folk root their non-DNS namespace under a DNS 422 namespace that they control (Joe Abley) 424 Authors' Addresses 426 Warren Kumari 427 Google 428 1600 Amphitheatre Parkway 429 Mountain View, CA 94043 430 US 432 Email: warren@kumari.net 434 Andrew Sullivan 435 Dyn 436 150 Dow Street 437 Manchester, NH 03101 438 US 440 Email: asullivan@dyn.com