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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Faltstrom 3 Internet-Draft Cisco 4 Intended status: Standards Track O. Kolkman 5 Expires: January 14, 2009 NLNet 6 July 13, 2008 8 The Uniform Resource Identifier (URI) DNS Resource Record 9 draft-faltstrom-uri-01.txt 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on January 14, 2009. 36 Abstract 38 This document defines a new DNS resource record, called the Uniform 39 Resource Identifier (URI) RR, for publishing mappings from hostnames 40 to URIs. 42 Table of Contents 44 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 45 2. Applicability Statement . . . . . . . . . . . . . . . . . . . 3 46 3. DNS considerations . . . . . . . . . . . . . . . . . . . . . . 4 47 4. The format of the URI RR . . . . . . . . . . . . . . . . . . . 4 48 4.1. Ownername, class and type . . . . . . . . . . . . . . . . 4 49 4.2. Priority . . . . . . . . . . . . . . . . . . . . . . . . . 5 50 4.3. Weight . . . . . . . . . . . . . . . . . . . . . . . . . . 5 51 4.4. Target . . . . . . . . . . . . . . . . . . . . . . . . . . 5 52 4.5. URI RDATA Wire Format . . . . . . . . . . . . . . . . . . 5 53 4.6. The URI RR Presentation Format . . . . . . . . . . . . . . 6 54 5. Definition of the flag 'D' for NAPTR records . . . . . . . . . 6 55 6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 56 6.1. Homepage at one domain, but two domains in use . . . . . . 7 57 7. Relation to U-NAPTR . . . . . . . . . . . . . . . . . . . . . 7 58 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 59 8.1. Registration of the URI Resource Record Type . . . . . . . 8 60 9. Security Considerations . . . . . . . . . . . . . . . . . . . 8 61 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 62 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 63 11.1. Normative References . . . . . . . . . . . . . . . . . . . 8 64 11.2. Non-normative references . . . . . . . . . . . . . . . . . 9 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 66 Intellectual Property and Copyright Statements . . . . . . . . . . 10 68 1. Introduction 70 This document explains the use of the Domain Name System (DNS) for 71 storage of URIs, and how to resolve hostnames to such URIs that can 72 be used by various applications. For resolution the application need 73 to know both the hostname and the protocol that the URI is to be used 74 for. The protocol is registered by IANA. 76 Currently, looking up URIs given a hostname uses the DDDS [RFC3401] 77 application framework with the DNS as a database as specified in RFC 78 3404 [RFC3404]. This have a number of implications as described in 79 draft-iab-dns-choices [I-D.iab-dns-choices] such as the inability to 80 select what NAPTR records that match the query is interesting. The 81 RRSet returned will always consist of all URIs "connected" with the 82 domain in question. 84 The URI resource record specified in this document create an ability 85 for the querying party to select which ones of the NAPTR records one 86 is interested in. This because data in the service field of the 87 NAPTR record is included in the owner part of the URI resource record 88 type. 90 Querying for the URI resource record type is not replacing querying 91 for the NAPTR (or S-NAPTR [RFC3958]) resource record type. Instead 92 it is a complementary mechanism to use when one know already what 93 service field is interesting. One can with the URI resource record 94 type directly query for the specific subset of the otherwise possibly 95 large RRSet given back when querying for NAPTR resource records. 97 This document updates RFC 3958 and RFC 3404 by adding the flag "D" to 98 the list of defined terminal flags in section 2.2.3 of RFC 3958 and 99 4.3 of RFC 3404. 101 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 102 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 103 document are to be interpreted as described in BCP 14, RFC 2119 104 [RFC2119]. 106 2. Applicability Statement 108 In general, it is expected that URI records will be used by clients 109 for applications where the relevant protocol to be used is known, but 110 for example extra abstraction given by separating a hostname from a 111 point of service (as address by the URI) is needed. Example of such 112 a situation is when an organisation have many domain names, but only 113 one official web page. 115 Applications MUST know the specific service fields to prepend the 116 hostname with. Using repetitive queries for URI records MUST NOT be 117 a replacement for querying for NAPTR or S-NAPTR records. NAPTR and 118 S-NAPTR records are for discovery of the various services and URI for 119 looking up access point for a given service. Those are two very 120 different kinds of needs. 122 3. DNS considerations 124 Using prefix labels, such as underscored service tags, prevents the 125 use of wildcards [I-D.iab-dns-choices], as constructs as 126 _s2._s1.*.example.net. are not possible in the DNS, see RFC 4592 127 [RFC4592]. Besides, underscored service tags used for the URI RR 128 (based on the NAPTR service descriptions) may have slightly different 129 semantics than service tags used for underscored prefix labels that 130 are used in combination with other (yet unspecified) RR types. This 131 may cause subtle management problems when delegation structure that 132 has developed within the context of URI RRs is also to be used for 133 other RR types. Since the service labels might be overloaded 134 applications should carefully check that the application level 135 protocol is indeed the protocol they expect. 137 Subtle management issues may also arise when the delegations from 138 service to sub service label involves several parties and different 139 stake holders. 141 4. The format of the URI RR 143 This is the format of the URI RR, whose DNS type code is TBD1 (to be 144 assigned by IANA). 146 Ownername TTL Class URI Priority Weight Target 148 4.1. Ownername, class and type 150 The URI ownername is subject to special conventions. 152 Just like the SRV RR [ref] the URI RR has service information encoded 153 in its ownername. In order to encode the service for a specific 154 owner name one use service parameters. Valid service parameters used 155 are those as registered by IANA for Enumservice Registrations. The 156 service parameters are reversed (subtype(s) before type), prepended 157 with an underscore (_) and prepended to the owner name in separate 158 labels. The underscore is prepended to the service parameters to 159 avoid collisions with DNS labels that occur in nature, and the order 160 is reversed to make it possible to do delegations, if needed, to 161 different zones (and therefore providers of DNS). 163 For example, suppose we are looking for the URI for a service with 164 Service Parameter "A:B:C" for host example.com.. Then we would query 165 for (QNAME,QTYPE)=("_C._B._A.example.com","URI") 167 The type number for the URI record is TBD1 (to be assigned by IANA). 169 The URI resource record is class independent. 171 The URI RR has no special TTL requirements. 173 4.2. Priority 175 The priority of this target URI. A client MUST attempt to contact 176 the URI with the lowest-numbered priority it can reach; URIs with the 177 same priority SHOULD be tried in an order defined by the weight 178 field. The range is 0-65535. This is a 16 bit unsigned integer in 179 network byte order. 181 4.3. Weight 183 A server selection mechanism. The weight field specifies a relative 184 weight for entries with the same priority. Larger weights SHOULD be 185 given a proportionately higher probability of being selected. The 186 range of this number is 0-65535. This is a 16 bit unsigned integer 187 in network byte order. 189 4.4. Target 191 The URI of the target. Resolution of the URI is according to the 192 definitions for the URI Scheme the URI consists of. 194 The URI is encoded as one or more RFC1035 section 195 3.3 [RFC1035]. 197 4.5. URI RDATA Wire Format 199 The RDATA for a URI RR consists of a 2 octet Priority field, a two 200 octet Weight field, and a variable length target field. 202 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 203 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 205 | Priority | Weight | 206 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 207 / / 208 / Target / 209 / / 210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 4.6. The URI RR Presentation Format 214 The presentation format of the RDATA portion is as follows: 216 Priority field MUST be represented as an unsigned decimal integer. 218 The Weight Type field MUST be represented as an unsigned decimal 219 integer. 221 The target URI is enclosed in double-quotes ("). If the total length 222 of the URI exceeds 255 characters the URI will be encoded in multiple 223 . 225 5. Definition of the flag 'D' for NAPTR records 227 This document specifies the flag "D" for use as a flag in NAPTR 228 records. The flag indicate a terminal NAPTR record because it 229 denotes the end of the DDDS/NAPTR processing rules. In the case of a 230 "D" flag, the Replacement field in the NAPTR record, prepended with 231 the service flags, is used as the Owner of a DNS query for URI 232 records, and normal URI processing as defined in this document is 233 applied. 235 The replacement field MUST NOT include any of the service parameters. 236 Those are to be prepended (together with underscore) as described in 237 other places in this document. 239 The Regexp field in the NAPTR record MUST be empty when the 'D' flag 240 is in use. 242 6. Examples 243 6.1. Homepage at one domain, but two domains in use 245 An organisation have the domain names example.com and example.net, 246 but the official URI http://www.example.com/. Given the service type 247 "web" and subtype "http" (from the IANA registry), the following URI 248 Resource Records could be made available in the respective zones 249 (example.com and example.net): 251 $ORIGIN example.com. 252 _http._web IN URI 10 1 "http://www.example.com/" 254 $ORIGIN example.net. 255 _http._web IN URI 10 1 "http://www.example.com/" 257 7. Relation to U-NAPTR 259 The URI Resource Record Type is not a replacement for the U-NAPTR. 260 It is instead an extension and more powerful second step in the 261 resolution than the SRV record. As such, it could be referred to as 262 the target in a terminal rule in any of the NAPTR specifications. 264 If one know exactly what service type one is looking for one can do a 265 direct lookup of the URI record without first looking up the NAPTR. 266 In the example below, if one where looking for EM:protA service in 267 the example.com domain, one could look for the URI Resource Record 268 Type with the owner _protA._EM.example.com directly. 270 Example from U-NAPTR (URI resolution is not included): 272 $ORIGIN example.com. 273 IN NAPTR 200 10 "u" "EM:protA" ( ; service 274 "!.*!prota://someisp.example.com!" ; regexp 275 "" ) ; replacement 277 With URI records, and the use of the new flag 'D': 279 $ORIGIN example.com. 280 IN NAPTR 200 10 "D" "EM:protA" ( ; service 281 "" ; regexp 282 "example.com." ) ; replacement 283 _protA._EM IN URI "prota://somehost.example.com/" 285 8. IANA Considerations 287 8.1. Registration of the URI Resource Record Type 289 IANA has assigned Resource Record Type TBD1 to the URI Resource 290 Record Type to be added to the registry named Resource Record (RR) 291 TYPEs and QTYPEs as defined in RFC 2929 [RFC2929] and RFC 1035 292 [RFC1035]. 294 TYPE Value and meaning Reference 295 ----------- --------------------------------------------- --------- 296 URI TBD1 a URI as RDATA [RFCXXXX] 298 9. Security Considerations 300 10. Acknowledgements 302 Ideas on how to split the two different kind of queries "What 303 services exists for this domain name" and "What is the URI for this 304 service" came from Scott Bradner and Lawrence Conroy. Other people 305 that have contributed to this document include Leslie Daigle, Olafur 306 Gudmundsson, Maria Hall, Peter Koch, Ted Hardie and Penn Pfautz. 308 11. References 310 11.1. Normative References 312 [E164] ITU-T, "The International Public Telecommunication Number 313 Plan", Recommendation E.164, May 1997. 315 [RFC1035] Mockapetris, P., "Domain names - implementation and 316 specification", STD 13, RFC 1035, November 1987. 318 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 319 Requirement Levels", BCP 14, RFC 2119, March 1997. 321 [RFC2929] Eastlake, D., Brunner-Williams, E., and B. Manning, 322 "Domain Name System (DNS) IANA Considerations", BCP 42, 323 RFC 2929, September 2000. 325 [RFC3404] Mealling, M., "Dynamic Delegation Discovery System (DDDS) 326 Part Four: The Uniform Resource Identifiers (URI)", 327 RFC 3404, October 2002. 329 [RFC3958] Daigle, L. and A. Newton, "Domain-Based Application 330 Service Location Using SRV RRs and the Dynamic Delegation 331 Discovery Service (DDDS)", RFC 3958, January 2005. 333 11.2. Non-normative references 335 [I-D.iab-dns-choices] 336 Faltstrom, P., Austein, R., and P. Koch, "Design Choices 337 When Expanding DNS", draft-iab-dns-choices-05 (work in 338 progress), February 2008. 340 [RFC3401] Mealling, M., "Dynamic Delegation Discovery System (DDDS) 341 Part One: The Comprehensive DDDS", RFC 3401, October 2002. 343 [RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name 344 System", RFC 4592, July 2006. 346 [RFC4848] Daigle, L., "Domain-Based Application Service Location 347 Using URIs and the Dynamic Delegation Discovery Service 348 (DDDS)", RFC 4848, April 2007. 350 Authors' Addresses 352 Patrik Faltstrom 353 Cisco Systems 355 Email: paf@cisco.com 357 Olaf Kolkman 358 NLnet Labs 360 Email: olaf@NLnetLabs.nl 362 Full Copyright Statement 364 Copyright (C) The IETF Trust (2008). 366 This document is subject to the rights, licenses and restrictions 367 contained in BCP 78, and except as set forth therein, the authors 368 retain all their rights. 370 This document and the information contained herein are provided on an 371 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 372 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 373 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 374 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 375 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 376 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 378 Intellectual Property 380 The IETF takes no position regarding the validity or scope of any 381 Intellectual Property Rights or other rights that might be claimed to 382 pertain to the implementation or use of the technology described in 383 this document or the extent to which any license under such rights 384 might or might not be available; nor does it represent that it has 385 made any independent effort to identify any such rights. 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