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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 dnsop D. Crocker 3 Internet-Draft Brandenburg InternetWorking 4 Intended status: Best Current Practice March 19, 2018 5 Expires: September 20, 2018 7 DNS Scoped Data Through '_Underscore' Naming of Attribute Leaves 8 draft-ietf-dnsop-attrleaf-03 10 Abstract 12 Formally, any DNS resource record may occur for any domain name. 13 However some services have defined an operational convention that 14 applies to DNS leaf nodes that are under a DNS branch that has one or 15 more reserved node names that begin with an underscore. The 16 underscore naming construct defines a semantic scope for DNS records 17 that are associated with the parent domain, above the underscored 18 branch. This specification explores the nature of this DNS usage and 19 defines the "DNS Global Underscore Scoped Entry Registry" with IANA. 20 The purpose of the Underscore registry is to avoid collisions 21 resulting from the use of the same underscore-based name, for 22 different services. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on September 20, 2018. 41 Copyright Notice 43 Copyright (c) 2018 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 59 1.1. _Underscore Scoping . . . . . . . . . . . . . . . . . . . 3 60 1.2. Scaling Benefits for TXT, SRV, and URI Resource Records . 4 61 2. DNS Underscore Scoped Entry Registries Function . . . . . . . 4 62 2.1. DNS Underscore Global Scoped Entry Registry Definition . 5 63 2.2. DNS Common Second-Level Underscore Scoped Entry Registry 64 Definition . . . . . . . . . . . . . . . . . . . . . . . 6 65 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 66 3.1. DNS Underscore Global Scoped Entry Registry . . . . . . . 7 67 3.2. DNS Common Second-Level Underscore Scoped Entry 68 Registry . . . . . . . . . . . . . . . . . . . . . . . . 8 69 4. Security Considerations . . . . . . . . . . . . . . . . . . . 11 70 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 71 5.1. Normative References . . . . . . . . . . . . . . . . . . 11 72 5.2. References -- Informative . . . . . . . . . . . . . . . . 11 73 5.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 14 74 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 14 75 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14 77 1. Introduction 79 The core Domain Name System (DNS) technical specifications assign no 80 semantics to domain names or their parts, and no constraints upon 81 which resource records (RRs) are permitted to be associated with 82 particular names.[RFC1035] Over time, some leaf node names, such as 83 "www" and "ftp" have come to imply support for particular services, 84 but this is a matter of operational convention, rather than defined 85 protocol semantics. This freedom in the basic technology has 86 permitted a wide range of administrative and semantic policies to be 87 used -- in parallel. DNS data semantics have been limited to the 88 specification of particular resource records, on the expectation that 89 new ones would be added as needed. Unfortunately, the addition of 90 new resource records has proved extremely challenging, over the life 91 of the DNS, with significant adoption and use barriers. 93 1.1. _Underscore Scoping 95 As an alternative to defining new RRs, some DNS service enhancements 96 call for using an existing resource record, but specify a restricted 97 scope for its occurrence. That scope is a leaf node, within which 98 the uses of specific resource records can be formally defined and 99 constrained. The leaf occurs in a branch having a distinguished 100 naming convention: At the top of the branch -- beneath the parent 101 domain name to which the scope applies -- one or more reserved DNS 102 node names begin with an underscore ("_"). Because the DNS rules for 103 a "host" (host name) are not allowed to use the underscore character, 104 this distinguishes the underscore name from all legal host names 105 [RFC1035]. Effectively, this convention for leaf node naming creates 106 a space for the listing of 'attributes' -- in the form of resource 107 records -- that are associated with the parent domain, above the 108 underscore sub-branch. 110 The scoping feature is particularly useful when generalized resource 111 records are used -- notably "TXT", "SRV", and "URI" 112 [RFC1035],[RFC2782],[RFC7553]. It provides efficient separation of 113 one use of them from others. Absent this separation, an 114 undifferentiated mass of these "RR"s is returned to the DNS client, 115 which then must parse through the internals of the records in the 116 hope of finding ones that are relevant. Worse, in some cases the 117 results are ambiguous because the records do not adequately self- 118 identify. With underscore-based scoping, only the relevant "RR"s are 119 returned. 121 A simple example is DKIM [RFC6376] , which uses "_domainkeys" for 122 defining a place to hold a "TXT" record containing signing 123 information for the parent domain. 125 This specification formally defines how underscore labels are used as 126 "attribute" enhancements for their parent domain names. For example, 127 domain name "_domainkey.example." acts as attribute of parent domain 128 name "example." To avoid collisions resulting from the use of the 129 same underscore-based labels for different applications, this 130 document establishes DNS Underscore Global Scoped Entry IANA Registry 131 for the highest-level reserved names that begin with _underscore; 132 _underscore-based names that are farther down the hierarchy are 133 handled within the scope of the highest-level _underscore name. 135 Discussion Venue: Discussion about this draft should be directed 136 to the dnsop@ietf.org [1] mailing list. 138 NOTE TO RFC EDITOR: Please remove "Discussion Venue" paragraph 139 prior to publication. 141 1.2. Scaling Benefits for TXT, SRV, and URI Resource Records 143 Some resource records are generic and support a variety of uses. 144 Each additional use defines its own rules and, possibly, its own 145 internal syntax and node-naming conventions to distinguish among 146 particular types. The "TXT", "SRV", and "URI" records are notable 147 examples. Their use can scale poorly, particularly when the same 148 "RR" can be present in the same leaf node, but with different uses. 150 An increasingly-popular approach, with excellent scaling properties, 151 place the RR undr a node wit an underscore-based name, at a defined 152 place in the DNS tree, so as to constrain to the use of particular 153 "RR"s farther down the branch using that name. This means that a 154 direct lookup produces only the desired records, at no greater cost 155 than a typical DNS lookup. 157 The definition of a underscore global registry, provided in this 158 specification, primarily attends to the "upper-level" names used for 159 RRs; that is the _underscore "global" names. For efficiency, a 160 single, subordinate _underscore second-level table also is defined, 161 for use with a common set of applications. 163 2. DNS Underscore Scoped Entry Registries Function 165 A global registry for DNS nodes names that begin with an _underscore 166 is defined here. The names are used to define scope of use for 167 specific resource records, associated with the domain name that is 168 the "parent" to the branch defined by the _underscore naming. 170 A given name defines a specific, constrained context for one or 171 more RR records, in which use of such records MUST conform to the 172 defined constraints. Within this scope, other resource records 173 that are not specified MAY be used. 175 The purpose of the Underscore Global Registry is to avoid collisions 176 resulting from the use of the same _underscore-based name, for 177 different applications. 179 Structurally, the registry is defined as a single, flat table of 180 names that begin with _underscore. In some cases, such as for use of 181 an "SRV" record, the full scoping name might be multi-part, as a 182 sequence of underscore names. Semantically, that sequence represents 183 a hierarchical model and it is theoretically reasonable to allow re- 184 use of a subordinate underscore name in different underscore context; 185 that is, a subordinate name is meaningful only within the scope of 186 the first (top-level) underscore name. Therefore they are ignored by 187 this DNS Underscore Global Scoped Entry Registry. This registry is 188 for the definition of highest-level -- ie, global -- underscore node 189 name used. 191 +----------------------------+ 192 | NAME | 193 +----------------------------+ 194 | _service1 | 195 | ._protoB._service2 | 196 | _protoB._service3 | 197 | _protoC._service3 | 198 | _useX._protoD._service4 | 199 | _protoE._region._authority | 200 +----------------------------+ 202 Example of Underscore Names 204 Only the right-most names are registered in the IANA Underscore 205 Global table. Definition and registration of the subordinate names 206 is the responsibility of the specification that creates the highest- 207 level (right-most) registry entry. 209 For convenience, an Underscore Common Second-Level Names table is 210 also defined, to cover some popular cases involving the subordinate 211 name used with two-level _underscore naming. In particular, this 212 table covers uses of second-level names that scope SRV RRs use. 214 2.1. DNS Underscore Global Scoped Entry Registry Definition 216 Additions/Removals/Changes: Please post to the list or send the 217 author direct email, that indicates the exact details of 218 changes needed to this table. If a reference needs to be added 219 or changed, the xml for this would be ideal. Thanks. /d . 221 NOTE TO RFC EDITOR: Please remove "Additions/Removals/ 222 Changes" paragraph prior to publication. 224 A registry entry contains: 226 ID: Specifies a textual name for a scoped portion of the DNS. 227 The name will usually be taken from the specification cited in 228 the "Purpose" column and is intended for use in discussions 229 about the entry. 231 _Node Name: Specifies a single _underscore name that defines a 232 reserved name; this name is the "global" entry name for the 233 scoped resource records that are associated with that name. 235 Constraints: Specifies any restrictions on use of the DNS 236 Label. 238 RR(s): Lists the RRs that are defined for use within this 239 scope. 241 References Lists specifications that define the records and their 242 use under this Name. 244 Purpose: Specifies the particular purpose/use for specific 245 "RR"(s), defined for use within the scope of the registered 246 underscore name. 248 2.2. DNS Common Second-Level Underscore Scoped Entry Registry 249 Definition 251 A registry entry contains: 253 ID: Specifies a textual name for a scoped portion of the DNS, 254 occurring under a 'global' -- right-most -- _underscore node 255 name. The name will usually be taken from the specification 256 cited in the "Purpose" column and is intended for use in 257 discussions about the entry. 259 _Node Name: Specifies a single _underscore name that defines a 260 reserved name; this name is the "second-level" entry name for 261 the scoped resource records that are associated with that name. 263 Constraints: Specifies any restrictions on use of the name. 265 RR(s): Lists the RRs that are defined for use within this 266 scope. 268 References Lists specifications that define the records and their 269 use under this Name. 271 Purpose: Specifies the particular purpose/use for specific 272 "RR"(s), defined for use within the scope of the registered 273 underscore name. 275 3. IANA Considerations 277 Per [RFC8126], IANA is requested to establish two registries: 279 1. DNS Underscore Global Scoped Entry Registry 281 2. DNS Underscore Common Second-Level Scoped Entry Registry 283 This section describes actions requested of IANA. The guidance in 284 [IANA] is used. 286 3.1. DNS Underscore Global Scoped Entry Registry 288 The DNS Global Underscore Scoped Entry Registry is for DNS node names 289 that begin with the underscore character (_) and occur at the "top" 290 of a DNS branch -- ie, are right-most -- under a "parent" domain 291 name. 293 This registry is to operate under the IANA rules for "First Come 294 First Served" registration. 296 The contents of each entry in the Global registry are defined in 297 Section 2.1. 299 Additions/Removals/Changes: Please post to the list or send the 300 author direct email, that indicates the exact details of 301 changes needed to this table. If a reference needs to be added 302 or changed, the xml for this would be ideal. Thanks. /d . 304 NOTE TO RFC EDITOR: Please remove "Additions/Removals/ 305 Changes" paragraph prior to publication. 307 Initial entries in the registry are: 309 +-------+------------+-----+------------+---------------------------+ 310 | ID | _NODE NAME | RR | REFERENCE | PURPOSE | 311 +-------+------------+-----+------------+---------------------------+ 312 | SRV | _tcp | SRV | [RFC2782] | Use of SRV for a TCP- | 313 | TCP | | | | based service | 314 | SRV | _udp | SRV | [RFC2782] | Use of SRV for a UDP- | 315 | UDP | | | | based service | 316 | SPF | _spf | TXT | [RFC7208] | Authorized IP addresses | 317 | | | | | for sending mail | 318 | DKIM | _domainkey | TXT | [RFC6376] | Public key for verifying | 319 | | | | | DKIM signature. | 320 | VBR | _vouch | TXT | [RFC5518] | Vouch-by-refererence | 321 | | | | | domain assertion | 322 +-------+------------+-----+------------+---------------------------+ 324 Table 1: Underscore Global Registry (initial entries) 326 3.2. DNS Common Second-Level Underscore Scoped Entry Registry 328 A DNS Common Second-Level Underscore Scoped Entry Registry is for DNS 329 node names that begin with the underscore character (_) and occur 330 immediately below a Global ("top-level") node name beginning with an 331 _underscore. 333 This registry is to operate under the IANA rules for "First Come 334 First Served" registration. 336 The contents of each entry in the Common, Second-Level registry are 337 defined in Section 2.2. 339 Initial entries in the registry are: 341 +-------------+--------------+---------+----------+-----------------+ 342 | ID | _NODE NAME | RR | REFERENC | PURPOSE | 343 | | | | E | | 344 +-------------+--------------+---------+----------+-----------------+ 345 | LDAP | _ldap | SRV | [RFC2782 | LDAP server | 346 | | | | ] | | 347 | SIP | _sip | NAPTR | [RFC3263 | Locating SIP | 348 | | | | ] [RFC60 | Servers and UA | 349 | | | | 11] | configuration | 350 | PKI LDAP | _PKIXREP | SRV | [RFC4386 | PKI Repository | 351 | | | | ] | | 352 | DDDS | --???!-- | SRV | [RFC3404 | Mapping DDDS | 353 | | | | ] | query to DNS | 354 | | | | | records | 355 | SOAP BEEP | _soap-beep | SRV | [RFC4227 | SOAP over BEEP | 356 | | | | ] | lookup, when no | 357 | | | | | port specified | 358 | XMLRPC BEEP | _xmlrpc-beep | SRV | [RFC3529 | Resolve url for | 359 | | | | ] | XML-RPC using | 360 | | | | | BEEP | 361 | Diameter | _diameter | SRV | [RFC6733 | Diameter | 362 | | | | ] | rendezvous | 363 | Tunnel | _tunnel | SRV | [RFC3620 | Finding the | 364 | | | | ] | appropriate | 365 | | | | | address for | 366 | | | | | tunneling into | 367 | | | | | a particular | 368 | | | | | domain | 369 | SLP | _slpda | SRV | [RFC3832 | Discovering | 370 | | | | ] | desired | 371 | | | | | services in | 372 | | | | | given DNS | 373 | | | | | domains | 374 | Msg Track | _mtqp | SRV | [RFC3887 | Assist in | 375 | | | | ] | determining the | 376 | | | | | path that a | 377 | | | | | particular | 378 | | | | | message has | 379 | | | | | taken through a | 380 | | | | | messaging | 381 | | | | | system | 382 | XMPP Client | _xmpp-client | SRV | [RFC6120 | XMPP client | 383 | | | | ] | lookup of | 384 | | | | | server | 385 | XMPP Server | _xmpp-server | SRV | [RFC6120 | XMPP server- | 386 | | | | ] | server lookup | 387 | DDDS SRV | _??? | SRV | [RFC3958 | Map domain | 388 | | | (and | ] | name, | 389 | | | NAPTR?) | | application | 390 | | | | | service name, | 391 | | | | | and application | 392 | | | | | protocol | 393 | | | | | dynamically to | 394 | | | | | target server | 395 | | | | | and port | 396 | Kerberos | _kerberos | SRV | [RFC4120 | purpose | 397 | | | | ] | | 398 | PKI | _pkixrep | SRV | [RFC4386 | Enables | 399 | | | | ] | certificate- | 400 | | | | | using systems | 401 | | | | | to locate PKI | 402 | | | | | repositories | 403 | Certificate | _certificate | SRV | [RFC4387 | Obtain | 404 | s | s | | ] | certificates | 405 | | | | | and certificate | 406 | | | | | revocation | 407 | | | | | lists (CRLs) | 408 | | | | | from PKI | 409 | | | | | repositories | 410 | PGP Key | _pgpkeys | SRV | [RFC4387 | Obtain | 411 | Store | | | ] | certificates | 412 | | | | | and certificate | 413 | | | | | revocation | 414 | | | | | lists (CRLs) | 415 | | | | | from PKI | 416 | | | | | repositories | 417 | MSRP Relay | _msrp | SRV | [RFC4976 | purpose | 418 | Locator | | | ] | | 419 | Mobile IPv6 | _mip6 | SRV | [RFC5026 | Bootstrap | 420 | Bootstrap | | | ] [RFC55 | Mobile IPv6 | 421 | | | | 55] | Home Agent | 422 | | | | | information | 423 | | | | | from non- | 424 | | | | | topological | 425 | | | | | information | 426 | Digital | _dvbservdsc | SRV | [RFC5328 | Discover non- | 427 | Video Broad | | | ] | default DVB | 428 | casting | | | | entry points | 429 | | | | | addresses | 430 | CAPWAP AC | _capwap- | rrs | [RFC5415 | Discover the | 431 | | control | | ] | CAPWAP AC | 432 | | | | | address(es) | 433 | IEEE 802.21 | _mihis | NAPTR, | [RFC5679 | Discovering | 434 | Mobility | | SRV | ] | servers that | 435 | | | | | provide IEEE | 436 | | | | | 802.21-defined | 437 | | | | | Mobility | 438 | | | | | Services | 439 | STUN Client | _stun | SRV | [RFC5389 | Find a STUN | 440 | /Server | | | ] | server | 441 | TURN | _turn | SRV | [RFC5766 | Control the | 442 | | | | ] [RFC59 | operation of a | 443 | | | | 28] | relay to bypass | 444 | | | | | NAT | 445 | STUN NAT | _stun- | SRV | [RFC5780 | Discover the | 446 | Behavior | behavior | | ] | presence and | 447 | Discovery | | | | current | 448 | | | | | behavior of | 449 | | | | | NATs and | 450 | | | | | firewalls | 451 | | | | | between the | 452 | | | | | STUN client and | 453 | | | | | the STUN server | 454 | Sieve | _sieve | SRV | [RFC5804 | Manage Sieve | 455 | Management | | | ] | scripts on a | 456 | | | | | remote server | 457 | AFS VLDB | _afs3-vlserv | SRV | [RFC5864 | Locate services | 458 | | er | | ] | for the AFS | 459 | | | | | distributed | 460 | | | | | file system | 461 | AFS PTS | _afs3-prserv | SRV | [RFC5864 | Locate services | 462 | | er | | ] | for the AFS | 463 | | | | | distributed | 464 | | | | | file system | 465 | Mail MSA | _submission | SRV | [RFC6186 | Locate email | 466 | Submission | | | ] | services | 467 | IMAP | _imap | SRV | [RFC6186 | Locate email | 468 | | | | ] | services | 469 | POP | _pop3 | SRV | [RFC6186 | Locate email | 470 | | | | ] | services | 471 | POP TLS | _pop3s | SRV | [RFC6186 | Locate email | 472 | | | | ] | services | 473 +-------------+--------------+---------+----------+-----------------+ 475 Table 2: Underscore 2d-Level Registry (initial entries) 477 4. Security Considerations 479 This memo raises no security issues. 481 5. References 483 5.1. Normative References 485 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 486 Writing an IANA Considerations Section in RFCs", RFC 8126, 487 June 2017. 489 5.2. References -- Informative 491 [IANA] M. Cotton, B. Leiba, and T. Narten, "Guidelines for 492 Writing an IANA Considerations Section in RFCs", I-D 493 draft-leiba-cotton-iana-5226bis-11, 2017. 495 [RFC1035] Mockapetris, P., "Domain names - implementation and 496 specification", STD 13, RFC 1035, November 1987. 498 [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for 499 specifying the location of services (DNS SRV)", RFC 2782, 500 February 2000. 502 [RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation 503 Protocol (SIP): Locating SIP Servers", RFC 3263, June 504 2002. 506 [RFC3404] Mealling, M., "Dynamic Delegation Discovery System (DDDS) 507 Part Four: The Uniform Resource Identifiers (URI) 508 Resolution Application", RFC 3404, October 2002. 510 [RFC3529] Harold, W., "Using Extensible Markup Language-Remote 511 Procedure Calling (XML-RPC) in Blocks Extensible Exchange 512 Protocol (BEEP)", RFC 3529, April 2003. 514 [RFC3620] New, D., "The TUNNEL Profile", RFC 3620, October 2003. 516 [RFC3832] Columbia University, Columbia University, Sun 517 Microsystems, IBM, and IBM, "Remote Service Discovery in 518 the Service Location Protocol (SLP) via DNS SRV", 519 RFC 3832, July 2004. 521 [RFC3887] "Message Tracking Query Protocol", RFC 3887, September 522 2007. 524 [RFC3958] Daigle, L. and A. Newton, "Domain-Based Application 525 Service Location Using SRV RRs and the Dynamic Delegation 526 Discovery Service (DDDS)", RFC 3958, January 2005. 528 [RFC4120] USC-ISI, MIT, MIT, and MIT, "The Kerberos Network 529 Authentication Service (V5)", RFC 4120, July 2005. 531 [RFC4227] O'Tuathail, E. and M. Rose, "Using the Simple Object 532 Access Protocol (SOAP) in Blocks Extensible Exchange 533 Protocol (BEEP)", RFC 4227, January 2006. 535 [RFC4386] Boeyen, S. and P. Hallam-Baker, "Internet X.509 Public Key 536 Infrastructure: Repository Locator Service", RFC 4386, 537 February 2006. 539 [RFC4387] Gutmann, P., Ed., "Internet X.509 Public Key 540 Infrastructure Operational Protocols: Certificate Store 541 Access via HTTP", RFC 4387, February 2006. 543 [RFC4976] Jennings, C., Mahy, R., and Roach, "Relay Extensions for 544 the Message Session Relay Protocol (MSRP)", RFC 4976, 545 September 2007. 547 [RFC5026] Giaretta, G., Ed., Kempf, J., and V. Devarapalli, Ed., 548 "Mobile IPv6 Bootstrapping in Split Scenario", RFC 5026, 549 October 2007. 551 [RFC5328] Adolf, A. and P. MacAvock, "A Uniform Resource Name (URN) 552 Namespace for the Digital Video Broadcasting Project 553 (DVB)", RFC 5328, September 2008. 555 [RFC5389] Rosenberg, Mahy, Matthews, and Wing, "Session Traversal 556 Utilities for NAT (STUN)", RFC 5389, October 2008. 558 [RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, 559 Ed., "Control And Provisioning of Wireless Access Points 560 (CAPWAP) Protocol Specification", RFC 5415, March 2009. 562 [RFC5518] Hoffman, P., Levine, J., and A. Hathcock, "Vouch By 563 Reference", RFC 5518, April 2009. 565 [RFC5555] Soliman, H., Ed., "Mobile IPv6 Support for Dual Stack 566 Hosts and Routers", RFC 5555, June 2009. 568 [RFC5679] Bajko, G., "Locating IEEE 802.21 Mobility Services Using 569 DNS", RFC 5679, December 2009. 571 [RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using 572 Relays around NAT (TURN): Relay Extensions to Session 573 Traversal Utilities for NAT (STUN)", RFC 5766, April 2010. 575 [RFC5780] MacDonald, D. and B. Lowekamp, "NAT Behavior Discovery 576 Using Session Traversal Utilities for NAT (STUN)", 577 RFC 5780, May 2010. 579 [RFC5804] Melnikov, A., Ed. and T. Martin, "A Protocol for Remotely 580 Managing Sieve Scripts", RFC 5804, July 2010. 582 [RFC5864] Allbery, R., "NS SRV Resource Records for AFS", RFC 5864, 583 April 2010. 585 [RFC5928] Petit-Huguenin, M., "Traversal Using Relays around NAT 586 (TURN) Resolution Mechanism", RFC 5928, August 2010. 588 [RFC6011] Lawrence, S., Ed. and J. Elwell, "Session Initiation 589 Protocol (SIP) User Agent Configuration", RFC 6011, 590 October 2010. 592 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence 593 Protocol (XMPP): Core", RFC 6120, March 2011. 595 [RFC6186] Daboo, C., "Use of SRV Records for Locating Email 596 Submission/Access Services", RFC 6186, March 2011. 598 [RFC6376] Crocker, D., Hansen, T., and M. Kucherawy, "DomainKeys 599 Identified Mail (DKIM) Signatures", RFC 6376, Sept 2011. 601 [RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn, 602 "Diameter Base Protocol", RFC 6733, October 2012. 604 [RFC7208] Kitterman, S., "Sender Policy Framework (SPF) for 605 Authorizing Use of Domains in E-Mail, Version 1", 606 RFC 7208, April 2014. 608 [RFC7553] Falstrom, P. and O. Kolkman, "The Uniform Resource 609 Identifier (URI) DNS Resource Record", RFC 7553, 610 ISSN 2070-1721, June 2015. 612 5.3. URIs 614 [1] mailto:dnsop@ietf.org 616 Appendix A. Acknowledgements 618 Thanks go to Bill Fenner, Tony Hansen, Peter Koch, Olaf Kolkman, and 619 Andrew Sullivan for diligent review of the (much) earlier drafts. 620 For the later enhancements, thanks to: Stephane Bortzmeyer, Bob 621 Harold, John Levine, Joel Jaeggli, Petr Špaček, Ondřej 622 Surř, Tim Wicinski, and Paul Wouters. 624 Special thanks to Ray Bellis for more than 12 years of persistent 625 encouragement to continue this effort, as well as the suggestion for 626 an essential simplification to the registration model. 628 Author's Address 630 Dave Crocker 631 Brandenburg InternetWorking 632 675 Spruce Dr. 633 Sunnyvale, CA 94086 634 USA 636 Phone: +1.408.246.8253 637 Email: dcrocker@bbiw.net 638 URI: http://bbiw.net/