1 Internet Engineering Task Force (IETF) P. Hoffman 2 Request for Comments: 7719 ICANN 3 Category: Informational A. Sullivan 4 ISSN: 2070-1721 Dyn 5 K. Fujiwara 6 JPRS 7 December 2015 8 9 10 DNS Terminology 11 12 Abstract 13 14 The DNS is defined in literally dozens of different RFCs. The 15 terminology used by implementers and developers of DNS protocols, and 16 by operators of DNS systems, has sometimes changed in the decades 17 since the DNS was first defined. This document gives current 18 definitions for many of the terms used in the DNS in a single 19 document. 20 21 Status of This Memo 22 23 This document is not an Internet Standards Track specification; it is 24 published for informational purposes. 25 26 This document is a product of the Internet Engineering Task Force 27 (IETF). It represents the consensus of the IETF community. It has 28 received public review and has been approved for publication by the 29 Internet Engineering Steering Group (IESG). Not all documents 30 approved by the IESG are a candidate for any level of Internet 31 Standard; see Section 2 of RFC 5741. 32 33 Information about the current status of this document, any errata, 34 and how to provide feedback on it may be obtained at 35 http://www.rfc-editor.org/info/rfc7719. 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 Hoffman, et al. Informational [Page 1] 53 RFC 7719 DNS Terminology December 2015 54 55 56 Copyright Notice 57 58 Copyright (c) 2015 IETF Trust and the persons identified as the 59 document authors. All rights reserved. 60 61 This document is subject to BCP 78 and the IETF Trust's Legal 62 Provisions Relating to IETF Documents 63 (http://trustee.ietf.org/license-info) in effect on the date of 64 publication of this document. Please review these documents 65 carefully, as they describe your rights and restrictions with respect 66 to this document. Code Components extracted from this document must 67 include Simplified BSD License text as described in Section 4.e of 68 the Trust Legal Provisions and are provided without warranty as 69 described in the Simplified BSD License. 70 71 Table of Contents 72 73 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 74 2. Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 75 3. DNS Header and Response Codes . . . . . . . . . . . . . . . . 6 76 4. Resource Records . . . . . . . . . . . . . . . . . . . . . . 7 77 5. DNS Servers and Clients . . . . . . . . . . . . . . . . . . . 9 78 6. Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 79 7. Registration Model . . . . . . . . . . . . . . . . . . . . . 17 80 8. General DNSSEC . . . . . . . . . . . . . . . . . . . . . . . 18 81 9. DNSSEC States . . . . . . . . . . . . . . . . . . . . . . . . 20 82 10. Security Considerations . . . . . . . . . . . . . . . . . . . 22 83 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 84 11.1. Normative References . . . . . . . . . . . . . . . . . . 22 85 11.2. Informative References . . . . . . . . . . . . . . . . . 24 86 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 27 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 88
The IETF is responsible for the creation and maintenance of the DNS RFCs. The ICANN DNS RFC annotation project provides a forum for collecting community annotations on these RFCs as an aid to understanding for implementers and any interested parties. The annotations displayed here are not the result of the IETF consensus process.
This RFC is included in the DNS RFCs annotation project whose home page is here.
89 1. Introduction 90 91 The Domain Name System (DNS) is a simple query-response protocol 92 whose messages in both directions have the same format. The protocol 93 and message format are defined in [RFC1034] and [RFC1035]. These 94 RFCs defined some terms, but later documents defined others. Some of 95 the terms from RFCs 1034 and 1035 now have somewhat different 96 meanings than they did in 1987. 97 98 This document collects a wide variety of DNS-related terms. Some of 99 them have been precisely defined in earlier RFCs, some have been 100 loosely defined in earlier RFCs, and some are not defined in any 101 earlier RFC at all. 102 103 104 105 106 107 Hoffman, et al. Informational [Page 2] 108 RFC 7719 DNS Terminology December 2015 109 110 111 Most of the definitions here are the consensus definition of the DNS 112 community -- both protocol developers and operators. Some of the 113 definitions differ from earlier RFCs, and those differences are 114 noted. In this document, where the consensus definition is the same 115 as the one in an RFC, that RFC is quoted. Where the consensus 116 definition has changed somewhat, the RFC is mentioned but the new 117 stand-alone definition is given. 118 119 It is important to note that, during the development of this 120 document, it became clear that some DNS-related terms are interpreted 121 quite differently by different DNS experts. Further, some terms that 122 are defined in early DNS RFCs now have definitions that are generally 123 agreed to, but that are different from the original definitions. 124 Therefore, the authors intend to follow this document with a 125 substantial revision in the not-distant future. That revision will 126 probably have more in-depth discussion of some terms as well as new 127 terms; it will also update some of the RFCs with new definitions. 128 129 The terms are organized loosely by topic. Some definitions are for 130 new terms for things that are commonly talked about in the DNS 131 community but that never had terms defined for them. 132 133 Other organizations sometimes define DNS-related terms their own way. 134 For example, the W3C defines "domain" at 135 https://specs.webplatform.org/url/webspecs/develop/. 136 137 Note that there is no single consistent definition of "the DNS". It 138 can be considered to be some combination of the following: a commonly 139 used naming scheme for objects on the Internet; a distributed 140 database representing the names and certain properties of these 141 objects; an architecture providing distributed maintenance, 142 resilience, and loose coherency for this database; and a simple 143 query-response protocol (as mentioned below) implementing this 144 architecture. 145 146 Capitalization in DNS terms is often inconsistent among RFCs and 147 various DNS practitioners. The capitalization used in this document 148 is a best guess at current practices, and is not meant to indicate 149 that other capitalization styles are wrong or archaic. In some 150 cases, multiple styles of capitalization are used for the same term 151 due to quoting from different RFCs. 152 153 154 155 156 157 158 159 160 161 162 Hoffman, et al. Informational [Page 3] 163 RFC 7719 DNS Terminology December 2015 164 165
The RFC should be edited to reflect the intended content. Unfortunately, although I am technical, I do not have knowledge of the original. There are also other dead references.... and a reference to a "dead project" which is still living, here, but with little reference to DNS or domains. RFC Editor note: Errata are typically not used to correct URLs that were functioning at the time of publication. For this case, please see RFC 8499 (which obsoleted RFC 7719) for the current information. --VERIFIER NOTES-- Thank you for submitting this. RFC 7719 has been updated by RFC8499 (published after your errata was submitted), which doesn't contain the reference. Thanks again W
166 2. Names 167 168 Domain name: Section 3.1 of [RFC1034] talks of "the domain name 169 space" as a tree structure. "Each node has a label, which is zero 170 to 63 octets in length. ... The domain name of a node is the list 171 of the labels on the path from the node to the root of the tree. 172 ... To simplify implementations, the total number of octets that 173 represent a domain name (i.e., the sum of all label octets and 174 label lengths) is limited to 255." Any label in a domain name can 175 contain any octet value. 176 177 Fully qualified domain name (FQDN): This is often just a clear way 178 of saying the same thing as "domain name of a node", as outlined 179 above. However, the term is ambiguous. Strictly speaking, a 180 fully qualified domain name would include every label, including 181 the final, zero-length label of the root: such a name would be 182 written "www.example.net." (note the terminating dot). But 183 because every name eventually shares the common root, names are 184 often written relative to the root (such as "www.example.net") and 185 are still called "fully qualified". This term first appeared in 186 [RFC819]. In this document, names are often written relative to 187 the root. 188 189 The need for the term "fully qualified domain name" comes from the 190 existence of partially qualified domain names, which are names 191 where some of the right-most names are left off and are understood 192 only by context. 193 194 Label: The identifier of an individual node in the sequence of nodes 195 identified by a fully qualified domain name. 196 197 Host name: This term and its equivalent, "hostname", have been 198 widely used but are not defined in [RFC1034], [RFC1035], 199 [RFC1123], or [RFC2181]. The DNS was originally deployed into the 200 Host Tables environment as outlined in [RFC952], and it is likely 201 that the term followed informally from the definition there. Over 202 time, the definition seems to have shifted. "Host name" is often 203 meant to be a domain name that follows the rules in Section 3.5 of 204 [RFC1034], the "preferred name syntax". Note that any label in a 205 domain name can contain any octet value; hostnames are generally 206 considered to be domain names where every label follows the rules 207 in the "preferred name syntax", with the amendment that labels can 208 start with ASCII digits (this amendment comes from Section 2.1 of 209 [RFC1123]). 210 211 People also sometimes use the term hostname to refer to just the 212 first label of an FQDN, such as "printer" in 213 "printer.admin.example.com". (Sometimes this is formalized in 214 215 216 217 Hoffman, et al. Informational [Page 4] 218 RFC 7719 DNS Terminology December 2015 219 220 221 configuration in operating systems.) In addition, people 222 sometimes use this term to describe any name that refers to a 223 machine, and those might include labels that do not conform to the 224 "preferred name syntax". 225 226 TLD: A Top-Level Domain, meaning a zone that is one layer below the 227 root, such as "com" or "jp". There is nothing special, from the 228 point of view of the DNS, about TLDs. Most of them are also 229 delegation-centric zones, and there are significant policy issues 230 around their operation. TLDs are often divided into sub-groups 231 such as Country Code Top-Level Domains (ccTLDs), Generic Top-Level 232 Domains (gTLDs), and others; the division is a matter of policy, 233 and beyond the scope of this document. 234 235 IDN: The common abbreviation for "Internationalized Domain Name". 236 The IDNA protocol is the standard mechanism for handling domain 237 names with non-ASCII characters in applications in the DNS. The 238 current standard, normally called "IDNA2008", is defined in 239 [RFC5890], [RFC5891], [RFC5892], [RFC5893], and [RFC5894]. These 240 documents define many IDN-specific terms such as "LDH label", 241 "A-label", and "U-label". [RFC6365] defines more terms that 242 relate to internationalization (some of which relate to IDNs), and 243 [RFC6055] has a much more extensive discussion of IDNs, including 244 some new terminology. 245 246 Subdomain: "A domain is a subdomain of another domain if it is 247 contained within that domain. This relationship can be tested by 248 seeing if the subdomain's name ends with the containing domain's 249 name." (Quoted from [RFC1034], Section 3.1). For example, in the 250 host name "nnn.mmm.example.com", both "mmm.example.com" and 251 "nnn.mmm.example.com" are subdomains of "example.com". 252 253 Alias: The owner of a CNAME resource record, or a subdomain of the 254 owner of a DNAME resource record [RFC6672]. See also "canonical 255 name". 256 257 Canonical name: A CNAME resource record "identifies its owner name 258 as an alias, and specifies the corresponding canonical name in the 259 RDATA section of the RR." (Quoted from [RFC1034], Section 3.6.2) 260 This usage of the word "canonical" is related to the mathematical 261 concept of "canonical form". 262 263 CNAME: "It is traditional to refer to the owner of a CNAME record as 264 'a CNAME'. This is unfortunate, as 'CNAME' is an abbreviation of 265 'canonical name', and the owner of a CNAME record is an alias, not 266 a canonical name." (Quoted from [RFC2181], Section 10.1.1) 267 268 269 270 271 272 Hoffman, et al. Informational [Page 5] 273 RFC 7719 DNS Terminology December 2015 274 275 276 Public suffix: "A domain that is controlled by a public registry." 277 (Quoted from [RFC6265], Section 5.3) A common definition for this 278 term is a domain under which subdomains can be registered, and on 279 which HTTP cookies ([RFC6265]) should not be set. There is no 280 indication in a domain name whether it is a public suffix; that 281 can only be determined by outside means. In fact, both a domain 282 and a subdomain of that domain can be public suffixes. At the 283 time this document is published, the IETF DBOUND Working Group 284 [DBOUND] is dealing with issues concerning public suffixes. 285 286 There is nothing inherent in a domain name to indicate whether it 287 is a public suffix. One resource for identifying public suffixes 288 is the Public Suffix List (PSL) maintained by Mozilla 289 (http://publicsuffix.org/). 290 291 For example, at the time this document is published, the "com.au" 292 domain is listed as a public suffix in the PSL. (Note that this 293 example might change in the future.) 294 295 Note that the term "public suffix" is controversial in the DNS 296 community for many reasons, and may be significantly changed in 297 the future. One example of the difficulty of calling a domain a 298 public suffix is that designation can change over time as the 299 registration policy for the zone changes, such as the case of the 300 "uk" TLD around the time this document is published. 301 302 3. DNS Header and Response Codes 303 304 The header of a DNS message is its first 12 octets. Many of the 305 fields and flags in the header diagram in Sections 4.1.1 through 306 4.1.3 of [RFC1035] are referred to by their names in that diagram. 307 For example, the response codes are called "RCODEs", the data for a 308 record is called the "RDATA", and the authoritative answer bit is 309 often called "the AA flag" or "the AA bit". 310 311 Some of response codes that are defined in [RFC1035] have gotten 312 their own shorthand names. Some common response code names that 313 appear without reference to the numeric value are "FORMERR", 314 "SERVFAIL", and "NXDOMAIN" (the latter of which is also referred to 315 as "Name Error"). All of the RCODEs are listed at 316 http://www.iana.org/assignments/dns-parameters, although that site 317 uses mixed-case capitalization, while most documents use all-caps. 318 319 NODATA: "A pseudo RCODE which indicates that the name is valid for 320 the given class, but there are no records of the given type. A 321 NODATA response has to be inferred from the answer." (Quoted from 322 [RFC2308], Section 1.) "NODATA is indicated by an answer with the 323 RCODE set to NOERROR and no relevant answers in the answer 324 325 326 327 Hoffman, et al. Informational [Page 6] 328 RFC 7719 DNS Terminology December 2015 329 330 331 section. The authority section will contain an SOA record, or 332 there will be no NS records there." (Quoted from [RFC2308], 333 Section 2.2.) Note that referrals have a similar format to NODATA 334 replies; [RFC2308] explains how to distinguish them. 335 336 The term "NXRRSET" is sometimes used as a synonym for NODATA. 337 However, this is a mistake, given that NXRRSET is a specific error 338 code defined in [RFC2136]. 339 340 Negative response: A response that indicates that a particular RRset 341 does not exist, or whose RCODE indicates the nameserver cannot 342 answer. Sections 2 and 7 of [RFC2308] describe the types of 343 negative responses in detail. 344 345 Referrals: Data from the authority section of a non-authoritative 346 answer. [RFC1035] Section 2.1 defines "authoritative" data. 347 However, referrals at zone cuts (defined in Section 6) are not 348 authoritative. Referrals may be zone cut NS resource records and 349 their glue records. NS records on the parent side of a zone cut 350 are an authoritative delegation, but are normally not treated as 351 authoritative data. In general, a referral is a way for a server 352 to send an answer saying that the server does not know the answer, 353 but knows where the query should be directed in order to get an 354 answer. Historically, many authoritative servers answered with a 355 referral to the root zone when queried for a name for which they 356 were not authoritative, but this practice has declined. 357 358 4. Resource Records 359 360 RR: An acronym for resource record. ([RFC1034], Section 3.6.) 361 362 RRset: A set of resource records with the same label, class and 363 type, but with different data. (Definition from [RFC2181]) Also 364 spelled RRSet in some documents. As a clarification, "same label" 365 in this definition means "same owner name". In addition, 366 [RFC2181] states that "the TTLs of all RRs in an RRSet must be the 367 same". (This definition is definitely not the same as "the 368 response one gets to a query for QTYPE=ANY", which is an 369 unfortunate misunderstanding.) 370 371 EDNS: The extension mechanisms for DNS, defined in [RFC6891]. 372 Sometimes called "EDNS0" or "EDNS(0)" to indicate the version 373 number. EDNS allows DNS clients and servers to specify message 374 sizes larger than the original 512 octet limit, to expand the 375 response code space, and potentially to carry additional options 376 that affect the handling of a DNS query. 377 378 379 380 381 382 Hoffman, et al. Informational [Page 7] 383 RFC 7719 DNS Terminology December 2015 384 385 386 OPT: A pseudo-RR (sometimes called a "meta-RR") that is used only to 387 contain control information pertaining to the question-and-answer 388 sequence of a specific transaction. (Definition from [RFC6891], 389 Section 6.1.1) It is used by EDNS. 390 391 Owner: The domain name where a RR is found ([RFC1034], Section 3.6). 392 Often appears in the term "owner name". 393 394 SOA field names: DNS documents, including the definitions here, 395 often refer to the fields in the RDATA of an SOA resource record 396 by field name. Those fields are defined in Section 3.3.13 of 397 [RFC1035]. The names (in the order they appear in the SOA RDATA) 398 are MNAME, RNAME, SERIAL, REFRESH, RETRY, EXPIRE, and MINIMUM. 399 Note that the meaning of MINIMUM field is updated in Section 4 of 400 [RFC2308]; the new definition is that the MINIMUM field is only 401 "the TTL to be used for negative responses". This document tends 402 to use field names instead of terms that describe the fields. 403 404 TTL: The maximum "time to live" of a resource record. "A TTL value 405 is an unsigned number, with a minimum value of 0, and a maximum 406 value of 2147483647. That is, a maximum of 2^31 - 1. When 407 transmitted, the TTL is encoded in the less significant 31 bits of 408 the 32 bit TTL field, with the most significant, or sign, bit set 409 to zero." (Quoted from [RFC2181], Section 8) (Note that [RFC1035] 410 erroneously stated that this is a signed integer; that was fixed 411 by [RFC2181].) 412 413 The TTL "specifies the time interval that the resource record may 414 be cached before the source of the information should again be 415 consulted". (Quoted from [RFC1035], Section 3.2.1) Also: "the 416 time interval (in seconds) that the resource record may be cached 417 before it should be discarded". (Quoted from [RFC1035], 418 Section 4.1.3). Despite being defined for a resource record, the 419 TTL of every resource record in an RRset is required to be the 420 same ([RFC2181], Section 5.2). 421 422 The reason that the TTL is the maximum time to live is that a 423 cache operator might decide to shorten the time to live for 424 operational purposes, such as if there is a policy to disallow TTL 425 values over a certain number. Also, if a value is flushed from 426 the cache when its value is still positive, the value effectively 427 becomes zero. Some servers are known to ignore the TTL on some 428 RRsets (such as when the authoritative data has a very short TTL) 429 even though this is against the advice in RFC 1035. 430 431 432 433 434 435 436 437 Hoffman, et al. Informational [Page 8] 438 RFC 7719 DNS Terminology December 2015 439 440 441 There is also the concept of a "default TTL" for a zone, which can 442 be a configuration parameter in the server software. This is 443 often expressed by a default for the entire server, and a default 444 for a zone using the $TTL directive in a zone file. The $TTL 445 directive was added to the master file format by [RFC2308]. 446 447 Class independent: A resource record type whose syntax and semantics 448 are the same for every DNS class. A resource record type that is 449 not class independent has different meanings depending on the DNS 450 class of the record, or the meaning is undefined for classes other 451 than IN (class 1, the Internet). 452 453 5. DNS Servers and Clients 454 455 This section defines the terms used for the systems that act as DNS 456 clients, DNS servers, or both. 457 458 Resolver: A program "that extract[s] information from name servers 459 in response to client requests." (Quoted from [RFC1034], 460 Section 2.4) "The resolver is located on the same machine as the 461 program that requests the resolver's services, but it may need to 462 consult name servers on other hosts." (Quoted from [RFC1034], 463 Section 5.1) A resolver performs queries for a name, type, and 464 class, and receives answers. The logical function is called 465 "resolution". In practice, the term is usually referring to some 466 specific type of resolver (some of which are defined below), and 467 understanding the use of the term depends on understanding the 468 context. 469 470 Stub resolver: A resolver that cannot perform all resolution itself. 471 Stub resolvers generally depend on a recursive resolver to 472 undertake the actual resolution function. Stub resolvers are 473 discussed but never fully defined in Section 5.3.1 of [RFC1034]. 474 They are fully defined in Section 184.108.40.206 of [RFC1123]. 475 476 Iterative mode: A resolution mode of a server that receives DNS 477 queries and responds with a referral to another server. 478 Section 2.3 of [RFC1034] describes this as "The server refers the 479 client to another server and lets the client pursue the query". A 480 resolver that works in iterative mode is sometimes called an 481 "iterative resolver". 482 483 Recursive mode: A resolution mode of a server that receives DNS 484 queries and either responds to those queries from a local cache or 485 sends queries to other servers in order to get the final answers 486 to the original queries. Section 2.3 of [RFC1034] describes this 487 as "The first server pursues the query for the client at another 488 server". A server operating in recursive mode may be thought of 489 490 491 492 Hoffman, et al. Informational [Page 9] 493 RFC 7719 DNS Terminology December 2015 494 495 496 as having a name server side (which is what answers the query) and 497 a resolver side (which performs the resolution function). Systems 498 operating in this mode are commonly called "recursive servers". 499 Sometimes they are called "recursive resolvers". While strictly 500 the difference between these is that one of them sends queries to 501 another recursive server and the other does not, in practice it is 502 not possible to know in advance whether the server that one is 503 querying will also perform recursion; both terms can be observed 504 in use interchangeably. 505 506 Full resolver: This term is used in [RFC1035], but it is not defined 507 there. RFC 1123 defines a "full-service resolver" that may or may 508 not be what was intended by "full resolver" in [RFC1035]. This 509 term is not properly defined in any RFC. 510 511 Full-service resolver: Section 220.127.116.11 of [RFC1123] defines this 512 term to mean a resolver that acts in recursive mode with a cache 513 (and meets other requirements). 514 515 Priming: The mechanism used by a resolver to determine where to send 516 queries before there is anything in the resolver's cache. Priming 517 is most often done from a configuration setting that contains a 518 list of authoritative servers for the root zone. 519 520 Negative caching: "The storage of knowledge that something does not 521 exist, cannot give an answer, or does not give an answer." 522 (Quoted from [RFC2308], Section 1) 523 524 Authoritative server: "A server that knows the content of a DNS zone 525 from local knowledge, and thus can answer queries about that zone 526 without needing to query other servers." (Quoted from [RFC2182], 527 Section 2.) It is a system that responds to DNS queries with 528 information about zones for which it has been configured to answer 529 with the AA flag in the response header set to 1. It is a server 530 that has authority over one or more DNS zones. Note that it is 531 possible for an authoritative server to respond to a query without 532 the parent zone delegating authority to that server. 533 Authoritative servers also provide "referrals", usually to child 534 zones delegated from them; these referrals have the AA bit set to 535 0 and come with referral data in the Authority and (if needed) the 536 Additional sections. 537 538 Authoritative-only server: A name server that only serves 539 authoritative data and ignores requests for recursion. It will 540 "not normally generate any queries of its own. Instead, it 541 answers non-recursive queries from iterative resolvers looking for 542 information in zones it serves." (Quoted from [RFC4697], 543 Section 2.4) 544 545 546 547 Hoffman, et al. Informational [Page 10] 548 RFC 7719 DNS Terminology December 2015 549 550 551 Zone transfer: The act of a client requesting a copy of a zone and 552 an authoritative server sending the needed information. (See 553 Section 6 for a description of zones.) There are two common 554 standard ways to do zone transfers: the AXFR ("Authoritative 555 Transfer") mechanism to copy the full zone (described in 556 [RFC5936], and the IXFR ("Incremental Transfer") mechanism to copy 557 only parts of the zone that have changed (described in [RFC1995]). 558 Many systems use non-standard methods for zone transfer outside 559 the DNS protocol. 560 561 Secondary server: "An authoritative server which uses zone transfer 562 to retrieve the zone" (Quoted from [RFC1996], Section 2.1). 563 [RFC2182] describes secondary servers in detail. Although early 564 DNS RFCs such as [RFC1996] referred to this as a "slave", the 565 current common usage has shifted to calling it a "secondary". 566 Secondary servers are also discussed in [RFC1034]. 567 568 Slave server: See secondary server. 569 570 Primary server: "Any authoritative server configured to be the 571 source of zone transfer for one or more [secondary] servers" 572 (Quoted from [RFC1996], Section 2.1) or, more specifically, "an 573 authoritative server configured to be the source of AXFR or IXFR 574 data for one or more [secondary] servers" (Quoted from [RFC2136]). 575 Although early DNS RFCs such as [RFC1996] referred to this as a 576 "master", the current common usage has shifted to "primary". 577 Primary servers are also discussed in [RFC1034]. 578 579 Master server: See primary server. 580 581 Primary master: "The primary master is named in the zone's SOA MNAME 582 field and optionally by an NS RR". (Quoted from [RFC1996], 583 Section 2.1). [RFC2136] defines "primary master" as "Master 584 server at the root of the AXFR/IXFR dependency graph. The primary 585 master is named in the zone's SOA MNAME field and optionally by an 586 NS RR. There is by definition only one primary master server per 587 zone." The idea of a primary master is only used by [RFC2136], 588 and is considered archaic in other parts of the DNS. 589 590 Stealth server: This is "like a slave server except not listed in an 591 NS RR for the zone." (Quoted from [RFC1996], Section 2.1) 592 593 594 595 596 597 598 599 600 601 602 Hoffman, et al. Informational [Page 11] 603 RFC 7719 DNS Terminology December 2015 604 605 606 Hidden master: A stealth server that is a master for zone transfers. 607 "In this arrangement, the master name server that processes the 608 updates is unavailable to general hosts on the Internet; it is not 609 listed in the NS RRset." (Quoted from [RFC6781], Section 3.4.3.) 610 An earlier RFC, [RFC4641], said that the hidden master's name 611 appears in the SOA RRs MNAME field, although in some setups, the 612 name does not appear at all in the public DNS. A hidden master 613 can be either a secondary or a primary master. 614 615 Forwarding: The process of one server sending a DNS query with the 616 RD bit set to 1 to another server to resolve that query. 617 Forwarding is a function of a DNS resolver; it is different than 618 simply blindly relaying queries. 619 620 [RFC5625] does not give a specific definition for forwarding, but 621 describes in detail what features a system that forwards need to 622 support. Systems that forward are sometimes called "DNS proxies", 623 but that term has not yet been defined (even in [RFC5625]). 624 625 Forwarder: Section 1 of [RFC2308] describes a forwarder as "a 626 nameserver used to resolve queries instead of directly using the 627 authoritative nameserver chain". [RFC2308] further says "The 628 forwarder typically either has better access to the internet, or 629 maintains a bigger cache which may be shared amongst many 630 resolvers." That definition appears to suggest that forwarders 631 normally only query authoritative servers. In current use, 632 however, forwarders often stand between stub resolvers and 633 recursive servers. [RFC2308] is silent on whether a forwarder is 634 iterative-only or can be a full-service resolver. 635 636 Policy-implementing resolver: A resolver acting in recursive mode 637 that changes some of the answers that it returns based on policy 638 criteria, such as to prevent access to malware sites or 639 objectionable content. In general, a stub resolver has no idea 640 whether upstream resolvers implement such policy or, if they do, 641 the exact policy about what changes will be made. In some cases, 642 the user of the stub resolver has selected the policy-implementing 643 resolver with the explicit intention of using it to implement the 644 policies. In other cases, policies are imposed without the user 645 of the stub resolver being informed. 646 647 Open resolver: A full-service resolver that accepts and processes 648 queries from any (or nearly any) stub resolver. This is sometimes 649 also called a "public resolver", although the term "public 650 resolver" is used more with open resolvers that are meant to be 651 open, as compared to the vast majority of open resolvers that are 652 probably misconfigured to be open. 653 654 655 656 657 Hoffman, et al. Informational [Page 12] 658 RFC 7719 DNS Terminology December 2015 659 660 661 View: A configuration for a DNS server that allows it to provide 662 different answers depending on attributes of the query. 663 Typically, views differ by the source IP address of a query, but 664 can also be based on the destination IP address, the type of query 665 (such as AXFR), whether it is recursive, and so on. Views are 666 often used to provide more names or different addresses to queries 667 from "inside" a protected network than to those "outside" that 668 network. Views are not a standardized part of the DNS, but they 669 are widely implemented in server software. 670 671 Passive DNS: A mechanism to collect large amounts of DNS data by 672 storing DNS responses from servers. Some of these systems also 673 collect the DNS queries associated with the responses; this can 674 raise privacy issues. Passive DNS databases can be used to answer 675 historical questions about DNS zones such as which records were 676 available for them at what times in the past. Passive DNS 677 databases allow searching of the stored records on keys other than 678 just the name, such as "find all names which have A records of a 679 particular value". 680 681 Anycast: "The practice of making a particular service address 682 available in multiple, discrete, autonomous locations, such that 683 datagrams sent are routed to one of several available locations." 684 (Quoted from [RFC4786], Section 2) 685 686 6. Zones 687 688 This section defines terms that are used when discussing zones that 689 are being served or retrieved. 690 691 Zone: "Authoritative information is organized into units called 692 'zones', and these zones can be automatically distributed to the 693 name servers which provide redundant service for the data in a 694 zone." (Quoted from [RFC1034], Section 2.4) 695 696 Child: "The entity on record that has the delegation of the domain 697 from the Parent." (Quoted from [RFC7344], Section 1.1) 698 699 Parent: "The domain in which the Child is registered." (Quoted from 700 [RFC7344], Section 1.1) Earlier, "parent name server" was defined 701 in [RFC882] as "the name server that has authority over the place 702 in the domain name space that will hold the new domain". (Note 703 that [RFC882] was obsoleted by [RFC1034] and [RFC1035].) [RFC819] 704 also has some description of the relationship between parents and 705 children. 706 707 708 709 710 711 712 Hoffman, et al. Informational [Page 13] 713 RFC 7719 DNS Terminology December 2015 714 715 716 Origin: 717 718 (a) "The domain name that appears at the top of a zone (just below 719 the cut that separates the zone from its parent). The name of the 720 zone is the same as the name of the domain at the zone's origin." 721 (Quoted from [RFC2181], Section 6.) These days, this sense of 722 "origin" and "apex" (defined below) are often used 723 interchangeably. 724 725 (b) The domain name within which a given relative domain name 726 appears in zone files. Generally seen in the context of 727 "$ORIGIN", which is a control entry defined in [RFC1035], 728 Section 5.1, as part of the master file format. For example, if 729 the $ORIGIN is set to "example.org.", then a master file line for 730 "www" is in fact an entry for "www.example.org.". 731 732 Apex: The point in the tree at an owner of an SOA and corresponding 733 authoritative NS RRset. This is also called the "zone apex". 734 [RFC4033] defines it as "the name at the child's side of a zone 735 cut". The "apex" can usefully be thought of as a data-theoretic 736 description of a tree structure, and "origin" is the name of the 737 same concept when it is implemented in zone files. The 738 distinction is not always maintained in use, however, and one can 739 find uses that conflict subtly with this definition. [RFC1034] 740 uses the term "top node of the zone" as a synonym of "apex", but 741 that term is not widely used. These days, the first sense of 742 "origin" (above) and "apex" are often used interchangeably. 743 744 Zone cut: The delimitation point between two zones where the origin 745 of one of the zones is the child of the other zone. 746 747 "Zones are delimited by 'zone cuts'. Each zone cut separates a 748 'child' zone (below the cut) from a 'parent' zone (above the cut). 749 (Quoted from [RFC2181], Section 6; note that this is barely an 750 ostensive definition.) Section 4.2 of [RFC1034] uses "cuts" as 751 'zone cut'." 752 753 Delegation: The process by which a separate zone is created in the 754 name space beneath the apex of a given domain. Delegation happens 755 when an NS RRset is added in the parent zone for the child origin. 756 Delegation inherently happens at a zone cut. The term is also 757 commonly a noun: the new zone that is created by the act of 758 delegating. 759 760 761 762 763 764 765 766 767 Hoffman, et al. Informational [Page 14] 768 RFC 7719 DNS Terminology December 2015 769 770 771 Glue records: "[Resource records] which are not part of the 772 authoritative data [of the zone], and are address resource records 773 for the [name servers in subzones]. These RRs are only necessary 774 if the name server's name is 'below' the cut, and are only used as 775 part of a referral response." Without glue "we could be faced 776 with the situation where the NS RRs tell us that in order to learn 777 a name server's address, we should contact the server using the 778 address we wish to learn." (Definition from [RFC1034], 779 Section 4.2.1) 780 781 A later definition is that glue "includes any record in a zone 782 file that is not properly part of that zone, including nameserver 783 records of delegated sub-zones (NS records), address records that 784 accompany those NS records (A, AAAA, etc), and any other stray 785 data that might appear" ([RFC2181], Section 5.4.1). Although glue 786 is sometimes used today with this wider definition in mind, the 787 context surrounding the [RFC2181] definition suggests it is 788 intended to apply to the use of glue within the document itself 789 and not necessarily beyond. 790 791 In-bailiwick: 792 793 (a) An adjective to describe a name server whose name is either 794 subordinate to or (rarely) the same as the zone origin. In- 795 bailiwick name servers require glue records in their parent zone 796 (using the first of the definitions of "glue records" in the 797 definition above). 798 799 (b) Data for which the server is either authoritative, or else 800 authoritative for an ancestor of the owner name. This sense of 801 the term normally is used when discussing the relevancy of glue 802 records in a response. For example, the server for the parent 803 zone "example.com" might reply with glue records for 804 "ns.child.example.com". Because the "child.example.com" zone is a 805 descendant of the "example.com" zone, the glue records are in- 806 bailiwick. 807 808 Out-of-bailiwick: The antonym of in-bailiwick. 809 810 Authoritative data: "All of the RRs attached to all of the nodes 811 from the top node of the zone down to leaf nodes or nodes above 812 cuts around the bottom edge of the zone." (Quoted from [RFC1034], 813 Section 4.2.1) It is noted that this definition might 814 inadvertently also include any NS records that appear in the zone, 815 even those that might not truly be authoritative because there are 816 identical NS RRs below the zone cut. This reveals the ambiguity 817 818 819 820 821 822 Hoffman, et al. Informational [Page 15] 823 RFC 7719 DNS Terminology December 2015 824 825 826 in the notion of authoritative data, because the parent-side NS 827 records authoritatively indicate the delegation, even though they 828 are not themselves authoritative data. 829 830 Root zone: The zone whose apex is the zero-length label. Also 831 sometimes called "the DNS root". 832 833 Empty non-terminals: "Domain names that own no resource records but 834 have subdomains that do." (Quoted from [RFC4592], Section 2.2.2.) 835 A typical example is in SRV records: in the name 836 "_sip._tcp.example.com", it is likely that "_tcp.example.com" has 837 no RRsets, but that "_sip._tcp.example.com" has (at least) an SRV 838 RRset. 839 840 Delegation-centric zone: A zone that consists mostly of delegations 841 to child zones. This term is used in contrast to a zone that 842 might have some delegations to child zones, but also has many data 843 resource records for the zone itself and/or for child zones. The 844 term is used in [RFC4956] and [RFC5155], but is not defined there. 845 846 Wildcard: [RFC1034] defined "wildcard", but in a way that turned out 847 to be confusing to implementers. Special treatment is given to 848 RRs with owner names starting with the label "*". "Such RRs are 849 called 'wildcards'. Wildcard RRs can be thought of as 850 instructions for synthesizing RRs." (Quoted from [RFC1034], 851 Section 4.3.3) For an extended discussion of wildcards, including 852 clearer definitions, see [RFC4592]. 853 854 Occluded name: "The addition of a delegation point via dynamic 855 update will render all subordinate domain names to be in a limbo, 856 still part of the zone, but not available to the lookup process. 857 The addition of a DNAME resource record has the same impact. The 858 subordinate names are said to be 'occluded'." (Quoted from 859 [RFC5936], Section 3.5) 860 861 Fast flux DNS: This "occurs when a domain is found in DNS using A 862 records to multiple IP addresses, each of which has a very short 863 Time-to-Live (TTL) value associated with it. This means that the 864 domain resolves to varying IP addresses over a short period of 865 time." (Quoted from [RFC6561], Section 1.1.5, with typo 866 corrected) It is often used to deliver malware. Because the 867 addresses change so rapidly, it is difficult to ascertain all the 868 hosts. It should be noted that the technique also works with AAAA 869 records, but such use is not frequently observed on the Internet 870 as of this writing. 871 872 873 874 875 876 877 Hoffman, et al. Informational [Page 16] 878 RFC 7719 DNS Terminology December 2015 879 880 881 7. Registration Model 882 883 Registry: The administrative operation of a zone that allows 884 registration of names within that zone. People often use this 885 term to refer only to those organizations that perform 886 registration in large delegation-centric zones (such as TLDs); but 887 formally, whoever decides what data goes into a zone is the 888 registry for that zone. This definition of "registry" is from a 889 DNS point of view; for some zones, the policies that determine 890 what can go in the zone are decided by superior zones and not the 891 registry operator. 892 893 Registrant: An individual or organization on whose behalf a name in 894 a zone is registered by the registry. In many zones, the registry 895 and the registrant may be the same entity, but in TLDs they often 896 are not. 897 898 Registrar: A service provider that acts as a go-between for 899 registrants and registries. Not all registrations require a 900 registrar, though it is common to have registrars involved in 901 registrations in TLDs. 902 903 EPP: The Extensible Provisioning Protocol (EPP), which is commonly 904 used for communication of registration information between 905 registries and registrars. EPP is defined in [RFC5730]. 906 907 WHOIS: A protocol specified in [RFC3912], often used for querying 908 registry databases. WHOIS data is frequently used to associate 909 registration data (such as zone management contacts) with domain 910 names. The term "WHOIS data" is often used as a synonym for the 911 registry database, even though that database may be served by 912 different protocols, particularly RDAP. The WHOIS protocol is 913 also used with IP address registry data. 914 915 RDAP: The Registration Data Access Protocol, defined in [RFC7480], 916 [RFC7481], [RFC7482], [RFC7483], [RFC7484], and [RFC7485]. The 917 RDAP protocol and data format are meant as a replacement for 918 WHOIS. 919 920 DNS operator: An entity responsible for running DNS servers. For a 921 zone's authoritative servers, the registrant may act as their own 922 DNS operator, or their registrar may do it on their behalf, or 923 they may use a third-party operator. For some zones, the registry 924 function is performed by the DNS operator plus other entities who 925 decide about the allowed contents of the zone. 926 927 928 929 930 931 932 Hoffman, et al. Informational [Page 17] 933 RFC 7719 DNS Terminology December 2015 934 935 936 8. General DNSSEC 937 938 Most DNSSEC terms are defined in [RFC4033], [RFC4034], [RFC4035], and 939 [RFC5155]. The terms that have caused confusion in the DNS community 940 are highlighted here. 941 942 DNSSEC-aware and DNSSEC-unaware: These two terms, which are used in 943 some RFCs, have not been formally defined. However, Section 2 of 944 [RFC4033] defines many types of resolvers and validators, 945 including "non-validating security-aware stub resolver", "non- 946 validating stub resolver", "security-aware name server", 947 "security-aware recursive name server", "security-aware resolver", 948 "security-aware stub resolver", and "security-oblivious 949 'anything'". (Note that the term "validating resolver", which is 950 used in some places in DNSSEC-related documents, is also not 951 defined.) 952 953 Signed zone: "A zone whose RRsets are signed and that contains 954 properly constructed DNSKEY, Resource Record Signature (RRSIG), 955 Next Secure (NSEC), and (optionally) DS records." (Quoted from 956 [RFC4033], Section 2.) It has been noted in other contexts that 957 the zone itself is not really signed, but all the relevant RRsets 958 in the zone are signed. Nevertheless, if a zone that should be 959 signed contains any RRsets that are not signed (or opted out), 960 those RRsets will be treated as bogus, so the whole zone needs to 961 be handled in some way. 962 963 It should also be noted that, since the publication of [RFC6840], 964 NSEC records are no longer required for signed zones: a signed 965 zone might include NSEC3 records instead. [RFC7129] provides 966 additional background commentary and some context for the NSEC and 967 NSEC3 mechanisms used by DNSSEC to provide authenticated denial- 968 of-existence responses. 969 970 Unsigned zone: Section 2 of [RFC4033] defines this as "a zone that 971 is not signed". Section 2 of [RFC4035] defines this as "A zone 972 that does not include these records [properly constructed DNSKEY, 973 Resource Record Signature (RRSIG), Next Secure (NSEC), and 974 (optionally) DS records] according to the rules in this section". 975 There is an important note at the end of Section 5.2 of [RFC4035] 976 that defines an additional situation in which a zone is considered 977 unsigned: "If the resolver does not support any of the algorithms 978 listed in an authenticated DS RRset, then the resolver will not be 979 able to verify the authentication path to the child zone. In this 980 case, the resolver SHOULD treat the child zone as if it were 981 unsigned." 982 983 984 985 986 987 Hoffman, et al. Informational [Page 18] 988 RFC 7719 DNS Terminology December 2015 989 990 991 NSEC: "The NSEC record allows a security-aware resolver to 992 authenticate a negative reply for either name or type non- 993 existence with the same mechanisms used to authenticate other DNS 994 replies." (Quoted from [RFC4033], Section 3.2.) In short, an 995 NSEC record provides authenticated denial of existence. 996 997 "The NSEC resource record lists two separate things: the next 998 owner name (in the canonical ordering of the zone) that contains 999 authoritative data or a delegation point NS RRset, and the set of 1000 RR types present at the NSEC RR's owner name." (Quoted from 1001 Section 4 of RFC 4034) 1002 1003 NSEC3: Like the NSEC record, the NSEC3 record also provides 1004 authenticated denial of existence; however, NSEC3 records mitigate 1005 against zone enumeration and support Opt-Out. NSEC3 resource 1006 records are defined in [RFC5155]. 1007 1008 Note that [RFC6840] says that [RFC5155] "is now considered part of 1009 the DNS Security Document Family as described by Section 10 of 1010 [RFC4033]". This means that some of the definitions from earlier 1011 RFCs that only talk about NSEC records should probably be 1012 considered to be talking about both NSEC and NSEC3. 1013 1014 Opt-out: "The Opt-Out Flag indicates whether this NSEC3 RR may cover 1015 unsigned delegations." (Quoted from [RFC5155], Section 18.104.22.168.) 1016 Opt-out tackles the high costs of securing a delegation to an 1017 insecure zone. When using Opt-Out, names that are an insecure 1018 delegation (and empty non-terminals that are only derived from 1019 insecure delegations) don't require an NSEC3 record or its 1020 corresponding RRSIG records. Opt-Out NSEC3 records are not able 1021 to prove or deny the existence of the insecure delegations. 1022 (Adapted from [RFC7129], Section 5.1) 1023 1024 Zone enumeration: "The practice of discovering the full content of a 1025 zone via successive queries." (Quoted from [RFC5155], 1026 Section 1.3.) This is also sometimes called "zone walking". Zone 1027 enumeration is different from zone content guessing where the 1028 guesser uses a large dictionary of possible labels and sends 1029 successive queries for them, or matches the contents of NSEC3 1030 records against such a dictionary. 1031 1032 Key signing key (KSK): DNSSEC keys that "only sign the apex DNSKEY 1033 RRset in a zone."(Quoted from [RFC6781], Section 3.1) 1034 1035 1036 1037 1038 1039 1040 1041 1042 Hoffman, et al. Informational [Page 19] 1043 RFC 7719 DNS Terminology December 2015 1044 1045 1046 Zone signing key (ZSK): "DNSSEC keys that can be used to sign all 1047 the RRsets in a zone that require signatures, other than the apex 1048 DNSKEY RRset." (Quoted from [RFC6781], Section 3.1) Note that the 1049 roles KSK and ZSK are not mutually exclusive: a single key can be 1050 both KSK and ZSK at the same time. Also note that a ZSK is 1051 sometimes used to sign the apex DNSKEY RRset. 1052 1053 Combined signing key (CSK): "In cases where the differentiation 1054 between the KSK and ZSK is not made, i.e., where keys have the 1055 role of both KSK and ZSK, we talk about a Single-Type Signing 1056 Scheme." (Quoted from [RFC6781], Section 3.1) This is sometimes 1057 called a "combined signing key" or CSK. It is operational 1058 practice, not protocol, that determines whether a particular key 1059 is a ZSK, a KSK, or a CSK. 1060 1061 Secure Entry Point (SEP): A flag in the DNSKEY RDATA that "can be 1062 used to distinguish between keys that are intended to be used as 1063 the secure entry point into the zone when building chains of 1064 trust, i.e., they are (to be) pointed to by parental DS RRs or 1065 configured as a trust anchor. Therefore, it is suggested that the 1066 SEP flag be set on keys that are used as KSKs and not on keys that 1067 are used as ZSKs, while in those cases where a distinction between 1068 a KSK and ZSK is not made (i.e., for a Single-Type Signing 1069 Scheme), it is suggested that the SEP flag be set on all keys." 1070 (Quoted from [RFC6781], Section 3.2.3.) Note that the SEP flag is 1071 only a hint, and its presence or absence may not be used to 1072 disqualify a given DNSKEY RR from use as a KSK or ZSK during 1073 validation. 1074 1075 DNSSEC Policy (DP): A statement that "sets forth the security 1076 requirements and standards to be implemented for a DNSSEC-signed 1077 zone." (Quoted from [RFC6841], Section 2) 1078 1079 DNSSEC Practice Statement (DPS): "A practices disclosure document 1080 that may support and be a supplemental document to the DNSSEC 1081 Policy (if such exists), and it states how the management of a 1082 given zone implements procedures and controls at a high level." 1083 (Quoted from [RFC6841], Section 2) 1084 1085 9. DNSSEC States 1086 1087 A validating resolver can determine that a response is in one of four 1088 states: secure, insecure, bogus, or indeterminate. These states are 1089 defined in [RFC4033] and [RFC4035], although the two definitions 1090 differ a bit. This document makes no effort to reconcile the two 1091 definitions, and takes no position as to whether they need to be 1092 reconciled. 1093 1094 1095 1096 1097 Hoffman, et al. Informational [Page 20] 1098 RFC 7719 DNS Terminology December 2015 1099 1100 1101 Section 5 of [RFC4033] says: 1102 1103 A validating resolver can determine the following 4 states: 1104 1105 Secure: The validating resolver has a trust anchor, has a chain 1106 of trust, and is able to verify all the signatures in the 1107 response. 1108 1109 Insecure: The validating resolver has a trust anchor, a chain 1110 of trust, and, at some delegation point, signed proof of the 1111 non-existence of a DS record. This indicates that subsequent 1112 branches in the tree are provably insecure. A validating 1113 resolver may have a local policy to mark parts of the domain 1114 space as insecure. 1115 1116 Bogus: The validating resolver has a trust anchor and a secure 1117 delegation indicating that subsidiary data is signed, but 1118 the response fails to validate for some reason: missing 1119 signatures, expired signatures, signatures with unsupported 1120 algorithms, data missing that the relevant NSEC RR says 1121 should be present, and so forth. 1122 1123 Indeterminate: There is no trust anchor that would indicate that a 1124 specific portion of the tree is secure. This is the default 1125 operation mode. 1126 1127 Section 4.3 of [RFC4035] says: 1128 1129 A security-aware resolver must be able to distinguish between four 1130 cases: 1131 1132 Secure: An RRset for which the resolver is able to build a chain 1133 of signed DNSKEY and DS RRs from a trusted security anchor to 1134 the RRset. In this case, the RRset should be signed and is 1135 subject to signature validation, as described above. 1136 1137 Insecure: An RRset for which the resolver knows that it has no 1138 chain of signed DNSKEY and DS RRs from any trusted starting 1139 point to the RRset. This can occur when the target RRset lies 1140 in an unsigned zone or in a descendent [sic] of an unsigned 1141 zone. In this case, the RRset may or may not be signed, but 1142 the resolver will not be able to verify the signature. 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 Hoffman, et al. Informational [Page 21] 1153 RFC 7719 DNS Terminology December 2015 1154 1155 1156 Bogus: An RRset for which the resolver believes that it ought to 1157 be able to establish a chain of trust but for which it is 1158 unable to do so, either due to signatures that for some reason 1159 fail to validate or due to missing data that the relevant 1160 DNSSEC RRs indicate should be present. This case may indicate 1161 an attack but may also indicate a configuration error or some 1162 form of data corruption. 1163 1164 Indeterminate: An RRset for which the resolver is not able to 1165 determine whether the RRset should be signed, as the resolver 1166 is not able to obtain the necessary DNSSEC RRs. This can occur 1167 when the security-aware resolver is not able to contact 1168 security-aware name servers for the relevant zones. 1169 1170 10. Security Considerations 1171 1172 These definitions do not change any security considerations for the 1173 DNS. 1174 1175 11. References 1176 1177 11.1. Normative References 1178 1179 [RFC882] Mockapetris, P., "Domain names: Concepts and facilities", 1180 RFC 882, DOI 10.17487/RFC0882, November 1983, 1181 <http://www.rfc-editor.org/info/rfc882>. 1182 1183 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1184 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1185 <http://www.rfc-editor.org/info/rfc1034>. 1186 1187 [RFC1035] Mockapetris, P., "Domain names - implementation and 1188 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 1189 November 1987, <http://www.rfc-editor.org/info/rfc1035>. 1190 1191 [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - 1192 Application and Support", STD 3, RFC 1123, 1193 DOI 10.17487/RFC1123, October 1989, 1194 <http://www.rfc-editor.org/info/rfc1123>. 1195 1196 [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone 1197 Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996, 1198 August 1996, <http://www.rfc-editor.org/info/rfc1996>. 1199 1200 [RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound, 1201 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 1202 RFC 2136, DOI 10.17487/RFC2136, April 1997, 1203 <http://www.rfc-editor.org/info/rfc2136>. 1204 1205 1206 1207 Hoffman, et al. Informational [Page 22] 1208 RFC 7719 DNS Terminology December 2015 1209 1210 1211 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS 1212 Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997, 1213 <http://www.rfc-editor.org/info/rfc2181>. 1214 1215 [RFC2182] Elz, R., Bush, R., Bradner, S., and M. Patton, "Selection 1216 and Operation of Secondary DNS Servers", BCP 16, RFC 2182, 1217 DOI 10.17487/RFC2182, July 1997, 1218 <http://www.rfc-editor.org/info/rfc2182>. 1219 1220 [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS 1221 NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998, 1222 <http://www.rfc-editor.org/info/rfc2308>. 1223 1224 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1225 Rose, "DNS Security Introduction and Requirements", 1226 RFC 4033, DOI 10.17487/RFC4033, March 2005, 1227 <http://www.rfc-editor.org/info/rfc4033>. 1228 1229 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1230 Rose, "Resource Records for the DNS Security Extensions", 1231 RFC 4034, DOI 10.17487/RFC4034, March 2005, 1232 <http://www.rfc-editor.org/info/rfc4034>. 1233 1234 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1235 Rose, "Protocol Modifications for the DNS Security 1236 Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005, 1237 <http://www.rfc-editor.org/info/rfc4035>. 1238 1239 [RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name 1240 System", RFC 4592, DOI 10.17487/RFC4592, July 2006, 1241 <http://www.rfc-editor.org/info/rfc4592>. 1242 1243 [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS 1244 Security (DNSSEC) Hashed Authenticated Denial of 1245 Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008, 1246 <http://www.rfc-editor.org/info/rfc5155>. 1247 1248 [RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)", 1249 STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009, 1250 <http://www.rfc-editor.org/info/rfc5730>. 1251 1252 [RFC5936] Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol 1253 (AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010, 1254 <http://www.rfc-editor.org/info/rfc5936>. 1255 1256 1257 1258 1259 1260 1261 1262 Hoffman, et al. Informational [Page 23] 1263 RFC 7719 DNS Terminology December 2015 1264 1265 1266 [RFC6561] Livingood, J., Mody, N., and M. O'Reirdan, 1267 "Recommendations for the Remediation of Bots in ISP 1268 Networks", RFC 6561, DOI 10.17487/RFC6561, March 2012, 1269 <http://www.rfc-editor.org/info/rfc6561>. 1270 1271 [RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the 1272 DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012, 1273 <http://www.rfc-editor.org/info/rfc6672>. 1274 1275 [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC 1276 Operational Practices, Version 2", RFC 6781, 1277 DOI 10.17487/RFC6781, December 2012, 1278 <http://www.rfc-editor.org/info/rfc6781>. 1279 1280 [RFC6840] Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and 1281 Implementation Notes for DNS Security (DNSSEC)", RFC 6840, 1282 DOI 10.17487/RFC6840, February 2013, 1283 <http://www.rfc-editor.org/info/rfc6840>. 1284 1285 [RFC6841] Ljunggren, F., Eklund Lowinder, AM., and T. Okubo, "A 1286 Framework for DNSSEC Policies and DNSSEC Practice 1287 Statements", RFC 6841, DOI 10.17487/RFC6841, January 2013, 1288 <http://www.rfc-editor.org/info/rfc6841>. 1289 1290 [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms 1291 for DNS (EDNS(0))", STD 75, RFC 6891, 1292 DOI 10.17487/RFC6891, April 2013, 1293 <http://www.rfc-editor.org/info/rfc6891>. 1294 1295 [RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating 1296 DNSSEC Delegation Trust Maintenance", RFC 7344, 1297 DOI 10.17487/RFC7344, September 2014, 1298 <http://www.rfc-editor.org/info/rfc7344>. 1299 1300 11.2. Informative References 1301 1302 [DBOUND] IETF, "Domain Boundaries (dbound) Working Group", 2015, 1303 <https://datatracker.ietf.org/wg/dbound/charter/>. 1304 1305 [RFC819] Su, Z. and J. Postel, "The Domain Naming Convention for 1306 Internet User Applications", RFC 819, 1307 DOI 10.17487/RFC0819, August 1982, 1308 <http://www.rfc-editor.org/info/rfc819>. 1309 1310 [RFC952] Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet 1311 host table specification", RFC 952, DOI 10.17487/RFC0952, 1312 October 1985, <http://www.rfc-editor.org/info/rfc952>. 1313 1314 1315 1316 1317 Hoffman, et al. Informational [Page 24] 1318 RFC 7719 DNS Terminology December 2015 1319 1320 1321 [RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995, 1322 DOI 10.17487/RFC1995, August 1996, 1323 <http://www.rfc-editor.org/info/rfc1995>. 1324 1325 [RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912, 1326 DOI 10.17487/RFC3912, September 2004, 1327 <http://www.rfc-editor.org/info/rfc3912>. 1328 1329 [RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices", 1330 RFC 4641, DOI 10.17487/RFC4641, September 2006, 1331 <http://www.rfc-editor.org/info/rfc4641>. 1332 1333 [RFC4697] Larson, M. and P. Barber, "Observed DNS Resolution 1334 Misbehavior", BCP 123, RFC 4697, DOI 10.17487/RFC4697, 1335 October 2006, <http://www.rfc-editor.org/info/rfc4697>. 1336 1337 [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast 1338 Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786, 1339 December 2006, <http://www.rfc-editor.org/info/rfc4786>. 1340 1341 [RFC4956] Arends, R., Kosters, M., and D. Blacka, "DNS Security 1342 (DNSSEC) Opt-In", RFC 4956, DOI 10.17487/RFC4956, July 1343 2007, <http://www.rfc-editor.org/info/rfc4956>. 1344 1345 [RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines", 1346 BCP 152, RFC 5625, DOI 10.17487/RFC5625, August 2009, 1347 <http://www.rfc-editor.org/info/rfc5625>. 1348 1349 [RFC5890] Klensin, J., "Internationalized Domain Names for 1350 Applications (IDNA): Definitions and Document Framework", 1351 RFC 5890, DOI 10.17487/RFC5890, August 2010, 1352 <http://www.rfc-editor.org/info/rfc5890>. 1353 1354 [RFC5891] Klensin, J., "Internationalized Domain Names in 1355 Applications (IDNA): Protocol", RFC 5891, 1356 DOI 10.17487/RFC5891, August 2010, 1357 <http://www.rfc-editor.org/info/rfc5891>. 1358 1359 [RFC5892] Faltstrom, P., Ed., "The Unicode Code Points and 1360 Internationalized Domain Names for Applications (IDNA)", 1361 RFC 5892, DOI 10.17487/RFC5892, August 2010, 1362 <http://www.rfc-editor.org/info/rfc5892>. 1363 1364 [RFC5893] Alvestrand, H., Ed. and C. Karp, "Right-to-Left Scripts 1365 for Internationalized Domain Names for Applications 1366 (IDNA)", RFC 5893, DOI 10.17487/RFC5893, August 2010, 1367 <http://www.rfc-editor.org/info/rfc5893>. 1368 1369 1370 1371 1372 Hoffman, et al. Informational [Page 25] 1373 RFC 7719 DNS Terminology December 2015 1374 1375 1376 [RFC5894] Klensin, J., "Internationalized Domain Names for 1377 Applications (IDNA): Background, Explanation, and 1378 Rationale", RFC 5894, DOI 10.17487/RFC5894, August 2010, 1379 <http://www.rfc-editor.org/info/rfc5894>. 1380 1381 [RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on 1382 Encodings for Internationalized Domain Names", RFC 6055, 1383 DOI 10.17487/RFC6055, February 2011, 1384 <http://www.rfc-editor.org/info/rfc6055>. 1385 1386 [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, 1387 DOI 10.17487/RFC6265, April 2011, 1388 <http://www.rfc-editor.org/info/rfc6265>. 1389 1390 [RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in 1391 Internationalization in the IETF", BCP 166, RFC 6365, 1392 DOI 10.17487/RFC6365, September 2011, 1393 <http://www.rfc-editor.org/info/rfc6365>. 1394 1395 [RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of 1396 Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129, 1397 February 2014, <http://www.rfc-editor.org/info/rfc7129>. 1398 1399 [RFC7480] Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the 1400 Registration Data Access Protocol (RDAP)", RFC 7480, 1401 DOI 10.17487/RFC7480, March 2015, 1402 <http://www.rfc-editor.org/info/rfc7480>. 1403 1404 [RFC7481] Hollenbeck, S. and N. Kong, "Security Services for the 1405 Registration Data Access Protocol (RDAP)", RFC 7481, 1406 DOI 10.17487/RFC7481, March 2015, 1407 <http://www.rfc-editor.org/info/rfc7481>. 1408 1409 [RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access 1410 Protocol (RDAP) Query Format", RFC 7482, 1411 DOI 10.17487/RFC7482, March 2015, 1412 <http://www.rfc-editor.org/info/rfc7482>. 1413 1414 [RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the 1415 Registration Data Access Protocol (RDAP)", RFC 7483, 1416 DOI 10.17487/RFC7483, March 2015, 1417 <http://www.rfc-editor.org/info/rfc7483>. 1418 1419 [RFC7484] Blanchet, M., "Finding the Authoritative Registration Data 1420 (RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March 1421 2015, <http://www.rfc-editor.org/info/rfc7484>. 1422 1423 1424 1425 1426 1427 Hoffman, et al. Informational [Page 26] 1428 RFC 7719 DNS Terminology December 2015 1429 1430 1431 [RFC7485] Zhou, L., Kong, N., Shen, S., Sheng, S., and A. Servin, 1432 "Inventory and Analysis of WHOIS Registration Objects", 1433 RFC 7485, DOI 10.17487/RFC7485, March 2015, 1434 <http://www.rfc-editor.org/info/rfc7485>. 1435 1436 Acknowledgements 1437 1438 The authors gratefully acknowledge all of the authors of DNS-related 1439 RFCs that proceed this one. Comments from Tony Finch, Stephane 1440 Bortzmeyer, Niall O'Reilly, Colm MacCarthaigh, Ray Bellis, John 1441 Kristoff, Robert Edmonds, Paul Wouters, Shumon Huque, Paul Ebersman, 1442 David Lawrence, Matthijs Mekking, Casey Deccio, Bob Harold, Ed Lewis, 1443 John Klensin, David Black, and many others in the DNSOP Working Group 1444 have helped shape this document. 1445 1446 Authors' Addresses 1447 1448 Paul Hoffman 1449 ICANN 1450 1451 Email: email@example.com 1452 1453 1454 Andrew Sullivan 1455 Dyn 1456 150 Dow Street, Tower 2 1457 Manchester, NH 03101 1458 United States 1459 1460 Email: firstname.lastname@example.org 1461 1462 1463 Kazunori Fujiwara 1464 Japan Registry Services Co., Ltd. 1465 Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda 1466 Chiyoda-ku, Tokyo 101-0065 1467 Japan 1468 1469 Phone: +81 3 5215 8451 1470 Email: email@example.com 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 Hoffman, et al. Informational [Page 27] 1483
CNAME: "It is traditional to refer to the owner of a CNAME record as 'a CNAME'. This is unfortunate, as 'CNAME' is an abbreviation of 'canonical name', and the owner of a CNAME record is most certainly not a canonical name." (Quoted from [RFC2181], Section 10.1.1)
CNAME: "It is traditional to refer to the label of a CNAME record as 'a CNAME'. This is unfortunate, as 'CNAME' is an abbreviation of 'canonical name', and the label of a CNAME record is an alias, not a canonical name." (Quoted from [RFC2181], Section 10.1.1)
Incorrect quote from RFC 2181. --VERIFIER NOTES-- Not a technical erratum. is corrected already in https://tools.ietf.org/html/draft-ietf-dnsop-terminology-bis-05 which should be examined for consistency