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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Hoffman 3 Internet-Draft ICANN 4 Obsoletes: 7719 (if approved) A. Sullivan 5 Intended status: Best Current Practice Dyn 6 Expires: January 9, 2017 K. Fujiwara 7 JPRS 8 July 8, 2016 10 DNS Terminology 11 draft-ietf-dnsop-terminology-bis-01 13 Abstract 15 The DNS is defined in literally dozens of different RFCs. The 16 terminology used by implementers and developers of DNS protocols, and 17 by operators of DNS systems, has sometimes changed in the decades 18 since the DNS was first defined. This document gives current 19 definitions for many of the terms used in the DNS in a single 20 document. 22 This document will be the successor to RFC 7719. It will update many 23 of the original RFCs. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on January 9, 2017. 42 Copyright Notice 44 Copyright (c) 2016 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 3. DNS Header and Response Codes . . . . . . . . . . . . . . . . 6 62 4. Resource Records . . . . . . . . . . . . . . . . . . . . . . 7 63 5. DNS Servers and Clients . . . . . . . . . . . . . . . . . . . 9 64 6. Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 65 7. Registration Model . . . . . . . . . . . . . . . . . . . . . 17 66 8. General DNSSEC . . . . . . . . . . . . . . . . . . . . . . . 18 67 9. DNSSEC States . . . . . . . . . . . . . . . . . . . . . . . . 21 68 10. Security Considerations . . . . . . . . . . . . . . . . . . . 23 69 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 70 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 71 12.1. Normative References . . . . . . . . . . . . . . . . . . 23 72 12.2. Informative References . . . . . . . . . . . . . . . . . 26 73 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 29 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 76 1. Introduction 78 The Domain Name System (DNS) is a simple query-response protocol 79 whose messages in both directions have the same format. The protocol 80 and message format are defined in [RFC1034] and [RFC1035]. These 81 RFCs defined some terms, but later documents defined others. Some of 82 the terms from RFCs 1034 and 1035 now have somewhat different 83 meanings than they did in 1987. 85 This document collects a wide variety of DNS-related terms. Some of 86 them have been precisely defined in earlier RFCs, some have been 87 loosely defined in earlier RFCs, and some are not defined in any 88 earlier RFC at all. 90 Most of the definitions here are the consensus definition of the DNS 91 community -- both protocol developers and operators. Some of the 92 definitions differ from earlier RFCs, and those differences are 93 noted. In this document, where the consensus definition is the same 94 as the one in an RFC, that RFC is quoted. Where the consensus 95 definition has changed somewhat, the RFC is mentioned but the new 96 stand-alone definition is given. During the progression of this 97 draft, it is expected that, where the consensus definition is 98 different than the RFC, the RFC will then be updated by this 99 document. 101 It is important to note that, during the development of this 102 document, it became clear that some DNS-related terms are interpreted 103 quite differently by different DNS experts. Further, some terms that 104 are defined in early DNS RFCs now have definitions that are generally 105 agreed to, but that are different from the original definitions. 106 Therefore, this document is a substantial revision to [RFC7719]. 108 The terms are organized loosely by topic. Some definitions are for 109 new terms for things that are commonly talked about in the DNS 110 community but that never had terms defined for them. 112 Other organizations sometimes define DNS-related terms their own way. 113 For example, the W3C defines "domain" at 114 https://specs.webplatform.org/url/webspecs/develop/. 116 Note that there is no single consistent definition of "the DNS". It 117 can be considered to be some combination of the following: a commonly 118 used naming scheme for objects on the Internet; a distributed 119 database representing the names and certain properties of these 120 objects; an architecture providing distributed maintenance, 121 resilience, and loose coherency for this database; and a simple 122 query-response protocol (as mentioned below) implementing this 123 architecture. 125 Capitalization in DNS terms is often inconsistent among RFCs and 126 various DNS practitioners. The capitalization used in this document 127 is a best guess at current practices, and is not meant to indicate 128 that other capitalization styles are wrong or archaic. In some 129 cases, multiple styles of capitalization are used for the same term 130 due to quoting from different RFCs. 132 2. Names 134 Domain name: Section 3.1 of [RFC1034] talks of "the domain name 135 space" as a tree structure. "Each node has a label, which is zero 136 to 63 octets in length. ... The domain name of a node is the list 137 of the labels on the path from the node to the root of the tree. 138 ... To simplify implementations, the total number of octets that 139 represent a domain name (i.e., the sum of all label octets and 140 label lengths) is limited to 255." Any label in a domain name can 141 contain any octet value. 143 The term "domain name" was defined before [RFC1034], most likely 144 in [RFC0799], which precedes the existence of the DNS. In this 145 document, domain names are only described in terms of the DNS. 147 Fully qualified domain name (FQDN): This is often just a clear way 148 of saying the same thing as "domain name of a node", as outlined 149 above. However, the term is ambiguous. Strictly speaking, a 150 fully qualified domain name would include every label, including 151 the final, zero-length label of the root: such a name would be 152 written "www.example.net." (note the terminating dot). But 153 because every name eventually shares the common root, names are 154 often written relative to the root (such as "www.example.net") and 155 are still called "fully qualified". This term first appeared in 156 [RFC0819]. In this document, names are often written relative to 157 the root. 159 The need for the term "fully qualified domain name" comes from the 160 existence of partially qualified domain names, which are names 161 where some of the right-most names are left off and are understood 162 only by context. 164 Label: The identifier of an individual node in the sequence of nodes 165 identified by a fully qualified domain name. 167 Host name: This term and its equivalent, "hostname", have been 168 widely used but are not defined in [RFC1034], [RFC1035], 169 [RFC1123], or [RFC2181]. The DNS was originally deployed into the 170 Host Tables environment as outlined in [RFC0952], and it is likely 171 that the term followed informally from the definition there. Over 172 time, the definition seems to have shifted. "Host name" is often 173 meant to be a domain name that follows the rules in Section 3.5 of 174 [RFC1034], the "preferred name syntax". Note that any label in a 175 domain name can contain any octet value; hostnames are generally 176 considered to be domain names where every label follows the rules 177 in the "preferred name syntax", with the amendment that labels can 178 start with ASCII digits (this amendment comes from Section 2.1 of 179 [RFC1123]). 181 People also sometimes use the term hostname to refer to just the 182 first label of an FQDN, such as "printer" in 183 "printer.admin.example.com". (Sometimes this is formalized in 184 configuration in operating systems.) In addition, people 185 sometimes use this term to describe any name that refers to a 186 machine, and those might include labels that do not conform to the 187 "preferred name syntax". 189 TLD: A Top-Level Domain, meaning a zone that is one layer below the 190 root, such as "com" or "jp". There is nothing special, from the 191 point of view of the DNS, about TLDs. Most of them are also 192 delegation-centric zones, and there are significant policy issues 193 around their operation. TLDs are often divided into sub-groups 194 such as Country Code Top-Level Domains (ccTLDs), Generic Top-Level 195 Domains (gTLDs), and others; the division is a matter of policy, 196 and beyond the scope of this document. 198 IDN: The common abbreviation for "Internationalized Domain Name". 199 The IDNA protocol is the standard mechanism for handling domain 200 names with non-ASCII characters in applications in the DNS. The 201 current standard, normally called "IDNA2008", is defined in 202 [RFC5890], [RFC5891], [RFC5892], [RFC5893], and [RFC5894]. These 203 documents define many IDN-specific terms such as "LDH label", 204 "A-label", and "U-label". [RFC6365] defines more terms that 205 relate to internationalization (some of which relate to IDNs), and 206 [RFC6055] has a much more extensive discussion of IDNs, including 207 some new terminology. 209 Subdomain: "A domain is a subdomain of another domain if it is 210 contained within that domain. This relationship can be tested by 211 seeing if the subdomain's name ends with the containing domain's 212 name." (Quoted from [RFC1034], Section 3.1). For example, in the 213 host name "nnn.mmm.example.com", both "mmm.example.com" and 214 "nnn.mmm.example.com" are subdomains of "example.com". 216 Alias: The owner of a CNAME resource record, or a subdomain of the 217 owner of a DNAME resource record [RFC6672]. See also "canonical 218 name". 220 Canonical name: A CNAME resource record "identifies its owner name 221 as an alias, and specifies the corresponding canonical name in the 222 RDATA section of the RR." (Quoted from [RFC1034], Section 3.6.2) 223 This usage of the word "canonical" is related to the mathematical 224 concept of "canonical form". 226 CNAME: "It is traditional to refer to the owner of a CNAME record as 227 'a CNAME'. This is unfortunate, as 'CNAME' is an abbreviation of 228 'canonical name', and the owner of a CNAME record is an alias, not 229 a canonical name." (Quoted from [RFC2181], Section 10.1.1) 231 Public suffix: "A domain that is controlled by a public registry." 232 (Quoted from [RFC6265], Section 5.3) A common definition for this 233 term is a domain under which subdomains can be registered, and on 234 which HTTP cookies ([RFC6265]) should not be set. There is no 235 indication in a domain name whether it is a public suffix; that 236 can only be determined by outside means. In fact, both a domain 237 and a subdomain of that domain can be public suffixes. At the 238 time this document is published, the IETF DBOUND Working Group 239 [DBOUND] is dealing with issues concerning public suffixes. 241 There is nothing inherent in a domain name to indicate whether it 242 is a public suffix. One resource for identifying public suffixes 243 is the Public Suffix List (PSL) maintained by Mozilla 244 (http://publicsuffix.org/). 246 For example, at the time this document is published, the "com.au" 247 domain is listed as a public suffix in the PSL. (Note that this 248 example might change in the future.) 250 Note that the term "public suffix" is controversial in the DNS 251 community for many reasons, and may be significantly changed in 252 the future. One example of the difficulty of calling a domain a 253 public suffix is that designation can change over time as the 254 registration policy for the zone changes, such as the case of the 255 "uk" TLD around the time this document is published. 257 3. DNS Header and Response Codes 259 The header of a DNS message is its first 12 octets. Many of the 260 fields and flags in the header diagram in Sections 4.1.1 through 261 4.1.3 of [RFC1035] are referred to by their names in that diagram. 262 For example, the response codes are called "RCODEs", the data for a 263 record is called the "RDATA", and the authoritative answer bit is 264 often called "the AA flag" or "the AA bit". 266 Some of response codes that are defined in [RFC1035] have acquired 267 their own shorthand names. Some common response code names that 268 appear without reference to the numeric value are "FORMERR", 269 "SERVFAIL", and "NXDOMAIN" (the latter of which is also referred to 270 as "Name Error"). All of the RCODEs are listed at 271 http://www.iana.org/assignments/dns-parameters, although that site 272 uses mixed-case capitalization, while most documents use all-caps. 274 NODATA: "A pseudo RCODE which indicates that the name is valid for 275 the given class, but there are no records of the given type. A 276 NODATA response has to be inferred from the answer." (Quoted from 277 [RFC2308], Section 1.) "NODATA is indicated by an answer with the 278 RCODE set to NOERROR and no relevant answers in the answer 279 section. The authority section will contain an SOA record, or 280 there will be no NS records there." (Quoted from [RFC2308], 281 Section 2.2.) Note that referrals have a similar format to NODATA 282 replies; [RFC2308] explains how to distinguish them. 284 The term "NXRRSET" is sometimes used as a synonym for NODATA. 285 However, this is a mistake, given that NXRRSET is a specific error 286 code defined in [RFC2136]. 288 Negative response: A response that indicates that a particular RRset 289 does not exist, or whose RCODE indicates the nameserver cannot 290 answer. Sections 2 and 7 of [RFC2308] describe the types of 291 negative responses in detail. 293 Referrals: Data from the authority section of a non-authoritative 294 answer. [RFC1035] Section 2.1 defines "authoritative" data. 295 However, referrals at zone cuts (defined in Section 6) are not 296 authoritative. Referrals may be zone cut NS resource records and 297 their glue records. NS records on the parent side of a zone cut 298 are an authoritative delegation, but are normally not treated as 299 authoritative data. In general, a referral is a way for a server 300 to send an answer saying that the server does not know the answer, 301 but knows where the query should be directed in order to get an 302 answer. Historically, many authoritative servers answered with a 303 referral to the root zone when queried for a name for which they 304 were not authoritative, but this practice has declined. 306 4. Resource Records 308 RR: An acronym for resource record. ([RFC1034], Section 3.6.) 310 RRset: A set of resource records with the same label, class and 311 type, but with different data. (Definition from [RFC2181]) Also 312 spelled RRSet in some documents. As a clarification, "same label" 313 in this definition means "same owner name". In addition, 314 [RFC2181] states that "the TTLs of all RRs in an RRSet must be the 315 same". (This definition is definitely not the same as "the 316 response one gets to a query for QTYPE=ANY", which is an 317 unfortunate misunderstanding.) 319 EDNS: The extension mechanisms for DNS, defined in [RFC6891]. 320 Sometimes called "EDNS0" or "EDNS(0)" to indicate the version 321 number. EDNS allows DNS clients and servers to specify message 322 sizes larger than the original 512 octet limit, to expand the 323 response code space, and potentially to carry additional options 324 that affect the handling of a DNS query. 326 OPT: A pseudo-RR (sometimes called a "meta-RR") that is used only to 327 contain control information pertaining to the question-and-answer 328 sequence of a specific transaction. (Definition from [RFC6891], 329 Section 6.1.1) It is used by EDNS. 331 Owner: The domain name where a RR is found ([RFC1034], Section 3.6). 332 Often appears in the term "owner name". 334 SOA field names: DNS documents, including the definitions here, 335 often refer to the fields in the RDATA of an SOA resource record 336 by field name. Those fields are defined in Section 3.3.13 of 337 [RFC1035]. The names (in the order they appear in the SOA RDATA) 338 are MNAME, RNAME, SERIAL, REFRESH, RETRY, EXPIRE, and MINIMUM. 339 Note that the meaning of MINIMUM field is updated in Section 4 of 340 [RFC2308]; the new definition is that the MINIMUM field is only 341 "the TTL to be used for negative responses". This document tends 342 to use field names instead of terms that describe the fields. 344 TTL: The maximum "time to live" of a resource record. "A TTL value 345 is an unsigned number, with a minimum value of 0, and a maximum 346 value of 2147483647. That is, a maximum of 2^31 - 1. When 347 transmitted, the TTL is encoded in the less significant 31 bits of 348 the 32 bit TTL field, with the most significant, or sign, bit set 349 to zero." (Quoted from [RFC2181], Section 8) (Note that [RFC1035] 350 erroneously stated that this is a signed integer; that was fixed 351 by [RFC2181].) 353 The TTL "specifies the time interval that the resource record may 354 be cached before the source of the information should again be 355 consulted". (Quoted from [RFC1035], Section 3.2.1) Also: "the 356 time interval (in seconds) that the resource record may be cached 357 before it should be discarded". (Quoted from [RFC1035], 358 Section 4.1.3). Despite being defined for a resource record, the 359 TTL of every resource record in an RRset is required to be the 360 same ([RFC2181], Section 5.2). 362 The reason that the TTL is the maximum time to live is that a 363 cache operator might decide to shorten the time to live for 364 operational purposes, such as if there is a policy to disallow TTL 365 values over a certain number. Also, if a value is flushed from 366 the cache when its value is still positive, the value effectively 367 becomes zero. Some servers are known to ignore the TTL on some 368 RRsets (such as when the authoritative data has a very short TTL) 369 even though this is against the advice in RFC 1035. 371 There is also the concept of a "default TTL" for a zone, which can 372 be a configuration parameter in the server software. This is 373 often expressed by a default for the entire server, and a default 374 for a zone using the $TTL directive in a zone file. The $TTL 375 directive was added to the master file format by [RFC2308]. 377 Class independent: A resource record type whose syntax and semantics 378 are the same for every DNS class. A resource record type that is 379 not class independent has different meanings depending on the DNS 380 class of the record, or the meaning is undefined for classes other 381 than IN (class 1, the Internet). 383 5. DNS Servers and Clients 385 This section defines the terms used for the systems that act as DNS 386 clients, DNS servers, or both. 388 Resolver: A program "that extract[s] information from name servers 389 in response to client requests." (Quoted from [RFC1034], 390 Section 2.4) "The resolver is located on the same machine as the 391 program that requests the resolver's services, but it may need to 392 consult name servers on other hosts." (Quoted from [RFC1034], 393 Section 5.1) A resolver performs queries for a name, type, and 394 class, and receives answers. The logical function is called 395 "resolution". In practice, the term is usually referring to some 396 specific type of resolver (some of which are defined below), and 397 understanding the use of the term depends on understanding the 398 context. 400 Stub resolver: A resolver that cannot perform all resolution itself. 401 Stub resolvers generally depend on a recursive resolver to 402 undertake the actual resolution function. Stub resolvers are 403 discussed but never fully defined in Section 5.3.1 of [RFC1034]. 404 They are fully defined in Section 6.1.3.1 of [RFC1123]. 406 Iterative mode: A resolution mode of a server that receives DNS 407 queries and responds with a referral to another server. 408 Section 2.3 of [RFC1034] describes this as "The server refers the 409 client to another server and lets the client pursue the query". A 410 resolver that works in iterative mode is sometimes called an 411 "iterative resolver". 413 Recursive mode: A resolution mode of a server that receives DNS 414 queries and either responds to those queries from a local cache or 415 sends queries to other servers in order to get the final answers 416 to the original queries. Section 2.3 of [RFC1034] describes this 417 as "The first server pursues the query for the client at another 418 server". A server operating in recursive mode may be thought of 419 as having a name server side (which is what answers the query) and 420 a resolver side (which performs the resolution function). Systems 421 operating in this mode are commonly called "recursive servers". 422 Sometimes they are called "recursive resolvers". While strictly 423 the difference between these is that one of them sends queries to 424 another recursive server and the other does not, in practice it is 425 not possible to know in advance whether the server that one is 426 querying will also perform recursion; both terms can be observed 427 in use interchangeably. 429 Full resolver: This term is used in [RFC1035], but it is not defined 430 there. RFC 1123 defines a "full-service resolver" that may or may 431 not be what was intended by "full resolver" in [RFC1035]. This 432 term is not properly defined in any RFC. 434 Full-service resolver: Section 6.1.3.1 of [RFC1123] defines this 435 term to mean a resolver that acts in recursive mode with a cache 436 (and meets other requirements). 438 Priming: The mechanism used by a resolver to determine where to send 439 queries before there is anything in the resolver's cache. Priming 440 is most often done from a configuration setting that contains a 441 list of authoritative servers for the root zone. 443 Negative caching: "The storage of knowledge that something does not 444 exist, cannot give an answer, or does not give an answer." 445 (Quoted from [RFC2308], Section 1) 447 Authoritative server: "A server that knows the content of a DNS zone 448 from local knowledge, and thus can answer queries about that zone 449 without needing to query other servers." (Quoted from [RFC2182], 450 Section 2.) It is a system that responds to DNS queries with 451 information about zones for which it has been configured to answer 452 with the AA flag in the response header set to 1. It is a server 453 that has authority over one or more DNS zones. Note that it is 454 possible for an authoritative server to respond to a query without 455 the parent zone delegating authority to that server. 456 Authoritative servers also provide "referrals", usually to child 457 zones delegated from them; these referrals have the AA bit set to 458 0 and come with referral data in the Authority and (if needed) the 459 Additional sections. 461 Authoritative-only server: A name server that only serves 462 authoritative data and ignores requests for recursion. It will 463 "not normally generate any queries of its own. Instead, it 464 answers non-recursive queries from iterative resolvers looking for 465 information in zones it serves." (Quoted from [RFC4697], 466 Section 2.4) 468 Zone transfer: The act of a client requesting a copy of a zone and 469 an authoritative server sending the needed information. (See 470 Section 6 for a description of zones.) There are two common 471 standard ways to do zone transfers: the AXFR ("Authoritative 472 Transfer") mechanism to copy the full zone (described in 473 [RFC5936], and the IXFR ("Incremental Transfer") mechanism to copy 474 only parts of the zone that have changed (described in [RFC1995]). 475 Many systems use non-standard methods for zone transfer outside 476 the DNS protocol. 478 Secondary server: "An authoritative server which uses zone transfer 479 to retrieve the zone" (Quoted from [RFC1996], Section 2.1). 480 [RFC2182] describes secondary servers in detail. Although early 481 DNS RFCs such as [RFC1996] referred to this as a "slave", the 482 current common usage has shifted to calling it a "secondary". 483 Secondary servers are also discussed in [RFC1034]. 485 Slave server: See secondary server. 487 Primary server: "Any authoritative server configured to be the 488 source of zone transfer for one or more [secondary] servers" 489 (Quoted from [RFC1996], Section 2.1) or, more specifically, "an 490 authoritative server configured to be the source of AXFR or IXFR 491 data for one or more [secondary] servers" (Quoted from [RFC2136]). 492 Although early DNS RFCs such as [RFC1996] referred to this as a 493 "master", the current common usage has shifted to "primary". 494 Primary servers are also discussed in [RFC1034]. 496 Master server: See primary server. 498 Primary master: "The primary master is named in the zone's SOA MNAME 499 field and optionally by an NS RR". (Quoted from [RFC1996], 500 Section 2.1). [RFC2136] defines "primary master" as "Master 501 server at the root of the AXFR/IXFR dependency graph. The primary 502 master is named in the zone's SOA MNAME field and optionally by an 503 NS RR. There is by definition only one primary master server per 504 zone." The idea of a primary master is only used by [RFC2136], 505 and is considered archaic in other parts of the DNS. 507 Stealth server: This is "like a slave server except not listed in an 508 NS RR for the zone." (Quoted from [RFC1996], Section 2.1) 510 Hidden master: A stealth server that is a master for zone transfers. 511 "In this arrangement, the master name server that processes the 512 updates is unavailable to general hosts on the Internet; it is not 513 listed in the NS RRset." (Quoted from [RFC6781], Section 3.4.3.) 514 An earlier RFC, [RFC4641], said that the hidden master's name 515 appears in the SOA RRs MNAME field, although in some setups, the 516 name does not appear at all in the public DNS. A hidden master 517 can be either a secondary or a primary master. 519 Forwarding: The process of one server sending a DNS query with the 520 RD bit set to 1 to another server to resolve that query. 522 Forwarding is a function of a DNS resolver; it is different than 523 simply blindly relaying queries. 525 [RFC5625] does not give a specific definition for forwarding, but 526 describes in detail what features a system that forwards need to 527 support. Systems that forward are sometimes called "DNS proxies", 528 but that term has not yet been defined (even in [RFC5625]). 530 Forwarder: Section 1 of [RFC2308] describes a forwarder as "a 531 nameserver used to resolve queries instead of directly using the 532 authoritative nameserver chain". [RFC2308] further says "The 533 forwarder typically either has better access to the internet, or 534 maintains a bigger cache which may be shared amongst many 535 resolvers." That definition appears to suggest that forwarders 536 normally only query authoritative servers. In current use, 537 however, forwarders often stand between stub resolvers and 538 recursive servers. [RFC2308] is silent on whether a forwarder is 539 iterative-only or can be a full-service resolver. 541 Policy-implementing resolver: A resolver acting in recursive mode 542 that changes some of the answers that it returns based on policy 543 criteria, such as to prevent access to malware sites or 544 objectionable content. In general, a stub resolver has no idea 545 whether upstream resolvers implement such policy or, if they do, 546 the exact policy about what changes will be made. In some cases, 547 the user of the stub resolver has selected the policy-implementing 548 resolver with the explicit intention of using it to implement the 549 policies. In other cases, policies are imposed without the user 550 of the stub resolver being informed. 552 Open resolver: A full-service resolver that accepts and processes 553 queries from any (or nearly any) stub resolver. This is sometimes 554 also called a "public resolver", although the term "public 555 resolver" is used more with open resolvers that are meant to be 556 open, as compared to the vast majority of open resolvers that are 557 probably misconfigured to be open. 559 View: A configuration for a DNS server that allows it to provide 560 different answers depending on attributes of the query. 561 Typically, views differ by the source IP address of a query, but 562 can also be based on the destination IP address, the type of query 563 (such as AXFR), whether it is recursive, and so on. Views are 564 often used to provide more names or different addresses to queries 565 from "inside" a protected network than to those "outside" that 566 network. Views are not a standardized part of the DNS, but they 567 are widely implemented in server software. 569 Passive DNS: A mechanism to collect large amounts of DNS data by 570 storing DNS responses from servers. Some of these systems also 571 collect the DNS queries associated with the responses; this can 572 raise privacy issues. Passive DNS databases can be used to answer 573 historical questions about DNS zones such as which records were 574 available for them at what times in the past. Passive DNS 575 databases allow searching of the stored records on keys other than 576 just the name, such as "find all names which have A records of a 577 particular value". 579 Anycast: "The practice of making a particular service address 580 available in multiple, discrete, autonomous locations, such that 581 datagrams sent are routed to one of several available locations." 582 (Quoted from [RFC4786], Section 2) 584 6. Zones 586 This section defines terms that are used when discussing zones that 587 are being served or retrieved. 589 Zone: "Authoritative information is organized into units called 590 'zones', and these zones can be automatically distributed to the 591 name servers which provide redundant service for the data in a 592 zone." (Quoted from [RFC1034], Section 2.4) 594 Child: "The entity on record that has the delegation of the domain 595 from the Parent." (Quoted from [RFC7344], Section 1.1) 597 Parent: "The domain in which the Child is registered." (Quoted from 598 [RFC7344], Section 1.1) Earlier, "parent name server" was defined 599 in [RFC0882] as "the name server that has authority over the place 600 in the domain name space that will hold the new domain". (Note 601 that [RFC0882] was obsoleted by [RFC1034] and [RFC1035].) 602 [RFC0819] also has some description of the relationship between 603 parents and children. 605 Origin: 607 (a) "The domain name that appears at the top of a zone (just below 608 the cut that separates the zone from its parent). The name of the 609 zone is the same as the name of the domain at the zone's origin." 610 (Quoted from [RFC2181], Section 6.) These days, this sense of 611 "origin" and "apex" (defined below) are often used 612 interchangeably. 614 (b) The domain name within which a given relative domain name 615 appears in zone files. Generally seen in the context of 616 "$ORIGIN", which is a control entry defined in [RFC1035], 617 Section 5.1, as part of the master file format. For example, if 618 the $ORIGIN is set to "example.org.", then a master file line for 619 "www" is in fact an entry for "www.example.org.". 621 Apex: The point in the tree at an owner of an SOA and corresponding 622 authoritative NS RRset. This is also called the "zone apex". 623 [RFC4033] defines it as "the name at the child's side of a zone 624 cut". The "apex" can usefully be thought of as a data-theoretic 625 description of a tree structure, and "origin" is the name of the 626 same concept when it is implemented in zone files. The 627 distinction is not always maintained in use, however, and one can 628 find uses that conflict subtly with this definition. [RFC1034] 629 uses the term "top node of the zone" as a synonym of "apex", but 630 that term is not widely used. These days, the first sense of 631 "origin" (above) and "apex" are often used interchangeably. 633 Zone cut: The delimitation point between two zones where the origin 634 of one of the zones is the child of the other zone. 636 "Zones are delimited by 'zone cuts'. Each zone cut separates a 637 'child' zone (below the cut) from a 'parent' zone (above the cut). 638 (Quoted from [RFC2181], Section 6; note that this is barely an 639 ostensive definition.) Section 4.2 of [RFC1034] uses "cuts" as 640 'zone cut'." 642 Delegation: The process by which a separate zone is created in the 643 name space beneath the apex of a given domain. Delegation happens 644 when an NS RRset is added in the parent zone for the child origin. 645 Delegation inherently happens at a zone cut. The term is also 646 commonly a noun: the new zone that is created by the act of 647 delegating. 649 Glue records: "[Resource records] which are not part of the 650 authoritative data [of the zone], and are address resource records 651 for the [name servers in subzones]. These RRs are only necessary 652 if the name server's name is 'below' the cut, and are only used as 653 part of a referral response." Without glue "we could be faced 654 with the situation where the NS RRs tell us that in order to learn 655 a name server's address, we should contact the server using the 656 address we wish to learn." (Definition from [RFC1034], 657 Section 4.2.1) 659 A later definition is that glue "includes any record in a zone 660 file that is not properly part of that zone, including nameserver 661 records of delegated sub-zones (NS records), address records that 662 accompany those NS records (A, AAAA, etc), and any other stray 663 data that might appear" ([RFC2181], Section 5.4.1). Although glue 664 is sometimes used today with this wider definition in mind, the 665 context surrounding the [RFC2181] definition suggests it is 666 intended to apply to the use of glue within the document itself 667 and not necessarily beyond. 669 In-bailiwick: 671 (a) An adjective to describe a name server whose name is either 672 subordinate to or (rarely) the same as the zone origin. In- 673 bailiwick name servers require glue records in their parent zone 674 (using the first of the definitions of "glue records" in the 675 definition above). 677 (b) Data for which the server is either authoritative, or else 678 authoritative for an ancestor of the owner name. This sense of 679 the term normally is used when discussing the relevancy of glue 680 records in a response. For example, the server for the parent 681 zone "example.com" might reply with glue records for 682 "ns.child.example.com". Because the "child.example.com" zone is a 683 descendant of the "example.com" zone, the glue records are in- 684 bailiwick. 686 Out-of-bailiwick: The antonym of in-bailiwick. 688 Authoritative data: "All of the RRs attached to all of the nodes 689 from the top node of the zone down to leaf nodes or nodes above 690 cuts around the bottom edge of the zone." (Quoted from [RFC1034], 691 Section 4.2.1) It is noted that this definition might 692 inadvertently also include any NS records that appear in the zone, 693 even those that might not truly be authoritative because there are 694 identical NS RRs below the zone cut. This reveals the ambiguity 695 in the notion of authoritative data, because the parent-side NS 696 records authoritatively indicate the delegation, even though they 697 are not themselves authoritative data. 699 Root zone: The zone whose apex is the zero-length label. Also 700 sometimes called "the DNS root". 702 Empty non-terminals: "Domain names that own no resource records but 703 have subdomains that do." (Quoted from [RFC4592], Section 2.2.2.) 704 A typical example is in SRV records: in the name 705 "_sip._tcp.example.com", it is likely that "_tcp.example.com" has 706 no RRsets, but that "_sip._tcp.example.com" has (at least) an SRV 707 RRset. 709 Delegation-centric zone: A zone that consists mostly of delegations 710 to child zones. This term is used in contrast to a zone that 711 might have some delegations to child zones, but also has many data 712 resource records for the zone itself and/or for child zones. The 713 term is used in [RFC4956] and [RFC5155], but is not defined there. 715 Wildcard: [RFC1034] defined "wildcard", but in a way that turned out 716 to be confusing to implementers. Special treatment is given to 717 RRs with owner names starting with the label "*". "Such RRs are 718 called 'wildcards'. Wildcard RRs can be thought of as 719 instructions for synthesizing RRs." (Quoted from [RFC1034], 720 Section 4.3.3) For an extended discussion of wildcards, including 721 clearer definitions, see [RFC4592]. 723 Asterisk label: "The first octet is the normal label type and length 724 for a 1-octet-long label, and the second octet is the ASCII 725 representation for the '*' character. A descriptive name of a 726 label equaling that value is an 'asterisk label'." (Quoted from 727 [RFC4592], Section 2.1.1) 729 Wildcard domain name: "A 'wildcard domain name' is defined by having 730 its initial (i.e., leftmost or least significant) label be 731 asterisk label." (Quoted from [RFC4592], Section 2.1.1) 733 Closest encloser: "The longest existing ancestor of a name." 734 (Quoted from [RFC5155], Section 1.3) An earlier definition is "The 735 node in the zone's tree of existing domain names that has the most 736 labels matching the query name (consecutively, counting from the 737 root label downward). Each match is a 'label match' and the order 738 of the labels is the same." (Quoted from [RFC4592], 739 Section 3.3.1) 741 Closest provable encloser: "The longest ancestor of a name that can 742 be proven to exist. Note that this is only different from the 743 closest encloser in an Opt-Out zone." (Quoted from [RFC5155], 744 Section 1.3) 746 Next closer name: "The name one label longer than the closest 747 provable encloser of a name." (Quoted from [RFC5155], 748 Section 1.3) 750 Source of Synthesis: "The source of synthesis is defined in the 751 context of a query process as that wildcard domain name 752 immediately descending from the closest encloser, provided that 753 this wildcard domain name exists. 'Immediately descending' means 754 that the source of synthesis has a name of the form: >asterisk 755 label<.>closest encloser<." (Quoted from [RFC4592], Section 3.3.1) 757 Occluded name: "The addition of a delegation point via dynamic 758 update will render all subordinate domain names to be in a limbo, 759 still part of the zone, but not available to the lookup process. 761 The addition of a DNAME resource record has the same impact. The 762 subordinate names are said to be 'occluded'." (Quoted from 763 [RFC5936], Section 3.5) 765 Fast flux DNS: This "occurs when a domain is found in DNS using A 766 records to multiple IP addresses, each of which has a very short 767 Time-to-Live (TTL) value associated with it. This means that the 768 domain resolves to varying IP addresses over a short period of 769 time." (Quoted from [RFC6561], Section 1.1.5, with typo 770 corrected) It is often used to deliver malware. Because the 771 addresses change so rapidly, it is difficult to ascertain all the 772 hosts. It should be noted that the technique also works with AAAA 773 records, but such use is not frequently observed on the Internet 774 as of this writing. 776 Reverse DNS, reverse lookup: "The process of mapping an address to a 777 name is generally known as a 'reverse lookup', and the IN- 778 ADDR.ARPA and IP6.ARPA zones are said to support the 'reverse 779 DNS'." (Quoted from [RFC5855], Section 1) 781 Forward lookup: "Hostname-to-address translation". (Quoted from 782 [RFC2133], Section 6) 784 arpa: Address and Routing Parameter Area Domain: "The 'arpa' domain 785 was originally established as part of the initial deployment of 786 the DNS, to provide a transition mechanism from the Host Tables 787 that were common in the ARPANET, as well as a home for the IPv4 788 reverse mapping domain. During 2000, the abbreviation was 789 redesignated to 'Address and Routing Parameter Area' in the hope 790 of reducing confusion with the earlier network name." (Quoted 791 from [RFC3172], Section 2.) 793 Infrastructure domain: A domain whose "role is to support the 794 operating infrastructure of the Internet". (Quoted from 795 [RFC3172], Section 2.) 797 Service name: "Service names are the unique key in the Service Name 798 and Transport Protocol Port Number registry. This unique symbolic 799 name for a service may also be used for other purposes, such as in 800 DNS SRV records." (Quoted from [RFC6335], Section 5.) 802 7. Registration Model 804 Registry: The administrative operation of a zone that allows 805 registration of names within that zone. People often use this 806 term to refer only to those organizations that perform 807 registration in large delegation-centric zones (such as TLDs); but 808 formally, whoever decides what data goes into a zone is the 809 registry for that zone. This definition of "registry" is from a 810 DNS point of view; for some zones, the policies that determine 811 what can go in the zone are decided by superior zones and not the 812 registry operator. 814 Registrant: An individual or organization on whose behalf a name in 815 a zone is registered by the registry. In many zones, the registry 816 and the registrant may be the same entity, but in TLDs they often 817 are not. 819 Registrar: A service provider that acts as a go-between for 820 registrants and registries. Not all registrations require a 821 registrar, though it is common to have registrars involved in 822 registrations in TLDs. 824 EPP: The Extensible Provisioning Protocol (EPP), which is commonly 825 used for communication of registration information between 826 registries and registrars. EPP is defined in [RFC5730]. 828 WHOIS: A protocol specified in [RFC3912], often used for querying 829 registry databases. WHOIS data is frequently used to associate 830 registration data (such as zone management contacts) with domain 831 names. The term "WHOIS data" is often used as a synonym for the 832 registry database, even though that database may be served by 833 different protocols, particularly RDAP. The WHOIS protocol is 834 also used with IP address registry data. 836 RDAP: The Registration Data Access Protocol, defined in [RFC7480], 837 [RFC7481], [RFC7482], [RFC7483], [RFC7484], and [RFC7485]. The 838 RDAP protocol and data format are meant as a replacement for 839 WHOIS. 841 DNS operator: An entity responsible for running DNS servers. For a 842 zone's authoritative servers, the registrant may act as their own 843 DNS operator, or their registrar may do it on their behalf, or 844 they may use a third-party operator. For some zones, the registry 845 function is performed by the DNS operator plus other entities who 846 decide about the allowed contents of the zone. 848 8. General DNSSEC 850 Most DNSSEC terms are defined in [RFC4033], [RFC4034], [RFC4035], and 851 [RFC5155]. The terms that have caused confusion in the DNS community 852 are highlighted here. 854 DNSSEC-aware and DNSSEC-unaware: These two terms, which are used in 855 some RFCs, have not been formally defined. However, Section 2 of 856 [RFC4033] defines many types of resolvers and validators, 857 including "non-validating security-aware stub resolver", "non- 858 validating stub resolver", "security-aware name server", 859 "security-aware recursive name server", "security-aware resolver", 860 "security-aware stub resolver", and "security-oblivious 861 'anything'". (Note that the term "validating resolver", which is 862 used in some places in DNSSEC-related documents, is also not 863 defined.) 865 Signed zone: "A zone whose RRsets are signed and that contains 866 properly constructed DNSKEY, Resource Record Signature (RRSIG), 867 Next Secure (NSEC), and (optionally) DS records." (Quoted from 868 [RFC4033], Section 2.) It has been noted in other contexts that 869 the zone itself is not really signed, but all the relevant RRsets 870 in the zone are signed. Nevertheless, if a zone that should be 871 signed contains any RRsets that are not signed (or opted out), 872 those RRsets will be treated as bogus, so the whole zone needs to 873 be handled in some way. 875 It should also be noted that, since the publication of [RFC6840], 876 NSEC records are no longer required for signed zones: a signed 877 zone might include NSEC3 records instead. [RFC7129] provides 878 additional background commentary and some context for the NSEC and 879 NSEC3 mechanisms used by DNSSEC to provide authenticated denial- 880 of-existence responses. 882 Unsigned zone: Section 2 of [RFC4033] defines this as "a zone that 883 is not signed". Section 2 of [RFC4035] defines this as "A zone 884 that does not include these records [properly constructed DNSKEY, 885 Resource Record Signature (RRSIG), Next Secure (NSEC), and 886 (optionally) DS records] according to the rules in this section". 887 There is an important note at the end of Section 5.2 of [RFC4035] 888 that defines an additional situation in which a zone is considered 889 unsigned: "If the resolver does not support any of the algorithms 890 listed in an authenticated DS RRset, then the resolver will not be 891 able to verify the authentication path to the child zone. In this 892 case, the resolver SHOULD treat the child zone as if it were 893 unsigned." 895 NSEC: "The NSEC record allows a security-aware resolver to 896 authenticate a negative reply for either name or type non- 897 existence with the same mechanisms used to authenticate other DNS 898 replies." (Quoted from [RFC4033], Section 3.2.) In short, an 899 NSEC record provides authenticated denial of existence. 901 "The NSEC resource record lists two separate things: the next 902 owner name (in the canonical ordering of the zone) that contains 903 authoritative data or a delegation point NS RRset, and the set of 904 RR types present at the NSEC RR's owner name." (Quoted from 905 Section 4 of RFC 4034) 907 NSEC3: Like the NSEC record, the NSEC3 record also provides 908 authenticated denial of existence; however, NSEC3 records mitigate 909 against zone enumeration and support Opt-Out. NSEC3 resource 910 records are defined in [RFC5155]. 912 Note that [RFC6840] says that [RFC5155] "is now considered part of 913 the DNS Security Document Family as described by Section 10 of 914 [RFC4033]". This means that some of the definitions from earlier 915 RFCs that only talk about NSEC records should probably be 916 considered to be talking about both NSEC and NSEC3. 918 Opt-out: "The Opt-Out Flag indicates whether this NSEC3 RR may cover 919 unsigned delegations." (Quoted from [RFC5155], Section 3.1.2.1.) 920 Opt-out tackles the high costs of securing a delegation to an 921 insecure zone. When using Opt-Out, names that are an insecure 922 delegation (and empty non-terminals that are only derived from 923 insecure delegations) don't require an NSEC3 record or its 924 corresponding RRSIG records. Opt-Out NSEC3 records are not able 925 to prove or deny the existence of the insecure delegations. 926 (Adapted from [RFC7129], Section 5.1) 928 Zone enumeration: "The practice of discovering the full content of a 929 zone via successive queries." (Quoted from [RFC5155], 930 Section 1.3.) This is also sometimes called "zone walking". Zone 931 enumeration is different from zone content guessing where the 932 guesser uses a large dictionary of possible labels and sends 933 successive queries for them, or matches the contents of NSEC3 934 records against such a dictionary. 936 Key signing key (KSK): DNSSEC keys that "only sign the apex DNSKEY 937 RRset in a zone."(Quoted from [RFC6781], Section 3.1) 939 Zone signing key (ZSK): "DNSSEC keys that can be used to sign all 940 the RRsets in a zone that require signatures, other than the apex 941 DNSKEY RRset." (Quoted from [RFC6781], Section 3.1) Note that the 942 roles KSK and ZSK are not mutually exclusive: a single key can be 943 both KSK and ZSK at the same time. Also note that a ZSK is 944 sometimes used to sign the apex DNSKEY RRset. 946 Combined signing key (CSK): "In cases where the differentiation 947 between the KSK and ZSK is not made, i.e., where keys have the 948 role of both KSK and ZSK, we talk about a Single-Type Signing 949 Scheme." (Quoted from [RFC6781], Section 3.1) This is sometimes 950 called a "combined signing key" or CSK. It is operational 951 practice, not protocol, that determines whether a particular key 952 is a ZSK, a KSK, or a CSK. 954 Secure Entry Point (SEP): A flag in the DNSKEY RDATA that "can be 955 used to distinguish between keys that are intended to be used as 956 the secure entry point into the zone when building chains of 957 trust, i.e., they are (to be) pointed to by parental DS RRs or 958 configured as a trust anchor. Therefore, it is suggested that the 959 SEP flag be set on keys that are used as KSKs and not on keys that 960 are used as ZSKs, while in those cases where a distinction between 961 a KSK and ZSK is not made (i.e., for a Single-Type Signing 962 Scheme), it is suggested that the SEP flag be set on all keys." 963 (Quoted from [RFC6781], Section 3.2.3.) Note that the SEP flag is 964 only a hint, and its presence or absence may not be used to 965 disqualify a given DNSKEY RR from use as a KSK or ZSK during 966 validation. 968 The oginal defintion of SEPs was in [RFC3757]. That definition 969 clearly indicated that the SEP was a key, not just a bit in the 970 key. The abstract of [RFC3757] says: "With the Delegation Signer 971 (DS) resource record (RR), the concept of a public key acting as a 972 secure entry point (SEP) has been introduced. During exchanges of 973 public keys with the parent there is a need to differentiate SEP 974 keys from other public keys in the Domain Name System KEY (DNSKEY) 975 resource record set. A flag bit in the DNSKEY RR is defined to 976 indicate that DNSKEY is to be used as a SEP." That definition of 977 the SEP as a key was made obsolete by [RFC4034], and the 978 definition from [RFC6781] is consistent with [RFC4034]. 980 DNSSEC Policy (DP): A statement that "sets forth the security 981 requirements and standards to be implemented for a DNSSEC-signed 982 zone." (Quoted from [RFC6841], Section 2) 984 DNSSEC Practice Statement (DPS): "A practices disclosure document 985 that may support and be a supplemental document to the DNSSEC 986 Policy (if such exists), and it states how the management of a 987 given zone implements procedures and controls at a high level." 988 (Quoted from [RFC6841], Section 2) 990 9. DNSSEC States 992 A validating resolver can determine that a response is in one of four 993 states: secure, insecure, bogus, or indeterminate. These states are 994 defined in [RFC4033] and [RFC4035], although the two definitions 995 differ a bit. This document makes no effort to reconcile the two 996 definitions, and takes no position as to whether they need to be 997 reconciled. 999 Section 5 of [RFC4033] says: 1001 A validating resolver can determine the following 4 states: 1003 Secure: The validating resolver has a trust anchor, has a chain 1004 of trust, and is able to verify all the signatures in the 1005 response. 1007 Insecure: The validating resolver has a trust anchor, a chain 1008 of trust, and, at some delegation point, signed proof of the 1009 non-existence of a DS record. This indicates that subsequent 1010 branches in the tree are provably insecure. A validating 1011 resolver may have a local policy to mark parts of the domain 1012 space as insecure. 1014 Bogus: The validating resolver has a trust anchor and a secure 1015 delegation indicating that subsidiary data is signed, but 1016 the response fails to validate for some reason: missing 1017 signatures, expired signatures, signatures with unsupported 1018 algorithms, data missing that the relevant NSEC RR says 1019 should be present, and so forth. 1021 Indeterminate: There is no trust anchor that would indicate that a 1022 specific portion of the tree is secure. This is the default 1023 operation mode. 1025 Section 4.3 of [RFC4035] says: 1027 A security-aware resolver must be able to distinguish between four 1028 cases: 1030 Secure: An RRset for which the resolver is able to build a chain 1031 of signed DNSKEY and DS RRs from a trusted security anchor to 1032 the RRset. In this case, the RRset should be signed and is 1033 subject to signature validation, as described above. 1035 Insecure: An RRset for which the resolver knows that it has no 1036 chain of signed DNSKEY and DS RRs from any trusted starting 1037 point to the RRset. This can occur when the target RRset lies 1038 in an unsigned zone or in a descendent [sic] of an unsigned 1039 zone. In this case, the RRset may or may not be signed, but 1040 the resolver will not be able to verify the signature. 1042 Bogus: An RRset for which the resolver believes that it ought to 1043 be able to establish a chain of trust but for which it is 1044 unable to do so, either due to signatures that for some reason 1045 fail to validate or due to missing data that the relevant 1046 DNSSEC RRs indicate should be present. This case may indicate 1047 an attack but may also indicate a configuration error or some 1048 form of data corruption. 1050 Indeterminate: An RRset for which the resolver is not able to 1051 determine whether the RRset should be signed, as the resolver 1052 is not able to obtain the necessary DNSSEC RRs. This can occur 1053 when the security-aware resolver is not able to contact 1054 security-aware name servers for the relevant zones. 1056 10. Security Considerations 1058 These definitions do not change any security considerations for the 1059 DNS. 1061 11. IANA Considerations 1063 None. 1065 12. References 1067 12.1. Normative References 1069 [RFC0882] Mockapetris, P., "Domain names: Concepts and facilities", 1070 RFC 882, DOI 10.17487/RFC0882, November 1983, 1071 . 1073 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1074 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1075 . 1077 [RFC1035] Mockapetris, P., "Domain names - implementation and 1078 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 1079 November 1987, . 1081 [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - 1082 Application and Support", STD 3, RFC 1123, 1083 DOI 10.17487/RFC1123, October 1989, 1084 . 1086 [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone 1087 Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996, 1088 August 1996, . 1090 [RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound, 1091 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 1092 RFC 2136, DOI 10.17487/RFC2136, April 1997, 1093 . 1095 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS 1096 Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997, 1097 . 1099 [RFC2182] Elz, R., Bush, R., Bradner, S., and M. Patton, "Selection 1100 and Operation of Secondary DNS Servers", BCP 16, RFC 2182, 1101 DOI 10.17487/RFC2182, July 1997, 1102 . 1104 [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS 1105 NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998, 1106 . 1108 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1109 Rose, "DNS Security Introduction and Requirements", 1110 RFC 4033, DOI 10.17487/RFC4033, March 2005, 1111 . 1113 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1114 Rose, "Resource Records for the DNS Security Extensions", 1115 RFC 4034, DOI 10.17487/RFC4034, March 2005, 1116 . 1118 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1119 Rose, "Protocol Modifications for the DNS Security 1120 Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005, 1121 . 1123 [RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name 1124 System", RFC 4592, DOI 10.17487/RFC4592, July 2006, 1125 . 1127 [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS 1128 Security (DNSSEC) Hashed Authenticated Denial of 1129 Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008, 1130 . 1132 [RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)", 1133 STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009, 1134 . 1136 [RFC5855] Abley, J. and T. Manderson, "Nameservers for IPv4 and IPv6 1137 Reverse Zones", BCP 155, RFC 5855, DOI 10.17487/RFC5855, 1138 May 2010, . 1140 [RFC5936] Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol 1141 (AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010, 1142 . 1144 [RFC6561] Livingood, J., Mody, N., and M. O'Reirdan, 1145 "Recommendations for the Remediation of Bots in ISP 1146 Networks", RFC 6561, DOI 10.17487/RFC6561, March 2012, 1147 . 1149 [RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the 1150 DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012, 1151 . 1153 [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC 1154 Operational Practices, Version 2", RFC 6781, 1155 DOI 10.17487/RFC6781, December 2012, 1156 . 1158 [RFC6840] Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and 1159 Implementation Notes for DNS Security (DNSSEC)", RFC 6840, 1160 DOI 10.17487/RFC6840, February 2013, 1161 . 1163 [RFC6841] Ljunggren, F., Eklund Lowinder, AM., and T. Okubo, "A 1164 Framework for DNSSEC Policies and DNSSEC Practice 1165 Statements", RFC 6841, DOI 10.17487/RFC6841, January 2013, 1166 . 1168 [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms 1169 for DNS (EDNS(0))", STD 75, RFC 6891, 1170 DOI 10.17487/RFC6891, April 2013, 1171 . 1173 [RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating 1174 DNSSEC Delegation Trust Maintenance", RFC 7344, 1175 DOI 10.17487/RFC7344, September 2014, 1176 . 1178 [RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS 1179 Terminology", RFC 7719, DOI 10.17487/RFC7719, December 1180 2015, . 1182 12.2. Informative References 1184 [DBOUND] IETF, "Domain Boundaries (dbound) Working Group", 2015, 1185 . 1187 [RFC0799] Mills, D., "Internet name domains", RFC 799, 1188 DOI 10.17487/RFC0799, September 1981, 1189 . 1191 [RFC0819] Su, Z. and J. Postel, "The Domain Naming Convention for 1192 Internet User Applications", RFC 819, 1193 DOI 10.17487/RFC0819, August 1982, 1194 . 1196 [RFC0952] Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet 1197 host table specification", RFC 952, DOI 10.17487/RFC0952, 1198 October 1985, . 1200 [RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995, 1201 DOI 10.17487/RFC1995, August 1996, 1202 . 1204 [RFC2133] Gilligan, R., Thomson, S., Bound, J., and W. Stevens, 1205 "Basic Socket Interface Extensions for IPv6", RFC 2133, 1206 DOI 10.17487/RFC2133, April 1997, 1207 . 1209 [RFC3172] Huston, G., Ed., "Management Guidelines & Operational 1210 Requirements for the Address and Routing Parameter Area 1211 Domain ("arpa")", BCP 52, RFC 3172, DOI 10.17487/RFC3172, 1212 September 2001, . 1214 [RFC3757] Kolkman, O., Schlyter, J., and E. Lewis, "Domain Name 1215 System KEY (DNSKEY) Resource Record (RR) Secure Entry 1216 Point (SEP) Flag", RFC 3757, DOI 10.17487/RFC3757, April 1217 2004, . 1219 [RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912, 1220 DOI 10.17487/RFC3912, September 2004, 1221 . 1223 [RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices", 1224 RFC 4641, DOI 10.17487/RFC4641, September 2006, 1225 . 1227 [RFC4697] Larson, M. and P. Barber, "Observed DNS Resolution 1228 Misbehavior", BCP 123, RFC 4697, DOI 10.17487/RFC4697, 1229 October 2006, . 1231 [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast 1232 Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786, 1233 December 2006, . 1235 [RFC4956] Arends, R., Kosters, M., and D. Blacka, "DNS Security 1236 (DNSSEC) Opt-In", RFC 4956, DOI 10.17487/RFC4956, July 1237 2007, . 1239 [RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines", 1240 BCP 152, RFC 5625, DOI 10.17487/RFC5625, August 2009, 1241 . 1243 [RFC5890] Klensin, J., "Internationalized Domain Names for 1244 Applications (IDNA): Definitions and Document Framework", 1245 RFC 5890, DOI 10.17487/RFC5890, August 2010, 1246 . 1248 [RFC5891] Klensin, J., "Internationalized Domain Names in 1249 Applications (IDNA): Protocol", RFC 5891, 1250 DOI 10.17487/RFC5891, August 2010, 1251 . 1253 [RFC5892] Faltstrom, P., Ed., "The Unicode Code Points and 1254 Internationalized Domain Names for Applications (IDNA)", 1255 RFC 5892, DOI 10.17487/RFC5892, August 2010, 1256 . 1258 [RFC5893] Alvestrand, H., Ed. and C. Karp, "Right-to-Left Scripts 1259 for Internationalized Domain Names for Applications 1260 (IDNA)", RFC 5893, DOI 10.17487/RFC5893, August 2010, 1261 . 1263 [RFC5894] Klensin, J., "Internationalized Domain Names for 1264 Applications (IDNA): Background, Explanation, and 1265 Rationale", RFC 5894, DOI 10.17487/RFC5894, August 2010, 1266 . 1268 [RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on 1269 Encodings for Internationalized Domain Names", RFC 6055, 1270 DOI 10.17487/RFC6055, February 2011, 1271 . 1273 [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, 1274 DOI 10.17487/RFC6265, April 2011, 1275 . 1277 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. 1278 Cheshire, "Internet Assigned Numbers Authority (IANA) 1279 Procedures for the Management of the Service Name and 1280 Transport Protocol Port Number Registry", BCP 165, 1281 RFC 6335, DOI 10.17487/RFC6335, August 2011, 1282 . 1284 [RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in 1285 Internationalization in the IETF", BCP 166, RFC 6365, 1286 DOI 10.17487/RFC6365, September 2011, 1287 . 1289 [RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of 1290 Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129, 1291 February 2014, . 1293 [RFC7480] Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the 1294 Registration Data Access Protocol (RDAP)", RFC 7480, 1295 DOI 10.17487/RFC7480, March 2015, 1296 . 1298 [RFC7481] Hollenbeck, S. and N. Kong, "Security Services for the 1299 Registration Data Access Protocol (RDAP)", RFC 7481, 1300 DOI 10.17487/RFC7481, March 2015, 1301 . 1303 [RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access 1304 Protocol (RDAP) Query Format", RFC 7482, 1305 DOI 10.17487/RFC7482, March 2015, 1306 . 1308 [RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the 1309 Registration Data Access Protocol (RDAP)", RFC 7483, 1310 DOI 10.17487/RFC7483, March 2015, 1311 . 1313 [RFC7484] Blanchet, M., "Finding the Authoritative Registration Data 1314 (RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March 1315 2015, . 1317 [RFC7485] Zhou, L., Kong, N., Shen, S., Sheng, S., and A. Servin, 1318 "Inventory and Analysis of WHOIS Registration Objects", 1319 RFC 7485, DOI 10.17487/RFC7485, March 2015, 1320 . 1322 Acknowledgements 1324 The following is the Acknowledgements for RFC 7719. Additional 1325 acknowledgements may be added as this draft is worked on. 1327 The authors gratefully acknowledge all of the authors of DNS-related 1328 RFCs that proceed this one. Comments from Tony Finch, Stephane 1329 Bortzmeyer, Niall O'Reilly, Colm MacCarthaigh, Ray Bellis, John 1330 Kristoff, Robert Edmonds, Paul Wouters, Shumon Huque, Paul Ebersman, 1331 David Lawrence, Matthijs Mekking, Casey Deccio, Bob Harold, Ed Lewis, 1332 John Klensin, David Black, and many others in the DNSOP Working Group 1333 helped shape RFC 7719. 1335 Additional people contributed to this document, including: John 1336 Dickinson [[ MORE NAMES WILL APPEAR HERE AS FOLKS CONTRIBUTE]]. 1338 Authors' Addresses 1340 Paul Hoffman 1341 ICANN 1343 Email: paul.hoffman@icann.org 1344 Andrew Sullivan 1345 Dyn 1346 150 Dow Street, Tower 2 1347 Manchester, NH 03101 1348 United States 1350 Email: asullivan@dyn.com 1352 Kazunori Fujiwara 1353 Japan Registry Services Co., Ltd. 1354 Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda 1355 Chiyoda-ku, Tokyo 101-0065 1356 Japan 1358 Phone: +81 3 5215 8451 1359 Email: fujiwara@jprs.co.jp