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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: February 5, 2017 K. Fujiwara 7 JPRS 8 August 4, 2016 10 DNS Terminology 11 draft-ietf-dnsop-terminology-bis-02 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. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on February 5, 2017. 41 Copyright Notice 43 Copyright (c) 2016 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 59 2. Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 3. DNS Header and Response Codes . . . . . . . . . . . . . . . . 6 61 4. Resource Records . . . . . . . . . . . . . . . . . . . . . . 7 62 5. DNS Servers and Clients . . . . . . . . . . . . . . . . . . . 9 63 6. Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 64 7. Registration Model . . . . . . . . . . . . . . . . . . . . . 17 65 8. General DNSSEC . . . . . . . . . . . . . . . . . . . . . . . 18 66 9. DNSSEC States . . . . . . . . . . . . . . . . . . . . . . . . 22 67 10. Security Considerations . . . . . . . . . . . . . . . . . . . 23 68 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 69 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 70 12.1. Normative References . . . . . . . . . . . . . . . . . . 23 71 12.2. Informative References . . . . . . . . . . . . . . . . . 26 72 Appendix A. Definitions Updated by this Document . . . . . . . . 29 73 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 29 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 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. See Appendix A for a list of the 97 definitions that this document updates. 99 It is important to note that, during the development of this 100 document, it became clear that some DNS-related terms are interpreted 101 quite differently by different DNS experts. Further, some terms that 102 are defined in early DNS RFCs now have definitions that are generally 103 agreed to, but that are different from the original definitions. 104 Therefore, this document is a substantial revision to [RFC7719]. 106 The terms are organized loosely by topic. Some definitions are for 107 new terms for things that are commonly talked about in the DNS 108 community but that never had terms defined for them. 110 Other organizations sometimes define DNS-related terms their own way. 111 For example, the W3C defines "domain" at 112 https://specs.webplatform.org/url/webspecs/develop/. 114 Note that there is no single consistent definition of "the DNS". It 115 can be considered to be some combination of the following: a commonly 116 used naming scheme for objects on the Internet; a distributed 117 database representing the names and certain properties of these 118 objects; an architecture providing distributed maintenance, 119 resilience, and loose coherency for this database; and a simple 120 query-response protocol (as mentioned below) implementing this 121 architecture. 123 Capitalization in DNS terms is often inconsistent among RFCs and 124 various DNS practitioners. The capitalization used in this document 125 is a best guess at current practices, and is not meant to indicate 126 that other capitalization styles are wrong or archaic. In some 127 cases, multiple styles of capitalization are used for the same term 128 due to quoting from different RFCs. 130 2. Names 132 Domain name: Section 3.1 of [RFC1034] talks of "the domain name 133 space" as a tree structure. "Each node has a label, which is zero 134 to 63 octets in length. ... The domain name of a node is the list 135 of the labels on the path from the node to the root of the tree. 136 ... To simplify implementations, the total number of octets that 137 represent a domain name (i.e., the sum of all label octets and 138 label lengths) is limited to 255." Any label in a domain name can 139 contain any octet value. 141 The term "domain name" was defined before [RFC1034], most likely 142 in [RFC0799], which precedes the existence of the DNS. In this 143 document, domain names are only described in terms of the DNS. 145 Fully qualified domain name (FQDN): This is often just a clear way 146 of saying the same thing as "domain name of a node", as outlined 147 above. However, the term is ambiguous. Strictly speaking, a 148 fully qualified domain name would include every label, including 149 the final, zero-length label of the root: such a name would be 150 written "www.example.net." (note the terminating dot). But 151 because every name eventually shares the common root, names are 152 often written relative to the root (such as "www.example.net") and 153 are still called "fully qualified". This term first appeared in 154 [RFC0819]. In this document, names are often written relative to 155 the root. 157 The need for the term "fully qualified domain name" comes from the 158 existence of partially qualified domain names, which are names 159 where some of the right-most names are left off and are understood 160 only by context. 162 Label: The identifier of an individual node in the sequence of nodes 163 identified by a fully qualified domain name. 165 Host name: This term and its equivalent, "hostname", have been 166 widely used but are not defined in [RFC1034], [RFC1035], 167 [RFC1123], or [RFC2181]. The DNS was originally deployed into the 168 Host Tables environment as outlined in [RFC0952], and it is likely 169 that the term followed informally from the definition there. Over 170 time, the definition seems to have shifted. "Host name" is often 171 meant to be a domain name that follows the rules in Section 3.5 of 172 [RFC1034], the "preferred name syntax". Note that any label in a 173 domain name can contain any octet value; hostnames are generally 174 considered to be domain names where every label follows the rules 175 in the "preferred name syntax", with the amendment that labels can 176 start with ASCII digits (this amendment comes from Section 2.1 of 177 [RFC1123]). 179 People also sometimes use the term hostname to refer to just the 180 first label of an FQDN, such as "printer" in 181 "printer.admin.example.com". (Sometimes this is formalized in 182 configuration in operating systems.) In addition, people 183 sometimes use this term to describe any name that refers to a 184 machine, and those might include labels that do not conform to the 185 "preferred name syntax". 187 TLD: A Top-Level Domain, meaning a zone that is one layer below the 188 root, such as "com" or "jp". There is nothing special, from the 189 point of view of the DNS, about TLDs. Most of them are also 190 delegation-centric zones, and there are significant policy issues 191 around their operation. TLDs are often divided into sub-groups 192 such as Country Code Top-Level Domains (ccTLDs), Generic Top-Level 193 Domains (gTLDs), and others; the division is a matter of policy, 194 and beyond the scope of this document. 196 IDN: The common abbreviation for "Internationalized Domain Name". 197 The IDNA protocol is the standard mechanism for handling domain 198 names with non-ASCII characters in applications in the DNS. The 199 current standard, normally called "IDNA2008", is defined in 200 [RFC5890], [RFC5891], [RFC5892], [RFC5893], and [RFC5894]. These 201 documents define many IDN-specific terms such as "LDH label", 202 "A-label", and "U-label". [RFC6365] defines more terms that 203 relate to internationalization (some of which relate to IDNs), and 204 [RFC6055] has a much more extensive discussion of IDNs, including 205 some new terminology. 207 Subdomain: "A domain is a subdomain of another domain if it is 208 contained within that domain. This relationship can be tested by 209 seeing if the subdomain's name ends with the containing domain's 210 name." (Quoted from [RFC1034], Section 3.1). For example, in the 211 host name "nnn.mmm.example.com", both "mmm.example.com" and 212 "nnn.mmm.example.com" are subdomains of "example.com". 214 Alias: The owner of a CNAME resource record, or a subdomain of the 215 owner of a DNAME resource record [RFC6672]. See also "canonical 216 name". 218 Canonical name: A CNAME resource record "identifies its owner name 219 as an alias, and specifies the corresponding canonical name in the 220 RDATA section of the RR." (Quoted from [RFC1034], Section 3.6.2) 221 This usage of the word "canonical" is related to the mathematical 222 concept of "canonical form". 224 CNAME: "It is traditional to refer to the owner of a CNAME record as 225 'a CNAME'. This is unfortunate, as 'CNAME' is an abbreviation of 226 'canonical name', and the owner of a CNAME record is an alias, not 227 a canonical name." (Quoted from [RFC2181], Section 10.1.1) 229 Public suffix: "A domain that is controlled by a public registry." 230 (Quoted from [RFC6265], Section 5.3) A common definition for this 231 term is a domain under which subdomains can be registered, and on 232 which HTTP cookies ([RFC6265]) should not be set. There is no 233 indication in a domain name whether it is a public suffix; that 234 can only be determined by outside means. In fact, both a domain 235 and a subdomain of that domain can be public suffixes. At the 236 time this document is published, the IETF DBOUND Working Group 237 [DBOUND] is dealing with issues concerning public suffixes. 239 There is nothing inherent in a domain name to indicate whether it 240 is a public suffix. One resource for identifying public suffixes 241 is the Public Suffix List (PSL) maintained by Mozilla 242 (http://publicsuffix.org/). 244 For example, at the time this document is published, the "com.au" 245 domain is listed as a public suffix in the PSL. (Note that this 246 example might change in the future.) 248 Note that the term "public suffix" is controversial in the DNS 249 community for many reasons, and may be significantly changed in 250 the future. One example of the difficulty of calling a domain a 251 public suffix is that designation can change over time as the 252 registration policy for the zone changes, such as the case of the 253 "uk" TLD around the time this document is published. 255 3. DNS Header and Response Codes 257 The header of a DNS message is its first 12 octets. Many of the 258 fields and flags in the header diagram in Sections 4.1.1 through 259 4.1.3 of [RFC1035] are referred to by their names in that diagram. 260 For example, the response codes are called "RCODEs", the data for a 261 record is called the "RDATA", and the authoritative answer bit is 262 often called "the AA flag" or "the AA bit". 264 Some of response codes that are defined in [RFC1035] have acquired 265 their own shorthand names. Some common response code names that 266 appear without reference to the numeric value are "FORMERR", 267 "SERVFAIL", and "NXDOMAIN" (the latter of which is also referred to 268 as "Name Error"). All of the RCODEs are listed at 269 http://www.iana.org/assignments/dns-parameters, although that site 270 uses mixed-case capitalization, while most documents use all-caps. 272 NODATA: "A pseudo RCODE which indicates that the name is valid for 273 the given class, but there are no records of the given type. A 274 NODATA response has to be inferred from the answer." (Quoted from 275 [RFC2308], Section 1.) "NODATA is indicated by an answer with the 276 RCODE set to NOERROR and no relevant answers in the answer 277 section. The authority section will contain an SOA record, or 278 there will be no NS records there." (Quoted from [RFC2308], 279 Section 2.2.) Note that referrals have a similar format to NODATA 280 replies; [RFC2308] explains how to distinguish them. 282 The term "NXRRSET" is sometimes used as a synonym for NODATA. 283 However, this is a mistake, given that NXRRSET is a specific error 284 code defined in [RFC2136]. 286 Negative response: A response that indicates that a particular RRset 287 does not exist, or whose RCODE indicates the nameserver cannot 288 answer. Sections 2 and 7 of [RFC2308] describe the types of 289 negative responses in detail. 291 Referrals: Data from the authority section of a non-authoritative 292 answer. [RFC1035] Section 2.1 defines "authoritative" data. 293 However, referrals at zone cuts (defined in Section 6) are not 294 authoritative. Referrals may be zone cut NS resource records and 295 their glue records. NS records on the parent side of a zone cut 296 are an authoritative delegation, but are normally not treated as 297 authoritative data. In general, a referral is a way for a server 298 to send an answer saying that the server does not know the answer, 299 but knows where the query should be directed in order to get an 300 answer. Historically, many authoritative servers answered with a 301 referral to the root zone when queried for a name for which they 302 were not authoritative, but this practice has declined. 304 4. Resource Records 306 RR: An acronym for resource record. ([RFC1034], Section 3.6.) 308 RRset: A set of resource records with the same label, class and 309 type, but with different data. (Definition from [RFC2181]) Also 310 spelled RRSet in some documents. As a clarification, "same label" 311 in this definition means "same owner name". In addition, 312 [RFC2181] states that "the TTLs of all RRs in an RRSet must be the 313 same". (This definition is definitely not the same as "the 314 response one gets to a query for QTYPE=ANY", which is an 315 unfortunate misunderstanding.) 317 EDNS: The extension mechanisms for DNS, defined in [RFC6891]. 318 Sometimes called "EDNS0" or "EDNS(0)" to indicate the version 319 number. EDNS allows DNS clients and servers to specify message 320 sizes larger than the original 512 octet limit, to expand the 321 response code space, and potentially to carry additional options 322 that affect the handling of a DNS query. 324 OPT: A pseudo-RR (sometimes called a "meta-RR") that is used only to 325 contain control information pertaining to the question-and-answer 326 sequence of a specific transaction. (Definition from [RFC6891], 327 Section 6.1.1) It is used by EDNS. 329 Owner: The domain name where a RR is found ([RFC1034], Section 3.6). 330 Often appears in the term "owner name". 332 SOA field names: DNS documents, including the definitions here, 333 often refer to the fields in the RDATA of an SOA resource record 334 by field name. Those fields are defined in Section 3.3.13 of 335 [RFC1035]. The names (in the order they appear in the SOA RDATA) 336 are MNAME, RNAME, SERIAL, REFRESH, RETRY, EXPIRE, and MINIMUM. 337 Note that the meaning of MINIMUM field is updated in Section 4 of 338 [RFC2308]; the new definition is that the MINIMUM field is only 339 "the TTL to be used for negative responses". This document tends 340 to use field names instead of terms that describe the fields. 342 TTL: The maximum "time to live" of a resource record. "A TTL value 343 is an unsigned number, with a minimum value of 0, and a maximum 344 value of 2147483647. That is, a maximum of 2^31 - 1. When 345 transmitted, the TTL is encoded in the less significant 31 bits of 346 the 32 bit TTL field, with the most significant, or sign, bit set 347 to zero." (Quoted from [RFC2181], Section 8) (Note that [RFC1035] 348 erroneously stated that this is a signed integer; that was fixed 349 by [RFC2181].) 351 The TTL "specifies the time interval that the resource record may 352 be cached before the source of the information should again be 353 consulted". (Quoted from [RFC1035], Section 3.2.1) Also: "the 354 time interval (in seconds) that the resource record may be cached 355 before it should be discarded". (Quoted from [RFC1035], 356 Section 4.1.3). Despite being defined for a resource record, the 357 TTL of every resource record in an RRset is required to be the 358 same ([RFC2181], Section 5.2). 360 The reason that the TTL is the maximum time to live is that a 361 cache operator might decide to shorten the time to live for 362 operational purposes, such as if there is a policy to disallow TTL 363 values over a certain number. Also, if a value is flushed from 364 the cache when its value is still positive, the value effectively 365 becomes zero. Some servers are known to ignore the TTL on some 366 RRsets (such as when the authoritative data has a very short TTL) 367 even though this is against the advice in RFC 1035. 369 There is also the concept of a "default TTL" for a zone, which can 370 be a configuration parameter in the server software. This is 371 often expressed by a default for the entire server, and a default 372 for a zone using the $TTL directive in a zone file. The $TTL 373 directive was added to the master file format by [RFC2308]. 375 Class independent: A resource record type whose syntax and semantics 376 are the same for every DNS class. A resource record type that is 377 not class independent has different meanings depending on the DNS 378 class of the record, or the meaning is undefined for classes other 379 than IN (class 1, the Internet). 381 5. DNS Servers and Clients 383 This section defines the terms used for the systems that act as DNS 384 clients, DNS servers, or both. 386 Resolver: A program "that extract[s] information from name servers 387 in response to client requests." (Quoted from [RFC1034], 388 Section 2.4) "The resolver is located on the same machine as the 389 program that requests the resolver's services, but it may need to 390 consult name servers on other hosts." (Quoted from [RFC1034], 391 Section 5.1) A resolver performs queries for a name, type, and 392 class, and receives answers. The logical function is called 393 "resolution". In practice, the term is usually referring to some 394 specific type of resolver (some of which are defined below), and 395 understanding the use of the term depends on understanding the 396 context. 398 Stub resolver: A resolver that cannot perform all resolution itself. 399 Stub resolvers generally depend on a recursive resolver to 400 undertake the actual resolution function. Stub resolvers are 401 discussed but never fully defined in Section 5.3.1 of [RFC1034]. 402 They are fully defined in Section 6.1.3.1 of [RFC1123]. 404 Iterative mode: A resolution mode of a server that receives DNS 405 queries and responds with a referral to another server. 406 Section 2.3 of [RFC1034] describes this as "The server refers the 407 client to another server and lets the client pursue the query". A 408 resolver that works in iterative mode is sometimes called an 409 "iterative resolver". 411 Recursive mode: A resolution mode of a server that receives DNS 412 queries and either responds to those queries from a local cache or 413 sends queries to other servers in order to get the final answers 414 to the original queries. Section 2.3 of [RFC1034] describes this 415 as "The first server pursues the query for the client at another 416 server". A server operating in recursive mode may be thought of 417 as having a name server side (which is what answers the query) and 418 a resolver side (which performs the resolution function). Systems 419 operating in this mode are commonly called "recursive servers". 420 Sometimes they are called "recursive resolvers". While strictly 421 the difference between these is that one of them sends queries to 422 another recursive server and the other does not, in practice it is 423 not possible to know in advance whether the server that one is 424 querying will also perform recursion; both terms can be observed 425 in use interchangeably. 427 Full resolver: This term is used in [RFC1035], but it is not defined 428 there. RFC 1123 defines a "full-service resolver" that may or may 429 not be what was intended by "full resolver" in [RFC1035]. This 430 term is not properly defined in any RFC. 432 Full-service resolver: Section 6.1.3.1 of [RFC1123] defines this 433 term to mean a resolver that acts in recursive mode with a cache 434 (and meets other requirements). 436 Priming: The mechanism used by a resolver to determine where to send 437 queries before there is anything in the resolver's cache. Priming 438 is most often done from a configuration setting that contains a 439 list of authoritative servers for the root zone. 441 Root hints: "Operators who manage a DNS recursive resolver typically 442 need to configure a 'root hints file'. This file contains the 443 names and IP addresses of the authoritative name servers for the 444 root zone, so the software can bootstrap the DNS resolution 445 process. For many pieces of software, this list comes built into 446 the software." (Quoted from [IANA_RootFiles]) 448 Negative caching: "The storage of knowledge that something does not 449 exist, cannot give an answer, or does not give an answer." 450 (Quoted from [RFC2308], Section 1) 452 Authoritative server: "A server that knows the content of a DNS zone 453 from local knowledge, and thus can answer queries about that zone 454 without needing to query other servers." (Quoted from [RFC2182], 455 Section 2.) It is a system that responds to DNS queries with 456 information about zones for which it has been configured to answer 457 with the AA flag in the response header set to 1. It is a server 458 that has authority over one or more DNS zones. Note that it is 459 possible for an authoritative server to respond to a query without 460 the parent zone delegating authority to that server. 461 Authoritative servers also provide "referrals", usually to child 462 zones delegated from them; these referrals have the AA bit set to 463 0 and come with referral data in the Authority and (if needed) the 464 Additional sections. 466 Authoritative-only server: A name server that only serves 467 authoritative data and ignores requests for recursion. It will 468 "not normally generate any queries of its own. Instead, it 469 answers non-recursive queries from iterative resolvers looking for 470 information in zones it serves." (Quoted from [RFC4697], 471 Section 2.4) 473 Zone transfer: The act of a client requesting a copy of a zone and 474 an authoritative server sending the needed information. (See 475 Section 6 for a description of zones.) There are two common 476 standard ways to do zone transfers: the AXFR ("Authoritative 477 Transfer") mechanism to copy the full zone (described in 478 [RFC5936], and the IXFR ("Incremental Transfer") mechanism to copy 479 only parts of the zone that have changed (described in [RFC1995]). 480 Many systems use non-standard methods for zone transfer outside 481 the DNS protocol. 483 Secondary server: "An authoritative server which uses zone transfer 484 to retrieve the zone" (Quoted from [RFC1996], Section 2.1). 485 [RFC2182] describes secondary servers in detail. Although early 486 DNS RFCs such as [RFC1996] referred to this as a "slave", the 487 current common usage has shifted to calling it a "secondary". 488 Secondary servers are also discussed in [RFC1034]. 490 Slave server: See secondary server. 492 Primary server: "Any authoritative server configured to be the 493 source of zone transfer for one or more [secondary] servers" 494 (Quoted from [RFC1996], Section 2.1) or, more specifically, "an 495 authoritative server configured to be the source of AXFR or IXFR 496 data for one or more [secondary] servers" (Quoted from [RFC2136]). 497 Although early DNS RFCs such as [RFC1996] referred to this as a 498 "master", the current common usage has shifted to "primary". 499 Primary servers are also discussed in [RFC1034]. 501 Master server: See primary server. 503 Primary master: "The primary master is named in the zone's SOA MNAME 504 field and optionally by an NS RR". (Quoted from [RFC1996], 505 Section 2.1). [RFC2136] defines "primary master" as "Master 506 server at the root of the AXFR/IXFR dependency graph. The primary 507 master is named in the zone's SOA MNAME field and optionally by an 508 NS RR. There is by definition only one primary master server per 509 zone." The idea of a primary master is only used by [RFC2136], 510 and is considered archaic in other parts of the DNS. 512 Stealth server: This is "like a slave server except not listed in an 513 NS RR for the zone." (Quoted from [RFC1996], Section 2.1) 515 Hidden master: A stealth server that is a master for zone transfers. 516 "In this arrangement, the master name server that processes the 517 updates is unavailable to general hosts on the Internet; it is not 518 listed in the NS RRset." (Quoted from [RFC6781], Section 3.4.3.) 519 An earlier RFC, [RFC4641], said that the hidden master's name 520 appears in the SOA RRs MNAME field, although in some setups, the 521 name does not appear at all in the public DNS. A hidden master 522 can be either a secondary or a primary master. 524 Forwarding: The process of one server sending a DNS query with the 525 RD bit set to 1 to another server to resolve that query. 526 Forwarding is a function of a DNS resolver; it is different than 527 simply blindly relaying queries. 529 [RFC5625] does not give a specific definition for forwarding, but 530 describes in detail what features a system that forwards need to 531 support. Systems that forward are sometimes called "DNS proxies", 532 but that term has not yet been defined (even in [RFC5625]). 534 Forwarder: Section 1 of [RFC2308] describes a forwarder as "a 535 nameserver used to resolve queries instead of directly using the 536 authoritative nameserver chain". [RFC2308] further says "The 537 forwarder typically either has better access to the internet, or 538 maintains a bigger cache which may be shared amongst many 539 resolvers." That definition appears to suggest that forwarders 540 normally only query authoritative servers. In current use, 541 however, forwarders often stand between stub resolvers and 542 recursive servers. [RFC2308] is silent on whether a forwarder is 543 iterative-only or can be a full-service resolver. 545 Policy-implementing resolver: A resolver acting in recursive mode 546 that changes some of the answers that it returns based on policy 547 criteria, such as to prevent access to malware sites or 548 objectionable content. In general, a stub resolver has no idea 549 whether upstream resolvers implement such policy or, if they do, 550 the exact policy about what changes will be made. In some cases, 551 the user of the stub resolver has selected the policy-implementing 552 resolver with the explicit intention of using it to implement the 553 policies. In other cases, policies are imposed without the user 554 of the stub resolver being informed. 556 Open resolver: A full-service resolver that accepts and processes 557 queries from any (or nearly any) stub resolver. This is sometimes 558 also called a "public resolver", although the term "public 559 resolver" is used more with open resolvers that are meant to be 560 open, as compared to the vast majority of open resolvers that are 561 probably misconfigured to be open. 563 View: A configuration for a DNS server that allows it to provide 564 different answers depending on attributes of the query. 565 Typically, views differ by the source IP address of a query, but 566 can also be based on the destination IP address, the type of query 567 (such as AXFR), whether it is recursive, and so on. Views are 568 often used to provide more names or different addresses to queries 569 from "inside" a protected network than to those "outside" that 570 network. Views are not a standardized part of the DNS, but they 571 are widely implemented in server software. 573 Passive DNS: A mechanism to collect large amounts of DNS data by 574 storing DNS responses from servers. Some of these systems also 575 collect the DNS queries associated with the responses; this can 576 raise privacy issues. Passive DNS databases can be used to answer 577 historical questions about DNS zones such as which records were 578 available for them at what times in the past. Passive DNS 579 databases allow searching of the stored records on keys other than 580 just the name, such as "find all names which have A records of a 581 particular value". 583 Anycast: "The practice of making a particular service address 584 available in multiple, discrete, autonomous locations, such that 585 datagrams sent are routed to one of several available locations." 586 (Quoted from [RFC4786], Section 2) 588 6. Zones 590 This section defines terms that are used when discussing zones that 591 are being served or retrieved. 593 Zone: "Authoritative information is organized into units called 594 'zones', and these zones can be automatically distributed to the 595 name servers which provide redundant service for the data in a 596 zone." (Quoted from [RFC1034], Section 2.4) 598 Child: "The entity on record that has the delegation of the domain 599 from the Parent." (Quoted from [RFC7344], Section 1.1) 601 Parent: "The domain in which the Child is registered." (Quoted from 602 [RFC7344], Section 1.1) Earlier, "parent name server" was defined 603 in [RFC0882] as "the name server that has authority over the place 604 in the domain name space that will hold the new domain". (Note 605 that [RFC0882] was obsoleted by [RFC1034] and [RFC1035].) 606 [RFC0819] also has some description of the relationship between 607 parents and children. 609 Origin: 611 (a) "The domain name that appears at the top of a zone (just below 612 the cut that separates the zone from its parent). The name of the 613 zone is the same as the name of the domain at the zone's origin." 614 (Quoted from [RFC2181], Section 6.) These days, this sense of 615 "origin" and "apex" (defined below) are often used 616 interchangeably. 618 (b) The domain name within which a given relative domain name 619 appears in zone files. Generally seen in the context of 620 "$ORIGIN", which is a control entry defined in [RFC1035], 621 Section 5.1, as part of the master file format. For example, if 622 the $ORIGIN is set to "example.org.", then a master file line for 623 "www" is in fact an entry for "www.example.org.". 625 Apex: The point in the tree at an owner of an SOA and corresponding 626 authoritative NS RRset. This is also called the "zone apex". 627 [RFC4033] defines it as "the name at the child's side of a zone 628 cut". The "apex" can usefully be thought of as a data-theoretic 629 description of a tree structure, and "origin" is the name of the 630 same concept when it is implemented in zone files. The 631 distinction is not always maintained in use, however, and one can 632 find uses that conflict subtly with this definition. [RFC1034] 633 uses the term "top node of the zone" as a synonym of "apex", but 634 that term is not widely used. These days, the first sense of 635 "origin" (above) and "apex" are often used interchangeably. 637 Zone cut: The delimitation point between two zones where the origin 638 of one of the zones is the child of the other zone. 640 "Zones are delimited by 'zone cuts'. Each zone cut separates a 641 'child' zone (below the cut) from a 'parent' zone (above the cut). 642 (Quoted from [RFC2181], Section 6; note that this is barely an 643 ostensive definition.) Section 4.2 of [RFC1034] uses "cuts" as 644 'zone cut'." 646 Delegation: The process by which a separate zone is created in the 647 name space beneath the apex of a given domain. Delegation happens 648 when an NS RRset is added in the parent zone for the child origin. 649 Delegation inherently happens at a zone cut. The term is also 650 commonly a noun: the new zone that is created by the act of 651 delegating. 653 Glue records: "[Resource records] which are not part of the 654 authoritative data [of the zone], and are address resource records 655 for the [name servers in subzones]. These RRs are only necessary 656 if the name server's name is 'below' the cut, and are only used as 657 part of a referral response." Without glue "we could be faced 658 with the situation where the NS RRs tell us that in order to learn 659 a name server's address, we should contact the server using the 660 address we wish to learn." (Definition from [RFC1034], 661 Section 4.2.1) 663 A later definition is that glue "includes any record in a zone 664 file that is not properly part of that zone, including nameserver 665 records of delegated sub-zones (NS records), address records that 666 accompany those NS records (A, AAAA, etc), and any other stray 667 data that might appear" ([RFC2181], Section 5.4.1). Although glue 668 is sometimes used today with this wider definition in mind, the 669 context surrounding the [RFC2181] definition suggests it is 670 intended to apply to the use of glue within the document itself 671 and not necessarily beyond. 673 In-bailiwick: 675 (a) An adjective to describe a name server whose name is either 676 subordinate to or (rarely) the same as the zone origin. In- 677 bailiwick name servers require glue records in their parent zone 678 (using the first of the definitions of "glue records" in the 679 definition above). 681 (b) Data for which the server is either authoritative, or else 682 authoritative for an ancestor of the owner name. This sense of 683 the term normally is used when discussing the relevancy of glue 684 records in a response. For example, the server for the parent 685 zone "example.com" might reply with glue records for 686 "ns.child.example.com". Because the "child.example.com" zone is a 687 descendant of the "example.com" zone, the glue records are in- 688 bailiwick. 690 Out-of-bailiwick: The antonym of in-bailiwick. 692 Authoritative data: "All of the RRs attached to all of the nodes 693 from the top node of the zone down to leaf nodes or nodes above 694 cuts around the bottom edge of the zone." (Quoted from [RFC1034], 695 Section 4.2.1) It is noted that this definition might 696 inadvertently also include any NS records that appear in the zone, 697 even those that might not truly be authoritative because there are 698 identical NS RRs below the zone cut. This reveals the ambiguity 699 in the notion of authoritative data, because the parent-side NS 700 records authoritatively indicate the delegation, even though they 701 are not themselves authoritative data. 703 Root zone: The zone whose apex is the zero-length label. Also 704 sometimes called "the DNS root". 706 Empty non-terminals: "Domain names that own no resource records but 707 have subdomains that do." (Quoted from [RFC4592], Section 2.2.2.) 708 A typical example is in SRV records: in the name 709 "_sip._tcp.example.com", it is likely that "_tcp.example.com" has 710 no RRsets, but that "_sip._tcp.example.com" has (at least) an SRV 711 RRset. 713 Delegation-centric zone: A zone that consists mostly of delegations 714 to child zones. This term is used in contrast to a zone that 715 might have some delegations to child zones, but also has many data 716 resource records for the zone itself and/or for child zones. The 717 term is used in [RFC4956] and [RFC5155], but is not defined there. 719 Wildcard: [RFC1034] defined "wildcard", but in a way that turned out 720 to be confusing to implementers. Special treatment is given to 721 RRs with owner names starting with the label "*". "Such RRs are 722 called 'wildcards'. Wildcard RRs can be thought of as 723 instructions for synthesizing RRs." (Quoted from [RFC1034], 724 Section 4.3.3) For an extended discussion of wildcards, including 725 clearer definitions, see [RFC4592]. 727 Asterisk label: "The first octet is the normal label type and length 728 for a 1-octet-long label, and the second octet is the ASCII 729 representation for the '*' character. A descriptive name of a 730 label equaling that value is an 'asterisk label'." (Quoted from 731 [RFC4592], Section 2.1.1) 733 Wildcard domain name: "A 'wildcard domain name' is defined by having 734 its initial (i.e., leftmost or least significant) label be 735 asterisk label." (Quoted from [RFC4592], Section 2.1.1) 737 Closest encloser: "The longest existing ancestor of a name." 738 (Quoted from [RFC5155], Section 1.3) An earlier definition is "The 739 node in the zone's tree of existing domain names that has the most 740 labels matching the query name (consecutively, counting from the 741 root label downward). Each match is a 'label match' and the order 742 of the labels is the same." (Quoted from [RFC4592], 743 Section 3.3.1) 745 Closest provable encloser: "The longest ancestor of a name that can 746 be proven to exist. Note that this is only different from the 747 closest encloser in an Opt-Out zone." (Quoted from [RFC5155], 748 Section 1.3) 750 Next closer name: "The name one label longer than the closest 751 provable encloser of a name." (Quoted from [RFC5155], 752 Section 1.3) 754 Source of Synthesis: "The source of synthesis is defined in the 755 context of a query process as that wildcard domain name 756 immediately descending from the closest encloser, provided that 757 this wildcard domain name exists. 'Immediately descending' means 758 that the source of synthesis has a name of the form: .." (Quoted from [RFC4592], 760 Section 3.3.1) 762 Occluded name: "The addition of a delegation point via dynamic 763 update will render all subordinate domain names to be in a limbo, 764 still part of the zone, but not available to the lookup process. 765 The addition of a DNAME resource record has the same impact. The 766 subordinate names are said to be 'occluded'." (Quoted from 767 [RFC5936], Section 3.5) 769 Fast flux DNS: This "occurs when a domain is found in DNS using A 770 records to multiple IP addresses, each of which has a very short 771 Time-to-Live (TTL) value associated with it. This means that the 772 domain resolves to varying IP addresses over a short period of 773 time." (Quoted from [RFC6561], Section 1.1.5, with typo 774 corrected) It is often used to deliver malware. Because the 775 addresses change so rapidly, it is difficult to ascertain all the 776 hosts. It should be noted that the technique also works with AAAA 777 records, but such use is not frequently observed on the Internet 778 as of this writing. 780 Reverse DNS, reverse lookup: "The process of mapping an address to a 781 name is generally known as a 'reverse lookup', and the IN- 782 ADDR.ARPA and IP6.ARPA zones are said to support the 'reverse 783 DNS'." (Quoted from [RFC5855], Section 1) 785 Forward lookup: "Hostname-to-address translation". (Quoted from 786 [RFC2133], Section 6) 788 arpa: Address and Routing Parameter Area Domain: "The 'arpa' domain 789 was originally established as part of the initial deployment of 790 the DNS, to provide a transition mechanism from the Host Tables 791 that were common in the ARPANET, as well as a home for the IPv4 792 reverse mapping domain. During 2000, the abbreviation was 793 redesignated to 'Address and Routing Parameter Area' in the hope 794 of reducing confusion with the earlier network name." (Quoted 795 from [RFC3172], Section 2.) 797 Infrastructure domain: A domain whose "role is to support the 798 operating infrastructure of the Internet". (Quoted from 799 [RFC3172], Section 2.) 801 Service name: "Service names are the unique key in the Service Name 802 and Transport Protocol Port Number registry. This unique symbolic 803 name for a service may also be used for other purposes, such as in 804 DNS SRV records." (Quoted from [RFC6335], Section 5.) 806 7. Registration Model 808 Registry: The administrative operation of a zone that allows 809 registration of names within that zone. People often use this 810 term to refer only to those organizations that perform 811 registration in large delegation-centric zones (such as TLDs); but 812 formally, whoever decides what data goes into a zone is the 813 registry for that zone. This definition of "registry" is from a 814 DNS point of view; for some zones, the policies that determine 815 what can go in the zone are decided by superior zones and not the 816 registry operator. 818 Registrant: An individual or organization on whose behalf a name in 819 a zone is registered by the registry. In many zones, the registry 820 and the registrant may be the same entity, but in TLDs they often 821 are not. 823 Registrar: A service provider that acts as a go-between for 824 registrants and registries. Not all registrations require a 825 registrar, though it is common to have registrars involved in 826 registrations in TLDs. 828 EPP: The Extensible Provisioning Protocol (EPP), which is commonly 829 used for communication of registration information between 830 registries and registrars. EPP is defined in [RFC5730]. 832 WHOIS: A protocol specified in [RFC3912], often used for querying 833 registry databases. WHOIS data is frequently used to associate 834 registration data (such as zone management contacts) with domain 835 names. The term "WHOIS data" is often used as a synonym for the 836 registry database, even though that database may be served by 837 different protocols, particularly RDAP. The WHOIS protocol is 838 also used with IP address registry data. 840 RDAP: The Registration Data Access Protocol, defined in [RFC7480], 841 [RFC7481], [RFC7482], [RFC7483], [RFC7484], and [RFC7485]. The 842 RDAP protocol and data format are meant as a replacement for 843 WHOIS. 845 DNS operator: An entity responsible for running DNS servers. For a 846 zone's authoritative servers, the registrant may act as their own 847 DNS operator, or their registrar may do it on their behalf, or 848 they may use a third-party operator. For some zones, the registry 849 function is performed by the DNS operator plus other entities who 850 decide about the allowed contents of the zone. 852 8. General DNSSEC 854 Most DNSSEC terms are defined in [RFC4033], [RFC4034], [RFC4035], and 855 [RFC5155]. The terms that have caused confusion in the DNS community 856 are highlighted here. 858 DNSSEC-aware and DNSSEC-unaware: These two terms, which are used in 859 some RFCs, have not been formally defined. However, Section 2 of 861 [RFC4033] defines many types of resolvers and validators, 862 including "non-validating security-aware stub resolver", "non- 863 validating stub resolver", "security-aware name server", 864 "security-aware recursive name server", "security-aware resolver", 865 "security-aware stub resolver", and "security-oblivious 866 'anything'". (Note that the term "validating resolver", which is 867 used in some places in DNSSEC-related documents, is also not 868 defined.) 870 Signed zone: "A zone whose RRsets are signed and that contains 871 properly constructed DNSKEY, Resource Record Signature (RRSIG), 872 Next Secure (NSEC), and (optionally) DS records." (Quoted from 873 [RFC4033], Section 2.) It has been noted in other contexts that 874 the zone itself is not really signed, but all the relevant RRsets 875 in the zone are signed. Nevertheless, if a zone that should be 876 signed contains any RRsets that are not signed (or opted out), 877 those RRsets will be treated as bogus, so the whole zone needs to 878 be handled in some way. 880 It should also be noted that, since the publication of [RFC6840], 881 NSEC records are no longer required for signed zones: a signed 882 zone might include NSEC3 records instead. [RFC7129] provides 883 additional background commentary and some context for the NSEC and 884 NSEC3 mechanisms used by DNSSEC to provide authenticated denial- 885 of-existence responses. 887 Unsigned zone: Section 2 of [RFC4033] defines this as "a zone that 888 is not signed". Section 2 of [RFC4035] defines this as "A zone 889 that does not include these records [properly constructed DNSKEY, 890 Resource Record Signature (RRSIG), Next Secure (NSEC), and 891 (optionally) DS records] according to the rules in this section". 892 There is an important note at the end of Section 5.2 of [RFC4035] 893 that defines an additional situation in which a zone is considered 894 unsigned: "If the resolver does not support any of the algorithms 895 listed in an authenticated DS RRset, then the resolver will not be 896 able to verify the authentication path to the child zone. In this 897 case, the resolver SHOULD treat the child zone as if it were 898 unsigned." 900 NSEC: "The NSEC record allows a security-aware resolver to 901 authenticate a negative reply for either name or type non- 902 existence with the same mechanisms used to authenticate other DNS 903 replies." (Quoted from [RFC4033], Section 3.2.) In short, an 904 NSEC record provides authenticated denial of existence. 906 "The NSEC resource record lists two separate things: the next 907 owner name (in the canonical ordering of the zone) that contains 908 authoritative data or a delegation point NS RRset, and the set of 909 RR types present at the NSEC RR's owner name." (Quoted from 910 Section 4 of RFC 4034) 912 NSEC3: Like the NSEC record, the NSEC3 record also provides 913 authenticated denial of existence; however, NSEC3 records mitigate 914 against zone enumeration and support Opt-Out. NSEC3 resource 915 records are defined in [RFC5155]. 917 Note that [RFC6840] says that [RFC5155] "is now considered part of 918 the DNS Security Document Family as described by Section 10 of 919 [RFC4033]". This means that some of the definitions from earlier 920 RFCs that only talk about NSEC records should probably be 921 considered to be talking about both NSEC and NSEC3. 923 Opt-out: "The Opt-Out Flag indicates whether this NSEC3 RR may cover 924 unsigned delegations." (Quoted from [RFC5155], Section 3.1.2.1.) 925 Opt-out tackles the high costs of securing a delegation to an 926 insecure zone. When using Opt-Out, names that are an insecure 927 delegation (and empty non-terminals that are only derived from 928 insecure delegations) don't require an NSEC3 record or its 929 corresponding RRSIG records. Opt-Out NSEC3 records are not able 930 to prove or deny the existence of the insecure delegations. 931 (Adapted from [RFC7129], Section 5.1) 933 Zone enumeration: "The practice of discovering the full content of a 934 zone via successive queries." (Quoted from [RFC5155], 935 Section 1.3.) This is also sometimes called "zone walking". Zone 936 enumeration is different from zone content guessing where the 937 guesser uses a large dictionary of possible labels and sends 938 successive queries for them, or matches the contents of NSEC3 939 records against such a dictionary. 941 Key signing key (KSK): DNSSEC keys that "only sign the apex DNSKEY 942 RRset in a zone."(Quoted from [RFC6781], Section 3.1) 944 Zone signing key (ZSK): "DNSSEC keys that can be used to sign all 945 the RRsets in a zone that require signatures, other than the apex 946 DNSKEY RRset." (Quoted from [RFC6781], Section 3.1) Note that the 947 roles KSK and ZSK are not mutually exclusive: a single key can be 948 both KSK and ZSK at the same time. Also note that a ZSK is 949 sometimes used to sign the apex DNSKEY RRset. 951 Combined signing key (CSK): "In cases where the differentiation 952 between the KSK and ZSK is not made, i.e., where keys have the 953 role of both KSK and ZSK, we talk about a Single-Type Signing 954 Scheme." (Quoted from [RFC6781], Section 3.1) This is sometimes 955 called a "combined signing key" or CSK. It is operational 956 practice, not protocol, that determines whether a particular key 957 is a ZSK, a KSK, or a CSK. 959 Secure Entry Point (SEP): A flag in the DNSKEY RDATA that "can be 960 used to distinguish between keys that are intended to be used as 961 the secure entry point into the zone when building chains of 962 trust, i.e., they are (to be) pointed to by parental DS RRs or 963 configured as a trust anchor. Therefore, it is suggested that the 964 SEP flag be set on keys that are used as KSKs and not on keys that 965 are used as ZSKs, while in those cases where a distinction between 966 a KSK and ZSK is not made (i.e., for a Single-Type Signing 967 Scheme), it is suggested that the SEP flag be set on all keys." 968 (Quoted from [RFC6781], Section 3.2.3.) Note that the SEP flag is 969 only a hint, and its presence or absence may not be used to 970 disqualify a given DNSKEY RR from use as a KSK or ZSK during 971 validation. 973 The original defintion of SEPs was in [RFC3757]. That definition 974 clearly indicated that the SEP was a key, not just a bit in the 975 key. The abstract of [RFC3757] says: "With the Delegation Signer 976 (DS) resource record (RR), the concept of a public key acting as a 977 secure entry point (SEP) has been introduced. During exchanges of 978 public keys with the parent there is a need to differentiate SEP 979 keys from other public keys in the Domain Name System KEY (DNSKEY) 980 resource record set. A flag bit in the DNSKEY RR is defined to 981 indicate that DNSKEY is to be used as a SEP." That definition of 982 the SEP as a key was made obsolete by [RFC4034], and the 983 definition from [RFC6781] is consistent with [RFC4034]. 985 Trust anchor: "A configured DNSKEY RR or DS RR hash of a DNSKEY RR. 986 A validating security-aware resolver uses this public key or hash 987 as a starting point for building the authentication chain to a 988 signed DNS response." (Quoted from [RFC4033], Section 2) 990 DNSSEC Policy (DP): A statement that "sets forth the security 991 requirements and standards to be implemented for a DNSSEC-signed 992 zone." (Quoted from [RFC6841], Section 2) 994 DNSSEC Practice Statement (DPS): "A practices disclosure document 995 that may support and be a supplemental document to the DNSSEC 996 Policy (if such exists), and it states how the management of a 997 given zone implements procedures and controls at a high level." 998 (Quoted from [RFC6841], Section 2) 1000 9. DNSSEC States 1002 A validating resolver can determine that a response is in one of four 1003 states: secure, insecure, bogus, or indeterminate. These states are 1004 defined in [RFC4033] and [RFC4035], although the two definitions 1005 differ a bit. This document makes no effort to reconcile the two 1006 definitions, and takes no position as to whether they need to be 1007 reconciled. 1009 Section 5 of [RFC4033] says: 1011 A validating resolver can determine the following 4 states: 1013 Secure: The validating resolver has a trust anchor, has a chain 1014 of trust, and is able to verify all the signatures in the 1015 response. 1017 Insecure: The validating resolver has a trust anchor, a chain 1018 of trust, and, at some delegation point, signed proof of the 1019 non-existence of a DS record. This indicates that subsequent 1020 branches in the tree are provably insecure. A validating 1021 resolver may have a local policy to mark parts of the domain 1022 space as insecure. 1024 Bogus: The validating resolver has a trust anchor and a secure 1025 delegation indicating that subsidiary data is signed, but 1026 the response fails to validate for some reason: missing 1027 signatures, expired signatures, signatures with unsupported 1028 algorithms, data missing that the relevant NSEC RR says 1029 should be present, and so forth. 1031 Indeterminate: There is no trust anchor that would indicate that a 1032 specific portion of the tree is secure. This is the default 1033 operation mode. 1035 Section 4.3 of [RFC4035] says: 1037 A security-aware resolver must be able to distinguish between four 1038 cases: 1040 Secure: An RRset for which the resolver is able to build a chain 1041 of signed DNSKEY and DS RRs from a trusted security anchor to 1042 the RRset. In this case, the RRset should be signed and is 1043 subject to signature validation, as described above. 1045 Insecure: An RRset for which the resolver knows that it has no 1046 chain of signed DNSKEY and DS RRs from any trusted starting 1047 point to the RRset. This can occur when the target RRset lies 1048 in an unsigned zone or in a descendent [sic] of an unsigned 1049 zone. In this case, the RRset may or may not be signed, but 1050 the resolver will not be able to verify the signature. 1052 Bogus: An RRset for which the resolver believes that it ought to 1053 be able to establish a chain of trust but for which it is 1054 unable to do so, either due to signatures that for some reason 1055 fail to validate or due to missing data that the relevant 1056 DNSSEC RRs indicate should be present. This case may indicate 1057 an attack but may also indicate a configuration error or some 1058 form of data corruption. 1060 Indeterminate: An RRset for which the resolver is not able to 1061 determine whether the RRset should be signed, as the resolver 1062 is not able to obtain the necessary DNSSEC RRs. This can occur 1063 when the security-aware resolver is not able to contact 1064 security-aware name servers for the relevant zones. 1066 10. Security Considerations 1068 These definitions do not change any security considerations for the 1069 DNS. 1071 11. IANA Considerations 1073 None. 1075 12. References 1077 12.1. Normative References 1079 [IANA_RootFiles] 1080 Internet Assigned Numbers Authority, "IANA Root Files", 1081 2016, . 1083 [RFC0882] Mockapetris, P., "Domain names: Concepts and facilities", 1084 RFC 882, DOI 10.17487/RFC0882, November 1983, 1085 . 1087 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1088 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1089 . 1091 [RFC1035] Mockapetris, P., "Domain names - implementation and 1092 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 1093 November 1987, . 1095 [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - 1096 Application and Support", STD 3, RFC 1123, 1097 DOI 10.17487/RFC1123, October 1989, 1098 . 1100 [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone 1101 Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996, 1102 August 1996, . 1104 [RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound, 1105 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 1106 RFC 2136, DOI 10.17487/RFC2136, April 1997, 1107 . 1109 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS 1110 Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997, 1111 . 1113 [RFC2182] Elz, R., Bush, R., Bradner, S., and M. Patton, "Selection 1114 and Operation of Secondary DNS Servers", BCP 16, RFC 2182, 1115 DOI 10.17487/RFC2182, July 1997, 1116 . 1118 [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS 1119 NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998, 1120 . 1122 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1123 Rose, "DNS Security Introduction and Requirements", 1124 RFC 4033, DOI 10.17487/RFC4033, March 2005, 1125 . 1127 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1128 Rose, "Resource Records for the DNS Security Extensions", 1129 RFC 4034, DOI 10.17487/RFC4034, March 2005, 1130 . 1132 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1133 Rose, "Protocol Modifications for the DNS Security 1134 Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005, 1135 . 1137 [RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name 1138 System", RFC 4592, DOI 10.17487/RFC4592, July 2006, 1139 . 1141 [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS 1142 Security (DNSSEC) Hashed Authenticated Denial of 1143 Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008, 1144 . 1146 [RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)", 1147 STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009, 1148 . 1150 [RFC5855] Abley, J. and T. Manderson, "Nameservers for IPv4 and IPv6 1151 Reverse Zones", BCP 155, RFC 5855, DOI 10.17487/RFC5855, 1152 May 2010, . 1154 [RFC5936] Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol 1155 (AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010, 1156 . 1158 [RFC6561] Livingood, J., Mody, N., and M. O'Reirdan, 1159 "Recommendations for the Remediation of Bots in ISP 1160 Networks", RFC 6561, DOI 10.17487/RFC6561, March 2012, 1161 . 1163 [RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the 1164 DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012, 1165 . 1167 [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC 1168 Operational Practices, Version 2", RFC 6781, 1169 DOI 10.17487/RFC6781, December 2012, 1170 . 1172 [RFC6840] Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and 1173 Implementation Notes for DNS Security (DNSSEC)", RFC 6840, 1174 DOI 10.17487/RFC6840, February 2013, 1175 . 1177 [RFC6841] Ljunggren, F., Eklund Lowinder, AM., and T. Okubo, "A 1178 Framework for DNSSEC Policies and DNSSEC Practice 1179 Statements", RFC 6841, DOI 10.17487/RFC6841, January 2013, 1180 . 1182 [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms 1183 for DNS (EDNS(0))", STD 75, RFC 6891, 1184 DOI 10.17487/RFC6891, April 2013, 1185 . 1187 [RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating 1188 DNSSEC Delegation Trust Maintenance", RFC 7344, 1189 DOI 10.17487/RFC7344, September 2014, 1190 . 1192 [RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS 1193 Terminology", RFC 7719, DOI 10.17487/RFC7719, December 1194 2015, . 1196 12.2. Informative References 1198 [DBOUND] IETF, "Domain Boundaries (dbound) Working Group", 2016, 1199 . 1201 [RFC0799] Mills, D., "Internet name domains", RFC 799, 1202 DOI 10.17487/RFC0799, September 1981, 1203 . 1205 [RFC0819] Su, Z. and J. Postel, "The Domain Naming Convention for 1206 Internet User Applications", RFC 819, 1207 DOI 10.17487/RFC0819, August 1982, 1208 . 1210 [RFC0952] Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet 1211 host table specification", RFC 952, DOI 10.17487/RFC0952, 1212 October 1985, . 1214 [RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995, 1215 DOI 10.17487/RFC1995, August 1996, 1216 . 1218 [RFC2133] Gilligan, R., Thomson, S., Bound, J., and W. Stevens, 1219 "Basic Socket Interface Extensions for IPv6", RFC 2133, 1220 DOI 10.17487/RFC2133, April 1997, 1221 . 1223 [RFC3172] Huston, G., Ed., "Management Guidelines & Operational 1224 Requirements for the Address and Routing Parameter Area 1225 Domain ("arpa")", BCP 52, RFC 3172, DOI 10.17487/RFC3172, 1226 September 2001, . 1228 [RFC3757] Kolkman, O., Schlyter, J., and E. Lewis, "Domain Name 1229 System KEY (DNSKEY) Resource Record (RR) Secure Entry 1230 Point (SEP) Flag", RFC 3757, DOI 10.17487/RFC3757, April 1231 2004, . 1233 [RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912, 1234 DOI 10.17487/RFC3912, September 2004, 1235 . 1237 [RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices", 1238 RFC 4641, DOI 10.17487/RFC4641, September 2006, 1239 . 1241 [RFC4697] Larson, M. and P. Barber, "Observed DNS Resolution 1242 Misbehavior", BCP 123, RFC 4697, DOI 10.17487/RFC4697, 1243 October 2006, . 1245 [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast 1246 Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786, 1247 December 2006, . 1249 [RFC4956] Arends, R., Kosters, M., and D. Blacka, "DNS Security 1250 (DNSSEC) Opt-In", RFC 4956, DOI 10.17487/RFC4956, July 1251 2007, . 1253 [RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines", 1254 BCP 152, RFC 5625, DOI 10.17487/RFC5625, August 2009, 1255 . 1257 [RFC5890] Klensin, J., "Internationalized Domain Names for 1258 Applications (IDNA): Definitions and Document Framework", 1259 RFC 5890, DOI 10.17487/RFC5890, August 2010, 1260 . 1262 [RFC5891] Klensin, J., "Internationalized Domain Names in 1263 Applications (IDNA): Protocol", RFC 5891, 1264 DOI 10.17487/RFC5891, August 2010, 1265 . 1267 [RFC5892] Faltstrom, P., Ed., "The Unicode Code Points and 1268 Internationalized Domain Names for Applications (IDNA)", 1269 RFC 5892, DOI 10.17487/RFC5892, August 2010, 1270 . 1272 [RFC5893] Alvestrand, H., Ed. and C. Karp, "Right-to-Left Scripts 1273 for Internationalized Domain Names for Applications 1274 (IDNA)", RFC 5893, DOI 10.17487/RFC5893, August 2010, 1275 . 1277 [RFC5894] Klensin, J., "Internationalized Domain Names for 1278 Applications (IDNA): Background, Explanation, and 1279 Rationale", RFC 5894, DOI 10.17487/RFC5894, August 2010, 1280 . 1282 [RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on 1283 Encodings for Internationalized Domain Names", RFC 6055, 1284 DOI 10.17487/RFC6055, February 2011, 1285 . 1287 [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, 1288 DOI 10.17487/RFC6265, April 2011, 1289 . 1291 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. 1292 Cheshire, "Internet Assigned Numbers Authority (IANA) 1293 Procedures for the Management of the Service Name and 1294 Transport Protocol Port Number Registry", BCP 165, 1295 RFC 6335, DOI 10.17487/RFC6335, August 2011, 1296 . 1298 [RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in 1299 Internationalization in the IETF", BCP 166, RFC 6365, 1300 DOI 10.17487/RFC6365, September 2011, 1301 . 1303 [RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of 1304 Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129, 1305 February 2014, . 1307 [RFC7480] Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the 1308 Registration Data Access Protocol (RDAP)", RFC 7480, 1309 DOI 10.17487/RFC7480, March 2015, 1310 . 1312 [RFC7481] Hollenbeck, S. and N. Kong, "Security Services for the 1313 Registration Data Access Protocol (RDAP)", RFC 7481, 1314 DOI 10.17487/RFC7481, March 2015, 1315 . 1317 [RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access 1318 Protocol (RDAP) Query Format", RFC 7482, 1319 DOI 10.17487/RFC7482, March 2015, 1320 . 1322 [RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the 1323 Registration Data Access Protocol (RDAP)", RFC 7483, 1324 DOI 10.17487/RFC7483, March 2015, 1325 . 1327 [RFC7484] Blanchet, M., "Finding the Authoritative Registration Data 1328 (RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March 1329 2015, . 1331 [RFC7485] Zhou, L., Kong, N., Shen, S., Sheng, S., and A. Servin, 1332 "Inventory and Analysis of WHOIS Registration Objects", 1333 RFC 7485, DOI 10.17487/RFC7485, March 2015, 1334 . 1336 Appendix A. Definitions Updated by this Document 1338 The following definitions from RFCs are updated by this document: 1340 o Forwarder in [RFC2308] 1342 o Secure Entry Point (SEP) in [RFC3757] 1344 Acknowledgements 1346 The following is the Acknowledgements for RFC 7719. Additional 1347 acknowledgements may be added as this draft is worked on. 1349 The authors gratefully acknowledge all of the authors of DNS-related 1350 RFCs that proceed this one. Comments from Tony Finch, Stephane 1351 Bortzmeyer, Niall O'Reilly, Colm MacCarthaigh, Ray Bellis, John 1352 Kristoff, Robert Edmonds, Paul Wouters, Shumon Huque, Paul Ebersman, 1353 David Lawrence, Matthijs Mekking, Casey Deccio, Bob Harold, Ed Lewis, 1354 John Klensin, David Black, and many others in the DNSOP Working Group 1355 helped shape RFC 7719. 1357 Additional people contributed to this document, including: John 1358 Dickinson, Bob Harold, [[ MORE NAMES WILL APPEAR HERE AS FOLKS 1359 CONTRIBUTE]]. 1361 Authors' Addresses 1363 Paul Hoffman 1364 ICANN 1366 Email: paul.hoffman@icann.org 1368 Andrew Sullivan 1369 Dyn 1370 150 Dow Street, Tower 2 1371 Manchester, NH 03101 1372 United States 1374 Email: asullivan@dyn.com 1376 Kazunori Fujiwara 1377 Japan Registry Services Co., Ltd. 1378 Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda 1379 Chiyoda-ku, Tokyo 101-0065 1380 Japan 1382 Phone: +81 3 5215 8451 1383 Email: fujiwara@jprs.co.jp