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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 Intended status: Informational A. Sullivan 5 Expires: March 27, 2016 Dyn 6 K. Fujiwara 7 JPRS 8 September 24, 2015 10 DNS Terminology 11 draft-ietf-dnsop-dns-terminology-05 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 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on March 27, 2016. 39 Copyright Notice 41 Copyright (c) 2015 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. DNS Header and Response Codes . . . . . . . . . . . . . . . . 6 59 4. Resource Records . . . . . . . . . . . . . . . . . . . . . . 7 60 5. DNS Servers and Clients . . . . . . . . . . . . . . . . . . . 8 61 6. Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 62 7. Registration Model . . . . . . . . . . . . . . . . . . . . . 16 63 8. General DNSSEC . . . . . . . . . . . . . . . . . . . . . . . 17 64 9. DNSSEC States . . . . . . . . . . . . . . . . . . . . . . . . 20 65 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 66 11. Security Considerations . . . . . . . . . . . . . . . . . . . 21 67 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 68 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 69 13.1. Normative References . . . . . . . . . . . . . . . . . . 22 70 13.2. Informative References . . . . . . . . . . . . . . . . . 24 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 73 1. Introduction 75 The domain name system (DNS) is a simple query-response protocol 76 whose messages in both directions have the same format. The protocol 77 and message format are defined in [RFC1034] and [RFC1035]. These 78 RFCs defined some terms, but later documents defined others. Some of 79 the terms from RFCs 1034 and 1035 now have somewhat different 80 meanings than they did in 1987. 82 This document collects a wide variety of DNS-related terms. Some of 83 them have been precisely defined in earlier RFCs, some have been 84 loosely defined in earlier RFCs, and some are not defined in any 85 earlier RFC at all. 87 Most of the definitions here are the consensus definition of the DNS 88 community - both protocol developers and operators. Some of the 89 definitions differ from earlier RFCs, and those differences are 90 noted. In this document, where the consensus definition is the same 91 as the one in an RFC, that RFC is quoted. Where the consensus 92 definition has changed somewhat, the RFC is mentioned but the new 93 stand-alone definition is given. 95 It is important to note that, during the development of this 96 document, it became clear that some DNS-related terms are interpreted 97 quite differently by different DNS experts. Further, some terms that 98 are defined in early DNS RFCs now have definitions that are generally 99 agreed to, but that are different from the original definitions. 100 Therefore, the authors intend to follow this document with a 101 substantial revision in the not-distant future. That revision will 102 probably have more in-depth discussion of some terms as well as new 103 terms; it will also update some of the RFCs with new definitions. 105 The terms are organized loosely by topic. Some definitions are for 106 new terms for things that are commonly talked about in the DNS 107 community but that never had terms defined for them. 109 Other organizations sometimes define DNS-related terms their own way. 110 For example, the W3C defines "domain" at 111 https://specs.webplatform.org/url/webspecs/develop/. 113 Note that there is no single consistent definition of "the DNS". It 114 can be considered to be some combination of the following: a 115 commonly-used naming scheme for objects on the Internet; a 116 distributed database representing the names and certain properties of 117 these objects; an architecture providing distributed maintenance, 118 resilience, and loose coherency for this database; and a simple 119 query-response protocol (as mentioned below) implementing this 120 architecture. 122 Capitalization in DNS terms is often inconsistent among RFCs and 123 various DNS practitioners. The capitalization used in this document 124 is a best guess at current practices, and is not meant to indicate 125 that other capitalization styles are wrong or archaic. In some 126 cases, multiple styles of capitalization are used for the same term 127 due to quoting from different RFCs. 129 2. Names 131 Domain name: Section 3.1 of [RFC1034] talks of "the domain name 132 space" as a tree structure. "Each node has a label, which is zero 133 to 63 octets in length. ... The domain name of a node is the list 134 of the labels on the path from the node to the root of the tree. 135 ... To simplify implementations, the total number of octets that 136 represent a domain name (i.e., the sum of all label octets and 137 label lengths) is limited to 255." Any label in a domain name can 138 contain any octet value. 140 Fully-qualified domain name (FQDN): This is often just a clear way 141 of saying the same thing as "domain name of a node", as outlined 142 above. However, the term is ambiguous. Strictly speaking, a 143 fully-qualified domain name would include every label, including 144 the final, zero-length label of the root: such a name would be 145 written "www.example.net." (note the terminating dot). But 146 because every name eventually shares the common root, names are 147 often written relative to the root (such as "www.example.net") and 148 are still called "fully qualified". 149 This term first appeared in [RFC0819]. 151 The need for the term "fully-qualified domain name" comes from the 152 existence of partially-qualified domain names, which are names 153 where some of the right-most names are left off and are understood 154 only by context. 156 Label: The identifier of an individual node in the sequence of nodes 157 identified by a fully-qualified domain name. 159 Host name: This term and its equivalent, "hostname", have been 160 widely used but are not defined in [RFC1034], [RFC1035], 161 [RFC1123], or [RFC2181]. The DNS was originally deployed into the 162 Host Tables environment as outlined in [RFC0952], and it is likely 163 that the term followed informally from the definition there. Over 164 time, the definition seems to have shifted. "Host name" is often 165 meant to be a domain name that follows the rules in Section 3.5 of 166 [RFC1034], the "preferred name syntax". Note that any label in a 167 domain name can contain any octet value; hostnames are generally 168 considered to be domain names where every label follows the rules 169 in the "preferred name syntax", with the amendment that labels can 170 start with ASCII digits (this amendment comes from Section 2.1 of 171 [RFC1123]). 173 People also sometimes use the term hostname to refer to just the 174 first label of an FQDN, such as "printer" in 175 "printer.admin.example.com". (Sometimes this is formalized in 176 configuration in operating systems.) In addition, people 177 sometimes use this term to describe any name that refers to a 178 machine, and those might include labels that do not conform to the 179 "preferred name syntax". 181 TLD: A Top-Level Domain, meaning a zone that is one layer below the 182 root, such as "com" or "jp". There is nothing special, from the 183 point of view of the DNS, about TLDs. Most of them are also 184 delegation-centric zones, and there are significant policy issues 185 around their operation. TLDs are often divided into sub-groups 186 such as "ccTLDs", "gTLDs", and others; the division is a matter of 187 policy, and beyond the scope of this document. 189 IDN: The common abbreviation for "internationalized domain name". 190 The IDNA protocol is the standard mechanism for handling domain 191 names with non-ASCII characters in applications in the DNS. The 192 current standard, normally called "IDNA2008", is defined in 194 [RFC5890], [RFC5891], [RFC5892], [RFC5893], and [RFC5894]. These 195 documents define many IDN-specific terms such as "LDH label", 196 "A-label", and "U-label". [RFC6365] defines more terms that 197 relate to internationalization (some of which relate to IDNs), and 198 [RFC6055] has a much more extensive discussion of IDNs, including 199 some new terminology. 201 Subdomain: A domain is a subdomain of another domain if it is 202 contained within that domain. This relationship can be tested by 203 seeing if the subdomain's name ends with the containing domain's 204 name. (Quoted from [RFC1034], section 3.1) For example, in the 205 host name "nnn.mmm.example.com", both "mmm.example.com" and 206 "nnn.mmm.example.com" are subdomains of "example.com". 208 Alias: The owner of a CNAME resource record, or a subdomain of the 209 owner of a DNAME resource record [RFC6672]. See also "canonical 210 name". 212 Canonical name: A CNAME resource record identifies its owner name as 213 an alias, and specifies the corresponding canonical name in the 214 RDATA section of the RR. (Quoted from [RFC1034], section 3.6.2) 215 This usage of the word "canonical" is related to the mathematical 216 concept of "canonical form". 218 CNAME: It is traditional to refer to the owner of a CNAME record as 219 "a CNAME". This is unfortunate, as "CNAME" is an abbreviation of 220 "canonical name", and the owner of a CNAME record is an alias not 221 a canonical name. (Quoted from [RFC2181], section 10.1.1) 223 Public suffix: A domain that is controlled by a public registry. 224 (Quoted from [RFC6265], section 5.3) A common definition for this 225 term is a domain under which subdomains can be registered, and on 226 which HTTP cookies ([RFC6265]) should not be set. There is no 227 indication in a domain name whether it is a public suffix; that 228 can only be determined by outside means. In fact, both a domain 229 and a subdomain of that domain can be public suffixes. At the 230 time this document is published, the IETF DBOUND Working Group 231 [DBOUND] is dealing with issues concerning public suffixes. 233 There is nothing inherent in a domain name to indicate whether it 234 is a public suffix. One resource for identifying public suffixes 235 is the Public Suffix List (PSL) maintained by Mozilla 236 (http://publicsuffix.org/). 238 For example, at the time this document is published, the "com.au" 239 domain is listed as a public suffix in the PSL. (Note that this 240 example might change in the future.) 241 Note that the term "public suffix" is controversial in the DNS 242 community for many reasons, and may be significantly changed in 243 the future. One example of the difficulty of calling a domain a 244 public suffix is that designation can change over time as the 245 registration policy for the zone changes, such as the case of the 246 "uk" TLD around the time this document is published. 248 3. DNS Header and Response Codes 250 The header of a DNS message is the first 12 octets. Many of the 251 fields and flags in the header diagram in sections 4.1.1 through 252 4.1.3 of [RFC1035] are referred to by their names in that diagram. 253 For example, the response codes are called "RCODEs", the data for a 254 record is called the "RDATA", and the authoritative answer bit is 255 often called "the AA flag" or "the AA bit". 257 Some of response codes that are defined in [RFC1035] have gotten 258 their own shorthand names. Some common response code names that 259 appear without reference to the numeric value are "FORMERR", 260 "SERVFAIL", and "NXDOMAIN" (the latter of which is also referred to 261 as "Name Error"). All of the RCODEs are listed at 262 http://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml, 263 although that site uses mixed-case capitalization, while most 264 documents use all-caps. 266 NODATA: A pseudo RCODE which indicates that the name is valid for 267 the given class, but there are no records of the given type. A 268 NODATA response has to be inferred from the answer. (Quoted from 269 [RFC2308], section 1.) NODATA is indicated by an answer with the 270 RCODE set to NOERROR and no relevant answers in the answer 271 section. The authority section will contain an SOA record, or 272 there will be no NS records there. (Quoted from [RFC2308], 273 section 2,2.) Note that referrals have a similar format to NODATA 274 replies; [RFC2308] explains how to distinguish them. 276 The term "NXRRSET" is sometimes used as a synonym for NODATA. 277 However, this is a mistake, given that NXRRSET is a specific error 278 code defined in [RFC2136]. 280 Negative response: A response which indicates that a particular 281 RRset does not exist, or whose RCODE indicates the nameserver 282 cannot answer. Sections 2 and 7 of [RFC2308] describe the types 283 of negative responses in detail. 285 Referrals: Data from the authority section of a non-authoritative 286 answer. [RFC1035] section 2.1 defines "authoritative" data. 287 However, referrals at zone cuts (defined in Section 6) are not 288 authoritative. Referrals may be zone cut NS resource records and 289 their glue records. NS records on the parent side of a zone cut 290 are an authoritative delegation, but are normally not treated as 291 authoritative data by the client. In general, a referral is a way 292 for a server to send an answer saying that the server does not 293 know the answer, but knows where the query should be directed in 294 order to get an answer. Historically, many authoritative servers 295 answered with a referral to the root zone when queried for a name 296 for which they were not authoritative, but this practice has 297 declined. 299 4. Resource Records 301 RR: An acronym for resource record. ([RFC1034], section 3.6.) 303 RRset: A set of resource records with the same label, class and 304 type, but with different data. (Definition from [RFC2181]) Also 305 spelled RRSet in some documents. As a clarification, "same label" 306 in this definition means "same owner name". In addition, 307 [RFC2181] states that "the TTLs of all RRs in an RRSet must be the 308 same". (This definition is definitely not the same as "the 309 response one gets to a query for QTYPE=ANY", which is a 310 unfortunate misunderstanding.) 312 EDNS: The extension mechanisms for DNS, defined in [RFC6891]. 313 Sometimes called "EDNS0" or "EDNS(0)" to indicate the version 314 number. EDNS allows DNS clients and servers to specify message 315 sizes larger than the original 512 octet limit, to expand the 316 response code space, and potentially to carry additional options 317 that affect the handling of a DNS query. 319 OPT: A pseudo-RR (sometimes called a meta-RR) that is used only to 320 contain control information pertaining to the question-and-answer 321 sequence of a specific transaction. (Definition from [RFC6891], 322 section 6.1.1) It is used by EDNS. 324 Owner: The domain name where a RR is found ([RFC1034], section 3.6). 325 Often appears in the term "owner name". 327 SOA field names: DNS documents, including the definitions here, 328 often refer to the fields in the RDATA of an SOA resource record 329 by field name. Those fields are defined in Section 3.3.13 of 330 [RFC1035]. The names (in the order they appear in the SOA RDATA) 331 are MNAME, RNAME, SERIAL, REFRESH, RETRY, EXPIRE, and MINIMUM. 332 Note that the meaning of MINIMUM field is updated in Section 4 of 333 [RFC2308]; the new definition is that the MINIMUM field is only 334 "the TTL to be used for negative responses". This document tends 335 to use field names instead of terms that describe the fields. 337 TTL: The maximum "time to live" of a resource record. A TTL value 338 is an unsigned number, with a minimum value of 0, and a maximum 339 value of 2147483647. That is, a maximum of 2^31 - 1. When 340 transmitted, the TTL is encoded in the less significant 31 bits of 341 the 32 bit TTL field, with the most significant, or sign, bit set 342 to zero. (Quoted from [RFC2181], section 8) (Note that [RFC1035] 343 erroneously stated that this is a signed integer; that was fixed 344 by [RFC2181].) 346 The TTL "specifies the time interval that the resource record may 347 be cached before the source of the information should again be 348 consulted". (Quoted from [RFC1035], section 3.2.1) Also: "the 349 time interval (in seconds) that the resource record may be cached 350 before it should be discarded". (Quoted from [RFC1035], section 351 4.1.3). Despite being defined for a resource record, the TTL of 352 every resource record in an RRset is required to be the same 353 ([RFC2181], section 5.2). 355 The reason that the TTL is the maximum time to live is that a 356 cache operator might decide to shorten the time to live for 357 operational purposes, such as if there is a policy to not allow 358 TTL values over a certain number. Also, if a value is flushed 359 from the cache when its value is still positive, the value 360 effectively becomes zero. 361 Some servers are known to ignore the TTL on some RRsets (such as 362 when the authoritative data has a very short TTL) even though this 363 is against the advice in RFC 1035. 365 There is also the concept of a "default TTL" for a zone, which can 366 be a configuration parameter in the server software. This is 367 often expressed by a default for the entire server, and a default 368 for a zone using the $TTL directive in a zone file. The $TTL 369 directive was added to the master file format by [RFC2308]. 371 Class independent: A resource record type whose syntax and semantics 372 are the same for every DNS class. A resource record type that is 373 not class independent has different meanings depending on the DNS 374 class of the record, or the meaning is undefined for classes other 375 than IN (class 1, the Internet). 377 5. DNS Servers and Clients 379 This section defines the terms used for the systems that act as DNS 380 clients, DNS servers, or both. 382 Resolver: A program that extracts information from name servers in 383 response to client requests. (Quoted from [RFC1034], section 2.4) 384 The resolver is located on the same machine as the program that 385 requests the resolver's services, but it may need to consult name 386 servers on other hosts. (Quoted from [RFC1034], section 5.1) A 387 resolver performs queries for a name, type, and class, and 388 receives answers. The logical function is called "resolution". 389 In practice, the term is usually referring to some specific type 390 of resolver (some of which are defined below), and understanding 391 the use of the term depends on understanding the context. 393 Stub resolver: A resolver that cannot perform all resolution itself. 394 Stub resolvers generally depend on a recursive resolver to 395 undertake the actual resolution function. Stub resolvers are 396 discussed but never fully defined in Section 5.3.1 of [RFC1034]. 397 They are fully defined in Section 6.1.3.1 of [RFC1123]. 399 Iterative mode: A resolution mode of a server that receives DNS 400 queries and responds with a referral to another server. 401 Section 2.3 of [RFC1034] describes this as "The server refers the 402 client to another server and lets the client pursue the query". A 403 resolver that works in iterative mode is sometimes called an 404 "iterative resolver". 406 Recursive mode: A resolution mode of a server that receives DNS 407 queries and either responds to those queries from a local cache or 408 sends queries to other servers in order to get the final answers 409 to the original queries. Section 2.3 of [RFC1034] describes this 410 as "The first server pursues the query for the client at another 411 server". A server operating in recursive mode may be thought of 412 as having a name server side (which is what answers the query) and 413 a resolver side (which performs the resolution function). Systems 414 operating in this mode are commonly called "recursive servers". 415 Sometimes they are called "recursive resolvers". While strictly 416 the difference between these is that one of them sends queries to 417 another recursive server and the other does not, in practice it is 418 not possible to know in advance whether the server that one is 419 querying will also perform recursion; both terms can be observed 420 in use interchangeably. 422 Full resolver: This term is used in [RFC1035], but it is not defined 423 there. RFC 1123 defines a "full-service resolver" that may or may 424 not be what was intended by "full resolver" in [RFC1035]. This 425 term is not properly defined in any RFC. 427 Full-service resolver: Section 6.1.3.1 of [RFC1123] defines this 428 term to mean a resolver that acts in recursive mode with a cache 429 (and meets other requirements). 431 Priming: The mechanism used by a resolver to determine where to send 432 queries before there is anything in the resolver's cache. Priming 433 is most often done from a configuration setting that contains a 434 list of authoritative servers for the root zone. 436 Negative caching: The storage of knowledge that something does not 437 exist, cannot give an answer, or does not give an answer. (Quoted 438 from [RFC2308], section 1) 440 Authoritative server: A server that knows the content of a DNS zone 441 from local knowledge, and thus can answer queries about that zone 442 without needing to query other servers. (Quoted from [RFC2182], 443 section 2.) It is a system that responds to DNS queries with 444 information about zones for which it has been configured to answer 445 with the AA flag in the response header set to 1. It is a server 446 that has authority over one or more DNS zones. Note that it is 447 possible for an authoritative server to respond to a query without 448 the parent zone delegating authority to that server. 449 Authoritative servers also provide "referrals", usually to child 450 zones delegated from them; these referrals have the AA bit set to 451 0 and come with referral data in the Authority and (if needed) the 452 Additional sections. 454 Authoritative-only server: A name server that only serves 455 authoritative data and ignores requests for recursion. It will 456 "not normally generate any queries of its own. Instead, it 457 answers non-recursive queries from iterative resolvers looking for 458 information in zones it serves." (Quoted from [RFC4697], section 459 2.4) 461 Zone transfer: The act of a client requesting a copy of a zone and 462 an authoritative server sending the needed information. (See 463 Section 6 for a description of zones.) There are two common 464 standard ways to do zone transfers: the AXFR ("Authoritative 465 Transfer") mechanism to copy the full zone (described in 466 [RFC5936], and the IXFR ("Incremental Transfer") mechanism to copy 467 only parts of the zone that have changed (described in [RFC1995]). 468 Many systems use non-standard methods for zone transfer outside 469 the DNS protocol. 471 Secondary server: "An authoritative server which uses zone transfer 472 to retrieve the zone" (quoted from [RFC1996], section 2.1). 473 [RFC2182] describes secondary servers in detail. Although early 474 DNS RFCs such as [RFC1996] referred to this as a "slave", the 475 current common usage has shifted to calling it a "secondary". 476 Secondary servers are also discussed in [RFC1034]. 478 Slave server: See secondary server. 480 Primary server: "Any authoritative server configured to be the 481 source of zone transfer for one or more [secondary] servers" 482 (quoted from [RFC1996], section 2.1) or, more specifically, "an 483 authoritative server configured to be the source of AXFR or IXFR 484 data for one or more [secondary] servers" (quoted from [RFC2136]). 485 Although early DNS RFCs such as [RFC1996] referred to this as a 486 "master", the current common usage has shifted to "primary". 487 Primary servers are also discussed in [RFC1034]. 489 Master server: See primary server. 491 Primary master: The primary master is named in the zone's SOA MNAME 492 field and optionally by an NS resource record. (Quoted from 493 [RFC1996], section 2.1) [RFC2136] defines "primary master" as 494 "Master server at the root of the AXFR/IXFR dependency graph. The 495 primary master is named in the zone's SOA MNAME field and 496 optionally by an NS RR. There is by definition only one primary 497 master server per zone." The idea of a primary master is only 498 used by [RFC2136], and is considered archaic in other parts of the 499 DNS. 501 Stealth server: This is the same as a slave server except that it is 502 not listed in an NS resource record for the zone. (Quoted from 503 [RFC1996], section 2.1) 505 Hidden master: A stealth server that is a master for zone transfers. 506 In this arrangement, the master name server that processes the 507 updates is unavailable to general hosts on the Internet; it is not 508 listed in the NS RRset. (Quoted from [RFC6781], section 3.4.3.) 509 An earlier RFC, [RFC4641], said that the hidden master's name 510 appears in the SOA RRs MNAME field, although in some setups, the 511 name does not appear at all in the public DNS. A hidden master 512 can be either a secondary or a primary master. 514 Forwarding: The process of one server sending a DNS query with the 515 RD bit set to 1 to another server to resolve that query. 516 Forwarding is a function of a DNS resolver; it is different than 517 simply blindly relaying queries. 519 [RFC5625] does not give a specific definition for forwarding, but 520 describes in detail what features a system that forwards need to 521 support. Systems that forward are sometimes called "DNS proxies", 522 but that term has not yet been defined (even in [RFC5625]). 524 Forwarder: Section 1 of [RFC2308] describes a forwarder as "a 525 nameserver used to resolve queries instead of directly using the 526 authoritative nameserver chain". [RFC2308] further says "The 527 forwarder typically either has better access to the internet, or 528 maintains a bigger cache which may be shared amongst many 529 resolvers." That definition appears to suggest that forwarders 530 normally only query authoritative servers. In current use, 531 however, forwarders often stand between stub resolvers and 532 recursive servers. [RFC2308] is silent on whether a forwarder is 533 iterative-only or can be a full-service resolver. 535 Policy-implementing resolver: A resolver acting in recursive mode 536 that changes some of the answers that it returns based on policy 537 criteria, such as to prevent access to malware sites or 538 objectionable content. In general, a stub resolver has no idea 539 whether upstream resolvers implement such policy or, if they do, 540 the exact policy about what changes will be made. In some cases, 541 the user of the stub resolver has selected the policy-implementing 542 resolver with the explicit intention of using it to implement the 543 policies. In other cases, policies are imposed without the user 544 of the stub resolver being informed. 546 Open resolver: A full-service resolver that accepts and processes 547 queries from any (or nearly any) stub resolver. This is sometimes 548 also called a "public resolver", although the term "public 549 resolver" is used more with open resolvers that are meant to be 550 open, as compared to the vast majority of open resolvers that are 551 probably misconfigured to be open. 553 View: A configuration for a DNS server that allows it to provide 554 different answers depending on attributes of the query. 555 Typically, views differ by the source IP address of a query, but 556 can also be based on the destination IP address, the type of query 557 (such as AXFR), whether it is recursive, and so on. Views are 558 often used to provide more names or different addresses to queries 559 from "inside" a protected network than to those "outside" that 560 network. Views are not a standardized part of the DNS, but they 561 are widely implemented in server software. 563 Passive DNS: A mechanism to collect large amounts of DNS data by 564 storing DNS responses from servers. Some of these systems also 565 collect the DNS queries associated with the responses; this can 566 raise privacy issues. Passive DNS databases can be used to answer 567 historical questions about DNS zones such as which records were 568 available for them at what times in the past. Passive DNS 569 databases allow searching of the stored records on keys other than 570 just the name, such as "find all names which have A records of a 571 particular value". 573 Anycast: The practice of making a particular service address 574 available in multiple, discrete, autonomous locations, such that 575 datagrams sent are routed to one of several available locations. 576 (Quoted from [RFC4786], Section 2) 578 6. Zones 580 This section defines terms that are used when discussing zones that 581 are being served or retrieved. 583 Zone: A unit of organization of authoritative data. Zones can be 584 automatically distributed to the name servers which provide 585 redundant service for the data in a zone. (Quoted from [RFC1034], 586 section 2.4) 588 Child: The entity on record that has the delegation of the domain 589 from the Parent. (Quoted from [RFC7344], section 1.1) 591 Parent: The domain in which the Child is registered. (Quoted from 592 [RFC7344], section 1.1) Earlier, "parent name server" was defined 593 in [RFC0882] as "the name server that has authority over the place 594 in the domain name space that will hold the new domain". 595 [RFC0819] also has some description of the relationship between 596 parents and children. 598 Origin: 600 (a) The domain name that appears at the top of a zone (just below 601 the cut that separates the zone from its parent). The name of the 602 zone is the same as the name of the domain at the zone's origin. 603 (Quoted from [RFC2181], section 6.) These days, this sense of 604 "origin" and "apex" (defined below) are often used 605 interchangeably. 607 (b) The domain name within which a given relative domain name 608 appears in zone files. Generally seen in the context of 609 "$ORIGIN", which is a control entry defined in [RFC1035], section 610 5.1, as part of the master file format. For example, if the 611 $ORIGIN is set to "example.org.", then a master file line for 612 "www" is in fact an entry for "www.example.org.". 614 Apex: The point in the tree at an owner of an SOA and corresponding 615 authoritative NS RRset. This is also called the "zone apex". 616 [RFC4033] defines it as "the name at the child's side of a zone 617 cut". The "apex" can usefully be thought of as a data-theoretic 618 description of a tree structure, and "origin" is the name of the 619 same concept when it is implemented in zone files. The 620 distinction is not always maintained in use, however, and one can 621 find uses that conflict subtly with this definition. [RFC1034] 622 uses the term "top node of the zone" as a synonym of "apex", but 623 that term is not widely used. These days, the first sense of 624 "origin" (above) and "apex" are often used interchangeably. 626 Zone cut: The delimitation point between two zones where the origin 627 of one of the zones is the child of the other zone. 629 Zones are delimited by "zone cuts". Each zone cut separates a 630 "child" zone (below the cut) from a "parent" zone (above the cut). 631 (Quoted from [RFC2181], section 6; note that this is barely an 632 ostensive definition.) Section 4.2 of [RFC1034] uses "cuts" as 633 "zone cut". 635 Delegation: The process by which a separate zone is created in the 636 name space beneath the apex of a given domain. Delegation happens 637 when an NS RRset is added in the parent zone for the child origin. 638 Delegation inherently happens at a zone cut. The term is also 639 commonly a noun: the new zone that is created by the act of 640 delegating. 642 Glue records: "[Resource records] which are not part of the 643 authoritative data [of the zone], and are address resource records 644 for the [name servers in subzones]. These RRs are only necessary 645 if the name server's name is 'below' the cut, and are only used as 646 part of a referral response." Without glue "we could be faced 647 with the situation where the NS RRs tell us that in order to learn 648 a name server's address, we should contact the server using the 649 address we wish to learn." (Definition from [RFC1034], section 650 4.2.1) 652 A later definition is that glue "includes any record in a zone 653 file that is not properly part of that zone, including nameserver 654 records of delegated sub-zones (NS records), address records that 655 accompany those NS records (A, AAAA, etc), and any other stray 656 data that might appear" ([RFC2181], section 5.4.1). Although glue 657 is sometimes used today with this wider definition in mind, the 658 context surrounding the [RFC2181] definition suggests it is 659 intended to apply to the use of glue within the document itself 660 and not necessarily beyond. 662 In-bailiwick: 664 (a) An adjective to describe a name server whose name is either 665 subordinate to or (rarely) the same as the zone origin. In- 666 bailiwick name servers require glue records in their parent zone 667 (using the first of the definitions of "glue records" in the 668 definition above). 670 (b) Data for which the server is either authoritative, or else 671 authoritative for an ancestor of the owner name. This sense of 672 the term normally is used when discussing the relevancy of glue 673 records in a response. For example, the server for the parent 674 zone "example.com" might reply with glue records for 675 "ns.child.example.com". Because the "child.example.com" zone is a 676 descendant of the "example.com" zone, the glue records are in- 677 bailiwick. 679 Out-of-bailiwick: The antonym of in-bailiwick. 681 Authoritative data: All of the RRs attached to all of the nodes from 682 the top node of the zone down to leaf nodes or nodes above cuts 683 around the bottom edge of the zone. (Quoted from [RFC1034], 684 section 4.2.1) It is noted that this definition might 685 inadvertently also include any NS records that appear in the zone, 686 even those that might not truly be authoritative because there are 687 identical NS RRs below the zone cut. This reveals the ambiguity 688 in the notion of authoritative data, because the parent-side NS 689 records authoritatively indicate the delegation, even though they 690 are not themselves authoritative data. 692 Root zone: The zone whose apex is the zero-length label. Also 693 sometimes called "the DNS root". 695 Empty non-terminals: Domain names that own no resource records but 696 have subdomains that do. (Quoted from [RFC4592], section 2.2.2.) 697 A typical example is in SRV records: in the name 698 "_sip._tcp.example.com", it is likely that "_tcp.example.com" has 699 no RRsets, but that "_sip._tcp.example.com" has (at least) an SRV 700 RRset. 702 Delegation-centric zone: A zone which consists mostly of delegations 703 to child zones. This term is used in contrast to a zone which 704 might have some delegations to child zones, but also has many data 705 resource records for the zone itself and/or for child zones. The 706 term is used in [RFC4956] and [RFC5155], but is not defined there. 708 Wildcard: [RFC1034] defined "wildcard", but in a way that turned out 709 to be confusing to implementers. Special treatment is given to 710 RRs with owner names starting with the label "*". Such RRs are 711 called wildcards. Wildcard RRs can be thought of as instructions 712 for synthesizing RRs. (Quoted from [RFC1034], section 4.3.3) For 713 an extended discussion of wildcards, including clearer 714 definitions, see [RFC4592]. 716 Occluded name: The addition of a delegation point via dynamic update 717 will render all subordinate domain names to be in a limbo, still 718 part of the zone but not available to the lookup process. The 719 addition of a DNAME resource record has the same impact. The 720 subordinate names are said to be "occluded". (Quoted from 721 [RFC5936], Section 3.5) 723 Fast flux DNS: This occurs when a domain is found in DNS using A 724 records to multiple IP addresses, each of which has a very short 725 Time-to-Live (TTL) value associated with it. This means that the 726 domain resolves to varying IP addresses over a short period of 727 time. (Quoted from [RFC6561], section 1.1.5, with typo corrected) 728 It is often used to deliver malware. Because the addresses change 729 so rapidly, it is difficult to acertain all the hosts. It should 730 be noted that the technique also works with AAAA records, but such 731 use is not frequently observed on the Internet as of this writing. 733 7. Registration Model 735 Registry: The administrative operation of a zone that allows 736 registration of names within that zone. People often use this 737 term to refer only to those organizations that perform 738 registration in large delegation-centric zones (such as TLDs); but 739 formally, whoever decides what data goes into a zone is the 740 registry for that zone. This definition of "registry" is from a 741 DNS point of view; for some zones, the policies that determine 742 what can go in the zone are decided by superior zones and not the 743 registry operator. 745 Registrant: An individual or organization on whose behalf a name in 746 a zone is registered by the registry. In many zones, the registry 747 and the registrant may be the same entity, but in TLDs they often 748 are not. 750 Registrar: A service provider that acts as a go-between for 751 registrants and registries. Not all registrations require a 752 registrar, though it is common to have registrars be involved in 753 registrations in TLDs. 755 EPP: The Extensible Provisioning Protocol (EPP), which is commonly 756 used for communication of registration information between 757 registries and registrars. EPP is defined in [RFC5730]. 759 WHOIS: A protocol specified in [RFC3912], often used for querying 760 registry databases. WHOIS data is frequently used to associate 761 registration data (such as zone management contacts) with domain 762 names. The term "WHOIS data" is often used as a synonym for the 763 registry database, even though that database may be served by 764 different protocols, particularly RDAP. The WHOIS protocol is 765 also used with IP address registry data. 767 RDAP: The Registration Data Access Protocol, defined in [RFC7480], 768 [RFC7481], [RFC7482], [RFC7483], [RFC7484], and [RFC7485]. The 769 RDAP protocol and data format are meant as a replacement for 770 WHOIS. 772 DNS operator: An entity responsible for running DNS servers. For a 773 zone's authoritative servers, the registrant may act as their own 774 DNS operator, or their registrar may do it on their behalf, or 775 they may use a third-party operator. For some zones, the registry 776 function is performed by the DNS operator plus other entities who 777 decide about the allowed contents of the zone. 779 8. General DNSSEC 781 Most DNSSEC terms are defined in [RFC4033], [RFC4034], [RFC4035], and 782 [RFC5155]. The terms that have caused confusion in the DNS community 783 are highlighted here. 785 DNSSEC-aware and DNSSEC-unaware: These two terms, which are used in 786 some RFCs, have not been formally defined. However, Section 2 of 787 [RFC4033] defines many types of resolvers and validators, 788 including "non-validating security-aware stub resolver", "non- 789 validating stub resolver", "security-aware name server", 790 "security-aware recursive name server", "security-aware resolver", 791 "security-aware stub resolver", and "security-oblivious 792 'anything'". (Note that the term "validating resolver", which is 793 used in some places in DNSSEC-related documents, is also not 794 defined.) 796 Signed zone: A zone whose RRsets are signed and that contains 797 properly constructed DNSKEY, Resource Record Signature (RRSIG), 798 Next Secure (NSEC), and (optionally) DS records. (Quoted from 799 [RFC4033], section 2.) It has been noted in other contexts that 800 the zone itself is not really signed, but all the relevant RRsets 801 in the zone are signed. Nevertheless, if a zone that should be 802 signed contains any RRsets that are not signed (or opted out), 803 those RRsets will be treated as bogus, so the whole zone needs to 804 be handled in some way. 806 It should also be noted that, since the publication of [RFC6840], 807 NSEC records are no longer required for signed zones: a signed 808 zone might include NSEC3 records instead. [RFC7129] provides 809 additional background commentary and some context for the NSEC and 810 NSEC3 mechanisms used by DNSSEC to provide authenticated denial- 811 of-existence responses. 813 Unsigned zone: Section 2 of [RFC4033] defines this as "a zone that 814 is not signed". Section 2 of [RFC4035] defines this as "A zone 815 that does not include these records [properly constructed DNSKEY, 816 Resource Record Signature (RRSIG), Next Secure (NSEC), and 817 (optionally) DS records] according to the rules in this section". 818 There is an important note at the end of Section 5.2 of [RFC4035] 819 that defines an additional situation in which a zone is considered 820 unsigned: "If the resolver does not support any of the algorithms 821 listed in an authenticated DS RRset, then the resolver will not be 822 able to verify the authentication path to the child zone. In this 823 case, the resolver SHOULD treat the child zone as if it were 824 unsigned." 826 NSEC: "The NSEC record allows a security-aware resolver to 827 authenticate a negative reply for either name or type non- 828 existence with the same mechanisms used to authenticate other DNS 829 replies." (Quoted from [RFC4033], section 3.2.) In short, an 830 NSEC record provides authenticated denial of existence. 832 The NSEC resource record lists two separate things: the next owner 833 name (in the canonical ordering of the zone) that contains 834 authoritative data or a delegation point NS RRset, and the set of 835 RR types present at the NSEC RR's owner name. (Quoted from 836 Section 4 of 4034) 838 NSEC3: Like the NSEC record, the NSEC3 record also provides 839 authenticated denial of existence; however, NSEC3 records mitigate 840 against zone enumeration and support Opt-Out. NSEC3 resource 841 records are defined in [RFC5155]. 843 Note that [RFC6840] says that [RFC5155] "is now considered part of 844 the DNS Security Document Family as described by Section 10 of 845 [RFC4033]". This means that some of the definitions from earlier 846 RFCs that only talk about NSEC records should probably be 847 considered to be talking about both NSEC and NSEC3. 849 Opt-out: The Opt-Out Flag indicates whether this NSEC3 RR may cover 850 unsigned delegations. (Quoted from [RFC5155], section 3.1.2.1.) 851 Opt-out tackles the high costs of securing a delegation to an 852 insecure zone. When using Opt-Out, names that are an insecure 853 delegation (and empty non-terminals that are only derived from 854 insecure delegations) don't require an NSEC3 record or its 855 corresponding RRSIG records. Opt-Out NSEC3 records are not able 856 to prove or deny the existence of the insecure delegations. 857 (Adapted from [RFC7129], section 5.1) 859 Zone enumeration: The practice of discovering the full content of a 860 zone via successive queries. (Quoted from [RFC5155], section 861 1.3.) This is also sometimes call "zone walking". Zone 862 enumeration is different from zone content guessing where the 863 guesser uses a large dictionary of possible labels and sends 864 successive queries for them, or matches the contents of NSEC3 865 records against such a dictionary. 867 Key signing key (KSK): DNSSEC keys that only sign the apex DNSKEY 868 RRset in a zone. (Quoted from [RFC6781], section 3.1) 870 Zone signing key (ZSK): DNSSEC keys that can be used to sign all the 871 RRsets in a zone that require signatures, other than the apex 872 DNSKEY RRset. (Quoted from [RFC6781], section 3.1) Note that the 873 roles KSK and ZSK are not mutually exclusive: a single key can be 874 both KSK and ZSK at the same time. Also note that a ZSK is 875 sometimes used to sign the apex DNSKEY RRset. 877 Combined signing key (CSK): In cases where the differentiation 878 between the KSK and ZSK is not made, i.e., where keys have the 879 role of both KSK and ZSK, we talk about a Single-Type Signing 880 Scheme. (Quoted from [RFC6781], Section 3.1) This is sometimes 881 called a "combined signing key" or CSK. It is operational 882 practice, not protocol, that determines whether a particular key 883 is a ZSK, a KSK, or a CSK. 885 Secure Entry Point (SEP): A flag in the DNSKEY RDATA that can be 886 used to distinguish between keys that are intended to be used as 887 the secure entry point into the zone when building chains of 888 trust, i.e., they are (to be) pointed to by parental DS RRs or 889 configured as a trust anchor. Therefore, it is suggested that the 890 SEP flag be set on keys that are used as KSKs and not on keys that 891 are used as ZSKs, while in those cases where a distinction between 892 a KSK and ZSK is not made (i.e., for a Single-Type Signing 893 Scheme), it is suggested that the SEP flag be set on all keys. 894 (Quoted from [RFC6781], section 3.2.3.) Note that the SEP flag is 895 only a hint, and its presence or absence may not be used to 896 disqualify a given DNSKEY RR from use as a KSK or ZSK during 897 validation. 899 DNSSEC Policy (DP): A statement that sets forth the security 900 requirements and standards to be implemented for a DNSSEC-signed 901 zone. (Quoted from [RFC6841], section 2) 903 DNSSEC Practice Statement (DPS): A practices disclosure document 904 that may support and be a supplemental document to the DNSSEC 905 Policy (if such exists), and it states how the management of a 906 given zone implements procedures and controls at a high level. 907 (Quoted from [RFC6841], section 2) 909 9. DNSSEC States 911 A validating resolver can determine that a response is in one of four 912 states: secure, insecure, bogus, or indeterminate. These states are 913 defined in [RFC4033] and [RFC4035], although the two definitions 914 differ a bit. This document makes no effort to reconcile the two 915 definitions, and takes no position as to whether they need to be 916 reconciled. 918 Section 5 of [RFC4033] says: 920 A validating resolver can determine the following 4 states: 922 Secure: The validating resolver has a trust anchor, has a chain of 923 trust, and is able to verify all the signatures in the response. 925 Insecure: The validating resolver has a trust anchor, a chain of 926 trust, and, at some delegation point, signed proof of the 927 non-existence of a DS record. This indicates that subsequent 928 branches in the tree are provably insecure. A validating resolver 929 may have a local policy to mark parts of the domain space as 930 insecure. 932 Bogus: The validating resolver has a trust anchor and a secure 933 delegation indicating that subsidiary data is signed, but the 934 response fails to validate for some reason: missing signatures, 935 expired signatures, signatures with unsupported algorithms, data 936 missing that the relevant NSEC RR says should be present, and so 937 forth. 939 Indeterminate: There is no trust anchor that would indicate that a 940 specific portion of the tree is secure. This is the default 941 operation mode. 943 Section 4.3 of [RFC4035] says: 945 A security-aware resolver must be able to distinguish between four 946 cases: 948 Secure: An RRset for which the resolver is able to build a chain of 949 signed DNSKEY and DS RRs from a trusted security anchor to the 950 RRset. In this case, the RRset should be signed and is subject to 951 signature validation, as described above. 953 Insecure: An RRset for which the resolver knows that it has no chain 954 of signed DNSKEY and DS RRs from any trusted starting point to the 955 RRset. This can occur when the target RRset lies in an unsigned 956 zone or in a descendent of an unsigned zone. In this case, the 957 RRset may or may not be signed, but the resolver will not be able 958 to verify the signature. 960 Bogus: An RRset for which the resolver believes that it ought to be 961 able to establish a chain of trust but for which it is unable to 962 do so, either due to signatures that for some reason fail to 963 validate or due to missing data that the relevant DNSSEC RRs 964 indicate should be present. This case may indicate an attack but 965 may also indicate a configuration error or some form of data 966 corruption. 968 Indeterminate: An RRset for which the resolver is not able to 969 determine whether the RRset should be signed, as the resolver is 970 not able to obtain the necessary DNSSEC RRs. This can occur when 971 the security-aware resolver is not able to contact security-aware 972 name servers for the relevant zones. 974 10. IANA Considerations 976 This document has no IANA actions. 978 11. Security Considerations 980 These definitions do not change any security considerations for the 981 DNS. 983 12. Acknowledgements 985 The authors gratefully acknowledge all of the authors of DNS-related 986 RFCs that proceed this one. Comments from Tony Finch, Stephane 987 Bortzmeyer, Niall O'Reilly, Colm MacCarthaigh, Ray Bellis, John 988 Kristoff, Robert Edmonds, Paul Wouters, Shumon Huque, Paul Ebersman, 989 David Lawrence, Matthijs Mekking, Casey Deccio, Bob Harold, Ed Lewis, 990 John Klensin, David Black, and many others in the DNSOP Working Group 991 have helped shape this document. 993 13. References 995 13.1. Normative References 997 [RFC0882] Mockapetris, P., "Domain names: Concepts and facilities", 998 RFC 882, DOI 10.17487/RFC0882, November 1983, 999 . 1001 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1002 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1003 . 1005 [RFC1035] Mockapetris, P., "Domain names - implementation and 1006 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 1007 November 1987, . 1009 [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - 1010 Application and Support", STD 3, RFC 1123, DOI 10.17487/ 1011 RFC1123, October 1989, 1012 . 1014 [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone 1015 Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996, 1016 August 1996, . 1018 [RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound, 1019 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 1020 RFC 2136, DOI 10.17487/RFC2136, April 1997, 1021 . 1023 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS 1024 Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997, 1025 . 1027 [RFC2182] Elz, R., Bush, R., Bradner, S., and M. Patton, "Selection 1028 and Operation of Secondary DNS Servers", BCP 16, RFC 2182, 1029 DOI 10.17487/RFC2182, July 1997, 1030 . 1032 [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS 1033 NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998, 1034 . 1036 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1037 Rose, "DNS Security Introduction and Requirements", RFC 1038 4033, DOI 10.17487/RFC4033, March 2005, 1039 . 1041 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1042 Rose, "Resource Records for the DNS Security Extensions", 1043 RFC 4034, DOI 10.17487/RFC4034, March 2005, 1044 . 1046 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1047 Rose, "Protocol Modifications for the DNS Security 1048 Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005, 1049 . 1051 [RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name 1052 System", RFC 4592, DOI 10.17487/RFC4592, July 2006, 1053 . 1055 [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS 1056 Security (DNSSEC) Hashed Authenticated Denial of 1057 Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008, 1058 . 1060 [RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)", 1061 STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009, 1062 . 1064 [RFC5936] Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol 1065 (AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010, 1066 . 1068 [RFC6561] Livingood, J., Mody, N., and M. O'Reirdan, 1069 "Recommendations for the Remediation of Bots in ISP 1070 Networks", RFC 6561, DOI 10.17487/RFC6561, March 2012, 1071 . 1073 [RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the 1074 DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012, 1075 . 1077 [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC 1078 Operational Practices, Version 2", RFC 6781, DOI 10.17487/ 1079 RFC6781, December 2012, 1080 . 1082 [RFC6840] Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and 1083 Implementation Notes for DNS Security (DNSSEC)", RFC 6840, 1084 DOI 10.17487/RFC6840, February 2013, 1085 . 1087 [RFC6841] Ljunggren, F., Eklund Lowinder, AM., and T. Okubo, "A 1088 Framework for DNSSEC Policies and DNSSEC Practice 1089 Statements", RFC 6841, DOI 10.17487/RFC6841, January 2013, 1090 . 1092 [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms 1093 for DNS (EDNS(0))", STD 75, RFC 6891, DOI 10.17487/ 1094 RFC6891, April 2013, 1095 . 1097 [RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating 1098 DNSSEC Delegation Trust Maintenance", RFC 7344, DOI 1099 10.17487/RFC7344, September 2014, 1100 . 1102 13.2. Informative References 1104 [DBOUND] "DBOUND Working Group", 2015, 1105 . 1107 [RFC0819] Su, Z. and J. Postel, "Domain naming convention for 1108 Internet user applications", RFC 819, DOI 10.17487/ 1109 RFC0819, August 1982, 1110 . 1112 [RFC0952] Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet 1113 host table specification", RFC 952, DOI 10.17487/RFC0952, 1114 October 1985, . 1116 [RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995, 1117 DOI 10.17487/RFC1995, August 1996, 1118 . 1120 [RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912, DOI 1121 10.17487/RFC3912, September 2004, 1122 . 1124 [RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices", 1125 RFC 4641, DOI 10.17487/RFC4641, September 2006, 1126 . 1128 [RFC4697] Larson, M. and P. Barber, "Observed DNS Resolution 1129 Misbehavior", BCP 123, RFC 4697, DOI 10.17487/RFC4697, 1130 October 2006, . 1132 [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast 1133 Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786, 1134 December 2006, . 1136 [RFC4956] Arends, R., Kosters, M., and D. Blacka, "DNS Security 1137 (DNSSEC) Opt-In", RFC 4956, DOI 10.17487/RFC4956, July 1138 2007, . 1140 [RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines", BCP 1141 152, RFC 5625, DOI 10.17487/RFC5625, August 2009, 1142 . 1144 [RFC5890] Klensin, J., "Internationalized Domain Names for 1145 Applications (IDNA): Definitions and Document Framework", 1146 RFC 5890, DOI 10.17487/RFC5890, August 2010, 1147 . 1149 [RFC5891] Klensin, J., "Internationalized Domain Names in 1150 Applications (IDNA): Protocol", RFC 5891, DOI 10.17487/ 1151 RFC5891, August 2010, 1152 . 1154 [RFC5892] Faltstrom, P., Ed., "The Unicode Code Points and 1155 Internationalized Domain Names for Applications (IDNA)", 1156 RFC 5892, DOI 10.17487/RFC5892, August 2010, 1157 . 1159 [RFC5893] Alvestrand, H., Ed. and C. Karp, "Right-to-Left Scripts 1160 for Internationalized Domain Names for Applications 1161 (IDNA)", RFC 5893, DOI 10.17487/RFC5893, August 2010, 1162 . 1164 [RFC5894] Klensin, J., "Internationalized Domain Names for 1165 Applications (IDNA): Background, Explanation, and 1166 Rationale", RFC 5894, DOI 10.17487/RFC5894, August 2010, 1167 . 1169 [RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on 1170 Encodings for Internationalized Domain Names", RFC 6055, 1171 DOI 10.17487/RFC6055, February 2011, 1172 . 1174 [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, 1175 DOI 10.17487/RFC6265, April 2011, 1176 . 1178 [RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in 1179 Internationalization in the IETF", BCP 166, RFC 6365, DOI 1180 10.17487/RFC6365, September 2011, 1181 . 1183 [RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of 1184 Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129, 1185 February 2014, . 1187 [RFC7480] Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the 1188 Registration Data Access Protocol (RDAP)", RFC 7480, DOI 1189 10.17487/RFC7480, March 2015, 1190 . 1192 [RFC7481] Hollenbeck, S. and N. Kong, "Security Services for the 1193 Registration Data Access Protocol (RDAP)", RFC 7481, DOI 1194 10.17487/RFC7481, March 2015, 1195 . 1197 [RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access 1198 Protocol (RDAP) Query Format", RFC 7482, DOI 10.17487/ 1199 RFC7482, March 2015, 1200 . 1202 [RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the 1203 Registration Data Access Protocol (RDAP)", RFC 7483, DOI 1204 10.17487/RFC7483, March 2015, 1205 . 1207 [RFC7484] Blanchet, M., "Finding the Authoritative Registration Data 1208 (RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March 1209 2015, . 1211 [RFC7485] Zhou, L., Kong, N., Shen, S., Sheng, S., and A. Servin, 1212 "Inventory and Analysis of WHOIS Registration Objects", 1213 RFC 7485, DOI 10.17487/RFC7485, March 2015, 1214 . 1216 Authors' Addresses 1218 Paul Hoffman 1219 ICANN 1221 Email: paul.hoffman@icann.org 1223 Andrew Sullivan 1224 Dyn 1225 150 Dow St, Tower 2 1226 Manchester, NH 1604 1227 USA 1229 Email: asullivan@dyn.com 1230 Kazunori Fujiwara 1231 Japan Registry Services Co., Ltd. 1232 Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda 1233 Chiyoda-ku, Tokyo 101-0065 1234 Japan 1236 Phone: +81 3 5215 8451 1237 Email: fujiwara@jprs.co.jp