1 Internet Engineering Task Force (IETF) P. Hoffman
2 Request for Comments: 7719 ICANN
3 Category: Informational A. Sullivan
4 ISSN: 2070-1721 Dyn
5 K. Fujiwara
6 JPRS
7 December 2015
8
9
10 DNS Terminology
11
12 Abstract
13
14 The DNS is defined in literally dozens of different RFCs. The
15 terminology used by implementers and developers of DNS protocols, and
16 by operators of DNS systems, has sometimes changed in the decades
17 since the DNS was first defined. This document gives current
18 definitions for many of the terms used in the DNS in a single
19 document.
20
21 Status of This Memo
22
23 This document is not an Internet Standards Track specification; it is
24 published for informational purposes.
25
26 This document is a product of the Internet Engineering Task Force
27 (IETF). It represents the consensus of the IETF community. It has
28 received public review and has been approved for publication by the
29 Internet Engineering Steering Group (IESG). Not all documents
30 approved by the IESG are a candidate for any level of Internet
31 Standard; see Section 2 of RFC 5741.
32
33 Information about the current status of this document, any errata,
34 and how to provide feedback on it may be obtained at
35 http://www.rfc-editor.org/info/rfc7719.
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56 Copyright Notice
57
58 Copyright (c) 2015 IETF Trust and the persons identified as the
59 document authors. All rights reserved.
60
61 This document is subject to BCP 78 and the IETF Trust's Legal
62 Provisions Relating to IETF Documents
63 (http://trustee.ietf.org/license-info) in effect on the date of
64 publication of this document. Please review these documents
65 carefully, as they describe your rights and restrictions with respect
66 to this document. Code Components extracted from this document must
67 include Simplified BSD License text as described in Section 4.e of
68 the Trust Legal Provisions and are provided without warranty as
69 described in the Simplified BSD License.
70
71 Table of Contents
72
73 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
74 2. Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
75 3. DNS Header and Response Codes . . . . . . . . . . . . . . . . 6
76 4. Resource Records . . . . . . . . . . . . . . . . . . . . . . 7
77 5. DNS Servers and Clients . . . . . . . . . . . . . . . . . . . 9
78 6. Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
79 7. Registration Model . . . . . . . . . . . . . . . . . . . . . 17
80 8. General DNSSEC . . . . . . . . . . . . . . . . . . . . . . . 18
81 9. DNSSEC States . . . . . . . . . . . . . . . . . . . . . . . . 20
82 10. Security Considerations . . . . . . . . . . . . . . . . . . . 22
83 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
84 11.1. Normative References . . . . . . . . . . . . . . . . . . 22
85 11.2. Informative References . . . . . . . . . . . . . . . . . 24
86 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 27
87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
88
The IETF is responsible for the creation and maintenance of the DNS RFCs. The ICANN DNS RFC annotation project provides a forum for collecting community annotations on these RFCs as an aid to understanding for implementers and any interested parties. The annotations displayed here are not the result of the IETF consensus process.
This RFC is included in the DNS RFCs annotation project whose home page is here.
89 1. Introduction
90
91 The Domain Name System (DNS) is a simple query-response protocol
92 whose messages in both directions have the same format. The protocol
93 and message format are defined in [RFC1034] and [RFC1035]. These
94 RFCs defined some terms, but later documents defined others. Some of
95 the terms from RFCs 1034 and 1035 now have somewhat different
96 meanings than they did in 1987.
97
98 This document collects a wide variety of DNS-related terms. Some of
99 them have been precisely defined in earlier RFCs, some have been
100 loosely defined in earlier RFCs, and some are not defined in any
101 earlier RFC at all.
102
103
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110
111 Most of the definitions here are the consensus definition of the DNS
112 community -- both protocol developers and operators. Some of the
113 definitions differ from earlier RFCs, and those differences are
114 noted. In this document, where the consensus definition is the same
115 as the one in an RFC, that RFC is quoted. Where the consensus
116 definition has changed somewhat, the RFC is mentioned but the new
117 stand-alone definition is given.
118
119 It is important to note that, during the development of this
120 document, it became clear that some DNS-related terms are interpreted
121 quite differently by different DNS experts. Further, some terms that
122 are defined in early DNS RFCs now have definitions that are generally
123 agreed to, but that are different from the original definitions.
124 Therefore, the authors intend to follow this document with a
125 substantial revision in the not-distant future. That revision will
126 probably have more in-depth discussion of some terms as well as new
127 terms; it will also update some of the RFCs with new definitions.
128
129 The terms are organized loosely by topic. Some definitions are for
130 new terms for things that are commonly talked about in the DNS
131 community but that never had terms defined for them.
132
133 Other organizations sometimes define DNS-related terms their own way.
134 For example, the W3C defines "domain" at
135 https://specs.webplatform.org/url/webspecs/develop/.
136
137 Note that there is no single consistent definition of "the DNS". It
138 can be considered to be some combination of the following: a commonly
139 used naming scheme for objects on the Internet; a distributed
140 database representing the names and certain properties of these
141 objects; an architecture providing distributed maintenance,
142 resilience, and loose coherency for this database; and a simple
143 query-response protocol (as mentioned below) implementing this
144 architecture.
145
146 Capitalization in DNS terms is often inconsistent among RFCs and
147 various DNS practitioners. The capitalization used in this document
148 is a best guess at current practices, and is not meant to indicate
149 that other capitalization styles are wrong or archaic. In some
150 cases, multiple styles of capitalization are used for the same term
151 due to quoting from different RFCs.
152
153
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165
https://specs.webplatform.org/url/webspecs/develop
https://webplatform.github.io/
The RFC should be edited to reflect the intended content. Unfortunately, although I am technical, I do not have knowledge of the original. There are also other dead references.... and a reference to a "dead project" which is still living, here, but with little reference to DNS or domains. RFC Editor note: Errata are typically not used to correct URLs that were functioning at the time of publication. For this case, please see RFC 8499 (which obsoleted RFC 7719) for the current information. --VERIFIER NOTES-- Thank you for submitting this. RFC 7719 has been updated by RFC8499 (published after your errata was submitted), which doesn't contain the reference. Thanks again W
166 2. Names
167
168 Domain name: Section 3.1 of [RFC1034] talks of "the domain name
169 space" as a tree structure. "Each node has a label, which is zero
170 to 63 octets in length. ... The domain name of a node is the list
171 of the labels on the path from the node to the root of the tree.
172 ... To simplify implementations, the total number of octets that
173 represent a domain name (i.e., the sum of all label octets and
174 label lengths) is limited to 255." Any label in a domain name can
175 contain any octet value.
176
177 Fully qualified domain name (FQDN): This is often just a clear way
178 of saying the same thing as "domain name of a node", as outlined
179 above. However, the term is ambiguous. Strictly speaking, a
180 fully qualified domain name would include every label, including
181 the final, zero-length label of the root: such a name would be
182 written "www.example.net." (note the terminating dot). But
183 because every name eventually shares the common root, names are
184 often written relative to the root (such as "www.example.net") and
185 are still called "fully qualified". This term first appeared in
186 [RFC819]. In this document, names are often written relative to
187 the root.
188
189 The need for the term "fully qualified domain name" comes from the
190 existence of partially qualified domain names, which are names
191 where some of the right-most names are left off and are understood
192 only by context.
193
194 Label: The identifier of an individual node in the sequence of nodes
195 identified by a fully qualified domain name.
196
197 Host name: This term and its equivalent, "hostname", have been
198 widely used but are not defined in [RFC1034], [RFC1035],
199 [RFC1123], or [RFC2181]. The DNS was originally deployed into the
200 Host Tables environment as outlined in [RFC952], and it is likely
201 that the term followed informally from the definition there. Over
202 time, the definition seems to have shifted. "Host name" is often
203 meant to be a domain name that follows the rules in Section 3.5 of
204 [RFC1034], the "preferred name syntax". Note that any label in a
205 domain name can contain any octet value; hostnames are generally
206 considered to be domain names where every label follows the rules
207 in the "preferred name syntax", with the amendment that labels can
208 start with ASCII digits (this amendment comes from Section 2.1 of
209 [RFC1123]).
210
211 People also sometimes use the term hostname to refer to just the
212 first label of an FQDN, such as "printer" in
213 "printer.admin.example.com". (Sometimes this is formalized in
214
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221 configuration in operating systems.) In addition, people
222 sometimes use this term to describe any name that refers to a
223 machine, and those might include labels that do not conform to the
224 "preferred name syntax".
225
226 TLD: A Top-Level Domain, meaning a zone that is one layer below the
227 root, such as "com" or "jp". There is nothing special, from the
228 point of view of the DNS, about TLDs. Most of them are also
229 delegation-centric zones, and there are significant policy issues
230 around their operation. TLDs are often divided into sub-groups
231 such as Country Code Top-Level Domains (ccTLDs), Generic Top-Level
232 Domains (gTLDs), and others; the division is a matter of policy,
233 and beyond the scope of this document.
234
235 IDN: The common abbreviation for "Internationalized Domain Name".
236 The IDNA protocol is the standard mechanism for handling domain
237 names with non-ASCII characters in applications in the DNS. The
238 current standard, normally called "IDNA2008", is defined in
239 [RFC5890], [RFC5891], [RFC5892], [RFC5893], and [RFC5894]. These
240 documents define many IDN-specific terms such as "LDH label",
241 "A-label", and "U-label". [RFC6365] defines more terms that
242 relate to internationalization (some of which relate to IDNs), and
243 [RFC6055] has a much more extensive discussion of IDNs, including
244 some new terminology.
245
246 Subdomain: "A domain is a subdomain of another domain if it is
247 contained within that domain. This relationship can be tested by
248 seeing if the subdomain's name ends with the containing domain's
249 name." (Quoted from [RFC1034], Section 3.1). For example, in the
250 host name "nnn.mmm.example.com", both "mmm.example.com" and
251 "nnn.mmm.example.com" are subdomains of "example.com".
252
253 Alias: The owner of a CNAME resource record, or a subdomain of the
254 owner of a DNAME resource record [RFC6672]. See also "canonical
255 name".
256
257 Canonical name: A CNAME resource record "identifies its owner name
258 as an alias, and specifies the corresponding canonical name in the
259 RDATA section of the RR." (Quoted from [RFC1034], Section 3.6.2)
260 This usage of the word "canonical" is related to the mathematical
261 concept of "canonical form".
262
263 CNAME: "It is traditional to refer to the owner of a CNAME record as
264 'a CNAME'. This is unfortunate, as 'CNAME' is an abbreviation of
265 'canonical name', and the owner of a CNAME record is an alias, not
266 a canonical name." (Quoted from [RFC2181], Section 10.1.1)
267
268
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276 Public suffix: "A domain that is controlled by a public registry."
277 (Quoted from [RFC6265], Section 5.3) A common definition for this
278 term is a domain under which subdomains can be registered, and on
279 which HTTP cookies ([RFC6265]) should not be set. There is no
280 indication in a domain name whether it is a public suffix; that
281 can only be determined by outside means. In fact, both a domain
282 and a subdomain of that domain can be public suffixes. At the
283 time this document is published, the IETF DBOUND Working Group
284 [DBOUND] is dealing with issues concerning public suffixes.
285
286 There is nothing inherent in a domain name to indicate whether it
287 is a public suffix. One resource for identifying public suffixes
288 is the Public Suffix List (PSL) maintained by Mozilla
289 (http://publicsuffix.org/).
290
291 For example, at the time this document is published, the "com.au"
292 domain is listed as a public suffix in the PSL. (Note that this
293 example might change in the future.)
294
295 Note that the term "public suffix" is controversial in the DNS
296 community for many reasons, and may be significantly changed in
297 the future. One example of the difficulty of calling a domain a
298 public suffix is that designation can change over time as the
299 registration policy for the zone changes, such as the case of the
300 "uk" TLD around the time this document is published.
301
302 3. DNS Header and Response Codes
303
304 The header of a DNS message is its first 12 octets. Many of the
305 fields and flags in the header diagram in Sections 4.1.1 through
306 4.1.3 of [RFC1035] are referred to by their names in that diagram.
307 For example, the response codes are called "RCODEs", the data for a
308 record is called the "RDATA", and the authoritative answer bit is
309 often called "the AA flag" or "the AA bit".
310
311 Some of response codes that are defined in [RFC1035] have gotten
312 their own shorthand names. Some common response code names that
313 appear without reference to the numeric value are "FORMERR",
314 "SERVFAIL", and "NXDOMAIN" (the latter of which is also referred to
315 as "Name Error"). All of the RCODEs are listed at
316 http://www.iana.org/assignments/dns-parameters, although that site
317 uses mixed-case capitalization, while most documents use all-caps.
318
319 NODATA: "A pseudo RCODE which indicates that the name is valid for
320 the given class, but there are no records of the given type. A
321 NODATA response has to be inferred from the answer." (Quoted from
322 [RFC2308], Section 1.) "NODATA is indicated by an answer with the
323 RCODE set to NOERROR and no relevant answers in the answer
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331 section. The authority section will contain an SOA record, or
332 there will be no NS records there." (Quoted from [RFC2308],
333 Section 2.2.) Note that referrals have a similar format to NODATA
334 replies; [RFC2308] explains how to distinguish them.
335
336 The term "NXRRSET" is sometimes used as a synonym for NODATA.
337 However, this is a mistake, given that NXRRSET is a specific error
338 code defined in [RFC2136].
339
340 Negative response: A response that indicates that a particular RRset
341 does not exist, or whose RCODE indicates the nameserver cannot
342 answer. Sections 2 and 7 of [RFC2308] describe the types of
343 negative responses in detail.
344
345 Referrals: Data from the authority section of a non-authoritative
346 answer. [RFC1035] Section 2.1 defines "authoritative" data.
347 However, referrals at zone cuts (defined in Section 6) are not
348 authoritative. Referrals may be zone cut NS resource records and
349 their glue records. NS records on the parent side of a zone cut
350 are an authoritative delegation, but are normally not treated as
351 authoritative data. In general, a referral is a way for a server
352 to send an answer saying that the server does not know the answer,
353 but knows where the query should be directed in order to get an
354 answer. Historically, many authoritative servers answered with a
355 referral to the root zone when queried for a name for which they
356 were not authoritative, but this practice has declined.
357
358 4. Resource Records
359
360 RR: An acronym for resource record. ([RFC1034], Section 3.6.)
361
362 RRset: A set of resource records with the same label, class and
363 type, but with different data. (Definition from [RFC2181]) Also
364 spelled RRSet in some documents. As a clarification, "same label"
365 in this definition means "same owner name". In addition,
366 [RFC2181] states that "the TTLs of all RRs in an RRSet must be the
367 same". (This definition is definitely not the same as "the
368 response one gets to a query for QTYPE=ANY", which is an
369 unfortunate misunderstanding.)
370
371 EDNS: The extension mechanisms for DNS, defined in [RFC6891].
372 Sometimes called "EDNS0" or "EDNS(0)" to indicate the version
373 number. EDNS allows DNS clients and servers to specify message
374 sizes larger than the original 512 octet limit, to expand the
375 response code space, and potentially to carry additional options
376 that affect the handling of a DNS query.
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386 OPT: A pseudo-RR (sometimes called a "meta-RR") that is used only to
387 contain control information pertaining to the question-and-answer
388 sequence of a specific transaction. (Definition from [RFC6891],
389 Section 6.1.1) It is used by EDNS.
390
391 Owner: The domain name where a RR is found ([RFC1034], Section 3.6).
392 Often appears in the term "owner name".
393
394 SOA field names: DNS documents, including the definitions here,
395 often refer to the fields in the RDATA of an SOA resource record
396 by field name. Those fields are defined in Section 3.3.13 of
397 [RFC1035]. The names (in the order they appear in the SOA RDATA)
398 are MNAME, RNAME, SERIAL, REFRESH, RETRY, EXPIRE, and MINIMUM.
399 Note that the meaning of MINIMUM field is updated in Section 4 of
400 [RFC2308]; the new definition is that the MINIMUM field is only
401 "the TTL to be used for negative responses". This document tends
402 to use field names instead of terms that describe the fields.
403
404 TTL: The maximum "time to live" of a resource record. "A TTL value
405 is an unsigned number, with a minimum value of 0, and a maximum
406 value of 2147483647. That is, a maximum of 2^31 - 1. When
407 transmitted, the TTL is encoded in the less significant 31 bits of
408 the 32 bit TTL field, with the most significant, or sign, bit set
409 to zero." (Quoted from [RFC2181], Section 8) (Note that [RFC1035]
410 erroneously stated that this is a signed integer; that was fixed
411 by [RFC2181].)
412
413 The TTL "specifies the time interval that the resource record may
414 be cached before the source of the information should again be
415 consulted". (Quoted from [RFC1035], Section 3.2.1) Also: "the
416 time interval (in seconds) that the resource record may be cached
417 before it should be discarded". (Quoted from [RFC1035],
418 Section 4.1.3). Despite being defined for a resource record, the
419 TTL of every resource record in an RRset is required to be the
420 same ([RFC2181], Section 5.2).
421
422 The reason that the TTL is the maximum time to live is that a
423 cache operator might decide to shorten the time to live for
424 operational purposes, such as if there is a policy to disallow TTL
425 values over a certain number. Also, if a value is flushed from
426 the cache when its value is still positive, the value effectively
427 becomes zero. Some servers are known to ignore the TTL on some
428 RRsets (such as when the authoritative data has a very short TTL)
429 even though this is against the advice in RFC 1035.
430
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441 There is also the concept of a "default TTL" for a zone, which can
442 be a configuration parameter in the server software. This is
443 often expressed by a default for the entire server, and a default
444 for a zone using the $TTL directive in a zone file. The $TTL
445 directive was added to the master file format by [RFC2308].
446
447 Class independent: A resource record type whose syntax and semantics
448 are the same for every DNS class. A resource record type that is
449 not class independent has different meanings depending on the DNS
450 class of the record, or the meaning is undefined for classes other
451 than IN (class 1, the Internet).
452
453 5. DNS Servers and Clients
454
455 This section defines the terms used for the systems that act as DNS
456 clients, DNS servers, or both.
457
458 Resolver: A program "that extract[s] information from name servers
459 in response to client requests." (Quoted from [RFC1034],
460 Section 2.4) "The resolver is located on the same machine as the
461 program that requests the resolver's services, but it may need to
462 consult name servers on other hosts." (Quoted from [RFC1034],
463 Section 5.1) A resolver performs queries for a name, type, and
464 class, and receives answers. The logical function is called
465 "resolution". In practice, the term is usually referring to some
466 specific type of resolver (some of which are defined below), and
467 understanding the use of the term depends on understanding the
468 context.
469
470 Stub resolver: A resolver that cannot perform all resolution itself.
471 Stub resolvers generally depend on a recursive resolver to
472 undertake the actual resolution function. Stub resolvers are
473 discussed but never fully defined in Section 5.3.1 of [RFC1034].
474 They are fully defined in Section 6.1.3.1 of [RFC1123].
475
476 Iterative mode: A resolution mode of a server that receives DNS
477 queries and responds with a referral to another server.
478 Section 2.3 of [RFC1034] describes this as "The server refers the
479 client to another server and lets the client pursue the query". A
480 resolver that works in iterative mode is sometimes called an
481 "iterative resolver".
482
483 Recursive mode: A resolution mode of a server that receives DNS
484 queries and either responds to those queries from a local cache or
485 sends queries to other servers in order to get the final answers
486 to the original queries. Section 2.3 of [RFC1034] describes this
487 as "The first server pursues the query for the client at another
488 server". A server operating in recursive mode may be thought of
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496 as having a name server side (which is what answers the query) and
497 a resolver side (which performs the resolution function). Systems
498 operating in this mode are commonly called "recursive servers".
499 Sometimes they are called "recursive resolvers". While strictly
500 the difference between these is that one of them sends queries to
501 another recursive server and the other does not, in practice it is
502 not possible to know in advance whether the server that one is
503 querying will also perform recursion; both terms can be observed
504 in use interchangeably.
505
506 Full resolver: This term is used in [RFC1035], but it is not defined
507 there. RFC 1123 defines a "full-service resolver" that may or may
508 not be what was intended by "full resolver" in [RFC1035]. This
509 term is not properly defined in any RFC.
510
511 Full-service resolver: Section 6.1.3.1 of [RFC1123] defines this
512 term to mean a resolver that acts in recursive mode with a cache
513 (and meets other requirements).
514
515 Priming: The mechanism used by a resolver to determine where to send
516 queries before there is anything in the resolver's cache. Priming
517 is most often done from a configuration setting that contains a
518 list of authoritative servers for the root zone.
519
520 Negative caching: "The storage of knowledge that something does not
521 exist, cannot give an answer, or does not give an answer."
522 (Quoted from [RFC2308], Section 1)
523
524 Authoritative server: "A server that knows the content of a DNS zone
525 from local knowledge, and thus can answer queries about that zone
526 without needing to query other servers." (Quoted from [RFC2182],
527 Section 2.) It is a system that responds to DNS queries with
528 information about zones for which it has been configured to answer
529 with the AA flag in the response header set to 1. It is a server
530 that has authority over one or more DNS zones. Note that it is
531 possible for an authoritative server to respond to a query without
532 the parent zone delegating authority to that server.
533 Authoritative servers also provide "referrals", usually to child
534 zones delegated from them; these referrals have the AA bit set to
535 0 and come with referral data in the Authority and (if needed) the
536 Additional sections.
537
538 Authoritative-only server: A name server that only serves
539 authoritative data and ignores requests for recursion. It will
540 "not normally generate any queries of its own. Instead, it
541 answers non-recursive queries from iterative resolvers looking for
542 information in zones it serves." (Quoted from [RFC4697],
543 Section 2.4)
544
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550
551 Zone transfer: The act of a client requesting a copy of a zone and
552 an authoritative server sending the needed information. (See
553 Section 6 for a description of zones.) There are two common
554 standard ways to do zone transfers: the AXFR ("Authoritative
555 Transfer") mechanism to copy the full zone (described in
556 [RFC5936], and the IXFR ("Incremental Transfer") mechanism to copy
557 only parts of the zone that have changed (described in [RFC1995]).
558 Many systems use non-standard methods for zone transfer outside
559 the DNS protocol.
560
561 Secondary server: "An authoritative server which uses zone transfer
562 to retrieve the zone" (Quoted from [RFC1996], Section 2.1).
563 [RFC2182] describes secondary servers in detail. Although early
564 DNS RFCs such as [RFC1996] referred to this as a "slave", the
565 current common usage has shifted to calling it a "secondary".
566 Secondary servers are also discussed in [RFC1034].
567
568 Slave server: See secondary server.
569
570 Primary server: "Any authoritative server configured to be the
571 source of zone transfer for one or more [secondary] servers"
572 (Quoted from [RFC1996], Section 2.1) or, more specifically, "an
573 authoritative server configured to be the source of AXFR or IXFR
574 data for one or more [secondary] servers" (Quoted from [RFC2136]).
575 Although early DNS RFCs such as [RFC1996] referred to this as a
576 "master", the current common usage has shifted to "primary".
577 Primary servers are also discussed in [RFC1034].
578
579 Master server: See primary server.
580
581 Primary master: "The primary master is named in the zone's SOA MNAME
582 field and optionally by an NS RR". (Quoted from [RFC1996],
583 Section 2.1). [RFC2136] defines "primary master" as "Master
584 server at the root of the AXFR/IXFR dependency graph. The primary
585 master is named in the zone's SOA MNAME field and optionally by an
586 NS RR. There is by definition only one primary master server per
587 zone." The idea of a primary master is only used by [RFC2136],
588 and is considered archaic in other parts of the DNS.
589
590 Stealth server: This is "like a slave server except not listed in an
591 NS RR for the zone." (Quoted from [RFC1996], Section 2.1)
592
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606 Hidden master: A stealth server that is a master for zone transfers.
607 "In this arrangement, the master name server that processes the
608 updates is unavailable to general hosts on the Internet; it is not
609 listed in the NS RRset." (Quoted from [RFC6781], Section 3.4.3.)
610 An earlier RFC, [RFC4641], said that the hidden master's name
611 appears in the SOA RRs MNAME field, although in some setups, the
612 name does not appear at all in the public DNS. A hidden master
613 can be either a secondary or a primary master.
614
615 Forwarding: The process of one server sending a DNS query with the
616 RD bit set to 1 to another server to resolve that query.
617 Forwarding is a function of a DNS resolver; it is different than
618 simply blindly relaying queries.
619
620 [RFC5625] does not give a specific definition for forwarding, but
621 describes in detail what features a system that forwards need to
622 support. Systems that forward are sometimes called "DNS proxies",
623 but that term has not yet been defined (even in [RFC5625]).
624
625 Forwarder: Section 1 of [RFC2308] describes a forwarder as "a
626 nameserver used to resolve queries instead of directly using the
627 authoritative nameserver chain". [RFC2308] further says "The
628 forwarder typically either has better access to the internet, or
629 maintains a bigger cache which may be shared amongst many
630 resolvers." That definition appears to suggest that forwarders
631 normally only query authoritative servers. In current use,
632 however, forwarders often stand between stub resolvers and
633 recursive servers. [RFC2308] is silent on whether a forwarder is
634 iterative-only or can be a full-service resolver.
635
636 Policy-implementing resolver: A resolver acting in recursive mode
637 that changes some of the answers that it returns based on policy
638 criteria, such as to prevent access to malware sites or
639 objectionable content. In general, a stub resolver has no idea
640 whether upstream resolvers implement such policy or, if they do,
641 the exact policy about what changes will be made. In some cases,
642 the user of the stub resolver has selected the policy-implementing
643 resolver with the explicit intention of using it to implement the
644 policies. In other cases, policies are imposed without the user
645 of the stub resolver being informed.
646
647 Open resolver: A full-service resolver that accepts and processes
648 queries from any (or nearly any) stub resolver. This is sometimes
649 also called a "public resolver", although the term "public
650 resolver" is used more with open resolvers that are meant to be
651 open, as compared to the vast majority of open resolvers that are
652 probably misconfigured to be open.
653
654
655
656
657 Hoffman, et al. Informational [Page 12]
658 RFC 7719 DNS Terminology December 2015
659
660
661 View: A configuration for a DNS server that allows it to provide
662 different answers depending on attributes of the query.
663 Typically, views differ by the source IP address of a query, but
664 can also be based on the destination IP address, the type of query
665 (such as AXFR), whether it is recursive, and so on. Views are
666 often used to provide more names or different addresses to queries
667 from "inside" a protected network than to those "outside" that
668 network. Views are not a standardized part of the DNS, but they
669 are widely implemented in server software.
670
671 Passive DNS: A mechanism to collect large amounts of DNS data by
672 storing DNS responses from servers. Some of these systems also
673 collect the DNS queries associated with the responses; this can
674 raise privacy issues. Passive DNS databases can be used to answer
675 historical questions about DNS zones such as which records were
676 available for them at what times in the past. Passive DNS
677 databases allow searching of the stored records on keys other than
678 just the name, such as "find all names which have A records of a
679 particular value".
680
681 Anycast: "The practice of making a particular service address
682 available in multiple, discrete, autonomous locations, such that
683 datagrams sent are routed to one of several available locations."
684 (Quoted from [RFC4786], Section 2)
685
686 6. Zones
687
688 This section defines terms that are used when discussing zones that
689 are being served or retrieved.
690
691 Zone: "Authoritative information is organized into units called
692 'zones', and these zones can be automatically distributed to the
693 name servers which provide redundant service for the data in a
694 zone." (Quoted from [RFC1034], Section 2.4)
695
696 Child: "The entity on record that has the delegation of the domain
697 from the Parent." (Quoted from [RFC7344], Section 1.1)
698
699 Parent: "The domain in which the Child is registered." (Quoted from
700 [RFC7344], Section 1.1) Earlier, "parent name server" was defined
701 in [RFC882] as "the name server that has authority over the place
702 in the domain name space that will hold the new domain". (Note
703 that [RFC882] was obsoleted by [RFC1034] and [RFC1035].) [RFC819]
704 also has some description of the relationship between parents and
705 children.
706
707
708
709
710
711
712 Hoffman, et al. Informational [Page 13]
713 RFC 7719 DNS Terminology December 2015
714
715
716 Origin:
717
718 (a) "The domain name that appears at the top of a zone (just below
719 the cut that separates the zone from its parent). The name of the
720 zone is the same as the name of the domain at the zone's origin."
721 (Quoted from [RFC2181], Section 6.) These days, this sense of
722 "origin" and "apex" (defined below) are often used
723 interchangeably.
724
725 (b) The domain name within which a given relative domain name
726 appears in zone files. Generally seen in the context of
727 "$ORIGIN", which is a control entry defined in [RFC1035],
728 Section 5.1, as part of the master file format. For example, if
729 the $ORIGIN is set to "example.org.", then a master file line for
730 "www" is in fact an entry for "www.example.org.".
731
732 Apex: The point in the tree at an owner of an SOA and corresponding
733 authoritative NS RRset. This is also called the "zone apex".
734 [RFC4033] defines it as "the name at the child's side of a zone
735 cut". The "apex" can usefully be thought of as a data-theoretic
736 description of a tree structure, and "origin" is the name of the
737 same concept when it is implemented in zone files. The
738 distinction is not always maintained in use, however, and one can
739 find uses that conflict subtly with this definition. [RFC1034]
740 uses the term "top node of the zone" as a synonym of "apex", but
741 that term is not widely used. These days, the first sense of
742 "origin" (above) and "apex" are often used interchangeably.
743
744 Zone cut: The delimitation point between two zones where the origin
745 of one of the zones is the child of the other zone.
746
747 "Zones are delimited by 'zone cuts'. Each zone cut separates a
748 'child' zone (below the cut) from a 'parent' zone (above the cut).
749 (Quoted from [RFC2181], Section 6; note that this is barely an
750 ostensive definition.) Section 4.2 of [RFC1034] uses "cuts" as
751 'zone cut'."
752
753 Delegation: The process by which a separate zone is created in the
754 name space beneath the apex of a given domain. Delegation happens
755 when an NS RRset is added in the parent zone for the child origin.
756 Delegation inherently happens at a zone cut. The term is also
757 commonly a noun: the new zone that is created by the act of
758 delegating.
759
760
761
762
763
764
765
766
767 Hoffman, et al. Informational [Page 14]
768 RFC 7719 DNS Terminology December 2015
769
770
771 Glue records: "[Resource records] which are not part of the
772 authoritative data [of the zone], and are address resource records
773 for the [name servers in subzones]. These RRs are only necessary
774 if the name server's name is 'below' the cut, and are only used as
775 part of a referral response." Without glue "we could be faced
776 with the situation where the NS RRs tell us that in order to learn
777 a name server's address, we should contact the server using the
778 address we wish to learn." (Definition from [RFC1034],
779 Section 4.2.1)
780
781 A later definition is that glue "includes any record in a zone
782 file that is not properly part of that zone, including nameserver
783 records of delegated sub-zones (NS records), address records that
784 accompany those NS records (A, AAAA, etc), and any other stray
785 data that might appear" ([RFC2181], Section 5.4.1). Although glue
786 is sometimes used today with this wider definition in mind, the
787 context surrounding the [RFC2181] definition suggests it is
788 intended to apply to the use of glue within the document itself
789 and not necessarily beyond.
790
791 In-bailiwick:
792
793 (a) An adjective to describe a name server whose name is either
794 subordinate to or (rarely) the same as the zone origin. In-
795 bailiwick name servers require glue records in their parent zone
796 (using the first of the definitions of "glue records" in the
797 definition above).
798
799 (b) Data for which the server is either authoritative, or else
800 authoritative for an ancestor of the owner name. This sense of
801 the term normally is used when discussing the relevancy of glue
802 records in a response. For example, the server for the parent
803 zone "example.com" might reply with glue records for
804 "ns.child.example.com". Because the "child.example.com" zone is a
805 descendant of the "example.com" zone, the glue records are in-
806 bailiwick.
807
808 Out-of-bailiwick: The antonym of in-bailiwick.
809
810 Authoritative data: "All of the RRs attached to all of the nodes
811 from the top node of the zone down to leaf nodes or nodes above
812 cuts around the bottom edge of the zone." (Quoted from [RFC1034],
813 Section 4.2.1) It is noted that this definition might
814 inadvertently also include any NS records that appear in the zone,
815 even those that might not truly be authoritative because there are
816 identical NS RRs below the zone cut. This reveals the ambiguity
817
818
819
820
821
822 Hoffman, et al. Informational [Page 15]
823 RFC 7719 DNS Terminology December 2015
824
825
826 in the notion of authoritative data, because the parent-side NS
827 records authoritatively indicate the delegation, even though they
828 are not themselves authoritative data.
829
830 Root zone: The zone whose apex is the zero-length label. Also
831 sometimes called "the DNS root".
832
833 Empty non-terminals: "Domain names that own no resource records but
834 have subdomains that do." (Quoted from [RFC4592], Section 2.2.2.)
835 A typical example is in SRV records: in the name
836 "_sip._tcp.example.com", it is likely that "_tcp.example.com" has
837 no RRsets, but that "_sip._tcp.example.com" has (at least) an SRV
838 RRset.
839
840 Delegation-centric zone: A zone that consists mostly of delegations
841 to child zones. This term is used in contrast to a zone that
842 might have some delegations to child zones, but also has many data
843 resource records for the zone itself and/or for child zones. The
844 term is used in [RFC4956] and [RFC5155], but is not defined there.
845
846 Wildcard: [RFC1034] defined "wildcard", but in a way that turned out
847 to be confusing to implementers. Special treatment is given to
848 RRs with owner names starting with the label "*". "Such RRs are
849 called 'wildcards'. Wildcard RRs can be thought of as
850 instructions for synthesizing RRs." (Quoted from [RFC1034],
851 Section 4.3.3) For an extended discussion of wildcards, including
852 clearer definitions, see [RFC4592].
853
854 Occluded name: "The addition of a delegation point via dynamic
855 update will render all subordinate domain names to be in a limbo,
856 still part of the zone, but not available to the lookup process.
857 The addition of a DNAME resource record has the same impact. The
858 subordinate names are said to be 'occluded'." (Quoted from
859 [RFC5936], Section 3.5)
860
861 Fast flux DNS: This "occurs when a domain is found in DNS using A
862 records to multiple IP addresses, each of which has a very short
863 Time-to-Live (TTL) value associated with it. This means that the
864 domain resolves to varying IP addresses over a short period of
865 time." (Quoted from [RFC6561], Section 1.1.5, with typo
866 corrected) It is often used to deliver malware. Because the
867 addresses change so rapidly, it is difficult to ascertain all the
868 hosts. It should be noted that the technique also works with AAAA
869 records, but such use is not frequently observed on the Internet
870 as of this writing.
871
872
873
874
875
876
877 Hoffman, et al. Informational [Page 16]
878 RFC 7719 DNS Terminology December 2015
879
880
881 7. Registration Model
882
883 Registry: The administrative operation of a zone that allows
884 registration of names within that zone. People often use this
885 term to refer only to those organizations that perform
886 registration in large delegation-centric zones (such as TLDs); but
887 formally, whoever decides what data goes into a zone is the
888 registry for that zone. This definition of "registry" is from a
889 DNS point of view; for some zones, the policies that determine
890 what can go in the zone are decided by superior zones and not the
891 registry operator.
892
893 Registrant: An individual or organization on whose behalf a name in
894 a zone is registered by the registry. In many zones, the registry
895 and the registrant may be the same entity, but in TLDs they often
896 are not.
897
898 Registrar: A service provider that acts as a go-between for
899 registrants and registries. Not all registrations require a
900 registrar, though it is common to have registrars involved in
901 registrations in TLDs.
902
903 EPP: The Extensible Provisioning Protocol (EPP), which is commonly
904 used for communication of registration information between
905 registries and registrars. EPP is defined in [RFC5730].
906
907 WHOIS: A protocol specified in [RFC3912], often used for querying
908 registry databases. WHOIS data is frequently used to associate
909 registration data (such as zone management contacts) with domain
910 names. The term "WHOIS data" is often used as a synonym for the
911 registry database, even though that database may be served by
912 different protocols, particularly RDAP. The WHOIS protocol is
913 also used with IP address registry data.
914
915 RDAP: The Registration Data Access Protocol, defined in [RFC7480],
916 [RFC7481], [RFC7482], [RFC7483], [RFC7484], and [RFC7485]. The
917 RDAP protocol and data format are meant as a replacement for
918 WHOIS.
919
920 DNS operator: An entity responsible for running DNS servers. For a
921 zone's authoritative servers, the registrant may act as their own
922 DNS operator, or their registrar may do it on their behalf, or
923 they may use a third-party operator. For some zones, the registry
924 function is performed by the DNS operator plus other entities who
925 decide about the allowed contents of the zone.
926
927
928
929
930
931
932 Hoffman, et al. Informational [Page 17]
933 RFC 7719 DNS Terminology December 2015
934
935
936 8. General DNSSEC
937
938 Most DNSSEC terms are defined in [RFC4033], [RFC4034], [RFC4035], and
939 [RFC5155]. The terms that have caused confusion in the DNS community
940 are highlighted here.
941
942 DNSSEC-aware and DNSSEC-unaware: These two terms, which are used in
943 some RFCs, have not been formally defined. However, Section 2 of
944 [RFC4033] defines many types of resolvers and validators,
945 including "non-validating security-aware stub resolver", "non-
946 validating stub resolver", "security-aware name server",
947 "security-aware recursive name server", "security-aware resolver",
948 "security-aware stub resolver", and "security-oblivious
949 'anything'". (Note that the term "validating resolver", which is
950 used in some places in DNSSEC-related documents, is also not
951 defined.)
952
953 Signed zone: "A zone whose RRsets are signed and that contains
954 properly constructed DNSKEY, Resource Record Signature (RRSIG),
955 Next Secure (NSEC), and (optionally) DS records." (Quoted from
956 [RFC4033], Section 2.) It has been noted in other contexts that
957 the zone itself is not really signed, but all the relevant RRsets
958 in the zone are signed. Nevertheless, if a zone that should be
959 signed contains any RRsets that are not signed (or opted out),
960 those RRsets will be treated as bogus, so the whole zone needs to
961 be handled in some way.
962
963 It should also be noted that, since the publication of [RFC6840],
964 NSEC records are no longer required for signed zones: a signed
965 zone might include NSEC3 records instead. [RFC7129] provides
966 additional background commentary and some context for the NSEC and
967 NSEC3 mechanisms used by DNSSEC to provide authenticated denial-
968 of-existence responses.
969
970 Unsigned zone: Section 2 of [RFC4033] defines this as "a zone that
971 is not signed". Section 2 of [RFC4035] defines this as "A zone
972 that does not include these records [properly constructed DNSKEY,
973 Resource Record Signature (RRSIG), Next Secure (NSEC), and
974 (optionally) DS records] according to the rules in this section".
975 There is an important note at the end of Section 5.2 of [RFC4035]
976 that defines an additional situation in which a zone is considered
977 unsigned: "If the resolver does not support any of the algorithms
978 listed in an authenticated DS RRset, then the resolver will not be
979 able to verify the authentication path to the child zone. In this
980 case, the resolver SHOULD treat the child zone as if it were
981 unsigned."
982
983
984
985
986
987 Hoffman, et al. Informational [Page 18]
988 RFC 7719 DNS Terminology December 2015
989
990
991 NSEC: "The NSEC record allows a security-aware resolver to
992 authenticate a negative reply for either name or type non-
993 existence with the same mechanisms used to authenticate other DNS
994 replies." (Quoted from [RFC4033], Section 3.2.) In short, an
995 NSEC record provides authenticated denial of existence.
996
997 "The NSEC resource record lists two separate things: the next
998 owner name (in the canonical ordering of the zone) that contains
999 authoritative data or a delegation point NS RRset, and the set of
1000 RR types present at the NSEC RR's owner name." (Quoted from
1001 Section 4 of RFC 4034)
1002
1003 NSEC3: Like the NSEC record, the NSEC3 record also provides
1004 authenticated denial of existence; however, NSEC3 records mitigate
1005 against zone enumeration and support Opt-Out. NSEC3 resource
1006 records are defined in [RFC5155].
1007
1008 Note that [RFC6840] says that [RFC5155] "is now considered part of
1009 the DNS Security Document Family as described by Section 10 of
1010 [RFC4033]". This means that some of the definitions from earlier
1011 RFCs that only talk about NSEC records should probably be
1012 considered to be talking about both NSEC and NSEC3.
1013
1014 Opt-out: "The Opt-Out Flag indicates whether this NSEC3 RR may cover
1015 unsigned delegations." (Quoted from [RFC5155], Section 3.1.2.1.)
1016 Opt-out tackles the high costs of securing a delegation to an
1017 insecure zone. When using Opt-Out, names that are an insecure
1018 delegation (and empty non-terminals that are only derived from
1019 insecure delegations) don't require an NSEC3 record or its
1020 corresponding RRSIG records. Opt-Out NSEC3 records are not able
1021 to prove or deny the existence of the insecure delegations.
1022 (Adapted from [RFC7129], Section 5.1)
1023
1024 Zone enumeration: "The practice of discovering the full content of a
1025 zone via successive queries." (Quoted from [RFC5155],
1026 Section 1.3.) This is also sometimes called "zone walking". Zone
1027 enumeration is different from zone content guessing where the
1028 guesser uses a large dictionary of possible labels and sends
1029 successive queries for them, or matches the contents of NSEC3
1030 records against such a dictionary.
1031
1032 Key signing key (KSK): DNSSEC keys that "only sign the apex DNSKEY
1033 RRset in a zone."(Quoted from [RFC6781], Section 3.1)
1034
1035
1036
1037
1038
1039
1040
1041
1042 Hoffman, et al. Informational [Page 19]
1043 RFC 7719 DNS Terminology December 2015
1044
1045
1046 Zone signing key (ZSK): "DNSSEC keys that can be used to sign all
1047 the RRsets in a zone that require signatures, other than the apex
1048 DNSKEY RRset." (Quoted from [RFC6781], Section 3.1) Note that the
1049 roles KSK and ZSK are not mutually exclusive: a single key can be
1050 both KSK and ZSK at the same time. Also note that a ZSK is
1051 sometimes used to sign the apex DNSKEY RRset.
1052
1053 Combined signing key (CSK): "In cases where the differentiation
1054 between the KSK and ZSK is not made, i.e., where keys have the
1055 role of both KSK and ZSK, we talk about a Single-Type Signing
1056 Scheme." (Quoted from [RFC6781], Section 3.1) This is sometimes
1057 called a "combined signing key" or CSK. It is operational
1058 practice, not protocol, that determines whether a particular key
1059 is a ZSK, a KSK, or a CSK.
1060
1061 Secure Entry Point (SEP): A flag in the DNSKEY RDATA that "can be
1062 used to distinguish between keys that are intended to be used as
1063 the secure entry point into the zone when building chains of
1064 trust, i.e., they are (to be) pointed to by parental DS RRs or
1065 configured as a trust anchor. Therefore, it is suggested that the
1066 SEP flag be set on keys that are used as KSKs and not on keys that
1067 are used as ZSKs, while in those cases where a distinction between
1068 a KSK and ZSK is not made (i.e., for a Single-Type Signing
1069 Scheme), it is suggested that the SEP flag be set on all keys."
1070 (Quoted from [RFC6781], Section 3.2.3.) Note that the SEP flag is
1071 only a hint, and its presence or absence may not be used to
1072 disqualify a given DNSKEY RR from use as a KSK or ZSK during
1073 validation.
1074
1075 DNSSEC Policy (DP): A statement that "sets forth the security
1076 requirements and standards to be implemented for a DNSSEC-signed
1077 zone." (Quoted from [RFC6841], Section 2)
1078
1079 DNSSEC Practice Statement (DPS): "A practices disclosure document
1080 that may support and be a supplemental document to the DNSSEC
1081 Policy (if such exists), and it states how the management of a
1082 given zone implements procedures and controls at a high level."
1083 (Quoted from [RFC6841], Section 2)
1084
1085 9. DNSSEC States
1086
1087 A validating resolver can determine that a response is in one of four
1088 states: secure, insecure, bogus, or indeterminate. These states are
1089 defined in [RFC4033] and [RFC4035], although the two definitions
1090 differ a bit. This document makes no effort to reconcile the two
1091 definitions, and takes no position as to whether they need to be
1092 reconciled.
1093
1094
1095
1096
1097 Hoffman, et al. Informational [Page 20]
1098 RFC 7719 DNS Terminology December 2015
1099
1100
1101 Section 5 of [RFC4033] says:
1102
1103 A validating resolver can determine the following 4 states:
1104
1105 Secure: The validating resolver has a trust anchor, has a chain
1106 of trust, and is able to verify all the signatures in the
1107 response.
1108
1109 Insecure: The validating resolver has a trust anchor, a chain
1110 of trust, and, at some delegation point, signed proof of the
1111 non-existence of a DS record. This indicates that subsequent
1112 branches in the tree are provably insecure. A validating
1113 resolver may have a local policy to mark parts of the domain
1114 space as insecure.
1115
1116 Bogus: The validating resolver has a trust anchor and a secure
1117 delegation indicating that subsidiary data is signed, but
1118 the response fails to validate for some reason: missing
1119 signatures, expired signatures, signatures with unsupported
1120 algorithms, data missing that the relevant NSEC RR says
1121 should be present, and so forth.
1122
1123 Indeterminate: There is no trust anchor that would indicate that a
1124 specific portion of the tree is secure. This is the default
1125 operation mode.
1126
1127 Section 4.3 of [RFC4035] says:
1128
1129 A security-aware resolver must be able to distinguish between four
1130 cases:
1131
1132 Secure: An RRset for which the resolver is able to build a chain
1133 of signed DNSKEY and DS RRs from a trusted security anchor to
1134 the RRset. In this case, the RRset should be signed and is
1135 subject to signature validation, as described above.
1136
1137 Insecure: An RRset for which the resolver knows that it has no
1138 chain of signed DNSKEY and DS RRs from any trusted starting
1139 point to the RRset. This can occur when the target RRset lies
1140 in an unsigned zone or in a descendent [sic] of an unsigned
1141 zone. In this case, the RRset may or may not be signed, but
1142 the resolver will not be able to verify the signature.
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152 Hoffman, et al. Informational [Page 21]
1153 RFC 7719 DNS Terminology December 2015
1154
1155
1156 Bogus: An RRset for which the resolver believes that it ought to
1157 be able to establish a chain of trust but for which it is
1158 unable to do so, either due to signatures that for some reason
1159 fail to validate or due to missing data that the relevant
1160 DNSSEC RRs indicate should be present. This case may indicate
1161 an attack but may also indicate a configuration error or some
1162 form of data corruption.
1163
1164 Indeterminate: An RRset for which the resolver is not able to
1165 determine whether the RRset should be signed, as the resolver
1166 is not able to obtain the necessary DNSSEC RRs. This can occur
1167 when the security-aware resolver is not able to contact
1168 security-aware name servers for the relevant zones.
1169
1170 10. Security Considerations
1171
1172 These definitions do not change any security considerations for the
1173 DNS.
1174
1175 11. References
1176
1177 11.1. Normative References
1178
1179 [RFC882] Mockapetris, P., "Domain names: Concepts and facilities",
1180 RFC 882, DOI 10.17487/RFC0882, November 1983,
1181 <http://www.rfc-editor.org/info/rfc882>.
1182
1183 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
1184 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
1185 <http://www.rfc-editor.org/info/rfc1034>.
1186
1187 [RFC1035] Mockapetris, P., "Domain names - implementation and
1188 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
1189 November 1987, <http://www.rfc-editor.org/info/rfc1035>.
1190
1191 [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts -
1192 Application and Support", STD 3, RFC 1123,
1193 DOI 10.17487/RFC1123, October 1989,
1194 <http://www.rfc-editor.org/info/rfc1123>.
1195
1196 [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone
1197 Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996,
1198 August 1996, <http://www.rfc-editor.org/info/rfc1996>.
1199
1200 [RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
1201 "Dynamic Updates in the Domain Name System (DNS UPDATE)",
1202 RFC 2136, DOI 10.17487/RFC2136, April 1997,
1203 <http://www.rfc-editor.org/info/rfc2136>.
1204
1205
1206
1207 Hoffman, et al. Informational [Page 22]
1208 RFC 7719 DNS Terminology December 2015
1209
1210
1211 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
1212 Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
1213 <http://www.rfc-editor.org/info/rfc2181>.
1214
1215 [RFC2182] Elz, R., Bush, R., Bradner, S., and M. Patton, "Selection
1216 and Operation of Secondary DNS Servers", BCP 16, RFC 2182,
1217 DOI 10.17487/RFC2182, July 1997,
1218 <http://www.rfc-editor.org/info/rfc2182>.
1219
1220 [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
1221 NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,
1222 <http://www.rfc-editor.org/info/rfc2308>.
1223
1224 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
1225 Rose, "DNS Security Introduction and Requirements",
1226 RFC 4033, DOI 10.17487/RFC4033, March 2005,
1227 <http://www.rfc-editor.org/info/rfc4033>.
1228
1229 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
1230 Rose, "Resource Records for the DNS Security Extensions",
1231 RFC 4034, DOI 10.17487/RFC4034, March 2005,
1232 <http://www.rfc-editor.org/info/rfc4034>.
1233
1234 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
1235 Rose, "Protocol Modifications for the DNS Security
1236 Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
1237 <http://www.rfc-editor.org/info/rfc4035>.
1238
1239 [RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name
1240 System", RFC 4592, DOI 10.17487/RFC4592, July 2006,
1241 <http://www.rfc-editor.org/info/rfc4592>.
1242
1243 [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
1244 Security (DNSSEC) Hashed Authenticated Denial of
1245 Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008,
1246 <http://www.rfc-editor.org/info/rfc5155>.
1247
1248 [RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)",
1249 STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009,
1250 <http://www.rfc-editor.org/info/rfc5730>.
1251
1252 [RFC5936] Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol
1253 (AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010,
1254 <http://www.rfc-editor.org/info/rfc5936>.
1255
1256
1257
1258
1259
1260
1261
1262 Hoffman, et al. Informational [Page 23]
1263 RFC 7719 DNS Terminology December 2015
1264
1265
1266 [RFC6561] Livingood, J., Mody, N., and M. O'Reirdan,
1267 "Recommendations for the Remediation of Bots in ISP
1268 Networks", RFC 6561, DOI 10.17487/RFC6561, March 2012,
1269 <http://www.rfc-editor.org/info/rfc6561>.
1270
1271 [RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the
1272 DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012,
1273 <http://www.rfc-editor.org/info/rfc6672>.
1274
1275 [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC
1276 Operational Practices, Version 2", RFC 6781,
1277 DOI 10.17487/RFC6781, December 2012,
1278 <http://www.rfc-editor.org/info/rfc6781>.
1279
1280 [RFC6840] Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and
1281 Implementation Notes for DNS Security (DNSSEC)", RFC 6840,
1282 DOI 10.17487/RFC6840, February 2013,
1283 <http://www.rfc-editor.org/info/rfc6840>.
1284
1285 [RFC6841] Ljunggren, F., Eklund Lowinder, AM., and T. Okubo, "A
1286 Framework for DNSSEC Policies and DNSSEC Practice
1287 Statements", RFC 6841, DOI 10.17487/RFC6841, January 2013,
1288 <http://www.rfc-editor.org/info/rfc6841>.
1289
1290 [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
1291 for DNS (EDNS(0))", STD 75, RFC 6891,
1292 DOI 10.17487/RFC6891, April 2013,
1293 <http://www.rfc-editor.org/info/rfc6891>.
1294
1295 [RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating
1296 DNSSEC Delegation Trust Maintenance", RFC 7344,
1297 DOI 10.17487/RFC7344, September 2014,
1298 <http://www.rfc-editor.org/info/rfc7344>.
1299
1300 11.2. Informative References
1301
1302 [DBOUND] IETF, "Domain Boundaries (dbound) Working Group", 2015,
1303 <https://datatracker.ietf.org/wg/dbound/charter/>.
1304
1305 [RFC819] Su, Z. and J. Postel, "The Domain Naming Convention for
1306 Internet User Applications", RFC 819,
1307 DOI 10.17487/RFC0819, August 1982,
1308 <http://www.rfc-editor.org/info/rfc819>.
1309
1310 [RFC952] Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet
1311 host table specification", RFC 952, DOI 10.17487/RFC0952,
1312 October 1985, <http://www.rfc-editor.org/info/rfc952>.
1313
1314
1315
1316
1317 Hoffman, et al. Informational [Page 24]
1318 RFC 7719 DNS Terminology December 2015
1319
1320
1321 [RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995,
1322 DOI 10.17487/RFC1995, August 1996,
1323 <http://www.rfc-editor.org/info/rfc1995>.
1324
1325 [RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912,
1326 DOI 10.17487/RFC3912, September 2004,
1327 <http://www.rfc-editor.org/info/rfc3912>.
1328
1329 [RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices",
1330 RFC 4641, DOI 10.17487/RFC4641, September 2006,
1331 <http://www.rfc-editor.org/info/rfc4641>.
1332
1333 [RFC4697] Larson, M. and P. Barber, "Observed DNS Resolution
1334 Misbehavior", BCP 123, RFC 4697, DOI 10.17487/RFC4697,
1335 October 2006, <http://www.rfc-editor.org/info/rfc4697>.
1336
1337 [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast
1338 Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786,
1339 December 2006, <http://www.rfc-editor.org/info/rfc4786>.
1340
1341 [RFC4956] Arends, R., Kosters, M., and D. Blacka, "DNS Security
1342 (DNSSEC) Opt-In", RFC 4956, DOI 10.17487/RFC4956, July
1343 2007, <http://www.rfc-editor.org/info/rfc4956>.
1344
1345 [RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines",
1346 BCP 152, RFC 5625, DOI 10.17487/RFC5625, August 2009,
1347 <http://www.rfc-editor.org/info/rfc5625>.
1348
1349 [RFC5890] Klensin, J., "Internationalized Domain Names for
1350 Applications (IDNA): Definitions and Document Framework",
1351 RFC 5890, DOI 10.17487/RFC5890, August 2010,
1352 <http://www.rfc-editor.org/info/rfc5890>.
1353
1354 [RFC5891] Klensin, J., "Internationalized Domain Names in
1355 Applications (IDNA): Protocol", RFC 5891,
1356 DOI 10.17487/RFC5891, August 2010,
1357 <http://www.rfc-editor.org/info/rfc5891>.
1358
1359 [RFC5892] Faltstrom, P., Ed., "The Unicode Code Points and
1360 Internationalized Domain Names for Applications (IDNA)",
1361 RFC 5892, DOI 10.17487/RFC5892, August 2010,
1362 <http://www.rfc-editor.org/info/rfc5892>.
1363
1364 [RFC5893] Alvestrand, H., Ed. and C. Karp, "Right-to-Left Scripts
1365 for Internationalized Domain Names for Applications
1366 (IDNA)", RFC 5893, DOI 10.17487/RFC5893, August 2010,
1367 <http://www.rfc-editor.org/info/rfc5893>.
1368
1369
1370
1371
1372 Hoffman, et al. Informational [Page 25]
1373 RFC 7719 DNS Terminology December 2015
1374
1375
1376 [RFC5894] Klensin, J., "Internationalized Domain Names for
1377 Applications (IDNA): Background, Explanation, and
1378 Rationale", RFC 5894, DOI 10.17487/RFC5894, August 2010,
1379 <http://www.rfc-editor.org/info/rfc5894>.
1380
1381 [RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on
1382 Encodings for Internationalized Domain Names", RFC 6055,
1383 DOI 10.17487/RFC6055, February 2011,
1384 <http://www.rfc-editor.org/info/rfc6055>.
1385
1386 [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
1387 DOI 10.17487/RFC6265, April 2011,
1388 <http://www.rfc-editor.org/info/rfc6265>.
1389
1390 [RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
1391 Internationalization in the IETF", BCP 166, RFC 6365,
1392 DOI 10.17487/RFC6365, September 2011,
1393 <http://www.rfc-editor.org/info/rfc6365>.
1394
1395 [RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of
1396 Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129,
1397 February 2014, <http://www.rfc-editor.org/info/rfc7129>.
1398
1399 [RFC7480] Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the
1400 Registration Data Access Protocol (RDAP)", RFC 7480,
1401 DOI 10.17487/RFC7480, March 2015,
1402 <http://www.rfc-editor.org/info/rfc7480>.
1403
1404 [RFC7481] Hollenbeck, S. and N. Kong, "Security Services for the
1405 Registration Data Access Protocol (RDAP)", RFC 7481,
1406 DOI 10.17487/RFC7481, March 2015,
1407 <http://www.rfc-editor.org/info/rfc7481>.
1408
1409 [RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access
1410 Protocol (RDAP) Query Format", RFC 7482,
1411 DOI 10.17487/RFC7482, March 2015,
1412 <http://www.rfc-editor.org/info/rfc7482>.
1413
1414 [RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the
1415 Registration Data Access Protocol (RDAP)", RFC 7483,
1416 DOI 10.17487/RFC7483, March 2015,
1417 <http://www.rfc-editor.org/info/rfc7483>.
1418
1419 [RFC7484] Blanchet, M., "Finding the Authoritative Registration Data
1420 (RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March
1421 2015, <http://www.rfc-editor.org/info/rfc7484>.
1422
1423
1424
1425
1426
1427 Hoffman, et al. Informational [Page 26]
1428 RFC 7719 DNS Terminology December 2015
1429
1430
1431 [RFC7485] Zhou, L., Kong, N., Shen, S., Sheng, S., and A. Servin,
1432 "Inventory and Analysis of WHOIS Registration Objects",
1433 RFC 7485, DOI 10.17487/RFC7485, March 2015,
1434 <http://www.rfc-editor.org/info/rfc7485>.
1435
1436 Acknowledgements
1437
1438 The authors gratefully acknowledge all of the authors of DNS-related
1439 RFCs that proceed this one. Comments from Tony Finch, Stephane
1440 Bortzmeyer, Niall O'Reilly, Colm MacCarthaigh, Ray Bellis, John
1441 Kristoff, Robert Edmonds, Paul Wouters, Shumon Huque, Paul Ebersman,
1442 David Lawrence, Matthijs Mekking, Casey Deccio, Bob Harold, Ed Lewis,
1443 John Klensin, David Black, and many others in the DNSOP Working Group
1444 have helped shape this document.
1445
1446 Authors' Addresses
1447
1448 Paul Hoffman
1449 ICANN
1450
1451 Email: paul.hoffman@icann.org
1452
1453
1454 Andrew Sullivan
1455 Dyn
1456 150 Dow Street, Tower 2
1457 Manchester, NH 03101
1458 United States
1459
1460 Email: asullivan@dyn.com
1461
1462
1463 Kazunori Fujiwara
1464 Japan Registry Services Co., Ltd.
1465 Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda
1466 Chiyoda-ku, Tokyo 101-0065
1467 Japan
1468
1469 Phone: +81 3 5215 8451
1470 Email: fujiwara@jprs.co.jp
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482 Hoffman, et al. Informational [Page 27]
1483
CNAME: "It is traditional to refer to the owner of a CNAME record as 'a CNAME'. This is unfortunate, as 'CNAME' is an abbreviation of 'canonical name', and the owner of a CNAME record is most certainly not a canonical name." (Quoted from [RFC2181], Section 10.1.1)
CNAME: "It is traditional to refer to the label of a CNAME record as 'a CNAME'. This is unfortunate, as 'CNAME' is an abbreviation of 'canonical name', and the label of a CNAME record is an alias, not a canonical name." (Quoted from [RFC2181], Section 10.1.1)
Incorrect quote from RFC 2181. --VERIFIER NOTES-- Not a technical erratum. is corrected already in https://tools.ietf.org/html/draft-ietf-dnsop-terminology-bis-05 which should be examined for consistency