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Checking references for intended status: Best Current Practice ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 882 (Obsoleted by RFC 1034, RFC 1035) ** Obsolete normative reference: RFC 1206 (Obsoleted by RFC 1325) ** Downref: Normative reference to an Informational RFC: RFC 6561 ** Downref: Normative reference to an Informational RFC: RFC 6781 ** Downref: Normative reference to an Informational RFC: RFC 6841 -- Obsolete informational reference (is this intentional?): RFC 4641 (Obsoleted by RFC 6781) Summary: 6 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Hoffman 3 Internet-Draft VPN Consortium 4 Intended status: Best Current Practice A. Sullivan 5 Expires: December 24, 2015 Dyn 6 K. Fujiwara 7 JPRS 8 June 22, 2015 10 DNS Terminology 11 draft-ietf-dnsop-dns-terminology-03 13 Abstract 15 The DNS is defined in literally dozens of different RFCs. The 16 terminology used in by implementers and developers of DNS protocols, 17 and 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 December 24, 2015. 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 . . . . . . . . . . . . . . . . 5 59 4. Resource Records . . . . . . . . . . . . . . . . . . . . . . 6 60 5. DNS Servers . . . . . . . . . . . . . . . . . . . . . . . . . 8 61 6. Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 62 7. Registration Model . . . . . . . . . . . . . . . . . . . . . 15 63 8. General DNSSEC . . . . . . . . . . . . . . . . . . . . . . . 16 64 9. DNSSEC States . . . . . . . . . . . . . . . . . . . . . . . . 18 65 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 66 11. Security Considerations . . . . . . . . . . . . . . . . . . . 20 67 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 68 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 69 13.1. Normative References . . . . . . . . . . . . . . . . . . 21 70 13.2. Informative References . . . . . . . . . . . . . . . . . 22 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24 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 The definitions here are believed to be the consensus definition of 88 the DNS community, both protocol developers and operators. Some of 89 the definitions differ from earlier RFCs, and those differences are 90 noted. The terms are organized loosely by topic. Some definitions 91 are for new terms for things that are commonly talked about in the 92 DNS community but that never had terms defined for them. 94 During the development of this document, it became clear that some 95 DNS-related terms are interpreted quite differently by different DNS 96 experts. Further, some terms that are defined in early DNS RFCs now 97 have definitions that are generally agreed to that are different from 98 the original definitions. Therefore, the authors intend to follow 99 this document with a substantial revision in the not-distant future. 100 That revision will probably have more in-depth discussion of some 101 terms as well as new terms; it will also update some of the RFCs with 102 new definitions. 104 In this document, where the consensus definition is the same as the 105 one in an RFC, that RFC is quoted. Where the consensus definition 106 has changed somewhat, the RFC is mentioned but the new stand-alone 107 definition is given. 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 database 116 representing the names and certain properties of these objects; an 117 architecture providing distributed maintenance, resilience, and loose 118 coherency for this database; and a simple query-response protocol (as 119 mentioned below) implementing this architecture. 121 Capitalization in DNS terms is often inconsistent between RFCs and 122 between DNS practitioners. The capitalization used in this document 123 is a best guess at current practices, and is not meant to indicate 124 that other capitalization styles are wrong or archaic. In some 125 cases, multiple styles of capitalization are used for the same term 126 due to quoting from different RFCs. 128 2. Names 130 Domain name: Section 3.1 of [RFC1034] talks of "the domain name 131 space" as a tree structure. "Each node has a label, which is zero 132 to 63 octets in length. ... The domain name of a node is the list 133 of the labels on the path from the node to the root of the tree. 134 ... To simplify implementations, the total number of octets that 135 represent a domain name (i.e., the sum of all label octets and 136 label lengths) is limited to 255." 138 Fully-qualified domain name (FQDN): This is often just a clear way 139 of saying the same thing as "domain name of a node", as outlined 140 above. However, the term is ambiguous. Strictly speaking, a 141 fully-qualified name would include every label, including the 142 final, zero-length label of the root zone: such a name would be 143 written "www.example.net." (note the terminating dot). But 144 because every name eventually shares the common root, names are 145 often written relative to the root (such as "www.example.net") and 146 are still called "fully qualified". 147 This term first appeared in [RFC1206]. 149 The need for the term "fully-qualified domain name" comes from the 150 existence of partially-qualified domain names, which are names 151 where some of the right-most names are left off and are understood 152 only by context. 154 Label: The identifier of an individual node in the sequence of nodes 155 that comprise a fully-qualified domain name. 157 Host name: This term and its equivalent, "hostname", have been 158 widely used but are not defined in [RFC1034], [RFC1035], 159 [RFC1123], or [RFC2181]. The DNS was originally deployed into the 160 Host Tables environment as outlined in [RFC0952], and it is likely 161 that the term followed informally from the definition there. Over 162 time, the definition seems to have shifted. "Host name" is often 163 meant to be a domain name that follows the rules in Section 3.5 of 164 [RFC1034], the "preferred name syntax". Note that any label in 165 any domain name can contain any octet value; hostnames are 166 generally considered to be domain names where every label follows 167 the rules in the "preferred name syntax", with the amendment that 168 labels can start with ASCII digits (this amendment comes from 169 Section 2.1 of [RFC1123]). 171 People also sometimes use the term hostname to refer to just the 172 first label of an FQDN. In addition, people sometimes use this 173 term to describe any name that refers to a machine, and those 174 might include labels that do not conform to the "preferred name 175 syntax". 177 TLD: A Top-Level Domain, meaning a zone that is one layer below the 178 root, such as .com or .jp. There is nothing special, from the 179 point of view of the DNS, about TLDs. Most of them are also 180 delegation-centric zones, and there are significant policy issues 181 around their operation. TLDs are often divided into sub-groups 182 such as "ccTLDs", "gTLDs", and others; the division is a matter of 183 policy, and beyond the scope of this document. 185 IDN: The common abbreviation for "internationalized domain name". 186 IDNs are the current standard mechanism for handling domain names 187 with non-ASCII characters in applications. The current standard, 188 normally called "IDNA2008", is defined in [RFC5890], [RFC5891], 189 [RFC5892], [RFC5893], and [RFC5894]. These documents define many 190 IDN-specific terms such as "LDH label", "A-label", and "U-label". 192 Alias: The owner of a CNAME resource record, or a subdomain of the 193 owner of a DNAME resource record [RFC6672]. See also "canonical 194 name". 196 Canonical name: A CNAME resource record identifies its owner name as 197 an alias, and specifies the corresponding canonical name in the 198 RDATA section of the RR. (Quoted from [RFC1034], section 3.6.2) 199 This usage of the word "canonical" is related to the mathematical 200 concept of "canonical form". 202 CNAME: It is traditional to refer to the owner of a CNAME record as 203 "a CNAME". This is unfortunate, as "CNAME" is an abbreviation of 204 "canonical name", and the owner of a CNAME record is an alias not 205 a canonical name. (Quoted from [RFC2181], section 10.1.1) 207 Public suffix: A domain under which subdomains can be registered, 208 and on which HTTP cookies ([RFC6265]) should not be set. There is 209 no indication in a domain name whether or not it is a public 210 suffix; that can only be determined by outside means. The IETF 211 DBOUND Working Group [DBOUND] deals with issues with public 212 suffixes. 214 For example, at the time this document is published, .com.au is 215 considered a public suffix, but .au is not. (Note that this 216 example might change in the future.) 218 Note that the term "public suffix" is controversial in the DNS 219 community for many reasons, and may be significantly changed in 220 the future. One example of the difficulty of calling a domain a 221 public suffix is that designation can change over time as the 222 registration policy for the zone changes, such as the case of the 223 .uk zone around the time this document is published. 225 3. DNS Header and Response Codes 227 The header of a DNS message is first 12 octets. Many of the fields 228 and flags in the header diagram in section 4.1.1 of [RFC1035] are 229 referred to by their names in that diagram. For example, the 230 response codes are called "RCODEs", the data for a record is called 231 the "RDATA", and the authoritative answer bit is often called "the AA 232 flag" or "the AA bit". 234 Some of response codes that are defined in [RFC1035] have gotten 235 their own shorthand names. Some common response code names that 236 appear without reference to the numeric value are "FORMERR", 237 "SERVFAIL", and "NXDOMAIN" (the latter of which is also referred to 238 as "Name Error"). All of the RCODEs are listed at 239 http://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml, 240 although that site uses mixed-case capitalization, while most 241 documents use all-caps. 243 NODATA: A pseudo RCODE which indicates that the name is valid for 244 the given class, but are no records of the given type. A NODATA 245 response has to be inferred from the answer. (Quoted from 246 [RFC2308], section 1.) NODATA is indicated by an answer with the 247 RCODE set to NOERROR and no relevant answers in the answer 248 section. The authority section will contain an SOA record, or 249 there will be no NS records there. (Quoted from [RFC2308], 250 section 2,2.) Note that referrals have a similar format to NODATA 251 replies; [RFC2308] explains how to distinguish them. 253 The term "NXRRSET" is sometimes used as a synonym for NODATA. 254 However, this is a mistake, given that NXRRSET is a specific error 255 code defined in [RFC2136]. 257 Negative response: A response which indicates that a particular 258 RRset does not exist, or whose RCODE indicates the nameserver 259 cannot answer. Sections 2 and 7 of [RFC2308] describe the types 260 of negative responses in detail. 262 Referrals: Data from the authority section of a non-authoritative 263 answer. [RFC1035] section 2.1 defines "authoritative" data. 264 However, referrals at zone cuts are not authoritative. Referrals 265 may be a zone cut NS resource records and their glue records. NS 266 records on the parent side of a zone cut are an authoritative 267 delegation, but are normally not treated as authoritative data by 268 the client. In general, a referral is a way for a server to send 269 an answer saying that the server does not know the answer, but 270 knows where the query should be directed in order to get an 271 answer. Historically, many authoritative servers answered with a 272 referral to the root zone when queried for a name for which they 273 were not authoritative, but this practice has declined. 275 4. Resource Records 277 RR: A short form for resource record. ([RFC1034], section 3.6.) 279 RRset: A set of resource records with the same label, class and 280 type, but with different data. (Definition from [RFC2181]) Also 281 spelled RRSet in some documents. As a clarification, "same label" 282 in this definition means "same owner name". In addition, 283 [RFC2181] states that "the TTLs of all RRs in an RRSet must be the 284 same". 286 EDNS: The extension mechanisms for DNS, defined in [RFC6891]. 287 Sometimes called "EDNS0" or "EDNS(0)" to indicate the version 288 number. EDNS allows DNS clients and servers to specify message 289 sizes larger than the original 512 octet limit, to expand the 290 response code space, and to potentially carry additional options 291 that affect the handling of a DNS query. 293 OPT: A pseudo-RR (sometimes called a meta-RR) that is used only to 294 contain control information pertaining to the question-and-answer 295 sequence of a specific transaction. (Definition from [RFC6891], 296 section 6.1.1) It is used by EDNS. 298 Owner: The domain name where a RR is found ([RFC1034], section 3.6). 299 Often appears in the term "owner name". 301 SOA field names: DNS documents, including the definitions here, 302 often refer to the fields in the RDATA an SOA resource record by 303 field name. Those fields are defined in Section 3.3.13 of 304 [RFC1035]. The names (in the order they appear in the SOA RDATA) 305 are MNAME, RNAME, SERIAL, REFRESH, RETRY, EXPIRE, and MINIMUM. 306 Note that the meaning of MINIMUM field is updated in Section 4 of 307 [RFC2308]; the new definition is that the MINIMUM field is only 308 "the TTL to be used for negative responses". 310 TTL: The maximum "time to live" of a resource record. A TTL value 311 is an unsigned number, with a minimum value of 0, and a maximum 312 value of 2147483647. That is, a maximum of 2^31 - 1. When 313 transmitted, the TTL is encoded in the less significant 31 bits of 314 the 32 bit TTL field, with the most significant, or sign, bit set 315 to zero. (Quoted from [RFC2181], section 8) (Note that [RFC1035] 316 erroneously stated that this is a signed integer; it is fixed in 317 an erratum.) 319 The TTL "specifies the time interval that the resource record may 320 be cached before the source of the information should again be 321 consulted". (Quoted from [RFC1035], section 3.2.1) Also: "the 322 time interval (in seconds) that the resource record may be cached 323 before it should be discarded". (Quoted from [RFC1035], section 324 4.1.3). Despite being defined for a resource record, the TTL of 325 every resource record in an RRset is required to be the same 326 (RFC2181, section 5.2). 328 The reason that the TTL is the maximum time to live is that a 329 cache operator might decide to shorten the time to live for 330 operational purposes, such as if there is a policy to not allow 331 TTL values over a certain number. Also, if a value is flushed 332 from the cache when its value is still positive, the value 333 effectively becomes zero. Some servers do not honor the TTL on an 334 RRset from the authoritative servers, such as when when the 335 authoritative data has a very short TTL. 337 There is also the concept of a "default TTL" for a zone, which can 338 be a configuration parameter in the server software. This is 339 often expressed by a default for the entire server, and a default 340 for a zone using the $TTL directive in a zone file. The $TTL 341 directive was added to the master file format by [RFC2308]. 343 Class independent: A resource record type whose syntax and semantics 344 are the same for every DNS class. A resource record type that is 345 not class independent has different meanings depending on the DNS 346 class of the record, or the meaning is undefined for classes other 347 than IN. 349 5. DNS Servers 351 This section defines the terms used for the systems that act as DNS 352 clients, DNS servers, or both. Some terms about servers describe 353 servers that do and do not use DNSSEC; see Section 8 for those 354 definitions. 356 Resolver: A program that extracts information from name servers in 357 response to client requests. (Quoted from [RFC1034], section 2.4) 358 The resolver is located on the same machine as the program that 359 requests the resolver's services, but it may need to consult name 360 servers on other hosts. (Quoted from [RFC1034], section 5.1) A 361 resolver performs queries for a name, type, and class, and 362 receives answers. The logical function is called "resolution". 363 In practice, the term is usually referring to some specific type 364 of resolver (some of which are defined below), and understanding 365 the use of the term depends on understanding the context. 367 Stub resolver: A resolver that cannot perform all resolution itself. 368 Stub resolvers generally depend on a recursive resolver to 369 undertake the actual resolution function. Stub resolvers are 370 discussed but never fully defined in Section 5.3.1 of [RFC1034]. 371 They are fully defined in Section 6.1.3.1 of [RFC1123]. 373 Iterative mode: A resolution mode of a server that receives DNS 374 queries and responds with a referral to another server. 375 Section 2.3 of [RFC1034] describes this as "The server refers the 376 client to another server and lets the client pursue the query". A 377 resolver that works in iterative mode is sometimes called an 378 "iterative resolver". 380 Recursive mode: A resolution mode of a server that receives DNS 381 queries and either responds to those queries from a local cache or 382 sends queries to other servers in order to get the final answers 383 to the original queries. Section 2.3 of [RFC1034] describes this 384 as "The first server pursues the query for the client at another 385 server". A server operating in recursive mode may be thought of 386 as having a name server side (which is what answers the query) and 387 a resolver side (which performs the resolution function). Systems 388 operating in this mode are commonly called "recursive servers". 389 Sometimes they are called "recursive resolvers". While strictly 390 the difference between these is that one of them sends queries to 391 another recursive server and the other does not, in practice it is 392 not possible to know in advance whether the server that one is 393 querying will also perform recursion; both terms can be observed 394 in use interchangeably. 396 Full resolver: This term is used in [RFC1035], but it is not defined 397 there. RFC 1123 defines a "full-service resolver" that may or may 398 not be what was intended by "full resolver" in [RFC1035]. 400 Full-service resolver: Section 6.1.3.1 of [RFC1123] defines this 401 term to mean a resolver that acts in recursive mode with a cache 402 (and meets other requirements). 404 Priming: The mechanism used by a resolver to determine where to send 405 queries before there is anything in the resolver's cache. Priming 406 is most often done from a configuration setting that contains a 407 list of authoritative servers for the DNS root zone. 409 Negative caching: The storage of knowledge that something does not 410 exist, cannot give an answer, or does not give an answer. (Quoted 411 from [RFC2308], section 1) 413 Authoritative server: A server that knows the content of a DNS zone 414 from local knowledge, and thus can answer queries about that zone 415 without needing to query other servers. (Quoted from [RFC2182], 416 section 2.) It is a system that responds to DNS queries with 417 information about zones for which it has been configured to answer 418 with the AA flag in the response header set to 1. It is a server 419 that has authority over one or more DNS zones. Note that it is 420 possible for an authoritative server to respond to a query without 421 the parent zone delegating authority to that server. 422 Authoritative servers also provide "referrals", usually to child 423 zones delegated from them; these referrals have the AA bit set to 424 0 and come with referral data in the Authority and (if needed) the 425 Additional sections. 427 Authoritative-only server: A name server which only serves 428 authoritative data and ignore requests for recursion. It will not 429 normally generate any queries of its own. Instead, it answers 430 non-recursive queries from iterative resolvers looking for 431 information in zones it serves. (Quoted from [RFC4697], section 432 2.4) 434 Zone transfer: The act of a client requesting a copy of a zone and 435 an authoritative server sending the needed information. There are 436 two common standard ways to do zone transfers: the AXFR 437 ("Authoritative Transfer") mechanism to copy the full zone 438 (described in [RFC5936], and the IXFR ("Incremental Transfer") 439 mechanism to copy only parts of the zone that have changed 440 (described in [RFC1995]). Many systems use non-standard methods 441 for zone transfer outside the DNS protocol. 443 Secondary server: "An authoritative server which uses zone transfer 444 to retrieve the zone" (quoted from [RFC1996], section 2.1). 445 [RFC2182] describes secondary servers in detail. Although early 446 DNS RFCs such as [RFC1996] referred to this as a "slave", the 447 current common usage has shifted to calling it a "secondary". 449 Slave server: See secondary server. 451 Primary server: "Any authoritative server configured to be the 452 source of zone transfer for one or more [secondary] servers" 453 (quoted from [RFC1996], section 2.1) or, more specifically, "an 454 authoritative server configured to be the source of AXFR or IXFR 455 data for one or more [secondary] servers" (quoted from [RFC2136]). 456 Although early DNS RFCs such as [RFC1996] referred to this as a 457 "master", the current common usage has shifted to "primary". 459 Master server: See primary server. 461 Primary master: The primary master is named in the zone's SOA MNAME 462 field and optionally by an NS resource record. (Quoted from 463 [RFC1996], section 2.1) [RFC2136] defines "primary master" as 464 "Master server at the root of the AXFR/IXFR dependency graph. The 465 primary master is named in the zone's SOA MNAME field and 466 optionally by an NS RR. There is by definition only one primary 467 master server per zone." The idea of a primary master is only 468 used by [RFC2136], and is considered archaic in other parts of the 469 DNS. 471 Stealth server: This is the same as a slave server except that it is 472 not listed in an NS resource record for the zone. (Quoted from 473 [RFC1996], section 2.1) 475 Hidden master: A stealth server that is a master for zone transfers. 476 In this arrangement, the master name server that processes the 477 updates is unavailable to general hosts on the Internet; it is not 478 listed in the NS RRset. (Quoted from [RFC6781], section 3.4.3.) 479 An earlier RFC, [RFC4641], said that the hidden master's name 480 appears in the SOA RRs MNAME field, although in some setups, the 481 name does not appear at all in the public DNS. A hidden master 482 can be either a secondary or a primary master. 484 Forwarding: The process of one server sending a DNS query with the 485 RD bit set to 1 to another server to resolve that query. 486 Forwarding is a function of a DNS resolver; it is different than 487 simply blindly relaying queries. 489 [RFC5625] does not give a specific definition for forwarding, but 490 describes in detail what features a system that forwards need to 491 support. Systems that forward are sometimes called "DNS proxies", 492 but that term has not yet been defined (even in [RFC5625]). 494 Forwarder: Section 1 of [RFC2308] describes a forwarder as "a 495 nameserver used to resolve queries instead of directly using the 496 authoritative nameserver chain". [RFC2308] further says "The 497 forwarder typically either has better access to the internet, or 498 maintains a bigger cache which may be shared amongst many 499 resolvers." That definition appears to suggest that forwarders 500 normally only query authoritative servers. In current use, 501 however, forwarders often stand between stub resolvers and 502 recursive servers. [RFC2308] is silent on whether a forwarder is 503 iterative-only or can be a full-service resolver. 505 Policy-implementing resolver: A resolver acting in recursive mode 506 that changes some of the answers that it returns based on policy 507 criteria, such as to prevent access to malware sites or 508 objectionable content. In general, a stub resolver has no idea 509 whether or not upstream resolvers implement such policy or, if 510 they do, the exact policy about what changes will be made. In 511 some cases, the user of the stub resolver has selected the policy- 512 implementing resolver with the explicit intention of using it to 513 implement the policies. In other cases, policies are imposed 514 without the user of the stub resolver being informed. 516 Open resolver: A full-service resolver that accepts and processes 517 queries from any (or nearly any) stub resolver. This is sometimes 518 also called a "public resolver", although the term "public 519 resolver" is used more with open resolvers that are meant to be 520 open, as compared to the vast majority of open resolvers that are 521 probably misconfigured to be open. 523 View: A configuration for a DNS server that allows it to provide 524 different answers depending on attributes of the query. 525 Typically, views differ by the source IP address of a query, but 526 can also be based on the destination IP address, the type of query 527 (such as AXFR), whether or not it is recursive, and so on. Views 528 are often used to provide more names or different addresses to 529 queries from "inside" a protected network than to those "outside" 530 that network. Views are not a standardized part of the DNS, but 531 they are widely implemented in server software. 533 Passive DNS: A mechanism to collect large amounts of DNS data by 534 storing DNS responses from servers. Some of these systems also 535 collect the DNS queries associated with the responses; this can 536 raise privacy issues. Passive DNS databases can be used to answer 537 historical questions about DNS zones such as which records were 538 available for them at what times in the past. Passive DNS 539 databases allow searching of the stored records on keys other than 540 just the name, such as "find all names which have A records of a 541 particular value". 543 Anycast: The practice of making a particular service address 544 available in multiple, discrete, autonomous locations, such that 545 datagrams sent are routed to one of several available locations. 546 (Quoted from [RFC4786], Section 2) 548 6. Zones 550 This section defines terms that are used when discussing zones that 551 are being served or retrieved. 553 Zone: A unit of organization of authoritative data. Zones can be 554 automatically distributed to the name servers which provide 555 redundant service for the data in a zone. (Quoted from [RFC1034], 556 section 2.4). 558 Child: The entity on record that has the delegation of the domain 559 from the Parent. (Quoted from [RFC7344], section 1.1) 561 Parent: The domain in which the Child is registered. (Quoted from 562 [RFC7344], section 1.1) Earlier, "parent name server" was defined 563 in [RFC0882] as "the name server that has authority over the place 564 in the domain name space that will hold the new domain". 566 Origin: 568 (a) The domain name that appears at the top of a zone (just below 569 the cut that separates the zone from its parent). The name of the 570 zone is the same as the name of the domain at the zone's origin. 571 (Quoted from [RFC2181], section 6.) These days, this sense of 572 "origin" and "apex" (defined below) are often used 573 interchangeably. 575 (b) The domain name within which a given relative domain name 576 appears in zone files. Generally seen in the context of 577 "$ORIGIN", which is a control entry defined in [RFC1035], section 578 5.1, as part of the master file format. For example, if the 579 $ORIGIN is set to "example.org.", then a master file line for 580 "www" is in fact an entry for "www.example.org.". 582 Apex: The point in the tree at an owner of an SOA and corresponding 583 authoritative NS RRset. This is also called the "zone apex". 584 [RFC4033] defines it as "the name at the child's side of a zone 585 cut". The "apex" can usefully be thought of as a data-theoretic 586 description of a tree structure, and "origin" is the name of the 587 same concept when it is implemented in zone files. The 588 distinction is not always maintained in use, however, and one can 589 find uses that conflict subtly with this definition. [RFC1034] 590 uses the term "top node of the zone" instead of "apex". These 591 days, the first sense of "origin" (above) and "apex" are often 592 used interchangeably. 594 Zone cut: The delimitation point between two zones where the origin 595 of one of the zones is the child of the other zone. 597 Zones are delimited by "zone cuts". Each zone cut separates a 598 "child" zone (below the cut) from a "parent" zone (above the cut). 599 (Quoted from [RFC2181], section 6; note that this is barely an 600 ostensive definition.) Section 4.2 of [RFC1034] uses "cuts" as 601 "zone cut". 603 Delegation: The process by which a separate zone is created in the 604 name space beneath the apex of a given domain. Delegation happens 605 when an NS RRset is added in the parent zone for the child origin. 606 Delegation inherently happens at a zone cut. The term is also 607 commonly a noun: the new zone that is created by the act of 608 delegating. 610 Glue records: "[Resource records] which are not part of the 611 authoritative data [of the zone], and are address resource records 612 for the [name servers in subzones]. These RRs are only necessary 613 if the name server's name is 'below' the cut, and are only used as 614 part of a referral response." Without glue "we could be faced 615 with the situation where the NS RRs tell us that in order to learn 616 a name server's address, we should contact the server using the 617 address we wish to learn." (Definition from [RFC1034], section 618 4.2.1) 620 A later definition is that glue "includes any record in a zone 621 file that is not properly part of that zone, including nameserver 622 records of delegated sub-zones (NS records), address records that 623 accompany those NS records (A, AAAA, etc), and any other stray 624 data that might appear" ([RFC2181], section 5.4.1). Although glue 625 is sometimes used today with this wider definition in mind, the 626 context surrounding the [RFC2181] definition suggests it is 627 intended to apply to the use of glue within the document itself 628 and not necessarily beyond. 630 In-bailiwick: 632 (a) An adjective to describe a name server whose name is either 633 subordinate to or (rarely) the same as the zone origin. In- 634 bailiwick name servers require glue in their parent zone. 636 (b) Data for which the server is either authoritative, or else 637 authoritative for an ancestor of the owner name. This sense of 638 the term normally is used when discussing the relevancy of glue 639 records in a response. For example, the server for the parent 640 zone example.com might reply with glue records for 641 ns.child.example.com. Because the child.example.com zone is a 642 descendant of the example.com zone, the glue records are in- 643 bailiwick. 645 Out-of-bailiwick: The antonym of in-bailiwick. 647 Authoritative data: All of the RRs attached to all of the nodes from 648 the top node of the zone down to leaf nodes or nodes above cuts 649 around the bottom edge of the zone. (Quoted from [RFC1034], 650 section 4.2.1) It is noted that this definition might 651 inadvertently also include any NS records that appear in the zone, 652 even those that might not truly be authoritative because there are 653 identical NS RRs below the zone cut. This reveals the ambiguity 654 in the notion of authoritative data, because the parent-side NS 655 records authoritatively indicate the delegation, even though they 656 are not themselves authoritative data. 658 Root zone: The zone whose apex is the zero-length label. Also 659 sometimes called "the DNS root". 661 Empty non-terminals: Domain names that own no resource records but 662 have subdomains that do. (Quoted from [RFC4592], section 2.2.2.) 663 A typical example is in SRV records: in the name 664 "_sip._tcp.example.com", it is likely that "_tcp.example.com" has 665 no RRsets, but that "_sip._tcp.example.com" has (at least) an SRV 666 RRset. 668 Delegation-centric zone: A zone which consists mostly of delegations 669 to child zones. This term is used in contrast to a zone which 670 might have some delegations to child zones, but also has many data 671 resource records for the zone itself and/or for child zones. The 672 term is used in [RFC4956] and [RFC5155], but is not defined there. 674 Wildcard: [RFC1034] defined "wildcard", but in a way that turned out 675 to be confusing to implementers. Special treatment is given to 676 RRs with owner names starting with the label "*". Such RRs are 677 called wildcards. Wildcard RRs can be thought of as instructions 678 for synthesizing RRs. (Quoted from [RFC1034], section 4.3.3) For 679 an extended discussion of wildcards, including clearer 680 definitions, see [RFC4592]. 682 Occluded name: The addition of a delegation point via dynamic update 683 will render all subordinate domain names to be in a limbo, still 684 part of the zone but not available to the lookup process. The 685 addition of a DNAME resource record has the same impact. The 686 subordinate names are said to be "occluded". (Quoted from 687 [RFC5936], Section 3.5) 689 Fast flux DNS: This occurs when a domain is bound in DNS using A 690 records to multiple IP addresses, each of which has a very short 691 Time-to-Live (TTL) value associated with it. This means that the 692 domain resolves to varying IP addresses over a short period of 693 time. (Quoted from [RFC6561], section 1.1.5) It is often to 694 deliver malware. Because the addresses change so rapidly, it is 695 difficult to definitively find all the hosts. It should be noted 696 that the technique also works with AAAA records, but such use is 697 not frequently observed on the Internet as of this writing. 699 7. Registration Model 701 Registry: The administrative operation of a zone that allows 702 registration of names within that zone. People often use this 703 term to refer only to those organizations that perform 704 registration in large delegation-centric zones (such as TLDs); but 705 formally, whoever decides what data goes into a zone is the 706 registry for that zone. 708 Registrant: An individual or organization on whose behalf a name in 709 a zone is registered by the registry. In many zones, the registry 710 and the registrant may be the same entity, but in TLDs they often 711 are not. 713 Registrar: A service provider that acts as a go-between for 714 registrants and registries. Not all registrations require a 715 registrar, though it is common to have registrars be involved in 716 registrations in TLDs. 718 EPP: The Extensible Provisioning Protocol (EPP), which is commonly 719 used for communication of registration information between 720 registries and registrars. EPP is defined in [RFC5730]. 722 WHOIS: A protocol specified in [RFC3912], often used for querying 723 registry databases. WHOIS data is frequently used to associate 724 registration data (such as zone management contacts) with domain 725 names. 727 DNS operator: An entity responsible for running DNS servers. For a 728 zone's authoritative servers, the registrant may act as their own 729 DNS operator, or their registrar may do it on their behalf, or 730 they may use a third-party operator. 732 8. General DNSSEC 734 Most DNSSEC terms are defined in [RFC4033], [RFC4034], [RFC4035], and 735 [RFC5155]. The terms that have caused confusion in the DNS community 736 are highlighted here. 738 DNSSEC-aware and DNSSEC-unaware: Section 2 of [RFC4033] defines many 739 types of resolvers and validators, including "non-validating 740 security-aware stub resolver", "non-validating stub resolver", 741 "security-aware name server", "security-aware recursive name 742 server", "security-aware resolver", "security-aware stub 743 resolver", and "security-oblivious 'anything'". (Note that the 744 term "validating resolver", which is used in some places in those 745 documents, is nevertheless not defined in that section.) 747 Signed zone: A zone whose RRsets are signed and that contains 748 properly constructed DNSKEY, Resource Record Signature (RRSIG), 749 Next Secure (NSEC), and (optionally) DS records. (Quoted from 750 [RFC4033], section 2.) It has been noted in other contexts that 751 the zone itself is not really signed, but all the relevant RRsets 752 in the zone are signed. Nevertheless, if a zone that should be 753 signed contains any RRsets that are not signed (or opted out), 754 those RRsets will be treated as bogus, so the whole zone needs to 755 be handled in some way. 757 It should also be noted that, since the publication of [RFC6840], 758 NSEC records are no longer required for signed zones: a signed 759 zone might include NSEC3 records instead. [RFC7129] provides 760 additional background commentary and some context for the NSEC and 761 NSEC3 mechanisms used by DNSSEC to provide authenticated denial- 762 of-existence responses. 764 Unsigned zone: Section 2 of [RFC4033] defines this as "a zone that 765 is not signed". Section 2 of [RFC4035] defines this as "A zone 766 that does not include these records [properly constructed DNSKEY, 767 Resource Record Signature (RRSIG), Next Secure (NSEC), and 768 (optionally) DS records] according to the rules in this section". 769 There is an important note at the end of Section 5.2 of [RFC4035] 770 adding an additional situation when a zone is considered unsigned: 771 "If the resolver does not support any of the algorithms listed in 772 an authenticated DS RRset, then the resolver will not be able to 773 verify the authentication path to the child zone. In this case, 774 the resolver SHOULD treat the child zone as if it were unsigned." 776 NSEC: "The NSEC record allows a security-aware resolver to 777 authenticate a negative reply for either name or type non- 778 existence with the same mechanisms used to authenticate other DNS 779 replies." (Quoted from [RFC4033], section 3.2.) In short, an 780 NSEC record provides authenticated denial of existence. 782 The NSEC resource record lists two separate things: the next owner 783 name (in the canonical ordering of the zone) that contains 784 authoritative data or a delegation point NS RRset, and the set of 785 RR types present at the NSEC RR's owner name. (Quoted from 786 Section 4 of 4034) 788 NSEC3: Like the NSEC record, the NSEC3 record also provides 789 authenticated denial of existence; however, NSEC3 records 790 mitigates against zone enumeration and support Opt-Out. NSEC3 791 resource records are defined in [RFC5155]. 793 Note that [RFC6840] says that [RFC5155] "is now considered part of 794 the DNS Security Document Family as described by Section 10 of 795 [RFC4033]". This means that some of the definitions from earlier 796 RFCs that only talk about NSEC records should probably be 797 considered to be talking about both NSEC and NSEC3. 799 Opt-out: The Opt-Out Flag indicates whether this NSEC3 RR may cover 800 unsigned delegations. (Quoted from [RFC5155], section 3.1.2.1.) 801 Opt-out tackles the high costs of securing a delegation to an 802 insecure zone. When using Opt-Out, names that are an insecure 803 delegation (and empty non-terminals that are only derived from 804 insecure delegations) don't require an NSEC3 record or its 805 corresponding RRSIG records. Opt-Out NSEC3 records are not able 806 to prove or deny the existence of the insecure delegations. 807 (Adapted from [RFC7129], section 5.1) 809 Zone enumeration: The practice of discovering the full content of a 810 zone via successive queries. (Quoted from [RFC5155], section 811 1.3.) This is also sometimes call "zone walking". Zone 812 enumeration is different from zone content guessing where the 813 guesser uses a large dictionary of possible labels and sends 814 successive queries for them, or matches the contents of NSEC3 815 records against such a dictionary. 817 Key signing key (KSK): DNSSEC keys that only sign the apex DNSKEY 818 RRset in a zone. (Quoted from [RFC6781], section 3.1) 820 Zone signing key (ZSK): DNSSEC keys that can be used to sign all the 821 RRsets in a zone that require signatures, other than the apex 822 DNSKEY RRset. (Quoted from [RFC6781], section 3.1) Note that the 823 roles KSK and ZSK are not mutually exclusive: a single key can be 824 both KSK and ZSK at the same time. Also note that a ZSK is 825 sometimes used to sign the apex DNSKEY RRset. 827 Combined signing key (CSK): In cases where the differentiation 828 between the KSK and ZSK is not made, i.e., where keys have the 829 role of both KSK and ZSK, we talk about a Single-Type Signing 830 Scheme. (Quoted from [RFC6781], Section 3.1) This is sometimes 831 called a "combined signing key" or CSK. It is operational 832 practice, not protocol, that determines whether a particular key 833 is a ZSK, a KSK, or a CSK. 835 Secure Entry Point (SEP): A flag in the DNSKEY RDATA that can be 836 used to distinguish between keys that are intended to be used as 837 the secure entry point into the zone when building chains of 838 trust, i.e., they are (to be) pointed to by parental DS RRs or 839 configured as a trust anchor. Therefore, it is suggested that the 840 SEP flag be set on keys that are used as KSKs and not on keys that 841 are used as ZSKs, while in those cases where a distinction between 842 a KSK and ZSK is not made (i.e., for a Single-Type Signing 843 Scheme), it is suggested that the SEP flag be set on all keys. 844 (Quoted from [RFC6781], section 3.2.3.) Note that the SEP flag is 845 only a hint, and its presence or absence may not be used to 846 disqualify a given DNSKEY RR from use as a KSK or ZSK during 847 validation. 849 DNSSEC Policy (DP): A statement that sets forth the security 850 requirements and standards to be implemented for a DNSSEC-signed 851 zone. (Quoted from [RFC6841], section 2) 853 DNSSEC Practice Statement (DPS): A practices disclosure document 854 that may support and be a supplemental document to the DNSSEC 855 Policy (if such exists), and it states how the management of a 856 given zone implements procedures and controls at a high level. 857 (Quoted from [RFC6841], section 2) 859 9. DNSSEC States 861 A validating resolver can determine that a response is in one of four 862 states: secure, insecure, bogus, or indeterminate. These states are 863 defined in [RFC4033] and [RFC4035], although the two definitions 864 differ a bit. 866 Section 5 of [RFC4033] says: 868 A validating resolver can determine the following 4 states: 870 Secure: The validating resolver has a trust anchor, has a chain of 871 trust, and is able to verify all the signatures in the response. 873 Insecure: The validating resolver has a trust anchor, a chain of 874 trust, and, at some delegation point, signed proof of the 875 non-existence of a DS record. This indicates that subsequent 876 branches in the tree are provably insecure. A validating resolver 877 may have a local policy to mark parts of the domain space as 878 insecure. 880 Bogus: The validating resolver has a trust anchor and a secure 881 delegation indicating that subsidiary data is signed, but the 882 response fails to validate for some reason: missing signatures, 883 expired signatures, signatures with unsupported algorithms, data 884 missing that the relevant NSEC RR says should be present, and so 885 forth. 887 Indeterminate: There is no trust anchor that would indicate that a 888 specific portion of the tree is secure. This is the default 889 operation mode. 891 Section 4.3 of [RFC4035] says: 893 A security-aware resolver must be able to distinguish between four 894 cases: 896 Secure: An RRset for which the resolver is able to build a chain of 897 signed DNSKEY and DS RRs from a trusted security anchor to the 898 RRset. In this case, the RRset should be signed and is subject to 899 signature validation, as described above. 901 Insecure: An RRset for which the resolver knows that it has no chain 902 of signed DNSKEY and DS RRs from any trusted starting point to the 903 RRset. This can occur when the target RRset lies in an unsigned 904 zone or in a descendent of an unsigned zone. In this case, the 905 RRset may or may not be signed, but the resolver will not be able 906 to verify the signature. 908 Bogus: An RRset for which the resolver believes that it ought to be 909 able to establish a chain of trust but for which it is unable to 910 do so, either due to signatures that for some reason fail to 911 validate or due to missing data that the relevant DNSSEC RRs 912 indicate should be present. This case may indicate an attack but 913 may also indicate a configuration error or some form of data 914 corruption. 916 Indeterminate: An RRset for which the resolver is not able to 917 determine whether the RRset should be signed, as the resolver is 918 not able to obtain the necessary DNSSEC RRs. This can occur when 919 the security-aware resolver is not able to contact security-aware 920 name servers for the relevant zones. 922 10. IANA Considerations 924 This document has no IANA actions. 926 11. Security Considerations 928 These definitions do not change any security considerations for the 929 DNS. 931 12. Acknowledgements 933 The authors gratefully acknowledge all of the authors of DNS-related 934 RFCs that proceed this one. Comments from Tony Finch, Stephane 935 Bortzmeyer, Niall O'Reilly, Colm MacCarthaigh, Ray Bellis, John 936 Kristoff, Robert Edmonds, Paul Wouters, Shumon Huque, Paul Ebersman, 937 David Lawrence, Matthijs Mekking, Casey Deccio, Bob Harold, Ed Lewis, 938 and many others in the DNSOP Working Group have helped shape this 939 document. 941 13. References 943 13.1. Normative References 945 [RFC0882] Mockapetris, P., "Domain names: Concepts and facilities", 946 RFC 882, November 1983. 948 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 949 STD 13, RFC 1034, November 1987. 951 [RFC1035] Mockapetris, P., "Domain names - implementation and 952 specification", STD 13, RFC 1035, November 1987. 954 [RFC1123] Braden, R., "Requirements for Internet Hosts - Application 955 and Support", STD 3, RFC 1123, October 1989. 957 [RFC1206] Malkin, G. and A. Marine, "FYI on Questions and Answers: 958 Answers to commonly asked "new Internet user" questions", 959 RFC 1206, February 1991. 961 [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone 962 Changes (DNS NOTIFY)", RFC 1996, August 1996. 964 [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, 965 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 966 RFC 2136, April 1997. 968 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS 969 Specification", RFC 2181, July 1997. 971 [RFC2182] Elz, R., Bush, R., Bradner, S., and M. Patton, "Selection 972 and Operation of Secondary DNS Servers", BCP 16, RFC 2182, 973 July 1997. 975 [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS 976 NCACHE)", RFC 2308, March 1998. 978 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 979 Rose, "DNS Security Introduction and Requirements", RFC 980 4033, March 2005. 982 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 983 Rose, "Resource Records for the DNS Security Extensions", 984 RFC 4034, March 2005. 986 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 987 Rose, "Protocol Modifications for the DNS Security 988 Extensions", RFC 4035, March 2005. 990 [RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name 991 System", RFC 4592, July 2006. 993 [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS 994 Security (DNSSEC) Hashed Authenticated Denial of 995 Existence", RFC 5155, March 2008. 997 [RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)", 998 STD 69, RFC 5730, August 2009. 1000 [RFC5936] Lewis, E. and A. Hoenes, "DNS Zone Transfer Protocol 1001 (AXFR)", RFC 5936, June 2010. 1003 [RFC6561] Livingood, J., Mody, N., and M. O'Reirdan, 1004 "Recommendations for the Remediation of Bots in ISP 1005 Networks", RFC 6561, March 2012. 1007 [RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the 1008 DNS", RFC 6672, June 2012. 1010 [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC 1011 Operational Practices, Version 2", RFC 6781, December 1012 2012. 1014 [RFC6840] Weiler, S. and D. Blacka, "Clarifications and 1015 Implementation Notes for DNS Security (DNSSEC)", RFC 6840, 1016 February 2013. 1018 [RFC6841] Ljunggren, F., Eklund Lowinder, AM., and T. Okubo, "A 1019 Framework for DNSSEC Policies and DNSSEC Practice 1020 Statements", RFC 6841, January 2013. 1022 [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms 1023 for DNS (EDNS(0))", STD 75, RFC 6891, April 2013. 1025 [RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating 1026 DNSSEC Delegation Trust Maintenance", RFC 7344, September 1027 2014. 1029 13.2. Informative References 1031 [DBOUND] "DBOUND Working Group", 2015, 1032 . 1034 [RFC0952] Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet 1035 host table specification", RFC 952, October 1985. 1037 [RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995, 1038 August 1996. 1040 [RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912, 1041 September 2004. 1043 [RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices", 1044 RFC 4641, September 2006. 1046 [RFC4697] Larson, M. and P. Barber, "Observed DNS Resolution 1047 Misbehavior", BCP 123, RFC 4697, October 2006. 1049 [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast 1050 Services", BCP 126, RFC 4786, December 2006. 1052 [RFC4956] Arends, R., Kosters, M., and D. Blacka, "DNS Security 1053 (DNSSEC) Opt-In", RFC 4956, July 2007. 1055 [RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines", BCP 1056 152, RFC 5625, August 2009. 1058 [RFC5890] Klensin, J., "Internationalized Domain Names for 1059 Applications (IDNA): Definitions and Document Framework", 1060 RFC 5890, August 2010. 1062 [RFC5891] Klensin, J., "Internationalized Domain Names in 1063 Applications (IDNA): Protocol", RFC 5891, August 2010. 1065 [RFC5892] Faltstrom, P., "The Unicode Code Points and 1066 Internationalized Domain Names for Applications (IDNA)", 1067 RFC 5892, August 2010. 1069 [RFC5893] Alvestrand, H. and C. Karp, "Right-to-Left Scripts for 1070 Internationalized Domain Names for Applications (IDNA)", 1071 RFC 5893, August 2010. 1073 [RFC5894] Klensin, J., "Internationalized Domain Names for 1074 Applications (IDNA): Background, Explanation, and 1075 Rationale", RFC 5894, August 2010. 1077 [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, 1078 April 2011. 1080 [RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of 1081 Existence in the DNS", RFC 7129, February 2014. 1083 Authors' Addresses 1085 Paul Hoffman 1086 VPN Consortium 1087 127 Segre Place 1088 Santa Cruz, CA 95060 1089 USA 1091 Email: paul.hoffman@vpnc.org 1093 Andrew Sullivan 1094 Dyn 1095 150 Dow St, Tower 2 1096 Manchester, NH 1604 1097 USA 1099 Email: asullivan@dyn.com 1101 Kazunori Fujiwara 1102 Japan Registry Services Co., Ltd. 1103 Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda 1104 Chiyoda-ku, Tokyo 101-0065 1105 Japan 1107 Phone: +81 3 5215 8451 1108 Email: fujiwara@jprs.co.jp