draft-ietf-dnsop-dns-terminology-05.txt   rfc7719.txt 
Network Working Group P. Hoffman Internet Engineering Task Force (IETF) P. Hoffman
Internet-Draft ICANN Request for Comments: 7719 ICANN
Intended status: Informational A. Sullivan Category: Informational A. Sullivan
Expires: March 27, 2016 Dyn ISSN: 2070-1721 Dyn
K. Fujiwara K. Fujiwara
JPRS JPRS
September 24, 2015 December 2015
DNS Terminology DNS Terminology
draft-ietf-dnsop-dns-terminology-05
Abstract Abstract
The DNS is defined in literally dozens of different RFCs. The The DNS is defined in literally dozens of different RFCs. The
terminology used by implementers and developers of DNS protocols, and terminology used by implementers and developers of DNS protocols, and
by operators of DNS systems, has sometimes changed in the decades by operators of DNS systems, has sometimes changed in the decades
since the DNS was first defined. This document gives current since the DNS was first defined. This document gives current
definitions for many of the terms used in the DNS in a single definitions for many of the terms used in the DNS in a single
document. document.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for informational purposes.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
This Internet-Draft will expire on March 27, 2016. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7719.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. DNS Header and Response Codes . . . . . . . . . . . . . . . . 6 3. DNS Header and Response Codes . . . . . . . . . . . . . . . . 6
4. Resource Records . . . . . . . . . . . . . . . . . . . . . . 7 4. Resource Records . . . . . . . . . . . . . . . . . . . . . . 7
5. DNS Servers and Clients . . . . . . . . . . . . . . . . . . . 8 5. DNS Servers and Clients . . . . . . . . . . . . . . . . . . . 9
6. Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6. Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Registration Model . . . . . . . . . . . . . . . . . . . . . 16 7. Registration Model . . . . . . . . . . . . . . . . . . . . . 17
8. General DNSSEC . . . . . . . . . . . . . . . . . . . . . . . 17 8. General DNSSEC . . . . . . . . . . . . . . . . . . . . . . . 18
9. DNSSEC States . . . . . . . . . . . . . . . . . . . . . . . . 20 9. DNSSEC States . . . . . . . . . . . . . . . . . . . . . . . . 20
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 10. Security Considerations . . . . . . . . . . . . . . . . . . . 22
11. Security Considerations . . . . . . . . . . . . . . . . . . . 21 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 11.1. Normative References . . . . . . . . . . . . . . . . . . 22
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 11.2. Informative References . . . . . . . . . . . . . . . . . 24
13.1. Normative References . . . . . . . . . . . . . . . . . . 22 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 27
13.2. Informative References . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction 1. Introduction
The domain name system (DNS) is a simple query-response protocol The Domain Name System (DNS) is a simple query-response protocol
whose messages in both directions have the same format. The protocol whose messages in both directions have the same format. The protocol
and message format are defined in [RFC1034] and [RFC1035]. These and message format are defined in [RFC1034] and [RFC1035]. These
RFCs defined some terms, but later documents defined others. Some of RFCs defined some terms, but later documents defined others. Some of
the terms from RFCs 1034 and 1035 now have somewhat different the terms from RFCs 1034 and 1035 now have somewhat different
meanings than they did in 1987. meanings than they did in 1987.
This document collects a wide variety of DNS-related terms. Some of This document collects a wide variety of DNS-related terms. Some of
them have been precisely defined in earlier RFCs, some have been them have been precisely defined in earlier RFCs, some have been
loosely defined in earlier RFCs, and some are not defined in any loosely defined in earlier RFCs, and some are not defined in any
earlier RFC at all. earlier RFC at all.
Most of the definitions here are the consensus definition of the DNS Most of the definitions here are the consensus definition of the DNS
community - both protocol developers and operators. Some of the community -- both protocol developers and operators. Some of the
definitions differ from earlier RFCs, and those differences are definitions differ from earlier RFCs, and those differences are
noted. In this document, where the consensus definition is the same noted. In this document, where the consensus definition is the same
as the one in an RFC, that RFC is quoted. Where the consensus as the one in an RFC, that RFC is quoted. Where the consensus
definition has changed somewhat, the RFC is mentioned but the new definition has changed somewhat, the RFC is mentioned but the new
stand-alone definition is given. stand-alone definition is given.
It is important to note that, during the development of this It is important to note that, during the development of this
document, it became clear that some DNS-related terms are interpreted document, it became clear that some DNS-related terms are interpreted
quite differently by different DNS experts. Further, some terms that quite differently by different DNS experts. Further, some terms that
are defined in early DNS RFCs now have definitions that are generally are defined in early DNS RFCs now have definitions that are generally
skipping to change at page 3, line 21 skipping to change at page 3, line 32
The terms are organized loosely by topic. Some definitions are for The terms are organized loosely by topic. Some definitions are for
new terms for things that are commonly talked about in the DNS new terms for things that are commonly talked about in the DNS
community but that never had terms defined for them. community but that never had terms defined for them.
Other organizations sometimes define DNS-related terms their own way. Other organizations sometimes define DNS-related terms their own way.
For example, the W3C defines "domain" at For example, the W3C defines "domain" at
https://specs.webplatform.org/url/webspecs/develop/. https://specs.webplatform.org/url/webspecs/develop/.
Note that there is no single consistent definition of "the DNS". It Note that there is no single consistent definition of "the DNS". It
can be considered to be some combination of the following: a can be considered to be some combination of the following: a commonly
commonly-used naming scheme for objects on the Internet; a used naming scheme for objects on the Internet; a distributed
distributed database representing the names and certain properties of database representing the names and certain properties of these
these objects; an architecture providing distributed maintenance, objects; an architecture providing distributed maintenance,
resilience, and loose coherency for this database; and a simple resilience, and loose coherency for this database; and a simple
query-response protocol (as mentioned below) implementing this query-response protocol (as mentioned below) implementing this
architecture. architecture.
Capitalization in DNS terms is often inconsistent among RFCs and Capitalization in DNS terms is often inconsistent among RFCs and
various DNS practitioners. The capitalization used in this document various DNS practitioners. The capitalization used in this document
is a best guess at current practices, and is not meant to indicate is a best guess at current practices, and is not meant to indicate
that other capitalization styles are wrong or archaic. In some that other capitalization styles are wrong or archaic. In some
cases, multiple styles of capitalization are used for the same term cases, multiple styles of capitalization are used for the same term
due to quoting from different RFCs. due to quoting from different RFCs.
skipping to change at page 3, line 47 skipping to change at page 4, line 16
Domain name: Section 3.1 of [RFC1034] talks of "the domain name Domain name: Section 3.1 of [RFC1034] talks of "the domain name
space" as a tree structure. "Each node has a label, which is zero space" as a tree structure. "Each node has a label, which is zero
to 63 octets in length. ... The domain name of a node is the list to 63 octets in length. ... The domain name of a node is the list
of the labels on the path from the node to the root of the tree. of the labels on the path from the node to the root of the tree.
... To simplify implementations, the total number of octets that ... To simplify implementations, the total number of octets that
represent a domain name (i.e., the sum of all label octets and represent a domain name (i.e., the sum of all label octets and
label lengths) is limited to 255." Any label in a domain name can label lengths) is limited to 255." Any label in a domain name can
contain any octet value. contain any octet value.
Fully-qualified domain name (FQDN): This is often just a clear way Fully qualified domain name (FQDN): This is often just a clear way
of saying the same thing as "domain name of a node", as outlined of saying the same thing as "domain name of a node", as outlined
above. However, the term is ambiguous. Strictly speaking, a above. However, the term is ambiguous. Strictly speaking, a
fully-qualified domain name would include every label, including fully qualified domain name would include every label, including
the final, zero-length label of the root: such a name would be the final, zero-length label of the root: such a name would be
written "www.example.net." (note the terminating dot). But written "www.example.net." (note the terminating dot). But
because every name eventually shares the common root, names are because every name eventually shares the common root, names are
often written relative to the root (such as "www.example.net") and often written relative to the root (such as "www.example.net") and
are still called "fully qualified". are still called "fully qualified". This term first appeared in
This term first appeared in [RFC0819]. [RFC819]. In this document, names are often written relative to
the root.
The need for the term "fully-qualified domain name" comes from the The need for the term "fully qualified domain name" comes from the
existence of partially-qualified domain names, which are names existence of partially qualified domain names, which are names
where some of the right-most names are left off and are understood where some of the right-most names are left off and are understood
only by context. only by context.
Label: The identifier of an individual node in the sequence of nodes Label: The identifier of an individual node in the sequence of nodes
identified by a fully-qualified domain name. identified by a fully qualified domain name.
Host name: This term and its equivalent, "hostname", have been Host name: This term and its equivalent, "hostname", have been
widely used but are not defined in [RFC1034], [RFC1035], widely used but are not defined in [RFC1034], [RFC1035],
[RFC1123], or [RFC2181]. The DNS was originally deployed into the [RFC1123], or [RFC2181]. The DNS was originally deployed into the
Host Tables environment as outlined in [RFC0952], and it is likely Host Tables environment as outlined in [RFC952], and it is likely
that the term followed informally from the definition there. Over that the term followed informally from the definition there. Over
time, the definition seems to have shifted. "Host name" is often time, the definition seems to have shifted. "Host name" is often
meant to be a domain name that follows the rules in Section 3.5 of meant to be a domain name that follows the rules in Section 3.5 of
[RFC1034], the "preferred name syntax". Note that any label in a [RFC1034], the "preferred name syntax". Note that any label in a
domain name can contain any octet value; hostnames are generally domain name can contain any octet value; hostnames are generally
considered to be domain names where every label follows the rules considered to be domain names where every label follows the rules
in the "preferred name syntax", with the amendment that labels can in the "preferred name syntax", with the amendment that labels can
start with ASCII digits (this amendment comes from Section 2.1 of start with ASCII digits (this amendment comes from Section 2.1 of
[RFC1123]). [RFC1123]).
skipping to change at page 4, line 45 skipping to change at page 5, line 14
configuration in operating systems.) In addition, people configuration in operating systems.) In addition, people
sometimes use this term to describe any name that refers to a sometimes use this term to describe any name that refers to a
machine, and those might include labels that do not conform to the machine, and those might include labels that do not conform to the
"preferred name syntax". "preferred name syntax".
TLD: A Top-Level Domain, meaning a zone that is one layer below the TLD: A Top-Level Domain, meaning a zone that is one layer below the
root, such as "com" or "jp". There is nothing special, from the root, such as "com" or "jp". There is nothing special, from the
point of view of the DNS, about TLDs. Most of them are also point of view of the DNS, about TLDs. Most of them are also
delegation-centric zones, and there are significant policy issues delegation-centric zones, and there are significant policy issues
around their operation. TLDs are often divided into sub-groups around their operation. TLDs are often divided into sub-groups
such as "ccTLDs", "gTLDs", and others; the division is a matter of such as Country Code Top-Level Domains (ccTLDs), Generic Top-Level
policy, and beyond the scope of this document. Domains (gTLDs), and others; the division is a matter of policy,
and beyond the scope of this document.
IDN: The common abbreviation for "internationalized domain name". IDN: The common abbreviation for "Internationalized Domain Name".
The IDNA protocol is the standard mechanism for handling domain The IDNA protocol is the standard mechanism for handling domain
names with non-ASCII characters in applications in the DNS. The names with non-ASCII characters in applications in the DNS. The
current standard, normally called "IDNA2008", is defined in current standard, normally called "IDNA2008", is defined in
[RFC5890], [RFC5891], [RFC5892], [RFC5893], and [RFC5894]. These [RFC5890], [RFC5891], [RFC5892], [RFC5893], and [RFC5894]. These
documents define many IDN-specific terms such as "LDH label", documents define many IDN-specific terms such as "LDH label",
"A-label", and "U-label". [RFC6365] defines more terms that "A-label", and "U-label". [RFC6365] defines more terms that
relate to internationalization (some of which relate to IDNs), and relate to internationalization (some of which relate to IDNs), and
[RFC6055] has a much more extensive discussion of IDNs, including [RFC6055] has a much more extensive discussion of IDNs, including
some new terminology. some new terminology.
Subdomain: A domain is a subdomain of another domain if it is Subdomain: "A domain is a subdomain of another domain if it is
contained within that domain. This relationship can be tested by contained within that domain. This relationship can be tested by
seeing if the subdomain's name ends with the containing domain's seeing if the subdomain's name ends with the containing domain's
name. (Quoted from [RFC1034], section 3.1) For example, in the name." (Quoted from [RFC1034], Section 3.1). For example, in the
host name "nnn.mmm.example.com", both "mmm.example.com" and host name "nnn.mmm.example.com", both "mmm.example.com" and
"nnn.mmm.example.com" are subdomains of "example.com". "nnn.mmm.example.com" are subdomains of "example.com".
Alias: The owner of a CNAME resource record, or a subdomain of the Alias: The owner of a CNAME resource record, or a subdomain of the
owner of a DNAME resource record [RFC6672]. See also "canonical owner of a DNAME resource record [RFC6672]. See also "canonical
name". name".
Canonical name: A CNAME resource record identifies its owner name as Canonical name: A CNAME resource record "identifies its owner name
an alias, and specifies the corresponding canonical name in the as an alias, and specifies the corresponding canonical name in the
RDATA section of the RR. (Quoted from [RFC1034], section 3.6.2) RDATA section of the RR." (Quoted from [RFC1034], Section 3.6.2)
This usage of the word "canonical" is related to the mathematical This usage of the word "canonical" is related to the mathematical
concept of "canonical form". concept of "canonical form".
CNAME: It is traditional to refer to the owner of a CNAME record as 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 'a CNAME'. This is unfortunate, as 'CNAME' is an abbreviation of
"canonical name", and the owner of a CNAME record is an alias not 'canonical name', and the owner of a CNAME record is an alias, not
a canonical name. (Quoted from [RFC2181], section 10.1.1) a canonical name." (Quoted from [RFC2181], Section 10.1.1)
Public suffix: A domain that is controlled by a public registry. Public suffix: "A domain that is controlled by a public registry."
(Quoted from [RFC6265], section 5.3) A common definition for this (Quoted from [RFC6265], Section 5.3) A common definition for this
term is a domain under which subdomains can be registered, and on term is a domain under which subdomains can be registered, and on
which HTTP cookies ([RFC6265]) should not be set. There is no which HTTP cookies ([RFC6265]) should not be set. There is no
indication in a domain name whether it is a public suffix; that indication in a domain name whether it is a public suffix; that
can only be determined by outside means. In fact, both a domain can only be determined by outside means. In fact, both a domain
and a subdomain of that domain can be public suffixes. At the and a subdomain of that domain can be public suffixes. At the
time this document is published, the IETF DBOUND Working Group time this document is published, the IETF DBOUND Working Group
[DBOUND] is dealing with issues concerning public suffixes. [DBOUND] is dealing with issues concerning public suffixes.
There is nothing inherent in a domain name to indicate whether it There is nothing inherent in a domain name to indicate whether it
is a public suffix. One resource for identifying public suffixes is a public suffix. One resource for identifying public suffixes
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[DBOUND] is dealing with issues concerning public suffixes. [DBOUND] is dealing with issues concerning public suffixes.
There is nothing inherent in a domain name to indicate whether it There is nothing inherent in a domain name to indicate whether it
is a public suffix. One resource for identifying public suffixes is a public suffix. One resource for identifying public suffixes
is the Public Suffix List (PSL) maintained by Mozilla is the Public Suffix List (PSL) maintained by Mozilla
(http://publicsuffix.org/). (http://publicsuffix.org/).
For example, at the time this document is published, the "com.au" For example, at the time this document is published, the "com.au"
domain is listed as a public suffix in the PSL. (Note that this domain is listed as a public suffix in the PSL. (Note that this
example might change in the future.) example might change in the future.)
Note that the term "public suffix" is controversial in the DNS Note that the term "public suffix" is controversial in the DNS
community for many reasons, and may be significantly changed in community for many reasons, and may be significantly changed in
the future. One example of the difficulty of calling a domain a the future. One example of the difficulty of calling a domain a
public suffix is that designation can change over time as the public suffix is that designation can change over time as the
registration policy for the zone changes, such as the case of the registration policy for the zone changes, such as the case of the
"uk" TLD around the time this document is published. "uk" TLD around the time this document is published.
3. DNS Header and Response Codes 3. DNS Header and Response Codes
The header of a DNS message is the first 12 octets. Many of the The header of a DNS message is its first 12 octets. Many of the
fields and flags in the header diagram in sections 4.1.1 through fields and flags in the header diagram in Sections 4.1.1 through
4.1.3 of [RFC1035] are referred to by their names in that diagram. 4.1.3 of [RFC1035] are referred to by their names in that diagram.
For example, the response codes are called "RCODEs", the data for a For example, the response codes are called "RCODEs", the data for a
record is called the "RDATA", and the authoritative answer bit is record is called the "RDATA", and the authoritative answer bit is
often called "the AA flag" or "the AA bit". often called "the AA flag" or "the AA bit".
Some of response codes that are defined in [RFC1035] have gotten Some of response codes that are defined in [RFC1035] have gotten
their own shorthand names. Some common response code names that their own shorthand names. Some common response code names that
appear without reference to the numeric value are "FORMERR", appear without reference to the numeric value are "FORMERR",
"SERVFAIL", and "NXDOMAIN" (the latter of which is also referred to "SERVFAIL", and "NXDOMAIN" (the latter of which is also referred to
as "Name Error"). All of the RCODEs are listed at as "Name Error"). All of the RCODEs are listed at
http://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml, http://www.iana.org/assignments/dns-parameters, although that site
although that site uses mixed-case capitalization, while most uses mixed-case capitalization, while most documents use all-caps.
documents use all-caps.
NODATA: A pseudo RCODE which indicates that the name is valid for NODATA: "A pseudo RCODE which indicates that the name is valid for
the given class, but there are no records of the given type. A the given class, but there are no records of the given type. A
NODATA response has to be inferred from the answer. (Quoted from NODATA response has to be inferred from the answer." (Quoted from
[RFC2308], section 1.) NODATA is indicated by an answer with the [RFC2308], Section 1.) "NODATA is indicated by an answer with the
RCODE set to NOERROR and no relevant answers in the answer RCODE set to NOERROR and no relevant answers in the answer
section. The authority section will contain an SOA record, or section. The authority section will contain an SOA record, or
there will be no NS records there. (Quoted from [RFC2308], there will be no NS records there." (Quoted from [RFC2308],
section 2,2.) Note that referrals have a similar format to NODATA Section 2.2.) Note that referrals have a similar format to NODATA
replies; [RFC2308] explains how to distinguish them. replies; [RFC2308] explains how to distinguish them.
The term "NXRRSET" is sometimes used as a synonym for NODATA. The term "NXRRSET" is sometimes used as a synonym for NODATA.
However, this is a mistake, given that NXRRSET is a specific error However, this is a mistake, given that NXRRSET is a specific error
code defined in [RFC2136]. code defined in [RFC2136].
Negative response: A response which indicates that a particular Negative response: A response that indicates that a particular RRset
RRset does not exist, or whose RCODE indicates the nameserver does not exist, or whose RCODE indicates the nameserver cannot
cannot answer. Sections 2 and 7 of [RFC2308] describe the types answer. Sections 2 and 7 of [RFC2308] describe the types of
of negative responses in detail. negative responses in detail.
Referrals: Data from the authority section of a non-authoritative Referrals: Data from the authority section of a non-authoritative
answer. [RFC1035] section 2.1 defines "authoritative" data. answer. [RFC1035] Section 2.1 defines "authoritative" data.
However, referrals at zone cuts (defined in Section 6) are not However, referrals at zone cuts (defined in Section 6) are not
authoritative. Referrals may be zone cut NS resource records and authoritative. Referrals may be zone cut NS resource records and
their glue records. NS records on the parent side of a zone cut their glue records. NS records on the parent side of a zone cut
are an authoritative delegation, but are normally not treated as are an authoritative delegation, but are normally not treated as
authoritative data by the client. In general, a referral is a way authoritative data. In general, a referral is a way for a server
for a server to send an answer saying that the server does not to send an answer saying that the server does not know the answer,
know the answer, but knows where the query should be directed in but knows where the query should be directed in order to get an
order to get an answer. Historically, many authoritative servers answer. Historically, many authoritative servers answered with a
answered with a referral to the root zone when queried for a name referral to the root zone when queried for a name for which they
for which they were not authoritative, but this practice has were not authoritative, but this practice has declined.
declined.
4. Resource Records 4. Resource Records
RR: An acronym for resource record. ([RFC1034], section 3.6.) RR: An acronym for resource record. ([RFC1034], Section 3.6.)
RRset: A set of resource records with the same label, class and RRset: A set of resource records with the same label, class and
type, but with different data. (Definition from [RFC2181]) Also type, but with different data. (Definition from [RFC2181]) Also
spelled RRSet in some documents. As a clarification, "same label" spelled RRSet in some documents. As a clarification, "same label"
in this definition means "same owner name". In addition, in this definition means "same owner name". In addition,
[RFC2181] states that "the TTLs of all RRs in an RRSet must be the [RFC2181] states that "the TTLs of all RRs in an RRSet must be the
same". (This definition is definitely not the same as "the same". (This definition is definitely not the same as "the
response one gets to a query for QTYPE=ANY", which is a response one gets to a query for QTYPE=ANY", which is an
unfortunate misunderstanding.) unfortunate misunderstanding.)
EDNS: The extension mechanisms for DNS, defined in [RFC6891]. EDNS: The extension mechanisms for DNS, defined in [RFC6891].
Sometimes called "EDNS0" or "EDNS(0)" to indicate the version Sometimes called "EDNS0" or "EDNS(0)" to indicate the version
number. EDNS allows DNS clients and servers to specify message number. EDNS allows DNS clients and servers to specify message
sizes larger than the original 512 octet limit, to expand the sizes larger than the original 512 octet limit, to expand the
response code space, and potentially to carry additional options response code space, and potentially to carry additional options
that affect the handling of a DNS query. that affect the handling of a DNS query.
OPT: A pseudo-RR (sometimes called a meta-RR) that is used only to OPT: A pseudo-RR (sometimes called a "meta-RR") that is used only to
contain control information pertaining to the question-and-answer contain control information pertaining to the question-and-answer
sequence of a specific transaction. (Definition from [RFC6891], sequence of a specific transaction. (Definition from [RFC6891],
section 6.1.1) It is used by EDNS. Section 6.1.1) It is used by EDNS.
Owner: The domain name where a RR is found ([RFC1034], section 3.6). Owner: The domain name where a RR is found ([RFC1034], Section 3.6).
Often appears in the term "owner name". Often appears in the term "owner name".
SOA field names: DNS documents, including the definitions here, SOA field names: DNS documents, including the definitions here,
often refer to the fields in the RDATA of an SOA resource record often refer to the fields in the RDATA of an SOA resource record
by field name. Those fields are defined in Section 3.3.13 of by field name. Those fields are defined in Section 3.3.13 of
[RFC1035]. The names (in the order they appear in the SOA RDATA) [RFC1035]. The names (in the order they appear in the SOA RDATA)
are MNAME, RNAME, SERIAL, REFRESH, RETRY, EXPIRE, and MINIMUM. are MNAME, RNAME, SERIAL, REFRESH, RETRY, EXPIRE, and MINIMUM.
Note that the meaning of MINIMUM field is updated in Section 4 of Note that the meaning of MINIMUM field is updated in Section 4 of
[RFC2308]; the new definition is that the MINIMUM field is only [RFC2308]; the new definition is that the MINIMUM field is only
"the TTL to be used for negative responses". This document tends "the TTL to be used for negative responses". This document tends
to use field names instead of terms that describe the fields. to use field names instead of terms that describe the fields.
TTL: The maximum "time to live" of a resource record. A TTL value TTL: The maximum "time to live" of a resource record. "A TTL value
is an unsigned number, with a minimum value of 0, and a maximum is an unsigned number, with a minimum value of 0, and a maximum
value of 2147483647. That is, a maximum of 2^31 - 1. When value of 2147483647. That is, a maximum of 2^31 - 1. When
transmitted, the TTL is encoded in the less significant 31 bits of transmitted, the TTL is encoded in the less significant 31 bits of
the 32 bit TTL field, with the most significant, or sign, bit set the 32 bit TTL field, with the most significant, or sign, bit set
to zero. (Quoted from [RFC2181], section 8) (Note that [RFC1035] to zero." (Quoted from [RFC2181], Section 8) (Note that [RFC1035]
erroneously stated that this is a signed integer; that was fixed erroneously stated that this is a signed integer; that was fixed
by [RFC2181].) by [RFC2181].)
The TTL "specifies the time interval that the resource record may The TTL "specifies the time interval that the resource record may
be cached before the source of the information should again be be cached before the source of the information should again be
consulted". (Quoted from [RFC1035], section 3.2.1) Also: "the consulted". (Quoted from [RFC1035], Section 3.2.1) Also: "the
time interval (in seconds) that the resource record may be cached time interval (in seconds) that the resource record may be cached
before it should be discarded". (Quoted from [RFC1035], section before it should be discarded". (Quoted from [RFC1035],
4.1.3). Despite being defined for a resource record, the TTL of Section 4.1.3). Despite being defined for a resource record, the
every resource record in an RRset is required to be the same TTL of every resource record in an RRset is required to be the
([RFC2181], section 5.2). same ([RFC2181], Section 5.2).
The reason that the TTL is the maximum time to live is that a The reason that the TTL is the maximum time to live is that a
cache operator might decide to shorten the time to live for cache operator might decide to shorten the time to live for
operational purposes, such as if there is a policy to not allow operational purposes, such as if there is a policy to disallow TTL
TTL values over a certain number. Also, if a value is flushed values over a certain number. Also, if a value is flushed from
from the cache when its value is still positive, the value the cache when its value is still positive, the value effectively
effectively becomes zero. becomes zero. Some servers are known to ignore the TTL on some
Some servers are known to ignore the TTL on some RRsets (such as RRsets (such as when the authoritative data has a very short TTL)
when the authoritative data has a very short TTL) even though this even though this is against the advice in RFC 1035.
is against the advice in RFC 1035.
There is also the concept of a "default TTL" for a zone, which can There is also the concept of a "default TTL" for a zone, which can
be a configuration parameter in the server software. This is be a configuration parameter in the server software. This is
often expressed by a default for the entire server, and a default often expressed by a default for the entire server, and a default
for a zone using the $TTL directive in a zone file. The $TTL for a zone using the $TTL directive in a zone file. The $TTL
directive was added to the master file format by [RFC2308]. directive was added to the master file format by [RFC2308].
Class independent: A resource record type whose syntax and semantics Class independent: A resource record type whose syntax and semantics
are the same for every DNS class. A resource record type that is are the same for every DNS class. A resource record type that is
not class independent has different meanings depending on the DNS not class independent has different meanings depending on the DNS
class of the record, or the meaning is undefined for classes other class of the record, or the meaning is undefined for classes other
than IN (class 1, the Internet). than IN (class 1, the Internet).
5. DNS Servers and Clients 5. DNS Servers and Clients
This section defines the terms used for the systems that act as DNS This section defines the terms used for the systems that act as DNS
clients, DNS servers, or both. clients, DNS servers, or both.
Resolver: A program that extracts information from name servers in Resolver: A program "that extract[s] information from name servers
response to client requests. (Quoted from [RFC1034], section 2.4) in response to client requests." (Quoted from [RFC1034],
The resolver is located on the same machine as the program that Section 2.4) "The resolver is located on the same machine as the
requests the resolver's services, but it may need to consult name program that requests the resolver's services, but it may need to
servers on other hosts. (Quoted from [RFC1034], section 5.1) A consult name servers on other hosts." (Quoted from [RFC1034],
resolver performs queries for a name, type, and class, and Section 5.1) A resolver performs queries for a name, type, and
receives answers. The logical function is called "resolution". class, and receives answers. The logical function is called
In practice, the term is usually referring to some specific type "resolution". In practice, the term is usually referring to some
of resolver (some of which are defined below), and understanding specific type of resolver (some of which are defined below), and
the use of the term depends on understanding the context. understanding the use of the term depends on understanding the
context.
Stub resolver: A resolver that cannot perform all resolution itself. Stub resolver: A resolver that cannot perform all resolution itself.
Stub resolvers generally depend on a recursive resolver to Stub resolvers generally depend on a recursive resolver to
undertake the actual resolution function. Stub resolvers are undertake the actual resolution function. Stub resolvers are
discussed but never fully defined in Section 5.3.1 of [RFC1034]. discussed but never fully defined in Section 5.3.1 of [RFC1034].
They are fully defined in Section 6.1.3.1 of [RFC1123]. They are fully defined in Section 6.1.3.1 of [RFC1123].
Iterative mode: A resolution mode of a server that receives DNS Iterative mode: A resolution mode of a server that receives DNS
queries and responds with a referral to another server. queries and responds with a referral to another server.
Section 2.3 of [RFC1034] describes this as "The server refers the Section 2.3 of [RFC1034] describes this as "The server refers the
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Full-service resolver: Section 6.1.3.1 of [RFC1123] defines this Full-service resolver: Section 6.1.3.1 of [RFC1123] defines this
term to mean a resolver that acts in recursive mode with a cache term to mean a resolver that acts in recursive mode with a cache
(and meets other requirements). (and meets other requirements).
Priming: The mechanism used by a resolver to determine where to send Priming: The mechanism used by a resolver to determine where to send
queries before there is anything in the resolver's cache. Priming queries before there is anything in the resolver's cache. Priming
is most often done from a configuration setting that contains a is most often done from a configuration setting that contains a
list of authoritative servers for the root zone. list of authoritative servers for the root zone.
Negative caching: The storage of knowledge that something does not Negative caching: "The storage of knowledge that something does not
exist, cannot give an answer, or does not give an answer. (Quoted exist, cannot give an answer, or does not give an answer."
from [RFC2308], section 1) (Quoted from [RFC2308], Section 1)
Authoritative server: A server that knows the content of a DNS zone Authoritative server: "A server that knows the content of a DNS zone
from local knowledge, and thus can answer queries about that zone from local knowledge, and thus can answer queries about that zone
without needing to query other servers. (Quoted from [RFC2182], without needing to query other servers." (Quoted from [RFC2182],
section 2.) It is a system that responds to DNS queries with Section 2.) It is a system that responds to DNS queries with
information about zones for which it has been configured to answer information about zones for which it has been configured to answer
with the AA flag in the response header set to 1. It is a server with the AA flag in the response header set to 1. It is a server
that has authority over one or more DNS zones. Note that it is that has authority over one or more DNS zones. Note that it is
possible for an authoritative server to respond to a query without possible for an authoritative server to respond to a query without
the parent zone delegating authority to that server. the parent zone delegating authority to that server.
Authoritative servers also provide "referrals", usually to child Authoritative servers also provide "referrals", usually to child
zones delegated from them; these referrals have the AA bit set to zones delegated from them; these referrals have the AA bit set to
0 and come with referral data in the Authority and (if needed) the 0 and come with referral data in the Authority and (if needed) the
Additional sections. Additional sections.
Authoritative-only server: A name server that only serves Authoritative-only server: A name server that only serves
authoritative data and ignores requests for recursion. It will authoritative data and ignores requests for recursion. It will
"not normally generate any queries of its own. Instead, it "not normally generate any queries of its own. Instead, it
answers non-recursive queries from iterative resolvers looking for answers non-recursive queries from iterative resolvers looking for
information in zones it serves." (Quoted from [RFC4697], section information in zones it serves." (Quoted from [RFC4697],
2.4) Section 2.4)
Zone transfer: The act of a client requesting a copy of a zone and Zone transfer: The act of a client requesting a copy of a zone and
an authoritative server sending the needed information. (See an authoritative server sending the needed information. (See
Section 6 for a description of zones.) There are two common Section 6 for a description of zones.) There are two common
standard ways to do zone transfers: the AXFR ("Authoritative standard ways to do zone transfers: the AXFR ("Authoritative
Transfer") mechanism to copy the full zone (described in Transfer") mechanism to copy the full zone (described in
[RFC5936], and the IXFR ("Incremental Transfer") mechanism to copy [RFC5936], and the IXFR ("Incremental Transfer") mechanism to copy
only parts of the zone that have changed (described in [RFC1995]). only parts of the zone that have changed (described in [RFC1995]).
Many systems use non-standard methods for zone transfer outside Many systems use non-standard methods for zone transfer outside
the DNS protocol. the DNS protocol.
Secondary server: "An authoritative server which uses zone transfer Secondary server: "An authoritative server which uses zone transfer
to retrieve the zone" (quoted from [RFC1996], section 2.1). to retrieve the zone" (Quoted from [RFC1996], Section 2.1).
[RFC2182] describes secondary servers in detail. Although early [RFC2182] describes secondary servers in detail. Although early
DNS RFCs such as [RFC1996] referred to this as a "slave", the DNS RFCs such as [RFC1996] referred to this as a "slave", the
current common usage has shifted to calling it a "secondary". current common usage has shifted to calling it a "secondary".
Secondary servers are also discussed in [RFC1034]. Secondary servers are also discussed in [RFC1034].
Slave server: See secondary server. Slave server: See secondary server.
Primary server: "Any authoritative server configured to be the Primary server: "Any authoritative server configured to be the
source of zone transfer for one or more [secondary] servers" source of zone transfer for one or more [secondary] servers"
(quoted from [RFC1996], section 2.1) or, more specifically, "an (Quoted from [RFC1996], Section 2.1) or, more specifically, "an
authoritative server configured to be the source of AXFR or IXFR authoritative server configured to be the source of AXFR or IXFR
data for one or more [secondary] servers" (quoted from [RFC2136]). data for one or more [secondary] servers" (Quoted from [RFC2136]).
Although early DNS RFCs such as [RFC1996] referred to this as a Although early DNS RFCs such as [RFC1996] referred to this as a
"master", the current common usage has shifted to "primary". "master", the current common usage has shifted to "primary".
Primary servers are also discussed in [RFC1034]. Primary servers are also discussed in [RFC1034].
Master server: See primary server. Master server: See primary server.
Primary master: The primary master is named in the zone's SOA MNAME Primary master: "The primary master is named in the zone's SOA MNAME
field and optionally by an NS resource record. (Quoted from field and optionally by an NS RR". (Quoted from [RFC1996],
[RFC1996], section 2.1) [RFC2136] defines "primary master" as Section 2.1). [RFC2136] defines "primary master" as "Master
"Master server at the root of the AXFR/IXFR dependency graph. The server at the root of the AXFR/IXFR dependency graph. The primary
primary master is named in the zone's SOA MNAME field and master is named in the zone's SOA MNAME field and optionally by an
optionally by an NS RR. There is by definition only one primary NS RR. There is by definition only one primary master server per
master server per zone." The idea of a primary master is only zone." The idea of a primary master is only used by [RFC2136],
used by [RFC2136], and is considered archaic in other parts of the and is considered archaic in other parts of the DNS.
DNS.
Stealth server: This is the same as a slave server except that it is Stealth server: This is "like a slave server except not listed in an
not listed in an NS resource record for the zone. (Quoted from NS RR for the zone." (Quoted from [RFC1996], Section 2.1)
[RFC1996], section 2.1)
Hidden master: A stealth server that is a master for zone transfers. Hidden master: A stealth server that is a master for zone transfers.
In this arrangement, the master name server that processes the "In this arrangement, the master name server that processes the
updates is unavailable to general hosts on the Internet; it is not updates is unavailable to general hosts on the Internet; it is not
listed in the NS RRset. (Quoted from [RFC6781], section 3.4.3.) listed in the NS RRset." (Quoted from [RFC6781], Section 3.4.3.)
An earlier RFC, [RFC4641], said that the hidden master's name An earlier RFC, [RFC4641], said that the hidden master's name
appears in the SOA RRs MNAME field, although in some setups, the appears in the SOA RRs MNAME field, although in some setups, the
name does not appear at all in the public DNS. A hidden master name does not appear at all in the public DNS. A hidden master
can be either a secondary or a primary master. can be either a secondary or a primary master.
Forwarding: The process of one server sending a DNS query with the Forwarding: The process of one server sending a DNS query with the
RD bit set to 1 to another server to resolve that query. RD bit set to 1 to another server to resolve that query.
Forwarding is a function of a DNS resolver; it is different than Forwarding is a function of a DNS resolver; it is different than
simply blindly relaying queries. simply blindly relaying queries.
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Passive DNS: A mechanism to collect large amounts of DNS data by Passive DNS: A mechanism to collect large amounts of DNS data by
storing DNS responses from servers. Some of these systems also storing DNS responses from servers. Some of these systems also
collect the DNS queries associated with the responses; this can collect the DNS queries associated with the responses; this can
raise privacy issues. Passive DNS databases can be used to answer raise privacy issues. Passive DNS databases can be used to answer
historical questions about DNS zones such as which records were historical questions about DNS zones such as which records were
available for them at what times in the past. Passive DNS available for them at what times in the past. Passive DNS
databases allow searching of the stored records on keys other than databases allow searching of the stored records on keys other than
just the name, such as "find all names which have A records of a just the name, such as "find all names which have A records of a
particular value". particular value".
Anycast: The practice of making a particular service address Anycast: "The practice of making a particular service address
available in multiple, discrete, autonomous locations, such that available in multiple, discrete, autonomous locations, such that
datagrams sent are routed to one of several available locations. datagrams sent are routed to one of several available locations."
(Quoted from [RFC4786], Section 2) (Quoted from [RFC4786], Section 2)
6. Zones 6. Zones
This section defines terms that are used when discussing zones that This section defines terms that are used when discussing zones that
are being served or retrieved. are being served or retrieved.
Zone: A unit of organization of authoritative data. Zones can be Zone: "Authoritative information is organized into units called
automatically distributed to the name servers which provide 'zones', and these zones can be automatically distributed to the
redundant service for the data in a zone. (Quoted from [RFC1034], name servers which provide redundant service for the data in a
section 2.4) zone." (Quoted from [RFC1034], Section 2.4)
Child: The entity on record that has the delegation of the domain Child: "The entity on record that has the delegation of the domain
from the Parent. (Quoted from [RFC7344], section 1.1) from the Parent." (Quoted from [RFC7344], Section 1.1)
Parent: The domain in which the Child is registered. (Quoted from Parent: "The domain in which the Child is registered." (Quoted from
[RFC7344], section 1.1) Earlier, "parent name server" was defined [RFC7344], Section 1.1) Earlier, "parent name server" was defined
in [RFC0882] as "the name server that has authority over the place in [RFC882] as "the name server that has authority over the place
in the domain name space that will hold the new domain". in the domain name space that will hold the new domain". (Note
[RFC0819] also has some description of the relationship between that [RFC882] was obsoleted by [RFC1034] and [RFC1035].) [RFC819]
parents and children. also has some description of the relationship between parents and
children.
Origin: Origin:
(a) The domain name that appears at the top of a zone (just below (a) "The domain name that appears at the top of a zone (just below
the cut that separates the zone from its parent). The name of the the cut that separates the zone from its parent). The name of the
zone is the same as the name of the domain at the zone's origin. zone is the same as the name of the domain at the zone's origin."
(Quoted from [RFC2181], section 6.) These days, this sense of (Quoted from [RFC2181], Section 6.) These days, this sense of
"origin" and "apex" (defined below) are often used "origin" and "apex" (defined below) are often used
interchangeably. interchangeably.
(b) The domain name within which a given relative domain name (b) The domain name within which a given relative domain name
appears in zone files. Generally seen in the context of appears in zone files. Generally seen in the context of
"$ORIGIN", which is a control entry defined in [RFC1035], section "$ORIGIN", which is a control entry defined in [RFC1035],
5.1, as part of the master file format. For example, if the Section 5.1, as part of the master file format. For example, if
$ORIGIN is set to "example.org.", then a master file line for the $ORIGIN is set to "example.org.", then a master file line for
"www" is in fact an entry for "www.example.org.". "www" is in fact an entry for "www.example.org.".
Apex: The point in the tree at an owner of an SOA and corresponding Apex: The point in the tree at an owner of an SOA and corresponding
authoritative NS RRset. This is also called the "zone apex". authoritative NS RRset. This is also called the "zone apex".
[RFC4033] defines it as "the name at the child's side of a zone [RFC4033] defines it as "the name at the child's side of a zone
cut". The "apex" can usefully be thought of as a data-theoretic cut". The "apex" can usefully be thought of as a data-theoretic
description of a tree structure, and "origin" is the name of the description of a tree structure, and "origin" is the name of the
same concept when it is implemented in zone files. The same concept when it is implemented in zone files. The
distinction is not always maintained in use, however, and one can distinction is not always maintained in use, however, and one can
find uses that conflict subtly with this definition. [RFC1034] find uses that conflict subtly with this definition. [RFC1034]
uses the term "top node of the zone" as a synonym of "apex", but uses the term "top node of the zone" as a synonym of "apex", but
that term is not widely used. These days, the first sense of that term is not widely used. These days, the first sense of
"origin" (above) and "apex" are often used interchangeably. "origin" (above) and "apex" are often used interchangeably.
Zone cut: The delimitation point between two zones where the origin Zone cut: The delimitation point between two zones where the origin
of one of the zones is the child of the other zone. of one of the zones is the child of the other zone.
Zones are delimited by "zone cuts". Each zone cut separates a "Zones are delimited by 'zone cuts'. Each zone cut separates a
"child" zone (below the cut) from a "parent" zone (above the cut). 'child' zone (below the cut) from a 'parent' zone (above the cut).
(Quoted from [RFC2181], section 6; note that this is barely an (Quoted from [RFC2181], Section 6; note that this is barely an
ostensive definition.) Section 4.2 of [RFC1034] uses "cuts" as ostensive definition.) Section 4.2 of [RFC1034] uses "cuts" as
"zone cut". 'zone cut'."
Delegation: The process by which a separate zone is created in the Delegation: The process by which a separate zone is created in the
name space beneath the apex of a given domain. Delegation happens name space beneath the apex of a given domain. Delegation happens
when an NS RRset is added in the parent zone for the child origin. when an NS RRset is added in the parent zone for the child origin.
Delegation inherently happens at a zone cut. The term is also Delegation inherently happens at a zone cut. The term is also
commonly a noun: the new zone that is created by the act of commonly a noun: the new zone that is created by the act of
delegating. delegating.
Glue records: "[Resource records] which are not part of the Glue records: "[Resource records] which are not part of the
authoritative data [of the zone], and are address resource records authoritative data [of the zone], and are address resource records
for the [name servers in subzones]. These RRs are only necessary for the [name servers in subzones]. These RRs are only necessary
if the name server's name is 'below' the cut, and are only used as if the name server's name is 'below' the cut, and are only used as
part of a referral response." Without glue "we could be faced part of a referral response." Without glue "we could be faced
with the situation where the NS RRs tell us that in order to learn with the situation where the NS RRs tell us that in order to learn
a name server's address, we should contact the server using the a name server's address, we should contact the server using the
address we wish to learn." (Definition from [RFC1034], section address we wish to learn." (Definition from [RFC1034],
4.2.1) Section 4.2.1)
A later definition is that glue "includes any record in a zone A later definition is that glue "includes any record in a zone
file that is not properly part of that zone, including nameserver file that is not properly part of that zone, including nameserver
records of delegated sub-zones (NS records), address records that records of delegated sub-zones (NS records), address records that
accompany those NS records (A, AAAA, etc), and any other stray accompany those NS records (A, AAAA, etc), and any other stray
data that might appear" ([RFC2181], section 5.4.1). Although glue data that might appear" ([RFC2181], Section 5.4.1). Although glue
is sometimes used today with this wider definition in mind, the is sometimes used today with this wider definition in mind, the
context surrounding the [RFC2181] definition suggests it is context surrounding the [RFC2181] definition suggests it is
intended to apply to the use of glue within the document itself intended to apply to the use of glue within the document itself
and not necessarily beyond. and not necessarily beyond.
In-bailiwick: In-bailiwick:
(a) An adjective to describe a name server whose name is either (a) An adjective to describe a name server whose name is either
subordinate to or (rarely) the same as the zone origin. In- subordinate to or (rarely) the same as the zone origin. In-
bailiwick name servers require glue records in their parent zone bailiwick name servers require glue records in their parent zone
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authoritative for an ancestor of the owner name. This sense of authoritative for an ancestor of the owner name. This sense of
the term normally is used when discussing the relevancy of glue the term normally is used when discussing the relevancy of glue
records in a response. For example, the server for the parent records in a response. For example, the server for the parent
zone "example.com" might reply with glue records for zone "example.com" might reply with glue records for
"ns.child.example.com". Because the "child.example.com" zone is a "ns.child.example.com". Because the "child.example.com" zone is a
descendant of the "example.com" zone, the glue records are in- descendant of the "example.com" zone, the glue records are in-
bailiwick. bailiwick.
Out-of-bailiwick: The antonym of in-bailiwick. Out-of-bailiwick: The antonym of in-bailiwick.
Authoritative data: All of the RRs attached to all of the nodes from Authoritative data: "All of the RRs attached to all of the nodes
the top node of the zone down to leaf nodes or nodes above cuts from the top node of the zone down to leaf nodes or nodes above
around the bottom edge of the zone. (Quoted from [RFC1034], cuts around the bottom edge of the zone." (Quoted from [RFC1034],
section 4.2.1) It is noted that this definition might Section 4.2.1) It is noted that this definition might
inadvertently also include any NS records that appear in the zone, inadvertently also include any NS records that appear in the zone,
even those that might not truly be authoritative because there are even those that might not truly be authoritative because there are
identical NS RRs below the zone cut. This reveals the ambiguity identical NS RRs below the zone cut. This reveals the ambiguity
in the notion of authoritative data, because the parent-side NS in the notion of authoritative data, because the parent-side NS
records authoritatively indicate the delegation, even though they records authoritatively indicate the delegation, even though they
are not themselves authoritative data. are not themselves authoritative data.
Root zone: The zone whose apex is the zero-length label. Also Root zone: The zone whose apex is the zero-length label. Also
sometimes called "the DNS root". sometimes called "the DNS root".
Empty non-terminals: Domain names that own no resource records but Empty non-terminals: "Domain names that own no resource records but
have subdomains that do. (Quoted from [RFC4592], section 2.2.2.) have subdomains that do." (Quoted from [RFC4592], Section 2.2.2.)
A typical example is in SRV records: in the name A typical example is in SRV records: in the name
"_sip._tcp.example.com", it is likely that "_tcp.example.com" has "_sip._tcp.example.com", it is likely that "_tcp.example.com" has
no RRsets, but that "_sip._tcp.example.com" has (at least) an SRV no RRsets, but that "_sip._tcp.example.com" has (at least) an SRV
RRset. RRset.
Delegation-centric zone: A zone which consists mostly of delegations Delegation-centric zone: A zone that consists mostly of delegations
to child zones. This term is used in contrast to a zone which to child zones. This term is used in contrast to a zone that
might have some delegations to child zones, but also has many data might have some delegations to child zones, but also has many data
resource records for the zone itself and/or for child zones. The resource records for the zone itself and/or for child zones. The
term is used in [RFC4956] and [RFC5155], but is not defined there. term is used in [RFC4956] and [RFC5155], but is not defined there.
Wildcard: [RFC1034] defined "wildcard", but in a way that turned out Wildcard: [RFC1034] defined "wildcard", but in a way that turned out
to be confusing to implementers. Special treatment is given to to be confusing to implementers. Special treatment is given to
RRs with owner names starting with the label "*". Such RRs are RRs with owner names starting with the label "*". "Such RRs are
called wildcards. Wildcard RRs can be thought of as instructions called 'wildcards'. Wildcard RRs can be thought of as
for synthesizing RRs. (Quoted from [RFC1034], section 4.3.3) For instructions for synthesizing RRs." (Quoted from [RFC1034],
an extended discussion of wildcards, including clearer Section 4.3.3) For an extended discussion of wildcards, including
definitions, see [RFC4592]. clearer definitions, see [RFC4592].
Occluded name: The addition of a delegation point via dynamic update Occluded name: "The addition of a delegation point via dynamic
will render all subordinate domain names to be in a limbo, still update will render all subordinate domain names to be in a limbo,
part of the zone but not available to the lookup process. The still part of the zone, but not available to the lookup process.
addition of a DNAME resource record has the same impact. The The addition of a DNAME resource record has the same impact. The
subordinate names are said to be "occluded". (Quoted from subordinate names are said to be 'occluded'." (Quoted from
[RFC5936], Section 3.5) [RFC5936], Section 3.5)
Fast flux DNS: This occurs when a domain is found in DNS using A Fast flux DNS: This "occurs when a domain is found in DNS using A
records to multiple IP addresses, each of which has a very short records to multiple IP addresses, each of which has a very short
Time-to-Live (TTL) value associated with it. This means that the Time-to-Live (TTL) value associated with it. This means that the
domain resolves to varying IP addresses over a short period of domain resolves to varying IP addresses over a short period of
time. (Quoted from [RFC6561], section 1.1.5, with typo corrected) time." (Quoted from [RFC6561], Section 1.1.5, with typo
It is often used to deliver malware. Because the addresses change corrected) It is often used to deliver malware. Because the
so rapidly, it is difficult to acertain all the hosts. It should addresses change so rapidly, it is difficult to ascertain all the
be noted that the technique also works with AAAA records, but such hosts. It should be noted that the technique also works with AAAA
use is not frequently observed on the Internet as of this writing. records, but such use is not frequently observed on the Internet
as of this writing.
7. Registration Model 7. Registration Model
Registry: The administrative operation of a zone that allows Registry: The administrative operation of a zone that allows
registration of names within that zone. People often use this registration of names within that zone. People often use this
term to refer only to those organizations that perform term to refer only to those organizations that perform
registration in large delegation-centric zones (such as TLDs); but registration in large delegation-centric zones (such as TLDs); but
formally, whoever decides what data goes into a zone is the formally, whoever decides what data goes into a zone is the
registry for that zone. This definition of "registry" is from a registry for that zone. This definition of "registry" is from a
DNS point of view; for some zones, the policies that determine DNS point of view; for some zones, the policies that determine
what can go in the zone are decided by superior zones and not the what can go in the zone are decided by superior zones and not the
registry operator. registry operator.
Registrant: An individual or organization on whose behalf a name in Registrant: An individual or organization on whose behalf a name in
a zone is registered by the registry. In many zones, the registry a zone is registered by the registry. In many zones, the registry
and the registrant may be the same entity, but in TLDs they often and the registrant may be the same entity, but in TLDs they often
are not. are not.
Registrar: A service provider that acts as a go-between for Registrar: A service provider that acts as a go-between for
registrants and registries. Not all registrations require a registrants and registries. Not all registrations require a
registrar, though it is common to have registrars be involved in registrar, though it is common to have registrars involved in
registrations in TLDs. registrations in TLDs.
EPP: The Extensible Provisioning Protocol (EPP), which is commonly EPP: The Extensible Provisioning Protocol (EPP), which is commonly
used for communication of registration information between used for communication of registration information between
registries and registrars. EPP is defined in [RFC5730]. registries and registrars. EPP is defined in [RFC5730].
WHOIS: A protocol specified in [RFC3912], often used for querying WHOIS: A protocol specified in [RFC3912], often used for querying
registry databases. WHOIS data is frequently used to associate registry databases. WHOIS data is frequently used to associate
registration data (such as zone management contacts) with domain registration data (such as zone management contacts) with domain
names. The term "WHOIS data" is often used as a synonym for the names. The term "WHOIS data" is often used as a synonym for the
skipping to change at page 17, line 34 skipping to change at page 18, line 22
some RFCs, have not been formally defined. However, Section 2 of some RFCs, have not been formally defined. However, Section 2 of
[RFC4033] defines many types of resolvers and validators, [RFC4033] defines many types of resolvers and validators,
including "non-validating security-aware stub resolver", "non- including "non-validating security-aware stub resolver", "non-
validating stub resolver", "security-aware name server", validating stub resolver", "security-aware name server",
"security-aware recursive name server", "security-aware resolver", "security-aware recursive name server", "security-aware resolver",
"security-aware stub resolver", and "security-oblivious "security-aware stub resolver", and "security-oblivious
'anything'". (Note that the term "validating resolver", which is 'anything'". (Note that the term "validating resolver", which is
used in some places in DNSSEC-related documents, is also not used in some places in DNSSEC-related documents, is also not
defined.) defined.)
Signed zone: A zone whose RRsets are signed and that contains Signed zone: "A zone whose RRsets are signed and that contains
properly constructed DNSKEY, Resource Record Signature (RRSIG), properly constructed DNSKEY, Resource Record Signature (RRSIG),
Next Secure (NSEC), and (optionally) DS records. (Quoted from Next Secure (NSEC), and (optionally) DS records." (Quoted from
[RFC4033], section 2.) It has been noted in other contexts that [RFC4033], Section 2.) It has been noted in other contexts that
the zone itself is not really signed, but all the relevant RRsets the zone itself is not really signed, but all the relevant RRsets
in the zone are signed. Nevertheless, if a zone that should be in the zone are signed. Nevertheless, if a zone that should be
signed contains any RRsets that are not signed (or opted out), signed contains any RRsets that are not signed (or opted out),
those RRsets will be treated as bogus, so the whole zone needs to those RRsets will be treated as bogus, so the whole zone needs to
be handled in some way. be handled in some way.
It should also be noted that, since the publication of [RFC6840], It should also be noted that, since the publication of [RFC6840],
NSEC records are no longer required for signed zones: a signed NSEC records are no longer required for signed zones: a signed
zone might include NSEC3 records instead. [RFC7129] provides zone might include NSEC3 records instead. [RFC7129] provides
additional background commentary and some context for the NSEC and additional background commentary and some context for the NSEC and
skipping to change at page 18, line 18 skipping to change at page 19, line 8
that defines an additional situation in which a zone is considered that defines an additional situation in which a zone is considered
unsigned: "If the resolver does not support any of the algorithms unsigned: "If the resolver does not support any of the algorithms
listed in an authenticated DS RRset, then the resolver will not be listed in an authenticated DS RRset, then the resolver will not be
able to verify the authentication path to the child zone. In this able to verify the authentication path to the child zone. In this
case, the resolver SHOULD treat the child zone as if it were case, the resolver SHOULD treat the child zone as if it were
unsigned." unsigned."
NSEC: "The NSEC record allows a security-aware resolver to NSEC: "The NSEC record allows a security-aware resolver to
authenticate a negative reply for either name or type non- authenticate a negative reply for either name or type non-
existence with the same mechanisms used to authenticate other DNS existence with the same mechanisms used to authenticate other DNS
replies." (Quoted from [RFC4033], section 3.2.) In short, an replies." (Quoted from [RFC4033], Section 3.2.) In short, an
NSEC record provides authenticated denial of existence. NSEC record provides authenticated denial of existence.
The NSEC resource record lists two separate things: the next owner "The NSEC resource record lists two separate things: the next
name (in the canonical ordering of the zone) that contains owner name (in the canonical ordering of the zone) that contains
authoritative data or a delegation point NS RRset, and the set of authoritative data or a delegation point NS RRset, and the set of
RR types present at the NSEC RR's owner name. (Quoted from RR types present at the NSEC RR's owner name." (Quoted from
Section 4 of 4034) Section 4 of RFC 4034)
NSEC3: Like the NSEC record, the NSEC3 record also provides NSEC3: Like the NSEC record, the NSEC3 record also provides
authenticated denial of existence; however, NSEC3 records mitigate authenticated denial of existence; however, NSEC3 records mitigate
against zone enumeration and support Opt-Out. NSEC3 resource against zone enumeration and support Opt-Out. NSEC3 resource
records are defined in [RFC5155]. records are defined in [RFC5155].
Note that [RFC6840] says that [RFC5155] "is now considered part of Note that [RFC6840] says that [RFC5155] "is now considered part of
the DNS Security Document Family as described by Section 10 of the DNS Security Document Family as described by Section 10 of
[RFC4033]". This means that some of the definitions from earlier [RFC4033]". This means that some of the definitions from earlier
RFCs that only talk about NSEC records should probably be RFCs that only talk about NSEC records should probably be
considered to be talking about both NSEC and NSEC3. considered to be talking about both NSEC and NSEC3.
Opt-out: The Opt-Out Flag indicates whether this NSEC3 RR may cover Opt-out: "The Opt-Out Flag indicates whether this NSEC3 RR may cover
unsigned delegations. (Quoted from [RFC5155], section 3.1.2.1.) unsigned delegations." (Quoted from [RFC5155], Section 3.1.2.1.)
Opt-out tackles the high costs of securing a delegation to an Opt-out tackles the high costs of securing a delegation to an
insecure zone. When using Opt-Out, names that are an insecure insecure zone. When using Opt-Out, names that are an insecure
delegation (and empty non-terminals that are only derived from delegation (and empty non-terminals that are only derived from
insecure delegations) don't require an NSEC3 record or its insecure delegations) don't require an NSEC3 record or its
corresponding RRSIG records. Opt-Out NSEC3 records are not able corresponding RRSIG records. Opt-Out NSEC3 records are not able
to prove or deny the existence of the insecure delegations. to prove or deny the existence of the insecure delegations.
(Adapted from [RFC7129], section 5.1) (Adapted from [RFC7129], Section 5.1)
Zone enumeration: The practice of discovering the full content of a Zone enumeration: "The practice of discovering the full content of a
zone via successive queries. (Quoted from [RFC5155], section zone via successive queries." (Quoted from [RFC5155],
1.3.) This is also sometimes call "zone walking". Zone Section 1.3.) This is also sometimes called "zone walking". Zone
enumeration is different from zone content guessing where the enumeration is different from zone content guessing where the
guesser uses a large dictionary of possible labels and sends guesser uses a large dictionary of possible labels and sends
successive queries for them, or matches the contents of NSEC3 successive queries for them, or matches the contents of NSEC3
records against such a dictionary. records against such a dictionary.
Key signing key (KSK): DNSSEC keys that only sign the apex DNSKEY Key signing key (KSK): DNSSEC keys that "only sign the apex DNSKEY
RRset in a zone. (Quoted from [RFC6781], section 3.1) RRset in a zone."(Quoted from [RFC6781], Section 3.1)
Zone signing key (ZSK): DNSSEC keys that can be used to sign all the Zone signing key (ZSK): "DNSSEC keys that can be used to sign all
RRsets in a zone that require signatures, other than the apex the RRsets in a zone that require signatures, other than the apex
DNSKEY RRset. (Quoted from [RFC6781], section 3.1) Note that the DNSKEY RRset." (Quoted from [RFC6781], Section 3.1) Note that the
roles KSK and ZSK are not mutually exclusive: a single key can be roles KSK and ZSK are not mutually exclusive: a single key can be
both KSK and ZSK at the same time. Also note that a ZSK is both KSK and ZSK at the same time. Also note that a ZSK is
sometimes used to sign the apex DNSKEY RRset. sometimes used to sign the apex DNSKEY RRset.
Combined signing key (CSK): In cases where the differentiation Combined signing key (CSK): "In cases where the differentiation
between the KSK and ZSK is not made, i.e., where keys have the between the KSK and ZSK is not made, i.e., where keys have the
role of both KSK and ZSK, we talk about a Single-Type Signing role of both KSK and ZSK, we talk about a Single-Type Signing
Scheme. (Quoted from [RFC6781], Section 3.1) This is sometimes Scheme." (Quoted from [RFC6781], Section 3.1) This is sometimes
called a "combined signing key" or CSK. It is operational called a "combined signing key" or CSK. It is operational
practice, not protocol, that determines whether a particular key practice, not protocol, that determines whether a particular key
is a ZSK, a KSK, or a CSK. is a ZSK, a KSK, or a CSK.
Secure Entry Point (SEP): A flag in the DNSKEY RDATA that can be Secure Entry Point (SEP): A flag in the DNSKEY RDATA that "can be
used to distinguish between keys that are intended to be used as used to distinguish between keys that are intended to be used as
the secure entry point into the zone when building chains of the secure entry point into the zone when building chains of
trust, i.e., they are (to be) pointed to by parental DS RRs or trust, i.e., they are (to be) pointed to by parental DS RRs or
configured as a trust anchor. Therefore, it is suggested that the configured as a trust anchor. Therefore, it is suggested that the
SEP flag be set on keys that are used as KSKs and not on keys that SEP flag be set on keys that are used as KSKs and not on keys that
are used as ZSKs, while in those cases where a distinction between are used as ZSKs, while in those cases where a distinction between
a KSK and ZSK is not made (i.e., for a Single-Type Signing a KSK and ZSK is not made (i.e., for a Single-Type Signing
Scheme), it is suggested that the SEP flag be set on all keys. Scheme), it is suggested that the SEP flag be set on all keys."
(Quoted from [RFC6781], section 3.2.3.) Note that the SEP flag is (Quoted from [RFC6781], Section 3.2.3.) Note that the SEP flag is
only a hint, and its presence or absence may not be used to only a hint, and its presence or absence may not be used to
disqualify a given DNSKEY RR from use as a KSK or ZSK during disqualify a given DNSKEY RR from use as a KSK or ZSK during
validation. validation.
DNSSEC Policy (DP): A statement that sets forth the security DNSSEC Policy (DP): A statement that "sets forth the security
requirements and standards to be implemented for a DNSSEC-signed requirements and standards to be implemented for a DNSSEC-signed
zone. (Quoted from [RFC6841], section 2) zone." (Quoted from [RFC6841], Section 2)
DNSSEC Practice Statement (DPS): A practices disclosure document DNSSEC Practice Statement (DPS): "A practices disclosure document
that may support and be a supplemental document to the DNSSEC that may support and be a supplemental document to the DNSSEC
Policy (if such exists), and it states how the management of a Policy (if such exists), and it states how the management of a
given zone implements procedures and controls at a high level. given zone implements procedures and controls at a high level."
(Quoted from [RFC6841], section 2) (Quoted from [RFC6841], Section 2)
9. DNSSEC States 9. DNSSEC States
A validating resolver can determine that a response is in one of four A validating resolver can determine that a response is in one of four
states: secure, insecure, bogus, or indeterminate. These states are states: secure, insecure, bogus, or indeterminate. These states are
defined in [RFC4033] and [RFC4035], although the two definitions defined in [RFC4033] and [RFC4035], although the two definitions
differ a bit. This document makes no effort to reconcile the two differ a bit. This document makes no effort to reconcile the two
definitions, and takes no position as to whether they need to be definitions, and takes no position as to whether they need to be
reconciled. reconciled.
Section 5 of [RFC4033] says: Section 5 of [RFC4033] says:
A validating resolver can determine the following 4 states: A validating resolver can determine the following 4 states:
Secure: The validating resolver has a trust anchor, has a chain of Secure: The validating resolver has a trust anchor, has a chain
trust, and is able to verify all the signatures in the response. of trust, and is able to verify all the signatures in the
response.
Insecure: The validating resolver has a trust anchor, a chain of Insecure: The validating resolver has a trust anchor, a chain
trust, and, at some delegation point, signed proof of the of trust, and, at some delegation point, signed proof of the
non-existence of a DS record. This indicates that subsequent non-existence of a DS record. This indicates that subsequent
branches in the tree are provably insecure. A validating resolver branches in the tree are provably insecure. A validating
may have a local policy to mark parts of the domain space as resolver may have a local policy to mark parts of the domain
insecure. space as insecure.
Bogus: The validating resolver has a trust anchor and a secure Bogus: The validating resolver has a trust anchor and a secure
delegation indicating that subsidiary data is signed, but the delegation indicating that subsidiary data is signed, but
response fails to validate for some reason: missing signatures, the response fails to validate for some reason: missing
expired signatures, signatures with unsupported algorithms, data signatures, expired signatures, signatures with unsupported
missing that the relevant NSEC RR says should be present, and so algorithms, data missing that the relevant NSEC RR says
forth. should be present, and so forth.
Indeterminate: There is no trust anchor that would indicate that a Indeterminate: There is no trust anchor that would indicate that a
specific portion of the tree is secure. This is the default specific portion of the tree is secure. This is the default
operation mode. operation mode.
Section 4.3 of [RFC4035] says: Section 4.3 of [RFC4035] says:
A security-aware resolver must be able to distinguish between four A security-aware resolver must be able to distinguish between four
cases: cases:
Secure: An RRset for which the resolver is able to build a chain of
signed DNSKEY and DS RRs from a trusted security anchor to the
RRset. In this case, the RRset should be signed and is subject to
signature validation, as described above.
Insecure: An RRset for which the resolver knows that it has no chain
of signed DNSKEY and DS RRs from any trusted starting point to the
RRset. This can occur when the target RRset lies in an unsigned
zone or in a descendent of an unsigned zone. In this case, the
RRset may or may not be signed, but the resolver will not be able
to verify the signature.
Bogus: An RRset for which the resolver believes that it ought to be Secure: An RRset for which the resolver is able to build a chain
able to establish a chain of trust but for which it is unable to of signed DNSKEY and DS RRs from a trusted security anchor to
do so, either due to signatures that for some reason fail to the RRset. In this case, the RRset should be signed and is
validate or due to missing data that the relevant DNSSEC RRs subject to signature validation, as described above.
indicate should be present. This case may indicate an attack but
may also indicate a configuration error or some form of data
corruption.
Indeterminate: An RRset for which the resolver is not able to Insecure: An RRset for which the resolver knows that it has no
determine whether the RRset should be signed, as the resolver is chain of signed DNSKEY and DS RRs from any trusted starting
not able to obtain the necessary DNSSEC RRs. This can occur when point to the RRset. This can occur when the target RRset lies
the security-aware resolver is not able to contact security-aware in an unsigned zone or in a descendent [sic] of an unsigned
name servers for the relevant zones. zone. In this case, the RRset may or may not be signed, but
the resolver will not be able to verify the signature.
10. IANA Considerations Bogus: An RRset for which the resolver believes that it ought to
be able to establish a chain of trust but for which it is
unable to do so, either due to signatures that for some reason
fail to validate or due to missing data that the relevant
DNSSEC RRs indicate should be present. This case may indicate
an attack but may also indicate a configuration error or some
form of data corruption.
This document has no IANA actions. Indeterminate: An RRset for which the resolver is not able to
determine whether the RRset should be signed, as the resolver
is not able to obtain the necessary DNSSEC RRs. This can occur
when the security-aware resolver is not able to contact
security-aware name servers for the relevant zones.
11. Security Considerations 10. Security Considerations
These definitions do not change any security considerations for the These definitions do not change any security considerations for the
DNS. DNS.
12. Acknowledgements 11. References
The authors gratefully acknowledge all of the authors of DNS-related
RFCs that proceed this one. Comments from Tony Finch, Stephane
Bortzmeyer, Niall O'Reilly, Colm MacCarthaigh, Ray Bellis, John
Kristoff, Robert Edmonds, Paul Wouters, Shumon Huque, Paul Ebersman,
David Lawrence, Matthijs Mekking, Casey Deccio, Bob Harold, Ed Lewis,
John Klensin, David Black, and many others in the DNSOP Working Group
have helped shape this document.
13. References
13.1. Normative References 11.1. Normative References
[RFC0882] Mockapetris, P., "Domain names: Concepts and facilities", [RFC882] Mockapetris, P., "Domain names: Concepts and facilities",
RFC 882, DOI 10.17487/RFC0882, November 1983, RFC 882, DOI 10.17487/RFC0882, November 1983,
<http://www.rfc-editor.org/info/rfc882>. <http://www.rfc-editor.org/info/rfc882>.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<http://www.rfc-editor.org/info/rfc1034>. <http://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and [RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <http://www.rfc-editor.org/info/rfc1035>. November 1987, <http://www.rfc-editor.org/info/rfc1035>.
[RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts -
Application and Support", STD 3, RFC 1123, DOI 10.17487/ Application and Support", STD 3, RFC 1123,
RFC1123, October 1989, DOI 10.17487/RFC1123, October 1989,
<http://www.rfc-editor.org/info/rfc1123>. <http://www.rfc-editor.org/info/rfc1123>.
[RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone
Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996, Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996,
August 1996, <http://www.rfc-editor.org/info/rfc1996>. August 1996, <http://www.rfc-editor.org/info/rfc1996>.
[RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound, [RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)", "Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, DOI 10.17487/RFC2136, April 1997, RFC 2136, DOI 10.17487/RFC2136, April 1997,
<http://www.rfc-editor.org/info/rfc2136>. <http://www.rfc-editor.org/info/rfc2136>.
skipping to change at page 22, line 49 skipping to change at page 23, line 19
[RFC2182] Elz, R., Bush, R., Bradner, S., and M. Patton, "Selection [RFC2182] Elz, R., Bush, R., Bradner, S., and M. Patton, "Selection
and Operation of Secondary DNS Servers", BCP 16, RFC 2182, and Operation of Secondary DNS Servers", BCP 16, RFC 2182,
DOI 10.17487/RFC2182, July 1997, DOI 10.17487/RFC2182, July 1997,
<http://www.rfc-editor.org/info/rfc2182>. <http://www.rfc-editor.org/info/rfc2182>.
[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998, NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,
<http://www.rfc-editor.org/info/rfc2308>. <http://www.rfc-editor.org/info/rfc2308>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC Rose, "DNS Security Introduction and Requirements",
4033, DOI 10.17487/RFC4033, March 2005, RFC 4033, DOI 10.17487/RFC4033, March 2005,
<http://www.rfc-editor.org/info/rfc4033>. <http://www.rfc-editor.org/info/rfc4033>.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions", Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005, RFC 4034, DOI 10.17487/RFC4034, March 2005,
<http://www.rfc-editor.org/info/rfc4034>. <http://www.rfc-editor.org/info/rfc4034>.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005, Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
skipping to change at page 23, line 42 skipping to change at page 24, line 15
[RFC6561] Livingood, J., Mody, N., and M. O'Reirdan, [RFC6561] Livingood, J., Mody, N., and M. O'Reirdan,
"Recommendations for the Remediation of Bots in ISP "Recommendations for the Remediation of Bots in ISP
Networks", RFC 6561, DOI 10.17487/RFC6561, March 2012, Networks", RFC 6561, DOI 10.17487/RFC6561, March 2012,
<http://www.rfc-editor.org/info/rfc6561>. <http://www.rfc-editor.org/info/rfc6561>.
[RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the [RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the
DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012, DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012,
<http://www.rfc-editor.org/info/rfc6672>. <http://www.rfc-editor.org/info/rfc6672>.
[RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC
Operational Practices, Version 2", RFC 6781, DOI 10.17487/ Operational Practices, Version 2", RFC 6781,
RFC6781, December 2012, DOI 10.17487/RFC6781, December 2012,
<http://www.rfc-editor.org/info/rfc6781>. <http://www.rfc-editor.org/info/rfc6781>.
[RFC6840] Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and [RFC6840] Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and
Implementation Notes for DNS Security (DNSSEC)", RFC 6840, Implementation Notes for DNS Security (DNSSEC)", RFC 6840,
DOI 10.17487/RFC6840, February 2013, DOI 10.17487/RFC6840, February 2013,
<http://www.rfc-editor.org/info/rfc6840>. <http://www.rfc-editor.org/info/rfc6840>.
[RFC6841] Ljunggren, F., Eklund Lowinder, AM., and T. Okubo, "A [RFC6841] Ljunggren, F., Eklund Lowinder, AM., and T. Okubo, "A
Framework for DNSSEC Policies and DNSSEC Practice Framework for DNSSEC Policies and DNSSEC Practice
Statements", RFC 6841, DOI 10.17487/RFC6841, January 2013, Statements", RFC 6841, DOI 10.17487/RFC6841, January 2013,
<http://www.rfc-editor.org/info/rfc6841>. <http://www.rfc-editor.org/info/rfc6841>.
[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891, DOI 10.17487/ for DNS (EDNS(0))", STD 75, RFC 6891,
RFC6891, April 2013, DOI 10.17487/RFC6891, April 2013,
<http://www.rfc-editor.org/info/rfc6891>. <http://www.rfc-editor.org/info/rfc6891>.
[RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating [RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating
DNSSEC Delegation Trust Maintenance", RFC 7344, DOI DNSSEC Delegation Trust Maintenance", RFC 7344,
10.17487/RFC7344, September 2014, DOI 10.17487/RFC7344, September 2014,
<http://www.rfc-editor.org/info/rfc7344>. <http://www.rfc-editor.org/info/rfc7344>.
13.2. Informative References 11.2. Informative References
[DBOUND] "DBOUND Working Group", 2015, [DBOUND] IETF, "Domain Boundaries (dbound) Working Group", 2015,
<https://datatracker.ietf.org/wg/dbound/charter/>. <https://datatracker.ietf.org/wg/dbound/charter/>.
[RFC0819] Su, Z. and J. Postel, "Domain naming convention for [RFC819] Su, Z. and J. Postel, "The Domain Naming Convention for
Internet user applications", RFC 819, DOI 10.17487/ Internet User Applications", RFC 819,
RFC0819, August 1982, DOI 10.17487/RFC0819, August 1982,
<http://www.rfc-editor.org/info/rfc819>. <http://www.rfc-editor.org/info/rfc819>.
[RFC0952] Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet [RFC952] Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet
host table specification", RFC 952, DOI 10.17487/RFC0952, host table specification", RFC 952, DOI 10.17487/RFC0952,
October 1985, <http://www.rfc-editor.org/info/rfc952>. October 1985, <http://www.rfc-editor.org/info/rfc952>.
[RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995, [RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995,
DOI 10.17487/RFC1995, August 1996, DOI 10.17487/RFC1995, August 1996,
<http://www.rfc-editor.org/info/rfc1995>. <http://www.rfc-editor.org/info/rfc1995>.
[RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912, DOI [RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912,
10.17487/RFC3912, September 2004, DOI 10.17487/RFC3912, September 2004,
<http://www.rfc-editor.org/info/rfc3912>. <http://www.rfc-editor.org/info/rfc3912>.
[RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices", [RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices",
RFC 4641, DOI 10.17487/RFC4641, September 2006, RFC 4641, DOI 10.17487/RFC4641, September 2006,
<http://www.rfc-editor.org/info/rfc4641>. <http://www.rfc-editor.org/info/rfc4641>.
[RFC4697] Larson, M. and P. Barber, "Observed DNS Resolution [RFC4697] Larson, M. and P. Barber, "Observed DNS Resolution
Misbehavior", BCP 123, RFC 4697, DOI 10.17487/RFC4697, Misbehavior", BCP 123, RFC 4697, DOI 10.17487/RFC4697,
October 2006, <http://www.rfc-editor.org/info/rfc4697>. October 2006, <http://www.rfc-editor.org/info/rfc4697>.
[RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast
Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786, Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786,
December 2006, <http://www.rfc-editor.org/info/rfc4786>. December 2006, <http://www.rfc-editor.org/info/rfc4786>.
[RFC4956] Arends, R., Kosters, M., and D. Blacka, "DNS Security [RFC4956] Arends, R., Kosters, M., and D. Blacka, "DNS Security
(DNSSEC) Opt-In", RFC 4956, DOI 10.17487/RFC4956, July (DNSSEC) Opt-In", RFC 4956, DOI 10.17487/RFC4956, July
2007, <http://www.rfc-editor.org/info/rfc4956>. 2007, <http://www.rfc-editor.org/info/rfc4956>.
[RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines", BCP [RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines",
152, RFC 5625, DOI 10.17487/RFC5625, August 2009, BCP 152, RFC 5625, DOI 10.17487/RFC5625, August 2009,
<http://www.rfc-editor.org/info/rfc5625>. <http://www.rfc-editor.org/info/rfc5625>.
[RFC5890] Klensin, J., "Internationalized Domain Names for [RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework", Applications (IDNA): Definitions and Document Framework",
RFC 5890, DOI 10.17487/RFC5890, August 2010, RFC 5890, DOI 10.17487/RFC5890, August 2010,
<http://www.rfc-editor.org/info/rfc5890>. <http://www.rfc-editor.org/info/rfc5890>.
[RFC5891] Klensin, J., "Internationalized Domain Names in [RFC5891] Klensin, J., "Internationalized Domain Names in
Applications (IDNA): Protocol", RFC 5891, DOI 10.17487/ Applications (IDNA): Protocol", RFC 5891,
RFC5891, August 2010, DOI 10.17487/RFC5891, August 2010,
<http://www.rfc-editor.org/info/rfc5891>. <http://www.rfc-editor.org/info/rfc5891>.
[RFC5892] Faltstrom, P., Ed., "The Unicode Code Points and [RFC5892] Faltstrom, P., Ed., "The Unicode Code Points and
Internationalized Domain Names for Applications (IDNA)", Internationalized Domain Names for Applications (IDNA)",
RFC 5892, DOI 10.17487/RFC5892, August 2010, RFC 5892, DOI 10.17487/RFC5892, August 2010,
<http://www.rfc-editor.org/info/rfc5892>. <http://www.rfc-editor.org/info/rfc5892>.
[RFC5893] Alvestrand, H., Ed. and C. Karp, "Right-to-Left Scripts [RFC5893] Alvestrand, H., Ed. and C. Karp, "Right-to-Left Scripts
for Internationalized Domain Names for Applications for Internationalized Domain Names for Applications
(IDNA)", RFC 5893, DOI 10.17487/RFC5893, August 2010, (IDNA)", RFC 5893, DOI 10.17487/RFC5893, August 2010,
skipping to change at page 25, line 48 skipping to change at page 26, line 20
[RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on [RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on
Encodings for Internationalized Domain Names", RFC 6055, Encodings for Internationalized Domain Names", RFC 6055,
DOI 10.17487/RFC6055, February 2011, DOI 10.17487/RFC6055, February 2011,
<http://www.rfc-editor.org/info/rfc6055>. <http://www.rfc-editor.org/info/rfc6055>.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011, DOI 10.17487/RFC6265, April 2011,
<http://www.rfc-editor.org/info/rfc6265>. <http://www.rfc-editor.org/info/rfc6265>.
[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in [RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
Internationalization in the IETF", BCP 166, RFC 6365, DOI Internationalization in the IETF", BCP 166, RFC 6365,
10.17487/RFC6365, September 2011, DOI 10.17487/RFC6365, September 2011,
<http://www.rfc-editor.org/info/rfc6365>. <http://www.rfc-editor.org/info/rfc6365>.
[RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of [RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of
Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129, Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129,
February 2014, <http://www.rfc-editor.org/info/rfc7129>. February 2014, <http://www.rfc-editor.org/info/rfc7129>.
[RFC7480] Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the [RFC7480] Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the
Registration Data Access Protocol (RDAP)", RFC 7480, DOI Registration Data Access Protocol (RDAP)", RFC 7480,
10.17487/RFC7480, March 2015, DOI 10.17487/RFC7480, March 2015,
<http://www.rfc-editor.org/info/rfc7480>. <http://www.rfc-editor.org/info/rfc7480>.
[RFC7481] Hollenbeck, S. and N. Kong, "Security Services for the [RFC7481] Hollenbeck, S. and N. Kong, "Security Services for the
Registration Data Access Protocol (RDAP)", RFC 7481, DOI Registration Data Access Protocol (RDAP)", RFC 7481,
10.17487/RFC7481, March 2015, DOI 10.17487/RFC7481, March 2015,
<http://www.rfc-editor.org/info/rfc7481>. <http://www.rfc-editor.org/info/rfc7481>.
[RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access [RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access
Protocol (RDAP) Query Format", RFC 7482, DOI 10.17487/ Protocol (RDAP) Query Format", RFC 7482,
RFC7482, March 2015, DOI 10.17487/RFC7482, March 2015,
<http://www.rfc-editor.org/info/rfc7482>. <http://www.rfc-editor.org/info/rfc7482>.
[RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the [RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the
Registration Data Access Protocol (RDAP)", RFC 7483, DOI Registration Data Access Protocol (RDAP)", RFC 7483,
10.17487/RFC7483, March 2015, DOI 10.17487/RFC7483, March 2015,
<http://www.rfc-editor.org/info/rfc7483>. <http://www.rfc-editor.org/info/rfc7483>.
[RFC7484] Blanchet, M., "Finding the Authoritative Registration Data [RFC7484] Blanchet, M., "Finding the Authoritative Registration Data
(RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March (RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March
2015, <http://www.rfc-editor.org/info/rfc7484>. 2015, <http://www.rfc-editor.org/info/rfc7484>.
[RFC7485] Zhou, L., Kong, N., Shen, S., Sheng, S., and A. Servin, [RFC7485] Zhou, L., Kong, N., Shen, S., Sheng, S., and A. Servin,
"Inventory and Analysis of WHOIS Registration Objects", "Inventory and Analysis of WHOIS Registration Objects",
RFC 7485, DOI 10.17487/RFC7485, March 2015, RFC 7485, DOI 10.17487/RFC7485, March 2015,
<http://www.rfc-editor.org/info/rfc7485>. <http://www.rfc-editor.org/info/rfc7485>.
Acknowledgements
The authors gratefully acknowledge all of the authors of DNS-related
RFCs that proceed this one. Comments from Tony Finch, Stephane
Bortzmeyer, Niall O'Reilly, Colm MacCarthaigh, Ray Bellis, John
Kristoff, Robert Edmonds, Paul Wouters, Shumon Huque, Paul Ebersman,
David Lawrence, Matthijs Mekking, Casey Deccio, Bob Harold, Ed Lewis,
John Klensin, David Black, and many others in the DNSOP Working Group
have helped shape this document.
Authors' Addresses Authors' Addresses
Paul Hoffman Paul Hoffman
ICANN ICANN
Email: paul.hoffman@icann.org Email: paul.hoffman@icann.org
Andrew Sullivan Andrew Sullivan
Dyn Dyn
150 Dow St, Tower 2 150 Dow Street, Tower 2
Manchester, NH 1604 Manchester, NH 03101
USA United States
Email: asullivan@dyn.com Email: asullivan@dyn.com
Kazunori Fujiwara Kazunori Fujiwara
Japan Registry Services Co., Ltd. Japan Registry Services Co., Ltd.
Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda
Chiyoda-ku, Tokyo 101-0065 Chiyoda-ku, Tokyo 101-0065
Japan Japan
Phone: +81 3 5215 8451 Phone: +81 3 5215 8451
Email: fujiwara@jprs.co.jp Email: fujiwara@jprs.co.jp
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