Independent Submission                                        J. Klensin
Request for Comments: 8324                                 February 2018
Category: Informational
ISSN: 2070-1721
Independent Submission                                        J. Klensin
Request for Comments: 8324                                 February 2018
Category: Informational
ISSN: 2070-1721

DNS Privacy, Authorization, Special Uses, Encoding, Characters, Matching, and Root Structure: Time for Another Look?




The basic design of the Domain Name System was completed almost 30 years ago. The last half of that period has been characterized by significant changes in requirements and expectations, some of which either require changes to how the DNS is used or can be accommodated only poorly or not at all. This document asks the question of whether it is time to either redesign and replace the DNS to match contemporary requirements and expectations (rather than continuing to try to design and implement incremental patches that are not fully satisfactory) or draw some clear lines about functionality that is not really needed or that should be performed in some other way.


Status of This Memo


This document is not an Internet Standards Track specification; it is published for informational purposes.


This is a contribution to the RFC Series, independently of any other RFC stream. The RFC Editor has chosen to publish this document at its discretion and makes no statement about its value for implementation or deployment. Documents approved for publication by the RFC Editor are not candidates for any level of Internet Standard; see Section 2 of RFC 7841.

这是对RFC系列的贡献,独立于任何其他RFC流。RFC编辑器已选择自行发布此文档,并且未声明其对实现或部署的价值。RFC编辑批准发布的文件不适用于任何级别的互联网标准;见RFC 7841第2节。

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at


Copyright Notice


Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved.

版权所有(c)2018 IETF信托基金和确定为文件作者的人员。版权所有。

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents ( in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document.

本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(自本文件出版之日起生效。请仔细阅读这些文件,因为它们描述了您对本文件的权利和限制。

Table of Contents


   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Background and Hypothesis . . . . . . . . . . . . . . . . . .   5
   3.  Warts and Tensions with the Current DNS . . . . . . . . . . .   6
     3.1.  Multi-type Queries  . . . . . . . . . . . . . . . . . . .   6
     3.2.  Matching Part I: Case Sensitivity in Labels and Other
           Anomalies . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Matching Part II: Non-ASCII ("Internationalized") Domain
           Name Labels . . . . . . . . . . . . . . . . . . . . . . .   7
     3.4.  Matching Part III: Label Synonyms, Equivalent Names, and
           Variants  . . . . . . . . . . . . . . . . . . . . . . . .   8
     3.5.  Query Privacy . . . . . . . . . . . . . . . . . . . . . .  10
     3.6.  Alternate Namespaces for Public Use in the DNS Framework:
           The CLASS Problem . . . . . . . . . . . . . . . . . . . .  10
     3.7.  Loose Synchronization . . . . . . . . . . . . . . . . . .  10
     3.8.  Private Namespaces and Special Names  . . . . . . . . . .  11
     3.9.  Alternate Query or Response Encodings . . . . . . . . . .  12
     3.10. Distribution and Management of Root Servers . . . . . . .  12
     3.11. Identifiers versus Brands and Other Convenience Names . .  13
     3.12. A Single Hierarchy with a Centrally Controlled Root . . .  14
     3.13. Newer Application Protocols, New Requirements, and DNS
           Evolution . . . . . . . . . . . . . . . . . . . . . . . .  14
       3.13.1.  The Extensions . . . . . . . . . . . . . . . . . . .  15
       3.13.2.  Extensions and Deployment Pressures -- The TXT
                RRTYPE . . . . . . . . . . . . . . . . . . . . . . .  15
       3.13.3.  Periods and Zone Cut Issues  . . . . . . . . . . . .  16
     3.14. Scaling of Reputation and Other Ancillary Information . .  17
     3.15. Tensions among Transport, Scaling, and Content  . . . . .  18
   4.  The Inverse Lookup Requirement  . . . . . . . . . . . . . . .  19
   5.  Internet Scale, Function Support, and Incremental Deployment   20
   6.  Searching and the DNS -- An Historical Note . . . . . . . . .  20
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  21
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  22
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  22
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  22
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  29
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  29
   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Background and Hypothesis . . . . . . . . . . . . . . . . . .   5
   3.  Warts and Tensions with the Current DNS . . . . . . . . . . .   6
     3.1.  Multi-type Queries  . . . . . . . . . . . . . . . . . . .   6
     3.2.  Matching Part I: Case Sensitivity in Labels and Other
           Anomalies . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Matching Part II: Non-ASCII ("Internationalized") Domain
           Name Labels . . . . . . . . . . . . . . . . . . . . . . .   7
     3.4.  Matching Part III: Label Synonyms, Equivalent Names, and
           Variants  . . . . . . . . . . . . . . . . . . . . . . . .   8
     3.5.  Query Privacy . . . . . . . . . . . . . . . . . . . . . .  10
     3.6.  Alternate Namespaces for Public Use in the DNS Framework:
           The CLASS Problem . . . . . . . . . . . . . . . . . . . .  10
     3.7.  Loose Synchronization . . . . . . . . . . . . . . . . . .  10
     3.8.  Private Namespaces and Special Names  . . . . . . . . . .  11
     3.9.  Alternate Query or Response Encodings . . . . . . . . . .  12
     3.10. Distribution and Management of Root Servers . . . . . . .  12
     3.11. Identifiers versus Brands and Other Convenience Names . .  13
     3.12. A Single Hierarchy with a Centrally Controlled Root . . .  14
     3.13. Newer Application Protocols, New Requirements, and DNS
           Evolution . . . . . . . . . . . . . . . . . . . . . . . .  14
       3.13.1.  The Extensions . . . . . . . . . . . . . . . . . . .  15
       3.13.2.  Extensions and Deployment Pressures -- The TXT
                RRTYPE . . . . . . . . . . . . . . . . . . . . . . .  15
       3.13.3.  Periods and Zone Cut Issues  . . . . . . . . . . . .  16
     3.14. Scaling of Reputation and Other Ancillary Information . .  17
     3.15. Tensions among Transport, Scaling, and Content  . . . . .  18
   4.  The Inverse Lookup Requirement  . . . . . . . . . . . . . . .  19
   5.  Internet Scale, Function Support, and Incremental Deployment   20
   6.  Searching and the DNS -- An Historical Note . . . . . . . . .  20
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  21
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  22
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  22
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  22
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  29
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  29
1. Introduction
1. 介绍

This document explores contemporary expectations of the Internet's domain system (DNS) and compares them to the assumptions and properties of the DNS design, including both those documented in the RFC Series, an important early paper by the principal author of the original RFCs [Mockapetris-1988], and a certain amount of oral tradition. It is primarily intended to ask the question of whether the differences are causing enough stresses on the system, stresses that cannot be resolved satisfactorily by further patching, that the Internet community should be considering designing a new system, one that is better adapted to current needs and expectations, and developing a deployment and transition strategy for it. For those (perhaps the majority of us) for whom actually replacing the DNS is too radical to be realistic, the document may be useful in two other ways. It may provide a foundation for discussing what functions the DNS should not be expected to support and how those functions can be supported in other ways, perhaps via an intermediate system that then calls on the DNS or by using some other type of database technology for some set of functions while leaving the basic DNS functions intact. Or it may provide a basis for "better just get used to that and the way it works" discussions to replace fantasies about what the DNS might do in some alternate reality.


There is a key design or philosophical question associated with the analysis in this document that the document does not address. It is whether changes to perceived requirements to DNS functionality as described here are, in most respects, evolutionary or whether many of them are instances of trying to utilize the DNS for new requirements because it exists and is already deployed independent of whether the DNS is really appropriate or not. The latter might be an instance of a problem often described in the IETF as "when all you have is a hammer, everything looks like a nail".


Other recent work, including a short article by Vint Cerf [Cerf2017], has discussed an overlapping set of considerations from a different perspective, reinforcing the view that it may be time to ask fundamental questions about the evolution and future of the DNS.

其他最近的工作,包括Vint Cerf[Cerf2017]的一篇短文,从不同的角度讨论了一组重叠的考虑因素,强化了这样一种观点,即现在可能是时候提出有关DNS的演变和未来的基本问题了。

While this document does not assume deep technical or operational knowledge of the DNS, it does assume some knowledge and at least general familiarity with the concepts of RFC 1034 [RFC1034] and RFC 1035 [RFC1035] and the terminology discussed in RFC 7719 [RFC7719] and elsewhere. Although some of the comments it contains might be taken as hints or examples of different ways to think about the design issues, it makes no attempt to explore, much less offer a tutorial on, alternate naming systems or database technologies.

虽然本文件并未假定对DNS有深入的技术或操作知识,但它假定对RFC 1034[RFC1034]和RFC 1035[RFC1035]的概念以及RFC 7719[RFC7719]和其他地方讨论的术语有一定的了解,至少一般熟悉。虽然它包含的一些注释可能被视为思考设计问题的不同方式的提示或示例,但它没有尝试探索,更不用说提供关于替代命名系统或数据库技术的教程。

It is perhaps worth noting that, while the perspective is different and more than a dozen years have passed, many of the issues discussed in this document were analyzed and described (most of them with more extensive explanations) in a 2005 US National Research Council report [NRC-Signposts].


Readers should note that several references are to obsolete documents. That was done because they are intended to show the documents and dates that introduced particular features or concepts. When current versions are intended, they are referenced.


2. Background and Hypothesis
2. 背景与假设

The Domain Name System (DNS) [RFC1034] was designed starting in the early 1980s [RFC0799] [RFC0881] [RFC0882] [RFC0883] with the main goal of replacing the flat, centrally administered, host table system [RFC0810] [RFC0952] [RFC0953] with a hierarchical, administratively distributed, system. The DNS design included some features that, after initial implementation and deployment, were judged to be unworkable and either replaced (e.g., the mail destination (MD) and mail forwarder (MF) approach [RFC0882] that were replaced by the MX approach [RFC0974]), abandoned (e.g., the mechanism for using email local parts as labels described in RFC 1034, Section 3.3), or deprecated (e.g., the WKS RR TYPE [RFC1123]). Newer ideas and requirements have identified a number of other features, some of which were less developed than others. Of course the original designers could not anticipate everything that has come to be expected of the DNS in the last 30 years.

域名系统(DNS)[RFC1034]是从20世纪80年代初开始设计的[RFC0799][RFC0881][RFC0882][RFC0883],其主要目标是将扁平的、集中管理的主机表系统[RFC0810][RFC0952][RFC0953]替换为分层的、管理分布式的系统。DNS设计包括一些功能,在初始实施和部署后,这些功能被判定为不可行,或者被替换(例如,被MX方法[RFC0974]替换的邮件目的地(MD)和邮件转发器(MF)方法[RFC0882]),或者被放弃(例如,RFC 1034第3.3节中描述的将电子邮件本地部分用作标签的机制)或已弃用(例如,WKS RR类型[RFC1123])。更新的想法和要求确定了许多其他功能,其中一些功能的开发程度低于其他功能。当然,最初的设计师无法预测过去30年中DNS的所有预期功能。

In recent years, demand for new and extended services and uses of the DNS have, in turn, led to proposals for DNS extensions or changes of various sorts. Some have been adopted, including a model for negotiating extended functionality [RFC2671] (commonly known as EDNS(0)) and to support IPv6 [RFC3596], others were found to be impracticable, and still others continue to be under consideration. Some examples of the latter two categories are discussed below. A few features of the original DNS specification, such as the CLASS property and label types, have also been suggested to be so badly specified that they should be deprecated [Sullivan-Class].

近年来,对新的和扩展的服务以及DNS的使用的需求反过来导致了对DNS扩展或各种更改的建议。一些已经被采用,包括协商扩展功能[RFC2671](通常称为EDN(0))的模型和支持IPv6的模型[RFC3596],其他模型被认为是不可行的,还有一些仍在考虑之中。下文将讨论后两类的一些例子。原始DNS规范的一些功能,如类属性和标签类型,也被认为是指定得非常糟糕,应该弃用[Sullivan CLASS]。

Unlike earlier changes such as the Internationalized Domain Names for Applications (IDNA) mechanisms for better incorporating non-ASCII labels without modifying the DNS structure itself [RFC3490] [RFC5890], some recent proposals require or strongly suggest changes to APIs, formats, or interfaces by programs that need to retrieve information from the DNS or interpret that information. Differences between the DNS architecture and the requirements that imply those proposals suggest that it may be time to stop patching the DNS or


trying to extend it in small increments. Instead, we should be considering moving some current or proposed functionality elsewhere or developing a new system that better meets today's needs and a transition strategy to it.


The next section of this document discusses a number of issues with the current DNS design that could appropriately be addressed by a different and newer design model. In at least some cases, changing the model and protocols could bring significant benefits to the Internet and/or its administration.


This document is not a proposal for a new protocol. It is intended to stimulate thought about how far we want to try to push the existing DNS, to examine whether expectations of it are already exceeding its plausible capabilities, and to start discussion of a redesign or alternatives to one if the time for that decision has come.


3. Warts and Tensions with the Current DNS
3. 与当前DNS的缺点和紧张关系

As suggested above, there are many signs that the DNS is incapable of meeting contemporary expectations of how it should work and functionality it should support. Some of those expectations are unrealistic under any imaginable circumstances; others are impossible (or merely problematic) in the current DNS structure but could be accommodated in a redesign. These are examples, rather than a comprehensive list, and do not appear in any particular order.


3.1. Multi-type Queries
3.1. 多类型查询

The DNS does not gracefully support multi-type queries. The current case where this problem rears its head involves attempts at solutions that return both TYPE A (IPv4) and type AAA (IPv6) addresses collectively. The problem was originally seen with "QTYPE=MAILA" [RFC0882] for the original MA and MD RRTYPEs, an experience that strongly suggests that some very careful thinking about cache effects (and possibly additional DNS changes) would be needed. Other solutions might seem equally or more plausible. What they, including "two types of addresses", probably have in common is that they illustrate stresses on the system and that changing the DNS to deal with those stresses is not straightforward or likely to be problem-free.

DNS不支持多类型查询。当前出现此问题的案例涉及尝试同时返回A型(IPv4)和AAA型(IPv6)地址的解决方案。问题最初出现在原始MA和MD RRTYPE的“QTYPE=MAILA”[RFC0882]上,这一经验强烈表明,需要非常仔细地考虑缓存效应(以及可能的附加DNS更改)。其他解决方案似乎同样或更合理。它们(包括“两种类型的地址”)的共同点可能是,它们说明了系统上的压力,并且更改DNS以处理这些压力并不简单,也不可能没有问题。

3.2. Matching Part I: Case Sensitivity in Labels and Other Anomalies
3.2. 匹配第一部分:标签和其他异常中的区分大小写

The DNS specifications assume that labels are octet strings and octets with the high bit zero have seven-bit ASCII codes in the remaining bits. They require that, when a domain name used in a query is matched to one stored in the database, those ASCII characters be interpreted in a case-independent way, i.e., upper- and lower-case letters are treated as equivalent (digits and symbols are not affected) [RFC4343]. For non-ASCII octets, i.e., octets in labels with the first bit turned on, there are no assumptions about the character coding used, much less any rules about character case equivalence -- strings must be compared by matching bits in sequence. Even though the current model for handling non-ASCII (i.e., "internationalized") domain name labels (IDNs) [RFC5890] (see Section 3.3 below) encodes information so the DNS is not directly affected, the notion that some characters in labels are handled in a case-insensitive way and that others are case sensitive (or that upper case must be prohibited entirely as IDNA does) has caused a good deal of confusion and resentment. Those concerns and complaints about inconsistent behavior and mishandling (or suboptimal handling) of case relationships for some languages have not been mitigated by repeated explanations that the relationships between "decorated" lower-case characters and their upper-case equivalents are often sensitive to language and locality and therefore not deterministic with information available to DNS servers.


3.3. Matching Part II: Non-ASCII ("Internationalized") Domain Name Labels

3.3. 匹配第二部分:非ASCII(“国际化”)域名标签

Quite independent of the case-sensitivity problem, one of the fundamental properties of Unicode [Unicode] is that some abstract characters can be represented in multiple ways, such as by a single, precomposed, code point or by a base code point followed by one or more code points that specify combining characters. While Unicode Normalization can be used to eliminate many (but not all) of those distinctions for comparison (matching) purposes, it is best applied during matching rather than by changing one string into another. The first version of IDNA ("IDNA2003") made the choice to change strings during processing for either storage or retrieval [RFC3490] [RFC3491]; the second ("IDNA2008") required that all strings be normalized and that upper-case characters are not allowed at all [RFC5891]. Neither is optimal, if only because, independent of where they are changed if they are changed at all, transforming the strings themselves implies that the input string in an application may not be the same as the string used in processing and perhaps later display.


It would almost certainly be preferable, and more consistent with Unicode recommendations, to use normalization (and perhaps other techniques if they are appropriate) at matching time rather than altering the strings at all, even if there were still only a single matching algorithm, i.e., normalization were added to the existing ASCII-only case folding. However, even Unicode's discussion of normalization [Unicode-UAX15] indicates that there are special, language-dependent, cases (the most commonly cited example is the dotless "i" (U+0131)). Not only does the DNS lack any information about languages that could be used in a mapping algorithm, but, as long as there is a requirement that there be only one mapping algorithm for the entire system, that information could not be used even if it were available. One could imagine a successor system that would use information stored at nodes in the hierarchy to specify different matching rules for subsidiary nodes (or equivalent arrangements for non-hierarchical systems). It is not clear whether that would be a good idea, but it certainly is not possible with the DNS as we know it.


3.4. Matching Part III: Label Synonyms, Equivalent Names, and Variants
3.4. 匹配第三部分:标签同义词、等效名称和变体

As the initial phases of work on IDNs started to conclude, it became obvious that the nature and evolution of human language and writing systems required treating some names as "the same as" others. The first important example of this involved the relatively recent effort to simplify the Chinese writing system, thereby creating a distinction between "Simplified" and "Traditional" Chinese even though the meaning of the characters remained the same in almost all cases (in so-called ideographic character sets, characters have meaning rather than exclusively representing sounds). A joint effort among the relevant Country Code Top-Level Domain (ccTLD) registries and some other interested parties produced a set of recommendations for dealing with the issues with that script [RFC3743] and introduced the concept of "variant" characters and domain names.


However, when names are seen as having meanings, rather than merely being mnemonics, especially when they represent brands or the equivalent, or when spelling for a particular written language is not completely standardized, demands to treat different strings as exact equivalents are obvious and inevitable. As a trivial English-language example, it is widely understood that "colour" and "color" represent the same word, so does that imply that, if they are used as DNS labels in domain names all of whose other labels are identical, the two domain names should be treated as identical? Examples for other languages or writing systems, especially ones in which some or all markings that distinguish characters or words by sound or tone or that change the pronunciation of words are optional, are often more numerous and more problematic than national spelling differences in


English, but they are harder to explain to those unfamiliar with those other languages or writing systems (and hard to illustrate in ASCII-only Internet-Drafts and RFCs). Although approximations are possible, the DNS cannot handle that requirement: not only do its aliasing mechanisms (CNAME, DNAME, and various proposals for newer and different types of aliasing [DNS-Aliases] [DNS-BNAME]) not provide a strong enough binding, but the ability to use those aliases from a subtree controlled by one administrative entity to that of another one implies that there is little or no possibility of the owner (in either the DNS sense or the registrar-registrant one) of a particular name to control the synonyms for it. Some of that issue can be dealt with at the application level, e.g., by redirects in web protocols, but taking that approach, which is the essential characteristic of "if both names belong to the same owner, everything is OK" approaches, results in names being handled in inconsistent ways in different protocols.


A different way of looking at part of this issue (and, to some degree, of the one discussed above in Section 3.3) is that these perceived equivalences and desired transformations are context-dependent, but the DNS resolution process is not [RFC6912].


Similar problems arise as people notice that some characters are easily mistaken for others and that might be an opportunity for user confusion and attacks. Commonly cited examples include the Latin and Cyrillic script "a" characters, which are identical [CACM-Homograph], the characters in many scripts that look like open circles or vertical or horizontal lines, and even the Latin script letter "l" and the European digit "1", but examples abound in other scripts and combinations of scripts as well. The most common proposed solution within the DNS context has been to treat these cases, as well as those involving orthographic variations, as "variants" (but variants different from the system for Chinese characters mentioned above) and either ban all but one (or a few) of the possible labels from the DNS (possibly on a first come, first served basis) or ensure that any collection of such strings that are delegated as assigned to the same ownership (see above). Neither solution is completely satisfactory: if all but one string is excluded, users who guess at a different form, perhaps in trying to transcribe characters from written or printed form, don't find what they are looking for and, as pointed out above, "same ownership" is sufficient only with carefully designed and administered applications protocol support, and sometimes not then.


Some of these issues are discussed at more length in an ICANN report [ICANN-VIP].


3.5. Query Privacy
3.5. 查询隐私

There has been growing concern in recent years that DNS queries occur in cleartext on the public Internet and that, if those queries can be intercepted, they can expose a good deal of information about interests and contacts that could compromise individual privacy. While a number of proposals, including query name minimization [RFC7816] and running DNS over an encrypted tunnel [RFC7858], have been made to mitigate that problem, they all appear to share the common properties of security patches rather than designed-in security or privacy mechanisms. While experience may prove otherwise once (and if) they are widely deployed, it does not appear that any of them are as satisfactory as a system with query privacy designed in might be. More general tutorials on this issue have appeared recently [Huston2017a].


3.6. Alternate Namespaces for Public Use in the DNS Framework: The CLASS Problem

3.6. DNS框架中公共使用的备用名称空间:类问题

The DNS standards include specification of a CLASS value, which "identifies a protocol family or instance of a protocol" (RFC 1034, Section 3.6, and elsewhere). While CLASS was used effectively in the early days of the DNS to manage different protocol families within the same administrative environment, recent attempts to use it to either partition the DNS namespace in other ways such as for non-ASCII names (partially to address the issues in Sections 3.2 and 3.3) or use DNS mechanisms for entirely different namespaces have exposed fundamental problems with the mechanism [Sullivan-Class]. Perhaps the most fundamental of those problems is disagreement about whether multiple CLASSes were intended to exist within a given zone (with records within RRSETs) or whether different CLASSes implied different zones. Different implementations make different assumptions [Faltstrom-2004] [Vixie-20170704]. These problems have led to recommendations that it be dropped entirely [Sullivan-Class], but discussions on the IETF list and in WGs in mid-2017 made it clear that there is no clear consensus on that matter.

DNS标准包括类值的规范,该类值“标识协议系列或协议实例”(RFC 1034,第3.6节和其他地方)。虽然在DNS早期,类被有效地用于在同一管理环境中管理不同的协议系列,但最近尝试使用它以其他方式(如非ASCII名称)对DNS命名空间进行分区(部分是为了解决第3.2节和第3.3节中的问题)或者对完全不同的名称空间使用DNS机制暴露了该机制的基本问题[Sullivan Class]。也许这些问题中最基本的是关于多个类是否打算存在于给定区域内(记录在RRSET内)或不同类是否意味着不同区域的分歧。不同的实施会做出不同的假设[Faltstrom-2004][Vixie-20170704]。这些问题导致建议完全取消[沙利文级],但2017年年中关于IETF列表和WGs的讨论表明,在这一问题上没有明确的共识。

3.7. Loose Synchronization
3.7. 松散同步

The DNS model of master and slave servers, with the latter initiating updates based on expiration interval values, and local caches with updates based on TTL values, depends heavily on an approach that has come to be called "loose synchronization", i.e., that there can be no expectation that all of the servers that might reasonably answer a query will have exactly the same data unless those data have been unchanged for a rather long period. Put differently, if some or all of the records associated with a particular node in the DNS


(informally, a fully qualified domain name (FQDN)) change, one cannot expect those changes to be propagated immediately.


That model has worked rather well since the DNS was first deployed, protecting the system from requirements for mechanisms that are typical where a simultaneous update of multiple systems is needed. Such mechanisms include elaborate locking, complex update procedures and handshaking, or journaling. As has often been pointed out with the Internet, implementation and operational complexity are often the enemy of stability, security, and robustness. Loose synchronization has helped keep the DNS as simple and robust as possible.


A number of recent ideas about using the DNS to store data for which important changes occur very rapidly are, however, largely incompatible with loose synchronization. Efforts to use very short (or zero) refresh times (in SOA records for slave updates from masters) and TTLs (for caches) to simulate nearly simultaneous updating may work up to a point but appear to impose very heavy loads on servers and distribution mechanisms that were not designed to accommodate that style of working. Similar observations can be made about attempts to use the NOTIFY extension [RFC1996] or dynamic, "server-push", updating rather than the traditional DNS mechanisms. While the NOTIFY and push mechanisms normally provide refresh times and update mechanisms faster than those specified in RFCs 1034 and 1035, they imply that a "master" server must know the identities of (and have good connectivity to all of) its slaves. That defeats at least some of the advantages associated with stealth slaves, particularly those associated with reduction of query traffic across the Internet. Those mechanisms do nothing for cache updates: unless servers keep track of the source of every query for names associated with a specific zone and then somehow notify the query source systems, the only alternative to having information that might be obsolete stored in caches is to use very short or zero TTLs so the cached data time out almost immediately after being stored (or are not stored at all), requiring a new query to an authoritative server each time a resolver attempts to look up a name.

然而,最近关于使用DNS来存储数据的一些想法在很大程度上与松散同步不兼容,因为这些数据的重要更改会非常迅速地发生。使用非常短(或零)的刷新时间(在主服务器的从属更新的SOA记录中)和TTL(用于缓存)来模拟几乎同时更新的努力可能会在一定程度上起作用,但似乎会对服务器和分发机制施加非常重的负载,而这些服务器和分发机制的设计并不能适应这种工作方式。对于尝试使用NOTIFY扩展[RFC1996]或动态“服务器推送”更新而不是传统的DNS机制,也可以进行类似的观察。虽然通知和推送机制通常提供的刷新时间和更新机制比RFCs 1034和1035中指定的要快,但它们意味着“主”服务器必须知道其从属服务器的身份(并与所有从属服务器具有良好的连接)。这至少挫败了隐形奴隶的一些优势,特别是那些与减少互联网上的查询流量相关的优势。这些机制对缓存更新没有任何作用:除非服务器跟踪与特定区域关联的名称的每个查询的源,然后以某种方式通知查询源系统,将可能过时的信息存储在缓存中的唯一替代方法是使用非常短或零的TTL,这样缓存的数据在存储(或根本不存储)后几乎立即超时,每次解析程序尝试查找名称时都需要向权威服务器进行新的查询。

3.8. Private Namespaces and Special Names
3.8. 私有名称空间和特殊名称

Almost since the DNS was first deployed, there have been situations in which it is desirable to use DNS-like names, and often DNS resolution mechanisms or modifications of them, with namespaces for which globally available and consistent resolution using the public DNS is either unfeasible or undesirable (and for which the use of CLASS is not an appropriate mechanism). The need to isolate names and addresses on LANs from the public Internet, typically via "split horizon" approaches, is one example of this requirement although often not recognized as such. Another example that has generated a


good deal of controversy involves "special names" -- labels or pseudo-labels, often in TLD positions, that signal that the full name should not be subject to normal DNS resolution or other processing [RFC6761] [RFC8244].


Independent of troublesome policy questions about who should allocate such names and the procedures to be used, they almost inherently require either a syntax convention to identify them (there actually was such a convention, but it was abandoned many years ago and there is no plausible way to reinstitute it) or tables of such names that are known to, and kept updated on, every resolver on the Internet, at least if spurious queries to the root servers are to be avoided.


If the DNS were to be redesigned and replaced, we could recognize this requirement as part of the design and handle it much better than it is possible to handle it today.


3.9. Alternate Query or Response Encodings
3.9. 替代查询或响应编码

The DNS specifies formats for queries and data responses, based on the state of the art and best practices at the time it was designed. Recent work has suggested that there would be significant advantages to supporting at least a description of the DNS messages in one or more alternate formats, such as JSON [Hoffman-DNS-JSON] [Hoffman-SimpleDNS-JSON]. While that work has been carefully done to avoid requiring changes to the DNS, much of the argument for having such a JSON-based description format could easily be turned into an argument that, if the DNS were being revised, that format might be preferable as a more direct alternative to having DNS queries and responses in the original form.

DNS根据设计时的最新技术和最佳实践,指定查询和数据响应的格式。最近的工作表明,至少以一种或多种替代格式支持DNS消息的描述,例如JSON[Hoffman DNS JSON][Hoffman SimpleDNS JSON],将具有显著的优势。虽然这项工作已经仔细完成,以避免需要更改DNS,但使用这种基于JSON的描述格式的许多论点可以很容易地转化为一个论点,即如果DNS正在修改,那么这种格式可能会比使用原始形式的DNS查询和响应更直接。

3.10. Distribution and Management of Root Servers
3.10. 根服务器的分发和管理

The DNS model requires a collection of root servers that hold, at minimum, information about top-level domains. Over the years, that requirement has evolved from a technically fairly minor function, normally carried out as a service to the broader Internet community and its users and systems, to a subject that is intensely controversial with regard to control of those servers, including how they should be distributed and where they should be located. While a number of mechanisms, most recently including making the information more local [RFC7706], have been proposed and one (anycast [RFC7094]) is in very active use to mitigate some of the real and perceived problems, it seems obvious that a DNS successor, designed for today's global Internet and perceived requirements, could handle these problems in a technically more appropriate and less controversial way. Some additional discussion of the issues involved appears in a recent paper [Huston2017b].


3.11. Identifiers versus Brands and Other Convenience Names
3.11. 标识符与品牌和其他便利名称

A key design element of the original network object naming systems for the ARPANET, largely inherited by the DNS, was that the names, while expected to be mnemonic, were identifiers and their being highly distinguishable and not prone to ambiguity was important. That led to restrictive rules about what could appear in a name. Those restrictions originated with the host table and even earlier [RFC0236] [RFC0247] and came to the DNS (largely via SMTP) as the "preferred syntax" (RFC 1034, Section 3.5) or what we now often call the letter-digit-hyphen (LDH) rule. Similar rules to make identifiers easier to use, less prone to ambiguity, or less likely to interfere with syntax occur frequently in more formal languages. For example, almost every programming language has restrictions on what can appear in an identifier, and Unicode provides general recommendations about identifier composition [Unicode-USA31]. Both are quite restrictive as compared to the number of characters and total number of strings that can be written using that character coding system.

最初的ARPANET网络对象命名系统主要由DNS继承,其一个关键设计元素是,这些名称虽然被认为是助记符,但却是标识符,它们的高度可分辨性和不易产生歧义非常重要。这导致了关于名字中可能出现的内容的限制性规则。这些限制源于主机表,甚至更早的[RFC0236][RFC0247],并作为“首选语法”(RFC 1034,第3.5节)或我们现在经常称之为字母数字连字符(LDH)规则来到DNS(主要通过SMTP)。类似的规则使标识符更易于使用,不易产生歧义,或不太可能干扰语法,这些规则在更正式的语言中经常出现。例如,几乎每种编程语言都对标识符中可能出现的内容有限制,Unicode提供了关于标识符组合的一般建议[Unicode-USA31]。与使用该字符编码系统可以写入的字符数和字符串总数相比,两者都有很大的限制。

That model, which originally prohibited labels starting with digits in order to avoid any possible confusion with IP addresses, began to break down in 1987 or 1988 when a company named 3Com wanted to use its corporate name as a label within the COM TLD, and the rule was relaxed [RFC1123].

该模式最初禁止以数字开头的标签,以避免与IP地址的任何可能混淆,但在1987年或1988年,一家名为3Com的公司希望在COM TLD中使用其公司名称作为标签,该规则被放宽[RFC1123]。

In the last decade or two, the perspective that company names should be supported if possible has expanded and done so largely without its limits, if any, being explicitly understood or acknowledged. In the current form, the DNS is really (and primarily) a system for expressing thoughts and concepts. Those include free expression of ideas in as close to natural language as possible as well as representation of product names and brands. That view requires letter-like characters that might not be reasonable in identifiers along with a variety of symbols and punctuation. It may also require indicators of preferred type styles to provide information in a form that exactly matches personal or legal preferences. At least if carried to an extreme, that perspective would argue for standardizing word and sentence separators, removing the limit of 63 octets per label and probably the limit of 255 octets on the total length of a domain name, and perhaps even eliminating the hierarchy or allowing separators for labels in presentation form (now fixed at "." for the DNS) to be different according to context. It suggests that, at least, the original design was defective in not prioritizing those uses over the more restrictive approach associated with prioritizing unique and unambiguous identifiers.


So we have two or, depending on how one counts, three very different use cases. The historical one is support for unique identifiers. The other is expression of ideas and, if one considers them separate, presentation of brand and product names. Because they inherently involve different constraints, priorities, and success criteria, these perspectives are, at best, only loosely compatible.


We cannot simultaneously optimize both the identifier perspective and either or both of the others in the same system. At best, there are some complex trade-offs involved. Even then, it is not clear that the same DNS (or other system) can accommodate all of them. Until we come to terms with that, the differences manifest themselves with friction among communities, most often with tension between "we want to do (or use or sell) these types of labels" and "not good for the operational Internet or the DNS".


3.12. A Single Hierarchy with a Centrally Controlled Root
3.12. 具有集中控制的根目录的单个层次结构

A good many Internet policy discussions in the last two decades have revolved around such questions of how many top-level domains there should be, what they should be, who should control them and how, how (or if) their individual operations and policy decisions should be accountable to others, and what processes should be used (and by what entities or organizational structures) to make those decisions. Several people have pointed out that, if we were designing a next-generation DNS using today's technology, it should be possible to remove the technical requirement for a central authority over the root (some people have suggested that blockchain approaches would be helpful for this purpose; others believe they just would not scale adequately, at least at acceptable cost, but that other options are possible). Whether elimination of a single, centrally controlled, root would be desirable or not is fairly obviously a question of perspective and priorities.


3.13. Newer Application Protocols, New Requirements, and DNS Evolution
3.13. 更新的应用程序协议、新的要求和DNS发展

New work done in other areas has led to demands for new DNS features, many of them involving data values that require recursively referencing the DNS. Early record types that did that were accompanied by restrictions that reduced the risk of looping references or other difficulties. For example, while the MX RRTYPE has a fully qualified domain name as its data, SMTP imposes "primary name" restrictions that prevent the name used from being, e.g., a CNAME. While loops with CNAMEs are possible, Section 3.6 of RFC 1034 includes a discussion about ways to avoid problems and how they should be handled. Some newer protocols and conventions can cause more stress. There are separate issues with additions and with how the DNS has been extended to try to deal with them.

在其他领域所做的新工作导致了对新DNS功能的需求,其中许多涉及需要递归引用DNS的数据值。这样做的早期记录类型伴随着减少循环引用风险或其他困难的限制。例如,虽然MX RRTYPE有一个完全限定的域名作为其数据,但SMTP施加了“主要名称”限制,以防止使用的名称成为CNAME等名称。虽然可以使用CNAMEs进行循环,但RFC 1034第3.6节讨论了避免问题的方法以及应如何处理这些问题。一些较新的协议和约定可能会造成更大的压力。关于添加和DNS如何扩展以尝试处理它们,存在着不同的问题。

3.13.1. The Extensions
3.13.1. 扩展

Some examples of DNS extensions for new protocol demands that illustrate, or have led to, increased stress include:


NAPTR: Requires far more complex data in the DNS for ENUM (e.g., Voice over IP (VoIP), specifically SIP) support, including URI information and hence recursive or repeated lookups, than any of the RRTYPEs originally supported. The RRSET associated with these records can become quite large because the separator between the various records is part of the RDATA, and not the {owner, class, type} triple (a problem slightly related to the problem with overloading of TXT RRTYPE discussed in Section 3.13.2). This problem, and similar ones for some of the cases below. may suggest that any future design is in need of a different TYPE model such as systematic arrangements for subtypes or some explicit hierarchy in the TYPEs.

NAPTR:需要DNS中更复杂的数据来支持枚举(例如,IP语音(VoIP),特别是SIP),包括URI信息,因此需要递归或重复查找,而不是最初支持的任何RRT类型。与这些记录相关联的RRSET可能变得相当大,因为不同记录之间的分隔符是RDATA的一部分,而不是{owner,class,type}三元组(这个问题与第3.13.2节讨论的TXT RRTYPE重载问题稍有关联)。这个问题,以及下面一些情况下的类似问题。可能表明未来的任何设计都需要不同的类型模型,例如子类型的系统安排或类型中的某些明确层次结构。

URI: Has a URI as its data, typically also requiring recursive or repeated lookups.


Service location (SRV) and credential information (including Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM)): Require structured data and, especially for the latter two, significantly more data than most original RRTYPEs.


URI/URL: The early design decision for the World Wide Web that its mechanism for identifying digital web content (now known as Uniform Resource Identifiers [RFC3986]) did so by using domain names and hence the network location of the information or other material. That, in turn, has required systems intended to improve web performance by locating and retrieving a "nearest copy" (rather than the single copy designated by the URL) to intercept DNS queries and respond with values that are not precisely those stored for the designated domain name in the DNS or to otherwise access information in a way not supported by the DNS itself.


3.13.2. Extensions and Deployment Pressures -- The TXT RRTYPE
3.13.2. 扩展和部署压力——TXT RRTYPE

Unfortunately (but unsurprisingly), and despite IETF efforts to make things easier [RFC6895], DNS support libraries have often been slow to add full support for new RRTYPEs. This has impeded deployment of applications that depend on those types and that must ask (query) explicitly for them. Both to get faster deployment and, at least until recently, to avoid burdensome IETF approval procedures, many application designers have chosen to push protocol-critical


information into records with TXT RRTYPE, a record type that was originally intended to include only information equivalent to comments.

使用TXT RRTYPE将信息转换为记录,该记录类型最初旨在仅包含与注释等效的信息。

This causes two problems. First, TXT records used this way tend to get long and complex, which is a problem in itself if one is trying to minimize TCP connections. Second, applications that are attempting to obtain data cannot merely ask for the relevant QTYPE; they must obtain all of the records with QTYPE TXT and parse them to determine which ones are of interest. That would be easier if there was some standard for how to do that parsing, but, at least in part because the clear preference in the DNS design is for distinct RRTYPEs for different kinds of information, there is no such standard. (There was a proposal in 1993 to structure the TXT DATA in a way that would have addressed the issue [RFC1464], but it apparently never went anywhere.)

这导致了两个问题。首先,以这种方式使用的TXT记录往往会变得长而复杂,如果试图最小化TCP连接,这本身就是一个问题。第二,试图获取数据的应用程序不能仅仅要求相关的QTYPE;他们必须获得QTYPE TXT的所有记录,并对其进行解析以确定感兴趣的记录。如果有一些关于如何进行解析的标准,这将更容易,但是,至少部分是因为DNS设计中明确的偏好是针对不同类型的信息使用不同的RRTYPE,因此没有这样的标准。(1993年,有人提议以一种能够解决这个问题的方式来构造TXT数据[RFC1464],但显然从未付诸实施。)

On the other hand, this issue is somewhat different from most of the others described in this document because (as the IETF has recommended several times) the problem is easily solved within the current DNS design by allocating and supporting new RRTYPEs when needed rather than using TXT as a workaround (that does not mean that other solutions are impossible, either with the current DNS or with some other design). The problem then lies in the implementations and/or mechanisms that deter or impede rapid deployment of support for new RRTYPEs.


3.13.3. Periods and Zone Cut Issues
3.13.3. 周期和分区削减问题

One of the DNS characteristics that is poorly understood by non-experts is that the period (".", U+002E) character can be used in four different ways:


o As a label separator in the presentation form that also designates a "zone break" (delegation boundary). For example, indicates the owner, "foo", of records in the "" zone.

o 作为演示表单中的标签分隔符,该分隔符还指定“区域分隔符”(委派边界)。例如,表示“”区域中记录的所有者“foo”。

o As a label separator in the presentation form that does not designate a zone break. For example, indicates the owner, "", of records in the "" zone.

o 作为表示形式中的标签分隔符,不指定区域分隔符。例如,表示“”区域中记录的所有者“”。

o As a character within a label, including as a substitute for an at-sign ("@") when an email address appears in an SOA record or in a label that denotes such an address (see Section 2 above). The ability to embed periods in labels in this way has also led to attacks in which, e.g., a domain name consisting of the labels

o 作为标签中的一个字符,包括当电子邮件地址出现在SOA记录或表示此类地址的标签中时,作为at符号(“@”)的替代物(见上文第2节)。以这种方式在标签中嵌入句点的能力也导致了攻击,例如,由标签组成的域名

"example" followed by "com" is deliberately confused with the single label "" with an embedded period.


o At the end of a fully qualified domain name to designate the root zone, e.g., "" (RFC 1034, Section 3.1).

o 在完全限定域名的末尾指定根区域,例如,“”(RFC 1034,第3.1节)。

In general, these cases cannot be distinguished by looking at them. The third is problematic for non-DNS reasons, e.g., "" can be interpreted as either a simple FQDN or as a notation for,, or even (at least in principle) john.doe.example@net.


The distinction between the FQDN interpretation and the first email-like one was probably not important as the DNS was originally intended to be used. However, as soon as RRTYPEs (other than NS records that define the zone cut) are used that are sensitive to the boundaries between zones, the distinctions become important to people other than the relevant zone administrators. DNSSEC [RFC4033] involves one such set of relationships. It increases the importance of questions about what should go in a parent zone and what should go in child zones and how much difference it makes if NS records in a parent zone for a child zone are consistent with the records and data in the child zone. This also causes application issues and may raise questions about relationships between registrars and one or more registries or, if they are separate, DNS operators.


3.14. Scaling of Reputation and Other Ancillary Information
3.14. 声誉和其他辅助信息的扩展

The original design for DNS administration, reflected in RFC 1591 [RFC1591] and elsewhere, assumed that all domains would exhibit a very high level of responsibility toward and for the community and that level of responsibility would be enforced if necessary.

最初的DNS管理设计反映在RFC 1591[RFC1591]和其他地方,假设所有域对社区和对社区都表现出很高的责任水平,并且在必要时将强制执行该责任水平。

More recent decisions, many of them associated with commercialization of the DNS, have eroded those very strong assumptions of registry responsibility and accountability to the point that many consider decisions about delegation of names, identification of registrants, and relationships among names to be matters of "registrant beware" and even "user and applications beware". While some recent protocols and proposals at least partially reflect that original model of a high level of responsibility (see, e.g., IDNA [RFC5890] and a more recent discussion [Klensin-5891bis]), other decisions and actions tend to shift responsibility to the registrant or try to avoid accountability entirely. One possible approach to the problems, especially security problems, that are enabled by those new trends and the associated environment is to establish reputation systems associated with clearly defined administrative boundaries and with


warnings to users, even if those reputation systems are managed by parties not directly associated with the DNS.


The IETF DBOUND WG [IETF-DBOUND] addressed ways to establish and document boundaries more precise than simple dependencies on TLDs, but it was not successful in producing a standard.


A TLD reputation-based approach was adopted by some web browsers after IDNs and a growing number of Generic Top-Level Domains (gTLDs) were introduced; that approach was based on a simple list and does not scale to the current size of the DNS or even the DNS root.


3.15. Tensions among Transport, Scaling, and Content
3.15. 传输、扩展和内容之间的紧张关系

The original design for the DNS envisaged a simple query and response protocol where both the command and the response could be readily mapped into a single IP packet. The host requirements specification [RFC1123] required all DNS applications to accept a UDP query or response over UDP with up to 512 octets of DNS payload. TCP was seen as a fallback when the response was greater than this 512-octet limit, and this fallback to use TCP as the transport protocol was considered to be the exception rather than the rule.


Over the intervening years, we have seen the rise of a common assumption of an Internet-wide Maximum Transmission Unit (MTU) size of 1,500 octets, accompanied with an assumption that UDP fragmentation is generally viable. This underpins the adoption of the Extension Mechanisms for DNS (EDNS(0)) [RFC6891] to, among other things, specify a UDP buffer size larger than 512 octets and a suggestion within that specification to use 4,096 as a suitable compromise for the UDP payload size. This has proved to be fortuitous for the DNSSEC security extensions where the addition of DNSSEC security credentials in DNS responses [RFC4034] can lead to the use of large DNS responses. However, this exposes some tensions over the handling of fragmentation in IP, where UDP fragments have been observed to be filtered by various firewalls. Additionally for IPv6, there are the factors of filtering the ICMPv6 Packet Too Big diagnostic messages and discarding the IPv6 packets that contain extension headers [RFC7872]. More generally, fragmented UDP packets appear to have a lower level of reliability than unfragmented TCP packets.


Behind this observation about relative reliability of delivery is the tension between the lightweight load of UDP and the downside of elevated probability of discarding of packet fragments as compared to TCP, which offers increased levels of assurance of content delivery, but with the associated imposition of TCP session state and the downside of reduced DNS scalability and increased operational cost.


4. The Inverse Lookup Requirement
4. 反向查找要求

The requirement for an inverse lookup capability, i.e., the ability to find a domain name given an address and, in principle, to find the owner of a record by any of its data elements, was recognized in RFC 882. The feature was identified as optional but carried forward into RFCs 1034 and 1035 but was explicitly deprecated by RFC 1034 for address-to-hostname lookup (although RFC 1035 uses exactly that type of lookup in an example). Despite the discussion of inverted forms of the database in RFC 1035, inverse lookup has rarely, if ever, been implemented, at least in its general form. The fundamental difficulties with inverse lookup in either the form described in RFC 882 or the "" approach mentioned below are consistent with the problems described in fundamental papers on database management [Codd1970] but were not described in RFC 1035 or related contemporary IETF documents.

RFC 882中确认了反向查找功能的要求,即能够找到给定地址的域名,并且原则上能够通过记录的任何数据元素找到记录的所有者。该功能被标识为可选功能,但转入了RFC 1034和1035,但RFC 1034明确反对将其用于从地址到主机名的查找(尽管RFC 1035在示例中正是使用这种类型的查找)。尽管在RFC1035中讨论了数据库的反转形式,但反转查找很少(如果有的话)被实现,至少在一般形式上是如此。以RFC 882中所述的形式或下文所述的“in”方法进行反向查找的基本困难与数据库管理基础论文[Codd1970]中所述的问题一致,但RFC 1035或相关的当代IETF文件中没有描述。

It is interesting to speculate on how many of the current requirements to treat aliases as an integrated set of synonyms (e.g., for variant handling) would have been addressed if inverse lookups could reliably produce the owners of CNAME records.


At the same time, it was obviously important to have some mechanism for address-to-name resolution. It was provided by PTR RRTYPE entries in the IN-ADDR.ARPA zone, with delegations on octet boundaries. However, that approach required that information be maintained in parallel, in separate zones, for the name-to-address and address-to-name mappings. That synchronization requirement for two copies of essentially the same data was another popular topic in the database management literature a decade or more before the DNS and, predictably, led to many inconsistencies and other failures.

同时,显然有一些地址到名称的解析机制很重要。它由in-ADDR.ARPA区域中的PTR RRTYPE条目提供,并在八位字节边界上授权。然而,这种方法要求在单独的区域中并行维护名称到地址和地址到名称映射的信息。对基本相同数据的两个副本的同步要求是DNS出现前十年或更长时间数据库管理文献中的另一个热门话题,可以预见,这导致了许多不一致和其他故障。

The introduction of Classless Inter-Domain Routing (CIDR) [RFC1518] and Provider-Dependent addresses made the situation even more difficult, because it was no longer possible to delegate the administration of reverse mapping records for small networks to the actual operators of those networks. ISPs and other aggregators often had no incentive to maintain reverse mapping records consistent with network operator assignment of domain names. A proposal to use binary labels to work around that issue [RFC2673] was abandoned somewhat over three years later [RFC6891].


Independent of how much or little harm the absence of a general inverse lookup facility has caused and how effective the "" approach has been, inverse lookup remains a facility that was anticipated and known to be useful in the original DNS design but that has never been fully realized.


5. Internet Scale, Function Support, and Incremental Deployment
5. 互联网规模、功能支持和增量部署

In addition to the stresses caused by the new functions, including those described in Section 3.13, incremental deployment of systems that utilize them means that some functions will work in some environments and not others. This has been especially problematic with complex, multi-record, capabilities like DNSSEC that provide or require special validation mechanisms and with some EDNS(0) extensions [RFC6891] that require both the client and server to accept particular extensions. When DNS functionality is required in embedded devices, deployment of new features across the entire Internet in a reasonable period of time is nearly impossible.


If one were redesigning the DNS, one could imagine ways to address these issues that would make them slightly more tractable, and, of course, the features that are known to be necessary today could become part of the baseline, "mandatory to implement", specification.


6. Searching and the DNS -- An Historical Note
6. 搜索和DNS——一个历史注释

Some of the issues identified above might reasonably be addressed, not by changing the DNS itself but by changing our model of what it is about and how it is used. Specifically, one key assumption when the DNS (and the host table system before it) was designed was that it was a naming system for network resources, not, e.g., digital content. As such, exact matching was important, it was reasonable to have labels treated as mnemonics that did not necessarily have linguistic or semantic meaning except to those using them, and so on. A return to that model, presumably by having user-facing applications call on an intermediate layer to disambiguate user-friendly names and map them to DNS names (or network object locators more generally), would significantly reduce stress on the DNS and would also allow dealing with types of matching and similar or synonymous strings that cannot be handled algorithmically no matter how much DNS matching rules were altered.


In some respects, search engines based on free-text analysis and linkages among information have come to serve many of the functions of such an intermediate layer. Many studies and sources have pointed out that few users actually understand, much less care about, the distinction between a DNS name and a search term. Recent versions of some web browsers have both recognized the failure of that distinction and reinforced it by eliminating the separation between "URL" and "search bar".


It is worth noting that, while that "search" approach, or some other approach that abstracted and separated several of the issues identified in Section 3 from the DNS protocol and database themselves, it does not address all of them. At least some elements of several of those issues, such as the synchronization ones described in Section 3.7 and the transport ones described in Section 3.15, are inherent in the DNS design, and, if we are not going to replace the DNS, we had best get used to them.


In the early part of the last decade, the IETF engaged in some preliminary exploration of the intermediate-layer approach in the context of IDNs and what were then called "Internet keywords" [DNS-search]. While that exploratory effort met several times informally, it never became an organized IETF activity, largely because of the choice of what became the IDNA approach but also in part by signs that the "Internet keywords" efforts were beginning to fall apart.


   It may be time to reexamine intermediate-layer approaches.  If so,
   the effort should examine use of those approaches by appropriate
   user-facing applications that might be used to address some of the
   issues identified above.  The Internet and the DNS have changed
   considerably since the 2000-2003 period.  Several of those changes
   are discussed elsewhere in this document; others, including
   repurposing of the DNAME RRTYPE from support for transitions
   [RFC2672] to a general-purpose mechanism for aliases of subtrees
   [RFC6672] and the addition of over a thousand new TLDs
   [IANA-TLD-registry], are not but nonetheless are part of the context
   for intermediate-layer work that did not exist in 2003.
   It may be time to reexamine intermediate-layer approaches.  If so,
   the effort should examine use of those approaches by appropriate
   user-facing applications that might be used to address some of the
   issues identified above.  The Internet and the DNS have changed
   considerably since the 2000-2003 period.  Several of those changes
   are discussed elsewhere in this document; others, including
   repurposing of the DNAME RRTYPE from support for transitions
   [RFC2672] to a general-purpose mechanism for aliases of subtrees
   [RFC6672] and the addition of over a thousand new TLDs
   [IANA-TLD-registry], are not but nonetheless are part of the context
   for intermediate-layer work that did not exist in 2003.
7. Security Considerations
7. 安全考虑

A wide range of security issues related to both securing the DNS and also to abilities to use namespaces for nefarious purposes have arisen. Issues of securing the DNS would obviously be essential to a replacement of the DNS. Issues of preventing nefarious use of the namespace (e.g. use of the name that appears or disappears as a signal to bots) would appear to be harder to solve within the naming system.


8. References
8. 工具书类
8.1. Normative References
8.1. 规范性引用文件

[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, <>.

[RFC1034]Mockapetris,P.,“域名-概念和设施”,STD 13,RFC 1034,DOI 10.17487/RFC1034,1987年11月<>.

[RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, November 1987, <>.

[RFC1035]Mockapetris,P.,“域名-实现和规范”,STD 13,RFC 1035,DOI 10.17487/RFC1035,1987年11月<>.

8.2. Informative References
8.2. 资料性引用

[CACM-Homograph] Gabrilovich, E. and A. Gontmakher, "The Homograph Attack", Communications of the ACM, Volume 45, Issue 2, pp. 128, DOI 10.1145/503124.503156, February 2002, < homograph_full.pdf>.

[CACM同形词]Gabrilovich,E.和A.Gontmakher,“同形词攻击”,ACM通讯,第45卷,第2期,第128页,DOI 10.1145/503124.503156,2002年2月<\u full.pdf>。

[Cerf2017] Cerf, V., "Desirable Properties of Internet Identifiers", IEEE Internet Computing, Volume 21, Issue 6, pp. 63-64, DOI 10.1109/MIC.2017.4180839, November/December 2017.

[Cerf2017]Cerf,V.,“互联网标识符的理想属性”,IEEE互联网计算,第21卷,第6期,第63-64页,DOI 10.1109/MIC.2017.4180839,2017年11月/12月。

[Codd1970] Codd, E., "A Relational Model of Data for Large Shared Data Banks", Communications of the ACM, Volume 13, Issue 6, pp. 377-387, DOI 10.1145/362384.362685, June 1970, <>.

[Codd1970]Codd,E.,“大型共享数据库的数据关系模型”,《ACM通讯》,第13卷,第6期,第377-387页,DOI 10.1145/362384.3626851970年6月<>.

[DNS-Aliases] Woolf, S., Lee, X., and J. Yao, "Problem Statement: DNS Resolution of Aliased Names", Work in Progress, draft-ietf-dnsext-aliasing-requirements-01, March 2011.


[DNS-BNAME] Yao, J., Lee, X., and P. Vixie, "Bundled DNS Name Redirection", Work in Progress, draft-yao-dnsext-bname-06, May 2016.


[DNS-search] IETF, "Internet Resource Name Search Service (IRNSS)", 2003, <>.


[Faltstrom-2004] Faltstrom, P. and R. Austein, "Design Choices When Expanding DNS", Work in Progress, draft-ymbk-dns-choices-00, May 2004.


[Hoffman-DNS-JSON] Hoffman, P., "Representing DNS Messages in JSON", Work in Progress, draft-hoffman-dns-in-json-13, October 2017.

[Hoffman DNS JSON]Hoffman,P.,“用JSON表示DNS消息”,正在进行的工作,草稿-Hoffman-DNS-in-JSON-132017年10月。

[Hoffman-SimpleDNS-JSON] Hoffman, P., "Simple DNS Queries and Responses in JSON", Work in Progress, draft-hoffman-simplednsjson-01, November 2017.

[Hoffman SimpleDNS JSON]Hoffman,P.,“JSON中的简单DNS查询和响应”,正在进行的工作,草稿-Hoffman-simplednsjson-01,2017年11月。

[Huston2017a] Huston, G. and J. Silva Dama, "DNS Privacy", The Internet Protocol Journal, Vol. 20, No. 1, March 2017, < issues/2017/ipj20-1.pdf>.

[Huston2017a]Huston,G.和J.Silva Dama,“DNS隐私”,互联网协议杂志,第20卷,第1期,2017年3月< issues/2017/ipj20-1.pdf>。

[Huston2017b] Huston, G., "The Root of the Domain Name System", The Internet Protocol Journal, Vol. 20, No. 2, pp. 15-25, June 2017, < 2017/08/ipj20-2.pdf>.

[Huston2017b]Huston,G.,“域名系统的根”,《互联网协议杂志》,第20卷,第2期,第15-25页,2017年6月< 2017/08/ipj20-2.pdf>。

[IANA-TLD-registry] Internet Assigned Numbers Authority (IANA), "Root Zone Database", <>.

[IANA TLD注册表]互联网分配号码管理局(IANA),“根区域数据库”<>.

[ICANN-VIP] ICANN, "IDN Variant Issues Project: Final Integrated Issues Report Published and Proposed Project Plan for Next Steps is Now Open for Public Comment", February 2012, <>.


[IETF-DBOUND] IETF, "Domain Boundaries (dbound)", 2017, <>.


[Klensin-5891bis] Klensin, J. and A. Freytag, "Internationalized Domain Names in Applications (IDNA): Registry Restrictions and Recommendations", Work in Progress, draft-klensin-idna-rfc5891bis-01, September 2017.


[Mockapetris-1988] Mockapetris, P. and K. Dunlap, "Development of the Domain Name System", SIGCOMM '88 Symposium, pp. 123-133, available from ISI Reprint Series, ISI/RS-88-219 <>, DOI 10.1145/52324.52338, August 1988, <>.

[Mockapetris-1988]Mockapetris,P.和K.Dunlap,“域名系统的开发”,SIGCOMM'88研讨会,第123-133页,可从ISI重印系列ISI/RS-88-219获得<>,DOI 10.1145/52324.523381988年8月<>.

[NRC-Signposts] National Research Council, Signposts in Cyberspace: The Domain Name System and Internet Navigation, ISBN 0-309-54979-5, 2005, < catalog/11258/signposts-in-cyberspace-the-domain-name-system-and-internet-navigation>.

[NRC路标]国家研究委员会,《网络空间中的路标:域名系统和互联网导航》,ISBN 0-309-54979-52005< catalog/11258/signposts in cyberspace域名系统和互联网导航>。

[RFC0236] Postel, J., "Standard host names", RFC 236, DOI 10.17487/RFC0236, September 1971, <>.

[RFC0236]Postel,J.,“标准主机名”,RFC 236,DOI 10.17487/RFC0236,1971年9月<>.

[RFC0247] Karp, P., "Proffered set of standard host names", RFC 247, DOI 10.17487/RFC0247, October 1971, <>.

[RFC0247]Karp,P.,“提供的标准主机名集”,RFC 247,DOI 10.17487/RFC0247,1971年10月<>.

[RFC0799] Mills, D., "Internet name domains", RFC 799, DOI 10.17487/RFC0799, September 1981, <>.

[RFC0799]Mills,D.,“互联网域名”,RFC 799,DOI 10.17487/RFC0799,1981年9月<>.

[RFC0810] Feinler, E., Harrenstien, K., Su, Z., and V. White, "DoD Internet host table specification", RFC 810, DOI 10.17487/RFC0810, March 1982, <>.

[RFC0810]Feinler,E.,Harrenstien,K.,Su,Z.,和V.White,“国防部互联网主机表规范”,RFC 810,DOI 10.17487/RFC0810,1982年3月<>.

[RFC0881] Postel, J., "Domain names plan and schedule", RFC 881, DOI 10.17487/RFC0881, November 1983, <>.

[RFC0881]Postel,J.,“域名计划和时间表”,RFC 881,DOI 10.17487/RFC08811983年11月<>.

[RFC0882] Mockapetris, P., "Domain names: Concepts and facilities", RFC 882, DOI 10.17487/RFC0882, November 1983, <>.

[RFC0882]Mockapetris,P.,“域名:概念和设施”,RFC 882,DOI 10.17487/RFC0882,1983年11月<>.

[RFC0883] Mockapetris, P., "Domain names: Implementation specification", RFC 883, DOI 10.17487/RFC0883, November 1983, <>.

[RFC0883]Mockapetris,P.,“域名:实现规范”,RFC 883,DOI 10.17487/RFC0883,1983年11月<>.

[RFC0952] Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet host table specification", RFC 952, DOI 10.17487/RFC0952, October 1985, <>.

[RFC0952]Harrenstien,K.,Stahl,M.和E.Feinler,“国防部互联网主机表规范”,RFC 952,DOI 10.17487/RFC0952,1985年10月<>.

[RFC0953] Harrenstien, K., Stahl, M., and E. Feinler, "Hostname Server", RFC 953, DOI 10.17487/RFC0953, October 1985, <>.

[RFC0953]Harrenstien,K.,Stahl,M.和E.Feinler,“主机名服务器”,RFC 953,DOI 10.17487/RFC0953,1985年10月<>.

[RFC0974] Partridge, C., "Mail routing and the domain system", STD 10, RFC 974, DOI 10.17487/RFC0974, January 1986, <>.

[RFC0974]帕特里奇,C.,“邮件路由和域系统”,STD 10,RFC 974,DOI 10.17487/RFC0974,1986年1月<>.

[RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - Application and Support", STD 3, RFC 1123, DOI 10.17487/RFC1123, October 1989, <>.

[RFC1123]Braden,R.,Ed.“互联网主机的要求-应用和支持”,STD 3,RFC 1123,DOI 10.17487/RFC1123,1989年10月<>.

[RFC1464] Rosenbaum, R., "Using the Domain Name System To Store Arbitrary String Attributes", RFC 1464, DOI 10.17487/RFC1464, May 1993, <>.

[RFC1464]Rosenbaum,R.,“使用域名系统存储任意字符串属性”,RFC 1464,DOI 10.17487/RFC1464,1993年5月<>.

[RFC1518] Rekhter, Y. and T. Li, "An Architecture for IP Address Allocation with CIDR", RFC 1518, DOI 10.17487/RFC1518, September 1993, <>.

[RFC1518]Rekhter,Y.和T.Li,“具有CIDR的IP地址分配架构”,RFC 1518,DOI 10.17487/RFC1518,1993年9月<>.

[RFC1591] Postel, J., "Domain Name System Structure and Delegation", RFC 1591, DOI 10.17487/RFC1591, March 1994, <>.

[RFC1591]Postel,J.,“域名系统结构和授权”,RFC 1591,DOI 10.17487/RFC15911994年3月<>.

[RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996, August 1996, <>.

[RFC1996]Vixie,P.,“区域变更即时通知机制(DNS通知)”,RFC 1996,DOI 10.17487/RFC1996,1996年8月<>.

[RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671, DOI 10.17487/RFC2671, August 1999, <>.

[RFC2671]Vixie,P.,“DNS的扩展机制(EDNS0)”,RFC 2671,DOI 10.17487/RFC26711999年8月<>.

[RFC2672] Crawford, M., "Non-Terminal DNS Name Redirection", RFC 2672, DOI 10.17487/RFC2672, August 1999, <>.

[RFC2672]克劳福德,M.,“非终端DNS名称重定向”,RFC 2672,DOI 10.17487/RFC2672,1999年8月<>.

[RFC2673] Crawford, M., "Binary Labels in the Domain Name System", RFC 2673, DOI 10.17487/RFC2673, August 1999, <>.

[RFC2673]克劳福德,M.,“域名系统中的二进制标签”,RFC 2673,DOI 10.17487/RFC2673,1999年8月<>.

[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, "Internationalizing Domain Names in Applications (IDNA)", RFC 3490, DOI 10.17487/RFC3490, March 2003, <>.

[RFC3490]Faltstrom,P.,Hoffman,P.,和A.Costello,“应用程序中的域名国际化(IDNA)”,RFC 3490,DOI 10.17487/RFC3490,2003年3月<>.

[RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep Profile for Internationalized Domain Names (IDN)", RFC 3491, DOI 10.17487/RFC3491, March 2003, <>.

[RFC3491]Hoffman,P.和M.Blanchet,“Nameprep:国际化域名(IDN)的Stringprep配置文件”,RFC 3491,DOI 10.17487/RFC34912003年3月<>.

[RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, "DNS Extensions to Support IP Version 6", STD 88, RFC 3596, DOI 10.17487/RFC3596, October 2003, <>.

[RFC3596]Thomson,S.,Huitema,C.,Ksinant,V.,和M.Souissi,“支持IP版本6的DNS扩展”,STD 88,RFC 3596,DOI 10.17487/RFC3596,2003年10月<>.

[RFC3743] Konishi, K., Huang, K., Qian, H., and Y. Ko, "Joint Engineering Team (JET) Guidelines for Internationalized Domain Names (IDN) Registration and Administration for Chinese, Japanese, and Korean", RFC 3743, DOI 10.17487/RFC3743, April 2004, <>.

[RFC3743]Konishi,K.,Huang,K.,Qian,H.,和Y.Ko,“中国,日本和韩国国际域名(IDN)注册和管理联合工程团队(JET)指南”,RFC 3743,DOI 10.17487/RFC3743,2004年4月<>.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, <>.

[RFC3986]Berners Lee,T.,Fielding,R.,和L.Masinter,“统一资源标识符(URI):通用语法”,STD 66,RFC 3986,DOI 10.17487/RFC3986,2005年1月<>.

[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS Security Introduction and Requirements", RFC 4033, DOI 10.17487/RFC4033, March 2005, <>.

[RFC4033]Arends,R.,Austein,R.,Larson,M.,Massey,D.,和S.Rose,“DNS安全介绍和要求”,RFC 4033,DOI 10.17487/RFC4033,2005年3月<>.

[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "Resource Records for the DNS Security Extensions", RFC 4034, DOI 10.17487/RFC4034, March 2005, <>.

[RFC4034]Arends,R.,Austein,R.,Larson,M.,Massey,D.,和S.Rose,“DNS安全扩展的资源记录”,RFC 4034,DOI 10.17487/RFC4034,2005年3月<>.

[RFC4343] Eastlake 3rd, D., "Domain Name System (DNS) Case Insensitivity Clarification", RFC 4343, DOI 10.17487/RFC4343, January 2006, <>.

[RFC4343]Eastlake 3rd,D.,“域名系统(DNS)案例不敏感澄清”,RFC 4343,DOI 10.17487/RFC4343,2006年1月<>.

[RFC5890] Klensin, J., "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", RFC 5890, DOI 10.17487/RFC5890, August 2010, <>.

[RFC5890]Klensin,J.,“应用程序的国际化域名(IDNA):定义和文档框架”,RFC 5890,DOI 10.17487/RFC5890,2010年8月<>.

[RFC5891] Klensin, J., "Internationalized Domain Names in Applications (IDNA): Protocol", RFC 5891, DOI 10.17487/RFC5891, August 2010, <>.

[RFC5891]Klensin,J.,“应用程序中的国际化域名(IDNA):协议”,RFC 5891,DOI 10.17487/RFC5891,2010年8月<>.

[RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012, <>.

[RFC6672]Rose,S.和W.Wijngaards,“DNS中的DNAME重定向”,RFC 6672,DOI 10.17487/RFC6672,2012年6月<>.

[RFC6761] Cheshire, S. and M. Krochmal, "Special-Use Domain Names", RFC 6761, DOI 10.17487/RFC6761, February 2013, <>.

[RFC6761]Cheshire,S.和M.Krochmal,“特殊用途域名”,RFC 6761,DOI 10.17487/RFC6761,2013年2月<>.

[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms for DNS (EDNS(0))", STD 75, RFC 6891, DOI 10.17487/RFC6891, April 2013, <>.

[RFC6891]Damas,J.,Graff,M.,和P.Vixie,“DNS的扩展机制(EDNS(0)),STD 75,RFC 6891,DOI 10.17487/RFC68911913年4月<>.

[RFC6895] Eastlake 3rd, D., "Domain Name System (DNS) IANA Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895, April 2013, <>.

[RFC6895]Eastlake 3rd,D.,“域名系统(DNS)IANA注意事项”,BCP 42,RFC 6895,DOI 10.17487/RFC6895,2013年4月<>.

[RFC6912] Sullivan, A., Thaler, D., Klensin, J., and O. Kolkman, "Principles for Unicode Code Point Inclusion in Labels in the DNS", RFC 6912, DOI 10.17487/RFC6912, April 2013, <>.

[RFC6912]Sullivan,A.,Thaler,D.,Klensin,J.,和O.Kolkman,“DNS标签中包含Unicode码点的原则”,RFC 6912,DOI 10.17487/RFC6912,2013年4月<>.

[RFC7094] McPherson, D., Oran, D., Thaler, D., and E. Osterweil, "Architectural Considerations of IP Anycast", RFC 7094, DOI 10.17487/RFC7094, January 2014, <>.

[RFC7094]McPherson,D.,Oran,D.,Thaler,D.,和E.Osterweil,“IP选播的架构考虑”,RFC 7094,DOI 10.17487/RFC7094,2014年1月<>.

[RFC7706] Kumari, W. and P. Hoffman, "Decreasing Access Time to Root Servers by Running One on Loopback", RFC 7706, DOI 10.17487/RFC7706, November 2015, <>.

[RFC7706]Kumari,W.和P.Hoffman,“通过在环回上运行一个来减少对根服务器的访问时间”,RFC 7706,DOI 10.17487/RFC7706,2015年11月<>.

[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS Terminology", RFC 7719, DOI 10.17487/RFC7719, December 2015, <>.

[RFC7719]Hoffman,P.,Sullivan,A.和K.Fujiwara,“DNS术语”,RFC 7719,DOI 10.17487/RFC77192015年12月<>.

[RFC7816] Bortzmeyer, S., "DNS Query Name Minimisation to Improve Privacy", RFC 7816, DOI 10.17487/RFC7816, March 2016, <>.

[RFC7816]Bortzmeyer,S.,“DNS查询名称最小化以改善隐私”,RFC 7816,DOI 10.17487/RFC7816,2016年3月<>.

[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D., and P. Hoffman, "Specification for DNS over Transport Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May 2016, <>.

[RFC7858]Hu,Z.,Zhu,L.,Heidemann,J.,Mankin,A.,Wessels,D.,和P.Hoffman,“DNS传输层安全规范(TLS)”,RFC 7858,DOI 10.17487/RFC7858,2016年5月<>.

[RFC7872] Gont, F., Linkova, J., Chown, T., and W. Liu, "Observations on the Dropping of Packets with IPv6 Extension Headers in the Real World", RFC 7872, DOI 10.17487/RFC7872, June 2016, <>.

[RFC7872]Gont,F.,Linkova,J.,Chown,T.,和W.Liu,“关于在现实世界中使用IPv6扩展头丢弃数据包的观察”,RFC 7872,DOI 10.17487/RFC7872,2016年6月<>.

[RFC8244] Lemon, T., Droms, R., and W. Kumari, "Special-Use Domain Names Problem Statement", RFC 8244, DOI 10.17487/RFC8244, October 2017, <>.

[RFC8244]Lemon,T.,Droms,R.,和W.Kumari,“特殊用途域名问题声明”,RFC 8244,DOI 10.17487/RFC82442017年10月<>.

[Sullivan-Class] Sullivan, A., "The DNS Is Not Classy: DNS Classes Considered Useless", Work in Progress, draft-sullivan-dns-class-useless-03, July 2016.

[Sullivan Class]Sullivan,A.,“DNS不是一流的:DNS类被认为是无用的”,正在进行的工作,草稿-Sullivan-DNS-Class-Uffused-032016年7月。

[Unicode] The Unicode Consortium, The Unicode Standard, Version 9.0.0, (Mountain View, CA: The Unicode Consortium, 2016. ISBN 978-1-936213-13-9), <>.

[Unicode]Unicode联盟,Unicode标准,版本9.0.0,(加利福尼亚州山景城:Unicode联盟,2016年。ISBN 978-1-936213-13-9)<>.

[Unicode-UAX15] Davis, M. and K. Whistler, "Unicode Standard Annex #15: Unicode Normalization Forms", February 2016, <>.


[Unicode-USA31] Davis, M., "Unicode Standard Annex #31: Unicode Identifier and Pattern Syntax", May 2016, <>.


[Vixie-20170704] Vixie, P., "Subject: Re: new DNS classes", message to the IETF dnsop mailing list, 4 July 2017, < msg103486.html>.

[Vixie-20170704]Vixie,P.,“主题:Re:新DNS类”,发送给IETF dnsop邮件列表的信息,2017年7月4日< msg103486.html>。



Many of the concerns and ideas described in this document reflect conversations over a period of many years, some rooted in DNS "keyword" and "search" discussions that paralleled the development of IDNs. Conversations with, or writings of, Rob Austein, Christine Borgman, Carolina Carvalho, Vint Cerf, Lyman Chapin, Nazli Choucri, Patrik Faltstrom, Geoff Huston, Xiaodong Lee, Karen Liu, Gervase Markham, Yaqub Mueller, Andrew Sullivan, Paul Twomey, Nico Williams, Suzanne Woolf, Jiankang Yao, other participants in the circa 2003 "DNS Search" effort and in the ICANN SSAC Working Party on IDNs, and some others whose names were sadly forgotten, were particularly important to either the content of this document or the motivation for writing it even though they may not agree with the conclusions I have reached and bear no responsibility for them.

本文档中描述的许多关注点和想法反映了多年来的对话,其中一些来源于DNS“关键字”和与IDN开发并行的“搜索”讨论。与罗布·奥斯汀、克里斯蒂娜·博格曼、卡罗莱纳·卡瓦略、文特·瑟夫、莱曼·查宾、纳兹利·乔克里、帕特里克·法特斯特罗姆、杰夫·休斯顿、李晓东、刘凯伦、格瓦塞·马卡姆、雅库布·穆勒、安德鲁·沙利文、保罗·托梅伊、尼科·威廉姆斯、苏珊娜·伍尔夫、姚建康以及2003年左右“域名搜索”的其他参与者的对话或其作品ICANN SSAC IDN工作组的努力和努力,以及其他一些名字不幸被遗忘的人,对于本文件的内容或写作动机尤其重要,尽管他们可能不同意我得出的结论,并且对这些结论不承担任何责任。

Many of the subsections of Section 3 were extracted from comments first made in conjunction with recent email discussions. Comments from Suzanne Woolf about an earlier draft version were particularly important as was material developed with suggestions from Patrik Faltstrom, especially Section 3.13. Feedback and suggestions from several of the above and from Stephane Bortzmeyer, Tony Finch, Bob Harold, Warren Kumari, Craig Partridge, and George Sadowsky were extremely helpful for improving the clarity and accuracy of parts of the document, especially so for a broader audience. Craig Partridge also contributed much of the material about queries for multiple types. Geoff Huston made several useful comments and contributed most of Section 3.15, and Bill Manning pointed out some broader requirements about integrity of information and DNS management and operations.

第3节中的许多小节摘自最早与最近的电子邮件讨论相关的评论。苏珊娜·伍尔夫(Suzanne Woolf)对早期版本草案的评论尤其重要,正如根据帕特里克·法特斯特罗姆(Patrik Faltstrom)的建议编写的材料一样,尤其是第3.13节。上述几位人士以及Stephane Bortzmeyer、Tony Finch、Bob Harold、Warren Kumari、Craig Partridge和George Sadowsky的反馈和建议对提高文件部分的清晰度和准确性极为有用,尤其是对更广泛的读者。Craig Partridge还提供了许多关于查询多种类型的资料。杰夫·休斯顿(Geoff Huston)发表了几条有用的评论,并对第3.15节的大部分内容做出了贡献,比尔·曼宁(Bill Manning)指出了关于信息完整性和DNS管理与操作的一些更广泛的要求。

Special thanks are due to Karen Moore of the RFC Production Center for her efforts, patience, and persistence in preparing this document for publication, a process that raised far more issues that required careful discussion than usual.

特别要感谢RFC制作中心的Karen Moore,感谢她在准备本文件出版过程中所做的努力、耐心和坚持,这一过程提出了比平时更多需要仔细讨论的问题。

Author's Address


John C. Klensin 1770 Massachusetts Ave, Ste 322 Cambridge, MA 02140 United States of America


   Phone: +1 617 245 1457
   Phone: +1 617 245 1457