RFC3404 日本語訳
3404 Dynamic Delegation Discovery System (DDDS) Part Four: The UniformResource Identifiers (URI). M. Mealling. October 2002. (Format: TXT=40124 bytes) (Obsoletes RFC2915, RFC2168) (Status: PROPOSED STANDARD)
プログラムでの自動翻訳です。
英語原文
Network Working Group M. Mealling Request for Comments: 3404 VeriSign Obsoletes: 2915, 2168 October 2002 Category: Standards Track
コメントを求める要求を荒びきにして、作業部会M.をネットワークでつないでください: 3404 ベリサインは以下を時代遅れにします。 2915、2168年2002年10月のカテゴリ: 標準化過程
Dynamic Delegation Discovery System (DDDS)
Part Four: The Uniform Resource Identifiers (URI)
Resolution Application
ダイナミックな代表団発見システム(DDDS)パートFour: Uniform Resource Identifier(URI)解決アプリケーション
Status of this Memo
このMemoの状態
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
このドキュメントは、インターネットコミュニティにインターネット標準化過程プロトコルを指定して、改良のために議論と提案を要求します。 このプロトコルの標準化状態と状態への「インターネット公式プロトコル標準」(STD1)の現行版を参照してください。 このメモの分配は無制限です。
Copyright Notice
版権情報
Copyright (C) The Internet Society (2002). All Rights Reserved.
Copyright(C)インターネット協会(2002)。 All rights reserved。
Abstract
要約
This document describes a specification for taking Uniform Resource Identifiers (URI) and locating an authoritative server for information about that URI. The method used to locate that authoritative server is the Dynamic Delegation Discovery System.
このドキュメントはそのURIの情報のためにUniform Resource Identifier(URI)を取って、正式のサーバの場所を見つけるための仕様を説明します。 その正式のサーバの場所を見つけるのに使用される方法はDynamic DelegationディスカバリーSystemです。
This document is part of a series that is specified in "Dynamic Delegation Discovery System (DDDS) Part One: The Comprehensive DDDS" (RFC 3401). It is very important to note that it is impossible to read and understand any document in this series without reading the others.
このドキュメントはシリーズの一部です、すなわち、指定されて、「ダイナミックな代表団発見システム(DDDS)は1つを分けます」。 「包括的なDDDS。」(RFC3401) 他のものを読まないでこのシリーズでどんなドキュメントも読んで、理解しているのが不可能であることに注意するのは非常に重要です。
Table of Contents
目次
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 3. The Distinction between URNs and URIs . . . . . . . . . . . 3 4. The URI and URN Resolution Application Specifications . . . 4 4.1 Application Unique String . . . . . . . . . . . . . . . . . 4 4.2 First Well Known Rule . . . . . . . . . . . . . . . . . . . 4 4.3 Flags . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.4 Services Parameters . . . . . . . . . . . . . . . . . . . . 5 4.4.1 Services . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.4.2 protocols . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.4.3 Applicability of Services . . . . . . . . . . . . . . . . . 7
1. 序論. . . . . . . . . . . . . . . . . . . . . . . . 2 2。 用語. . . . . . . . . . . . . . . . . . . . . . . . 3 3。 つぼとURI. . . . . . . . . . . 3 4の区別。 URIとつぼの解決アプリケーション仕様. . . 4 4.1のアプリケーションのユニークなストリング. . . . . . . . . . . . . . . . . 4 4.2Firstのよく知られている規則. . . . . . . . . . . . . . . . . . . 4 4.3は.4 4に旗を揚げさせます; Services. . . . . . . . . . . . . . . . . 7の4つのサービスParameters. . . . . . . . . . . . . . . . . . . . 5 4.4.1Services. . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.4.2のプロトコル. . . . . . . . . . . . . . . . . . . . . . . . . 6 4.4.3Applicability
Mealling Standards Track [Page 1] RFC 3404 DDDS Based URI Resolution October 2002
URI解決2002年10月に基づいた標準化過程[1ページ]RFC3404DDDSを荒びきにします。
4.5 Valid Databases . . . . . . . . . . . . . . . . . . . . . . 7
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1 An example using a URN . . . . . . . . . . . . . . . . . . . 8
5.2 CID URI Scheme Example . . . . . . . . . . . . . . . . . . . 9
5.3 Resolving an HTTP URI Scheme . . . . . . . . . . . . . . . . 11
6. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . 12
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 13
References . . . . . . . . . . . . . . . . . . . . . . . . . 13
Appendix A: Pseudo Code . . . . . . . . . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . 17
Full Copyright Statement . . . . . . . . . . . . . . . . . . 18
4.5 有効なデータベース. . . . . . . . . . . . . . . . . . . . . . 7 5。 URN. . . . . . . . . . . . . . . . . . . 8 5.2CID URI Scheme Example. . . . . . . . . . . . . . . . . . . 9 5.3Resolvingを使用する例. . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1のAnの例、HTTP URI Scheme. . . . . . . . . . . . . . . . 11 6 注意. . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7。 IANA問題. . . . . . . . . . . . . . . . . . . . 12 8。 セキュリティ問題. . . . . . . . . . . . . . . . . . 12 9。 承認. . . . . . . . . . . . . . . . . . . . . . 13参照. . . . . . . . . . . . . . . . . . . . . . . . . 13付録A: 中間コード. . . . . . . . . . . . . . . . . . 15作者のアドレスの.17の完全な著作権宣言文. . . . . . . . . . . . . . . . . . 18
1. Introduction
1. 序論
The Dynamic Delegation Discovery System (DDDS) is used to implement lazy binding of strings to data, in order to support dynamically configured delegation systems. The DDDS functions by mapping some unique string to data stored within a DDDS Database by iteratively applying string transformation rules until a terminal condition is reached.
Dynamic DelegationディスカバリーSystem(DDDS)はストリングの怠惰な結合をデータに実行するのに使用されます、ダイナミックに構成された代表団システムをサポートするために。DDDSは、末期的状態に達するまでストリング変換規則を適用しながらDDDS Databaseの中に繰り返しによって格納されたデータに何らかのユニークなストリングを写像することによって、機能します。
This document describes a DDDS Application for resolving Uniform Resource Identifiers (URI). It does not define the DDDS Algorithm or a Database. The entire series of documents that do so are specified in "Dynamic Delegation Discovery System (DDDS) Part One: The Comprehensive DDDS" (RFC 3401) [1]. It is very important to note that it is impossible to read and understand any document in that series without reading the related documents.
このドキュメントは、Uniform Resource Identifier(URI)を決議するためにDDDS Applicationについて説明します。 それはDDDS AlgorithmかDatabaseを定義しません。 そうするドキュメントのシリーズもの全巻は指定されて、「ダイナミックな代表団発見システム(DDDS)は1つを分ける」ということです。 「包括的なDDDS」(RFC3401)[1]。 関連するドキュメントを読まないでそのシリーズでどんなドキュメントも読んで、理解しているのが不可能であることに注意するのは非常に重要です。
Uniform Resource Identifiers (URI) have been a significant advance in retrieving Internet-accessible resources. However, their brittle nature over time has been recognized for several years. The Uniform Resource Identifier working group proposed the development of Uniform Resource Names (URN) [8] to serve as persistent, location-independent identifiers for Internet resources in order to overcome most of the problems with URIs. RFC 1737 [6] sets forth requirements on URNs.
Uniform Resource Identifier(URI)はインターネットアクセス可能なリソースを検索することにおいて重要な進歩です。 しかしながら、時間がたつにつれての彼らのもろい本質は数年間認識されています。 Uniform Resource Identifierワーキンググループは、URIに関する問題の大部分を克服するためにインターネット資料のためのしつこくて、位置から独立している識別子として機能するようにUniform Resource Names(URN)[8]の開発を提案しました。 RFC1737[6]はURNsに先へ必要条件を定めます。
During the lifetime of the URI-WG, a number of URN proposals were generated. The developers of several of those proposals met in a series of meetings, resulting in a compromise known as the Knoxville framework. The major principle behind the Knoxville framework is that the resolution system must be separate from the way names are assigned. This is in marked contrast to most URIs, which identify the host to contact and the protocol to use. Readers are referred to [7] for background on the Knoxville framework and for additional information on the context and purpose of this proposal.
URI-WGの生涯、多くのURN提案が発生しました。 それらのいくつかの提案の開発者は一連のミーティングで会いました、ノクスビル枠組みとして知られている妥協をもたらして。 ノクスビル枠組みの後ろの主要な原則は解決システムが名前が割り当てられる方法から別々であるに違いないということです。 これはほとんどのURIと著しい対照をなしてあります。URIは連絡するホストと使用するプロトコルを特定します。 読者はノクスビル枠組みに関するバックグラウンドと文脈に関する追加情報とこの提案の目的のための[7]を参照されます。
Mealling Standards Track [Page 2] RFC 3404 DDDS Based URI Resolution October 2002
URI解決2002年10月に基づいた標準化過程[2ページ]RFC3404DDDSを荒びきにします。
Separating the way names are resolved from the way they are constructed provides several benefits. It allows multiple naming approaches and resolution approaches to compete, as it allows different protocols and resolvers to be used. There is just one problem with such a separation - how do we resolve a name when it can't give us directions to its resolver?
それらが組み立てられる方法から名前が決議されている方法で分離するのはいくつかの利益を提供します。 それで、異なったプロトコルとレゾルバが使用されるのを許容するとき、複数の命名アプローチと解決アプローチは競争します。 そのような分離に関するちょうど1つの問題があります--それがレゾルバへの指示を私たちに与えることができないとき、私たちはどのように名前を決議しますか?
For the short term, the Domain Name System (DNS) is the obvious candidate for the resolution framework, since it is widely deployed and understood. However, it is not appropriate to use DNS to maintain information on a per-resource basis. First of all, DNS was never intended to handle that many records. Second, the limited record size is inappropriate for catalog information. Third, domain names are not appropriate as URNs.
短期的に、ドメインネームシステム(DNS)は解決枠組みの明白な候補です、それが広く配備されて、理解されているので。 しかしながら、1リソースあたり1個のベースの情報を保守するのにDNSを使用するのは適切ではありません。 まず、DNSがそんなに多くの記録を扱うことを決して意図しませんでした。 2番目に、カタログ情報には、限られたレコード・サイズは不適当です。 3番目に、ドメイン名はURNsとして適切ではありません。
Therefore our approach is to use the DDDS to locate "resolvers" that can provide information on individual resources, potentially including the resource itself. To accomplish this, we "rewrite" the URI into a Key following the rules found in the DDDS. This document describes URI Resolution as an application of the DDDS and specifies the use of at least one Database based on DNS.
したがって、私たちのアプローチは個々のリソースの情報を提供できる「レゾルバ」の場所を見つけるのにDDDSを使用することです、潜在的にリソース自体を含んでいて。 これを達成するために、DDDSで見つけられた規則に従って、私たちはURIをKeyに「書き直します」。 このドキュメントは、DDDSのアプリケーションとしてURI Resolutionを記述して、DNSに基づく少なくとも1Databaseの使用を指定します。
2. Terminology
2. 用語
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
キーワード“MUST"、「必須NOT」が「必要です」、“SHALL"、「」、“SHOULD"、「「推薦され」て、「5月」の、そして、「任意」のNOTはRFC2119で説明されるように本書では解釈されることであるべきです。
All capitalized terms are taken from the vocabulary found in the DDDS algorithm specification found in RFC 3403 [3].
すべての大文字で書かれた用語がRFC3403[3]で見つけられたDDDSアルゴリズム仕様で見つけられたボキャブラリーからかかります。
3. The Distinction Between URNs and URIs
3. つぼとURIの区別
From the point of view of this system, there is no theoretical difference between resolving URIs in the general case and URNs in the specific case. Operationally however, there is a difference that stems from URI resolution possibly not becoming of widespread use. If URN resolution is collapsed into generic URI resolution, URNs may suffer by the lack of adoption of URI resolution.
このシステムの観点から、一般的なケースとURNsでURIを決議するとき、どんな理論上の違いも特定の場合で来ていません。 ことによると普及使用を一体どうならせないURI解決による違いが操作上あります。 URN解決が一般的なURI解決まで潰されているなら、URNsはURI解決の採用の不足で苦しむかもしれません。
The solution is to allow for shortcutting for URN resolution. In the following specification generic URI resolution starts by inserting rules for known URI schemes into the 'uri.arpa.' registry. For the 'URN:' URI scheme, one of the rules found in 'uri.arpa.' would be for the 'urn' URI scheme. This rule would simply delegate to the 'urn.arpa.' zone for additional NAPTRs based on the URN namespace. Essentially, the URI Resolution Rewrite Rule for 'URN:' is the URN Resolution Application's First Well Known Rule.
解決策はURN解決のためにshortcuttingすると考慮することです。 以下の仕様ジェネリックURI解決では、知られているURI計画のために'uri.arpa'に規則を挿入することによって. 登録は始まっています。 規則の1つによって、'uri.arpa'でURN: 'URIが計画するのがわかりました。''つぼには、あるだろう'URIを、計画してください。 この規則は単に'urn.arpa'に委任するでしょう。追加NAPTRsのためのゾーンはURN名前空間を基礎づけました。 本質的には、'URNのためのURI Resolution Rewrite Rule: 'URN Resolution ApplicationのものはFirst Well Known Ruleですか?
Mealling Standards Track [Page 3] RFC 3404 DDDS Based URI Resolution October 2002
URI解決2002年10月に基づいた標準化過程[3ページ]RFC3404DDDSを荒びきにします。
Therefore, this document specifies two DDDS Applications. One is for URI Resolution and the other is for URN Resolution. Both are technically identical but by separating the two URN Resolution can still proceed without the dependency.
したがって、このドキュメントは2DDDS Applicationsを指定します。 1つはURI Resolutionのためのものです、そして、もう片方がURN Resolutionのためのものです。 両方が技術的に同じですが、二人を引き離すことによって、URN Resolutionは依存なしでまだ続くことができます。
4. The URI and URN Resolution Application Specifications
4. URIとつぼの解決アプリケーション仕様
This template defines the URI and URN Resolution DDDS Application according to the rules and requirements found in [3]. The DDDS database used by this Application is found in [4] which is the document that defines the Naming Authority Pointer (NAPTR) DNS Resource Record (RR) type.
[3]で見つけられた規則と要件に従って、このテンプレートはURIとURN Resolution DDDS Applicationを定義します。 このApplicationによって使用されたDDDSデータベースはNaming Authority Pointer(NAPTR)DNS Resource Record(RR)タイプを定義するドキュメントである[4]で見つけられます。
4.1 Application Unique String
4.1 アプリケーションのユニークなストリング
The Application Unique String is the URI or URN for which an authoritative server is being located. This URI or URN MUST be canonicalized and hex encoded according to the "absolute-uri" production found in the Collected ABNF from RFC 2396 [15].
Application Unique Stringは正式のサーバが見つけられているURIかURNです。 いてください。このURIかURN MUST、Collected ABNFでRFC2396[15]から見つけられた「絶対uri」生産に従ってコード化されて、canonicalizedして、魔法をかけます。
4.2 First Well Known Rule
4.2/1によく知られている規則
In the URI case, the first known key is created by taking the URI scheme. In the URN case, the first known key is the Namespace Identifier. For example, the URI 'http://www.example.com/' would have a 'http' as its Key. The URN 'urn:foo:foospace' would have 'foo' as its first Key.
URI場合では、最初の知られているキーは、URI計画を取ることによって、作成されます。 URN場合では、最初の知られているキーはNamespace Identifierです。 例えば、URI' http://www.example.com/ 'には、Keyとして'http'があるでしょう。 URN'つぼ:foo:foospace'には、最初のKeyとして'foo'があるでしょう。
4.3 Flags
4.3個の旗
At this time only four flags, "S", "A", "U", and "P", are defined. The "S", "A" and "U" flags are for a terminal lookup. This means that the Rule is the last one and that the flag determines what the next stage should be. The "S" flag means that the output of this Rule is a domain-name for which one or more SRV [9] records exist. See Section 5 for additional information on how URI and URN Resolution use the SRV record type. "A" means that the output of the Rule is a domain-name and should be used to lookup either A, AAAA, or A6 records for that domain. The "U" flag means that the output of the Rule is a URI [15].
このとき、「S」、「A」、「U」、および「P」という4個の旗だけが、定義されます。 旗がある「S」、「A」、および「u」a端末のルックアップ。 これは、Ruleが最後のものであり、旗が、次のステージが何であるべきであるかを決定することを意味します。 「S」旗は、この規則の出力が1つ以上のSRV[9]記録が存在するドメイン名であることを意味します。 URIとURN ResolutionがどうSRVレコード種類を使用するかに関する追加情報に関してセクション5を見てください。 「A」は、Ruleの出力がドメイン名であることを意味して、A、AAAA、またはA6がそのドメインに記録するルックアップに使用されるべきです。 「U」旗は、規則の出力がURI[15]であることを意味します。
The "P" flag says that the remainder of the DDDS Algorithm is ignored and that the rest of the process is application specific and outside the scope of this document. An application can use the Protocol part found in the Services field to identify which Application specific set of rules that should be followed next. The record that contains the 'P' flag is the last record that is interpreted by the rules in this document. One might think that this would also make the "P"
「P」旗は、DDDSアルゴリズムの残りが無視されて、過程の残りがアプリケーション特有であると言って、このドキュメントの範囲の外でそうします。 アプリケーションは次に、従われるべきであるどのApplicationの特定のセットの規則を特定するかためにServices野原で発見されるプロトコル一部を使用できます。 'P'旗を含む記録は規則で本書では解釈される最後の記録です。 人は、また、これが「P」になると思うかもしれません。
Mealling Standards Track [Page 4] RFC 3404 DDDS Based URI Resolution October 2002
URI解決2002年10月に基づいた標準化過程[4ページ]RFC3404DDDSを荒びきにします。
flag an indicator of a terminal lookup but this would be incorrect since a "terminal" Rule is a DDDS concept and this flag indicates that anything after this rule does not adhere to DDDS concepts at all.
端末のルックアップのインディケータに旗を揚げさせなさい、ただし、「端末」のRuleがDDDS概念であり、この規則が全くDDDS概念を固く守らなかった後にこの旗がその何でも示すので、これは不正確でしょう。
The remaining alphabetic flags are reserved for future versions of this specification. The numeric flags may be used for local experimentation. The S, A, U and P flags are all mutually exclusive, and resolution libraries MAY signal an error if more than one is given. (Experimental code and code for assisting in the creation of Rewrite Rules would be more likely to signal such an error than a client such as a browser.) It is anticipated that multiple flags will be allowed in the future, so implementers MUST NOT assume that the flags field can only contain 0 or 1 characters. Finally, if a client encounters a record with an unknown flag, it MUST ignore it and move to the next Rule. This test takes precedence over any ordering since flags can control the interpretation placed on fields. A novel flag might change the interpretation of the regexp and/or replacement fields such that it is impossible to determine if a record matched a given target.
残っているアルファベット旗はこの仕様の将来のバージョンのために予約されます。 数値旗は地方の実験に使用されるかもしれません。 S、A、U、およびP旗はすべて互いに排他的です、そして、1つ以上を与えるなら、解決ライブラリは誤りを示すかもしれません。 (Rewrite Rulesの創造を助けるための実験コードとコードはブラウザなどのクライアントよりそのような誤りに合図しそうでしょう。) implementersが、旗の分野が0か1文字しか含むことができないと仮定してはいけなくて、複数の旗が将来許容されると予期されます。 最終的に、未知の旗でクライアントが記録に遭遇するなら、それは、それを無視して、次のRuleに動かなければなりません。 旗がフィールドに置かれた解釈を制御できるので、このテストはどんな注文の上でも優先します。 目新しい旗がregexp、そして/または、交換分野の解釈を変えるかもしれないので、記録が与えられた目標に合っていたかどうか決定するのは不可能です。
The "S", "A", and "U" flags are called 'terminal' flags since they halt the looping DDDS algorithm. If those flags are not present, clients may assume that another Rule exists at the Key produced by the current Rewrite Rule.
ループDDDSアルゴリズムを止めるので、「S」、「」 「旗が呼ばれるU」'端末'は弛みます。 それらの旗が存在していないなら、クライアントは、別のRuleが現在のRewrite Ruleによって生産されたKeyに存在すると仮定するかもしれません。
4.4 Services Parameters
4.4 サービスパラメタ
Service Parameters for this Application take the form of a string of characters that follow this ABNF:
このApplicationのためのサービスParametersはこのABNFの後をつける一連のキャラクタの形を取ります:
service_field = [ [protocol] *("+" rs)]
protocol = ALPHA *31ALPHANUM
rs = ALPHA *31ALPHANUM
; The protocol and rs fields are limited to 32
; characters and must start with an alphabetic.
サービス_分野=[[プロトコル]*(「+」 rs)]プロトコル=アルファ*31ALPHANUM rsはアルファ*31ALPHANUMと等しいです。 プロトコルとrs分野は32に制限されます。 キャラクタと必須が始まる、アルファベットです。
In other words, an optional protocol specification followed by 0 or more resolution services. Each resolution service is indicated by an initial '+' character.
言い換えれば、0つ以上の解決サービスで任意のプロトコル仕様は従いました。 各解決サービスは初期の'+'キャラクタによって示されます。
Mealling Standards Track [Page 5] RFC 3404 DDDS Based URI Resolution October 2002
URI解決2002年10月に基づいた標準化過程[5ページ]RFC3404DDDSを荒びきにします。
The empty string is also valid. This will typically be seen at the beginning of a series of Rules, when it is impossible to know what services and protocols will be offered at the end of a particular delegation path.
また、空のストリングも有効です。 これは一連のRulesの始めに通常見られるでしょう。(その時、どんなサービスとプロトコルが特定の代表団経路の端で提供されるかを知るのは不可能です)。
4.4.1 Services
4.4.1 サービス
The service identifiers that make up the 'rs' production are generic for both URI and URN resolution since the input value types itself based on the URI scheme. The list of valid services are defined in [11].
入力値がURI計画に基づいてそれ自体をタイプするので、URIとURN解決の両方に、'rs'生産を作るサービス識別子は一般的です。 有効にサービスのリストは[11]で定義されます。
Examples of some of these services are:
これらのサービスのいくつかに関する例は以下の通りです。
I2L: given a URI return one URI that identifies a location where the
original URI can be found.
I2L: URIを考えて、オリジナルのURIを見つけることができる位置を特定する1つのURIを返してください。
I2Ls: given a URI return one or more URIs that identify multiple
locations where the original URI can be found.
I2Ls: URIを考えて、オリジナルのURIを見つけることができる複数の所在地を特定する1つ以上のURIを返してください。
I2R: given a URI return one instance of the resource identified by
that URI.
I2R: URIを考えて、そのURIによって特定されたリソースの1つの例を返してください。
I2Rs: given a URI return one or more instances of the resources
identified by that URI.
I2Rs: URIを考えて、そのURIによって特定されたリソースの1つ以上の例を返してください。
I2C: given a URI return one instance of a description of that
resource.
I2C: URIを考えて、そのリソースの記述の1つの例を返してください。
I2N: given a URI return one URN that names the resource (Caution:
equality with respect to URNs is non-trivial. See [6] for
examples of why.)
I2N: URIを考えて、リソースを命名する1URNを返してください。(警告: URNsに関する平等は重要です。 例のための[6]を見る、なぜです。)
4.4.2 Protocols
4.4.2 プロトコル
The protocol identifiers that are valid for the 'protocol' production MUST be defined by documents that are specific to URI resolution. At present the THTTP [10] protocol is the only such specification.
URI解決に特定のドキュメントで'プロトコル'生産に、有効なプロトコル識別子を定義しなければなりません。 現在のところ、THTTP[10]プロトコルは唯一のそのような仕様です。
It is extremely important to realize that simply specifying any protocol in the services field is insufficient since there are additional semantics surrounding URI resolution that are not defined within the protocols. For example, if Z39.50 were to be specified as a valid protocol it would have to additionally define how it would encode requests for specific services, how the URI is encoded, and what information is returned.
そこ以来単にサービス分野のどんなプロトコルも指定するのが不十分であるとわかるために非常に重要であるのが、プロトコルの中で定義されない意味論の追加周辺URI解決であるということです。 例えば、Z39.50が有効なプロトコルとして指定されることになっているなら、それは、どのように特定のサービスを求める要求をコード化するか、そして、URIがどのようにコード化されるか、そして、どんな情報が返されるかをさらに、定義しなければならないでしょうに。
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4.4.3 Applicability of Services
4.4.3 サービスの適用性
Since it is possible for there to be a complex set of possible protocols and services a client application may often need to apply a more complex decision making process to a set of records than simply matching on an ordered list of protocols. For example, if there are 4 rules that are applicable the last one may have a more desirable Service field than the first. But since the client may be satisfied by the first it will never know about the 4th one which may be 'better'.
以来、そこに、クライアントアプリケーションがしばしばより複雑な意志決定の過程を1セットの記録に適用する必要があるかもしれない複雑な可能なプロトコルの、そして、サービスのセットであることはプロトコルの規則正しいリストで単に合っているより可能です。 例えば、4つの適切な規則があれば、最後の1番目より望ましいService分野があるかもしれません。 しかし、クライアントが1日までに満足するかもしれないので、それは4番目の'より良いかもしれない'ものに関して決して知らないでしょう。
To mitigate this the client may want to slightly modify the DDDS algorithm (for this application only!) in order to determine if more applicable protocols/services exist. This can safely be done for this application by using a more complex interaction between steps 3 and 4 of the DDDS algorithm in order to find the optimal path to follow. For example, once a client has found a rule who's Substitution Expression produces a result and who's Service description is acceptable, it may make note of this but continue to look at further rules that apply (all the while adhering to the Order!) in order to find a better one. If none are found it can use the one it made note of.
これを緩和するように、クライアントは、より適用されるプロトコル/サービスが存在するかどうか決定するように、DDDSアルゴリズム(このアプリケーションだけのための!)をわずかに変更したがっているかもしれません。 このアプリケーションのために続くように最適経路を見つけるのにDDDSアルゴリズムのステップ3と4の間の、より複雑な相互作用を使用することによって、安全にこれができます。 より良いものを見つけるために例えば、クライアントがいったん規則を見つける後、だれがSubstitution Expressionであるかは結果を生んで、だれがService記述であるかは許容できますが、このメモを作るかもしれませんが、ずっと適用されるさらなる規則を見てください(ずっとOrderを固く守ります!)。 なにも見つけられないなら、それはメモを作ったものを使用できます。
Keep in mind that in order for this to remain safe, the input to step 3 and the output of step 4 MUST be identical to the basic algorithm. The client software MUST NOT attempt to do this optimization outside a specific set of Rewrite Rules (i.e., across delegation paths).
ステップ3への入力とステップ4の出力がこれが安全なままで残るように基本的なアルゴリズムと同じでなければならないことを覚えておいてください。 クライアントソフトウェアは、Rewrite Rules(すなわち、代表団経路の向こう側の)の特定のセットの外でこの最適化をするのを試みてはいけません。
4.5 Valid Databases
4.5 有効なデータベース
At present only one DDDS Database is specified for this Application. "Dynamic Delegation Discovery System (DDDS) Part Three: The Domain Name System (DNS) Database" (RFC 3403) [4] specifies a DDDS Database that uses the NAPTR DNS resource record to contain the rewrite rules. The Keys for this database are encoded as domain-names.
現在のところ、1DDDS DatabaseだけがこのApplicationに指定されます。 「ダイナミックな代表団発見システム(DDDS)パートThree:」 「ドメインネームシステム(DNS)データベース」(RFC3403)[4]は書換規則を含むのにNAPTR DNSリソース記録を使用するDDDS Databaseを指定します。 このデータベースのためのキーズはドメイン名としてコード化されます。
The output of the First Well Known Rule for the URI Resolution Application is the URI's scheme. In order to convert this to a unique key in this Database the string '.uri.arpa.' is appended to the end. This domain-name is used to request NAPTR records which produces new keys in the form of domain-names.
URI Resolution ApplicationのためのFirst Well Known Ruleの出力はURIの計画です。 a特有にこれを変換するためにこのDatabaseでストリング'.uri.arpaを合わせてください。. '終わりまで追加します。 このドメイン名は、NAPTRが、どれがドメイン名の形で新しいキーを生産するかを記録するよう要求するのに使用されます。
The output of the First Well Known Rule of the URN Resolution Application is the URN's namespace id. In order to convert this to a unique key in this Database the string '.urn.arpa.' is appended to the end. This domain-name is used to request NAPTR records which produces new keys in the form of domain-names.
URN Resolution ApplicationのFirst Well Known Ruleの出力はURNの名前空間イドです。 a特有にこれを変換するためにこのDatabaseでストリング'.urn.arpaを合わせてください。. '終わりまで追加します。 このドメイン名は、NAPTRが、どれがドメイン名の形で新しいキーを生産するかを記録するよう要求するのに使用されます。
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DNS servers MAY interpret Flag values and use that information to include appropriate SRV and A records in the Additional Information portion of the DNS packet. Clients are encouraged to check for additional information but are not required to do so. See the Additional Information Processing section of RFC 3404 for more information on NAPTR records and the Additional Information section of a DNS response packet.
DNSサーバは、DNSパケットのAdditional情報部分に適切なSRVとA記録を含むのにFlag値を解釈して、その情報を使用するかもしれません。 クライアントは、追加情報がないかどうかチェックするよう奨励されますが、そうする必要はありません。 NAPTR記録に関する詳しい情報のためのRFC3404のAdditional情報Processing部とDNS応答パケットのAdditional情報部を見てください。
The character set used to encode the substitution expression is UTF-8. The allowed input characters are all those characters that are allowed anywhere in a URI. The characters allowed to be in a Key are those that are currently defined for DNS domain-names. The "i" flag to the substitution expression is used to denote that, where appropriate for the code points in question, any matches should be done in a case-insensitive way.
代替表現をコード化するのに使用される文字の組はUTF-8です。 許容入力キャラクタは皆URIでどこでも許容されているそれらのキャラクタです。 Keyにあることができたキャラクタは現在DNSドメイン名のために定義されるものです。 代替表現への「i」旗は、問題のコード・ポイントに適切であるところでは、大文字と小文字を区別しない方法でどんなマッチもするべきであるのを指示するのに使用されます。
5. Examples
5. 例
5.1 An Example Using a URN
5.1 つぼを使用する例
Consider a URN that uses the hypothetical FOO namespace. FOO numbers are identifiers for approximately 30 million registered businesses around the world, assigned and maintained by Fred, Otto and Orvil, Inc. The URN might look like:
仮定しているFOO名前空間を使用するURNを考えてください。 FOO番号はURNが似るかもしれないフレッド、オットー、およびOrvil Inc.によって割り当てられて、維持された世界の周りのおよそ3000万の登録されたビジネスのための識別子です:
urn:foo:002372413:annual-report-1997
つぼ:foo:002372413: 年に一度のレポート1997
The first step in the resolution process is to find out about the FOO namespace. The namespace identifier [8], "foo", is extracted from the URN and prepended to '.urn.arpa.', producing 'foo.urn.arpa.'. The DNS is queried for NAPTR records for this domain which produces the following results:
解決の過程による第一歩はFOO名前空間を見つけることです。 名前空間識別子[8]"foo"がURNから抽出されて、'.urn.arpa'にprependedされる、'foo.urn.arpa'を生産します。 DNSは以下の結果を生むこのドメインのためのNAPTR記録のために質問されます:
foo.urn.arpa. ;; order pref flags service regexp replacement IN NAPTR 100 10 "s" "foolink+I2L+I2C" "" foolink.udp.example.com. IN NAPTR 100 20 "s" "rcds+I2C" "" rcds.udp.example.com. IN NAPTR 100 30 "s" "thttp+I2L+I2C+I2R" "" thttp.tcp.example.com.
foo.urn.arpa。 ;; オーダーprefがサービスregexp交換IN NAPTR100 10「s」「foolink+I2L+I2C」に旗を揚げさせる、「「foolink.udp.example.com。」 IN NAPTR100 20「s」「rcds+I2C」、「「rcds.udp.example.com。」 IN NAPTR100 30「s」「thttp+I2L+I2C+I2R」、「「thttp.tcp.example.com。」
The order field contains equal values, indicating that no order has to be followed. The preference field indicates that the provider would like clients to use the special 'foolink' protocol, followed by the RCDS protocol, and that THTTP is offered as a last resort. All the records specify the "s" flag which means that the record is terminal and that the next step is to retrieve an SRV record from DNS for the given domain-name.
オーダーに全く従ってはいけないのを示して、オーダー分野は等しい値を含んでいます。 選択領域は、RCDSプロトコルがあとに続いた特別な'foolink'プロトコルを使用するためにプロバイダーがクライアントのようにそうするのを示します、そして、そのTHTTPは最後の手段として申し出られます。 すべての記録が次のステップが記録が端末であり、与えられたドメイン名のためにDNSからのSRV記録を検索することであることを意味する「s」旗を、指定します。
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The service fields say that if we speak of foolink, we will be able to issue either the I2L, I2C or I2R requests to obtain a URI or ask some complicated questions about the resource. The Resource Cataloging and Distribution Service (RCDS) [12] could be used to get some metadata for the resource, while THTTP could be used to get a URI for the current location of the resource.
サービス分野は、私たちがI2L、I2CまたはI2RがURIを得るよう要求するどちらかを発行するか、またはfoolinkについて話すと、リソースに関するいくつかの難問を尋ねることができると言います。 リソースのための何らかのメタデータを得るのにResource CatalogingとDistribution Service(RCDS)[12]を使用できました、リソースの現在の位置にURIを届けるのにTHTTPを使用できましたが。
Assuming our client does not know the foolink protocol but does know the RCDS protocol, our next action is to lookup SRV RRs for rcds.udp.example.com, which will tell us hosts that can provide the necessary resolution service. That lookup might return:
私たちのクライアントがfoolinkプロトコルを知りませんが、RCDSプロトコルを知っていると仮定して、rcds.udp.example.comのためのルックアップSRV RRsには私たちの次の動作があります。(rcds.udp.example.comは私たち必要な解決サービスを提供できるホストに言うでしょう)。 そのルックアップは戻るかもしれません:
;; Pref Weight Port Target
rcds.udp.example.com IN SRV 0 0 1000 deffoo.example.com.
IN SRV 0 0 1000 dbexample.com.au.
IN SRV 0 0 1000 ukexample.com.uk.
;; Pref Weight Port Target rcds.udp.example.com IN SRV0 0 1000deffoo.example.com。 IN SRV0 0 1000dbexample.com.au。 IN SRV0 0 1000ukexample.com.uk。
telling us three hosts that could actually do the resolution, and giving us the port we should use to talk to their RCDS server. (The reader is referred to the SRV specification [9] for the interpretation of the fields above.)
彼らのRCDSサーバと話すように私たち実際に解決ができた3人のホストと、ポートを私たちに与えるのに私たちが使用するべきである言います。(読者は上の分野の解釈のためのSRV仕様[9]を参照されます。)
There is opportunity for significant optimization here. RFC 3404 defines that Additional Information section may be available. In this case the the SRV records may be returned as additional information for terminal NAPTRs lookups (as well as the A records for those SRVs). This is a significant optimization. In conjunction with a long TTL for *.urn.arpa. records, the average number of probes to DNS for resolving most URIs would approach one.
重要な最適化の機会がここにあります。 RFC3404はそれを定義します。Additional情報部は利用可能であるかもしれません。 この場合、端末のNAPTRsルックアップ(それらのSRVsのためのA記録と同様に)のための追加情報としてSRV記録を返すかもしれません。 これは重要な最適化です。 *.urn.arpa記録のための長いTTLに関連して、ほとんどのURIを決議するためのDNSへの徹底的調査の平均した数は1つにアプローチするでしょう。
Note that the example NAPTR records above are intended to represent the result of a NAPTR lookup using some client software like nslookup; zone administrators should consult the documentation accompanying their domain name servers to verify the precise syntax they should use for zone files.
上記の記録が意図する例のNAPTRがnslookupのような何らかのクライアントソフトウェアを使用するNAPTRルックアップの結果を表すことに注意してください。 ゾーンの管理者はそれらがゾーンファイルに使用するべきである正確な構文について確かめるために彼らのドメイン名サーバに伴うドキュメンテーションを参照するべきです。
Also note that there could have been an additional first step where the URN was resolved as a generic URI by looking up urn.uri.arpa. The resulting rule would have specified that the NID be extracted from the URN and '.urn.arpa.' appended to it resulting in the new key 'foo.urn.arpa.' which is the first step from above.
また、追加第一歩がURNが一般的なURIとしてurn.uri.arpaを見上げることによって決議されたところにあったかもしれないことに注意してください。 . '上から第一歩である。結果として起こる規則は、NIDがURNと'.urn.arpa'から抽出されると指定したでしょう。新しさをもたらしながらそれに追加して、'foo.urn.arpaを合わせてください。
5.2 CID URI Scheme Example
5.2 Cid URI計画の例
Consider a URI scheme based on MIME Content-Ids. The URI might look like this:
MIME Content-イドに基づくURI計画を考えてください。 URIはこれに似るかもしれません:
cid:199606121851.1@bar.example.com
Cid: 199606121851.1@bar.example.com
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(Note that this example is chosen for pedagogical purposes, and does not conform to the CID URI scheme.)
(この例が教育学の目的に選ばれていて、CID URI計画に従わないことに注意してください。)
The first step in the resolution process is to find out about the CID scheme. The scheme is extracted from the URI, prepended to '.uri.arpa.', and the NAPTR for 'cid.uri.arpa.' looked up in the DNS. It might return records of the form:
解決の過程による第一歩はCID計画を見つけることです。 計画は'cid.uri.arpaのために'.uri.arpa'NAPTRにprependedされたURIから抽出されます。. 'DNSを調べました。 それはフォームに関する記録を返すかもしれません:
cid.uri.arpa. ;; order pref flags service regexp replacement IN NAPTR 100 10 "" "" "!^cid:.+@([^\.]+\.)(.*)$!\2!i" .
cid.uri.arpa。 ;; order pref flags service regexp replacement IN NAPTR 100 10 "" "" "!^cid:.+@([^\.]+\.)(.*)$!\2!i" .
Since there is only one record, ordering the responses is not a problem. The replacement field is empty, so the pattern provided in the regexp field is used. We apply that regexp to the entire URI to see if it matches, which it does. The \2 part of the substitution expression returns the string "example.com". Since the flags field is empty, the lookup is not terminal and our next probe to DNS is for more NAPTR records where the new domain is 'example.com'.
1つの記録しかないので、応答を命令するのは、問題ではありません。 交換分野が人影がないので、regexp分野に提供されたパターンは使用されています。 私たちはそれが合っているかどうかを見る全体のURIにそのregexpを適用します。(それはそれをします)。 代替表現の2円の部分がストリング"example.com"を返します。 旗以来、分野は人影がありません、そして、ルックアップは端末ではありません、そして、DNSへの私たちの次の徹底的調査は、より多くのNAPTR記録のために新しいドメインが'example.com'であるところにあります。
Note that the rule does not extract the full domain name from the CID, instead it assumes the CID comes from a host and extracts its domain. While all hosts, such as 'bar', could have their very own NAPTR, maintaining those records for all the machines at a site could be an intolerable burden. Wildcards are not appropriate here since they only return results when there is no exactly matching names already in the system.
規則がCIDから完全なドメイン名を抜粋しないというメモ、代わりに、それはCIDがホストから来て、ドメインを抽出すると仮定します。 'バー'などのすべてのホストがそれら自身のNAPTRを持つことができた間、サイトのすべてのマシンのためのそれらの記録を保守するのは、耐えられない重荷であるかもしれません。 まさに既にシステムで名前を合わせてはいけないときだけ、結果を返すので、ワイルドカードはここで適切ではありません。
The record returned from the query on "example.com" might look like:
"example.com"における質問から返された記録に似るかもしれません:
example.com. ;; order pref flags service regexp replacement IN NAPTR 100 50 "s" "z3950+I2L+I2C" "" z3950.tcp.example.com. IN NAPTR 100 50 "s" "rescap+I2C" "" rescap.udp.example.com. IN NAPTR 100 50 "s" "thttp+I2L+I2C+I2R" "" thttp.tcp.example.com.
example.com. ;; order pref flags service regexp replacement IN NAPTR 100 50 "s" "z3950+I2L+I2C" "" z3950.tcp.example.com. IN NAPTR 100 50 "s" "rescap+I2C" "" rescap.udp.example.com. IN NAPTR 100 50 "s" "thttp+I2L+I2C+I2R" "" thttp.tcp.example.com.
Continuing with the example, note that the values of the order fields are equal for all records, so the client is free to pick any record. The Application defines the flag 's' to mean a terminal lookup and that the output of the rewrite will be a domain-name for which an SRV record should be queried. Once the client has done that, it has the following information: the host, port, the protocol, and the services available via that protocol. Given these bits of information the client has enough to be able to contact that server and ask it questions about the cid URI.
Continuing with the example, note that the values of the order fields are equal for all records, so the client is free to pick any record. The Application defines the flag 's' to mean a terminal lookup and that the output of the rewrite will be a domain-name for which an SRV record should be queried. Once the client has done that, it has the following information: the host, port, the protocol, and the services available via that protocol. Given these bits of information the client has enough to be able to contact that server and ask it questions about the cid URI.
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Recall that the regular expression used \2 to extract a domain name from the CID, and \. for matching the literal '.' characters separating the domain name components. Since '\' is the escape character, literal occurrences of a backslash must be escaped by another backslash. For the case of the cid.uri.arpa record above, the regular expression entered into the master file should be "!^cid:.+@([^\\.]+\\.)(.*)$!\\2!i". When the client code actually receives the record, the pattern will have been converted to "!^cid:.+@([^\.]+\.)(.*)$!\2!i".
Recall that the regular expression used \2 to extract a domain name from the CID, and \. for matching the literal '.' characters separating the domain name components. Since '\' is the escape character, literal occurrences of a backslash must be escaped by another backslash. For the case of the cid.uri.arpa record above, the regular expression entered into the master file should be "!^cid:.+@([^\\.]+\\.)(.*)$!\\2!i". When the client code actually receives the record, the pattern will have been converted to "!^cid:.+@([^\.]+\.)(.*)$!\2!i".
5.3 Resolving an HTTP URI Scheme
5.3 Resolving an HTTP URI Scheme
Even if URN systems were in place now, there would still be a tremendous number of host based URIs. It should be possible to develop a URI resolution system that can also provide location independence for those URIs.
Even if URN systems were in place now, there would still be a tremendous number of host based URIs. It should be possible to develop a URI resolution system that can also provide location independence for those URIs.
Assume we have the URI for a very popular piece of software that the publisher wishes to mirror at multiple sites around the world:
Assume we have the URI for a very popular piece of software that the publisher wishes to mirror at multiple sites around the world:
http://www.example.com/software/latest-beta.exe
http://www.example.com/software/latest-beta.exe
We extract the prefix, "http", and lookup NAPTR records for 'http.uri.arpa.'. This might return a record of the form:
We extract the prefix, "http", and lookup NAPTR records for 'http.uri.arpa.'. This might return a record of the form:
http.uri.arpa. IN NAPTR
;; order pref flags service regexp replacement
100 90 "" "" "!^http://([^/:]+)!1!i" .
http.uri.arpa. IN NAPTR ;; order pref flags service regexp replacement 100 90 "" "" "!^http://([^/:]+)!1!i" .
This expression returns everything after the first double slash and before the next slash or colon. (We use the '!' character to delimit the parts of the substitution expression. Otherwise we would have to use backslashes to escape the forward slashes, and would have a regexp in the zone file that looked like this: "/^http:\\/\\/([^\\/:]+)/\\1/i").
This expression returns everything after the first double slash and before the next slash or colon. (We use the '!' character to delimit the parts of the substitution expression. Otherwise we would have to use backslashes to escape the forward slashes, and would have a regexp in the zone file that looked like this: "/^http:\\/\\/([^\\/:]+)/\\1/i").
Applying this pattern to the URI extracts "www.example.com". Looking up NAPTR records for that might return:
Applying this pattern to the URI extracts "www.example.com". Looking up NAPTR records for that might return:
www.example.com.
;; order pref flags service regexp replacement
IN NAPTR 100 100 "s" "thttp+L2R" "" thttp.example.com.
IN NAPTR 100 100 "s" "ftp+L2R" "" ftp.example.com.
www.example.com. ;; order pref flags service regexp replacement IN NAPTR 100 100 "s" "thttp+L2R" "" thttp.example.com. IN NAPTR 100 100 "s" "ftp+L2R" "" ftp.example.com.
Looking up SRV records for thttp.example.com would return information on the hosts that example.com has designated to be its mirror sites. The client can then pick one for the user.
Looking up SRV records for thttp.example.com would return information on the hosts that example.com has designated to be its mirror sites. The client can then pick one for the user.
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Mealling Standards Track [Page 11] RFC 3404 DDDS Based URI Resolution October 2002
6. Notes
6. Notes
o Registration procedures for the 'urn.arpa.' and 'uri.arpa.' DNS
zones are specified in "Dynamic Delegation Discovery System (DDDS)
Part Five: URI.ARPA Assignment Procedures" (RFC 3405 [5].
o Registration procedures for the 'urn.arpa.' and 'uri.arpa.' DNS zones are specified in "Dynamic Delegation Discovery System (DDDS) Part Five: URI.ARPA Assignment Procedures" (RFC 3405 [5].
o If a record at a particular order matches the URI, but the client
doesn't know the specified protocol and service, the client SHOULD
continue to examine records that have the same order. The client
MUST NOT consider records with a higher value of order. This is
necessary to make delegation of portions of the namespace work.
The order field is what lets site administrators say "all requests
for URIs matching pattern x go to server 1, all others go to
server 2".
o If a record at a particular order matches the URI, but the client doesn't know the specified protocol and service, the client SHOULD continue to examine records that have the same order. The client MUST NOT consider records with a higher value of order. This is necessary to make delegation of portions of the namespace work. The order field is what lets site administrators say "all requests for URIs matching pattern x go to server 1, all others go to server 2".
o Note that SRV RRs impose additional requirements on clients.
o Note that SRV RRs impose additional requirements on clients.
7. IANA Considerations
7. IANA Considerations
The use of the "urn.arpa." and "uri.arpa." zones requires registration policies and procedures to be followed and for the operation of those DNS zones to be maintained. These policies and procedures are spelled out in a "Dynamic Delegation Discovery System (DDDS) Part Five: URI.ARPA Assignment Procedures (RFC 3405)" [5]. The operation of those zones imposes operational and administrative responsibilities on the IANA.
The use of the "urn.arpa." and "uri.arpa." zones requires registration policies and procedures to be followed and for the operation of those DNS zones to be maintained. These policies and procedures are spelled out in a "Dynamic Delegation Discovery System (DDDS) Part Five: URI.ARPA Assignment Procedures (RFC 3405)" [5]. The operation of those zones imposes operational and administrative responsibilities on the IANA.
The registration method used for values in the Services and Flags fields is for a specification to be approved by the IESG and published as either an Informational or standards track RFC.
The registration method used for values in the Services and Flags fields is for a specification to be approved by the IESG and published as either an Informational or standards track RFC.
The registration policies for URIs is found in RFC 2717 [17]. URN NID registration policies are found in RFC 2611 [16].
The registration policies for URIs is found in RFC 2717 [17]. URN NID registration policies are found in RFC 2611 [16].
8. Security Considerations
8. Security Considerations
The use of "urn.arpa." and "uri.arpa." as the registry for namespaces is subject to denial of service attacks, as well as other DNS spoofing attacks. The interactions with DNSSEC are currently being studied. It is expected that NAPTR records will be signed with SIG records once the DNSSEC work is deployed.
The use of "urn.arpa." and "uri.arpa." as the registry for namespaces is subject to denial of service attacks, as well as other DNS spoofing attacks. The interactions with DNSSEC are currently being studied. It is expected that NAPTR records will be signed with SIG records once the DNSSEC work is deployed.
The rewrite rules make identifiers from other namespaces subject to the same attacks as normal domain names. Since they have not been easily resolvable before, this may or may not be considered a problem.
The rewrite rules make identifiers from other namespaces subject to the same attacks as normal domain names. Since they have not been easily resolvable before, this may or may not be considered a problem.
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Mealling Standards Track [Page 12] RFC 3404 DDDS Based URI Resolution October 2002
Regular expressions should be checked for sanity, not blindly passed to something like PERL.
Regular expressions should be checked for sanity, not blindly passed to something like PERL.
This document has discussed a way of locating a resolver, but has not discussed any detail of how the communication with the resolver takes place. There are significant security considerations attached to the communication with a resolver. Those considerations are outside the scope of this document, and must be addressed by the specifications for particular resolver communication protocols.
This document has discussed a way of locating a resolver, but has not discussed any detail of how the communication with the resolver takes place. There are significant security considerations attached to the communication with a resolver. Those considerations are outside the scope of this document, and must be addressed by the specifications for particular resolver communication protocols.
9. Acknowledgments
9. Acknowledgments
The editors would like to thank Keith Moore for all his consultations during the development of this document. We would also like to thank Paul Vixie for his assistance in debugging our implementation, and his answers on our questions. Finally, we would like to acknowledge our enormous intellectual debt to the participants in the Knoxville series of meetings, as well as to the participants in the URI and URN working groups.
The editors would like to thank Keith Moore for all his consultations during the development of this document. We would also like to thank Paul Vixie for his assistance in debugging our implementation, and his answers on our questions. Finally, we would like to acknowledge our enormous intellectual debt to the participants in the Knoxville series of meetings, as well as to the participants in the URI and URN working groups.
Specific recognition is given to Ron Daniel who was co-author on the original versions of these documents. His early implementations and clarity of thinking was invaluable in clearing up many of the potential boundary cases.
Specific recognition is given to Ron Daniel who was co-author on the original versions of these documents. His early implementations and clarity of thinking was invaluable in clearing up many of the potential boundary cases.
References
References
[1] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
One: The Comprehensive DDDS", RFC 3401, October 2002.
[1] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part One: The Comprehensive DDDS", RFC 3401, October 2002.
[2] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Two: The Algorithm", RFC 3402, October 2002.
[2] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part Two: The Algorithm", RFC 3402, October 2002.
[3] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Three: The Domain Name System (DNS) Database", RFC 3403, October
2002.
[3] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part Three: The Domain Name System (DNS) Database", RFC 3403, October 2002.
[4] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Four: The Uniform Resource Identifiers (URI) Resolution
Application", RFC 3404, October 2002.
[4] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part Four: The Uniform Resource Identifiers (URI) Resolution Application", RFC 3404, October 2002.
[5] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Five: URI.ARPA Assignment Procedures", RFC 3405y, October 2002.
[5] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part Five: URI.ARPA Assignment Procedures", RFC 3405y, October 2002.
[6] Sollins, K. and L. Masinter, "Functional Requirements for
Uniform Resource Names", RFC 1737, December 1994.
[6] Sollins, K. and L. Masinter, "Functional Requirements for Uniform Resource Names", RFC 1737, December 1994.
Mealling Standards Track [Page 13] RFC 3404 DDDS Based URI Resolution October 2002
Mealling Standards Track [Page 13] RFC 3404 DDDS Based URI Resolution October 2002
[7] Arms, B., "The URN Implementors, Uniform Resource Names: A
Progress Report", D-Lib Magazine, February 1996.
[7] Arms, B., "The URN Implementors, Uniform Resource Names: A Progress Report", D-Lib Magazine, February 1996.
[8] Moats, R., "URN Syntax", RFC 2141, May 1997.
[8] Moats, R., "URN Syntax", RFC 2141, May 1997.
[9] Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[9] Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782, February 2000.
[10] Daniel, R., "A Trivial Convention for using HTTP in URN
Resolution", RFC 2169, June 1997.
[10] Daniel, R., "A Trivial Convention for using HTTP in URN Resolution", RFC 2169, June 1997.
[11] Mealling, M., "URI Resolution Services Necessary for URN
Resolution", RFC 2483, January 1999.
[11] Mealling, M., "URI Resolution Services Necessary for URN Resolution", RFC 2483, January 1999.
[12] Moore, K., Browne, S., Cox, J. and J. Gettler, "Resource
Cataloging and Distribution System", Technical Report CS-97-346,
December 1996.
[12] Moore, K., Browne, S., Cox, J. and J. Gettler, "Resource Cataloging and Distribution System", Technical Report CS-97-346, December 1996.
[13] Sollins, K., "Architectural Principles of Uniform Resource Name
Resolution", RFC 2276, January 1998.
[13] Sollins, K., "Architectural Principles of Uniform Resource Name Resolution", RFC 2276, January 1998.
[14] Daniel, R. and M. Mealling, "Resolution of Uniform Resource
Identifiers using the Domain Name System", RFC 2168, June 1997.
[14] Daniel, R. and M. Mealling, "Resolution of Uniform Resource Identifiers using the Domain Name System", RFC 2168, June 1997.
[15] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[15] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[16] Daigle, L., van Gulik, D., Iannella, R. and P. Falstrom, "URN
Namespace Definition Mechanisms", RFC 2611, BCP 33, June 1999.
[16] Daigle, L., van Gulik, D., Iannella, R. and P. Falstrom, "URN Namespace Definition Mechanisms", RFC 2611, BCP 33, June 1999.
[17] Petke, R. and I. King, "Registration Procedures for URL Scheme
Names", RFC 2717, BCP 35, November 1999.
[17] Petke, R. and I. King, "Registration Procedures for URL Scheme Names", RFC 2717, BCP 35, November 1999.
[18] Mealling, M. and R. Daniel, "The Naming Authority Pointer
(NAPTR) DNS Resource Record", RFC 2915, August 2000.
[18] Mealling, M. and R. Daniel, "The Naming Authority Pointer (NAPTR) DNS Resource Record", RFC 2915, August 2000.
Mealling Standards Track [Page 14] RFC 3404 DDDS Based URI Resolution October 2002
Mealling Standards Track [Page 14] RFC 3404 DDDS Based URI Resolution October 2002
Appendix A. Pseudo Code
Appendix A. Pseudo Code
For the edification of implementers, pseudocode for a client routine using NAPTRs is given below. This code is provided merely as a convenience, it does not have any weight as a standard way to process NAPTR records. Also, as is the case with pseudocode, it has never been executed and may contain logical errors. You have been warned.
For the edification of implementers, pseudocode for a client routine using NAPTRs is given below. This code is provided merely as a convenience, it does not have any weight as a standard way to process NAPTR records. Also, as is the case with pseudocode, it has never been executed and may contain logical errors. You have been warned.
//
// findResolver(URN)
// Given a URN, find a host that can resolve it.
//
findResolver(string URN) {
// prepend prefix to ".urn.arpa."
sprintf(key, "%s.urn.arpa.", extractNS(URN));
do {
rewrite_flag = false;
terminal = false;
if (key has been seen) {
quit with a loop detected error
}
add key to list of "seens"
records = lookup(type=NAPTR, key); // get all NAPTR RRs for 'key'
// // findResolver(URN) // Given a URN, find a host that can resolve it. // findResolver(string URN) { // prepend prefix to ".urn.arpa." sprintf(key, "%s.urn.arpa.", extractNS(URN)); do { rewrite_flag = false; terminal = false; if (key has been seen) { quit with a loop detected error } add key to list of "seens" records = lookup(type=NAPTR, key); // get all NAPTR RRs for 'key'
discard any records with an unknown value in the "flags" field.
sort NAPTR records by "order" field and "preference" field
(with "order" being more significant than "preference").
n_naptrs = number of NAPTR records in response.
curr_order = records[0].order;
max_order = records[n_naptrs-1].order;
discard any records with an unknown value in the "flags" field. sort NAPTR records by "order" field and "preference" field (with "order" being more significant than "preference"). n_naptrs = number of NAPTR records in response. curr_order = records[0].order; max_order = records[n_naptrs-1].order;
// Process current batch of NAPTRs according to "order" field.
for (j=0; j < n_naptrs && records[j].order <= max_order; j++) {
if (unknown_flag) // skip this record and go to next one
continue;
newkey = rewrite(URN, naptr[j].replacement, naptr[j].regexp);
if (!newkey) // Skip to next record if the rewrite didn't
match continue;
// We did do a rewrite, shrink max_order to current value
// so that delegation works properly
max_order = naptr[j].order;
// Will we know what to do with the protocol and services
// specified in the NAPTR? If not, try next record.
if(!isKnownProto(naptr[j].services)) {
continue;
}
if(!isKnownService(naptr[j].services)) {
continue;
// Process current batch of NAPTRs according to "order" field. for (j=0; j < n_naptrs && records[j].order <= max_order; j++) { if (unknown_flag) // skip this record and go to next one continue; newkey = rewrite(URN, naptr[j].replacement, naptr[j].regexp); if (!newkey) // Skip to next record if the rewrite didn't match continue; // We did do a rewrite, shrink max_order to current value // so that delegation works properly max_order = naptr[j].order; // Will we know what to do with the protocol and services // specified in the NAPTR? If not, try next record. if(!isKnownProto(naptr[j].services)) { continue; } if(!isKnownService(naptr[j].services)) { continue;
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Mealling Standards Track [Page 15] RFC 3404 DDDS Based URI Resolution October 2002
}
}
// At this point we have a successful rewrite and we will
// know how to speak the protocol and request a known
// resolution service. Before we do the next lookup, check
// the flags to see if we're done.
// Note: it is possible to rewrite this so that this valid
// record could be noted as such but continue on in order
// to find a 'better' record. But that code would be to
// voluminous and application specific to be illustrative.
if (strcasecmp(flags, "S")
|| strcasecmp(flags, "P"))
|| strcasecmp(flags, "A")) {
terminal = true;
services = naptr[j].services;
addnl = any SRV and/or A records returned as additional
info for naptr[j].
}
key = newkey;
rewriteflag = true;
break;
}
} while (rewriteflag && !terminal);
// At this point we have a successful rewrite and we will // know how to speak the protocol and request a known // resolution service. Before we do the next lookup, check // the flags to see if we're done. // Note: it is possible to rewrite this so that this valid // record could be noted as such but continue on in order // to find a 'better' record. But that code would be to // voluminous and application specific to be illustrative. if (strcasecmp(flags, "S") || strcasecmp(flags, "P")) || strcasecmp(flags, "A")) { terminal = true; services = naptr[j].services; addnl = any SRV and/or A records returned as additional info for naptr[j]. } key = newkey; rewriteflag = true; break; } } while (rewriteflag && !terminal);
// Did we not find our way to a resolver?
if (!rewrite_flag) {
report an error
return NULL;
}
// Did we not find our way to a resolver? if (!rewrite_flag) { report an error return NULL; }
// Leave rest to another protocol?
if (strcasecmp(flags, "P")) {
return key as host to talk to;
}
// Leave rest to another protocol? if (strcasecmp(flags, "P")) { return key as host to talk to; }
// If not, keep plugging
if (!addnl) { // No SRVs came in as additional info, look them up
srvs = lookup(type=SRV, key);
}
// If not, keep plugging if (!addnl) { // No SRVs came in as additional info, look them up srvs = lookup(type=SRV, key); }
sort SRV records by preference, weight, ...
for each (SRV record) { // in order of preference
try contacting srv[j].target using the protocol and one of the
resolution service requests from the "services" field of the
last NAPTR record.
if (successful)
return (target, protocol, service);
// Actually we would probably return a result, but this
sort SRV records by preference, weight, ... for each (SRV record) { // in order of preference try contacting srv[j].target using the protocol and one of the resolution service requests from the "services" field of the last NAPTR record. if (successful) return (target, protocol, service); // Actually we would probably return a result, but this
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// code was supposed to just tell us a good host to talk to.
}
die with an "unable to find a host" error;
}
// code was supposed to just tell us a good host to talk to. } die with an "unable to find a host" error; }
Author's Address
Author's Address
Michael Mealling VeriSign 21345 Ridgetop Circle Sterling, VA 20166 US
Michael Mealling VeriSign 21345 Ridgetop Circle Sterling, VA 20166 US
EMail: michael@neonym.net URI: http://www.verisignlabs.com
EMail: michael@neonym.net URI: http://www.verisignlabs.com
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Full Copyright Statement
Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Acknowledgement
Funding for the RFC Editor function is currently provided by the Internet Society.
Funding for the RFC Editor function is currently provided by the Internet Society.
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Mealling Standards Track [Page 18]
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