Network Working Group                                          T. Narten
Request for Comments: 3041                                           IBM
Category: Standards Track                                      R. Draves
                                                      Microsoft Research
                                                            January 2001

Privacy Extensions for Stateless Address Autoconfiguration in IPv6


Status of this Memo


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.

この文書は、インターネットコミュニティのためのインターネット標準トラックプロトコルを指定し、改善のための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」(STD 1)の最新版を参照してください。このメモの配布は無制限です。

Copyright Notice


Copyright (C) The Internet Society (2001). All Rights Reserved.




Nodes use IPv6 stateless address autoconfiguration to generate addresses without the necessity of a Dynamic Host Configuration Protocol (DHCP) server. Addresses are formed by combining network prefixes with an interface identifier. On interfaces that contain embedded IEEE Identifiers, the interface identifier is typically derived from it. On other interface types, the interface identifier is generated through other means, for example, via random number generation. This document describes an extension to IPv6 stateless address autoconfiguration for interfaces whose interface identifier is derived from an IEEE identifier. Use of the extension causes nodes to generate global-scope addresses from interface identifiers that change over time, even in cases where the interface contains an embedded IEEE identifier. Changing the interface identifier (and the global-scope addresses generated from it) over time makes it more difficult for eavesdroppers and other information collectors to identify when different addresses used in different transactions actually correspond to the same node.

ノードは、DHCP(Dynamic Host Configuration Protocol)サーバを必要とせずにアドレスを生成するためのIPv6ステートレスアドレス自動設定を使用します。アドレスは、インターフェース識別子とネットワーク・プレフィックスとを組み合わせることによって形成されます。埋め込みIEEE識別子を含むインターフェース上に、インタフェース識別子は、典型的にはそれから誘導されます。他のインタフェースタイプに、インタフェース識別子は、乱数生成を介して、例えば、他の手段によって生成されます。この文書では、インタフェース識別子IEEE識別子から導出されるインターフェイスのIPv6ステートレスアドレス自動設定の拡張を記述しています。拡張の使用は、ノードがあっても、インターフェイスが埋め込まIEEE識別子が含まれている場合には、経時的に変化インターフェース識別子からグローバルスコープのアドレスを生成させます。経時的(そこから生成され、グローバルスコープのアドレス)インタフェース識別子を変更すると、異なるトランザクションに使用される異なるアドレスが実際には同じノードに対応する場合に同定する盗聴者や他の情報収集のためにそれをより困難にします。

Table of Contents


   1.  Introduction.............................................    2
   2.  Background...............................................    3
      2.1.  Extended Use of the Same Identifier.................    3
      2.2.  Address Usage in IPv4 Today.........................    4
      2.3.  The Concern With IPv6 Addresses.....................    5
      2.4.  Possible Approaches.................................    6
   3.  Protocol Description.....................................    7
      3.1.  Assumptions.........................................    8
      3.2.  Generation Of Randomized Interface Identifiers......    9
      3.3.  Generating Temporary Addresses......................   10
      3.4.  Expiration of Temporary Addresses...................   11
      3.5.  Regeneration of Randomized Interface Identifiers....   12
   4.  Implications of Changing Interface Identifiers...........   13
   5.  Defined Constants........................................   14
   6.  Future Work..............................................   14
   7.  Security Considerations..................................   15
   8.  Acknowledgments..........................................   15
   9.  References...............................................   15
   10. Authors' Addresses.......................................   16
   11. Full Copyright Statement.................................   17
1. Introduction
1. はじめに

Stateless address autoconfiguration [ADDRCONF] defines how an IPv6 node generates addresses without the need for a DHCP server. Some types of network interfaces come with an embedded IEEE Identifier (i.e., a link-layer MAC address), and in those cases stateless address autoconfiguration uses the IEEE identifier to generate a 64- bit interface identifier [ADDRARCH]. By design, the interface identifier is likely to be globally unique when generated in this fashion. The interface identifier is in turn appended to a prefix to form a 128-bit IPv6 address.

ステートレスアドレス自動設定は[ADDRCONF] IPv6ノードがDHCPサーバを必要とせずにアドレスを生成する方法を定義します。ネットワークインターフェースのいくつかのタイプは、埋め込みIEEE識別子(すなわち、リンク層のMACアドレス)が付属して、それらの場合にはステートレスアドレス自動設定は、64ビットのインタフェース識別子[ADDRARCH]を生成するために、IEEE識別子を使用します。この方法で生成されたときに設計することで、インタフェース識別子は、グローバルに一意である可能性が高いです。インタフェース識別子は、次に、128ビットのIPv6アドレスを形成するために、プレフィックスに付加されます。

All nodes combine interface identifiers (whether derived from an IEEE identifier or generated through some other technique) with the reserved link-local prefix to generate link-local addresses for their attached interfaces. Additional addresses, including site-local and global-scope addresses, are then created by combining prefixes advertised in Router Advertisements via Neighbor Discovery [DISCOVERY] with the interface identifier.


Not all nodes and interfaces contain IEEE identifiers. In such cases, an interface identifier is generated through some other means (e.g., at random), and the resultant interface identifier is not globally unique and may also change over time. The focus of this document is on addresses derived from IEEE identifiers, as the concern being addressed exists only in those cases where the interface identifier is globally unique and non-changing. The rest of this document assumes that IEEE identifiers are being used, but the techniques described may also apply to interfaces with other types of globally unique and/or persistent identifiers.


This document discusses concerns associated with the embedding of non-changing interface identifiers within IPv6 addresses and describes extensions to stateless address autoconfiguration that can help mitigate those concerns for individual users and in environments where such concerns are significant. Section 2 provides background information on the issue. Section 3 describes a procedure for generating alternate interface identifiers and global-scope addresses. Section 4 discusses implications of changing interface identifiers.


2. Background

This section discusses the problem in more detail, provides context for evaluating the significance of the concerns in specific environments and makes comparisons with existing practices.


2.1. Extended Use of the Same Identifier
2.1. 同じ識別子の長時間使用

The use of a non-changing interface identifier to form addresses is a specific instance of the more general case where a constant identifier is reused over an extended period of time and in multiple independent activities. Anytime the same identifier is used in multiple contexts, it becomes possible for that identifier to be used to correlate seemingly unrelated activity. For example, a network sniffer placed strategically on a link across which all traffic to/from a particular host crosses could keep track of which destinations a node communicated with and at what times. Such information can in some cases be used to infer things, such as what hours an employee was active, when someone is at home, etc.


One of the requirements for correlating seemingly unrelated activities is the use (and reuse) of an identifier that is recognizable over time within different contexts. IP addresses provide one obvious example, but there are more. Many nodes also have DNS names associated with their addresses, in which case the DNS name serves as a similar identifier. Although the DNS name associated with an address is more work to obtain (it may require a DNS query) the information is often readily available. In such cases, changing the address on a machine over time would do little to address the concerns raised in this document, unless the DNS name is changed as well (see Section 4).

一見無関係な活動を相関させるための要件の1つは、異なるコンテキスト内の時間にわたって認識された識別子の使用(再利用)です。 IPアドレスが1つの明白な例を提供しますが、より多くのがあります。多くのノードはDNS名が同様の識別子として機能する場合にはそのアドレスに関連付けられているDNS名を持っています。アドレスに関連付けられているDNS名を取得するために、より多くの作業があるが、情報は多くの場合、容易に利用可能である(これは、DNSクエリが必要な場合があります)。このような場合には、時間をかけてマシン上のアドレスを変更すると、DNS名も同様に変更されない限り(セクション4を参照)、この文書の懸念に対処するために少しをするでしょう。

Web browsers and servers typically exchange "cookies" with each other [COOKIES]. Cookies allow web servers to correlate a current activity with a previous activity. One common usage is to send back targeted advertising to a user by using the cookie supplied by the browser to identify what earlier queries had been made (e.g., for what type of information). Based on the earlier queries, advertisements can be targeted to match the (assumed) interests of the end-user.


The use of a constant identifier within an address is of special concern because addresses are a fundamental requirement of communication and cannot easily be hidden from eavesdroppers and other parties. Even when higher layers encrypt their payloads, addresses in packet headers appear in the clear. Consequently, if a mobile host (e.g., laptop) accessed the network from several different locations, an eavesdropper might be able to track the movement of that mobile host from place to place, even if the upper layer payloads were encrypted [SERIALNUM].


2.2. Address Usage in IPv4 Today
2.2. IPv4のアドレスの使用今日

Addresses used in today's Internet are often non-changing in practice for extended periods of time, especially in non-home environments (e.g., corporations, campuses, etc.). In such sites, addresses are assigned statically and typically change infrequently. Over the last few years, sites have begun moving away from static allocation to dynamic allocation via DHCP [DHCP]. In theory, the address a client gets via DHCP can change over time, but in practice servers often return the same address to the same client (unless addresses are in such short supply that they are reused immediately by a different node when they become free). Thus, even within sites using DHCP, clients frequently end up using the same address for weeks to months at a time.

今日のインターネットで使用されるアドレスは、特に非家庭環境(例えば、企業、キャンパスなど)で、多くの場合、長時間の練習に非変更されています。このようなサイトでは、アドレスが静的に割り当てられ、通常はまれにしか変更されています。過去数年間で、サイトでは、DHCP [DHCP]を経由して離れ動的割り当てへの静的割り当てから移動し始めています。理論的には、クライアントがDHCP経由で取得するアドレスは、時間の経過とともに変化することができますが、(アドレスは、彼らが自由になったときに、彼らは別のノードですぐに再利用されるように不足している場合を除き)、実際にサーバーには、多くの場合、同じクライアントに同じアドレスを返します。したがって、でもDHCPを使用してサイト内では、クライアントが頻繁に一度に数週間から数ヶ月のために同じアドレスを使用して終了します。

For home users accessing the Internet over dialup lines, the situation is generally different. Such users do not have permanent connections and are often assigned temporary addresses each time they connect to their ISP (e.g., AOL). Consequently, the addresses they use change frequently over time and are shared among a number of different users. Thus, an address does not reliably identify a particular device over time spans of more than a few minutes.


A more interesting case concerns always-on connections (e.g., cable modems, ISDN, DSL, etc.) that result in a home site using the same address for extended periods of time. This is a scenario that is just starting to become common in IPv4 and promises to become more of a concern as always-on internet connectivity becomes widely available. Although it might appear that changing an address regularly in such environments would be desirable to lessen privacy concerns, it should be noted that the network prefix portion of an address also serves as a constant identifier. All nodes at (say) a home, would have the same network prefix, which identifies the topological location of those nodes. This has implications for privacy, though not at the same granularity as the concern that this document addresses. Specifically, all nodes within a home would be grouped together for the purposes of collecting information. This issue is difficult to address, because the routing prefix part of an address contains topology information and cannot contain arbitrary values.


Finally, it should be noted that nodes that need a (non-changing) DNS name generally have static addresses assigned to them to simplify the configuration of DNS servers. Although Dynamic DNS [DDNS] can be used to update the DNS dynamically, it is not yet widely deployed. In addition, changing an address but keeping the same DNS name does not really address the underlying concern, since the DNS name becomes a non-changing identifier. Servers generally require a DNS name (so clients can connect to them), and clients often do as well (e.g., some servers refuse to speak to a client whose address cannot be mapped into a DNS name that also maps back into the same address). Section 4 describes one approach to this issue.

最後に、(非変化)DNS名を必要とするノードは、一般的にDNSサーバの構成を簡素化するためにそれらに割り当てられた静的アドレスを持っていることに留意すべきです。ダイナミックDNSは、[DDNS]動的DNSを更新するために使用することができるが、それはまだ広く展開されていません。 DNS名が非変更識別子なるのでまた、アドレスの変更が、同じDNS名を維持することは、本当に、根本的な問題に対処しません。 (例えば、いくつかのサーバは、そのアドレスも同じアドレスに戻すマップするDNS名にマップすることができないクライアントに話すことを拒否)(クライアントがそれらに接続できるように)サーバは、一般的にDNS名を必要とし、クライアントは、多くの場合、同様に行います。第4節では、この問題への一つのアプローチを説明します。

2.3. The Concern With IPv6 Addresses
2.3. IPv6のアドレスを持つ懸念

The division of IPv6 addresses into distinct topology and interface identifier portions raises an issue new to IPv6 in that a fixed portion of an IPv6 address (i.e., the interface identifier) can contain an identifier that remains constant even when the topology portion of an address changes (e.g., as the result of connecting to a different part of the Internet). In IPv4, when an address changes, the entire address (including the local part of the address) usually changes. It is this new issue that this document addresses.


If addresses are generated from an interface identifier, a home user's address could contain an interface identifier that remains the same from one dialup session to the next, even if the rest of the address changes. The way PPP is used today, however, PPP servers typically unilaterally inform the client what address they are to use (i.e., the client doesn't generate one on its own). This practice, if continued in IPv6, would avoid the concerns that are the focus of this document.

アドレスは、インタフェース識別子から生成されている場合は、ホームユーザーのアドレスは、偶数アドレスの変更の残りの場合は、次の1つのダイヤルアップセッションから同じままインタフェース識別子を含めることができます。 PPPは、今日使用されている方法は、しかし、PPPサーバは、一般的に一方的に(つまり、クライアントが独自に1つずつ生成されません)彼らが使用しているどのようなアドレスをクライアントに通知します。このような行為は、IPv6では続ければ、このドキュメントの焦点である懸念を避けるだろう。

A more troubling case concerns mobile devices (e.g., laptops, PDAs, etc.) that move topologically within the Internet. Whenever they move (in the absence of technology such as mobile IP [MOBILEIP]), they form new addresses for their current topological point of attachment. This is typified today by the "road warrior" who has

より厄介な場合は、インターネット内でトポロジー的に移動モバイル機器(例えば、ラップトップ、PDA、等)に関する。彼らは(モバイルIP [MOBILEIP]などの技術が存在しない場合に)移動するとき、彼らは添付ファイルの彼らの現在のトポロジカルポイントの新しいアドレスを形成します。これは持っている「道路の戦士」が本日代表されます

Internet connectivity both at home and at the office. While the node's address changes as it moves, however, the interface identifier contained within the address remains the same (when derived from an IEEE Identifier). In such cases, the interface identifier can be used to track the movement and usage of a particular machine [SERIALNUM]. For example, a server that logs usage information together with a source addresses, is also recording the interface identifier since it is embedded within an address. Consequently, any data-mining technique that correlates activity based on addresses could easily be extended to do the same using the interface identifier. This is of particular concern with the expected proliferation of next-generation network-connected devices (e.g., PDAs, cell phones, etc.) in which large numbers of devices are in practice associated with individual users (i.e., not shared). Thus, the interface identifier embedded within an address could be used to track activities of an individual, even as they move topologically within the internet.


In summary, IPv6 addresses on a given interface generated via Stateless Autoconfiguration contain the same interface identifier, regardless of where within the Internet the device connects. This facilitates the tracking of individual devices (and thus potentially users). The purpose of this document is to define mechanisms that eliminate this issue, in those situations where it is a concern.


2.4. Possible Approaches
2.4. 可能なアプローチ

One way to avoid some of the problems discussed above is to use DHCP for obtaining addresses. With DHCP, the DHCP server could arrange to hand out addresses that change over time.

上述の問題のいくつかを回避する1つの方法は、アドレスを取得するためにDHCPを使用することです。 DHCPを使用すると、DHCPサーバは、時間の経過とともに変化するアドレスを配るように手配できます。

Another approach, compatible with the stateless address autoconfiguration architecture, would be to change the interface id portion of an address over time and generate new addresses from the interface identifier for some address scopes. Changing the interface identifier can make it more difficult to look at the IP addresses in independent transactions and identify which ones actually correspond to the same node, both in the case where the routing prefix portion of an address changes and when it does not.


Many machines function as both clients and servers. In such cases, the machine would need a DNS name for its use as a server. Whether the address stays fixed or changes has little privacy implication since the DNS name remains constant and serves as a constant identifier. When acting as a client (e.g., initiating communication), however, such a machine may want to vary the addresses it uses. In such environments, one may need multiple addresses: a "public" (i.e., non-secret) server address, registered in the DNS, that is used to accept incoming connection requests from other machines, and a "temporary" address used to shield the identity of the client when it initiates communication. These two cases are roughly analogous to telephone numbers and caller ID, where a user may list their telephone number in the public phone book, but disable the display of its number via caller ID when initiating calls.

多くのマシンは、クライアントとサーバーの両方として機能します。このような場合には、マシンがサーバーとしての使用のためのDNS名が必要になります。 DNS名は一定のまま、一定の識別子として機能しますので、アドレスが固定または変更したままかどうかは、少しプライバシー意味合いを持っています。 (例えば、通信を開始する)クライアントとして動作する場合、しかし、そのようなマシンは、それが使用するアドレスを変更することもできます。このような環境では、1は、複数のアドレスが必要な場合があります。DNSに登録されている「公共の」(すなわち、非秘密)サーバーのアドレスを、それは他のマシンからの着信接続要求を受け入れるために使用され、かつ遮蔽するために使用される「一時的な」アドレスそれが通信を開始するクライアントのID。これらの2つのケースは、ユーザーが公衆電話帳に自分の電話番号の一覧を表示する電話番号と発信者ID、とほぼ類似しているが、通話を開始する際に、発信者IDを経由してその番号の表示を無効にします。

To make it difficult to make educated guesses as to whether two different interface identifiers belong to the same node, the algorithm for generating alternate identifiers must include input that has an unpredictable component from the perspective of the outside entities that are collecting information. Picking identifiers from a pseudo-random sequence suffices, so long as the specific sequence cannot be determined by an outsider examining information that is readily available or easily determinable (e.g., by examining packet contents). This document proposes the generation of a pseudo-random sequence of interface identifiers via an MD5 hash. Periodically, the next interface identifier in the sequence is generated, a new set of temporary addresses is created, and the previous temporary addresses are deprecated to discourage their further use. The precise pseudo-random sequence depends on both a random component and the globally unique interface identifier (when available), to increase the likelihood that different nodes generate different sequences.


3. Protocol Description

The goal of this section is to define procedures that:


1) Do not result in any changes to the basic behavior of addresses generated via stateless address autoconfiguration [ADDRCONF].


2) Create additional global-scope addresses based on a random interface identifier for use with global scope addresses. Such addresses would be used to initiate outgoing sessions. These "random" or temporary addresses would be used for a short period of time (hours to days) and would then be deprecated. Deprecated address can continue to be used for already established connections, but are not used to initiate new connections. New temporary addresses are generated periodically to replace temporary addresses that expire, with the exact time between address generation a matter of local policy.


3) Produce a sequence of temporary global-scope addresses from a sequence of interface identifiers that appear to be random in the sense that it is difficult for an outside observer to predict a future address (or identifier) based on a current one and it is difficult to determine previous addresses (or identifiers) knowing only the present one.


4) Generate a set of addresses from the same (randomized) interface identifier, one address for each prefix for which a global address has been generated via stateless address autoconfiguration. Using the same interface identifier to generate a set of temporary addresses reduces the number of IP multicast groups a host must join. Nodes join the solicited-node multicast address for each unicast address they support, and solicited-node addresses are dependent only on the low-order bits of the corresponding address. This decision was made to address the concern that a node that joins a large number of multicast groups may be required to put its interface into promiscuous mode, resulting in possible reduced performance.


3.1. Assumptions
3.1. 仮定

The following algorithm assumes that each interface maintains an associated randomized interface identifier. When temporary addresses are generated, the current value of the associated randomized interface identifier is used. The actual value of the identifier changes over time as described below, but the same identifier can be used to generate more than one temporary address.


The algorithm also assumes that for a given temporary address, an implementation can determine the corresponding public address from which it was generated. When a temporary address is deprecated, a new temporary address is generated. The specific valid and preferred lifetimes for the new address are dependent on the corresponding lifetime values in the public address.


Finally, this document assumes that when a node initiates outgoing communication, temporary addresses can be given preference over public addresses. This can mean that all connections initiated by the node use temporary addresses by default, or that applications individually indicate whether they prefer to use temporary or public addresses. Giving preference to temporary address is consistent with on-going work that addresses the topic of source-address selection in the more general case [ADDR_SELECT]. An implementation may make it a policy that it does not select a public address in the event that no temporary address is available (e.g., if generation of a useable temporary address fails).

最後に、この文書では、ノードが、発信の通信を開始する際に、一時的なアドレスがパブリックアドレスより優先することができることを前提としています。これは、ノードによって開始されたすべての接続は、デフォルトでは、一時的なアドレスを使用すること、またはアプリケーションが個別に、彼らは一時的またはパブリックアドレスを使用することを好むかどうかを示すことを意味します。一時アドレスを優先することは、より一般的なケース[ADDR_SELECT]でソースアドレス選択のトピックを扱い、進行中の作業と一致しています。 (使用可能な一時アドレスの生成が失敗した場合、例えば)実装は、それは一時的なアドレスが利用できないという場合に、パブリックアドレスを選択しない方針行うことがあります。

3.2. Generation Of Randomized Interface Identifiers.
3.2. ランダムインタフェース識別子の生成。

We describe two approaches for the maintenance of the randomized interface identifier. The first assumes the presence of stable storage that can be used to record state history for use as input into the next iteration of the algorithm across system restarts. A second approach addresses the case where stable storage is unavailable and there is a need to generate randomized interface identifiers without previous state.


3.2.1. When Stable Storage Is Present
3.2.1. 安定したストレージが存在する場合には

The following algorithm assumes the presence of a 64-bit "history value" that is used as input in generating a randomized interface identifier. The very first time the system boots (i.e., out-of-the-box), a random value should be generated using techniques that help ensure the initial value is hard to guess [RANDOM]. Whenever a new interface identifier is generated, a value generated by the computation is saved in the history value for the next iteration of the algorithm.


A randomized interface identifier is created as follows:


1) Take the history value from the previous iteration of this algorithm (or a random value if there is no previous value) and append to it the interface identifier generated as described in [ADDRARCH]. 2) Compute the MD5 message digest [MD5] over the quantity created in the previous step. 3) Take the left-most 64-bits of the MD5 digest and set bit 6 (the left-most bit is numbered 0) to zero. This creates an interface identifier with the universal/local bit indicating local significance only. Save the generated identifier as the associated randomized interface identifier. 4) Take the rightmost 64-bits of the MD5 digest computed in step 2) and save them in stable storage as the history value to be used in the next iteration of the algorithm.

1)[ADDRARCH]で説明されるように生成されたインタフェース識別子を以前の値がない場合、このアルゴリズム(またはランダムな値の前の反復からの履歴値を取る)と、それに追加。 2)前のステップで作成された量よりMD5メッセージダイジェスト[MD5]を計算します。 3)ゼロにMD5ダイジェストの最も左側の64ビットと設定されたビット6(最も左のビットが0番号さ)を取ります。これはローカルな意味を表すユニバーサル/ローカルビットとのインタフェース識別子を生成します。関連する無作為化インタフェース識別子として生成された識別子を保存します。 4)ステップ2で計算されたMD5ダイジェストの右端の64ビット)を取り、履歴値は、アルゴリズムの次の反復で使用されるように安定したストレージに保存。

MD5 was chosen for convenience, and because its particular properties were adequate to produce the desired level of randomization. IPv6 nodes are already required to implement MD5 as part of IPsec [IPSEC], thus the code will already be present on IPv6 machines.

MD5は、便宜のために選択した、その特定の特性が適切であったため、ランダム化の所望のレベルを生成します。 IPv6ノードは、すでにこのようにコードが既にIPv6のマシン上に存在する、IPsecの[IPSEC]の一部としてMD5を実装するために必要とされます。

In theory, generating successive randomized interface identifiers using a history scheme as above has no advantages over generating them at random. In practice, however, generating truly random numbers can be tricky. Use of a history value is intended to avoid the particular scenario where two nodes generate the same randomized interface identifier, both detect the situation via DAD, but then proceed to generate identical randomized interface identifiers via the same (flawed) random number generation algorithm. The above algorithm avoids this problem by having the interface identifier (which will often be globally unique) used in the calculation that generates subsequent randomized interface identifiers. Thus, if two nodes happen to generate the same randomized interface identifier, they should generate different ones on the followup attempt.

理論的には、上記のように履歴方式を用いて連続したランダムインタフェース識別子を生成することは、ランダムにそれらを生成に対して何ら効果を有していません。しかし実際には、真の乱数を生成することは難しいことができます。履歴値の使用は、2つのノードが同じランダムインタフェース識別子を生成する特定のシナリオを回避するため、両方のDADを介して状況を検出し、その後、同じ(欠陥)乱数生成アルゴリズムを介して同じランダムインタフェース識別子を生成するように進行することを意図しています。上記のアルゴリズムは、後続のランダムインタフェース識別子を生成する計算に使用される(多くの場合、グローバルに一意であろう)インタフェース識別子を有することによって、この問題を回避します。 2つのノードが同じランダム化されたインタフェース識別子を生成するために起こる場合はこのように、彼らはフォローの試みで異なるものを生成する必要があります。

3.2.2. In The Absence of Stable Storage
3.2.2. 安定記憶のない状態で

In the absence of stable storage, no history value will be available across system restarts to generate a pseudo-random sequence of interface identifiers. Consequently, the initial history value used above will need to be generated at random. A number of techniques might be appropriate. Consult [RANDOM] for suggestions on good sources for obtaining random numbers. Note that even though machines may not have stable storage for storing a history value, they will in many cases have configuration information that differs from one machine to another (e.g., user identity, security keys, serial numbers, etc.). One approach to generating a random initial history value in such cases is to use the configuration information to generate some data bits (which may remain constant for the life of the machine, but will vary from one machine to another), append some random data and compute the MD5 digest as before.


3.3. Generating Temporary Addresses
3.3. 一時アドレスの生成

[ADDRCONF] describes the steps for generating a link-local address when an interface becomes enabled as well as the steps for generating addresses for other scopes. This document extends [ADDRCONF] as follows. When processing a Router Advertisement with a Prefix Information option carrying a global-scope prefix for the purposes of address autoconfiguration (i.e., the A bit is set), perform the following steps:


1) Process the Prefix Information Option as defined in [ADDRCONF], either creating a public address or adjusting the lifetimes of existing addresses, both public and temporary. When adjusting the lifetimes of an existing temporary address, only lower the lifetimes. Implementations must not increase the lifetimes of an existing temporary address when processing a Prefix Information Option. 2) When a new public address is created as described in [ADDRCONF] (because the prefix advertised does not match the prefix of any address already assigned to the interface, and the Valid Lifetime in the option is not zero), also create a new temporary address.

パブリックアドレスを作成またはパブリック一時両方既存のアドレスの寿命を調節することのいずれか、[ADDRCONF]で定義されるように1)プレフィックス情報オプションを処理。既存の一時的なアドレスの寿命を調整する場合、唯一の寿命を下げます。プレフィックス情報オプションを処理する際の実装は、既存の一時的なアドレスの寿命を増加させてはなりません。 2)既にインタフェースに割り当てられたアドレスのプレフィックス、およびオプションで有効寿命と一致しないアドバタイズプレフィックスがゼロではないので([ADDRCONF]で説明したように、新しいパブリックアドレスが作成されると)、また、新規作成一時アドレス。

3) When creating a temporary address, the lifetime values are derived from the corresponding public address as follows:


- Its Valid Lifetime is the lower of the Valid Lifetime of the public address or TEMP_VALID_LIFETIME. - Its Preferred Lifetime is the lower of the Preferred Lifetime of the public address or TEMP_PREFERRED_LIFETIME - DESYNC_FACTOR.

- その有効寿命は、パブリックアドレスまたはTEMP_VALID_LIFETIMEの有効寿命の低下です。 - DESYNC_FACTOR - その好ましい寿命は、パブリックアドレスまたはTEMP_PREFERRED_LIFETIMEの優先寿命の低下です。

A temporary address is created only if this calculated Preferred Lifetime is greater than REGEN_ADVANCE time units. In particular, an implementation must not create a temporary address with a zero Preferred Lifetime. 4) New temporary addresses are created by appending the interface's current randomized interface identifier to the prefix that was used to generate the corresponding public address. If by chance the new temporary address is the same as an address already assigned to the interface, generate a new randomized interface identifier and repeat this step. 5) Perform duplicate address detection (DAD) on the generated temporary address. If DAD indicates the address is already in use, generate a new randomized interface identifier as described in Section 3.2 above, and repeat the previous steps as appropriate up to 5 times. If after 5 consecutive attempts no non-unique address was generated, log a system error and give up attempting to generate temporary addresses for that interface.

一時アドレスは、この算出された好ましい寿命がREGEN_ADVANCE時間単位よりも大きい場合にのみ作成されます。特に、実装はゼロ優先寿命で一時アドレスを作成してはいけません。 4)新しい一時アドレスは、対応するパブリックアドレスを生成するために使用されたプレフィックスにインターフェイスの現在の無作為化インタフェース識別子を付加することによって作成されます。偶然に新しい一時的なアドレスが既にインタフェースに割り当てられたアドレスと同じである場合、新しいランダム化されたインタフェース識別子を生成し、この手順を繰り返します。 5)生成された一時的なアドレスに重複アドレス検出(DAD)を実行します。 DADは、アドレスが既に使用中であることを示す場合、上記セクション3.2に記載したように、新しいランダムインタフェース識別子を生成し、そして5回まで必要に応じて上記の手順を繰り返します。連続5回の試行後に何の非固有のアドレスが生成されなかった場合は、システム・エラーを記録し、そのインターフェイスの一時アドレスを生成しようとあきらめます。

Note: because multiple temporary addresses are generated from the same associated randomized interface identifier, there is little benefit in running DAD on every temporary address. This document recommends that DAD be run on the first address generated from a given randomized identifier, but that DAD be skipped on all subsequent addresses generated from the same randomized interface identifier.


3.4. Expiration of Temporary Addresses
3.4. 一時アドレスの有効期限

When a temporary address becomes deprecated, a new one should be generated. This is done by repeating the actions described in Section 3.3, starting at step 3). Note that, except for the transient period when a temporary address is being regenerated, in normal operation at most one temporary address corresponding to a public address should be in a non-deprecated state at any given time. Note that if a temporary address becomes deprecated as result of processing a Prefix Information Option with a zero Preferred Lifetime, then a new temporary address must not be generated. The Prefix Information Option will also deprecate the corresponding public address.


To insure that a preferred temporary address is always available, a new temporary address should be regenerated slightly before its predecessor is deprecated. This is to allow sufficient time to avoid race conditions in the case where generating a new temporary address is not instantaneous, such as when duplicate address detection must be run. It is recommended that an implementation start the address regeneration process REGEN_ADVANCE time units before a temporary address would actually be deprecated.


As an optional optimization, an implementation may wish to remove a deprecated temporary address that is not in use by applications or upper-layers. For TCP connections, such information is available in control blocks. For UDP-based applications, it may be the case that only the applications have knowledge about what addresses are actually in use. Consequently, one may need to use heuristics in deciding when an address is no longer in use (e.g., the default TEMP_VALID_LIFETIME suggested above).

オプションの最適化として、実装はアプリケーションや上位層で使用されていない非推奨の一時的なアドレスを削除したい場合があります。 TCP接続の場合、このような情報は、制御ブロックで利用可能です。 UDPベースのアプリケーションでは、アプリケーションのみがアドレスが実際に使用中であるかについての知識を持っている場合があります。その結果、1はアドレスが(例えば、デフォルトのTEMP_VALID_LIFETIMEは、上記の提案)使用されなくなったときに決めないでヒューリスティックを使用する必要があります。

3.5. Regeneration of Randomized Interface Identifiers
3.5. ランダムインタフェース識別子の再生

The frequency at which temporary addresses should change depends on how a device is being used (e.g., how frequently it initiates new communication) and the concerns of the end user. The most egregious privacy concerns appear to involve addresses used for long periods of time (weeks to months to years). The more frequently an address changes, the less feasible collecting or coordinating information keyed on interface identifiers becomes. Moreover, the cost of collecting information and attempting to correlate it based on interface identifiers will only be justified if enough addresses contain non-changing identifiers to make it worthwhile. Thus, having large numbers of clients change their address on a daily or weekly basis is likely to be sufficient to alleviate most privacy concerns.


There are also client costs associated with having a large number of addresses associated with a node (e.g., in doing address lookups, the need to join many multicast groups, etc.). Thus, changing addresses frequently (e.g., every few minutes) may have performance implications.


This document recommends that implementations generate new temporary addresses on a periodic basis. This can be achieved automatically by generating a new randomized interface identifier at least once every (TEMP_PREFERRED_LIFETIME - REGEN_ADVANCE - DESYNC_FACTOR) time units. As described above, generating a new temporary address REGEN_ADVANCE time units before a temporary address becomes deprecated produces addresses with a preferred lifetime no larger than TEMP_PREFERRED_LIFETIME. The value DESYNC_FACTOR is a random value (different for each client) that ensures that clients don't synchronize with each other and generate new addresses at exactly the same time. When the preferred lifetime expires, a new temporary address is generated using the new randomized interface identifier.

この文書では、実装が定期的に新しい一時アドレスを生成することをお勧めします。時間単位これは、少なくとも一度( - - REGEN_ADVANCE DESYNC_FACTOR TEMP_PREFERRED_LIFETIME)新しいランダムインタフェース識別子を生成することによって自動的に達成することができます。上述したように、一時的アドレスは廃止になる前に、新しい一時的なアドレスREGEN_ADVANCE時間単位を生成するTEMP_PREFERRED_LIFETIMEより大きくない好ましい寿命とアドレスを生成します。値DESYNC_FACTORは、クライアントが互いに同期とまったく同じ時刻に新しいアドレスを生成しないことを保証します(クライアントごとに異なる)ランダムな値です。好適寿命の期限が切れると、新しい一時アドレスは新しいランダム化されたインタフェース識別子を使用して生成されます。

Because the precise frequency at which it is appropriate to generate new addresses varies from one environment to another, implementations should provide end users with the ability to change the frequency at which addresses are regenerated. The default value is given in TEMP_PREFERRED_LIFETIME and is one day. In addition, the exact time at which to invalidate a temporary address depends on how applications are used by end users. Thus the default value given of one week (TEMP_VALID_LIFETIME) may not be appropriate in all environments. Implementations should provide end users with the ability to override both of these default values.


Finally, when an interface connects to a new link, a new randomized interface identifier should be generated immediately together with a new set of temporary addresses. If a device moves from one ethernet to another, generating a new set of temporary addresses from a different randomized interface identifier ensures that the device uses different randomized interface identifiers for the temporary addresses associated with the two links, making it more difficult to correlate addresses from the two different links as being from the same node.


4. Implications of Changing Interface Identifiers

The IPv6 addressing architecture goes to some lengths to ensure that interface identifiers are likely to be globally unique where easy to do so. During the IPng discussions of the GSE proposal [GSE], it was felt that keeping interface identifiers globally unique in practice might prove useful to future transport protocols. Usage of the algorithms in this document may complicate providing such a future flexibility.

IPv6のアドレス体系は、そのインターフェイス識別子がどこそうするのは簡単、グローバルに一意である可能性が高いことを確認するために、いくつかの長さになります。 GSE提案[GSE]ののIPng議論の中で、それは実際にはグローバルにユニークなインタフェース識別子を維持することは、将来のトランスポートプロトコルに有用であることが分かるかもしれないと感じました。この文書に記載されているアルゴリズムの使用法は、このような将来の柔軟性を提供複雑にするかもしれません。

The desires of protecting individual privacy vs. the desire to effectively maintain and debug a network can conflict with each other. Having clients use addresses that change over time will make it more difficult to track down and isolate operational problems. For example, when looking at packet traces, it could become more difficult to determine whether one is seeing behavior caused by a single errant machine, or by a number of them.


Some servers refuse to grant access to clients for which no DNS name exists. That is, they perform a DNS PTR query to determine the DNS name, and may then also perform an A query on the returned name to verify that the returned DNS name maps back into the address being used. Consequently, clients not properly registered in the DNS may be unable to access some services. As noted earlier, however, a node's DNS name (if non-changing) serves as a constant identifier. The wide deployment of the extension described in this document could challenge the practice of inverse-DNS-based "authentication," which has little validity, though it is widely implemented. In order to meet server challenges, nodes could register temporary addresses in the DNS using random names (for example a string version of the random address itself).

一部のサーバーにはDNS名が存在しないため、クライアントへのアクセスを許可することを拒否します。それは、彼らがDNS名を決定するためにDNS PTRクエリを実行し、その後も返さDNS名が戻って使用されているアドレスにマップすることを確認するために、返された名前でクエリを実行する場合があります。その結果、適切にDNSに登録されていないクライアントは、いくつかのサービスにアクセスできないことがあります。前述のように、しかし、ノードのDNS名(非変更の場合)一定の識別子として機能します。このドキュメントで説明する拡張機能の広い展開は、それが広く実装されているが、少し妥当性を持って逆DNSベースの「認証」の実践に挑戦できます。サーバー上の課題に対応するために、ノードは、(例えば、ランダムなアドレス自体の文字列バージョン)をランダムな名前を使用してDNSに一時アドレスを登録することができます。

Use of the extensions defined in this document may complicate debugging and other operational troubleshooting activities. Consequently, it may be site policy that temporary addresses should not be used. Implementations may provide a method for a trusted administrator to override the use of temporary addresses.


5. Defined Constants

Constants defined in this document include:


TEMP_VALID_LIFETIME -- Default value: 1 week. Users should be able to override the default value. TEMP_PREFERRED_LIFETIME -- Default value: 1 day. Users should be able to override the default value. REGEN_ADVANCE -- 5 seconds MAX_DESYNC_FACTOR -- 10 minutes. Upper bound on DESYNC_FACTOR. DESYNC_FACTOR -- A random value within the range 0 - MAX_DESYNC_FACTOR. It is computed once at system start (rather than each time it is used) and must never be greater than (TEMP_VALID_LIFETIME - REGEN_ADVANCE).

TEMP_VALID_LIFETIME - デフォルト値:1週間。ユーザーは、デフォルト値を上書きすることができるはずです。 TEMP_PREFERRED_LIFETIME - デフォルト値:1日。ユーザーは、デフォルト値を上書きすることができるはずです。 REGEN_ADVANCE - 5秒MA​​X_DESYNC_FACTOR - 10分。アッパーはDESYNC_FACTORに結合しました。 DESYNC_FACTOR - MAX_DESYNC_FACTOR - 範囲0内のランダムな値。それは、(むしろそれが使用されるたびに比べて)システム起動時に一度計算されると(TEMP_VALID_LIFETIME - REGEN_ADVANCE)以上にすることはできません。

6. Future Work

An implementation might want to keep track of which addresses are being used by upper layers so as to be able to remove a deprecated temporary address from internal data structures once no upper layer protocols are using it (but not before). This is in contrast to current approaches where addresses are removed from an interface when they become invalid [ADDRCONF], independent of whether or not upper layer protocols are still using them. For TCP connections, such information is available in control blocks. For UDP-based applications, it may be the case that only the applications have knowledge about what addresses are actually in use. Consequently, an implementation generally will need to use heuristics in deciding when an address is no longer in use (e.g., as is suggested in Section 3.4).

実装には、上位層プロトコルがそれを使用していない(ただし前)されると、内部データ構造から非推奨の一時的なアドレスを削除することができるようにアドレスが上位層によって使用されているかを追跡することができます。これは、上位層プロトコルがまだそれらを使用しているか否かとは無関係に、それらが無効[ADDRCONF]になったときのアドレスがインタフェースから削除される現在のアプローチとは対照的です。 TCP接続の場合、このような情報は、制御ブロックで利用可能です。 UDPベースのアプリケーションでは、アプリケーションのみがアドレスが実際に使用中であるかについての知識を持っている場合があります。その結果、実装は一般的にアドレス(例えば、3.4節で提案されたように)使用されなくなったときに決めないでヒューリスティックを使用する必要があります。

The determination as to whether to use public vs. temporary addresses can in some cases only be made by an application. For example, some applications may always want to use temporary addresses, while others may want to use them only in some circumstances or not at all. Suitable API extensions will likely need to be developed to enable individual applications to indicate with sufficient granularity their needs with regards to the use of temporary addresses.


7. Security Considerations

The motivation for this document stems from privacy concerns for individuals. This document does not appear to add any security issues beyond those already associated with stateless address autoconfiguration [ADDRCONF].


8. Acknowledgments

The authors would like to acknowledge the contributions of the IPNGWG working group and, in particular, Matt Crawford, Steve Deering and Allison Mankin for their detailed comments.


9. References

[ADDRARCH] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 2373, July 1998.

[ADDRARCH] HindenとR.とS.デアリング、 "IPバージョン6アドレッシング体系"、RFC 2373、1998年7月。

[ADDRCONF] Thomson, S. and T. Narten, "IPv6 Address Autoconfiguration", RFC 2462, December 1998.

[ADDRCONF]トムソン、S.とT. Narten氏、 "IPv6アドレスの自動構成"、RFC 2462、1998年12月。

[ADDR_SELECT] Draves, R. "Default Address Selection for IPv6", Work in Progress.

[ADDR_SELECT] Draves、R. "IPv6のデフォルトのアドレス選択" が進行中で働いています。

[COOKIES] Kristol, D. and L. Montulli, "HTTP State Management Mechanism", RFC 2965, October 2000.

[COOKIES]クリストル、D.およびL. Montulli、 "HTTP状態管理機構"、RFC 2965、2000年10月。

[DHCP] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997.

[DHCP] Droms、R.、 "動的ホスト構成プロトコル"、RFC 2131、1997年3月。

[DDNS] Vixie, R., Thomson, S., Rekhter, Y. and J. Bound, "Dynamic Updates in the Domain Name System (DNS UPDATE)", RFC 2136, April 1997.

[DDNS]いるVixie、R.、トムソン、S.、Rekhter、Y.、およびJ.はバウンド、 "ドメインネームシステムにおける動的更新(DNS更新)"、RFC 2136、1997年4月。

[DISCOVERY] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998.

[DISCOVERY] Narten氏、T.、Nordmarkと、E.およびW.シンプソン、 "IPバージョン6のための近隣探索(IPv6)の"、RFC 2461、1998年12月。

[GSE] Crawford, et al., "Separating Identifiers and Locators in Addresses: An Analysis of the GSE Proposal for IPv6", Work in Progress.


[IPSEC] Kent, S., Atkinson, R., "Security Architecture for the Internet Protocol", RFC 2401, November 1998.

[IPSEC]ケント、S.、アトキンソン、R.、 "インターネットプロトコルのためのセキュリティー体系"、RFC 2401、1998年11月。

[MD5] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April 1992.

[MD5] Rivest氏、R.、 "MD5メッセージダイジェストアルゴリズム"、RFC 1321、1992年4月。

[MOBILEIP] Perkins, C., "IP Mobility Support", RFC 2002, October 1996.

[MOBILEIP]パーキンス、C.、 "IPモビリティサポート"、RFC 2002、1996年10月。

[RANDOM] Eastlake 3rd, D., Crocker S. and J. Schiller, "Randomness Recommendations for Security", RFC 1750, December 1994.

[RANDOM]イーストレイク3日、D.、クロッカーS.とJ.シラー、 "セキュリティのためのランダム性に関する推奨事項"、RFC 1750、1994年12月。

[SERIALNUM] Moore, K., "Privacy Considerations for the Use of Hardware Serial Numbers in End-to-End Network Protocols", Work in Progress.


10. Authors' Addresses

Thomas Narten IBM Corporation P.O. Box 12195 Research Triangle Park, NC 27709-2195 USA

トーマスNarten氏IBM社の私書箱12195リサーチトライアングルパーク、NC 27709から2195 USA箱

Phone: +1 919 254 7798 EMail:

電話:+1 919 254 7798 Eメール

Richard Draves Microsoft Research One Microsoft Way Redmond, WA 98052

リチャードDravesマイクロソフトリサーチ1つのマイクロソフト道、レッドモンド、WA 98052

Phone: +1 425 936 2268 EMail:

電話:+1 425 936 2268 Eメール

11. Full Copyright Statement

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