Network Working Group                                           JH. Choi
Request for Comments: 4135                                   Samsung AIT
Category: Informational                                         G. Daley
                                                  CTIE Monash University
                                                             August 2005
        
Network Working Group                                           JH. Choi
Request for Comments: 4135                                   Samsung AIT
Category: Informational                                         G. Daley
                                                  CTIE Monash University
                                                             August 2005
        

Goals of Detecting Network Attachment in IPv6

IPv6中检测网络连接的目标

Status of This Memo

关于下段备忘

This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

本备忘录为互联网社区提供信息。它没有规定任何类型的互联网标准。本备忘录的分发不受限制。

Copyright Notice

版权公告

Copyright (C) The Internet Society (2005).

版权所有(C)互联网协会(2005年)。

Abstract

摘要

When a host establishes a new link-layer connection, it may or may not have a valid IP configuration for Internet connectivity. The host may check for link change (i.e., determine whether a link change has occurred), and then, based on the result, it can automatically decide whether its IP configuration is still valid. During link identity detection, the host may also collect necessary information to initiate a new IP configuration if the IP subnet has changed. In this memo, this procedure is called Detecting Network Attachment (DNA). DNA schemes should be precise, sufficiently fast, secure, and of limited signaling.

当主机建立新的链路层连接时,它可能具有或不具有有效的Internet连接IP配置。主机可以检查链路更改(即,确定是否发生了链路更改),然后根据结果自动确定其IP配置是否仍然有效。在链路标识检测期间,如果IP子网已更改,主机还可能收集必要的信息以启动新的IP配置。在本备忘录中,此过程称为检测网络连接(DNA)。DNA方案应该精确、足够快、安全且信号有限。

Table of Contents

目录

   1. Introduction ....................................................2
   2. Problems in Detecting Network Attachment ........................3
      2.1. Wireless Link Properties ...................................3
      2.2. Link Identity Detection with a Single RA ...................3
      2.3. Delays .....................................................4
   3. Goals for Detecting Network Attachment ..........................5
      3.1. Goals List .................................................6
   4. Security Considerations .........................................6
   5. Acknowledgements ................................................7
   6. References ......................................................8
      6.1. Normative References .......................................8
      6.2. Informative References .....................................8
        
   1. Introduction ....................................................2
   2. Problems in Detecting Network Attachment ........................3
      2.1. Wireless Link Properties ...................................3
      2.2. Link Identity Detection with a Single RA ...................3
      2.3. Delays .....................................................4
   3. Goals for Detecting Network Attachment ..........................5
      3.1. Goals List .................................................6
   4. Security Considerations .........................................6
   5. Acknowledgements ................................................7
   6. References ......................................................8
      6.1. Normative References .......................................8
      6.2. Informative References .....................................8
        
1. Introduction
1. 介绍

When a host has established a new link-layer connection, it can send and receive some IPv6 packets on the link, including those used for configuration. On the other hand, the host has Internet connectivity only when it is able to exchange packets with off-link destinations.

当主机建立了新的链路层连接时,它可以在链路上发送和接收一些IPv6数据包,包括用于配置的数据包。另一方面,主机只有在能够与非链接目的地交换数据包时才具有Internet连接。

When a link-layer connection is established or re-established, the host may not know whether its existing IP configuration is still valid for Internet connectivity. A subnet change might have occurred when the host changed its point of attachment.

当建立或重新建立链路层连接时,主机可能不知道其现有IP配置是否仍然适用于Internet连接。当主机更改其连接点时,可能发生了子网更改。

In practice, the host doesn't know which of its addresses are valid on the newly attached link. It also doesn't know whether its existing default router is on this link or whether its neighbor cache entries are valid. Correct configuration of each of these components is necessary in order to send packets on and off the link.

实际上,主机不知道在新连接的链接上哪些地址是有效的。它也不知道它现有的默认路由器是否在这个链接上,或者它的邻居缓存条目是否有效。为了在链路上和链路下发送数据包,必须正确配置这些组件中的每一个。

To examine the status of the existing configuration, a host may check whether a 'link change' has occurred. In this document, the term 'link' is as defined in RFC 2461 [1]. The notion 'link' is not identical with the notion 'subnet', as defined in RFC 3753 [2]. For example, there may be more than one subnet on a link, and a host connected to a link may be part of one or more of the subnets on the link.

要检查现有配置的状态,主机可以检查是否发生了“链接更改”。在本文件中,“链接”一词的定义见RFC 2461[1]。“链路”的概念与RFC 3753[2]中定义的“子网”的概念不同。例如,链路上可能有多个子网,连接到链路的主机可能是链路上一个或多个子网的一部分。

Today, a link change necessitates an IP configuration change. Whenever a host detects that it has remained at the same link, it can usually assume its IP configuration is still valid. Otherwise, the existing one is no longer valid, and a new configuration must be acquired. Therefore, to examine the validity of an IP configuration, all that is required is that the host checks for link change.

如今,链路更改需要更改IP配置。每当主机检测到它保持在同一链路上时,它通常可以假定其IP配置仍然有效。否则,现有配置将不再有效,必须获取新配置。因此,要检查IP配置的有效性,只需主机检查链路更改。

In the process of checking for link change, a host may collect some of the necessary information for a new IP configuration, such as on-link prefixes. So, when an IP subnet change has occurred, the host can immediately initiate the process of getting a new IP configuration. This may reduce handoff delay and minimize signaling.

在检查链路更改的过程中,主机可能会收集新IP配置的一些必要信息,例如链路前缀。因此,当IP子网发生更改时,主机可以立即启动获取新IP配置的过程。这可以减少切换延迟并最小化信令。

Rapid attachment detection is required for a device that changes subnet while having on-going sessions. This may be the case if a host is connected intermittently, is a mobile node, or has urgent data to transmit upon attachment to a link.

对于在进行会话时更改子网的设备,需要快速连接检测。如果主机间歇性连接、是移动节点或在连接到链路时有紧急数据要传输,则可能出现这种情况。

Detecting Network Attachment (DNA) is the process by which a host collects the appropriate information and detects the identity of its currently attached link to ascertain the validity of its IP configuration.

检测网络连接(DNA)是主机收集适当信息并检测其当前连接链路的身份以确定其IP配置有效性的过程。

DNA schemes are typically run per interface. When a host has multiple interfaces, the host separately checks for link changes on each interface.

DNA方案通常按接口运行。当主机具有多个接口时,主机将分别检查每个接口上的链接更改。

It is important to note that DNA process does not include the actual IP configuration procedure. For example, with respect to DHCP, the DNA process may determine that the host needs to get some configuration information from a DHCP server. However, the process of actually retrieving the information from a DHCP server falls beyond the scope of DNA.

需要注意的是,DNA过程不包括实际的IP配置过程。例如,关于DHCP,DNA过程可以确定主机需要从DHCP服务器获取一些配置信息。然而,从DHCP服务器实际检索信息的过程超出了DNA的范围。

This document considers the DNA procedure only from the IPv6 point of view, unless explicitly mentioned otherwise. Thus, the term "IP" is to be understood to denote IPv6, by default. For the IPv4 case, refer to [7].

除非另有明确说明,本文件仅从IPv6的角度考虑DNA程序。因此,术语“IP”在默认情况下被理解为表示IPv6。有关IPv4的情况,请参阅[7]。

2. Problems in Detecting Network Attachment
2. 网络连接检测中的几个问题

A number of issues make DNA complicated. First, wireless connectivity is not as clear-cut as wired connectivity. Second, it's difficult for a single Router Advertisement (RA) message to indicate a link change. Third, the current Router Discovery specification specifies that routers wait a random delay of 0-.5 seconds prior to responding with a solicited RA. This delay can be significant and may result in service disruption.

许多问题使DNA变得复杂。首先,无线连接不像有线连接那样清晰。其次,单个路由器广告(RA)消息很难指示链路更改。第三,当前的路由器发现规范规定路由器在响应请求的RA之前等待0-0.5秒的随机延迟。此延迟可能非常严重,并可能导致服务中断。

2.1. Wireless Link Properties
2.1. 无线链路属性

Unlike in wired environments, what constitutes a wireless link is variable both in time and space. Wireless links do not have clear boundaries. This may be illustrated by the fact that a host may be within the coverage area of multiple (802.11) access points at the same time. Moreover, connectivity on a wireless link can be very volatile, which may make link identity detection hard. For example, it takes time for a host to check for link change. If the host ping-pongs between two links and doesn't stay long enough at a given link, it can't complete the DNA procedure.

与有线环境不同,无线链路的组成在时间和空间上都是可变的。无线链路没有明确的边界。这可以通过主机可以同时位于多个(802.11)接入点的覆盖区域内的事实来说明。此外,无线链路上的连接可能非常不稳定,这可能使链路身份检测变得困难。例如,主机检查链接更改需要时间。如果宿主在两条链路之间乒乓,并且在给定链路上停留的时间不够长,则无法完成DNA过程。

2.2. Link Identity Detection with a Single RA
2.2. 单RA链路身份检测

Usually, a host gets the information necessary for IP configuration from RA messages. Based on the current definition [1], it's difficult for a host to check for link change upon receipt of a single RA.

通常,主机从RA消息获取IP配置所需的信息。根据当前定义[1],主机很难在收到单个RA后检查链路更改。

To detect link identity, a host may compare the information in an RA, such as router address or prefixes, with the locally stored information.

为了检测链路标识,主机可以将RA中的信息(例如路由器地址或前缀)与本地存储的信息进行比较。

The host may use received router addresses to check for link change. The router address in the source address field of an RA is of link-local scope, however, so its uniqueness is not guaranteed outside a link. If it happens that two different router interfaces on different links have the same link-local address, the host can't detect that it has moved from one link to another by checking the router address in RA messages.

主机可以使用收到的路由器地址检查链路更改。RA的源地址字段中的路由器地址属于链路本地范围,因此在链路外部不能保证其唯一性。如果不同链路上的两个不同路由器接口具有相同的链路本地地址,则主机无法通过检查RA消息中的路由器地址来检测它是否已从一个链路移动到另一个链路。

The set of all global prefixes assigned to a link can represent link identity. The host may compare the prefixes in an incoming RA with the currently stored ones. An unsolicited RA message, however, can omit some prefixes for convenience [1], and it's not easy for a host to attain and retain all the prefixes on a link with certainty. Therefore, neither the absence of a previously known prefix nor the presence of a previously unknown prefix in the RA guarantees that a link change has occurred.

分配给链接的所有全局前缀的集合可以表示链接标识。主机可以将传入RA中的前缀与当前存储的前缀进行比较。然而,出于方便[1],未经请求的RA消息可以省略一些前缀,并且主机不容易确定地获得并保留链接上的所有前缀。因此,在RA中不存在先前已知的前缀或存在先前未知的前缀都不能保证链路改变已经发生。

2.3. Delays
2.3. 耽搁

The following issues cause DNA delay that may result in communication disruption.

以下问题导致DNA延迟,可能导致通信中断。

1) Delay for receiving a hint

1) 延迟接收提示

A hint is an indication that a link change might have occurred. This hint itself doesn't confirm a link change, but initiates appropriate DNA procedures to detect the identity of the currently attached link.

提示表示可能发生了链接更改。此提示本身并不确认链接更改,但会启动适当的DNA程序来检测当前连接链接的身份。

Hints come in various forms and differ in how they indicate a possible link change. They can be link-layer event notifications [6], the lack of RA from the default router, or the receipt of a new RA. The time taken to receive a hint also varies.

提示的形式多种多样,在表示可能的链接更改的方式上有所不同。它们可以是链路层事件通知[6]、默认路由器缺少RA或收到新RA。接收提示所需的时间也各不相同。

As soon as a new link-layer connection has been made, the link layer may send a link-up notification to the IP layer. A host may interpret the new link-layer connection as a hint for a possible link change. With link-layer support, a host can receive such a hint almost instantly.

一旦建立了新的链路层连接,链路层就可以向IP层发送链路启动通知。主机可能会将新的链路层连接解释为可能的链路更改提示。有了链接层支持,主机几乎可以立即收到这样的提示。

Mobile IPv6 [4] defines the use of RA Interval Timer expiry for a hint. A host keeps monitoring for periodic RAs and interprets the lack of them as a hint. It may implement its own policy to determine the number of missing RAs needed to interpret that as a hint. Thus, the delay depends on the Router Advertisement interval.

移动IPv6[4]定义使用RA间隔计时器到期作为提示。主机保持对周期性RAs的监视,并将缺少RAs解释为提示。它可以实施自己的策略来确定将其解释为提示所需的缺失RAs的数量。因此,延迟取决于路由器播发间隔。

Without schemes such as those above, a host must receive a new RA from a new router to detect a possible link change. The detection time then also depends on the Router Advertisement frequency.

如果没有上述方案,主机必须从新路由器接收新RA以检测可能的链路更改。检测时间也取决于路由器广告频率。

Periodic RA beaconing transmits packets within an interval varying randomly between MinRtrAdvInterval to MaxRtrAdvInterval seconds. Because a network attachment is unrelated to the advertisement time on the new link, hosts are expected to arrive, on average, halfway through the interval. This is approximately 1.75 seconds with Neighbor Discovery [1] advertisement rates.

周期性RA信标在MinRtrAdvInterval到MaxRtrAdvInterval秒之间随机变化的间隔内传输数据包。因为网络连接与新链接上的广告时间无关,所以主机平均在间隔的一半到达。对于邻居发现[1]广告速率,这大约是1.75秒。

2) Random delay execution for RS/RA exchange

2) RS/RA交换的随机延迟执行

Router Solicitation and Router Advertisement messages are used for Router Discovery. According to [1], it is sometimes necessary for a host to wait a random amount of time before it may send an RS, and for a router to wait before it may reply with an RA.

路由器请求和路由器广告消息用于路由器发现。根据[1],有时主机在发送RS之前需要等待一段随机时间,路由器在发送RA之前需要等待一段随机时间。

According to RFC 2461 [1], the following apply:

根据RFC 2461[1],以下内容适用:

- Before a host sends an initial solicitation, it SHOULD delay the transmission for a random amount of time between 0 and MAX_RTR_SOLICITATION_DELAY (1 second).

- 在主机发送初始请求之前,它应该将传输延迟0到最大请求延迟(1秒)之间的随机时间量。

- Furthermore, any RA sent in response to a Router Solicitation MUST be delayed by a random time between 0 and MAX_RA_DELAY_TIME (0.5 seconds).

- 此外,响应路由器请求而发送的任何RA必须延迟0到最大RA延迟时间(0.5秒)之间的随机时间。

3. Goals for Detecting Network Attachment
3. 检测网络连接的目标

The DNA working group has been chartered to define an improved scheme for detecting IPv6 network attachment. In this section, we define the goals that any such solution should aim to fulfill.

DNA工作组被授权定义一种检测IPv6网络连接的改进方案。在本节中,我们将定义任何此类解决方案都应该实现的目标。

DNA solutions should correctly determine whether a link change has occurred. Additionally, they should be sufficiently fast so that there would be no or at most minimal service disruption. They should neither flood the link with related signaling nor introduce new security holes.

DNA解决方案应正确确定是否发生了链接更改。此外,它们应该足够快,这样就不会或最多只会造成最小的服务中断。它们既不应该用相关的信令淹没链路,也不应该引入新的安全漏洞。

When defining new solutions, it is necessary to investigate the usage of available tools, Neighbor Solicitation/Neighbor Advertisement messages, RS/RA messages, link-layer event notifications [6], and other features. This will allow precise description of procedures for efficient DNA Schemes.

定义新解决方案时,有必要调查可用工具、邻居请求/邻居广告消息、RS/RA消息、链路层事件通知[6]和其他功能的使用情况。这将允许精确描述有效DNA方案的程序。

3.1. Goals List
3.1. 目标清单

G1 DNA schemes should detect the identity of the currently attached link to ascertain the validity of the existing IP configuration. They should recognize and determine whether a link change has occurred and initiate the process of acquiring a new configuration if necessary.

G1 DNA方案应检测当前连接链路的身份,以确定现有IP配置的有效性。他们应识别并确定是否发生了链路更改,并在必要时启动获取新配置的过程。

G2 DNA schemes should detect the identity of an attached link with minimal latency lest there should be service disruption.

G2 DNA方案应以最小延迟检测连接链路的身份,以免出现服务中断。

G3 If a host has not changed a link, DNA schemes should not falsely assume a link change, and an IP configuration change should not occur.

G3如果主机未更改链路,则DNA方案不应错误地假设链路更改,并且不应发生IP配置更改。

G4 DNA schemes should not cause undue signaling on a link.

G4 DNA方案不应在链路上引起不适当的信号。

G5 DNA schemes should make use of existing signaling mechanisms where available.

G5 DNA方案应利用现有的信号机制。

G6 DNA schemes should make use of signaling within the link (particularly link-local scope messages), because communication off-link may not be achievable in the case of a link change.

G6 DNA方案应利用链路内的信令(尤其是链路本地范围消息),因为在链路改变的情况下,可能无法实现非链路通信。

G7 DNA schemes should be compatible with security schemes such as Secure Neighbor Discovery [3].

G7 DNA方案应与安全方案兼容,如安全邻居发现[3]。

G8 DNA schemes should not introduce new security vulnerabilities. The node supporting DNA schemes should not expose itself or other nodes on a link to additional man-in-the-middle, identity-revealing, or denial-of-service attacks.

G8 DNA计划不应引入新的安全漏洞。支持DNA方案的节点不应将自身或链接上的其他节点暴露给其他中间人、身份泄露或拒绝服务攻击。

G9 Nodes (such as routers or hosts) that support DNA schemes should work appropriately with unmodified nodes that do not.

支持DNA方案的G9节点(如路由器或主机)应与不支持DNA方案的未修改节点一起正常工作。

G10 Hosts, especially in wireless environments, may perceive routers reachable on different links. DNA schemes should take into consideration the case where a host is attached to more than one link at the same time.

G10主机,尤其是在无线环境中,可能会感知到不同链路上可到达的路由器。DNA方案应考虑主机同时连接到多个链路的情况。

4. Security Considerations
4. 安全考虑

The DNA process is intimately related to the Neighbor Discovery protocol [1] and its trust model and threats have much in common with those presented in RFC 3756 [5]. Nodes connected over wireless interfaces may be particularly susceptible to jamming, monitoring, and packet-insertion attacks.

DNA过程与邻居发现协议[1]密切相关,其信任模型和威胁与RFC 3756[5]中提出的有很多共同点。通过无线接口连接的节点可能特别容易受到干扰、监视和数据包插入攻击。

With unsecured DNA schemes, it is inadvisable for a host to adjust its security based on which network it believes it is attached to. For example, it would be inappropriate for a host to disable its personal firewall because it believed that it had connected to a home network.

对于不安全的DNA方案,主机不应根据其认为连接到的网络调整其安全性。例如,主机禁用其个人防火墙是不合适的,因为它认为它已连接到家庭网络。

Even in the case where authoritative information (routing and prefix state) are advertised, wireless network attackers may still prevent soliciting nodes from receiving packets. This may cause unnecessary IP configuration change in some devices. Such attacks may be used to make a host preferentially select a particular configuration or network access.

即使在发布权威信息(路由和前缀状态)的情况下,无线网络攻击者仍可能阻止请求节点接收数据包。这可能会在某些设备中导致不必要的IP配置更改。此类攻击可用于使主机优先选择特定配置或网络访问。

Devices receiving confirmations of reachability (for example, from upper-layer protocols) should be aware that unless these indications are sufficiently authenticated, reachability may falsely be asserted by an attacker. Similarly, even if such reachability tests are known to originate from a trusted source, they should be ignored for reachability confirmation if the packets are not fresh or have been replayed. This may reduce the effective window for attackers replaying otherwise authentic data.

接收到可达性确认(例如,来自上层协议)的设备应该知道,除非这些指示经过充分验证,否则攻击者可能会错误地断言可达性。类似地,即使已知此类可达性测试源自可信源,如果数据包不新鲜或已被重放,则应忽略这些测试以进行可达性确认。这可能会减少攻击者重播其他真实数据的有效窗口。

It may be dangerous to receive link-change notifications from the link layer and network layer, if they are received from devices that are insufficiently authenticated. In particular, notifications that authentication has completed at the link layer may not imply that a security relationship is available at the network layer. Additional authentication may be required at the network layer to justify modification of IP configuration.

从链路层和网络层接收链路更改通知可能很危险,如果这些通知是从未充分验证的设备接收的。特别是,在链路层完成认证的通知可能并不意味着在网络层存在安全关系。可能需要在网络层进行额外的身份验证,以证明修改IP配置是合理的。

5. Acknowledgements
5. 致谢

Erik Nordmark has contributed significantly to work predating this document. Also Ed Remmell's comments on the inconsistency of RA information were most illuminating. The authors wish to express our appreciation to Pekka Nikander for valuable feedback. We gratefully acknowledge the generous assistance we received from Shubhranshu Singh for clarifying the structure of the arguments. Thanks to Brett Pentland, Nick Moore, Youn-Hee Han, JaeHoon Kim, Alper Yegin, Jim Bound, and Jari Arkko for their contributions to this document.

Erik Nordmark对本文件之前的工作做出了重大贡献。此外,Ed Remmell关于RA信息不一致性的评论最具启发性。作者希望对Pekka Nikander的宝贵反馈表示感谢。我们感谢Shubhranshu Singh为我们澄清论点结构提供的慷慨援助。感谢Brett Pentland、Nick Moore、Youn Hee Han、JaeHoon Kim、Alper Yegin、Jim Bound和Jari Arkko对本文件的贡献。

6. References
6. 工具书类
6.1. Normative References
6.1. 规范性引用文件

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

[1] Narten,T.,Nordmark,E.,和W.Simpson,“IP版本6(IPv6)的邻居发现”,RFC24611998年12月。

[2] Manner, J. and M. Kojo, "Mobility Related Terminology", RFC 3753, June 2004.

[2] Way,J.和M.Kojo,“机动性相关术语”,RFC 3753,2004年6月。

[3] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.

[3] Arkko,J.,Kempf,J.,Zill,B.,和P.Nikander,“安全邻居发现(SEND)”,RFC 39712005年3月。

6.2. Informative References
6.2. 资料性引用

[4] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004.

[4] Johnson,D.,Perkins,C.,和J.Arkko,“IPv6中的移动支持”,RFC 37752004年6月。

[5] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor Discovery (ND) Trust Models and Threats", RFC 3756, May 2004.

[5] Nikander,P.,Kempf,J.和E.Nordmark,“IPv6邻居发现(ND)信任模型和威胁”,RFC 3756,2004年5月。

[6] Yegin, A., "Link-layer Event Notifications for Detecting Network Attachments", work in progress, July 2005.

[6] Yegin,A.,“检测网络附件的链路层事件通知”,正在进行的工作,2005年7月。

[7] Aboba, B., "Detecting Network Attachment (DNA) in IPv4", work in progress, June 2005.

[7] Aboba,B.,“检测IPv4中的网络连接(DNA)”,正在进行的工作,2005年6月。

Authors' Addresses

作者地址

JinHyeock Choi Samsung AIT Communication & N/W Lab P.O.Box 111 Suwon 440-600 KOREA

韩国水原市111号实验室邮政信箱邮编:440-600

   Phone: +82 31 280 9233
   EMail: jinchoe@samsung.com
        
   Phone: +82 31 280 9233
   EMail: jinchoe@samsung.com
        

Greg Daley CTIE Monash University Centre for Telecommunications and Information Engineering Monash University Clayton 3800 Victoria Australia

Greg Daley CTIE莫纳什大学电信和信息工程中心莫纳什大学澳大利亚维多利亚州克莱顿3800

   Phone: +61 3 9905 4655
   EMail: greg.daley@eng.monash.edu.au
        
   Phone: +61 3 9905 4655
   EMail: greg.daley@eng.monash.edu.au
        

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确认

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