Internet Engineering Task Force (IETF) S. Krishnan
Request for Comments: 7559 Ericsson
Updates: 4861 D. Anipko
Category: Standards Track Unaffiliated
ISSN: 2070-1721 D. Thaler
Microsoft
May 2015
Internet Engineering Task Force (IETF) S. Krishnan
Request for Comments: 7559 Ericsson
Updates: 4861 D. Anipko
Category: Standards Track Unaffiliated
ISSN: 2070-1721 D. Thaler
Microsoft
May 2015
Packet-Loss Resiliency for Router Solicitations
路由器请求的丢包弹性
Abstract
摘要
When an interface on a host is initialized, the host transmits Router Solicitations in order to minimize the amount of time it needs to wait until the next unsolicited multicast Router Advertisement is received. In certain scenarios, these Router Solicitations transmitted by the host might be lost. This document specifies a mechanism for hosts to cope with the loss of the initial Router Solicitations.
当主机上的接口初始化时，主机会发送路由器请求，以尽量减少在收到下一个未经请求的多播路由器广告之前所需的等待时间。在某些情况下，主机发送的这些路由器请求可能会丢失。本文档指定了主机处理初始路由器请求丢失的机制。
Status of This Memo
关于下段备忘
This is an Internet Standards Track document.
这是一份互联网标准跟踪文件。
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。有关互联网标准的更多信息，请参见RFC 5741第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7559.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问http://www.rfc-editor.org/info/rfc7559.
Copyright Notice
版权公告
Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2015 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions Used in This Document . . . . . . . . . . . . 3
2. Proposed Algorithm . . . . . . . . . . . . . . . . . . . . . 3
2.1. Stopping the Retransmissions . . . . . . . . . . . . . . 3
3. Configuring the Use of Retransmissions . . . . . . . . . . . 4
4. Known Limitations . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions Used in This Document . . . . . . . . . . . . 3
2. Proposed Algorithm . . . . . . . . . . . . . . . . . . . . . 3
2.1. Stopping the Retransmissions . . . . . . . . . . . . . . 3
3. Configuring the Use of Retransmissions . . . . . . . . . . . 4
4. Known Limitations . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
As specified in [RFC4861], when an interface on a host is initialized, in order to obtain Router Advertisements quickly, a host transmits up to MAX_RTR_SOLICITATIONS (3) Router Solicitation (RS) messages, each separated by at least RTR_SOLICITATION_INTERVAL (4) seconds. In certain scenarios, these Router Solicitations transmitted by the host might be lost. For example, the host is connected to a bridged residential gateway over Ethernet or Wi-Fi. LAN connectivity is achieved at interface initialization, but the upstream WAN connectivity is not active yet. In this case, the host just gives up after the initial RS retransmits.
如[RFC4861]中所述，当主机上的接口初始化时，为了快速获得路由器广告，主机最多发送MAX_RTR_请求（3）个路由器请求（RS）消息，每个消息之间至少间隔RTR_请求间隔（4）秒。在某些情况下，主机发送的这些路由器请求可能会丢失。例如，主机通过以太网或Wi-Fi连接到桥接的住宅网关。LAN连接在接口初始化时实现，但上游WAN连接尚未激活。在这种情况下，主机只是在初始RS重新传输后放弃。
Once the initial RSs are lost, the host gives up and assumes that there are no routers on the link as specified in Section 6.3.7 of [RFC4861]. The host will not have any form of Internet connectivity until the next unsolicited multicast Router Advertisement is received. These Router Advertisements are transmitted at most
一旦初始RSs丢失，主机将放弃，并假设链路上没有[RFC4861]第6.3.7节规定的路由器。在收到下一个未经请求的多播路由器广告之前，主机将不会具有任何形式的Internet连接。这些路由器广告最多只能传输
MaxRtrAdvInterval seconds apart (maximum value 1800 seconds). Thus, in the worst-case scenario a host would be without any connectivity for 30 minutes. This delay may be unacceptable in some scenarios.
最大间隔时间为秒（最大值为1800秒）。因此，在最坏的情况下，主机将在30分钟内没有任何连接。在某些情况下，这种延迟可能是不可接受的。
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 [RFC2119].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[RFC2119]中所述进行解释。
To achieve resiliency to packet loss, the host needs to continue retransmitting the Router Solicitations until it receives a Router Advertisement, or until it is willing to accept that no router exists. If the host continues retransmitting the RSs at RTR_SOLICITATION_INTERVAL second intervals, it may cause excessive network traffic if a large number of such hosts exists. To achieve resiliency while keeping the aggregate network traffic low, the host can use some form of exponential backoff algorithm to retransmit the RSs.
为了实现对数据包丢失的恢复能力，主机需要继续重新传输路由器请求，直到它收到路由器公告，或者直到它愿意接受不存在路由器为止。如果主机继续以RTR_请求_间隔秒的间隔重新传输RSs，则如果存在大量此类主机，则可能会导致网络流量过大。为了在保持聚合网络流量较低的同时实现弹性，主机可以使用某种形式的指数退避算法来重新传输RSs。
Hosts complying to this specification MUST use the exponential backoff algorithm for retransmits that is described in Section 14 of [RFC3315] in order to continuously retransmit the Router Solicitations until a Router Advertisement is received. The hosts SHOULD use the following variables as input to the retransmission algorithm:
符合本规范的主机必须使用[RFC3315]第14节所述的指数退避算法进行重新传输，以便连续重新传输路由器请求，直到收到路由器公告。主机应使用以下变量作为重传算法的输入：
IRT (Initial Retransmission Time): 4 seconds MRT (Maximum Retransmission Time): 3600 seconds MRC (Maximum Retransmission Count): 0 MRD (Maximum Retransmission Duration): 0
IRT（初始重传时间）：4秒MRT（最大重传时间）：3600秒MRC（最大重传计数）：0 MRD（最大重传持续时间）：0
The initial value IRT was chosen to be in line with the current retransmission interval (RTR_SOLICITATION_INTERVAL) that is specified by [RFC4861], and the maximum retransmission time MRT was chosen to be in line with the new value of SOL_MAX_RT as specified by [RFC7083]. This is to ensure that the short-term behavior of the RSs is similar to what is experienced in current networks, and that longer-term persistent retransmission behavior trends towards being similar to that of DHCPv6 [RFC3315] [RFC7083].
初始值IRT被选择为与[RFC4861]指定的当前重传间隔（RTR_请求_间隔）一致，最大重传时间MRT被选择为与[RFC7083]指定的新的SOL_MAX_RT值一致。这是为了确保RSs的短期行为类似于当前网络中所经历的行为，并且长期持续重传行为趋向于类似于DHCPv6[RFC3315][RFC7083]的行为。
On multicast-capable links, the hosts following this specification SHOULD stop retransmitting the RSs when Router Discovery is successful (i.e., an RA with a non-zero Router Lifetime that results
在支持多播的链路上，当路由器发现成功时，遵循此规范的主机应停止重新传输RSs（即，结果为路由器寿命非零的RA）
in a default route is received). If an RA is received from a router and it does not result in a default route (i.e., Router Lifetime is zero), the host MUST continue retransmitting the RSs.
在默认情况下，会接收到路由）。如果从路由器接收到RA，并且不会产生默认路由（即，路由器生存期为零），则主机必须继续重新传输RSs。
On non-multicast links, the hosts following this specification MUST continue retransmitting the RSs even after an RA that results in a default route is received. This is required because, in such links, sending an RA can only be triggered by an RS. Please note that such links have special mechanisms for sending RSs as well. For example, the mechanism specified in Section 8.3.4 of the Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) [RFC5214] unicasts the RSs to specific routers.
在非多播链路上，遵循此规范的主机必须继续重新传输RSs，即使在接收到导致默认路由的RA之后也是如此。这是必需的，因为在此类链接中，发送RA只能由RS触发。请注意，此类链接也具有发送RSs的特殊机制。例如，站点内自动隧道寻址协议（ISATAP）[RFC5214]第8.3.4节中规定的机制将RSs单播到特定路由器。
Implementations of this specification are encouraged to provide a configuration option to enable or disable potentially infinite RS retransmissions. If a configuration option is provided, it MUST enable RS retransmissions by default. Providing an option to enable/ disable retransmissions on a per-interface basis allows network operators to configure RS behavior in the most applicable way for each connected link.
鼓励本规范的实现提供一个配置选项，以启用或禁用可能无限的RS重传。如果提供了配置选项，则默认情况下必须启用RS重传。提供一个选项来启用/禁用每个接口的重传，允许网络运营商以最适用的方式为每个连接的链路配置RS行为。
When an IPv6-capable host attaches to a network that does not have IPv6 enabled, it transmits 3 (MAX_RTR_SOLICITATIONS) Router Solicitations as specified in [RFC4861]. If it receives no Router Advertisements, it assumes that there are no routers present on the link and it ceases to send further RSs. With the mechanism specified in this document, the host will continue to retransmit RSs indefinitely at the rate of approximately 1 RS per hour. It is unclear how to differentiate between such a network with no IPv6 routers and a link where an IPv6 router is temporarily unreachable but could become reachable in the future.
当支持IPv6的主机连接到未启用IPv6的网络时，它将按照[RFC4861]中的规定传输3个（最大RTR请求）路由器请求。如果它没有收到路由器广告，则假定链路上没有路由器，并且它停止发送进一步的RSs。使用本文档中指定的机制，主机将继续以大约每小时1rs的速率无限期地重新传输RSs。目前尚不清楚如何区分这种没有IPv6路由器的网络和IPv6路由器暂时无法访问但将来可能可以访问的链路。
This document does not present any additional security issues beyond those discussed in [RFC4861] and those RFCs that update [RFC4861].
除[RFC4861]和更新[RFC4861]的RFC中讨论的安全问题外，本文件未提出任何其他安全问题。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，DOI 10.17487/RFC2119，1997年3月<http://www.rfc-editor.org/info/rfc2119>.
[RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 2003, <http://www.rfc-editor.org/info/rfc3315>.
[RFC3315]Droms，R.，Ed.，Bound，J.，Volz，B.，Lemon，T.，Perkins，C.，和M.Carney，“IPv6的动态主机配置协议（DHCPv6）”，RFC 3315，DOI 10.17487/RFC3315，2003年7月<http://www.rfc-editor.org/info/rfc3315>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, <http://www.rfc-editor.org/info/rfc4861>.
[RFC4861]Narten，T.，Nordmark，E.，Simpson，W.，和H.Soliman，“IP版本6（IPv6）的邻居发现”，RFC 4861，DOI 10.17487/RFC48612007年9月<http://www.rfc-editor.org/info/rfc4861>.
[RFC7083] Droms, R., "Modification to Default Values of SOL_MAX_RT and INF_MAX_RT", RFC 7083, DOI 10.17487/RFC7083, November 2013, <http://www.rfc-editor.org/info/rfc7083>.
[RFC7083]Droms，R.，“修改SOL_MAX_RT和INF_MAX_RT的默认值”，RFC 7083，DOI 10.17487/RFC7083，2013年11月<http://www.rfc-editor.org/info/rfc7083>.
[RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, DOI 10.17487/RFC5214, March 2008, <http://www.rfc-editor.org/info/rfc5214>.
[RFC5214]Templin，F.，Gleeson，T.，和D.Thaler，“站点内自动隧道寻址协议（ISATAP）”，RFC 5214，DOI 10.17487/RFC5214，2008年3月<http://www.rfc-editor.org/info/rfc5214>.
Acknowledgements
致谢
The authors would like to thank Steve Baillargeon, Erik Kline, Andrew Yourtchenko, Ole Troan, Erik Nordmark, Lorenzo Colitti, Thomas Narten, Ran Atkinson, Allison Mankin, Les Ginsberg, Brian Carpenter, Barry Leiba, Brian Haberman, Spencer Dawkins, Alia Atlas, Stephen Farrell, and Mehmet Ersue for their reviews and suggestions that made this document better.
作者要感谢Steve Baillargeon、Erik Kline、Andrew Yourtchenko、Ole Troan、Erik Nordmark、Lorenzo Coletti、Thomas Narten、Ran Atkinson、Allison Mankin、Les Ginsberg、Brian Carpenter、Barry Leiba、Brian Haberman、Spencer Dawkins、Alia Atlas、Stephen Farrell、，和Mehmet Ersue，感谢他们的评论和建议，这些评论和建议使本文件变得更好。
Authors' Addresses
作者地址
Suresh Krishnan Ericsson 8400 Decarie Blvd. Town of Mount Royal, QC Canada
苏雷什·克里希南·爱立信德卡里大道8400号。加拿大皇家山镇
Phone: +1 514 345 7900 x42871
EMail: suresh.krishnan@ericsson.com
Phone: +1 514 345 7900 x42871
EMail: suresh.krishnan@ericsson.com
Dmitry Anipko Unaffiliated
Dmitry Anipko非附属公司
Phone: +1 425 442 6356
EMail: dmitry.anipko@gmail.com
Phone: +1 425 442 6356
EMail: dmitry.anipko@gmail.com
Dave Thaler Microsoft One Microsoft Way Redmond, WA United States
Dave Thaler美国华盛顿州雷德蒙微软一路
EMail: dthaler@microsoft.com
EMail: dthaler@microsoft.com