Network Working Group P. Traina
Request for Comments: 3065 Juniper Networks, Inc.
Obsoletes: 1965 D. McPherson
Category: Standards Track Amber Networks, Inc.
J. Scudder
Cisco Systems, Inc.
February 2001
Network Working Group P. Traina
Request for Comments: 3065 Juniper Networks, Inc.
Obsoletes: 1965 D. McPherson
Category: Standards Track Amber Networks, Inc.
J. Scudder
Cisco Systems, Inc.
February 2001
Autonomous System Confederations for BGP
BGP自治系统联合会
Status of this Memo
本备忘录的状况
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.
本文件规定了互联网社区的互联网标准跟踪协议，并要求进行讨论和提出改进建议。有关本协议的标准化状态和状态，请参考当前版本的“互联网官方协议标准”（STD 1）。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2001). All Rights Reserved.
版权所有（C）互联网协会（2001年）。版权所有。
Abstract
摘要
The Border Gateway Protocol (BGP) is an inter-autonomous system routing protocol designed for Transmission Control Protocol/Internet Protocol (TCP/IP) networks. BGP requires that all BGP speakers within a single autonomous system (AS) must be fully meshed. This represents a serious scaling problem that has been well documented in a number of proposals.
边界网关协议（BGP）是一种为传输控制协议/互联网协议（TCP/IP）网络设计的自治系统间路由协议。BGP要求单个自治系统（AS）内的所有BGP扬声器必须完全啮合。这是一个严重的缩放问题，在许多提案中都有很好的记录。
This document describes an extension to BGP which may be used to create a confederation of autonomous systems that is represented as a single autonomous system to BGP peers external to the confederation, thereby removing the "full mesh" requirement. The intention of this extension is to aid in policy administration and reduce the management complexity of maintaining a large autonomous system.
本文档描述了对BGP的扩展，该扩展可用于创建自治系统联盟，该联盟表示为联盟外部BGP对等点的单个自治系统，从而消除“全网格”要求。此扩展的目的是帮助策略管理，降低维护大型自治系统的管理复杂性。
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].
本文件中的关键词“必须”、“不得”、“要求”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[RFC 2119]中所述进行解释。
As currently defined, BGP requires that all BGP speakers within a single AS must be fully meshed. The result is that for n BGP speakers within an AS n*(n-1)/2 unique IBGP sessions are required. This "full mesh" requirement clearly does not scale when there are a large number of IBGP speakers within the autonomous system, as is common in many networks today.
根据目前的定义，BGP要求单个As内的所有BGP扬声器必须完全啮合。结果是，对于AS n*（n-1）/2中的n名BGP演讲者，需要唯一的IBGP会话。当自治系统中有大量IBGP扬声器时，这种“全网状”要求显然无法扩展，这在当今许多网络中很常见。
This scaling problem has been well documented and a number of proposals have been made to alleviate this [3,5]. This document represents another alternative in alleviating the need for a "full mesh" and is known as "Autonomous System Confederations for BGP", or simply, "BGP Confederations". It can also be said the BGP Confederations MAY provide improvements in routing policy control.
这一缩放问题已得到充分记录，并提出了许多建议来缓解这一问题[3,5]。本文件代表了另一种缓解“全网格”需求的替代方案，称为“BGP自治系统联合会”，或简称为“BGP联合会”。也可以说，BGP联盟可以在路由策略控制方面提供改进。
This document is a revision of RFC 1965 [4] and it includes editorial changes, clarifications and corrections based on the deployment experience with BGP Confederations. These revisions are summarized in Appendix A.
本文件是RFC 1965[4]的修订版，包括编辑性修改、澄清和基于BGP联盟部署经验的更正。附录A中总结了这些修订。
AS Confederation
作为同盟
A collection of autonomous systems advertised as a single AS number to BGP speakers that are not members of the confederation.
向非联邦成员的BGP演讲者宣传为单个as号码的自治系统集合。
AS Confederation Identifier
作为联邦标识符
An externally visible autonomous system number that identifies the confederation as a whole.
一种外部可见的自治系统编号，用于识别整个联邦。
Member-AS
成员身份
An autonomous system that is contained in a given AS confederation.
一个自治系统，包含在一个给定的联邦中。
Member-AS Number
成员编号
An autonomous system number visible only internal to a BGP confederation.
仅在BGP联盟内部可见的自治系统编号。
It may be useful to subdivide autonomous systems with a very large number of BGP speakers into smaller domains for purposes of controlling routing policy via information contained in the BGP
为了通过BGP中包含的信息控制路由策略，可以将具有大量BGP扬声器的自治系统细分为更小的域
AS_PATH attribute. For example, one may choose to consider all BGP speakers in a geographic region as a single entity. In addition to potential improvements in routing policy control, if techniques such as those presented here or in [5] are not employed, [1] requires BGP speakers in the same autonomous system to establish a full mesh of TCP connections among all speakers for the purpose of exchanging exterior routing information. In autonomous systems the number of intra-domain connections that need to be maintained by each border router can become significant.
作为路径属性。例如，可以选择将地理区域中的所有BGP扬声器视为单个实体。除了路由策略控制方面的潜在改进外，如果未采用此处或[5]中介绍的技术，[1]要求同一自治系统中的BGP扬声器在所有扬声器之间建立完整的TCP连接网格，以便交换外部路由信息。在自治系统中，需要由每个边界路由器维护的域内连接的数量可能变得非常重要。
Subdividing a large autonomous system allows a significant reduction in the total number of intra-domain BGP connections, as the connectivity requirements simplify to the model used for inter-domain connections.
细分大型自治系统可以显著减少域内BGP连接的总数，因为连接要求简化为用于域间连接的模型。
Unfortunately subdividing an autonomous system may increase the complexity of routing policy based on AS_PATH information for all members of the Internet. Additionally, this division increases the maintenance overhead of coordinating external peering when the internal topology of this collection of autonomous systems is modified.
不幸的是，对自治系统进行细分可能会增加基于互联网所有成员的AS_路径信息的路由策略的复杂性。此外，当修改自治系统集合的内部拓扑时，该划分增加了协调外部对等的维护开销。
Finally, dividing a large AS may unnecessarily increase the length of the sequence portions of the AS_PATH attribute. Several common BGP implementations can use the number of "AS hops" required to reach a given destination as part of the path selection criteria. While this is not an optimal method of determining route preference, given the lack of other in-band information, it provides a reasonable default behavior which is widely used across the Internet. Therefore, division of an autonomous system into separate systems may adversely affect optimal routing of packets through the Internet.
最后，划分大AS可能会不必要地增加AS_PATH属性的序列部分的长度。一些常见的BGP实现可以使用到达给定目的地所需的“AS hops”数量作为路径选择标准的一部分。虽然这不是确定路由偏好的最佳方法，但由于缺少其他带内信息，它提供了一种合理的默认行为，在互联网上广泛使用。因此，将自治系统划分为单独的系统可能会对通过因特网的分组的最佳路由产生不利影响。
However, there is usually no need to expose the internal topology of this divided autonomous system, which means it is possible to regard a collection of autonomous systems under a common administration as a single entity or autonomous system when viewed from outside the confines of the confederation of autonomous systems itself.
然而，通常不需要公开这种分割的自治系统的内部拓扑，这意味着从自治系统联盟本身的范围之外看，可以将共同管理下的自治系统集合视为单个实体或自治系统。
Currently, BGP specifies that the AS_PATH attribute is a well-known mandatory attribute that is composed of a sequence of AS path segments. Each AS path segment is represented by a triple <path segment type, path segment length, path segment value>.
目前，BGP指定AS_路径属性是众所周知的强制属性，由一系列AS路径段组成。每个AS路径段由三个<path segment type、path segment length、path segment value>表示。
In [1], the path segment type is a 1-octet long field with the two following values defined:
在[1]中，路径段类型是一个1-octet长字段，定义了以下两个值：
Value Segment Type
值段类型
1 AS_SET: unordered set of ASs a route in the UPDATE message has traversed
1 AS_SET：更新消息中路由所经过的无序ASs集
2 AS_SEQUENCE: ordered set of ASs a route in the UPDATE message has traversed
2 AS_序列：更新消息中路由所经过的有序ASs集合
This document reserves two additional segment types:
本文件保留两种额外的段类型：
3 AS_CONFED_SEQUENCE: ordered set of Member AS Numbers in the local confederation that the UPDATE message has traversed
3 AS_CONFED_序列：在更新消息所经过的本地联盟中，成员作为数字的有序集合
4 AS_CONFED_SET: unordered set of Member AS Numbers in the local confederation that the UPDATE message has traversed
4 AS_-CONFED_集：更新消息所经过的本地联盟中作为数字的无序成员集
A member of a BGP confederation will use its AS Confederation ID in all transactions with peers that are not members of its confederation. This confederation identifier is considered to be the "externally visible" AS number and this number is used in OPEN messages and advertised in the AS_PATH attribute.
BGP联盟的成员将在与非联盟成员的对等方的所有事务中使用其AS联盟ID。该联盟标识符被视为“外部可见”AS编号，该编号用于打开的消息中，并在AS_路径属性中公布。
A member of a BGP confederation will use its Member AS Number in all transactions with peers that are members of the same confederation as the given router.
BGP联盟的成员将在与作为给定路由器的同一联盟成员的对等方的所有事务中使用其成员作为编号。
A BGP speaker receiving an AS_PATH attribute containing an autonomous system matching its own confederation shall treat the path in the same fashion as if it had received a path containing its own AS number.
BGP演讲者接收到包含与其联盟匹配的自治系统的AS_路径属性时，应以与接收到包含其自身AS编号的路径相同的方式处理该路径。
A BGP speaker receiving an AS_PATH attribute containing an AS_CONFED_SEQUENCE or AS_CONFED_SET which contains its own Member AS Number shall treat the path in the same fashion as if it had received a path containing its own AS number.
BGP说话人接收到包含AS_-CONFED_序列的AS_路径属性或包含其自身成员AS编号的AS_-CONFED_集合时，应以与接收到包含其自身AS编号的路径相同的方式处理该路径。
Section 5.1.2 of [1] is replaced with the following text:
[1]第5.1.2节替换为以下内容：
When a BGP speaker propagates a route which it has learned from another BGP speaker's UPDATE message, it shall modify the route's AS_PATH attribute based on the location of the BGP speaker to which the route will be sent:
当BGP演讲者传播其从另一个BGP演讲者的更新消息中学习到的路由时，它应根据路由将发送到的BGP演讲者的位置修改路由的AS_PATH属性：
a) When a given BGP speaker advertises the route to another BGP speaker located in its own autonomous system, the advertising speaker shall not modify the AS_PATH attribute associated with the route.
a) 当给定BGP扬声器向位于其自身自治系统中的另一BGP扬声器播发路由时，播发扬声器不得修改与路由相关联的AS_路径属性。
b) When a given BGP speaker advertises the route to a BGP speaker located in a neighboring autonomous system that is a member of the local autonomous system confederation, then the advertising speaker shall update the AS_PATH attribute as follows:
b) 当给定BGP扬声器向位于相邻自治系统中的BGP扬声器播发路由时，该自治系统是本地自治系统联盟的成员，则播发扬声器应更新AS_路径属性，如下所示：
1) if the first path segment of the AS_PATH is of type AS_CONFED_SEQUENCE, the local system shall prepend its own AS number as the last element of the sequence (put it in the leftmost position).
1) 如果AS_路径的第一个路径段属于AS_CONFED_序列类型，则本地系统应将其自身的AS编号作为序列的最后一个元素（将其置于最左侧位置）。
2) if the first path segment of the AS_PATH is not of type AS_CONFED_SEQUENCE the local system shall prepend a new path segment of type AS_CONFED_SEQUENCE to the AS_PATH, including its own confederation identifier in that segment.
2) 如果AS_路径的第一个路径段不是AS_-CONFED_序列类型，则本地系统应将AS_-CONFED_序列类型的新路径段预先添加到AS_路径，包括该段中自己的联盟标识符。
c) When a given BGP speaker advertises the route to a BGP speaker located in a neighboring autonomous system that is not a member of the current autonomous system confederation, the advertising speaker shall update the AS_PATH attribute as follows:
c) 当给定BGP扬声器向位于相邻自治系统（不是当前自治系统联盟的成员）中的BGP扬声器播发路由时，播发扬声器应更新AS_路径属性，如下所示：
1) if the first path segment of the AS_PATH is of type AS_CONFED_SEQUENCE, that segment and any immediately following segments of the type AS_CONFED_SET or AS_CONFED_SEQUENCE are removed from the AS_PATH attribute, leaving the sanitized AS_PATH attribute to be operated on by steps 2, or 3.
1) 如果AS_路径的第一个路径段属于AS_-CONFED_序列类型，则该段以及AS_-CONFED_集合或AS_-CONFED_序列类型的任何紧随其后的段都将从AS_路径属性中删除，留下经过消毒的AS_路径属性由步骤2或3操作。
2) if the first path segment of the remaining AS_PATH is of type AS_SEQUENCE, the local system shall prepend its own confederation ID as the last element of the sequence (put it in the leftmost position).
2) 如果剩余AS_路径的第一个路径段属于AS_序列类型，则本地系统应将其自身的联邦ID作为序列的最后一个元素（将其置于最左侧位置）。
3) if there are no path segments following the removal of the first AS_CONFED_SET/AS_CONFED_SEQUENCE segments, or if the first path segment of the remaining AS_PATH is of type AS_SET the local system shall prepend a new path segment of type AS_SEQUENCE to the AS_PATH, including its own confederation ID in that segment.
3) 如果在移除第一个AS_-CONFED_集/AS_-CONFED_序列段后没有路径段，或者如果剩余AS_路径的第一个路径段为AS_集类型，则本地系统应在AS_路径上预先添加一个AS_序列类型的新路径段，包括该段中自己的联盟ID。
When a BGP speaker originates a route:
当BGP扬声器发起路由时：
a) the originating speaker shall include an empty AS_PATH attribute in all UPDATE messages sent to BGP speakers located in its own Member AS Number. (An empty AS_PATH attribute is one whose length field contains the value zero).
a) 始发扬声器应在发送给位于其自身成员AS编号内的BGP扬声器的所有更新消息中包含空AS_路径属性。（空AS_PATH属性是其长度字段包含值零的属性）。
b) the originating speaker shall include its own Member AS Number in an AS_CONFED_SEQUENCE segment of the AS_PATH attribute of all UPDATE messages sent to BGP speakers located in neighboring Member-AS that are members of the local confederation (i.e., the originating speaker's Member AS Number will be the only entry in the AS_PATH attribute).
b) 始发扬声器应将其自身的成员AS编号包含在所有更新消息的AS_路径属性的AS_CONFED_序列段中，这些更新消息发送给位于相邻成员AS的BGP扬声器，这些BGP扬声器是本地联盟的成员（即，始发扬声器的成员AS编号将是AS_路径属性中的唯一条目）。
c) the originating speaker shall include its own autonomous system in an AS_SEQUENCE segment of the AS_PATH attribute of all UPDATE messages sent to BGP speakers located in neighboring autonomous systems that are not members of the local confederation. (In this case, the autonomous system number of the originating speaker's member confederation will be the only entry in the AS_PATH attribute).
c) 始发扬声器应将其自身的自治系统包含在所有更新消息的AS_路径属性的AS_序列段中，这些更新消息发送给位于相邻自治系统中的BGP扬声器，这些自治系统不是本地联邦的成员。（在这种情况下，始发发言者成员联盟的自治系统编号将是AS_路径属性中的唯一条目）。
It is reasonable for member ASs of a confederation to share a common administration and IGP information for the entire confederation.
联邦成员共享整个联邦的共同管理和IGP信息是合理的。
It shall be legal for a BGP speaker to advertise an unchanged NEXT_HOP and MULTI_EXIT_DISCRIMINATOR (MED) attribute to peers in a neighboring AS within the same confederation. In addition, the restriction against sending the LOCAL_PREFERENCE attribute to peers in a neighboring AS within the same confederation is removed. Path selection criteria for information received from members inside a confederation MUST follow the same rules used for information received from members inside the same autonomous system, as specified in [1].
BGP演讲者向同一联盟内相邻的对等方宣传未更改的下一跳和多跳出口鉴别器（MED）属性是合法的。此外，取消了禁止将本地_偏好属性发送给同一联盟内相邻联盟中的对等方的限制。从联邦内部成员接收的信息的路径选择标准必须遵循与从同一自治系统内部成员接收的信息相同的规则，如[1]中所述。
All BGP speakers participating in a confederation must recognize the AS_CONFED_SET and AS_CONFED_SEQUENCE segment type extensions to the AS_PATH attribute.
参与联盟的所有BGP扬声器必须识别AS_CONFED_集合和AS_CONFED_序列段类型扩展到AS_路径属性。
Any BGP speaker not supporting these extensions will generate a notification message specifying an "UPDATE Message Error" and a sub-code of "Malformed AS_PATH".
任何不支持这些扩展的BGP扬声器将生成一条通知消息，指定“更新消息错误”和子代码“格式错误的AS_路径”。
This compatibility issue implies that all BGP speakers participating in a confederation MUST support BGP confederations. However, BGP speakers outside the confederation need not support these extensions.
此兼容性问题意味着所有参加联盟的BGP发言者必须支持BGP联盟。但是，联邦以外的BGP扬声器不需要支持这些扩展。
BGP confederations have been widely deployed throughout the Internet for a number of years and are supported by multiple vendors.
BGP联盟已经在互联网上广泛部署多年，并得到多家供应商的支持。
Improper configuration of BGP confederations can cause routing information within an AS to be duplicated unnecessarily. This duplication of information will waste system resources, cause unnecessary route flaps, and delay convergence.
BGP联盟的不当配置可能导致AS内的路由信息被不必要地复制。这种信息重复将浪费系统资源，导致不必要的路线调整，并延迟收敛。
Care should be taken to manually filter duplicate advertisements caused by reachability information being relayed through multiple member autonomous systems based upon the topology and redundancy requirements of the confederation.
应注意根据联邦的拓扑和冗余要求，手动过滤通过多成员自治系统中继的可达性信息引起的重复广告。
Additionally, confederations (as well as route reflectors), by excluding different reachability information from consideration at different locations in a confederation, have been shown to cause permanent oscillation between candidate routes when using the tie breaking rules required by BGP [1]. Care must be taken when selecting MED values and tie breaking policy to avoid these situations.
此外，联邦（以及路由反射器）通过在联邦的不同位置排除不同的可达性信息，已证明在使用BGP要求的平局打破规则时，会导致候选路由之间的永久振荡[1]。在选择中间值和中断策略时必须小心，以避免这些情况。
One potential way to avoid this is by configuring inter-Member-AS IGP metrics higher than intra-Member-AS IGP metrics and/or using other tie breaking policies to avoid BGP route selection based on incomparable MEDs.
避免这种情况的一种潜在方法是，将成员间配置为高于成员内的IGP度量，并/或使用其他中断连接策略，以避免基于不可比较MED的BGP路由选择。
This extension to BGP does not change the underlying security issues inherent in the existing BGP, such as those defined in [6].
对BGP的扩展不会改变现有BGP固有的潜在安全问题，如[6]中定义的问题。
The general concept of BGP confederations was taken from IDRP's Routing Domain Confederations [2]. Some of the introductory text in this document was taken from [5].
BGP联盟的一般概念取自IDRP的路由域联盟[2]。本文件中的一些介绍性文本摘自[5]。
The authors would like to acknowledge Bruce Cole of Juniper Networks for his implementation feedback and extensive analysis of the limitations of the protocol extensions described in this document and [5]. We would also like to acknowledge Srihari Ramachandra of Cisco Systems, Inc., for his feedback.
作者要感谢Juniper Networks的Bruce Cole对本文档和[5]中描述的协议扩展局限性的实现反馈和广泛分析。我们还要感谢思科系统公司的Srihari Ramachandra，感谢他的反馈。
Finally, we'd like to acknowledge Ravi Chandra and Yakov Rekhter for providing constructive and valuable feedback on earlier versions of this document.
最后，我们要感谢Ravi Chandra和Yakov Rekhter对本文件早期版本提供了建设性和有价值的反馈。
[1] Rekhter, Y. and T. Li, "A Border Gateway Protocol 4 (BGP-4)", RFC 1771, March 1995.
[1] Rekhter，Y.和T.Li，“边境网关协议4（BGP-4）”，RFC 17711995年3月。
[2] Kunzinger, C., Editor, "Inter-Domain Routing Protocol", ISO/IEC 10747, October 1993.
[2] Kunzinger，C.，编辑，“域间路由协议”，ISO/IEC 10747，1993年10月。
[3] Haskin, D., "A BGP/IDRP Route Server alternative to a full mesh routing", RFC 1863, October 1995.
[3] Haskin，D.，“全网状路由的BGP/IDRP路由服务器替代方案”，RFC 1863，1995年10月。
[4] Traina, P. "Autonomous System Confederations for BGP", RFC 1965, June 1996.
[4] Traina，P.“BGP自治系统联合会”，RFC 1965，1996年6月。
[5] Bates, T., Chandra, R. and E. Chen, "BGP Route Reflection An Alternative to Full Mesh IBGP", RFC 2796, April 2000.
[5] Bates，T.，Chandra，R.和E.Chen，“BGP路线反射是全网IBGP的替代方案”，RFC 2796，2000年4月。
[6] Heffernan, A., "Protection of BGP Sessions via the TCP MD5 Signature Option", RFC 2385, August 1998.
[6] Heffernan，A.，“通过TCP MD5签名选项保护BGP会话”，RFC 2385，1998年8月。
Paul Traina Juniper Networks, Inc. 1194 N. Mathilda Ave. Sunnyvale, CA 94089 USA
Paul Traina Juniper Networks，Inc.美国加利福尼亚州桑尼维尔市马蒂尔达大道北1194号，邮编94089
Phone: +1 408 745-2000
EMail: pst+confed@juniper.net
Phone: +1 408 745-2000
EMail: pst+confed@juniper.net
Danny McPherson Amber Networks, Inc. 48664 Milmont Drive Fremont, CA 94538
Danny McPherson Amber Networks，Inc.加利福尼亚州弗里蒙特市密尔蒙特大道48664号，邮编94538
Phone: +1 510.687.5226
EMail: danny@ambernetworks.com
Phone: +1 510.687.5226
EMail: danny@ambernetworks.com
John G. Scudder Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134
John G.Scudder Cisco Systems，Inc.加利福尼亚州圣何塞西塔斯曼大道170号，邮编95134
Phone: +1 734.669.8800
EMail: jgs@cisco.com
Phone: +1 734.669.8800
EMail: jgs@cisco.com
Appendix A: Comparison with RFC 1965
附录A：与RFC 1965的比较
The most notable change from [1] is that of reversing the values AS_CONFED_SEQUENCE(4) and AS_CONFED_SET(3) to those defined in section "AS_CONFED Segment Type Extension". The reasoning for this is that in the initial implementation, which was already widely deployed, they were implemented backwards from [4], and as such, subsequent implementations implemented them backwards as well. In order to foster interoperability and compliance with deployed implementations, they've therefore been changed here as well.
与[1]相比，最显著的变化是将值AS_-CONFED_序列（4）和AS-CONFED_集（3）反转为“AS-CONFED段类型扩展”一节中定义的值。其原因是，在已经广泛部署的初始实现中，它们是从[4]向后实现的，因此，后续实现也向后实现它们。为了促进与已部署实现的互操作性和法规遵从性，这里也对它们进行了更改。
The "Compatibility Discussion" was removed and incorporated into other discussions in the document. Also, the mention of hierarchical confederations is removed. The use of the term "Routing Domain Identifier" was replaced with Member AS Number.
删除了“兼容性讨论”，并将其纳入文件中的其他讨论。此外，还删除了对等级联盟的提及。术语“路由域标识符”的使用被替换为成员编号。
Finally, the "Deployment Considerations" section was expanded a few subtle grammar changes were made and a bit more introductory text was added.
最后，对“部署注意事项”部分进行了扩展，进行了一些微妙的语法更改，并添加了更多的介绍性文本。
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完整版权声明
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Acknowledgement
确认
Funding for the RFC Editor function is currently provided by the Internet Society.
RFC编辑功能的资金目前由互联网协会提供。