Internet Engineering Task Force (IETF) R. Raszuk, Ed.
Request for Comments: 6774 NTT MCL
Category: Informational R. Fernando
ISSN: 2070-1721 K. Patel
Cisco Systems
D. McPherson
Verisign
K. Kumaki
KDDI Corporation
November 2012
Internet Engineering Task Force (IETF) R. Raszuk, Ed.
Request for Comments: 6774 NTT MCL
Category: Informational R. Fernando
ISSN: 2070-1721 K. Patel
Cisco Systems
D. McPherson
Verisign
K. Kumaki
KDDI Corporation
November 2012
Distribution of Diverse BGP Paths
不同BGP路径的分布
Abstract
摘要
The BGP4 protocol specifies the selection and propagation of a single best path for each prefix. As defined and widely deployed today, BGP has no mechanisms to distribute alternate paths that are not considered best path between its speakers. This behavior results in a number of disadvantages for new applications and services.
BGP4协议为每个前缀指定单个最佳路径的选择和传播。根据目前的定义和广泛部署，BGP没有任何机制来分配扬声器之间被认为不是最佳路径的备用路径。这种行为导致了新应用程序和服务的许多缺点。
The main objective of this document is to observe that by simply adding a new session between a route reflector and its client, the Nth best path can be distributed. This document also compares existing solutions and proposed ideas that enable distribution of more paths than just the best path.
本文档的主要目的是观察通过简单地在路由反射器及其客户机之间添加新会话，可以分布第n条最佳路径。本文档还比较了现有的解决方案和建议的想法，这些解决方案和建议能够分配更多的路径，而不仅仅是最佳路径。
This proposal does not specify any changes to the BGP protocol definition. It does not require a software upgrade of provider edge (PE) routers acting as route reflector clients.
本提案未规定BGP协议定义的任何变更。它不需要对充当路由反射器客户端的提供商边缘（PE）路由器进行软件升级。
Status of This Memo
关于下段备忘
This document is not an Internet Standards Track specification; it is published for informational purposes.
本文件不是互联网标准跟踪规范；它是为了提供信息而发布的。
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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see 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。并非IESG批准的所有文件都适用于任何级别的互联网标准；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/rfc6774.
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/rfc6774.
Copyright Notice
版权公告
Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2012 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
2. History .........................................................3
2.1. BGP Add-Paths Proposal .....................................3
3. Goals ...........................................................5
4. Multi-Plane Route Reflection ....................................6
4.1. Co-located Best- and Backup-Path RRs .......................8
4.2. Randomly Located Best- and Backup-Path RRs ................10
4.3. Multi-Plane Route Servers for Internet Exchanges ..........12
5. Discussion on Current Models of IBGP Route Distribution ........13
5.1. Full Mesh .................................................13
5.2. Confederations ............................................14
5.3. Route Reflectors ..........................................15
6. Deployment Considerations ......................................15
7. Summary of Benefits ............................................17
8. Applications ...................................................18
9. Security Considerations ........................................19
10. Contributors ..................................................19
11. Acknowledgments ...............................................20
12. References ....................................................20
12.1. Normative References ....................................20
12.2. Informative References ..................................20
1. Introduction ....................................................2
2. History .........................................................3
2.1. BGP Add-Paths Proposal .....................................3
3. Goals ...........................................................5
4. Multi-Plane Route Reflection ....................................6
4.1. Co-located Best- and Backup-Path RRs .......................8
4.2. Randomly Located Best- and Backup-Path RRs ................10
4.3. Multi-Plane Route Servers for Internet Exchanges ..........12
5. Discussion on Current Models of IBGP Route Distribution ........13
5.1. Full Mesh .................................................13
5.2. Confederations ............................................14
5.3. Route Reflectors ..........................................15
6. Deployment Considerations ......................................15
7. Summary of Benefits ............................................17
8. Applications ...................................................18
9. Security Considerations ........................................19
10. Contributors ..................................................19
11. Acknowledgments ...............................................20
12. References ....................................................20
12.1. Normative References ....................................20
12.2. Informative References ..................................20
The current BGP4 protocol specification [RFC4271] allows for the selection and propagation of only one best path for each prefix. As defined today, the BGP protocol has no mechanism to distribute paths other than best path between its speakers. This behavior results in a number of problems in the deployment of new applications and services.
当前的BGP4协议规范[RFC4271]只允许为每个前缀选择和传播一条最佳路径。正如今天所定义的那样，BGP协议除了在其说话人之间分配最佳路径之外，没有其他机制来分配路径。这种行为会导致新应用程序和服务的部署出现许多问题。
This document presents a mechanism for solving the problem based on the conceptual creation of parallel route-reflector planes. It also compares existing solutions and proposes ideas that enable distribution of more paths than just the best path. The parallel route-reflector planes solution brings very significant benefits at a negligible capex and opex deployment price as compared to the alternative techniques (full BGP mesh or add-paths [ADD-PATHS]) and is being considered by a number of network operators for deployment in their networks.
本文档介绍了一种基于平行路线反射面概念创建的解决问题的机制。它还比较了现有的解决方案，并提出了能够分配更多路径而不仅仅是最佳路径的想法。与替代技术（全BGP网格或添加路径[add-Path]）相比，平行路由反射器平面解决方案以可忽略的资本支出和运营支出部署价格带来了非常显著的好处，许多网络运营商正在考虑在其网络中进行部署。
This proposal does not specify any changes to the BGP protocol definition. It does not require upgrades to provider edge or core routers, nor does it need network-wide upgrades. The only upgrade required is the new functionality on the new or current route reflectors.
本提案未规定BGP协议定义的任何变更。它不需要升级到提供商边缘或核心路由器，也不需要网络范围的升级。唯一需要升级的是新的或当前路线反射器上的新功能。
The need to disseminate more paths than just the best path is primarily driven by three issues. The first is the problem of BGP oscillations [RFC3345]. The second is the desire for faster reachability restoration in the event of failure of the network link or network element. The third is a need to enhance BGP load-balancing capabilities. These issues have led to the proposal of BGP add-paths [ADD-PATHS].
传播更多路径而不仅仅是最佳路径的需要主要由三个问题驱动。第一个是BGP振荡问题[RFC3345]。第二是在网络链路或网元发生故障时，希望更快地恢复可达性。第三是需要增强BGP负载平衡能力。这些问题导致了BGP添加路径[添加路径]的提议。
As it has been proven that distribution of only the best path of a route is not sufficient to meet the needs of the continuously growing number of services carried over BGP, the add-paths proposal was submitted in 2002 to enable BGP to distribute more than one path. This is achieved by including an additional four-octet value called the "Path Identifier" as a part of the Network Layer Reachability Information (NLRI).
由于已经证明，仅分发路由的最佳路径不足以满足通过BGP承载的不断增长的服务数量的需要，因此在2002年提交了添加路径提案，以使BGP能够分发多条路径。这是通过将称为“路径标识符”的附加四个八位组值作为网络层可达性信息（NLRI）的一部分来实现的。
The implication of this change on a BGP implementation is that it must now maintain a per-path, instead of per-prefix, peer advertisement state to track to which of the peers a given path was advertised. This new requirement comes with its own memory and processing cost.
这一变化对BGP实现的影响是，BGP现在必须保持每路径（而不是每前缀）的对等播发状态，以跟踪给定路径播发到哪个对等方。这一新需求有其自身的内存和处理成本。
An important observation is that distribution of more than one best path by the Autonomous System Border Routers (ASBRs) with multiple External BGP (EBGP) peers attached where no "next-hop self" is set may result in inconsistent best-path selection within the autonomous system. Therefore, it is also required to attach the possible tiebreakers in the form of a new attribute and propagate those within
一个重要的观察结果是，自治系统边界路由器（ASBR）与多个连接的外部BGP（EBGP）对等点（未设置“下一跳自我”）分配多条最佳路径可能导致自治系统内的最佳路径选择不一致。因此，还需要以新属性的形式附加可能的分界线，并在其中传播这些分界线
the domain. The example of such an attribute for the purpose of fast connectivity restoration to address that very case of ASBR injecting multiple external paths into the Internal BGP (IBGP) mesh has been presented and discussed in "Advertisement of Multiple Paths in BGP" [ADD-PATHS]. Based on the additionally propagated information, best-path selection is recommended to be modified to make sure that best-and backup-path selection within the domain stays consistent. More discussion on this particular point is contained in Section 6, "Deployment Considerations". In the proposed solution in this document, we observe that to address most of the applications, just use of the best external advertisement is required. For ASBRs that are peering to multiple upstream domains, setting "next-hop self" is recommended.
域名。为了快速恢复连接以解决ASBR将多条外部路径注入内部BGP（IBGP）网格的情况，此类属性的示例已在“BGP中的多条路径公告”[添加路径]中介绍和讨论。根据额外传播的信息，建议修改最佳路径选择，以确保域内的最佳路径选择和备份路径选择保持一致。关于这一点的更多讨论载于第6节“部署注意事项”。在本文提出的解决方案中，我们注意到，为了解决大多数应用，只需要使用最好的外部广告。对于正在对等多个上游域的ASBR，建议设置“下一跳自”。
The add-paths protocol extensions have to be implemented by all the routers within an Autonomous System (AS) in order for the system to work correctly. Analyzing the benefits or risks associated with partial add-paths deployments remains quite a topic for research. The risk becomes even greater in networks not using some form of edge-to-edge encapsulation.
添加路径协议扩展必须由自治系统（AS）内的所有路由器实现，以便系统正常工作。分析与部分添加路径部署相关的好处或风险仍然是一个相当重要的研究课题。在不使用某种形式的边到边封装的网络中，风险变得更大。
The required code modifications can offer the foundation for enhancements, such as the "Fast Connectivity Restoration Using BGP Add-path" [FAST-CONN]. The deployment of such technology in an entire service-provider network requires software, and perhaps sometimes, in the case of End-of-Engineering or End-of-Life equipment, even hardware upgrades. Such an operation may or may not be economically feasible. Even if add-path functionality was available today on all commercial routing equipment and across all vendors, experience indicates that it may easily take years to achieve 100% deployment coverage within any medium or large global network.
所需的代码修改可以为增强提供基础，例如“使用BGP添加路径的快速连接恢复”[FASTCONN]。在整个服务提供商网络中部署此类技术需要软件，有时，在工程或寿命终止设备的情况下，甚至需要硬件升级。这种操作在经济上可能可行，也可能不可行。即使现在所有商用路由设备和所有供应商都可以使用添加路径功能，经验表明，在任何中型或大型全球网络中实现100%的部署覆盖率可能需要数年时间。
While it needs to be clearly acknowledged that the add-path mechanism provides the most general way to address the problem of distributing many paths between BGP speakers, this document provides a solution that is much easier to deploy and requires no modification to the BGP protocol where only a few additional paths may be required. The alternative method presented is capable of addressing critical service-provider requirements for disseminating more than a single path across an AS with a significantly lower deployment cost. That, in light of the number of general network scaling concerns documented in RFC 4984 [RFC4984], "Report from the IAB Workshop on Routing and Addressing", may provide a significant advantage.
虽然需要明确承认的是，添加路径机制提供了解决BGP扬声器之间分配多条路径问题的最通用方法，但本文档提供了一种更易于部署且不需要修改BGP协议的解决方案，其中可能只需要少数额外路径。提出的替代方法能够解决关键服务提供商的需求，即在AS中传播多条路径，并且部署成本显著降低。鉴于RFC 4984[RFC4984]中记录的一般网络扩展问题的数量，“IAB路由和寻址研讨会报告”可能提供了一个显著的优势。
The proposal described in this document is not intended to compete with add-paths. It provides an interim solution until add-paths are standardized and implemented and until support for that function can be deployed across the network.
本文件中描述的方案无意与add PATH竞争。它提供了一个临时解决方案，直到添加路径被标准化和实现，直到可以在网络上部署对该功能的支持。
It is presented to network operators as a possible choice and provides those operators who need additional paths today an alternative from the need to transition to a full mesh. The Nth best path describes a set of N paths with different BGP next hops with no implication of ordering or preference among said N paths.
它作为一种可能的选择提供给网络运营商，并为那些今天需要额外路径的运营商提供了一种从需要过渡到完全网状的替代方案。第N条最佳路径描述了具有不同BGP下一跳的N条路径的集合，在所述N条路径中没有顺序或偏好的含义。
It is intended as a way to buy more time, allowing for a smoother and gradual migration where router upgrades will be required for, perhaps, different reasons. It will also allow the time required so that standard RP/RE memory size can easily accommodate the associated overhead with other techniques without any compromises.
它的目的是为了争取更多的时间，允许更平滑、渐进的迁移，因为可能出于不同的原因，需要升级路由器。它还将允许所需的时间，以便标准RP/RE内存大小可以轻松地适应与其他技术相关的开销，而不会有任何妥协。
The idea contained in the proposal assumes the use of route reflection within the network.
提案中包含的想法假设在网络中使用路由反射。
Let's observe today's picture of a simple route-reflected domain:
让我们观察一下今天的简单路由反射域的图片：
ASBR3
***
* *
+------------* *-----------+
| AS1 * * |
| *** |
| |
| |
| |
| RR1 *** RR2 |
| *** * * *** |
|* * * P * * *|
|* * * * * *|
| *** *** *** |
| |
| IBGP |
| |
| |
| *** *** |
| * * * * |
+-----* *---------* *----+
* * * *
*** ***
ASBR1 ASBR2
EBGP
Figure 1: Simple route reflection
ASBR3
***
* *
+------------* *-----------+
| AS1 * * |
| *** |
| |
| |
| |
| RR1 *** RR2 |
| *** * * *** |
|* * * P * * *|
|* * * * * *|
| *** *** *** |
| |
| IBGP |
| |
| |
| *** *** |
| * * * * |
+-----* *---------* *----+
* * * *
*** ***
ASBR1 ASBR2
EBGP
Figure 1: Simple route reflection
Abbreviations used: RR - Route Reflector P - Core router
使用的缩写：RR-路由反射器P-核心路由器
Figure 1 shows an AS that is connected via EBGP peering at ASBR1 and ASBR2 to an upstream AS or set of ASes. For a given destination "D", ASBR1 and ASBR2 may have an external path P1 and P2, respectively. The AS network uses two route reflectors, RR1 and RR2, for redundancy reasons. The route reflectors propagate the single BGP best path for each route to all clients. All ASBRs are clients of RR1 and RR2.
图1显示了通过ASBR1和ASBR2处的EBGP对等连接到上游AS或ASE集的AS。对于给定目的地“D”，ASBR1和ASBR2可分别具有外部路径P1和P2。出于冗余原因，AS网络使用两个路由反射器RR1和RR2。路由反射器将每条路由的单个BGP最佳路径传播到所有客户端。所有ASBR都是RR1和RR2的客户。
Following are the possible cases of the path information that ASBR3 may receive from route reflectors RR1 and RR2:
以下是ASBR3可能从路线反射器RR1和RR2接收的路径信息的可能情况：
1. When the best-path tiebreaker is the IGP distance: When paths P1 and P2 are considered to be equally good best-path candidates, the selection will depend on the distance of the path's next hops from the route reflector making the decision. Depending on the positioning of the route reflectors in the IGP topology, they may choose the same best path or a different one. In such a case, ASBR3 may receive either the same path or different paths from each of the route reflectors.
1. 当最佳路径分接器是IGP距离时：当路径P1和P2被认为是同样好的最佳路径候选时，选择将取决于路径的下一跳距做出决定的路由反射器的距离。根据IGP拓扑中路由反射器的位置，它们可以选择相同的最佳路径或不同的路径。在这种情况下，ASBR3可以从每个路由反射器接收相同路径或不同路径。
2. When the best-path tiebreaker is MULTI_EXIT_DISC (MED) or LOCAL_PREF: In this case, only one path from the preferred exit point ASBR will be available to RRs since the other peering ASBR will consider the IBGP path as best and will not announce (or if already announced will withdraw) its own external path. The exception here is the use of the BGP Best-External proposal [EXT-PATH], which will allow a stated ASBR to still propagate to the RRs on its own external path. Unfortunately, RRs will not be able to distribute it any further to other clients, as only the overall best path will be reflected.
2. 当最佳路径Te断路器是MulyOxExtIdC盘（MED）或LoalAlpRePF：在这种情况下，只有一条来自优选退出点ASBR的路径将可用于RRS，因为另一个对等ASBR将尽可能地考虑IGBP路径，并且不会宣布（或者如果已经宣布退出）它自己的外部路径。这里的例外情况是使用BGP最佳外部提案[EXT-PATH]，这将允许声明的ASBR仍然通过其自身的外部路径传播到RRs。不幸的是，RRs将无法将其进一步分发给其他客户机，因为只会反映总体最佳路径。
There is no requirement of path ordering. The "Nth best path" really describes set of N paths with different BGP next hops.
没有路径排序的要求。“第N条最佳路径”实际上描述了具有不同BGP下一跳的N条路径的集合。
The proposed solution is based on the use of additional route reflectors or new functionality enabled on the existing route reflectors that, instead of distributing the best path for each route, will distribute an alternative path other than best. The best-path (main) reflector plane distributes the best path for each route as it does today. The second plane distributes the second best path for each route, and so on. Distribution of N paths for each route can be achieved by using N reflector planes.
建议的解决方案基于使用额外的路线反射器或在现有路线反射器上启用的新功能，这些反射器不是为每条路线分配最佳路径，而是分配最佳路径以外的替代路径。最佳路径（主）反射器平面像今天一样为每条路线分配最佳路径。第二个平面为每条路线分配第二条最佳路径，依此类推。使用N个反射面可以实现每条路线的N条路径分布。
As diverse-path functionality may be enabled on a per-peer basis, one of the deployment models can be realized to continue advertisement of the overall best path from both route reflectors, while in addition a new session can be provisioned to get an additional path. This will allow the uninterrupted use of the best path, even if one of the RRs goes down, provided that the overall best path is still a valid one.
由于可以在每个对等点的基础上启用不同的路径功能，因此可以实现其中一个部署模型以继续从两个路由反射器播发总体最佳路径，同时另外可以提供新会话以获得附加路径。这将允许不间断地使用最佳路径，即使其中一个RRs出现故障，只要总体最佳路径仍然有效。
Each plane of the route reflectors is a logical entity and may or may not be co-located with the existing best-path route reflectors. Adding a route-reflector plane to a network may be as easy as enabling a logical router partition, new BGP process, or just a new configuration knob on an existing route reflector and configuring an additional IBGP session from the current clients if required. There
路由反射器的每个平面是一个逻辑实体，可能与现有最佳路径路由反射器位于同一位置，也可能与现有最佳路径路由反射器不在同一位置。将路由反射器平面添加到网络可能与启用逻辑路由器分区、新的BGP进程或仅在现有路由反射器上启用新的配置旋钮以及在需要时从当前客户端配置额外的IBGP会话一样简单。那里
are no code changes required on the route-reflector clients for this mechanism to work. It is easy to observe that the installation of one or more additional route-reflector control planes is much cheaper and is easier than upgrading hundreds of route-reflector clients in the entire network to support different BGP protocol encoding.
route reflector客户端上无需更改代码即可使此机制正常工作。很容易观察到，安装一个或多个额外的路由反射器控制平面比升级整个网络中的数百个路由反射器客户端以支持不同的BGP协议编码便宜得多，也更容易。
Diverse-path route reflectors need the new ability to calculate and propagate the Nth best path instead of the overall best path. An implementation is encouraged to enable this new functionality on a per-neighbor basis.
不同的路径反射器需要新的能力来计算和传播第n条最佳路径，而不是总的最佳路径。鼓励实现在每个邻居的基础上启用此新功能。
While this is an implementation detail, the code to calculate the Nth best path is also required by other BGP solutions. For example, in the application of fast connectivity restoration, BGP must calculate a backup path for installation into the Routing Information Base (RIB) and Forwarding Information Base (FIB) ahead of the actual failure.
虽然这是一个实现细节，但其他BGP解决方案也需要计算第n条最佳路径的代码。例如，在快速连接恢复的应用中，BGP必须计算备份路径，以便在实际故障之前安装到路由信息库（RIB）和转发信息库（FIB）中。
To address the problem of external paths not being available to route reflectors due to LOCAL_PREF or MED factors, it is recommended that ASBRs enable [EXT-PATH] functionality in order to always inject their external paths to the route reflectors.
为了解决由于本地_PREF或MED因素导致路由反射器无法使用外部路径的问题，建议ASBR启用[EXT-PATH]功能，以便始终将其外部路径注入路由反射器。
To simplify the description, let's assume that we only use two route-reflector planes (N=2). When co-located, the additional second-best-path reflectors are connected to the network at the same points from the perspective of the IGP as the existing best-path RRs. Let's also assume that best-external functionality is enabled on all ASBRs.
为了简化描述，假设我们只使用两个路由反射器平面（N=2）。当位于同一位置时，从IGP的角度来看，附加的第二最佳路径反射器在与现有最佳路径RRs相同的点处连接到网络。我们还假设在所有ASBR上都启用了最佳外部功能。
ASBR3
***
* *
+------------* *-----------+
| AS1 * * |
| *** |
| |
| RR1 RR2 |
| *** *** |
|* * *** * *|
|* * * * * *|
| *** * P * *** |
|* * * * * *|
|* * *** * *|
| *** *** |
| RR1' IBGP RR2'|
| |
| |
| *** *** |
| * * * * |
+-----* *---------* *----+
* * * *
*** ***
ASBR1 ASBR2
ASBR3
***
* *
+------------* *-----------+
| AS1 * * |
| *** |
| |
| RR1 RR2 |
| *** *** |
|* * *** * *|
|* * * * * *|
| *** * P * *** |
|* * * * * *|
|* * *** * *|
| *** *** |
| RR1' IBGP RR2'|
| |
| |
| *** *** |
| * * * * |
+-----* *---------* *----+
* * * *
*** ***
ASBR1 ASBR2
EBGP
EBGP
Figure 2: Co-located Second-Best-Path RR Plane
图2：位于同一位置的第二最佳路径RR平面
The following is a list of configuration changes required to enable the second-best-path route-reflector plane:
以下是启用第二最佳路径路由反射器平面所需的配置更改列表：
1. Unless the same RR1/RR2 platform is being used, adding RR1' and RR2' either as the logical or physical new control-plane RRs in the same IGP points as RR1 and RR2, respectively.
1. 除非使用相同的RR1/RR2平台，否则在与RR1和RR2相同的IGP点中分别添加RR1'和RR2'作为逻辑或物理新控制平面RRs。
2. Enabling best-external functionality on ASBRs.
2. 在ASBR上实现最佳外部功能。
3. Enabling RR1' and RR2' for second plane route reflection. Alternatively, instructing existing RR1 and RR2 to calculate the second-best path also.
3. 为第二平面路线反射启用RR1'和RR2'。或者，指示现有RR1和RR2也计算第二最佳路径。
4. Unless one of the existing RRs is set to advertise only diverse path to its current clients, configuring new ASBRs-RR' IBGP sessions.
4. 除非其中一个现有RRs设置为仅向其当前客户端播发不同路径，否则请配置新的ASBRs RR“IBGP会话”。
The expected behavior is that under any BGP condition, the ASBR3 and P routers will receive both paths P1 and P2 for destination D. The availability of both paths will allow them to implement a number of new services as listed in Section 8 ("Applications").
预期行为是，在任何BGP条件下，ASBR3和P路由器将接收目的地D的路径P1和P2。这两条路径的可用性将允许它们实现第8节（“应用”）中列出的许多新服务。
As an alternative to fully meshing all RRs and RRs', an operator that has a large number of reflectors deployed today may choose to peer newly introduced RRs' to a hierarchical RR', which would be an IBGP interconnect point within the second plane as well as between planes.
作为完全啮合所有RRs和RRs’的替代方案，今天部署了大量反射器的运营商可以选择将新引入的RRs‘对等于分层RR’，这将是第二个平面内以及平面之间的IBGP互连点。
One deployment model of this scenario can be achieved by simply upgrading the existing route reflectors without deploying any new logical or physical platforms. Such an upgrade would allow route reflectors to service both peers that have upgraded to add-paths, as well as those peers that cannot be immediately upgraded while at the same time allowing distribution of more than a single best path. The obvious protocol benefit of using existing RRs to distribute towards their clients' best and diverse BGP paths over different IBGP sessions is the automatic assurance that such a client would always get different paths with their next hop being different.
此场景的一种部署模型可以通过简单地升级现有路由反射器而不部署任何新的逻辑或物理平台来实现。这种升级将允许路由反射器为已升级以添加路径的对等方以及无法立即升级的对等方提供服务，同时允许分发多条最佳路径。使用现有RRs在不同的IBGP会话中向其客户机的最佳和多样的BGP路径分发的明显协议好处是，自动保证这样的客户机在下一跳不同的情况下总是获得不同的路径。
The way to accomplish this would be to create a separate IBGP session for each Nth BGP path. Such a session should be preferably terminated at a different loopback address of the route reflector. At the BGP OPEN stage of each such session, a different bgp_router_id may be used. Correspondingly, the route reflector should also allow its clients to use the same bgp_router_id on each such session.
实现这一点的方法是为每个第n个BGP路径创建一个单独的IBGP会话。这样的会话应当优选地在路由反射器的不同环回地址处终止。在每个这样的会话的BGP打开阶段，可以使用不同的BGP_路由器_id。相应地，路由反射器还应允许其客户端在每个此类会话上使用相同的bgp_路由器_id。
Now let's consider a deployment case in which an operator wishes to enable a second RR' plane using only a single additional router in a different network location from his current route reflectors. This model would be of particular use in networks in which some form of end-to-end encapsulation (IP or MPLS) is enabled between provider-edge routers.
现在让我们考虑一个部署案例，其中一个操作员希望在他当前的路由反射器中只使用一个附加的路由器在另一个网络位置上启用第二个RR’平面。该模型特别适用于在提供商边缘路由器之间启用某种形式的端到端封装（IP或MPLS）的网络。
Note that this model of operation assumes that the present best-path route reflectors are only control-plane devices. If the route reflector is in the data-forwarding path, then the implementation must be able to clearly separate the Nth best-path selection from the selection of the paths to be used for data forwarding. The basic premise of this mode of deployment assumes that all reflector planes have the same information to choose from, which includes the same set of BGP paths. It also requires the ability to ignore the step of comparison of the IGP metric to reach the BGP next hop during best-path calculation.
请注意，此操作模型假定当前最佳路径反射器仅为控制平面设备。如果路由反射器位于数据转发路径中，则实现必须能够清楚地将第n个最佳路径选择与用于数据转发的路径选择分开。这种部署模式的基本前提是，所有反射面都有相同的信息可供选择，其中包括相同的BGP路径集。它还需要能够忽略IGP度量的比较步骤，以便在最佳路径计算期间达到BGP下一跳。
ASBR3
***
* *
+------------* *-----------+
| AS1 * * |
| IBGP *** |
| |
| *** |
| * * |
| RR1 * P * RR2 |
| *** * * *** |
|* * *** * *|
|* * * *|
| *** RR' *** |
| *** |
| * * |
| * * |
| *** |
| *** *** |
| * * * * |
+-----* *---------* *----+
* * * *
*** ***
ASBR1 ASBR2
ASBR3
***
* *
+------------* *-----------+
| AS1 * * |
| IBGP *** |
| |
| *** |
| * * |
| RR1 * P * RR2 |
| *** * * *** |
|* * *** * *|
|* * * *|
| *** RR' *** |
| *** |
| * * |
| * * |
| *** |
| *** *** |
| * * * * |
+-----* *---------* *----+
* * * *
*** ***
ASBR1 ASBR2
EBGP
EBGP
Figure 3: Experimental Deployment of Second-Best-Path RR Plane
图3：第二最佳路径RR平面的实验部署
The following is a list of configuration changes required to enable the second-best-path route reflector RR' as a single platform or to enable one of the existing control-plane RRs for diverse-path functionality:
以下是将次优路径路由反射器RR'作为单个平台启用或为多种路径功能启用一个现有控制平面RRs所需的配置更改列表：
1. If needed, adding RR' logical or physical as a new route reflector anywhere in the network.
1. 如果需要，在网络中的任何位置添加RR'逻辑或物理作为新路由反射器。
2. Enabling best-external functionality on ASBRs.
2. 在ASBR上实现最佳外部功能。
3. Disabling IGP metric check in BGP best path on all route reflectors.
3. 在所有路由反射器上的BGP最佳路径中禁用IGP度量检查。
4. Enabling RR' or any of the existing RR for second plane path calculation.
4. 为第二个平面路径计算启用RR'或任何现有RR。
5. If required, fully meshing newly added RRs' with all the other reflectors in both planes. This condition does not apply if the newly added RR'(s) already have peering to all ASBRs/PEs.
5. 如果需要，将新添加的RRs'与两个平面中的所有其他反射器完全啮合。如果新添加的RR已对所有ASBR/PE进行对等，则此条件不适用。
6. Configure new BGP sessions between ASBRs and RRs (unless one of the existing RRs is set to advertise only diverse path to its current clients).
6. 在ASBR和RRs之间配置新的BGP会话（除非其中一个现有RRs设置为仅向其当前客户端公布不同路径）。
In this scenario, the operator has the flexibility to introduce the new additional route-reflector functionality on any existing or new hardware in the network. Any existing routers that are not already members of the best-path route-reflector plane can be easily configured to serve the second plane either by using a logical/virtual router partition or by having their BGP implementation compliant to this specification.
在这种情况下，运营商可以灵活地在网络中的任何现有或新硬件上引入新的额外路由反射器功能。通过使用逻辑/虚拟路由器分区或通过使其BGP实现符合本规范，可以容易地将尚未是最佳路径路由反射器平面的成员的任何现有路由器配置为服务于第二平面。
Even if the IGP metric is not taken into consideration when comparing paths during the best-path calculation, an implementation still has to consider paths with unreachable next hops invalid. It is worth pointing out that some implementations today already allow for configuration that results in no IGP metric comparison during the best-path calculation.
即使在最佳路径计算过程中比较路径时没有考虑到IGP度量，一个实现仍然需要考虑具有不可达下一跳的路径无效。值得指出的是，今天的一些实现已经允许在最佳路径计算期间不进行IGP度量比较的配置。
The additional planes of route reflectors do not need to be fully redundant as the primary plane does. If we are preparing for a single network failure event, a failure of a non-backed-up Nth best-path route reflector would not result in a connectivity outage of the actual data plane. The reason is that this would, at most, affect the presence of a backup path (not an active one) on the same parts of the network. If the operator chooses to create the Nth best-path plane redundantly by installing not one, but two or more route reflectors serving each additional plane, the additional robustness will be achieved.
路线反射器的附加平面不需要像主平面那样完全冗余。如果我们正在准备单个网络故障事件，则未备份的第n个最佳路径路由反射器的故障不会导致实际数据平面的连接中断。原因是，这最多会影响网络相同部分上备份路径（不是活动路径）的存在。如果操作员选择通过安装不是一个而是两个或更多为每个附加平面服务的路由反射器来冗余地创建第n个最佳路径平面，则将实现附加鲁棒性。
As a result of this solution, ASBR3 and other ASBRs peering to RR' will be receiving the second best path.
作为此解决方案的结果，ASBR3和其他对等于RR'的ASBR将接收次优路径。
Similarly to Section 4.1, as an alternative to fully meshing all RRs and diverse path RRs', operators may choose to peer newly introduced RRs' to a hierarchical RR', which would be an IBGP interconnect point between planes.
与第4.1节类似，作为完全啮合所有RRs和不同路径RRs’的替代方案，运营商可选择将新引入的RRs‘对等于分层RR’，这将是平面之间的IBGP互连点。
It is recommended that an implementation advertise the overall best path over the Nth diverse-path session if there is no other BGP path with a different next hop present. This is equivalent to today's case where the client is connected to more than one RR.
如果没有其他具有不同下一跳的BGP路径，建议实现在第n个不同路径会话上公布总体最佳路径。这相当于今天客户端连接到多个RR的情况。
Another group of devices in which the proposed multi-plane architecture may be of particular applicability is the EBGP route servers used at many Internet exchange points.
提议的多平面架构可能具有特别适用性的另一组设备是在许多因特网交换点使用的EBGP路由服务器。
In such cases, hundreds of ISPs are interconnected on a common LAN. Instead of having hundreds of direct EBGP sessions on each exchange client, a single peering is created to the transparent route server. The route server can only propagate a single best path. Mandating the upgrade for hundreds of different service providers in order to implement add-path may be much more difficult as compared to asking them to provision one new EBGP session to an Nth best path route server plane. This allows the distribution of more than the single best BGP path from a given route server to such an Internet exchange point (IX) peer.
在这种情况下，数百个ISP在一个公共LAN上互连。每个exchange客户机上没有数百个直接EBGP会话，而是创建一个到透明路由服务器的对等。路由服务器只能传播单个最佳路径。与要求数百家不同的服务提供商向第n个最佳路径路由服务器平面提供一个新的EBGP会话相比，强制升级以实现add path可能要困难得多。这允许将多个最佳BGP路径从给定的路由服务器分发到这样的Internet交换点（IX）对等点。
The solution proposed in this document fits very well with the requirement of having broader EBGP path diversity among the members of any Internet exchange point.
本文档中提出的解决方案非常适合在任何Internet交换点的成员之间具有更广泛EBGP路径多样性的要求。
In today's networks, BGP4 operates as specified in [RFC4271].
在当今的网络中，BGP4按照[RFC4271]中的规定运行。
There are a number of technology choices for intra-AS BGP route distribution:
内部AS BGP路由分发有多种技术选择：
1. Full mesh
1. 全网
2. Confederations
2. 联合会
3. Route reflectors
3. 路线反射器
A full mesh, the most basic IBGP architecture, exists when all BGP speaking routers within the AS peer directly with all other BGP speaking routers within the AS, irrespective of where a given router resides within the AS (e.g., P router, PE router, etc.).
当AS内的所有讲BGP的路由器直接与AS内的所有其他讲BGP的路由器对等时，无论给定路由器位于AS内的何处（例如，P路由器、PE路由器等），即存在最基本的IBGP体系结构——全网。
While this is the simplest intra-domain path-distribution method, historically, there have been a number of challenges in realizing such an IBGP full mesh in a large-scale network. While some of these challenges are no longer applicable, the following (as well as others) may still apply:
虽然这是最简单的域内路径分布方法，但从历史上看，在大规模网络中实现这样一个IBGP全网格存在许多挑战。虽然其中一些挑战不再适用，但以下（以及其他）问题可能仍然适用：
1. Number of TCP sessions: The number of IBGP sessions on a single router in a full-mesh topology of a large-scale service provider can easily reach hundreds. Such numbers could be a concern on hardware and software used in the late 70s, 80s, and 90s. Today, customer requirements for the number of BGP sessions per box are reaching thousands. This is already an order of magnitude more than the potential number of IBGP sessions. Advancements in the
1. TCP会话数：在大型服务提供商的全网状拓扑结构中，单个路由器上的IBGP会话数很容易达到数百个。这些数字可能与70年代末、80年代和90年代使用的硬件和软件有关。如今，客户对每个盒子的BGP会话数的要求达到了数千。这已经比IBGP会话的潜在数量多了一个数量级。新技术的进展
hardware and software used in production routers means that running a full mesh of IBGP sessions should not be dismissed due to the resulting number of TCP sessions alone.
生产路由器中使用的硬件和软件意味着，运行一个完整的IBGP会话网格不应该因为产生的TCP会话数量而被忽略。
2. Provisioning: When operating and troubleshooting large networks, one of the topmost requirements is to keep the design as simple as possible. When the autonomous system's network is composed of hundreds of nodes, it becomes very difficult to manually provision a full mesh of IBGP sessions. Adding or removing a router requires reconfiguration of all other routers in the AS. While this is a real concern today, there is already work in progress in the IETF to define IBGP peering automation through an IBGP Auto Discovery mechanism [AUTO-MESH].
2. 资源调配：在操作大型网络并对其进行故障排除时，最重要的要求之一是使设计尽可能简单。当自治系统的网络由数百个节点组成时，手动提供完整的IBGP会话网格变得非常困难。添加或删除路由器需要重新配置AS中的所有其他路由器。虽然这是一个真正的问题，但IETF中已经在通过IBGP自动发现机制[Auto-MESH]定义IBGP对等自动化。
3. Number of paths: Another concern when deploying a full IBGP mesh is the number of BGP paths for each route that have to be stored at every node. This number is very tightly related to the number of external peerings of an AS, the use of LOCAL_PREF or MED techniques, and the presence of best-external [EXT-PATH] advertisement configuration. If we make a rough assumption that the BGP4-path data structure consumes about 80-100 bytes, the resulting control-plane memory requirement for 500,000 IPv4 routes with one additional external path is 38-48 MB, while for 1 million IPv4 routes, it grows linearly to 76-95 MB. It is not possible to reach a general conclusion if this condition is negligible or if it is a show stopper for a full-mesh deployment without direct reference to a given network.
3. 路径数：部署完整IBGP网格时的另一个问题是每个节点上必须存储的每个路由的BGP路径数。这个数字与AS的外部对等数量、本地预处理或MED技术的使用以及最佳外部[EXT-PATH]广告配置的存在密切相关。如果我们粗略地假设BGP4路径数据结构消耗约80-100字节，那么对于500000条IPv4路由和一条额外的外部路径，其控制平面内存需求为38-48 MB，而对于100万条IPv4路由，其线性增长为76-95 MB。如果这个条件可以忽略，或者如果它是一个完整网格部署的显示阻碍，而不直接参考给定的网络，则不可能得出一般结论。
To summarize, a full-mesh IBGP peering can offer natural dissemination of multiple external paths among BGP speakers. When realized with the help of IBGP Auto Discovery peering automation, this seems like a viable deployment, especially in medium- and small-scale networks.
总之，全网格IBGP对等可以在BGP扬声器之间自然传播多条外部路径。在IBGP自动发现对等自动化的帮助下实现时，这似乎是一种可行的部署，特别是在中小型网络中。
For the purpose of this document, let's observe that confederations [RFC5065] can be viewed as a hierarchical full-mesh model.
在本文档中，让我们观察一下联合会[RFC5065]可以被视为一个分层的全网格模型。
Within each sub-AS, BGP speakers are fully meshed, and as discussed in Section 2.1, all full-mesh characteristics (number of TCP sessions, provisioning, and potential concern over number of paths still apply in the sub-AS scale).
在每个子AS中，BGP扬声器完全啮合，如第2.1节所述，所有全啮合特征（TCP会话数量、供应和对路径数量的潜在关注仍然适用于子AS规模）。
In addition to the direct peering of all BGP speakers within each sub-AS, all sub-AS border routers must also be fully meshed with each other. Sub-AS border routers configured with best-external functionality can inject additional (diverse) paths within a sub-AS.
除了每个子AS内所有BGP扬声器的直接对等外，所有子AS边界路由器也必须彼此完全啮合。配置了最佳外部功能的Sub-AS边界路由器可以在Sub-AS内注入额外的（不同的）路径。
To summarize, it is technically sound to use confederations with the combination of best-external to achieve distribution of more than a single best path per route in a large autonomous systems.
总而言之，在大型自治系统中，使用联合会和最佳外部路径的组合来实现每条路线的多条最佳路径的分配在技术上是合理的。
In topologies where route reflectors are deployed within the confederation sub-ASes, the technique described here applies.
在联邦子ASE内部署路由反射器的拓扑中，此处描述的技术适用。
The main motivation behind the use of route reflectors [RFC4456] is the avoidance of the full-mesh session management problem described above. Route reflectors, for good or for bad, are the most common solution today for interconnecting BGP speakers within an internal routing domain.
使用路由反射器[RFC4456]的主要动机是避免上述全网状会话管理问题。路由反射器无论好坏，都是目前在内部路由域内互连BGP扬声器的最常见解决方案。
Route-reflector peerings follow the advertisement rules defined by the BGP4 protocol. As a result, only a single best path per prefix is sent to client BGP peers. This is the main reason many current networks are exposed to a phenomenon called BGP path starvation, which essentially results in the inability to deliver a number of applications discussed later.
路由反射器对等遵循BGP4协议定义的播发规则。因此，每个前缀只向客户端BGP对等方发送一条最佳路径。这是当前许多网络暴露于称为BGP路径饥饿现象的主要原因，这从本质上导致无法交付稍后讨论的许多应用程序。
When interconnecting BGP speakers between domains, the route reflection equivalent is popularly called the "Route Server" and is globally deployed today in many Internet exchange points.
当在域之间互连BGP扬声器时，路由反射等效物通常被称为“路由服务器”，目前在全球许多Internet交换点部署。
Distribution of the diverse-BGP-paths proposal allows the dissemination of more paths than just the best path to the route-reflector or route-server clients of today's BGP4 implementations. As a deployment recommendation, it needs to be mentioned that fast connectivity restoration as well as a majority of intra-domain BGP-level load balancing needs can be accommodated with only two paths (overall best and second best). Therefore, as a deployment recommendation, this document suggests use of N=2 with diverse-path.
多样化BGP路径方案的分发允许传播更多的路径，而不仅仅是今天BGP4实现的路由反射器或路由服务器客户端的最佳路径。作为一项部署建议，需要指出的是，快速连接恢复以及大多数域内BGP级负载平衡需求只能通过两条路径（总体最佳和次最佳）来满足。因此，作为一项部署建议，本文档建议使用具有不同路径的N=2。
From the client's point of view, receiving additional paths via separate IBGP sessions terminated at the new route-reflector plane is functionally equivalent to constructing a full-mesh peering without the problems such a full mesh would come with, as discussed in earlier section.
从客户的角度来看，通过在新路由反射器平面终止的单独IBGP会话接收额外路径在功能上等同于构建全网格对等，而不存在如前一节所述的全网格将带来的问题。
By precisely defining the number of reflector planes, network operators have full control over the number of redundant paths in the network. This number can be defined to address the needs of the service(s) being deployed.
通过精确定义反射器平面的数量，网络运营商可以完全控制网络中冗余路径的数量。可以定义此编号以满足所部署服务的需要。
The Nth-plane route reflectors should act as control-plane network entities. While they can be provisioned on the current production routers, selected Nth-best BGP paths should not be used directly in the date plane with the exception of such paths being BGP multipath eligible and such functionality is enabled. Regarding RRs being in the data plane unless multipath is enabled, the second best path is expected to be a backup path and should be installed as such into the local RIB/FIB.
第n个平面路由反射器应充当控制平面网络实体。虽然可以在当前生产路由器上配置这些路径，但选定的第n个最佳BGP路径不应直接在日期平面中使用，除非这些路径符合BGP多路径条件，并且启用了此类功能。关于数据平面中的RRs，除非启用多路径，否则第二个最佳路径应为备份路径，并应安装在本地RIB/FIB中。
The use of the term "planes" in this document is more of a conceptual nature. In practice, all paths are still kept in the single table where normal best path is calculated. This means that tools like the looking glass should not observe any changes or impact when diverse-path has been enabled.
本文件中“平面”一词的使用更具概念性。实际上，所有路径仍然保留在单个表中，在该表中计算正常最佳路径。这意味着，当启用了多样化路径时，像观察镜这样的工具不应观察到任何变化或影响。
The proposed architecture deployed along with the BGP best-external functionality covers all three cases where the classic BGP route-reflection paradigm would fail to distribute alternate (diverse) paths. These are
与BGP最佳外部功能一起部署的拟议架构涵盖了经典BGP路由反射范例无法分布备用（多样化）路径的所有三种情况。这些是
1. ASBRs advertising their single best-external paths with no LOCAL_PREF or MED present.
1. ASBR在没有本地PREF或MED的情况下宣传其单一最佳外部路径。
2. ASBRs advertising their single best-external paths with LOCAL_PREF or MED present and with BGP best-external functionality enabled.
2. ASBR宣传其单个最佳外部路径，提供本地预处理或MED，并启用BGP最佳外部功能。
3. ASBRs with multiple external paths.
3. 具有多个外部路径的ASBR。
This section focuses on discussion of case 3 above in more detail. This describes the scenario of a single ASBR connected to multiple EBGP peers. In practice, this peering scenario is quite common. It is mostly due to the geographic location of EBGP peers and the diversity of those peers (for example, peering to multiple tier-1 ISPs, etc.). It is not designed for failure-recovery scenarios, as single failure of the ASBR would simultaneously result in loss of connectivity to all of the peers. In most medium and large geographically distributed networks, there is always another ASBR or multiple ASBRs providing peering backups, typically in other geographically diverse locations in the network.
本节着重于更详细地讨论上述案例3。这描述了单个ASBR连接到多个EBGP对等点的场景。实际上，这种对等场景非常常见。这主要是由于EBGP对等点的地理位置以及这些对等点的多样性（例如，对等多个一级ISP等）。它不是为故障恢复场景而设计的，因为ASBR的单个故障将同时导致与所有对等方的连接丢失。在大多数中大型地理分布网络中，通常在网络中其他地理位置不同的位置，总有另一个或多个ASBR提供对等备份。
When an operator uses ASBRs with multiple peerings, setting next-hop self will effectively allow local repair of the atomic failure of any external peer without any compromise to the data plane. Traditionally, the most common reason for not setting next-hop self is the associated drawback of losing the ability to signal the external failures of peering ASBRs or links to those ASBRs by fast IGP flooding. Such a potential drawback can be easily avoided by using a different peering address from the address used for next-hop mapping and removing the next-hop from the IGP at the last possible BGP path failure.
当操作员使用具有多个对等点的ASBR时，设置下一跳自我将有效地允许本地修复任何外部对等点的原子故障，而不会损害数据平面。传统上，不设置下一跳self的最常见原因是相关联的缺点，即失去通过快速IGP泛洪向对等ASBR或到这些ASBR的链接的外部故障发送信号的能力。通过使用与用于下一跳映射的地址不同的对等地址，并在最后一次可能的BGP路径故障时从IGP中删除下一跳，可以轻松避免这种潜在缺陷。
Herein, one may correctly observe that in the case of setting next-hop self on an ASBR, attributes of other external paths such that the ASBR is peering with may be different from the attributes of its best external path. Therefore, not injecting all of those external paths with their corresponding attributes cannot be compared to equivalent paths for the same prefix coming from different ASBRs.
在此，可以正确地观察到，在ASBR上设置下一跳self的情况下，其他外部路径的属性（例如ASBR正在与其对等）可能与其最佳外部路径的属性不同。因此，不将所有这些外部路径及其相应属性注入，无法与来自不同ASBR的相同前缀的等效路径进行比较。
While such observation, in principle, is correct, one should put things in perspective of the overall goal, which is to provide data-plane connectivity upon a single failure with minimal interruption/packet loss. During such transient conditions, using even potentially suboptimal exit points is reasonable, so long as forwarding information loops are not introduced. In the mean time, the BGP control plane will on its own re-advertise the newly elected best external path, and route-reflector planes will calculate their Nth best paths and propagate them to its clients. The result is that after seconds, even if potential suboptimality were encountered, it will be quickly and naturally healed.
虽然这样的观察在原则上是正确的，但我们应该从总体目标的角度来考虑问题，即在单一故障时提供数据平面连接，并将中断/数据包丢失降至最低。在这种瞬态条件下，只要不引入转发信息循环，使用甚至可能次优的出口点也是合理的。同时，BGP控制平面将自行重新公布新选择的最佳外部路径，路由反射器平面将计算其第n条最佳路径并将其传播到其客户端。结果是，几秒钟后，即使遇到潜在的次优情况，也会很快自然痊愈。
Distribution of the diverse-BGP-paths proposal provides the following benefits when compared to the alternatives:
与备选方案相比，多样化BGP路径方案的分发提供了以下好处：
1. No modifications to the BGP4 protocol.
1. 不修改BGP4协议。
2. No requirement for upgrades to edge and core routers (as required in [ADD-PATHS]). It is backward compatible with the existing BGP deployments.
2. 无需升级到边缘和核心路由器（如[ADD-Path]中所要求）。它与现有BGP部署向后兼容。
3. Can be easily enabled by the introduction of a new route reflector, a route server plane dedicated to the selection and distribution of Nth best-path, or just by new configuration of the upgraded current route reflector(s).
3. 可通过引入新的路由反射器、专用于选择和分配第n条最佳路径的路由服务器平面，或仅通过升级当前路由反射器的新配置轻松启用。
4. Does not require major modification to BGP implementations in the entire network, which would result in an unnecessary increase of memory and CPU consumption due to the shift from today's per-prefix to a per-path advertisement state tracking.
4. 不需要对整个网络中的BGP实现进行重大修改，这将导致不必要的内存和CPU消耗增加，这是因为从今天的每前缀转向了每路径广告状态跟踪。
5. Can be safely deployed gradually on an RR cluster basis.
5. 可以在RR集群的基础上安全地逐步部署。
6. The proposed solution is equally applicable to any BGP address family as described in "Multiprotocol Extensions for BGP-4" [RFC4760]. In particular, it can be used "as is" without any modifications to both IPv4 and IPv6 address families.
6. 建议的解决方案同样适用于“BGP-4的多协议扩展”[RFC4760]中所述的任何BGP地址系列。特别是，它可以“按原样”使用，而无需对IPv4和IPv6地址系列进行任何修改。
This section lists the most common applications that require the presence of redundant BGP paths:
本节列出了需要存在冗余BGP路径的最常见应用程序：
1. Fast connectivity restoration in which backup paths with alternate exit points would be pre-installed as well as pre-resolved in the FIB of routers. This allows for a local action upon reception of a critical event notification of network/node failure. This failure recovery mechanism that is based on the presence of backup paths is also suitable for gracefully addressing scheduled maintenance requirements as described in [BGP-SHUTDOWN].
1. 快速连接恢复，其中带有备用出口点的备份路径将在路由器的FIB中预安装和预解决。这允许在接收到网络/节点故障的关键事件通知时进行本地操作。这种基于备份路径存在的故障恢复机制也适用于优雅地满足[BGP-SHUTDOWN]中所述的计划维护要求。
2. Multi-path load balancing for both IBGP and EBGP.
2. IBGP和EBGP的多路径负载平衡。
3. BGP control-plane churn reduction for both intra-domain and inter-domain.
3. 域内和域间的BGP控制平面搅动减少。
An important point to observe is that all of the above intra-domain applications are based on the use of reflector planes but are also applicable in the inter-domain Internet exchange point examples. As discussed in Section 4.3, an Internet exchange can conceptually deploy shadow route server planes, each responsible for distribution of an Nth best path to its EBGP peers. In practice, it may just be equal to a new short configuration and establishment of new BGP sessions to IX peers.
需要注意的一点是，上述所有域内应用都基于反射器平面的使用，但也适用于域间互联网交换点示例。如第4.3节所述，Internet exchange可以在概念上部署影子路由服务器平面，每个平面负责将第n条最佳路径分发给其EBGP对等方。在实践中，它可能只相当于一个新的短配置和建立到IX对等方的新BGP会话。
The new mechanism for diverse BGP path dissemination proposed in this document does not introduce any new security concerns as compared to the base BGP4 specification [RFC4271] and especially when compared against full-IBGP-mesh topology.
与基本BGP4规范[RFC4271]相比，本文件中提出的多样化BGP路径传播的新机制没有引入任何新的安全问题，尤其是与完整的IBGP网状拓扑相比。
In addition, the authors observe that all BGP security issues as described in [RFC4272] apply to the additional BGP session or sessions as recommended by this specification. Therefore, all recommended mitigation techniques to BGP security are applicable here.
此外，作者注意到[RFC4272]中描述的所有BGP安全问题适用于本规范建议的附加BGP会话。因此，所有推荐的BGP安全缓解技术均适用于此处。
The following people contributed significantly to the content of the document:
以下人员对本文件的内容做出了重大贡献：
Selma Yilmaz Cisco Systems 170 West Tasman Drive San Jose, CA 95134 US Email: seyilmaz@cisco.com
Selma Yilmaz Cisco Systems 170西塔斯曼大道圣何塞，加利福尼亚州95134美国电子邮件：seyilmaz@cisco.com
Satish Mynam Juniper Networks 1194 N. Mathilda Ave Sunnyvale, CA 94089 US Email: smynam@juniper.net
Satish Mynam Juniper Networks 1194 N.Mathilda Ave Sunnyvale，CA 94089美国电子邮件：smynam@juniper.net
Isidor Kouvelas Cisco Systems 170 West Tasman Drive San Jose, CA 95134 US Email: kouvelas@cisco.com
Isidor Kouvelas Cisco Systems 170西塔斯曼大道圣何塞，加利福尼亚州95134美国电子邮件：kouvelas@cisco.com
The authors would like to thank Bruno Decraene, Bart Peirens, Eric Rosen, Jim Uttaro, Renwei Li, Wes George, and Adrian Farrel for their valuable input.
作者要感谢Bruno Decarene、Bart Peirens、Eric Rosen、Jim Uttaro、Renwei Li、Wes George和Adrian Farrel的宝贵意见。
The authors would also like to express a special thank you to a number of operators who helped optimize the provided solution to be as close as possible to their daily operational practices. In particular, many thanks to Ted Seely, Shane Amante, Benson Schliesser, and Seiichi Kawamura.
作者还想特别感谢许多运营商，他们帮助优化了提供的解决方案，使其尽可能接近日常运营实践。特别要感谢Ted Seely、Shane Amante、Benson Schliesser和Seichi Kawamura。
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4271]Rekhter，Y.，Ed.，Li，T.，Ed.，和S.Hares，Ed.，“边境网关协议4（BGP-4）”，RFC 42712006年1月。
[RFC4456] Bates, T., Chen, E., and R. Chandra, "BGP Route Reflection: An Alternative to Full Mesh Internal BGP (IBGP)", RFC 4456, April 2006.
[RFC4456]Bates，T.，Chen，E.，和R.Chandra，“BGP路由反射：全网格内部BGP（IBGP）的替代方案”，RFC 4456，2006年4月。
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, January 2007.
[RFC4760]Bates，T.，Chandra，R.，Katz，D.，和Y.Rekhter，“BGP-4的多协议扩展”，RFC 4760，2007年1月。
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
[RFC5226]Narten，T.和H.Alvestrand，“在RFCs中编写IANA注意事项部分的指南”，BCP 26，RFC 5226，2008年5月。
[ADD-PATHS] Walton, D., Chen, E., Retana, A., and J. Scudder, "Advertisement of Multiple Paths in BGP", Work in Progress, June 2012.
[添加路径]Walton，D.，Chen，E.，Retana，A.，和J.Scudder，“BGP中多路径的广告”，正在进行的工作，2012年6月。
[AUTO-MESH] Raszuk, R., "IBGP Auto Mesh", Work in Progress, January 2004.
[自动网格]Raszuk，R.，“IBGP自动网格”，正在进行的工作，2004年1月。
[BGP-SHUTDOWN] Decraene, B., Francois, P., Pelsser, C., Ahmad, Z., and A. Armengol, "Requirements for the Graceful Shutdown of BGP Sessions", Work in Progress, September 2009.
[BGP-SHUTDOWN]Decaene，B.，Francois，P.，Pelsser，C.，Ahmad，Z.，和A.Armengol，“BGP会话正常关闭的要求”，正在进行的工作，2009年9月。
[EXT-PATH] Marques, P., Fernando, R., Chen, E., Mohapatra, P., and H. Gredler, "Advertisement of the Best External Route in BGP", Work in Progress, January 2012.
[EXT-PATH]Marques，P.，Fernando，R.，Chen，E.，Mohapatra，P.，和H.Gredler，“BGP最佳外部路线广告”，正在进行的工作，2012年1月。
[FAST-CONN] Mohapatra, P., Fernando, R., Filsfils, C., and R. Raszuk, "Fast Connectivity Restoration Using BGP Add-path", Work in Progress), October 2011.
[FAST-CONN]Mohapatra，P.，Fernando，R.，Filsfils，C.，和R.Raszuk，“使用BGP添加路径的快速连接恢复”，正在进行的工作），2011年10月。
[RFC3345] McPherson, D., Gill, V., Walton, D., and A. Retana, "Border Gateway Protocol (BGP) Persistent Route Oscillation Condition", RFC 3345, August 2002.
[RFC3345]McPherson，D.，Gill，V.，Walton，D.，和A.Retana，“边界网关协议（BGP）持续路由振荡条件”，RFC 33452002年8月。
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", RFC 4272, January 2006.
[RFC4272]Murphy，S.，“BGP安全漏洞分析”，RFC 4272，2006年1月。
[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous System Confederations for BGP", RFC 5065, August 2007.
[RFC5065]Traina，P.，McPherson，D.，和J.Scudder，“BGP自治系统联合会”，RFC 5065，2007年8月。
Authors' Addresses
作者地址
Robert Raszuk (editor) NTT MCL 101 S Ellsworth Avenue Suite 350 San Mateo, CA 94401 United States
Robert Raszuk（编辑）NTT MCL 101 S Ellsworth大道350号套房，美国加利福尼亚州圣马特奥94401
EMail: robert@raszuk.net
EMail: robert@raszuk.net
Rex Fernando Cisco Systems 170 West Tasman Drive San Jose, CA 95134 United States
美国加利福尼亚州圣何塞西塔斯曼大道170号，邮编95134
EMail: rex@cisco.com
EMail: rex@cisco.com
Keyur Patel Cisco Systems 170 West Tasman Drive San Jose, CA 95134 United States
美国加利福尼亚州圣何塞市西塔斯曼大道170号凯尔-帕特尔思科系统公司，邮编95134
EMail: keyupate@cisco.com
EMail: keyupate@cisco.com
Danny McPherson Verisign, Inc. 12061 Bluemont Way Reston, VA 20190 United States
Danny McPherson Verisign，Inc.美国弗吉尼亚州雷斯顿市Bluemont Way 12061号，邮编：20190
EMail: dmcpherson@verisign.com
EMail: dmcpherson@verisign.com
Kenji Kumaki KDDI Corporation Garden Air Tower Iidabashi, Chiyoda-ku, Tokyo 102-8460 Japan
日本东京千代田区三大坂市久木健二株式会社花园航空塔，102-8460
EMail: ke-kumaki@kddi.com
EMail: ke-kumaki@kddi.com