Network Working Group J. Stewart
Request for Comments: 2270 ISI
Category: Informational T. Bates
R. Chandra
E. Chen
Cisco
January 1998
Network Working Group J. Stewart
Request for Comments: 2270 ISI
Category: Informational T. Bates
R. Chandra
E. Chen
Cisco
January 1998
Using a Dedicated AS for Sites Homed to a Single Provider
使用专用AS作为单一提供商的站点
Status of this Memo
本备忘录的状况
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 (1998). All Rights Reserved.
版权所有（C）互联网协会（1998年）。版权所有。
Abstract
摘要
With the increased growth of the Internet, the number of customers using BGP4 has grown significantly. RFC1930 outlines a set of guidelines for when one needs and should use an AS. However, the customer and service provider (ISP) are left with a problem as a result of this in that while there is no need for an allocated AS under the guidelines, certain conditions make the use of BGP4 a very pragmatic and perhaps only way to connect a customer homed to a single ISP. This paper proposes a solution to this problem in line with recommendations set forth in RFC1930.
随着互联网的增长，使用BGP4的客户数量显著增加。RFC1930概述了一套关于何时需要和应该使用AS的指南。然而，客户和服务提供商（ISP）因此存在一个问题，即虽然不需要按照指南分配，但某些条件使得使用BGP4成为非常实用的，并且可能是将客户与单个ISP连接的唯一方式。本文根据RFC1930中提出的建议，提出了该问题的解决方案。
With the increased growth of the Internet, the number of customers using BGP4 [1],[2] has grown significantly. RFC1930 [4] outlines a set of guidelines for when one needs and should use an AS. However, the customer and service provider (ISP) are left with a problem as a result of this in that while there is no need for an allocated AS under the guidelines, certain conditions make the use of BGP4 a very pragmatic and perhaps only way to connect a customer homed to a single ISP. These conditions are as follows:
随着互联网的增长，使用BGP4[1]、[2]的客户数量显著增加。RFC1930[4]概述了一套关于何时需要和应该使用AS的指南。然而，客户和服务提供商（ISP）因此存在一个问题，即虽然不需要按照指南分配，但某些条件使得使用BGP4成为非常实用的，并且可能是将客户与单个ISP连接的唯一方式。这些条件如下：
1) Customers multi-homed to single provider
1) 客户从多个主机到单个提供商
Consider the scenario outlined in Figure 1 below.
考虑下面的图1所概述的场景。
+-------+ +-------+
+----+ | | |
+------+ | | ISP A +------+ ISP B |
| Cust.+---+ | | | |
| X +--------+ | | |
+------+ ++-----++\ +-------+
| | \
| | \ +--------+
++-----++ +-| |
| Cust. | | ISP C |
| Y | | |
+-------+ +--------+
+-------+ +-------+
+----+ | | |
+------+ | | ISP A +------+ ISP B |
| Cust.+---+ | | | |
| X +--------+ | | |
+------+ ++-----++\ +-------+
| | \
| | \ +--------+
++-----++ +-| |
| Cust. | | ISP C |
| Y | | |
+-------+ +--------+
Figure 1: Customers multi-home to a single provider
图1：客户从多个家庭到单个提供商
Here both customer X and customer Y are multi-homed to a single provider, ISP A. Because these multiple connections are "localized" between the ISP A and its customers, the rest of the routing system (ISP B and ISP C in this case) doesn't need to see routing information for a single multi-homed customer any differently than a singly-homed customer as it has the same routing policy as ISP A relative to ISP B and ISP C. In other words, with respect to the rest of the Internet routing system the organization is singly-homed, so the complexity of the multiple connections is not relevant in a global sense. Autonomous System Numbers (AS) are identifiers used in routing protocols and are needed by routing domains as part of the global routing system. However, as [4] correctly outlines, organizations with the same routing policy as their upstream provider do not need an AS.
这里，客户X和客户Y都是多址的，由一个提供商ISP a提供。由于这些多个连接在ISP a及其客户之间“本地化”，路由系统的其余部分（本例中为ISP B和ISP C）不需要查看单个多宿客户的路由信息，因为它与ISP a相对于ISP B和ISP C具有相同的路由策略。换句话说，对于Internet路由系统的其余部分，该组织是单宿的，因此，多个连接的复杂性与全局意义无关。自治系统号（AS）是路由协议中使用的标识符，路由域需要它作为全局路由系统的一部分。然而，正如[4]正确概述的，与上游提供商具有相同路由策略的组织不需要as。
Despite this fact, a problem exists in that many ISPs can only support the load-sharing and reliability requirements of a multi-homed customer if that customer exchanges routing information using BGP-4 which does require an AS as part of the protocol.
尽管如此，仍然存在一个问题，即如果多宿客户使用BGP-4交换路由信息，则许多ISP只能支持多宿客户的负载共享和可靠性要求，而BGP-4确实需要AS作为协议的一部分。
2) Singly-homed customers requiring dynamic advertisement of NLRI's
2) 需要NLRI动态广告的单家客户
While this is not a common case as static routing is generally used for this purpose, if a large amount of NLRI's need to be advertised from the customer to the ISP it is often administratively easier for these prefixes to be advertised using a dynamic routing protocol. Today, the only exterior gateway protocol (EGP) that is able to do this is BGP. This leads to the same problem outlined in condition 1 above.
虽然这不是常见的情况，因为静态路由通常用于此目的，但如果需要从客户向ISP通告大量NLRI，则通常使用动态路由协议在管理上更容易通告这些前缀。今天，唯一能够做到这一点的外部网关协议（EGP）是BGP。这会导致上述条件1中概述的相同问题。
As can be seen there is clearly a problem with the recommendations set forth in [4] and the practice of using BGP4 in the scenarios above. Section 2 proposes a solution to this problem with following sections describing the implications and application of the proposed solution.
可以看出，[4]中提出的建议和在上述场景中使用BGP4的实践显然存在问题。第2节提出了该问题的解决方案，以下各节描述了拟议解决方案的含义和应用。
It should also be noted that if a customer is multi-homed to more than one ISP then they are advised to obtain an official allocated AS from their allocation registry.
还应注意的是，如果一个客户是多个ISP的多址用户，则建议他们从其分配注册表获取正式分配的AS。
The solution we are proposing is that all BGP customers homed to the same single ISP use a single, dedicated AS specified by the ISP.
我们建议的解决方案是，所有居住在同一个ISP的BGP客户使用ISP指定的单一专用设备。
Logically, this solution results in an ISP having many peers with the same AS, although that AS exists in "islands" completely disconnected from one another.
从逻辑上讲，这种解决方案会导致ISP拥有许多与相同的对等点，尽管这些对等点存在于彼此完全断开的“孤岛”中。
Several practical implications of this solution are discussed in the next section.
下一节将讨论此解决方案的几个实际含义。
The solution precludes the ability for a BGP customer using the dedicated AS to receive 100% full routes. Because of routing loop detection of AS path, a BGP speaker rejects routes with its own AS number in the AS path. Imagine Customer X and Customer Y maintain BGP peers with Provider A using AS number N. Then, Customer X will not be able to received routes of Customer Y. We do not believe that this would cause a problem for Customer X, though, because Customer X and Customer Y are both stub networks so default routing is adequate, and the absence of a very small portion of the full routing table is unlikely to have a noticeable impact on traffic patterns guided by MEDs received.
该解决方案排除了BGP客户使用专用AS接收100%完整路由的能力。由于AS路径的路由环路检测，BGP扬声器拒绝AS路径中具有自己AS编号的路由。假设客户X和客户Y使用AS编号N与提供商A保持BGP对等。那么，客户X将无法接收客户Y的路由。不过，我们认为这不会给客户X带来问题，因为客户X和客户Y都是存根网络，所以默认路由就足够了，而缺少完整路由表的一小部分不太可能对接收到的MED引导的流量模式产生明显影响。
A BGP customer using the dedicated AS must carry a default route (preferably receiving from its provider via BGP).
使用专用AS的BGP客户必须携带默认路由（最好通过BGP从其提供商处接收）。
The dedicated AS specified by a provider is purely for use in peering between its customers and the provider. When a customer using the dedicated AS changes its external connectivity, it may be necessary for the customer to reconfigure their network to use a different AS number (either a globally unique one if homed to multiple providers,
提供商指定的专用端口纯粹用于其客户和提供商之间的对等。当使用专用AS的客户更改其外部连接时，客户可能需要重新配置其网络，以使用不同的AS号码（如果驻留在多个提供商处，则为全局唯一的AS号码，
or a dedicated AS of a different provider).
或其他提供商的专用服务）。
As BGP customers using this dedicated AS are only homed to one ISP, their routes allocated from its providers CIDR block do not need to be announced upstream by its provider as the providers will already be originating the larger block. [6].
由于使用此专用As的BGP客户仅归属于一家ISP，其供应商无需向上游宣布其从其供应商CIDR区块分配的路由，因为供应商将已经发起较大区块。[6].
The Internet Routing Registry (IRR) [5] is used by providers to generate route filtering lists. Such lists are derived primarily from the "origin" attribute of the route objects. The "origin" is the AS that originates the route. With multiple customers using the same AS, finer granularity will be necessary to generate the correct route filtering. For example, the "mntner" attribute or the "community" attribute of a route object can be used along with the "origin" attribute in generating the filtering lists.
Internet路由注册表（IRR）[5]由提供商用于生成路由筛选列表。此类列表主要源自管线对象的“原点”属性。“始发地”是始发路线的AS。如果多个客户使用相同的，则需要更精细的粒度来生成正确的路由筛选。例如，路由对象的“mntner”属性或“community”属性可以与“origin”属性一起用于生成过滤列表。
The AS number specified by a provider can either be an AS from the private AS space (64512 - 65535) [4], or be an AS previously allocated to the provider. With the former, the dedicated AS like all other private AS's should be stripped from its AS path while the route is being propagated to the rest of the Internet routing system.
提供程序指定的AS编号可以是来自专用AS空间（64512-65535）[4]的AS，也可以是先前分配给提供程序的AS。对于前者，当路由传播到Internet路由系统的其余部分时，应将专用AS和所有其他专用AS从其AS路径中剥离。
The usage of AS numbers described in this document has no effective security impact. Acceptance and filtering of AS numbers from customers is an issue dealt with in other documents.
使用本文档中描述的AS编号不会对安全产生有效影响。接受和过滤来自客户的AS编号是其他文件中处理的问题。
The authors would like to thank Roy Alcala of MCI and Arpakorn Boonkongchuen for their input to this document. The members of the IDR Working Group also provided helpful comments.
作者要感谢MCI的Roy Alcala和Arpakorn Boonkongchuen对本文件的投入。IDR工作组成员也提供了有益的意见。
[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] Rekhter, Y., and P. Gross, "Application of the Border Gateway Protocol in the Internet", RFC 1772, March 1995.
[2] Rekhter，Y.和P.Gross，“互联网中边界网关协议的应用”，RFC 1772，1995年3月。
[3] Rekhter, Y., "Routing in a Multi-provider Internet", RFC 1787, April 1995.
[3] Rekhter，Y.，“多提供商互联网中的路由”，RFC 1787，1995年4月。
[4] Hawkinson, J., and T. Bates, "Guidelines for creation, selection, and registration of an Autonomous System (AS)", RFC 1930, March 1996.
[4] 霍金森，J.和T.贝茨，“自主系统（AS）的创建、选择和注册指南”，RFC 1930，1996年3月。
[5] Bates, T., Gerich, E., Joncheray, L., Jouanigot, J-M, Karrenberg, D., Terpstra, M., and J. Yu., "Representation of IP Routing Policies in a Routing Registry (ripe-81++)", RFC 1786, March 1995.
[5] Bates，T.，Gerich，E.，Joncheray，L.，Jouanigot，J-M，Karrenberg，D.，Terpstra，M.，和J.Yu.，“路由注册表中IP路由策略的表示（RIME-81++）”，RFC 17861995年3月。
[6] Chen, E., and J. Stewart., "A Framework for Inter-Domain Route Aggregation", Work in Progress.
[6] Chen，E.和J.Stewart.，“域间路由聚合框架”，正在进行中。
John Stewart USC/ISI 4350 North Fairfax Drive Suite 620 Arlington, VA 22203
约翰·斯图尔特南加州/ISI 4350北费尔法克斯大道620号套房，弗吉尼亚州阿灵顿22203
EMail: jstewart@isi.edu
EMail: jstewart@isi.edu
Tony Bates Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134
Tony Bates Cisco Systems，Inc.加利福尼亚州圣何塞西塔斯曼大道170号，邮编95134
EMail: tbates@cisco.com
EMail: tbates@cisco.com
Ravi Chandra Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134
拉维·钱德拉·思科系统公司，加利福尼亚州圣何塞西塔斯曼大道170号，邮编95134
EMail: rchandra@cisco.com
EMail: rchandra@cisco.com
Enke Chen Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134
Enke Chen Cisco Systems，Inc.加利福尼亚州圣何塞西塔斯曼大道170号，邮编95134
EMail: enkechen@cisco.com
EMail: enkechen@cisco.com
Copyright (C) The Internet Society (1998). All Rights Reserved.
版权所有（C）互联网协会（1998年）。版权所有。
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