Internet Engineering Task Force (IETF) Q. Vohra
Request for Comments: 6793 Juniper Networks
Obsoletes: 4893 E. Chen
Updates: 4271 Cisco Systems
Category: Standards Track December 2012
ISSN: 2070-1721
Internet Engineering Task Force (IETF) Q. Vohra
Request for Comments: 6793 Juniper Networks
Obsoletes: 4893 E. Chen
Updates: 4271 Cisco Systems
Category: Standards Track December 2012
ISSN: 2070-1721
BGP Support for Four-Octet Autonomous System (AS) Number Space
BGP支持四个八位组自治系统（AS）数字空间
Abstract
摘要
The Autonomous System number is encoded as a two-octet entity in the base BGP specification. This document describes extensions to BGP to carry the Autonomous System numbers as four-octet entities. This document obsoletes RFC 4893 and updates RFC 4271.
在基本BGP规范中，自治系统编号编码为两个八位组实体。本文档描述了BGP的扩展，将自治系统编号作为四个八位字节实体进行携带。本文件淘汰了RFC 4893，并更新了RFC 4271。
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/rfc6793.
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/rfc6793.
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。
In the base BGP specification [RFC4271], the Autonomous System (AS) number is encoded as a two-octet entity. To prepare for the anticipated exhaustion of the two-octet AS numbers, this document describes extensions to BGP to carry the AS numbers as four-octet entities.
在基本BGP规范[RFC4271]中，自治系统（AS）编号编码为两个八位组实体。为了准备两个八位组AS号的预期耗尽，本文档描述了BGP的扩展，以将AS号作为四个八位组实体携带。
More specifically, this document defines a BGP capability code, "support for four-octet AS number capability", to be used by a BGP speaker to indicate its support for four-octet AS numbers. Two attributes, AS4_PATH and AS4_AGGREGATOR, are introduced that can be used to propagate four-octet-based AS path information across BGP speakers that do not support four-octet AS numbers. This document also specifies mechanisms for constructing the AS path information from the AS_PATH attribute and the AS4_PATH attribute.
更具体地说，本文档定义了一个BGP能力代码，“支持四个八位组作为数字能力”，BGP扬声器使用该代码来表示支持四个八位组作为数字。引入了两个属性AS4_PATH和AS4_AGGREGATOR，可用于在不支持四个八位组作为数字的BGP扬声器之间传播四个八位组作为路径信息。本文档还指定了从AS_path属性和AS4_path属性构造AS路径信息的机制。
The extensions specified in this document allow a gradual transition from two-octet AS numbers to four-octet AS numbers.
本文档中指定的扩展允许从两个八位组作为数字逐渐过渡到四个八位组作为数字。
This document obsoletes RFC 4893 and updates RFC 4271. It includes several clarifications and editorial changes, and it specifies the error handling for the new attributes.
本文件淘汰了RFC 4893，并更新了RFC 4271。它包括一些澄清和编辑更改，并指定了新属性的错误处理。
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。
For the purpose of this document, we define a BGP speaker that does not support the new four-octet AS number extensions as an OLD BGP speaker, and a BGP speaker that supports the new four-octet AS number extensions as a NEW BGP speaker.
在本文档中，我们将不支持新四个八位字节作为数字扩展的BGP扬声器定义为旧BGP扬声器，将支持新四个八位字节作为数字扩展的BGP扬声器定义为新BGP扬声器。
BGP carries the AS numbers in the "My Autonomous System" field of the OPEN message, in the AS_PATH attribute of the UPDATE message, and in the AGGREGATOR attribute of the UPDATE message. BGP also carries the AS numbers in the BGP Communities attribute.
BGP在打开消息的“我的自治系统”字段、更新消息的AS_路径属性和更新消息的聚合器属性中携带AS编号。BGP还携带BGP社区属性中的AS编号。
A NEW BGP speaker uses BGP Capabilities Advertisements [RFC5492] to advertise to its neighbors (either internal or external) that it supports four-octet AS number extensions, as specified in this document.
新的BGP扬声器使用BGP功能播发[RFC5492]向其邻居（内部或外部）播发其支持四个八位组作为数字扩展，如本文档所述。
The capability that is used by a BGP speaker to convey to its BGP peer the four-octet Autonomous System number capability also carries the AS number (encoded as a four-octet entity) of the speaker in the Capability Value field of the capability. The Capability Length field of the capability is set to 4.
BGP扬声器用于向其BGP对等方传送四个八位组自治系统编号能力的能力，也在能力的能力值字段中携带扬声器的AS编号（编码为四个八位组实体）。能力的能力长度字段设置为4。
The AS path information exchanged between NEW BGP speakers is carried in the existing AS_PATH attribute, except that each AS number in the attribute is encoded as a four-octet entity (instead of a two-octet entity). The same applies to the AGGREGATOR attribute -- the same attribute is used between NEW BGP speakers, except that the AS number carried in the attribute is encoded as a four-octet entity.
新BGP扬声器之间交换的AS路径信息包含在现有AS_路径属性中，但属性中的每个AS编号都编码为四个八位字节实体（而不是两个八位字节实体）。这同样适用于聚合器属性——在新的BGP扬声器之间使用相同的属性，除了属性中携带的AS编号编码为四个八位组实体。
The AS_PATH attribute and the AGGREGATOR attribute carried between a NEW BGP speaker and an OLD BGP speaker will continue to contain two-octet AS numbers.
新BGP扬声器和旧BGP扬声器之间携带的AS_PATH属性和AGGREGATOR属性将继续包含两个八位组AS编号。
To preserve the AS path information with four-octet AS numbers across OLD BGP speakers, this document defines a new BGP path attribute called AS4_PATH. This is an optional transitive attribute that contains the AS path encoded with four-octet AS numbers. The AS4_PATH attribute has the same semantics and the same encoding as the AS_PATH attribute, except that it is "optional transitive", and it carries four-octet AS numbers.
为了在旧BGP扬声器中保留四个八位组AS编号的AS路径信息，本文档定义了一个新的BGP路径属性，称为AS4_路径。这是一个可选的可传递属性，它包含用四个八位组作为数字编码的AS路径。AS4_路径属性与as_路径属性具有相同的语义和编码，只是它是“可选传递的”，并且携带四个八位字节作为数字。
To prevent the possible propagation of Confederation-related path segments outside of a Confederation, the path segment types AS_CONFED_SEQUENCE and AS_CONFED_SET [RFC5065] are declared invalid for the AS4_PATH attribute and MUST NOT be included in the AS4_PATH attribute of an UPDATE message.
为防止联盟相关路径段可能在联盟之外传播，路径段类型（如_-CONFED_序列和_-CONFED_集合[RFC5065]）对于AS4 _路径属性无效，并且不得包含在更新消息的AS4 _路径属性中。
Similarly, this document defines a new BGP path attribute called AS4_AGGREGATOR, which is optional transitive. The AS4_AGGREGATOR attribute has the same semantics and the same encoding as the AGGREGATOR attribute, except that it carries a four-octet AS number.
类似地，本文档定义了一个名为AS4_AGGREGATOR的新BGP路径属性，它是可选的可传递属性。AS4_AGGREGATOR属性与AGGREGATOR属性具有相同的语义和编码，只是它带有一个四个八位组作为数字。
Currently assigned two-octet AS numbers are converted into four-octet AS numbers by setting the two high-order octets of the four-octet field to zero. Such a four-octet AS number is said to be mappable to a two-octet AS number.
通过将“四个八位组”字段的两个高阶八位组设置为零，当前分配的两个八位组作为数字转换为四个八位组作为数字。这样一个四个八位组的数字可以映射为一个两个八位组的数字。
This document reserves a two-octet AS number called "AS_TRANS". AS_TRANS can be used to represent non-mappable four-octet AS numbers as two-octet AS numbers in AS path information that is encoded with two-octet AS numbers. (In this context, four-octet AS numbers that are not mapped from two-octet AS numbers are referred to as "non-mappable".) We denote this special AS number as AS_TRANS for ease of description in the rest of this specification. This AS
本文件保留一个称为“AS_TRANS”的两个八位数字。AS_TRANS可用于将不可映射的四个八位组表示为数字，将两个八位组表示为数字，并将两个八位组编码为数字。（在此上下文中，四个八位组作为数字而不是两个八位组作为数字映射的数字被称为“不可映射”。）为了便于在本规范的其余部分中描述，我们将此特殊数字表示为AS_TRANS。这是
number is also placed in the "My Autonomous System" field of the OPEN message originated by a NEW BGP speaker, if and only if the speaker does not have a (globally unique) two-octet AS number.
当且仅当新的BGP说话人没有（全局唯一的）两个八位组作为数字时，数字也被放置在开放消息的“我的自主系统”字段中。
A BGP speaker that supports four-octet AS numbers SHALL advertise this to its peers using BGP Capabilities Advertisements. The AS number of the BGP speaker MUST be carried in the Capability Value field of the "support for four-octet AS number capability".
支持四个八位组作为数字的BGP扬声器应使用BGP播发功能向其对等方播发。BGP扬声器的AS编号必须在“支持四个八位组AS编号能力”的能力值字段中携带。
When a NEW BGP speaker processes an OPEN message from another NEW BGP speaker, it MUST use the AS number encoded in the Capability Value field of the "support for four-octet AS number capability" in lieu of the "My Autonomous System" field of the OPEN message.
当一个新的BGP扬声器处理另一个新的BGP扬声器发出的开放消息时，它必须使用“支持四个八位组作为号码能力”的能力值字段中编码的AS号码，而不是开放消息的“我的自主系统”字段。
A BGP speaker that advertises such a capability to a particular peer, and receives from that peer the advertisement of such a capability, MUST encode AS numbers as four-octet entities in both the AS_PATH attribute and the AGGREGATOR attribute in the updates it sends to the peer and MUST assume that these attributes in the updates received from the peer encode AS numbers as four-octet entities.
BGP演讲者，向特定对等方宣传该能力，并从该对等方接收该能力的宣传，在发送给对等方的更新中，必须在AS_PATH属性和AGGREGATOR属性中以数字形式编码为四个八位字节实体，并且必须假设从对等方接收的更新中的这些属性以数字形式编码为四个八位字节实体。
The new attributes, AS4_PATH and AS4_AGGREGATOR, MUST NOT be carried in an UPDATE message between NEW BGP speakers. A NEW BGP speaker that receives the AS4_PATH attribute or the AS4_AGGREGATOR attribute in an UPDATE message from another NEW BGP speaker MUST discard the path attribute and continue processing the UPDATE message.
新属性AS4_路径和AS4_聚合器不得在新BGP扬声器之间的更新消息中携带。从另一个新BGP扬声器接收更新消息中的AS4_路径属性或AS4_聚合器属性的新BGP扬声器必须放弃路径属性并继续处理更新消息。
Note that peering between a NEW BGP speaker and an OLD BGP speaker is possible only if the NEW BGP speaker has a two-octet AS number. However, this document does not assume that an Autonomous System with NEW BGP speakers has to have a globally unique two-octet AS number -- AS_TRANS MUST be used when the NEW BGP speaker does not have a two-octet AS number (even if multiple Autonomous Systems would use it).
请注意，只有当新BGP扬声器有两个八位组作为数字时，才可能在新BGP扬声器和旧BGP扬声器之间进行对等。但是，本文档并不假设具有新BGP扬声器的自治系统必须具有全局唯一的两个八位组作为编号——当新BGP扬声器没有两个八位组作为编号时，必须使用AS_TRANS（即使多个自治系统将使用它）。
When communicating with an OLD BGP speaker, a NEW BGP speaker MUST send the AS path information in the AS_PATH attribute encoded with two-octet AS numbers. The NEW BGP speaker MUST also send the AS path information in the AS4_PATH attribute (encoded with four-octet AS numbers), except for the case where all of the AS path information is composed of mappable four-octet AS numbers only. In this case, the NEW BGP speaker MUST NOT send the AS4_PATH attribute.
当与旧BGP扬声器通信时，新BGP扬声器必须发送AS_path属性中的AS路径信息，该属性使用两个八位组AS编号编码。新的BGP扬声器还必须发送AS4_路径属性中的AS路径信息（用四个八位组AS编号编码），除非所有AS路径信息仅由可映射的四个八位组AS编号组成。在这种情况下，新的BGP扬声器不得发送AS4_路径属性。
In the AS_PATH attribute encoded with two-octet AS numbers, non-mappable four-octet AS numbers are represented by the well-known two-octet AS number, AS_TRANS. This will preserve the path length property of the AS path information and also help in updating the AS path information received on a NEW BGP speaker from an OLD BGP speaker, as explained in the next section.
在用两个八位组作为数字编码的AS_路径属性中，不可映射的四个八位组作为数字由众所周知的两个八位组作为数字表示，即AS_TRANS。这将保留AS路径信息的路径长度属性，并有助于更新新BGP扬声器从旧BGP扬声器接收到的AS路径信息，如下一节所述。
The NEW BGP speaker constructs the AS4_PATH attribute from the AS path information. Whenever the AS path information contains the AS_CONFED_SEQUENCE or AS_CONFED_SET path segment, the NEW BGP speaker MUST exclude such path segments from the AS4_PATH attribute being constructed.
新的BGP扬声器根据AS路径信息构造AS4_路径属性。每当AS路径信息包含AS_CONFED_序列或AS_CONFED_集合路径段时，新BGP扬声器必须从正在构建的AS4_路径属性中排除此类路径段。
The AS4_PATH attribute, being optional transitive, will be carried across a series of OLD BGP speakers without modification and will help preserve the non-mappable four-octet AS numbers in the AS path information.
AS4_路径属性是可选的可传递属性，将在一系列旧BGP扬声器中携带，无需修改，并有助于在AS路径信息中保留不可映射的四个八位组AS编号。
Similarly, if the NEW BGP speaker has to send the AGGREGATOR attribute, and if the aggregating Autonomous System's AS number is a non-mappable four-octet AS number, then the speaker MUST use the AS4_AGGREGATOR attribute and set the AS number field in the existing AGGREGATOR attribute to the reserved AS number, AS_TRANS. Note that if the AS number is mappable, then the AS4_AGGREGATOR attribute MUST NOT be sent.
类似地，如果新BGP演讲者必须发送聚合器属性，并且聚合自治系统的AS编号是不可映射的四个八位组AS编号，则演讲者必须使用AS4_聚合器属性，并将现有聚合器属性中的AS编号字段设置为保留AS编号AS_TRANS。请注意，如果AS编号可映射，则不得发送AS4_聚合器属性。
When a NEW BGP speaker receives an update from an OLD BGP speaker, it MUST be prepared to receive the AS4_PATH attribute along with the existing AS_PATH attribute. If the AS4_PATH attribute is also received, both of the attributes will be used to construct the exact AS path information, and therefore the information carried by both of the attributes will be considered for AS path loop detection.
当新的BGP扬声器接收到来自旧BGP扬声器的更新时，它必须准备好接收AS4_路径属性以及现有的AS_路径属性。如果还接收到AS4_路径属性，则这两个属性都将用于构造精确的AS路径信息，因此这两个属性携带的信息将被视为AS路径循环检测。
Note that a route may have traversed a series of Autonomous Systems with two-octet AS numbers and OLD BGP speakers only. In that case, if the route carries the AS4_PATH attribute, this attribute would have remained unmodified since the route left the last NEW BGP speaker. The trailing AS path information (representing Autonomous Systems with two-octet AS numbers and OLD BGP speakers only) is contained only in the current AS_PATH attribute (encoded in the leading part of the AS_PATH attribute).
请注意，一条路由可能穿越了一系列自治系统，其中两个八位组作为数字，只有旧的BGP扬声器。在这种情况下，如果路由带有AS4_路径属性，则该属性将保持不变，因为路由离开了最后一个新的BGP扬声器。尾随AS路径信息（仅表示具有两个八位组AS数字和旧BGP扬声器的自治系统）仅包含在当前AS_路径属性（编码在AS_路径属性的前导部分）中。
Under certain conditions, it may not be possible to reconstruct all of the AS path information from the AS_PATH and the AS4_PATH attributes of a route. This occurs, for example, when two or more routes that carry the AS4_PATH attribute are aggregated by an OLD BGP speaker, and the AS4_PATH attribute of at least one of these routes carries at least one four-octet AS number (as opposed to a two-octet AS number that is encoded in 4 octets). Depending on the implementation, either the AS4_PATH attribute would be lost during route aggregation, or both the AS_PATH attribute and the AS4_PATH attribute would contain valid, partial information that cannot be combined seamlessly, resulting in incomplete AS path information in these cases.
在某些情况下，可能无法从路由的AS_路径和AS4_路径属性重建所有AS路径信息。例如，当携带AS4_路径属性的两个或多个路由被旧BGP说话者聚合，并且这些路由中至少一个的AS4_路径属性携带至少一个四个八位组作为数字（与编码在四个八位组中的两个八位组作为数字相反）。根据实现的不同，AS4_路径属性可能会在路由聚合过程中丢失，或者AS_路径属性和AS4_路径属性都包含无法无缝组合的有效部分信息，从而在这些情况下导致AS路径信息不完整。
A NEW BGP speaker MUST also be prepared to receive the AS4_AGGREGATOR attribute along with the AGGREGATOR attribute from an OLD BGP speaker. When both of the attributes are received, if the AS number in the AGGREGATOR attribute is not AS_TRANS, then:
新的BGP扬声器还必须准备好从旧的BGP扬声器接收AS4_聚合器属性以及聚合器属性。当接收到这两个属性时，如果聚合器属性中的AS编号不是AS_TRANS，则：
- the AS4_AGGREGATOR attribute and the AS4_PATH attribute SHALL be ignored,
- 应忽略AS4_聚合器属性和AS4_路径属性，
- the AGGREGATOR attribute SHALL be taken as the information about the aggregating node, and
- 聚合器属性应作为有关聚合节点的信息，并且
- the AS_PATH attribute SHALL be taken as the AS path information.
- AS_路径属性应作为AS路径信息。
Otherwise,
否则
- the AGGREGATOR attribute SHALL be ignored,
- 应忽略聚合器属性，
- the AS4_AGGREGATOR attribute SHALL be taken as the information about the aggregating node, and
- AS4_聚合器属性应作为聚合节点的信息，以及
- the AS path information would need to be constructed, as in all other cases.
- 与所有其他情况一样，需要构造AS路径信息。
In order to construct the AS path information, it is necessary to first calculate the number of AS numbers in the AS_PATH and AS4_PATH attributes using the method specified in Section 9.1.2.2 of [RFC4271] and in [RFC5065] for route selection.
为了构造AS路径信息，必须首先使用[RFC4271]第9.1.2.2节和[RFC5065]中规定的路由选择方法计算AS_路径和AS4_路径属性中的AS编号数量。
If the number of AS numbers in the AS_PATH attribute is less than the number of AS numbers in the AS4_PATH attribute, then the AS4_PATH attribute SHALL be ignored, and the AS_PATH attribute SHALL be taken as the AS path information.
如果AS_路径属性中的AS编号数量小于AS4_路径属性中的AS编号数量，则应忽略AS4_路径属性，并将AS_路径属性作为AS路径信息。
If the number of AS numbers in the AS_PATH attribute is larger than or equal to the number of AS numbers in the AS4_PATH attribute, then the AS path information SHALL be constructed by taking as many AS numbers and path segments as necessary from the leading part of the AS_PATH attribute, and then prepending them to the AS4_PATH attribute so that the AS path information has a number of AS numbers identical to that of the AS_PATH attribute. Note that a valid AS_CONFED_SEQUENCE or AS_CONFED_SET path segment SHALL be prepended if it is either the leading path segment or is adjacent to a path segment that is prepended.
如果AS_路径属性中AS编号的数量大于或等于AS4_路径属性中AS编号的数量，则AS路径信息应通过从AS_路径属性的前导部分获取所需数量和路径段来构建，然后将它们预先添加到AS4_路径属性，以便AS路径信息具有与AS_路径属性相同的AS编号。请注意，如果有效的AS_-CONFED_序列或AS_-CONFED_集合路径段是前导路径段或与预先指定的路径段相邻，则应预先指定该路径段。
As specified in [RFC1997], when the high-order two octets of the community attribute is neither 0x0000 nor 0xffff, these two octets encode the AS number. Quite clearly, this would not work for a NEW BGP speaker with a non-mappable four-octet AS number. Such BGP speakers should use four-octet AS specific extended communities [RFC5668] instead.
如[RFC1997]中所述，当community属性的高阶两个八位字节既不是0x0000也不是0xffff时，这两个八位字节对As编号进行编码。很明显，这不适用于一个新的BGP扬声器，它的数字是不可映射的四个八位组。此类BGP扬声器应使用四个八位字节作为特定的扩展社区[RFC5668]。
This section provides an update to RFC 4271 [RFC4271] with respect to the error conditions noted here and their handling.
本节提供了RFC 4271[RFC4271]关于此处所述错误条件及其处理的更新。
Given that the two-octet AS numbers dominate during the transition and are carried in the AS_PATH attribute by an OLD BGP speaker, in this document the "attribute discard" approach is chosen to handle a malformed AS4_PATH attribute.
鉴于两个八位组AS数在转换过程中占主导地位，并且由老BGP扬声器携带在AS_路径属性中，因此本文选择“属性丢弃”方法来处理格式错误的AS4_路径属性。
Similarly, as the AS4_AGGREGATOR is just informational, the "attribute discard" approach is chosen to handle a malformed AS4_AGGREGATOR attribute.
类似地，由于AS4_聚合器只是信息性的，因此选择“属性丢弃”方法来处理格式错误的AS4_聚合器属性。
The AS4_PATH attribute and AS4_AGGREGATOR attribute MUST NOT be carried in an UPDATE message between NEW BGP speakers. A NEW BGP speaker that receives the AS4_PATH attribute or the AS4_AGGREGATOR attribute in an UPDATE message from another NEW BGP speaker MUST discard the path attribute and continue processing the UPDATE message. This case SHOULD be logged locally for analysis.
新BGP扬声器之间的更新消息中不得携带AS4_路径属性和AS4_聚合器属性。从另一个新BGP扬声器接收更新消息中的AS4_路径属性或AS4_聚合器属性的新BGP扬声器必须放弃路径属性并继续处理更新消息。应在本地记录此案例以进行分析。
In addition, the path segment types AS_CONFED_SEQUENCE and AS_CONFED_SET [RFC5065] MUST NOT be carried in the AS4_PATH attribute of an UPDATE message. A NEW BGP speaker that receives these path segment types in the AS4_PATH attribute of an UPDATE message from an OLD BGP speaker MUST discard these path segments, adjust the relevant attribute fields accordingly, and continue processing the UPDATE message. This case SHOULD be logged locally for analysis.
此外，更新消息的AS4路径属性中不得携带路径段类型AS_CONFED_SEQUENCE和AS_CONFED_SET[RFC5065]。从旧BGP扬声器接收更新消息的AS4_路径属性中的这些路径段类型的新BGP扬声器必须丢弃这些路径段，相应地调整相关属性字段，并继续处理更新消息。应在本地记录此案例以进行分析。
The AS4_PATH attribute in an UPDATE message SHALL be considered malformed under the following conditions:
在以下情况下，更新消息中的AS4_路径属性应视为格式不正确：
- the attribute length is not a multiple of two or is too small (i.e., less than 6) for the attribute to carry at least one AS number, or
- 属性长度不是2的倍数，或者太小（即小于6），属性无法携带至少一个作为数字，或者
- the path segment length in the attribute is either zero or is inconsistent with the attribute length, or
- 属性中的路径段长度为零或与属性长度不一致，或
- the path segment type in the attribute is not one of the types defined: AS_SEQUENCE, AS_SET, AS_CONFED_SEQUENCE, and AS_CONFED_SET.
- 属性中的路径段类型不是定义的类型之一：AS_SEQUENCE、AS_SET、AS_CONFED_SEQUENCE和AS_CONFED_SET。
A NEW BGP speaker that receives a malformed AS4_PATH attribute in an UPDATE message from an OLD BGP speaker MUST discard the attribute and continue processing the UPDATE message. The error SHOULD be logged locally for analysis.
从旧BGP扬声器接收更新消息中格式错误的AS4_路径属性的新BGP扬声器必须放弃该属性并继续处理更新消息。应在本地记录错误以进行分析。
The AS4_AGGREGATOR attribute in an UPDATE message SHALL be considered malformed if the attribute length is not 8.
如果属性长度不是8，则更新消息中的AS4_聚合器属性应视为格式不正确。
A NEW BGP speaker that receives a malformed AS4_AGGREGATOR attribute in an UPDATE message from an OLD BGP speaker MUST discard the attribute and continue processing the UPDATE message. The error SHOULD be logged locally for analysis.
从旧BGP扬声器接收更新消息中格式错误的AS4_聚合器属性的新BGP扬声器必须放弃该属性并继续处理更新消息。应在本地记录错误以进行分析。
When an Autonomous System is using a two-octet AS number, then the BGP speakers within that Autonomous System MAY be upgraded to support the four-octet AS number extensions on a piecemeal basis. There is no requirement for a coordinated upgrade of the four-octet AS number capability in this case. However, if an Autonomous System wishes to use a four-octet AS number as its own AS number, then this document assumes that an Autonomous System can use a four-octet AS number only after all the BGP speakers within that Autonomous System have been upgraded to support four-octet AS numbers.
当自治系统使用两个八位组作为数字时，则该自治系统内的BGP扬声器可升级为支持四个八位组作为零碎的数字扩展。在这种情况下，不需要协调升级四个八位组作为数字的能力。但是，如果自治系统希望使用四个八位组作为其自身的AS编号，则本文档假设自治系统只能在该自治系统内的所有BGP扬声器升级为支持四个八位组作为编号后，才能使用四个八位组作为编号。
A non-mappable four-octet AS number cannot be used as a "Member AS Number" of a BGP Confederation until all the BGP speakers within the Confederation have transitioned to support four-octet AS numbers.
不可映射的四个八位组AS编号不能用作BGP联盟的“成员AS编号”，除非联盟内的所有BGP扬声器都已转换为支持四个八位组AS编号。
In an environment where an Autonomous System that has OLD BGP speakers peers with two or more Autonomous Systems that have NEW BGP speakers and use AS_TRANS (rather than having a globally unique mappable AS number), the use of the MULTI_EXIT_DISC attribute [RFC4271] by the Autonomous System with the OLD BGP speakers may result in a situation where the MULTI_EXIT_DISC attribute will influence route selection among the routes that were received from different neighboring Autonomous Systems.
在具有旧BGP扬声器的自治系统与具有新BGP扬声器并使用AS_TRANS（而不是具有全局唯一可映射AS编号）的两个或多个自治系统对等的环境中，使用MULTI_EXIT_DISC属性[RFC4271]使用旧BGP扬声器的自治系统可能导致多个退出盘属性将影响从不同相邻自治系统接收的路由之间的路由选择的情况。
Under certain conditions, it may not be possible to reconstruct all of the AS path information from the AS_PATH and the AS4_PATH attributes of a route. This occurs when two or more routes that carry the AS4_PATH attribute are aggregated by an OLD BGP speaker, and the AS4_PATH attribute of at least one of these routes carries at least one four-octet AS number (as opposed to a two-octet AS number that is encoded in 4 octets). When such aggregation results in creating a route that is less specific than any of the component routes (routes whose Network Layer Reachability Information (NLRI) covers the NLRI of all the component routes), loss of the AS path information does not create the risk of a routing loop. In all other cases, loss of the AS path information does create the risk of a routing loop.
在某些情况下，可能无法从路由的AS_路径和AS4_路径属性重建所有AS路径信息。当两个或多个带有AS4_路径属性的路由被旧BGP扬声器聚合，并且至少一个路由的AS4_路径属性带有至少一个四个八位组作为编号（与编码在四个八位组中的两个八位组作为编号相反）时，就会发生这种情况。当这种聚合导致创建的路由不如任何组件路由（其网络层可达性信息（NLRI）覆盖所有组件路由的NLRI）具体时，AS路径信息的丢失不会产生路由循环的风险。在所有其他情况下，AS路径信息的丢失确实会产生路由循环的风险。
If the BGP4-MIB [RFC4273] is supported, there are no additional manageability concerns that arise from the use of four-octet AS numbers, since the InetAutonomousSystemNumber textual convention [RFC4001] is defined as Unsigned32.
如果支持BGP4-MIB[RFC4273]，则不会因使用四个八位字节作为数字而产生额外的可管理性问题，因为InetAutonomousSystemNumber文本约定[RFC4001]定义为Unsigned32。
When IP Flow Information Export (IPFIX) [RFC5101] is supported, there are no additional manageability concerns that arise from the use of four-octet AS numbers. The bgpSourceAsNumber and bgpDestinationAsNumber information elements [IANA-IPFIX] can continue to be used, with a new template record, specifying the new length of 4 bytes.
当支持IP流信息导出（IPFIX）[RFC5101]时，使用四个八位组作为数字不会产生额外的可管理性问题。bgpSourceAsNumber和bgpDestinationAsNumber信息元素[IANA-IPFIX]可以与新的模板记录一起继续使用，并指定4字节的新长度。
This document expands the pool for AS numbers from 0-65535 to 0-4294967295. The AS numbers are managed by the IANA "Autonomous System Numbers" registry. Other than expanding the AS number pool, this document does not propose any modifications to the existing policies and procedures pertaining to the allocation of AS numbers.
本文档将AS编号的池从0-65535扩展到0-4294967295。AS编号由IANA“自主系统编号”注册表管理。除扩展AS编号池外，本文件不建议对与AS编号分配相关的现有政策和程序进行任何修改。
This document uses a BGP capability code to indicate that a BGP speaker supports four-octet AS numbers. Capability Code 65 has been assigned by IANA per [RFC5492].
本文档使用BGP功能代码表示BGP扬声器支持四个八位组作为数字。IANA根据[RFC5492]分配了能力代码65。
In addition, this document introduces two BGP optional transitive attributes, and their type codes have been assigned by IANA. The first one is the AS4_PATH attribute, value 17, which preserves the AS path information with four-octet AS numbers across old BGP speakers. The second one is the AS4_AGGREGATOR attribute, value 18, which is similar in use to the current AGGREGATOR attribute, but it carries a four-octet AS number.
此外，本文档还介绍了两个BGP可选传递属性，它们的类型代码由IANA分配。第一个是AS4_路径属性，值17，它保留了AS路径信息，在旧BGP扬声器中有四个八位组AS编号。第二个是AS4_AGGREGATOR属性，值18，与当前AGGREGATOR属性的用法类似，但它携带一个四个八位组作为数字。
Finally, IANA has replaced a reference to RFC 4893 with a reference to this document for a reserved two-octet AS number -- AS_TRANS (23456). Also, IANA has replaced a reference to RFC 4893 with a reference to this document for the "32-bit Autonomous System Numbers" registry.
最后，IANA已将RFC4893的引用替换为本文档中保留的两个八位组AS编号——AS_TRANS（23456）。此外，IANA已将对RFC 4893的引用替换为对“32位自治系统编号”注册表的本文件的引用。
This extension to BGP does not change the underlying security issues inherent in the existing BGP, except for the following:
BGP的此扩展不会改变现有BGP固有的基本安全问题，但以下情况除外：
The inconsistency between the AS_PATH attribute and the AS4_PATH attribute can create loss of the AS path information, and potential routing loops in certain cases, as discussed in this document. This could be exploited by an attacker.
AS_路径属性和AS4_路径属性之间的不一致会造成AS路径信息的丢失，并在某些情况下造成潜在的路由循环，如本文所述。攻击者可能会利用此漏洞。
It is a misconfiguration to assign a non-mappable four-octet AS number as the "Member AS Number" in a BGP Confederation before all the BGP speakers within the Confederation have transitioned to support four-octet AS numbers. Such a misconfiguration would weaken AS path loop detection within a Confederation.
在BGP联盟内的所有BGP发言者都转换为支持四个八位组作为数字之前，将不可映射的四个八位组作为数字指定为BGP联盟中的“成员作为数字”，这是一种错误配置。这样的错误配置会随着联盟内的路径循环检测而减弱。
The authors would like to thank Yakov Rekhter, Chaitanya Kodeboyina, and Jeffrey Haas for the numerous discussions that went into the making of this document.
作者要感谢雅科夫·雷赫特、柴坦尼亚·科德博伊纳和杰弗里·哈斯在编写本文件过程中进行的大量讨论。
The authors would also like to thank members of the IDR Working Group for their review and comments.
作者还要感谢IDR工作组成员的审查和评论。
[RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities Attribute", RFC 1997, August 1996.
[RFC1997]Chandra，R.，Traina，P.，和T.Li，“BGP社区属性”，RFC 1997，1996年8月。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[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。
[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。
[RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement with BGP-4", RFC 5492, February 2009.
[RFC5492]Scudder，J.和R.Chandra，“BGP-4的能力广告”，RFC 5492，2009年2月。
[RFC5668] Rekhter, Y., Sangli, S., and D. Tappan, "4-Octet AS Specific BGP Extended Community", RFC 5668, October 2009.
[RFC5668]Rekhter，Y.，Sangli，S.，和D.Tappan，“4-八位字节作为特定BGP扩展社区”，RFC 5668，2009年10月。
[IANA-IPFIX] IANA, "IP Flow Information Export (IPFIX) Entities", <http://www.iana.org/assignments/ipfix>.
[IANA-IPFIX]IANA，“IP流信息导出（IPFIX）实体”<http://www.iana.org/assignments/ipfix>.
[RFC4001] Daniele, M., Haberman, B., Routhier, S., and J. Schoenwaelder, "Textual Conventions for Internet Network Addresses", RFC 4001, February 2005.
[RFC4001]Daniele，M.，Haberman，B.，Routhier，S.，和J.Schoenwaeld，“互联网网络地址的文本约定”，RFC 4001，2005年2月。
[RFC4273] Haas, J., Ed., and S. Hares, Ed., "Definitions of Managed Objects for BGP-4", RFC 4273, January 2006.
[RFC4273]Haas，J.，Ed.，和S.Hares，Ed.，“BGP-4管理对象的定义”，RFC 4273，2006年1月。
[RFC5101] Claise, B., Ed., "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of IP Traffic Flow Information", RFC 5101, January 2008.
[RFC5101]Claise，B.，Ed.，“交换IP流量信息的IP流量信息导出（IPFIX）协议规范”，RFC 5101，2008年1月。
Authors' Addresses
作者地址
Quaizar Vohra Juniper Networks 1194 N. Mathilda Ave. Sunnyvale, CA 94089 USA
Quaizar Vohra Juniper Networks 1194 N.Mathilda Ave.Sunnyvale，加利福尼亚州94089
EMail: quaizar.vohra@gmail.com
EMail: quaizar.vohra@gmail.com
Enke Chen Cisco Systems, Inc. 170 W. Tasman Dr. San Jose, CA 95134 USA
Enke Chen思科系统有限公司170 W.Tasman Dr.San Jose，CA 95134美国
EMail: enkechen@cisco.com
EMail: enkechen@cisco.com