Internet Engineering Task Force (IETF) R. Aggarwal
Request for Comments: 6514 Juniper Networks
Category: Standards Track E. Rosen
ISSN: 2070-1721 Cisco Systems, Inc.
T. Morin
France Telecom - Orange
Y. Rekhter
Juniper Networks
February 2012
Internet Engineering Task Force (IETF) R. Aggarwal
Request for Comments: 6514 Juniper Networks
Category: Standards Track E. Rosen
ISSN: 2070-1721 Cisco Systems, Inc.
T. Morin
France Telecom - Orange
Y. Rekhter
Juniper Networks
February 2012
BGP Encodings and Procedures for Multicast in MPLS/BGP IP VPNs
MPLS/BGP IP VPN中的BGP编码和多播过程
Abstract
摘要
This document describes the BGP encodings and procedures for exchanging the information elements required by Multicast in MPLS/BGP IP VPNs, as specified in RFC 6513.
本文档描述了RFC 6513中规定的用于交换MPLS/BGP IP VPN中多播所需信息元素的BGP编码和过程。
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/rfc6514.
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/rfc6514.
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 ....................................................4
2. Specification of Requirements ...................................4
3. Terminology .....................................................4
4. MCAST-VPN NLRI ..................................................5
4.1. Intra-AS I-PMSI A-D Route ...................................6
4.2. Inter-AS I-PMSI A-D Route ...................................7
4.3. S-PMSI A-D Route ............................................7
4.4. Leaf A-D Route ..............................................8
4.5. Source Active A-D Route .....................................9
4.6. C-Multicast Route ..........................................10
5. PMSI Tunnel Attribute ..........................................10
6. Source AS Extended Community ...................................13
7. VRF Route Import Extended Community ............................14
8. PE Distinguisher Labels Attribute ..............................15
9. MVPN Auto-Discovery/Binding ....................................16
9.1. MVPN Auto-Discovery/Binding - Intra-AS Operations ..........16
9.1.1. Originating Intra-AS I-PMSI A-D Routes .................16
9.1.2. Receiving Intra-AS I-PMSI A-D Routes ...................19
9.2. MVPN Auto-Discovery/Binding - Inter-AS Operations ..........20
9.2.1. Originating Inter-AS I-PMSI A-D Routes .................22
9.2.2. When Not to Originate Inter-AS I-PMSI A-D Routes .......23
9.2.3. Propagating Inter-AS I-PMSI A-D Routes .................23
9.2.3.1. Propagating Inter-AS I-PMSI A-D Routes - Overview ..23
9.2.3.2. Inter-AS I-PMSI A-D Route Received via EBGP ........24
9.2.3.2.1. Originating Leaf A-D Route into EBGP ...........25
9.2.3.3. Leaf A-D Route Received via EBGP ...................26
9.2.3.4. Inter-AS I-PMSI A-D Route Received via IBGP ........27
9.2.3.4.1. Originating Leaf A-D Route into IBGP ...........28
9.2.3.5. Leaf A-D Route Received via IBGP ...................29
9.2.3.6. Optimizing Bandwidth by IP Filtering on ASBRs ......30
10. Non-Congruent Unicast and Multicast Connectivity ..............30
11. Exchange of C-Multicast Routing Information among PEs .........32
11.1. Originating C-Multicast Routes by a PE ....................32
11.1.1. Originating Routes: PIM as the C-Multicast Protocol ...32
11.1.1.1. Originating Source Tree Join C-Multicast Route ....33
11.1.1.2. Originating Shared Tree Join C-Multicast Route ....33
11.1.2. Originating Routes: mLDP as the C-Multicast Protocol ..34
11.1.3. Constructing the Rest of the C-Multicast Route ........34
11.1.4. Unicast Route Changes .................................35
11.2. Propagating C-Multicast Routes by an ASBR .................36
11.3. Receiving C-Multicast Routes by a PE ......................37
11.3.1. Receiving Routes: PIM as the C-Multicast Protocol .....37
11.3.1.1. Receiving Source Tree Join C-Multicast Route ......38
11.3.1.2. Receiving Shared Tree Join C-Multicast Route ......38
11.3.2. Receiving Routes: mLDP as the C-Multicast Protocol ....39
11.4. C-Multicast Routes Aggregation ............................39
1. Introduction ....................................................4
2. Specification of Requirements ...................................4
3. Terminology .....................................................4
4. MCAST-VPN NLRI ..................................................5
4.1. Intra-AS I-PMSI A-D Route ...................................6
4.2. Inter-AS I-PMSI A-D Route ...................................7
4.3. S-PMSI A-D Route ............................................7
4.4. Leaf A-D Route ..............................................8
4.5. Source Active A-D Route .....................................9
4.6. C-Multicast Route ..........................................10
5. PMSI Tunnel Attribute ..........................................10
6. Source AS Extended Community ...................................13
7. VRF Route Import Extended Community ............................14
8. PE Distinguisher Labels Attribute ..............................15
9. MVPN Auto-Discovery/Binding ....................................16
9.1. MVPN Auto-Discovery/Binding - Intra-AS Operations ..........16
9.1.1. Originating Intra-AS I-PMSI A-D Routes .................16
9.1.2. Receiving Intra-AS I-PMSI A-D Routes ...................19
9.2. MVPN Auto-Discovery/Binding - Inter-AS Operations ..........20
9.2.1. Originating Inter-AS I-PMSI A-D Routes .................22
9.2.2. When Not to Originate Inter-AS I-PMSI A-D Routes .......23
9.2.3. Propagating Inter-AS I-PMSI A-D Routes .................23
9.2.3.1. Propagating Inter-AS I-PMSI A-D Routes - Overview ..23
9.2.3.2. Inter-AS I-PMSI A-D Route Received via EBGP ........24
9.2.3.2.1. Originating Leaf A-D Route into EBGP ...........25
9.2.3.3. Leaf A-D Route Received via EBGP ...................26
9.2.3.4. Inter-AS I-PMSI A-D Route Received via IBGP ........27
9.2.3.4.1. Originating Leaf A-D Route into IBGP ...........28
9.2.3.5. Leaf A-D Route Received via IBGP ...................29
9.2.3.6. Optimizing Bandwidth by IP Filtering on ASBRs ......30
10. Non-Congruent Unicast and Multicast Connectivity ..............30
11. Exchange of C-Multicast Routing Information among PEs .........32
11.1. Originating C-Multicast Routes by a PE ....................32
11.1.1. Originating Routes: PIM as the C-Multicast Protocol ...32
11.1.1.1. Originating Source Tree Join C-Multicast Route ....33
11.1.1.2. Originating Shared Tree Join C-Multicast Route ....33
11.1.2. Originating Routes: mLDP as the C-Multicast Protocol ..34
11.1.3. Constructing the Rest of the C-Multicast Route ........34
11.1.4. Unicast Route Changes .................................35
11.2. Propagating C-Multicast Routes by an ASBR .................36
11.3. Receiving C-Multicast Routes by a PE ......................37
11.3.1. Receiving Routes: PIM as the C-Multicast Protocol .....37
11.3.1.1. Receiving Source Tree Join C-Multicast Route ......38
11.3.1.2. Receiving Shared Tree Join C-Multicast Route ......38
11.3.2. Receiving Routes: mLDP as the C-Multicast Protocol ....39
11.4. C-Multicast Routes Aggregation ............................39
12. Using S-PMSI A-D Routes to Bind C-Trees to P-Tunnels ..........40
12.1. Originating S-PMSI A-D Routes .............................40
12.2. Handling S-PMSI A-D Routes by ASBRs .......................43
12.2.1. Merging S-PMSI into an I-PMSI .........................43
12.3. Receiving S-PMSI A-D Routes by PEs ........................44
13. Switching from Shared a C-Tree to a Source C-Tree .............45
13.1. Source within a Site - Source Active Advertisement ........46
13.2. Receiving Source Active A-D Route .........................47
13.2.1. Pruning Sources off the Shared Tree ...................48
14. Supporting PIM-SM without Inter-Site Shared C-Trees ...........49
14.1. Discovering Active Multicast Sources ......................50
14.2. Receiver(s) within a Site .................................51
14.3. Receiving C-Multicast Routes by a PE ......................52
15. Carrier's Carrier .............................................52
16. Scalability Considerations ....................................52
16.1. Dampening C-Multicast Routes ..............................54
16.1.1. Dampening Withdrawals of C-Multicast Routes ...........54
16.1.2. Dampening Source/Shared Tree Join C-Multicast Routes ..55
16.2. Dampening Withdrawals of Leaf A-D Routes ..................55
17. Security Considerations .......................................55
18. IANA Considerations ...........................................56
19. Acknowledgements ..............................................57
20. References ....................................................57
20.1. Normative References ......................................57
20.2. Informative References ....................................58
12. Using S-PMSI A-D Routes to Bind C-Trees to P-Tunnels ..........40
12.1. Originating S-PMSI A-D Routes .............................40
12.2. Handling S-PMSI A-D Routes by ASBRs .......................43
12.2.1. Merging S-PMSI into an I-PMSI .........................43
12.3. Receiving S-PMSI A-D Routes by PEs ........................44
13. Switching from Shared a C-Tree to a Source C-Tree .............45
13.1. Source within a Site - Source Active Advertisement ........46
13.2. Receiving Source Active A-D Route .........................47
13.2.1. Pruning Sources off the Shared Tree ...................48
14. Supporting PIM-SM without Inter-Site Shared C-Trees ...........49
14.1. Discovering Active Multicast Sources ......................50
14.2. Receiver(s) within a Site .................................51
14.3. Receiving C-Multicast Routes by a PE ......................52
15. Carrier's Carrier .............................................52
16. Scalability Considerations ....................................52
16.1. Dampening C-Multicast Routes ..............................54
16.1.1. Dampening Withdrawals of C-Multicast Routes ...........54
16.1.2. Dampening Source/Shared Tree Join C-Multicast Routes ..55
16.2. Dampening Withdrawals of Leaf A-D Routes ..................55
17. Security Considerations .......................................55
18. IANA Considerations ...........................................56
19. Acknowledgements ..............................................57
20. References ....................................................57
20.1. Normative References ......................................57
20.2. Informative References ....................................58
This document describes the BGP encodings and procedures for exchanging the information elements required by Multicast in MPLS/BGP IP VPNs, as specified in [MVPN]. This document assumes a thorough familiarity with the procedures, concepts, and terms described in [MVPN].
本文档描述了[MVPN]中规定的用于交换MPLS/BGP IP VPN中多播所需信息元素的BGP编码和过程。本文件假设完全熟悉[MVPN]中描述的程序、概念和术语。
This document defines a new Network Layer Reachability Information (NLRI), MCAST-VPN NLRI. The MCAST-VPN NLRI is used for MVPN auto-discovery, advertising MVPN to Inclusive P-Multicast Service Interface (I-PMSI) tunnel binding, advertising (C-S,C-G) to Selective PMSI (S-PMSI) tunnel binding, VPN customer multicast routing information exchange among Provider Edge routers (PEs), choosing a single forwarder PE, and for procedures in support of co-locating a Customer Rendezvous Point (C-RP) on a PE.
本文档定义了一个新的网络层可达性信息（NLRI），即MCAST-VPN NLRI。MCAST-VPN NLRI用于MVPN自动发现、将MVPN播发到包容性P多播服务接口（I-PMSI）隧道绑定、将（C-S、C-G）播发到选择性PMSI（S-PMSI）隧道绑定、在提供商边缘路由器（PE）之间交换VPN客户多播路由信息、选择单个转发器PE、，以及支持在PE上共同定位客户集合点（C-RP）的程序。
This document specifies two new BGP attributes: the P-Multicast Service Interface Tunnel (PMSI Tunnel) attribute and the PE Distinguisher Label attribute.
本文档指定了两个新的BGP属性：P多播服务接口隧道（PMSI隧道）属性和PE识别器标签属性。
This document also defines two new BGP Extended Communities: the Source Autonomous System (AS) Extended Community and the VPN Routing and Forwarding (VRF) Route Import Extended Community.
本文档还定义了两个新的BGP扩展社区：源自治系统（AS）扩展社区和VPN路由和转发（VRF）路由导入扩展社区。
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。
In the context of this document, we will refer to the MVPN auto-discovery/binding information carried in BGP as "auto-discovery routes" ("A-D routes"). For a given MVPN, there are the following types of A-D routes:
在本文档中，我们将BGP中的MVPN自动发现/绑定信息称为“自动发现路由”（“A-D路由”）。对于给定的MVPN，有以下类型的a-D路由：
+ Intra-AS I-PMSI A-D route;
+ AS内I-PMSI A-D路由；
+ Inter-AS I-PMSI A-D route;
+ 内部AS I-PMSI A-D路由；
+ S-PMSI A-D route;
+ S-PMSI A-D路线；
+ Leaf A-D route;
+ 叶片A-D路径；
+ Source Active A-D route.
+ 源激活A-D路由。
In the context of this document, we will refer to the MVPN customers' multicast routing information carried in BGP as "C-multicast routes". For a given MVPN, there are the following types of C-multicast routes:
在本文档的上下文中，我们将BGP中携带的MVPN客户的多播路由信息称为“C多播路由”。对于给定的MVPN，有以下类型的C多播路由：
+ Shared Tree Join route;
+ 共享树连接路由；
+ Source Tree Join route;
+ 源树连接路径；
For each MVPN present on a PE, the PE maintains a Tree Information Base (MVPN-TIB). This is the same as TIB defined in [RFC4601], except that instead of a single TIB, a PE maintains multiple MVPN-TIBs: one per each MVPN.
对于PE上存在的每个MVPN，PE维护一个树信息库（MVPN-TIB）。这与[RFC4601]中定义的TIB相同，不同之处在于，PE不是单个TIB，而是维护多个MVPN TIB：每个MVPN一个。
Throughout this document, we will use the term "VPN-IP route" to mean a route that is either in the VPN-IPv4 address family [RFC4364] or in the VPN-IPv6 address family [RFC4659].
在本文档中，我们将使用术语“VPN-IP路由”来表示VPN-IPv4地址系列[RFC4364]或VPN-IPv6地址系列[RFC4659]中的路由。
This document defines a new BGP NLRI, called the MCAST-VPN NLRI.
本文档定义了一个新的BGP NLRI，称为MCAST-VPN NLRI。
The following is the format of the MCAST-VPN NLRI:
以下是MCAST-VPN NLRI的格式：
+-----------------------------------+
| Route Type (1 octet) |
+-----------------------------------+
| Length (1 octet) |
+-----------------------------------+
| Route Type specific (variable) |
+-----------------------------------+
+-----------------------------------+
| Route Type (1 octet) |
+-----------------------------------+
| Length (1 octet) |
+-----------------------------------+
| Route Type specific (variable) |
+-----------------------------------+
The Route Type field defines the encoding of the rest of MCAST-VPN NLRI (Route Type specific MCAST-VPN NLRI).
路由类型字段定义了MCAST-VPN NLRI（路由类型特定的MCAST-VPN NLRI）其余部分的编码。
The Length field indicates the length in octets of the Route Type specific field of the MCAST-VPN NLRI.
长度字段表示MCAST-VPN NLRI路由类型特定字段的长度（以八位字节为单位）。
This document defines the following Route Types for A-D routes:
本文件定义了A-D路线的以下路线类型：
+ 1 - Intra-AS I-PMSI A-D route;
+ 2 - Inter-AS I-PMSI A-D route;
+ 3 - S-PMSI A-D route;
+ 4 - Leaf A-D route;
+ 5 - Source Active A-D route.
+ 1 - Intra-AS I-PMSI A-D route;
+ 2 - Inter-AS I-PMSI A-D route;
+ 3 - S-PMSI A-D route;
+ 4 - Leaf A-D route;
+ 5 - Source Active A-D route.
This document defines the following Route Types for C-multicast routes:
本文档定义了C多播路由的以下路由类型：
+ 6 - Shared Tree Join route;
+ 7 - Source Tree Join route;
+ 6 - Shared Tree Join route;
+ 7 - Source Tree Join route;
The MCAST-VPN NLRI is carried in BGP [RFC4271] using BGP Multiprotocol Extensions [RFC4760] with an Address Family Identifier (AFI) of 1 or 2 and a Subsequent AFI (SAFI) of MCAST-VPN. The NLRI field in the MP_REACH_NLRI/MP_UNREACH_NLRI attribute contains the MCAST-VPN NLRI (encoded as specified above). The value of the AFI field in the MP_REACH_NLRI/MP_UNREACH_NLRI attribute that carries the MCAST-VPN NLRI determines whether the multicast source and multicast group addresses carried in the S-PMSI A-D routes, Source Active A-D routes, and C-multicast routes are IPv4 or IPv6 addresses (AFI 1 indicates IPv4 addresses, AFI 2 indicates IPv6 addresses).
MCAST-VPN NLRI在BGP[RFC4271]中使用BGP多协议扩展[RFC4760]，地址族标识符（AFI）为1或2，随后使用MCAST-VPN的AFI（SAFI）。MP_REACH_NLRI/MP_UNREACH_NLRI属性中的NLRI字段包含MCAST-VPN NLRI（编码如上所述）。MP_REACH_NLRI/MP_unrach_NLRI属性中携带MCAST-VPN NLRI的AFI字段的值确定S-PMSI A-D路由、源活动A-D路由和C-multicast路由中携带的多播源和多播组地址是IPv4地址还是IPv6地址（AFI 1表示IPv4地址，AFI 2表示IPv6地址）.
In order for two BGP speakers to exchange labeled MCAST-VPN NLRIs, they must use a BGP Capabilities Advertisement to ensure that they both are capable of properly processing such an NLRI. This is done as specified in [RFC4760], by using capability code 1 (multiprotocol BGP) with an AFI of 1 or 2 and an SAFI of MCAST-VPN.
为了让两个BGP扬声器交换标有MCAST-VPN NLRI的NLRI，他们必须使用BGP功能广告，以确保他们都能够正确处理此类NLRI。这是按照[RFC4760]中的规定，通过使用AFI为1或2且SAFI为MCAST-VPN的能力代码1（多协议BGP）实现的。
The following describes the format of the Route Type specific MCAST-VPN NLRI for various Route Types defined in this document.
以下描述了本文档中定义的各种路由类型的特定于路由类型的MCAST-VPN NLRI的格式。
An Intra-AS I-PMSI A-D Route Type specific MCAST-VPN NLRI consists of the following:
AS I-PMSI A-D路由类型特定的MCAST-VPN NLRI由以下部分组成：
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Originating Router's IP Addr |
+-----------------------------------+
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Originating Router's IP Addr |
+-----------------------------------+
The Route Distinguisher (RD) is encoded as described in [RFC4364].
路由识别器（RD）按照[RFC4364]中所述进行编码。
Usage of Intra-AS I-PMSI A-D routes is described in Section 9.2.
第9.2节描述了内部AS I-PMSI A-D路由的使用。
An Inter-AS I-PMSI A-D Route Type specific MCAST-VPN NLRI consists of the following:
AS I-PMSI A-D路由类型特定的MCAST-VPN NLRI由以下部分组成：
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Source AS (4 octets) |
+-----------------------------------+
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Source AS (4 octets) |
+-----------------------------------+
The RD is encoded as described in [RFC4364].
RD按照[RFC4364]中所述进行编码。
The Source AS contains an Autonomous System Number (ASN).
源AS包含一个自治系统编号（ASN）。
Two-octet ASNs are encoded in the two low-order octets of the Source AS field, with the two high-order octets set to zero.
两个八位字节ASN编码在源AS字段的两个低阶八位字节中，两个高阶八位字节设置为零。
Usage of Inter-AS I-PMSI A-D routes is described in Section 9.1.
第9.1节描述了内部AS I-PMSI A-D路由的使用。
An S-PMSI A-D Route Type specific MCAST-VPN NLRI consists of the following:
S-PMSI A-D路由类型特定的MCAST-VPN NLRI由以下部分组成：
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Multicast Source Length (1 octet) |
+-----------------------------------+
| Multicast Source (variable) |
+-----------------------------------+
| Multicast Group Length (1 octet) |
+-----------------------------------+
| Multicast Group (variable) |
+-----------------------------------+
| Originating Router's IP Addr |
+-----------------------------------+
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Multicast Source Length (1 octet) |
+-----------------------------------+
| Multicast Source (variable) |
+-----------------------------------+
| Multicast Group Length (1 octet) |
+-----------------------------------+
| Multicast Group (variable) |
+-----------------------------------+
| Originating Router's IP Addr |
+-----------------------------------+
The RD is encoded as described in [RFC4364].
RD按照[RFC4364]中所述进行编码。
The Multicast Source field contains the C-S address. If the Multicast Source field contains an IPv4 address, then the value of the Multicast Source Length field is 32. If the Multicast Source field contains an IPv6 address, then the value of the Multicast Source Length field is 128.
多播源字段包含C-S地址。如果多播源字段包含IPv4地址，则多播源长度字段的值为32。如果多播源字段包含IPv6地址，则多播源长度字段的值为128。
The Multicast Group field contains the C-G address or C-LDP (Label Distribution Protocol) MP Opaque Value Element (use of C-LDP MP Opaque Value Element is described in the Section 11.3.2. If the Multicast Group field contains an IPv4 address, then the value of the Multicast Group Length field is 32. If the Multicast Group field contains an IPv6 address, then the value of the Multicast Group Length field is 128.
多播组字段包含C-G地址或C-LDP（标签分发协议）MP不透明值元素（第11.3.2节描述了C-LDP MP不透明值元素的使用。如果多播组字段包含IPv4地址，则多播组长度字段的值为32。如果多播组字段包含IPv6地址，则多播组长度字段的值为128。
Usage of other values of the Multicast Source Length and Multicast Group Length fields is outside the scope of this document.
多播源长度和多播组长度字段的其他值的使用超出了本文档的范围。
Usage of S-PMSI A-D routes is described in Section 12.
第12节描述了S-PMSI A-D路线的使用。
A Leaf A-D Route Type specific MCAST-VPN NLRI consists of the following:
叶A-D路由类型特定的MCAST-VPN NLRI由以下部分组成：
+-----------------------------------+
| Route Key (variable) |
+-----------------------------------+
| Originating Router's IP Addr |
+-----------------------------------+
+-----------------------------------+
| Route Key (variable) |
+-----------------------------------+
| Originating Router's IP Addr |
+-----------------------------------+
Leaf A-D routes may be originated as a result of processing a received Inter-AS I-PMSI A-D route or S-PMSI A-D route. A Leaf A-D route is originated in these situations only if the received route has a PMSI Tunnel attribute whose "Leaf Information Required" bit is set to 1.
叶A-D路由可作为将接收到的帧间路由处理为I-PMSI A-D路由或S-PMSI A-D路由的结果而发起。仅当接收到的路由具有“需要叶信息”位设置为1的PMSI隧道属性时，才会在这些情况下发起叶A-D路由。
If a Leaf A-D route is originated as a result of processing one of the received routes specified in the previous paragraph, the Route Key of the Leaf A-D route is set to the NLRI of the received route.
如果叶a-D路由是由于处理上一段中指定的一个接收路由而产生的，则叶a-D路由的路由密钥设置为接收路由的NLRI。
Details of the use of the Leaf A-D route may be found in Sections 9.2.3.2.1, 9.2.3.3, 9.2.3.4.1, 9.2.3.5, and 12.3.
第9.2.3.2.1节、第9.2.3.3节、第9.2.3.4.1节、第9.2.3.5节和第12.3节详细介绍了Leaf A-D路线的使用。
A Source Active A-D Route Type specific MCAST-VPN NLRI consists of the following:
源活动A-D路由类型特定的MCAST-VPN NLRI由以下部分组成：
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Multicast Source Length (1 octet) |
+-----------------------------------+
| Multicast Source (variable) |
+-----------------------------------+
| Multicast Group Length (1 octet) |
+-----------------------------------+
| Multicast Group (variable) |
+-----------------------------------+
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Multicast Source Length (1 octet) |
+-----------------------------------+
| Multicast Source (variable) |
+-----------------------------------+
| Multicast Group Length (1 octet) |
+-----------------------------------+
| Multicast Group (variable) |
+-----------------------------------+
The RD is encoded as described in [RFC4364].
RD按照[RFC4364]中所述进行编码。
The Multicast Source field contains the C-S address. If the Multicast Source field contains an IPv4 address, then the value of the Multicast Source Length field is 32. If the Multicast Source field contains an IPv6 address, then the value of the Multicast Source Length field is 128.
多播源字段包含C-S地址。如果多播源字段包含IPv4地址，则多播源长度字段的值为32。如果多播源字段包含IPv6地址，则多播源长度字段的值为128。
Use of the Source Active A-D routes with the Multicast Source Length field of 0 is outside the scope of this document.
使用多播源长度字段为0的源活动A-D路由超出了本文档的范围。
The Multicast Group field contains the C-G address. If the Multicast Group field contains an IPv4 address, then the value of the Multicast Group Length field is 32. If the Multicast Group field contains an IPv6 address, then the value of the Multicast Group Length field is 128.
多播组字段包含C-G地址。如果多播组字段包含IPv4地址，则多播组长度字段的值为32。如果多播组字段包含IPv6地址，则多播组长度字段的值为128。
Source Active A-D routes with a Multicast group belonging to the Source Specific Multicast (SSM) range (as defined in [RFC4607], and potentially extended locally on a router) MUST NOT be advertised by a router and MUST be discarded if received.
具有属于源特定多播（SSM）范围的多播组的源活动A-D路由（如[RFC4607]中所定义，并且可能在路由器上本地扩展）不得由路由器播发，并且在收到时必须丢弃。
Usage of Source Active A-D routes is described in Sections 13 and 14.
第13节和第14节描述了源激活A-D路由的使用。
A Shared Tree Join route and a Source Tree Join Route Type specific MCAST-VPN NLRI consists of the following:
共享树连接路由和源树连接路由类型特定的MCAST-VPN NLRI由以下部分组成：
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Source AS (4 octets) |
+-----------------------------------+
| Multicast Source Length (1 octet) |
+-----------------------------------+
| Multicast Source (variable) |
+-----------------------------------+
| Multicast Group Length (1 octet) |
+-----------------------------------+
| Multicast Group (variable) |
+-----------------------------------+
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Source AS (4 octets) |
+-----------------------------------+
| Multicast Source Length (1 octet) |
+-----------------------------------+
| Multicast Source (variable) |
+-----------------------------------+
| Multicast Group Length (1 octet) |
+-----------------------------------+
| Multicast Group (variable) |
+-----------------------------------+
The RD is encoded as described in [RFC4364].
RD按照[RFC4364]中所述进行编码。
The Source AS contains an ASN. Two-octet ASNs are encoded in the low-order two octets of the Source AS field.
源AS包含ASN。在源AS字段的低阶两个八位字节中编码两个八位字节ASN。
For a Shared Tree Join route, the Multicast Source field contains the C-RP address; for a Source Tree Join route, the Multicast Source field contains the C-S address. If the Multicast Source field contains an IPv4 address, then the value of the Multicast Source Length field is 32. If the Multicast Source field contains an IPv6 address, then the value of the Multicast Source Length field is 128.
对于共享树连接路由，多播源字段包含C-RP地址；对于源树连接路由，多播源字段包含C-S地址。如果多播源字段包含IPv4地址，则多播源长度字段的值为32。如果多播源字段包含IPv6地址，则多播源长度字段的值为128。
The Multicast Group field contains the C-G address or C-MP Opaque Value Element. If the Multicast Group field contains an IPv4 address, then the value of the Multicast Group Length field is 32. If the Multicast Group field contains an IPv6 address, then the value of the Multicast Group Length field is 128.
多播组字段包含C-G地址或C-MP不透明值元素。如果多播组字段包含IPv4地址，则多播组长度字段的值为32。如果多播组字段包含IPv6地址，则多播组长度字段的值为128。
Usage of C-multicast routes is described in Section 11.
第11节描述了C多播路由的使用。
This document defines and uses a new BGP attribute called the "P-Multicast Service Interface Tunnel (PMSI Tunnel) attribute". This is an optional transitive BGP attribute. The format of this attribute is defined as follows:
本文档定义并使用了一个新的BGP属性，称为“P-多播服务接口隧道（PMSI隧道）属性”。这是可选的可传递BGP属性。此属性的格式定义如下：
+---------------------------------+
| Flags (1 octet) |
+---------------------------------+
| Tunnel Type (1 octets) |
+---------------------------------+
| MPLS Label (3 octets) |
+---------------------------------+
| Tunnel Identifier (variable) |
+---------------------------------+
+---------------------------------+
| Flags (1 octet) |
+---------------------------------+
| Tunnel Type (1 octets) |
+---------------------------------+
| MPLS Label (3 octets) |
+---------------------------------+
| Tunnel Identifier (variable) |
+---------------------------------+
The Flags field has the following format:
“标志”字段的格式如下：
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| reserved |L|
+-+-+-+-+-+-+-+-+
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| reserved |L|
+-+-+-+-+-+-+-+-+
This document defines the following flags:
本文件定义了以下标志：
+ Leaf Information Required (L)
+ 所需叶信息（L）
The Tunnel Type identifies the type of the tunneling technology used to establish the PMSI tunnel. The type determines the syntax and semantics of the Tunnel Identifier field. This document defines the following Tunnel Types:
隧道类型标识用于建立PMSI隧道的隧道技术类型。类型决定隧道标识符字段的语法和语义。本文件定义了以下隧道类型：
+ 0 - No tunnel information present
+ 1 - RSVP-TE P2MP LSP
+ 2 - mLDP P2MP LSP
+ 3 - PIM-SSM Tree
+ 4 - PIM-SM Tree
+ 5 - BIDIR-PIM Tree
+ 6 - Ingress Replication
+ 7 - mLDP MP2MP LSP
+ 0 - No tunnel information present
+ 1 - RSVP-TE P2MP LSP
+ 2 - mLDP P2MP LSP
+ 3 - PIM-SSM Tree
+ 4 - PIM-SM Tree
+ 5 - BIDIR-PIM Tree
+ 6 - Ingress Replication
+ 7 - mLDP MP2MP LSP
If the MPLS Label field is non-zero, then it contains an MPLS label encoded as 3 octets, where the high-order 20 bits contain the label value. Absence of an MPLS Label is indicated by setting the MPLS Label field to zero.
如果MPLS标签字段非零，则它包含编码为3个八位字节的MPLS标签，其中高阶20位包含标签值。将MPLS标签字段设置为零表示缺少MPLS标签。
When the Tunnel Type is set to "No tunnel information present", the PMSI Tunnel attribute carries no tunnel information (no Tunnel Identifier). This type is to be used only in the following case: to enable explicit tracking for a particular customer multicast flow (by setting the Leaf Information Required flag to 1), but without binding this flow to a particular provider tunnel (by omitting any tunnel information).
当隧道类型设置为“无隧道信息存在”时，PMSI隧道属性不携带隧道信息（无隧道标识符）。此类型仅在以下情况下使用：启用特定客户多播流的显式跟踪（通过将Leaf Information Required标志设置为1），但不将此流绑定到特定的提供者通道（通过省略任何通道信息）。
When the Tunnel Type is set to RSVP - Traffic Engineering (RSVP-TE) Point-to-Multipoint (P2MP) Label Switched Path (LSP), the Tunnel Identifier is <Extended Tunnel ID, Reserved, Tunnel ID, P2MP ID> as carried in the RSVP-TE P2MP LSP SESSION Object [RFC4875].
当隧道类型设置为RSVP-流量工程（RSVP-TE）点对多点（P2MP）标签交换路径（LSP）时，隧道标识符为RSVP-TE P2MP LSP会话对象[RFC4875]中携带的<Extended Tunnel ID，Reserved，Tunnel ID，P2MP ID>。
When the Tunnel Type is set to multipoint Label Distribution Protocol (mLDP) P2MP LSP, the Tunnel Identifier is a P2MP Forwarding Equivalence Class (FEC) Element [mLDP].
当隧道类型设置为多点标签分发协议（mLDP）P2MP LSP时，隧道标识符为P2MP转发等价类（FEC）元素[mLDP]。
When the Tunnel Type is set to Protocol Independent Multicast - Sparse Mode (PIM-SM) tree, the Tunnel Identifier is <Sender Address, P-Multicast Group>. The node that originated the attribute MUST use the address carried in the Sender Address as the source IP address for the IP/GRE (Generic Routing Encapsulation) encapsulation of the MVPN data.
当隧道类型设置为协议独立多播-稀疏模式（PIM-SM）树时，隧道标识符为<Sender Address，P-Multicast Group>。发起该属性的节点必须使用发送方地址中包含的地址作为MVPN数据的IP/GRE（通用路由封装）封装的源IP地址。
When the Tunnel Type is set to PIM-SSM tree, the Tunnel Identifier is <P-Root Node Address, P-Multicast Group>. The node that originates the attribute MUST use the address carried in the P-Root Node Address as the source IP address for the IP/GRE encapsulation of the MVPN data. The P-Multicast Group in the Tunnel Identifier of the Tunnel attribute MUST NOT be expected to be the same group for all Intra-AS A-D routes for the same MVPN. According to [RFC4607], the group address can be locally allocated by the originating PE without any consideration for the group address used by other PE on the same MVPN.
当隧道类型设置为PIM-SSM树时，隧道标识符为<P-Root节点地址，P-Multicast Group>。发起属性的节点必须使用P根节点地址中携带的地址作为MVPN数据IP/GRE封装的源IP地址。对于同一MVPN的所有帧内A-D路由，隧道属性的隧道标识符中的P多播组不能期望为同一组。根据[RFC4607]，发起PE可以本地分配组地址，而不考虑同一MVPN上其他PE使用的组地址。
When the Tunnel Type is set to BIDIR-PIM tree, the Tunnel Identifier is <Sender Address, P-Multicast Group>. The node that originated the attribute MUST use the address carried in the Sender Address as the source IP address for the IP/GRE encapsulation of the MVPN data.
当隧道类型设置为BIDIR-PIM树时，隧道标识符为<Sender Address，P-Multicast Group>。发起该属性的节点必须使用发送方地址中包含的地址作为MVPN数据IP/GRE封装的源IP地址。
When the Tunnel Type is set to PIM-SM or BIDIR-PIM tree, then the P-Multicast Group in the Tunnel Identifier of the Tunnel attribute SHOULD contain the same multicast group address for all Intra-AS I-PMSI A-D routes for the same MVPN originated by PEs within a given AS. How this multicast group address is chosen is outside the scope of this specification.
当隧道类型设置为PIM-SM或BIDIR-PIM树时，隧道属性的隧道标识符中的P多播组应包含给定AS内PEs发起的相同MVPN的所有AS内I-PMSI A-D路由的相同多播组地址。如何选择此多播组地址超出了本规范的范围。
When the Tunnel Type is set to Ingress Replication, the Tunnel Identifier carries the unicast tunnel endpoint IP address of the local PE that is to be this PE's receiving endpoint address for the tunnel.
当隧道类型设置为入口复制时，隧道标识符携带本地PE的单播隧道端点IP地址，该地址将成为该PE的隧道接收端点地址。
When the Tunnel Type is set to mLDP Multipoint-to-Multipoint (MP2MP) LSP, the Tunnel Identifier is an MP2MP FEC Element [mLDP].
当隧道类型设置为mLDP多点对多点（MP2MP）LSP时，隧道标识符为MP2MP FEC元素[mLDP]。
The use of mLDP MP2MP LSPs as Provider tunnels (P-tunnels) requires procedures that are outside the scope of this document.
将mLDP MP2MP LSP用作提供商隧道（P隧道）需要的程序不在本文件范围内。
A router that supports the PMSI Tunnel attribute considers this attribute to be malformed if either (a) it contains an undefined tunnel type in the Tunnel Type field of the attribute, or (b) the router cannot parse the Tunnel Identifier field of the attribute as a tunnel identifier of the tunnel types specified in the Tunnel Type field of the attribute.
如果（A）支持PMSI隧道属性的隧道类型字段中包含未定义的隧道类型，或者（b），则支持PMSI隧道属性的路由器认为该属性的格式不正确路由器无法将属性的隧道标识符字段解析为属性的隧道类型字段中指定的隧道类型的隧道标识符。
When a router that receives a BGP Update that contains the PMSI Tunnel attribute with its Partial bit set determines that the attribute is malformed, the router SHOULD treat this Update as though all the routes contained in this Update had been withdrawn.
当接收到包含PMSI隧道属性及其部分位集的BGP更新的路由器确定该属性的格式不正确时，路由器应将此更新视为此更新中包含的所有路由都已撤回。
An implementation MUST provide debugging facilities to permit issues caused by a malformed PMSI Tunnel attribute to be diagnosed. At a minimum, such facilities MUST include logging an error when such an attribute is detected.
实现必须提供调试工具，以允许诊断由格式错误的PMSI隧道属性引起的问题。至少，当检测到此类属性时，此类设施必须包括记录错误。
The PMSI Tunnel attribute is used in conjunction with Intra-AS I-PMSI A-D routes, Inter-AS I-PMSI A-D routes, S-PMSI A-D routes, and Leaf A-D routes.
PMSI隧道属性与内部AS I-PMSI A-D路由、内部AS I-PMSI A-D路由、S-PMSI A-D路由和叶A-D路由一起使用。
This document defines a new BGP Extended Community called "Source AS".
本文档定义了一个名为“源AS”的新BGP扩展社区。
The Source AS is an AS-specific Extended Community, of an extended type, and is transitive across AS boundaries [RFC4360].
源AS是一个特定于AS的扩展社区，属于扩展类型，可以跨AS边界传递[RFC4360]。
The Global Administrator field of this Community MUST be set to the ASN of the PE. The Local Administrator field of this Community MUST be set to 0.
此社区的全局管理员字段必须设置为PE的ASN。此社区的本地管理员字段必须设置为0。
Consider a given MVPN that uses BGP for exchanging C-multicast routes, and/or uses segmented inter-AS tunnels. A PE that has sites of that MVPN connected to it, and originates a (unicast) route to VPN-IP addresses associated with the destinations within these sites, MUST include in the BGP Update message that carries this route the Source AS Extended Community.
考虑给定的MVPN，使用BGP交换C多播路由，和/或使用分段的AS间隧道。将该MVPN的站点连接到PE，并发起（单播）到与这些站点内的目的地相关联的VPN-IP地址的路由的PE，必须在承载该路由的BGP更新消息中包含源作为扩展社区。
The usage of a received Source AS Extended Community is described in Section 11.1.3.
第11.1.3节描述了接收源作为扩展社区的使用。
This document defines a new BGP Extended Community called "VRF Route Import".
本文档定义了一个名为“VRF路由导入”的新BGP扩展社区。
The VRF Route Import is an IP-address-specific Extended Community, of an extended type, and is transitive across AS boundaries [RFC4360].
VRF路由导入是一个特定于IP地址的扩展社区，属于扩展类型，可跨AS边界传递[RFC4360]。
To support MVPN in addition to the import/export Route Target(s) Extended Communities used by the unicast routing, each VRF on a PE MUST have an import Route Target Extended Community, except if it is known a priori that none of the (local) MVPN sites associated with the VRF contain multicast source(s) and/or C-RP; in which case, the VRF need not have this import Route Target.
除了单播路由使用的导入/导出路由目标扩展社区外，为了支持MVPN，PE上的每个VRF必须具有导入路由目标扩展社区，除非事先知道与VRF相关联的（本地）MVPN站点中没有一个包含多播源和/或C-RP；在这种情况下，VRF不需要有此导入路由目标。
We refer to this Route Target as the "C-multicast Import RT", as this Route Target controls imports of C-multicast routes into a particular VRF.
我们将此路由目标称为“C-多播导入RT”，因为此路由目标控制C-多播路由导入特定VRF。
A PE constructs C-multicast Import RT as follows:
PE按如下方式构造C-multicast导入RT：
+ The Global Administrator field of the C-multicast Import RT MUST be set to an IP address of the PE. This address SHOULD be common for all the VRFs on the PE (e.g., this address may be the PE's loopback address).
+ C-multicast导入RT的全局管理员字段必须设置为PE的IP地址。该地址对于PE上的所有VRF都应该是通用的（例如，该地址可能是PE的环回地址）。
+ The Local Administrator field of the C-multicast Import RT associated with a given VRF contains a 2-octet number that uniquely identifies that VRF within the PE that contains the VRF (procedures for assigning such numbers are purely local to the PE and are outside the scope of this document).
+ 与给定VRF关联的C-多播导入RT的本地管理员字段包含一个2-octet编号，该编号唯一标识包含VRF的PE中的该VRF（分配此类编号的过程对于PE而言完全是本地的，不在本文档的范围内）。
The way C-multicast Import RT is constructed allows it to uniquely identify a VRF.
C-multicast导入RT的构造方式允许它唯一地标识VRF。
A PE that has site(s) of a given MVPN connected to it needs to communicate the value of the C-multicast Import RT associated with the VRF of that MVPN on the PE to all other PEs that have sites of that MVPN. To accomplish this, a PE that originates a (unicast) route to VPN-IP addresses MUST include in the BGP Updates message that carries this route the VRF Route Import Extended Community that has the value of the C-multicast Import RT of the VRF associated with the route, except if it is known a priori (e.g., via provisioning) that none of these addresses could act as multicast sources and/or RP; in which case, the (unicast) route MUST NOT carry the VRF Route Import Extended Community.
具有与之连接的给定MVPN的站点的PE需要将与PE上该MVPN的VRF相关联的C多播导入RT的值传递给具有该MVPN站点的所有其他PE。为此，发起到VPN-IP地址的（单播）路由的PE必须在承载该路由的BGP更新消息中包括VRF路由导入扩展社区，该社区具有与该路由相关联的VRF的C多播导入RT的值，除非事先已知（例如，通过供应）这些地址都不能用作多播源和/或RP；在这种情况下，（单播）路由不得承载VRF路由导入扩展社区。
If a PE uses Route Target Constraint [RT-CONSTRAIN], the PE SHOULD advertise all such C-multicast Import RTs using Route Target Constraints (note that doing this requires just a single Route Target Constraint advertisement by the PE). This allows each C-multicast route to reach only the relevant PE. To constrain distribution of the Route Target Constraint routes to the AS of the advertising PE, these routes SHOULD carry the NO_EXPORT Community [RFC1997].
如果PE使用路由目标约束[RT-Constraint]，则PE应使用路由目标约束播发所有此类C-multicast导入RT（注意，这样做只需要PE发布一个路由目标约束）。这允许每个C多播路由仅到达相关PE。要将路由目标约束路由的分布约束到广告PE的AS，这些路由应包含NO_导出社区[RFC1997]。
Usage of VRF Route Import Extended Community is described in Section 11.1.3.
第11.1.3节描述了VRF路由导入扩展社区的使用。
This document defines a new BGP attribute, called the "PE Distinguisher Labels" attribute. This is an optional transitive BGP attribute. The format of this attribute is defined as follows:
本文档定义了一个新的BGP属性，称为“PE识别器标签”属性。这是可选的可传递BGP属性。此属性的格式定义如下：
+---------------------------------+
| PE Address |
+---------------------------------+
| Label (3 octets) |
+---------------------------------+
.......
+---------------------------------+
| PE Address |
+---------------------------------+
| Label (3 octets) |
+---------------------------------+
+---------------------------------+
| PE Address |
+---------------------------------+
| Label (3 octets) |
+---------------------------------+
.......
+---------------------------------+
| PE Address |
+---------------------------------+
| Label (3 octets) |
+---------------------------------+
The Label field contains an MPLS label encoded as 3 octets, where the high-order 20 bits contain the label value.
标签字段包含编码为3个八位字节的MPLS标签，其中高阶20位包含标签值。
A router that supports the PE Distinguisher Labels attribute considers this attribute to be malformed if the PE Address field does not contain a unicast address. The attribute is also considered to be malformed if: (a) the PE Address field is expected to be an IPv4 address, and the length of the attribute is not a multiple of 7 or (b) the PE Address field is expected to be an IPv6 address, and the length of the attribute is not a multiple of 19. The length of the Route Type field of MCAST-VPN NLRI of the route that carries the PE Distinguisher Labels attribute provides the information on whether the PE Address field contains an IPv4 or IPv6 address. Each of the PE addresses in the PE Distinguisher Labels attribute MUST be of the same address family as the "Originating Router's IP Address" of the route that is carrying the attribute.
如果PE地址字段不包含单播地址，则支持PE Discriminator Labels属性的路由器会认为此属性的格式不正确。如果：（a）PE地址字段预期为IPv4地址，且属性长度不是7的倍数，或者（b）PE地址字段预期为IPv6地址，且属性长度不是19的倍数，则该属性也被视为格式不正确。带有PE Discriminator Labels属性的路由的MCAST-VPN NLRI的路由类型字段的长度提供有关PE地址字段是否包含IPv4或IPv6地址的信息。PE Discriminator Labels属性中的每个PE地址必须与承载该属性的路由的“原始路由器的IP地址”具有相同的地址族。
When a router that receives a BGP Update that contains the PE Distinguisher Labels attribute with its Partial bit set determines that the attribute is malformed, the router SHOULD treat this Update as though all the routes contained in this Update had been withdrawn.
当接收到包含PE Discriminator Labels属性及其部分位集的BGP更新的路由器确定该属性的格式不正确时，路由器应将此更新视为此更新中包含的所有路由都已撤回。
An implementation MUST provide debugging facilities to permit issues caused by malformed PE Distinguisher Label attribute to be diagnosed. At a minimum, such facilities MUST include logging an error when such an attribute is detected.
实现必须提供调试工具，以允许诊断由格式错误的PE Discriminator Label属性引起的问题。至少，当检测到此类属性时，此类设施必须包括记录错误。
Usage of this attribute is described in [MVPN].
[MVPN]中描述了此属性的用法。
This section specifies procedures for the auto-discovery of MVPN memberships and the distribution of information used to instantiate I-PMSIs.
本节规定了自动发现MVPN成员身份和分发用于实例化I-PMSI的信息的程序。
There are two MVPN auto-discovery/binding mechanisms, dubbed "intra-AS" and "inter-AS" respectively.
有两种MVPN自动发现/绑定机制，分别称为“内部AS”和“内部AS”。
The intra-AS mechanisms provide auto-discovery/binding within a single AS.
内部AS机制在单个AS中提供自动发现/绑定。
The intra-AS mechanisms also provide auto-discovery/binding across multiple ASes when non-segmented inter-AS tunnels are being used.
当使用非分段AS间隧道时，AS内机制还提供跨多个ASE的自动发现/绑定。
The inter-AS mechanisms provide auto-discovery/binding across multiple ASes when segmented inter-AS tunnels are being used.
当使用分段的AS间隧道时，AS间机制提供跨多个AS的自动发现/绑定。
Note that if a multi-AS system uses option (a) of section 10 of [RFC4364], the notion of inter-AS tunnels does not apply, and so it needs only the intra-AS mechanisms.
请注意，如果多AS系统使用[RFC4364]第10节的选项（a），则AS间隧道的概念不适用，因此它只需要AS内机制。
This section describes exchanges of Intra-AS I-PMSI A-D routes originated/received by PEs within the same AS, or if non-segmented inter-AS tunnels are used, then by all PEs.
本节描述了由PEs在同一AS内发起/接收的AS I-PMSI A-D内部路由的交换，或者如果使用了非分段AS间隧道，则由所有PEs进行交换。
To participate in the MVPN auto-discovery/binding, a PE router that has a given VRF of a given MVPN MUST, except for the cases specified in this section, originate an Intra-AS I-PMSI A-D route and advertises this route in IBGP. The route is constructed as follows.
要参与MVPN自动发现/绑定，具有给定MVPN的给定VRF的PE路由器必须（本节规定的情况除外）发起一个内部AS I-PMSI a-D路由，并在IBGP中公布该路由。路线构造如下。
The route carries a single MCAST-VPN NLRI with the RD set to the RD of the VRF, and the Originating Router's IP Address field set to the IP address that the PE places in the Global Administrator field of the VRF Route Import Extended Community of the VPN-IP routes advertised by the PE. Note that the <RD, Originating Router's IP Address> tuple uniquely identifies a given multicast VRF.
该路由携带一个MCAST-VPN NLRI，RD设置为VRF的RD，原始路由器的IP地址字段设置为PE在VRF路由的全局管理员字段中放置的IP地址。导入PE公布的VPN-IP路由的扩展社区。请注意，<RD，原始路由器的IP地址>元组唯一地标识给定的多播VRF。
The route carries the PMSI Tunnel attribute if and only if an I-PMSI is used for the MVPN (the conditions under which an I-PMSI is used can be found in [MVPN]). Depending on the technology used for the P-tunnel for the MVPN on the PE, the PMSI Tunnel attribute of the Intra-AS I-PMSI A-D route is constructed as follows.
当且仅当I-PMSI用于MVPN时（使用I-PMSI的条件可在[MVPN]中找到），路由携带PMSI隧道属性。根据PE上MVPN的P隧道使用的技术，内部AS I-PMSI A-D路由的PMSI隧道属性构造如下。
+ If the PE that originates the advertisement uses a P-multicast tree for the P-tunnel for the MVPN, the PMSI Tunnel attribute MUST contain the identity of the tree (note that the PE could create the identity of the tree prior to the actual instantiation of the tree).
+ 如果发起广告的PE为MVPN的P隧道使用P多播树，则PMSI隧道属性必须包含树的标识（请注意，PE可以在树的实际实例化之前创建树的标识）。
+ A PE that uses a P-multicast tree for the P-tunnel MAY aggregate two or more MVPNs present on the PE onto the same tree. In this case, in addition to carrying the identity of the tree, the PMSI Tunnel attribute of the Intra-AS I-PMSI A-D route MUST carry an MPLS upstream-assigned label that the PE has bound uniquely to the MVPN associated with this route (as determined by its RTs).
+ 为P隧道使用P多播树的PE可以将PE上存在的两个或多个mvpn聚合到同一棵树上。在这种情况下，除了携带树的标识外，帧内AS I-PMSI A-D路由的PMSI隧道属性还必须携带MPLS上游分配的标签，该标签由PE唯一绑定到与该路由相关联的MVPN（由其RTs确定）。
If the PE has already advertised Intra-AS I-PMSI A-D routes for two or more MVPNs that it now desires to aggregate, then the PE MUST re-advertise those routes. The re-advertised routes MUST be the same as the original ones, except for the PMSI Tunnel attribute and the label carried in that attribute.
如果PE已经为其现在希望聚合的两个或多个MVPN发布了内部I-PMSI A-D路由，则PE必须重新发布这些路由。重新公布的路线必须与原始路线相同，但PMSI隧道属性和该属性中包含的标签除外。
+ If the PE that originates the advertisement uses ingress replication for the P-tunnel for the MVPN, the route MUST include the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication and Tunnel Identifier set to a routable address of the PE. The PMSI Tunnel attribute MUST carry a downstream-assigned MPLS label. This label is used to demultiplex the MVPN traffic received over a unicast tunnel by the PE.
+ 如果发起播发的PE对MVPN的P隧道使用入口复制，则路由必须包括PMSI隧道属性，隧道类型设置为入口复制，隧道标识符设置为PE的可路由地址。PMSI隧道属性必须带有下游分配的MPLS标签。此标签用于将PE通过单播隧道接收的MVPN通信量解复用。
+ The Leaf Information Required flag of the PMSI Tunnel attribute MUST be set to zero and MUST be ignored on receipt.
+ PMSI Tunnel属性的Leaf Information Required标志必须设置为零，并且在收到时必须忽略。
Discovery of PE capabilities in terms of what tunnel types they support is outside the scope of this document. Within a given AS, PEs participating in an MVPN are expected to advertise tunnel bindings whose tunnel types are supported by all other PEs that are
根据PE支持的隧道类型发现PE功能超出了本文档的范围。在给定的AS中，参与MVPN的PE预期会公布其隧道类型受所有其他支持的PE支持的隧道绑定
participating in this MVPN and are part of the same AS. In addition, in the inter-AS scenario with non-segmented inter-AS tunnels, the tunnel types have to be supported by all PEs that are participating in this MVPN, irrespective of whether or not these PEs are in the same AS.
参与本MVPN，并且是与的一部分。此外，在具有非分段AS间隧道的AS间场景中，隧道类型必须由参与此MVPN的所有PE支持，无论这些PE是否与相同。
The Next Hop field of the MP_REACH_NLRI attribute of the route MUST be set to the same IP address as the one carried in the Originating Router's IP Address field.
路由的MP_REACH_NLRI属性的下一跳字段必须设置为与原始路由器的IP地址字段中携带的IP地址相同的IP地址。
By default, the distribution of the Intra-AS I-PMSI A-D routes is controlled by the same Route Targets as the ones used for the distribution of VPN-IP unicast routes. That is, by default, the Intra-AS I-PMSI A-D route MUST carry the export Route Target used by the unicast routing. If any other PE has one of these Route Targets configured as an import Route Target for a VRF present on the PE, it treats the advertising PE as a member in the MVPN to which the VRF belongs. The default could be modified via configuration by having a set of Route Targets used for the Intra-AS I-PMSI A-D routes being distinct from the ones used for the VPN-IP unicast routes (see also Section 10).
默认情况下，内部AS I-PMSI A-D路由的分发由与用于分发VPN-IP单播路由的路由目标相同的路由目标控制。也就是说，默认情况下，帧内AS I-PMSI A-D路由必须携带单播路由使用的导出路由目标。如果任何其他PE将这些路由目标中的一个配置为PE上存在的VRF的导入路由目标，则它将广告PE视为VRF所属MVPN中的成员。可以通过配置修改默认设置，使用于内部AS I-PMSI a-D路由的一组路由目标不同于用于VPN-IP单播路由的路由目标（另请参见第10节）。
To constrain distribution of the intra-AS membership/binding information to the AS of the advertising PE, the BGP Update message originated by the advertising PE SHOULD carry the NO_EXPORT Community [RFC1997].
为了将内部AS成员资格/绑定信息的分发限制到广告PE的AS，广告PE发出的BGP更新消息应携带NO_导出社区[RFC1997]。
Note that if non-segmented inter-AS P-tunnels are being used, then the Intra-AS I-PMSI routes need to be distributed to other ASes and MUST NOT carry the NO_EXPORT Community.
请注意，如果正在使用非分段的AS间P隧道，则AS内I-PMSI路由需要分配给其他ASE，并且不得承载NO_导出社区。
When BGP is used to exchange C-multicast routes, if (a) it is known a priori that, as a matter of policy, none of the MVPN sites connected to a given PE are allowed to send multicast traffic to other sites of that MVPN (in other words, all these sites are only in the Receiver Sites set), (b) the PE does not use ingress replication for the incoming traffic of that MVPN, and (c) none of the other PEs that have VRFs of that MVPN use RSVP-TE P2MP LSP for that MVPN, then the local PE SHOULD NOT originate an Intra-AS I-PMSI A-D route.
当使用BGP交换C-多播路由时，如果（a）根据策略，先验地知道连接到给定PE的MVPN站点中没有一个被允许向该MVPN的其他站点发送多播流量（换句话说，所有这些站点仅在接收方站点集中），（b）PE不对该MVPN的传入流量使用入口复制，并且（c）具有该MVPN的VRF的其他PE均不对该MVPN使用RSVP-TE P2MP LSP，则本地PE不应发起内部AS I-PMSI A-D路由。
When BGP is used to exchange C-multicast routes, if it is known a priori that, as a matter of policy, none of the MVPN sites connected to a given PE can receive multicast traffic from other sites of that MVPN (in other words, all these sites are only in the Sender Sites set), and the PE uses ingress replication for that MVPN, then the PE SHOULD NOT originate an Intra-AS I-PMSI A-D route for that MVPN.
当BGP用于交换C-多播路由时，如果事先知道，作为策略问题，连接到给定PE的MVPN站点中没有一个可以从该MVPN的其他站点接收多播流量（换句话说，所有这些站点仅在发送方站点集中），并且PE使用该MVPN的入口复制，然后，PE不应为该MVPN发起内部AS I-PMSI A-D路由。
When a PE receives a BGP Update message that carries an Intra-AS I-PMSI A-D route such that (a) at least one of the Route Targets of the route matches one of the import Route Targets configured for a particular VRF on the local PE, (b) either the route was originated by some other PE within the same AS as the local PE, or the MVPN associated with the VRF uses non-segmented inter-AS tunnels, and (c) the BGP route selection determines that this is the best route with respect to the NLRI carried by the route, the PE performs the following.
当PE接收到携带内部AS I-PMSI a-D路由的BGP更新消息时，使得（a）路由的至少一个路由目标与为本地PE上的特定VRF配置的导入路由目标之一匹配，（b）路由由与本地PE相同的内部的某个其他PE发起，或者与VRF相关联的MVPN使用非分段的内部AS隧道，并且（c）BGP路由选择确定这是相对于路由所承载的NLRI的最佳路由，PE执行以下操作。
If the route does not carry the PMSI Tunnel attribute and ingress replication is not used, either a) the PE that originated the route will be using only S-PMSIs to send traffic to remote PEs, or b) as a matter of policy, the PE that originated the route cannot send multicast traffic from the MVPN sites connected to it to other sites of that MVPN (in other words, the sites connected to the PE are only in the Receiver Sites set).
如果路由不具有PMSI隧道属性且未使用入口复制，则a）发起路由的PE将仅使用S-PMSI向远程PE发送流量，或b）根据策略，发起路由的PE无法从与其连接的MVPN站点向该MVPN的其他站点发送多播流量（换句话说，连接到PE的站点仅在接收器站点集中）。
When BGP is used to exchange C-multicast routes, to distinguish between cases (a) and (b), we use the presence/absence of the VRF Route Import Extended Community in the unicast VPN routes, as follows. As specified in Section 7, if it is know a priori that none of the addresses carried in the NLRI of a given (unicast) VPN route could act as multicast sources and/or C-RP, then such a route does not carry the VRF Route Import Extended Community. Hence, based on the Upstream Multicast Hop (UMH) selection algorithm specified in [MVPN], such a route will be ineligible for the UMH selection. This implies that if a given VPN route is selected by the UMH selection procedures, and the PE that originates this VPN route also originates an Intra-AS I-PMSI A-D route, but this route does not carry the PMSI Tunnel attribute, then this PE will be using only S-PMSIs for sending (multicast) data.
当使用BGP交换C-多播路由时，为了区分情况（a）和（b），我们使用单播VPN路由中是否存在VRF路由导入扩展社区，如下所示。如第7节所述，如果事先知道给定（单播）VPN路由的NLRI中携带的任何地址都不能充当多播源和/或C-RP，则该路由不携带VRF路由导入扩展社区。因此，基于[MVPN]中指定的上行多播跳（UMH）选择算法，这样的路由将不适合UMH选择。这意味着，如果UMH选择过程选择了给定的VPN路由，并且发起该VPN路由的PE也发起了内部AS I-PMSI a-D路由，但该路由不携带PMSI隧道属性，则该PE将仅使用S-PMSI发送（多播）数据。
If the route carries the PMSI Tunnel attribute, then:
如果路线具有PMSI隧道属性，则：
+ If the Tunnel Type in the PMSI Tunnel attribute is set to Ingress Replication, then the MPLS label and the address carried in the Tunnel Identifier field of the PMSI Tunnel attribute should be used when the local PE sends multicast traffic to the PE that originated the route.
+ 如果PMSI隧道属性中的隧道类型设置为入口复制，则当本地PE向发起路由的PE发送多播流量时，应使用PMSI隧道属性的隧道标识符字段中携带的MPLS标签和地址。
+ If the Tunnel Type in the PMSI Tunnel attribute is set to mLDP P2MP LSP, mLDP MP2MP LSP, PIM-SSM tree, PIM-SM tree, or BIDIR-PIM tree, the PE SHOULD join as soon as possible the P-multicast tree whose identity is carried in the Tunnel Identifier.
+ 如果PMSI隧道属性中的隧道类型设置为mLDP P2MP LSP、mLDP MP2MP LSP、PIM-SSM树、PIM-SM树或BIDIR-PIM树，则PE应尽快加入其标识包含在隧道标识符中的P-多播树。
+ If the Tunnel Type in the PMSI Tunnel attribute is set to RSVP-TE P2MP LSP, then the PE that originated the route MUST establish an RSVP-TE P2MP LSP with the local PE as a leaf. This LSP may have been established before the local PE receives the route, or it may be established after the local PE receives the route.
+ 如果PMSI Tunnel属性中的隧道类型设置为RSVP-TE P2MP LSP，则发起路由的PE必须以本地PE为叶建立RSVP-TE P2MP LSP。该LSP可能在本地PE接收到路由之前建立，也可能在本地PE接收到路由之后建立。
+ The receiving PE has to establish the appropriate state to properly handle the traffic received on the P-multicast tree.
+ 接收PE必须建立适当的状态，以正确处理在P-多播树上接收的流量。
+ If the PMSI Tunnel attribute does not carry a label, then all packets that are received on the P-multicast tree, as identified by the PMSI Tunnel attribute, are forwarded using the VRF that has at least one of its import Route Targets that matches one of the Route Targets of the received Intra-AS I-PMSI A-D route.
+ 如果PMSI隧道属性未携带标签，则使用VRF转发在P-多播树上接收的所有数据包（由PMSI隧道属性标识），该VRF具有至少一个其导入路由目标，该导入路由目标与所接收的帧内as I-PMSI a-D路由的一个路由目标相匹配。
+ If the PMSI Tunnel attribute has the Tunnel Type set to mLDP P2MP LSP, PIM-SSM tree, PIM-SM tree, BIDIR-PIM tree, or RSVP-TE P2MP LSP, and the attribute also carries an MPLS label, then this is an upstream-assigned label, and all packets that are received on the P-multicast tree, as identified by the PMSI Tunnel attribute, with that upstream-assigned label are forwarded using the VRF that has at least one of its import Route Targets that matches one of the Route Targets of the received Intra-AS I-PMSI A-D route.
+ 如果PMSI隧道属性将隧道类型设置为mLDP P2MP LSP、PIM-SSM树、PIM-SM树、BIDIR-PIM树或RSVP-TE P2MP LSP，并且该属性还携带MPLS标签，则这是上游分配的标签，以及在P多播树上接收的所有数据包，如PMSI隧道属性所标识，利用该上游分配的标签，使用具有至少一个其导入路由目标的VRF转发，该导入路由目标与所接收的帧内AS I-PMSI A-D路由的一个路由目标匹配。
Irrespective of whether the route carries the PMSI Tunnel attribute, if the local PE uses RSVP-TE P2MP LSP for sending (multicast) traffic from the VRF to the sites attached to other PEs, then the local PE uses the Originating Router's IP address information carried in the route to add the PE that originated the route as a leaf node to the LSP.
无论路由是否携带PMSI隧道属性，如果本地PE使用RSVP-TE P2MP LSP从VRF向连接到其他PE的站点发送（多播）流量，则本地PE使用路由中携带的发起路由器的IP地址信息将发起路由的PE作为叶节点添加到LSP。
This section applies only to the case where segmented inter-AS tunnels are used.
本节仅适用于使用分段式AS隧道的情况。
An Autonomous System Border Router (ASBR) may be configured to support a particular MVPN as follows:
自治系统边界路由器（ASBR）可配置为支持特定MVPN，如下所示：
+ An ASBR MUST be configured with a set of (import) Route Targets (RTs) that specifies the set of MVPNs supported by the ASBR. These Route Targets control acceptance of Intra-AS/Inter-AS I-PMSI A-D routes by the ASBR. As long as unicast and multicast connectivity are congruent, this could be the same set of Route Targets as the one used for supporting unicast (and therefore would not require any additional configuration above and beyond of
+ ASBR必须配置一组（导入）路由目标（RTs），指定ASBR支持的MVPN集。这些路由目标控制ASBR对AS内/AS间I-PMSI A-D路由的接受。只要单播和多播连接是一致的，这就可以是与用于支持单播的路由目标相同的路由目标集（因此不需要任何超出
what is required for unicast). Note that instead of being configured, the ASBR MAY obtain this set of (import) Route Targets (RTs) by using Route Target Constraint [RT-CONSTRAIN].
单播所需的内容）。请注意，ASBR可以通过使用路由目标约束[RT-Constraint]获得这组（导入）路由目标（RTs），而不是进行配置。
+ The ASBR MUST be (auto-)configured with an import Route Target called "ASBR Import RT". ASBR Import RT controls acceptance of Leaf A-D routes and C-multicast routes by the ASBR, and is used to constrain distribution of both Leaf A-D routes and C-multicast routes (see Section 11).
+ ASBR必须（自动）配置一个名为“ASBR导入RT”的导入路由目标。ASBR导入RT控制ASBR对叶A-D路由和C-多播路由的接受，并用于约束叶A-D路由和C-多播路由的分布（参见第11节）。
ASBR Import RT is an IP-address-specific Route Target. The Global Administrator field of the ASBR Import RT MUST be set to the IP address carried in the Next Hop of all the Inter-AS I-PMSI A-D routes and S-PMSI A-D routes advertised by this ASBR (if the ASBR uses different Next Hops, then the ASBR MUST be (auto-)configured with multiple ASBR Import RTs, one per each such Next Hop). The Local Administrator field of the ASBR Import RT MUST be set to 0.
ASBR导入RT是IP地址特定的路由目标。ASBR导入RT的全局管理员字段必须设置为该ASBR播发的所有AS间I-PMSI A-D路由和S-PMSI A-D路由的下一跳中携带的IP地址（如果ASBR使用不同的下一跳，则ASBR必须（自动）配置多个ASBR导入RT，每个下一跳一个）。ASBR导入RT的本地管理员字段必须设置为0。
If the ASBR supports Route Target Constraint [RT-CONSTRAIN], the ASBR SHOULD advertise its ASBR Import RT within its own AS using Route Target Constraints. To constrain distribution of the Route Target Constraint routes to the AS of the advertising ASBR, these routes SHOULD carry the NO_EXPORT Community [RFC1997].
如果ASBR支持路由目标约束[RT-Constraint]，则ASBR应在其自身内将其ASBR导入RT公告为使用路由目标约束。要将路由目标约束路由的分布约束到广告ASBR的AS，这些路由应包含NO_导出社区[RFC1997]。
+ The ASBR MUST be configured with the tunnel types for the intra-AS segments of the MVPNs supported by the ASBR, as well as (depending on the tunnel type) the information needed to create the PMSI attribute for these tunnel types. Note that instead of being configured, the ASBR MAY derive the tunnel types from the Intra-AS I-PMSI A-D routes received by the ASBR.
+ ASBR必须配置ASBR支持的MVPN内部AS段的隧道类型，以及（取决于隧道类型）为这些隧道类型创建PMSI属性所需的信息。注意，ASBR可以从ASBR接收的AS I-PMSI A-D路由中派生隧道类型，而不是进行配置。
+ If the ASBR originates an Inter-AS I-PMSI A-D route for a particular MVPN present on some of the PEs within its own AS, the ASBR MUST be (auto-)configured with an RD for that MVPN. It is RECOMMENDED that one of the following two options be used:
+ 如果ASBR为其自身AS中某些PE上存在的特定MVPN发起AS间I-PMSI A-D路由，则ASBR必须（自动）为该MVPN配置RD。建议使用以下两个选项之一：
(1) To allow more aggregation of Inter-AS I-PMSI A-D routes, it is recommended that all the ASBRs within an AS that are configured to originate an Inter-AS I-PMSI A-D route for a particular MVPN be configured with the same RD (although for a given MVPN each AS may assign this RD on its own, without coordination with other ASes).
(1) 为了允许更多的AS间I-PMSI A-D路由聚合，建议使用相同的RD配置AS内所有配置为发起特定MVPN的AS间I-PMSI A-D路由的ASBR（尽管对于给定的MVPN，每个AS可自行分配此RD，而无需与其他ASE协调）。
(2) To allow more control over spreading MVPN traffic among multiple ASBRs within a given AS, it is recommended that each ASBR have a distinct RD per each MVPN; in which case, such an RD SHOULD be auto-configured.
(2) 为了允许在给定AS内的多个ASBR之间对MVPN流量的扩展进行更多控制，建议每个ASBR对每个MVPN具有不同的RD；在这种情况下，应自动配置此类RD。
If an ASBR is configured to support a particular MVPN, the ASBR MUST participate in the intra-AS MVPN auto-discovery/binding procedures for that MVPN within the ASBR's own AS, as specified in Section 9.1.
如果ASBR配置为支持特定MVPN，则ASBR必须按照第9.1节的规定，在ASBR自身的AS内参与该MVPN的内部AS MVPN自动发现/绑定过程。
Moreover, in addition to the above, the ASBR performs procedures described in Sections 9.2.1, 9.2.2, and 9.2.3.
此外，除上述内容外，ASBR还执行第9.2.1、9.2.2和9.2.3节所述的程序。
For a given MVPN configured on an ASBR when the ASBR determines (using the intra-AS auto-discovery procedures) that at least one of the PEs of its own AS has (directly) connected site(s) of the MVPN, the ASBR originates an Inter-AS I-PMSI A-D route and advertises it in External BGP (EBGP). The route is constructed as follows:
对于ASBR上配置的给定MVPN，当ASBR确定（使用内部AS自动发现过程）其自身AS的至少一个PE已（直接）连接MVPN的站点时，ASBR发起AS I-PMSI a-D路由并在外部BGP（EBGP）中播发。路线构造如下：
+ The route carries a single MCAST-VPN NLRI with the RD set to the RD configured for that MVPN on the ASBR, and the Source AS set to the ASN of the ASBR.
+ 路由携带单个MCAST-VPN NLRI，RD设置为ASBR上为该MVPN配置的RD，源AS设置为ASBR的ASN。
+ The route carries the PMSI Tunnel attribute if and only if an I-PMSI is used for the MVPN. The Tunnel Type in the attribute is set to Ingress Replication; the Leaf Information Required flag is set to 1; the attribute carries no MPLS labels.
+ 当且仅当I-PMSI用于MVPN时，该路由携带PMSI隧道属性。属性中的隧道类型设置为入口复制；叶信息要求标志设置为1；该属性不携带MPLS标签。
+ The Next Hop field of the MP_REACH_NLRI attribute is set to a routable IP address of the ASBR.
+ MP_REACH_NLRI属性的下一跳字段设置为ASBR的可路由IP地址。
+ The default policy for aggregation of Intra-AS I-PMSI A-D routes into an Inter-AS I-PMSI A-D route is that a given Inter-AS I-PMSI A-D route aggregates only the Intra-AS I-PMSI A-D routes that carry exactly the same set of RTs (note that this set may have just one RT). In this case, an Inter-AS I-PMSI A-D route originated by an ASBR carries exactly the same RT(s) as the RT(s) carried by the Intra-AS I-PMSI A-D routes that the ASBR aggregates into that Inter-AS I-PMSI A-D route. An implementation MUST support the default policy for aggregation of Intra-AS I-PMSI A-D routes into an Inter-AS I-PMSI A-D route.
+ 将内部AS I-PMSI A-D路由聚合为内部AS I-PMSI A-D路由的默认策略是，给定的内部AS I-PMSI A-D路由仅聚合承载完全相同RTs集的内部AS I-PMSI A-D路由（注意，该集可能只有一个RT）。在这种情况下，ASBR发起的内部AS I-PMSI A-D路由携带的RT与ASBR聚合到该内部AS I-PMSI A-D路由中的内部AS I-PMSI A-D路由携带的RT完全相同。实现必须支持将内部AS I-PMSI A-D路由聚合为内部AS I-PMSI A-D路由的默认策略。
+ The default policy for aggregation could be modified via configuration on the ASBR. An implementation MAY support such functionality. Modified policy MUST include rules for constructing RTs carried by the Inter-AS I-PMSI A-D routes originated by the ASBR.
+ 可以通过ASBR上的配置修改聚合的默认策略。实现可以支持这种功能。修改后的策略必须包括用于构建由ASBR发起的AS间I-PMSI A-D路由承载的RTs的规则。
An Inter-AS I-PMSI A-D route for a given <AS, MVPN> indicates the presence of the MVPN sites connected to one or more PEs of the AS.
给定<AS，MVPN>的AS间I-PMSI A-D路由表示存在连接到AS的一个或多个pe的MVPN站点。
An Inter-AS I-PMSI A-D route originated by an ASBR aggregates Intra-AS I-PMSI A-D routes originated within the ASBR's own AS. Thus, while the Intra-AS I-PMSI A-D routes originated within an AS are at the granularity of <PE, MVPN> within that AS, outside of that AS the (aggregated) Inter-AS I-PMSI A-D routes could be at the granularity of <AS, MVPN>.
ASBR发起的AS间I-PMSI A-D路由聚合ASBR自身AS内发起的AS内I-PMSI A-D路由。因此，虽然起源于AS内的AS内I-PMSI A-D路由在该AS内的粒度为<PE，MVPN>，但在该AS外（聚合的）AS间I-PMSI A-D路由的粒度可以为<AS，MVPN>。
If, for a given MVPN and a given AS, all of the sites connected to the PEs within the AS are known a priori to have no multicast sources, then ASBRs of that AS MAY refrain from originating an Inter-AS I-PMSI A-D route for that MVPN at all.
如果对于给定MVPN和给定AS，先验地知道AS内连接到PEs的所有站点没有多播源，则该AS的asbr可能根本不为该MVPN发起AS间I-PMSI a-D路由。
An Inter-AS I-PMSI A-D route for a given MVPN originated by an ASBR within a given AS is propagated via BGP to other ASes.
由给定AS内的ASBR发起的给定MVPN的AS间I-PMSI A-D路由通过BGP传播到其他ASE。
Suppose that ASBR A installs an Inter-AS I-PMSI A-D route for MVPN V that originated at a particular AS, AS1. The BGP Next Hop of that route becomes A's "upstream multicast hop" on a multicast distribution tree for V that is rooted at AS1. When the Inter-AS I-PMSI A-D routes have been distributed to all the necessary ASes, they define a "reverse path" from any AS that supports MVPN V back to AS1. For instance, if AS2 supports MVPN V, then there will be a reverse path for MVPN V from AS2 to AS1. This path is a sequence of ASBRs, the first of which is in AS2, and the last of which is in AS1. Each ASBR in the sequence is the BGP Next Hop of the previous ASBR in the sequence on the given Inter-AS I-PMSI A-D route.
假设ASBR A为源自特定AS AS1的MVPN V安装了一条AS间I-PMSI A-D路由。该路由的BGP下一个跃点成为A的“上游多播跃点”，位于以AS1为根的V的多播分发树上。当AS间I-PMSI A-D路由已分配给所有必要的AS时，它们定义了从支持MVPN V的任何AS到AS1的“反向路径”。例如，如果AS2支持MVPN V，那么MVPN V将有一条从AS2到AS1的反向路径。此路径是一个ASBR序列，第一个在AS2中，最后一个在AS1中。序列中的每个ASBR是给定的Inter-AS I-PMSI A-D路由上序列中先前ASBR的BGP下一跳。
This reverse path information can be used to construct a unidirectional multicast distribution tree for MVPN V, containing all the ASes that support V, and having AS1 at the root. We call such a tree an "inter-AS tree". Multicast data originating in MVPN sites connected to PEs within a given AS will travel downstream along the tree, which is rooted at that AS.
此反向路径信息可用于为MVPN V构建一个单向多播分发树，其中包含支持V的所有ASE，并且根上有AS1。我们称这种树为“树”。源自连接到给定AS内PEs的MVPN站点的多播数据将沿着树向下游移动，树的根位于该AS。
The path along an inter-AS tree is a sequence of ASBRs; it is still necessary to specify how the multicast data gets from a given ASBR to the set of ASBRs that are immediately downstream of the given ASBR along the tree. This is done by creating "segments": ASBRs in adjacent ASes will be connected by inter-AS segments, ASBRs in the same AS will be connected by "intra-AS segments".
沿内部AS树的路径是ASBR序列；仍然有必要指定多播数据如何从给定ASBR获取到树上给定ASBR下游的ASBR集。这是通过创建“段”来实现的：相邻ASE中的ASBR将通过内部AS段连接，与之相同的ASBR将通过“内部AS段”连接。
An ASBR initiates creation of an intra-AS segment when the ASBR receives an Inter-AS I-PMSI A-D route from an EBGP neighbor. Creation of the segment is completed as a result of distributing, via IBGP, this route within the ASBR's own AS.
当ASBR从EBGP邻居接收到AS间I-PMSI A-D路由时，ASBR启动AS内段的创建。通过IBGP在ASBR自己的as内分发该路线，完成了段的创建。
For a given inter-AS tunnel, each of its intra-AS segments could be constructed by its own independent mechanism. Moreover, by using upstream-assigned labels within a given AS multiple intra-AS segments of different inter-AS tunnels of either the same or different MVPNs may share the same P-multicast tree.
对于给定的内部AS隧道，每个内部AS段都可以由其自己的独立机制构造。此外，通过在相同或不同mvpn的不同AS间隧道的给定AS内多个AS内段内使用上游分配的标签，可以共享相同的P多播树。
If the P-multicast tree that serves as a particular intra-AS segment of an inter-AS tunnel is created by a multicast control protocol that uses receiver-initiated joins (e.g., mLDP, any PIM variant), and this P-multicast tree does not aggregate multiple segments, then all the information needed to create that segment is present in the PMSI Tunnel attribute of the Inter-AS I-PMSI A-D routes. However, if the P-multicast tree that serves as the segment is created by a protocol that does not use receiver-initiated joins (e.g., RSVP-TE, ingress unicast replication), or if this P-multicast tree aggregates multiple segments (irrespective of the multicast control protocol used to create the tree), then it is also necessary to use Leaf A-D routes. The precise conditions under which Leaf A-D routes need to be used are described in subsequent sections.
如果用作内部as隧道的特定内部as段的P-多播树是由使用接收器发起的联接（例如，mLDP，任何PIM变体）的多播控制协议创建的，并且该P-多播树不聚合多个段，然后，创建该段所需的所有信息都显示在Inter AS I-PMSI A-D路由的PMSI Tunnel属性中。但是，如果用作段的P多播树是由不使用接收器发起的联接的协议（例如，RSVP-TE、入口单播复制）创建的，或者如果该P多播树聚合多个段（无论用于创建树的多播控制协议如何），然后还需要使用叶A-D路由。叶A-D路线需要使用的精确条件将在后续章节中描述。
Since (aggregated) Inter-AS I-PMSI A-D routes could have granularity of <AS, MVPN>, an MVPN that is present in N ASes could have a total of N inter-AS tunnels. Thus, for a given MVPN, the number of inter-AS tunnels constituting the I-PMSIs is independent of the number of PEs that have this MVPN.
由于（聚合的）AS间I-PMSI A-D路由的粒度可能小于AS，MVPN>，因此存在于N个AS中的MVPN可能总共有N个AS间隧道。因此，对于给定的MVPN，构成I-PMSI的AS间隧道的数量与具有该MVPN的PE的数量无关。
The precise rules for distributing and processing the Inter-AS I-PMSI A-D routes across ASes are given in the following sections.
以下部分给出了跨ASE分配和处理AS间I-PMSI A-D路由的精确规则。
When an ASBR receives, from one of its EBGP neighbors, a BGP Update message that carries an Inter-AS I-PMSI A-D route, if (a) at least one of the Route Targets carried in the message matches one of the import Route Targets configured on the ASBR, and (b) the ASBR determines that the received route is the best route for its NLRI, the ASBR re-advertises this route to other PEs and ASBRs within its own AS (handling of this route by other PEs and ASBRs is described in Section 9.2.3.4).
当ASBR从其一个EBGP邻居接收到一条BGP更新消息，该消息包含一条作为内部I-PMSI a-D路由，如果（a）消息中包含的至少一个路由目标与ASBR上配置的一个导入路由目标匹配，并且（b）ASBR确定接收到的路由是其NLRI的最佳路由，ASBR向其自身AS内的其他PEs和ASBR重新宣传该路线（第9.2.3.4节描述了其他PEs和ASBR对该路线的处理）。
When re-advertising an Inter-AS I-PMSI A-D route, the ASBR MUST set the Next Hop field of the MP_REACH_NLRI attribute to a routable IP address of the ASBR.
当重新公布一条国际AS I-PMSI A-D路由时，ASBR必须将MP_REACH_NLRI属性的下一跳字段设置为ASBR的可路由IP地址。
If the received Inter-AS I-PMSI A-D route carries the PMSI Tunnel attribute, then, depending on the technology used to instantiate the intra-AS segment of the inter-AS tunnel, the ASBR constructs the PMSI Tunnel attribute of the re-advertised Inter-AS I-PMSI A-D route as follows.
如果接收到的Inter-AS I-PMSI A-D路由携带PMSI隧道属性，则根据用于实例化Inter-AS隧道的intra-AS段的技术，ASBR如下构造重新播发的Inter-AS I-PMSI A-D路由的PMSI隧道属性。
+ If the ASBR uses ingress replication for the intra-AS segment of the inter-AS tunnel, the re-advertised route MUST carry the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication, but no MPLS labels.
+ 如果ASBR对内部AS隧道的内部AS段使用入口复制，则重新公布的路由必须带有PMSI隧道属性，隧道类型设置为入口复制，但不带MPLS标签。
+ If the ASBR uses a P-multicast tree for the intra-AS segment of the inter-AS tunnel, the PMSI Tunnel attribute MUST contain the identity of the tree (note that the ASBR could create the identity of the tree prior to the actual instantiation of the tree). If, in order to instantiate the tree, the ASBR needs to know the leaves of the tree, then the ASBR obtains this information from the Leaf A-D routes received from other PEs/ASBRs in the ASBR's own AS (as described in Section 9.2.3.5) by setting the Leaf Information Required flag in the PMSI Tunnel attribute to 1.
+ 如果ASBR对内部AS隧道的内部AS段使用P多播树，则PMSI隧道属性必须包含树的标识（请注意，ASBR可以在树的实际实例化之前创建树的标识）。如果为了实例化树，ASBR需要知道树的叶子，则ASBR通过将PMSI Tunnel属性中的Leaf information Required标志设置为1，从ASBR自身AS中从其他PE/ASBR接收的叶子A-D路由（如第9.2.3.5节所述）中获取该信息。
+ An ASBR that uses a P-multicast tree as the intra-AS segment of the inter-AS tunnel MAY aggregate two or more MVPNs present on the ASBR onto the same tree. In this case, in addition to the identity of the tree, the PMSI Tunnel attribute of the Inter-AS I-PMSI A-D route MUST carry an MPLS upstream-assigned label that the PE has bound uniquely to the MVPN associated with this route (as determined by its RTs).
+ 使用P多播树作为内部as隧道的内部as段的ASBR可以将ASBR上存在的两个或多个mvpn聚合到同一棵树上。在这种情况下，除了树的标识外，Inter-AS I-PMSI A-D路由的PMSI Tunnel属性必须携带MPLS上游分配的标签，该标签由PE唯一绑定到与该路由相关联的MVPN（由其RTs确定）。
If the ASBR has already advertised Inter-AS I-PMSI A-D routes for two or more MVPNs that it now desires to aggregate, then the ASBR MUST re-advertise those routes. The re-advertised routes MUST be the same as the original ones, except for the PMSI Tunnel attribute and the MVPN label.
如果ASBR已经将两个或多个MVPN的Inter作为I-PMSI A-D路由进行了广告，并且现在希望聚合这些MVPN，则ASBR必须重新广告这些路由。重新公布的路由必须与原始路由相同，但PMSI隧道属性和MVPN标签除外。
In addition, the ASBR MUST send to the EBGP neighbor from whom it received the Inter-AS I-PMSI A-D route, a BGP Update message that carries a Leaf A-D route constructed as follows.
此外，ASBR必须向其接收到Inter-AS I-PMSI A-D路由的EBGP邻居发送BGP更新消息，该消息包含如下构造的叶A-D路由。
+ The route carries a single MCAST-VPN NLRI with the Route Key field set to the MCAST-VPN NLRI of the Inter-AS I-PMSI A-D route received from that neighbor and the Originating Router's IP address set to the IP address of the ASBR (this MUST be a routable IP address).
+ 该路由携带一个MCAST-VPN NLRI，其中路由密钥字段设置为从该邻居接收到的Inter-AS I-PMSI a-D路由的MCAST-VPN NLRI，原始路由器的IP地址设置为ASBR的IP地址（这必须是可路由的IP地址）。
+ The Leaf A-D route MUST include the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication and the Tunnel Identifier set to a routable address of the advertising router. The PMSI Tunnel attribute MUST carry a downstream-assigned MPLS label that is used by the advertising router to demultiplex the MVPN traffic received over a unicast tunnel from the EBGP neighbor.
+ 叶A-D路由必须包括PMSI隧道属性，隧道类型设置为入口复制，隧道标识符设置为播发路由器的可路由地址。PMSI隧道属性必须携带下游分配的MPLS标签，广告路由器使用该标签来解复用通过单播隧道从EBGP邻居接收的MVPN流量。
+ The ASBR constructs an IP-based Route Target Extended Community by placing the IP address carried in the Next Hop of the received Inter-AS I-PMSI A-D route in the Global Administrator field of the Community, with the Local Administrator field of this Community set to 0 and setting the Extended Communities attribute of the Leaf A-D route to that Community. Note that this Route Target is the same as the ASBR Import RT of the EBGP neighbor from which the ASBR received the Inter-AS I-PMSI A-D route.
+ ASBR通过将接收到的Inter-AS I-PMSI A-D路由的下一跳中携带的IP地址放置在社区的全局管理员字段中，构建基于IP的路由目标扩展社区，将此社区的本地管理员字段设置为0，并将叶A-D路由的扩展社区属性设置为该社区。请注意，此路由目标与ASBR从中接收Inter-as I-PMSI A-D路由的EBGP邻居的ASBR导入RT相同。
+ The Next Hop field of the MP_REACH_NLRI attribute of the route MUST be set to the same IP address as the one carried in the Originating Router's IP Address field of the route.
+ 路由的MP_REACH_NLRI属性的下一跳字段必须设置为与路由的原始路由器IP地址字段中携带的IP地址相同的IP地址。
+ To constrain the distribution scope of this route, the route MUST carry the NO_ADVERTISE BGP Community [RFC1997].
+ 若要限制此路由的分发范围，该路由必须承载无广告BGP社区[RFC1997]。
Handling of this Leaf A-D route by the EBGP neighbor is described in Section 9.2.3.3.
第9.2.3.3节描述了EBGP邻居对该叶A-D路由的处理。
The ASBR MUST set up its forwarding state such that packets that arrive on the one-hop ASBR-ASBR LSP, as specified in the PMSI Tunnel attribute of the Leaf A-D route, are transmitted on the intra-AS segment, as specified in the PMSI Tunnel attribute of the Inter-AS I-PMSI A-D route that the ASBR re-advertises in its own AS. However, the packets MAY be filtered before forwarding, as specified in Section 9.2.3.6.
ASBR必须设置其转发状态，以使到达一跳ASBR-ASBR LSP的数据包（如叶A-D路由的PMSI隧道属性所指定）在as内段上传输，如ASBR在其自身as中重新播发的as间I-PMSI A-D路由的PMSI隧道属性所指定。但是，按照第9.2.3.6节的规定，可在转发前对数据包进行过滤。
When an ASBR receives, via EBGP, a Leaf A-D route originated by its neighbor ASBR, if the Route Target carried in the Extended Communities attribute of the route matches one of the ASBR Import RT (auto-)configured on the ASBR, the ASBR performs the following.
当ASBR通过EBGP接收到由其邻居ASBR发起的叶a-D路由时，如果路由的“扩展社区”属性中包含的路由目标与ASBR上配置的ASBR导入RT（自动）之一匹配，则ASBR执行以下操作。
+ The ASBR finds an Inter-AS I-PMSI A-D route whose MCAST-VPN NLRI has the same value as the Route Key field of the Leaf A-D route.
+ ASBR查找其MCAST-VPN NLRI与叶A-D路由的路由密钥字段具有相同值的内部AS I-PMSI A-D路由。
+ If the found Inter-AS I-PMSI A-D route was originated by ASBR itself, then the ASBR sets up its forwarding state such that packets received on the intra-AS tunnels originating in the ASBR's own AS are transmitted on the one-hop ASBR-ASBR LSP specified by
+ 如果发现的AS间I-PMSI A-D路由是由ASBR本身发起的，则ASBR设置其转发状态，以便在源自ASBR自身AS的AS内AS隧道上接收的数据包在ASBR指定的一跳ASBR-ASBR LSP上传输
the MPLS label carried in the PMSI Tunnel attribute of the received Leaf A-D route. (However, the packets MAY be filtered before transmission as specified in Section 9.2.3.6). The intra-AS tunnels are specified in the PMSI Tunnel attribute of all the Intra-AS I-PMSI A-D routes received by the ASBR that the ASBR aggregated into the Inter-AS I-PMSI A-D route. For each of these intra-AS tunnels, if a non-zero MPLS label is carried in the PMSI Tunnel attribute (i.e., aggregation is used), then only packets received on the inner LSP corresponding to that label MUST be forwarded, not the packets received on the outer LSP, as the outer LSP possibly carries the traffic of other VPNs.
接收到的叶A-D路由的PMSI隧道属性中携带的MPLS标签。（但是，按照第9.2.3.6节的规定，可在传输前对数据包进行过滤）。内部AS隧道在ASBR接收的所有内部AS I-PMSI A-D路由的PMSI隧道属性中指定，ASBR聚合到内部AS I-PMSI A-D路由中。对于这些内部AS隧道中的每一个，如果在PMSI隧道属性中携带非零MPLS标签（即，使用聚合），则必须仅转发在与该标签对应的内部LSP上接收的分组，而不是在外部LSP上接收的分组，因为外部LSP可能携带其他VPN的流量。
+ If the found Inter-AS I-PMSI A-D route was originated by some other ASBR, then the ASBR sets up its forwarding state such that packets received on the intra-AS tunnel segment, as specified in the PMSI Tunnel attribute of the found Inter-AS I-PMSI A-D route, are transmitted on the one-hop ASBR-ASBR LSP, as specified by the MPLS label carried in the PMSI Tunnel attribute of the Leaf A-D route.
+ 如果找到的Inter-AS I-PMSI A-D路由是由某个其他ASBR发起的，则ASBR设置其转发状态，以便在所找到的Inter-AS I-PMSI A-D路由的PMSI tunnel属性中指定的AS内隧道段上接收的数据包在一跳ASBR-ASBR LSP上传输，由叶A-D路由的PMSI隧道属性中携带的MPLS标签指定。
In the context of this section, we use the term "PE/ASBR router" to denote either a PE or an ASBR router.
在本节的上下文中，我们使用术语“PE/ASBR路由器”来表示PE或ASBR路由器。
If a given Inter-AS I-PMSI A-D route is received via IBGP by a BGP route reflector, the BGP route reflector MUST NOT modify the Next Hop field of the MP_REACH_NLRI attribute when re-advertising the route into IBGP (this is because the information carried in the Next Hop is used for controlling flow of C-multicast routes, as specified in Section 11.2).
如果BGP路由反射器通过IBGP接收到给定的内部AS I-PMSI a-D路由，则BGP路由反射器在向IBGP重新播发路由时不得修改MP_REACH_NLRI属性的下一跳字段（这是因为下一跳中携带的信息用于控制C-多播路由的流量，如第11.2节所述）。
If a given Inter-AS I-PMSI A-D route is advertised within an AS by multiple ASBRs of that AS, the BGP best route selection performed by other PE/ASBR routers within the AS does not require all these PE/ASBR routers to select the route advertised by the same ASBR -- to the contrary, different PE/ASBR routers may select routes advertised by different ASBRs.
如果给定的AS间I-PMSI a-D路由在AS内由该AS的多个ASBR播发，则AS内其他PE/ASBR路由器执行的BGP最佳路由选择并不要求所有这些PE/ASBR路由器选择由同一ASBR播发的路由，相反，不同的PE/ASBR路由器可以选择由不同的ASBR播发的路由。
When a PE/ASBR router receives, from one of its IBGP neighbors, a BGP Update message that carries an Inter-AS I-PMSI A-D route, if (a) at least one of the Route Targets carried in the message matches one of the import Route Targets configured on the PE/ASBR, and (b) the PE/ASBR determines that the received route is the best route to the destination carried in the NLRI of the route, the PE/ASBR performs the following operations.
当PE/ASBR路由器从其一个IBGP邻居接收到一条BGP更新消息时，如果（a）消息中至少有一个路由目标与PE/ASBR上配置的一个导入路由目标匹配，则该消息将承载一条内部AS I-PMSI a-D路由，以及（b）PE/ASBR确定接收到的路由是该路由的NLRI中携带的到目的地的最佳路由，PE/ASBR执行以下操作。
+ If the router is a PE, then the router imports the route into the VRF(s) that have the matching import Route Targets.
+ 如果路由器是PE，则路由器将路由导入具有匹配导入路由目标的VRF。
+ If the router is an ASBR, then the ASBR propagates the route to its EBGP neighbors. When propagating the route to the EBGP neighbors, the ASBR MUST set the Next Hop field of the MP_REACH_NLRI attribute to a routable IP address of the ASBR. If the received Inter-AS I-PMSI A-D route carries the PMSI Tunnel attribute, then the propagated route MUST carry the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication; the attribute carries no MPLS labels.
+ 如果路由器是ASBR，则ASBR将路由传播到其EBGP邻居。将路由传播到EBGP邻居时，ASBR必须将MP_REACH_NLRI属性的下一跳字段设置为ASBR的可路由IP地址。如果接收到的Inter-AS I-PMSI A-D路由携带PMSI隧道属性，则传播的路由必须携带隧道类型设置为入口复制的PMSI隧道属性；该属性不携带MPLS标签。
+ If the received Inter-AS I-PMSI A-D route carries the PMSI Tunnel attribute with the Tunnel Type set to mLDP P2MP LSP, PIM-SSM tree, PIM-SM tree, or BIDIR-PIM tree, the PE/ASBR SHOULD join as soon as possible the P-multicast tree whose identity is carried in the Tunnel Identifier.
+ 如果接收到的Inter-AS I-PMSI A-D路由携带隧道类型设置为mLDP P2MP LSP、PIM-SSM树、PIM-SM树或BIDIR-PIM树的PMSI隧道属性，则PE/ASBR应尽快加入其标识包含在隧道标识符中的P-多播树。
+ If the received Inter-AS I-PMSI A-D route carries the PMSI Tunnel attribute with the Tunnel Identifier set to RSVP-TE P2MP LSP, then the ASBR that originated the route MUST establish an RSVP-TE P2MP LSP with the local PE/ASBR as a leaf. This LSP MAY have been established before the local PE/ASBR receives the route, or it MAY be established after the local PE receives the route.
+ 如果接收到的Inter-AS I-PMSI A-D路由带有PMSI隧道属性，且隧道标识符设置为RSVP-TE P2MP LSP，则发起路由的ASBR必须建立一个RSVP-TE P2MP LSP，本地PE/ASBR作为叶。该LSP可能在本地PE/ASBR接收到路由之前建立，也可能在本地PE接收到路由之后建立。
+ If the received Inter-AS I-PMSI A-D route carries the PMSI Tunnel attribute with the Tunnel Type set to mLDP P2MP LSP, RSVP-TE P2MP LSP, PIM-SSM, PIM-SM tree, or BIDIR-PIM tree, but the attribute does not carry a label, then the P-multicast tree, as identified by the PMSI Tunnel attribute, is an intra-AS LSP segment that is part of the inter-AS tunnel for the MVPN advertised by the Inter-AS I-PMSI A-D route and rooted at the AS that originated the Inter-AS I-PMSI A-D route. If the PMSI Tunnel attribute carries a (upstream-assigned) label, then a combination of this tree and the label identifies the intra-AS segment. If the receiving router is an ASBR, this intra-AS segment may further be stitched to the ASBR-ASBR inter-AS segment of the inter-AS tunnel. If the PE/ASBR has local receivers in the MVPN, packets received over the intra-AS segment must be forwarded to the local receivers using the local VRF.
+ 如果接收到的Inter-AS I-PMSI A-D路由携带隧道类型设置为mLDP P2MP LSP、RSVP-TE P2MP LSP、PIM-SSM、PIM-SM树或BIDIR-PIM树的PMSI隧道属性，但该属性未携带标签，则该P-多播树由PMSI隧道属性标识，是内部AS LSP段，其是由内部AS I-PMSI A-D路由播发的MVPN的内部AS隧道的一部分，并且扎根于发起内部AS I-PMSI A-D路由的AS。如果PMSI Tunnel属性带有（上游指定的）标签，则此树和标签的组合将识别内部AS段。如果接收路由器是ASBR，则该AS内段可进一步缝合到AS间隧道的ASBR-ASBR AS间段。如果PE/ASBR在MVPN中有本地接收器，则必须使用本地VRF将通过内部AS段接收的数据包转发给本地接收器。
If the Leaf Information Required flag in the PMSI Tunnel attribute of the received Inter-AS I-PMSI A-D route is set to 1, then the PE/ASBR MUST originate a new Leaf A-D route as follows.
如果接收到的Inter-AS I-PMSI A-D路由的PMSI Tunnel属性中的Leaf Information Required标志设置为1，则PE/ASBR必须按照如下方式发起新的Leaf A-D路由。
+ The route carries a single MCAST-VPN NLRI with the Route Key field set to the MCAST-VPN NLRI of the Inter-AS I-PMSI A-D route received from that neighbor and the Originating Router's IP address set to the IP address of the PE/ASBR (this MUST be a routable IP address).
+ 该路由携带一个MCAST-VPN NLRI，其中路由密钥字段设置为从该邻居接收到的Inter-AS I-PMSI a-D路由的MCAST-VPN NLRI，原始路由器的IP地址设置为PE/ASBR的IP地址（这必须是可路由的IP地址）。
+ If the received Inter-AS I-PMSI A-D route carries the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication, then the Leaf A-D route MUST carry the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication. The Tunnel Identifier MUST carry a routable address of the PE/ASBR. The PMSI Tunnel attribute MUST carry a downstream-assigned MPLS label that is used to demultiplex the MVPN traffic received over a unicast tunnel by the PE/ASBR.
+ 如果接收到的Inter-AS I-PMSI A-D路由携带隧道类型设置为入口复制的PMSI隧道属性，则叶A-D路由必须携带隧道类型设置为入口复制的PMSI隧道属性。隧道标识符必须携带PE/ASBR的可路由地址。PMSI隧道属性必须携带下游分配的MPLS标签，该标签用于对PE/ASBR通过单播隧道接收的MVPN流量进行解复用。
+ The PE/ASBR constructs an IP-based Route Target Extended Community by placing the IP address carried in the Next Hop of the received Inter-AS I-PMSI A-D route in the Global Administrator field of the Community, with the Local Administrator field of this Community set to 0 and setting the Extended Communities attribute of the Leaf A-D route to that Community.
+ PE/ASBR通过将接收到的Inter-AS I-PMSI A-D路由的下一跳中携带的IP地址放置在社区的全局管理员字段中，构建基于IP的路由目标扩展社区，将此社区的本地管理员字段设置为0，并将叶A-D路由的扩展社区属性设置为该社区。
+ The Next Hop field of the MP_REACH_NLRI attribute of the route MUST be set to the same IP address as the one carried in the Originating Router's IP Address field of the route.
+ 路由的MP_REACH_NLRI属性的下一跳字段必须设置为与路由的原始路由器IP地址字段中携带的IP地址相同的IP地址。
+ To constrain the distribution scope of this route, the route MUST carry the NO_EXPORT Community [RFC1997].
+ 要限制此路由的分发范围，该路由必须包含NO_导出社区[RFC1997]。
+ Once the Leaf A-D route is constructed, the PE/ASBR advertises this route into IBGP.
+ 构建叶A-D路由后，PE/ASBR将该路由播发到IBGP中。
When an ASBR receives, via IBGP, a Leaf A-D route, if the Route Target carried in the Extended Communities attribute of the route matches one of the ASBR Import RT (auto-)configured on the ASBR, the ASBR performs the following.
当ASBR通过IBGP接收到叶a-D路由时，如果路由的Extended Communities属性中包含的路由目标与ASBR上配置的ASBR导入RT（自动）匹配，ASBR将执行以下操作。
The ASBR finds an Inter-AS I-PMSI A-D route whose MCAST-VPN NLRI has the same value as the Route Key field of the Leaf A-D route.
ASBR查找其MCAST-VPN NLRI与叶A-D路由的路由密钥字段具有相同值的内部AS I-PMSI A-D路由。
The received route may carry either (a) no PMSI Tunnel attribute, or (b) the PMSI Tunnel attribute, but only with the Tunnel Type set to Ingress Replication.
接收到的路由可携带（a）无PMSI隧道属性，或（b）PMSI隧道属性，但仅当隧道类型设置为入口复制时。
If the received route does not carry the PMSI Tunnel attribute, the ASBR uses the information from the received route to determine the leaves of the P-multicast tree rooted at the ASBR that would be used for the intra-AS segment associated with the found Inter-AS I-PMSI A-D route. The IP address of a leaf is the IP address carried in the Originating Router's IP address field of the received Leaf A-D route.
如果接收到的路由不携带PMSI隧道属性，则ASBR使用来自接收到的路由的信息来确定根在ASBR的P多播树的叶子，该叶子将用于与找到的AS间I-PMSI A-D路由相关联的AS内段。叶的IP地址是在接收到的叶a-D路由的发起路由器的IP地址字段中携带的IP地址。
If the received route carries the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication, the ASBR uses the information carried by the route to construct the intra-AS segment with ingress replication.
如果接收到的路由携带PMSI隧道属性，且隧道类型设置为入口复制，则ASBR使用路由携带的信息构造具有入口复制的AS内段。
An ASBR that has a given Inter-AS I-PMSI A-D route MAY discard some of the traffic carried in the tunnel specified in the PMSI Tunnel attribute of this route, if the ASBR determines that there are no downstream receivers for that traffic.
如果ASBR确定该流量没有下游接收器，则具有给定的内部AS I-PMSI a-D路由的ASBR可以丢弃该路由的PMSI隧道属性中指定的隧道中承载的部分流量。
When BGP is being used to distribute C-multicast routes, an ASBR that has a given Inter-AS I-PMSI A-D route MAY discard traffic from a particular customer multicast source C-S and destined to a particular customer multicast group address C-G that is carried over the tunnel specified in the PMSI Tunnel attribute of the route, if none of the C-multicast routes on the ASBR with RD and Source AS being the same as the RD and Source AS of the Inter-AS I-PMSI A-D route matches the (C-S,C-G) tuple. A C-multicast route is said to match a (C-S,C-G) tuple, if it is a Source Tree Join route with Multicast Source set to C-S and Multicast Group set to C-G or a Shared Tree Join route with Multicast Group set to C-G.
当BGP被用于分发C-多播路由时，具有给定的AS间I-PMSI a-D路由的ASBR可以丢弃来自特定客户多播源C-S并发送到特定客户多播组地址C-G的通信量，该地址通过路由的PMSI隧道属性中指定的隧道传送，如果ASBR上RD和Source与INTERA AS I-PMSI A-D路由的RD和Source相同的C多播路由中没有一个与（C-S，C-G）元组匹配。如果C-多播路由是源树连接路由，其中多播源设置为C-S，多播组设置为C-G，或者是共享树连接路由，其中多播组设置为C-G，则C-多播路由称为匹配（C-S，C-G）元组。
The above procedures MAY also apply to an ASBR that originates a given Inter-AS I-PMSI A-D route. In this case, the ASBR applies them to the traffic carried over the tunnels specified in the PMSI Tunnel attribute of the Intra-AS I-PMSI A-D routes that the ASBR aggregates into the Inter-AS I-PMSI A-D route and whose tails are stitched to the one-hop ASBR-ASBR tunnel specified in the Inter-AS I-PMSI A-D route.
上述程序也可适用于发起给定AS间I-PMSI a-D路由的ASBR。在这种情况下，ASBR将其应用于在AS I-PMSI A-D内部路由的PMSI Tunnel属性中指定的隧道上承载的流量，ASBR聚合到AS I-PMSI A-D内部路由中，其尾部缝合到AS I-PMSI A-D内部路由中指定的单跳ASBR-ASBR隧道上。
It is possible to deploy MVPN such that the multicast routing and the unicast routing are "non-congruent". For instance, the CEs may be distributing to the PEs a special set of unicast routes that are to be used exclusively for the purpose of upstream multicast hop selection, and not used for unicast routing at all. (For example, when BGP is the CE-PE unicast routing protocol, the CEs may be using SAFI 2 ("Network Layer Reachability Information used for multicast
可以部署MVPN，使得多播路由和单播路由“不一致”。例如，CEs可以向PEs分发一组特殊的单播路由，该单播路由专门用于上游多播跳选择，而根本不用于单播路由。（例如，当BGP是CE-PE单播路由协议时，CEs可以使用SAFI 2（“用于多播的网络层可达性信息”）
forwarding" [IANA-SAFI]), and either IPv4 or IPv6 AFI to distribute a special set of routes that are to be used for, and only for, upstream multicast hop selection.) In such a situation, we will speak of the MVPN as having two VRFs on a given PE: one containing the routes that are used for unicast, the other containing the unicast routes that are used for UMH selection. We will call the former the "unicast routing VRF" and the latter the "UMH VRF" (upstream-multicast-hop VRF).
转发“[IANA-SAFI])）在这种情况下，我们将MVPN称为在给定PE上有两个VRF：一个包含用于单播的路由，另一个包含用于UMH选择的单播路由。我们将前者称为“单播路由VRF”，后者称为“UMH VRF”（上行多播跳VRF）。
In this document, when we speak without qualification of the MVPN's VRF, then if the MVPN has both a unicast VRF and a UMH VRF, we are speaking of the UMH VRF. (Of course, if there is no separate UMH VRF, then we are speaking of the unicast VRF.)
在本文件中，当我们在未限定MVPN的VRF的情况下发言时，如果MVPN同时具有单播VRF和UMH VRF，则我们指的是UMH VRF。（当然，如果没有单独的UMH VRF，那么我们说的是单播VRF。）
If there is a separate UMH VRF, it MAY have its own import and export Route Targets, different from the ones used by the unicast VRF. These Route Targets MUST be used to control distribution of auto-discovery routes. In addition, the export Route Targets of the UMH VRF are added to the Route Targets used by the unicast VRF when originating (unicast) VPN-IP routes. The import Route Targets associated with a given UMH VRF are used to determine which of the received (unicast) VPN-IP routes should be accepted into the UMH VRF.
如果有一个单独的UMH VRF，它可能有自己的导入和导出路由目标，与单播VRF使用的目标不同。这些路由目标必须用于控制自动发现路由的分布。此外，UMH VRF的导出路由目标被添加到单播VRF在发起（单播）VPN-IP路由时使用的路由目标中。与给定UMH VRF相关联的导入路由目标用于确定接收到的（单播）VPN-IP路由中的哪一个应该被UMH VRF接受。
If a PE maintains an UMH VRF for that MVPN, then it is RECOMMENDED that the UMH VRF use the same RD as the one used by the unicast VRF of that MVPN.
如果PE为该MVPN维护UMH VRF，则建议UMH VRF使用与该MVPN的单播VRF使用的RD相同的RD。
If an MVPN site is multihomed to several PEs, then to support non-congruent unicast and multicast connectivity, on each of these PEs, the UMH VRF of the MVPN MUST use its own distinct RD (although on a given PE, the RD used by the UMH VRF SHOULD be the same as the one used by the unicast VRF).
如果一个MVPN站点多宿于多个PE，那么为了支持非一致单播和多播连接，在每个PE上，MVPN的UMH VRF必须使用其自己的独特RD（尽管在给定PE上，UMH VRF使用的RD应该与单播VRF使用的RD相同）。
If an MVPN has a UMH VRF distinct from its unicast VRF, then one option to support non-congruency is to exchange the routes to/from that UMH VRF by using the same AFI/SAFI as used by the routes from the unicast VRF.
如果MVPN具有与其单播VRF不同的UMH VRF，则支持非一致性的一个选项是通过使用与来自单播VRF的路由所使用的相同AFI/SAFI来交换与该UMH VRF的路由。
Another option is to exchange the routes to/from the UMH VRF using the IPv4 or IPv6 AFI (as appropriate), but with the SAFI set to SAFI 129 "Multicast for BGP/MPLS IP Virtual Private Networks (VPNs)" [IANA-SAFI]. The NLRI carried by these routes is defined as follows:
另一种选择是使用IPv4或IPv6 AFI（视情况而定）交换与UMH VRF之间的路由，但SAFI设置为SAFI 129“BGP/MPLS IP虚拟专用网络（VPN）的多播”[IANA-SAFI]。这些路线的NLRI定义如下：
+---------------------------+
| Length (1 octet) |
+---------------------------+
| Prefix (variable) |
+---------------------------+
+---------------------------+
| Length (1 octet) |
+---------------------------+
| Prefix (variable) |
+---------------------------+
The use and the meaning of these fields are as follows:
这些字段的用途和含义如下：
a) Length:
a) 长度：
The Length field indicates the length, in bits, of the address prefix.
长度字段以位表示地址前缀的长度。
b) Prefix:
b) 前缀：
The Prefix field contains a Route Distinguisher as defined in [RFC4364] prepended to an IPv4 or IPv6 address prefix, followed by enough trailing bits to make the end of the field fall on an octet boundary. Note that the value of trailing bits is irrelevant.
前缀字段包含[RFC4364]中定义的路由识别器，前置于IPv4或IPv6地址前缀，后跟足够的尾随位，以使字段结尾位于八位字节边界上。请注意，尾随位的值是无关的。
These routes MUST carry the VRF Route Import Extended Community. If, for a given MVPN, BGP is used for exchanging C-multicast routes, or if segmented inter-AS tunnels are used, then these routes MUST also carry the Source AS Extended Community.
这些路由必须承载VRF路由导入扩展社区。如果对于给定的MVPN，BGP用于交换C-多播路由，或者如果使用分段的内部AS隧道，则这些路由还必须将源作为扩展社区进行传输。
The detailed procedures for selecting forwarder PE in the presence of such routes are outside the scope of this document. However, this document requires these procedures to preserve the constraints imposed by the single forwarder PE selection procedures, as specified in [MVPN].
在存在此类路线的情况下选择货运代理PE的详细程序不在本文件范围内。然而，本文件要求这些程序保留[MVPN]中规定的单一转发商PE选择程序施加的约束。
VPN C-Multicast Routing Information is exchanged among PEs by using C-multicast routes that are carried using an MCAST-VPN NLRI. These routes are originated and propagated as follows.
VPN C多播路由信息通过使用MCAST-VPN NLRI承载的C多播路由在PEs之间交换。这些路线的起源和传播如下。
Part of the procedures for constructing MCAST-VPN NLRI depends on the multicast routing protocol between CE and PE (C-multicast protocol).
构造MCAST-VPN NLRI的部分过程取决于CE和PE之间的多播路由协议（C多播协议）。
The following specifies the construction of MCAST-VPN NLRI of C-multicast routes for the case where the C-multicast protocol is PIM. These C-multicast routes are originated as a result of updates in the (C-S,C-G), or (C-*,C-G) state learned by a PE via the C-multicast protocol.
以下说明了在C-多播协议为PIM的情况下，C-多播路由的MCAST-VPN NLRI的构造。这些C-多播路由是PE通过C-多播协议学习到的（C-S，C-G）或（C-*，C-G）状态更新的结果。
Note that creation and deletion of (C-S,C-G,rpt) states on a PE when the C-multicast protocol is PIM do not result in any BGP actions.
请注意，当C多播协议为PIM时，PE上（C-S、C-G、rpt）状态的创建和删除不会导致任何BGP操作。
Whenever (a) a C-PIM instance on a particular PE creates a new (C-S,C-G) state, and (b) the selected upstream PE for C-S (see [MVPN]) is not the local PE, then the local PE MUST originate a C-multicast route of type Source Tree Join. The Multicast Source field in the MCAST-VPN NLRI of the route is set to C-S; the Multicast Group field is set of C-G.
每当（a）特定PE上的C-PIM实例创建新的（C-S，C-G）状态，并且（b）为C-S选择的上游PE（参见[MVPN]）不是本地PE时，本地PE必须发起源树连接类型的C-多播路由。路由的MCAST-VPN NLRI中的多播源字段设置为C-S；多播组字段设置为C-G。
This C-multicast route is said to "correspond" to the C-PIM (C-S,C-G) state.
这种C-多播路由被称为“对应于”C-PIM（C-S，C-G）状态。
The semantics of the route are such that the PE has one or more receivers for (C-S,C-G) in the sites connected to the PE (the route has the (C-S,C-G) Join semantics).
路由的语义使得PE在连接到PE的站点中具有（C-S，C-G）的一个或多个接收器（路由具有（C-S，C-G）连接语义）。
Whenever a C-PIM instance on a particular PE deletes a (C-S,C-G) state, the corresponding C-multicast route MUST be withdrawn. (The withdrawal of the route has the (C-S,C-G) Prune semantics). The MCAST-VPN NLRI of the withdrawn route is carried in the MP_UNREACH_NLRI attribute.
每当特定PE上的C-PIM实例删除（C-S，C-G）状态时，必须撤回相应的C-multicast路由。（路由的撤回具有（C-S，C-G）删减语义）。撤回路由的MCAST-VPN NLRI包含在MP_UNREACH_NLRI属性中。
Whenever (a) a C-PIM instance on a particular PE creates a new (C-*,C-G) state, and (b) the selected upstream PE for the C-RP corresponding to the C-G (see [MVPN]) is not the local PE, then the local PE MUST originate a C-multicast route of type Shared Tree Join. The Multicast Source field in the MCAST-VPN NLRI of the route is set to the C-RP address. The Multicast Group field in the MCAST-VPN NLRI is set to the C-G address.
无论何时（a）特定PE上的C-PIM实例创建新的（C-*，C-G）状态，以及（b）对应于C-G的C-RP的所选上游PE（参见[MVPN]）不是本地PE，则本地PE必须发起共享树连接类型的C-多播路由。路由的MCAST-VPN NLRI中的多播源字段设置为C-RP地址。MCAST-VPN NLRI中的多播组字段设置为C-G地址。
This C-multicast route is said to "correspond" to the C-PIM (C-*,C-G) state.
这种C-多播路由被称为“对应于”C-PIM（C-*，C-G）状态。
The semantics of the route are such that the PE has one or more receivers for (C-*,C-G) in the sites connected to the PE (the route has the (C-*,C-G) Join semantics).
路由的语义使得PE在连接到PE的站点中具有一个或多个（C-*，C-G）接收器（路由具有（C-*，C-G）连接语义）。
Whenever a C-PIM instance on a particular PE deletes a (C-*,C-G) state, the corresponding C-multicast route MUST be withdrawn. (The withdrawal of the route has the (C-S,C-G) Prune semantics). The MCAST-VPN NLRI of the withdrawn route is carried in the MP_UNREACH_NLRI attribute.
每当特定PE上的C-PIM实例删除（C-*，C-G）状态时，必须撤回相应的C-multicast路由。（路由的撤回具有（C-S，C-G）删减语义）。撤回路由的MCAST-VPN NLRI包含在MP_UNREACH_NLRI属性中。
The following specifies the construction of the MCAST-VPN NLRI of C-multicast routes for the case where the C-multicast protocol is mLDP [mLDP].
以下说明了在C-多播协议为mLDP[mLDP]的情况下，C-多播路由的MCAST-VPN NLRI的构造。
Whenever a PE receives, from one of its CEs, a P2MP Label Map <X, Y, L> over interface I, where X is the Root Node Address, Y is the Opaque Value, and L is an MPLS label, the PE checks whether it already has state for <X, Y> in the VRF associated with the CE. If so, then all the PE needs to do in this case is to update its forwarding state by adding <I, L> to the forwarding state associated with <X, Y>.
每当PE从其一个CE接收到接口I上的P2MP标签映射<X，Y，L>，其中X是根节点地址，Y是不透明值，L是MPLS标签时，PE检查其是否已经在与CE相关联的VRF中具有<X，Y>的状态。如果是这样，那么在这种情况下，PE需要做的就是通过将<I，L>添加到与<X，Y>关联的转发状态来更新其转发状态。
If the PE does not have state for <X, Y> in the VRF associated with the CE, then the PE constructs a Source Tree Join C-multicast route whose MCAST-VPN NLRI contains X as the Multicast Source field, and Y as the Multicast Group field.
如果PE在与CE关联的VRF中没有<X，Y>的状态，则PE构造一个源树连接C-多播路由，其MCAST-VPN NLRI包含X作为多播源字段，Y作为多播组字段。
Whenever a PE deletes a previously created <X, Y> state that had resulted in originating a C-multicast route, the PE withdraws the C-multicast route. The MCAST-VPN NLRI of the withdrawn route is carried in the MP_UNREACH_NLRI attribute.
每当PE删除先前创建的导致发起C-多播路由的<X，Y>状态时，PE将撤回C-多播路由。撤回路由的MCAST-VPN NLRI包含在MP_UNREACH_NLRI属性中。
The rest of the C-multicast route is constructed as follows (the same procedures apply to both PIM and mLDP as the C-Multicast protocol).
C-多播路由的其余部分构造如下（与C-多播协议相同的过程适用于PIM和mLDP）。
The local PE executes the procedures of [MVPN] to find the selected Upstream Multicast Hop (UMH) route and the selected upstream PE for the address carries in the Multicast Source field of MCAST-VPN NLRI.
本地PE执行[MVPN]过程，在MCAST-VPN NLRI的多播源字段中查找所选的上行多播跃点（UMH）路由和地址承载的所选上行PE。
From the selected UMH route, the local PE extracts (a) the ASN of the upstream PE (as carried in the Source AS Extended Community of the route), and (b) the C-multicast Import RT of the VRF on the upstream PE (the value of this C-multicast Import RT is the value of the VRF Route Import Extended Community carried by the route). The Source AS field in the C-multicast route is set to that AS. The Route Target Extended Community of the C-multicast route is set to that C-multicast Import RT.
从选定的UMH路由中，本地PE提取（a）上游PE的ASN（作为路由的扩展社区携带在源中），和（b）上游PE上VRF的C多播导入RT（该C多播导入RT的值是路由携带的VRF路由导入扩展社区的值）。C多播路由中的源AS字段设置为AS。C-多播路由的路由目标扩展社区设置为该C-多播导入RT。
If there is more than one (remote) PE that originates the (unicast) route to the address carried in the Multicast Source field of the MCAST-VPN NLRI, then the procedures for selecting the UMH route and the upstream PE to reach that address are as specified in [MVPN].
如果有多个（远程）PE发起（单播）路由到MCAST-VPN NLRI的多播源字段中携带的地址，则选择UMH路由和上游PE以到达该地址的过程如[MVPN]中所述。
If the local and the upstream PEs are in the same AS, then the RD of the advertised MCAST-VPN NLRI is set to the RD of the VPN-IP route that contains the address carried in the Multicast Source field.
如果本地和上游PEs与相同，则播发的MCAST-VPN NLRI的RD设置为包含多播源字段中携带的地址的VPN-IP路由的RD。
The C-multicast route is then advertised into IBGP.
然后将C多播路由播发到IBGP中。
If the local and the upstream PEs are in different ASes, then the local PE finds in its VRF an Inter-AS I-PMSI A-D route whose Source AS field carries the ASN of the upstream PE. The RD of the found Inter-AS I-PMSI A-D route is used as the RD of the advertised C-multicast route. The local PE constructs an IP-based Route Target Extended Community by placing the Next Hop of the found Inter-AS I-PMSI A-D route in the Global Administrator field of this Community, with the Local Administrator field of this Community set to 0; it then adds this Community to the Extended Communities attribute of the C-multicast route. (Note that this Route Target is the same as the ASBR Import RT of the ASBR identified by the Next Hop of the found Inter-AS I-PMSI A-D route.)
如果本地和上游PE处于不同的ASE中，则本地PE在其VRF中找到一条AS间I-PMSI A-D路由，其源AS字段承载上游PE的ASN。找到的Inter-AS I-PMSI A-D路由的RD用作播发的C-多播路由的RD。本地PE通过将找到的Inter-AS I-PMSI A-D路由的下一跳放在该社区的全局管理员字段中，并将该社区的本地管理员字段设置为0，构建基于IP的路由目标扩展社区；然后将此社区添加到C多播路由的扩展社区属性中。（请注意，此路由目标与ASBR的ASBR导入RT相同，ASBR由找到的Inter as I-PMSI A-D路由的下一个跃点标识。）
Inter-AS I-PMSI A-D routes are not used to support non-segmented inter-AS tunnels. To support non-segmented inter-AS tunnels, if the local and the upstream PEs are in different ASes, the local system finds in its VRF an Intra-AS I-PMSI A-D route from the upstream PE (the Originating Router's IP Address field of that route has the same value as the one carried in the VRF Route Import of the (unicast) route to the address carried in the Multicast Source field). The RD of the found Intra-AS I-PMSI A-D route is used as the RD of the advertised C-multicast route. The Source AS field in the C-multicast route is set to value of the Originating Router's IP Address field of the found Intra-AS I-PMSI A-D route.
AS间I-PMSI A-D路线不用于支持非分段AS间隧道。为了支持非分段的AS间隧道，如果本地和上游PE处于不同的ASE中，本地系统在其VRF中找到来自上游PE的AS内I-PMSI A-D路由（该路由的发起路由器的IP地址字段与（单播）的VRF路由导入中携带的值相同）路由到多播源字段中携带的地址）。找到的帧内AS I-PMSI A-D路由的RD用作播发的C多播路由的RD。C-多播路由中的源AS字段设置为找到的内部AS I-PMSI A-D路由的发起路由器IP地址字段的值。
The Next Hop field of the MP_REACH_NLRI attribute MUST be set to a routable IP address of the local PE.
MP_REACH_NLRI属性的下一跳字段必须设置为本地PE的可路由IP地址。
If the Next Hop of the found (Inter-AS or Intra-AS) I-PMSI A-D route is an EBGP neighbor of the local PE, then the PE advertises the C-multicast route to that neighbor. If the Next Hop of the found (Inter-AS or Intra-AS) I-PMSI A-D route is within the same AS as the local PE, then the PE advertises the C-multicast route into IBGP.
如果找到的（AS间或AS内）I-PMSI A-D路由的下一跳是本地PE的EBGP邻居，则PE向该邻居播发C多播路由。如果找到的（AS间或AS内）I-PMSI A-D路由的下一跳与本地PE在同一跳内，则PE将C多播路由播发到IBGP中。
The particular UMH route that is selected by a given PE for a given C-S may be influenced by the network's unicast routing. In that case, a change in the unicast routing may invalidate prior choices of the UMH route for some C-S. If this happens, the local PE MUST execute the UMH route selection procedures for C-S again. If the
由给定PE为给定C-S选择的特定UMH路由可能受到网络的单播路由的影响。在这种情况下，单播路由的改变可能使一些C-S的UMH路由的先前选择无效。如果发生这种情况，本地PE必须再次执行C-S的UMH路由选择过程。如果
result is that a different UMH route is selected, then for all C-G, any previously originated C-multicast routes for (C-S,C-G) MUST be re-originated.
结果是选择了不同的UMH路由，然后对于所有C-G，必须重新发起（C-S，C-G）的任何先前发起的C-多播路由。
Similarly, if a unicast routing change results in a change of the UMH route for a C-RP, then for all C-G such that C-RP is the RP associated with C-G, any previously originated C-multicast routes for (C-*,C-G) MUST be re-originated.
类似地，如果单播路由改变导致C-RP的UMH路由改变，则对于所有C-G，使得C-RP是与C-G相关联的RP，则必须重新发起（C-*，C-G）的任何先前发起的C-multicast路由。
When an ASBR receives a BGP Update message that carries a C-multicast route, if at least one of the Route Targets of the route matches one of the ASBR Import RTs (auto-)configured on the ASBR, the ASBR finds an Inter-AS I-PMSI A-D route whose RD and Source AS matches the RD and Source AS carried in the C-multicast route. If no matching route is found, the ASBR takes no further action. If a matching route is found, the ASBR proceeds as follows.
当ASBR收到承载C-多播路由的BGP更新消息时，如果路由的至少一个路由目标与ASBR上配置的ASBR导入RTs（自动）之一匹配，ASBR将查找其RD和源AS与C-多播路由中承载的RD和源AS匹配的Inter-AS I-PMSI a-D路由。如果没有找到匹配的路由，ASBR将不采取进一步的操作。如果找到匹配的路由，ASBR将按如下方式进行。
To support non-segmented inter-AS tunnels, instead of matching the RD and Source AS carried in the C-multicast route against the RD and Source AS of an Inter-AS I-PMSI A-D route, the ASBR should match it against the RD and the Originating Router's IP Address of the Intra-AS I-PMSI A-D routes.
为了支持非分段的AS间隧道，ASBR不应将C多播路由中携带的RD和源与AS间I-PMSI A-D路由中的RD和源AS进行匹配，而应将其与RD和AS内I-PMSI A-D路由的原始路由器IP地址进行匹配。
The ASBR first checks if it already has one or more C-multicast routes that have the same MCAST-VPN NLRI as the newly received route. If such a route(s) already exists, the ASBR keeps the newly received route, but SHALL NOT re-advertise the newly received route. Otherwise, the ASBR re-advertises the route, as described in this section.
ASBR首先检查是否已经有一个或多个C多播路由与新接收的路由具有相同的MCAST-VPN NLRI。如果此类路由已经存在，ASBR保留新接收的路由，但不应重新公布新接收的路由。否则，ASBR将重新公布路线，如本节所述。
When an ASBR receives a BGP Update message that carries a withdrawal of a previously advertised C-multicast route, the ASBR first checks if it already has at least one other C-multicast route that has the same MCAST-VPN NLRI. If such a route already exists, the ASBR processes the withdrawn route, but SHALL NOT re-advertise the withdrawal. Otherwise, the ASBR re-advertises the withdrawal of the previously advertised C-multicast route, as described below.
当ASBR接收到BGP更新消息，该消息携带先前公布的C-多播路由的撤回时，ASBR首先检查是否已经至少有一个其他C-多播路由具有相同的MCAST-VPN NLRI。如果该路线已经存在，ASBR处理撤回的路线，但不得重新公布撤回。否则，ASBR重新通告先前通告的C-多播路由的撤回，如下所述。
If the ASBR is the ASBR that originated the found Inter-AS I-PMSI A-D route, then before re-advertising the C-multicast route into IBGP, the ASBR removes from the route the Route Target that matches one of the ASBR Import RTs (auto-)configured on the ASBR.
如果ASBR是发起找到的内部AS I-PMSI A-D路由的ASBR，则在将C多播路由重新播发到IBGP之前，ASBR会从路由中删除与ASBR上配置的ASBR导入RTs（自动）之一匹配的路由目标。
If the ASBR is not the ASBR that originated the found Inter-AS I-PMSI A-D route, then before re-advertising the C-multicast route, the ASBR modifies the Extended Communities attribute of the C-multicast route
如果ASBR不是发起找到的Inter-AS I-PMSI A-D路由的ASBR，则在重新公布C-多播路由之前，ASBR修改C-多播路由的“扩展社区”属性
by replacing the Route Target of the route that matches one of the ASBR Import RTs (auto-)configured on the ASBR with a new Route Target constructed as follows. The new Route Target is an IP-based Route Target that has the Global Administrator field set to the Next Hop of the found Inter-AS I-PMSI A-D route, and Local Administrator field of this Community set to 0. Note that this newly constructed Route Target is the same as the ASBR Import RT of the ASBR identified by the Next Hop of the found Inter-AS I-PMSI A-D route. The rest of the Extended Communities attribute of the route SHOULD be passed unmodified.
通过将与ASBR上配置的ASBR导入RTs（自动-）之一匹配的路由的路由目标替换为如下构造的新路由目标。新路由目标是基于IP的路由目标，其全局管理员字段设置为找到的Inter AS I-PMSI A-D路由的下一个跃点，此社区的本地管理员字段设置为0。注意，这个新构造的路由目标与ASBR的ASBR导入RT相同，ASBR由找到的Inter-as I-PMSI A-D路由的下一个跃点标识。路由的“扩展社区”属性的其余部分应在未修改的情况下传递。
The Next Hop field of the MP_REACH_NLRI attribute SHOULD be set to an IP address of the ASBR.
MP_REACH_NLRI属性的下一个跃点字段应设置为ASBR的IP地址。
If the Next Hop field of the MP_REACH_NLRI of the found (Inter-AS or Intra-AS) I-PMSI A-D route is an EBGP neighbor of the ASBR, then the ASBR re-advertises the C-multicast route to that neighbor. If the Next Hop field of the MP_REACH_NLRI of the found (Inter-AS or Intra-AS) I-PMSI A-D route is an IBGP neighbor of the ASBR, the ASBR re-advertises the C-multicast route into IBGP. If it is the ASBR that originated the found Inter-AS I-PMSI A-D route in the first place, then the ASBR just re-advertises the C-multicast route into IBGP.
如果找到的（AS间或AS内）I-PMSI A-D路由的MP_到达_NLRI的下一跳字段是ASBR的EBGP邻居，则ASBR向该邻居重新播发C多播路由。如果找到的（AS间或AS内）I-PMSI A-D路由的MP_REACH_NLRI的下一跳字段是ASBR的IBGP邻居，则ASBR将C多播路由重新播发到IBGP中。如果是ASBR首先发起了找到的Inter-AS I-PMSI A-D路由，那么ASBR只是将C多播路由重新播发到IBGP中。
When a PE receives a C-multicast route the PE checks if any of the Route Target Extended Communities carried in the Extended Communities attribute of the route match any of the C-multicast Import RTs associated with the VRFs of any MVPN maintained by the PE. If no match is found, the PE SHOULD discard the route. Otherwise, (if a match is found), the PE checks if the address carried in the Multicast Source field of the C-multicast route matches one of the (unicast) VPN-IP routes advertised by PE from the VRF. If no match is found the PE SHOULD discard the route. Otherwise, (if a match is found), the PE proceeds as follows, depending on the multicast routing protocol between CE and PE (C-multicast protocol).
当PE接收到C-多播路由时，PE检查路由的“扩展社区”属性中携带的任何路由目标扩展社区是否与PE维护的任何MVPN的VRF关联的任何C-多播导入RT匹配。如果未找到匹配项，PE应放弃路由。否则，（如果找到匹配项），PE检查C-多播路由的多播源字段中携带的地址是否与PE从VRF播发的（单播）VPN-IP路由之一匹配。如果未找到匹配项，则PE应放弃该路线。否则，（如果找到匹配项），PE将按照如下方式进行，具体取决于CE和PE之间的多播路由协议（C多播协议）。
The following describes procedures when PIM is used as the multicast routing protocol between CE and PE (C-multicast protocol).
以下描述将PIM用作CE和PE之间的多播路由协议（C多播协议）时的过程。
Since C-multicast routing information is disseminated by BGP, PIM messages are never sent from one PE to another.
由于C多播路由信息由BGP传播，因此PIM消息从不从一个PE发送到另一个PE。
If the received route has the Route Type set to Source Tree Join, then the PE creates a new (C-S,C-G) state in its MVPN-TIB from the Multicast Source and Multicast Group fields in the MCAST-VPN NLRI of the route, if such a state does not already exist.
如果接收到的路由将路由类型设置为源树连接，则PE将从路由的MCAST-VPN NLRI中的多播源和多播组字段在其MVPN-TIB中创建一个新的（C-S、C-G）状态（如果该状态尚不存在）。
If the local policy on the PE is to bind (C-S,C-G) to an S-PMSI, then the PE adds the S-PMSI to the outgoing interface list of the (C-S,C-G) state, if it is not already there. Otherwise, the PE adds an I-PMSI to the outgoing interface list of the (C-S,C-G) state, if it is not already there.
如果PE上的本地策略要将（C-S，C-G）绑定到S-PMSI，则PE会将S-PMSI添加到（C-S，C-G）状态的传出接口列表中（如果尚未存在）。否则，PE会将I-PMSI添加到（C-S，C-G）状态的传出接口列表中（如果它还没有）。
When, for a said VRF, the last Source Tree Join C-multicast route for (C-S,C-G) is withdrawn, resulting in the situation where the VRF contains no Source Tree Join C-multicast route for (C-S,C-G), the PE MUST remove the I-PMSI/S-PMSI from the outgoing interface list of the (C-S,C-G) state. Depending on the (C-S,C-G) state of the PE-CE interfaces, this may result in the PE using PIM procedures to prune itself off the (C-S,C-G) tree. If C-G is not in the SSM range for the VRF, then removing the I-PMSI/S-PMSI from the outgoing interface list of the (C-S,C-G) state SHOULD be done after a delay that is controlled by a timer. The value of the timer MUST be configurable.
对于所述VRF，当（C-S，C-G）的最后一个源树加入C-多播路由被撤回时，导致VRF不包含（C-S，C-G）的源树加入C-多播路由的情况，PE必须从（C-S，C-G）状态的传出接口列表中移除I-PMSI/S-PMSI。根据PE-CE接口的（C-S，C-G）状态，这可能导致PE使用PIM过程将自身从（C-S，C-G）树中剪除。如果C-G不在VRF的SSM范围内，则应从（C-S，C-G）状态的输出接口列表中删除I-PMSI/S-PMSI应在定时器控制的延迟后完成。计时器的值必须是可配置的。
The purpose of this timer is to ensure that the PE does not stop forwarding (C-S,C-G) onto a PMSI tunnel until all the PEs of the same MVPN have had time to receive the withdrawal of the Source Active A-D route for (C-S,C-G) (see Section 13.1), and the PE connected to C-RP starts forwarding (C-S,C-G) on the C-RPT.
该计时器的目的是确保PE不会停止向PMSI隧道转发（C-S，C-G），直到同一MVPN的所有PE都有时间接收（C-S，C-G）的源活动a-D路由的撤回（见第13.1节），并且连接到C-RP的PE开始在C-RPT上转发（C-S，C-G）。
Note that before the PE stops forwarding (C-S,C-G), there is a possibility to have (C-S,C-G) packets being sent at the same time on the PMSI by both the local PE and the PE connected to the site that contains C-RP. This would result in a transient unnecessary traffic on the provider backbone. However, no duplicates will reach customer hosts subscribed to C-G as long as the downstream PEs apply procedures described in Section 9.1 of [MVPN].
请注意，在PE停止转发（C-S，C-G）之前，本地PE和连接到包含C-RP的站点的PE有可能同时在PMSI上发送（C-S，C-G）数据包。这将导致提供商主干上出现暂时的不必要流量。但是，只要下游PEs采用[MVPN]第9.1节所述的程序，订阅C-G的客户主机将不会收到任何副本。
If the received route has the Route Type set to Shared Tree Join, then the PE creates a new (C-*,C-G) state in its MVPN-TIB with the RP address for that state taken from the Multicast Source, and C-G for that state taken from the Multicast Group fields of the MCAST-VPN NLRI of the route, if such a state does not already exist. If there is no S-PMSI for (C-*,C-G), then the PE adds I-PMSI to the outgoing
如果接收到的路由的路由类型设置为共享树连接，则PE在其MVPN-TIB中创建一个新的（C-*，C-G）状态，该状态的RP地址取自多播源，而C-G地址取自路由的MCAST-VPN NLRI的多播组字段（如果该状态不存在）。如果（C-*，C-G）没有S-PMSI，则PE会将I-PMSI添加到输出
interface list of the state if it is not already there. If there is an S-PMSI for (C-*,C-G), then the PE adds S-PMSI to the outgoing interface list of the state if it is not already there.
状态的接口列表（如果尚未存在）。如果（C-*，C-G）存在S-PMSI，则PE将S-PMSI添加到状态的传出接口列表中（如果该列表不存在）。
When, for a said VRF, the last Shared Tree Join C-multicast route for (C-*,C-G) is withdrawn, resulting in the situation where the VRF contains no Shared Tree Join C-multicast route for (C-*,C-G), the PE MUST remove the I-PMSI/S-PMSI from the outgoing interface list of the (C-*,C-G) state. Depending on the (C-*,C-G) state of the PE-CE interfaces, this may result in the PE using PIM procedures to prune itself off the (C-*,C-G) tree.
对于所述VRF，当（C-*，C-G）的最后一个共享树连接C-多播路由被撤回时，导致VRF不包含（C-*，C-G）的共享树连接C-多播路由的情况，PE必须从（C-*，C-G）状态的传出接口列表中移除I-PMSI/S-PMSI。根据PE-CE接口的（C-*，C-G）状态，这可能会导致PE使用PIM过程将自身从（C-*，C-G）树中剪除。
The following describes procedures when mLDP is used as the multicast routing protocol between CE and PE (C-multicast protocol).
以下描述了将mLDP用作CE和PE（C-多播协议）之间的多播路由协议时的过程。
When mLDP is used as a C-multicast protocol, the only valid type of a C-multicast route that a PE could receive is a Source Tree Join C-multicast route.
当mLDP用作C多播协议时，PE可以接收的唯一有效的C多播路由类型是源树连接C多播路由。
When the PE receives a Source Tree Join C-multicast route, the PE applies, in the scope of this VRF, the P2MP mLDP procedures for a transit node using the value carried in the Multicast Source field of the route as the C-Root Node Identifier, and the value carried in the Multicast Group of the route as the C-LDP MP Opaque Value Element.
当PE接收到源树加入C-多播路由时，在该VRF的范围内，PE使用路由的多播源字段中携带的值作为C-根节点标识符，并使用路由的多播组中携带的值作为C-LDP MP不透明值元素，为中转节点应用P2MP mLDP过程。
If there is no S-PMSI for <C-Root Node Identifier, C-LDP MP Opaque Value Element>, then the PE creates and advertises an S-PMSI as described in Section 12 using C-Root Node Identifier as the value for the Multicast Source field of the S-PMSI A-D route and C-LDP MP Opaque Value Element as the value for the Multicast Group field of the route.
如果<C-Root Node Identifier，C-LDP MP不透明值元素>没有S-PMSI，则PE创建并播发S-PMSI，如第12节所述，使用C-Root Node Identifier作为S-PMSI A-D路由的多播源字段的值，使用C-LDP MP不透明值元素作为路由的多播组字段的值。
To improve scalability when mLDP is used as the C-Multicast protocol for a given MVPN, within each AS that has sites of that MVPN connected to the PEs of that AS, all the S-PMSIs of that MVPN MAY be aggregated into a single P-multicast tree (by using upstream-assigned labels).
为了提高当mLDP用作给定MVPN的C多播协议时的可伸缩性，在每个as中，该MVPN的站点连接到该as的PE，该MVPN的所有S-PMSI可以聚合到单个P多播树中（通过使用上游分配的标签）。
Note that C-multicast routes are "de facto" aggregated by BGP. This is because the MCAST-VPN NLRIs advertised by multiple PEs, for a C-multicast route for a particular C-S and C-G (or a particular C-* and C-G) of a given MVPN are identical.
请注意，C多播路由是由BGP“事实上”聚合的。这是因为多个PE为给定MVPN的特定C-S和C-G（或特定C-*和C-G）的C多播路由宣传的MCAST-VPN NLRI是相同的。
Hence, a BGP route reflector or ASBR that receives multiple such routes with the same NLRI will re-advertise only one of these routes to other BGP speakers.
因此，接收具有相同NLRI的多条此类路由的BGP路由反射器或ASBR将仅向其他BGP扬声器重新公布其中一条路由。
This implies that C-multicast routes for a given (S,G) of a given MVPN originated by PEs that are clients of a given route reflector are aggregated by the route reflector. For instance, if multiple PEs that are clients of a route reflector, have receivers for a specific SSM channel of a MVPN, they will all advertise an identical NLRI for the Source Tree Join C-multicast route. However, only one C-multicast route will be advertised by the route reflector for this specific SSM channel of that MVPN, to other PEs and route reflectors that are clients of the route reflector.
这意味着由作为给定路由反射器的客户端的PEs发起的给定MVPN的给定（S，G）的C多播路由由路由反射器聚合。例如，如果作为路由反射器的客户端的多个PE具有MVPN的特定SSM信道的接收器，则它们都将为源树连接C多播路由播发相同的NLRI。然而，对于该MVPN的该特定SSM信道，路由反射器将仅向作为路由反射器的客户端的其他pe和路由反射器通告一条C多播路由。
This also implies that an ASBR aggregates all the received C-multicast routes for a given (S,G) (or a given (*,G)) of a given MVPN into a single C-multicast route.
这还意味着ASBR将给定MVPN的给定（S，G）（或给定（*，G））的所有接收到的C-多播路由聚合为单个C-多播路由。
To further reduce the routing churn due to C-multicast routes changes, a route reflector that re-advertises a C-multicast route SHOULD set the Next Hop field of the MP_REACH_NLRI attribute of the route to an IP address of the route reflector. Likewise, an ASBR that re-advertises a C-multicast route SHOULD set the Next Hop field of the MP_REACH_NLRI attribute of the route to an IP address of the ASBR.
为了进一步减少由于C-多播路由改变而引起的路由搅动，重新播发C-多播路由的路由反射器应将路由的MP_REACH_NLRI属性的下一跳字段设置为路由反射器的IP地址。同样，重新播发C多播路由的ASBR应将路由的MP_REACH_NLRI属性的下一跳字段设置为ASBR的IP地址。
Further, a BGP receiver, which receives multiple such routes with the same NLRI for the same C-multicast route, will potentially create forwarding state based on a single C-multicast route. Per the procedures described in Section 11.3, this forwarding state will be the same as the state that would have been created based on another route with same NLRI.
此外，对于相同的C-多播路由接收具有相同NLRI的多个此类路由的BGP接收器将潜在地基于单个C-多播路由创建转发状态。根据第11.3节中描述的程序，此转发状态将与基于具有相同NLRI的另一条路由创建的状态相同。
This section describes BGP-based procedures for using S-PMSIs A-D routes to bind (C-S,C-G) trees to P-tunnels.
本节介绍使用S-PMSIs A-D路由将（C-S、C-G）树绑定到P隧道的基于BGP的程序。
The following describes procedures for originating S-PMSI A-D routes by a PE.
以下描述了PE发起S-PMSI A-D路由的过程。
The PE constructs the MCAST-VPN NLRI of an S-PMSI A-D route for a given (C-S,C-G) as follows.
PE为给定（C-S，C-G）构建S-PMSI A-D路由的MCAST-VPN NLRI，如下所示。
+ The RD in this NLRI is set to the RD of the MVPN's VRF associated with (C-S,C-G).
+ 此NLRI中的RD设置为与（C-s，C-G）关联的MVPN VRF的RD。
+ The Multicast Source field MUST contain the source address associated with the C-multicast stream, and the Multicast Source Length field is set appropriately to reflect this.
+ 多播源字段必须包含与C多播流关联的源地址，并且多播源长度字段的设置适当地反映了这一点。
+ The Multicast Group field MUST contain the group address associated with the C-multicast stream, and the Multicast Group Length field is set appropriately to reflect this.
+ 多播组字段必须包含与C多播流关联的组地址，并且多播组长度字段的设置适当地反映了这一点。
+ The Originating Router's IP Address field MUST be set to the IP address that the (local) PE places in the Global Administrator field of the VRF Route Import Extended Community of the VPN-IP routes advertised by the PE. Note that the <RD, Originating Router's IP address> tuple uniquely identifies a given multicast VRF.
+ 发起路由器的IP地址字段必须设置为（本地）PE在VRF路由导入扩展社区（由PE播发的VPN-IP路由）的全局管理员字段中放置的IP地址。请注意，<RD，原始路由器的IP地址>元组唯一地标识给定的多播VRF。
The PE constructs the rest of the S-PMSI A-D route as follows.
PE构建S-PMSI A-D路由的其余部分，如下所示。
Depending on the type of P-multicast tree used for the P-tunnel, the PMSI Tunnel attribute of the S-PMSI A-D route is constructed as follows:
根据用于P隧道的P多播树的类型，S-PMSI A-D路由的PMSI隧道属性构造如下：
+ The PMSI Tunnel attribute MUST contain the identity of the P-multicast tree (note that the PE could create the identity of the tree prior to the actual instantiation of the tree).
+ PMSI Tunnel属性必须包含P-multicast树的标识（注意，PE可以在树的实际实例化之前创建树的标识）。
+ If, in order to establish the P-multicast tree, the PE needs to know the leaves of the tree within its own AS, then the PE obtains this information from the Leaf A-D routes received from other PEs/ASBRs within its own AS (as other PEs/ASBRs originate Leaf A-D routes in response to receiving the S-PMSI A-D route) by setting the Leaf Information Required flag in the PMSI Tunnel attribute to 1.
+ 如果为了建立P-多播树，PE需要知道其自身AS内的树的叶子，则PE从其自身AS内的其他PE/ASBR接收的叶子A-D路由中获取该信息（因为其他PE/ASBR响应于接收S-PMSI A-D路由而发起叶子A-D路由）通过将PMSI隧道属性中的Leaf Information Required标志设置为1。
+ If a PE originates S-PMSI A-D routes with the Leaf Information Required flag in the PMSI Tunnel attribute set to 1, then the PE MUST be (auto-)configured with an import Route Target, which controls acceptance of Leaf A-D routes by the PE. (Procedures for originating Leaf A-D routes by the PEs that receive the S-PMSI A-D route are described in Section 12.3.)
+ 如果PE发起S-PMSI a-D路由时，PMSI隧道属性中的“需要叶信息”标志设置为1，则PE必须（自动）配置导入路由目标，该目标控制PE接受叶a-D路由。（第12.3节描述了接收S-PMSI A-D路由的PEs发起叶A-D路由的程序。）
This Route Target is IP address specific. The Global Administrator field of this Route Target MUST be set to the IP address carried in the Next Hop of all the S-PMSI A-D routes advertised by this PE (if the PE uses different Next Hops, then the PE MUST be (auto-)configured with multiple import RTs, one per each such Next Hop). The Local Administrator field of this Route Target MUST be set to 0.
此路由目标是特定于IP地址的。此路由目标的全局管理员字段必须设置为该PE播发的所有S-PMSI A-D路由的下一跳中携带的IP地址（如果该PE使用不同的下一跳，则该PE必须（自动）配置多个导入RTs，每个下一跳一个）。此路由目标的本地管理员字段必须设置为0。
If the PE supports Route Target Constraint [RT-CONSTRAIN], the PE SHOULD advertise this import Route Target within its own AS using Route Target Constraints. To constrain distribution of the Route Target Constraint routes to the AS of the advertising PE, these routes SHOULD carry the NO_EXPORT Community [RFC1997].
如果PE支持路由目标约束[RT-Constraint]，则PE应使用路由目标约束在其自身内公布此导入路由目标。要将路由目标约束路由的分布约束到广告PE的AS，这些路由应包含NO_导出社区[RFC1997]。
+ A PE MAY aggregate two or more S-PMSIs originated by the PE onto the same P-multicast tree. If the PE already advertises S-PMSI A-D routes for these S-PMSIs, then aggregation requires the PE to re-advertise these routes. The re-advertised routes MUST be the same as the original ones, except for the PMSI Tunnel attribute. If the PE has not previously advertised S-PMSI A-D routes for these S-PMSIs, then the aggregation requires the PE to advertise (new) S-PMSI A-D routes for these S-PMSIs. The PMSI Tunnel attribute in the newly advertised/re-advertised routes MUST carry the identity of the P-multicast tree that aggregates the S-PMSIs. If at least some of the S-PMSIs aggregated onto the same P-multicast tree belong to different MVPNs, then all these routes MUST carry an MPLS upstream-assigned label [RFC5331].
+ PE可以将PE发起的两个或多个S-PMSI聚合到同一个P多播树上。如果PE已经为这些S-PMSI播发S-PMSI A-D路由，则聚合要求PE重新播发这些路由。重新公布的路由必须与原始路由相同，但PMSI隧道属性除外。如果PE之前没有为这些S-PMSI播发S-PMSI A-D路由，则聚合要求PE为这些S-PMSI播发（新的）S-PMSI A-D路由。新公布/重新公布的路由中的PMSI隧道属性必须具有聚合S-PMSI的P-多播树的标识。如果聚合到同一P-多播树上的至少一些S-pmsi属于不同的mvpn，则所有这些路由必须携带MPLS上游分配的标签[RFC5331]。
If all these aggregated S-PMSIs belong to the same MVPN, and this MVPN uses PIM as its C-multicast routing protocol, then the corresponding S-PMSI A-D routes MAY carry an MPLS upstream-assigned label [RFC5331]. Moreover, in this case, the labels MUST be distinct on a per-MVPN basis and MAY be distinct on a per-route basis.
如果所有这些聚合的S-PMSI属于相同的MVPN，并且该MVPN使用PIM作为其C-多播路由协议，则相应的S-PMSI A-D路由可以携带MPLS上游分配的标签[RFC5331]。此外，在这种情况下，标签必须在每个MVPN的基础上是不同的，并且可能在每个路由的基础上是不同的。
If all these aggregated S-PMSIs belong to the MVPN(s) that uses mLDP as its C-multicast routing protocol, then the corresponding S-PMSI A-D routes MUST carry an MPLS upstream-assigned label [RFC5331], and these labels MUST be distinct on a per-route (per-mLDP FEC) basis, irrespective of whether the aggregated S-PMSIs belong to the same or different MVPNs.
如果所有这些聚合的S-PMSI属于使用mLDP作为其C-多播路由协议的MVPN，则相应的S-PMSI A-D路由必须携带MPLS上游分配的标签[RFC5331]，并且这些标签必须在每个路由（每个mLDP FEC）的基础上是不同的，无论聚合的S-PMSI是否属于相同或不同的MVPN。
The Next Hop field of the MP_REACH_NLRI attribute of the route MUST be set to the same IP address as the one carried in the Originating Router's IP Address field.
路由的MP_REACH_NLRI属性的下一跳字段必须设置为与原始路由器的IP地址字段中携带的IP地址相同的IP地址。
The route always carries a set of Route Targets. The default set of Route Targets is determined as follows:
路线始终包含一组路线目标。路由目标的默认设置如下所示：
+ If there is a (unicast) VPN-IP route to C-S originated from the VRF, but no (unicast) VPN-IP route to C-RP originated from the VRF, then the set of Route Targets is formed by a set intersection between the set of Route Targets carried in the Intra-AS I-PMSI A-D route originated from the VRF and the set of Route Targets carried by the (unicast) VPN-IP route to C-S.
+ 如果存在源自VRF的到C-S的（单播）VPN-IP路由，但没有源自VRF的到C-RP的（单播）VPN-IP路由，则路由目标集由源自VRF的内部AS I-PMSI a-D路由中携带的路由目标集和源自VRF的（单播）路由目标集之间的集合交叉点形成到C-S的VPN-IP路由。
+ If there is no (unicast) VPN-IP route to C-S originated from the VRF, but there is a (unicast) VPN-IP route to C-RP originated from the VRF, then the set of Route Targets is formed by a set intersection between the set of Route Targets carried in the intra-AS I-PMSI A-D route originated from the VRF and the set of Route Targets carried by the (unicast) VPN-IP route to C-RP.
+ 如果不存在源自VRF的到C-S的（单播）VPN-IP路由，但存在源自VRF的到C-RP的（单播）VPN-IP路由，则路由目标集由源自VRF的内部AS I-PMSI a-D路由中携带的路由目标集与由VRF携带的路由目标集之间的集合交叉形成（单播）到C-RP的VPN-IP路由。
+ If there is a (unicast) VPN-IP route to C-S originated from the VRF, and a (unicast) VPN-IP route to C-RP originated from the VRF, then the set of Route Targets is formed by a set intersection between the set of Route Targets carried in the Intra-AS I-PMSI A-D route originated from the VRF and the set union of Route Targets carried by the (unicast) VPN-IP route to C-S and the (unicast) VPN-IP route to C-RP.
+ 如果存在源自VRF的到C-S的（单播）VPN-IP路由和源自VRF的到C-RP的（单播）VPN-IP路由，则路由目标集由源自VRF的内部AS I-PMSI a-D路由中携带的路由目标集和源自VRF的路由目标集并集之间的集合交集形成到C-S的VPN-IP路由和到C-RP的（单播）VPN-IP路由。
In each of the above cases, an implementation MUST allow the set of Route Targets carried by the route to be specified by configuration. In the absence of a configured set of Route Targets, the route MUST carry the default set of Route Targets, as specified above.
在上述每种情况下，实现必须允许通过配置指定路由携带的路由目标集。如果没有一组已配置的路由目标，则该路由必须包含一组默认路由目标，如上所述。
Procedures for handling an S-PMSI A-D route by ASBRs (both within and outside of the AS of the PE that originates the route) are the same as specified in Section 9.2.3, except that instead of Inter-AS I-PMSI A-D routes, the procedures apply to S-PMSI A-D routes.
ASBR处理S-PMSI A-D路由的程序（在发起路由的PE的AS内部和外部）与第9.2.3节中的规定相同，不同之处在于，该程序适用于S-PMSI A-D路由，而非AS I-PMSI A-D路由。
Consider the situation where:
考虑以下情况：
+ An ASBR is receiving (or expecting to receive) inter-AS (C-S,C-G) data from upstream via an S-PMSI.
+ ASBR正在通过S-PMSI从上游接收（或预期接收）AS间（C-S，C-G）数据。
+ The ASBR is sending (or expecting to send) the inter-AS (C-S,C-G) data downstream via an I-PMSI.
+ ASBR正在通过I-PMSI向下游发送（或期望发送）AS间（C-S，C-G）数据。
This situation may occur if the upstream providers have a policy of using S-PMSIs but the downstream providers have a policy of using I-PMSIs. To support this situation, an ASBR MAY, under certain conditions, merge one or more upstream S-PMSIs into a downstream I-PMSI.
如果上游供应商有使用S-PMSI的政策，但下游供应商有使用I-PMSI的政策，则可能出现这种情况。为了支持这种情况，ASBR可在特定条件下将一个或多个上游S-PMSI合并为下游I-PMSI。
An S-PMSI (corresponding to a particular S-PMSI A-D route) MAY be merged by a particular ASBR into an I-PMSI (corresponding to a particular Inter-AS I-PMSI A-D route) if and only if the following conditions all hold:
当且仅当以下条件均成立时，特定ASBR可将S-PMSI（对应于特定S-PMSI a-D路由）合并为I-PMSI（对应于特定AS间I-PMSI a-D路由）：
+ BGP is used to exchange C-multicast routes.
+ BGP用于交换C多播路由。
+ The S-PMSI A-D route and the Inter-AS I-PMSI A-D route originate in the same AS. The Inter-AS I-PMSI A-D route carries the originating AS in the Source AS field of the NLRI of the route and in the AS_PATH attribute of the route. The S-PMSI A-D route carries the originating AS in the AS_PATH attribute of the route.
+ S-PMSI A-D路由和AS间I-PMSI A-D路由起源于相同的AS。Inter-AS I-PMSI A-D路由在路由的NLRI的Source AS字段和路由的AS_PATH属性中携带始发AS。S-PMSI A-D路由在路由的AS_路径属性中携带始发AS。
+ The S-PMSI A-D route and the Inter-AS I-PMSI A-D route have exactly the same set of RTs.
+ S-PMSI A-D路由和Inter-AS I-PMSI A-D路由具有完全相同的RTs集。
+ For each (C-S,C-G) mentioned in the S-PMSI route, if the ASBR has installed a Source Tree Join (C-S,C-G) C-multicast route, then the S-PMSI route was originated by the upstream PE of the C-multicast route. The address of the upstream PE is carried in the RT of the C-multicast route. The address of the PE that originated the S-PMSI route is carried in the Originating Router's IP Address field of the MCAST-VPN NLRI of the route.
+ 对于S-PMSI路由中提到的每个（C-S，C-G），如果ASBR安装了源树连接（C-S，C-G）C-multicast路由，则S-PMSI路由由C-multicast路由的上游PE发起。上游PE的地址在C-多播路由的RT中携带。发起S-PMSI路由的PE地址携带在路由的MCAST-VPN NLRI的发起路由器IP地址字段中。
+ The ASBR supports the optional capability to discard (C-S,C-G) traffic received on an I-PMSI.
+ ASBR支持丢弃I-PMSI上接收的（C-S、C-G）流量的可选功能。
An ASBR performs merging by stitching the tail end of the P-tunnel, as specified in the PMSI Tunnel attribute of the S-PMSI A-D route received by the ASBR, to the head of the P-tunnel, as specified in the PMSI Tunnel attribute of the Inter-AS I-PMSI A-D route re-advertised by the ASBR.
ASBR通过将P隧道的尾端（如ASBR接收的S-PMSI A-D路由的PMSI隧道属性中指定）缝合到P隧道的头部（如ASBR重新公布的as间I-PMSI A-D路由的PMSI隧道属性中指定）来执行合并。
IP processing during merge: If an ASBR merges a (C-S,C-G) S-PMSI A-D route into an Inter-AS I-PMSI A-D route, the ASBR MUST discard all (C-S,C-G) traffic it receives on the tunnel advertised in the I-PMSI A-D route.
合并期间的IP处理：如果ASBR将（C-S，C-G）S-PMSI a-D路由合并到AS间I-PMSI a-D路由中，ASBR必须丢弃它在I-PMSI a-D路由中公布的隧道上接收的所有（C-S，C-G）流量。
An ASBR that merges an S-PMSI A-D route into an Inter-AS I-PMSI A-D route MUST NOT re-advertise the S-PMSI A-D route.
将S-PMSI A-D路由合并到AS间I-PMSI A-D路由的ASBR不得重新公布S-PMSI A-D路由。
Consider a PE that receives an S-PMSI A-D route. If one or more of the VRFs on the PE have their import Route Targets that contain one or more of the Route Targets carried by the received S-PMSI A-D route, then for each such VRF (and associated MVPN-TIB) the PE performs the following.
考虑一个PE接收一个PS-PMSI A- D路由。如果PE上的一个或多个VRF的导入路由目标包含接收到的S-PMSI A-D路由携带的一个或多个路由目标，则对于每个此类VRF（以及相关的MVPN-TIB），PE执行以下操作。
Procedures for receiving an S-PMSI A-D route by a PE (both within and outside of the AS of the PE that originates the route) are the same as specified in Section 9.2.3.4 except that (a) instead of Inter-AS
PE接收S-PMSI A-D路由的程序（在发起路由的PE的AS内部和外部）与第9.2.3.4节中规定的程序相同，除了（A）而不是AS之间
I-PMSI A-D routes, the procedures apply to S-PMSI A-D routes and (b) a PE performs procedures specified in that section only if, in addition to the criteria there, one of the following is true:
I-PMSI A-D路线，程序适用于S-PMSI A-D路线，且（b）PE仅在符合该部分标准的情况下执行该部分中规定的程序，且符合以下条件之一：
+ the PE originates a Source Tree Join (C-S,C-G) C-multicast route, and the upstream PE of that route is the PE that originates the S-PMSI A-D route; or
+ PE发起源树连接（C-S，C-G）C多播路由，该路由的上游PE是发起S-PMSI a-D路由的PE；或
+ the PE does not originate a Source Tree Join (C-S,C-G) C-multicast route, but it originates a Shared Tree Join (C-*,C-G) C-multicast route. The best (as determined by the BGP route selection procedures) Source Active A-D route for (C-S,C-G) selected by the PE is originated by the same PE as the one that originates the S-PMSI A-D route; or
+ PE不发起源树连接（C-S，C-G）C多播路由，但发起共享树连接（C-*，C-G）C多播路由。PE选择的（C-S，C-G）的最佳（由BGP路由选择程序确定）源活动A-D路由由发起S-PMSI A-D路由的PE发起；或
+ the PE does not originate a Source Tree Join (C-S,C-G), has not received any Source Active A-D routes for (C-S,C-G), but does originate a Shared Tree Join (C-*,C-G) route. The upstream PE for that route is the PE that originates the received S-PMSI A-D route.
+ PE未发起源树连接（C-S，C-G），未收到（C-S，C-G）的任何源活动a-D路由，但发起共享树连接（C-*，C-G）路由。该路由的上游PE是发起接收到的S-PMSI A-D路由的PE。
If the received S-PMSI A-D route has a PMSI Tunnel attribute with the Leaf Information Required flag set to 1, then the PE originates a Leaf A-D route. The Route Key of the Leaf A-D route is set to the MCAST-VPN NLRI of the S-PMSI A-D route. The rest of the Leaf A-D route is constructed using the same procedures as specified in section 9.2.3.4.1, except that instead of originating Leaf A-D routes in response to receiving Inter-AS I-PMSI A-D routes, the procedures apply to originating Leaf A-D routes in response to receiving S-PMSI A-D routes.
如果接收到的S-PMSI A-D路由具有PMSI Tunnel属性，且所需叶信息标志设置为1，则PE发起叶A-D路由。叶A-D路由的路由密钥设置为S-PMSI A-D路由的MCAST-VPN NLRI。叶A-D路由的其余部分使用第9.2.3.4.1节中规定的相同程序构建，除了响应于接收到内部as I-PMSI A-D路由的始发叶A-D路由之外，这些程序适用于响应于接收到S-PMSI A-D路由的始发叶A-D路由。
In addition to the procedures specified in Section 9.2.3.4.1, the PE MUST set up its forwarding path to receive (C-S,C-G) traffic from the tunnel advertised by the S-PMSI A-D route (the PE MUST switch to the S-PMSI).
除第9.2.3.4.1节中规定的程序外，PE必须设置其转发路径，以从S-PMSI A-D路由公布的隧道接收（C-S，C-G）流量（PE必须切换到S-PMSI）。
If a PE that is a leaf node of a particular Selective tunnel determines that it no longer needs to receive any of (C-S,C-G)s carried over that tunnel, the PE SHOULD prune itself off that tunnel. Procedures for pruning are specific to a particular tunneling technology.
如果作为特定选择性隧道的叶节点的PE确定它不再需要接收通过该隧道携带的（C-S，C-G）中的任何一个，则PE应将自己从该隧道中剪除。修剪程序特定于特定的隧道技术。
The procedures defined in this section only apply when the C-multicast routing protocol is PIM [RFC4601]; moreover, they only apply for the multicast ASM mode and MUST NOT be applied to multicast
本节中定义的程序仅适用于C-多播路由协议为PIM[RFC4601]时；此外，它们仅适用于多播ASM模式，不得应用于多播
group addresses belonging to the SSM range. The procedures also MUST NOT be applied when the C-multicast routing protocol is BIDIR-PIM [RFC5015].
属于SSM范围的组地址。当C-多播路由协议为BIDIR-PIM[RFC5015]时，也不得应用该程序。
The procedures of this section are applicable only to MVPNs that use both shared (i.e., rooted at a C-RP) and source (i.e., rooted at a C-S) inter-site C-trees.
本节的程序仅适用于使用共享（即以C-RP为根）和源（即以C-S为根）站点间C树的MVPN。
These procedures are not applicable to MVPNs that do not use shared inter-site C-trees and rely solely on source inter-site C-trees. See Section 14 for the procedures applicable to that scenario.
这些程序不适用于不使用共享站点间C树且仅依赖源站点间C树的MVPN。有关适用于该场景的程序，请参见第14节。
Whether or not a given MVPN uses both inter-site shared and source C-trees must be known a priori (e.g., via provisioning).
给定的MVPN是否同时使用站点间共享和源C树必须事先知道（例如，通过供应）。
In the scenario where an MVPN customer switches from a C-RP-based tree (RPT) to the shortest path tree (SPT), in order to avoid packet duplication, choosing of a single consistent upstream PE, as described in [MVPN], may not suffice. To illustrate this, consider a set of PEs {PE2, PE4, PE6} that are on the C-RP tree for (C-*,C-G) and have chosen a consistent upstream PE, as described in [MVPN], for (C-*,C-G) state. Further, this upstream PE, say PE1, is using a Multidirectional Inclusive PMSI (MI-PMSI) for (C-*,C-G). If a site attached to one of these PEs, say PE2, switches to the C-S tree for (C-S,C-G), PE2 generates a Source Tree Join C-multicast route towards the upstream PE that is on the path to C-S, say PE3. PE3 also uses the MI-PMSI for (C-S,C-G), as PE1 uses for (C-*,C-G). This results in {PE2, PE4, PE6} receiving duplicate traffic for (C-S,C-G) -- both on the C-RP tree (from PE1) and C-S tree (from PE3). If it is desirable to suppress receiving duplicate traffic, then it is necessary to choose a single forwarder PE for (C-S,C-G). The following describes how this is achieved.
在MVPN客户从基于C-RP的树（RPT）切换到最短路径树（SPT）的场景中，为了避免数据包重复，选择单个一致的上游PE（如[MVPN]中所述）可能不够。为了说明这一点，考虑一组PE-{PE2，PE4，PE6}在C-RP-树上（C-*，C-G），并选择了一致的上游PE，如[MVPN ]中所描述的（C-*，C-G）状态。此外，该上游PE（例如PE1）使用（C-*，C-G）的多向包容性PMSI（MI-PMSI）。如果连接到其中一个PE（如PE2）的站点切换到（C-S，C-G）的C-S树，则PE2将生成一个源树连接C-multicast路由，该路由指向位于C-S（如PE3）路径上的上游PE。PE3也使用MI-PMSI表示（C-S，C-G），正如PE1表示（C-*，C-G）。这导致{PE2，PE4，PE6}在C-RP树（来自PE1）和C-S树（来自PE3）上接收（C-S，C-G）的重复流量。如果希望抑制接收重复流量，则有必要为（C-S，C-G）选择单个转发器PE。下面介绍如何实现这一点。
When, as a result of receiving a Source Tree Join C-multicast route for (C-S,C-G) from some other PE the local PE adds either the S-PMSI or the I-PMSI to the outgoing interface list of the (C-S,C-G) state (see Section 11.3.1.1), the local PE MUST originate a Source Active A-D route if the PE has not originated such route already. The route carries a single MCAST-VPN NLRI constructed as follows:
当本地PE从某些其他PE接收到（C-S，C-G）的源树加入C-多播路由时，本地PE将S-PMSI或I-PMSI添加到（C-S，C-G）状态的传出接口列表中（参见第11.3.1.1节），如果PE尚未发起源活动a-D路由，则本地PE必须发起源活动a-D路由。该路由承载单个MCAST-VPN NLRI，其构造如下：
+ The RD in this NLRI is set to the RD of the VRF of the MVPN on the PE.
+ 此NLRI中的RD设置为PE上MVPN的VRF的RD。
+ The Multicast Source field MUST be set to C-S. The Multicast Source Length field is set appropriately to reflect this.
+ 多播源字段必须设置为C-S。多播源长度字段的设置适当反映了这一点。
+ The Multicast Group field MUST be set to C-G. The Multicast Group Length field is set appropriately to reflect this.
+ 多播组字段必须设置为C-G。多播组长度字段的设置应适当反映这一点。
The Next Hop field of the MP_REACH_NLRI attribute MUST be set to the IP address that the PE places in the Global Administrator field of the VRF Route Import Extended Community of the VPN-IP routes advertised by the PE from the MVPN's VRF.
MP_REACH_NLRI属性的下一个跃点字段必须设置为PE在VRF路由导入扩展社区的全局管理员字段中放置的IP地址，该扩展社区由PE从MVPN的VRF发布VPN-IP路由。
The route SHOULD carry the same set of Route Targets as the Intra-AS I-PMSI A-D route of the MVPN originated by the PE.
该路由应携带与PE发起的MVPN的帧内I-PMSI A-D路由相同的路由目标集。
Using the normal BGP procedures, the Source Active A-D route is propagated to all the PEs of the MVPN.
使用正常BGP程序，源活动A-D路由被传播到MVPN的所有PE。
Note that the advertisement of a Source Active A-D route for a given (C-S,C-G) could be combined, if desired, with the advertisement of an S-PMSI A-D route for the same (C-S,C-G). This is accomplished by using the same BGP Update message to carry both the NLRI of the S-PMSI A-D route and the NLRI of the Source Active A-D route.
注意，如果需要，可以将给定（C-S，C-G）的源活动a-D路由的通告与相同（C-S，C-G）的S-PMSI a-D路由的通告相结合。这是通过使用相同的BGP更新消息来携带S-PMSI A-D路由的NLRI和源活动A-D路由的NLRI来实现的。
Note that even if the originating PE advertises both the Source Active A-D route and the S-PMSI A-D route in the same BGP Update message, an implementation cannot assume that all other PEs will receive both of these routes in the same Update message.
注意，即使发起PE在同一BGP更新消息中播发源活动A-D路由和S-PMSI A-D路由，实现也不能假定所有其他PE将在同一更新消息中接收这两个路由。
When, as a result of receiving a withdrawal of the previously advertised Source Tree Join C-multicast route for (C-S,C-G), the PE is going to remove the S-PMSI/I-PMSI from the outgoing interface list of the (C-S,C-G) state. The local PE MUST also withdraw the Source Active A-D route for (C-S,C-G), if such a route has been advertised.
当作为接收到（C-S，C-G）的先前通告的源树加入C-多播路由的撤回的结果，PE将从（C-S，C-G）状态的传出接口列表中移除S-PMSI/I-PMSI。如果（C-S，C-G）的源活动A-D路由已公布，则本地PE还必须撤回该路由。
Note that if the PE is also acting as a C-RP, but inter-site shared trees are being used, the reception of a PIM Register message by the PE does not result in the origination of a Source Active A-D route.
注意，如果PE也充当C-RP，但正在使用站点间共享树，则PE接收PIM寄存器消息不会导致源活动a-D路由的发起。
When a PE receives a new Source Active A-D route from some other PE, the PE finds a VRF whose import Route Targets match one or more of the Route Targets carried by the route. If the match is found, then the PE updates the VRF with the received route.
当PE从其他PE接收到新的源活动a-D路由时，PE会找到一个VRF，其导入路由目标与路由携带的一个或多个路由目标匹配。如果找到匹配项，则PE使用接收到的路由更新VRF。
We say that a given (C-S,C-G) Source Active A-D route stored in a given VRF on a PE matches a given (C-*,C-G) entry present in the MVPN-TIB associated with the VRF if C-G carried by the route is the same as C-G of the entry, and the PE originates a Shared Tree Join C-multicast route for the same C-G as the C-G of the entry.
我们说，存储在PE上给定VRF中的给定（C-S，C-G）源活动a-D路由与MVPN-TIB中与VRF相关联的给定（C-*，C-G）条目相匹配，前提是该路由携带的C-G与该条目的C-G相同，并且PE为与该条目的C-G相同的C-G发起共享树连接C-multicast路由。
When (as a result of receiving PIM messages from one of its CEs) a PE creates in one of its MVPN-TIBs a (new) (C-*,C-G) entry with a non-empty outgoing interface list that contains one or more PE-CE interfaces, the PE MUST check if it has any matching Source Active A-D routes. If there is one or more such matching route, such that the PE does not have (C-S,C-G) state in its MVPN-TIB for (C-S,C-G) carried in the route, then the PE selects one of them (using the BGP route selection procedures), and sets up its forwarding path to receive (C-S,C-G) traffic from the tunnel that the originator of the selected Source Active A-D route uses for sending (C-S,C-G).
当（作为从其一个CE接收PIM消息的结果）PE在其一个MVPN TIB中创建一个（新）（C-*，C-G）条目，其中包含一个或多个PE-CE接口的非空传出接口列表时，PE必须检查是否有任何匹配的源活动a-D路由。如果存在一个或多个这样的匹配路由，使得PE在其MVPN-TIB中对于路由中携带的（C-S，C-G）不具有（C-S，C-G）状态，则PE选择其中一个（使用BGP路由选择过程），并设置其接收（C-S，C-G）的转发路径来自选定源活动A-D路由的发起者用于发送（C-S、C-G）的隧道的流量。
When, as a result of receiving a new Source Active A-D route, a PE updates its VRF with the route, the PE MUST check if the newly received route matches any (C-*,C-G) entries. If (a) there is a matching entry, (b) the PE does not have (C-S,C-G) state in its MVPN-TIB for (C-S,C-G) carried in the route, and (c) the received route is selected as the best (using the BGP route selection procedures), then the PE sets up its forwarding path to receive (C-S,C-G) traffic from the tunnel the originator of the selected Source Active A-D route uses for sending (C-S,C-G).
当收到新的源活动a-D路由后，PE用该路由更新其VRF时，PE必须检查新收到的路由是否匹配任何（C-*，C-G）条目。如果（a）存在匹配条目，（b）PE在其MVPN-TIB中没有（C-S，C-G）状态用于路由中携带的（C-S，C-G），并且（C）选择接收的路由作为最佳路由（使用BGP路由选择过程），则PE设置其接收的转发路径（C-S，C-G）来自所选源活动A-D路由的发起者用于发送（C-S、C-G）的隧道的流量。
Note that if the PE is also acting as a C-RP, and inter-site shared trees are being used, the BGP Source Active A-D routes do not replace the Multicast Source Discovery Protocol (MSDP) or PIM-based Anycast RP peerings among C-RPs that would be needed to disseminate source discovery information among C-RPs.
请注意，如果PE也充当C-RP，并且正在使用站点间共享树，则BGP源活动a-D路由不会取代C-RP之间的多播源发现协议（MSDP）或基于PIM的选播RP对等，而这是在C-RP之间传播源发现信息所需的。
In addition to the procedures in the previous section, a PE applies the following procedure when importing a Source Active A-D route for (C-S,C-G) into a VRF.
除上一节中的程序外，PE在将（C-S，C-G）的源激活a-D路由导入VRF时，还应用以下程序。
The PE finds a (C-*,C-G) entry in the MVPN-TIB whose C-G is the same as the C-G carried in the Multicast Group field of the Source Active A-D route.
PE在MVPN-TIB中找到一个（C-*，C-G）条目，该条目的C-G与源活动a-D路由的多播组字段中携带的C-G相同。
If the outgoing interface list (oif) for the found (C-*,C-G) entry in the MVPN-TIB on the PE contains either I-PMSI or S-PMSI, and the PE does not originate the Source Tree Join C-multicast route for (C-S,C-G) (where C-S is address carried in the Multicast Source field and C-G is the address carried in the Multicast Group field of the received Source Active A-D route), then the PE MUST transition the (C-S,C-G,rpt) downstream state machine on I-PMSI/S-PMSI to the Prune state. (Conceptually, the C-PIM state machine on the PE will act "as if" it had received Prune (C-S,C-G,rpt) on I-PMSI/S-PMSI, without
如果PE上MVPN-TIB中找到的（C-*，C-G）项的传出接口列表（oif）包含I-PMSI或S-PMSI，并且PE不发起（C-S，C-G）的源树加入C-多播路由（其中C-S是在多播源字段中携带的地址，C-G是在接收到的源活动A-D路由的多播组字段中携带的地址），则PE必须将I-PMSI/S-PMSI上的（C-S、C-G、rpt）下游状态机转换为Prune状态。（从概念上讲，PE上的C-PIM状态机将“好像”运行）它在I-PMSI/S-PMSI上收到了Prune（C-S，C-G，rpt），没有
actually having received one.) Depending on the (C-S,C-G,rpt) state of the PE-CE interfaces, this may result in the PE using PIM procedures to prune the C-S off the (C-*,C-G) tree.
根据PE-CE接口的（C-S、C-G、rpt）状态，这可能导致PE使用PIM过程从（C-*、C-G）树中删除C-S。
Transitioning the state machine to the Prune state SHOULD be done after a delay that is controlled by a timer. The value of the timer MUST be configurable. The purpose of this timer is to ensure that the C-S is not pruned off the shared tree until all PEs have had time to receive the Source Active A-D route for (C-S,C-G).
将状态机转换到Prune状态应该在计时器控制的延迟之后完成。计时器的值必须是可配置的。此计时器的目的是确保在所有PE都有时间接收（C-S，C-G）的源活动A-D路由之前，不会从共享树中删除C-S。
Note that before C-S is pruned off the shared tree, there is a possibility to have (C-S,C-G) packets sent at the same time on the PMSI by distinct PEs. This would result in a transient unnecessary traffic on the provider backbone. However, no duplicates will reach customer hosts subscribed to C-G as long as the downstream PEs apply procedures described in Section 9.1 of [MVPN].
注意，在从共享树上剪除C-S之前，有可能由不同的PE在PMSI上同时发送（C-S，C-G）数据包。这将导致提供程序主干上出现暂时的不必要流量。但是，只要下游PEs采用[MVPN]第9.1节所述的程序，订阅C-G的客户主机将不会收到任何副本。
The PE MUST keep the (C-S,C-G,rpt) downstream state machine on I-PMSI/S-PMSI in the Prune state for as long as (a) the outgoing interface list (oif) for the found (C-*,C-G) entry in the MVPN-TIB on the PE contains either I-PMSI or S-PMSI, (b) the PE has at least one Source Active A-D route for (C-S,C-G), and (c) the PE does not originate the Source Tree Join C-multicast route for (C-S,C-G). Once any of these conditions become no longer valid, the PE MUST transition the (C-S,C-G,rpt) downstream state machine on I-PMSI/S-PMSI to the NoInfo state.
PE必须将I-PMSI/S-PMSI上的（C-S，C-G，rpt）下游状态机保持在修剪状态，只要（a）PE上MVPN-TIB中找到的（C-*，C-G）项的传出接口列表（oif）包含I-PMSI或S-PMSI，（b）PE至少有一个源活动a-D路由用于（C-S，C-G）和（C）PE不为（C-S，C-G）发起源树加入C多播路由。一旦这些条件中的任何一个不再有效，PE必须将I-PMSI/S-PMSI上的（C-S、C-G、rpt）下游状态机转换为NoInfo状态。
Note that changing the state on the downstream state machine on I-PMSI/S-PMSI, as described above, does not imply exchanging PIM messages over I-PMSI/S-PMSI.
注意，如上所述，更改I-PMSI/S-PMSI上下游状态机的状态并不意味着通过I-PMSI/S-PMSI交换PIM消息。
Also, note that except for the scenario described in the third paragraph of this section, in all other scenarios relying solely on PIM procedures on the PE is sufficient to ensure the correct behavior when pruning sources off the shared tree.
另外，请注意，除了本节第三段中描述的场景外，在所有其他场景中，仅依赖PE上的PIM过程就足以确保在从共享树上修剪源时的正确行为。
The procedures defined in this section only apply when the C-multicast routing protocol is PIM [RFC4601]; moreover, only apply for the multicast ASM mode, and MUST NOT be applied to multicast group addresses belonging to the SSM range. The procedures also MUST NOT be applied when the C-multicast routing protocol is BIDIR-PIM [RFC5015].
本节中定义的程序仅适用于C-多播路由协议为PIM[RFC4601]时；此外，仅适用于多播ASM模式，不得应用于属于SSM范围的多播组地址。当C-多播路由协议为BIDIR-PIM[RFC5015]时，也不得应用该程序。
The procedures of this section are applicable only to MVPNs that do not use inter-site shared (i.e., rooted at a C-RP) C-trees.
本节程序仅适用于不使用站点间共享（即植根于C-RP）C树的MVPN。
These procedures are not applicable to MVPNs that use both shared and shortest path inter-site C-trees. See Section 13 for the procedures applicable to that scenario.
这些程序不适用于同时使用共享路径和最短路径站点间C树的MVPN。有关适用于该场景的程序，请参见第13节。
Whether or not a given MVPN uses inter-site shared C-trees must be known a priori (e.g., via provisioning).
给定的MVPN是否使用站点间共享的C树必须事先知道（例如，通过配置）。
A PE can obtain information about active multicast sources within a given MVPN in a variety of ways. One way is for the PE to act as a fully functional customer RP (C-RP) for that MVPN. Another way is to use PIM Anycast RP procedures [PIM-ANYCAST-RP] to convey information about active multicast sources from one or more of the MVPN C-RPs to the PE. Yet another way is to use MSDP [MSDP] to convey information about active multicast sources from the MVPN C-RPs to the PE.
PE可以通过多种方式获得关于给定MVPN内活动多播源的信息。一种方法是让PE充当该MVPN的全功能客户RP（C-RP）。另一种方法是使用PIM-Anycast-RP过程[PIM-Anycast-RP]将关于活动多播源的信息从一个或多个MVPN C-RP传送到PE。另一种方法是使用MSDP[MSDP]将有关活动多播源的信息从mvpnc-RPs传送到PE。
When a PE using any of the above methods first learns of a new (multicast) source within that MVPN, the PE constructs a Source Active A-D route and sends this route to all other PEs that have one or more sites of that MVPN connected to them. The route carries a single MCAST-VPN NLRI constructed as follows:
当使用上述任何方法的PE首先获悉该MVPN内的新（多播）源时，PE构造一个源活动a-D路由，并将该路由发送到具有该MVPN的一个或多个站点连接到它们的所有其他PE。该路由承载单个MCAST-VPN NLRI，其构造如下：
+ The RD in this NLRI is set to the RD of the VRF of the MVPN on the PE.
+ 此NLRI中的RD设置为PE上MVPN的VRF的RD。
+ The Multicast Source field MUST be set to the source IP address of the multicast data packet carried in the PIM Register message (RP/PIM register case) or of the MSDP Source-Active message (MSDP case). The Multicast Source Length field is set appropriately to reflect this.
+ 多播源字段必须设置为PIM注册消息（RP/PIM注册案例）或MSDP源活动消息（MSDP案例）中承载的多播数据包的源IP地址。多播源长度字段被适当设置以反映这一点。
+ The Multicast Group field MUST be set to the group IP address of the multicast data packet carried in the PIM Register message (RP/PIM register case) or of the MSDP Source-Active message (MSDP case). The Multicast Group Length field is set appropriately to reflect this.
+ 多播组字段必须设置为PIM注册消息（RP/PIM注册案例）或MSDP源活动消息（MSDP案例）中承载的多播数据包的组IP地址。多播组长度字段被适当设置以反映这一点。
The Next Hop field of the MP_REACH_NLRI attribute MUST be set to the IP address that the PE places in the Global Administrator field of the VRF Route Import Extended Community of the VPN-IP routes advertised by the PE.
MP_REACH_NLRI属性的下一个跃点字段必须设置为PE放置在PE播发的VPN-IP路由的VRF路由导入扩展社区的全局管理员字段中的IP地址。
The route SHOULD carry the same set of Route Targets as the Intra-AS I-PMSI A-D route of the MVPN originated by the PE.
该路由应携带与PE发起的MVPN的帧内I-PMSI A-D路由相同的路由目标集。
Using the normal BGP procedures, the Source Active A-D route is propagated to all the PEs of the MVPN.
使用正常BGP程序，源活动A-D路由被传播到MVPN的所有PE。
When a PE that previously advertised a Source Active A-D route for a given (multicast) source learns that the source is no longer active (the PE learns this by using the same mechanism by which the PE learned that the source was active), the PE SHOULD withdraw the previously advertised Source Active route.
当先前为给定（多播）源播发源活动a-D路由的PE得知该源不再活动时（PE通过使用PE得知该源活动的相同机制得知该消息），PE应撤回先前播发的源活动路由。
A PE follows the procedures specified in Section 11.1, except that the procedures specified in Section 11.1.1.2 are replaced with the procedures specified in this section.
PE遵循第11.1节规定的程序，但第11.1.1.2节规定的程序替换为本节规定的程序。
When a PE receives a new Source Active A-D route, the PE finds a VRF whose import Route Targets match one or more of the Route Targets carried by the route. If the match is found, then the PE updates the VRF with the received route.
当PE接收到一个新的源活动a-D路由时，PE会找到一个VRF，该VRF的导入路由目标与路由携带的一个或多个路由目标匹配。如果找到匹配项，则PE使用接收到的路由更新VRF。
We say that a given (C-S,C-G) Source Active A-D route stored in a given VRF matches a given (C-*,C-G) entry present in the MVPN-TIB associated with the VRF if C-G carried by the route is the same as C-G of the entry.
我们说，如果路由携带的C-G与条目的C-G相同，则存储在给定VRF中的给定（C-S，C-G）源活动a-D路由与MVPN-TIB中与VRF相关的给定（C-*，C-G）条目匹配。
When (as a result of receiving PIM messages from one of its CEs) a PE creates, in one of its MVPN-TIBs, a (new) (C-*,C-G) entry with a non-empty outgoing interface list that contains one or more PE-CE interfaces, the PE MUST check if it has any matching Source Active A-D routes. If there is one or more such matching routes, and the best path to C-S carried in the matching route(s) is reachable through some other PE, then for each such route the PE MUST originate a Source Tree Join C-multicast route. If there is one or more such matching routes, and the best path to C-S carried in the matching route(s) is reachable through a CE connected to the PE, then for each such route the PE MUST originate a PIM Join (C-S,C-G) towards the CE.
当（作为从其一个CE接收PIM消息的结果）PE在其一个MVPN TIB中创建一个（新）（C-*，C-G）条目，其中包含一个或多个PE-CE接口的非空传出接口列表时，PE必须检查是否有任何匹配的源活动a-D路由。如果存在一个或多个这样的匹配路由，并且匹配路由中携带的到C-S的最佳路径可以通过一些其他PE到达，那么对于每个这样的路由，PE必须发起一个源树连接C-多播路由。如果存在一个或多个这样的匹配路由，并且匹配路由中携带的到C-S的最佳路径可通过连接到PE的CE到达，则对于每个这样的路由，PE必须发起朝向CE的PIM连接（C-S，C-G）。
When, as a result of receiving a new Source Active A-D route, a PE updates its VRF with the route, the PE MUST check if the newly received route matches any (C-*,C-G) entries. If there is a matching entry, and the best path to C-S carried in the (A-D) route is reachable through some other PE, the PE MUST originate a Source Tree Join C-multicast route for the (C-S,C-G) carried by the route. If there is a matching entry, and the best path to C-S carried in the (A-D) route is reachable through a CE connected to the PE, the PE MUST originate a PIM Join (C-S,C-G) towards the CE.
当收到新的源活动a-D路由后，PE用该路由更新其VRF时，PE必须检查新收到的路由是否匹配任何（C-*，C-G）条目。如果存在匹配条目，并且（a-D）路由中携带的C-S的最佳路径可以通过其他PE到达，则PE必须为该路由携带的（C-S，C-G）发起源树加入C-多播路由。如果存在匹配条目，并且（a-D）路由中携带的C-S的最佳路径可通过连接到PE的CE到达，则PE必须向CE发起PIM连接（C-S，C-G）。
Construction and distribution of the Source Tree Join C-multicast route follows the procedures specified in Section 11.1.1.1, except that the Multicast Source Length, Multicast Source, Multicast Group
源树连接C-多播路由的构建和分发遵循第11.1.1.1节规定的程序，但多播源长度、多播源、多播组除外
Length, and Multicast Group fields in the MCAST-VPN NLRI of the Source Tree Join C-multicast route are copied from the corresponding field in the Source Active A-D route.
源树连接C多播路由的MCAST-VPN NLRI中的长度和多播组字段从源活动A-D路由中的相应字段复制。
A PE MUST withdraw a Source Tree Join C-multicast route for (C-S,C-G) if, as a result of having received PIM messages from one of its CEs, the PE creates a Prune (C-S,C-G,rpt) upstream state in one of its MVPN-TIBs but has no (C-S,C-G) Joined state in that MVPN-TIB and had previously advertised the said route. (This is even if the VRF associated with the MVPN-TIB still has a (C-S,C-G) Source Active A-D route.)
如果由于从其一个CE接收到PIM消息，PE在其一个MVPN TIB中创建了一个剪枝（C-S，C-G，rpt）上游状态，但在该MVPN-TIB中没有（C-S，C-G）连接状态，并且之前已经公布了所述路由，则PE必须撤回（C-S，C-G）的源树连接C-多播路由。（即使与MVPN-TIB相关联的VRF仍然具有（C-S、C-G）源激活a-D路由，这也是如此。）
A PE MUST withdraw a Source Tree Join C-multicast route for (C-S,C-G) if the Source Active A-D route that triggered the advertisement of the C-multicast route is withdrawn.
如果触发C多播路由播发的源活动A-D路由被撤回，则PE必须撤回（C-S，C-G）的源树加入C多播路由。
When a PE deletes the (C-*,C-G) state (e.g., due to receiving PIM Prune (C-*,C-G) from its CEs), the PE MUST withdraw all the Source Tree Join C-multicast routes for C-G that have been advertised by the PE, except for the routes for which the PE still maintains the corresponding (C-S,C-G) state.
当PE删除（C-*，C-G）状态（例如，由于从其CEs接收到PIM Prune（C-*，C-G））时，PE必须撤回所有已由PE播发的C-G源树加入C-多播路由，但PE仍保持相应（C-S，C-G）状态的路由除外。
Even though PIM is used as a C-multicast protocol, procedures described in Section 11.1.1.2 do not apply here, as only the Source Tree Join C-multicast routes are exchanged among PEs.
尽管PIM用作C-多播协议，但第11.1.1.2节中描述的程序在此不适用，因为PEs之间仅交换源树连接C-多播路由。
In this model, the only valid type of a C-multicast route that a PE could receive is a Source Tree Join C-multicast route. Processing of such a route follows the procedures specified in Section 11.3.1.1.
在该模型中，PE可以接收的唯一有效的C多播路由类型是源树连接C多播路由。此类路线的处理遵循第11.3.1.1节规定的程序。
A way to support the Carrier's Carrier model is provided by using mLDP as the CE-PE multicast routing and label distribution protocol, as specified in this document.
如本文件所述，通过使用mLDP作为CE-PE多播路由和标签分发协议，提供了一种支持运营商运营商模型的方法。
To improve scalability, it is RECOMMENDED that for the Carrier's Carrier scenario within an AS, all the S-PMSIs of a given MVPN be aggregated into a single P-multicast tree (by using upstream-assigned labels).
为了提高可伸缩性，建议对于AS中的运营商的运营商场景，将给定MVPN的所有s-PMSI聚合到单个P-多播树中（通过使用上游分配的标签）。
A PE should use Route Target Constraint [RT-CONSTRAIN] to advertise the Route Targets that the PE uses for the VRF Route Imports Extended Community (note that doing this requires just a single Route Target
PE应该使用路由目标约束[RT-Constraint]来公布PE用于VRF路由导入扩展社区的路由目标（注意，这样做只需要一个路由目标）
Constraint advertisement by the PE). This allows each C-multicast route to reach only the relevant PE, rather than all the PEs participating the an MVPN.
限制（由PE发布）。这允许每个C多播路由仅到达相关PE，而不是所有参与MVPN的PE。
To keep the intra-AS membership/binding information within the AS of the advertising router the BGP Update message originated by the advertising router SHOULD carry the NO_EXPORT Community [RFC1997].
为了将AS内部成员资格/绑定信息保留在广告路由器的AS内，广告路由器发出的BGP更新消息应携带NO_导出社区[RFC1997]。
An Inter-AS I-PMSI A-D route originated by an ASBR aggregates Intra-AS I-PMSI A-D routes originated within the ASBR's own AS. Thus, while the Intra-AS I-PMSI A-D routes originated within an AS are at the granularity of <PE, MVPN> within that AS, outside of that AS the (aggregated) Inter-AS I-PMSI A-D routes are at the granularity of <AS, MVPN>. An Inter-AS I-PMSI A-D route for a given <AS, MVPN> indicates the presence of one or more sites of the MVPN connected to the PEs of the AS.
ASBR发起的AS间I-PMSI A-D路由聚合ASBR自身AS内发起的AS内I-PMSI A-D路由。因此，虽然起源于AS内的AS内I-PMSI A-D路由在该AS内的粒度为<PE，MVPN>，但在该AS外（聚合的）AS间I-PMSI A-D路由的粒度为<AS，MVPN>。给定<AS，MVPN>的AS间I-PMSI A-D路由指示存在连接到AS的PEs的MVPN的一个或多个站点。
For a given inter-AS tunnel, each of its intra-AS segments could be constructed by its own mechanism. Moreover, by using upstream-assigned labels within a given AS, multiple intra-AS segments of different inter-AS tunnels of either the same or different MVPNs may share the same P-multicast tree.
对于给定的内部AS隧道，每个内部AS段都可以由其自身的机制构造。此外，通过在给定AS内使用上游分配的标签，相同或不同mvpn的不同AS间隧道的多个AS内段可以共享相同的P多播树。
Since (aggregated) Inter-AS I-PMSI A-D routes may have a granularity of <AS, MVPN>, an MVPN that is present in N ASes would have total of N inter-AS tunnels. Thus, for a given MVPN, the number of inter-AS tunnels is independent of the number of PEs that have this MVPN.
由于（聚合的）AS间I-PMSI A-D路由可能具有<AS，MVPN>的粒度，因此存在于N个AS中的MVPN将具有总共N个AS间隧道。因此，对于给定的MVPN，AS间隧道的数量与具有该MVPN的PE的数量无关。
Within each Autonomous System, BGP route reflectors can be partitioned among MVPNs present in that Autonomous System so that each partition carries routes for only a subset of the MVPNs supported by the service provider. Thus, no single route reflector is required to maintain routes for all MVPNs. Moreover, route reflectors used for MVPN do not have to be used for VPN-IP routes (although they may be used for VPN-IP routes as well).
在每个自治系统内，BGP路由反射器可以在该自治系统中存在的MVPN之间进行分区，以便每个分区仅承载服务提供商支持的MVPN的子集的路由。因此，不需要单路由反射器来维护所有MVPN的路由。此外，用于MVPN的路由反射器不必用于VPN-IP路由（尽管它们也可以用于VPN-IP路由）。
As described in Section 11.4, C-multicast routes for a given (S,G) of a given MVPN originated by PEs that are clients of a given route reflector are aggregated by the route reflector. Therefore, even if, within a route reflector cluster, there are multiple C-multicast routes for a given (S,G) of a given MVPN, outside of the cluster, all these routes are aggregated into a single C-multicast route. Additional aggregation of C-multicast routes occurs at ASBRs, where an ASBR aggregates all the received C-multicast routes for a given (S,G) of a given MVPN into a single C-multicast route. Moreover, both route reflectors and ASBRs maintain C-multicast routes only in the control plane, but not in the data plane.
如第11.4节所述，由作为给定路由反射器客户端的PEs发起的给定MVPN的给定（S，G）的C-多播路由由路由反射器聚合。因此，即使在路由反射器集群内，对于给定MVPN的给定（S，G）存在多个C-多播路由，在集群外，所有这些路由都聚合为单个C-多播路由。C-多播路由的附加聚合发生在ASBR，其中ASBR将给定MVPN的给定（S，G）的所有接收的C-多播路由聚合为单个C-多播路由。此外，路由反射器和ASBR都只在控制平面上维护C多播路由，而不在数据平面上维护。
The rate of C-multicast routing changes advertised by a PE is not necessarily directly proportional to the rate of multicast routing changes within the MVPN sites connected to the PE, as after the first (C-S,C-G) Join originated within a site, all the subsequent Joins for same (C-S,C-G) originated within the sites of the same MVPN connected to the PE do not cause origination of new C-multicast routes by the PE.
PE公布的C多播路由更改的速率不一定与连接到PE的MVPN站点内的多播路由更改的速率成正比，因为在站点内发起第一个（C-S，C-G）连接后，所有后续连接都是相同的（C-S，C-G）在连接到PE的同一MVPN的站点内发起不会导致PE发起新的C多播路由。
Depending on how multicast VPN is engineered, dynamic addition and removal of P2MP RSVP-TE leaves through advertisement/withdrawal of Leaf A-D routes will happen. Dampening techniques can be used to limit corresponding processing.
根据多播VPN的工程方式，将通过叶A-D路由的广告/撤回动态添加和移除P2MP RSVP-TE叶。阻尼技术可用于限制相应的处理。
To lessen the control plane overhead associated with the processing of C-multicast routes, this document proposes OPTIONAL route dampening procedures similar to what is described in [RFC2439]. The following OPTIONAL procedures can be enabled on a PE, ASBR, or BGP Route Reflector advertising or receiving C-multicast routes.
为了减少与C-多播路由处理相关的控制平面开销，本文件提出了与[RFC2439]中所述类似的可选路由抑制程序。可以在PE、ASBR或BGP路由上启用以下可选过程，以广告或接收C多播路由。
A PE/ASBR/route reflector can OPTIONALLY delay the advertisement of withdrawals of C-multicast routes. An implementation SHOULD provide the ability to control the delay via a configurable timer, possibly with some backoff algorithm to adapt the delay to multicast routing activity.
PE/ASBR/路由反射器可选择性地延迟C-多播路由的撤回的通告。一个实现应该能够通过一个可配置的计时器来控制延迟，可能还需要一些退避算法来调整延迟以适应多播路由活动。
Dampening of withdrawals of C-multicast routes does not impede the multicast Join latency observed by MVPN customers, and it also does not impede the multicast leave latency observed by a CE, as multicast forwarding from the VRF will stop as soon as C-multicast state is removed in the VRF.
抑制C-多播路由的退出不会妨碍MVPN客户观察到的多播加入延迟，也不会妨碍CE观察到的多播离开延迟，因为一旦在VRF中移除C-多播状态，来自VRF的多播转发就会停止。
The potential drawbacks of dampening of withdrawals of C-multicast routes are as follows:
抑制C-多播路由撤回的潜在缺点如下：
+ Until the withdrawals are actually sent, multicast traffic for the C-multicast routes in question will be continued to be transmitted to the PE, which will just have to discard it. Note that the PE may receive useless (multicast) traffic anyway, irrespective of dampening of withdrawals of C-multicast routes due to the use of I-PMSIs.
+ 在实际发送取款之前，所讨论的C-多播路由的多播流量将继续传输到PE，而PE将不得不丢弃它。注意，不管由于使用I-PMSIs而导致的C-multicast路由的撤回受到抑制，PE无论如何都可能接收无用的（多播）通信量。
+ Any state in the upstream PEs that would be removed as a result of processing the withdrawals will remain until the withdrawals are sent.
+ 上游PEs中因处理取款而被删除的任何状态将保留，直到取款被发送。
Discussion on whether the potential drawbacks mentioned above are of any practical significance is outside the scope of this document.
关于上述潜在缺陷是否具有实际意义的讨论超出了本文件的范围。
A PE/ASBR/route reflector can OPTIONALLY delay the advertisement of Source/Shared Tree Join C-multicast routes. An implementation SHOULD provide the ability to control the delay via a configurable timer, possibly with some backoff algorithm to adapt the delay to multicast routing activity.
PE/ASBR/路由反射器可以选择性地延迟源/共享树连接C多播路由的播发。一个实现应该能够通过一个可配置的计时器来控制延迟，可能还需要一些退避算法来调整延迟以适应多播路由活动。
Dampening Source/Shared Tree Join C-multicast routes will not impede multicast Join latency observed by a given MVPN, except if the PE advertising the Source/Shared Tree Join C-multicast route for a particular C-S/C-RP is the first to do so for all the sites of the MVPN that share the same upstream PE with respect to the C-S/C-RP.
抑制源/共享树连接C-多播路由不会妨碍给定MVPN观察到的多播连接延迟，除非为特定C-S/C-RP播发源/共享树连接C-多播路由的PE是第一个为MVPN中所有与C-S/C-RP共享相同上游PE的站点这样做的PE。
Similar to the procedures proposed above for withdrawal of C-multicast routes, dampening can be applied to the withdrawal of Leaf A-D routes.
与上面提出的退出C-多播路由的程序类似，阻尼可应用于叶A-D路由的退出。
The mechanisms described in this document could reuse the existing BGP security mechanisms [RFC4271] [RFC4272]. The security model and threats specific to Provider Provisioned VPNs, including L3VPNs, are discussed in [RFC4111]. [MVPN] discusses additional threats specific to the use of multicast in L3VPNs. There is currently work in progress to improve the security of TCP authentication. When the document is finalized as an RFC, the method defined in [RFC5925] SHOULD be used where authentication of BGP control packets is needed.
本文档中描述的机制可以重用现有的BGP安全机制[RFC4271][RFC4272]。[RFC4111]中讨论了特定于提供商提供的VPN（包括L3VPN）的安全模型和威胁。[MVPN]讨论了L3VPN中使用多播所特有的其他威胁。目前正在进行改进TCP身份验证安全性的工作。当文件最终确定为RFC时，需要验证BGP控制数据包时，应使用[RFC5925]中定义的方法。
A PE router MUST NOT accept, from CEs routes, with MCAST-VPN SAFI.
PE路由器不得从CEs路由接受MCAST-VPN SAFI。
If BGP is used as a CE-PE routing protocol, then when a PE receives a route from a CE, if this route carries the VRF Route Import Extended Community, the PE MUST remove this Community from the route before turning it into a VPN-IP route. Routes that a PE advertises to a CE MUST NOT carry the VRF Route Import Extended Community.
如果BGP用作CE-PE路由协议，则当PE从CE接收到路由时，如果该路由承载VRF路由导入扩展社区，则PE必须在将其转换为VPN-IP路由之前从路由中删除该社区。PE向CE发布广告的路线不得携带VRF路线导入扩展社区。
It is important to protect the control plane resources within the PE to prevent any one VPN from hogging excessive resources. This is the subject of the remainder of the Security Considerations section.
保护PE内的控制平面资源以防止任何一个VPN占用过多的资源非常重要。这是安全注意事项部分其余部分的主题。
When C-multicast routing information is exchanged among PEs using BGP, an implementation SHOULD provide the ability to rate limit BGP messages used for this exchange. This SHOULD be provided on a per-PE, per-MVPN granularity.
当使用BGP在PEs之间交换C多播路由信息时，实现应提供对用于此交换的BGP消息进行速率限制的能力。这应该在每个PE、每个MVPN粒度上提供。
An implementation SHOULD provide capabilities to impose an upper bound on the number of S-PMSI A-D routes, as well as on how frequently they may be originated. This SHOULD be provided on a per-PE, per-MVPN granularity.
实现应提供对S-PMSI A-D路由的数量以及它们可能发起的频率施加上限的能力。这应该在每个PE、每个MVPN粒度上提供。
In conjunction with the procedures specified in Section 14, an implementation SHOULD provide capabilities to impose an upper bound on the number of Source Active A-D routes, as well as on how frequently they may be originated. This SHOULD be provided on a per-PE, per-MVPN granularity.
结合第14节中规定的程序，实施应提供对源活动A-D路由的数量以及它们可能发起的频率施加上限的能力。这应该在每个PE、每个MVPN粒度上提供。
In conjunction with the procedures specified in Section 13 limiting the amount of (C-S,C-G) state would limit the amount of Source Active A-D route, as in the context of this section, Source Active A-D routes are created in response to Source Tree Join C-multicast routes, and Source Tree Join C-multicast routes are created as a result of creation of (C-S,C-G) state on PEs. However, to provide an extra level of robustness in the context of these procedures, an implementation MAY provide capabilities to impose an upper bound on the number of Source Active A-D routes, as well as on how frequently they may be originated. This MAY be provided on a per-PE, per-MVPN granularity.
结合第13节规定的程序，限制（C-S，C-G）状态的数量将限制源活动A-D路由的数量，如在本节上下文中，源活动A-D路由是响应源树加入C-多播路由而创建的，在PEs上创建（C-S，C-G）状态后，将创建源树连接C-多播路由。然而，为了在这些过程的上下文中提供额外级别的健壮性，实现可以提供对源活动A-D路由的数量以及它们可能发起的频率施加上限的能力。这可以在每个PE、每个MVPN粒度上提供。
Section 16.1.1 describes optional procedures for dampening withdrawals of C-multicast routes. It is RECOMMENDED that an implementation support such procedures.
第16.1.1节描述了抑制C-多播路由撤回的可选程序。建议执行机构支持此类程序。
Section 16.1.1 describes optional procedures for dampening withdrawals of Leaf A-D routes. It is RECOMMENDED that an implementation support such procedures.
第16.1.1节描述了抑制叶片A-D路线提取的可选程序。建议执行机构支持此类程序。
This document defines a new BGP Extended Community called "Source AS". This Community is of an extended type and is transitive. The Type value for this Community has been allocated from the two-octet AS-Specific Extended Community registry as 0x0009 and from the four-octet AS-Specific Extended Community registry as 0x0209.
本文档定义了一个名为“源AS”的新BGP扩展社区。此社区是扩展类型，并且是可传递的。此社区的类型值已从作为特定扩展社区注册表的两个八位字节（0x0009）和作为特定扩展社区注册表的四个八位字节（0x0209）中分配。
This document defines a new BGP Extended Community called "VRF Route Import" (Type value 0x010b). This Community is IP address specific, of an extended type, and is transitive.
本文档定义了一个新的BGP扩展社区，称为“VRF路由导入”（类型值0x010b）。此社区是特定于IP地址的扩展类型，并且是可传递的。
This document defines a new NLRI, called "MCAST-VPN", to be carried in BGP using multiprotocol extensions. It has been assigned SAFI 5. Also, SAFI 129 has been assigned to "Multicast for BGP/MPLS IP Virtual Private Networks (VPNs)".
本文档定义了一个新的NLRI，称为“MCAST-VPN”，将使用多协议扩展在BGP中进行。它已被指定为SAFI 5。此外，SAFI 129已分配给“BGP/MPLS IP虚拟专用网络（VPN）的多播”。
This document defines a new BGP optional transitive attribute, called "PMSI_TUNNEL". IANA has assigned the codepoint 22 in the "BGP Path Attributes" registry to the PMSI_TUNNEL attribute.
本文档定义了一个新的BGP可选传递属性，称为“PMSI_TUNNEL”。IANA已将“BGP路径属性”注册表中的代码点22分配给PMSI_隧道属性。
This document defines a new BGP optional transitive attribute, called "PE Distinguisher Labels". IANA has assigned the codepoint 27 in the "BGP Path Attributes" registry to the PE Distinguisher Labels attribute.
本文档定义了一个新的BGP可选传递属性，称为“PE识别标签”。IANA已将“BGP路径属性”注册表中的代码点27分配给PE识别器标签属性。
We would like to thank Chaitanya Kodeboniya for helpful discussions. We would also like to thank members of the L3VPN IETF Working Group for insightful comments and review.
我们要感谢柴坦尼亚-柯达博尼亚的有益讨论。我们还要感谢L3VPN IETF工作组的成员提出了富有洞察力的评论和评论。
[IANA-SAFI] IANA, "Subsequent Address Family Identifiers (SAFI) Parameters", http://www.iana.org.
[IANA-SAFI]IANA，“后续地址系列标识符（SAFI）参数”，http://www.iana.org.
[MVPN] Rosen, E., Ed. and R. Aggarwal, Ed., "Mulitcast in MPLS/BGP IP VPNs", RFC 6513, February 2012.
[MVPN]Rosen，E.，Ed.和R.Aggarwal，Ed.，“MPLS/BGP IP VPN中的多播”，RFC 6513，2012年2月。
[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。
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, February 2006.
[RFC4360]Sangli，S.，Tappan，D.和Y.Rekhter，“BGP扩展社区属性”，RFC 4360，2006年2月。
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, February 2006.
[RFC4364]Rosen，E.和Y.Rekhter，“BGP/MPLS IP虚拟专用网络（VPN）”，RFC 4364，2006年2月。
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC4601]Fenner，B.，Handley，M.，Holbrook，H.，和I.Kouvelas，“协议独立多播-稀疏模式（PIM-SM）：协议规范（修订版）”，RFC 46012006年8月。
[RFC4659] De Clercq, J., Ooms, D., Carugi, M., and F. Le Faucheur, "BGP-MPLS IP Virtual Private Network (VPN) Extension for IPv6 VPN", RFC 4659, September 2006.
[RFC4659]De Clercq，J.，Ooms，D.，Carugi，M.，和F.Le Faucheur，“用于IPv6 VPN的BGP-MPLS IP虚拟专用网络（VPN）扩展”，RFC 46592006年9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。
[mLDP] Wijnands, IJ., Ed., Minei, I., Ed., Kompella, K., and B. Thomas, "Label Distribution Protocol Extensions for Point-to-Multipoint and Multipoint-to-Multipoint Label Switched Paths", RFC 6388, November 2011.
[mLDP]Wijnands，IJ.，Ed.，Minei，I.，Ed.，Kompella，K.，和B.Thomas，“点对多点和多点对多点标签交换路径的标签分发协议扩展”，RFC 6388，2011年11月。
[MSDP] Fenner, B., Ed., and D. Meyer, Ed., "Multicast Source Discovery Protocol (MSDP)", RFC 3618, October 2003.
[MSDP]Fenner，B.，Ed.，和D.Meyer，Ed.，“多播源发现协议（MSDP）”，RFC 3618，2003年10月。
[PIM-ANYCAST-RP] Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol Independent Multicast (PIM)", RFC 4610, August 2006.
[PIM-ANYCAST-RP]Farinaci，D.和Y.Cai，“使用协议独立多播（PIM）的ANYCAST RP”，RFC 4610，2006年8月。
[RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream Label Assignment and Context-Specific Label Space", RFC 5331, August 2008.
[RFC5331]Aggarwal，R.，Rekhter，Y.，和E.Rosen，“MPLS上游标签分配和上下文特定标签空间”，RFC 53312008年8月。
[RT-CONSTRAIN] Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk, R., Patel, K., and J. Guichard, "Constrained Route Distribution for Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual Private Networks (VPNs)", RFC 4684, November 2006.
[RT-Constraint]Marques，P.，Bonica，R.，Fang，L.，Martini，L.，Raszuk，R.，Patel，K.，和J.Guichard，“边界网关协议/多协议标签交换（BGP/MPLS）互联网协议（IP）虚拟专用网络（VPN）的受限路由分布”，RFC 46842006年11月。
[RFC2439] Villamizar, C., Chandra, R., and R. Govindan, "BGP Route Flap Damping", RFC 2439, November 1998.
[RFC2439]Villamizar，C.，Chandra，R.，和R.Govindan，“BGP路线襟翼阻尼”，RFC 2439，1998年11月。
[RFC4111] Fang, L., Ed., "Security Framework for Provider-Provisioned Virtual Private Networks (PPVPNs)", RFC 4111, July 2005.
[RFC4111]Fang，L.，Ed.“提供商提供的虚拟专用网络（PPVPN）的安全框架”，RFC 4111，2005年7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。
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP", RFC 4607, August 2006.
[RFC4607]Holbrook，H.和B.Cain，“IP的源特定多播”，RFC4607，2006年8月。
[RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S. Yasukawa, Ed., "Extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for Point-to-Multipoint TE Label Switched Paths (LSPs)", RFC 4875, May 2007.
[RFC4875]Aggarwal，R.，Ed.，Papadimitriou，D.，Ed.，和S.Yasukawa，Ed.，“资源预留协议的扩展-点对多点TE标签交换路径（LSP）的流量工程（RSVP-TE）”，RFC 48752007年5月。
[RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano, "Bidirectional Protocol Independent Multicast (BIDIR-PIM)", RFC 5015, October 2007.
[RFC5015]Handley，M.，Kouvelas，I.，Speakman，T.，和L.Vicisano，“双向协议独立多播（BIDIR-PIM）”，RFC 50152007年10月。
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP Authentication Option", RFC 5925, June 2010.
[RFC5925]Touch，J.，Mankin，A.，和R.Bonica，“TCP认证选项”，RFC 59252010年6月。
Authors' Addresses
作者地址
Rahul Aggarwal Juniper Networks 1194 North Mathilda Ave. Sunnyvale, CA 94089 EMail: raggarwa_1@yahoo.com
Rahul Aggarwal Juniper Networks 1194 North Mathilda Ave.Sunnyvale，CA 94089电子邮件：raggarwa_1@yahoo.com
Eric C. Rosen Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA, 01719 EMail: erosen@cisco.com
Eric C.Rosen Cisco Systems，Inc.马萨诸塞州伯斯堡马萨诸塞大道1414号，邮编01719电子邮件：erosen@cisco.com
Thomas Morin France Telecom - Orange 2, avenue Pierre-Marzin 22307 Lannion Cedex France EMail: thomas.morin@orange.com
托马斯·莫林法国电信-皮埃尔·马津大街橙色2号22307兰尼昂·塞德克斯法国电子邮件：托马斯。morin@orange.com
Yakov Rekhter Juniper Networks 1194 North Mathilda Ave. Sunnyvale, CA 94089 EMail: yakov@juniper.net
Yakov Rekhter Juniper Networks 1194 North Mathilda Ave.Sunnyvale，CA 94089电子邮件：yakov@juniper.net