Internet Engineering Task Force (IETF) R. Key, Ed.
Request for Comments: 7152 S. Delord
Category: Informational Telstra
ISSN: 2070-1721 F. Jounay
Orange CH
L. Huang
China Mobile
Z. Liu
China Telecom
M. Paul
Deutsche Telekom
March 2014
Internet Engineering Task Force (IETF) R. Key, Ed.
Request for Comments: 7152 S. Delord
Category: Informational Telstra
ISSN: 2070-1721 F. Jounay
Orange CH
L. Huang
China Mobile
Z. Liu
China Telecom
M. Paul
Deutsche Telekom
March 2014
Requirements for Metro Ethernet Forum (MEF) Ethernet-Tree (E-Tree) Support in Layer 2 Virtual Private Network (L2VPN)
第2层虚拟专用网（L2VPN）中对城域以太网论坛（MEF）以太网树（E-Tree）支持的要求
Abstract
摘要
This document provides functional requirements for the support of Metro Ethernet Forum (MEF) Ethernet Tree (E-Tree) in multipoint Layer 2 Virtual Private Network solutions (referred to as simply "L2VPN"). It is intended that potential solutions will use these requirements as guidelines.
本文档提供了在多点第2层虚拟专用网络解决方案（简称“L2VPN”）中支持Metro Ethernet Forum（MEF）以太网树（E-Tree）的功能要求。预期潜在解决方案将使用这些要求作为指南。
Status of This Memo
关于下段备忘
This document is not an Internet Standards Track specification; it is published for informational purposes.
本文件不是互联网标准跟踪规范；它是为了提供信息而发布的。
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。并非IESG批准的所有文件都适用于任何级别的互联网标准；见RFC 5741第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7152.
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/rfc7152.
Copyright Notice
版权公告
Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2014 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 ....................................................3
1.1. Conventions Used in This Document ..........................3
2. IETF Multipoint Ethernet L2VPN Services .........................3
2.1. VPLS .......................................................3
2.2. Ethernet Virtual Private Network (E-VPN) ...................3
3. MEF Multipoint Ethernet Services ................................4
3.1. Similarities between E-LAN and E-Tree ......................4
3.2. Differences between E-LAN and E-Tree .......................4
3.3. E-Tree Use Cases ...........................................5
3.4. Generic E-Tree Service .....................................6
4. Problem Statement ...............................................6
4.1. Motivation .................................................6
4.2. Leaf-to-Leaf Communication Restriction .....................6
5. Requirements ....................................................7
5.1. Functional Requirements ....................................7
5.2. Applicability ..............................................8
5.3. Backward Compatibility .....................................8
5.4. External Network Network Interface (ENNI) ..................8
6. Security Considerations .........................................8
7. Contributors ....................................................8
8. Acknowledgements ................................................9
9. References ......................................................9
9.1. Normative References .......................................9
9.2. Informative References ....................................10
Appendix A. Frequently Asked Question .............................11
A.1. Are E-Tree Requirements Addressed in the Virtual
Private Multicast Service (VPMS) Requirements? ...............11
1. Introduction ....................................................3
1.1. Conventions Used in This Document ..........................3
2. IETF Multipoint Ethernet L2VPN Services .........................3
2.1. VPLS .......................................................3
2.2. Ethernet Virtual Private Network (E-VPN) ...................3
3. MEF Multipoint Ethernet Services ................................4
3.1. Similarities between E-LAN and E-Tree ......................4
3.2. Differences between E-LAN and E-Tree .......................4
3.3. E-Tree Use Cases ...........................................5
3.4. Generic E-Tree Service .....................................6
4. Problem Statement ...............................................6
4.1. Motivation .................................................6
4.2. Leaf-to-Leaf Communication Restriction .....................6
5. Requirements ....................................................7
5.1. Functional Requirements ....................................7
5.2. Applicability ..............................................8
5.3. Backward Compatibility .....................................8
5.4. External Network Network Interface (ENNI) ..................8
6. Security Considerations .........................................8
7. Contributors ....................................................8
8. Acknowledgements ................................................9
9. References ......................................................9
9.1. Normative References .......................................9
9.2. Informative References ....................................10
Appendix A. Frequently Asked Question .............................11
A.1. Are E-Tree Requirements Addressed in the Virtual
Private Multicast Service (VPMS) Requirements? ...............11
This document provides functional requirements for the support of Metro Ethernet Forum (MEF) Ethernet Tree (E-Tree) in multipoint Layer 2 Virtual Private Network solutions (referred to as simply "L2VPN"). It is intended that potential solutions will use these requirements as guidelines.
本文档提供了在多点第2层虚拟专用网络解决方案（简称“L2VPN”）中支持Metro Ethernet Forum（MEF）以太网树（E-Tree）的功能要求。预期潜在解决方案将使用这些要求作为指南。
A considerable number of service providers have adopted Virtual Private LAN Service (VPLS) to provide MEF Ethernet LAN (E-LAN) services to customers. Service providers currently need a simple and effective solution to emulate E-Tree services in addition to E-LAN services on their MPLS networks.
相当多的服务提供商已经采用虚拟专用LAN服务（VPLS）为客户提供MEF以太网LAN（E-LAN）服务。除了在MPLS网络上提供E-LAN服务外，服务提供商目前还需要一种简单有效的解决方案来模拟E-Tree服务。
Service providers also expect E-Tree support in any newly developed L2VPN technologies.
服务提供商还希望在任何新开发的L2VPN技术中支持E-Tree。
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。
VPLS [RFC4761] [RFC4762] is an L2VPN service that provides multipoint-to-multipoint connectivity for Ethernet across an IP or MPLS-enabled IP Packet Switched Network (IP/MPLS PSN). VPLS emulates the Ethernet VLAN functionality of traditional Ethernet networks. Thus, in VPLS, the customer Ethernet frame is transported over the IP/MPLS PSN from the ingress Provider Edge (PE) to the egress PE where the destination is connected based on the Ethernet frame destination Media Access Control (MAC) address in the context of the virtual switching instance (VSI) to which it belongs.
VPLS[RFC4761][RFC4762]是一种L2VPN服务，通过IP或支持MPLS的IP分组交换网络（IP/MPLS PSN）为以太网提供多点到多点连接。VPLS模拟传统以太网的以太网VLAN功能。因此，在VPLS中，客户以太网帧通过IP/MPLS PSN从入口提供商边缘（PE）传输到出口PE，其中目的地基于其所属的虚拟交换实例（VSI）上下文中的以太网帧目的地媒体访问控制（MAC）地址连接。
E-VPN is an enhanced L2 service that emulates an Ethernet VLAN across an IP/MPLS PSN, primarily targeted to support large scale L2VPNs with resiliency requirements not satisfied by other L2VPN solutions.
E-VPN是一种增强的二级服务，它跨IP/MPLS PSN模拟以太网VLAN，主要用于支持具有其他L2VPN解决方案无法满足的弹性要求的大规模L2VPN。
E-VPN is currently under development. Please refer to [EVPN].
E-VPN目前正在开发中。请参阅[EVPN]。
MEF has defined two multipoint Ethernet service types:
MEF定义了两种多点以太网服务类型：
- E-LAN (Ethernet LAN), multipoint-to-multipoint service - E-Tree (Ethernet Tree), rooted-multipoint service
- E-LAN（以太网LAN），多点对多点服务-E-Tree（以太网树），根多点服务
For the full specifications, please refer to [MEF6.1] and [MEF10.2].
有关完整规格，请参考[MEF6.1]和[MEF10.2]。
The following are the similarities between E-LAN and E-Tree services.
以下是E-LAN和E-Tree服务之间的相似之处。
- Data frame is an Ethernet frame. - Data forwarding is MAC-based forwarding. - A generic E-LAN/E-Tree service is always bidirectional in the sense that ingress frames can originate at any endpoint in the service.
- 数据帧是以太网帧。-数据转发是基于MAC的转发。-一般E-LAN/E-Tree服务始终是双向的，因为入口帧可以在服务中的任何端点处发起。
Within the context of a multipoint Ethernet service, each endpoint is designated as either a Root or a Leaf. A Root can communicate with all other endpoints in the same multipoint Ethernet service; however, a Leaf can only communicate with Roots but not Leaves.
在多点以太网服务的上下文中，每个端点被指定为根或叶。根节点可以与同一个多点以太网服务中的所有其他端点通信；然而，叶子只能与根沟通，而不能与叶沟通。
The only differences between E-LAN and E-Tree are:
E-LAN和E-Tree之间的唯一区别是：
- E-LAN has Root endpoints only, which implies there is no communication restriction between endpoints. - E-Tree has both Root and Leaf endpoints, which implies there is a need to enforce communication restriction between Leaf endpoints.
- E-LAN只有根端点，这意味着端点之间没有通信限制。-E-Tree同时具有根端点和叶端点，这意味着需要在叶端点之间实施通信限制。
Table 1 presents some major E-Tree use cases.
表1给出了一些主要的E-Tree用例。
+---------------------------+--------------+------------+
| Use Case | Root | Leaf |
+---+---------------------------+--------------+------------+
| 1 | Hub & Spoke VPN | Hub Site | Spoke Site |
+---+---------------------------+--------------+------------+
| 2 | Wholesale Access | Customer's | Customer's |
| | | Interconnect | Subscriber |
+---+---------------------------+--------------+------------+
| 3 | Mobile Backhaul | Radio Access | RAN Base |
| | | Network (RAN)| Station |
| | | Network | |
| | | Controller | |
+---+---------------------------+--------------+------------+
| 4 | IEEE 1588 PTPv2 | Precision | PTP Client |
| | Clock Synchronisation | Time Protocol| |
| | [IEEE1588] | (PTP) Server | |
+---+---------------------------+--------------+------------+
| 5 | Internet Access | Broadband | Subscriber |
| | [TR-101] | Network | |
| | | Gateway | |
+---+---------------------------+--------------+------------+
| 6 | Broadcast Video | Video Source | Subscriber |
| | (unidirectional only) | | |
+---+---------------------------+--------------+------------+
| 7 | Broadcast/Multicast Video | Video Source | Subscriber |
| | plus Control Channel | | |
+---+---------------------------+--------------+------------+
| 8 | Device Management | Management | Managed |
| | | System | Device |
+---+---------------------------+--------------+------------+
+---------------------------+--------------+------------+
| Use Case | Root | Leaf |
+---+---------------------------+--------------+------------+
| 1 | Hub & Spoke VPN | Hub Site | Spoke Site |
+---+---------------------------+--------------+------------+
| 2 | Wholesale Access | Customer's | Customer's |
| | | Interconnect | Subscriber |
+---+---------------------------+--------------+------------+
| 3 | Mobile Backhaul | Radio Access | RAN Base |
| | | Network (RAN)| Station |
| | | Network | |
| | | Controller | |
+---+---------------------------+--------------+------------+
| 4 | IEEE 1588 PTPv2 | Precision | PTP Client |
| | Clock Synchronisation | Time Protocol| |
| | [IEEE1588] | (PTP) Server | |
+---+---------------------------+--------------+------------+
| 5 | Internet Access | Broadband | Subscriber |
| | [TR-101] | Network | |
| | | Gateway | |
+---+---------------------------+--------------+------------+
| 6 | Broadcast Video | Video Source | Subscriber |
| | (unidirectional only) | | |
+---+---------------------------+--------------+------------+
| 7 | Broadcast/Multicast Video | Video Source | Subscriber |
| | plus Control Channel | | |
+---+---------------------------+--------------+------------+
| 8 | Device Management | Management | Managed |
| | | System | Device |
+---+---------------------------+--------------+------------+
Table 1: E-Tree Use Cases
表1：电子树用例
Common to all use cases, direct L2 Leaf-to-Leaf communication is not required or must be inhibited.
对于所有用例来说，直接L2叶到叶通信是不需要的，或者必须被禁止。
If direct L2 Leaf-to-Leaf communication is not allowed due to a security concern, then E-Tree should be used to prohibit communication between Leaf endpoints. Otherwise, E-LAN is also a feasible option.
如果出于安全考虑不允许直接L2叶到叶通信，则应使用E-Tree禁止叶端点之间的通信。否则，电子局域网也是一个可行的选择。
A generic E-Tree service supports multiple Root endpoints. The need for multiple Root endpoints is usually driven by a redundancy requirement. Whether a particular E-Tree service needs to support single or multiple Roots depends on the target application.
通用E-Tree服务支持多个根端点。对多个根端点的需求通常由冗余需求驱动。特定的E-Tree服务需要支持单个根还是多个根取决于目标应用程序。
A generic E-Tree service supports all the following traffic flows:
通用E-Tree服务支持以下所有流量：
- Ethernet Unicast from Root to Leaf - Ethernet Unicast from Leaf to Root - Ethernet Unicast from Root to Root - Ethernet Broadcast/Multicast from Root to other Roots and Leaves - Ethernet Broadcast/Multicast from Leaf to Roots
- 从根到叶的以太网单播-从叶到根的以太网单播-从根到根的以太网单播-从根到其他根和叶的以太网广播/多播-从叶到根的以太网广播/多播
A particular E-Tree service may need to support all the above or only a subset depending on the target application.
特定的E-Tree服务可能需要支持上述所有内容，或者仅支持一个子集，具体取决于目标应用程序。
L2VPN can be used to emulate MEF E-LAN service over an IP/MPLS PSN.
L2VPN可用于通过IP/MPLS PSN模拟MEF E-LAN服务。
Service providers also require E-Tree support in L2VPN.
服务提供商还需要L2VPN中的E-Tree支持。
In this section, VPLS is used to illustrate the problem; however, the same principle applies to other L2VPN technologies.
在本节中，VPLS用于说明问题；然而，同样的原理也适用于其他L2VPN技术。
VPLS treats all attachment circuits (ACs) equally (essentially as Roots, although they not classified into Root or Leaf) and provides any-to-any connectivity among all ACs. VPLS does not include any mechanism for communication restriction between specific ACs. Therefore, it is insufficient for emulating generic E-Tree service over an IP/MPLS PSN.
VPLS平等地对待所有连接电路（ACs）（本质上是根，尽管它们不分为根或叶），并提供所有ACs之间的任意对任意连接。VPLS不包括任何限制特定ACs之间通信的机制。因此，它不足以在IP/MPLS PSN上模拟通用E-Tree服务。
As an example of the problems not addressed in VPLS solutions, consider the scenario in Figure 1 where there are two PEs, each with a Root AC and a Leaf AC and where VPLS is used to emulate an E-Tree service interconnecting these ACs over an IP/MPLS PSN.
作为VPLS解决方案中未解决的问题的一个例子，考虑图1中的情况，其中有两个PES，每个都具有根AC和叶AC，其中VPLS用于模拟通过IP / MPLS PSN互连这些ACS的E-Trice服务。
<------------E-Tree------------>
+---------+ +---------+
| PE1 | | PE2 |
+---+ | +---+ | | +---+ | +---+
|CE1+-----AC1----+--+ | | | | +--+----AC3-----+CE3|
+---+ (Root AC) | | V | | Ethernet | | V | | (Root AC) +---+
| | S +--+-----PW-----+--+ S | |
+---+ | | I | | | | I | | +---+
|CE2+-----AC2----+--+ | | | | +--+----AC4-----+CE4|
+---+ (Leaf AC) | +---+ | | +---+ | (Leaf AC) +---+
+---------+ +---------+
<------------E-Tree------------>
+---------+ +---------+
| PE1 | | PE2 |
+---+ | +---+ | | +---+ | +---+
|CE1+-----AC1----+--+ | | | | +--+----AC3-----+CE3|
+---+ (Root AC) | | V | | Ethernet | | V | | (Root AC) +---+
| | S +--+-----PW-----+--+ S | |
+---+ | | I | | | | I | | +---+
|CE2+-----AC2----+--+ | | | | +--+----AC4-----+CE4|
+---+ (Leaf AC) | +---+ | | +---+ | (Leaf AC) +---+
+---------+ +---------+
Figure 1: Problem Scenario for Leaf-to-Leaf Communication Restriction
图1：叶到叶通信限制的问题场景
When PE2 receives a frame from PE1 via the Ethernet pseudowire (PW),
当PE2通过以太网伪线（PW）从PE1接收帧时，
- PE2 does not know which AC on PE1 is the ingress AC - PE2 does not know whether or not the ingress AC is a Leaf AC - PE2 does not have sufficient information to enforce the Leaf-to-Leaf communication restriction
- PE2不知道PE1上的哪个AC是入口AC-PE2不知道入口AC是否是叶AC-PE2没有足够的信息来实施叶到叶通信限制
Examples where the problems arise:
出现问题的例子：
- Customer Edge 2 (CE2) sends a Broadcast/Multicast Ethernet frame to PE1 via AC2 - CE2 sends a Unicast Ethernet frame to PE1 via AC2 with a destination MAC address corresponding to CE4's MAC address
- 客户边缘2（CE2）通过AC2向PE1发送广播/多播以太网帧-CE2通过AC2向PE1发送单播以太网帧，目标MAC地址对应于CE4的MAC地址
Note: Figure 1 is a hypothetical case solely used for explaining the problem; it is not meant to represent a typical E-Tree service.
注：图1是一个仅用于解释问题的假设案例；它并不代表典型的E-Tree服务。
There are some possible ways to get around this problem that do not require extensions to existing VPLS solutions, but they all come with significant design complexity or deployment constraints.
有一些可能的方法可以绕过这个问题，这些方法不需要扩展到现有的VPLS解决方案，但它们都具有显著的设计复杂性或部署限制。
The following are the E-Tree L2VPN functional requirements:
以下是E-Tree L2VPN的功能要求：
(1) A solution MUST prohibit communication between any two Leaf ACs in an L2VPN instance.
(1) 解决方案必须禁止L2VPN实例中任意两个叶ACs之间的通信。
(2) A solution MUST allow multiple Root ACs in an L2VPN instance.
(2) 解决方案必须允许L2VPN实例中存在多个根ACs。
(3) A solution MUST allow a Root AC and Leaf AC of an L2VPN instance to coexist on any PE.
(3) 解决方案必须允许L2VPN实例的根AC和叶AC在任何PE上共存。
A solution MUST identify the L2VPN technology ([RFC4761], [RFC4762], [EVPN]) to which the solution is applicable.
解决方案必须确定解决方案适用的L2VPN技术（[RFC4761]、[RFC4762]、[EVPN]）。
A solution SHOULD minimise the impact on VPLS and E-VPN L2VPN solutions, especially for the MEF E-LAN services already in operation.
解决方案应尽量减少对VPLS和E-VPN L2VPN解决方案的影响，尤其是对于已经运行的MEF E-LAN服务。
A solution SHOULD be backward compatible with the VPLS and E-VPN L2VPN solutions. It SHOULD allow a case where a common L2VPN instance is composed of both PEs supporting the solution and PEs not supporting it, and the Leaf-to-Leaf communication restriction is enforced within the scope of the compliant PEs.
解决方案应与VPLS和E-VPN L2VPN解决方案向后兼容。它应该允许一个公共L2VPN实例由支持该解决方案的PE和不支持该解决方案的PE组成，并且在兼容的PE的范围内强制执行叶到叶的通信限制。
A solution SHOULD support Root Operator Virtual Connection (OVC) End Point, Leaf OVC End Point and Trunk OVC End Point specified in [MEF26.1].
解决方案应支持[MEF26.1]中规定的根操作员虚拟连接（OVC）端点、叶OVC端点和主干OVC端点。
This document introduces a requirement of prohibiting communication between any two Leaf ACs in an L2VPN instance. In some use cases, such a requirement is imposed because of security reasons. Other than that, there are no additional security considerations beyond those already described in [RFC4761], [RFC4762], and [EVPN].
本文档介绍了在L2VPN实例中禁止任何两个叶ACs之间通信的要求。在某些用例中，由于安全原因而强制执行这样的要求。除此之外，除了[RFC4761]、[RFC4762]和[EVPN]中已经描述的安全注意事项外，没有其他安全注意事项。
Ruediger Kunze Deutsche Telekom Winterfeldtstr. 21-27 10781 Berlin, Germany EMail: ruediger.kunze@telekom.de
德国电信温特费尔德公司。21-27 10781德国柏林电子邮件：ruediger。kunze@telekom.de
Nick Del Regno Verizon 400 International Pkwy Richardson, TX 75081, USA EMail: nick.delregno@verizon.com
Nick Del Regno Verizon 400国际Pkwy Richardson，德克萨斯州75081，美国电子邮件：Nick。delregno@verizon.com
Josh Rogers Time Warner Cable 11921 N Mo Pac Expy Suite 210B Austin, TX 78759, USA EMail: josh.rogers@twcable.com
乔希·罗杰斯时代华纳有线电视11921 N Mo Pac Expy Suite 210B德克萨斯州奥斯汀78759美国电子邮件：乔希。rogers@twcable.com
The authors would like to thank Lizhong Jin, Lucy Yong, Yuji Kamite, and Wim Henderickx for their valuable input and support.
作者要感谢Jin Lizhong、Yong Lucy、Kamite Yuji和Wim Henderickx的宝贵投入和支持。
[MEF6.1] Metro Ethernet Forum, "Ethernet Services Definitions - Phase 2", Technical Specification MEF 6.1, April 2008, <http://metroethernetforum.org/Assets/ Technical_Specifications/PDF/MEF6-1.pdf>.
[MEF6.1]城域以太网论坛，“以太网服务定义-第2阶段”，技术规范MEF 6.12008年4月<http://metroethernetforum.org/Assets/ 技术规范/PDF/MEF6-1.PDF>。
[MEF10.2] Metro Ethernet Forum, "Ethernet Services Attributes Phase 2", Technical Specification MEF 10.2, October 2009, <http://metroethernetforum.org/Assets/ Technical_Specifications/PDF/MEF10.2.pdf>.
[MEF10.2]城域以太网论坛，“以太网服务属性第2阶段”，技术规范MEF 10.22009年10月<http://metroethernetforum.org/Assets/ 技术规范/PDF/MEF10.2.PDF>。
[MEF26.1] Metro Ethernet Forum, "External Network Network Interface (ENNI) Phase 2", Technical Specification, MEF 26.1, January 2012, <http://metroethernetforum.org/Assets/ Technical_Specifications/PDF/MEF_26.1.pdf>.
[MEF26.1]城域以太网论坛，“外部网络接口（ENNI）第2阶段”，技术规范，MEF 26.12012年1月<http://metroethernetforum.org/Assets/ 技术规范/PDF/MEF\U 26.1.PDF>。
[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。
[RFC4761] Kompella, K., Ed., and Y. Rekhter, Ed., "Virtual Private LAN Service (VPLS) Using BGP for Auto-Discovery and Signaling", RFC 4761, January 2007.
[RFC4761]Kompella，K.，Ed.，和Y.Rekhter，Ed.，“使用BGP进行自动发现和信令的虚拟专用LAN服务（VPLS）”，RFC 4761，2007年1月。
[RFC4762] Lasserre, M., Ed., and V. Kompella, Ed., "Virtual Private LAN Service (VPLS) Using Label Distribution Protocol (LDP) Signaling", RFC 4762, January 2007.
[RFC4762]Lasserre，M.，Ed.，和V.Kompella，Ed.，“使用标签分发协议（LDP）信令的虚拟专用LAN服务（VPLS）”，RFC 4762，2007年1月。
[EVPN] Sajassi, A., Aggarwal, R., Uttaro, J., Bitar, N., Henderickx, W., and A. Isaac, "Requirements for Ethernet VPN (EVPN)", Work in Progress, February 2014.
[EVPN]Sajassi，A.，Aggarwal，R.，Uttaro，J.，Bitar，N.，Henderickx，W.，和A.Isaac，“以太网VPN（EVPN）的要求”，正在进行的工作，2014年2月。
[IEEE1588] IEEE, "1588-2008 Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems", July 2008.
[IEEE1588]IEEE，“1588-2008网络测量和控制系统精密时钟同步协议标准”，2008年7月。
[TR-101] Broadband Forum, "Migration to Ethernet-Based DSL Aggregation", Technical Report, DSL Forum TR-101, April 2006, <http://www.broadband-forum.org/ technical/download/TR-101.pdf>.
[TR-101]宽带论坛，“迁移到基于以太网的DSL聚合”，技术报告，DSL论坛TR-101，2006年4月<http://www.broadband-forum.org/ 技术/下载/TR-101.pdf>。
[VPMS] Kamite, Y., Jounay, F., Niven-Jenkins, B., Brungard, D., and L. Jin, "Framework and Requirements for Virtual Private Multicast Service (VPMS)", Work in Progress, October 2012.
[VPMS]Kamite，Y.，Jounay，F.，Niven Jenkins，B.，Brungard，D.，和L.Jin，“虚拟专用多播服务（VPMS）的框架和要求”，正在进行的工作，2012年10月。
A.1. Are E-Tree Requirements Addressed in the Virtual Private Multicast Service (VPMS) Requirements?
A.1. 虚拟专用多播服务（VPMS）需求中是否解决了E-Tree需求？
VPMS requirements are defined in [VPMS].
VPMS要求在[VPMS]中定义。
The focus of VPMS is to provide point-to-multipoint connectivity.
VPMS的重点是提供点对多点连接。
VPMS provides single coverage of receiver membership (i.e., there is no distinct differentiation for multiple multicast groups). A VPMS service supports single or multiple Root ACs. All traffic from a Root AC will be forwarded to all Leaf ACs (i.e., Point-to-Multipoint (P2MP), from Root to all Leaves). The destination address in an Ethernet frame is not used in data forwarding. As an optional capability, a VPMS service may support reverse traffic from a Leaf AC to a Root AC (i.e., point-to-point (P2P), from Leaf to Root).
VPMS提供接收器成员的单一覆盖范围（即，对于多个多播组没有明显的区别）。VPMS服务支持单个或多个根ACs。来自根AC的所有流量将转发到所有叶AC（即点对多点（P2MP），从根到所有叶）。以太网帧中的目标地址不用于数据转发。作为可选功能，VPMS服务可支持从叶AC到根AC的反向流量（即，从叶到根的点对点（P2P））。
In contrast, the focus of MEF E-Tree is that a Leaf can only communicate with Roots, not Leaves.
相比之下，MEF E-Tree的重点是叶子只能与根沟通，而不能与叶沟通。
A generic MEF E-Tree service supports multiple Root endpoints. Whether a particular E-Tree service needs to support single or multiple Root endpoints depends on the target application.
通用MEF E-Tree服务支持多个根端点。特定的E-Tree服务是否需要支持单个或多个根端点取决于目标应用程序。
As discussion in a previous section, a generic MEF E-Tree service supports all the following traffic flows:
如前一节所述，通用MEF E-Tree服务支持以下所有流量：
- Ethernet Unicast bidirectional Root to/from Root - Ethernet Unicast bidirectional Root to/from Leaf - Ethernet Broadcast/Multicast unidirectional Root to all Roots and Leaves - Ethernet Broadcast/Multicast unidirectional Leaf to all Roots
- 以太网单播双向根到/从根-以太网单播双向根到/从叶-以太网广播/多播单向根到所有根和叶-以太网广播/多播单向叶到所有根
A particular E-Tree service may need to support all the above or only a subset depending on the target application.
特定的E-Tree服务可能需要支持上述所有内容，或者仅支持一个子集，具体取决于目标应用程序。
The IETF's VPMS definition and MEF's E-Tree definition are significantly different.
IETF的VPMS定义和MEF的E-Tree定义有很大不同。
VPMS may be acceptable in cases where E-Tree service is needed, such as in the following cases:
在需要E-Tree服务的情况下，例如在以下情况下，VPM是可以接受的：
- No Unicast traffic from Root destined for a specific Leaf (or there is no concern if such Unicast traffic is forwarded to all Leaves) - No traffic between Roots
- 没有来自根的单播通信流发送到特定的叶（或者如果这种单播通信流被转发到所有叶，则无需担心）-根之间没有通信
For generic E-Tree service, VPMS will not be able to meet the requirements.
对于通用E-Tree服务，VPMS将无法满足要求。
Authors' Addresses
作者地址
Raymond Key (editor)
雷蒙德·基（编辑）
EMail: raymond.key@ieee.org
EMail: raymond.key@ieee.org
Simon Delord Telstra
西蒙德洛德电信
EMail: simon.delord@gmail.com
EMail: simon.delord@gmail.com
Frederic Jounay Orange CH 4 rue caudray 1020 Renens Switzerland
Frederic Jounay Orange CH 4 caudray路1020瑞士雷南
EMail: frederic.jounay@orange.ch
EMail: frederic.jounay@orange.ch
Lu Huang China Mobile Unit 2, 28 Xuanwumenxi Ave, Xuanwu District Beijing 100053, China
中国移动北京市宣武区宣武门西大街28号路黄路2单元，邮编：100053
EMail: huanglu@chinamobile.com
EMail: huanglu@chinamobile.com
Zhihua Liu China Telecom 109 Zhongshan Ave., Guangzhou 510630, China
中国电信广州中山大道109号，邮编：510630
EMail: zhliu@gsta.com
EMail: zhliu@gsta.com
Manuel Paul Deutsche Telekom Winterfeldtstr. 21-27 10781 Berlin, Germany
Manuel Paul Deutsche Telekom Winterfeldtstr。21-27 10781德国柏林
EMail: manuel.paul@telekom.de
EMail: manuel.paul@telekom.de