Internet Engineering Task Force (IETF) A. Sajassi, Ed.
Request for Comments: 6136 Cisco
Category: Informational D. Mohan, Ed.
ISSN: 2070-1721 Nortel
March 2011
Internet Engineering Task Force (IETF) A. Sajassi, Ed.
Request for Comments: 6136 Cisco
Category: Informational D. Mohan, Ed.
ISSN: 2070-1721 Nortel
March 2011
Layer 2 Virtual Private Network (L2VPN) Operations, Administration, and Maintenance (OAM) Requirements and Framework
第2层虚拟专用网（L2VPN）操作、管理和维护（OAM）要求和框架
Abstract
摘要
This document provides framework and requirements for Layer 2 Virtual Private Network (L2VPN) Operations, Administration, and Maintenance (OAM). The OAM framework is intended to provide OAM layering across L2VPN services, pseudowires (PWs), and Packet Switched Network (PSN) tunnels. This document is intended to identify OAM requirements for L2VPN services, i.e., Virtual Private LAN Service (VPLS), Virtual Private Wire Service (VPWS), and IP-only LAN Service (IPLS). Furthermore, if L2VPN service OAM requirements impose specific requirements on PW OAM and/or PSN OAM, those specific PW and/or PSN OAM requirements are also identified.
本文档提供了第2层虚拟专用网络（L2VPN）操作、管理和维护（OAM）的框架和要求。OAM框架旨在跨L2VPN服务、伪线（PWs）和分组交换网络（PSN）隧道提供OAM分层。本文档旨在确定L2VPN服务的OAM要求，即虚拟专用LAN服务（VPLS）、虚拟专用有线服务（VPWS）和纯IP LAN服务（IPLS）。此外，如果L2VPN服务OAM要求对PW OAM和/或PSN OAM施加特定要求，则还将确定这些特定PW和/或PSN OAM要求。
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/rfc6136.
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/rfc6136.
Copyright Notice
版权公告
Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2011 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。
This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English.
本文件可能包含2008年11月10日之前发布或公开的IETF文件或IETF贡献中的材料。控制某些材料版权的人员可能未授予IETF信托允许在IETF标准流程之外修改此类材料的权利。在未从控制此类材料版权的人员处获得充分许可的情况下，不得在IETF标准流程之外修改本文件，也不得在IETF标准流程之外创建其衍生作品，除了将其格式化以RFC形式发布或将其翻译成英语以外的其他语言。
Table of Contents
目录
1. Introduction ....................................................4
1.1. Specification of Requirements ..............................6
1.2. Relationship with Other OAM Work ...........................6
2. Terminology .....................................................7
3. L2VPN Services and Networks .....................................7
4. L2VPN OAM Framework .............................................8
4.1. OAM Layering ...............................................8
4.2. OAM Domains ................................................9
4.3. MEPs and MIPs .............................................10
4.4. MEP and MIP Identifiers ...................................11
5. OAM Framework for VPLS .........................................11
5.1. VPLS as Service/Network ...................................11
5.1.1. VPLS as Bridged LAN Service ........................11
5.1.2. VPLS as a Network ..................................12
5.1.3. VPLS as (V)LAN Emulation ...........................12
5.2. VPLS OAM ..................................................13
5.2.1. VPLS OAM Layering ..................................13
5.2.2. VPLS OAM Domains ...................................14
5.2.3. VPLS MEPs and MIPs .................................15
5.2.4. VPLS MEP and MIP Identifiers .......................16
6. OAM Framework for VPWS .........................................17
6.1. VPWS as Service ...........................................17
6.2. VPWS OAM ..................................................18
6.2.1. VPWS OAM Layering ..................................18
6.2.2. VPWS OAM Domains ...................................19
6.2.3. VPWS MEPs and MIPs .................................21
6.2.4. VPWS MEP and MIP Identifiers .......................23
7. VPLS OAM Requirements ..........................................23
7.1. Discovery .................................................24
7.2. Connectivity Fault Management .............................24
7.2.1. Connectivity Fault Detection .......................24
7.2.2. Connectivity Fault Verification ....................24
7.2.3. Connectivity Fault Localization ....................24
7.2.4. Connectivity Fault Notification and Alarm
Suppression ........................................25
7.3. Frame Loss ................................................25
7.4. Frame Delay ...............................................25
7.5. Frame Delay Variation .....................................26
7.6. Availability ..............................................26
7.7. Data Path Forwarding ......................................26
7.8. Scalability ...............................................27
7.9. Extensibility .............................................27
7.10. Security .................................................27
7.11. Transport Independence ...................................28
7.12. Application Independence .................................28
1. Introduction ....................................................4
1.1. Specification of Requirements ..............................6
1.2. Relationship with Other OAM Work ...........................6
2. Terminology .....................................................7
3. L2VPN Services and Networks .....................................7
4. L2VPN OAM Framework .............................................8
4.1. OAM Layering ...............................................8
4.2. OAM Domains ................................................9
4.3. MEPs and MIPs .............................................10
4.4. MEP and MIP Identifiers ...................................11
5. OAM Framework for VPLS .........................................11
5.1. VPLS as Service/Network ...................................11
5.1.1. VPLS as Bridged LAN Service ........................11
5.1.2. VPLS as a Network ..................................12
5.1.3. VPLS as (V)LAN Emulation ...........................12
5.2. VPLS OAM ..................................................13
5.2.1. VPLS OAM Layering ..................................13
5.2.2. VPLS OAM Domains ...................................14
5.2.3. VPLS MEPs and MIPs .................................15
5.2.4. VPLS MEP and MIP Identifiers .......................16
6. OAM Framework for VPWS .........................................17
6.1. VPWS as Service ...........................................17
6.2. VPWS OAM ..................................................18
6.2.1. VPWS OAM Layering ..................................18
6.2.2. VPWS OAM Domains ...................................19
6.2.3. VPWS MEPs and MIPs .................................21
6.2.4. VPWS MEP and MIP Identifiers .......................23
7. VPLS OAM Requirements ..........................................23
7.1. Discovery .................................................24
7.2. Connectivity Fault Management .............................24
7.2.1. Connectivity Fault Detection .......................24
7.2.2. Connectivity Fault Verification ....................24
7.2.3. Connectivity Fault Localization ....................24
7.2.4. Connectivity Fault Notification and Alarm
Suppression ........................................25
7.3. Frame Loss ................................................25
7.4. Frame Delay ...............................................25
7.5. Frame Delay Variation .....................................26
7.6. Availability ..............................................26
7.7. Data Path Forwarding ......................................26
7.8. Scalability ...............................................27
7.9. Extensibility .............................................27
7.10. Security .................................................27
7.11. Transport Independence ...................................28
7.12. Application Independence .................................28
8. VPWS OAM Requirements ..........................................28
8.1. Discovery .................................................29
8.2. Connectivity Fault Management .............................29
8.2.1. Connectivity Fault Detection .......................29
8.2.2. Connectivity Fault Verification ....................29
8.2.3. Connectivity Fault Localization ....................29
8.2.4. Connectivity Fault Notification and Alarm
Suppression ........................................30
8.3. Frame Loss ................................................30
8.4. Frame Delay ...............................................30
8.5. Frame Delay Variation .....................................31
8.6. Availability ..............................................31
8.7. Data Path Forwarding ......................................32
8.8. Scalability ...............................................32
8.9. Extensibility .............................................32
8.10. Security .................................................32
8.11. Transport Independence ...................................33
8.12. Application Independence .................................33
8.13. Prioritization ...........................................34
9. VPLS (V)LAN Emulation OAM Requirements .........................34
9.1. Partial-Mesh of PWs .......................................34
9.2. PW Fault Recovery .........................................34
9.3. Connectivity Fault Notification and Alarm Suppression .....35
10. OAM Operational Scenarios .....................................35
10.1. VPLS OAM Operational Scenarios ...........................36
11. Security Considerations .......................................37
12. Contributors ..................................................38
13. Acknowledgements ..............................................38
14. References ....................................................38
14.1. Normative References .....................................38
14.2. Informative References ...................................39
Appendix A. Alternate Management Models ...........................41
A.1. Alternate Model 1 (Minimal OAM) ..............................41
A.2. Alternate Model 2 (Segment OAM Interworking) .................41
8. VPWS OAM Requirements ..........................................28
8.1. Discovery .................................................29
8.2. Connectivity Fault Management .............................29
8.2.1. Connectivity Fault Detection .......................29
8.2.2. Connectivity Fault Verification ....................29
8.2.3. Connectivity Fault Localization ....................29
8.2.4. Connectivity Fault Notification and Alarm
Suppression ........................................30
8.3. Frame Loss ................................................30
8.4. Frame Delay ...............................................30
8.5. Frame Delay Variation .....................................31
8.6. Availability ..............................................31
8.7. Data Path Forwarding ......................................32
8.8. Scalability ...............................................32
8.9. Extensibility .............................................32
8.10. Security .................................................32
8.11. Transport Independence ...................................33
8.12. Application Independence .................................33
8.13. Prioritization ...........................................34
9. VPLS (V)LAN Emulation OAM Requirements .........................34
9.1. Partial-Mesh of PWs .......................................34
9.2. PW Fault Recovery .........................................34
9.3. Connectivity Fault Notification and Alarm Suppression .....35
10. OAM Operational Scenarios .....................................35
10.1. VPLS OAM Operational Scenarios ...........................36
11. Security Considerations .......................................37
12. Contributors ..................................................38
13. Acknowledgements ..............................................38
14. References ....................................................38
14.1. Normative References .....................................38
14.2. Informative References ...................................39
Appendix A. Alternate Management Models ...........................41
A.1. Alternate Model 1 (Minimal OAM) ..............................41
A.2. Alternate Model 2 (Segment OAM Interworking) .................41
This document provides framework and requirements for Layer 2 Virtual Private Network (L2VPN) Operation, Administration, and Maintenance (OAM).
本文档提供了第2层虚拟专用网（L2VPN）操作、管理和维护（OAM）的框架和要求。
The scope of OAM for any service and/or transport/network infrastructure technologies can be very broad in nature. OSI has defined the following five generic functional areas commonly abbreviated as "FCAPS" [NM-Standards]: a) Fault Management, b) Configuration Management, c) Accounting Management, d) Performance Management, and e) Security Management.
任何服务和/或传输/网络基础设施技术的OAM范围在性质上都可能非常广泛。OSI定义了以下五个通用功能领域，通常缩写为“FCAPS”[NM标准]：a）故障管理，b）配置管理，c）记帐管理，d）性能管理，以及e）安全管理。
This document focuses on the Fault and Performance Management aspects. Other functional aspects of FCAPS are for further study.
本文档重点介绍故障和性能管理方面。FCAP的其他功能方面有待进一步研究。
Fault Management can typically be viewed in terms of the following categories:
故障管理通常可按以下类别查看：
- Fault Detection
- 故障检测
- Fault Verification
- 故障验证
- Fault Isolation
- 故障隔离
- Fault Notification and Alarm Suppression
- 故障通知和报警抑制
- Fault Recovery
- 故障恢复
Fault detection deals with mechanism(s) that can detect both hard failures, such as link and device failures, and soft failures, such as software failure, memory corruption, misconfiguration, etc. Typically, a lightweight protocol is desirable to detect the fault and thus it would be prudent to verify the fault via a fault verification mechanism before taking additional steps in isolating the fault. After verifying that a fault has occurred along the data path, it is important to be able to isolate the fault to the level of a given device or link. Therefore, a fault isolation mechanism is needed in Fault Management. A fault notification mechanism can be used in conjunction with a fault detection mechanism to notify the devices upstream and downstream to the fault detection point. For example, when there is a client/server relationship between two layered networks, fault detection at the server layer may result in the following fault notifications:
故障检测涉及能够检测硬故障（如链路和设备故障）和软故障（如软件故障、内存损坏、错误配置等）的机制。通常，轻量级协议有助于检测故障，因此在采取额外步骤隔离故障之前，通过故障验证机制验证故障是明智的。在验证沿数据路径发生故障后，必须能够将故障隔离到给定设备或链路的级别。因此，在故障管理中需要一种故障隔离机制。故障通知机制可与故障检测机制结合使用，以通知故障检测点上游和下游的设备。例如，当两层网络之间存在客户机/服务器关系时，服务器层的故障检测可能会导致以下故障通知：
- Sending a forward fault notification from the server layer to the client layer network(s) using the fault notification format appropriate to the client layer
- 使用适用于客户端层的故障通知格式，从服务器层向客户端层网络发送转发故障通知
- Sending a backward fault notification at the server layer, if applicable, in the reverse direction
- 在服务器层以相反方向发送向后故障通知（如果适用）
- Sending a backward fault notification at the client layer, if applicable, in the reverse direction
- 在客户端层以相反方向发送向后故障通知（如果适用）
Finally, fault recovery deals with recovering from the detected failure by switching to an alternate available data path using alternate devices or links (e.g., device redundancy or link redundancy).
最后，故障恢复处理通过使用备用设备或链路（例如，设备冗余或链路冗余）切换到备用可用数据路径来从检测到的故障中恢复。
Performance Management deals with mechanism(s) that allow determining and measuring the performance of the network/services under consideration. Performance Management can be used to verify the compliance to both the service-level and network-level metric objectives/specifications. Performance Management typically consists of measurement of performance metrics, e.g., Frame Loss, Frame Delay, Frame Delay Variation (aka Jitter), etc., across managed entities when the managed entities are in available state. Performance Management is suspended across unavailable managed entities.
性能管理涉及允许确定和测量所考虑的网络/服务性能的机制。性能管理可用于验证是否符合服务级别和网络级别的度量目标/规范。性能管理通常包括在受管实体处于可用状态时跨受管实体测量性能指标，例如帧丢失、帧延迟、帧延迟变化（aka Jitter）等。性能管理在不可用的受管实体之间暂停。
[L2VPN-FRWK] specifies three different types of Layer 2 VPN services: Virtual Private LAN Service (VPLS), (Virtual Private Wire Service (VPWS), and IP-only LAN Service (IPLS).
[L2VPN-FRWK]指定三种不同类型的第2层VPN服务：虚拟专用LAN服务（VPLS），（虚拟专用有线服务（VPWS）和仅限IP的LAN服务（IPLS）。
This document provides a reference model for OAM as it relates to L2VPN services and their associated pseudowires (PWs) and Public Switched Network (PSN) tunnels. OAM requirements for L2VPN services (e.g., VPLS and VPWS) are also identified. Furthermore, if L2VPN service OAM requirements impose requirements for PW and/or PSN OAM, those specific PW and/or PSN OAM requirements are also identified.
本文档为OAM提供了一个参考模型，因为它涉及L2VPN服务及其相关的伪线（PWs）和公共交换网络（PSN）隧道。还确定了L2VPN服务（如VPLS和VPWS）的OAM要求。此外，如果L2VPN服务OAM要求对PW和/或PSN OAM施加要求，则还将确定这些特定PW和/或PSN OAM要求。
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。
This document leverages protocols, mechanisms, and concepts defined as part of other OAM work, specifically the following:
本文档利用了其他OAM工作中定义的协议、机制和概念，具体如下：
- IEEE Std. 802.1ag-2007 [IEEE802.1ag] specifies the Ethernet Connectivity Fault Management protocol, which defines the concepts of Maintenance Domains, Maintenance End Points, and Maintenance Intermediate Points. This standard also defines mechanisms and procedures for proactive fault detection (Continuity Check), fault notification (Remote Defect Indication (RDI)), fault verification (Loopback), and fault isolation (LinkTrace) in Ethernet networks.
- IEEE标准802.1ag-2007[IEEE802.1ag]规定了以太网连接故障管理协议，该协议定义了维护域、维护端点和维护中间点的概念。本标准还定义了以太网中主动故障检测（连续性检查）、故障通知（远程缺陷指示（RDI））、故障验证（环回）和故障隔离（链路跟踪）的机制和程序。
- ITU-T Std. Y.1731 [Y.1731] builds upon and extends IEEE 802.1ag in the following areas: it defines fault notification and alarm suppression functions for Ethernet (via Alarm Indication Signal (AIS)). It also specifies messages and procedures for Ethernet performance management, including loss, delay, jitter, and throughput measurement.
- ITU-T Std.Y.1731[Y.1731]在以下领域建立并扩展了IEEE 802.1ag：它定义了以太网的故障通知和报警抑制功能（通过报警指示信号（AIS））。它还指定了以太网性能管理的消息和过程，包括丢失、延迟、抖动和吞吐量测量。
This document introduces and uses the following terms. This document also uses the terms defined in [L2VPN-FRWK] and [L2VPN-TERM].
本文件介绍并使用以下术语。本文件还使用了[L2VPN-FRWK]和[L2VPN-TERM]中定义的术语。
AIS Alarm Indication Signal
AIS报警指示信号
IPLS IP-only LAN Service
IPLS纯IP局域网服务
ME Maintenance Entity, which is defined in a given OAM domain and represents an entity requiring management
ME维护实体，在给定OAM域中定义，表示需要管理的实体
MEG Maintenance Entity Group, which represents MEs belonging to the same service instance and is also called Maintenance Association (MA)
MEG维护实体组，表示属于同一服务实例的MEs，也称为维护关联（MA）
MEP Maintenance End Point is responsible for origination and termination of OAM frames for a given MEG.
MEP维护端点负责给定MEG的OAM帧的发起和终止。
MIP Maintenance Intermediate Point is located between peer MEPs and can process and respond to certain OAM frames but does not initiate or terminate them.
MIP维护中间点位于对等MEP之间，可以处理和响应某些OAM帧，但不会启动或终止它们。
OAM Domain OAM Domain represents a region over which OAM frames can operate unobstructed.
OAM域OAM域表示OAM帧可以无障碍运行的区域。
QinQ 802.1Q tag inside another 802.1Q tag
QinQ 802.1Q标签位于另一个802.1Q标签内
RDI Remote Defect Indication
远程缺陷指示
VPLS Virtual Private LAN Service
虚拟专用局域网服务
VPWS Virtual Private Wire Service
虚拟专用线路服务
Figure 1 shows an L2VPN reference model as described in [L2VPN-REQ]. L2VPN A represents a point-to-point service while L2VPN B represents a bridged service.
图1显示了[L2VPN-REQ]中描述的L2VPN参考模型。L2VPN A表示点对点服务，而L2VPN B表示桥接服务。
+-----+ +-----+
+ CE1 +--+ +--| CE2 |
+-----+ | ..................... | +-----+
L2VPN A | +----+ +----+ | L2VPN A
+--| PE |-- Service --| PE |--+
+----+ Provider +----+
/ . Backbone . \ --------_
+-----+ / . | . \ / \ +-----+
+ CE4 +--+ . | . +-\ Access \--| CE5 |
+-----+ . +----+ . | Network | +-----+
L2VPN B ........| PE |....... \ / L2VPN B
+----+ ^ -------
| | logical
| | switching
+-----+ | instance
| CE3 |
+-----+
L2VPN B
+-----+ +-----+
+ CE1 +--+ +--| CE2 |
+-----+ | ..................... | +-----+
L2VPN A | +----+ +----+ | L2VPN A
+--| PE |-- Service --| PE |--+
+----+ Provider +----+
/ . Backbone . \ --------_
+-----+ / . | . \ / \ +-----+
+ CE4 +--+ . | . +-\ Access \--| CE5 |
+-----+ . +----+ . | Network | +-----+
L2VPN B ........| PE |....... \ / L2VPN B
+----+ ^ -------
| | logical
| | switching
+-----+ | instance
| CE3 |
+-----+
L2VPN B
Figure 1: L2VPN Reference Model
图1:L2VPN参考模型
[L2VPN-FRWK] specifies VPWS, VPLS, and IPLS. VPWS is a point-to-point service where Customer Edges (CEs) are presented with point-to-point virtual circuits. VPLS is a bridged LAN service provided to a set of CEs that are members of a VPN. CEs that are members of the same service instance communicate with each other as if they were connected via a bridged LAN. IPLS is a special VPLS that is used to carry only IP service packets.
[L2VPN-FRWK]指定VPW、VPL和IPL。VPWS是一种点对点服务，其中客户边缘（CE）通过点对点虚拟电路呈现。VPLS是一种桥接LAN服务，提供给作为VPN成员的一组CE。属于同一服务实例的CE彼此通信，就像它们通过桥接LAN连接一样。IPLS是一种特殊的VPLS，仅用于承载IP服务数据包。
[L2VPN-REQ] assumes the availability of runtime monitoring protocols while defining requirements for management interfaces. This document specifies the requirements and framework for operations, administration, and maintenance (OAM) protocols between network devices.
[L2VPN-REQ]假设运行时监控协议可用，同时定义管理接口的要求。本文件规定了网络设备之间的操作、管理和维护（OAM）协议的要求和框架。
The point-to-point or bridged LAN functionality is emulated by a network of Provider Edges (PEs) to which the CEs are connected. This network of PEs can belong to a single network operator or can span across multiple network operators. Furthermore, it can belong to a single service provider or can span across multiple service providers. A service provider is responsible for providing L2VPN services to its customers, whereas a network operator (aka facility provider) provides the necessary facilities to the service provider(s) in support of their services. A network operator and a
点到点或桥接LAN功能由连接CE的提供商边缘（PE）网络模拟。PEs网络可以属于单个网络运营商，也可以跨越多个网络运营商。此外，它可以属于单个服务提供商，也可以跨越多个服务提供商。服务提供商负责向其客户提供L2VPN服务，而网络运营商（也称为设施提供商）为服务提供商提供必要的设施以支持其服务。网络运营商和
service provider can be part of the same administrative organization, or they can belong to different administrative organizations.
服务提供者可以是同一管理组织的一部分，也可以属于不同的管理组织。
The different layers involved in realizing L2VPNs include service layers and network layers. Network layers can be iterative. In the context of L2VPNs, the service layer consists of VPLS, VPWS (e.g., Ethernet, ATM, FR, HDLC, SONET, point-to-point emulation, etc.), and IPLS. Similarly, in the context of L2VPNs, network layers consist of MPLS/IP networks. The MPLS/IP networks can consist of networks links realized by different technologies, e.g., SONET, Ethernet, ATM, etc.
实现L2VPN涉及的不同层包括服务层和网络层。网络层可以是迭代的。在L2VPN的上下文中，服务层由VPL、VPW（例如以太网、ATM、FR、HDLC、SONET、点对点仿真等）和IPL组成。类似地，在L2VPN的上下文中，网络层由MPLS/IP网络组成。MPLS/IP网络可以由不同技术实现的网络链路组成，例如SONET、以太网、ATM等。
Each layer is responsible for its own OAM. This document provides the OAM framework and requirements for L2VPN services and networks.
每个层负责自己的OAM。本文档提供了L2VPN服务和网络的OAM框架和要求。
When discussing OAM tools for L2VPNs, it is important to provide OAM capabilities and functionality over each domain for which a service provider or a network operator is responsible. It is also important that OAM frames not be allowed to enter/exit other domains. We define an OAM domain as a network region over which OAM frames operate unobstructed, as explained below.
在讨论L2VPN的OAM工具时，必须在服务提供商或网络运营商负责的每个域上提供OAM功能。同样重要的是，不允许OAM帧进入/退出其他域。我们将OAM域定义为OAM帧在其上畅通无阻地运行的网络区域，如下所述。
At the edge of an OAM domain, filtering constructs should prevent OAM frames from exiting and entering that domain. OAM domains can be nested but not overlapped. In other words, if there is a hierarchy of the OAM domains, the OAM frames of a higher-level domain pass transparently through the lower-level domains, but the OAM frames of a lower-level domain get blocked/filtered at the edge of that domain.
在OAM域的边缘，过滤构造应该防止OAM帧退出和进入该域。OAM域可以嵌套，但不能重叠。换句话说，如果存在OAM域的层次结构，则较高级别域的OAM帧透明地通过较低级别域，但是较低级别域的OAM帧在该域的边缘被阻塞/过滤。
In order to facilitate the processing of OAM frames, each OAM domain can be associated with the level at which it operates. Higher-level OAM domains can contain lower-level OAM domains, but the converse is not true. It may be noted that the higher-level domain does not necessarily mean a higher numerical value of the level encoding in the OAM frame.
为了促进OAM帧的处理，每个OAM域可以与其操作的级别相关联。较高级别的OAM域可以包含较低级别的OAM域，但情况并非如此。可以注意到，更高级别域不一定意味着OAM帧中的级别编码的更高数值。
A PE can be part of several OAM domains, with each interface belonging to the same or a different OAM domain. A PE, with an interface at the boundary of an OAM domain, shall block outgoing OAM frames, filter out incoming OAM frames whose domain level is lower or the same as the one configured on that interface, and pass through the OAM frames whose domain level is higher than the one configured on that interface.
PE可以是几个OAM域的一部分，每个接口都属于同一个或不同的OAM域。接口位于OAM域边界的PE应阻止传出OAM帧，过滤出域级别低于或等于该接口上配置的OAM帧的传入OAM帧，并通过域级别高于该接口上配置的OAM帧。
Generically, L2VPNs can be viewed as consisting of a customer OAM domain, a service provider OAM domain, and network operator OAM domains as depicted in Figure 2.
通常，L2VPN可以被视为由客户OAM域、服务提供商OAM域和网络运营商OAM域组成，如图2所示。
--- ---
/ \ ------ ------- ----- / \
| CE-- / \ / \ / \ --CE |
\ / \ / \ / \ / \ / \ /
--- --PE P P PE-- ---
\ / \ / \ /
\ / \ / \ /
------ ------- -----
--- ---
/ \ ------ ------- ----- / \
| CE-- / \ / \ / \ --CE |
\ / \ / \ / \ / \ / \ /
--- --PE P P PE-- ---
\ / \ / \ /
\ / \ / \ /
------ ------- -----
Customer OAM Domain
|<-------------------------------------------->|
Customer OAM Domain
|<-------------------------------------------->|
Service Provider OAM Domain
|<------------------------------>|
Service Provider OAM Domain
|<------------------------------>|
Operator Operator Operator
|<-------->|<--------->|<------->|
OAM Domain OAM Domain OAM Domain
Operator Operator Operator
|<-------->|<--------->|<------->|
OAM Domain OAM Domain OAM Domain
Figure 2: OAM Domains
图2:OAM域
The OAM Domains can be categorized as follows:
OAM域可分为以下几类：
- Hierarchical OAM Domains: Hierarchical OAM Domains result from OAM Layering and imply a contractual agreement among the OAM Domain owning entities. In Figure 2, the customer OAM domain, the service provider OAM domain, and the operator OAM domains are hierarchical.
- 层次OAM域：层次OAM域是OAM分层的结果，意味着OAM域拥有实体之间的契约协议。在图2中，客户OAM域、服务提供商OAM域和运营商OAM域是分层的。
- Adjacent OAM Domains: Adjacent OAM Domains are typically independent of each other and do not have any relationship among them. In Figure 2, the different operator OAM domains are independent of each other.
- 相邻OAM域：相邻OAM域通常相互独立，并且它们之间没有任何关系。在图2中，不同的运营商OAM域相互独立。
Maintenance End Points (MEPs) are responsible for origination and termination of OAM frames. MEPs are located at the edge of their corresponding OAM domains. Maintenance Intermediate Points (MIPs) are located within their corresponding OAM domains, and they normally pass OAM frames but never initiate them. Since MEPs are located at the edge of their OAM domains, they are responsible for filtering outbound OAM frames from leaving the OAM domain or inbound OAM frames from entering the OAM domain.
维护端点（MEP）负责发起和终止OAM帧。MEP位于其相应OAM域的边缘。维护中间点（MIP）位于其相应的OAM域内，它们通常通过OAM帧，但从不启动它们。由于MEP位于其OAM域的边缘，因此它们负责过滤出站OAM帧以防止其离开OAM域，或过滤入站OAM帧以防止其进入OAM域。
An OAM frame is generally associated with a Maintenance Entity Group (MEG), where a MEG consists of a set of Maintenance Entities (MEs)
OAM框架通常与维护实体组（MEG）相关联，其中MEG由一组维护实体（MEs）组成
associated with the same service instance. An ME is a point-to-point association between a pair of MEPs and represents a monitored entity. For example, in a VPLS that involves n CEs, all the MEs associated with the VPLS in the customer OAM domain (i.e., from CE to CE) can be considered to be part of a VPLS MEG, where the n-point MEG consists of a maximum of n(n-1)/2 MEs. MEPs and MIPs correspond to a PE, or, more specifically, to an interface of a PE. For example, an OAM frame can be said to originate from an ingress PE or more specifically an ingress interface of that PE. A MEP on a PE receives messages from n-1 other MEPs (some of them may reside on the same PE) for a given MEG.
与同一服务实例关联。ME是一对MEP之间的点对点关联，表示受监控的实体。例如，在涉及n个CE的VPLS中，与客户OAM域（即从CE到CE）中的VPLS相关联的所有MEs可被视为VPLS MEG的一部分，其中n点MEG最多由n（n-1）/2个MEs组成。MEP和MIP对应于PE，或者更具体地说，对应于PE的接口。例如，可以说OAM帧源自入口PE，或者更具体地说源自该PE的入口接口。PE上的MEP接收来自给定MEG的n-1个其他MEP（其中一些可能位于同一PE）的消息。
In Hierarchical OAM Domains, a MEP of lower-level OAM domain can correspond to a MIP or a MEP of a higher-level OAM domain. Furthermore, the MIPs of a lower-level OAM domain are always transparent to the higher-level OAM domain (e.g., OAM frames of a higher-level OAM domain are not seen by MIPs of a lower-level OAM domain and get passed through them transparently). Further, the MEs (or MEGs) are hierarchically organized in hierarchical OAM domains. For example, in a VPWS, the VPWS ME in the customer OAM domain can overlap with the Attachment Circuit (AC) ME, PW ME, and another AC ME in service provider OAM domain. Similarly, the PW ME can overlap with different ME in operator OAM domains.
在分层OAM域中，较低级别OAM域的MEP可以对应于较高级别OAM域的MIP或MEP。此外，较低级别OAM域的mip始终对较高级别OAM域透明（例如，较低级别OAM域的mip看不到较高级别OAM域的OAM帧，并且透明地通过它们）。此外，MEs（或meg）在分层OAM域中分层组织。例如，在VPWS中，客户OAM域中的VPWS ME可以与连接电路（AC）ME、PW ME以及服务提供商OAM域中的另一个AC ME重叠。类似地，PW ME可以与运营商OAM域中的不同ME重叠。
As mentioned previously, OAM at each layer should be independent of other layers, e.g., a service layer OAM should be independent of an underlying transport layer. MEPs and MIPs at each layer should be identified with layer-specific identifiers.
如前所述，每层的OAM应独立于其他层，例如，服务层OAM应独立于底层传输层。各层的MEP和MIP应使用特定于层的标识符进行标识。
Virtual Private LAN Service (VPLS) is used in different contexts, such as the following: a) as a bridged LAN service over networks, some of which are MPLS/IP, b) as an MPLS/IP network supporting these bridged LAN services, and c) as (V)LAN emulation.
虚拟专用LAN服务（VPLS）在不同的环境中使用，例如：a）作为网络上的桥接LAN服务，其中一些是MPLS/IP，b）作为支持这些桥接LAN服务的MPLS/IP网络，以及c）作为（V）LAN仿真。
The most common definition for VPLS is for bridged LAN service over an MPLS/IP network. The service coverage is considered end-to-end from UNI to UNI (or AC to AC) among the CE devices, and it provides a virtual LAN service to the attached CEs belonging to that service instance. The reason it is called bridged LAN service is because the VPLS-capable PE providing this end-to-end virtual LAN service is
VPLS最常见的定义是MPLS/IP网络上的桥接LAN服务。服务覆盖被认为是CE设备之间从UNI到UNI（或AC到AC）的端到端，并且它向属于该服务实例的连接的CE提供虚拟LAN服务。之所以称之为桥接LAN服务，是因为提供这种端到端虚拟LAN服务的支持VPLS的PE是
performing bridging functions (either full or a subset) as described in [L2VPN-FRWK]. This VPLS definition, as specified in [L2VPN-REQ], includes both bridge module and LAN emulation module (as specified in [L2VPN-FRWK]).
执行[L2VPN-FRWK]中所述的桥接功能（完整或子集）。[L2VPN-REQ]中规定的VPLS定义包括网桥模块和LAN仿真模块（如[L2VPN-FRWK]中规定）。
Throughout this document, whenever the term "VPLS" is used by itself, it refers to the service as opposed to network or LAN emulation.
在本文档中，无论何时使用术语“VPLS”，它都是指与网络或LAN仿真相反的服务。
A VPLS instance is also analogous to a VLAN provided by IEEE 802.1Q networks since each VLAN provides a Virtual LAN service to its Media Access Control (MAC) users. Therefore, when a part of the service provider network is Ethernet based (such as H-VPLS with QinQ access network), there is a one-to-one correspondence between a VPLS instance and its corresponding provider VLAN in the service provider Ethernet network. To check the end-to-end service integrity, the OAM mechanism needs to cover the end-to-end VPLS as defined in [L2VPN-REQ], which is from AC to AC, including bridge module, VPLS forwarder, and the associated PWs for this service. This document specifies the framework and requirements for such OAM mechanisms.
VPLS实例也类似于IEEE 802.1Q网络提供的VLAN，因为每个VLAN都向其媒体访问控制（MAC）用户提供虚拟LAN服务。因此，当服务提供商网络的一部分是基于以太网的（例如带有QinQ接入网络的H-VPLS）时，在服务提供商以太网中，VPLS实例与其对应的提供商VLAN之间存在一对一的对应关系。为了检查端到端服务的完整性，OAM机制需要覆盖[L2VPN-REQ]中定义的端到端VPL，即从AC到AC，包括网桥模块、VPL转发器以及此服务的相关PWs。本文件规定了此类OAM机制的框架和要求。
Sometimes VPLS is also used to refer to the underlying network that supports bridged LAN services. This network can be an end-to-end MPLS/IP network, as in H-VPLS with MPLS/IP access, or it can be a hybrid network consisting of MPLS/IP core and Ethernet access network, as in H-VPLS with QinQ access. In either case, the network consists of a set of VPLS-capable PE devices capable of performing bridging functions (either full or a subset). These VPLS-capable PE devices can be arranged in a certain topology, such as hierarchical topology, distributed topology, or some other topologies such as multi-tier or star topologies. To check the network integrity regardless of the network topology, network-level OAM mechanisms (such as OAM for MPLS/IP networks) are needed. The discussion of network-level OAM is outside of the scope of this document.
有时，VPLS还用于指代支持桥接LAN服务的底层网络。该网络可以是端到端MPLS/IP网络，如具有MPLS/IP访问的H-VPLS，也可以是由MPLS/IP核心和以太网访问网络组成的混合网络，如具有QinQ访问的H-VPLS。在任何一种情况下，网络都由一组能够执行桥接功能（完整或子集）的支持VPLS的PE设备组成。这些支持VPLS的PE设备可以布置在特定拓扑中，例如分层拓扑、分布式拓扑或一些其他拓扑，例如多层或星形拓扑。为了检查网络完整性，而不考虑网络拓扑，需要网络级OAM机制（例如MPLS/IP网络的OAM）。关于网络级OAM的讨论超出了本文档的范围。
Sometimes VPLS also refers to (V)LAN emulation. In this context, VPLS only refers to the full mesh of PWs with split horizon that emulates a LAN segment over a MPLS/IP network for a given service instance and its associated VPLS forwarder. Since the emulated LAN segment is presented as a Virtual LAN (VLAN) to the bridge module of a VPLS-capable PE, the emulated segment is also referred to as an emulated VLAN. The OAM mechanisms in this context refer primarily to integrity check of VPLS forwarders and their associated full mesh of
有时VPLS也指（V）LAN仿真。在此上下文中，VPLS仅指具有分割地平线的PWs的完整网格，该网格模拟给定服务实例及其相关VPLS转发器的MPLS/IP网络上的LAN段。由于仿真LAN段作为虚拟LAN（VLAN）呈现给支持VPLS的PE的网桥模块，因此仿真段也称为仿真VLAN。本文中的OAM机制主要指VPLS转发器的完整性检查及其相关的完整网格
PWs and the ability to detect and notify a partial mesh failure. This document also covers the OAM framework and requirements for such OAM mechanisms.
PWs以及检测和通知部分网格故障的能力。本文档还涵盖了OAM框架和此类OAM机制的要求。
When discussing the OAM mechanisms for VPLS, it is important to consider that the end-to-end service can span across different types of L2VPN networks. For example, the access network on one side can be a bridged network, e.g., [IEEE802.1ad], as described in Section 11 of [VPLS-LDP]. The access network can also be a [IEEE802.1ah]-based bridged network. The access network on the other side can be MPLS-based, as described in Section 10 of [VPLS-LDP], and the core network connecting them can be IP, MPLS, ATM, or SONET. Similarly, the VPLS instance can span across [VPLS-BGP] and distributed VPLS as described in [L2VPN-SIG].
在讨论VPLS的OAM机制时，重要的是考虑端到端服务可以跨越不同类型的L2VPN网络。例如，一侧的接入网络可以是桥接网络，例如[IEEE802.1ad]，如[VPLS-LDP]第11节所述。接入网络也可以是基于[IEEE802.1ah]的桥接网络。另一方的接入网络可以是基于MPLS的，如[VPLS-LDP]第10节所述，连接它们的核心网络可以是IP、MPLS、ATM或SONET。类似地，VPLS实例可以跨越[VPLS-BGP]和分布式VPLS，如[L2VPN-SIG]中所述。
Therefore, it is important that the OAM mechanisms can be applied to all these network types. Each such network may be associated with a separate administrative domain, and multiple such networks may be associated with a single administrative domain. It is important to ensure that the OAM mechanisms are independent of the underlying transport mechanisms and solely rely on VPLS, i.e., the transparency of OAM mechanisms must be ensured over underlying transport technologies such as MPLS, IP, etc.
因此，OAM机制可以应用于所有这些网络类型是很重要的。每个这样的网络可以与单独的管理域相关联，并且多个这样的网络可以与单个管理域相关联。重要的是要确保OAM机制独立于底层传输机制，并且完全依赖于VPL，即，必须通过底层传输技术（如MPLS、IP等）确保OAM机制的透明度。
This proposal is aligned with the discussions in other standard bodies and groups such as ITU-T Q.5/13, IEEE 802.1, and Metro Ethernet Forum (MEF), which address Ethernet network and service OAM.
该提案与其他标准机构和小组的讨论一致，如ITU-T Q.5/13、IEEE 802.1和城域以太网论坛（MEF），它们解决以太网网络和服务OAM问题。
Figure 3 shows an example of a VPLS (with two CEs belonging to customer A) across a service provider network marked by UPE and NPE devices. More CE devices belonging to the same customer A can be connected across different customer sites. The service provider network is segmented into a core network and two types of access networks. In Figure 3, (A) shows the bridged access network represented by its bridge components marked B and the MPLS access and core network represented by MPLS components marked P. In Figure 3, (B) shows the service/network view at the Ethernet MAC layer marked by E.
图3显示了一个跨由UPE和NPE设备标记的服务提供商网络的VPL示例（其中两个CE属于客户a）。可以跨不同的客户站点连接属于同一客户A的更多CE设备。服务提供商网络分为核心网络和两种类型的接入网络。在图3中，（A）显示了由标记为B的桥接组件表示的桥接接入网络和由标记为P的MPLS组件表示的MPLS接入和核心网络。在图3中，（B）显示了由E标记的以太网MAC层的服务/网络视图。
--- ---
/ \ ------ ------- ---- / \
| A CE-- / \ / \ / \ --CE A |
\ / \ / \ / \ / \ / \ /
--- --UPE NPE NPE UPE-- ---
\ / \ / \ /
\ / \ / \ /
------ ------- ----
--- ---
/ \ ------ ------- ---- / \
| A CE-- / \ / \ / \ --CE A |
\ / \ / \ / \ / \ / \ /
--- --UPE NPE NPE UPE-- ---
\ / \ / \ /
\ / \ / \ /
------ ------- ----
(A) CE----UPE--B--B--NPE---P--P---NPE---P----UPE----CE
(A) CE----UPE--B--B--NPE---P--P---NPE---P----UPE----CE
(B) E------E---E--E---E------------E----------E-----E
(B) E------E---E--E---E------------E----------E-----E
Figure 3: VPLS-Specific Device View
图3:VPLS特定设备视图
As shown in (B) of Figure 3, only the devices with Ethernet functionality are visible to OAM mechanisms operating at the Ethernet MAC layer, and the P devices are invisible. Therefore, the OAM along the path of P devices (e.g., between two PEs) is covered by the transport layer, and it is outside the scope of this document.
如图3的（B）所示，只有具有以太网功能的设备对在以太网MAC层运行的OAM机制可见，而P设备不可见。因此，沿P设备路径（例如，两个pe之间）的OAM由传输层覆盖，不在本文档的范围内。
However, VPLSs may impose some specific requirements on PSN OAM. This document aims to identify such requirements.
然而，VPLS可能会对PSN OAM施加一些特定的要求。本文件旨在确定此类要求。
As described in the previous section, a VPLS for a given customer can span across one or more service providers and network operators. Figure 4 depicts three OAM domains: (A) customer domain, which is among the CEs of a given customer, (B) service provider domain, which is among the edge PEs of the given service provider, and (C) network operator domain, which is among the PEs of a given operator.
如前一节所述，给定客户的VPL可以跨越一个或多个服务提供商和网络运营商。图4描述了三个OAM域：（A）客户域，它位于给定客户的CE中，（B）服务提供商域，它位于给定服务提供商的边缘PE中，以及（C）网络运营商域，它位于给定运营商的PE中。
--- ---
/ \ ------ ------- ---- / \
| CE-- / \ / \ / \ --CE |
\ / \ / \ / \ / \ / \ /
--- --UPE NPE NPE UPE-- ---
\ / \ / \ /
\ / \ / \ /
------ ------- ----
--- ---
/ \ ------ ------- ---- / \
| CE-- / \ / \ / \ --CE |
\ / \ / \ / \ / \ / \ /
--- --UPE NPE NPE UPE-- ---
\ / \ / \ /
\ / \ / \ /
------ ------- ----
Customer OAM Domain
(A) |<----------------------------------------------->|
Customer OAM Domain
(A) |<----------------------------------------------->|
Provider OAM Domain
(B) |<---------------------------------->|
Provider OAM Domain
(B) |<---------------------------------->|
Operator Operator Operator
(C) |<--------->|<---------->|<-------->|
OAM Domain OAM Domain OAM Domain
Operator Operator Operator
(C) |<--------->|<---------->|<-------->|
OAM Domain OAM Domain OAM Domain
Figure 4: VPLS OAM Domains
图4:VPLS OAM域
As shown in Figure 5, (C) represents those MEPs and MIPs that are visible within the customer domain. The MIPs associated with (C) are expected to be implemented in the bridge module/VPLS forwarder of a PE device, as per [L2VPN-FRWK]. (D) represents the MEPs and MIPs visible within the service provider domain. These MEPs and MIPs are expected to be implemented in the bridge module/VPLS forwarder of a PE device, as per [L2VPN-FRWK]. (E) represents the MEPs and MIPs visible within each operator domain, where MIPs only exist in an Ethernet access network (i.e., an MPLS access network does not have MIPs at the operator level). Further, (F) represents the MEPs and MIPs corresponding to the MPLS layer and may apply MPLS-based mechanisms. The MPLS layer shown in Figure 5 is just an example; specific OAM mechanisms are outside the scope of this document.
如图5所示，（C）表示在客户域中可见的MEP和MIP。根据[L2VPN-FRWK]，与（C）相关的MIPs预计将在PE设备的网桥模块/VPLS转发器中实现。（D） 表示服务提供商域中可见的MEP和MIP。根据[L2VPN-FRWK]，这些MEP和MIP预计将在PE设备的网桥模块/VPLS转发器中实现。（E） 表示每个运营商域中可见的MEP和MIP，其中MIP仅存在于以太网接入网络中（即，MPLS接入网络在运营商级别没有MIP）。此外，（F）表示对应于MPLS层的mep和mip，并且可以应用基于MPLS的机制。图5所示的MPLS层只是一个示例；特定的OAM机制不在本文档的范围内。
--- ---
/ \ ------ ------- ---- / \
| A CE-- / \ / \ / \ --CE A |
\ / \ / \ / \ / \ / \ /
--- --UPE NPE NPE UPE-- ---
\ / \ / \ /
\ / \ / \ /
------ ------- ----
--- ---
/ \ ------ ------- ---- / \
| A CE-- / \ / \ / \ --CE A |
\ / \ / \ / \ / \ / \ /
--- --UPE NPE NPE UPE-- ---
\ / \ / \ /
\ / \ / \ /
------ ------- ----
(A) CE----UPE--B-----NPE---P------NPE---P----UPE----CE
(B) E------E---E------E------------E----------E-----E
(A) CE----UPE--B-----NPE---P------NPE---P----UPE----CE
(B) E------E---E------E------------E----------E-----E
Customer OAM Domain
(C) MEP---MIP--------------------------------MIP---MEP
Customer OAM Domain
(C) MEP---MIP--------------------------------MIP---MEP
Provider OAM Domain
(D) MEP--------MIP-----------MIP-------MEP
Provider OAM Domain
(D) MEP--------MIP-----------MIP-------MEP
Operator Operator Operator
(E) MEP-MIP--MEP|MEP-------MEP|MEP-----MEP
OAM domain OAM domain OAM domain
Operator Operator Operator
(E) MEP-MIP--MEP|MEP-------MEP|MEP-----MEP
OAM domain OAM domain OAM domain
MPLS OAM MPLS OAM (F) MEP--MIP--MEP|MEP-MIP-MEP domain domain
MPLS OAM MPLS OAM（F）MEP--MIP--MEP | MEP-MIP-MEP域
Figure 5: VPLS OAM Domains, MEPs, and MIPs
图5:VPLS OAM域、MEP和MIPs
In VPLS, for the Ethernet MAC layer, the MEPs and MIPs should be identified with their Ethernet MAC addresses and Maintenance Entity Group Identifier (MEG ID). As described in [VPLS-LDP], a VPLS instance can be identified in an Ethernet domain (e.g., 802.1ad domain) using a VLAN tag (service tag) while in an MPLS/IP network, PW-ids are used. Both PW-ids and VLAN tags for a given VPLS instance are associated with a Service Identifier (e.g., VPN identifier). MEPs and MIPs Identifiers, i.e., MEP Ids and MIP Ids, must be unique within their corresponding Service Identifiers within the OAM domains.
在VPLS中，对于以太网MAC层，MEP和MIP应使用其以太网MAC地址和维护实体组标识符（MEG ID）进行标识。如[VPLS-LDP]中所述，当在MPLS/IP网络中使用PW ID时，可以使用VLAN标签（服务标签）在以太网域（例如802.1ad域）中识别VPLS实例。给定VPLS实例的PW ID和VLAN标记都与服务标识符（例如VPN标识符）关联。MEP和MIPs标识符，即MEP ID和MIP ID，在OAM域中的相应服务标识符中必须是唯一的。
For Ethernet services, e.g., VPLS, Ethernet frames are used for OAM frames, and the source MAC address of the OAM frames represent the source MEP in that domain for a specific MEG. For unicast Ethernet OAM frames, the destination MAC address represents the destination MEP in that domain for a specific MEG. For multicast Ethernet OAM frames, the destination MAC addresses correspond to all MEPs in that domain for a specific MEG.
对于以太网服务，例如VPL，以太网帧用于OAM帧，OAM帧的源MAC地址表示该域中特定MEG的源MEP。对于单播以太网OAM帧，目标MAC地址表示该域中特定MEG的目标MEP。对于多播以太网OAM帧，目标MAC地址对应于该域中特定MEG的所有MEP。
Figure 6 shows the VPWS reference model. VPWS is a point-to-point service where CEs are presented with point-to-point virtual circuits. VPWS is realized by combining a pair of Attachment Circuits (ACs) and a single PW between two PEs.
图6显示了VPWS参考模型。VPWS是一种点对点服务，其中CE提供点对点虚拟电路。VPWS通过在两个PE之间组合一对连接电路（ACs）和一个PW来实现。
|<------------- VPWS1 <AC11,PW1,AC12> ------------>|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC11---| |.......PW1........| |--AC12----| |
| CE1| |PE1 | | PE2| |CE2 |
| |---AC21---| |.......PW2........| |--AC22----| |
+----+ | |==================| | +----+
| +----+ PSN Tunnel +----+ |
| |
|<------------- VPWS2 <AC21,PW2,AC22> ------------>|
|<------------- VPWS1 <AC11,PW1,AC12> ------------>|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC11---| |.......PW1........| |--AC12----| |
| CE1| |PE1 | | PE2| |CE2 |
| |---AC21---| |.......PW2........| |--AC22----| |
+----+ | |==================| | +----+
| +----+ PSN Tunnel +----+ |
| |
|<------------- VPWS2 <AC21,PW2,AC22> ------------>|
Figure 6: VPWS Reference Model
图6:VPWS参考模型
VPWS can be categorized as follows:
VPW可分为以下几类：
- VPWS with homogeneous ACs (where both ACs are same type)
- 具有同质ACs的VPW（其中两个ACs的类型相同）
- VPWS with heterogeneous ACs (where the ACs are of different Layer-2 encapsulation)
- 具有异构ACs的VPW（其中ACs具有不同的第2层封装）
Further, the VPWS can itself be classified as follows:
此外，VPW本身可分类如下：
- Homogeneous VPWS (when two ACs and PW are of the same type)
- 同质VPW（当两个ACs和PW属于同一类型时）
- Heterogeneous VPWS (when at least one AC or PW is a different type than the others)
- 异构VPW（当至少一个AC或PW与其他类型不同时）
Based on the above classifications, the heterogeneous VPWS may have either homogeneous or heterogeneous ACs. On the other hand, homogeneous VPWS can have only homogeneous ACs.
基于上述分类，异构VPW可能具有同质或异质ACs。另一方面，同构VPW只能具有同构ACs。
Throughout this document, whenever the term "VPWS" is used by itself, it refers to the service.
在本文档中，只要术语“VPWS”本身被使用，它就指服务。
When discussing the OAM mechanisms for VPWS, it is important to consider that the end-to-end service can span across different types of networks. As an example, the access network between the CE and PE on one side can be an Ethernet-bridged network, an ATM network, etc. In common scenarios, it could simply be a point-to-point interface such as Ethernet Physical Layer (PHY). The core network connecting PEs can be IP, MPLS, etc.
在讨论VPWS的OAM机制时，重要的是考虑端到端服务可以跨越不同类型的网络。例如，一侧的CE和PE之间的接入网络可以是以太网桥接网络、ATM网络等。在常见场景中，它可以只是点对点接口，例如以太网物理层（PHY）。连接PEs的核心网络可以是IP、MPLS等。
Therefore, it is important that the OAM mechanisms can be applied to different network types, some of which are mentioned above. Each such network may be associated with a separate administrative domain, and multiple such networks may be associated with a single administrative domain.
因此，OAM机制可以应用于不同的网络类型，这一点很重要，上面已经提到了其中的一些网络类型。每个这样的网络可以与单独的管理域相关联，并且多个这样的网络可以与单个管理域相关联。
Figure 7 shows an example of a VPWS (with two CE devices belonging to customer A) across a service provider network marked by PE devices. The service provider network can be considered to be segmented into a core network and two types of access networks.
图7显示了跨由PE设备标记的服务提供商网络的VPWS（具有属于客户a的两个CE设备）的示例。服务提供商网络可被视为分为一个核心网络和两种类型的接入网络。
In the most general case, a PE can be client service aware when it processes client service PDUs and is responsible for encapsulating and de-encapsulating client service PDUs onto PWs and ACs. This is particularly relevant for homogeneous VPWS. The service-specific device view for such a deployment is highlighted by (A) in Figure 7, for these are the devices that are expected to be involved in end-to-end VPWS OAM.
在最一般的情况下，PE在处理客户机服务PDU时可以感知客户机服务，并负责将客户机服务PDU封装和解封到PWs和ACs上。这与同类VPW特别相关。图7中的（a）突出显示了此类部署的特定于服务的设备视图，因为这些设备预计将参与端到端VPWS OAM。
In other instances, a PE can be client service unaware when it does not process native service PDUs but instead encapsulates access technology PDUs over PWs. This may be relevant for VPWS with heterogeneous ACs, such as Ethernet VPWS, which is offered across an ATM AC, ATM PW, and Ethernet AC. In this case, the PE that is attached to ATM AC and ATM PW may be transparent to the client Ethernet service PDUs. On the other hand, the PE that is attached to ATM PW and Ethernet AC is expected to be client Ethernet service aware. The service-specific device view for such a deployment is highlighted by (B) in Figure 7, for these are the devices that are expected to be involved in end-to-end VPWS OAM, where PE1 is expected to be client service unaware.
在其他情况下，当PE不处理本机服务PDU，而是通过PWs封装访问技术PDU时，PE可能不知道客户端服务。这可能与具有异构ACs的VPW有关，例如通过ATM AC、ATM PW和以太网AC提供的以太网VPW。在这种情况下，连接到ATM AC和ATM PW的PE可能对客户端以太网服务PDU透明。另一方面，连接到ATM PW和Ethernet AC的PE应具有客户机以太网服务意识。图7中的（B）突出显示了此类部署的特定于服务的设备视图，因为这些设备预计将参与端到端的VPWS OAM，其中PE1预计是不知道客户端服务的。
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
access core access
|<---------->|<---------------------->|<------------>|
access core access
|<---------->|<---------------------->|<------------>|
(A) CE----------PE-----------------------PE-------------CE
(A) CE----------PE-----------------------PE-------------CE
(B) CE-----------------------------------PE-------------CE
(B) CE-----------------------------------PE-------------CE
Figure 7: VPWS-Specific Device View
图7：特定于VPWS的设备视图
As described in the previous section, a VPWS for a given customer can span across one or more network operators.
如前一节所述，给定客户的VPWS可以跨越一个或多个网络运营商。
Figures 8a and 8b depict three OAM domains: (A) customer domain, which is among the CEs of a given customer, (B) service provider domain, which depends on the management model, and (C) network operator domain, which is among the PEs of a given operator and could also be present in the access network if the ACs are provided by a different network operator. The core network operator may be responsible for managing the PSN Tunnel in these examples.
图8a和8b描述了三个OAM域：（A）客户域，它是给定客户的CE之一，（B）服务提供商域，它取决于管理模型，以及（C）网络运营商域，在给定运营商的PEs中，如果ACs由不同的网络运营商提供，也可能存在于接入网络中。在这些示例中，核心网络运营商可能负责管理PSN隧道。
For the first management model, shown in Figure 8a, the CEs are expected to be managed by the customer, and the customer is responsible for running end-to-end service OAM if needed. The service provider is responsible for monitoring the PW ME, and the monitoring of the AC is the shared responsibility of the customer and the service provider. In most simple cases, when the AC is realized across a physical interface that connects the CE to PE, the monitoring requirements across the AC ME are minimal.
对于第一个管理模型，如图8a所示，CEs预期由客户管理，如果需要，客户负责运行端到端服务OAM。服务提供商负责监控PW ME，AC的监控是客户和服务提供商的共同责任。在大多数简单的情况下，当AC通过连接CE和PE的物理接口实现时，AC ME的监控要求最低。
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
Customer OAM Domain
(A) |<------------------------------------------------->|
Customer OAM Domain
(A) |<------------------------------------------------->|
Service Provider OAM Domain
(B) |<--------------------------->|
Service Provider OAM Domain
(B) |<--------------------------->|
Operator OAM Domain
(C) |<---------------->|
Operator OAM Domain
(C) |<---------------->|
Figure 8a: VPWS OAM Domains - Management Model 1
图8a:VPWS OAM域-管理模型1
Figure 8b highlights another management model, where the CEs are managed by the service provider and where CEs and PEs are connected via an access network. The access network between the CEs and PEs may or may not be provided by a distinct network operator. In this model, the VPWS ME spans between the CEs in the service provider OAM domain, as shown by (B) in Figure 8b. The service provider OAM domain may additionally monitor the AC MEs and PW MEs individually, as shown by (C) in Figure 8b. The network operators may be responsible for managing the access service MEs (e.g., access tunnels) and core PSN Tunnel MEs, as shown by (D) in Figure 8b. The distinction between (C) and (D) in Figure 8b is that in (C), MEs have MEPs at CEs and at PEs and have no MIPs. While in (D), MEs have MEPs at CEs and at PEs; furthermore, MIPs may be present in between the MEPs, thereby providing visibility of the network to the operator.
图8b突出显示了另一种管理模式，其中CEs由服务提供商管理，CEs和PEs通过接入网络连接。CEs和PEs之间的接入网络可能由不同的网络运营商提供，也可能不由不同的网络运营商提供。在此模型中，VPWS ME跨越服务提供商OAM域中的CEs，如图8b中的（B）所示。服务提供商OAM域还可以单独监控AC MEs和PW MEs，如图8b中的（C）所示。网络运营商可能负责管理接入服务MEs（例如，接入隧道）和核心PSN隧道MEs，如图8b中的（D）所示。图8b中（C）和（D）之间的区别在于（C）中，MEs在CEs和PEs具有MEP，并且没有MIP。而在（D）中，MEs在CEs和PEs有MEP；此外，mip可以存在于mep之间，从而向运营商提供网络的可视性。
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
Customer OAM Domain
(A) |<-------------------------------------------------->|
Customer OAM Domain
(A) |<-------------------------------------------------->|
Service Provider (SP) OAM Domain
(B) |<------------------------------------------------>|
Service Provider (SP) OAM Domain
(B) |<------------------------------------------------>|
SP OAM SP OAM SP OAM
(C) |<--------->|<----------------------->|<---------->|
Domain Domain Domain
SP OAM SP OAM SP OAM
(C) |<--------->|<----------------------->|<---------->|
Domain Domain Domain
Operator Operator Operator
(D) |<--------->|<----------------------->|<---------->|
OAM Domain OAM Domain OAM Domain
Operator Operator Operator
(D) |<--------->|<----------------------->|<---------->|
OAM Domain OAM Domain OAM Domain
Figure 8b: VPWS OAM Domains - Management Model 2
图8b:VPWS OAM域-管理模型2
Note: It may be noted that unlike VPLS OAM Domain in Figure 4, where multiple operator domains may occur between the User-facing PE (U-PE) devices, VPWS OAM domain in Figures 8a and 8b highlights a single operator domain between PE devices. This is since, unlike the distributed VPLS PE case (D-VPLS), where VPLS-aware U-PEs and Network-facing PEs (N-PEs) may be used to realize a distributed PE, the VPWS has no such distributed PE model. If the PSN involves multiple operator domains, resulting in a Multi-segment PW [MS-PW-Arch], VPWS OAM Domains remain unchanged since switched PEs are typically not aware of native service.
注意：可能需要注意的是，与图4中的VPLS OAM域不同，图4中的VPLS OAM域可能出现在面向用户的PE（U-PE）设备之间，图8a和8b中的VPWS OAM域突出显示了PE设备之间的单个操作员域。这是因为，与分布式VPLS PE案例（D-VPLS）不同，在分布式VPLS PE案例中，VPLS感知的U-PE和面向网络的PE（N-PE）可用于实现分布式PE，VPWS没有此类分布式PE模型。如果PSN涉及多个运营商域，导致多段PW[MS PW Arch]，VPWS OAM域保持不变，因为交换的PE通常不知道本机服务。
The location of MEPs and MIPs can be based upon the management model used in the VPWS scenarios. The interest remains in being able to monitor end-to-end service and also support segment monitoring in the network to allow isolation of faults to specific areas within the network.
MEP和MIP的位置可以基于VPWS场景中使用的管理模型。人们的兴趣仍然在于能够监控端到端服务，并支持网络中的段监控，以便将故障隔离到网络中的特定区域。
The end-to-end service monitoring is provided by an end-to-end ME, and additional segment OAM monitoring is provided by segment MEs, all in the service provider OAM domain. The end-to-end MEs and segment MEs are hierarchically organized as mentioned in Section 4.2 for hierarchical OAM domains. This is shown in (B) and (C) in Figure 8b.
端到端服务监控由端到端ME提供，额外的段OAM监控由段MEs提供，所有这些都在服务提供商OAM域中。端到端MEs和段MEs按照第4.2节中提到的分层OAM域进行分层组织。这如图8b中的（B）和（C）所示。
The CE interfaces support MEPs at the end-to-end service provider OAM level for VPWS as an end-to-end service as shown in (B1) and (B2) in Figure 9. In addition, PE interfaces may support MIPs at the end-to-end service provider OAM level when PEs are client service aware, as shown in (B2) in Figure 9. As an example, if one considers an end-to-end Ethernet line service offered using ATM transport (ATM over MPLS PW), then the PEs are considered to be Ethernet service unaware and therefore cannot support any Ethernet MIPs. (B1) in Figure 9 represents this particular situation. Of course, another view of the end-to-end service can be ATM, in which case PE1 and PE2 can be considered to be service aware and therefore support ATM MIPs. (B2) in Figure 9 represents this particular situation.
CE接口支持VPWS的端到端服务提供商OAM级别的MEP作为端到端服务，如图9中的（B1）和（B2）所示。此外，当PE支持客户端服务时，PE接口可以在端到端服务提供商OAM级别支持MIPs，如图9中的（B2）所示。例如，如果考虑使用ATM传输（ATM over MPLS PW）提供的端到端以太网线路服务，则PEs被视为不知道以太网服务，因此不能支持任何以太网MIP。图9中的（B1）表示这种特殊情况。当然，端到端服务的另一个视图可以是ATM，在这种情况下，PE1和PE2可以被认为是服务感知的，因此支持ATM MIPs。图9中的（B2）表示这种特殊情况。
In addition, CEs and PE interfaces support MEPs at a segment (lower level) service provider OAM level for AC and PW MEs, and no MIPs are involved at this segment service provider OAM level, as shown in (C) in Figure 9. Operators may also run segment OAM by having MEPs at network operator OAM level, as shown in (D) in Figure 9.
此外，CEs和PE接口支持AC和PW MEs的段（较低级别）服务提供商OAM级别的MEP，该段服务提供商OAM级别不涉及MIP，如图9（C）所示。运营商也可以通过网络运营商OAM级别的MEP来运行段OAM，如图9中的（D）所示。
The advantage of having layered OAM is that end-to-end and segment OAM can be carried out in an independent manner. It is also possible to carry out some optimizations, e.g., when proactive segment OAM monitoring is performed, proactive end-to-end monitoring may not be needed since client layer end-to-end ME could simply use fault notifications from the server layer segment MEs.
具有分层OAM的优点是可以以独立的方式执行端到端和段OAM。还可以执行一些优化，例如，当执行主动段OAM监控时，可能不需要主动端到端监控，因为客户端层端到端ME可以简单地使用来自服务器层段ME的故障通知。
Although many different OAM layers are possible, as shown in Figure 9, not all may be realized. For example, (B2) and (D) in Figure 9 may be adequate in some cases.
尽管许多不同的OAM层是可能的，如图9所示，但并非所有的都可以实现。例如，图9中的（B2）和（D）在某些情况下可能足够。
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
(B1) MEP-----------------------------------------------MEP
(B2) MEP----------MIP---------------------MIP----------MEP
(C) MEP-------MEP|MEP------------------MEP|MEP--------MEP
(D) MEP-------MEP|MEP------------------MEP|MEP--------MEP
(B1) MEP-----------------------------------------------MEP
(B2) MEP----------MIP---------------------MIP----------MEP
(C) MEP-------MEP|MEP------------------MEP|MEP--------MEP
(D) MEP-------MEP|MEP------------------MEP|MEP--------MEP
Figure 9: VPWS MEPs and MIPs
图9:VPWS MEP和MIPs
In VPWS, the MEPs and MIPs should be identified with their native addressing schemes. MEPs and MIPs Identifiers, i.e., MEP Ids and MIP Ids, must be unique to the VPWS instance and in the context of their corresponding OAM domains.
在VPWS中，MEP和MIP应使用其本机寻址方案进行标识。MEP和MIPs标识符，即MEP ID和MIP ID，对于VPWS实例以及在其相应OAM域的上下文中必须是唯一的。
These requirements are applicable to VPLS PE offering VPLS as an Ethernet Bridged LAN service, as described in Section 5.1.1. Further, the performance metrics used in requirements are based on [MEF10.1] and [RFC2544].
这些要求适用于提供VPLS作为以太网桥接LAN服务的VPLS PE，如第5.1.1节所述。此外，需求中使用的性能指标基于[MEF10.1]和[RFC2544]。
It is noted that OAM solutions that meet the following requirements may make use of existing OAM mechanisms, e.g., Ethernet OAM, VCCV, etc.; however, they must not break these existing OAM mechanisms. If extensions are required to existing OAM mechanisms, these should be coordinated with relevant groups responsible for these OAM mechanisms.
需要注意的是，满足以下要求的OAM解决方案可以利用现有的OAM机制，例如以太网OAM、VCCV等。；但是，它们不能破坏这些现有的OAM机制。如果需要对现有OAM机制进行扩展，则应与负责这些OAM机制的相关小组进行协调。
Discovery allows a VPLS-aware device to learn about other devices that support the same VPLS instance within a given domain.
发现允许VPLS感知设备了解在给定域中支持相同VPLS实例的其他设备。
Discovery also allows a VPLS-aware device to learn sufficient information (e.g., IP addresses, MAC addresses, etc.) from other VPLS-aware devices such that VPLS OAM frames can be exchanged among the service-aware devices.
发现还允许VPLS感知设备从其他VPLS感知设备学习足够的信息（例如，IP地址、MAC地址等），以便可以在感知服务的设备之间交换VPLS OAM帧。
(R1) VPLS OAM MUST allow a VPLS-aware device to discover other devices that share the same VPLS instance(s) within a given OAM domain.
（R1）VPLS OAM必须允许感知VPLS的设备发现在给定OAM域内共享相同VPLS实例的其他设备。
VPLS is realized by exchanging service frames/packets between devices that support the same VPLS instance. To allow the exchange of service frames, connectivity between these service-aware devices is required.
VPLS是通过在支持同一VPLS实例的设备之间交换服务帧/数据包来实现的。为了允许服务帧的交换，需要这些服务感知设备之间的连接。
To ensure service, proactive connectivity monitoring is required. Connectivity monitoring facilitates connectivity fault detection.
为确保服务，需要主动式连接监控。连接监控有助于连接故障检测。
(R2a) VPLS OAM MUST allow proactive connectivity monitoring between two VPLS-aware devices that support the same VPLS instance within a given OAM domain.
（R2a）VPLS OAM必须允许在给定OAM域中支持相同VPLS实例的两个支持VPLS的设备之间进行主动连接监控。
Once a connectivity fault is detected, connectivity fault verification may be performed.
一旦检测到连接故障，可以执行连接故障验证。
(R2b) VPLS OAM MUST allow connectivity fault verification between two VPLS-aware devices that support the same VPLS instance within a given OAM domain.
（R2b）VPLS OAM必须允许在给定OAM域内支持相同VPLS实例的两个支持VPLS的设备之间进行连接故障验证。
Further, localization of connectivity fault may be carried out.
此外，可以执行连接故障的定位。
(R2c) VPLS OAM MUST allow connectivity fault localization between two VPLS-aware devices that support the same instance within a given OAM domain.
（R2c）VPLS OAM必须允许在给定OAM域中支持同一实例的两个支持VPLS的设备之间进行连接故障定位。
Typically, when a connectivity fault is detected and optionally verified, the VPLS device may notify the NMS (Network Management System) via alarms.
通常，当检测到并可选地验证连接故障时，VPLS设备可通过警报通知NMS（网络管理系统）。
However, a single transport/network fault may cause multiple services to fail simultaneously, thereby causing multiple service alarms. Therefore, VPLS OAM must allow service-level fault notification to be triggered at the client layer as a result of transport/network faults in the service layer. This fault notification should be used for the suppression of service-level alarms at the client layer.
但是，单个传输/网络故障可能会导致多个服务同时失败，从而导致多个服务警报。因此，VPLS OAM必须允许由于服务层中的传输/网络故障而在客户端层触发服务级别故障通知。此故障通知应用于抑制客户端层的服务级别警报。
(R2d) VPLS OAM MUST support fault notification to be triggered as a result of transport/network faults. This fault notification SHOULD be used for the suppression of redundant service-level alarms.
（R2d）VPLS OAM必须支持因传输/网络故障而触发的故障通知。此故障通知应用于抑制冗余服务级别警报。
A VPLS may be considered degraded if service-layer frames/packets are lost during transit between the VPLS-aware devices. To determine if a VPLS is degraded due to frame/packet loss, measurement of frame/packet loss is required.
如果服务层帧/分组在VPLS感知设备之间传输期间丢失，则VPLS可能被视为降级。为了确定VPLS是否由于帧/分组丢失而降级，需要测量帧/分组丢失。
(R3) VPLS OAM MUST support measurement of per-service frame/packet loss between two VPLS-aware devices that support the same VPLS instance within a given OAM domain.
（R3）VPLS OAM必须支持测量给定OAM域内支持相同VPLS实例的两个支持VPLS的设备之间的每服务帧/数据包丢失。
A VPLS may be sensitive to delay experienced by the VPLS frames/packets during transit between the VPLS-aware devices. To determine if a VPLS is degraded due to frame/packet delay, measurement of frame/packet delay is required.
VPLS可能对VPLS帧/分组在VPLS感知设备之间传输期间所经历的延迟敏感。为了确定VPLS是否由于帧/分组延迟而降级，需要测量帧/分组延迟。
VPLS frame/packet delay measurement can be of two types:
VPLS帧/包延迟测量可以有两种类型：
1) One-way delay is used to characterize certain applications like multicast and broadcast applications. The measurement for one-way delay usually requires clock synchronization between the two devices in question.
1) 单向延迟用于描述某些应用，如多播和广播应用。测量单向延迟通常需要两个设备之间的时钟同步。
2) Two-way delay or round-trip delay does not require clock synchronization between the two devices involved in measurement and is usually sufficient to determine the frame/packet delay being experienced.
2) 双向延迟或往返延迟不需要测量所涉及的两个设备之间的时钟同步，并且通常足以确定所经历的帧/分组延迟。
(R4a) VPLS OAM MUST support measurement of per-service two-way frame/packet delay between two VPLS-aware devices that support the same VPLS instance within a given OAM domain.
（R4a）VPLS OAM必须支持测量给定OAM域内支持相同VPLS实例的两个支持VPLS的设备之间的每服务双向帧/数据包延迟。
(R4b) VPLS OAM SHOULD support measurement of per-service one-way frame/packet delay between two VPLS-aware devices that support the same VPLS instance within a given OAM domain.
（R4b）VPLS OAM应支持测量给定OAM域内支持相同VPLS实例的两个支持VPLS的设备之间的每服务单向帧/数据包延迟。
A VPLS may be sensitive to delay variation experienced by the VPLS frames/packets during transit between the VPLS-aware devices. To determine if a VPLS is degraded due to frame/packet delay variation, measurement of frame/packet delay variation is required. For frame/packet delay variation measurements, one-way mechanisms are considered to be sufficient.
VPLS可能对VPLS帧/分组在VPLS感知设备之间传输期间经历的延迟变化敏感。为了确定VPLS是否由于帧/分组延迟变化而降级，需要测量帧/分组延迟变化。对于帧/分组延迟变化测量，单向机制被认为是足够的。
(R5) VPLS OAM MUST support measurement of per-service frame/packet delay variation between two VPLS-aware devices that support the same VPLS instance within a given OAM domain.
（R5）VPLS OAM必须支持测量给定OAM域内支持相同VPLS实例的两个VPLS感知设备之间的每服务帧/数据包延迟变化。
A service may be considered unavailable if the service frames/packets do not reach their intended destination (e.g., connectivity is down or frame/packet loss is occurring) or the service is degraded (e.g., frame/packet delay and/or delay variation threshold is exceeded).
如果服务帧/分组未到达其预期目的地（例如，连接中断或发生帧/分组丢失）或服务降级（例如，超过帧/分组延迟和/或延迟变化阈值），则可认为服务不可用。
Entry and exit conditions may be defined for unavailable state. Availability itself may be defined in context of service type.
可以为不可用状态定义进入和退出条件。可用性本身可以在服务类型的上下文中定义。
Since availability measurement may be associated with connectivity, frame/packet loss, frame/packet delay, and frame/packet delay variation measurements, no additional requirements are specified currently.
由于可用性测量可能与连接性、帧/分组丢失、帧/分组延迟和帧/分组延迟变化测量相关，因此目前没有规定额外的要求。
If the VPLS OAM frames flow across a different path than the one used by VPLS frames/packets, accurate measurement and/or determination of service state may not be made. Therefore, data path, i.e., the one being taken by VPLS frames/packets, must be used for the VPLS OAM.
如果VPLS OAM帧流过与VPLS帧/分组使用的路径不同的路径，则可能无法进行准确的测量和/或服务状态的确定。因此，VPLS OAM必须使用数据路径，即VPLS帧/数据包采用的数据路径。
(R6) VPLS OAM frames MUST be forwarded along the same path (i.e., links and nodes) as the VPLS frames.
（R6）VPLS OAM帧必须沿着与VPLS帧相同的路径（即链路和节点）转发。
Mechanisms developed for VPLS OAM need to be such that per-service OAM can be supported even though the OAM may only be used for limited VPLS instances, e.g., premium VPLS instances, and may not be used for best-effort VPLSs.
为VPLS OAM开发的机制需要能够支持每服务OAM，即使OAM只能用于有限的VPLS实例，例如高级VPLS实例，并且不能用于尽力而为的VPLS。
(R7) VPLS OAM MUST be scalable such that a service-aware device can support OAM for each VPLS that is supported by the device.
（R7）VPLS OAM必须具有可扩展性，以便服务感知设备能够为设备支持的每个VPLS支持OAM。
Extensibility is intended to allow introduction of additional OAM functionality in the future such that backward compatibility can be maintained when interoperating with older version devices. In such a case, VPLS OAM with reduced functionality should still be possible. Further, VPLS OAM should be defined such that OAM incapable devices in the middle of the OAM domain should be able to forward the VPLS OAM frames similar to the regular VPLS data frames/packets.
可扩展性旨在允许将来引入额外的OAM功能，以便在与旧版本设备互操作时保持向后兼容性。在这种情况下，功能减少的VPLS OAM仍然是可能的。此外，应该定义VPLS OAM，使得在OAM域的中间的OAM不能够的设备应该能够转发类似于常规VPLS数据帧/包的VPLS OAM帧。
(R8a) VPLS OAM MUST be extensible such that new functionality and information elements related to this functionality can be introduced in the future.
（R8a）VPLS OAM必须是可扩展的，以便将来可以引入与此功能相关的新功能和信息元素。
(R8b) VPLS OAM MUST be defined such that devices not supporting the OAM are able to forward the OAM frames in a similar fashion as the regular VPLS data frames/packets.
（R8b）必须定义VPLS OAM，以便不支持OAM的设备能够以与常规VPLS数据帧/分组类似的方式转发OAM帧。
VPLS OAM frames belonging to an OAM domain originate and terminate within that OAM domain. Security implies that an OAM domain must be capable of filtering OAM frames. The filtering is such that the OAM frames are prevented from leaking outside their domain. Also, OAM frames from outside the OAM domains should be either discarded (when such OAM frames belong to the same level or to a lower-level OAM domain) or transparently passed (when such OAM frames belong to a higher-level OAM domain).
属于OAM域的VPLS OAM帧在该OAM域内发起和终止。安全性意味着OAM域必须能够过滤OAM帧。过滤是为了防止OAM帧泄漏到其域之外。此外，来自OAM域外部的OAM帧应该被丢弃（当此类OAM帧属于同一级别或较低级别的OAM域时）或透明地传递（当此类OAM帧属于较高级别的OAM域时）。
(R9a) VPLS OAM frames MUST be prevented from leaking outside their OAM domain.
（R9a）必须防止VPLS OAM帧泄漏到其OAM域之外。
(R9b) VPLS OAM frames from outside an OAM domain MUST be prevented from entering the OAM domain when such OAM frames belong to the same level or to a lower-level OAM domain.
（R9b）当来自OAM域外部的VPLS OAM帧属于同一级别或更低级别的OAM域时，必须防止这些OAM帧进入OAM域。
(R9c) VPLS OAM frames from outside an OAM domain MUST be transported transparently inside the OAM domain when such OAM frames belong to a higher-level OAM domain.
（R9c）当来自OAM域外部的VPLS OAM帧属于更高级别的OAM域时，必须在OAM域内部透明地传输这些OAM帧。
VPLS frame/packets delivery is carried out across transport infrastructure, also called network infrastructure. Though specific transport/network technologies may provide their own OAM capabilities, VPLS OAM must be independently supported as many different transport/network technologies can be used to carry service frame/packets.
VPLS帧/数据包交付是跨传输基础设施（也称为网络基础设施）进行的。尽管特定的传输/网络技术可能提供其自己的OAM功能，但必须独立支持VPLS OAM，因为可以使用许多不同的传输/网络技术来承载服务帧/数据包。
(R10a) VPLS OAM MUST be independent of the underlying transport/network technologies and specific transport/network OAM capabilities.
（R10a）VPLS OAM必须独立于底层传输/网络技术和特定传输/网络OAM功能。
(R10b) VPLS OAM MAY allow adaptation/interworking with specific transport/network OAM functions. For example, this would be useful to allow fault notifications from transport/network layer(s) to be sent to the VPLS layer.
（R10b）VPLS OAM可允许与特定的传输/网络OAM功能进行适配/互通。例如，这将有助于将传输/网络层的故障通知发送到VPLS层。
VPLS itself may be used to carry application frame/packets. The application may use its own OAM; service OAM must not be dependent on application OAM. As an example, a VPLS may be used to carry IP traffic; however, VPLS OAM should not assume IP or rely on the use of IP-level OAM functions.
VPL本身可用于承载应用程序帧/数据包。应用程序可以使用自己的OAM；服务OAM不能依赖于应用程序OAM。例如，VPLS可用于承载IP业务；但是，VPLS OAM不应采用IP或依赖IP级OAM功能的使用。
(R11a) VPLS OAM MUST be independent of the application technologies and specific application OAM capabilities.
（R11a）VPLS OAM必须独立于应用程序技术和特定应用程序OAM功能。
These requirements are applicable to VPWS PE. The performance metrics used in requirements are based on [MEF10.1] and [RFC2544], which are applicable to Ethernet services.
这些要求适用于VPWS PE。需求中使用的性能指标基于[MEF10.1]和[RFC2544]，适用于以太网服务。
It is noted that OAM solutions that meet the following requirements may make use of existing OAM mechanisms, e.g., Ethernet OAM, VCCV, etc.; however, they must not break these existing OAM mechanisms. If extensions are required to existing OAM mechanisms, these should be coordinated with relevant groups responsible for these OAM mechanisms.
需要注意的是，满足以下要求的OAM解决方案可以利用现有的OAM机制，例如以太网OAM、VCCV等。；但是，它们不能破坏这些现有的OAM机制。如果需要对现有OAM机制进行扩展，则应与负责这些OAM机制的相关小组进行协调。
Discovery allows a VPWS-aware device to learn about other devices that support the same VPWS instance within a given domain. Discovery also allows a VPWS-aware device to learn sufficient information (e.g., IP addresses, MAC addresses, etc.) from other VPWS-aware devices such that OAM frames can be exchanged among the VPWS-aware devices.
发现允许支持VPWS的设备了解在给定域中支持相同VPWS实例的其他设备。发现还允许VPWS感知设备从其他VPWS感知设备学习足够的信息（例如，IP地址、MAC地址等），以便可以在VPWS感知设备之间交换OAM帧。
(R12) VPWS OAM MUST allow a VPWS-aware device to discover other devices that share the same VPWS instance(s) within a given OAM domain.
（R12）VPWS OAM必须允许感知VPWS的设备发现在给定OAM域中共享相同VPWS实例的其他设备。
VPWS is realized by exchanging service frames/packets between devices that support the same VPWS instance. To allow the exchange of service frames, connectivity between these service-aware devices is required.
VPWS是通过在支持同一VPWS实例的设备之间交换服务帧/数据包来实现的。为了允许服务帧的交换，需要这些服务感知设备之间的连接。
To ensure service, proactive connectivity monitoring is required. Connectivity monitoring facilitates connectivity fault detection.
为确保服务，需要主动式连接监控。连接监控有助于连接故障检测。
(R13a) VPWS OAM MUST allow proactive connectivity monitoring between two VPWS-aware devices that support the same VPWS instance within a given OAM domain.
（R13a）VPWS OAM必须允许在给定OAM域中支持相同VPWS实例的两个支持VPWS的设备之间进行主动连接监控。
(R13b) VPWS OAM mechanism SHOULD allow detection of mis-branching or mis-connections.
（R13b）VPWS OAM机制应允许检测错误分支或错误连接。
Once a connectivity fault is detected, connectivity fault verification may be performed.
一旦检测到连接故障，可以执行连接故障验证。
(R13c) VPWS OAM MUST allow connectivity fault verification between two VPWS-aware devices that support the same VPWS instance within a given OAM domain.
（R13c）VPWS OAM必须允许在给定OAM域中支持相同VPWS实例的两个支持VPWS的设备之间进行连接故障验证。
Further, localization of connectivity fault may be carried out. This may amount to identifying the specific AC and/or PW that is resulting in the VPWS connectivity fault.
此外，可以执行连接故障的定位。这可能相当于识别导致VPWS连接故障的特定AC和/或PW。
(R13d) VPWS OAM MUST allow connectivity fault localization between two VPWS-aware devices that support the same VPWS instance within a given OAM domain.
（R13d）VPWS OAM必须允许在给定OAM域中支持相同VPWS实例的两个支持VPWS的设备之间进行连接故障定位。
Typically, when a connectivity fault is detected and optionally verified, the service device may notify the NMS (Network Management System) via alarms.
通常，当检测到并可选地验证连接故障时，服务设备可通过警报通知NMS（网络管理系统）。
However, a single transport/network fault may cause multiple services to fail simultaneously causing multiple service alarms. Therefore, OAM must allow service-level fault notification to be triggered at the client layer as a result of transport/network faults in the service layer. This fault notification should be used for the suppression of service-level alarms at the client layer.
但是，单个传输/网络故障可能会导致多个服务同时失败，从而导致多个服务报警。因此，OAM必须允许由于服务层中的传输/网络故障而在客户端层触发服务级别故障通知。此故障通知应用于抑制客户端层的服务级别警报。
For example, if an AC fails, both the local CE and the local PE, which are connected via the AC, may detect the connectivity failure. The local CE must notify the remote CE about the failure while the local PE must notify the remote PE about the failure.
例如，如果AC发生故障，则经由AC连接的本地CE和本地PE都可以检测到连接故障。本地CE必须将故障通知远程CE，而本地PE必须将故障通知远程PE。
(R13e) VPWS OAM MUST support fault notification to be triggered as a result of transport/network faults. This fault notification SHOULD be used for the suppression of redundant service-level alarms.
（R13e）VPWS OAM必须支持因传输/网络故障而触发的故障通知。此故障通知应用于抑制冗余服务级别警报。
(R13f) VPWS OAM SHOULD support fault notification in backward direction, to be triggered as a result of transport/network faults. This fault notification SHOULD be used for the suppression of redundant service-level alarms.
（R13f）VPWS OAM应支持在传输/网络故障时触发的反向故障通知。此故障通知应用于抑制冗余服务级别警报。
A VPWS may be considered degraded if service-layer frames/packets are lost during transit between the VPWS-aware devices. To determine if a VPWS is degraded due to frame/packet loss, measurement of frame/packet loss is required.
如果服务层帧/数据包在VPWS感知设备之间传输期间丢失，则VPWS可能被视为降级。为了确定VPWS是否由于帧/分组丢失而降级，需要测量帧/分组丢失。
(R14) VPWS OAM MUST support measurement of per-service frame/packet loss between two VPWS-aware devices that support the same VPWS instance within a given OAM domain.
（R14）VPWS OAM必须支持测量给定OAM域内支持相同VPWS实例的两个支持VPWS的设备之间的每服务帧/数据包丢失。
A VPWS may be sensitive to delay experienced by the VPWS frames/packets during transit between the VPWS-aware devices. To determine if a VPWS is degraded due to frame/packet delay, measurement of frame/packet delay is required.
VPWS可能对VPWS帧/包在VPWS感知设备之间传输期间所经历的延迟敏感。为了确定VPWS是否由于帧/包延迟而降级，需要测量帧/包延迟。
VPWS frame/packet delay measurement can be of two types:
VPWS帧/数据包延迟测量可以有两种类型：
1) One-way delay is used to characterize certain applications like multicast and broadcast applications. The measurement for one-way delay usually requires clock synchronization between the two devices in question.
1) 单向延迟用于描述某些应用，如多播和广播应用。测量单向延迟通常需要两个设备之间的时钟同步。
2) Two-way delay or round-trip delay does not require clock synchronization between the two devices involved in measurement and is usually sufficient to determine the frame/packet delay being experienced.
2) 双向延迟或往返延迟不需要测量所涉及的两个设备之间的时钟同步，并且通常足以确定所经历的帧/分组延迟。
(R15a) VPWS OAM MUST support measurement of per-service two-way frame/packet delay between two VPWS-aware devices that support the same VPWS instance within a given OAM domain.
（R15a）VPWS OAM必须支持测量给定OAM域内支持相同VPWS实例的两个支持VPWS的设备之间的每服务双向帧/数据包延迟。
(R15b) VPWS OAM SHOULD support measurement of per-service one-way frame/packet delay between two VPWS-aware devices that support the same VPWS instance within a given OAM domain.
（R15b）VPWS OAM应支持测量给定OAM域内支持相同VPWS实例的两个支持VPWS的设备之间的每服务单向帧/数据包延迟。
A VPWS may be sensitive to delay variation experienced by the VPWS frames/packets during transit between the VPWS-aware devices. To determine if a VPWS is degraded due to frame/packet delay variation, measurement of frame/packet delay variation is required. For frame/packet delay variation measurements, one-way mechanisms are considered to be sufficient.
VPWS可能对VPWS帧/包在VPWS感知设备之间传输期间经历的延迟变化敏感。为了确定VPWS是否由于帧/分组延迟变化而降级，需要测量帧/分组延迟变化。对于帧/分组延迟变化测量，单向机制被认为是足够的。
(R16) VPWS OAM MUST support measurement of per-service frame/packet delay variation between two VPWS-aware devices that support the same VPWS instance within a given OAM domain.
（R16）VPWS OAM必须支持测量给定OAM域内支持相同VPWS实例的两个支持VPWS的设备之间的每服务帧/数据包延迟变化。
A service may be considered unavailable if the service frames/packets do not reach their intended destination (e.g., connectivity is down or frame/packet loss is occurring) or the service is degraded (e.g., frame/packet delay and/or delay variation threshold is exceeded).
如果服务帧/分组未到达其预期目的地（例如，连接中断或发生帧/分组丢失）或服务降级（例如，超过帧/分组延迟和/或延迟变化阈值），则可认为服务不可用。
Entry and exit conditions may be defined for unavailable state. Availability itself may be defined in context of service type.
可以为不可用状态定义进入和退出条件。可用性本身可以在服务类型的上下文中定义。
Since availability measurement may be associated with connectivity, frame/packet loss, frame/packet delay, and frame/packet delay variation measurements, no additional requirements are specified currently.
由于可用性测量可能与连接性、帧/分组丢失、帧/分组延迟和帧/分组延迟变化测量相关，因此目前没有规定额外的要求。
If the VPWS OAM frames flow across a different path than the one used by VPWS frames/packets, accurate measurement and/or determination of service state may not be made. Therefore data path, i.e., the one being taken by VPWS frames/packets, must be used for the VPWS OAM.
如果VPWS OAM帧流经与VPWS帧/分组使用的路径不同的路径，则可能无法准确测量和/或确定服务状态。因此，VPWS OAM必须使用数据路径，即VPWS帧/数据包采用的数据路径。
(R17a) VPWS OAM frames MUST be forwarded along the same path as the VPWS data frames.
（R17a）必须沿着与VPWS数据帧相同的路径转发VPWS OAM帧。
(R17b) VPWS OAM MUST be forwarded using the transfer plane (data plane) as regular VPWS data frames/packets and must not rely on control plane messages.
（R17b）必须使用传输平面（数据平面）作为常规VPWS数据帧/数据包转发VPWS OAM，并且不得依赖控制平面消息。
Mechanisms developed for VPWS OAM need to be such that per-service OAM can be supported even though the OAM may only be used for limited VPWS instances, e.g., premium VPWS instance, and may not be used for best-effort services.
为VPWS OAM开发的机制需要能够支持每服务OAM，即使OAM可能仅用于有限的VPWS实例，例如高级VPWS实例，并且可能不用于尽力而为的服务。
(R18) VPWS OAM MUST be scalable such that a service-aware device can support OAM for each VPWS that is supported by the device.
（R18）VPWS OAM必须具有可扩展性，以便服务感知设备能够为设备支持的每个VPWS支持OAM。
Extensibility is intended to allow introduction of additional OAM functionality in the future such that backward compatibility can be maintained when interoperating with older version devices. In such a case, VPWS OAM with reduced functionality should still be possible. Further, VPWS OAM should be such that OAM incapable devices in the middle of the OAM domain should be able to forward the VPWS OAM frames similar to the regular VPWS data frames/packets.
可扩展性旨在允许将来引入额外的OAM功能，以便在与旧版本设备互操作时保持向后兼容性。在这种情况下，功能减少的VPWS OAM仍然是可能的。此外，VPWS OAM应该是这样的，在OAM域的中间的OAM不能够的设备应该能够转发类似于常规VPWS数据帧/包的VPWS OAM帧。
(R19a) VPWS OAM MUST be extensible such that new functionality and information elements related to this functionality can be introduced in the future.
（R19a）VPWS OAM必须是可扩展的，以便将来可以引入与此功能相关的新功能和信息元素。
(R19b) VPWS OAM MUST be defined such that devices not supporting the OAM are able to forward the VPWS OAM frames in a similar fashion as the regular VPWS data frames/packets.
（R19b）必须定义VPWS OAM，以便不支持OAM的设备能够以与常规VPWS数据帧/数据包类似的方式转发VPWS OAM帧。
VPWS OAM frames belonging to an OAM domain originate and terminate within that OAM domain. Security implies that an OAM domain must be capable of filtering OAM frames. The filtering is such that the VPWS OAM frames are prevented from leaking outside their domain. Also,
属于OAM域的VPWS OAM帧在该OAM域内发起和终止。安全性意味着OAM域必须能够过滤OAM帧。过滤可以防止VPWS OAM帧泄漏到其域之外。而且
VPWS OAM frames from outside the OAM domains should be either discarded (when such OAM frames belong to the same level or to a lower-level OAM domain) or transparently passed (when such OAM frames belong to a higher-level OAM domain).
来自OAM域外部的VPWS OAM帧应该被丢弃（当此类OAM帧属于同一级别或较低级别的OAM域时）或透明地传递（当此类OAM帧属于较高级别的OAM域时）。
(R20a) VPWS OAM frames MUST be prevented from leaking outside their OAM domain.
（R20a）必须防止VPWS OAM帧泄漏到其OAM域之外。
(R20b) VPWS OAM frames from outside an OAM domain MUST be prevented from entering the OAM domain when such OAM frames belong to the same level or to a lower-level OAM domain.
（R20b）当来自OAM域外部的VPWS OAM帧属于同一级别或更低级别的OAM域时，必须防止这些OAM帧进入OAM域。
(R20c) VPWS OAM frames from outside an OAM domain MUST be transported transparently inside the OAM domain when such OAM frames belong to a higher-level OAM domain.
（R20c）当来自OAM域外部的VPWS OAM帧属于更高级别的OAM域时，必须在OAM域内部透明地传输这些VPWS OAM帧。
VPWS frame/packets delivery is carried out across transport infrastructure, also called network infrastructure. Though specific transport/network technologies may provide their own OAM capabilities, VPWS OAM must be independently supported as many different transport/network technologies can be used to carry service frame/packets.
VPWS帧/数据包交付跨传输基础设施（也称为网络基础设施）执行。尽管特定的传输/网络技术可能提供它们自己的OAM功能，但必须独立支持VPWS OAM，因为可以使用许多不同的传输/网络技术来承载服务帧/数据包。
(R21a) VPWS OAM MUST be independent of the underlying transport/network technologies and specific transport/network OAM capabilities.
（R21a）VPWS OAM必须独立于底层传输/网络技术和特定的传输/网络OAM功能。
(R21b) VPWS OAM MAY allow adaptation/interworking with specific transport/network OAM functions. For example, this would be useful to allow fault notifications from transport/network layer(s) to be sent to the VPWS layer.
（R21b）VPWS OAM可允许与特定传输/网络OAM功能进行适配/互通。例如，这将有助于将传输/网络层的故障通知发送到VPWS层。
VPWS itself may be used to carry application frame/packets. The application may use its own OAM; VPWS OAM must not be dependent on application OAM. As an example, a VPWS may be used to carry IP traffic; however, VPWS OAM should not assume IP or rely on the use of IP-level OAM functions.
VPWS本身可用于承载应用程序帧/数据包。应用程序可以使用自己的OAM；VPWS OAM不能依赖于应用程序OAM。例如，VPWS可用于承载IP业务；但是，VPWS OAM不应采用IP或依赖IP级OAM功能的使用。
(R22a) OAM MUST be independent of the application technologies and specific application OAM capabilities.
（R22a）OAM必须独立于应用程序技术和特定的应用程序OAM功能。
VPWS could be composed of several data flows, each related to a given usage/application with specific requirements in terms of connectivity and/or performance. Dedicated VPWS OAM should be applicable to these flows.
VPW可以由多个数据流组成，每个数据流都与给定的用途/应用程序相关，在连接性和/或性能方面有特定的要求。专用VPWS OAM应适用于这些流。
(R23) VPWS OAM SHOULD support configurable prioritization for OAM packet/frames to be compatible with associated VPWS packets/frames.
（R23）VPWS OAM应支持OAM数据包/帧的可配置优先级，以与相关VPWS数据包/帧兼容。
As indicated in [BRIDGE-INTEROP], VPLS OAM relies upon bidirectional Ethernet links or (V)LAN segments and failure in one direction or link results in failure of the whole link or (V)LAN segment. Therefore, when partial-mesh failure occurs in (V)LAN emulation, either the entire PW mesh should be shut down when only an entire VPLS is acceptable or a subset of PWs should be shut down such that the remaining PWs have full connectivity among them when partial VPLS is acceptable.
如[BRIDGE-INTEROP]中所述，VPLS OAM依赖于双向以太网链路或（V）LAN段，一个方向或链路的故障导致整个链路或（V）LAN段的故障。因此，当（V）LAN仿真中出现部分网格故障时，当只有整个VPLS可接受时，应关闭整个PW网格，或者应关闭PWs的子集，以便在部分VPLS可接受时，其余PWs之间具有完全连接。
(R13a) PW OAM for PWs related to a (V)LAN emulation MUST allow detection of a partial-mesh failure condition.
（R13a）与（V）LAN仿真相关的PWs的PW OAM必须允许检测部分网格故障情况。
(R13b) PW OAM for PWs related to a (V)LAN emulation MUST allow the entire mesh of PWs to be shut down upon detection of a partial-mesh failure condition.
（R13b）与（V）LAN仿真相关的PWs的PW OAM必须允许在检测到部分网格故障情况时关闭PWs的整个网格。
(R13c) PW OAM for PWs related to a (V)LAN emulation MUST allow the subset of PWs to be shut down upon detection of a partial-mesh failure condition in a manner such that full mesh is present across the remaining subset.
（R13c）与（V）LAN仿真相关的PW的PW OAM必须允许在检测到部分网格故障条件时关闭PWs子集，以确保剩余子集上存在完整网格。
Note: Shutdown action in R13b and R13c may not necessarily involve withdrawal of labels, etc.
注：R13b和R13c中的停机操作不一定涉及标签的撤销等。
As indicated in [BRIDGE-INTEROP], VPLS OAM fault detection and recovery relies upon (V)LAN emulation recovery such that fault detection and recovery time in (V)LAN emulation should be less than the VPLS fault detection and recovery time to prevent unnecessary switch-over and temporary flooding/loop within the customer OAM domain that is dual-homed to the provider OAM domain.
如[BRIDGE-INTEROP]中所述，VPLS OAM故障检测和恢复依赖于（V）LAN仿真恢复，因此故障检测和恢复时间为（V）LAN仿真应小于VPLS故障检测和恢复时间，以防止客户OAM域内不必要的切换和临时泛洪/环路，该客户OAM域与提供商OAM域双宿。
(R14a) PW OAM for PWs related to a (V)LAN emulation MUST support a fault detection time in the provider OAM domain faster than the VPLS fault detection time in the customer OAM domain.
（R14a）与（V）LAN仿真相关的PWs的PW OAM必须支持提供商OAM域中的故障检测时间快于客户OAM域中的VPLS故障检测时间。
(R14b) PW OAM for PWs related to a (V)LAN emulation MUST support a fault recovery time in the provider OAM domain faster than the VPLS fault recovery time in the customer OAM domain.
（R14b）与（V）LAN仿真相关的PW的PW OAM必须支持提供商OAM域中的故障恢复时间快于客户OAM域中的VPLS故障恢复时间。
When a connectivity fault is detected in (V)LAN emulation, PE devices may notify the NMS (Network Management System) via alarms. However, a single (V)LAN emulation fault may result in CE devices or U-PE devices detecting a connectivity fault in VPLS and therefore also notifying the NMS. To prevent multiple alarms for the same fault, (V)LAN emulation OAM must provide alarm suppression capability in the VPLS OAM.
当在（V）LAN仿真中检测到连接故障时，PE设备可能会通过警报通知NMS（网络管理系统）。但是，单个（V）LAN仿真故障可能会导致CE设备或U-PE设备检测到VPLS中的连接故障，因此也会通知NMS。为了防止同一故障出现多个警报，（V）LAN仿真OAM必须在VPLS OAM中提供警报抑制功能。
(R15) PW OAM for PWs related to a (V)LAN emulation MUST support interworking with VPLS OAM to trigger fault notification and allow alarm suppression in the VPLS upon fault detection in (V)LAN emulation.
（R15）与（V）LAN仿真相关的PWs的PW OAM必须支持与VPLS OAM的互通，以触发故障通知，并允许在（V）LAN仿真中检测到故障时在VPLS中抑制报警。
This section highlights how the different OAM mechanisms can be applied as per the OAM framework for different L2VPN services.
本节重点介绍如何根据OAM框架为不同的L2VPN服务应用不同的OAM机制。
--- ---
/ \ ------ ------- ---- / \
| A CE-- / \ / \ / \ --CE A |
\ / \ / \ / \ / \ / \ /
--- --UPE NPE NPE UPE-- ---
\ / \ / \ /
\ / \ / \ /
------ ------- ----
--- ---
/ \ ------ ------- ---- / \
| A CE-- / \ / \ / \ --CE A |
\ / \ / \ / \ / \ / \ /
--- --UPE NPE NPE UPE-- ---
\ / \ / \ /
\ / \ / \ /
------ ------- ----
Customer OAM Domain
(C) MEP---MIP--------------------------------MIP---MEP
Customer OAM Domain
(C) MEP---MIP--------------------------------MIP---MEP
Service Provider (SP) OAM Domain
(D) MEP--------MIP-----------MIP-------MEP
Service Provider (SP) OAM Domain
(D) MEP--------MIP-----------MIP-------MEP
SP OAM SP OAM SP OAM
(D1) MEP-MIP--MEP|MEP-------MEP|MEP-----MEP
domain domain domain
SP OAM SP OAM SP OAM
(D1) MEP-MIP--MEP|MEP-------MEP|MEP-----MEP
domain domain domain
Operator Operator Operator
(E) MEP-MIP--MEP|MEP-------MEP|MEP-----MEP
OAM domain OAM domain OAM domain
Operator Operator Operator
(E) MEP-MIP--MEP|MEP-------MEP|MEP-----MEP
OAM domain OAM domain OAM domain
MPLS OAM MPLS OAM
(F) MEP--MIP-----MEP--MIP--MEP
domain domain
MPLS OAM MPLS OAM
(F) MEP--MIP-----MEP--MIP--MEP
domain domain
Figure 10: VPLS OAM Domains, MEPs, and MIPs
图10:VPLS OAM域、MEP和MIPs
Among the different MEs identified in Figure 5 for VPLS OAM in the customer OAM domain, [IEEE802.1ag] and [Y.1731] Ethernet OAM mechanisms can be applied to meet the various requirements identified in Section 7. The mechanisms can be applied across (C) in Figure 10 MEs.
在图5中为客户OAM域中的VPLS OAM确定的不同MEs中，[IEEE802.1ag]和[Y.1731]以太网OAM机制可用于满足第7节中确定的各种要求。这些机制可以应用于图10中的（C）。
Similarly, inside the service provider OAM domain, [IEEE802.1ag] and [Y.1731] Ethernet OAM mechanisms can be applied across (D) MEs in Figure 10 to meet the functional requirements identified in Section 7.
类似地，在服务提供商OAM域内，[IEEE802.1ag]和[Y.1731]以太网OAM机制可跨图10中的（D）个MEs应用，以满足第7节中确定的功能要求。
It may be noted that in the interim, when [IEEE802.1ag] and [Y.1731] capabilities are not available across the PE devices, the Fault Management option using segment OAM introduced in Section 6.2.3 can be applied, with the limitations cited below. In this option, the service provider can run segment OAM across the (D1) MEs in Figure
可能需要注意的是，在此期间，当[IEEE802.1ag]和[Y.1731]功能在PE设备中不可用时，可以应用第6.2.3节中介绍的使用段OAM的故障管理选项，但有以下限制。在该选项中，服务提供商可以跨图中的（D1）MEs运行段OAM
10. The OAM mechanisms across the (D1) MEs in Figure 10 can be non-Ethernet, e.g., Virtual Circuit Connectivity Verification (VCCV), or Bidirectional Forwarding Detection (BFD) when network technology is MPLS. The service provider can monitor each sub-network segment ME using the native technology OAM and, by performing interworking across the segment MEs, attempt to realize end-to-end monitoring between a pair of VPLS endpoints. However, such mechanisms do not fully exercise the data plane forwarding constructs as experienced by native (i.e., Ethernet) service PDUs. As a result, service monitoring ((D1) in Figure 10) is severely limited in the sense that it may lead to an indication that the ME between VPLS endpoints is functional while the customer may be experiencing end-to-end connectivity issues in the data plane.
10. 图10中跨越（D1）MEs的OAM机制可以是非以太网，例如，当网络技术为MPLS时，虚拟电路连接验证（VCCV）或双向转发检测（BFD）。服务提供商可以使用本机技术OAM监控每个子网段ME，并通过跨段ME执行互通，尝试在一对VPLS端点之间实现端到端监控。然而，这种机制并没有完全执行本机（即以太网）服务pdu所经历的数据平面转发构造。因此，服务监控（图10中的（D1））受到严重限制，因为它可能导致VPLS端点之间的ME正常工作，而客户可能在数据平面中遇到端到端连接问题。
Inside the network operator OAM domain, [IEEE802.1ag] and [Y.1731] Ethernet OAM mechanisms can also be applied across MEs in (E) in Figure 10 to meet the functional requirements identified in Section 7. In addition, the network operator could decide to use native OAM mechanisms, e.g., VCCV or BFD, across (F) MEs for additional monitoring or as an alternative to monitoring across (E) MEs.
在网络运营商OAM域内，[IEEE802.1ag]和[Y.1731]以太网OAM机制也可以跨图10（E）中的MEs应用，以满足第7节中确定的功能要求。此外，网络运营商可决定跨（F）MEs使用本机OAM机制（例如VCCV或BFD）进行额外监控，或作为跨（e）MEs监控的替代方案。
This specification assumes that L2VPN components within the OAM domain are mutually trusted. Based on that assumption, confidentiality issues are fully addressed by filtering to prevent OAM frames from leaking outside their designated OAM domain. Similarly, authentication issues are addressed by preventing OAM frames generated outside a given OAM domain from entering the domain in question. Requirements to prevent OAM messages from leaking outside an OAM domain and for OAM domains to be transparent to OAM frames from higher OAM domains are specified in Sections 7.10 and 8.10.
本规范假设OAM域中的L2VPN组件是相互信任的。基于该假设，机密性问题通过过滤来完全解决，以防止OAM帧泄漏到其指定的OAM域之外。类似地，通过防止在给定OAM域之外生成的OAM帧进入相关域来解决身份验证问题。第7.10节和第8.10节规定了防止OAM消息泄漏到OAM域之外以及OAM域对来自更高OAM域的OAM帧透明的要求。
For additional levels of security, solutions may be required to encrypt and/or authenticate OAM frames inside an OAM domain. However, these solutions are out of the scope of this document.
对于额外的安全级别，可能需要解决方案来加密和/或验证OAM域内的OAM帧。但是，这些解决方案不在本文档的范围内。
In addition to the authors listed above, the following individuals also contributed to this document.
除上述作者外，以下个人也对本文件作出了贡献。
Simon Delord Uecomm 658 Church St Richmond, VIC, 3121, Australia EMail: sdelord@uecomm.com.au
Simon Delord Uecomm 658 Church St Richmond，VIC，3121，澳大利亚电子邮件：sdelord@uecomm.com.au
Philippe Niger France Telecom 2 av. Pierre Marzin 22300 LANNION, France EMail: philippe.niger@francetelecom.com
菲利普尼日尔法国电信2号av。Pierre Marzin 22300 LANNION，法国电子邮件：philippe。niger@francetelecom.com
Samer Salam Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134 EMail: ssalam@cisco.com
Samer Salam Cisco Systems，Inc.加利福尼亚州圣何塞市西塔斯曼大道170号，邮编95134电子邮件：ssalam@cisco.com
The authors would like to thank Deborah Brungard, Vasile Radoaca, Lei Zhu, Yuichi Ikejiri, Yuichiro Wada, and Kenji Kumaki for their reviews and comments.
作者要感谢Deborah Brungard、Vasile Radoaca、Lei Zhu、Yuichi Ikejiri、Yuichiro Wada和Kenji Kumaki的评论和评论。
The authors would also like to thank Shahram Davari, Norm Finn, Dave Allan, Thomas Nadeau, Monique Morrow, Yoav Cohen, Marc Holness, Malcolm Betts, Paul Bottorff, Hamid-Ould Brahim, Lior Shabtay, and Dan Cauchy for their feedback.
作者还要感谢Shahram Davari、Norm Finn、Dave Allan、Thomas Nadeau、Monique Morrow、Yoav Cohen、Marc Holness、Malcolm Betts、Paul Bottorff、Hamid Ould Brahim、Lior Shabtay和Dan Cauchy的反馈。
[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。
[IEEE802.1ad] "IEEE Standard for Local and metropolitan area networks - Virtual Bridged Local Area Networks, Amendment 4: Provider Bridges", 2005.
[IEEE802.1ad]“局域网和城域网IEEE标准-虚拟桥接局域网，修改件4：提供商网桥”，2005年。
[IEEE802.1ag] "IEEE Standard for Local and metropolitan area networks - Virtual Bridged Local Area Networks, Amendment 5: Connectivity Fault Management", 2007.
[IEEE802.1ag]“局域网和城域网IEEE标准-虚拟桥接局域网，修改件5：连接故障管理”，2007年。
[IEEE802.1ah] "IEEE Standard for Local and metropolitan area networks - Virtual Bridged Local Area Networks, Amendment 6: Provider Backbone Bridges", 2008.
[IEEE802.1ah]“局域网和城域网IEEE标准-虚拟桥接局域网，修改件6：提供商主干网桥”，2008年。
[Y.1731] "ITU-T Recommendation Y.1731 (02/08) - OAM functions and mechanisms for Ethernet based networks", February 2008.
[Y.1731]“ITU-T建议Y.1731（02/08）-基于以太网的网络的OAM功能和机制”，2008年2月。
[L2VPN-FRWK] Andersson, L., Ed., and E. Rosen, Ed., "Framework for Layer 2 Virtual Private Networks (L2VPNs)", RFC 4664, September 2006.
[L2VPN-FRWK]Andersson，L.，Ed.，和E.Rosen，Ed.，“第二层虚拟专用网络（L2VPN）框架”，RFC 4664，2006年9月。
[L2VPN-REQ] Augustyn, W., Ed., and Y. Serbest, Ed., "Service Requirements for Layer 2 Provider-Provisioned Virtual Private Networks", RFC 4665, September 2006.
[L2VPN-REQ]Augustyn，W.，Ed.，和Y.Serbest，Ed.，“第2层提供商提供的虚拟专用网络的服务要求”，RFC 4665，2006年9月。
[L2VPN-TERM] Andersson, L. and T. Madsen, "Provider Provisioned Virtual Private Network (VPN) Terminology", RFC 4026, March 2005.
[L2VPN-TERM]Andersson，L.和T.Madsen，“提供商提供的虚拟专用网络（VPN）术语”，RFC 4026，2005年3月。
[MEF10.1] "Ethernet Services Attributes: Phase 2", MEF 10.1, 2006.
[MEF10.1]“以太网服务属性：第2阶段”，MEF 10.12006。
[NM-Standards] "TMN Management Functions", M.3400, February 2000.
[NM标准]“TMN管理功能”，M.3400，2000年2月。
[VPLS-BGP] Kompella, K., Ed., and Y. Rekhter, Ed., "Virtual Private LAN Service (VPLS) Using BGP for Auto-Discovery and Signaling", RFC 4761, January 2007.
[VPLS-BGP]Kompella，K.，Ed.，和Y.Rekhter，Ed.，“使用BGP进行自动发现和信令的虚拟专用局域网服务（VPLS）”，RFC 4761，2007年1月。
[VPLS-LDP] Lasserre, M., Ed., and V. Kompella, Ed., "Virtual Private LAN Service (VPLS) Using Label Distribution Protocol (LDP) Signaling", RFC 4762, January 2007.
[VPLS-LDP]Lasserre，M.，Ed.，和V.Kompella，Ed.，“使用标签分发协议（LDP）信令的虚拟专用局域网服务（VPLS）”，RFC 4762，2007年1月。
[BRIDGE-INTEROP] Sajassi, A. Ed., Brockners, F., Mohan, D., Ed., and Y. Serbest, "VPLS Interoperability with CE Bridges", Work in Progress, October 2010.
[BRIDGE-INTEROP]Sajassi，A.Ed.，Brockners，F.，Mohan，D.，Ed.，和Y.Serbest，“VPLS与CE Bridges的互操作性”，正在进行的工作，2010年10月。
[L2VPN-SIG] Rosen, E., Davie, B., Radoaca, V., and W. Luo, "Provisioning, Auto-Discovery, and Signaling in Layer 2 Virtual Private Networks (L2VPNs)", RFC 6074, January 2011.
[L2VPN-SIG]Rosen，E.，Davie，B.，Radoaca，V.，和W.Luo，“第二层虚拟专用网络（L2VPN）中的资源调配、自动发现和信令”，RFC 6074，2011年1月。
[MS-PW-Arch] Bocci, M. and S. Bryant, "An Architecture for Multi-Segment Pseudowire Emulation Edge-to-Edge", RFC 5659, October 2009.
[MS PW Arch]Bocci，M.和S.Bryant，“多段伪线边到边仿真的体系结构”，RFC 5659，2009年10月。
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for Network Interconnect Devices", RFC 2544, March 1999.
[RFC2544]Bradner，S.和J.McQuaid，“网络互连设备的基准测试方法”，RFC 2544，1999年3月。
In consideration of the management models that can be deployed besides the hierarchical models elaborated in this document, this appendix highlights some alternate models that are not recommended due to their limitations, as pointed out below. These alternatives have been highlighted as potential interim models while the network equipment is upgraded to support full functionality and meet the requirements set forward by this document.
考虑到除了本文件中阐述的分层模型之外，还可以部署管理模型，本附录重点介绍了一些由于其局限性而不推荐的替代模型，如下所述。当网络设备升级以支持全部功能并满足本文件提出的要求时，这些替代方案已被强调为潜在的临时模型。
In this model, the end-to-end service monitoring is provided by applying CE to CE ME in the service provider OAM domain.
在该模型中，通过将CE应用于服务提供商OAM域中的CE ME来提供端到端服务监控。
A MEP is located at each CE interface that is part of the VPWS, as shown in (B) in Figure A.1. The network operators can carry out segment (e.g., PSN Tunnel ME, etc.) monitoring independent of the VPWS end-to-end service monitoring, as shown in (D) in Figure A.1.
MEP位于作为VPWS一部分的每个CE接口处，如图A.1（B）所示。网络运营商可以进行独立于VPWS端到端服务监控的网段（如PSN隧道ME等）监控，如图A.1（D）所示。
The advantage of this option is that VPWS monitoring is limited to CEs. The limitation of this option is that the localization of faults is at the VPWS level.
此选项的优点是VPWS监视仅限于CEs。此选项的局限性在于故障定位在VPWS级别。
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
(B) MEP-----------------------------------------------MEP
(D) MEP-------MEP|MEP------------------MEP|MEP--------MEP
(B) MEP-----------------------------------------------MEP
(D) MEP-------MEP|MEP------------------MEP|MEP--------MEP
Figure A.1: VPWS MEPs and MIPs (Minimal OAM)
图A.1:VPWS MEP和MIPs（最小OAM）
In this model, end-to-end service monitoring is provided by interworking OAM across each segment. Typical segments involved in this case include two AC MEs and a PW ME, as shown in (C) in Figure A.2. These segments are expected in the service provider OAM domain. An interworking function is required to transfer the OAM information flows across the OAM segments for the purposes of end-to-end monitoring. Depending on whether homogenous VPWS is deployed or
在该模型中，端到端服务监控由跨每个段的互通OAM提供。本案例中涉及的典型段包括两个AC ME和一个PW ME，如图a.2（C）所示。这些段应位于服务提供商OAM域中。为了端到端监控的目的，需要一个互通功能来跨OAM段传输OAM信息流。取决于是否部署了同质VPWS或
heterogeneous VPWS is deployed, the interworking function could be straightforward or more involved.
如果部署了异构VPWS，则互通功能可以是直接的，也可以是更复杂的。
In this option, the CE and PE interfaces support MEPs for AC and PW MEs, and no MIPs are involved at the service provider OAM level, as shown in (C) in Figure A.2. Network operators may run segment OAM by having MEPs at the network operator OAM level, as shown in (D) in Figure A.2.
在该选项中，CE和PE接口支持AC和PW MEs的MEP，服务提供商OAM级别不涉及MIP，如图A.2（C）所示。网络运营商可以通过在网络运营商OAM级别设置MEP来运行段OAM，如图A.2（D）所示。
The limitations of this model are that it requires interworking across the OAM segments and does not conform to the OAM layering principles, where each OAM layer ought to be independent of the others. For end-to-end OAM determinations, the end-to-end service frame path is not necessarily exercised. Further, it requires interworking function implementation for all possible technologies across access and core that may be used to realize end-to-end services.
该模型的局限性在于，它需要跨OAM段进行互通，并且不符合OAM分层原则，即每个OAM层应该独立于其他层。对于端到端OAM确定，不必执行端到端服务帧路径。此外，它还需要实现跨接入和核心的所有可能技术的互通功能，这些技术可用于实现端到端服务。
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
|<--------------- VPWS <AC1,PW,AC2> -------------->|
| |
| +----+ +----+ |
+----+ | |==================| | +----+
| |---AC1----|............PW..............|--AC2-----| |
| CE1| |PE1 | | PE2| |CE2 |
+----+ | |==================| | +----+
+----+ PSN Tunnel +----+
(C) MEP-------MEP|MEP------------------MEP|MEP--------MEP
(D) MEP-------MEP|MEP------------------MEP|MEP--------MEP
(C) MEP-------MEP|MEP------------------MEP|MEP--------MEP
(D) MEP-------MEP|MEP------------------MEP|MEP--------MEP
Figure A.2: VPWS MEPs and MIPs (Segment OAM Interworking)
图A.2:VPWS-MEP和MIPs（段OAM互通）
Authors' Addresses
作者地址
Ali Sajassi (editor) Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134 USA EMail: sajassi@cisco.com
Ali Sajassi（编辑）Cisco Systems，Inc.美国加利福尼亚州圣何塞市西塔斯曼大道170号邮编：95134电子邮件：sajassi@cisco.com
Dinesh Mohan (editor) Nortel Ottawa, ON K2K3E5 EMail: dinmohan@hotmail.com
Dinesh Mohan（编辑）渥太华北电，K2K3E5电子邮件：dinmohan@hotmail.com