Internet Engineering Task Force (IETF) M. Aissaoui
Request for Comments: 6310 P. Busschbach
Category: Standards Track Alcatel-Lucent
ISSN: 2070-1721 L. Martini
M. Morrow
Cisco Systems, Inc.
T. Nadeau
CA Technologies
Y(J). Stein
RAD Data Communications
July 2011
Internet Engineering Task Force (IETF) M. Aissaoui
Request for Comments: 6310 P. Busschbach
Category: Standards Track Alcatel-Lucent
ISSN: 2070-1721 L. Martini
M. Morrow
Cisco Systems, Inc.
T. Nadeau
CA Technologies
Y(J). Stein
RAD Data Communications
July 2011
Pseudowire (PW) Operations, Administration, and Maintenance (OAM) Message Mapping
伪线（PW）操作、管理和维护（OAM）消息映射
Abstract
摘要
This document specifies the mapping and notification of defect states between a pseudowire (PW) and the Attachment Circuits (ACs) of the end-to-end emulated service. It standardizes the behavior of Provider Edges (PEs) with respect to PW and AC defects. It addresses ATM, Frame Relay, Time Division Multiplexing (TDM), and Synchronous Optical Network / Synchronous Digital Hierarchy (SONET/SDH) PW services, carried over MPLS, MPLS/IP, and Layer 2 Tunneling Protocol version 3/IP (L2TPv3/IP) Packet Switched Networks (PSNs).
本文档规定了端到端仿真服务的伪线（PW）和连接电路（ACs）之间缺陷状态的映射和通知。它规范了供应商边缘（PE）在PW和AC缺陷方面的行为。它解决ATM、帧中继、时分复用（TDM）和同步光网络/同步数字体系（SONET/SDH）PW服务，通过MPLS、MPLS/IP和第2层隧道协议版本3/IP（L2TPv3/IP）分组交换网络（PSN）承载。
Status of This Memo
关于下段备忘
This is an Internet Standards Track document.
这是一份互联网标准跟踪文件。
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。有关互联网标准的更多信息，请参见RFC 5741第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6310.
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/rfc6310.
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
2. Abbreviations and Conventions ...................................5
2.1. Abbreviations ..............................................5
2.2. Conventions ................................................6
3. Reference Model and Defect Locations ............................7
4. Abstract Defect States ..........................................8
5. OAM Modes .......................................................9
6. PW Defect States and Defect Notifications ......................11
6.1. PW Defect Notification Mechanisms .........................11
6.1.1. LDP Status TLV .....................................13
6.1.2. L2TP Circuit Status AVP ............................14
6.1.3. BFD Diagnostic Codes ...............................16
6.2. PW Defect State Entry/Exit ................................18
6.2.1. PW Receive Defect State Entry/Exit Criteria ........18
6.2.2. PW Transmit Defect State Entry/Exit Criteria .......19
7. Procedures for ATM PW Service ..................................19
7.1. AC Receive Defect State Entry/Exit Criteria ...............19
7.2. AC Transmit Defect State Entry/Exit Criteria ..............20
7.3. Consequent Actions ........................................21
7.3.1. PW Receive Defect State Entry/Exit .................21
7.3.2. PW Transmit Defect State Entry/Exit ................21
7.3.3. PW Defect State in ATM Port Mode PW Service ........22
7.3.4. AC Receive Defect State Entry/Exit .................22
7.3.5. AC Transmit Defect State Entry/Exit ................23
8. Procedures for Frame Relay PW Service ..........................24
8.1. AC Receive Defect State Entry/Exit Criteria ...............24
8.2. AC Transmit Defect State Entry/Exit Criteria ..............24
8.3. Consequent Actions ........................................24
8.3.1. PW Receive Defect State Entry/Exit .................24
8.3.2. PW Transmit Defect State Entry/Exit ................25
8.3.3. PW Defect State in the FR Port Mode PW Service .....25
8.3.4. AC Receive Defect State Entry/Exit .................25
8.3.5. AC Transmit Defect State Entry/Exit ................26
9. Procedures for TDM PW Service ..................................26
9.1. AC Receive Defect State Entry/Exit Criteria ...............27
9.2. AC Transmit Defect State Entry/Exit Criteria ..............27
9.3. Consequent Actions ........................................27
9.3.1. PW Receive Defect State Entry/Exit .................27
9.3.2. PW Transmit Defect State Entry/Exit ................27
9.3.3. AC Receive Defect State Entry/Exit .................28
10. Procedures for CEP PW Service .................................28
10.1. Defect States ............................................29
10.1.1. PW Receive Defect State Entry/Exit ................29
10.1.2. PW Transmit Defect State Entry/Exit ...............29
10.1.3. AC Receive Defect State Entry/Exit ................29
10.1.4. AC Transmit Defect State Entry/Exit ...............30
1. Introduction ....................................................4
2. Abbreviations and Conventions ...................................5
2.1. Abbreviations ..............................................5
2.2. Conventions ................................................6
3. Reference Model and Defect Locations ............................7
4. Abstract Defect States ..........................................8
5. OAM Modes .......................................................9
6. PW Defect States and Defect Notifications ......................11
6.1. PW Defect Notification Mechanisms .........................11
6.1.1. LDP Status TLV .....................................13
6.1.2. L2TP Circuit Status AVP ............................14
6.1.3. BFD Diagnostic Codes ...............................16
6.2. PW Defect State Entry/Exit ................................18
6.2.1. PW Receive Defect State Entry/Exit Criteria ........18
6.2.2. PW Transmit Defect State Entry/Exit Criteria .......19
7. Procedures for ATM PW Service ..................................19
7.1. AC Receive Defect State Entry/Exit Criteria ...............19
7.2. AC Transmit Defect State Entry/Exit Criteria ..............20
7.3. Consequent Actions ........................................21
7.3.1. PW Receive Defect State Entry/Exit .................21
7.3.2. PW Transmit Defect State Entry/Exit ................21
7.3.3. PW Defect State in ATM Port Mode PW Service ........22
7.3.4. AC Receive Defect State Entry/Exit .................22
7.3.5. AC Transmit Defect State Entry/Exit ................23
8. Procedures for Frame Relay PW Service ..........................24
8.1. AC Receive Defect State Entry/Exit Criteria ...............24
8.2. AC Transmit Defect State Entry/Exit Criteria ..............24
8.3. Consequent Actions ........................................24
8.3.1. PW Receive Defect State Entry/Exit .................24
8.3.2. PW Transmit Defect State Entry/Exit ................25
8.3.3. PW Defect State in the FR Port Mode PW Service .....25
8.3.4. AC Receive Defect State Entry/Exit .................25
8.3.5. AC Transmit Defect State Entry/Exit ................26
9. Procedures for TDM PW Service ..................................26
9.1. AC Receive Defect State Entry/Exit Criteria ...............27
9.2. AC Transmit Defect State Entry/Exit Criteria ..............27
9.3. Consequent Actions ........................................27
9.3.1. PW Receive Defect State Entry/Exit .................27
9.3.2. PW Transmit Defect State Entry/Exit ................27
9.3.3. AC Receive Defect State Entry/Exit .................28
10. Procedures for CEP PW Service .................................28
10.1. Defect States ............................................29
10.1.1. PW Receive Defect State Entry/Exit ................29
10.1.2. PW Transmit Defect State Entry/Exit ...............29
10.1.3. AC Receive Defect State Entry/Exit ................29
10.1.4. AC Transmit Defect State Entry/Exit ...............30
10.2. Consequent Actions .......................................30
10.2.1. PW Receive Defect State Entry/Exit ................30
10.2.2. PW Transmit Defect State Entry/Exit ...............30
10.2.3. AC Receive Defect State Entry/Exit ................30
11. Security Considerations .......................................31
12. Contributors and Acknowledgments ..............................31
13. References ....................................................32
13.1. Normative References .....................................32
13.2. Informative References ...................................34
Appendix A. Native Service Management (Informative) ...............36
A.1. Frame Relay Management .....................................36
A.2. ATM Management .............................................37
Appendix B. PW Defects and Detection Tools ........................38
B.1. PW Defects .................................................38
B.2. Packet Loss ................................................38
B.3. PW Defect Detection Tools ..................................38
B.4. PW Specific Defect Detection Mechanisms ....................39
10.2. Consequent Actions .......................................30
10.2.1. PW Receive Defect State Entry/Exit ................30
10.2.2. PW Transmit Defect State Entry/Exit ...............30
10.2.3. AC Receive Defect State Entry/Exit ................30
11. Security Considerations .......................................31
12. Contributors and Acknowledgments ..............................31
13. References ....................................................32
13.1. Normative References .....................................32
13.2. Informative References ...................................34
Appendix A. Native Service Management (Informative) ...............36
A.1. Frame Relay Management .....................................36
A.2. ATM Management .............................................37
Appendix B. PW Defects and Detection Tools ........................38
B.1. PW Defects .................................................38
B.2. Packet Loss ................................................38
B.3. PW Defect Detection Tools ..................................38
B.4. PW Specific Defect Detection Mechanisms ....................39
This document specifies the mapping and notification of defect states between a pseudowire and the Attachment Circuits (AC) of the end-to-end emulated service. It covers the case where the ACs and the PWs are of the same type in accordance to the Pseudowire Emulation Edge-to-Edge (PWE3) architecture [RFC3985] such that a homogeneous PW service can be constructed.
本文档规定了伪导线和端到端仿真服务的连接电路（AC）之间缺陷状态的映射和通知。它涵盖了根据伪线仿真边到边（PWE3）架构[RFC3985]ACs和PWs为同一类型的情况，从而可以构造同质PW服务。
This document is motivated by the requirements put forth in [RFC4377] and [RFC3916]. Its objective is to standardize the behavior of PEs with respect to defects on PWs and ACs, so that there is no ambiguity about the alarms generated and consequent actions undertaken by PEs in response to specific failure conditions.
本文件以[RFC4377]和[RFC3916]中提出的要求为依据。其目的是使PEs在PWs和ACs缺陷方面的行为标准化，从而使PEs在特定故障条件下产生的警报和采取的后续行动不存在歧义。
This document addresses PWs over MPLS, MPLS/IP, L2TPv3/IP PSNs, ATM, Frame Relay, TDM, and SONET/SDH PW native services. Due to its unique characteristics, the Ethernet PW service is covered in a separate document [Eth-OAM-Inter].
本文档通过MPLS、MPLS/IP、L2TPv3/IP PSN、ATM、帧中继、TDM和SONET/SDH PW本机服务解决PWs。由于其独特的特性，以太网PW服务包含在单独的文档[Eth OAM Inter]中。
This document provides procedures for PWs set up using Label Distribution Protocol (LDP) [RFC4447] or L2TPv3 [RFC3931] control protocols. While we mention fault reporting options for PWs established by other means (e.g., by static configuration or via BGP), we do not provide detailed procedures for such cases.
本文件提供了使用标签分发协议（LDP）[RFC4447]或L2TPv3[RFC3931]控制协议设置PWs的程序。虽然我们提到了通过其他方式（例如通过静态配置或通过BGP）建立的PWs故障报告选项，但我们没有提供此类情况的详细程序。
This document is scoped only to single segment PWs. The mechanisms described in this document could also be applied to terminating PEs (T-PEs) for multi-segment PWs (MS-PWs) ([RFC5254]). Section 10 of [RFC6073] details procedures for generating or relaying PW status by a switching PE (S-PE).
本文件仅适用于单段PWs。本文件中描述的机制也可用于多段PWs（MS PWs）（[RFC5254]）的端接PEs（T-PEs）。[RFC6073]第10节详细说明了通过切换PE（S-PE）生成或中继PW状态的程序。
AAL5 ATM Adaptation Layer 5 AIS Alarm Indication Signal AC Attachment Circuit ATM Asynchronous Transfer Mode AVP Attribute Value Pair BFD Bidirectional Forwarding Detection CC Continuity Check CDN Call Disconnect Notify CE Customer Edge CV Connectivity Verification DBA Dynamic Bandwidth Allocation DLC Data Link Connection FDI Forward Defect Indication FR Frame Relay FRBS Frame Relay Bearer Service ICMP Internet Control Message Protocol LB Loopback LCCE L2TP Control Connection Endpoint LDP Label Distribution Protocol LSP Label Switched Path L2TP Layer 2 Tunneling Protocol MPLS Multiprotocol Label Switching NE Network Element NS Native Service OAM Operations, Administration, and Maintenance PE Provider Edge PSN Packet Switched Network PW Pseudowire RDI Reverse Defect Indication PDU Protocol Data Unit SDH Synchronous Digital Hierarchy SDU Service Data Unit SONET Synchronous Optical Network TDM Time Division Multiplexing TLV Type Length Value VCC Virtual Channel Connection VCCV Virtual Connection Connectivity Verification VPC Virtual Path Connection
AAL5 ATM适配层5 AIS报警指示信号AC连接电路ATM异步传输模式AVP属性值对BFD双向转发检测CC连续性检查CDN呼叫断开通知CE客户边缘CV连接验证DBA动态带宽分配DLC数据链路连接FDI转发缺陷指示FR帧中继FRBS帧中继承载服务ICMP Internet控制消息协议LB环回LCCE L2TP控制连接端点LDP标签分发协议LSP标签交换路径L2TP第2层隧道协议MPLS多协议标签交换网元NS本机服务OAM操作、管理、，和维护PE提供商边缘PSN分组交换网络PW伪线RDI反向缺陷指示PDU协议数据单元SDH同步数字层次SDU业务数据单元SONET同步光网络TDM时分复用TLV类型长度值VCC虚拟通道连接VCCV虚拟连接连接连接验证VPC虚拟路径连接
The words "defect" and "fault" are used interchangeably to mean any condition that negatively impacts forwarding of user traffic between the CE endpoints of the PW service.
词语“缺陷”和“故障”可互换地用于表示对PW服务的CE端点之间的用户通信的转发产生负面影响的任何条件。
The words "defect notification" and "defect indication" are used interchangeably to mean any OAM message generated by a PE and sent to other nodes in the network to convey the defect state local to this PE.
词语“缺陷通知”和“缺陷指示”可交换地用于表示由PE生成并发送到网络中的其他节点以传送该PE本地的缺陷状态的任何OAM消息。
The PW can be carried over three types of Packet Switched Networks (PSNs). An "MPLS PSN" makes use of MPLS Label Switched Paths [RFC3031] as the tunneling technology to forward the PW packets. An "MPLS/IP PSN" makes use of MPLS-in-IP tunneling [RFC4023], with an MPLS shim header used as PW demultiplexer. An "L2TPv3/IP PSN" makes use of L2TPv3/IP [RFC3931] as the tunneling technology with the L2TPv3/IP Session ID as the PW demultiplexer.
PW可以通过三种类型的分组交换网络（PSN）承载。“MPLS PSN”利用MPLS标签交换路径[RFC3031]作为隧道技术来转发PW分组。“MPLS/IP PSN”在IP隧道[RFC4023]中使用MPLS，MPLS填充头用作PW解复用器。“L2TPv3/IP PSN”使用L2TPv3/IP[RFC3931]作为隧道技术，L2TPv3/IP会话ID作为PW解复用器。
If LSP-Ping [RFC4379] is run over a PW as described in [RFC5085], it will be referred to as "VCCV-Ping". If BFD is run over a PW as described in [RFC5885], it will be referred to as "VCCV-BFD".
如果LSP Ping[RFC4379]如[RFC5085]中所述在PW上运行，则它将被称为“VCCV Ping”。如[RFC5885]所述，若BFD在PW上运行，则将其称为“VCCV-BFD”。
While PWs are inherently bidirectional entities, defects and OAM messaging are related to a specific traffic direction. We use the terms "upstream" and "downstream" to identify PEs in relation to the traffic direction. A PE is upstream for the traffic it is forwarding and is downstream for the traffic it is receiving.
虽然PW本质上是双向实体，但缺陷和OAM消息传递与特定的通信方向有关。我们使用术语“上游”和“下游”来识别与交通方向相关的PEs。PE是其转发的流量的上游，是其接收的流量的下游。
We use the terms "local" and "remote" to identify native service networks and ACs in relation to a specific PE. The local AC is attached to the PE in question, while the remote AC is attached to the PE at the other end of the PW.
我们使用术语“本地”和“远程”来识别与特定PE相关的本机服务网络和ACs。本地AC连接到相关PE，而远程AC连接到PW另一端的PE。
A "transmit defect" is any defect that uniquely impacts traffic sent or relayed by the observing PE. A "receive defect" is any defect that impacts information transfer to the observing PE. Note that a receive defect also impacts traffic meant to be relayed, and thus can be considered to incorporate two defect states. Thus, when a PE enters both receive and transmit defect states of a PW service, the receive defect takes precedence over the transmit defect in terms of the consequent actions.
“传输缺陷”是唯一影响观察PE发送或中继的流量的任何缺陷。“接收缺陷”是指影响向观察PE传输信息的任何缺陷。请注意，接收缺陷也会影响要中继的通信量，因此可以将其视为包含两种缺陷状态。因此，当PE同时进入PW服务的接收和发送缺陷状态时，接收缺陷在后续动作方面优先于发送缺陷。
A "forward defect indication" (FDI) is sent in the same direction as the user traffic impacted by the defect. A "reverse defect indication" (RDI) is sent in the direction opposite to that of the impacted traffic.
“前向缺陷指示”（FDI）以与受缺陷影响的用户流量相同的方向发送。“反向缺陷指示”（RDI）以与受影响流量相反的方向发送。
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。
Figure 1 illustrates the PWE3 network reference model with an indication of the possible defect locations. This model will be referenced in the remainder of this document for describing the OAM procedures.
图1说明了PWE3网络参考模型，并指出了可能的缺陷位置。本文档的其余部分将引用此模型，以描述OAM过程。
ACs PSN tunnel ACs
+----+ +----+
+----+ | PE1|==================| PE2| +----+
| |---(a)---(b)..(c)......PW1..(d)..(e)..(f)---(g)---| |
| CE1| (N1) | | | | (N2) |CE2 |
| |----------|............PW2.............|----------| |
+----+ | |==================| | +----+
^ +----+ +----+ ^
| Provider Edge 1 Provider Edge 2 |
| |
|<-------------- Emulated Service ---------------->|
Customer Customer
Edge 1 Edge 2
ACs PSN tunnel ACs
+----+ +----+
+----+ | PE1|==================| PE2| +----+
| |---(a)---(b)..(c)......PW1..(d)..(e)..(f)---(g)---| |
| CE1| (N1) | | | | (N2) |CE2 |
| |----------|............PW2.............|----------| |
+----+ | |==================| | +----+
^ +----+ +----+ ^
| Provider Edge 1 Provider Edge 2 |
| |
|<-------------- Emulated Service ---------------->|
Customer Customer
Edge 1 Edge 2
Figure 1: PWE3 Network Defect Locations
图1:PWE3网络缺陷位置
The procedures will be described in this document from the viewpoint of PE1, so that N1 is the local native service network and N2 is the remote native service network. PE2 will typically implement the same functionality. Note that PE1 is the upstream PE for traffic originating in the local NS network N1, while it is the downstream PE for traffic originating in the remote NS network N2.
本文件将从PE1的角度描述这些过程，因此N1是本地本机服务网络，N2是远程本机服务网络。PE2通常会实现相同的功能。请注意，对于源自本地NS网络N1的流量，PE1是上游PE，而对于源自远程NS网络N2的流量，PE1是下游PE。
The following is a brief description of the defect locations:
以下是缺陷位置的简要说明：
a. Defect in NS network N1. This covers any defect in network N1 (including any CE1 defect) that impacts all or some ACs attached to PE1, and is thus a local AC defect. The defect is conveyed to PE1 and to NS network N2 using NS specific OAM defect indications.
a. NS网络N1中的缺陷。这包括网络N1中影响连接到PE1的所有或部分ACs的任何缺陷（包括任何CE1缺陷），因此属于局部AC缺陷。使用NS特定OAM缺陷指示将缺陷传送到PE1和NS网络N2。
b. Defect on a PE1 AC interface (another local AC defect).
b. PE1交流接口上的缺陷（另一个局部交流缺陷）。
c. Defect on a PE1 PSN interface.
c. PE1 PSN接口上的缺陷。
d. Defect in the PSN network. This covers any defect in the PSN that impacts all or some PWs between PE1 and PE2. The defect is conveyed to the PE using a PSN and/or a PW specific OAM defect
d. PSN网络中的缺陷。这包括PSN中影响PE1和PE2之间所有或部分PW的任何缺陷。使用PSN和/或特定于PW的OAM缺陷将缺陷传送到PE
indication. Note that both data plane defects and control plane defects must be taken into consideration. Although control messages may follow a different path than PW data plane traffic, a control plane defect may affect the PW status.
指示请注意，必须同时考虑数据平面缺陷和控制平面缺陷。尽管控制消息可能遵循与PW数据平面通信不同的路径，但控制平面缺陷可能会影响PW状态。
e. Defect on a PE2 PSN interface.
e. PE2 PSN接口上的缺陷。
f. Defect on a PE2 AC interface (a remote AC defect).
f. PE2交流接口上的缺陷（远程交流缺陷）。
g. Defect in NS network N2 (another remote AC defect). This covers any defect in N2 (including any CE2 defect) that impacts all or a subset of ACs attached to PE2. The defect is conveyed to PE2 and to NS network N1 using the NS OAM defect indication.
g. NS网络N2中存在缺陷（另一个远程交流缺陷）。这包括N2中的任何缺陷（包括任何CE2缺陷），这些缺陷会影响连接至PE2的所有或部分ACs。使用NS OAM缺陷指示将缺陷传送到PE2和NS网络N1。
PE1 must track four defect states that reflect the observed states of both directions of the PW service on both the AC and the PW sides. Defects may impact one or both directions of the PW service.
PE1必须跟踪反映交流侧和PW侧PW服务两个方向的观察状态的四种缺陷状态。缺陷可能影响PW服务的一个或两个方向。
The observed state is a combination of defects directly detected by PE1 and defects of which it has been made aware via notifications.
观察到的状态是PE1直接检测到的缺陷和通过通知告知的缺陷的组合。
+-----+
----AC receive---->| |-----PW transmit---->
CE1 | PE1 | PE2/CE2
<---AC transmit----| |<----PW receive-----
+-----+
(arrows indicate direction of user traffic impacted by a defect)
+-----+
----AC receive---->| |-----PW transmit---->
CE1 | PE1 | PE2/CE2
<---AC transmit----| |<----PW receive-----
+-----+
(arrows indicate direction of user traffic impacted by a defect)
Figure 2: Receive and Transmit Defect States
图2：接收和发送缺陷状态
PE1 will directly detect or be notified of AC receive or PW receive defects as they occur upstream of PE1 and impact traffic being sent to PE1. As a result, PE1 enters the AC or PW receive defect state.
当AC接收或PW接收缺陷发生在PE1上游并影响发送至PE1的流量时，PE1将直接检测或被通知AC接收或PW接收缺陷。因此，PE1进入AC或PW接收缺陷状态。
In Figure 2, PE1 may be notified of a receive defect in the AC by receiving a forward defect indication, e.g., ATM AIS, from CE1 or an intervening network. This defect notification indicates that user traffic sent by CE1 may not be received by PE1 due to a defect. PE1 can also directly detect an AC receive defect if it resulted from a failure of the receive side in the local port or link over which the AC is configured.
在图2中，可以通过从CE1或中间网络接收前向缺陷指示（例如ATM AIS）来通知PE1 AC中的接收缺陷。此缺陷通知表示由于缺陷，PE1可能无法接收CE1发送的用户通信量。如果AC接收端在配置AC的本地端口或链路中发生故障，PE1还可以直接检测AC接收缺陷。
Similarly, PE1 may detect or be notified of a receive defect in the PW by receiving a forward defect indication from PE2. If the PW status TLV is used for fault notification, this message will indicate a Local PSN-facing PW (egress) Transmit Fault or a Local AC (ingress)
类似地，PE1可以通过从PE2接收前向缺陷指示来检测PW中的接收缺陷或被通知PW中的接收缺陷。如果PW状态TLV用于故障通知，则此消息将指示面向PW（出口）传输故障的本地PSN或本地AC（入口）
Receive Fault at PE2, as described in Section 6.1.1. This defect notification indicates that user traffic sent by CE2 may not be received by PE1 due to a defect. As a result, PE1 enters the PW receive defect state.
在PE2处接收故障，如第6.1.1节所述。此缺陷通知表示由于缺陷，PE1可能无法接收CE2发送的用户通信量。结果，PE1进入PW接收缺陷状态。
Note that a forward defect indication is sent in the same direction as the user traffic impacted by the defect.
请注意，正向缺陷指示的发送方向与受缺陷影响的用户通信量的发送方向相同。
Generally, a PE cannot detect transmit defects by itself and will therefore need to be notified of AC transmit or PW transmit defects by other devices.
一般而言，PE自身无法检测传输缺陷，因此需要由其他设备通知AC传输或PW传输缺陷。
In Figure 2, PE1 may be notified of a transmit defect in the AC by receiving a reverse defect indication, e.g., ATM RDI, from CE1. This defect relates to the traffic sent by PE1 to CE1 on the AC.
在图2中，可以通过从CE1接收反向缺陷指示（例如ATM RDI）来通知PE1 AC中的发射缺陷。此缺陷与PE1在AC上发送到CE1的通信量有关。
Similarly, PE1 may be notified of a transmit defect in the PW by receiving a reverse defect indication from PE2. If PW status is used for fault notification, this message will indicate a Local PSN-facing PW (ingress) Receive Fault or a Local Attachment Circuit (egress) Transmit Fault at PE2, as described in Section 6.1.1. This defect impacts the traffic sent by PE1 to CE2. As a result, PE1 enters the PW transmit defect state.
类似地，可以通过从PE2接收反向缺陷指示来通知PE1 PW中的发射缺陷。如果PW状态用于故障通知，该消息将指示PE2处的本地PSN面对PW（入口）接收故障或本地连接电路（出口）传输故障，如第6.1.1节所述。此缺陷影响PE1发送到CE2的通信量。结果，PE1进入PW传输缺陷状态。
Note that a reverse defect indication is sent in the reverse direction to the user traffic impacted by the defect.
请注意，反向缺陷指示以相反方向发送给受缺陷影响的用户流量。
The procedures outlined in this document define the entry and exit criteria for each of the four states with respect to the set of PW services within the document scope and the consequent actions that PE1 must perform.
本文件中概述的程序定义了四个州的进入和退出标准，涉及文件范围内的一组PW服务以及PE1必须执行的后续行动。
When a PE enters both receive and transmit defect states related to the same PW service, then the receive defect takes precedence over transmit defect in terms of the consequent actions.
当PE进入与同一PW服务相关的接收和发送缺陷状态时，接收缺陷在后续动作方面优先于发送缺陷。
A homogeneous PW service forwards packets between an AC and a PW of the same type. It thus implements both NS OAM and PW OAM mechanisms. PW OAM defect notification messages are described in Section 6.1. NS OAM messages are described in Appendix A.
同质PW服务在AC和相同类型的PW之间转发数据包。因此，它实现了NS OAM和PW OAM机制。PW OAM缺陷通知消息见第6.1节。NS OAM消息在附录A中描述。
This document defines two different OAM modes, the distinction being the method of mapping between the NS and PW OAM defect notification messages.
本文档定义了两种不同的OAM模式，区别在于NS和PW OAM缺陷通知消息之间的映射方法。
The first mode, illustrated in Figure 3, is called the "single
emulated OAM loop" mode. Here, a single end-to-end NS OAM loop is
emulated by transparently passing NS OAM messages over the PW. Note
that the PW OAM is shown outside the PW in Figure 3, as it is
transported in LDP messages or in the associated channel, not inside
the PW itself.
+-----+ +-----+
+-----+ | |=================| | +-----+
| CE1 |-=NS-OAM=>| PE1 |----=NS-OAM=>----| PE2 |-=NS-OAM=>| CE2 |
+-----+ | |=================| | +-----+
+-----+ +-----+
\ /
-------=PW-OAM=>-------
The first mode, illustrated in Figure 3, is called the "single
emulated OAM loop" mode. Here, a single end-to-end NS OAM loop is
emulated by transparently passing NS OAM messages over the PW. Note
that the PW OAM is shown outside the PW in Figure 3, as it is
transported in LDP messages or in the associated channel, not inside
the PW itself.
+-----+ +-----+
+-----+ | |=================| | +-----+
| CE1 |-=NS-OAM=>| PE1 |----=NS-OAM=>----| PE2 |-=NS-OAM=>| CE2 |
+-----+ | |=================| | +-----+
+-----+ +-----+
\ /
-------=PW-OAM=>-------
Figure 3: Single Emulated OAM Loop Mode
图3：单模拟OAM循环模式
The single emulated OAM loop mode implements the following behavior:
单一模拟OAM循环模式实现以下行为：
a. The upstream PE (PE1) MUST transparently relay NS OAM messages over the PW.
a. 上游PE（PE1）必须通过PW透明地中继NS OAM消息。
b. The upstream PE MUST signal local defects affecting the AC using a NS defect notification message sent over the PW. In the case that it is not possible to generate NS OAM messages (e.g., because the defect interferes with NS OAM message generation), the PE MUST signal local defects affecting the AC using a PW defect notification message.
b. 上游PE必须使用通过PW发送的NS缺陷通知消息通知影响AC的局部缺陷。在不可能生成NS OAM消息的情况下（例如，由于缺陷干扰NS OAM消息的生成），PE必须使用PW缺陷通知消息向影响AC的本地缺陷发送信号。
c. The upstream PE MUST signal local defects affecting the PW using a PW defect notification message.
c. 上游PE必须使用PW缺陷通知消息通知影响PW的局部缺陷。
d. The downstream PE (PE2) MUST insert NS defect notification messages into its local AC when it detects or is notified of a defect in the PW or remote AC. This includes translating received PW defect notification messages into NS defect notification messages for defects signaled by the upstream PE.
d. 当下游PE（PE2）检测到PW或远程AC中的缺陷或被通知时，必须将NS缺陷通知消息插入其本地AC。这包括将收到的PW缺陷通知消息转换为上游PE发出信号的缺陷的NS缺陷通知消息。
The single emulated OAM loop mode is suitable for PW services that have a widely deployed NS OAM mechanism. This document specifies the use of this mode for ATM PW, TDM PW, and Circuit Emulation over Packet (CEP) PW services. It is the default mode of operation for all ATM cell mode PW services and the only mode specified for CEP and Structure-Agnostic TDM over Packets / Circuit Emulation Service over Packet Switched Network (SAToP/CESoPSN) TDM PW services. It is optional for AAL5 PDU transport and AAL5 SDU transport modes.
单模拟OAM循环模式适用于具有广泛部署的NS OAM机制的PW服务。本文件规定了在ATM PW、TDM PW和分组电路仿真（CEP）PW服务中使用此模式。它是所有ATM信元模式PW服务的默认操作模式，也是为CEP和结构无关的分组TDM/分组交换网络电路仿真服务（SAToP/CESoPSN）TDM PW服务指定的唯一模式。对于AAL5 PDU传输和AAL5 SDU传输模式，它是可选的。
The second OAM mode operates three OAM loops joined at the AC/PW
boundaries of the PEs. This is referred to as the "coupled OAM
loops" mode and is illustrated in Figure 4. Note that in contrast to
Figure 3, NS OAM messages are never carried over the PW.
+-----+ +-----+
+-----+ | |=================| | +-----+
| CE1 |-=NS-OAM=>| PE1 | | PE2 |-=NS-OAM=>| CE2 |
+-----+ | |=================| | +-----+
+-----+ +-----+
\ /
-------=PW-OAM=>-------
The second OAM mode operates three OAM loops joined at the AC/PW
boundaries of the PEs. This is referred to as the "coupled OAM
loops" mode and is illustrated in Figure 4. Note that in contrast to
Figure 3, NS OAM messages are never carried over the PW.
+-----+ +-----+
+-----+ | |=================| | +-----+
| CE1 |-=NS-OAM=>| PE1 | | PE2 |-=NS-OAM=>| CE2 |
+-----+ | |=================| | +-----+
+-----+ +-----+
\ /
-------=PW-OAM=>-------
Figure 4: Coupled OAM Loops Mode
图4：耦合OAM环路模式
The coupled OAM loops mode implements the following behavior:
耦合OAM循环模式实现以下行为：
a. The upstream PE (PE1) MUST terminate and translate a received NS defect notification message into a PW defect notification message.
a. 上游PE（PE1）必须终止并将收到的NS缺陷通知消息转换为PW缺陷通知消息。
b. The upstream PE MUST signal local failures affecting its local AC using PW defect notification messages to the downstream PE.
b. 上游PE必须使用PW缺陷通知消息向下游PE发送影响其本地AC的本地故障信号。
c. The upstream PE MUST signal local failures affecting the PW using PW defect notification messages.
c. 上游PE必须使用PW缺陷通知消息发出影响PW的本地故障信号。
d. The downstream PE (PE2) MUST insert NS defect notification messages into the AC when it detects or is notified of defects in the PW or remote AC. This includes translating received PW defect notification messages into NS defect notification messages.
d. 当下游PE（PE2）检测到PW或远程AC中的缺陷或收到缺陷通知时，必须将NS缺陷通知消息插入AC。这包括将收到的PW缺陷通知消息转换为NS缺陷通知消息。
This document specifies the coupled OAM loops mode as the default mode for the Frame Relay, ATM AAL5 PDU transport, and AAL5 SDU transport services. It is an optional mode for ATM VCC cell mode services. This mode is not specified for TDM, CEP, or ATM VPC cell mode PW services. RFC 5087 defines a similar but distinct mode, as will be explained in Section 9. For the ATM VPC cell mode case a pure coupled OAM loops mode is not possible as a PE MUST transparently pass VC-level (F5) ATM OAM cells over the PW while terminating and translating VP-level (F4) OAM cells.
本文档将耦合OAM环路模式指定为帧中继、ATM AAL5 PDU传输和AAL5 SDU传输服务的默认模式。它是ATM VCC信元模式服务的可选模式。此模式不适用于TDM、CEP或ATM VPC信元模式PW服务。RFC 5087定义了类似但不同的模式，如第9节所述。对于ATM VPC信元模式，纯耦合OAM环路模式是不可能的，因为PE必须在PW上透明地通过VC级（F5）ATM OAM信元，同时终止和转换VP级（F4）OAM信元。
For MPLS and MPLS/IP PSNs, a PE that establishes a PW using the Label Distribution Protocol [RFC5036], and that has negotiated use of the LDP status TLV per Section 5.4.3 of [RFC4447], MUST use the PW status
对于MPLS和MPLS/IP PSN，使用标签分发协议[RFC5036]建立PW并根据[RFC4447]第5.4.3节协商使用LDP状态TLV的PE必须使用PW状态
TLV mechanism for AC and PW status and defect notification. Additionally, such a PE MAY use VCCV-BFD Connectivity Verification (CV) for fault detection only (CV types 0x04 and 0x10 [RFC5885]).
AC和PW状态和缺陷通知的TLV机制。此外，此类PE可将VCCV-BFD连接验证（CV）仅用于故障检测（CV类型0x04和0x10[RFC5885]）。
A PE that establishes an MPLS PW using means other than LDP, e.g., by static configuration or by use of BGP, MUST support some alternative method of status reporting. The design of a suitable mechanism to carry the aforementioned status TLV in the PW associated channel is work in progress [Static-PW-Status]. Additionally, such a PE MAY use VCCV-BFD CV for both fault detection and status notification (CV types 0x08 and 0x20 [RFC5885]).
使用LDP以外的方法建立MPLS PW的PE，例如通过静态配置或使用BGP，必须支持某种状态报告的替代方法。在PW相关信道中承载上述状态TLV的适当机制的设计正在进行[静态PW状态]。此外，此类PE可将VCCV-BFD CV用于故障检测和状态通知（CV类型0x08和0x20[RFC5885]）。
For a L2TPv3/IP PSN, a PE SHOULD use the Circuit Status Attribute Value Pair (AVP) as the mechanism for AC and PW status and defect notification. In its most basic form, the Circuit Status AVP [RFC3931] in a Set-Link-Info (SLI) message can signal active/inactive AC status. The Circuit Status AVP as described in [RFC5641] is proposed to be extended to convey status and defects in the AC and the PSN-facing PW in both ingress and egress directions, i.e., four independent status bits, without the need to tear down the sessions or control connection.
对于L2TPv3/IP PSN，PE应使用电路状态属性值对（AVP）作为AC和PW状态和缺陷通知的机制。在其最基本的形式中，Set Link Info（SLI）消息中的电路状态AVP[RFC3931]可以表示激活/非激活AC状态。建议扩展[RFC5641]中所述的电路状态AVP，以在入口和出口方向（即四个独立的状态位）传输AC和面向PSN的PW中的状态和缺陷，而无需中断会话或控制连接。
When a PE does not support the Circuit Status AVP, it MAY use the Stop-Control-Connection-Notification (StopCCN) and the Call-Disconnect-Notify (CDN) messages to tear down L2TP sessions in a fashion similar to LDP's use of Label Withdrawal to tear down a PW. A PE may use the StopCCN to shut down the L2TP control connection, and implicitly all L2TP sessions associated with that control connection, without any explicit session control messages. This is useful for the case of a failure which impacts all L2TP sessions (all PWs) managed by the control connection. It MAY use CDN to disconnect a specific L2TP session when a failure only affects a specific PW.
当PE不支持电路状态AVP时，它可以使用停止控制连接通知（StopCCN）和呼叫断开通知（CDN）消息来中断L2TP会话，方式类似于LDP使用标签撤销来中断PW。PE可以使用StopCCN关闭L2TP控制连接，并隐式关闭与该控制连接关联的所有L2TP会话，而无需任何显式会话控制消息。这对于影响由控制连接管理的所有L2TP会话（所有PW）的故障非常有用。当故障仅影响特定PW时，它可以使用CDN断开特定L2TP会话。
Additionally, a PE MAY use VCCV-BFD CV types 0x04 and 0x10 for fault detection only, but SHOULD notify the remote PE using the Circuit Status AVP. A PE that establishes a PW using means other than the L2TP control plane, e.g., by static configuration or by use of BGP, MAY use VCCV-BFD CV types 0x08 and 0x20 for AC and PW status and defect notification. These CV types SHOULD NOT be used when the PW is established via the L2TP control plane.
此外，PE可使用VCCV-BFD CV类型0x04和0x10仅用于故障检测，但应使用电路状态AVP通知远程PE。使用L2TP控制平面以外的方式（例如通过静态配置或使用BGP）建立PW的PE可以使用VCCV-BFD CV类型0x08和0x20，用于AC和PW状态和缺陷通知。当通过L2TP控制平面建立PW时，不应使用这些CV类型。
The CV types are defined in Section 6.1.3 of this document.
本文件第6.1.3节定义了CV类型。
[RFC4446] defines the following PW status code points:
[RFC4446]定义了以下PW状态代码点：
0x00000000 - Pseudowire forwarding (clear all failures)
0x00000000-伪线转发（清除所有故障）
0x00000001 - Pseudowire Not Forwarding
0x00000001-伪线未转发
0x00000002 - Local Attachment Circuit (ingress) Receive Fault
0x00000002-本地连接电路（入口）接收故障
0x00000004 - Local Attachment Circuit (egress) Transmit Fault
0x00000004-本地连接电路（出口）传输故障
0x00000008 - Local PSN-facing PW (ingress) Receive Fault
0x00000008-面向PW（入口）的本地PSN接收故障
0x00000010 - Local PSN-facing PW (egress) Transmit Fault
0x00000010-本地PSN面对PW（出口）传输故障
[RFC4447] specifies that the "Pseudowire forwarding" code point is used to indicate that all faults are to be cleared. It also specifies that the "Pseudowire Not Forwarding" code point means that a defect has been detected that is not represented by the defined code points.
[RFC4447]指定“伪线转发”代码点用于指示要清除所有故障。它还指定“伪线不转发”代码点表示已检测到未由定义的代码点表示的缺陷。
The code points used in the LDP status TLV in a PW status notification message report defects from the viewpoint of the originating PE. The originating PE conveys this state in the form of a forward defect or a reverse defect indication.
PW状态通知消息中LDP状态TLV中使用的代码点从发起PE的角度报告缺陷。原始PE以正向缺陷或反向缺陷指示的形式传达该状态。
The forward and reverse defect indication definitions used in this document map to the LDP Status TLV codes as follows:
本文件中使用的正向和反向缺陷指示定义映射到LDP状态TLV代码，如下所示：
Forward defect indication corresponds to the logical OR of:
正向缺陷指示对应于以下逻辑或：
* Local Attachment Circuit (ingress) Receive Fault,
* 本地连接电路（入口）接收故障，
* Local PSN-facing PW (egress) Transmit Fault, and
* 面对PW（出口）传输故障的本地PSN，以及
* PW Not Forwarding.
* 不转发。
Reverse defect indication corresponds to the logical OR of:
反向缺陷指示对应于以下逻辑或：
* Local Attachment Circuit (egress) Transmit Fault and
* 本地连接电路（出口）传输故障和
* Local PSN-facing PW (ingress) Receive Fault.
* 面向PW（入口）的本地PSN接收故障。
A PE MUST use PW status notification messages to report all defects affecting the PW service including, but not restricted to, the following:
PE必须使用PW状态通知消息来报告影响PW服务的所有缺陷，包括但不限于以下内容：
o defects detected through fault detection mechanisms in the MPLS and MPLS/IP PSN,
o 通过MPLS和MPLS/IP PSN中的故障检测机制检测到的缺陷，
o defects detected through VCCV-Ping or VCCV-BFD CV types 0x04 and 0x10 for fault detection only,
o 通过VCCV Ping或VCCV-BFD CV类型0x04和0x10检测到的缺陷，仅用于故障检测，
o defects within the PE that result in an inability to forward traffic between the AC and the PW,
o PE内的缺陷导致无法转发AC和PW之间的通信量，
o defects of the AC or in the Layer 2 network affecting the AC as per the rules detailed in Section 5 for the "single emulated OAM loop" mode and "coupled OAM loops" modes.
o 根据第5节“单模拟OAM环路”模式和“耦合OAM环路”模式中详述的规则，影响AC的AC或第2层网络中的缺陷。
Note that there are two situations that require PW label withdrawal as opposed to a PW status notification by the PE. The first one is when the PW is taken down administratively in accordance with [RFC4447]. The second one is when the Target LDP session established between the two PEs is lost. In the latter case, the PW labels will need to be re-signaled when the Targeted LDP session is re-established.
请注意，有两种情况需要撤销PW标签，而不是PE发出PW状态通知。第一个是根据[RFC4447]以管理方式取下PW时。第二种情况是两个PE之间建立的目标LDP会话丢失。在后一种情况下，当重新建立目标LDP会话时，需要重新通知PW标签。
[RFC3931] defines the Circuit Status AVP in the Set-Link-Info (SLI) message to exchange initial status and status changes in the circuit to which the pseudowire is bound. [RFC5641] defines extensions to the Circuit Status AVP that are analogous to the PW Status TLV defined for LDP. Consequently, for L2TPv3/IP, the Circuit Status AVP is used in the same fashion as the PW Status described in the previous section. Extended circuit status for L2TPv3/IP is described in [RFC5641].
[RFC3931]在Set Link Info（SLI）消息中定义电路状态AVP，以交换虚拟线绑定到的电路中的初始状态和状态更改。[RFC5641]定义了电路状态AVP的扩展，类似于为LDP定义的PW状态TLV。因此，对于L2TPv3/IP，电路状态AVP的使用方式与前一节中描述的PW状态相同。L2TPv3/IP的扩展电路状态如[RFC5641]所述。
If the extended Circuit Status bits are not supported, and instead only the "A bit" (Active) is used as described in [RFC3931], a PE MAY use CDN messages to clear L2TPv3/IP sessions in the presence of session-level failures detected in the L2TPv3/IP PSN.
如果不支持扩展电路状态位，而只使用[RFC3931]中所述的“A位”（活动），则PE可使用CDN消息在L2TPv3/IP PSN中检测到会话级故障时清除L2TPv3/IP会话。
A PE MUST set the Active bit in the Circuit Status to clear all faults, and it MUST clear the Active bit in the Circuit Status to convey any defect that cannot be represented explicitly with specific Circuit Status flags from [RFC3931] or [RFC5641].
PE必须在电路状态下设置活动位以清除所有故障，并且必须在电路状态下清除活动位以传达无法通过[RFC3931]或[RFC5641]中的特定电路状态标志明确表示的任何缺陷。
The forward and reverse defect indication definitions used in this document map to the L2TP Circuit Status AVP as follows:
本文件中使用的正向和反向缺陷指示定义映射到L2TP电路状态AVP，如下所示：
Forward defect indication corresponds to the logical OR of:
正向缺陷指示对应于以下逻辑或：
* Local Attachment Circuit (ingress) Receive Fault,
* 本地连接电路（入口）接收故障，
* Local PSN-facing PW (egress) Transmit Fault, and
* 面对PW（出口）传输故障的本地PSN，以及
* PW Not Forwarding.
* 不转发。
Reverse defect indication corresponds to the logical OR of:
反向缺陷指示对应于以下逻辑或：
* Local Attachment Circuit (egress) Transmit Fault and
* 本地连接电路（出口）传输故障和
* Local PSN-facing PW (ingress) Receive Fault.
* 面向PW（入口）的本地PSN接收故障。
The status notification conveys defects from the viewpoint of the originating LCCE (PE).
状态通知从发起LCCE（PE）的角度传达缺陷。
When the extended Circuit Status definition of [RFC5641] is supported, a PE SHALL use the Circuit Status to report all failures affecting the PW service including, but not restricted to, the following:
当支持[RFC5641]的扩展电路状态定义时，PE应使用电路状态报告影响PW服务的所有故障，包括但不限于以下内容：
o defects detected through defect detection mechanisms in the L2TPv3/IP PSN,
o 通过L2TPv3/IP PSN中的缺陷检测机制检测到的缺陷，
o defects detected through VCCV-Ping or VCCV-BFD CV types 0x04 (BFD IP/UDP-encapsulated, for PW Fault Detection only) and 0x10 (BFD PW-ACH-encapsulated (without IP/UDP headers), for PW. Fault Detection and AC/PW Fault Status Signaling) for fault detection only which are described in Section 6.1.3 of this document,
o 通过VCCV Ping或VCCV-BFD CV类型0x04（BFD IP/UDP封装，仅用于PW故障检测）和0x10（BFD PW ACH封装（无IP/UDP头），仅用于PW故障检测和AC/PW故障状态信号）检测到的缺陷，如本文件第6.1.3节所述，
o defects within the PE that result in an inability to forward traffic between the AC and the PW,
o PE内的缺陷导致无法转发AC和PW之间的通信量，
o defects of the AC or in the L2 network affecting the AC as per the rules detailed in Section 5 for the "single emulated OAM loop" mode and the "coupled OAM loops" modes.
o 根据第5节“单模拟OAM环路”模式和“耦合OAM环路”模式详述的规则，影响AC的AC或L2网络中的缺陷。
When the extended Circuit Status definition of [RFC5641] is not supported, a PE SHALL use the A bit in the Circuit Status AVP in the SLI to report:
当[RFC5641]的扩展电路状态定义不受支持时，PE应使用SLI中电路状态AVP中的a位来报告：
o defects of the AC or in the L2 network affecting the AC as per the rules detailed in Section 5 for the "single emulated OAM loop" mode and the "coupled OAM loops" modes.
o 根据第5节“单模拟OAM环路”模式和“耦合OAM环路”模式详述的规则，影响AC的AC或L2网络中的缺陷。
When the extended Circuit Status definition of [RFC5641] is not supported, a PE MAY use the CDN and StopCCN messages in a similar way to an MPLS PW label withdrawal to report:
当[RFC5641]的扩展电路状态定义不受支持时，PE可使用CDN和StopCCN消息，以类似于MPLS PW标签撤回的方式报告：
o defects detected through defect detection mechanisms in the L2TPv3/IP PSN (using StopCCN),
o 通过L2TPv3/IP PSN中的缺陷检测机制检测到的缺陷（使用StopCCN），
o defects detected through VCCV (pseudowire level) (using CDN),
o 通过VCCV（伪线级）检测到的缺陷（使用CDN），
o defects within the PE that result in an inability to forward traffic between ACs and PW (using CDN).
o PE中的缺陷导致无法在ACs和PW之间转发流量（使用CDN）。
For ATM L2TPv3/IP pseudowires, in addition to the Circuit Status AVP, a PE MAY use the ATM Alarm Status AVP [RFC4454] to indicate the reason for the ATM circuit status and the specific alarm type, if any. This AVP is sent in the SLI message to indicate additional information about the ATM circuit status.
对于ATM L2TPv3/IP伪线，除了电路状态AVP外，PE还可以使用ATM报警状态AVP[RFC4454]来指示ATM电路状态的原因和特定报警类型（如果有）。此AVP在SLI消息中发送，以指示有关ATM电路状态的附加信息。
L2TP control connections use Hello messages as a keep-alive facility. It is important to note that if PSN failure is detected by keep-alive timeout, the control connection is cleared. L2TP Hello messages are sent in-band so as to follow the data plane with respect to the source and destination addresses, IP protocol number, and UDP port (when UDP is used).
L2TP控制连接使用Hello消息作为保持活动的工具。需要注意的是，如果通过保持活动超时检测到PSN故障，则清除控制连接。L2TP Hello消息在频带内发送，以便在源地址和目标地址、IP协议号和UDP端口（使用UDP时）方面遵循数据平面。
BFD [RFC5880] defines a set of diagnostic codes that partially overlap the set of defects that can be communicated through LDP Status TLV or L2TP Circuit Status AVP. This section describes the behavior of the PEs with respect to using one or both of these methods for detecting and propagating defect state.
BFD[RFC5880]定义了一组诊断代码，这些代码部分重叠了可通过LDP状态TLV或L2TP电路状态AVP进行通信的一组缺陷。本节描述了PEs使用其中一种或两种方法检测和传播缺陷状态的行为。
In the case of an MPLS PW established via LDP signaling, the PEs negotiate VCCV capabilities during the label mapping messages exchange used to establish the two directions of the PW. This is achieved by including a capability TLV in the PW Forward Error Correction (FEC) interface parameters TLV. In the L2TPv3/IP case, the PEs negotiate the use of VCCV during the pseudowire session initialization using the VCCV AVP [RFC5085].
在通过LDP信令建立MPLS PW的情况下，PEs在用于建立PW的两个方向的标签映射消息交换期间协商VCCV能力。这是通过在PW前向纠错（FEC）接口参数TLV中包括能力TLV来实现的。在L2TPv3/IP情况下，PEs使用VCCV AVP[RFC5085]在伪线会话初始化期间协商VCCV的使用。
The CV Type Indicators field in the OAM capability TLV or VCCV AVP defines a bitmask used to indicate the specific OAM capabilities that the PE can use over the PW being established.
OAM能力TLV或VCCV AVP中的CV类型指示符字段定义了一个位掩码，用于指示PE可以在正在建立的PW上使用的特定OAM能力。
A CV type of 0x04 or 0x10 [RFC5885] indicates that BFD is used for PW fault detection only. These CV types MAY be used any time the PW is established using LDP or L2TP control planes. In this mode, only the following diagnostic (Diag) codes specified in [RFC5880] will be used:
CV类型为0x04或0x10[RFC5885]表示BFD仅用于PW故障检测。在使用LDP或L2TP控制平面建立PW时，可随时使用这些CV类型。在此模式下，仅使用[RFC5880]中规定的以下诊断（Diag）代码：
0 - No diagnostic
0-无诊断
1 - Control detection time expired
1-控制检测时间已过期
3 - Neighbor signaled session down
3-邻居发出会话关闭信号
7 - Administratively Down
7-行政性下降
A PE using VCCV-BFD MUST use diagnostic code 0 to indicate to its peer PE that it is correctly receiving BFD control messages. It MUST use diagnostic code 1 to indicate to its peer that it has stopped receiving BFD control messages and will thus declare the PW to be down in the receive direction. It MUST use diagnostic code 3 to confirm to its peer that the BFD session is going down after receiving diagnostic code 1 from this peer. In this case, it will declare the PW to be down in the transmit direction. A PE MUST use diagnostic code 7 to bring down the BFD session when the PW is brought down administratively. All other defects, such as AC/PW defects and PE internal failures that prevent it from forwarding traffic, MUST be communicated through the LDP Status TLV in the case of MPLS or MPLS/IP PSN, or through the appropriate L2TP codes in the Circuit Status AVP in the case of L2TPv3/IP PSN.
使用VCCV-BFD的PE必须使用诊断代码0向其对等PE指示其正确接收BFD控制消息。它必须使用诊断代码1向其对等方指示它已停止接收BFD控制消息，并因此将宣布PW在接收方向下降。它必须使用诊断代码3向其对等方确认，在收到来自该对等方的诊断代码1后，BFD会话正在停止。在这种情况下，它将宣布PW在传输方向下降。管理性关闭PW时，PE必须使用诊断代码7关闭BFD会话。在MPLS或MPLS/IP PSN的情况下，所有其他缺陷（如AC/PW缺陷和PE内部故障）必须通过LDP状态TLV进行通信，在L2TPv3/IP PSN的情况下，必须通过电路状态AVP中的适当L2TP代码进行通信。
A CV type of 0x08 or 0x20 in the OAM capabilities TLV indicates that BFD is used for both PW fault detection and Fault Notification. In addition to the above diagnostic codes, a PE uses the following codes to signal AC defects and other defects impacting forwarding over the PW service:
OAM功能TLV中的CV类型0x08或0x20表示BFD用于PW故障检测和故障通知。除上述诊断代码外，PE还使用以下代码来表示AC缺陷和其他影响PW服务转发的缺陷：
6 - Concatenated Path Down
6-串联路径向下
8 - Reverse Concatenated Path Down
8-反向连接路径向下
As specified in [RFC5085], the PEs negotiate the use of VCCV during PW setup. When a PW transported over an MPLS-PSN is established using LDP, the PEs negotiate the use of the VCCV capabilities using the optional VCCV Capability Advertisement Sub-TLV parameter in the Interface Parameter Sub-TLV field of the LDP PW ID FEC or using an Interface Parameters TLV of the LDP Generalized PW ID FEC. In the case of L2TPv3/IP PSNs, the PEs negotiate the use of VCCV during the pseudowire session initialization using VCCV AVP.
按照[RFC5085]中的规定，PEs在PW设置期间协商VCCV的使用。当使用LDP建立通过MPLS-PSN传输的PW时，PEs使用LDP PW ID FEC的接口参数Sub TLV字段中的可选VCCV Capability Advertision Sub TLV参数或使用LDP通用PW ID FEC的接口参数TLV来协商VCCV能力的使用。在L2TPv3/IP PSN的情况下，PEs使用VCCV AVP在伪线会话初始化期间协商VCCV的使用。
Note that a defect that causes the generation of the "PW not forwarding code" (diagnostic code 6 or 8) does not necessarily result in the BFD session going down. However, if the BFD session times out, then diagnostic code 1 MUST be used since it signals a state change of the BFD session itself. In general, when a BFD session changes state, the PEs MUST use state change diagnostic codes 0, 1, 3, and 7 in accordance with [RFC5880], and they MUST override any of the AC/PW status diagnostic codes (codes 6 or 8) that may have been signaled prior to the BFD session changing state.
请注意，导致生成“PW不转发代码”（诊断代码6或8）的缺陷不一定会导致BFD会话停机。但是，如果BFD会话超时，则必须使用诊断代码1，因为它表示BFD会话本身的状态变化。一般来说，当BFD会话改变状态时，PEs必须根据[RFC5880]使用状态改变诊断代码0、1、3和7，并且必须覆盖BFD会话改变状态之前可能发出信号的任何AC/PW状态诊断代码（代码6或8）。
The forward and reverse defect indications used in this document map to the following BFD codes:
本文件中使用的正向和反向缺陷指示对应于以下BFD代码：
Forward defect indication corresponds to the logical OR of:
正向缺陷指示对应于以下逻辑或：
* Concatenated Path Down (BFD diagnostic code 06)
* 串联路径向下（BFD诊断代码06）
* Pseudowire Not Forwarding (PW status code 0x00000001).
* 伪线未转发（PW状态代码0x00000001）。
Reverse defect indication corresponds to:
反向缺陷指示对应于：
* Reverse Concatenated Path Down (BFD diagnostic code 08).
* 反向串联路径向下（BFD诊断代码08）。
These diagnostic codes are used to signal forward and reverse defect states, respectively, when the PEs negotiated the use of BFD as the mechanism for AC and PW fault detection and status signaling notification. As stated in Section 6.1, these CV types SHOULD NOT be used when the PW is established with the LDP or L2TP control plane.
当PEs协商将BFD用作AC和PW故障检测和状态信号通知机制时，这些诊断代码分别用于向正向和反向缺陷状态发送信号。如第6.1节所述，当使用LDP或L2TP控制平面建立PW时，不应使用这些CV类型。
PE1, as downstream PE, will enter the PW receive defect state if one or more of the following occurs:
如果出现以下一种或多种情况，作为下游PE的PE1将进入PW接收缺陷状态：
o It receives a forward defect indication (FDI) from PE2 indicating either a receive defect on the remote AC or that PE2 detected or was notified of downstream PW fault.
o 它从PE2接收前向缺陷指示（FDI），指示远程AC上的接收缺陷或PE2检测到或被通知下游PW故障。
o It detects loss of connectivity on the PSN tunnel upstream of PE1, which affects the traffic it receives from PE2.
o 它检测到PE1上游的PSN隧道上的连接丢失，这会影响它从PE2接收的流量。
o It detects a loss of PW connectivity through VCCV-BFD or VCCV-PING, which affects the traffic it receives from PE2.
o 它通过VCCV-BFD或VCCV-PING检测到PW连接丢失，这会影响它从PE2接收的流量。
Note that if the PW control session (LDP session, the L2TP session, or the L2TP control connection) between the PEs fails, the PW is torn down and needs to be re-established. However, the consequent actions towards the ACs are the same as if the PW entered the receive defect state.
请注意，如果PEs之间的PW控制会话（LDP会话、L2TP会话或L2TP控制连接）失败，PW将被拆除，需要重新建立。然而，对ACs的后续动作与PW进入接收缺陷状态时相同。
PE1 will exit the PW receive defect state when the following conditions are met. Note that this may result in a transition to the PW operational state or the PW transmit defect state.
当满足以下条件时，PE1将退出PW接收缺陷状态。注意，这可能导致转换到PW操作状态或PW传输缺陷状态。
o All previously detected defects have disappeared, and
o 所有先前检测到的缺陷均已消失，且
o PE2 cleared the FDI, if applicable.
o PE2清除了FDI（如适用）。
PE1, as upstream PE, will enter the PW transmit defect state if the following conditions occur:
如果出现以下情况，作为上游PE的PE1将进入PW传输缺陷状态：
o It receives a Reverse Defect Indication (RDI) from PE2 indicating either a transmit fault on the remote AC or that PE2 detected or was notified of a upstream PW fault, and
o 它从PE2接收反向缺陷指示（RDI），指示远程AC上的传输故障或PE2检测到上游PW故障或收到上游PW故障通知，以及
o it is not already in the PW receive defect state.
o 它尚未处于PW接收缺陷状态。
PE1 will exit the transmit defect state if it receives an OAM message from PE2 clearing the RDI, or it has entered the PW receive defect state.
如果PE1从清除RDI的PE2接收到OAM消息，或已进入PW接收缺陷状态，则PE1将退出传输缺陷状态。
For a PW over L2TPv3/IP using the basic Circuit Status AVP [RFC3931], the PW transmit defect state is not valid and a PE can only enter the PW receive defect state.
对于使用基本电路状态AVP[RFC3931]的L2TPv3/IP上的PW，PW传输缺陷状态无效，PE只能进入PW接收缺陷状态。
The following procedures apply to Asynchronous Transfer Mode (ATM) pseudowires [RFC4717]. ATM terminology is explained in Appendix A.2 of this document.
以下步骤适用于异步传输模式（ATM）伪线[RFC4717]。ATM术语解释见本文件附录A.2。
When operating in the coupled OAM loops mode, PE1 enters the AC receive defect state when any of the following conditions are met:
当在耦合OAM环路模式下运行时，当满足以下任一条件时，PE1进入AC接收缺陷状态：
a. It detects or is notified of a physical layer fault on the ATM interface.
a. 它检测到ATM接口上的物理层故障或收到该故障的通知。
b. It receives an end-to-end Flow 4 OAM (F4) Alarm Indication Signal (AIS) OAM flow on a Virtual Path (VP) AC or an end-to-end Flow 5 (F5) AIS OAM flow on a Virtual Circuit (VC) as per ITU-T Recommendation I.610 [I.610], indicating that the ATM VPC or VCC is down in the adjacent Layer 2 ATM network.
b. 根据ITU-T建议I.610[I.610]，它接收虚拟路径（VP）AC上的端到端流4 OAM（F4）报警指示信号（AIS）OAM流或虚拟电路（VC）上的端到端流5（F5）AIS OAM流，表明ATM VPC或VCC在相邻的第2层ATM网络中停机。
c. It receives a segment F4 AIS OAM flow on a VP AC, or a segment F5 AIS OAM flow on a VC AC, provided that the operator has provisioned segment OAM and the PE is not a segment endpoint.
c. 它在VP AC上接收段F4 AIS OAM流，或在VC AC上接收段F5 AIS OAM流，前提是运营商已配置段OAM且PE不是段端点。
d. It detects loss of connectivity on the ATM VPC/VCC while terminating segment or end-to-end ATM continuity check (ATM CC) cells with the local ATM network and CE.
d. 它检测ATM VPC/VCC上的连接丢失，同时终止与本地ATM网络和CE的段或端到端ATM连续性检查（ATM CC）信元。
When operating in the coupled OAM loops mode, PE1 exits the AC receive defect state when all previously detected defects have disappeared.
在耦合OAM环路模式下运行时，当所有先前检测到的缺陷消失时，PE1退出AC接收缺陷状态。
When operating in the single emulated OAM loop mode, PE1 enters the AC receive defect state if any of the following conditions are met:
在单模拟OAM环路模式下运行时，如果满足以下任何条件，PE1将进入AC接收缺陷状态：
a. It detects or is notified of a physical layer fault on the ATM interface.
a. 它检测到ATM接口上的物理层故障或收到该故障的通知。
b. It detects loss of connectivity on the ATM VPC/VCC while terminating segment ATM continuity check (ATM CC) cells with the local ATM network and CE.
b. 它检测ATM VPC/VCC上的连接丢失，同时终止与本地ATM网络和CE的段ATM连续性检查（ATM CC）信元。
When operating in the single emulated OAM loop mode, PE1 exits the AC receive defect state when all previously detected defects have disappeared.
在单模拟OAM环路模式下运行时，当所有先前检测到的缺陷消失时，PE1退出AC接收缺陷状态。
The exact conditions under which a PE enters and exits the AIS state, or declares that connectivity is restored via ATM CC, are defined in Section 9.2 of [I.610].
[I.610]第9.2节定义了PE进入和退出AIS状态或声明通过ATM CC恢复连接的确切条件。
When operating in the coupled OAM loops mode, PE1 enters the AC transmit defect state if any of the following conditions are met:
在耦合OAM环路模式下运行时，如果满足以下任一条件，PE1将进入AC传输缺陷状态：
a. It terminates an end-to-end F4 RDI OAM flow, in the case of a VPC, or an end-to-end F5 RDI OAM flow, in the case of a VCC, indicating that the ATM VPC or VCC is down in the adjacent L2 ATM.
a. 如果是VPC，则终止端到端F4 RDI OAM流；如果是VCC，则终止端到端F5 RDI OAM流，表明ATM VPC或VCC在相邻的L2 ATM中停机。
b. It receives a segment F4 RDI OAM flow on a VP AC, or a segment F5 RDI OAM flow on a VC AC, provided that the operator has provisioned segment OAM and the PE is not a segment endpoint.
b. 它在VP AC上接收段F4 RDI OAM流，或在VC AC上接收段F5 RDI OAM流，前提是运营商已配置段OAM且PE不是段端点。
PE1 exits the AC transmit defect state if the AC state transitions to working or to the AC receive defect state. The exact conditions for exiting the RDI state are described in Section 9.2 of [I.610].
如果交流状态转换为工作或交流接收缺陷状态，PE1将退出交流传输缺陷状态。退出RDI状态的确切条件见[I.610]第9.2节。
Note that the AC transmit defect state is not valid when operating in the single emulated OAM loop mode, as PE1 transparently forwards the received RDI cells as user cells over the ATM PW to the remote CE.
注意，当在单模拟OAM环路模式下操作时，AC传输缺陷状态无效，因为PE1通过ATM PW透明地将接收到的RDI信元作为用户信元转发给远程CE。
In the remainder of this section, the text refers to AIS, RDI, and CC without specifying whether there is an F4 (VP-level) flow or an F5 (VC-level) flow, or whether it is an end-to-end or a segment flow. Precise ATM OAM procedures for each type of flow are specified in Section 9.2 of [I.610].
在本节的其余部分中，文本涉及AIS、RDI和CC，但未指定是否存在F4（VP级）流或F5（VC级）流，或是端到端流还是段流。[I.610]第9.2节规定了每种流量的精确ATM OAM程序。
On entry to the PW receive defect state:
进入PW接收缺陷状态时：
a. PE1 MUST commence AIS insertion into the corresponding AC.
a. PE1必须开始将AIS插入相应的AC。
b. PE1 MUST cease generation of CC cells on the corresponding AC, if applicable.
b. 如果适用，PE1必须停止在相应AC上生成CC电池。
c. If the PW defect was detected by PE1 without receiving FDI from PE2, PE1 MUST assume PE2 has no knowledge of the defect and MUST notify PE2 by sending RDI.
c. 如果PE1在未收到PE2的FDI的情况下检测到PW缺陷，PE1必须假设PE2不知道该缺陷，并且必须通过发送RDI通知PE2。
On exit from the PW receive defect state:
从PW接收缺陷状态退出时：
a. PE1 MUST cease AIS insertion into the corresponding AC.
a. PE1必须停止将AIS插入相应的AC。
b. PE1 MUST resume any CC cell generation on the corresponding AC, if applicable.
b. 如果适用，PE1必须在相应的AC上恢复任何CC电池的生成。
c. PE1 MUST clear the RDI to PE2, if applicable.
c. 如果适用，PE1必须清除RDI至PE2。
On entry to the PW Transmit Defect State:
进入PW传输缺陷状态时：
a. PE1 MUST commence RDI insertion into the corresponding AC.
a. PE1必须开始将RDI插入相应的AC。
b. If the PW failure was detected by PE1 without receiving RDI from PE2, PE1 MUST assume PE2 has no knowledge of the defect and MUST notify PE2 by sending FDI.
b. 如果PE1在未收到PE2的RDI的情况下检测到PW故障，PE1必须假设PE2不知道缺陷，并且必须通过发送FDI通知PE2。
On exit from the PW Transmit Defect State:
退出PW传输缺陷状态时：
a. PE1 MUST cease RDI insertion into the corresponding AC.
a. PE1必须停止将RDI插入相应的AC。
b. PE1 MUST clear the FDI to PE2, if applicable.
b. 如果适用，PE1必须将FDI转给PE2。
In case of transparent cell transport PW service, i.e., "port mode", where the PE does not keep track of the status of individual ATM VPCs or VCCs, a PE cannot relay PW defect state over these VCCs and VPCs. If ATM CC is run on the VCCs and VPCs end-to-end (CE1 to CE2), or on a segment originating and terminating in the ATM network and spanning the PSN network, it will time out and cause the CE or ATM switch to enter the ATM AIS state.
在透明小区传输PW服务的情况下，即“端口模式”，其中PE不跟踪单个ATM VPC或VCC的状态，PE不能通过这些VCC和VPC中继PW缺陷状态。如果ATM CC在VCC和VPC端到端（CE1到CE2）上运行，或在ATM网络中发起和终止并跨越PSN网络的网段上运行，则它将超时并导致CE或ATM交换机进入ATM AIS状态。
On entry to the AC receive defect state and when operating in the coupled OAM loops mode:
在进入AC接收缺陷状态以及在耦合OAM环路模式下运行时：
a. PE1 MUST send FDI to PE2.
a. PE1必须向PE2输送外国直接投资。
b. PE1 MUST commence insertion of ATM RDI cells into the AC towards CE1.
b. PE1必须开始向CE1方向将ATM RDI信元插入AC。
When operating in the single emulated OAM loop mode, PE1 must be able to support two options, subject to the operator's preference. The default option is the following:
在单模拟OAM环路模式下运行时，PE1必须能够支持两个选项，取决于操作员的偏好。默认选项如下所示：
On entry to the AC receive defect state:
进入AC接收缺陷状态时：
a. PE1 MUST transparently relay ATM AIS cells, or, in the case of a local AC defect, commence insertion of ATM AIS cells into the corresponding PW towards CE2.
a. PE1必须透明地中继ATM AIS信元，或者，在局部AC缺陷的情况下，开始将ATM AIS信元插入到CE2对应的PW中。
b. If the defect interferes with NS OAM message generation, PE1 MUST send FDI to PE2.
b. 如果缺陷干扰NS OAM消息生成，PE1必须向PE2发送FDI。
c. PE1 MUST cease the generation of CC cells on the corresponding PW, if applicable.
c. 如果适用，PE1必须停止在相应PW上生成CC电池。
In certain operational models, for example, in the case that the ATM access network is owned by a different provider than the PW, an operator may want to distinguish between defects detected in the ATM access network and defects detected on the AC directly adjacent to the PE. Therefore, the following option MUST also be supported:
在某些操作模型中，例如，在ATM接入网络由不同于PW的提供商拥有的情况下，运营商可能希望区分在ATM接入网络中检测到的缺陷和在与PE直接相邻的AC上检测到的缺陷。因此，还必须支持以下选项：
a. PE1 MUST transparently relay ATM AIS cells over the corresponding PW towards CE2.
a. PE1必须通过相应的PW向CE2透明地中继ATM AIS信元。
b. Upon detection of a defect on the ATM interface on the PE or in the PE itself, PE1 MUST send FDI to PE2.
b. 当检测到PE上的ATM接口或PE本身存在缺陷时，PE1必须向PE2发送FDI。
c. PE1 MUST cease generation of CC cells on the corresponding PW, if applicable.
c. 如果适用，PE1必须停止在相应PW上生成CC电池。
On exit from the AC receive defect state and when operating in the coupled OAM loops mode:
从AC接收缺陷状态退出时，以及在耦合OAM环路模式下运行时：
a. PE1 MUST clear the FDI to PE2.
a. PE1必须将FDI转给PE2。
b. PE1 MUST cease insertion of ATM RDI cells into the AC.
b. PE1必须停止将ATM RDI信元插入AC。
On exit from the AC receive defect state and when operating in the single emulated OAM loop mode:
从AC接收缺陷状态退出时，以及在单模拟OAM环路模式下运行时：
a. PE1 MUST cease insertion of ATM AIS cells into the corresponding PW.
a. PE1必须停止将ATM AIS信元插入相应的PW。
b. PE1 MUST clear the FDI to PE2, if applicable.
b. 如果适用，PE1必须将FDI转给PE2。
c. PE1 MUST resume any CC cell generation on the corresponding PW, if applicable.
c. 如果适用，PE1必须在相应的PW上恢复任何CC电池的生成。
On entry to the AC transmit defect state and when operating in the coupled OAM loops mode:
在进入AC传输缺陷状态时以及在耦合OAM环路模式下运行时：
* PE1 MUST send RDI to PE2.
* PE1必须向PE2发送RDI。
On exit from the AC transmit defect state and when operating in the coupled OAM loops mode:
从AC传输缺陷状态退出时，以及在耦合OAM环路模式下运行时：
* PE1 MUST clear the RDI to PE2.
* PE1必须清除RDI至PE2。
The following procedures apply to Frame Relay (FR) pseudowires [RFC4619]. Frame Relay (FR) terminology is explained in Appendix A.1 of this document.
以下程序适用于帧中继（FR）伪线[RFC4619]。本文件附录A.1中解释了帧中继（FR）术语。
PE1 enters the AC receive defect state if one or more of the following conditions are met:
如果满足以下一个或多个条件，PE1将进入AC接收缺陷状态：
a. A Permanent Virtual Circuit (PVC) is not deleted from the FR network and the FR network explicitly indicates in a full status report (and optionally by the asynchronous status message) that this PVC is inactive [Q.933]. In this case, this status maps across the PE to the corresponding PW only.
a. 永久虚拟电路（PVC）不会从FR网络中删除，并且FR网络在完整状态报告中明确指出（可选地通过异步状态消息）该PVC处于非活动状态[Q.933]。在这种情况下，该状态仅在PE中映射到相应的PW。
b. The Link Integrity Verification (LIV) indicates that the link from the PE to the Frame Relay network is down [Q.933]. In this case, the link down indication maps across the PE to all corresponding PWs.
b. 链路完整性验证（LIV）表明从PE到帧中继网络的链路断开[Q.933]。在这种情况下，链路断开指示跨PE映射到所有相应的PW。
c. A physical layer alarm is detected on the FR interface. In this case, this status maps across the PE to all corresponding PWs.
c. 在FR接口上检测到物理层警报。在这种情况下，该状态在PE中映射到所有相应的PW。
PE1 exits the AC receive defect state when all previously detected defects have disappeared.
当所有先前检测到的缺陷消失时，PE1退出AC接收缺陷状态。
The AC transmit defect state is not valid for a FR AC.
AC传输缺陷状态对于FR AC无效。
The A (Active) bit indicates whether the FR PVC is ACTIVE (1) or INACTIVE (0) as explained in [RFC4591].
A（活动）位指示FR PVC是活动（1）还是非活动（0），如[RFC4591]中所述。
On entry to the PW receive defect state:
进入PW接收缺陷状态时：
a. PE1 MUST clear the Active bit for the corresponding FR AC in a full status report, and optionally in an asynchronous status message, as per [Q.933], Annex A.
a. 根据[Q.933]，附录a，PE1必须在完整状态报告中清除相应FR AC的活动位，也可以在异步状态消息中清除。
b. If the PW failure was detected by PE1 without receiving FDI from PE2, PE1 MUST assume PE2 has no knowledge of the defect and MUST notify PE2 by sending RDI.
b. 如果PE1在未收到PE2的FDI的情况下检测到PW故障，PE1必须假设PE2不知道缺陷，并且必须通过发送RDI通知PE2。
On exit from the PW receive defect state:
从PW接收缺陷状态退出时：
a. PE1 MUST set the Active bit for the corresponding FR AC in a full status report, and optionally in an asynchronous status message, as per [Q.933], Annex A. PE1 does not apply this procedure on a transition from the PW receive defect state to the PW transmit defect state.
a. 根据[Q.933]，附录a，PE1必须在完整状态报告中，或者在异步状态消息中，为相应的FR AC设置活动位。PE1不适用于从PW接收缺陷状态到PW传输缺陷状态的转换。
b. PE1 MUST clear the RDI to PE2, if applicable.
b. 如果适用，PE1必须清除RDI至PE2。
On entry to the PW transmit defect state:
进入PW传输缺陷状态时：
a. PE1 MUST clear the Active bit for the corresponding FR AC in a full status report, and optionally in an asynchronous status message, as per [Q.933], Annex A.
a. 根据[Q.933]，附录a，PE1必须在完整状态报告中清除相应FR AC的活动位，也可以在异步状态消息中清除。
b. If the PW failure was detected by PE1 without RDI from PE2, PE1 MUST assume PE2 has no knowledge of the defect and MUST notify PE2 by sending FDI.
b. 如果PE1在没有来自PE2的RDI的情况下检测到PW故障，PE1必须假设PE2不知道缺陷，并且必须通过发送FDI通知PE2。
On exit from the PW transmit defect state:
退出PW传输缺陷状态时：
a. PE1 MUST set the Active bit for the corresponding FR AC in a full status report, and optionally in an asynchronous status message, as per [Q.933], Annex A. PE1 does not apply this procedure on a transition from the PW transmit defect state to the PW receive defect state.
a. 根据[Q.933]，附录a，PE1必须在完整状态报告中，或者在异步状态消息中，为相应的FR AC设置活动位。PE1不适用于从PW传输缺陷状态到PW接收缺陷状态的转换。
b. PE1 MUST clear the FDI to PE2, if applicable.
b. 如果适用，PE1必须将FDI转给PE2。
In case of port mode PW service, STATUS ENQUIRY and STATUS messages are transported transparently over the PW. A PW Failure will therefore result in timeouts of the Q.933 link and PVC management protocol at the Frame Relay devices at one or both sites of the emulated interface.
对于端口模式PW服务，状态查询和状态消息通过PW透明传输。因此，PW故障将导致模拟接口一个或两个站点的帧中继设备上的Q.933链路和PVC管理协议超时。
On entry to the AC receive defect state:
进入AC接收缺陷状态时：
* PE1 MUST send FDI to PE2.
* PE1必须向PE2输送外国直接投资。
On exit from the AC receive defect state:
从AC接收缺陷状态退出时：
* PE1 MUST clear the FDI to PE2.
* PE1必须将FDI转给PE2。
The AC transmit defect state is not valid for an FR AC.
AC传输缺陷状态对于FR AC无效。
The following procedures apply to SAToP [RFC4553], CESoPSN [RFC5086] and TDMoIP [RFC5087]. These technologies utilize the single emulated OAM loop mode. RFC 5087 distinguishes between trail-extended and trail-terminated scenarios; the former is essentially the single emulated loop model. The latter applies to cases where the NS networks are run by different operators and defect notifications are not propagated across the PW.
以下程序适用于SAToP[RFC4553]、CESoPSN[RFC5086]和TDMoIP[RFC5087]。这些技术利用单模拟OAM循环模式。RFC 5087区分了追踪扩展和追踪终止场景；前者本质上是单仿真回路模型。后者适用于NS网络由不同运营商运行且缺陷通知未通过PW传播的情况。
Since TDM is inherently real-time in nature, many OAM indications must be generated or forwarded with minimal delay. This requirement rules out the use of messaging protocols, such as PW status messages. Thus, for TDM PWs, alternate mechanisms are employed.
由于TDM本质上是实时的，因此必须以最小的延迟生成或转发许多OAM指示。此要求排除了消息传递协议的使用，例如PW状态消息。因此，对于TDM PWs，采用了替代机制。
The fact that TDM PW packets are sent at a known constant rate can be exploited as an OAM mechanism. Thus, a PE enters the PW receive defect state whenever a preconfigured number of TDM PW packets do not arrive in a timely fashion. It exits this state when packets once again arrive at their proper rate.
TDM PW数据包以已知的恒定速率发送的事实可以作为OAM机制加以利用。因此，每当预配置数量的TDM PW分组没有及时到达时，PE进入PW接收缺陷状态。当数据包再次以正确的速率到达时，它将退出此状态。
Native TDM carries OAM indications in overhead fields that travel along with the data. TDM PWs emulate this behavior by sending urgent OAM messages in the PWE control word.
本机TDM在开销字段中携带OAM指示，这些字段随数据一起移动。TDM PWs通过在PWE控制字中发送紧急OAM消息来模拟此行为。
The TDM PWE3 control word contains a set of flags used to indicate PW and AC defect conditions. The L bit is an AC forward defect indication used by the upstream PE to signal NS network defects to the downstream PE. The M field may be used to modify the meaning of receive defects. The R bit is a PW reverse defect indication used by the PE to signal PSN failures to the remote PE. Upon reception of packets with the R bit set, a PE enters the PW transmit defect state. L bits and R bits are further described in [RFC5087].
TDM PWE3控制字包含一组用于指示PW和AC缺陷条件的标志。L位是上游PE用于向下游PE发送NS网络缺陷信号的AC前向缺陷指示。M字段可用于修改接收缺陷的含义。R位是PE用于向远程PE发送PSN故障信号的PW反向缺陷指示。在接收到设置了R位的分组时，PE进入PW发送缺陷状态。[RFC5087]中进一步描述了L位和R位。
PE1 enters the AC receive defect state if any of the following conditions are met:
如果满足以下任何条件，PE1进入AC接收缺陷状态：
a. It detects a physical layer fault on the TDM interface (Loss of Signal, Loss of Alignment, etc., as described in [G.775]).
a. 它检测TDM接口上的物理层故障（信号丢失、对准丢失等，如[G.775]所述）。
b. It is notified of a previous physical layer fault by detecting AIS.
b. 通过检测AIS，它将收到先前物理层故障的通知。
The exact conditions under which a PE enters and exits the AIS state are defined in [G.775]. Note that Loss of Signal and AIS detection can be performed by PEs for both structure-agnostic and structure-aware TDM PW types. Note that PEs implementing structure-agnostic PWs cannot detect Loss of Alignment.
PE进入和退出AIS状态的确切条件见[G.775]。请注意，对于结构不可知和结构感知TDM PW类型，PEs都可以执行信号丢失和AIS检测。注意，实现结构不可知PWs的PEs无法检测到对齐丢失。
PE1 enters the AC transmit defect state when it detects RDI according to the criteria in [G.775]. Note that PEs implementing structure-agnostic PWs cannot detect RDI.
PE1根据[G.775]中的标准检测到RDI时，进入交流传输缺陷状态。注意，实现结构不可知PWs的PEs无法检测RDI。
On entry to the PW receive defect state:
进入PW接收缺陷状态时：
a. PE1 MUST commence AIS insertion into the corresponding TDM AC.
a. PE1必须开始将AIS插入相应的TDM AC。
b. PE1 MUST set the R bit in all PW packets sent back to PE2.
b. PE1必须在发送回PE2的所有PW数据包中设置R位。
On exit from the PW receive defect state:
从PW接收缺陷状态退出时：
a. PE1 MUST cease AIS insertion into the corresponding TDM AC.
a. PE1必须停止将AIS插入相应的TDM AC。
b. PE1 MUST clear the R bit in all PW packets sent back to PE2.
b. PE1必须清除发送回PE2的所有PW数据包中的R位。
Note that AIS generation can, in general, be performed by both structure-aware and structure-agnostic PEs.
注意，AIS生成通常可以由结构感知和结构不可知的PEs执行。
On entry to the PW Transmit Defect State:
进入PW传输缺陷状态时：
* A structure-aware PE1 MUST commence RDI insertion into the corresponding AC.
* 结构感知PE1必须开始将RDI插入相应的AC。
On exit from the PW Transmit Defect State:
退出PW传输缺陷状态时：
* A structure-aware PE1 MUST cease RDI insertion into the corresponding AC.
* 结构感知PE1必须停止将RDI插入相应的AC。
Note that structure-agnostic PEs are not capable of injecting RDI into an AC.
注意，结构不可知的PEs不能将RDI注入AC。
On entry to the AC receive defect state and when operating in the single emulated OAM loop mode:
进入AC接收缺陷状态时，以及在单模拟OAM环路模式下运行时：
a. PE1 SHOULD overwrite the TDM data with AIS in the PW packets sent towards PE2.
a. PE1应使用发送至PE2的PW数据包中的AIS覆盖TDM数据。
b. PE1 MUST set the L bit in these packets.
b. PE1必须在这些数据包中设置L位。
c. PE1 MAY omit the payload in order to conserve bandwidth.
c. 为了节省带宽，PE1可以省略有效载荷。
d. A structure-aware PE1 SHOULD send RDI back towards CE1.
d. 感知结构的PE1应将RDI发送回CE1。
e. A structure-aware PE1 that detects a potentially correctable AC defect MAY use the M field to indicate this.
e. 检测到潜在可纠正AC缺陷的结构感知PE1可使用M字段来指示这一点。
On exit from the AC receive defect state and when operating in the single emulated OAM loop mode:
从AC接收缺陷状态退出时，以及在单模拟OAM环路模式下运行时：
a. PE1 MUST cease overwriting PW content with AIS and return to forwarding valid TDM data in PW packets sent towards PE2.
a. PE1必须停止用AIS覆盖PW内容，并返回转发发送至PE2的PW数据包中的有效TDM数据。
b. PE1 MUST clear the L bit in PW packets sent towards PE2.
b. PE1必须清除发送至PE2的PW数据包中的L位。
c. A structure-aware PE1 MUST cease sending RDI towards CE1.
c. 结构感知PE1必须停止向CE1发送RDI。
The following procedures apply to SONET/SDH Circuit Emulation [RFC4842]. They are based on the single emulated OAM loop mode.
以下程序适用于SONET/SDH电路仿真[RFC4842]。它们基于单模拟OAM循环模式。
Since SONET and SDH are inherently real-time in nature, many OAM indications must be generated or forwarded with minimal delay. This requirement rules out the use of messaging protocols, such as PW status messages. Thus, for CEP PWs alternate mechanisms are employed.
由于SONET和SDH本质上是实时的，因此必须以最小的延迟生成或转发许多OAM指示。此要求排除了消息传递协议的使用，例如PW状态消息。因此，对于CEP PWs，采用了替代机制。
The CEP PWE3 control word contains a set of flags used to indicate PW and AC defect conditions. The L bit is a forward defect indication used by the upstream PE to signal to the downstream PE a defect in its local attachment circuit. The R bit is a PW reverse defect indication used by the PE to signal PSN failures to the remote PE. The combination of N and P bits is used by the local PE to signal loss of pointer to the remote PE.
CEP PWE3控制字包含一组用于指示PW和AC缺陷条件的标志。L位是上游PE使用的正向缺陷指示，用于向下游PE发送其本地连接电路中的缺陷信号。R位是PE用于向远程PE发送PSN故障信号的PW反向缺陷指示。本地PE使用N位和P位的组合来表示指向远程PE的指针丢失。
The fact that CEP PW packets are sent at a known constant rate can be exploited as an OAM mechanism. Thus, a PE enters the PW receive defect state when it loses packet synchronization. It exits this state when it regains packet synchronization. See [RFC4842] for further details.
CEP PW数据包以已知的恒定速率发送这一事实可以作为OAM机制加以利用。因此，PE在丢失数据包同步时进入PW接收缺陷状态。它在恢复数据包同步时退出此状态。有关更多详细信息，请参阅[RFC4842]。
In addition to the conditions specified in Section 6.2.1, PE1 will enter the PW receive defect state when one of the following becomes true:
除第6.2.1节中规定的条件外，当以下情况之一变为真时，PE1将进入PW接收缺陷状态：
o It receives packets with the L bit set.
o 它接收设置了L位的数据包。
o It receives packets with both the N and P bits set.
o 它接收设置了N位和P位的数据包。
o It loses packet synchronization.
o 它会丢失数据包同步。
In addition to the conditions specified in Section 6.2.2, PE1 will enter the PW transmit defect state if it receives packets with the R bit set.
除第6.2.2节规定的条件外，如果PE1接收到设置了R位的数据包，则PE1将进入PW传输缺陷状态。
PE1 enters the AC receive defect state when any of the following conditions are met:
当满足以下任一条件时，PE1进入AC接收缺陷状态：
a. It detects a physical layer fault on the TDM interface (Loss of Signal, Loss of Alignment, etc.).
a. 它检测TDM接口上的物理层故障（信号丢失、对齐丢失等）。
b. It is notified of a previous physical layer fault by detecting of AIS.
b. 通过检测AIS，将先前的物理层故障通知给它。
The exact conditions under which a PE enters and exits the AIS state are defined in [G.707] and [G.783].
[G.707]和[G.783]中定义了PE进入和退出AIS状态的确切条件。
The AC transmit defect state is not valid for CEP PWs. RDI signals are forwarded transparently.
交流传输缺陷状态对CEP PWs无效。RDI信号是透明转发的。
On entry to the PW receive defect state:
进入PW接收缺陷状态时：
a. PE1 MUST commence AIS-P/V insertion into the corresponding AC. See [RFC4842].
a. PE1必须开始将AIS-P/V插入相应的AC中。参见[RFC4842]。
b. PE1 MUST set the R bit in all PW packets sent back to PE2.
b. PE1必须在发送回PE2的所有PW数据包中设置R位。
On exit from the PW receive defect state:
从PW接收缺陷状态退出时：
a. PE1 MUST cease AIS-P/V insertion into the corresponding AC.
a. PE1必须停止将AIS-P/V插入相应的AC中。
b. PE1 MUST clear the R bit in all PW packets sent back to PE2.
b. PE1必须清除发送回PE2的所有PW数据包中的R位。
See [RFC4842] for further details.
有关更多详细信息，请参阅[RFC4842]。
On entry to the PW Transmit Defect State:
进入PW传输缺陷状态时：
a. A structure-aware PE1 MUST commence RDI insertion into the corresponding AC.
a. 结构感知PE1必须开始将RDI插入相应的AC。
On exit from the PW Transmit Defect State:
退出PW传输缺陷状态时：
a. A structure-aware PE1 MUST cease RDI insertion into the corresponding AC.
a. 结构感知PE1必须停止将RDI插入相应的AC。
On entry to the AC receive defect state:
进入AC接收缺陷状态时：
a. PE1 MUST set the L bit in these packets.
a. PE1必须在这些数据包中设置L位。
b. If Dynamic Bandwidth Allocation (DBA) has been enabled, PE1 MAY omit the payload in order to conserve bandwidth.
b. 如果已启用动态带宽分配（DBA），PE1可能会忽略有效负载以节省带宽。
c. If Dynamic Bandwidth Allocation (DBA) is not enabled, PE1 SHOULD insert AIS-V/P in the SDH/SONET client layer in the PW packets sent towards PE2.
c. 如果未启用动态带宽分配（DBA），PE1应在发送至PE2的PW数据包中的SDH/SONET客户端层中插入AIS-V/P。
On exit from the AC receive defect state:
从AC接收缺陷状态退出时：
a. PE1 MUST cease overwriting PW content with AIS-P/V and return to forwarding valid data in PW packets sent towards PE2.
a. PE1必须停止使用AIS-P/V覆盖PW内容，并返回转发发送至PE2的PW数据包中的有效数据。
b. PE1 MUST clear the L bit in PW packets sent towards PE2.
b. PE1必须清除发送至PE2的PW数据包中的L位。
See [RFC4842] for further details.
有关更多详细信息，请参阅[RFC4842]。
The mapping messages described in this document do not change the security functions inherent in the actual messages. All generic security considerations applicable to PW traffic specified in Section 10 of [RFC3985] are applicable to NS OAM messages transferred inside the PW.
本文档中描述的映射消息不会更改实际消息中固有的安全功能。[RFC3985]第10节中规定的适用于PW通信的所有通用安全注意事项均适用于PW内传输的NS OAM消息。
Security considerations in Section 10 of RFC 5085 for VCCV apply to the OAM messages thus transferred. Security considerations applicable to the PWE3 control protocol of RFC 4447 Section 8.2 apply to OAM indications transferred using the LDP status message.
VCCV RFC 5085第10节中的安全注意事项适用于这样传输的OAM消息。适用于RFC 4447第8.2节PWE3控制协议的安全注意事项适用于使用LDP状态消息传输的OAM指示。
Since the mechanisms of this document enable propagation of OAM messages and fault conditions between native service networks and PSNs, continuity of the end-to-end service depends on a trust relationship between the operators of these networks. Security considerations for such scenarios are discussed in Section 7 of [RFC5254].
由于本文档的机制允许在本机服务网络和PSN之间传播OAM消息和故障条件，因此端到端服务的连续性取决于这些网络的运营商之间的信任关系。[RFC5254]第7节讨论了此类场景的安全注意事项。
Mustapha Aissaoui, Peter Busschbach, Luca Martini, Monique Morrow, Thomas Nadeau, and Yaakov (J) Stein, were each, in turn, editors of one or more revisions of this document. All of the above were contributing authors, as was Dave Allan, david.i.allan@ericsson.com.
Mustapha Aissaoui、Peter Busschbach、Luca Martini、Monique Morrow、Thomas Nadeau和Yaakov（J）Stein依次担任本文件一个或多个版本的编辑。以上所有人都是有贡献的作者，大卫·艾伦也是。allan@ericsson.com.
The following contributed significant ideas or text: Matthew Bocci, matthew.bocci@alcatel-lucent.co.uk Simon Delord, Simon.A.DeLord@team.telstra.com Yuichi Ikejiri, y.ikejiri@ntt.com Kenji Kumaki, kekumaki@kddi.com Satoru Matsushima, satoru.matsushima@tm.softbank.co.jp Teruyuki Oya, teruyuki.oya@tm.softbank.co.jp Carlos Pignataro, cpignata@cisco.com Vasile Radoaca, vasile.radoaca@alcatel-lucent.com Himanshu Shah, hshah@ciena.com David Watkinson, david.watkinson@alcatel-lucent.com
以下内容提供了重要的想法或文本：马修·博奇，马修。bocci@alcatel-lucent.co.uk西蒙·德洛德，西蒙·A。DeLord@team.telstra.com池池裕一，y。ikejiri@ntt.com久木健二，kekumaki@kddi.com松岛佐藤，佐藤。matsushima@tm.softbank.co.jpTeruyuki Oya，Teruyuki。oya@tm.softbank.co.jp卡洛斯·皮格纳塔罗， cpignata@cisco.com瓦西里·拉多卡，瓦西里。radoaca@alcatel-朗讯网Himanshu Shah，hshah@ciena.com大卫·沃特金森，大卫。watkinson@alcatel-朗讯网
The editors would like to acknowledge the contributions of Bertrand Duvivier, Adrian Farrel, Tiberiu Grigoriu, Ron Insler, Michel Khouderchah, Vanson Lim, Amir Maleki, Neil McGill, Chris Metz, Hari Rakotoranto, Eric Rosen, Mark Townsley, and Ben Washam.
编辑们要感谢伯特兰·杜维维尔、阿德里安·法雷尔、提比略·格里戈里奥、罗恩·因斯勒、米歇尔·考德查、范森·林、阿米尔·马莱基、尼尔·麦吉尔、克里斯·梅茨、哈里·拉科托兰托、埃里克·罗森、马克·汤斯利和本·瓦萨姆的贡献。
[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。
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures", RFC 4379, February 2006.
[RFC4379]Kompella，K.和G.Swallow，“检测多协议标签交换（MPLS）数据平面故障”，RFC 4379，2006年2月。
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4447]Martini，L.，Rosen，E.，El Aawar，N.，Smith，T.，和G.Heron，“使用标签分发协议（LDP）的伪线设置和维护”，RFC 4447，2006年4月。
[RFC4553] Vainshtein, A. and YJ. Stein, "Structure-Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)", RFC 4553, June 2006.
[RFC4553]Vainstein，A.和YJ。Stein，“分组上的结构不可知时分复用（TDM）（SAToP）”，RFC4553，2006年6月。
[RFC4591] Townsley, M., Wilkie, G., Booth, S., Bryant, S., and J. Lau, "Frame Relay over Layer 2 Tunneling Protocol Version 3 (L2TPv3)", RFC 4591, August 2006.
[RFC4591]Townsley，M.，Wilkie，G.，Booth，S.，Bryant，S.，和J.Lau，“第2层隧道协议第3版（L2TPv3）上的帧中继”，RFC 45912006年8月。
[RFC4619] Martini, L., Kawa, C., and A. Malis, "Encapsulation Methods for Transport of Frame Relay over Multiprotocol Label Switching (MPLS) Networks", RFC 4619, September 2006.
[RFC4619]Martini，L.，Kawa，C.，和A.Malis，“多协议标签交换（MPLS）网络上帧中继传输的封装方法”，RFC 4619，2006年9月。
[RFC4717] Martini, L., Jayakumar, J., Bocci, M., El-Aawar, N., Brayley, J., and G. Koleyni, "Encapsulation Methods for Transport of Asynchronous Transfer Mode (ATM) over MPLS Networks", RFC 4717, December 2006.
[RFC4717]Martini，L.，Jayakumar，J.，Bocci，M.，El-Aawar，N.，Brayley，J.，和G.Koleyni，“MPLS网络上异步传输模式（ATM）传输的封装方法”，RFC 47172006年12月。
[RFC4842] Malis, A., Pate, P., Cohen, R., and D. Zelig, "Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Circuit Emulation over Packet (CEP)", RFC 4842, April 2007.
[RFC4842]Malis，A.，Pate，P.，Cohen，R.，和D.Zelig，“同步光网络/同步数字体系（SONET/SDH）分组电路仿真（CEP）”，RFC 48422007年4月。
[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP Specification", RFC 5036, October 2007.
[RFC5036]Andersson，L.，Minei，I.，和B.Thomas，“LDP规范”，RFC 5036，2007年10月。
[RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, December 2007.
[RFC5085]Nadeau，T.和C.Pignataro，“伪线虚拟电路连接验证（VCCV）：伪线的控制通道”，RFC 5085，2007年12月。
[RFC5641] McGill, N. and C. Pignataro, "Layer 2 Tunneling Protocol Version 3 (L2TPv3) Extended Circuit Status Values", RFC 5641, August 2009.
[RFC5641]McGill，N.和C.Pignataro，“第2层隧道协议版本3（L2TPv3）扩展电路状态值”，RFC 56412009年8月。
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, June 2010.
[RFC5880]Katz，D.和D.Ward，“双向转发检测（BFD）”，RFC 58802010年6月。
[RFC5885] Nadeau, T. and C. Pignataro, "Bidirectional Forwarding Detection (BFD) for the Pseudowire Virtual Circuit Connectivity Verification (VCCV)", RFC 5885, June 2010.
[RFC5885]Nadeau，T.和C.Pignataro，“伪线虚拟电路连接验证（VCCV）的双向转发检测（BFD）”，RFC 58852010年6月。
[G.707] "Network node interface for the synchronous digital hierarchy", ITU-T Recommendation G.707, December 2003.
[G.707]“同步数字体系的网络节点接口”，ITU-T建议G.707，2003年12月。
[G.775] "Loss of Signal (LOS), Alarm Indication Signal (AIS) and Remote Defect Indication (RDI) defect detection and clearance criteria for PDH signals", ITU-T Recommendation G.775, October 1998.
[G.775]“PDH信号的信号丢失（LOS）、报警指示信号（AIS）和远程缺陷指示（RDI）缺陷检测和清除标准”，ITU-T建议G.775，1998年10月。
[G.783] "Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks", ITU-T Recommendation G.783, March 2006.
[G.783]“同步数字体系（SDH）设备功能块的特性”，ITU-T建议G.783，2006年3月。
[I.610] "B-ISDN operation and maintenance principles and functions", ITU-T Recommendation I.610, February 1999.
[I.610]“B-ISDN操作和维护原则及功能”，ITU-T建议I.610，1999年2月。
[Q.933] "ISDN Digital Subscriber Signalling System No. 1 (DSS1) Signalling specifications for frame mode switched and permanent virtual connection control and status monitoring", ITU- T Recommendation Q.993, February 2003.
[Q.933]“ISDN数字用户信令系统第1号（DSS1）帧模式交换和永久虚拟连接控制和状态监测的信令规范”，ITU-T建议Q.993，2003年2月。
[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, September 1981.
[RFC0792]Postel，J.，“互联网控制消息协议”，STD 5，RFC 792，1981年9月。
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001.
[RFC3031]Rosen，E.，Viswanathan，A.，和R.Callon，“多协议标签交换体系结构”，RFC 30312001年1月。
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001.
[RFC3209]Awduche，D.，Berger，L.，Gan，D.，Li，T.，Srinivasan，V.，和G.Swallow，“RSVP-TE：LSP隧道RSVP的扩展”，RFC 3209，2001年12月。
[RFC3916] Xiao, X., McPherson, D., and P. Pate, "Requirements for Pseudo-Wire Emulation Edge-to-Edge (PWE3)", RFC 3916, September 2004.
[RFC3916]Xiao，X.，McPherson，D.，和P.Pate，“伪线仿真边到边（PWE3）的要求”，RFC 39162004年9月。
[RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.
[RFC3931]Lau，J.，Townsley，M.，和I.Goyret，“第二层隧道协议-版本3（L2TPv3）”，RFC 39312005年3月。
[RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005.
[RFC3985]Bryant，S.和P.Pate，“伪线仿真边到边（PWE3）架构”，RFC 39852005年3月。
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating MPLS in IP or Generic Routing Encapsulation (GRE)", RFC 4023, March 2005.
[RFC4023]Worster，T.，Rekhter，Y.，和E.Rosen，“在IP或通用路由封装（GRE）中封装MPLS”，RFC 4023，2005年3月。
[RFC4377] Nadeau, T., Morrow, M., Swallow, G., Allan, D., and S. Matsushima, "Operations and Management (OAM) Requirements for Multi-Protocol Label Switched (MPLS) Networks", RFC 4377, February 2006.
[RFC4377]Nadeau，T.，Morrow，M.，Swallow，G.，Allan，D.，和S.Matsushima，“多协议标签交换（MPLS）网络的运营和管理（OAM）要求”，RFC 4377，2006年2月。
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, February 2006.
[RFC4385]Bryant，S.，Swallow，G.，Martini，L.，和D.McPherson，“用于MPLS PSN的伪线仿真边到边（PWE3）控制字”，RFC 43852006年2月。
[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)", BCP 116, RFC 4446, April 2006.
[RFC4446]Martini，L.，“伪线边到边仿真（PWE3）的IANA分配”，BCP 116，RFC 4446，2006年4月。
[RFC4454] Singh, S., Townsley, M., and C. Pignataro, "Asynchronous Transfer Mode (ATM) over Layer 2 Tunneling Protocol Version 3 (L2TPv3)", RFC 4454, May 2006.
[RFC4454]Singh，S.，Townsley，M.，和C.Pignataro，“第2层隧道协议第3版（L2TPv3）上的异步传输模式（ATM）”，RFC 4454，2006年5月。
[RFC5086] Vainshtein, A., Sasson, I., Metz, E., Frost, T., and P. Pate, "Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN)", RFC 5086, December 2007.
[RFC5086]Vainstein，A.，Sasson，I.，Metz，E.，Frost，T.，和P.Pate，“分组交换网络上的结构感知时分多路复用（TDM）电路仿真服务（CESoPSN）”，RFC 50862007年12月。
[RFC5087] Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi, "Time Division Multiplexing over IP (TDMoIP)", RFC 5087, December 2007.
[RFC5087]Stein，Y（J.），Shashoua，R.，Insler，R.，和M.Anavi，“IP时分多路复用（TDMoIP）”，RFC 5087，2007年12月。
[RFC5254] Bitar, N., Bocci, M., and L. Martini, "Requirements for Multi-Segment Pseudowire Emulation Edge-to-Edge (PWE3)", RFC 5254, October 2008.
[RFC5254]Bitar，N.，Bocci，M.，和L.Martini，“多段伪线仿真边到边（PWE3）的要求”，RFC 5254，2008年10月。
[RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M. Aissaoui, "Segmented Pseudowire", RFC 6073, January 2011.
[RFC6073]Martini，L.，Metz，C.，Nadeau，T.，Bocci，M.和M.Aissaoui，“分段伪线”，RFC 60732011年1月。
[Eth-OAM-Inter] Mohan, D., Bitar, N., DeLord, S., Niger, P., Sajassi, A., and R. Qiu, "MPLS and Ethernet OAM Interworking", Work in Progress, March 2011.
[Eth OAM Inter]Mohan，D.，Bitar，N.，DeLord，S.，Niger，P.，Sajassi，A.，和R.Qiu，“MPLS和以太网OAM互通”，正在进行的工作，2011年3月。
[Static-PW-Status] Martini, L., Swallow, G., Heron, G., and M. Bocci, "Pseudowire Status for Static Pseudowires", Work in Progress, June 2011.
[静态PW状态]Martini，L.，Swallow，G.，Heron，G.，和M.Bocci，“静态伪线的伪线状态”，在建工程，2011年6月。
[I.620] "Frame relay operation and maintenance principles and functions", ITU-T Recommendation I.620, October 1996.
[I.620]“帧中继操作和维护原则及功能”，ITU-T建议I.620，1996年10月。
Appendix A. Native Service Management (Informative)
附录A.本机服务管理（资料性）
The management of Frame Relay Bearer Service (FRBS) connections can be accomplished through two distinct methodologies:
帧中继承载业务（FRBS）连接的管理可以通过两种不同的方法实现：
a. Based on [Q.933], Annex A, Link Integrity Verification procedure, where STATUS and STATUS ENQUIRY signaling messages are sent using DLCI=0 over a given User-Network Interface (UNI) and Network-Network Interface (NNI) physical link.
a. 基于[Q.933]，附录A，链路完整性验证程序，其中通过给定用户网络接口（UNI）和网络网络接口（NNI）物理链路使用DLCI=0发送状态和状态查询信令消息。
b. Based on FRBS Local Management Interface (LMI), and similar to ATM Integrated LMI (ILMI) where LMI is common in private Frame Relay networks.
b. 基于FRBS本地管理接口（LMI），类似于ATM集成LMI（ILMI），其中LMI在专用帧中继网络中很常见。
In addition, ITU-T I.620 [I.620] addressed Frame Relay loopback. This Recommendation was withdrawn in 2004, and its deployment was limited.
此外，ITU-T I.620[I.620]寻址帧中继环回。这项建议于2004年被撤回，其部署受到限制。
It is possible to use either, or both, of the above options to manage Frame Relay interfaces. This document will refer exclusively to Q.933 messages.
可以使用上述选项之一或两者来管理帧中继接口。本文件仅参考Q.933信息。
The status of any provisioned Frame Relay PVC may be updated through:
可通过以下方式更新任何配置的帧中继PVC的状态：
a. Frame Relay STATUS messages in response to Frame Relay STATUS ENQUIRY messages; these are mandatory.
a. 响应于帧中继状态查询消息的帧中继状态消息；这些都是强制性的。
b. Optional unsolicited STATUS updates independent of STATUS ENQUIRY (typically, under the control of management system, these updates can be sent periodically (continuous monitoring) or only upon detection of specific defects based on configuration).
b. 独立于状态查询的可选未经请求的状态更新（通常，在管理系统的控制下，这些更新可以定期发送（连续监控）或仅在根据配置检测到特定缺陷时发送）。
In Frame Relay, a Data Link Connection (DLC) is either up or down. There is no distinction between different directions. To achieve commonality with other technologies, down is represented as a receive defect.
在帧中继中，数据链路连接（DLC）是向上或向下的。不同方向之间没有区别。为了实现与其他技术的通用性，down被表示为接收缺陷。
Frame Relay connection management is not implemented over the PW using either of the techniques native to FR; therefore, PW mechanisms are used to synchronize the view each PE has of the remote Native Service/Attachment Circuit (NS/AC). A PE will treat a remote NS/AC failure in the same way it would treat a PW or PSN failure, that is, using AC facing FR connection management to notify the CE that FR is down.
帧中继连接管理未使用FR固有的任何一种技术在PW上实现；因此，PW机制用于同步每个PE对远程本机服务/连接电路（NS/AC）的视图。PE处理远程NS/AC故障的方式与处理PW或PSN故障的方式相同，即使用面向AC的FR连接管理通知CE FR已关闭。
ATM management and OAM mechanisms are much more evolved than those of Frame Relay. There are five broad management-related categories, including fault management (FT), Performance management (PM), configuration management (CM), Accounting management (AC), and Security management (SM). [I.610] describes the functions for the operation and maintenance of the physical layer and the ATM layer, that is, management at the bit and cell levels. Because of its scope, this document will concentrate on ATM fault management functions. Fault management functions include the following:
ATM管理和OAM机制比帧中继机制更先进。有五大管理相关类别，包括故障管理（FT）、性能管理（PM）、配置管理（CM）、记帐管理（AC）和安全管理（SM）。[I.610]描述了物理层和ATM层的操作和维护功能，即比特和信元级别的管理。由于其范围，本文件将集中讨论ATM故障管理功能。故障管理功能包括以下内容：
a. Alarm Indication Signal (AIS).
a. 报警指示信号（AIS）。
b. Remote Defect Indication (RDI).
b. 远程缺陷指示（RDI）。
c. Continuity Check (CC).
c. 连续性检查（CC）。
d. Loopback (LB).
d. 环回（LB）。
Some of the basic ATM fault management functions are described as follows: Alarm Indication Signal (AIS) sends a message in the same direction as that of the signal, to the effect that an error has been detected.
一些基本的ATM故障管理功能描述如下：报警指示信号（AIS）以与信号相同的方向发送消息，大意是检测到错误。
The Remote Defect Indication (RDI) sends a message to the transmitting terminal that an error has been detected. Alarms related to the physical layer are indicated using path AIS/RDI. Virtual path AIS/RDI and virtual channel AIS/RDI are also generated for the ATM layer.
远程缺陷指示（RDI）向发送终端发送已检测到错误的消息。使用路径AIS/RDI指示与物理层相关的报警。还为ATM层生成了虚拟路径AIS/RDI和虚拟信道AIS/RDI。
OAM cells (F4 and F5 cells) are used to instrument virtual paths and virtual channels, respectively, with regard to their performance and availability. OAM cells in the F4 and F5 flows are used for monitoring a segment of the network and end-to-end monitoring. OAM cells in F4 flows have the same VPI as that of the connection being monitored. OAM cells in F5 flows have the same VPI and VCI as that of the connection being monitored. The AIS and RDI messages of the F4 and F5 flows are sent to the other network nodes via the VPC or the VCC to which the message refers. The type of error and its location can be indicated in the OAM cells. Continuity check is another fault management function. To check whether a VCC that has been idle for a period of time is still functioning, the network elements can send continuity-check cells along that VCC.
OAM单元（F4和F5单元）分别用于根据其性能和可用性为虚拟路径和虚拟通道提供仪器。F4和F5流中的OAM单元用于监控网络的一个网段和端到端监控。F4流中的OAM单元具有与被监视连接相同的VPI。F5流中的OAM单元具有与被监视连接相同的VPI和VCI。F4和F5流的AIS和RDI消息通过消息所指的VPC或VCC发送到其他网络节点。错误类型及其位置可以在OAM单元中指示。连续性检查是另一种故障管理功能。为了检查空闲一段时间的VCC是否仍在工作，网元可以沿着该VCC发送连续性检查单元。
Possible defects that impact PWs are the following:
影响PWs的可能缺陷如下：
a. Physical layer defect in the PSN interface.
a. PSN接口中的物理层缺陷。
b. PSN tunnel failure that results in a loss of connectivity between ingress and egress PE.
b. PSN隧道故障，导致入口和出口PE之间失去连接。
c. Control session failures between ingress and egress PE.
c. 控制入口和出口PE之间的会话故障。
In case of an MPLS PSN and an MPLS/IP PSN there are additional defects:
对于MPLS PSN和MPLS/IP PSN，还存在其他缺陷：
a. PW labeling error, which is due to a defect in the ingress PE, or to an over-writing of the PW label value somewhere along the LSP path.
a. PW标签错误，这是由于入口PE中的缺陷或沿LSP路径某处PW标签值的过度写入造成的。
b. LSP tunnel label swapping errors or LSP tunnel label merging errors in the MPLS network. This could result in the termination of a PW at the wrong egress PE.
b. MPLS网络中的LSP隧道标签交换错误或LSP隧道标签合并错误。这可能导致PW在错误的出口PE处终止。
c. Unintended self-replication; e.g., due to loops or denial-of-service attacks.
c. 非预期的自我复制；e、 例如，由于循环或拒绝服务攻击。
Persistent congestion in the PSN or in a PE could impact the proper operation of the emulated service.
PSN或PE中的持续拥塞可能会影响模拟服务的正常运行。
A PE can detect packet loss resulting from congestion through several methods. If a PE uses the sequence number field in the PWE3 Control Word for a specific pseudowire [RFC3985] and [RFC4385], it has the ability to detect packet loss. Translation of congestion detection to PW defect states is beyond the scope of this document.
PE可以通过多种方法检测拥塞导致的数据包丢失。如果PE使用特定伪线[RFC3985]和[RFC4385]的PWE3控制字中的序列号字段，则它能够检测数据包丢失。将拥塞检测转换为PW缺陷状态超出了本文档的范围。
There are congestion alarms that are raised in the node and to the management system when congestion occurs. The decision to declare the PW down and to select another path is usually at the discretion of the network operator.
发生拥塞时，节点和管理系统会发出拥塞警报。宣布PW关闭并选择另一条路径的决定通常由网络运营商自行决定。
To detect the defects listed above, Service Providers have a variety of options available.
为了检测上面列出的缺陷，服务提供商有多种选择。
Physical Layer defect detection and notification mechanisms include SONET/SDH Loss of Signal (LOS), Loss of Alignment (LOA), and AIS/RDI.
物理层缺陷检测和通知机制包括SONET/SDH信号丢失（LOS）、对齐丢失（LOA）和AIS/RDI。
PSN defect detection mechanisms vary according to the PSN type.
PSN缺陷检测机制因PSN类型而异。
For PWs over L2TPv3/IP PSNs, with L2TP as encapsulation protocol, the defect detection mechanisms described in [RFC3931] apply. These include, for example, the keep-alive mechanism performed with Hello messages for detection of loss of connectivity between a pair of LCCEs (i.e., dead PE peer and path detection). Furthermore, the tools Ping and Traceroute, based on ICMP Echo Messages [RFC0792] apply and can be used to detect defects on the IP PSN. Additionally, VCCV-Ping [RFC5085] and VCCV-BFD [RFC5885] can also be used to detect defects at the individual pseudowire level.
对于L2TPv3/IP PSN上的PWs，使用L2TP作为封装协议，[RFC3931]中描述的缺陷检测机制适用。例如，这些包括使用Hello消息执行的保持活动机制，用于检测一对lcce之间的连接丢失（即，死PE对等和路径检测）。此外，基于ICMP回显消息[RFC0792]的Ping和Traceroute工具适用，可用于检测IP PSN上的缺陷。此外，VCCV Ping[RFC5085]和VCCV-BFD[RFC5885]也可用于检测单个伪线级别的缺陷。
For PWs over MPLS or MPLS/IP PSNs, several tools can be used:
对于通过MPLS或MPLS/IP PSN的PWs，可以使用以下几种工具：
a. LSP-Ping and LSP-Traceroute [RFC4379] for LSP tunnel connectivity verification.
a. LSP Ping和LSP跟踪路由[RFC4379]用于LSP隧道连接验证。
b. LSP-Ping with Bi-directional Forwarding Detection [RFC5885] for LSP tunnel continuity checking.
b. 带有双向转发检测的LSP Ping[RFC5885]用于LSP隧道连续性检查。
c. Furthermore, if Resource Reservation Protocol - Traffic Engineering (RSVP-TE) is used to set up the PSN Tunnels between ingress and egress PE, the hello protocol can be used to detect loss of connectivity [RFC3209], but only at the control plane.
c. 此外，如果使用资源预留协议-流量工程（RSVP-TE）在入口和出口PE之间建立PSN隧道，则hello协议可用于检测连接丢失[RFC3209]，但仅在控制平面上。
[RFC4377] describes how LSP-Ping and BFD can be used over individual PWs for connectivity verification and continuity checking, respectively.
[RFC4377]描述了LSP Ping和BFD如何分别在单个PW上用于连接验证和连续性检查。
Furthermore, the detection of a fault could occur at different points in the network and there are several ways the observing PE determines a fault exists:
此外，故障检测可能发生在网络中的不同点，观察PE有几种方法确定故障存在：
a. Egress PE detection of failure (e.g., BFD).
a. 出口PE故障检测（如BFD）。
b. Ingress PE detection of failure (e.g., LSP-PING).
b. 入口PE故障检测（如LSP-PING）。
c. Ingress PE notification of failure (e.g., RSVP Path-err).
c. 入口PE故障通知（例如RSVP路径错误）。
Authors' Addresses
作者地址
Mustapha Aissaoui Alcatel-Lucent 600 March Rd Kanata, ON K2K 2E6 Canada EMail: mustapha.aissaoui@alcatel-lucent.com
Mustapha Aissaoui Alcatel-Lucent 600三月路卡纳塔，K2K 2E6加拿大电子邮件：Mustapha。aissaoui@alcatel-朗讯网
Peter Busschbach Alcatel-Lucent 67 Whippany Rd Whippany, NJ 07981 USA EMail: busschbach@alcatel-lucent.com
Peter Busschbach Alcatel-Lucent 67 Whippany Rd Whippany，NJ 07981美国电子邮件：busschbach@alcatel-朗讯网
Luca Martini Cisco Systems, Inc. 9155 East Nichols Avenue, Suite 400 Englewood, CO 80112 USA EMail: lmartini@cisco.com
Luca Martini Cisco Systems，Inc.地址：美国科罗拉多州恩格尔伍德东尼科尔斯大道9155号400室邮编：80112电子邮件：lmartini@cisco.com
Monique Morrow Cisco Systems, Inc. Richtistrase 7 CH-8304 Wallisellen Switzerland EMail: mmorrow@cisco.com
Monique Morrow Cisco Systems，Inc.Richtistrase 7 CH-8304 Wallisellen Switzerland电子邮件：mmorrow@cisco.com
Thomas Nadeau CA Technologies 273 Corporate Dr. Portsmouth, NH 03801 USA EMail: Thomas.Nadeau@ca.com
Thomas Nadeau CA Technologies 273 Corporate Dr.朴茨茅斯，NH 03801美国电子邮件：Thomas。Nadeau@ca.com
Yaakov (Jonathan) Stein RAD Data Communications 24 Raoul Wallenberg St., Bldg C Tel Aviv 69719 Israel EMail: yaakov_s@rad.com
雅科夫（Jonathan）Stein RAD数据通信公司以色列特拉维夫C栋Raoul Wallenberg街24号邮编：69719电子邮件：雅科夫_s@rad.com