Internet Engineering Task Force (IETF) J. Ryoo, Ed.
Request for Comments: 7271 ETRI
Updates: 6378 E. Gray, Ed.
Category: Standards Track Ericsson
ISSN: 2070-1721 H. van Helvoort
Huawei Technologies
A. D'Alessandro
Telecom Italia
T. Cheung
ETRI
E. Osborne
June 2014
Internet Engineering Task Force (IETF) J. Ryoo, Ed.
Request for Comments: 7271 ETRI
Updates: 6378 E. Gray, Ed.
Category: Standards Track Ericsson
ISSN: 2070-1721 H. van Helvoort
Huawei Technologies
A. D'Alessandro
Telecom Italia
T. Cheung
ETRI
E. Osborne
June 2014
MPLS Transport Profile (MPLS-TP) Linear Protection to Match the Operational Expectations of Synchronous Digital Hierarchy, Optical Transport Network, and Ethernet Transport Network Operators
MPLS传输配置文件（MPLS-TP）线性保护，以满足同步数字体系、光传输网络和以太网传输网络运营商的运营期望
Abstract
摘要
This document describes alternate mechanisms to perform some of the functions of MPLS Transport Profile (MPLS-TP) linear protection defined in RFC 6378, and also defines additional mechanisms. The purpose of these alternate and additional mechanisms is to provide operator control and experience that more closely models the behavior of linear protection seen in other transport networks.
本文档描述了执行RFC 6378中定义的MPLS传输配置文件（MPLS-TP）线性保护的一些功能的替代机制，并定义了其他机制。这些备用和附加机制的目的是提供操作员控制和经验，以更紧密地模拟其他运输网络中的线性保护行为。
This document also introduces capabilities and modes for linear protection. A capability is an individual behavior, and a mode is a particular combination of capabilities. Two modes are defined in this document: Protection State Coordination (PSC) mode and Automatic Protection Switching (APS) mode.
本文件还介绍了线性保护的功能和模式。能力是个体行为，模式是能力的特定组合。本文件定义了两种模式：保护状态协调（PSC）模式和自动保护切换（APS）模式。
This document describes the behavior of the PSC protocol including priority logic and state machine when all the capabilities associated with the APS mode are enabled.
本文档描述了在启用与APS模式相关的所有功能时，PSC协议的行为，包括优先级逻辑和状态机。
This document updates RFC 6378 in that the capability advertisement method defined here is an addition to that document.
本文档更新了RFC 6378，因为此处定义的功能公告方法是对该文档的补充。
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/rfc7271.
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/rfc7271.
Copyright Notice
版权公告
Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2014 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 5
3. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Capability 1: Priority Modification . . . . . . . . . . . . . 6
4.1. Motivation for Swapping Priorities of FS and SF-P . . . . 6
4.2. Motivation for Raising the Priority of SFc . . . . . . . 7
4.3. Motivation for Introducing the Freeze Command . . . . . . 7
4.4. Procedures in Support of Priority Modification . . . . . 8
5. Capability 2: Non-revertive Behavior Modification . . . . . . 8
6. Capability 3: Support of the MS-W Command . . . . . . . . . . 8
6.1. Motivation for adding MS-W . . . . . . . . . . . . . . . 8
6.2. Terminology to Support MS-W . . . . . . . . . . . . . . . 9
6.3. Behavior of MS-P and MS-W . . . . . . . . . . . . . . . . 9
6.4. Equal-Priority Resolution for MS . . . . . . . . . . . . 10
7. Capability 4: Support of Protection against SD . . . . . . . 10
7.1. Motivation for Supporting Protection against SD . . . . . 10
7.2. Terminology to Support SD . . . . . . . . . . . . . . . . 10
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 5
3. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Capability 1: Priority Modification . . . . . . . . . . . . . 6
4.1. Motivation for Swapping Priorities of FS and SF-P . . . . 6
4.2. Motivation for Raising the Priority of SFc . . . . . . . 7
4.3. Motivation for Introducing the Freeze Command . . . . . . 7
4.4. Procedures in Support of Priority Modification . . . . . 8
5. Capability 2: Non-revertive Behavior Modification . . . . . . 8
6. Capability 3: Support of the MS-W Command . . . . . . . . . . 8
6.1. Motivation for adding MS-W . . . . . . . . . . . . . . . 8
6.2. Terminology to Support MS-W . . . . . . . . . . . . . . . 9
6.3. Behavior of MS-P and MS-W . . . . . . . . . . . . . . . . 9
6.4. Equal-Priority Resolution for MS . . . . . . . . . . . . 10
7. Capability 4: Support of Protection against SD . . . . . . . 10
7.1. Motivation for Supporting Protection against SD . . . . . 10
7.2. Terminology to Support SD . . . . . . . . . . . . . . . . 10
7.3. Behavior of Protection against SD . . . . . . . . . . . . 11
7.4. Equal-Priority Resolution . . . . . . . . . . . . . . . . 12
8. Capability 5: Support of EXER Command . . . . . . . . . . . . 13
9. Capabilities and Modes . . . . . . . . . . . . . . . . . . . 14
9.1. Capabilities . . . . . . . . . . . . . . . . . . . . . . 14
9.1.1. Sending and Receiving the Capabilities TLV . . . . . 15
9.2. Modes . . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.2.1. PSC Mode . . . . . . . . . . . . . . . . . . . . . . 16
9.2.2. APS Mode . . . . . . . . . . . . . . . . . . . . . . 16
10. PSC Protocol in APS Mode . . . . . . . . . . . . . . . . . . 17
10.1. Request Field in PSC Protocol Message . . . . . . . . . 17
10.2. Priorities of Local Inputs and Remote Requests . . . . . 17
10.2.1. Equal-Priority Requests . . . . . . . . . . . . . . 18
10.3. Acceptance and Retention of Local Inputs . . . . . . . . 20
11. State Transition Tables in APS Mode . . . . . . . . . . . . . 20
11.1. State Transition by Local Inputs . . . . . . . . . . . . 23
11.2. State Transition by Remote Messages . . . . . . . . . . 25
11.3. State Transition for 1+1 Unidirectional Protection . . . 27
12. Provisioning Mismatch and Protocol Failure in APS Mode . . . 27
13. Security Considerations . . . . . . . . . . . . . . . . . . . 28
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
14.1. MPLS PSC Request Registry . . . . . . . . . . . . . . . 29
14.2. MPLS PSC TLV Registry . . . . . . . . . . . . . . . . . 29
14.3. MPLS PSC Capability Flag Registry . . . . . . . . . . . 29
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 30
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
16.1. Normative References . . . . . . . . . . . . . . . . . . 30
16.2. Informative References . . . . . . . . . . . . . . . . . 30
Appendix A. An Example of an Out-of-Service Scenario . . . . . . 32
Appendix B. An Example of a Sequence Diagram Showing
the Problem with the Priority Level of SFc . . . . . 33
Appendix C. Freeze Command . . . . . . . . . . . . . . . . . . . 34
Appendix D. Operation Examples of the APS Mode . . . . . . . . . 35
7.3. Behavior of Protection against SD . . . . . . . . . . . . 11
7.4. Equal-Priority Resolution . . . . . . . . . . . . . . . . 12
8. Capability 5: Support of EXER Command . . . . . . . . . . . . 13
9. Capabilities and Modes . . . . . . . . . . . . . . . . . . . 14
9.1. Capabilities . . . . . . . . . . . . . . . . . . . . . . 14
9.1.1. Sending and Receiving the Capabilities TLV . . . . . 15
9.2. Modes . . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.2.1. PSC Mode . . . . . . . . . . . . . . . . . . . . . . 16
9.2.2. APS Mode . . . . . . . . . . . . . . . . . . . . . . 16
10. PSC Protocol in APS Mode . . . . . . . . . . . . . . . . . . 17
10.1. Request Field in PSC Protocol Message . . . . . . . . . 17
10.2. Priorities of Local Inputs and Remote Requests . . . . . 17
10.2.1. Equal-Priority Requests . . . . . . . . . . . . . . 18
10.3. Acceptance and Retention of Local Inputs . . . . . . . . 20
11. State Transition Tables in APS Mode . . . . . . . . . . . . . 20
11.1. State Transition by Local Inputs . . . . . . . . . . . . 23
11.2. State Transition by Remote Messages . . . . . . . . . . 25
11.3. State Transition for 1+1 Unidirectional Protection . . . 27
12. Provisioning Mismatch and Protocol Failure in APS Mode . . . 27
13. Security Considerations . . . . . . . . . . . . . . . . . . . 28
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
14.1. MPLS PSC Request Registry . . . . . . . . . . . . . . . 29
14.2. MPLS PSC TLV Registry . . . . . . . . . . . . . . . . . 29
14.3. MPLS PSC Capability Flag Registry . . . . . . . . . . . 29
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 30
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
16.1. Normative References . . . . . . . . . . . . . . . . . . 30
16.2. Informative References . . . . . . . . . . . . . . . . . 30
Appendix A. An Example of an Out-of-Service Scenario . . . . . . 32
Appendix B. An Example of a Sequence Diagram Showing
the Problem with the Priority Level of SFc . . . . . 33
Appendix C. Freeze Command . . . . . . . . . . . . . . . . . . . 34
Appendix D. Operation Examples of the APS Mode . . . . . . . . . 35
Linear protection mechanisms for the MPLS Transport Profile (MPLS-TP) are described in RFC 6378 [RFC6378] to meet the requirements described in RFC 5654 [RFC5654].
RFC 6378[RFC6378]中描述了MPLS传输配置文件（MPLS-TP）的线性保护机制，以满足RFC 5654[RFC5654]中描述的要求。
This document describes alternate mechanisms to perform some of the functions of linear protection, and also defines additional mechanisms. The purpose of these alternate and additional mechanisms is to provide operator control and experience that more closely models the behavior of linear protection seen in other transport networks, such as Synchronous Digital Hierarchy (SDH), Optical Transport Network (OTN), and Ethernet transport networks. Linear protection for SDH, OTN, and Ethernet transport networks is defined in ITU-T Recommendations G.841 [G841], G.873.1 [G873.1], and G.8031 [G8031], respectively.
本文件描述了执行线性保护某些功能的替代机制，并定义了其他机制。这些备用和附加机制的目的是提供操作员控制和经验，更紧密地模拟其他传输网络（如同步数字体系（SDH）、光传输网络（OTN）和以太网传输网络）中的线性保护行为。SDH、OTN和以太网传输网络的线性保护分别在ITU-T建议G.841[G841]、G.873.1[G873.1]和G.8031[G8031]中定义。
The reader of this document is assumed to be familiar with [RFC6378].
假定本文件的读者熟悉[RFC6378]。
The alternative mechanisms described in this document are for the following capabilities:
本文件中描述的替代机制适用于以下功能：
1. Priority modification,
1. 优先权修改，
2. non-revertive behavior modification,
2. 非回复性行为修改，
and the following capabilities have been added to define additional mechanisms:
并添加了以下功能以定义其他机制：
3. support of the Manual Switch to Working path (MS-W) command,
3. 支持手动切换到工作路径（MS-W）命令，
4. support of protection against Signal Degrade (SD), and
4. 支持信号降级保护（SD），以及
5. support of the Exercise (EXER) command.
5. 支持演习指挥部。
The priority modification includes raising the priority of Signal Fail on Protection path (SF-P) relative to Forced Switch (FS), and raising the priority level of Clear Signal Fail (SFc) above SF-P.
优先级修改包括提高保护路径上信号故障（SF-P）相对于强制开关（FS）的优先级，以及将清除信号故障（SFc）的优先级提高到SF-P以上。
Non-revertive behavior is modified to align with the behavior defined in RFC 4427 [RFC4427] as well as to follow the behavior of linear protection seen in other transport networks.
对非回复行为进行了修改，以符合RFC 4427[RFC4427]中定义的行为，并遵循其他传输网络中的线性保护行为。
Support of the MS-W command to revert traffic to the working path in non-revertive operation is covered in this document.
本文档介绍了在非恢复操作中支持MS-W命令将流量恢复到工作路径。
Support of the protection-switching protocol against SD is covered in this document. The specifics for the method of identifying SD are out of the scope for this document and are treated similarly to Signal Fail (SF) in [RFC6378].
本文件涵盖了对SD保护交换协议的支持。识别SD方法的细节不在本文件范围内，与[RFC6378]中的信号失败（SF）类似。
Support of the EXER command to test if the Protection State Coordination (PSC) communication is operating correctly is also covered in this document. Without actually switching traffic, the EXER command tests and validates the linear protection mechanism and PSC protocol including the aliveness of the priority logic, the PSC state machine, the PSC message generation and reception, and the integrity of the protection path.
支持EXER命令，以测试保护状态协调（PSC）通信是否正常运行，本文件也包括在内。在不实际切换流量的情况下，EXER命令测试并验证线性保护机制和PSC协议，包括优先级逻辑的有效性、PSC状态机、PSC消息生成和接收以及保护路径的完整性。
This document introduces capabilities and modes. A capability is an individual behavior. The capabilities of a node are advertised using the method given in this document. A mode is a particular combination of capabilities. Two modes are defined in this document: PSC mode and Automatic Protection Switching (APS) mode.
本文档介绍了功能和模式。能力是一种个人行为。使用本文档中给出的方法公布节点的功能。模式是功能的特定组合。本文件定义了两种模式：PSC模式和自动保护切换（APS）模式。
Other modes may be defined as new combinations of the capabilities defined in this document or through the definition of additional capabilities. In either case, the specification defining a new mode will be responsible for documenting the behavior, the priority logic, and the state machine of the PSC protocol when the set of capabilities in the new mode is enabled.
其他模式可以定义为本文档中定义的功能的新组合，也可以通过定义其他功能来定义。在这两种情况下，定义新模式的规范将负责在启用新模式中的一组功能时记录PSC协议的行为、优先级逻辑和状态机。
This document describes the behavior, the priority logic, and the state machine of the PSC protocol when all the capabilities associated with the APS mode are enabled. The PSC protocol behavior for the PSC mode is as defined in [RFC6378].
本文档描述了所有与APS模式相关的功能启用时PSC协议的行为、优先级逻辑和状态机。PSC模式的PSC协议行为如[RFC6378]中所定义。
This document updates [RFC6378] by adding a capability advertisement mechanism. It is recommended that existing implementations of the PSC protocol be updated to support this capability. Backward compatibility with existing implementations that do not support this mechanism is described in Section 9.2.1.
本文档通过添加功能公告机制来更新[RFC6378]。建议更新PSC协议的现有实现以支持此功能。第9.2.1节描述了与不支持此机制的现有实现的向后兼容性。
Implementations are expected to be configured to support a specific set of capabilities (a mode) and to reject messages that indicate the use of a different set of capabilities (a different mode). Thus, the capability advertisement is not a negotiation but a verification that peers are using the same mode.
实现应配置为支持特定的功能集（模式），并拒绝指示使用不同功能集（不同模式）的消息。因此，能力公告不是协商，而是验证对等方正在使用相同的模式。
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 RFC 2119 [RFC2119].
本文件中的关键词“必须”、“不得”、“要求”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照RFC 2119[RFC2119]中所述进行解释。
This document uses the following acronyms:
本文件使用以下首字母缩略词：
APS Automatic Protection Switching DNR Do-not-Revert EXER Exercise FS Forced Switch LO Lockout of protection MS Manual Switch MS-P Manual Switch to Protection path MS-W Manual Switch to Working path MPLS-TP MPLS Transport Profile NR No Request OC Operator Clear OTN Optical Transport Network PSC Protection State Coordination RR Reverse Request SD Signal Degrade SD-P Signal Degrade on Protection path SD-W Signal Degrade on Working path SDH Synchronous Digital Hierarchy SF Signal Fail SF-P Signal Fail on Protection path SF-W Signal Fail on Working path SFc Clear Signal Fail SFDc Clear Signal Fail or Degrade WTR Wait-to-Restore
APS自动保护切换DNR不恢复EXER练习FS强制开关LO保护锁定MS手动开关MS-P手动开关到保护路径MS-W手动开关到工作路径MPLS-TP MPLS传输配置文件NR无请求OC操作员清除OTN光传输网络PSC保护状态协调RR反向请求SD信号降级SD-P信号在保护路径上降级SD-W信号在工作路径上降级SDH同步数字体系SF信号故障SF-P信号在保护路径上故障SF-W信号在工作路径上故障SFc清除信号故障SFDc清除信号故障或降级WTR等待恢复
[RFC6378] defines the priority of FS to be higher than that of SF-P. That document also defines the priority of Clear SF (SFc) to be low. This document defines the priority modification capability whereby the relative priorities of FS and SF-P are swapped, and the priority of Clear SF (SFc) is raised. In addition, this capability introduces the Freeze command as described in Appendix C. The rationale for these changes is detailed in the following subsections from both the technical and network operational aspects.
[RFC6378]定义了FS的优先级高于SF-P。该文件还定义了Clear SF（SFc）的优先级较低。本文件定义了优先权修改能力，通过该能力，FS和SF-P的相对优先权被交换，而清晰SF（SFc）的优先权被提高。此外，该能力引入了附录C中所述的冻结命令。以下小节从技术和网络操作两个方面详细介绍了这些更改的基本原理。
Defining the priority of FS higher than that of SF-P can result in a situation where the protected traffic is taken out of service. When the protection path fails, PSC communication may stop as a result. In this case, if any input that is supposed to be signaled to the other end has a higher priority than SF-P, then this can result in an
将FS的优先级定义为高于SF-P的优先级可能会导致受保护流量停止服务的情况。当保护路径失效时，PSC通信可能因此停止。在这种情况下，如果本应向另一端发送信号的任何输入具有比SF-P更高的优先级，则这可能导致
unpredictable protection-switching state. An example scenario that may result in an out-of-service situation is presented in Appendix A of this document.
不可预测的保护切换状态。本文件附录A中给出了可能导致停用情况的示例场景。
According to Section 2.4 of [RFC5654], it MUST be possible to operate an MPLS-TP network without using a control plane. This means that the PSC communication channel is very important for the transfer of external switching commands (e.g., FS), and these commands should not rely on the presence of a control plane. In consequence, the failure of the PSC communication channel has higher priority than FS.
根据[RFC5654]第2.4节，必须能够在不使用控制平面的情况下操作MPLS-TP网络。这意味着PSC通信信道对于外部开关命令（例如FS）的传输非常重要，并且这些命令不应依赖于控制平面的存在。因此，PSC通信信道的故障优先级高于FS。
In other transport networks (such as SDH, OTN, and Ethernet transport networks), the priority of SF-P has been higher than that of FS. It is therefore important to offer network operators the option of having the same behavior in their MPLS-TP networks so that they can have the same operational protection-switching behavior to which they have become accustomed. Typically, an FS command is issued before network maintenance jobs (e.g., replacing optical cables or other network components). When an operator pulls out a cable on the protection path, by mistake, the traffic should continue to be protected, and the operator expects this behavior based on his/her experience with traditional transport network operations.
在其他传输网络（如SDH、OTN和以太网传输网络）中，SF-P的优先级高于FS。因此，重要的是为网络运营商提供在其MPLS-TP网络中具有相同行为的选项，以便他们能够具有他们已经习惯的相同操作保护切换行为。通常，FS命令在网络维护作业（例如，更换光缆或其他网络组件）之前发出。当运营商错误地拔出保护路径上的电缆时，通信量应继续受到保护，运营商根据其在传统传输网络运营中的经验预期这种行为。
The priority level of SFc defined in [RFC6378] can cause traffic disruption when a node that has experienced local signal fails on both the working and the protection paths is recovering from these failures.
[RFC6378]中定义的SFc优先级可能会在经历本地信号的节点在工作路径和保护路径上都发生故障并正在从这些故障中恢复时导致通信中断。
A sequence diagram highlighting the problem with the priority level of SFc as defined in [RFC6378] is presented in Appendix B.
附录B中给出了一个序列图，突出了[RFC6378]中定义的SFc优先级问题。
With the priority swapping between FS and SF-P, the traffic is always moved back to the working path when SF-P occurs in Protecting Administrative state. In case network operators need an option to control their networks so that the traffic can remain on the protection path even when the PSC communication channel is broken, the Freeze command can be used. Freeze is defined to be a "local" command that is not signaled to the remote node. The use of the Freeze command is described in Appendix C.
通过FS和SF-P之间的优先级交换，当SF-P处于保护管理状态时，流量总是移回工作路径。如果网络运营商需要控制其网络的选项，以便即使PSC通信信道中断，通信量仍能保持在保护路径上，则可以使用冻结命令。冻结被定义为不向远程节点发送信号的“本地”命令。附录C中描述了冻结命令的使用。
When the modified priority order specified in this document is in use, the list of local requests in order of priority SHALL be as follows (from highest to lowest):
当使用本文件中规定的修改优先顺序时，按优先顺序排列的本地请求列表如下（从最高到最低）：
o Clear Signal Fail
o 清除信号失败
o Signal Fail on Protection path
o 保护路径上的信号故障
o Forced Switch
o 强制开关
o Signal Fail on Working path
o 工作路径上的信号故障
This requires modification of the PSC Control Logic (including the state machine) relative to that described in [RFC6378]. Sections 10 and 11 present the PSC Control Logic when all capabilities of APS mode are enabled.
这需要对PSC控制逻辑（包括状态机）进行修改，使其与[RFC6378]中所述的相关。第10节和第11节介绍了启用APS模式所有功能时的PSC控制逻辑。
Non-revertive operation of protection switching is defined in [RFC4427]. In this operation, the traffic does not return to the working path when switch-over requests are terminated.
[RFC4427]中定义了保护开关的非可逆操作。在此操作中，当切换请求终止时，通信量不会返回到工作路径。
However, the PSC protocol defined in [RFC6378] supports this operation only when recovering from a defect condition: it does not support the non-revertive function when an operator's switch-over command, such as FS or Manual Switch (MS), is cleared. To be aligned with the behavior in other transport networks and to be consistent with [RFC4427], a node should go into the Do-not-Revert (DNR) state not only when a failure condition on the working path is cleared, but also when an operator command that requested switch-over is cleared.
但是，[RFC6378]中定义的PSC协议仅在从缺陷状态恢复时支持此操作：当操作员的切换命令（如FS或手动切换（MS））被清除时，它不支持非恢复功能。为了与其他传输网络中的行为保持一致，并与[RFC4427]保持一致，节点不仅应在清除工作路径上的故障条件时，而且应在清除请求切换的操作员命令时，进入请勿恢复（DNR）状态。
This requires modification to the PSC Control Logic (including the state machine) relative to that described in [RFC6378]. Sections 10 and 11 present the PSC Control Logic when all capabilities of APS mode are enabled.
这需要对PSC控制逻辑（包括状态机）进行修改，使其与[RFC6378]中所述的逻辑相对应。第10节和第11节介绍了启用APS模式所有功能时的PSC控制逻辑。
Changing the non-revertive operation as described in Section 5 introduces the necessity of a new operator command to revert traffic to the working path in the DNR state. When the traffic is on the protection path in the DNR state, a Manual Switch to Working (MS-W) command is issued to switch the normal traffic back to the working
如第5节所述，更改非恢复操作将引入新操作员命令的必要性，以便在DNR状态下将通信量恢复到工作路径。当通信量处于DNR状态下的保护路径上时，发出手动切换到工作（MS-W）命令，将正常通信量切换回工作路径
path. According to Section 4.3.3.6 (Do-not-Revert State) in [RFC6378], "To revert back to the Normal state, the administrator SHALL issue a Lockout of protection command followed by a Clear command." However, using the Lockout of protection (LO) command introduces the potential risk of an unprotected situation while the LO is in effect.
路径根据[RFC6378]中的第4.3.3.6节（不恢复状态），“要恢复到正常状态，管理员应发出保护锁定命令，然后发出清除命令。”但是，使用保护锁定（LO）命令会在LO有效时引入未保护情况的潜在风险。
The "Manual switch-over for recovery LSP/span" command is defined in [RFC4427]. Requirement 83 in [RFC5654] states that the external commands defined in [RFC4427] MUST be supported. Since there is no support for this external command in [RFC6378], this functionality should be added to PSC. This support is provided by introducing the MS-W command. The MS-W command, as described here, corresponds to the "Manual switch-over for recovery LSP/span" command.
[RFC4427]中定义了“恢复LSP/span的手动切换”命令。[RFC5654]中的要求83规定必须支持[RFC4427]中定义的外部命令。由于[RFC6378]中不支持此外部命令，因此应将此功能添加到PSC中。这种支持是通过引入MS-W命令提供的。如本文所述，MS-W命令对应于“恢复LSP/span的手动切换”命令。
[RFC6378] uses the term "Manual Switch" and its acronym "MS". This document uses the term "Manual Switch to Protection path" and "MS-P" to have the same meaning, while avoiding confusion with "Manual Switch to Working path" and its acronym "MS-W".
[RFC6378]使用术语“手动开关”及其首字母缩略词“MS”。本文件使用术语“手动切换到保护路径”和“MS-P”具有相同的含义，同时避免与“手动切换到工作路径”及其首字母缩写“MS-W”混淆。
Similarly, we modify the name of "Protecting Administrative" state (as defined in [RFC6378]) to be "Switching Administrative" state to include the case where traffic is switched to the working path as a result of the external MS-W command.
类似地，我们将“保护管理”状态（如[RFC6378]中定义）的名称修改为“切换管理”状态，以包括由于外部MS-W命令而将通信量切换到工作路径的情况。
MS-P and MS-W SHALL have the same priority. We consider different instances of determining the priority of the commands when they are received either in succession or simultaneously.
MS-P和MS-W应具有相同的优先级。我们考虑不同的情况下确定优先级的命令时，他们是连续或同时接收。
o When two commands are received in succession, the command that is received after the initial command SHALL be cancelled.
o 当连续收到两个命令时，应取消在初始命令之后收到的命令。
o If two nodes simultaneously receive commands that indicate opposite operations (i.e., one node receives MS-P and the other node receives MS-W) and transmit the indications to the remote node, the MS-W SHALL be considered to have a higher priority, and the MS-P SHALL be cancelled and discarded.
o 如果两个节点同时接收指示相反操作的命令（即，一个节点接收MS-P，另一个节点接收MS-W）并将指示发送给远程节点，则应认为MS-W具有更高的优先级，并且应取消和丢弃MS-P。
Two commands, MS-P and MS-W, are transmitted using the same Request field value but SHALL indicate in the Fault Path (FPath) value the path from which the traffic is being diverted. When traffic is switched to the protection path, the FPath field value SHALL be set to 1, indicating that traffic is being diverted from the working path. When traffic is switched to the working path, the FPath field
使用相同的请求字段值发送两个命令MS-P和MS-W，但应在故障路径（FPath）值中指示交通分流的路径。当交通量切换到保护路径时，FPath字段值应设置为1，表示交通量正从工作路径分流。当流量切换到工作路径时，FPath字段
value SHALL be set to 0, indicating that traffic is being diverted from the protection path. The Data Path (Path) field SHALL indicate where user data traffic is being transported (i.e., if the working path is selected, then Path is set to 0; if the protection path is selected, then Path is set to 1).
该值应设置为0，表示交通正从保护路径分流。数据路径（Path）字段应指示用户数据流量传输的位置（即，如果选择了工作路径，则Path设置为0；如果选择了保护路径，则Path设置为1）。
When an MS command is in effect at a node, any subsequent MS or EXER command and any other lower-priority requests SHALL be ignored.
当MS命令在节点上生效时，应忽略任何后续MS或EXER命令以及任何其他低优先级请求。
[RFC6378] defines only one rule for the equal-priority condition in Section 4.3.2 as "The remote message from the far-end LER is assigned a priority just below the similar local input." In order to support the Manual Switch behavior described in Section 6.3, additional rules for equal-priority resolution are required. Since the support of protection against signal degrade also requires a similar equal-priority resolution, the rules are described in Section 7.4.
[RFC6378]在第4.3.2节中仅为等优先级条件定义了一条规则，即“来自远端LER的远程消息被分配了一个略低于类似本地输入的优先级”。为了支持第6.3节中所述的手动切换行为，需要其他等优先级解析规则。由于支持信号降级保护也需要类似的同等优先级分辨率，因此规则在第7.4节中描述。
Support of this function requires changes to the PSC Control Logic (including the state machine) relative to that shown in [RFC6378]. Sections 10 and 11 present the PSC Control Logic when all capabilities of APS mode are enabled.
支持此功能需要改变PSC控制逻辑（包括状态机）相对于[RFC6378]中所示的逻辑。第10节和第11节介绍了启用APS模式所有功能时的PSC控制逻辑。
In the MPLS-TP Survivability Framework [RFC6372], both SF and SD fault conditions can be used to trigger protection switching.
在MPLS-TP生存性框架[RFC6372]中，SF和SD故障条件均可用于触发保护切换。
[RFC6378], which defines the protection-switching protocol for MPLS-TP, does not specify how the SF and SD are detected, and specifies the protection-switching protocol associated with SF only.
[RFC6378]定义了MPLS-TP的保护交换协议，但没有指定如何检测SF和SD，只指定了与SF关联的保护交换协议。
The PSC protocol associated with SD is covered in this document, but the specifics for the method of identifying SD is out of scope for the protection protocol in the same way that SF detection and MS or FS command initiation are out of scope.
本文件涵盖了与SD相关的PSC协议，但识别SD方法的细节超出了保护协议的范围，正如SF检测和MS或FS命令启动超出范围一样。
In this document, the term Clear Signal Fail or Degrade (SFDc) is used to indicate the clearance of either a degraded condition or a failure condition.
在本文件中，术语清除信号故障或降级（SFDc）用于表示清除降级状态或故障状态。
The second paragraph of Section 4.3.3.2 (Unavailable State) in [RFC6378] shows the intention of including Signal Degrade on Protection path (SD-P) in the Unavailable state. Even though the protection path can be partially available under the condition of SD-P, this document follows the same state grouping as [RFC6378] for SD-P.
[RFC6378]中第4.3.3.2节（不可用状态）的第二段显示了在不可用状态下包括保护路径（SD-P）上的信号降级的意图。即使保护路径在SD-P条件下可以部分可用，本文档遵循与SD-P的[RFC6378]相同的状态分组。
The bulleted item on the Protecting Failure state in Section 3.6 of [RFC6378] includes the degraded condition in the Protecting Failure state. This document follows the same state grouping as [RFC6378] for Signal Degrade on Working path (SD-W).
[RFC6378]第3.6节中保护失效状态的项目符号包括保护失效状态下的降级状态。本文件遵循与[RFC6378]相同的状态分组，用于工作路径上的信号降级（SD-W）。
To better align the behavior of MPLS-TP networks with that of other transport networks (such as SDH, OTN, and Ethernet transport networks), we define the following:
为了更好地使MPLS-TP网络的行为与其他传输网络（如SDH、OTN和以太网传输网络）的行为保持一致，我们定义如下：
o The priorities of SD-P and SD-W SHALL be equal.
o SD-P和SD-W的优先级应相同。
o Once a switch has been completed due to SD on one path, it will not be overridden by SD on the other path (first come, first served behavior), to avoid protection switching that cannot improve signal quality.
o 一旦一条路径上的SD导致切换完成，它将不会被另一条路径上的SD覆盖（先到先得行为），以避免无法改善信号质量的保护切换。
The SD message indicates that the transmitting node has identified degradation of the signal or integrity of the packet received on either the working path or the protection path. The FPath field SHALL identify the path that is reporting the degraded condition (i.e., if the protection path, then FPath is set to 0; if the working path, then FPath is set to 1), and the Path field SHALL indicate where the data traffic is being transported (i.e., if the working path is selected, then Path is set to 0; if the protection path is selected, then Path is set to 1).
SD消息指示发送节点已识别在工作路径或保护路径上接收的分组的信号或完整性的退化。FPath字段应标识报告降级情况的路径（即，如果保护路径，则FPath设置为0；如果工作路径，则FPath设置为1），并且路径字段应指示数据流量传输的位置（即，如果选择了工作路径，则路径设置为0；如果选择了保护路径，则路径设置为1）。
When the SD condition is cleared and the protected domain is recovering from the situation, the Wait-to-Restore (WTR) timer SHALL be used if the protected domain is configured for revertive behavior. The WTR timer SHALL be started at the node that recovers from a local degraded condition on the working path.
当SD条件被清除且受保护域正在从该情况中恢复时，如果受保护域被配置为恢复行为，则应使用等待恢复（WTR）计时器。WTR定时器应在从工作路径上的局部降级状态恢复的节点处启动。
Protection switching against SD is always provided by a selector bridge duplicating user data traffic and feeding it to both the working path and the protection path under SD condition. When a local or remote SD occurs on either the working path or the protection path, the node SHALL duplicate user data traffic and SHALL feed it to both the working path and the protection path. The packet duplication SHALL continue as long as any SD condition exists in the
针对SD的保护切换始终由选择器网桥提供，该选择器网桥复制用户数据流量，并在SD条件下将其馈送至工作路径和保护路径。当本地或远程SD发生在工作路径或保护路径上时，节点应复制用户数据流量，并将其馈送至工作路径和保护路径。只要数据包中存在任何SD条件，数据包复制应继续进行
protected domain. When the SD condition is cleared, in revertive operation, the packet duplication SHALL continue in the WTR state and SHALL stop when the node leaves the WTR state; while in non-revertive operation, the packet duplication SHALL stop immediately.
受保护的域。当SD条件被清除时，在恢复操作中，数据包复制应在WTR状态下继续，并在节点离开WTR状态时停止；在非还原操作中，数据包复制应立即停止。
The selector bridge with the packet duplication under SD condition, which is a non-permanent bridge, is considered to be a 1:1 protection architecture.
SD条件下具有数据包复制的选择器网桥是一种非永久性网桥，被认为是1:1保护体系结构。
Protection switching against SD does not introduce any modification to the operation of the selector at the sink node described in [RFC6378]. The selector chooses either the working or protection path from which to receive the normal traffic in both 1:1 and 1+1 architectures. The position of the selector, i.e., which path to receive the traffic, is determined by the PSC protocol in bidirectional switching or by the local input in unidirectional switching.
针对SD的保护切换不会对[RFC6378]中所述的接收器节点处选择器的操作进行任何修改。选择器选择工作路径或保护路径，从中接收1:1和1+1体系结构中的正常流量。选择器的位置，即接收业务的路径，由双向交换中的PSC协议或单向交换中的本地输入确定。
In order to support the MS behavior described in Section 6.3 and the protection against SD described in Section 7.3, it is necessary to expand rules for treating equal-priority inputs.
为了支持第6.3节中描述的MS行为和第7.3节中描述的SD防护，有必要扩展处理同等优先级输入的规则。
For equal-priority local inputs, such as MS and SD, apply a simple first-come, first-served rule. Once a local input is determined as the highest priority local input, then a subsequent equal-priority local input requesting a different action, i.e., the action results in the same PSC Request field but different FPath value, will not be presented to the PSC Control Logic as the highest local request. Furthermore, in the case of an MS command, the subsequent local MS command requesting a different action will be cancelled.
对于同等优先级的本地输入，如MS和SD，应用简单的先到先得规则。一旦本地输入被确定为最高优先级的本地输入，则请求不同操作的后续同等优先级本地输入（即，该操作导致相同的PSC请求字段但不同的FPath值）将不会作为最高本地请求呈现给PSC控制逻辑。此外，在MS命令的情况下，请求不同操作的后续本地MS命令将被取消。
If a node is in a remote state due to a remote SD (or MS) message, a subsequent local input having the same priority but requesting a different action to the PSC Control Logic will be considered as having lower priority than the remote message and will be ignored. For example, if a node is in remote Switching Administrative state due to a remote MS-P, then any subsequent local MS-W SHALL be ignored and automatically cancelled. If a node is in remote Unavailable state due to a remote SD-P, then any subsequent local SD-W input will be ignored. However, the local SD-W SHALL continue to appear in the Local Request Logic as long as the SD condition exists, but it SHALL NOT be the top-priority global request, which determines the state transition at the PSC Control Logic.
如果由于远程SD（或MS）消息，节点处于远程状态，则具有相同优先级但向PSC控制逻辑请求不同操作的后续本地输入将被视为优先级低于远程消息，并将被忽略。例如，如果节点由于远程MS-P而处于远程切换管理状态，则应忽略并自动取消任何后续本地MS-W。如果节点由于远程SD-P而处于远程不可用状态，则将忽略任何后续的本地SD-W输入。然而，只要SD条件存在，本地SD-W应继续出现在本地请求逻辑中，但它不应是最高优先级的全局请求，它决定PSC控制逻辑的状态转换。
Cases where two end-points of the protected domain simultaneously receive local triggers of the same priority that request different actions may occur (for example, one node receives SD-P and the other receives SD-W). Subsequently, each node will receive a remote message with the opposing action indication. To address these cases, we define the following priority resolution rules:
受保护域的两个端点同时接收相同优先级的本地触发器，请求不同操作的情况可能会发生（例如，一个节点接收SD-P，另一个节点接收SD-W）。随后，每个节点将接收带有相反动作指示的远程消息。为了解决这些情况，我们定义了以下优先级解析规则：
o When MS-W and MS-P occur simultaneously at both nodes, MS-W SHALL be considered as having higher priority than MS-P at both nodes.
o 当MS-W和MS-P同时出现在两个节点上时，MS-W应被视为在两个节点上具有比MS-P更高的优先级。
o When SD-W and SD-P occur simultaneously at both nodes, the SD on the standby path (the path from which the selector does not select the user data traffic) is considered as having higher priority than the SD on the active path (the path from which the selector selects the user data traffic) regardless of its origin (local or remote message). Therefore, no unnecessary protection switching is performed, and the user data traffic continues to be selected from the active path.
o 当SD-W和SD-P同时出现在两个节点上时，备用路径（选择器不选择用户数据流量的路径）上的SD被视为比活动路径（选择器选择用户数据流量的路径）上的SD具有更高的优先级，而不管其来源（本地或远程消息）。因此，不执行不必要的保护切换，并且继续从活动路径选择用户数据业务。
In the preceding paragraphs, "simultaneously" refers to the case a sent SD (or MS) request has not been confirmed by the remote end in bidirectional protection switching. When a local node that has transmitted an SD message receives an SD (or MS) message that indicates a different value of Path field from the value of Path field in the transmitted SD (or MS) message, both the local and remote SD requests are considered to occur simultaneously.
在上述段落中，“同时”是指发送的SD（或MS）请求在双向保护切换中未被远端确认的情况。当已发送SD消息的本地节点接收到指示路径字段的值与所发送SD（或MS）消息中的路径字段的值不同的SD（或MS）消息时，本地和远程SD请求被认为同时发生。
The addition of support for protection against SD requires modification to the PSC Control Logic (including the state machine) relative to that described in [RFC6378]. Sections 10 and 11 present the PSC Control Logic when all capabilities of APS mode are enabled.
与[RFC6378]中所述相比，增加对SD保护的支持需要修改PSC控制逻辑（包括状态机）。第10节和第11节介绍了启用APS模式所有功能时的PSC控制逻辑。
The EXER command is used to verify the correct operation of the PSC communication, such as the aliveness of the Local Request Logic, the integrity of the PSC Control Logic, the PSC message generation and reception mechanism, and the integrity of the protection path. EXER does not trigger any actual traffic switching.
EXER命令用于验证PSC通信的正确操作，例如本地请求逻辑的有效性、PSC控制逻辑的完整性、PSC消息生成和接收机制以及保护路径的完整性。EXER不会触发任何实际的流量切换。
The command is only relevant for bidirectional protection switching, since it is dependent upon receiving a response from the remote node. The EXER command is assigned lower priority than any switching message. It may be used regardless of the traffic usage of the working path.
该命令仅与双向保护切换相关，因为它依赖于从远程节点接收响应。EXER命令的优先级低于任何切换消息。无论工作路径的流量使用情况如何，都可以使用它。
When a node receives a remote EXER message, it SHOULD respond with a Reverse Request (RR) message with the FPath and Path fields set according to the current condition of the node. The RR message SHALL be generated only in response to a remote EXER message.
当节点收到远程EXER消息时，它应该使用反向请求（RR）消息进行响应，并根据节点的当前条件设置FPath和Path字段。RR消息只能在响应远程EXER消息时生成。
This command is documented in R84 of [RFC5654].
该命令记录在[RFC5654]的R84中。
If EXER commands are input at both ends, then a race condition may arise. This is resolved as follows:
如果在两端输入EXER命令，则可能出现竞态条件。解决办法如下：
o If a node has issued EXER and receives EXER before receiving RR, it MUST treat the received EXER as it would an RR, and it SHOULD NOT respond with RR.
o 如果节点在接收RR之前已发出EXER并接收EXER，则必须将接收到的EXER视为RR，并且不应使用RR响应。
The following PSC Requests are added to the PSC Request field to support the Exercise command (see also Section 14.1):
以下PSC请求添加到PSC请求字段，以支持演习命令（另见第14.1节）：
(3) Exercise - indicates that the transmitting end-point is exercising the protection channel and mechanism. FPath and Path are set to the same value of the No Request (NR), RR, or DNR message whose transmission is stopped by EXER.
(3) 练习-表示传输端点正在练习保护通道和机制。FPath和Path设置为无请求（NR）、RR或DNR消息的相同值，其传输被EXER停止。
(2) Reverse Request - indicates that the transmitting end-point is responding to an EXER command from the remote node. FPath and Path are set to the same value of the NR or DNR message whose transmission is stopped by RR.
(2) 反向请求-表示传输端点正在响应来自远程节点的EXER命令。FPath和Path设置为其传输被RR停止的NR或DNR消息的相同值。
The relative priorities of EXER and RR are defined in Section 10.2.
第10.2节定义了EXER和RR的相对优先级。
A Capability is an individual behavior whose use is signaled in a Capabilities TLV, which is placed in Optional TLVs field inside the PSC message shown in Figure 2 of [RFC6378]. The format of the Capabilities TLV is:
能力是一种个人行为，其使用在能力TLV中发出信号，该TLV位于[RFC6378]图2所示PSC消息内的可选TLV字段中。能力TLV的格式为：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = Capabilities | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value = Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = Capabilities | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value = Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Format of Capabilities TLV
图1:TLV功能的格式
The value of the Type field is 1.
类型字段的值为1。
The value of the Length field is the length of the Flags field in octets. The length of the Flags field MUST be a multiple of 4 octets and MUST be the minimum required to signal all the required capabilities.
长度字段的值是标志字段的长度（以八位字节为单位）。标志字段的长度必须是4个八位字节的倍数，并且必须是发出所有所需功能信号所需的最小长度。
Section 4 to Section 8 discuss five capabilities that are signaled using the five most significant bits; if a node wishes to signal these five capabilities, it MUST send a Flags field of 4 octets. A node would send a Flags field greater than 4 octets only if it had more than 32 Capabilities to indicate. All unused bits MUST be set to zero.
第4节至第8节讨论了使用五个最高有效位发出信号的五种能力；如果节点希望向这五种功能发送信号，则必须发送4个八位字节的标志字段。只有当节点具有32个以上的指示功能时，才会发送大于4个八位字节的标志字段。所有未使用的位必须设置为零。
If the bit assigned for an individual capability is set to 1, it indicates the sending node's intent to use that capability in the protected domain. If a bit is set to 0, the sending node does not intend to use the indicated capability in the protected domain. Note that it is not possible to distinguish between the intent not to use a capability and a node's complete non-support (i.e., lack of implementation) of a given capability.
如果为单个功能分配的位设置为1，则表示发送节点打算在受保护域中使用该功能。如果位设置为0，则发送节点不打算在受保护域中使用指示的功能。请注意，无法区分不使用功能的意图和节点完全不支持（即缺乏实现）给定功能。
This document defines five specific capabilities that are described in Section 4 to Section 8. Each capability is assigned bit as follows:
本文件定义了第4节至第8节中描述的五种特定功能。每个能力的分配位如下所示：
0x80000000: priority modification
0x8000000:优先级修改
0x40000000: non-revertive behavior modification
0x40000000:非恢复性行为修改
0x20000000: support of MS-W command
0x20000000：支持MS-W命令
0x10000000: support of protection against SD
0x10000000:支持针对SD的保护
0x08000000: support of EXER command
0x08000000:支持EXER命令
If all the five capabilities should be used, a node SHALL set the Flags field to 0xF8000000.
如果应使用所有五种功能，则节点应将标志字段设置为0xF8000000。
A node MUST include its Capabilities TLV in every PSC message that it transmits. The transmission and acceptance of the PSC message is described in Section 4.1 of [RFC6378].
节点必须在其传输的每个PSC消息中包含其TLV功能。[RFC6378]第4.1节描述了PSC消息的传输和接受。
When a node receives a Capabilities TLV, it MUST compare the Flags value to its most recent Flags value transmitted by the node. If the two are equal, the protected domain is said to be running in the mode
当节点接收到功能TLV时，它必须将标志值与节点传输的最近标志值进行比较。如果两者相等，则表示受保护的域正在该模式下运行
indicated by that set of capabilities (see Section 9.2). If the sent and received Capabilities TLVs are not equal, this indicates a Capabilities TLV mismatch. When this happens, the node MUST alert the operator and MUST NOT perform any protection switching until the operator resolves the mismatch between the two end-points.
由该组功能指示（见第9.2节）。如果发送和接收的能力TLV不相等，则表示能力TLV不匹配。发生这种情况时，节点必须提醒操作员，并且在操作员解决两个端点之间的不匹配之前，不得执行任何保护切换。
A mode is a given set of Capabilities. Modes are shorthand; referring to a set of capabilities by their individual values or by the name of their mode does not change the protocol behavior. This document defines two modes -- PSC and APS. Capabilities TLVs with other combinations than the one specified by a mode are not supported in this specification.
模式是一组给定的功能。模式是速记；通过单独的值或模式名称引用一组功能不会改变协议行为。本文档定义了两种模式——PSC和APS。本规范不支持具有模式指定组合以外的其他组合的功能TLV。
PSC mode is defined as the lack of support for any of the additional capabilities defined in this document -- that is, a Capabilities set of 0x0. It is the behavior specified in [RFC6378].
PSC模式被定义为缺少对本文档中定义的任何附加功能的支持——即0x0的功能集。这是[RFC6378]中指定的行为。
There are two ways to declare PSC mode. A node can send no Capabilities TLV at all since there are no TLV units defined in [RFC6378], or it can send a Capabilities TLV with Flags value set to 0x0. In order to allow backward compatibility between two end-points -- one which supports sending the Capabilities TLV, and one which does not, the node that has the ability to send and process the PSC mode Capabilities TLV MUST be able to both send the PSC mode Capabilities TLV and send no Capabilities TLV at all. An implementation MUST be configurable between these two options.
有两种方法可以声明PSC模式。由于[RFC6378]中没有定义TLV单元，因此节点可以根本不发送功能TLV，也可以发送标志值设置为0x0的功能TLV。为了允许两个端点（一个支持发送能力TLV，另一个不支持发送能力TLV）之间的向后兼容性，能够发送和处理PSC模式能力TLV的节点必须能够发送PSC模式能力TLV，并且根本不发送能力TLV。必须在这两个选项之间配置实现。
APS mode is defined as the use of all the five specific capabilities, which are described in Sections 4 to 8 in this document. APS mode is indicated with the Flags value of 0xF8000000.
APS模式定义为使用本文件第4节至第8节中描述的所有五种特定功能。APS模式用标志值0xF8000000表示。
This section and the following section define the behavior of the PSC protocol when all of the aforementioned capabilities are enabled, i.e., APS mode.
本节和下一节定义了启用所有上述功能（即APS模式）时PSC协议的行为。
This document defines two new values for the "Request" field in the PSC protocol message that is shown in Figure 2 of [RFC6378] as follows:
本文件为[RFC6378]图2中显示的PSC协议消息中的“请求”字段定义了两个新值，如下所示：
(2) Reverse Request
(2) 反向请求
(3) Exercise
(3) 运动
See also Section 14.1 of this document.
另见本文件第14.1节。
Based on the description in Sections 3 and 4.3.2 in [RFC6378], the priorities of multiple outstanding local inputs are evaluated in the Local Request Logic, where the highest priority local input (highest local request) is determined. This highest local request is passed to the PSC Control Logic that will determine the higher-priority input (top-priority global request) between the highest local request and the last received remote message. When a remote message comes to the PSC Control Logic, the top-priority global request is determined between this remote message and the highest local request that is present. The top-priority global request is used to determine the state transition, which is described in Section 11. In this document, in order to simplify the description on the PSC Control Logic, we strictly decouple the priority evaluation from the state transition table lookup.
根据[RFC6378]第3节和第4.3.2节中的描述，在本地请求逻辑中评估多个未完成本地输入的优先级，其中确定最高优先级本地输入（最高本地请求）。该最高本地请求被传递到PSC控制逻辑，该逻辑将确定最高本地请求和最后接收到的远程消息之间的较高优先级输入（最高优先级全局请求）。当远程消息到达PSC控制逻辑时，在该远程消息和存在的最高本地请求之间确定最高优先级全局请求。最高优先级全局请求用于确定状态转换，如第11节所述。在本文中，为了简化对PSC控制逻辑的描述，我们将优先级评估与状态转换表查找严格解耦。
The priorities for both local and remote requests are defined as follows from highest to lowest:
本地和远程请求的优先级定义如下：
o Operator Clear (Local only)
o 操作员清除（仅限本地）
o Lockout of protection (Local and Remote)
o 保护锁定（本地和远程）
o Clear Signal Fail or Degrade (Local only)
o 清除信号失败或降级（仅限本地）
o Signal Fail on Protection path (Local and Remote)
o 保护路径上的信号故障（本地和远程）
o Forced Switch (Local and Remote)
o 强制开关（本地和远程）
o Signal Fail on Working path (Local and Remote)
o 工作路径上的信号故障（本地和远程）
o Signal Degrade on either Protection path or Working path (Local and Remote)
o 保护路径或工作路径上的信号降级（本地和远程）
o Manual Switch to either Protection path or Working path (Local and Remote)
o 手动切换到保护路径或工作路径（本地和远程）
o WTR Timer Expiry (Local only)
o WTR计时器到期（仅本地）
o WTR (Remote only)
o WTR（仅远程）
o Exercise (Local and Remote)
o 演习（本地和远程）
o Reverse Request (Remote only)
o 反向请求（仅远程）
o Do-Not-Revert (Remote only)
o 不还原（仅远程）
o No Request (Remote and Local)
o 无请求（远程和本地）
Note that the "Local only" requests are not transmitted to the remote node. Likewise, the "Remote only" requests do not exist in the Local Request Logic as local inputs. For example, the priority of WTR only applies to the received WTR message, which is generated from the remote node. The remote node that is running the WTR timer in the WTR state has no local request.
请注意，“仅本地”请求不会传输到远程节点。同样，“仅远程”请求在本地请求逻辑中不作为本地输入存在。例如，WTR的优先级仅适用于从远程节点生成的接收到的WTR消息。在WTR状态下运行WTR计时器的远程节点没有本地请求。
The remote SF and SD on either the working path or the protection path and the remote MS to either the working path or the protection path are indicated by the values of the Request and FPath fields in the PSC message.
工作路径或保护路径上的远程SF和SD以及工作路径或保护路径上的远程MS由PSC消息中请求和FPath字段的值指示。
The remote request from the remote node is assigned a priority just below the same local request except for NR and equal-priority requests, such as SD and MS. Since a received NR message needs to be used in the state transition table lookup when there is no outstanding local request, the remote NR request SHALL have a higher priority than the local NR. For the equal-priority requests, see Section 10.2.1.
来自远程节点的远程请求被分配的优先级略低于相同的本地请求，但NR和同等优先级请求除外，如SD和MS。因为在没有未完成的本地请求时，需要在状态转换表查找中使用收到的NR消息，远程NR请求的优先级应高于本地NR。对于同等优先级的请求，请参见第10.2.1节。
As stated in Section 10.2, the remote request from the remote node is assigned a priority just below the same local request. However, for equal-priority requests, such as SD and MS, the priority SHALL be evaluated as described in this section.
如第10.2节所述，来自远程节点的远程请求被分配的优先级略低于相同的本地请求。但是，对于同等优先级的请求，如SD和MS，应按照本节所述评估优先级。
For equal-priority local requests, the first-come, first-served rule SHALL be applied. Once a local request appears in the Local Request Logic, a subsequent equal-priority local request requesting a different action, i.e., the action results in the same Request value but a different FPath value, SHALL be considered to have a lower priority. Furthermore, in the case of an MS command, the subsequent local MS command requesting a different action SHALL be rejected and cleared.
对于同等优先级的本地请求，应采用先到先得原则。一旦本地请求出现在本地请求逻辑中，随后的同等优先级本地请求请求不同的操作，即该操作产生相同的请求值但不同的FPath值，应被视为具有较低的优先级。此外，在MS命令的情况下，应拒绝并清除请求不同操作的后续本地MS命令。
When the priority is evaluated in the PSC Control Logic between the highest local request and a remote request, the following equal-priority resolution rules SHALL be applied:
当在最高本地请求和远程请求之间的PSC控制逻辑中评估优先级时，应采用以下同等优先级解析规则：
o If two requests request the same action, i.e., the same Request and FPath values, then the local request SHALL be considered to have a higher priority than the remote request.
o 如果两个请求请求相同的操作，即相同的请求和FPath值，则本地请求的优先级应高于远程请求。
o When the highest local request comes to the PSC Control Logic, if the remote request that requests a different action exists, then the highest local request SHALL be ignored and the remote request SHALL remain to be the top-priority global request. In the case of an MS command, the local MS command requesting a different action SHALL be cancelled.
o 当最高本地请求到达PSC控制逻辑时，如果存在请求不同操作的远程请求，则应忽略最高本地请求，远程请求应保持为最高优先级全局请求。对于MS命令，应取消请求不同操作的本地MS命令。
o When the remote request comes to the PSC Control Logic, if the highest local request that requests a different action exists, then the top-priority global request SHALL be determined by the following rules:
o 当远程请求到达PSC控制逻辑时，如果存在请求不同操作的最高本地请求，则应根据以下规则确定最高优先级全局请求：
* For MS requests, the MS-W request SHALL be considered to have a higher priority than the MS-P request. The node that has the local MS-W request SHALL maintain the local MS-W request as the top-priority global request. The other node that has the local MS-P request SHALL cancel the MS-P command and SHALL generate "Operator Clear" internally as the top-priority global request.
* 对于MS请求，MS-W请求的优先级应高于MS-P请求。具有本地MS-W请求的节点应将本地MS-W请求保持为最高优先级全局请求。具有本地MS-P请求的其他节点应取消MS-P命令，并应在内部生成“操作员清除”作为最高优先级全局请求。
* For SD requests, the SD on the standby path (the path from which the selector does not select the user data traffic) SHALL be considered to have a higher priority than the SD on the active path (the path from which the selector selects the user data traffic) regardless of its origin (local or remote message). The node that has the SD on the standby path SHALL maintain the local SD on the standby path request as the top-priority global request. The other node that has local SD on the active path SHALL use the remote SD on the standby path as the top-priority global request to lookup the state transition
* 对于SD请求，备用路径（选择器不选择用户数据流量的路径）上的SD应被视为具有比活动路径（选择器选择用户数据流量的路径）上的SD更高的优先级，无论其来源（本地或远程消息）。在备用路径上具有SD的节点应将备用路径请求上的本地SD保持为最高优先级全局请求。在活动路径上具有本地SD的另一个节点应使用备用路径上的远程SD作为查找状态转换的最高优先级全局请求
table. The differentiation of the active and standby paths is based upon which path had been selected for the user data traffic when each node detected its local SD.
桌子主路径和备用路径的区别基于当每个节点检测到其本地SD时为用户数据流量选择的路径。
A local input indicating a defect, such as SF-P, SF-W, SD-P, and SD-W, SHALL be accepted and retained persistently in the Local Request Logic as long as the defect condition exists. If there is any higher-priority local input than the local defect input, the higher-priority local input is passed to the PSC Control Logic as the highest local request, but the local defect input cannot be removed but remains in the Local Request Logic. When the higher-priority local input is cleared, the local defect will become the highest local request if the defect condition still exists.
只要存在缺陷条件，指示缺陷的本地输入，如SF-P、SF-W、SD-P和SD-W，应被接受并持续保留在本地请求逻辑中。如果存在比本地缺陷输入更高优先级的本地输入，则将更高优先级的本地输入作为最高本地请求传递给PSC控制逻辑，但无法删除本地缺陷输入，而是保留在本地请求逻辑中。当清除更高优先级的本地输入时，如果缺陷条件仍然存在，则本地缺陷将成为最高的本地请求。
The Operator Clear (OC) command, SFDc, and WTR Timer Expiry are not persistent. Once they appear to the Local Request Logic and complete all the operations in the protection-switching control, they SHALL disappear.
操作员清除（OC）命令、SFDc和WTR计时器到期不是持久的。一旦它们出现在本地请求逻辑中并完成保护切换控制中的所有操作，它们将消失。
The LO, FS, MS, and EXER commands SHALL be rejected if there is any higher-priority local input in the Local Request Logic. If a new higher-priority local request (including an operator command) is accepted, any previous lower-priority local operator command SHALL be cancelled. When any higher-priority remote request is received, a lower-priority local operator command SHALL be cancelled. The cancelled operator command is cleared. If the operators wish to renew the cancelled command, then they should reissue the command.
如果本地请求逻辑中存在任何更高优先级的本地输入，则应拒绝LO、FS、MS和EXER命令。如果接受新的高优先级本地请求（包括操作员命令），则应取消先前的任何低优先级本地操作员命令。当收到任何较高优先级的远程请求时，应取消较低优先级的本地操作员命令。取消的操作员命令被清除。如果操作员希望更新已取消的命令，则应重新发出该命令。
When there is a change in the highest local request or in remote PSC messages, the top-priority global request SHALL be evaluated, and the state transition tables SHALL be looked up in the PSC Control Logic. The following rules are applied to the operation related to the state transition table lookup.
当最高本地请求或远程PSC消息发生变化时，应评估最高优先级全局请求，并在PSC控制逻辑中查找状态转换表。以下规则应用于与状态转换表查找相关的操作。
o If the top-priority global request, which determines the state transition, is the highest local request, the local state transition table in Section 11.1 SHALL be used to decide the next state of the node. Otherwise, the remote state transition table in Section 11.2 SHALL be used.
o 如果确定状态转换的最高优先级全局请求是最高本地请求，则应使用第11.1节中的本地状态转换表来确定节点的下一个状态。否则，应使用第11.2节中的远程状态转换表。
o If in remote state, the highest local defect condition (SF-P, SF-W, SD-P, or SD-W) SHALL always be reflected in the Request and FPath fields.
o 如果处于远程状态，最高局部缺陷条件（SF-P、SF-W、SD-P或SD-W）应始终反映在请求和FPath字段中。
o For the node currently in the local state, if the top-priority global request is changed to OC or SFDc, causing the next state to be Normal, WTR, or DNR, then all the local and remote requests SHALL be re-evaluated as if the node is in the state specified in the footnotes to the state transition tables, before deciding the final state. If there are no active requests, the node enters the state specified in the footnotes to the state transition tables. This re-evaluation is an internal operation confined within the local node, and the PSC messages are generated according to the final state.
o 对于当前处于本地状态的节点，如果最高优先级全局请求更改为OC或SFDc，导致下一个状态为Normal、WTR或DNR，则在决定最终状态之前，应重新评估所有本地和远程请求，就像节点处于状态转移表脚注中指定的状态一样。如果没有活动请求，则节点将进入状态转换表脚注中指定的状态。此重新评估是限制在本地节点内的内部操作，并且根据最终状态生成PSC消息。
o The WTR timer is started only when the node that has recovered from a local failure or degradation enters the WTR state. A node that is entering into the WTR state due to a remote WTR message does not start the WTR timer. The WTR timer SHALL be stopped when any local or remote request triggers the state change out of the WTR state.
o 仅当从本地故障或降级中恢复的节点进入WTR状态时，才会启动WTR计时器。由于远程WTR消息而进入WTR状态的节点不会启动WTR计时器。当任何本地或远程请求触发WTR状态变化时，WTR定时器应停止。
The extended states, as they appear in the table, are as follows:
表中显示的扩展状态如下所示：
N Normal state
UA:LO:L Unavailable state due to local LO command
UA:P:L Unavailable state due to local SF-P
UA:DP:L Unavailable state due to local SD-P
UA:LO:R Unavailable state due to remote LO message
UA:P:R Unavailable state due to remote SF-P message
UA:DP:R Unavailable state due to remote SD-P message
PF:W:L Protecting Failure state due to local SF-W
PF:DW:L Protecting Failure state due to local SD-W
PF:W:R Protecting Failure state due to remote SF-W message
PF:DW:R Protecting Failure state due to remote SD-W message
SA:F:L Switching Administrative state due to local FS command
SA:MW:L Switching Administrative state due to local MS-W command
SA:MP:L Switching Administrative state due to local MS-P command
SA:F:R Switching Administrative state due to remote FS message
SA:MW:R Switching Administrative state due to remote MS-W message
SA:MP:R Switching Administrative state due to remote MS-P message
WTR Wait-to-Restore state
DNR Do-not-Revert state
E::L Exercise state due to local EXER command
E::R Exercise state due to remote EXER message
N Normal state
UA:LO:L Unavailable state due to local LO command
UA:P:L Unavailable state due to local SF-P
UA:DP:L Unavailable state due to local SD-P
UA:LO:R Unavailable state due to remote LO message
UA:P:R Unavailable state due to remote SF-P message
UA:DP:R Unavailable state due to remote SD-P message
PF:W:L Protecting Failure state due to local SF-W
PF:DW:L Protecting Failure state due to local SD-W
PF:W:R Protecting Failure state due to remote SF-W message
PF:DW:R Protecting Failure state due to remote SD-W message
SA:F:L Switching Administrative state due to local FS command
SA:MW:L Switching Administrative state due to local MS-W command
SA:MP:L Switching Administrative state due to local MS-P command
SA:F:R Switching Administrative state due to remote FS message
SA:MW:R Switching Administrative state due to remote MS-W message
SA:MP:R Switching Administrative state due to remote MS-P message
WTR Wait-to-Restore state
DNR Do-not-Revert state
E::L Exercise state due to local EXER command
E::R Exercise state due to remote EXER message
Each state corresponds to the transmission of a particular set of Request, FPath, and Path fields. The table below lists the message that is generally sent in each particular state. If the message to be sent in a particular state deviates from the table below, it is noted in the footnotes of the state transition tables.
每个状态对应于一组特定的请求、FPath和Path字段的传输。下表列出了通常在每个特定状态下发送的消息。如果在特定状态下发送的信息与下表不同，则在状态转换表的脚注中注明。
State Request(FPath,Path)
------- ------------------------------------
N NR(0,0)
UA:LO:L LO(0,0)
UA:P:L SF(0,0)
UA:DP:L SD(0,0)
UA:LO:R highest local request(local FPath,0)
UA:P:R highest local request(local FPath,0)
UA:DP:R highest local request(local FPath,0)
PF:W:L SF(1,1)
PF:DW:L SD(1,1)
PF:W:R highest local request(local FPath,1)
PF:DW:R highest local request(local FPath,1)
SA:F:L FS(1,1)
SA:MW:L MS(0,0)
SA:MP:L MS(1,1)
SA:F:R highest local request(local FPath,1)
SA:MW:R NR(0,0)
SA:MP:R NR(0,1)
WTR WTR(0,1)
DNR DNR(0,1)
E::L EXER(0,x), where x is the existing Path value
when Exercise command is issued.
E::R RR(0,x), where x is the existing Path value
when RR message is generated.
State Request(FPath,Path)
------- ------------------------------------
N NR(0,0)
UA:LO:L LO(0,0)
UA:P:L SF(0,0)
UA:DP:L SD(0,0)
UA:LO:R highest local request(local FPath,0)
UA:P:R highest local request(local FPath,0)
UA:DP:R highest local request(local FPath,0)
PF:W:L SF(1,1)
PF:DW:L SD(1,1)
PF:W:R highest local request(local FPath,1)
PF:DW:R highest local request(local FPath,1)
SA:F:L FS(1,1)
SA:MW:L MS(0,0)
SA:MP:L MS(1,1)
SA:F:R highest local request(local FPath,1)
SA:MW:R NR(0,0)
SA:MP:R NR(0,1)
WTR WTR(0,1)
DNR DNR(0,1)
E::L EXER(0,x), where x is the existing Path value
when Exercise command is issued.
E::R RR(0,x), where x is the existing Path value
when RR message is generated.
Some operation examples of APS mode are shown in Appendix D.
附录D中给出了APS模式的一些操作示例。
In the state transition tables below, the letter 'i' stands for "ignore" and is an indication to remain in the current state and continue transmitting the current PSC message
在下面的状态转换表中，字母“i”代表“忽略”，表示保持当前状态并继续传输当前PSC消息
| OC | LO | SFDc | SF-P | FS | SF-W |
--------+-----+---------+------+--------+--------+--------+
N | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
UA:LO:L | (1) | i | i | i | i | i |
UA:P:L | i | UA:LO:L | (1) | i | i | i |
UA:DP:L | i | UA:LO:L | (1) | UA:P:L | SA:F:L | PF:W:L |
UA:LO:R | i | UA:LO:L | i | UA:P:L | i | PF:W:L |
UA:P:R | i | UA:LO:L | i | UA:P:L | i | PF:W:L |
UA:DP:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
PF:W:L | i | UA:LO:L | (2) | UA:P:L | SA:F:L | i |
PF:DW:L | i | UA:LO:L | (2) | UA:P:L | SA:F:L | PF:W:L |
PF:W:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
PF:DW:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:F:L | (3) | UA:LO:L | i | UA:P:L | i | i |
SA:MW:L | (1) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:MP:L | (3) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:F:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:MW:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:MP:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
WTR | (4) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
DNR | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
E::L | (5) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
E::R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
| OC | LO | SFDc | SF-P | FS | SF-W |
--------+-----+---------+------+--------+--------+--------+
N | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
UA:LO:L | (1) | i | i | i | i | i |
UA:P:L | i | UA:LO:L | (1) | i | i | i |
UA:DP:L | i | UA:LO:L | (1) | UA:P:L | SA:F:L | PF:W:L |
UA:LO:R | i | UA:LO:L | i | UA:P:L | i | PF:W:L |
UA:P:R | i | UA:LO:L | i | UA:P:L | i | PF:W:L |
UA:DP:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
PF:W:L | i | UA:LO:L | (2) | UA:P:L | SA:F:L | i |
PF:DW:L | i | UA:LO:L | (2) | UA:P:L | SA:F:L | PF:W:L |
PF:W:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
PF:DW:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:F:L | (3) | UA:LO:L | i | UA:P:L | i | i |
SA:MW:L | (1) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:MP:L | (3) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:F:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:MW:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:MP:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
WTR | (4) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
DNR | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
E::L | (5) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
E::R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
(Continued)
（续）
| SD-P | SD-W | MS-W | MS-P | WTRExp | EXER
--------+---------+---------+---------+---------+--------+------
N | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L
UA:LO:L | i | i | i | i | i | i
UA:P:L | i | i | i | i | i | i
UA:DP:L | i | i | i | i | i | i
UA:LO:R | UA:DP:L | PF:DW:L | i | i | i | i
UA:P:R | UA:DP:L | PF:DW:L | i | i | i | i
UA:DP:R | UA:DP:L | PF:DW:L | i | i | i | i
PF:W:L | i | i | i | i | i | i
PF:DW:L | i | i | i | i | i | i
PF:W:R | UA:DP:L | PF:DW:L | i | i | i | i
PF:DW:R | UA:DP:L | PF:DW:L | i | i | i | i
SA:F:L | i | i | i | i | i | i
SA:MW:L | UA:DP:L | PF:DW:L | i | i | i | i
SA:MP:L | UA:DP:L | PF:DW:L | i | i | i | i
SA:F:R | UA:DP:L | PF:DW:L | i | i | i | i
SA:MW:R | UA:DP:L | PF:DW:L | SA:MW:L | i | i | i
SA:MP:R | UA:DP:L | PF:DW:L | i | SA:MP:L | i | i
WTR | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | (6) | i
DNR | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L
E::L | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | i
E::R | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L
| SD-P | SD-W | MS-W | MS-P | WTRExp | EXER
--------+---------+---------+---------+---------+--------+------
N | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L
UA:LO:L | i | i | i | i | i | i
UA:P:L | i | i | i | i | i | i
UA:DP:L | i | i | i | i | i | i
UA:LO:R | UA:DP:L | PF:DW:L | i | i | i | i
UA:P:R | UA:DP:L | PF:DW:L | i | i | i | i
UA:DP:R | UA:DP:L | PF:DW:L | i | i | i | i
PF:W:L | i | i | i | i | i | i
PF:DW:L | i | i | i | i | i | i
PF:W:R | UA:DP:L | PF:DW:L | i | i | i | i
PF:DW:R | UA:DP:L | PF:DW:L | i | i | i | i
SA:F:L | i | i | i | i | i | i
SA:MW:L | UA:DP:L | PF:DW:L | i | i | i | i
SA:MP:L | UA:DP:L | PF:DW:L | i | i | i | i
SA:F:R | UA:DP:L | PF:DW:L | i | i | i | i
SA:MW:R | UA:DP:L | PF:DW:L | SA:MW:L | i | i | i
SA:MP:R | UA:DP:L | PF:DW:L | i | SA:MP:L | i | i
WTR | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | (6) | i
DNR | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L
E::L | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | i
E::R | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L
NOTES:
笔记：
(1) Re-evaluate to determine the final state as if the node is in the Normal state. If there are no active requests, the node enters the Normal State.
(1) 重新求值以确定最终状态，就像节点处于正常状态一样。如果没有活动请求，节点将进入正常状态。
(2) In the case that both local input after SFDc and the last received remote message are NR, the node enters into the WTR state when the domain is configured for revertive behavior, or the node enters into the DNR state when the domain is configured for non-revertive behavior. In all the other cases, where one or more active requests exist, re-evaluate to determine the final state as if the node is in the Normal state.
(2) 如果SFDc之后的本地输入和最后收到的远程消息均为NR，则当域配置为还原行为时，节点进入WTR状态，或者当域配置为非还原行为时，节点进入DNR状态。在存在一个或多个活动请求的所有其他情况下，重新计算以确定最终状态，就像节点处于正常状态一样。
(3) Re-evaluate to determine final state as if the node is in the Normal state when the domain is configured for revertive behavior, or as if the node is in the DNR state when the domain is configured for non-revertive behavior. If there are no active requests, the node enters either the Normal state when the domain is configured for revertive behavior or the DNR state when the domain is configured for non-revertive behavior.
(3) 重新求值以确定最终状态，就像当域配置为还原行为时节点处于正常状态，或者当域配置为非还原行为时节点处于DNR状态一样。如果没有活动请求，则当域配置为还原行为时，节点进入正常状态，或者当域配置为非还原行为时，节点进入DNR状态。
(4) Remain in the WTR state and send an NR(0,1) message. Stop the WTR timer if it is running. In APS mode, OC can cancel the WTR timer and hasten the state transition to the Normal state as in other transport networks.
(4) 保持WTR状态并发送NR（0,1）消息。如果WTR计时器正在运行，请停止该计时器。在APS模式下，OC可以取消WTR定时器，并加快状态转换到正常状态，就像在其他传输网络中一样。
(5) If Path value is 0, re-evaluate to determine final state as if the node is in the Normal state. If Path value is 1, re-evaluate to determine final state as if the node is in the DNR state. If there are no active requests, the node enters the Normal state when Path value is 0, or the DNR state when Path value is 1.
(5) 如果路径值为0，则重新计算以确定最终状态，就像节点处于正常状态一样。如果路径值为1，则重新计算以确定最终状态，就像节点处于DNR状态一样。如果没有活动请求，则当路径值为0时，节点进入正常状态，或当路径值为1时，节点进入DNR状态。
(6) Remain in the WTR state and send an NR(0,1) message.
(6) 保持WTR状态并发送NR（0,1）消息。
| LO | SF-P | FS | SF-W | SD-P | SD-W |
--------+---------+--------+--------+--------+---------+---------+
N | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
UA:LO:L | i | i | i | i | i | i |
UA:P:L | UA:LO:R | i | i | i | i | i |
UA:DP:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | i | (7) |
UA:LO:R | i | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
UA:P:R | UA:LO:R | i | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
UA:DP:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | i | PF:DW:R |
PF:W:L | UA:LO:R | UA:P:R | SA:F:R | i | i | i |
PF:DW:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | (8) | i |
PF:W:R | UA:LO:R | UA:P:R | SA:F:R | i | UA:DP:R | PF:DW:R |
PF:DW:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | i |
SA:F:L | UA:LO:R | UA:P:R | i | i | i | i |
SA:MW:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
SA:MP:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
SA:F:R | UA:LO:R | UA:P:R | i | PF:W:R | UA:DP:R | PF:DW:R |
SA:MW:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
SA:MP:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
WTR | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
DNR | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
E::L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
E::R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
| LO | SF-P | FS | SF-W | SD-P | SD-W |
--------+---------+--------+--------+--------+---------+---------+
N | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
UA:LO:L | i | i | i | i | i | i |
UA:P:L | UA:LO:R | i | i | i | i | i |
UA:DP:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | i | (7) |
UA:LO:R | i | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
UA:P:R | UA:LO:R | i | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
UA:DP:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | i | PF:DW:R |
PF:W:L | UA:LO:R | UA:P:R | SA:F:R | i | i | i |
PF:DW:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | (8) | i |
PF:W:R | UA:LO:R | UA:P:R | SA:F:R | i | UA:DP:R | PF:DW:R |
PF:DW:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | i |
SA:F:L | UA:LO:R | UA:P:R | i | i | i | i |
SA:MW:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
SA:MP:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
SA:F:R | UA:LO:R | UA:P:R | i | PF:W:R | UA:DP:R | PF:DW:R |
SA:MW:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
SA:MP:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
WTR | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
DNR | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
E::L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
E::R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
(Continued)
（续）
| MS-W | MS-P | WTR | EXER | RR | DNR | NR
--------+---------+---------+-----+------+----+------+----
N | SA:MW:R | SA:MP:R | i | E::R | i | i | i
UA:LO:L | i | i | i | i | i | i | i
UA:P:L | i | i | i | i | i | i | i
UA:DP:L | i | i | i | i | i | i | i
UA:LO:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N
UA:P:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N
UA:DP:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N
PF:W:L | i | i | i | i | i | i | i
PF:DW:L | i | i | i | i | i | i | i
PF:W:R | SA:MW:R | SA:MP:R | (9) | E::R | i | (10) | (11)
PF:DW:R | SA:MW:R | SA:MP:R | (9) | E::R | i | (10) | (11)
SA:F:L | i | i | i | i | i | i | i
SA:MW:L | i | i | i | i | i | i | i
SA:MP:L | i | i | i | i | i | i | i
SA:F:R | SA:MW:R | SA:MP:R | i | E::R | i | DNR | N
SA:MW:R | i | SA:MP:R | i | E::R | i | i | N
SA:MP:R | SA:MW:R | i | i | E::R | i | DNR | N
WTR | SA:MW:R | SA:MP:R | i | i | i | i | (12)
DNR | SA:MW:R | SA:MP:R | (13)| E::R | i | i | i
E::L | SA:MW:R | SA:MP:R | i | i | i | i | i
E::R | SA:MW:R | SA:MP:R | i | i | i | DNR | N
| MS-W | MS-P | WTR | EXER | RR | DNR | NR
--------+---------+---------+-----+------+----+------+----
N | SA:MW:R | SA:MP:R | i | E::R | i | i | i
UA:LO:L | i | i | i | i | i | i | i
UA:P:L | i | i | i | i | i | i | i
UA:DP:L | i | i | i | i | i | i | i
UA:LO:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N
UA:P:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N
UA:DP:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N
PF:W:L | i | i | i | i | i | i | i
PF:DW:L | i | i | i | i | i | i | i
PF:W:R | SA:MW:R | SA:MP:R | (9) | E::R | i | (10) | (11)
PF:DW:R | SA:MW:R | SA:MP:R | (9) | E::R | i | (10) | (11)
SA:F:L | i | i | i | i | i | i | i
SA:MW:L | i | i | i | i | i | i | i
SA:MP:L | i | i | i | i | i | i | i
SA:F:R | SA:MW:R | SA:MP:R | i | E::R | i | DNR | N
SA:MW:R | i | SA:MP:R | i | E::R | i | i | N
SA:MP:R | SA:MW:R | i | i | E::R | i | DNR | N
WTR | SA:MW:R | SA:MP:R | i | i | i | i | (12)
DNR | SA:MW:R | SA:MP:R | (13)| E::R | i | i | i
E::L | SA:MW:R | SA:MP:R | i | i | i | i | i
E::R | SA:MW:R | SA:MP:R | i | i | i | DNR | N
NOTES:
笔记：
(7) If the received SD-W message has Path=0, ignore the message. If the received SD-W message has Path=1, go to the PF:DW:R state and transmit an SD(0,1) message.
(7) 如果收到的SD-W消息路径为0，则忽略该消息。如果收到的SD-W消息路径=1，则转到PF:DW:R状态并发送SD（0,1）消息。
(8) If the received SD-P message has Path=1, ignore the message. If the received SD-P message has Path=0, go to the UA:DP:R state and transmit an SD(1,0) message.
(8) 如果收到的SD-P消息路径为1，则忽略该消息。如果收到的SD-P消息路径=0，则转到UA:DP:R状态并发送SD（1,0）消息。
(9) Transition to the WTR state and continue to send the current message.
(9) 转换到WTR状态并继续发送当前消息。
(10) Transition to the DNR state and continue to send the current message.
（10） 转换到DNR状态并继续发送当前消息。
(11) If the received NR message has Path=1, transition to the WTR state if the domain is configured for revertive behavior, else transition to the DNR state. If the received NR message has Path=0, transition to the Normal state.
（11） 如果收到的NR消息的Path=1，如果域配置为还原行为，则转换为WTR状态，否则转换为DNR状态。如果收到的NR消息路径为0，则转换到正常状态。
(12) If the receiving node's WTR timer is running, maintain the current state and message. If the WTR timer is not running, transition to the Normal state.
（12） 如果接收节点的WTR计时器正在运行，请保持当前状态和消息。如果WTR计时器未运行，则转换到正常状态。
(13) Transit to the WTR state and send an NR(0,1) message. The WTR timer is not initiated.
（13） 传输到WTR状态并发送NR（0,1）消息。WTR定时器未启动。
The state transition tables given in Sections 11.1 and 11.2 are for bidirectional protection switching, where remote PSC protocol messages are used to determine the protection-switching actions. 1+1 unidirectional protection switching does not require the remote information in the PSC protocol message and acts upon local inputs only. The state transition by local inputs in Section 11.1 SHALL be reused for 1+1 unidirectional protection under the following conditions:
第11.1节和第11.2节中给出的状态转换表用于双向保护切换，其中远程PSC协议消息用于确定保护切换动作。1+1单向保护切换不需要PSC协议消息中的远程信息，仅作用于本地输入。第11.1节中本地输入的状态转换应在以下条件下重新用于1+1单向保护：
o The value of Request field in the received remote message is ignored and always assumed to be no request.
o 接收到的远程消息中请求字段的值将被忽略，并始终假定为无请求。
o Replace footnote (4) with "Stop the WTR timer and transit to the Normal state."
o 将脚注（4）替换为“停止WTR定时器并过渡到正常状态。”
o Replace footnote (6) with "Transit to the Normal state."
o 将脚注（6）替换为“过渡到正常状态”
o Exercise command is not relevant.
o 演习指挥不相关。
The remote PSC message that is received from the remote node is subject to the detection of provisioning mismatch and protocol failure conditions. In APS mode, provisioning mismatches are handled as follows:
从远程节点接收的远程PSC消息会受到配置不匹配和协议故障条件的检测。在APS模式下，配置不匹配的处理如下：
o If the PSC message is received from the working path due to working/protection path configuration mismatch, the node MUST alert the operator and MUST NOT perform any protection switching until the operator resolves this path configuration mismatch.
o 如果由于工作/保护路径配置不匹配而从工作路径收到PSC消息，则节点必须提醒操作员，并且在操作员解决此路径配置不匹配之前，不得执行任何保护切换。
o In the case that the mismatch happens in the two-bit "Protection Type (PT)" field, which indicates permanent/selector bridge type and uni/bidirectional switching type:
o 如果不匹配发生在两位“保护类型（PT）”字段中，该字段表示永久/选择器电桥类型和单向/双向开关类型：
* If the value of the PT field of one side is 2 (i.e., selector bridge) and that of the other side is 1 or 3 (i.e., permanent bridge), then this event MUST be notified to the operator and each node MUST NOT perform any protection switching until the operator resolves this bridge type mismatch.
* 如果一侧的PT字段值为2（即选择器电桥），另一侧的PT字段值为1或3（即永久电桥），则必须将此事件通知操作员，并且在操作员解决此电桥类型不匹配之前，每个节点不得执行任何保护切换。
* If the bridge type matches but the switching type mismatches, i.e., one side has PT=1 (unidirectional switching) while the other side has PT=2 or 3 (bidirectional switching), then the node provisioned for bidirectional switching SHOULD fall back to unidirectional switching to allow interworking. The node SHOULD notify the operator of this event.
* 如果网桥类型匹配，但交换类型不匹配，即一侧具有PT=1（单向交换），而另一侧具有PT=2或3（双向交换），则为双向交换配置的节点应返回到单向交换以允许互通。节点应将此事件通知操作员。
o If the "Revertive (R)" bit mismatches, two sides will interwork and traffic is protected according to the state transition definition given in Section 11. The node SHOULD notify the operator of this event.
o 如果“回复（R）”位不匹配，则双方将互通，并根据第11节给出的状态转换定义保护通信量。节点应将此事件通知操作员。
o If the Capabilities TLV mismatches, the node MUST alert the operator and MUST NOT perform any protection switching until the operator resolves the mismatch in the Capabilities TLV.
o 如果功能TLV不匹配，则节点必须提醒操作员，并且在操作员解决功能TLV中的不匹配之前，不得执行任何保护切换。
The following are the protocol failure situations and the actions to be taken:
以下是协议故障情况和要采取的措施：
o No match in sent "Data Path (Path)" and received "Data Path (Path)" for more than 50 ms: The node MAY continue to perform protection switching and SHOULD notify the operator of this event.
o 发送的“数据路径（Path）”与接收的“数据路径（Path）”不匹配的时间超过50毫秒：节点可能会继续执行保护切换，并应将此事件通知操作员。
o No PSC message is received on the protection path during at least 3.5 times the long PSC message interval (e.g., at least 17.5 seconds with a default message interval of 5 seconds), and there is no defect on the protection path: The node MUST alert the operator and MUST NOT perform any protection switching until the operator resolves this defect.
o 在长PSC消息间隔的至少3.5倍期间（例如，至少17.5秒，默认消息间隔为5秒），保护路径上没有收到PSC消息，并且保护路径上没有缺陷：节点必须向操作员发出警报，并且在操作员解决此缺陷之前，不得执行任何保护切换。
This document introduces no new security risks. [RFC6378] points out that MPLS relies on assumptions about the difficulty of traffic injection and assumes that the control plane does not have end-to-end security. [RFC5920] describes MPLS security issues and generic methods for securing traffic privacy and integrity. MPLS use should conform to such advice.
本文档没有引入新的安全风险。[RFC6378]指出MPLS依赖于关于流量注入难度的假设，并假设控制平面没有端到端安全性。[RFC5920]描述了MPLS安全问题以及保护流量隐私和完整性的一般方法。MPLS的使用应符合此类建议。
In the "Generic Associated Channel (G-ACh) Parameters" registry, IANA maintains the "MPLS PSC Request Registry".
在“通用关联通道（G-ACh）参数”注册表中，IANA维护“MPLS PSC请求注册表”。
IANA has assigned the following two new code points from this registry.
IANA已从此注册表中分配了以下两个新代码点。
Value Description Reference
----- --------------------- ---------------
2 Reverse Request (this document)
3 Exercise (this document)
Value Description Reference
----- --------------------- ---------------
2 Reverse Request (this document)
3 Exercise (this document)
In the "Generic Associated Channel (G-ACh) Parameters" registry, IANA maintains the "MPLS PSC TLV Registry".
在“通用关联通道（G-ACh）参数”注册表中，IANA维护“MPLS PSC TLV注册表”。
This document defines the following new value for the Capabilities TLV type in the "MPLS PSC TLV Registry".
本文档为“MPLS PSC TLV注册表”中的功能TLV类型定义了以下新值。
Value Description Reference
------ --------------------- ---------------
1 Capabilities (this document)
Value Description Reference
------ --------------------- ---------------
1 Capabilities (this document)
IANA has created and now maintains a new registry within the "Generic Associated Channel (G-ACh) Parameters" registry called "MPLS PSC Capability Flag Registry". All flags within this registry SHALL be allocated according to the "Standards Action" procedures as specified in RFC 5226 [RFC5226].
IANA已经在“通用关联通道（G-ACh）参数”注册表中创建并维护了一个名为“MPLS PSC能力标志注册表”的新注册表。应根据RFC 5226[RFC5226]中规定的“标准行动”程序分配此注册表中的所有标志。
The length of each flag MUST be a multiple of 4 octets. This document defines 4-octet flags. Flags greater than 4 octets SHALL be used only if more than 32 Capabilities need to be defined. The flags defined in this document are:
每个标志的长度必须是4个八位字节的倍数。本文档定义了4个八位字节标志。仅当需要定义超过32个功能时，才应使用大于4个八位字节的标志。本文件中定义的标志为：
Bit Hex Value Capability Reference
---- ---------- ----------------------------------- ---------------
0 0x80000000 priority modification (this document)
1 0x40000000 non-revertive behavior modification (this document)
2 0x20000000 support of MS-W command (this document)
3 0x10000000 support of protection against SD (this document)
4 0x08000000 support of EXER command (this document)
5-31 Unassigned (this document)
Bit Hex Value Capability Reference
---- ---------- ----------------------------------- ---------------
0 0x80000000 priority modification (this document)
1 0x40000000 non-revertive behavior modification (this document)
2 0x20000000 support of MS-W command (this document)
3 0x10000000 support of protection against SD (this document)
4 0x08000000 support of EXER command (this document)
5-31 Unassigned (this document)
The authors would like to thank Yaacov Weingarten, Yuji Tochio, Malcolm Betts, Ross Callon, Qin Wu, and Xian Zhang for their valuable comments and suggestions on this document.
作者感谢Yaacov Weingarten、Yuji Tochio、Malcolm Betts、Ross Callon、秦武和Xian Zhang对本文件提出的宝贵意见和建议。
We would also like to acknowledge explicit text provided by Loa Andersson and Adrian Farrel.
我们还要感谢Loa Andersson和Adrian Farrel提供的明确文本。
[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。
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
[RFC5226]Narten，T.和H.Alvestrand，“在RFCs中编写IANA注意事项部分的指南”，BCP 26，RFC 5226，2008年5月。
[RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and S. Ueno, "Requirements of an MPLS Transport Profile", RFC 5654, September 2009.
[RFC5654]Niven Jenkins，B.，Brungard，D.，Betts，M.，Sprecher，N.，和S.Ueno，“MPLS传输配置文件的要求”，RFC 56542009年9月。
[RFC6378] Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N., and A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear Protection", RFC 6378, October 2011.
[RFC6378]Y.Weingarten、S.Bryant、E.Osborne、N.Sprecher和A.Fulignoli，“MPLS传输模式（MPLS-TP）线性保护”，RFC 6378，2011年10月。
[G8031] International Telecommunication Union, "Ethernet Linear Protection Switching", ITU-T Recommendation G.8031/Y.1342, June 2011.
[G8031]国际电信联盟，“以太网线性保护交换”，ITU-T建议G.8031/Y.1342，2011年6月。
[G841] International Telecommunication Union, "Types and characteristics of SDH network protection architectures", ITU-T Recommendation G.841, October 1998.
[G841]国际电信联盟，“SDH网络保护体系结构的类型和特征”，ITU-T建议G.841，1998年10月。
[G873.1] International Telecommunication Union, "Optical Transport Network (OTN): Linear protection", ITU-T Recommendation G.873.1, July 2011.
[G873.1]国际电信联盟，“光传输网络（OTN）：线性保护”，ITU-T建议G.873.11911年7月。
[RFC4427] Mannie, E. and D. Papadimitriou, "Recovery (Protection and Restoration) Terminology for Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4427, March 2006.
[RFC4427]Mannie，E.和D.Papadimitriou，“通用多协议标签交换（GMPLS）的恢复（保护和恢复）术语”，RFC 4427，2006年3月。
[RFC5920] Fang, L., "Security Framework for MPLS and GMPLS Networks", RFC 5920, July 2010.
[RFC5920]方，L，“MPLS和GMPLS网络的安全框架”，RFC 5920，2010年7月。
[RFC6372] Sprecher, N. and A. Farrel, "MPLS Transport Profile (MPLS-TP) Survivability Framework", RFC 6372, September 2011.
[RFC6372]Sprecher，N.和A.Farrel，“MPLS传输配置文件（MPLS-TP）生存能力框架”，RFC 63722011年9月。
The sequence diagram shown is an example of the out-of-service scenarios based on the priority level defined in [RFC6378]. The first PSC message that differs from the previous PSC message is shown.
所示的序列图是基于[RFC6378]中定义的优先级的停用场景示例。显示与前一条PSC消息不同的第一条PSC消息。
A Z
| |
(1) |-- NR(0,0) ------>| (1)
|<----- NR(0,0) ---|
| |
| |
| (FS issued at Z) | (2)
(3) |<------ FS(1,1) --|
|-- NR(0,1) ------>|
| |
| |
(4) | (SF on P(A<-Z)) |
| |
| |
| (Clear FS at Z) | (5)
(6) | X <- NR(0,0) --|
| |
| |
A Z
| |
(1) |-- NR(0,0) ------>| (1)
|<----- NR(0,0) ---|
| |
| |
| (FS issued at Z) | (2)
(3) |<------ FS(1,1) --|
|-- NR(0,1) ------>|
| |
| |
(4) | (SF on P(A<-Z)) |
| |
| |
| (Clear FS at Z) | (5)
(6) | X <- NR(0,0) --|
| |
| |
(1) Each end is in the Normal state and transmits NR(0,0) messages.
(1) 每一端处于正常状态，并传输NR（0,0）消息。
(2) When a FS command is issued at node Z, node Z goes into local Protecting Administrative state (PA:F:L) and begins transmission of an FS(1,1) message.
(2) 当在节点Z发出FS命令时，节点Z进入本地保护管理状态（PA:F:L），并开始传输FS（1,1）消息。
(3) A remote FS message causes node A to go into remote Protecting Administrative state (PA:F:R), and node A begins transmitting NR(0,1) messages.
(3) 远程FS消息使节点A进入远程保护管理状态（PA:F:R），节点A开始传输NR（0,1）消息。
(4) When node A detects a unidirectional SF-P, node A keeps sending an NR(0,1) message because SF-P is ignored under the PA:F:R state.
(4) 当节点A检测到单向SF-P时，节点A继续发送NR（0,1）消息，因为在PA:F:R状态下SF-P被忽略。
(5) When a Clear command is issued at node Z, node Z goes into the Normal state and begins transmission of NR(0,0) messages.
(5) 当在节点Z发出清除命令时，节点Z进入正常状态并开始传输NR（0,0）消息。
(6) But, node A cannot receive PSC message because of local unidirectional SF-P. Because no valid PSC message is received over a period of several successive message intervals, the last valid received message remains applicable, and the node A continue to transmit an NR(0,1) message in the PA:F:R state.
(6) 但是，由于本地单向SF-P，节点A无法接收PSC消息。因为在几个连续的消息间隔期间没有接收到有效的PSC消息，最后一个有效接收的消息仍然适用，并且节点A继续在PA:F:R状态下发送NR（0,1）消息。
Now, there exists a mismatch between the selector and bridge positions of node A (transmitting an NR(0,1) message) and node Z (transmitting an NR(0,0) message). It results in an out-of-service situation even when there is neither SF-W nor FS.
现在，节点a（发送NR（0,1）消息）和节点Z（发送NR（0,0）消息）的选择器和桥接器位置之间存在不匹配。即使没有SF-W或FS，也会导致停止使用。
Appendix B. An Example of a Sequence Diagram Showing the Problem with the Priority Level of SFc
附录B.显示SFc优先级问题的序列图示例
An example of a sequence diagram showing the problem with the priority level of SFc defined in [RFC6378] is given below. The following sequence diagram depicts the case when the bidirectional signal fails. However, other cases with unidirectional signal fails can result in the same problem. The first PSC message that differs from the previous PSC message is shown.
下面给出了显示[RFC6378]中定义的SFc优先级问题的序列图示例。以下序列图描述了双向信号故障的情况。然而，其他单向信号失效的情况也会导致同样的问题。显示与前一条PSC消息不同的第一条PSC消息。
A Z
| |
(1) |-- NR(0,0) ------>| (1)
|<----- NR(0,0) ---|
| |
| |
(2) | (SF on P(A<->Z)) | (2)
|-- SF(0,0) ------>|
|<------ SF(0,0) --|
| |
| |
(3) | (SF on W(A<->Z)) | (3)
| |
| |
(4) | (Clear SF-P) | (4)
| |
| |
(5) | (Clear SF-W) | (5)
| |
| |
A Z
| |
(1) |-- NR(0,0) ------>| (1)
|<----- NR(0,0) ---|
| |
| |
(2) | (SF on P(A<->Z)) | (2)
|-- SF(0,0) ------>|
|<------ SF(0,0) --|
| |
| |
(3) | (SF on W(A<->Z)) | (3)
| |
| |
(4) | (Clear SF-P) | (4)
| |
| |
(5) | (Clear SF-W) | (5)
| |
| |
(1) Each end is in the Normal state and transmits NR(0,0) messages.
(1) 每一端处于正常状态，并传输NR（0,0）消息。
(2) When SF-P occurs, each node enters into the UA:P:L state and transmits SF(0,0) messages. Traffic remains on the working path.
(2) 当SF-P发生时，每个节点进入UA:P:L状态并传输SF（0,0）消息。工作道路上仍有车辆通行。
(3) When SF-W occurs, each node remains in the UA:P:L state as SF-W has a lower priority than SF-P. Traffic is still on the working path. Traffic cannot be delivered, as both the working path and the protection path are experiencing signal fails.
(3) 当SF-W发生时，每个节点保持UA:P:L状态，因为SF-W的优先级低于SF-P。流量仍在工作路径上。无法传输通信量，因为工作路径和保护路径都遇到信号故障。
(4) When SF-P is cleared, the local "Clear SF-P" request cannot be presented to the PSC Control Logic, which takes the highest local request and runs the PSC state machine, since the priority of "Clear SF-P" is lower than that of SF-W. Consequently, there is no change in state, and the selector and/or bridge keep pointing at the working path, which has SF condition.
(4) 当清除SF-P时，本地“清除SF-P”请求无法提交给PSC控制逻辑，PSC控制逻辑接受最高的本地请求并运行PSC状态机，因为“清除SF-P”的优先级低于SF-W。因此，状态没有变化，选择器和/或桥接器始终指向工作路径，有SF状态。
Now, traffic cannot be delivered while the protection path is recovered and available. It should be noted that the same problem will occur in the case that the sequence of SF-P and SF-W events is changed.
现在，当保护路径恢复并可用时，无法传输流量。需要注意的是，如果SF-P和SF-W事件的顺序发生变化，同样的问题也会发生。
If we further continue with this sequence to see what will happen after SF-W is cleared:
如果我们继续此顺序，以了解SF-W清除后会发生什么：
(5) When SF-W is cleared, the local "Clear SF-W" request can be passed to the PSC Control Logic, as there is no higher-priority local input, but it will be ignored in the PSC Control Logic according to the state transition definition in [RFC6378]. There will be no change in state or protocol message transmitted.
(5) 当SF-W被清除时，本地“清除SF-W”请求可以传递给PSC控制逻辑，因为没有更高优先级的本地输入，但根据[RFC6378]中的状态转换定义，它将在PSC控制逻辑中被忽略。传输的状态或协议消息不会发生变化。
As SF-W is now cleared and the selector and/or bridge are still pointing at the working path, traffic delivery is resumed. However, each node is in the UA:P:L state and transmitting SF(0,0) messages, while there exists no outstanding request for protection switching. Moreover, any future legitimate protection-switching requests, such as SF-W, will be rejected as each node thinks the protection path is unavailable.
由于SF-W现在已清除，且选择器和/或桥接器仍指向工作路径，交通传输将恢复。然而，每个节点都处于UA:P:L状态并传输SF（0,0）消息，而不存在未完成的保护切换请求。此外，任何未来合法的保护切换请求（如SF-W）都将被拒绝，因为每个节点都认为保护路径不可用。
The "Freeze" command applies only to the local node of the protection group and is not signaled to the remote node. This command freezes the state of the protection group. Until the Freeze is cleared, additional local commands are rejected, and condition changes and received PSC information are ignored.
“冻结”命令仅适用于保护组的本地节点，不向远程节点发送信号。此命令冻结保护组的状态。在清除冻结之前，其他本地命令将被拒绝，条件更改和接收到的PSC信息将被忽略。
The "Clear Freeze" command clears the local freeze. When the Freeze command is cleared, the state of the protection group is recomputed based on the persistent condition of the local triggers.
“清除冻结”命令清除本地冻结。清除冻结命令后，将根据本地触发器的持续状态重新计算保护组的状态。
Because the freeze is local, if the freeze is issued at one end only, a failure of protocol can occur as the other end is open to accept any operator command or a fault condition.
由于冻结是本地的，如果仅在一端发出冻结，则当另一端打开以接受任何操作员命令或故障条件时，可能会发生协议故障。
The sequence diagrams shown in this section are only a few examples of the APS mode operations. The first PSC protocol message that differs from the previous message is shown. The operation of the hold-off timer is omitted. The Request, FPath, and Path fields whose values are changed during PSC message exchange are shown. For an example, SF(1,0) represents a PSC message with the following field values: Request=SF, FPath=1, and Path=0. The values of the other fields remain unchanged from the initial configuration. W(A->Z) and P(A->Z) indicate the working path and the protection path in the direction of A to Z, respectively.
本节所示的序列图只是APS模式操作的几个示例。显示与前一条消息不同的第一条PSC协议消息。暂停计时器的操作被省略。将显示在PSC消息交换期间其值发生更改的请求、FPath和Path字段。例如，SF（1,0）表示具有以下字段值的PSC消息：Request=SF、FPath=1和Path=0。与初始配置相比，其他字段的值保持不变。W（A->Z）和P（A->Z）分别表示A到Z方向的工作路径和保护路径。
Example 1. 1:1 bidirectional protection switching (revertive operation) - Unidirectional SF case
例1。1:1双向保护切换（反向操作）-单向SF外壳
A Z
| |
(1) |<---- NR(0,0)---->| (1)
| |
| |
(2) | (SF on W(Z->A)) |
|---- SF(1,1)----->| (3)
(4) |<----- NR(0,1)----|
| |
| |
(5) | (Clear SF-W) |
|---- WTR(0,1)---->|
/| |
| | |
WTR timer | |
| | |
\| |
(6) |---- NR(0,1)----->| (7)
(8) |<----- NR(0,0)----|
|---- NR(0,0)----->| (9)
| |
A Z
| |
(1) |<---- NR(0,0)---->| (1)
| |
| |
(2) | (SF on W(Z->A)) |
|---- SF(1,1)----->| (3)
(4) |<----- NR(0,1)----|
| |
| |
(5) | (Clear SF-W) |
|---- WTR(0,1)---->|
/| |
| | |
WTR timer | |
| | |
\| |
(6) |---- NR(0,1)----->| (7)
(8) |<----- NR(0,0)----|
|---- NR(0,0)----->| (9)
| |
(1) The protected domain is operating without any defect, and the working path is used for delivering the traffic in the Normal state.
(1) 受保护域运行时没有任何缺陷，工作路径用于在正常状态下传输流量。
(2) SF-W occurs in the Z to A direction. Node A enters into the PF:W:L state and generates an SF(1,1) message. Both the selector and bridge of node A are pointing at the protection path.
(2) SF-W发生在Z向A方向。节点A进入PF:W:L状态并生成SF（1,1）消息。节点A的选择器和桥接器都指向保护路径。
(3) Upon receiving an SF(1,1) message, node Z sets both the selector and bridge to the protection path. As there is no local request in node Z, node Z generates an NR(0,1) message in the PF:W:R state.
(3) 在接收到SF（1,1）消息后，节点Z将选择器和桥接器设置为保护路径。由于节点Z中没有本地请求，因此节点Z在PF:W:R状态下生成NR（0,1）消息。
(4) Node A confirms that the remote node is also selecting the protection path.
(4) 节点A确认远程节点也在选择保护路径。
(5) Node A detects clearing of SF condition, starts the WTR timer, and sends a WTR(0,1) message in the WTR state.
(5) 节点A检测到SF条件的清除，启动WTR定时器，并在WTR状态下发送WTR（0,1）消息。
(6) Upon expiration of the WTR timer, node A sets both the selector and bridge to the working path and sends an NR(0,1) message.
(6) WTR计时器到期时，节点A将选择器和桥接器设置为工作路径，并发送NR（0,1）消息。
(7) Node Z is notified that the remote request has been cleared. Node Z transits to the Normal state and sends an NR(0,0) message.
(7) 通知节点Z远程请求已被清除。节点Z转换到正常状态并发送NR（0,0）消息。
(8) Upon receiving an NR(0,0) message, node A transits to the Normal state and sends an NR(0,0) message.
(8) 在接收到NR（0,0）消息后，节点A转换到正常状态并发送NR（0,0）消息。
(9) It is confirmed that the remote node is also selecting the working path.
(9) 确认远程节点也在选择工作路径。
Example 2. 1:1 bidirectional protection switching (revertive operation) - Bidirectional SF case - Inconsistent WTR timers
例2。1:1双向保护切换（回复操作）-双向SF情况-WTR定时器不一致
A Z
| |
(1) |<---- NR(0,0)---->| (1)
| |
| |
(2) | (SF on W(A<->Z)) | (2)
|<---- SF(1,1)---->|
| |
| |
(3) | (Clear SF-W) | (3)
|<---- NR(0,1)---->|
(4) |<--- WTR(0,1) --->| (4)
/| |\
| | | |
WTR timer | | WTR timer
| | | |
| | |/
| |<------ NR(0,1)---| (5)
| | |
\| |
(6) |--- NR(0,1)------>|
|<------ NR(0,0)---| (7)
(8) |--- NR(0,0)------>|
| |
A Z
| |
(1) |<---- NR(0,0)---->| (1)
| |
| |
(2) | (SF on W(A<->Z)) | (2)
|<---- SF(1,1)---->|
| |
| |
(3) | (Clear SF-W) | (3)
|<---- NR(0,1)---->|
(4) |<--- WTR(0,1) --->| (4)
/| |\
| | | |
WTR timer | | WTR timer
| | | |
| | |/
| |<------ NR(0,1)---| (5)
| | |
\| |
(6) |--- NR(0,1)------>|
|<------ NR(0,0)---| (7)
(8) |--- NR(0,0)------>|
| |
(1) Each end is in the Normal state and transmits NR(0,0) messages.
(1) 每一端处于正常状态，并传输NR（0,0）消息。
(2) When SF-W occurs, each node enters into the PF:W:L state and transmits SF(1,1) messages. Traffic is switched to the protection path. Upon receiving an SF(1,1) message, each node confirms that the remote node is also sending and receiving the traffic from the protection path.
(2) 当SF-W发生时，每个节点进入PF:W:L状态并传输SF（1,1）消息。通信量切换到保护路径。在接收到SF（1,1）消息后，每个节点确认远程节点也在发送和接收来自保护路径的流量。
(3) When SF-W is cleared, each node transits to the PF:W:R state and transmits NR(0,1) messages as the last received message is SF-W.
(3) 当清除SF-W时，每个节点转换到PF:W:R状态，并发送NR（0,1）条消息，因为最后接收的消息是SF-W。
(4) Upon receiving NR(0,1) messages, each node goes into the WTR state, starts the WTR timer, and sends the WTR(0,1) messages.
(4) 在接收到NR（0,1）消息后，每个节点进入WTR状态，启动WTR定时器，并发送WTR（0,1）消息。
(5) Upon expiration of the WTR timer in node Z, node Z sends an NR(0,1) message as the last received APS message was WTR. When the NR(0,1) message arrives at node A, node A maintains the WTR state and keeps sending current WTR messages as described in the state transition table.
(5) 当节点Z中的WTR定时器到期时，节点Z发送NR（0,1）消息，因为最后接收到的APS消息是WTR。当NR（0,1）消息到达节点A时，节点A保持WTR状态并按照状态转换表中的描述持续发送当前WTR消息。
(6) Upon expiration of the WTR timer in node A, node A sends an NR(0,1) message.
(6) 当节点A中的WTR定时器到期时，节点A发送NR（0,1）消息。
(7) When the NR(0,1) message arrives at node Z, node Z moves to the Normal state, sets both the selector and bridge to the working path, and sends an NR(0,0) message.
(7) 当NR（0,1）消息到达节点Z时，节点Z移动到正常状态，将选择器和桥接器设置为工作路径，并发送NR（0,0）消息。
(8) The received NR(0,0) message causes node A to go to the Normal state. Now, the traffic is switched back to the working path.
(8) 接收到的NR（0,0）消息使节点A进入正常状态。现在，通信量被切换回工作路径。
Example 3. 1:1 bidirectional protection switching - R bit mismatch
例3。1:1双向保护切换-R位不匹配
This example shows that both sides will interwork and the traffic is protected when one side (node A) is configured as revertive operation and the other (node Z) is configured as non-revertive operation. The interworking is covered in the state transition tables.
此示例显示，当一侧（节点A）配置为还原操作，另一侧（节点Z）配置为非还原操作时，双方将互通，通信量受到保护。状态转换表中介绍了互通。
(revertive) A Z (non-revertive)
| |
(1) |<---- NR(0,0)---->| (1)
| |
| |
(2) | (SF on W(A<->Z)) | (2)
|<---- SF(1,1)---->|
| |
| |
(3) | (Clear SF-W) | (3)
|<---- NR(0,1)---->|
(4) |<----- DNR(0,1)---| (4)
/|-- WTR(0,1)------>|
| |<----- NR(0,1)----| (5)
| | |
WTR timer | |
| | |
| | |
\| |
(6) |--- NR(0,1)------>|
|<------ NR(0,0)---| (7)
(8) |--- NR(0,0)------>|
| |
(revertive) A Z (non-revertive)
| |
(1) |<---- NR(0,0)---->| (1)
| |
| |
(2) | (SF on W(A<->Z)) | (2)
|<---- SF(1,1)---->|
| |
| |
(3) | (Clear SF-W) | (3)
|<---- NR(0,1)---->|
(4) |<----- DNR(0,1)---| (4)
/|-- WTR(0,1)------>|
| |<----- NR(0,1)----| (5)
| | |
WTR timer | |
| | |
| | |
\| |
(6) |--- NR(0,1)------>|
|<------ NR(0,0)---| (7)
(8) |--- NR(0,0)------>|
| |
(1) Each end is in the Normal state and transmits NR(0,0) messages.
(1) 每一端处于正常状态，并传输NR（0,0）消息。
(2) When SF-W occurs, each node enters into the PF:W:L state and transmits SF(l,l) messages. Traffic is switched to the protection path. Upon receiving an SF(1,1) message, each node confirms that the remote node is also sending and receiving the traffic on the protection path.
(2) 当SF-W发生时，每个节点进入PF:W:L状态并传输SF（L，L）消息。通信量切换到保护路径。在接收到SF（1,1）消息后，每个节点确认远程节点也在发送和接收保护路径上的流量。
(3) When SF-W is cleared, each node transits to the PF:W:R state and transmits NR(0,1) messages as the last received message is SF-W.
(3) 当清除SF-W时，每个节点转换到PF:W:R状态，并发送NR（0,1）条消息，因为最后接收的消息是SF-W。
(4) Upon receiving NR(0,1) messages, node A goes into the WTR state, starts the WTR timer, and sends WTR(0,1) messages. At the same time, node Z transits to the DNR state and sends a DNR(0,1) message.
(4) 在接收到NR（0,1）消息后，节点A进入WTR状态，启动WTR定时器，并发送WTR（0,1）消息。同时，节点Z过渡到DNR状态并发送DNR（0,1）消息。
(5) When the WTR message arrives at node Z, node Z transits to the WTR state and sends an NR(0,1) message according to the state transition table. At the same time, the DNR message arrived at node Z is ignored according to the state transition table. Therefore, node Z, which is configured as non-revertive operation, is operating as if in revertive operation.
(5) 当WTR消息到达节点Z时，节点Z转换到WTR状态，并根据状态转换表发送NR（0,1）消息。同时，根据状态转换表忽略到达节点Z的DNR消息。因此，配置为非还原操作的节点Z正在像还原操作一样操作。
(6) Upon expiration of the WTR timer in node A, node A sends an NR(0,1) message.
(6) 当节点A中的WTR定时器到期时，节点A发送NR（0,1）消息。
(7) When the NR(0,1) message arrives at node Z, node Z moves to the Normal state, sets both the selector and bridge to the working path, and sends an NR(0,0) message.
(7) 当NR（0,1）消息到达节点Z时，节点Z移动到正常状态，将选择器和桥接器设置为工作路径，并发送NR（0,0）消息。
(8) The received NR(0,0) message causes node A to transit to the Normal state. Now, the traffic is switched back to the working path.
(8) 接收到的NR（0,0）消息使节点A过渡到正常状态。现在，通信量被切换回工作路径。
Authors' Addresses
作者地址
Jeong-dong Ryoo (editor) ETRI 218 Gajeongno Yuseong-gu, Daejeon 305-700 South Korea Phone: +82-42-860-5384 EMail: ryoo@etri.re.kr
Jeong dong Ryoo（编辑）ETRI 218 Gajeongno Yuseong gu，大田305-700韩国电话：+82-42-860-5384电子邮件：ryoo@etri.re.kr
Eric Gray (editor) Ericsson EMail: eric.gray@ericsson.com
埃里克·格雷（编辑）爱立信电子邮件：埃里克。gray@ericsson.com
Huub van Helvoort Huawei Technologies Karspeldreef 4, Amsterdam 1101 CJ The Netherlands Phone: +31 20 4300936 EMail: huub.van.helvoort@huawei.com
Huub van Helvoort华为技术公司阿姆斯特丹卡斯佩尔德雷夫4号1101 CJ荷兰电话：+31 20 4300936电子邮件：Huub.van。helvoort@huawei.com
Alessandro D'Alessandro Telecom Italia via Reiss Romoli, 274 Torino 10148 Italy Phone: +39 011 2285887 EMail: alessandro.dalessandro@telecomitalia.it
Alessandro D'Alessandro Telecom Italia通过Reiss Romoli，274都灵10148意大利电话：+39 011 2285887电子邮件：Alessandro。dalessandro@telecomitalia.it
Taesik Cheung ETRI 218 Gajeongno Yuseong-gu, Daejeon 305-700 South Korea Phone: +82-42-860-5646 EMail: cts@etri.re.kr
Taesik Cheung ETRI 218 Gajeongno Yuseong gu，大田305-700韩国电话：+82-42-860-5646电子邮件：cts@etri.re.kr
Eric Osborne EMail: eric.osborne@notcom.com
埃里克·奥斯本电子邮件：埃里克。osborne@notcom.com