Internet Engineering Task Force (IETF) E. Gray
Request for Comments: 6426 Ericsson
Updates: 4379 N. Bahadur
Category: Standards Track Juniper Networks, Inc.
ISSN: 2070-1721 S. Boutros
Cisco Systems, Inc.
R. Aggarwal
November 2011
Internet Engineering Task Force (IETF) E. Gray
Request for Comments: 6426 Ericsson
Updates: 4379 N. Bahadur
Category: Standards Track Juniper Networks, Inc.
ISSN: 2070-1721 S. Boutros
Cisco Systems, Inc.
R. Aggarwal
November 2011
MPLS On-Demand Connectivity Verification and Route Tracing
MPLS按需连接验证和路由跟踪
Abstract
摘要
Label Switched Path Ping (LSP ping) is an existing and widely deployed Operations, Administration, and Maintenance (OAM) mechanism for Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs). This document describes extensions to LSP ping so that LSP ping can be used for on-demand connectivity verification of MPLS Transport Profile (MPLS-TP) LSPs and pseudowires. This document also clarifies procedures to be used for processing the related OAM packets. Further, it describes procedures for using LSP ping to perform connectivity verification and route tracing functions in MPLS-TP networks. Finally, this document updates RFC 4379 by adding a new address type and creating an IANA registry.
标签交换路径Ping（LSP-Ping）是一种用于多协议标签交换（MPLS）标签交换路径（LSP）的现有且广泛部署的操作、管理和维护（OAM）机制。本文档描述了LSP ping的扩展，以便LSP ping可用于MPLS传输配置文件（MPLS-TP）LSP和伪线的按需连接验证。本文件还阐明了用于处理相关OAM数据包的程序。此外，它描述了在MPLS-TP网络中使用LSP ping执行连接验证和路由跟踪功能的过程。最后，本文档通过添加新地址类型和创建IANA注册表来更新RFC4379。
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/rfc6426.
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/rfc6426.
Copyright Notice
版权公告
Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2011 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . 3
1.2. On-Demand CV for MPLS-TP LSPs Using IP Encapsulation . . . 4
1.3. On-Demand CV for MPLS-TP LSPs Using Non-IP
Encapsulation . . . . . . . . . . . . . . . . . . . . . . 4
2. LSP Ping Extensions . . . . . . . . . . . . . . . . . . . . . 5
2.1. New Address Type for Downstream Mapping TLV . . . . . . . 5
2.1.1. DSMAP/DDMAP Non-IP Address Information . . . . . . . . 5
2.2. Source/Destination Identifier TLV . . . . . . . . . . . . 7
2.2.1. Source/Destination Identifier TLV Format . . . . . . . 7
2.2.2. Source Identifier TLV . . . . . . . . . . . . . . . . 7
2.2.3. Destination Identifier TLV . . . . . . . . . . . . . . 8
2.3. Identifying Statically Provisioned LSPs and PWs . . . . . 8
2.3.1. Static LSP Sub-TLV . . . . . . . . . . . . . . . . . . 9
2.3.2. Static Pseudowire Sub-TLV . . . . . . . . . . . . . . 10
3. Performing On-Demand CV over MPLS-TP LSPs . . . . . . . . . . 10
3.1. LSP Ping with IP Encapsulation . . . . . . . . . . . . . . 11
3.2. On-Demand CV with IP Encapsulation, over ACH . . . . . . . 11
3.3. Non-IP-Based On-Demand CV, Using ACH . . . . . . . . . . . 12
3.4. Reverse-Path Connectivity Verification . . . . . . . . . . 13
3.4.1. Requesting Reverse-Path Connectivity Verification . . 13
3.4.2. Responder Procedures . . . . . . . . . . . . . . . . . 13
3.4.3. Requester Procedures . . . . . . . . . . . . . . . . . 14
3.5. P2MP Considerations . . . . . . . . . . . . . . . . . . . 14
3.6. Management Considerations for Operation with Static
MPLS-TP . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.7. Generic Associated Channel Label (GAL) Processing . . . . 14
4. Performing On-Demand Route Tracing over MPLS-TP LSPs . . . . . 15
4.1. On-Demand LSP Route Tracing with IP Encapsulation . . . . 15
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . 3
1.2. On-Demand CV for MPLS-TP LSPs Using IP Encapsulation . . . 4
1.3. On-Demand CV for MPLS-TP LSPs Using Non-IP
Encapsulation . . . . . . . . . . . . . . . . . . . . . . 4
2. LSP Ping Extensions . . . . . . . . . . . . . . . . . . . . . 5
2.1. New Address Type for Downstream Mapping TLV . . . . . . . 5
2.1.1. DSMAP/DDMAP Non-IP Address Information . . . . . . . . 5
2.2. Source/Destination Identifier TLV . . . . . . . . . . . . 7
2.2.1. Source/Destination Identifier TLV Format . . . . . . . 7
2.2.2. Source Identifier TLV . . . . . . . . . . . . . . . . 7
2.2.3. Destination Identifier TLV . . . . . . . . . . . . . . 8
2.3. Identifying Statically Provisioned LSPs and PWs . . . . . 8
2.3.1. Static LSP Sub-TLV . . . . . . . . . . . . . . . . . . 9
2.3.2. Static Pseudowire Sub-TLV . . . . . . . . . . . . . . 10
3. Performing On-Demand CV over MPLS-TP LSPs . . . . . . . . . . 10
3.1. LSP Ping with IP Encapsulation . . . . . . . . . . . . . . 11
3.2. On-Demand CV with IP Encapsulation, over ACH . . . . . . . 11
3.3. Non-IP-Based On-Demand CV, Using ACH . . . . . . . . . . . 12
3.4. Reverse-Path Connectivity Verification . . . . . . . . . . 13
3.4.1. Requesting Reverse-Path Connectivity Verification . . 13
3.4.2. Responder Procedures . . . . . . . . . . . . . . . . . 13
3.4.3. Requester Procedures . . . . . . . . . . . . . . . . . 14
3.5. P2MP Considerations . . . . . . . . . . . . . . . . . . . 14
3.6. Management Considerations for Operation with Static
MPLS-TP . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.7. Generic Associated Channel Label (GAL) Processing . . . . 14
4. Performing On-Demand Route Tracing over MPLS-TP LSPs . . . . . 15
4.1. On-Demand LSP Route Tracing with IP Encapsulation . . . . 15
4.2. Non-IP-Based On-Demand LSP Route Tracing, Using ACH . . . 15
4.2.1. Requester Procedure for Sending Echo Request
Packets . . . . . . . . . . . . . . . . . . . . . . . 16
4.2.2. Requester Procedure for Receiving Echo Response
Packets . . . . . . . . . . . . . . . . . . . . . . . 16
4.2.3. Responder Procedure . . . . . . . . . . . . . . . . . 16
4.3. P2MP Considerations . . . . . . . . . . . . . . . . . . . 16
4.4. ECMP Considerations . . . . . . . . . . . . . . . . . . . 16
5. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
7.1. New Source and Destination Identifier TLVs . . . . . . . . 17
7.2. New Target FEC Stack Sub-TLVs . . . . . . . . . . . . . . 17
7.3. New Reverse-Path Target FEC Stack TLV . . . . . . . . . . 18
7.4. New Pseudowire Associated Channel Type . . . . . . . . . . 18
7.5. New Downstream Mapping Address Type Registry . . . . . . . 18
8. Contributing Authors and Acknowledgements . . . . . . . . . . 19
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . . 20
9.2. Informative References . . . . . . . . . . . . . . . . . . 20
4.2. Non-IP-Based On-Demand LSP Route Tracing, Using ACH . . . 15
4.2.1. Requester Procedure for Sending Echo Request
Packets . . . . . . . . . . . . . . . . . . . . . . . 16
4.2.2. Requester Procedure for Receiving Echo Response
Packets . . . . . . . . . . . . . . . . . . . . . . . 16
4.2.3. Responder Procedure . . . . . . . . . . . . . . . . . 16
4.3. P2MP Considerations . . . . . . . . . . . . . . . . . . . 16
4.4. ECMP Considerations . . . . . . . . . . . . . . . . . . . 16
5. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
7.1. New Source and Destination Identifier TLVs . . . . . . . . 17
7.2. New Target FEC Stack Sub-TLVs . . . . . . . . . . . . . . 17
7.3. New Reverse-Path Target FEC Stack TLV . . . . . . . . . . 18
7.4. New Pseudowire Associated Channel Type . . . . . . . . . . 18
7.5. New Downstream Mapping Address Type Registry . . . . . . . 18
8. Contributing Authors and Acknowledgements . . . . . . . . . . 19
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . . 20
9.2. Informative References . . . . . . . . . . . . . . . . . . 20
Label Switched Path Ping (LSP ping) [RFC4379] is an Operations, Administration, and Maintenance (OAM) mechanism for Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs). This document describes extensions to LSP ping so that LSP ping can be used for on-demand monitoring of MPLS Transport Profile (MPLS-TP) LSPs and pseudowires. It also clarifies the procedures to be used for processing the related OAM packets. This document describes how LSP ping can be used for on-demand connectivity verification (Section 3) and route tracing (Section 4) functions required in [RFC5860] and specified in [RFC6371].
标签交换路径Ping（LSP Ping）[RFC4379]是一种用于多协议标签交换（MPLS）标签交换路径（LSP）的操作、管理和维护（OAM）机制。本文档描述了LSP ping的扩展，以便LSP ping可用于MPLS传输配置文件（MPLS-TP）LSP和伪线的按需监控。它还澄清了用于处理相关OAM数据包的程序。本文件描述了LSP ping如何用于[RFC5860]中要求并在[RFC6371]中规定的按需连接验证（第3节）和路由跟踪（第4节）功能。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“建议”、“不建议”、“可”和“可选”应按照[RFC2119]中的说明进行解释。
There is considerable opportunity for confusion in use of the terms "on-demand connectivity verification" (CV), "on-demand route tracing" and "LSP ping." In this document, we try to use the terms consistently as follows:
在使用术语“按需连接验证”（CV）、“按需路由跟踪”和“LSP ping”时，存在相当大的混淆机会。在本文件中，我们尝试一致使用以下术语：
o LSP ping: refers to the mechanism - particularly as defined and used in referenced material;
o LSP ping：指机制，尤其是参考资料中定义和使用的机制；
o On-demand CV: refers to on-demand connectivity verification and -- where both apply equally -- on-demand route tracing, as implemented using the LSP ping mechanism extended for support of MPLS-TP;
o 按需CV：指按需连接性验证和（如果两者同等适用）按需路由跟踪，使用扩展用于支持MPLS-TP的LSP ping机制实现；
o On-demand route tracing: used in those cases where the LSP ping mechanism (as extended) is used exclusively for route tracing.
o 按需路由跟踪：用于LSP ping机制（扩展）专门用于路由跟踪的情况。
From the perspective of on-demand CV and route tracing, we use the concepts of "Requester" and "Responder" as follows:
从按需CV和路由跟踪的角度来看，我们使用“请求者”和“响应者”的概念如下：
o Requester: Originator of an OAM Request message,
o 请求者：OAM请求消息的发起人，
o Responder: Entity responding to an OAM Request message.
o 响应者：响应OAM请求消息的实体。
Since, in this document, all messages are assumed to be carried in an LSP, all Request messages would be injected at the ingress to an LSP. A Responder might or might not be at the egress of this same LSP, given that it could receive Request messages as a result of time-to-live (TTL) expiry. If a Reply is to be delivered via a reverse-path LSP, the message would again be inserted at the ingress of that LSP.
由于在本文档中，假设所有消息都在LSP中承载，因此所有请求消息都将在LSP入口注入。响应者可能在也可能不在同一LSP的出口处，因为它可能由于生存时间（TTL）到期而接收请求消息。如果要通过反向路径LSP发送回复，则消息将再次插入该LSP的入口。
LSP ping requires IP addressing on responding Label Switching Routers (LSRs) for performing OAM on MPLS-signaled LSPs and pseudowires. In particular, in these cases, LSP ping packets generated by a Requester are encapsulated in an IP/UDP header with the destination address from the 127/8 range and then encapsulated in the MPLS label stack ([RFC4379] , [RFC5884]). A Responder uses the presence of the 127/8 destination address to identify OAM packets and relies further on the UDP port number to determine whether the packet is an LSP ping packet. It is to be noted that this determination does not require IP forwarding capabilities. It requires the presence of an IP host stack, which enables responding LSRs to process packets with a destination address from the 127/8 range. [RFC1122] allocates the 127/8 range as "Internal host loopback address" and [RFC1812] states that "a router SHOULD NOT forward, except over a loopback interface, any packet that has a destination address on network 127".
LSP ping需要在响应标签交换路由器（LSR）上进行IP寻址，以便在MPLS信号LSP和伪线上执行OAM。特别是，在这些情况下，请求者生成的LSP ping数据包被封装在IP/UDP报头中，目标地址来自127/8范围，然后封装在MPLS标签堆栈中（[RFC4379]，[RFC5884]）。响应者使用127/8目的地地址的存在来识别OAM分组，并且进一步依赖UDP端口号来确定分组是否是LSP ping分组。应注意，该确定不需要IP转发能力。它需要IP主机堆栈的存在，这使响应的LSR能够处理目标地址为127/8范围的数据包。[RFC1122]将127/8范围分配为“内部主机环回地址”，并且[RFC1812]声明“路由器不应转发在网络127上具有目标地址的任何数据包，除非通过环回接口转发”。
In certain MPLS-TP deployment scenarios, IP addressing might not be available or use some form of non-IP encapsulation might be preferred for on-demand CV, route tracing, and BFD packets. In such scenarios, on-demand CV and/or route tracing SHOULD be run without IP addressing, using the Associated Channel (ACH) channel type specified in Section 3.
在某些MPLS-TP部署场景中，IP寻址可能不可用，或者对于按需CV、路由跟踪和BFD数据包，可能首选使用某种形式的非IP封装。在这种情况下，应使用第3节中指定的关联通道（ACH）通道类型，在不使用IP寻址的情况下运行按需CV和/或路由跟踪。
Section 3.3 and Section 4.2 describe the theory of operation for performing on-demand CV over MPLS-TP LSPs with any non-IP encapsulation.
第3.3节和第4.2节描述了使用任何非IP封装通过MPLS-TP LSP执行按需CV的操作原理。
[RFC4379] defines the Downstream Mapping (DSMAP) TLV. [RFC6424] further defines the Downstream Detailed Mapping (DDMAP) TLV. This document defines the following new address type, which MAY be used in any DSMAP or DDMAP TLV included in an on-demand CV message:
[RFC4379]定义了下游映射（DSMAP）TLV。[RFC6424]进一步定义了下游详细映射（DDMAP）TLV。本文档定义了以下新地址类型，可用于按需CV消息中包含的任何DSMAP或DDMAP TLV：
Type # Address Type K Octets
------ -------------- --------
5 Non IP 12
Type # Address Type K Octets
------ -------------- --------
5 Non IP 12
Figure 1: New Downstream Mapping Address Type
图1：新的下游映射地址类型
The new address type indicates that no address is present in the DSMAP or DDMAP TLV. However, IF_Num information (see definition of "IF_Num" in [RFC6370]) for both ingress and egress interfaces, as well as Multipath Information, is included in the format and MAY be present.
新地址类型表示DSMAP或DDMAP TLV中不存在地址。然而，入口和出口接口的IF_Num信息（参见[RFC6370]中“IF_Num”的定义）以及多路径信息包括在格式中，并且可能存在。
IF_Num values of zero indicate that no IF_Num applies in the field in which this value appears.
IF_Num值为零表示在显示该值的字段中不应用IF_Num。
The Multipath Type SHOULD be set to zero (no multipath) when using this address type.
使用此地址类型时，多路径类型应设置为零（无多路径）。
When this address type is used, on receipt of an LSP ping echo request, interface verification MUST be bypassed. Thus, the receiving node SHOULD only perform MPLS label control-plane/ data-plane consistency checks. Note that these consistency checks include checking the included identifier information.
使用此地址类型时，在收到LSP ping回显请求时，必须绕过接口验证。因此，接收节点应仅执行MPLS标签控制平面/数据平面一致性检查。请注意，这些一致性检查包括检查包含的标识符信息。
The new address type is also applicable to the Detailed Downstream Mapping (DDMAP) TLV defined in [RFC6424].
新地址类型也适用于[RFC6424]中定义的详细下游映射（DDMAP）TLV。
If the DSMAP (or DDMAP) TLV is included when sending on-demand CV packets using ACH, without IP encapsulation, the following information MUST be included in any DSMAP or DDMAP TLV that is included in the packet. This information forms the address portion of the DSMAP TLV (as defined in [RFC4379]) or DDMAP TLV (as defined in [RFC6424] using one of the address information fields defined in
如果在使用ACH发送按需CV数据包时包含DSMAP（或DDMAP）TLV，而不包含IP封装，则数据包中包含的任何DSMAP或DDMAP TLV中必须包含以下信息。该信息构成DSMAP TLV（定义见[RFC4379]）或DDMAP TLV（定义见[RFC6424]）的地址部分，使用中定义的地址信息字段之一
[RFC4379] and extended to include non-IP identifier types in this document).
[RFC4379]并扩展为包括本文档中的非IP标识符类型）。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MTU | Address Type | DS Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ingress IF_Num (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Egress IF_Num (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multipath Type| Depth Limit | Multipath Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MTU | Address Type | DS Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ingress IF_Num (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Egress IF_Num (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multipath Type| Depth Limit | Multipath Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: New DSMAP/DDMAP Address Format
图2：新的DSMAP/DDMAP地址格式
Address Type will be 5 (as shown in Section 2.1 above).
地址类型为5（如上文第2.1节所示）。
Ingress IF_Num identifies the ingress interface on the target node. A value of zero indicates that the interface is not part of the identifier.
Ingress IF_Num标识目标节点上的入口接口。值为零表示接口不是标识符的一部分。
Egress IF_Num identifies the egress interface on the target node. A value of zero indicates that the interface is not part of the identifier.
express IF_Num标识目标节点上的出口接口。值为零表示接口不是标识符的一部分。
The Multipath Type SHOULD be set to zero (no multipath) when using this address type.
使用此地址类型时，多路径类型应设置为零（无多路径）。
Including this TLV, with one or the other IF_Num (but not both) set to a non-zero value, in a request message that also includes a Destination Identifier TLV (as described in Section 2.2), is sufficient to identify the "per-interface" MIP in Section 7.3 of [RFC6370].
将该TLV（一个或另一个IF_Num（但不是两个）设置为非零值）包含在请求消息中，该请求消息还包括目标标识符TLV（如第2.2节所述），足以识别[RFC6370]第7.3节中的“每个接口”MIP。
Inclusion of this TLV with both IF_Num fields set to zero would be interpreted as specifying neither an ingress, nor an egress, interface. Note that this is the same as not including the TLV; hence, including this TLV with both IF_Num values set to zero is NOT RECOMMENDED.
如果将此TLV和IF_Num字段都设置为零，则会被解释为既不指定入口也不指定出口接口。注意，这与不包括TLV相同；因此，不建议将此TLV和IF_Num值都设置为零。
Including this TLV with both IF_NUM fields set to a non-zero value will result in the responder sending a Return Code of 5 ("Downstream Mapping Mis-match") if either IF_Num is incorrect for this LSP or PW.
如果将此TLV和IF_NUM字段都设置为非零值，则如果该LSP或PW的IF_NUM不正确，则响应程序将发送返回代码5（“下游映射不匹配”）。
The format for the identifier TLV is the same for both Source and Destination Identifier TLVs (only the type is different). The format is as specified in the figure below.
源标识符TLV和目标标识符TLV的标识符TLV格式相同（只是类型不同）。格式如下图所示。
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 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Global_ID (4 Octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node_ID (4 Octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Global_ID (4 Octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node_ID (4 Octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: New Source/Destination Identifier Format
图3：新的源/目标标识符格式
Type will be one of either 13 or 14, depending on whether the TLV in question is a Source or Destination Identifier TLV.
类型将是13或14之一，这取决于所讨论的TLV是源标识符还是目标标识符TLV。
Global_ID is as defined in [RFC6370].
全局_ID的定义见[RFC6370]。
Node_ID is as defined in [RFC6370].
节点ID如[RFC6370]中所定义。
When sending on-demand CV packets using ACH, without IP encapsulation, there MAY be a need to identify the source of the packet. This source identifier (Source ID) will be specified via the Source Identifier TLV, using the Identifier TLV defined in Section 2.2.1, containing the information specified above.
使用ACH发送按需CV数据包时，如果没有IP封装，则可能需要识别数据包的来源。该源标识符（源ID）将通过源标识符TLV指定，使用第2.2.1节中定义的标识符TLV，包含上述指定的信息。
An on-demand CV packet MUST NOT include more than one Source Identifier TLV. The Source Identifier TLV MUST specify the identifier of the originator of the packet. If more than one such TLV is present in an on-demand CV request packet, then error 1 (Malformed echo request received; see Section 3.1 of [RFC4379]) MUST be returned, if it is possible to unambiguously identify the source of the packet.
按需CV数据包不得包含多个源标识符TLV。源标识符TLV必须指定数据包发起人的标识符。如果按需CV请求数据包中存在多个此类TLV，则必须返回错误1（收到格式错误的回送请求；请参阅[RFC4379]第3.1节），前提是可以明确标识数据包的来源。
When sending on-demand CV packets using ACH, without IP encapsulation, there MAY be a need to identify the destination of the packet. This destination identifier (Destination ID) will be specified via the Destination Identifier TLV, using the Identifier TLV defined in Section 2.2.1, containing the information specified above.
当使用ACH发送按需CV数据包时，在没有IP封装的情况下，可能需要识别数据包的目的地。该目的地标识符（目的地ID）将通过目的地标识符TLV指定，使用第2.2.1节中定义的标识符TLV，包含上述指定的信息。
An on-demand CV packet MUST NOT include more than one Destination Identifier TLV. The Destination Identifier TLV MUST specify the destination node for the packet. If more than 1 such TLV is present in an on-demand CV Request packet, then error 1 (Malformed echo request received; see Section 3.1 of [RFC4379]) MUST be returned, if it is possible to unambiguously identify the source of the packet.
按需CV数据包不得包含多个目标标识符TLV。目标标识符TLV必须指定数据包的目标节点。如果按需CV请求数据包中存在超过1个这样的TLV，则必须返回错误1（收到格式错误的回送请求；参见[RFC4379]第3.1节），前提是可以明确标识数据包的来源。
[RFC4379] specifies how an MPLS LSP under test is identified in an echo request. A Target FEC Stack TLV is used to identify the LSP. In order to identify a statically provisioned LSP and PW, new target FEC Stack sub-TLVs are being defined. The new sub-TLVs are assigned sub-type identifiers as follows and are described in the following sections.
[RFC4379]指定如何在回显请求中识别测试中的MPLS LSP。目标FEC堆栈TLV用于识别LSP。为了识别静态配置的LSP和PW，正在定义新的目标FEC堆栈子TLV。新的子TLV被分配子类型标识符，如下所示，并在以下章节中描述。
Type # Sub-Type # Length Value Field
------ ---------- ------ -----------
1 22 24 Static LSP
1 23 32 Static Pseudowire
Type # Sub-Type # Length Value Field
------ ---------- ------ -----------
1 22 24 Static LSP
1 23 32 Static Pseudowire
Figure 4: New Target FEC Sub-Types
图4：新的目标FEC子类型
The format of the Static LSP sub-TLV value field is specified in the following figure. The value fields are taken from the definitions in [RFC6370].
静态LSP子TLV值字段的格式如下图所示。值字段取自[RFC6370]中的定义。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Global ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Node ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Tunnel Number | LSP Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Global ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Node ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Tunnel Number | Must be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Global ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Node ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Tunnel Number | LSP Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Global ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Node ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Tunnel Number | Must be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Static LSP FEC Sub-TLV
图5：静态LSP FEC子TLV
The Source Global ID and Destination Global ID MAY be set to zero. When set to zero, the field is not applicable.
源全局ID和目标全局ID可以设置为零。设置为零时，该字段不适用。
The format of the Static PW sub-TLV value field is specified in the following figure.
静态PW子TLV值字段的格式如下图所示。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Service Identifier +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Global ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Node ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source AC-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Global ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Node ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination AC-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Service Identifier +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Global ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Node ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source AC-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Global ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Node ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination AC-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Static PW FEC Sub-TLV
图6：静态PW FEC子TLV
The Service Identifier is a 64-bit unsigned integer that is included in the first two words, as shown. The Service Identifier identifies the service associated with the transport path under test. The value MAY, for example, be an Attachment Group Identifier (AGI), type 0x01, as defined in [RFC4446].
服务标识符是包含在前两个字中的64位无符号整数，如图所示。服务标识符标识与测试中的传输路径关联的服务。例如，该值可以是[RFC4446]中定义的类型为0x01的附件组标识符（AGI）。
The Source Global ID and Destination Global ID MAY be set to zero. When either of these fields is set to zero, the corresponding Global ID is not applicable. This might be done in a scenario where local scope is sufficient for uniquely identifying services.
源全局ID和目标全局ID可以设置为零。当这些字段中的任何一个设置为零时，相应的全局ID不适用。这可以在本地范围足以唯一标识服务的场景中完成。
The Global ID and Node ID fields are defined in [RFC6370]. The AC-ID fields are defined in [RFC5003].
[RFC6370]中定义了全局ID和节点ID字段。AC-ID字段在[RFC5003]中定义。
This section specifies how on-demand CV can be used in the context of MPLS-TP LSPs. The on-demand CV function meets the on-demand connectivity verification requirements specified in [RFC5860], Section 2.2.3. This function SHOULD NOT be performed except in the on-demand mode. This function SHOULD be performed between
本节指定如何在MPLS-TP LSP上下文中使用按需CV。按需CV功能满足[RFC5860]第2.2.3节中规定的按需连接验证要求。除按需模式外，不得执行此功能。此功能应在以下时间之间执行：
Maintenance Entity Group End Points (MEPs) and Maintenance Entity Group Intermediate Points (MIPs) of PWs and LSPs, and between End Points of PWs, LSPs, and Sections. In order for the on-demand CV packet to be processed at the desired MIP, the TTL of the MPLS label MUST be set such that it expires at the MIP to be probed.
PWs和LSP的维修实体组端点（MEP）和维修实体组中间点（MIP），以及PWs、LSP和区段端点之间的维修实体组端点（MEP）。为了在期望的MIP处处理按需CV分组，必须设置MPLS标签的TTL，以使其在要探测的MIP处过期。
[RFC5586] defines an ACH mechanism for MPLS LSPs. The mechanism is a generalization of the Associated Channel mechanism that [RFC4385] defined for use with pseudowires. As a result, it is possible to use a single Associated Channel Type for either an LSP or pseudowire.
[RFC5586]定义了MPLS LSP的ACH机制。该机制是[RFC4385]定义用于伪线的相关信道机制的推广。因此，可以为LSP或伪线使用单个关联信道类型。
A new Pseudowire Associated Channel Type (0x0025) is defined for use in performing on-demand connectivity verification. Its use is described in the following sections.
定义了一种新的伪线相关信道类型（0x0025），用于执行按需连接验证。以下各节将介绍其使用。
ACH TLVs SHALL NOT be associated with this channel type.
ACH TLV不得与该通道类型相关联。
Except as specifically stated in the sections below, message and TLV construction procedures for on-demand CV messages are as defined in [RFC4379].
除以下章节中特别说明的情况外，按需CV消息的消息和TLV构造程序如[RFC4379]所述。
LSP ping packets, as specified in [RFC4379], are sent over the MPLS LSP for which OAM is being performed and contain an IP/UDP packet within them. The IP header is not used for forwarding (since LSP forwarding is done using MPLS). The IP header is used mainly for addressing and can be used in the context of MPLS-TP LSPs. This form of on-demand CV OAM MUST be supported for MPLS-TP LSPs when IP addressing is in use.
[RFC4379]中规定的LSP ping数据包通过正在执行OAM的MPLS LSP发送，其中包含IP/UDP数据包。IP报头不用于转发（因为LSP转发是使用MPLS完成的）。IP报头主要用于寻址，可以在MPLS-TP LSP的上下文中使用。当使用IP寻址时，MPLS-TP LSP必须支持这种形式的按需CV OAM。
The on-demand CV echo response message MUST be sent on the reverse path of the LSP. The reply MUST contain IP/UDP headers followed by the on-demand CV payload. The destination address in the IP header MUST be set to that of the sender of the echo request message. The source address in the IP header MUST be set to a valid address of the replying node.
按需CV回波响应消息必须在LSP的反向路径上发送。回复必须包含IP/UDP标头，后跟按需CV负载。IP头中的目标地址必须设置为回显请求消息的发送方的地址。IP头中的源地址必须设置为应答节点的有效地址。
IP encapsulated on-demand CV packets MAY be sent over the MPLS LSP using the control channel (ACH). The IP ACH type specified in [RFC4385] MUST be used in such a case. The IP header is used mainly for addressing and can be used in the context of MPLS-TP LSPs.
IP封装的按需CV分组可以使用控制信道（ACH）通过MPLS LSP发送。在这种情况下，必须使用[RFC4385]中指定的IP ACH类型。IP报头主要用于寻址，可以在MPLS-TP LSP的上下文中使用。
Note that the application-level control channel in this case is the reverse path of the LSP (or Pseudowire) using ACH.
请注意，在这种情况下，应用程序级控制通道是使用ACH的LSP（或伪线）的反向路径。
The on-demand CV echo response message MUST be sent on the reverse path of the LSP. The response in this case SHOULD use ACH and SHOULD be IP encapsulated.
按需CV回波响应消息必须在LSP的反向路径上发送。这种情况下的响应应该使用ACH，并且应该是IP封装的。
If IP encapsulated, the destination address in the IP header MUST be set to that of the sender of the echo request message, and the source address in the IP header MUST be set to a valid address of the replying node.
如果是IP封装，则IP头中的目标地址必须设置为回显请求消息的发送方的地址，并且IP头中的源地址必须设置为应答节点的有效地址。
The OAM procedures defined in [RFC4379] require the use of IP addressing, and in some cases IP routing, to perform OAM functions.
[RFC4379]中定义的OAM过程需要使用IP寻址，在某些情况下还需要使用IP路由来执行OAM功能。
When the ACH header is used, IP addressing and routing is not needed. This section describes procedures for performing on-demand CV without a dependency on IP addressing and routing.
使用ACH报头时，不需要IP寻址和路由。本节介绍在不依赖IP寻址和路由的情况下执行按需CV的过程。
In the non-IP case, when using on-demand CV via LSP ping with the ACH header, the on-demand CV request payload MUST directly follow the ACH header, and the LSP ping Reply mode [RFC4379] in the LSP ping echo request SHOULD be set to 4 (Reply via application level control channel).
在非IP情况下，当通过LSP ping和ACH报头使用按需CV时，按需CV请求有效负载必须直接跟随ACH报头，并且LSP ping echo请求中的LSP ping应答模式[RFC4379]应设置为4（通过应用程序级控制信道应答）。
Note that the application-level control channel in this case is the reverse path of the LSP (or pseudowire) using ACH.
请注意，在这种情况下，应用程序级控制通道是使用ACH的LSP（或伪线）的反向路径。
The requesting node MAY attach a Source Identifier TLV (Section 2.2) to identify the node originating the request.
请求节点可附加源标识符TLV（第2.2节），以识别发起请求的节点。
If the Reply mode indicated in an on-demand CV Request is 4 (Reply via application level control channel), the on-demand CV reply message MUST be sent on the reverse path of the LSP using ACH. The on-demand CV payload MUST directly follow the ACH header, and IP and/or UDP headers MUST NOT be attached. The responding node MAY attach a Source Identifier TLV to identify the node sending the response.
如果按需CV请求中指示的回复模式为4（通过应用程序级控制通道进行回复），则必须使用ACH在LSP的反向路径上发送按需CV回复消息。按需CV有效负载必须直接跟随ACH报头，并且不得附加IP和/或UDP报头。响应节点可附加源标识符TLV以识别发送响应的节点。
If a node receives an MPLS echo request packet over ACH, without IP/ UDP headers, with a reply mode of 4, and if that node does not have a return MPLS LSP path to the echo request source, then the node SHOULD drop the echo request packet and not attempt to send a response.
如果节点通过ACH接收到回复模式为4的MPLS回显请求数据包（不带IP/UDP报头），并且该节点没有到回显请求源的返回MPLS LSP路径，则该节点应丢弃回显请求数据包，而不尝试发送响应。
If a node receives an MPLS echo request with a reply mode other than 4 (Reply via application level control channel), and if the node supports that reply mode, then it MAY respond using that reply mode. If the node does not support the reply mode requested, or is unable to reply using the requested reply mode in any specific instance, the
如果节点接收到具有非4种应答模式（通过应用程序级控制通道进行应答）的MPLS回显请求，并且如果节点支持该应答模式，则它可以使用该应答模式进行应答。如果节点不支持请求的回复模式，或者无法在任何特定实例中使用请求的回复模式进行回复，则
node MUST drop the echo request packet and not attempt to send a response.
节点必须丢弃回显请求数据包，并且不尝试发送响应。
A new Global flag, Validate Reverse Path (R), is being defined in the LSP ping packet header. When this flag is set in the echo request, the Responder SHOULD return reverse-path FEC information, as described in Section 3.4.2.
在LSP ping数据包头中定义了一个新的全局标志Validate Reverse Path（R）。当在回声请求中设置此标志时，响应者应返回反向路径FEC信息，如第3.4.2节所述。
The R flag MUST NOT be set in the echo response.
回声响应中不得设置R标志。
The Global Flags field is now a bit vector with the following format:
全局标志字段现在是具有以下格式的位向量：
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ |R|T|V|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ |R|T|V|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Global Flags Field
图7：全局标志字段
The V flag is defined in [RFC4379]. The T flag is defined in [RFC6425]. The R flag is defined in this document.
[RFC4379]中定义了V标志。[RFC6425]中定义了T标志。本文件中定义了R标志。
The Validate FEC Stack (V) flag MAY be set in the echo response when reverse-path connectivity verification is being performed.
当执行反向路径连接验证时，可在回波响应中设置验证FEC堆栈（V）标志。
When the R flag is set in the echo request, the responding node SHOULD attach a Reverse-path Target FEC Stack TLV in the echo response. The requesting node (on receipt of the response) can use the Reverse-path Target FEC Stack TLV to perform reverse-path connectivity verification. For co-routed bidirectional LSPs, the Reverse-path Target FEC Stack used for the on-demand CV will be the same in both the forward and reverse path of the LSP. For associated bidirectional LSPs, the Target FEC Stack MAY be different for the reverse path.
当在echo请求中设置R标志时，响应节点应在echo响应中附加反向路径目标FEC堆栈TLV。请求节点（在收到响应时）可以使用反向路径目标FEC堆栈TLV执行反向路径连接验证。对于共路由双向LSP，用于按需CV的反向路径目标FEC堆栈在LSP的正向和反向路径中都是相同的。对于相关联的双向lsp，目标FEC堆栈对于反向路径可能不同。
The format of the Reverse-path Target FEC Stack TLV is the same as that of the Target FEC Stack TLV defined in [RFC4379]. The rules for creating a Target FEC Stack TLV also apply to the Reverse-path Target FEC Stack TLV.
反向路径目标FEC堆栈TLV的格式与[RFC4379]中定义的目标FEC堆栈TLV的格式相同。创建目标FEC堆栈TLV的规则也适用于反向路径目标FEC堆栈TLV。
Type Meaning
-------- ------------------------------------
16 Reverse-path Target FEC Stack
Type Meaning
-------- ------------------------------------
16 Reverse-path Target FEC Stack
Figure 8: Reverse-Path Target FEC Stack TLV Type
图8：反向路径目标FEC堆栈TLV类型
On receipt of the echo response, the requesting node MUST perform the following checks:
收到回音响应后，请求节点必须执行以下检查：
1. Perform interface and label-stack validation to ensure that the packet is received on the reverse path of the bidirectional LSP.
1. 执行接口和标签堆栈验证，以确保在双向LSP的反向路径上接收数据包。
2. If the Reverse-path Target FEC Stack TLV is present in the echo response, then perform FEC validation.
2. 如果回波响应中存在反向路径目标FEC堆栈TLV，则执行FEC验证。
The verification in this case is performed as described for the Target FEC Stack in Section 3.6 of [RFC4379].
这种情况下的验证按照[RFC4379]第3.6节中针对目标FEC堆栈所述进行。
If any of the validations fail, then the requesting node MUST drop the echo response and SHOULD log and/or report an error.
如果任何验证失败，则请求节点必须丢弃回显响应，并应记录和/或报告错误。
[RFC6425] describes how LSP ping can be used for OAM on P2MP LSPs with IP encapsulation. This MUST be supported for MPLS-TP P2MP LSPs when IP addressing is used. When IP addressing is not used, then the procedures described in Section 3.3 can be applied to P2MP MPLS-TP LSPs as well.
[RFC6425]描述了LSP ping如何用于具有IP封装的P2MP LSP上的OAM。当使用IP寻址时，MPLS-TP P2MP LSP必须支持这一点。如果不使用IP寻址，则第3.3节中描述的程序也可应用于P2MP MPLS-TP LSP。
Support for on-demand CV on a static MPLS-TP LSP or pseudowire MAY require manageable objects to allow, for instance, configuring operating parameters such as identifiers associated with the statically configured LSP or PW.
对静态MPLS-TP LSP或伪线路上的按需CV的支持可能需要可管理的对象来允许，例如，配置操作参数，例如与静态配置的LSP或PW相关联的标识符。
The specifics of this manageability requirement are out-of-scope in this document and SHOULD be addressed in appropriate management specifications.
本可管理性要求的具体内容超出了本文件的范围，应在适当的管理规范中予以说明。
At the Requester, when encapsulating the LSP echo request (LSP ping) packet (with the IP ACH, or the Non IP ACH, codepoint), a GAL MUST be added before adding the MPLS LSP label, and sending the LSP Ping echo request packet in-band in the MPLS LSP.
在请求方，当封装LSP回显请求（LSP ping）数据包（使用IP ACH或非IP ACH码点）时，必须在添加MPLS LSP标签之前添加GAL，并在MPLS LSP中的频带内发送LSP ping回显请求数据包。
The GAL MUST NOT be considered as part of the MPLS label stack that requires verification by the Responder. For this reason, a Nil FEC TLV MUST NOT be added or associated with the GAL.
GAL不得被视为需要响应者验证的MPLS标签堆栈的一部分。因此，不得添加Nil FEC TLV或将其与GAL关联。
The GAL MUST NOT be included in DSMAP or DDMAP TLVs.
GAL不得包含在DSMAP或DDMAP TLV中。
Interface and Label Stack TLVs MUST include the whole label stack including the GAL.
接口和标签堆栈TLV必须包括整个标签堆栈，包括GAL。
This section specifies how on-demand CV route tracing can be used in the context of MPLS-TP LSPs. The on-demand CV route tracing function meets the route tracing requirement specified in [RFC5860], Section 2.2.3.
本节指定如何在MPLS-TP LSP上下文中使用按需CV路由跟踪。按需CV路线跟踪功能满足[RFC5860]第2.2.3节规定的路线跟踪要求。
This function SHOULD be performed on-demand. This function SHOULD be performed between End Points and Intermediate Points of PWs and LSPs, and between End Points of PWs, LSPs and Sections.
此功能应按需执行。该功能应在PWs和LSP的端点和中间点之间以及PWs、LSP和截面的端点之间执行。
When performing on-demand CV route tracing, the requesting node inserts a Downstream Mapping TLV to get the downstream node information and to enable LSP verification along the transit nodes. The Downstream Mapping TLV can be used as is for performing route tracing. If IP addressing is not in use, then the Address Type field in the Downstream Mapping TLV can be set to "Non IP" (Section 2.1). The Downstream Mapping TLV address type field can be extended to include other address types as needed.
当执行按需CV路由跟踪时，请求节点插入下游映射TLV，以获取下游节点信息，并沿运输节点启用LSP验证。下游映射TLV可按原样用于执行路线跟踪。如果未使用IP寻址，则下游映射TLV中的地址类型字段可以设置为“非IP”（第2.1节）。下游映射TLV地址类型字段可以根据需要扩展为包括其他地址类型。
The mechanics of on-demand CV route tracing are similar to those described for ping in Section 3.1. On-demand route tracing packets sent by the Requester MUST follow procedures described in [RFC4379]. This form of on-demand CV OAM MUST be supported for MPLS-TP LSPs, when IP addressing is used.
按需CV路线跟踪的机制与第3.1节中描述的ping类似。请求者发送的按需路由跟踪数据包必须遵循[RFC4379]中描述的过程。当使用IP寻址时，MPLS-TP LSP必须支持这种形式的按需CV OAM。
This section describes procedures for performing LSP route tracing when using LSP ping with the ACH header and without any dependency on IP addressing. The procedures specified in Section 3.3 with regards to the Source Identifier TLV apply to LSP route tracing as well.
本节描述了在对ACH头使用LSP ping且不依赖于IP寻址时执行LSP路由跟踪的过程。第3.3节中规定的关于源标识符TLV的程序也适用于LSP路由跟踪。
On-demand route tracing packets sent by the Requester MUST adhere to the format described in Section 3.3. MPLS-TTL expiry (as described in [RFC4379]) will be used to direct the packets to specific nodes along the LSP path.
请求者发送的按需路由跟踪数据包必须符合第3.3节中描述的格式。MPLS-TTL到期（如[RFC4379]中所述）将用于沿着LSP路径将数据包定向到特定节点。
The on-demand CV route tracing responses will be received on the LSP itself, and the presence of an ACH header with channel type of on-demand CV is an indicator that the packet contains an on-demand CV payload.
按需CV路由跟踪响应将在LSP本身上接收，并且信道类型为按需CV的ACH报头的存在指示分组包含按需CV有效载荷。
When an echo request reaches the Responder, the presence of the ACH channel type of on-demand CV will indicate that the packet contains on-demand CV data. The on-demand CV data, the label stack, and the destination identifier are sufficient to identify the LSP associated with the echo request packet. If there is an error and the node is unable to identify the LSP on which the echo response would be sent, the node MUST drop the echo request packet and not send any response back. All responses MUST always be sent on an LSP path using the ACH header and ACH channel type of on-demand CV.
当回声请求到达响应者时，存在按需CV的ACH信道类型将指示数据包包含按需CV数据。按需CV数据、标签堆栈和目的地标识符足以识别与回声请求分组相关联的LSP。如果出现错误且节点无法识别将在其上发送回显响应的LSP，则节点必须丢弃回显请求数据包，而不将任何响应发送回。所有响应必须始终使用按需CV的ACH标头和ACH通道类型在LSP路径上发送。
[RFC6425] describes how LSP ping can be used for OAM on P2MP LSPs. This MUST be supported for MPLS-TP P2MP LSPs when IP addressing is used. When IP addressing is not used, then the procedures described in Section 4.2 can be applied to P2MP MPLS-TP LSPs as well.
[RFC6425]描述了如何将LSP ping用于P2MP LSP上的OAM。当使用IP寻址时，MPLS-TP P2MP LSP必须支持这一点。如果不使用IP寻址，则第4.2节中描述的程序也可应用于P2MP MPLS-TP LSP。
On-demand CV using ACH SHOULD NOT be used when there is ECMP (Equal Cost Multi-Path) for a given LSP. The inclusion of the additional ACH header can modify the hashing behavior for OAM packets that could result in incorrect monitoring of the path taken by data traffic.
当给定LSP存在ECMP（等成本多路径）时，不应使用使用ACH的按需CV。包含额外的ACH报头可能会修改OAM数据包的哈希行为，从而导致对数据流量所采用路径的不正确监视。
The procedures specified in this document for non-IP encapsulation apply to MPLS-TP transport paths. This includes LSPs and PWs when IP encapsulation is not desired. However, when IP addressing is used, as in non MPLS-TP LSPs, procedures specified in [RFC4379] MUST be used.
本文档中规定的非IP封装过程适用于MPLS-TP传输路径。这包括不需要IP封装时的LSP和PWs。但是，当使用IP寻址时，如在非MPLS-TP LSP中，必须使用[RFC4379]中指定的过程。
This document does not itself introduce any new security considerations. Those discussed in [RFC4379] are applicable to this document.
本文件本身没有引入任何新的安全注意事项。[RFC4379]中讨论的内容适用于本文件。
Unlike typical deployment scenarios identified in [RFC4379], however, likely deployments of on-demand CV for transport paths involves a strong possibility that the techniques in this document may be used across MPLS administrative boundaries. Where this may occur, it is RECOMMENDED that on-demand OAM is configured as necessary to ensure that Source Identifier TLVs are included in on-demand CV messages. This will allow implementations to filter OAM messages arriving from an unexpected or unknown source.
然而，与[RFC4379]中确定的典型部署场景不同，传输路径按需CV的可能部署很可能涉及跨MPLS管理边界使用本文档中的技术。如果可能发生这种情况，建议根据需要配置按需OAM，以确保按需CV消息中包含源标识符TLV。这将允许实现过滤来自意外或未知源的OAM消息。
IANA has assigned the following TLV types from the "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters" registry, "TLVs and sub-TLVs" sub-registry (from the "Standards Action" TLV type range):
IANA已从“多协议标签交换（MPLS）标签交换路径（LSP）Ping参数”注册表、“TLV和子TLV”子注册表（从“标准操作”TLV类型范围）分配了以下TLV类型：
Length
Type # TLV Name Octets Reference
------ ----------------- ------ ---------------------------
13 Source ID 8 this document (Section 2.2)
14 Destination ID 8 this document (Section 2.2)
Length
Type # TLV Name Octets Reference
------ ----------------- ------ ---------------------------
13 Source ID 8 this document (Section 2.2)
14 Destination ID 8 this document (Section 2.2)
Figure 9: New Source and Destination Identifier TLV Types
图9：新的源和目标标识符TLV类型
Section 2.3 defines 2 new sub-TLV types for inclusion within the LSP ping [RFC4379] Target FEC Stack TLV (1).
第2.3节定义了两种新的子TLV类型，以包含在LSP ping[RFC4379]目标FEC堆栈TLV（1）中。
IANA has assigned sub-type values to the following sub-TLVs from the "Multi-Protocol Label Switching Architecture (MPLS) Label Switched Paths (LSPs) Ping Parameters" registry, "TLVs and sub-TLVs" sub-registry.
IANA已从“多协议标签交换体系结构（MPLS）标签交换路径（LSP）Ping参数”注册表、“TLV和子TLV”子注册表为以下子TLV分配了子类型值。
Value Meaning Reference
----- ------------------- -----------------------------
22 Static LSP this document (Section 2.4.1)
23 Static Pseudowire this document (Section 2.4.2)
Value Meaning Reference
----- ------------------- -----------------------------
22 Static LSP this document (Section 2.4.1)
23 Static Pseudowire this document (Section 2.4.2)
Section 3.4.2 defines a new TLV type for inclusion in the LSP ping packet.
第3.4.2节定义了包含在LSP ping数据包中的新TLV类型。
IANA has assigned a type value to the TLV from the "Multi-Protocol Label Switching Architecture (MPLS) Label Switched Paths (LSPs) Ping Parameters" registry, "TLVs and sub-TLVs" sub-registry.
IANA已从“多协议标签交换体系结构（MPLS）标签交换路径（LSP）Ping参数”注册表、“TLV和子TLV”子注册表为TLV分配了一个类型值。
Type Meaning Reference
----- -------------------------- ---------------------------
16 Reverse-path Target FEC this document (Section 3.4)
Stack TLV
Type Meaning Reference
----- -------------------------- ---------------------------
16 Reverse-path Target FEC this document (Section 3.4)
Stack TLV
The sub-TLV space and assignments for this TLV will be the same as that for the Target FEC Stack TLV. Sub-types for the Target FEC Stack TLV and the Reverse-path Target FEC Stack TLV MUST be kept the same. Any new sub-type added to the Target FEC Stack TLV MUST apply to the Reverse-path Target FEC Stack TLV as well.
此TLV的子TLV空间和分配将与目标FEC堆栈TLV的子TLV空间和分配相同。目标FEC堆栈TLV和反向路径目标FEC堆栈TLV的子类型必须保持相同。添加到目标FEC堆栈TLV的任何新子类型也必须应用于反向路径目标FEC堆栈TLV。
On-demand connectivity verification requires a unique Associated Channel Type. IANA has assigned a PW ACH Type from the "Pseudowire Associated Channel Types" registry as described below:
按需连接验证需要唯一的关联通道类型。IANA已从“伪线关联通道类型”注册表中分配了PW ACH类型，如下所述：
Value Description TLV Follows Reference
------ ------------- ----------- -------------------------
0x0025 On-Demand CV No this document (Section 3)
Value Description TLV Follows Reference
------ ------------- ----------- -------------------------
0x0025 On-Demand CV No this document (Section 3)
ACH TLVs SHALL NOT be associated with this channel type.
ACH TLV不得与该通道类型相关联。
[RFC4379] defined several registries. It also defined some value assignments without explicitly asking for IANA to create a registry to support additional value assignments. One such case is in defining address types associated with the Downstream Mapping (DSMAP) TLV.
[RFC4379]定义了几个注册表。它还定义了一些值分配，而没有明确要求IANA创建一个注册表来支持额外的值分配。其中一种情况是定义与下游映射（DSMAP）TLV关联的地址类型。
This document extends RFC 4379 by defining a new address type for use with the Downstream Mapping and Downstream Detailed Mapping TLVs.
本文档通过定义一种新的地址类型来扩展RFC4379，以用于下游映射和下游详细映射TLV。
Recognizing that the absence of a registry makes it possible to have collisions of "address-type" usages, IANA has established a new registry -- associated with both [RFC4379] and this document -- that initially allocates the following assignments:
IANA认识到缺少注册表可能导致“地址类型”用法的冲突，因此建立了一个新的注册表——与[RFC4379]和本文档关联——该注册表最初分配以下分配：
Type # Address Type K Octets Reference
------ ------------ -------- --------------------------
1 IPv4 Numbered 16 RFC 4379
2 IPv4 Unnumbered 16 RFC 4379
3 IPv6 Numbered 40 RFC 4379
4 IPv6 Unnumbered 28 RFC 4379
5 Non IP 12 this document (Sect. 2.1.1)
Type # Address Type K Octets Reference
------ ------------ -------- --------------------------
1 IPv4 Numbered 16 RFC 4379
2 IPv4 Unnumbered 16 RFC 4379
3 IPv6 Numbered 40 RFC 4379
4 IPv6 Unnumbered 28 RFC 4379
5 Non IP 12 this document (Sect. 2.1.1)
Downstream Mapping Address Type Registry
下游映射地址类型注册表
Because the field in this case is an 8-bit field, the allocation policy for this registry is "Standards Action."
因为本例中的字段是8位字段，所以此注册表的分配策略是“标准操作”
The following individuals contributed materially to this document:
以下个人对本文件作出了重大贡献：
o Thomas D. Nadeau, CA Technologies
o Thomas D.Nadeau，加利福尼亚州技术部
o Nurit Sprecher, Nokia Siemens Networks
o 诺基亚西门子网络公司Nurit Sprecher
o Yaacov Weingarten, Nokia Siemens Networks
o Yaacov Weingarten，诺基亚西门子网络公司
In addition, we would like to thank the following individuals for their efforts in reviewing and commenting on the document:
此外，我们要感谢以下个人在审查和评论该文件方面所作的努力：
o Adrian Farrel
o 阿德里安·法雷尔
o Alexander Vaishtein
o 亚历山大·维什坦
o David Sinicrope (Routing Directorate)
o David Sinicrope（路由董事会）
o Greg Mirsky
o 格雷格·米尔斯基
o Hideki Endo
o 远藤秀吉
o Huub van Helvoort
o 胡布·凡·赫尔沃特
o Joel Halpern (Routing Directorate)
o Joel Halpern（路由董事会）
o Loa Andersson
o 安徒生酒店
o Mach Chen
o 陈马赫
o Mahesh Akula
o 马赫什·阿库拉
o Sam Aldrin
o 萨姆·奥尔德林
o Sandra Murphy (Security Directorate)
o 桑德拉·墨菲（安全理事会）
o Yaacov Weingarten
o 亚科夫·温加滕
o Yoshinori Koike
o 小池善纪
o Zhenlong Cui
o 崔振龙
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures", RFC 4379, February 2006.
[RFC4379]Kompella，K.和G.Swallow，“检测多协议标签交换（MPLS）数据平面故障”，RFC 4379，2006年2月。
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, February 2006.
[RFC4385]Bryant，S.，Swallow，G.，Martini，L.，和D.McPherson，“用于MPLS PSN的伪线仿真边到边（PWE3）控制字”，RFC 43852006年2月。
[RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic Associated Channel", RFC 5586, June 2009.
[RFC5586]Bocci，M.，Vigoureux，M.，和S.Bryant，“MPLS通用关联信道”，RFC 55862009年6月。
[RFC6370] Bocci, M., Swallow, G., and E. Gray, "MPLS Transport Profile (MPLS-TP) Identifiers", RFC 6370, September 2011.
[RFC6370]Bocci，M.，Swallow，G.和E.Gray，“MPLS传输配置文件（MPLS-TP）标识符”，RFC 63702011年9月。
[RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for Performing Label Switched Path Ping (LSP Ping) over MPLS Tunnels", RFC 6424, November 2011.
[RFC6424]Bahadur，N.，Kompella，K.，和G.Swallow，“在MPLS隧道上执行标签交换路径Ping（LSP Ping）的机制”，RFC 64242011年11月。
[RFC6425] Saxena, S., Swallow, G., Ali, Z., Farrel, A., Yasukawa, S., and T. Nadeau, "Detecting Data-Plane Failures in Point-to-Multipoint MPLS - Extensions to LSP Ping", RFC 6425, November 2011.
[RFC6425]Saxena，S.，Swallow，G.，Ali，Z.，Farrel，A.，Yasukawa，S.，和T.Nadeau，“检测点对多点MPLS中的数据平面故障-LSP Ping扩展”，RFC 64252011年11月。
[RFC1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1122]Braden，R.，“互联网主机的要求-通信层”，标准3，RFC 1122，1989年10月。
[RFC1812] Baker, F., "Requirements for IP Version 4 Routers", RFC 1812, June 1995.
[RFC1812]Baker，F.，“IP版本4路由器的要求”，RFC1812，1995年6月。
[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)", BCP 116, RFC 4446, April 2006.
[RFC4446]Martini，L.，“伪线边到边仿真（PWE3）的IANA分配”，BCP 116，RFC 4446，2006年4月。
[RFC5003] Metz, C., Martini, L., Balus, F., and J. Sugimoto, "Attachment Individual Identifier (AII) Types for Aggregation", RFC 5003, September 2007.
[RFC5003]Metz，C.，Martini，L.，Balus，F.，和J.Sugimoto，“聚合的附件个人标识符（AII）类型”，RFC 5003，2007年9月。
[RFC5860] Vigoureux, M., Ward, D., and M. Betts, "Requirements for Operations, Administration, and Maintenance (OAM) in MPLS Transport Networks", RFC 5860, May 2010.
[RFC5860]Vigoureux，M.，Ward，D.，和M.Betts，“MPLS传输网络中的操作、管理和维护（OAM）要求”，RFC 5860，2010年5月。
[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, "Bidirectional Forwarding Detection (BFD) for MPLS Label Switched Paths (LSPs)", RFC 5884, June 2010.
[RFC5884]Aggarwal，R.，Kompella，K.，Nadeau，T.，和G.Swallow，“MPLS标签交换路径（LSP）的双向转发检测（BFD）”，RFC 58842010年6月。
[RFC6371] Busi, I. and D. Allan, "Operations, Administration, and Maintenance Framework for MPLS-Based Transport Networks", RFC 6371, September 2011.
[RFC6371]Busi，I.和D.Allan，“基于MPLS的传输网络的运营、管理和维护框架”，RFC 6371，2011年9月。
Authors' Addresses
作者地址
Eric Gray Ericsson 900 Chelmsford Street Lowell, MA 01851 US
美国马萨诸塞州洛厄尔切姆斯福德街900号Eric Gray Ericsson 01851
Phone: +1 978 275 7470
EMail: eric.gray@ericsson.com
Phone: +1 978 275 7470
EMail: eric.gray@ericsson.com
Nitin Bahadur Juniper Networks, Inc. 1194 N. Mathilda Avenue Sunnyvale, CA 94089 US
Nitin Bahadur Juniper Networks，Inc.美国加利福尼亚州桑尼维尔马蒂尔达大道北1194号，邮编94089
Phone: +1 408 745 2000
EMail: nitinb@juniper.net
URI: www.juniper.net
Phone: +1 408 745 2000
EMail: nitinb@juniper.net
URI: www.juniper.net
Sami Boutros Cisco Systems, Inc. 3750 Cisco Way San Jose, CA 95134 US
Sami Boutros Cisco Systems，Inc.美国加利福尼亚州圣何塞市思科大道3750号，邮编95134
EMail: sboutros@cisco.com
EMail: sboutros@cisco.com
Rahul Aggarwal
拉胡尔·阿加瓦尔
EMail: raggarwa_1@yahoo.com
EMail: raggarwa_1@yahoo.com