Internet Engineering Task Force (IETF) L. Martini, Ed.
Request for Comments: 8077 G. Heron, Ed.
STD: 84 Cisco
Obsoletes: 4447, 6723 February 2017
Category: Standards Track
ISSN: 2070-1721
Internet Engineering Task Force (IETF) L. Martini, Ed.
Request for Comments: 8077 G. Heron, Ed.
STD: 84 Cisco
Obsoletes: 4447, 6723 February 2017
Category: Standards Track
ISSN: 2070-1721
Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)
使用标签分发协议（LDP）的伪线设置和维护
Abstract
摘要
Layer 2 services (such as Frame Relay, Asynchronous Transfer Mode, and Ethernet) can be emulated over an MPLS backbone by encapsulating the Layer 2 Protocol Data Units (PDUs) and then transmitting them over pseudowires (PWs). It is also possible to use pseudowires to provide low-rate Time-Division Multiplexed and Synchronous Optical NETworking circuit emulation over an MPLS-enabled network. This document specifies a protocol for establishing and maintaining the pseudowires, using extensions to the Label Distribution Protocol (LDP). Procedures for encapsulating Layer 2 PDUs are specified in other documents.
第2层服务（如帧中继、异步传输模式和以太网）可以通过封装第2层协议数据单元（PDU），然后通过伪线（PWs）传输，在MPLS主干上进行仿真。还可以使用伪线在启用MPLS的网络上提供低速率时分复用和同步光网络电路仿真。本文件规定了使用标签分发协议（LDP）扩展建立和维护伪线的协议。其他文件中规定了封装第2层PDU的程序。
This document is a rewrite of RFC 4447 for publication as an Internet Standard.
本文件是对RFC 4447的重写，以作为互联网标准发布。
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 7841.
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 7841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/rfc8077.
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/rfc8077.
Copyright Notice
版权公告
Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2017 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English.
本文件可能包含2008年11月10日之前发布或公开的IETF文件或IETF贡献中的材料。控制某些材料版权的人员可能未授予IETF信托允许在IETF标准流程之外修改此类材料的权利。在未从控制此类材料版权的人员处获得充分许可的情况下，不得在IETF标准流程之外修改本文件，也不得在IETF标准流程之外创建其衍生作品，除了将其格式化以RFC形式发布或将其翻译成英语以外的其他语言。
Table of Contents
目录
1. Introduction ....................................................4
2. Changes from RFC 4447 ...........................................6
3. Specification of Requirements ...................................6
4. The Pseudowire Label ............................................7
5. Details Specific to Particular Emulated Services ................9
5.1. IP Layer 2 Transport .......................................9
6. LDP .............................................................9
6.1. The PWid FEC Element .......................................9
6.2. The Generalized PWid FEC Element ..........................11
6.2.1. Attachment Identifiers .............................12
6.2.2. Encoding the Generalized PWid FEC Element ..........14
6.2.2.1. PW Interface Parameters TLV ...............15
6.2.2.2. PW Group ID TLV ...........................15
6.2.3. Signaling Procedures ...............................16
6.3. Signaling of Pseudowire Status ............................17
6.3.1. Use of Label Mapping Messages ......................17
6.3.2. Signaling PW Status ................................18
6.3.3. Pseudowire Status Negotiation Procedures ...........19
6.4. Interface Parameter Sub-TLV ...............................20
6.5. LDP Label Withdrawal Procedures ...........................21
7. Control Word ...................................................22
7.1. PW Types for Which the Control Word Is REQUIRED ...........22
7.2. PW Types for Which the Control Word Is NOT Mandatory ......22
7.3. Control-Word Renegotiation by Label Request Message .......24
7.4. Sequencing Considerations .................................25
7.4.1. Label Advertisements ...............................25
7.4.2. Label Release ......................................25
8. IANA Considerations ............................................26
8.1. LDP TLV TYPE ..............................................26
8.2. LDP Status Codes ..........................................26
8.3. FEC Type Name Space .......................................26
9. Security Considerations ........................................26
9.1. Data-Plane Security .......................................27
9.2. Control-Plane Security ....................................28
10. Interoperability and Deployment ...............................29
11. References ....................................................29
11.1. Normative References .....................................29
11.2. Informative References ...................................30
Acknowledgments ...................................................31
Contributors ......................................................32
Authors' Addresses ................................................35
1. Introduction ....................................................4
2. Changes from RFC 4447 ...........................................6
3. Specification of Requirements ...................................6
4. The Pseudowire Label ............................................7
5. Details Specific to Particular Emulated Services ................9
5.1. IP Layer 2 Transport .......................................9
6. LDP .............................................................9
6.1. The PWid FEC Element .......................................9
6.2. The Generalized PWid FEC Element ..........................11
6.2.1. Attachment Identifiers .............................12
6.2.2. Encoding the Generalized PWid FEC Element ..........14
6.2.2.1. PW Interface Parameters TLV ...............15
6.2.2.2. PW Group ID TLV ...........................15
6.2.3. Signaling Procedures ...............................16
6.3. Signaling of Pseudowire Status ............................17
6.3.1. Use of Label Mapping Messages ......................17
6.3.2. Signaling PW Status ................................18
6.3.3. Pseudowire Status Negotiation Procedures ...........19
6.4. Interface Parameter Sub-TLV ...............................20
6.5. LDP Label Withdrawal Procedures ...........................21
7. Control Word ...................................................22
7.1. PW Types for Which the Control Word Is REQUIRED ...........22
7.2. PW Types for Which the Control Word Is NOT Mandatory ......22
7.3. Control-Word Renegotiation by Label Request Message .......24
7.4. Sequencing Considerations .................................25
7.4.1. Label Advertisements ...............................25
7.4.2. Label Release ......................................25
8. IANA Considerations ............................................26
8.1. LDP TLV TYPE ..............................................26
8.2. LDP Status Codes ..........................................26
8.3. FEC Type Name Space .......................................26
9. Security Considerations ........................................26
9.1. Data-Plane Security .......................................27
9.2. Control-Plane Security ....................................28
10. Interoperability and Deployment ...............................29
11. References ....................................................29
11.1. Normative References .....................................29
11.2. Informative References ...................................30
Acknowledgments ...................................................31
Contributors ......................................................32
Authors' Addresses ................................................35
[RFC4619], [RFC4717], [RFC4618], and [RFC4448] explain how to encapsulate a Layer 2 Protocol Data Unit (PDU) for transmission over an MPLS-enabled network. Those documents specify that a "pseudowire header", consisting of a demultiplexer field, will be prepended to the encapsulated PDU. The pseudowire demultiplexer field is prepended before transmitting a packet on a pseudowire. When the packet arrives at the remote endpoint of the pseudowire, the demultiplexer is what enables the receiver to identify the particular pseudowire on which the packet has arrived. To transmit the packet from one pseudowire endpoint to another, the packet may need to travel through a "Packet Switched Network (PSN) tunnel"; this will require that an additional header be prepended to the packet.
[RFC4619]、[RFC4717]、[RFC4618]和[RFC4448]解释如何封装第2层协议数据单元（PDU），以便在支持MPLS的网络上传输。这些文件规定，由解复用器字段组成的“伪线报头”将在封装的PDU前添加。伪线解复用器字段在伪线上传输数据包之前预先设置。当数据包到达伪线的远程端点时，解复用器使接收器能够识别数据包到达的特定伪线。为了将分组从一个伪线端点传输到另一个伪线端点，分组可能需要通过“分组交换网络（PSN）隧道”传输；这将要求在数据包前面加一个额外的报头。
[RFC4842] and [RFC4553] specify two methods for transporting time-division multiplexing (TDM) digital signals (TDM circuit emulation) over a packet-oriented MPLS-enabled network. The transmission system for circuit-oriented TDM signals is the Synchronous Optical Network (SONET) [ANSI] / Synchronous Digital Hierarchy (SDH) [ITUG]. To support TDM traffic, which includes voice, data, and private leased-line service, the pseudowires must emulate the circuit characteristics of SONET/SDH payloads. The TDM signals and payloads are encapsulated for transmission over pseudowires. A pseudowire demultiplexer and a PSN tunnel header are prepended to this encapsulation.
[RFC4842]和[RFC4553]指定了通过面向分组的MPLS启用网络传输时分复用（TDM）数字信号（TDM电路仿真）的两种方法。面向电路的TDM信号传输系统是同步光网络（SONET）[ANSI]/同步数字体系（SDH）[ITUG]。为了支持TDM业务，包括语音、数据和专用专线服务，伪线必须模拟SONET/SDH有效负载的电路特性。TDM信号和有效载荷被封装以通过伪线传输。一个伪线解复用器和一个PSN隧道头被预先封装到这个封装中。
[RFC4553] describes methods for transporting low-rate time-division multiplexing (TDM) digital signals (TDM circuit emulation) over PSNs, while [RFC4842] similarly describes transport of high-rate TDM (SONET/SDH). To support TDM traffic, the pseudowires must emulate the circuit characteristics of the original T1, E1, T3, E3, SONET, or SDH signals. [RFC4553] does this by encapsulating an arbitrary but constant amount of the TDM data in each packet, and the other methods encapsulate TDM structures.
[RFC4553]描述了通过PSN传输低速率时分复用（TDM）数字信号（TDM电路仿真）的方法，而[RFC4842]类似地描述了高速率TDM（SONET/SDH）的传输。为了支持TDM业务，伪线必须模拟原始T1、E1、T3、E3、SONET或SDH信号的电路特性。[RFC4553]通过在每个数据包中封装任意但恒定数量的TDM数据来实现这一点，其他方法封装TDM结构。
In this document, we specify the use of the MPLS Label Distribution Protocol (LDP) [RFC5036] as a protocol for setting up and maintaining the pseudowires. In particular, we define new TLVs, Forwarding Equivalence Class (FEC) elements, parameters, and codes for LDP, which enable LDP to identify pseudowires and to signal attributes of pseudowires. We specify how a pseudowire endpoint uses these TLVs in LDP to bind a demultiplexer field value to a pseudowire and how it informs the remote endpoint of the binding. We also specify procedures for reporting pseudowire status changes, for passing additional information about the pseudowire as needed, and for releasing the bindings. These procedures are intended to be independent of the underlying version of IP used for LDP signaling.
在本文档中，我们指定使用MPLS标签分发协议（LDP）[RFC5036]作为设置和维护伪线的协议。特别是，我们为LDP定义了新的TLV、转发等价类（FEC）元素、参数和代码，使LDP能够识别伪线并向伪线的属性发送信号。我们指定伪线端点如何在LDP中使用这些TLV将解复用器字段值绑定到伪线，以及如何通知远程端点绑定。我们还指定了报告伪线状态更改、根据需要传递有关伪线的附加信息以及释放绑定的过程。这些程序旨在独立于用于LDP信令的IP的底层版本。
In the protocol specified herein, the pseudowire demultiplexer field is an MPLS label. Thus, the packets that are transmitted from one end of the pseudowire to the other are MPLS packets, which must be transmitted through an MPLS tunnel. However, if the pseudowire endpoints are immediately adjacent and penultimate hop popping behavior is in use, the MPLS tunnel may not be necessary. Any sort of PSN tunnel can be used, as long as it is possible to transmit MPLS packets through it. The PSN tunnel can itself be an MPLS LSP, or any other sort of tunnel that can carry MPLS packets. Procedures for setting up and maintaining the MPLS tunnels are outside the scope of this document.
在本文指定的协议中，伪线解复用器字段是MPLS标签。因此，从伪线的一端传输到另一端的分组是MPLS分组，必须通过MPLS隧道传输。但是，如果伪线端点紧邻并且倒数第二跳弹出行为正在使用，则可能不需要MPLS隧道。可以使用任何类型的PSN隧道，只要可以通过它传输MPLS数据包。PSN隧道本身可以是MPLS LSP，或者可以承载MPLS数据包的任何其他类型的隧道。建立和维护MPLS隧道的程序不在本文件范围内。
This document deals only with the setup and maintenance of point-to-point pseudowires. Neither point-to-multipoint nor multipoint-to-point pseudowires are discussed.
本文档仅涉及点到点伪导线的设置和维护。未讨论点对多点或多点对点伪导线。
QoS-related issues are not discussed in this document.
本文档中不讨论与QoS相关的问题。
The following two figures describe the reference models that are derived from [RFC3985] to support the PW emulated services.
以下两幅图描述了从[RFC3985]衍生的参考模型，以支持PW模拟服务。
|<-------------- Emulated Service ---------------->|
| |
| |<------- Pseudowire ------->| |
| | | |
|Attachment| |<-- PSN Tunnel -->| |Attachment|
| Circuit V V V V Circuit |
V (AC) +----+ +----+ (AC) V
+-----+ | | PE1|==================| PE2| | +-----+
| |----------|............PW1.............|----------| |
| CE1 | | | | | | | | CE2 |
| |----------|............PW2.............|----------| |
+-----+ ^ | | |==================| | | ^ +-----+
^ | +----+ +----+ | | ^
| | Provider Edge 1 Provider Edge 2 | |
| | | |
Customer | | Customer
Edge 1 | | Edge 2
| |
native service native service
|<-------------- Emulated Service ---------------->|
| |
| |<------- Pseudowire ------->| |
| | | |
|Attachment| |<-- PSN Tunnel -->| |Attachment|
| Circuit V V V V Circuit |
V (AC) +----+ +----+ (AC) V
+-----+ | | PE1|==================| PE2| | +-----+
| |----------|............PW1.............|----------| |
| CE1 | | | | | | | | CE2 |
| |----------|............PW2.............|----------| |
+-----+ ^ | | |==================| | | ^ +-----+
^ | +----+ +----+ | | ^
| | Provider Edge 1 Provider Edge 2 | |
| | | |
Customer | | Customer
Edge 1 | | Edge 2
| |
native service native service
Figure 1: PWE3 Reference Model
图1:PWE3参考模型
+-----------------+ +-----------------+
|Emulated Service | |Emulated Service |
|(e.g., TDM, ATM) |<==== Emulated Service ===>|(e.g., TDM, ATM) |
+-----------------+ +-----------------+
| Payload | | Payload |
| Encapsulation |<====== Pseudowire =======>| Encapsulation |
+-----------------+ +-----------------+
|PW Demultiplexer | |PW Demultiplexer |
| PSN Tunnel, |<======= PSN Tunnel ======>| PSN Tunnel, |
| PSN & Physical | | PSN & Physical |
| Layers | | Layers |
+-------+---------+ ___________ +---------+-------+
| / \ |
+===============/ PSN \================+
\ /
\_____________/
+-----------------+ +-----------------+
|Emulated Service | |Emulated Service |
|(e.g., TDM, ATM) |<==== Emulated Service ===>|(e.g., TDM, ATM) |
+-----------------+ +-----------------+
| Payload | | Payload |
| Encapsulation |<====== Pseudowire =======>| Encapsulation |
+-----------------+ +-----------------+
|PW Demultiplexer | |PW Demultiplexer |
| PSN Tunnel, |<======= PSN Tunnel ======>| PSN Tunnel, |
| PSN & Physical | | PSN & Physical |
| Layers | | Layers |
+-------+---------+ ___________ +---------+-------+
| / \ |
+===============/ PSN \================+
\ /
\_____________/
Figure 2: PWE3 Protocol Stack Reference Model
图2:PWE3协议栈参考模型
For the purpose of this document, PE1 (Provider Edge 1) will be defined as the ingress router, and PE2 as the egress router. A Layer 2 PDU will be received at PE1, encapsulated at PE1, transported and decapsulated at PE2, and transmitted out of PE2.
在本文件中，PE1（提供商边缘1）将被定义为入口路由器，PE2将被定义为出口路由器。第2层PDU将在PE1处接收，在PE1处封装，在PE2处传输和解封，并从PE2处传输出去。
The changes in this document are mostly minor fixes to spelling and grammar, or clarifications to the text, which were either noted as errata to [RFC4447] or found by the editors.
本文档中的更改主要是对拼写和语法的小修改，或对文本的澄清，这些修改或被标注为[RFC4447]的勘误表，或由编辑发现。
Additionally, Section 7.3 ("Control-Word Renegotiation by Label Request Message") has been added, obsoleting [RFC6723]. The diagram of C-bit handling procedures has also been removed. A note has been added in Section 6.3.2 to clarify that the C-bit is part of the FEC.
此外，增加了第7.3节（“通过标签请求消息重新协商控制字”），废除了[RFC6723]。C位处理程序图也已删除。第6.3.2节中增加了一条注释，以澄清C位是FEC的一部分。
A reference has also been added to [RFC7358] to indicate the use of downstream unsolicited mode to distribute PW FEC label bindings, independent of the negotiated label advertisement mode of the LDP session.
[RFC7358]中还添加了一个参考，以指示使用下游未经请求的模式分发PW FEC标签绑定，与LDP会话的协商标签广告模式无关。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[RFC2119]中所述进行解释。
Suppose that it is desired to transport Layer 2 PDUs from ingress LSR PE1 to egress LSR PE2, across an intervening MPLS-enabled network. We assume that there is an MPLS tunnel from PE1 to PE2. That is, we assume that PE1 can cause a packet to be delivered to PE2 by encapsulating the packet in an "MPLS tunnel header" and sending the result to one of its adjacencies. The MPLS tunnel is an MPLS Label Switched Path (LSP); thus, putting on an MPLS tunnel encapsulation is a matter of pushing on an MPLS label.
假设希望通过中间启用MPLS的网络将第2层pdu从入口LSR PE1传输到出口LSR PE2。我们假设有一个从PE1到PE2的MPLS隧道。也就是说，我们假设PE1可以通过将数据包封装在“MPLS隧道报头”中并将结果发送到其一个相邻节点，从而将数据包交付给PE2。MPLS隧道是MPLS标签交换路径（LSP）；因此，采用MPLS隧道封装是一个推动MPLS标签的问题。
We presuppose that a large number of pseudowires can be carried through a single MPLS tunnel. Thus, it is never necessary to maintain state in the network core for individual pseudowires. We do not presuppose that the MPLS tunnels are point to point; although the pseudowires are point to point, the MPLS tunnels may be multipoint to point. We do not presuppose that PE2 will even be able to determine the MPLS tunnel through which a received packet was transmitted. (For example, if the MPLS tunnel is an LSP and penultimate hop popping is used, when the packet arrives at PE2, it will contain no information identifying the tunnel.)
我们假设大量的伪线可以通过单个MPLS隧道传输。因此，不需要为单个伪线维护网络核心中的状态。我们不假定MPLS隧道是点对点的；尽管伪线是点对点的，但MPLS隧道可能是多点对点的。我们并不假定PE2甚至能够确定接收到的数据包通过的MPLS隧道。（例如，如果MPLS隧道是LSP，并且使用倒数第二跳弹出，当数据包到达PE2时，它将不包含识别隧道的信息。）
When PE2 receives a packet over a pseudowire, it must be able to determine that the packet was in fact received over a pseudowire, and it must be able to associate that packet with a particular pseudowire. PE2 is able to do this by examining the MPLS label that serves as the pseudowire demultiplexer field shown in Figure 2. Call this label the "PW label".
当PE2通过伪线接收数据包时，它必须能够确定该数据包实际上是通过伪线接收的，并且它必须能够将该数据包与特定的伪线相关联。PE2可以通过检查MPLS标签来做到这一点，该标签用作图2所示的伪线解复用器字段。将此标签称为“PW标签”。
When PE1 sends a Layer 2 PDU to PE2, it creates an MPLS packet by adding the PW label to the packet, thus creating the first entry of the label stack. If the PSN tunnel is an MPLS LSP, the PE1 pushes another label (the tunnel label) onto the packet as the second entry of the label stack. The PW label is not visible again until the MPLS packet reaches PE2. PE2's disposition of the packet is based on the PW label.
当PE1向PE2发送第2层PDU时，它通过向数据包添加PW标签来创建MPLS数据包，从而创建标签堆栈的第一个条目。如果PSN隧道是MPLS LSP，则PE1将另一个标签（隧道标签）推送到数据包上，作为标签堆栈的第二个条目。直到MPLS数据包到达PE2，PW标签才再次可见。PE2对数据包的处理基于PW标签。
If the payload of the MPLS packet is, for example, an ATM Adaptation Layer 5 (AAL5) PDU, the PW label will generally correspond to a particular ATM Virtual Circuit (VC) at PE2. That is, PE2 needs to be able to infer from the PW label the outgoing interface and the VPI/VCI (Virtual Path Identifier / Virtual Circuit Identifier) value for the AAL5 PDU. If the payload is a Frame Relay PDU, then PE2 needs to be able to infer from the PW label the outgoing interface and the Data Link Connection Identifier (DLCI) value. If the payload is an Ethernet frame, then PE2 needs to be able to infer from the PW label the outgoing interface, and perhaps the VLAN identifier. This process is unidirectional and will be repeated independently for
如果MPLS分组的有效载荷例如是ATM适配层5（AAL5）PDU，则PW标签通常对应于PE2处的特定ATM虚拟电路（VC）。也就是说，PE2需要能够从PW标签推断AAL5 PDU的输出接口和VPI/VCI（虚拟路径标识符/虚拟电路标识符）值。如果有效载荷是帧中继PDU，则PE2需要能够从PW标签推断出输出接口和数据链路连接标识符（DLCI）值。如果有效负载是以太网帧，那么PE2需要能够从PW标签推断出输出接口，可能还有VLAN标识符。此过程是单向的，将独立重复一次
bidirectional operation. When using the PWid FEC Element, it is REQUIRED that the same PW ID and PW type be assigned for a given circuit in both directions. The Group ID (see below) MUST NOT be required to match in both directions. The transported frame MAY be modified when it reaches the egress router. If the header of the transported Layer 2 frame is modified, this MUST be done at the egress LSR only. Note that the PW label must always be at the bottom of the packet's label stack, and labels MUST be allocated from the per-platform label space.
双向操作。使用PWid FEC元件时，要求在两个方向上为给定电路指定相同的PW ID和PW类型。组ID（见下文）不必在两个方向上都匹配。传输的帧可以在到达出口路由器时被修改。如果传输的第2层帧的报头被修改，则这必须仅在出口LSR处完成。请注意，PW标签必须始终位于数据包标签堆栈的底部，并且必须从每个平台标签空间分配标签。
This document does not specify a method for distributing the MPLS tunnel label or any other labels that may appear above the PW label on the stack. Any acceptable method of MPLS label distribution will do. This document specifies a protocol for assigning and distributing the PW label. This protocol is LDP, extended as specified in the remainder of this document. An LDP session must be set up between the pseudowire endpoints. LDP MUST exchange PW FEC label bindings in downstream unsolicited mode, independent of the negotiated label advertisement mode of the LDP session according to the specifications in [RFC7358]. LDP's "liberal label retention" mode SHOULD be used. However, all the LDP procedures that are specified in [RFC5036] and that are also applicable to this protocol specification MUST be implemented.
本文档未指定分发MPLS隧道标签或可能出现在堆栈上PW标签上方的任何其他标签的方法。任何可接受的MPLS标签分发方法都可以。本文件规定了分配和分发PW标签的协议。本协议为LDP协议，按照本文件其余部分的规定进行扩展。必须在伪线端点之间设置LDP会话。根据[RFC7358]中的规范，LDP必须在下游非请求模式下交换PW FEC标签绑定，独立于LDP会话的协商标签广告模式。应使用LDP的“自由标签保留”模式。但是，必须执行[RFC5036]中规定的以及也适用于本协议规范的所有LDP程序。
This document requires that a receiving LSR MUST respond to a Label Request message with either a Label Mapping for the requested label or a Notification message that indicates why it cannot satisfy the request. These procedures are specified in [RFC5036], Sections 3.5.7 ("Label Mapping Message") and 3.5.8 ("Label Request Message"). Note that sending these responses is a stricter requirement than is specified in [RFC5036], but these response messages are REQUIRED to ensure correct operation of this protocol.
本文档要求接收LSR必须使用所请求标签的标签映射或指示其无法满足请求原因的通知消息来响应标签请求消息。[RFC5036]第3.5.7节（“标签映射消息”）和第3.5.8节（“标签请求消息”）中规定了这些程序。请注意，发送这些响应的要求比[RFC5036]中规定的更严格，但需要这些响应消息来确保该协议的正确运行。
In addition to the protocol specified herein, static assignment of PW labels may be used, and implementations of this protocol SHOULD provide support for static assignment. PW encapsulation is always symmetrical in both directions of traffic along a specific PW, whether or not the PW uses an LDP control plane.
除了本文指定的协议外，还可以使用PW标签的静态分配，并且该协议的实现应提供对静态分配的支持。无论PW是否使用LDP控制平面，PW封装始终在特定PW的两个通信量方向上对称。
This document specifies all the procedures necessary to set up and maintain the pseudowires needed to support "unswitched" point-to-point services, where each endpoint of the pseudowire is provisioned with the identity of the other endpoint. There are also protocol mechanisms specified herein that can be used to support switched services and other provisioning models. However, the use of the protocol mechanisms to support those other models and services is not described in this document.
本文档规定了设置和维护支持“无开关”点到点服务所需的伪线所需的所有过程，其中伪线的每个端点都提供了另一个端点的标识。这里还指定了一些协议机制，可用于支持交换服务和其他供应模型。但是，本文档中没有描述使用协议机制来支持这些其他模型和服务。
This mode carries IP packets over a pseudowire. The encapsulation used is according to [RFC3032]. The PW control word MAY be inserted between the MPLS label stack and the IP payload. The encapsulation of the IP packets for forwarding on the Attachment Circuit is implementation specific, is part of the native service processing (NSP) function [RFC3985], and is outside the scope of this document.
此模式通过伪线传输IP数据包。使用的封装符合[RFC3032]。PW控制字可以插入MPLS标签堆栈和IP有效负载之间。用于在连接电路上转发的IP数据包的封装是特定于实现的，是本机服务处理（NSP）功能[RFC3985]的一部分，不在本文档的范围内。
The PW label bindings are distributed using the LDP downstream unsolicited mode described in [RFC5036]. The PEs will establish an LDP session using the Extended Discovery mechanism described in Sections 2.4.2 and 2.5 of [RFC5036].
PW标签绑定使用[RFC5036]中所述的LDP下游非请求模式分发。PEs将使用[RFC5036]第2.4.2和2.5节所述的扩展发现机制建立LDP会话。
An LDP Label Mapping message contains a FEC TLV, a Label TLV, and zero or more optional parameter TLVs.
LDP标签映射消息包含FEC TLV、标签TLV和零个或多个可选参数TLV。
The FEC TLV is used to indicate the meaning of the label. In the current context, the FEC TLV would be used to identify the particular pseudowire that a particular label is bound to. In this specification, we define two new FEC TLVs to be used for identifying pseudowires. When setting up a particular pseudowire, only one of these FEC TLVs is used. The one to be used will depend on the particular service being emulated and on the particular provisioning model being supported.
FEC TLV用于指示标签的含义。在当前上下文中，FEC TLV将用于识别特定标签绑定到的特定伪线。在本规范中，我们定义了两个新的FEC TLV，用于识别伪线。设置特定伪线时，仅使用其中一个FEC TLV。要使用的配置取决于所模拟的特定服务和所支持的特定配置模型。
LDP allows each FEC TLV to consist of a set of FEC elements. For setting up and maintaining pseudowires, however, each FEC TLV MUST contain exactly one FEC element.
LDP允许每个FEC TLV由一组FEC元素组成。但是，为了设置和维护伪线，每个FEC TLV必须仅包含一个FEC元素。
The LDP base specification has several kinds of label TLVs, including the Generic Label TLV, as specified in Section 3.4.2.1 of [RFC5036]. For setting up and maintaining pseudowires, the Generic Label TLV MUST be used.
LDP基本规范有几种标签TLV，包括[RFC5036]第3.4.2.1节中规定的通用标签TLV。为了设置和维护伪导线，必须使用通用标签TLV。
The PWid FEC Element may be used whenever both pseudowire endpoints have been provisioned with the same 32-bit identifier for the pseudowire.
只要为两个伪线端点提供了相同的伪线32位标识符，就可以使用PWid FEC元素。
For this purpose, a new type of FEC element is defined. The FEC element type is 0x80 and is defined as follows:
为此，定义了一种新型FEC元件。FEC元素类型为0x80，定义如下：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PWid (0x80) |C| PW type |PW info length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PW ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface Parameter Sub-TLV |
| " |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PWid (0x80) |C| PW type |PW info length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PW ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface Parameter Sub-TLV |
| " |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- Control word bit (C)
- 控制字位（C）
The C-bit is used to flag the presence of a control word as follows:
C位用于标记控制字的存在，如下所示：
C = 1 control word present on this PW. C = 0 no control word present on this PW.
C=此PW上存在1个控制字。C=0此PW上不存在控制字。
Please see Section 7 ("Control Word") for further explanation.
请参阅第7节（“控制词”）了解更多解释。
- PW type
- PW型
A 15-bit quantity containing a value that represents the type of PW. Assigned Values are specified in "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)" [RFC4446].
包含代表PW类型的值的15位量。指定的值在“用于伪线边到边仿真（PWE3）的IANA分配”[RFC4446]中指定。
- PW info length
- PW信息长度
Length of the PW ID field and the Interface Parameter Sub-TLV field in octets. If this value is 0, then it references all PWs using the specified Group ID, and there is no PW ID present, nor are there any Interface Parameter Sub-TLVs.
PW ID字段和接口参数Sub TLV字段的长度（以八位字节为单位）。如果此值为0，则它使用指定的组ID引用所有PW，并且不存在PW ID，也不存在任何接口参数子TLV。
- Group ID
- 组ID
An arbitrary 32-bit value that represents a group of PWs that is used to create groups in the PW space. The Group ID is intended to be used as a port index or a virtual tunnel index. To simplify configuration, a particular PW Group ID at ingress could be part of a Group ID assigned to the virtual tunnel for transport to the egress router. The Group ID is very useful for sending wildcard label withdrawals or PW wildcard status Notification messages to remote PEs upon physical port failure.
表示用于在PW空间中创建组的PW组的任意32位值。组ID将用作端口索引或虚拟隧道索引。为了简化配置，入口处的特定PW组ID可以是分配给虚拟隧道以传输到出口路由器的组ID的一部分。组ID对于在物理端口出现故障时向远程PE发送通配符标签撤销或PW通配符状态通知消息非常有用。
- PW ID
- PW ID
A non-zero, 32-bit connection ID that together with the PW type identifies a particular PW. Note that the PW ID and the PW type MUST be the same at both endpoints.
与PW类型一起标识特定PW的非零32位连接ID。请注意，两个端点上的PW ID和PW类型必须相同。
- Interface Parameter Sub-TLV
- 接口参数子TLV
This variable length TLV is used to provide interface-specific parameters, such as Attachment Circuit MTU.
该可变长度TLV用于提供接口特定参数，如连接电路MTU。
Note that as the Interface Parameter Sub-TLV is part of the FEC, the rules of LDP make it impossible to change the interface parameters once the pseudowire has been set up. Thus, the interface parameters field must not be used to pass information, such as status information, that may change during the life of the pseudowire. Optional parameter TLVs should be used for that purpose.
注意，由于接口参数Sub-TLV是FEC的一部分，LDP的规则使得一旦建立了伪线，就不可能更改接口参数。因此，接口参数字段不得用于传递在伪线寿命期间可能更改的信息，如状态信息。为此，应使用可选参数TLV。
Using the PWid FEC, each of the two pseudowire endpoints independently initiates the setup of a unidirectional LSP. An outgoing LSP and an incoming LSP are bound together into a single pseudowire if they have the same PW ID and PW type.
使用PWid FEC，两个伪线端点中的每一个独立地启动单向LSP的设置。如果输出LSP和输入LSP具有相同的PW ID和PW类型，则将它们绑定到单个伪线中。
The PWid FEC Element can be used if a unique 32-bit value has been assigned to the PW and if each endpoint has been provisioned with that value. The Generalized PWid FEC Element requires that the PW endpoints be uniquely identified; the PW itself is identified as a pair of endpoints. In addition, the endpoint identifiers are structured to support applications where the identity of the remote endpoints needs to be auto-discovered rather than statically configured.
如果为PW分配了唯一的32位值，并且每个端点都配置了该值，则可以使用PWid FEC元素。广义PWid FEC元素要求PW端点唯一标识；PW本身被标识为一对端点。此外，端点标识符的结构支持需要自动发现而不是静态配置远程端点标识的应用程序。
The "Generalized PWid FEC Element" is FEC type 0x81.
“通用PWid FEC元素”是FEC类型0x81。
The Generalized PWid FEC Element does not contain anything corresponding to the Group ID of the PWid FEC Element. The functionality of the Group ID is provided by a separate optional LDP TLV, the PW Group ID TLV, described in Section 6.2.2.2. The interface parameters field of the PWid FEC Element is also absent; its functionality is replaced by the optional PW Interface Parameters TLV, described in Section 6.2.2.1.
广义PWid FEC元素不包含与PWid FEC元素的组ID对应的任何内容。组ID的功能由单独的可选LDP TLV（PW组ID TLV）提供，如第6.2.2.2节所述。PWid FEC元件的接口参数字段也不存在；其功能由第6.2.2.1节所述的可选PW接口参数TLV替代。
As discussed in [RFC3985], a pseudowire can be thought of as connecting two "forwarders". The protocol used to set up a pseudowire must allow the forwarder at one end of a pseudowire to identify the forwarder at the other end. We use the term "Attachment Identifier", or "AI", to refer to the field that the protocol uses to identify the forwarders. In the PWid FEC, the PWid field serves as the AI. In this section, we specify a more general form of AI that is structured and of variable length.
如[RFC3985]中所述，可以将伪线视为连接两个“转发器”。用于设置伪线的协议必须允许伪线一端的转发器识别另一端的转发器。我们使用术语“附件标识符”或“AI”来指代协议用于识别转发器的字段。在PWid FEC中，PWid字段用作AI。在本节中，我们将指定一种更通用的AI形式，它是结构化的，长度可变。
Every Forwarder in a PE must be associated with an Attachment Identifier (AI), either through configuration or through some algorithm. The Attachment Identifier must be unique in the context of the PE router in which the Forwarder resides. The combination <PE router IP address, AI> must be globally unique.
PE中的每个转发器必须通过配置或某种算法与附件标识符（AI）相关联。附件标识符在转发器所在的PE路由器的上下文中必须是唯一的。组合<PE路由器IP地址，AI>必须是全局唯一的。
It is frequently convenient to regard a set of Forwarders as being members of a particular "group", where PWs may only be set up among members of a group. In such cases, it is convenient to identify the Forwarders relative to the group, so that an Attachment Identifier would consist of an Attachment Group Identifier (AGI) plus an Attachment Individual Identifier (AII).
将一组货代视为特定“集团”的成员通常是方便的，其中PWs只能在集团成员之间建立。在这种情况下，相对于组识别转发器是方便的，因此附件标识符将由附件组标识符（AGI）加上附件个人标识符（AII）组成。
An Attachment Group Identifier may be thought of as a VPN-id, or a VLAN identifier, some attribute that is shared by all the Attachment PWs (or pools thereof) that are allowed to be connected.
附件组标识符可以被认为是VPN id或VLAN标识符，是允许连接的所有附件PW（或其池）共享的某个属性。
The details of how to construct the AGI and AII fields identifying the pseudowire endpoints are outside the scope of this specification. Different pseudowire applications, and different provisioning models, will require different sorts of AGI and AII fields. The specification of each such application and/or model must include the rules for constructing the AGI and AII fields.
如何构造标识伪线端点的AGI和AII字段的详细信息不在本规范的范围内。不同的伪线应用程序和不同的资源调配模型将需要不同种类的AGI和AII字段。每个此类应用程序和/或模型的规范必须包括构造AGI和AII字段的规则。
As previously discussed, a (bidirectional) pseudowire consists of a pair of unidirectional LSPs, one in each direction. If a particular pseudowire connects PE1 with PE2, the PW direction from PE1 to PE2 can be identified as:
如前所述，（双向）伪线由一对单向LSP组成，每个方向一个。如果特定的伪线连接PE1和PE2，则从PE1到PE2的PW方向可识别为：
<PE1, <AGI, AII1>, PE2, <AGI, AII2>>,
<PE1，<AGI，AII1>，PE2，<AGI，AII2>，
and the PW direction from PE2 to PE1 can be identified by:
从PE2到PE1的PW方向可通过以下方式识别：
<PE2, <AGI, AII2>, PE1, <AGI, AII1>>.
<PE2，<AGI，AII2>，PE1，<AGI，AII1>。
Note that the AGI must be the same at both endpoints, but the AII will in general be different at each endpoint. Thus, from the perspective of a particular PE, each pseudowire has a local or "Source AII", and a remote or "Target AII". The pseudowire setup protocol can carry all three of these quantities:
请注意，两个端点的AGI必须相同，但每个端点的AII通常不同。因此，从特定PE的角度来看，每个伪线具有本地或“源AII”和远程或“目标AII”。伪线设置协议可以承载以下三个数量：
- Attachment Group Identifier (AGI)
- 附件组标识符（AGI）
- Source Attachment Individual Identifier (SAII)
- 源附件个人标识符（SAII）
- Target Attachment Individual Identifier (TAII)
- 目标附件个人标识符（TAII）
If the AGI is non-null, then the Source AI (SAI) consists of the AGI together with the SAII, and the Target AI (TAI) consists of the TAII together with the AGI. If the AGI is null, then the SAII and TAII are the SAI and TAI, respectively.
如果AGI不为空，则源AI（SAI）由AGI和SAI组成，目标AI（TAI）由TAI和AGI组成。如果AGI为空，则SAII和TAII分别为SAI和TAI。
The interpretation of the SAI and TAI is a local matter at the respective endpoint.
SAI和TAI的解释是各自端点的本地事务。
The association of two unidirectional LSPs into a single bidirectional pseudowire depends on the SAI and the TAI. Each application and/or provisioning model that uses the Generalized PWid FEC must specify the rules for performing this association.
将两个单向LSP关联为单个双向伪线取决于SAI和TAI。使用通用PWid FEC的每个应用程序和/或供应模型必须指定执行此关联的规则。
FEC element type 0x81 is used. The FEC element is encoded as follows:
使用了类型为0x81的FEC元件。FEC元素编码如下：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Gen PWid (0x81)|C| PW Type |PW info length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AGI Type | Length | Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ AGI Value (contd.) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AII Type | Length | Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ SAII Value (contd.) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AII Type | Length | Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ TAII Value (contd.) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Gen PWid (0x81)|C| PW Type |PW info length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AGI Type | Length | Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ AGI Value (contd.) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AII Type | Length | Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ SAII Value (contd.) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AII Type | Length | Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ TAII Value (contd.) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This document does not specify the AII and AGI type field values; specification of the type field values to be used for a particular application is part of the specification of that application. IANA has assigned these values using the method defined in [RFC4446].
本文件未规定AII和AGI类型字段值；用于特定应用程序的类型字段值的规范是该应用程序规范的一部分。IANA已使用[RFC4446]中定义的方法分配这些值。
The SAII, TAII, and AGI are simply carried as octet strings. The Length byte specifies the size of the Value field. The null string can be sent by setting the Length byte to 0. If a particular application does not need all three of these sub-elements, it MUST send all the sub-elements but set the Length to 0 for the unused sub-elements.
SAII、TAII和AGI仅作为八位字节字符串携带。长度字节指定值字段的大小。通过将长度字节设置为0，可以发送空字符串。如果一个特定的应用程序不需要所有这三个子元素，它必须发送所有的子元素，但是对于未使用的子元素，将长度设置为0。
The PW information length field contains the length of the SAII, TAII, and AGI, combined in octets. If this value is 0, then it references all PWs using the specific Group ID (specified in the PW Group ID TLV). In this case, there are no other FEC element fields (AGI, SAII, etc.) present, nor any PW Interface Parameters TLVs.
PW信息长度字段包含SAII、TAII和AGI的长度，以八位字节组合。如果该值为0，则它使用特定组ID（在PW组ID TLV中指定）引用所有PW。在这种情况下，不存在其他FEC元素字段（AGI、SAII等），也不存在任何PW接口参数TLV。
Note that the interpretation of a particular field as AGI, SAII, or TAII depends on the order of its occurrence. The Type field identifies the type of the AGI, SAII, or TAII. When comparing two
请注意，将特定字段解释为AGI、SAII或TAII取决于其出现的顺序。类型字段标识AGI、SAII或TAII的类型。比较两个
occurrences of an AGI (or SAII or TAII), the two occurrences are considered identical if the Type, Length, and Value fields of one are identical, respectively, to those of the other.
AGI（或SAII或TAII）的出现，如果一个出现的类型、长度和值字段分别与另一个出现的类型、长度和值字段相同，则认为这两个出现相同。
This TLV MUST only be used when sending the Generalized PWid FEC. It specifies interface-specific parameters. Specific parameters, when applicable, MUST be used to validate that the PEs and the ingress and egress ports at the edges of the circuit have the necessary capabilities to interoperate with each other.
此TLV只能在发送通用PWid FEC时使用。它指定特定于接口的参数。如果适用，必须使用特定参数验证PEs和电路边缘的入口和出口端口是否具有相互互操作的必要能力。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| PW Intf P. TLV (0x096B) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLV Type | Length | Variable Length Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Length Value |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| PW Intf P. TLV (0x096B) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLV Type | Length | Variable Length Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Length Value |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A more detailed description of this field can be found in Section 6.4 ("Interface Parameter Sub-TLV").
有关该字段的更详细说明，请参见第6.4节（“接口参数子TLV”）。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| PW Group ID TLV (0x096C) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| PW Group ID TLV (0x096C) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The PW Group ID is an arbitrary 32-bit value that represents an arbitrary group of PWs. It is used to create group PWs; for example, a PW Group ID can be used as a port index and assigned to all PWs that lead to that port. Use of the PW Group ID enables a PE to send "wildcard" label withdrawals, or "wildcard" status Notification messages, to remote PEs upon physical port failure.
PW组ID是表示任意PW组的任意32位值。用于创建组PWs；例如，PW组ID可用作端口索引，并分配给通向该端口的所有PW。使用PW组ID使PE能够在物理端口出现故障时向远程PE发送“通配符”标签撤回或“通配符”状态通知消息。
Note Well: The PW Group ID is different from and has no relation to the Attachment Group Identifier.
请注意：PW组ID与附件组标识符不同，并且与附件组标识符没有关系。
The PW Group ID TLV is not part of the FEC and will not be advertised except in the PW FEC advertisement. The advertising PE MAY use the wildcard withdraw semantics, but the remote PEs MUST implement support for wildcard messages. This TLV MUST only be used when sending the Generalized PWid FEC.
PW组ID TLV不是FEC的一部分，除非在PW FEC广告中，否则不会进行广告。广告PE可以使用通配符收回语义，但远程PE必须实现对通配符消息的支持。此TLV只能在发送通用PWid FEC时使用。
To issue a wildcard command (status or withdraw):
要发出通配符命令（状态或撤消），请执行以下操作：
- Set the PW Info Length to 0 in the Generalized PWid FEC Element.
- 在广义PWid FEC元素中将PW Info长度设置为0。
- Send only the PW Group ID TLV with the FEC (no AGI/SAII/TAII is sent).
- 仅发送带有FEC的PW组ID TLV（不发送AGI/SAII/TAII）。
In order for PE1 to begin signaling PE2, PE1 must know the address of the remote PE2 and a TAI. This information may have been configured at PE1, or it may have been learned dynamically via some auto-discovery procedure.
为了让PE1开始向PE2发送信令，PE1必须知道远程PE2和TAI的地址。此信息可能已在PE1中配置，也可能已通过某些自动发现过程动态学习。
The egress PE (PE1), which has knowledge of the ingress PE, initiates the setup by sending a Label Mapping message to the ingress PE (PE2). The Label Mapping message contains the FEC TLV, carrying the Generalized PWid FEC Element (type 0x81). The Generalized PWid FEC Element contains the AGI, SAII, and TAII information.
知道入口PE的出口PE（PE1）通过向入口PE（PE2）发送标签映射消息来启动设置。标签映射消息包含FEC TLV，携带通用PWid FEC元素（类型0x81）。广义PWid FEC元素包含AGI、SAII和TAII信息。
Next, when PE2 receives such a Label Mapping message, PE2 interprets the message as a request to set up a PW whose endpoint (at PE2) is the Forwarder identified by the TAI. From the perspective of the signaling protocol, exactly how PE2 maps AIs to Forwarders is a local matter. In some Virtual Private Wire Service (VPWS) provisioning models, the TAI might, for example, be a string that identifies a particular Attachment Circuit, such as "ATM3VPI4VCI5", or it might, for example, be a string, such as "Fred", that is associated by configuration with a particular Attachment Circuit. In Virtual Private LAN Service (VPLS), the AGI could be a VPN-id, identifying a particular VPLS instance.
接下来，当PE2接收到这样的标签映射消息时，PE2将该消息解释为建立其端点（在PE2处）为TAI识别的转发器的PW的请求。从信令协议的角度来看，PE2如何将AIs映射到转发器是一个局部问题。在一些虚拟专用线服务（VPWS）供应模型中，TAI可以是例如标识特定连接电路的字符串，例如“ATM3VPI4VCI5”，或者它可以是例如通过配置与特定连接电路相关联的字符串，例如“Fred”。在虚拟专用LAN服务（VPLS）中，AGI可以是一个VPN id，用于标识特定的VPLS实例。
If PE2 cannot map the TAI to one of its Forwarders, then PE2 sends a Label Release message to PE1, with a Status Code of "Unassigned/Unrecognized TAI", and the processing of the Label Mapping message is complete.
如果PE2无法将TAI映射到其一个转发器，则PE2向PE1发送标签发布消息，状态代码为“未分配/未识别TAI”，标签映射消息的处理完成。
The FEC TLV sent in a Label Release message is the same as the FEC TLV received in the Label Mapping message being released (but without the interface parameter TLV). More generally, the FEC TLV is the
标签发布消息中发送的FEC TLV与正在发布的标签映射消息中接收的FEC TLV相同（但不带接口参数TLV）。更一般地说，FEC TLV是
same in all LDP messages relating to the same PW. In a Label Release message, this means that the SAII is the remote peer's AII and the TAII is the sender's local AII.
在与同一PW相关的所有LDP消息中相同。在标签发布消息中，这意味着SAII是远程对等方的AII，TAII是发送方的本地AII。
If the Label Mapping message has a valid TAI, PE2 must decide whether to accept it. The procedures for so deciding will depend on the particular type of Forwarder identified by the TAI. Of course, the Label Mapping message may be rejected due to standard LDP error conditions as detailed in [RFC5036].
如果标签映射消息具有有效的TAI，PE2必须决定是否接受它。决定的程序将取决于TAI确定的特定类型的货运代理。当然，由于[RFC5036]中详述的标准LDP错误条件，标签映射消息可能会被拒绝。
If PE2 decides to accept the Label Mapping message, then it has to make sure that a PW LSP is set up in the opposite (PE1-->PE2) direction. If it has already signaled for the corresponding PW LSP in that direction, nothing more needs to be done. Otherwise, it must initiate such signaling by sending a Label Mapping message to PE1. This is very similar to the Label Mapping message PE2 received, but the SAI and TAI are reversed.
如果PE2决定接受标签映射消息，则必须确保在相反（PE1-->PE2）方向设置PW LSP。如果它已经向该方向发出了相应PW LSP的信号，则无需执行更多操作。否则，它必须通过向PE1发送标签映射消息来启动此类信令。这与收到的标签映射消息PE2非常相似，但SAI和TAI相反。
Thus, a bidirectional PW consists of two LSPs, where the FEC of one has the SAII and TAII reversed with respect to the FEC of the other.
因此，双向PW由两个lsp组成，其中一个的FEC相对于另一个的FEC具有反转的SAII和TAII。
The PEs MUST send Label Mapping messages to their peers as soon as the PW is configured and administratively enabled, regardless of the Attachment Circuit state. The PW label should not be withdrawn unless the operator administratively configures the pseudowire down (or the PW configuration is deleted entirely). Using the procedures outlined in this section, a simple label withdraw method MAY also be supported as a legacy means of signaling PW status and AC status. In any case, if the label-to-PW binding is not available, the PW MUST be considered in the down state.
配置PW并启用管理功能后，PEs必须立即向其对等方发送标签映射消息，无论附件电路状态如何。除非操作员管理性地配置了伪导线（或完全删除了PW配置），否则不应撤销PW标签。使用本节中概述的程序，也可以支持简单的标签提取方法，作为发送PW状态和AC状态信号的传统方法。在任何情况下，如果标签到PW绑定不可用，则必须考虑PW处于关闭状态。
Once the PW status negotiation procedures are completed, if they result in the use of the label withdraw method for PW status communication, and this method is not supported by one of the PEs, then that PE must send a Label Release message to its peer with the following error:
一旦完成PW状态协商程序，如果它们导致使用标签撤销方法进行PW状态通信，并且其中一个PE不支持该方法，则该PE必须向其对等方发送标签释放消息，错误如下：
"Label Withdraw PW Status Method Not Supported"
“不支持标签撤消PW状态方法”
If the label withdraw method for PW status communication is selected for the PW, it will result in the Label Mapping message being advertised only if the Attachment Circuit is active. The PW status signaling procedures described in this section MUST be fully implemented.
如果为PW选择了PW状态通信的标签提取方法，则仅当连接电路激活时，才会显示标签映射消息。必须完全执行本节中描述的PW状态信号程序。
The PE devices use an LDP TLV to indicate status to their remote peers. This PW Status TLV contains more information than the alternative simple Label Withdraw message.
PE设备使用LDP TLV向其远程对等方指示状态。此PW Status TLV包含的信息比备用简单标签撤销消息更多。
The format of the PW Status TLV is:
PW状态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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0| PW Status (0x096A) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0| PW Status (0x096A) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The status code is a 4-octet bit field as specified in "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)" [RFC4446]. The Length field specifies the length of the Status Code field in octets (equal to 4).
状态代码是“用于伪线边到边仿真（PWE3）的IANA分配”中指定的4个八位字段[RFC4446]。长度字段以八位字节（等于4）指定状态代码字段的长度。
Each bit in the Status Code field can be set individually to indicate more than a single failure at once. Each fault can be cleared by sending an appropriate Notification message in which the respective bit is cleared. The presence of the lowest bit (PW Not Forwarding) acts only as a generic failure indication when there is a link-down event for which none of the other bits apply.
可以单独设置状态代码字段中的每个位，以一次指示多个故障。每个故障都可以通过发送相应的通知消息来清除，其中相应的位被清除。最低位（PW不转发）的存在仅在存在其他位均不适用的链路断开事件时作为一般故障指示。
The Status TLV is transported to the remote PW peer via the LDP Notification message as described in [RFC5036]. The format of the Notification message for carrying the PW Status is as follows:
状态TLV通过LDP通知消息传输到远程PW对等方，如[RFC5036]所述。携带PW状态的通知消息格式如下：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Notification (0x0001) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status (TLV) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PW Status TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PWid FEC TLV or Generalized ID FEC TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PW Group ID TLV (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Notification (0x0001) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status (TLV) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PW Status TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PWid FEC TLV or Generalized ID FEC TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PW Group ID TLV (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Status TLV status code is set to 0x00000028, "PW status", to indicate that PW status follows. Since this notification does not refer to any particular message, the Message ID field is set to 0.
状态TLV状态代码设置为0x00000028“PW状态”，以指示PW状态如下。由于此通知不引用任何特定消息，因此消息ID字段设置为0。
The PW FEC TLV SHOULD NOT include the Interface Parameter Sub-TLVs, as they are ignored in the context of this message. However, the PW FEC TLV MUST include the C-bit, where applicable, as it is part of the FEC. When a PE's Attachment Circuit encounters an error, use of the PW Notification message allows the PE to send a single "wildcard" status message, using a PW FEC TLV with only the Group ID set, to denote this change in status for all affected PW connections. This status message contains either the PW FEC TLV with only the Group ID set, or else it contains the Generalized FEC TLV with only the PW Group ID TLV.
PW FEC TLV不应包括接口参数Sub TLV，因为在此消息上下文中它们被忽略。然而，PW FEC TLV必须包括C位（如适用），因为它是FEC的一部分。当PE的连接电路遇到错误时，使用PW通知消息允许PE使用仅设置了组ID的PW FEC TLV发送单个“通配符”状态消息，以表示所有受影响PW连接的状态变化。此状态消息包含仅设置了组ID的PW FEC TLV，或者包含仅设置了PW组ID TLV的通用FEC TLV。
As mentioned above, the Group ID field of the PWid FEC Element, or the PW Group ID TLV used with the Generalized PWid FEC Element, can be used to send a status notification for all arbitrary sets of PWs. This procedure is OPTIONAL, and if it is implemented, the LDP Notification message should be as follows: If the PWid FEC Element is used, the PW information length field is set to 0, the PW ID field is not present, and the Interface Parameter Sub-TLVs are not present. If the Generalized FEC Element is used, the AGI, SAII, and TAII are not present, the PW information length field is set to 0, the PW Group ID TLV is included, and the PW Interface Parameters TLV is omitted. For the purpose of this document, this is called the "wildcard PW status notification procedure", and all PEs implementing this design are REQUIRED to accept such a Notification message but are not required to send it.
如上所述，PWid FEC元素的组ID字段，或与通用PWid FEC元素一起使用的PW组ID TLV，可用于发送所有任意PW集的状态通知。此过程是可选的，如果实现，LDP通知消息应如下所示：如果使用PWid FEC元素，PW信息长度字段设置为0，PW ID字段不存在，接口参数Sub TLV不存在。如果使用通用FEC元素，则AGI、SAII和TAII不存在，PW信息长度字段设置为0，包括PW组ID TLV，并且省略PW接口参数TLV。在本文件中，这被称为“通配符PW状态通知程序”，所有实施此设计的PE都需要接受此类通知消息，但不需要发送。
When a PW is first set up, the PEs MUST attempt to negotiate the usage of the PW Status TLV. This is accomplished as follows: A PE that supports the PW Status TLV MUST include it in the initial Label Mapping message following the PW FEC and the Interface Parameter Sub-TLVs. The PW Status TLV will then be used for the lifetime of the pseudowire. This is shown in the following diagram:
首次设置PW时，PEs必须尝试协商PW状态TLV的使用。这是通过以下方式实现的：支持PW状态TLV的PE必须将其包含在PW FEC和接口参数Sub TLV之后的初始标签映射消息中。PW状态TLV随后将用于伪导线的使用寿命。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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ PWid FEC or Generalized PWid FEC +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface Parameters |
| " |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| Generic Label (0x0200) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0| PW Status (0x096A) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ PWid FEC or Generalized PWid FEC +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface Parameters |
| " |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| Generic Label (0x0200) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0| PW Status (0x096A) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
If a PW Status TLV is included in the initial Label Mapping message for a PW, then if the Label Mapping message from the remote PE for that PW does not include a PW Status TLV, or if the remote PE does not support the PW Status TLV, the PW will revert to the label withdraw method of signaling PW status. Note that if the PW Status TLV is not supported by the remote peer, the peer will automatically ignore it, since the I (ignore) bit is set in the TLV. The PW Status TLV, therefore, will not be present in the corresponding FEC advertisement from the remote LDP peer, which results in exactly the above behavior.
如果PW的初始标签映射消息中包含PW状态TLV，则如果来自该PW的远程PE的标签映射消息不包含PW状态TLV，或者如果远程PE不支持PW状态TLV，则PW将恢复到发信号通知PW状态的标签撤回方法。请注意，如果远程对等方不支持PW状态TLV，则对等方将自动忽略它，因为TLV中设置了I（忽略）位。因此，PW状态TLV将不会出现在来自远程LDP对等方的相应FEC广告中，这恰恰导致上述行为。
If the PW Status TLV is not present following the FEC TLV in the initial PW Label Mapping message received by a PE, then the PW Status TLV will not be used, and both PEs supporting the pseudowire will revert to the label withdraw procedure for signaling status changes.
如果在PE接收到的初始PW标签映射消息中FEC TLV之后PW状态TLV不存在，则PW状态TLV将不被使用，并且支持伪线的两个PE将恢复到标签撤回程序，以发送状态更改的信号。
If the negotiation process results in the usage of the PW Status TLV, then the actual PW status is determined by the PW Status TLV that was sent within the initial PW Label Mapping message. Subsequent updates of PW status are conveyed through the Notification message.
如果协商过程导致使用PW状态TLV，则实际PW状态由初始PW标签映射消息中发送的PW状态TLV确定。PW状态的后续更新通过通知消息传达。
This field specifies interface-specific parameters. When applicable, it MUST be used to validate that the PEs and the ingress and egress ports at the edges of the circuit have the necessary capabilities to interoperate with each other. The field structure is defined as follows:
此字段指定特定于接口的参数。适用时，必须使用它来验证PEs和电路边缘的入口和出口端口是否具有相互互操作的必要能力。字段结构定义如下：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLV Type | Length | Variable Length Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Length Value |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLV Type | Length | Variable Length Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Length Value |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Length field is defined as the length of the interface parameter including the Sub-TLV Type and Length field itself. Processing of the interface parameters should continue when unknown interface parameters are encountered, and they MUST be silently ignored.
长度字段定义为接口参数的长度，包括子TLV类型和长度字段本身。当遇到未知的接口参数时，接口参数的处理应继续进行，并且必须以静默方式忽略这些参数。
The Interface Parameter Sub-TLV Type values are specified in "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)" [RFC4446].
接口参数子TLV类型值在“用于伪线边到边仿真（PWE3）的IANA分配”中指定[RFC4446]。
- Interface MTU sub-TLV type
- 接口MTU子TLV类型
A 2-octet value indicating the MTU in octets. This is the Maximum Transmission Unit, excluding encapsulation overhead, of the egress packet interface that will be transmitting the decapsulated PDU that is received from the MPLS-enabled network. This parameter is applicable only to PWs transporting packets and is REQUIRED for these PW types. If this parameter does not match in both directions of a specific PW, that PW MUST NOT be enabled.
以八位字节表示MTU的2位八位字节值。这是出口分组接口的最大传输单元，不包括封装开销，出口分组接口将传输从启用MPLS的网络接收的解除封装的PDU。此参数仅适用于传输数据包的PWs，并且对于这些PW类型是必需的。如果该参数在特定PW的两个方向上不匹配，则不得启用该PW。
- Optional Interface Description string sub-TLV type
- 可选接口描述字符串子TLV类型
This arbitrary, and OPTIONAL, interface description string is used to send a human-readable administrative string describing the interface to the remote PE. This parameter is OPTIONAL and is applicable to all PW types. The interface description parameter string length is variable and can be from 0 to 80 octets. Human-readable text MUST be provided in the UTF-8 charset using the Default Language [RFC2277].
此任意且可选的接口描述字符串用于将描述接口的可读管理字符串发送到远程PE。此参数为可选参数，适用于所有PW类型。接口描述参数字符串长度是可变的，可以是0到80个八位字节。必须使用默认语言[RFC2277]在UTF-8字符集中提供人类可读文本。
As mentioned above, the Group ID field of the PWid FEC Element, or the PW Group ID TLV used with the Generalized PWid FEC Element, can be used to withdraw all PW labels associated with a particular PW group. This procedure is OPTIONAL, and if it is implemented, the LDP Label Withdraw message should be as follows: If the PWid FEC Element is used, the PW information length field is set to 0, the PW ID field is not present, the Interface Parameter Sub-TLVs are not present, and the Label TLV is not present. If the Generalized FEC Element is used, the AGI, SAII, and TAII are not present, the PW information
如上所述，PWid FEC元素的Group ID字段或与通用PWid FEC元素一起使用的PW Group ID TLV可用于提取与特定PW组相关联的所有PW标签。此过程是可选的，如果实现，LDP标签撤销消息应如下：如果使用PWid FEC元素，PW信息长度字段设置为0，PW ID字段不存在，接口参数Sub TLV不存在，标签TLV不存在。如果使用广义FEC元素，则AGI、SAII和TAII不存在，PW信息
length field is set to 0, the PW Group ID TLV is included, the PW Interface Parameters TLV is not present, and the Label TLV is not present. For the purpose of this document, this is called the "wildcard withdraw procedure", and all PEs implementing this design are REQUIRED to accept such withdraw messages but are not required to send it. Note that the PW Group ID TLV only applies to PWs using the Generalized ID FEC Element, while the Group ID only applies to PWid FEC Element.
长度字段设置为0，包含PW组ID TLV，PW接口参数TLV不存在，标签TLV不存在。在本文件中，这称为“通配符撤销程序”，所有实施此设计的PE都需要接受此类撤销消息，但不需要发送。请注意，PW组ID TLV仅适用于使用通用ID FEC元素的PWs，而组ID仅适用于PWid FEC元素。
The Interface Parameter Sub-TLVs, or TLV, MUST NOT be present in any LDP PW Label Withdraw or Label Release message. A wildcard Label Release message MUST include only the Group ID or PW Group ID TLV. A Label Release message initiated by a PE router must always include the PW ID.
接口参数Sub TLV或TLV不得出现在任何LDP PW标签撤回或标签释放消息中。通配符标签发布消息必须仅包括组ID或PW组ID TLV。PE路由器发起的标签释放消息必须始终包含PW ID。
The Label Mapping messages that are sent in order to set up these PWs MUST have C=1. When a Label Mapping message for a PW of one of these types is received and C=0, a Label Release message MUST be sent, with an "Illegal C-bit" status code. In this case, the PW will not be enabled.
为设置这些PW而发送的标签映射消息必须具有C=1。当收到这些类型之一的PW的标签映射消息且C=0时，必须发送带有“非法C位”状态代码的标签释放消息。在这种情况下，PW将不会启用。
If a system is capable of sending and receiving the control word on PW types for which the control word is not mandatory, then each such PW endpoint MUST be configurable with a parameter that specifies whether the use of the control word is PREFERRED or NOT PREFERRED. For each PW, there MUST be a default value of this parameter. This specification does NOT state what the default value should be.
如果系统能够在控制字不是强制性的PW类型上发送和接收控制字，则每个此类PW端点必须可配置一个参数，该参数指定是否首选使用控制字。对于每个PW，必须有此参数的默认值。此规范没有说明默认值应该是什么。
If a system is NOT capable of sending and receiving the control word on PW types for which the control word is not mandatory, then it behaves exactly as if it were configured for the use of the control word to be NOT PREFERRED.
如果系统不能在PW类型上发送和接收控制字（对于PW类型，控制字不是强制性的），则其行为与配置为不首选使用控制字的行为完全相同。
If a Label Mapping message for the PW has already been received but no Label Mapping message for the PW has yet been sent, then the procedure is as follows:
如果已收到PW的标签映射消息，但尚未发送PW的标签映射消息，则程序如下：
-i. If the received Label Mapping message has C=0, send a Label Mapping message with C=0; the control word is not used.
-一,。如果收到的标签映射报文C=0，则发送C=0的标签映射报文；未使用控制字。
-ii. If the received Label Mapping message has C=1, and the PW is locally configured such that the use of the control word is preferred, then send a Label Mapping message with C=1; the control word is used.
-二,。如果接收到的标签映射消息具有C＝1，并且PW被本地配置为优选使用控制字，则发送具有C＝1的标签映射消息；使用控制字。
-iii. If the received Label Mapping message has C=1, and the PW is locally configured such that the use of the control word is not preferred or the control word is not supported, then act as if no Label Mapping message for the PW had been received (i.e., proceed to the next paragraph).
-iii.如果接收到的标签映射消息具有C=1，并且PW在本地配置为不优选使用控制字或不支持控制字，则如同未接收到PW的标签映射消息一样（即，继续下一段）。
If a Label Mapping message for the PW has not already been received (or if the received Label Mapping message had C=1 and either local configuration says that the use of the control word is not preferred or the control word is not supported), then send a Label Mapping message in which the C-bit is set to correspond to the locally configured preference for use of the control word. (That is, set C=1 if locally configured to prefer the control word, and set C=0 if locally configured to prefer not to use the control word or if the control word is not supported).
如果尚未接收到PW的标签映射消息（或者如果接收到的标签映射消息的C=1且本地配置表示不首选使用控制字或不支持控制字），然后发送标签映射消息，其中C位设置为与本地配置的首选项相对应，以使用控制字。（即，如果本地配置为首选控制字，则设置C=1；如果本地配置为首选不使用控制字或不支持控制字，则设置C=0）。
The next action depends on what control message is next received for that PW. The possibilities are as follows:
下一个动作取决于该PW下一次接收到的控制消息。可能性如下：
-i. A Label Mapping message with the same C-bit value as specified in the Label Mapping message that was sent. PW setup is now complete, and the control word is used if C=1 but is not used if C=0.
-一,。具有与发送的标签映射消息中指定的相同C位值的标签映射消息。PW设置现已完成，如果C=1，则使用控制字，但如果C=0，则不使用控制字。
-ii. A Label Mapping message with C=1, but the Label Mapping message that was sent has C=0. In this case, ignore the received Label Mapping message and continue to wait for the next control message for the PW.
-二,。C=1的标签映射消息，但发送的标签映射消息的C=0。在这种情况下，忽略收到的标签映射消息，继续等待PW的下一条控制消息。
-iii. A Label Mapping message with C=0, but the Label Mapping message that was sent has C=1. In this case, send a Label Withdraw message with a "Wrong C-bit" status code, followed by a Label Mapping message that has C=0. PW setup is now complete, and the control word is not used.
-iii.C=0的标签映射消息，但发送的标签映射消息的C=1。在这种情况下，发送一条带有“错误C位”状态代码的标签撤销消息，然后发送一条C=0的标签映射消息。PW设置现在已完成，并且未使用控制字。
-iv. A Label Withdraw message with the "Wrong C-bit" status code. Treat as a normal Label Withdraw message, but do not respond. Continue to wait for the next control message for the PW.
-iv.带有“错误C位”状态代码的标签撤销信息。将标签撤消消息视为正常消息，但不响应。继续等待PW的下一条控制消息。
If at any time after a Label Mapping message has been received a corresponding Label Withdraw or Release is received, the action taken is the same as for any Label Withdraw or Release messages that might be received at any time.
如果在收到标签映射消息后的任何时间收到相应的标签撤销或释放，则所采取的操作与可能在任何时间收到的任何标签撤销或释放消息相同。
If both endpoints prefer the use of the control word, this procedure will cause it to be used. If either endpoint prefers not to use the control word or does not support the control word, this procedure will cause it not to be used. If one endpoint prefers to use the control word but the other does not, the one that prefers not to use it has no extra protocol to execute; it just waits for a Label Mapping message that has C=0.
如果两个端点都喜欢使用控制字，则此过程将使用该控制字。如果任一端点不喜欢使用控制字或不支持该控制字，此过程将导致不使用该控制字。如果一个端点喜欢使用控制字，而另一个不喜欢，则不喜欢使用控制字的端点没有额外的协议可执行；它只等待C=0的标签映射消息。
It is possible that after the PW C-bit negotiation procedure described above is complete, the local PE is re-provisioned with a different control word preference. Therefore, once the control-word negotiation procedures are complete, the procedure can be restarted as follows:
在上述PW C位协商过程完成之后，可能用不同的控制字首选项重新供应本地PE。因此，一旦控制字协商程序完成，可按如下方式重新启动该程序：
-i. If the local PE previously sent a Label Mapping message, it MUST send a Label Withdraw message to the remote PE and wait until it has received a Label Release message from the remote PE.
-一,。如果本地PE先前发送了标签映射消息，则必须向远程PE发送标签撤销消息，并等待收到来自远程PE的标签释放消息。
-ii. The local PE MUST send a Label Release message to the remote PE for the specific label associated with the FEC that was advertised for this specific PW. Note: The above-mentioned steps of the Label Release message and Label Withdraw message are not required to be executed in any specific sequence.
-二,。本地PE必须向远程PE发送标签释放消息，以获取与针对该特定PW播发的FEC相关联的特定标签。注：标签释放消息和标签撤回消息的上述步骤不需要按任何特定顺序执行。
-iii. The local PE MUST send a Label Request message to the peer PE and then MUST wait until it receives a Label Mapping message containing the remote PE's currently configured preference for use of the control word.
-iii.本地PE必须向对等PE发送标签请求消息，然后必须等待，直到收到包含远程PE当前配置的控制字使用偏好的标签映射消息。
Once the remote PE has successfully processed the Label Withdraw message and Label Release messages, it will reset the C-bit negotiation state machine and its use of the control word with the locally configured preference.
一旦远程PE成功处理标签撤销消息和标签释放消息，它将重置C位协商状态机，并使用本地配置的首选项重置其对控制字的使用。
From this point on, the local and remote PEs will follow the C-bit negotiation procedures defined in the previous section.
从这一点开始，本地和远程PEs将遵循上一节中定义的C位协商程序。
The above C-bit renegotiation process SHOULD NOT be interrupted until it is completed, or unpredictable results might occur.
上述C位重新协商过程在完成之前不应中断，否则可能会出现不可预测的结果。
In the case where the router considers the sequence number field in the control word, it is important to note the following details when advertising labels.
在路由器考虑控制字中的序列号字段的情况下，在广告标签时注意以下细节很重要。
After a label has been withdrawn by the output router and/or released by the input router, care must be taken not to advertise (reuse) the same released label until the output router can be reasonably certain that old packets containing the released label no longer persist in the MPLS-enabled network.
在输出路由器撤回标签和/或输入路由器释放标签后，必须注意不要公布（重用）相同的释放标签，直到输出路由器能够合理地确定包含释放标签的旧数据包不再存在于启用MPLS的网络中。
This precaution is required to prevent the imposition router from restarting packet forwarding with a sequence number of 1 when it receives a Label Mapping message that binds the same FEC to the same label if there are still older packets in the network with a sequence number between 1 and 32768. For example, if there is a packet with sequence number=n, where n is in the interval [1,32768] traveling through the network, it would be possible for the disposition router to receive that packet after it re-advertises the label. Since the label has been released by the imposition router, the disposition router SHOULD be expecting the next packet to arrive with a sequence number of 1. Receipt of a packet with a sequence number equal to n will result in n packets potentially being rejected by the disposition router until the imposition router imposes a sequence number of n+1 into a packet. Possible methods to avoid this are for the disposition router always to advertise a different PW label, or for the disposition router to wait for a sufficient time before attempting to re-advertise a recently released label. This is only an issue when sequence number processing is enabled at the disposition router.
如果网络中仍然存在序列号在1和32768之间的较旧数据包，则当接收到将相同FEC绑定到相同标签的标签映射消息时，需要此预防措施以防止强制路由器重新启动序列号为1的数据包转发。例如，如果存在序列号为n的分组，其中n在通过网络的间隔[132768]中，则处置路由器可能在其重新播发标签之后接收该分组。由于标签已由强制路由器释放，因此处置路由器应期望下一个数据包以序列号1到达。接收序列号等于n的数据包将导致n个数据包可能被处置路由器拒绝，直到强制路由器将序列号n+1施加到数据包中。避免这种情况的可能方法是，处置路由器始终播发不同的PW标签，或者处置路由器在尝试重新播发最近发布的标签之前等待足够的时间。只有在处置路由器上启用序列号处理时，这才是一个问题。
In situations where the imposition router wants to restart forwarding of packets with sequence number 1, the router shall 1) send to the disposition router a Label Release message, and 2) send to the disposition router a Label Request message. When sequencing is supported, advertisement of a PW label in response to a Label Request message MUST also consider the issues discussed in Section 7.4.1 ("Label Advertisements").
在强制路由器想要重新发送序列号为1的数据包的情况下，路由器应1）向处置路由器发送标签释放消息，2）向处置路由器发送标签请求消息。当支持测序时，响应标签请求消息的PW标签的广告也必须考虑7.4.1节（“标签广告”）中讨论的问题。
This document uses several new LDP TLV types; IANA already maintains a registry titled "TLV Type Name Space", defined by RFC 5036. The following values have been assigned from said registry:
本文件使用了几种新的LDP TLV类型；IANA已经维护了一个名为“TLV类型名称空间”的注册表，该注册表由RFC 5036定义。已从所述注册表分配以下值：
TLV Type Description
=====================================
0x096A PW Status TLV
0x096B PW Interface Parameters TLV
0x096C PW Group ID TLV
TLV Type Description
=====================================
0x096A PW Status TLV
0x096B PW Interface Parameters TLV
0x096C PW Group ID TLV
This document uses several new LDP status codes; IANA already maintains a registry titled "Status Code Name Space", defined by RFC 5036. The following values have been assigned:
本文件使用了几种新的LDP状态码；IANA已经维护了一个名为“状态代码名称空间”的注册表，该注册表由RFC 5036定义。已指定以下值：
Range/Value E Description Reference
------------- ----- ---------------------- ---------
0x00000024 0 Illegal C-Bit [RFC8077]
0x00000025 0 Wrong C-Bit [RFC8077]
0x00000026 0 Incompatible bit-rate [RFC8077]
0x00000027 0 CEP-TDM mis-configuration [RFC8077]
0x00000028 0 PW Status [RFC8077]
0x00000029 0 Unassigned/Unrecognized TAI [RFC8077]
0x0000002A 0 Generic Misconfiguration Error [RFC8077]
0x0000002B 0 Label Withdraw PW Status [RFC8077]
Method Not Supported
Range/Value E Description Reference
------------- ----- ---------------------- ---------
0x00000024 0 Illegal C-Bit [RFC8077]
0x00000025 0 Wrong C-Bit [RFC8077]
0x00000026 0 Incompatible bit-rate [RFC8077]
0x00000027 0 CEP-TDM mis-configuration [RFC8077]
0x00000028 0 PW Status [RFC8077]
0x00000029 0 Unassigned/Unrecognized TAI [RFC8077]
0x0000002A 0 Generic Misconfiguration Error [RFC8077]
0x0000002B 0 Label Withdraw PW Status [RFC8077]
Method Not Supported
This document uses two new FEC element types, 0x80 and 0x81, from the registry "Forwarding Equivalence Class (FEC) Type Name Space" for the Label Distribution Protocol (LDP) [RFC5036].
本文档为标签分发协议（LDP）[RFC5036]使用注册表“转发等价类（FEC）类型名称空间”中的两种新FEC元素类型0x80和0x81。
This document specifies the LDP extensions that are needed for setting up and maintaining pseudowires. The purpose of setting up pseudowires is to enable Layer 2 frames to be encapsulated in MPLS and transmitted from one end of a pseudowire to the other. Therefore, we address the security considerations for both the data plane and the control plane.
本文件规定了设置和维护伪线所需的LDP扩展。设置伪线的目的是使第2层帧能够封装在MPLS中，并从伪线的一端传输到另一端。因此，我们解决了数据平面和控制平面的安全问题。
With regard to the security of the data plane, the following areas must be considered:
关于数据平面的安全性，必须考虑以下方面：
- MPLS PDU inspection - MPLS PDU spoofing - MPLS PDU alteration - MPLS PSN protocol security - Access Circuit security - Denial-of-service prevention on the PE routers
- MPLS PDU检查-MPLS PDU欺骗-MPLS PDU变更-MPLS PSN协议安全-访问电路安全-PE路由器上的拒绝服务预防
When an MPLS PSN is used to provide pseudowire service, there is a perception that security must be at least equal to the currently deployed Layer 2 native protocol networks that the MPLS/PW network combination is emulating. This means that the MPLS-enabled network SHOULD be isolated from outside packet insertion in such a way that it SHOULD NOT be possible to insert an MPLS packet into the network directly. To prevent unwanted packet insertion, it is also important to prevent unauthorized physical access to the PSN, as well as unauthorized administrative access to individual network elements.
当MPLS PSN用于提供伪线服务时，人们认为安全性必须至少等于MPLS/PW网络组合正在模拟的当前部署的第2层本机协议网络。这意味着启用MPLS的网络应该与外部分组插入隔离，这样就不可能将MPLS分组直接插入网络。为了防止不必要的数据包插入，还必须防止对PSN的未经授权的物理访问，以及对单个网元的未经授权的管理访问。
As mentioned above, an MPLS-enabled network should not accept MPLS packets from its external interfaces (i.e., interfaces to CE devices or to other providers' networks) unless the top label of the packet was legitimately distributed to the system from which the packet is being received. If the packet's incoming interface leads to a different Service Provider (SP) (rather than to a customer), an appropriate trust relationship must also be present, including the trust that the other SP also provides appropriate security measures.
如上所述，启用MPLS的网络不应接受来自其外部接口（即，到CE设备或到其他提供商网络的接口）的MPLS数据包，除非数据包的顶部标签被合法地分发到接收数据包的系统。如果数据包的传入接口指向不同的服务提供商（SP）（而不是客户），则还必须存在适当的信任关系，包括另一个SP也提供适当安全措施的信任关系。
The three main security problems faced when using an MPLS-enabled network to transport PWs are spoofing, alteration, and inspection. First, there is a possibility that the PE receiving PW PDUs will get a PDU that appears to be from the PE transmitting the PW into the PSN but that was not actually transmitted by the PE originating the PW. (That is, the specified encapsulations do not by themselves enable the decapsulator to authenticate the encapsulator.) A second problem is the possibility that the PW PDU will be altered between the time it enters the PSN and the time it leaves the PSN (i.e., the specified encapsulations do not by themselves assure the decapsulator of the packet's integrity.) A third problem is the possibility that the PDU's contents will be seen while the PDU is in transit through the PSN (i.e., the specification encapsulations do not ensure privacy.) How significant these issues are in practice depends on the security requirements of the applications whose traffic is being sent through the tunnel and how secure the PSN itself is.
使用支持MPLS的网络传输PWs时面临的三个主要安全问题是欺骗、更改和检查。首先，有可能接收PW PDU的PE将获得一个PDU，该PDU看起来来自将PW发送到PSN的PE，但实际上不是由发起PW的PE发送的。（也就是说，指定的封装本身不能使解封装器对封装器进行身份验证。）第二个问题是PW PDU在进入PSN和离开PSN之间可能会发生变化（即，指定的封装本身不能确保数据包的完整性。）第三个问题是，当PDU通过PSN传输时，可能会看到PDU的内容（即，规范封装不能确保隐私。）这些问题在实践中的重要性取决于通过隧道发送流量的应用程序的安全要求以及PSN本身的安全性。
General security considerations with regard to the use of LDP are specified in Section 5 of [RFC5036]. Those considerations also apply to the case where LDP is used to set up pseudowires.
[RFC5036]第5节规定了使用LDP的一般安全注意事项。这些考虑也适用于使用LDP建立伪线的情况。
A pseudowire connects two Attachment Circuits. It is important to make sure that LDP connections are not arbitrarily accepted from anywhere, or else a local Attachment Circuit might get connected to an arbitrary remote Attachment Circuit. Therefore, an incoming LDP session request MUST NOT be accepted unless its IP source address is known to be the source of an "eligible" LDP peer. The set of eligible peers could be preconfigured (either as a list of IP addresses or as a list of address/mask combinations), or it could be discovered dynamically via an auto-discovery protocol that is itself trusted. (Obviously, if the auto-discovery protocol were not trusted, the set of eligible peers it produces could not be trusted.)
伪导线连接两个连接电路。务必确保LDP连接不会从任何地方被任意接受，否则本地连接电路可能会连接到任意远程连接电路。因此，传入的LDP会话请求必须不被接受，除非其IP源地址已知是“合格”LDP对等方的源。可以预先配置一组合格的对等点（作为IP地址列表或地址/掩码组合列表），也可以通过自身受信任的自动发现协议动态发现该对等点。（显然，如果自动发现协议不受信任，则它生成的合格对等点集将不受信任。）
Even if an LDP connection request appears to come from an eligible peer, its source address may have been spoofed. Therefore, some means of preventing source address spoofing must be in place. For example, if all the eligible peers are in the same network, source address filtering at the border routers of that network could eliminate the possibility of source address spoofing.
即使LDP连接请求似乎来自合格的对等方，其源地址也可能被欺骗。因此，必须采取一些措施防止源地址欺骗。例如，如果所有符合条件的对等方都在同一网络中，则在该网络的边界路由器上进行源地址过滤可以消除源地址欺骗的可能性。
The LDP MD5 authentication key option, as described in Section 2.9 of [RFC5036], MUST be implemented, and for a greater degree of security, it must be used. This provides integrity and authentication for the LDP messages and eliminates the possibility of source address spoofing. Use of the MD5 option does not provide privacy, but privacy of the LDP control messages is not usually considered important. As the MD5 option relies on the configuration of pre-shared keys, it does not provide much protection against replay attacks. In addition, its reliance on pre-shared keys may make it very difficult to deploy when the set of eligible neighbors is determined by an auto-configuration protocol.
如[RFC5036]第2.9节所述，必须实施LDP MD5认证密钥选项，并且为了更大程度的安全性，必须使用该选项。这为LDP消息提供了完整性和身份验证，并消除了源地址欺骗的可能性。MD5选项的使用不提供隐私，但LDP控制消息的隐私通常并不重要。由于MD5选项依赖于预共享密钥的配置，因此无法提供太多针对重播攻击的保护。此外，当自动配置协议确定了一组合格的邻居时，它对预共享密钥的依赖可能会使部署变得非常困难。
When the Generalized PWid FEC Element is used, it is possible that a particular LDP peer may be one of the eligible LDP peers but may not be the right one to connect to the particular Attachment Circuit identified by the particular instance of the Generalized PWid FEC Element. However, given that the peer is known to be one of the eligible peers (as discussed above), this would be the result of a configuration error rather than a security problem. Nevertheless, it may be advisable for a PE to associate each of its local Attachment Circuits with a set of eligible peers rather than have just a single set of eligible peers associated with the PE as a whole.
当使用广义PWid FEC元件时，特定LDP对等方可能是合格的LDP对等方之一，但可能不是连接到由广义PWid FEC元件的特定实例识别的特定连接电路的正确的一个。然而，鉴于已知该对等方是合格对等方之一（如上所述），这将是配置错误而不是安全问题造成的。然而，PE最好将其每个本地连接电路与一组合格对等点相关联，而不是仅将一组合格对等点作为一个整体与PE相关联。
Section 2.2 of [RFC6410] specifies four requirements that an Internet Standard must meet. This section documents how this document meets those requirements.
[RFC6410]第2.2节规定了互联网标准必须满足的四个要求。本节记录了本文件如何满足这些要求。
The pseudowire technology was first deployed in 2001 and has been widely deployed by many carriers. [RFC7079] documents the results of a survey of PW implementations with specific emphasis on control-word usage. [EANTC] documents a public multi-vendor interoperability test of MPLS and Carrier Ethernet equipment, which included testing of Ethernet, ATM, and TDM pseudowires.
伪线技术于2001年首次部署，并已被许多运营商广泛部署。[RFC7079]记录了PW实现的调查结果，特别强调控制字的使用。[EANTC]记录了MPLS和运营商以太网设备的公共多供应商互操作性测试，包括以太网、ATM和TDM伪线的测试。
The errata against [RFC4447] are generally editorial in nature and have been addressed in this document.
[RFC4447]的勘误表通常是编辑性质的，并在本文件中进行了说明。
All features in this specification have been implemented by multiple vendors.
本规范中的所有功能已由多家供应商实施。
No IPR disclosures have been made to the IETF related to this document, to RFCs 4447 or 6723, or to the Internet-Drafts that resulted in RFCs 4447 and 6723.
未向IETF披露与本文件、RFCs 4447或6723或导致RFCs 4447和6723的互联网草案相关的知识产权。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，DOI 10.17487/RFC2119，1997年3月<http://www.rfc-editor.org/info/rfc2119>.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed., "LDP Specification", RFC 5036, DOI 10.17487/RFC5036, October 2007, <http://www.rfc-editor.org/info/rfc5036>.
[RFC5036]Andersson，L.，Ed.，Minei，I.，Ed.，和B.Thomas，Ed.“LDP规范”，RFC 5036，DOI 10.17487/RFC5036，2007年10月<http://www.rfc-editor.org/info/rfc5036>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, <http://www.rfc-editor.org/info/rfc3032>.
[RFC3032]Rosen，E.，Tappan，D.，Fedorkow，G.，Rekhter，Y.，Farinaci，D.，Li，T.，和A.Conta，“MPLS标签堆栈编码”，RFC 3032，DOI 10.17487/RFC3032，2001年1月<http://www.rfc-editor.org/info/rfc3032>.
[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)", BCP 116, RFC 4446, DOI 10.17487/RFC4446, April 2006, <http://www.rfc-editor.org/info/rfc4446>.
[RFC4446]Martini，L.，“伪线边到边仿真（PWE3）的IANA分配”，BCP 116，RFC 4446，DOI 10.17487/RFC4446，2006年4月<http://www.rfc-editor.org/info/rfc4446>.
[RFC7358] Raza, K., Boutros, S., Martini, L., and N. Leymann, "Label Advertisement Discipline for LDP Forwarding Equivalence Classes (FECs)", RFC 7358, DOI 10.17487/RFC7358, October 2014, <http://www.rfc-editor.org/info/rfc7358>.
[RFC7358]Raza，K.，Boutros，S.，Martini，L.，和N.Leymann，“LDP转发等价类（FEC）的标签广告规程”，RFC 7358，DOI 10.17487/RFC7358，2014年10月<http://www.rfc-editor.org/info/rfc7358>.
[RFC2277] Alvestrand, H., "IETF Policy on Character Sets and Languages", BCP 18, RFC 2277, DOI 10.17487/RFC2277, January 1998, <http://www.rfc-editor.org/info/rfc2277>.
[RFC2277]Alvestrand，H.，“IETF字符集和语言政策”，BCP 18，RFC 2277，DOI 10.17487/RFC2277，1998年1月<http://www.rfc-editor.org/info/rfc2277>.
[RFC3985] Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, DOI 10.17487/RFC3985, March 2005, <http://www.rfc-editor.org/info/rfc3985>.
[RFC3985]Bryant，S.，Ed.，和P.Pate，Ed.，“伪线仿真边到边（PWE3）架构”，RFC 3985，DOI 10.17487/RFC3985，2005年3月<http://www.rfc-editor.org/info/rfc3985>.
[RFC4842] Malis, A., Pate, P., Cohen, R., Ed., and D. Zelig, "Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Circuit Emulation over Packet (CEP)", RFC 4842, DOI 10.17487/RFC4842, April 2007, <http://www.rfc-editor.org/info/rfc4842>.
[RFC4842]Malis，A.，Pate，P.，Cohen，R.，Ed.，和D.Zelig，“同步光网络/同步数字体系（SONET/SDH）分组电路仿真（CEP）”，RFC 4842，DOI 10.17487/RFC4842，2007年4月<http://www.rfc-editor.org/info/rfc4842>.
[RFC4553] Vainshtein, A., Ed., and YJ. Stein, Ed., "Structure-Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006, <http://www.rfc-editor.org/info/rfc4553>.
[RFC4553]Vainstein，A.，Ed.，和YJ。Stein，Ed.“数据包上的结构不可知时分复用（TDM）（SAToP）”，RFC 4553，DOI 10.17487/RFC4553，2006年6月<http://www.rfc-editor.org/info/rfc4553>.
[RFC4619] Martini, L., Ed., Kawa, C., Ed., and A. Malis, Ed., "Encapsulation Methods for Transport of Frame Relay over Multiprotocol Label Switching (MPLS) Networks", RFC 4619, DOI 10.17487/RFC4619, September 2006, <http://www.rfc-editor.org/info/rfc4619>.
[RFC4619]Martini，L.，Ed.，Kawa，C.，Ed.，和A.Malis，Ed.，“多协议标签交换（MPLS）网络上帧中继传输的封装方法”，RFC 4619，DOI 10.17487/RFC4619，2006年9月<http://www.rfc-editor.org/info/rfc4619>.
[RFC4717] Martini, L., Jayakumar, J., Bocci, M., El-Aawar, N., Brayley, J., and G. Koleyni, "Encapsulation Methods for Transport of Asynchronous Transfer Mode (ATM) over MPLS Networks", RFC 4717, DOI 10.17487/RFC4717, December 2006, <http://www.rfc-editor.org/info/rfc4717>.
[RFC4717]Martini，L.，Jayakumar，J.，Bocci，M.，El Aawar，N.，Brayley，J.，和G.Koleyni，“MPLS网络上异步传输模式（ATM）传输的封装方法”，RFC 4717，DOI 10.17487/RFC4717，2006年12月<http://www.rfc-editor.org/info/rfc4717>.
[RFC4618] Martini, L., Rosen, E., Heron, G., and A. Malis, "Encapsulation Methods for Transport of PPP/High-Level Data Link Control (HDLC) over MPLS Networks", RFC 4618, DOI 10.17487/RFC4618, September 2006, <http://www.rfc-editor.org/info/rfc4618>.
[RFC4618]Martini，L.，Rosen，E.，Heron，G.，和A.Malis，“通过MPLS网络传输PPP/高级数据链路控制（HDLC）的封装方法”，RFC 4618，DOI 10.17487/RFC4618，2006年9月<http://www.rfc-editor.org/info/rfc4618>.
[RFC4448] Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron, "Encapsulation Methods for Transport of Ethernet over MPLS Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006, <http://www.rfc-editor.org/info/rfc4448>.
[RFC4448]Martini，L.，Ed.，Rosen，E.，El Aawar，N.，和G.Heron，“通过MPLS网络传输以太网的封装方法”，RFC 4448，DOI 10.17487/RFC4448，2006年4月<http://www.rfc-editor.org/info/rfc4448>.
[RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, DOI 10.17487/RFC4447, April 2006, <http://www.rfc-editor.org/info/rfc4447>.
[RFC4447]Martini，L.，Ed.，Rosen，E.，El Aawar，N.，Smith，T.，和G.Heron，“使用标签分发协议（LDP）的伪线设置和维护”，RFC 4447，DOI 10.17487/RFC4447，2006年4月<http://www.rfc-editor.org/info/rfc4447>.
[RFC6410] Housley, R., Crocker, D., and E. Burger, "Reducing the Standards Track to Two Maturity Levels", BCP 9, RFC 6410, DOI 10.17487/RFC6410, October 2011, <http://www.rfc-editor.org/info/rfc6410>.
[RFC6410]Housley，R.，Crocker，D.，和E.Burger，“将标准轨道降低到两个成熟度水平”，BCP 9，RFC 6410，DOI 10.17487/RFC6410，2011年10月<http://www.rfc-editor.org/info/rfc6410>.
[RFC6723] Jin, L., Ed., Key, R., Ed., Delord, S., Nadeau, T., and S. Boutros, "Update of the Pseudowire Control-Word Negotiation Mechanism", RFC 6723, DOI 10.17487/RFC6723, September 2012, <http://www.rfc-editor.org/info/rfc6723>.
[RFC6723]Jin，L.，Ed.，Key，R.，Ed.，Delord，S.，Nadeau，T.，和S.Boutros，“伪线控制字协商机制的更新”，RFC 6723，DOI 10.17487/RFC6723，2012年9月<http://www.rfc-editor.org/info/rfc6723>.
[RFC7079] Del Regno, N., Ed., and A. Malis, Ed., "The Pseudowire (PW) and Virtual Circuit Connectivity Verification (VCCV) Implementation Survey Results", RFC 7079, DOI 10.17487/RFC7079, November 2013, <http://www.rfc-editor.org/info/rfc7079>.
[RFC7079]Del Regno，N.，Ed.，和A.Malis，Ed.，“伪线（PW）和虚拟电路连接验证（VCCV）实施调查结果”，RFC 7079，DOI 10.17487/RFC7079，2013年11月<http://www.rfc-editor.org/info/rfc7079>.
[ANSI] American National Standards Institute, "Telecommunications - Synchronous Optical Network (SONET) - Basic Description Including Multiplex Structures, Rates, and Formats", ANSI T1.105, October 1995.
[ANSI]美国国家标准协会，“电信-同步光网络（SONET）-基本说明，包括多路复用结构、速率和格式”，ANSI T1.105，1995年10月。
[ITUG] International Telecommunications Union, "Network node interface for the synchronous digital hierarchy (SDH)", ITU-T Recommendation G.707, May 1996.
[ITUG]国际电信联盟，“同步数字体系（SDH）的网络节点接口”，ITU-T建议G.707，1996年5月。
[EANTC] European Advanced Networking Test Center, "MPLS and Carrier Ethernet: Service - Connect - Transport. Public Multi-Vendor Interoperability Test", February 2009.
[EANTC]欧洲高级网络测试中心，“MPLS和运营商以太网：服务-连接-传输。公共多供应商互操作性测试”，2009年2月。
Acknowledgments
致谢
The authors wish to acknowledge the contributions of Vach Kompella, Vanson Lim, Wei Luo, Himanshu Shah, and Nick Weeds. The authors wish to also acknowledge the contribution of the authors of RFC 6723, whose work has been incorporated in this document: Lizhong Jin, Raymond Key, Simon Delord, Tom Nadeau, and Sami Boutros.
作者希望感谢Vach Kompella、Vanson Lim、Wei Luo、Himanshu Shah和Nick Weeds的贡献。作者还希望感谢RFC 6723作者的贡献，他们的工作已纳入本文件：Lizhong Jin、Raymond Key、Simon Delord、Tom Nadeau和Sami Boutros。
Contributors
贡献者
The following individuals were either authors or contributing authors for RFC 4447. They are listed here in recognition of their work on that document.
以下个人是RFC 4447的作者或贡献作者。他们被列在这里，以表彰他们在该文件上的工作。
Nasser El-Aawar Level 3 Communications, LLC. 1025 Eldorado Blvd. Broomfield, CO 80021 United States of America
Nasser El Aawar三级通信有限责任公司，埃尔多拉多大道1025号。美国科罗拉多州布鲁姆菲尔德80021
Email: nna@level3.net
Email: nna@level3.net
Eric C. Rosen Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA 01719 United States of America
Eric C.Rosen Cisco Systems，Inc.美国马萨诸塞州Boxborough马萨诸塞大道1414号01719
Email: erosen@cisco.com
Email: erosen@cisco.com
Dan Tappan Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA 01719 United States of America
Dan Tappan Cisco Systems，Inc.美国马萨诸塞州Boxborough马萨诸塞大道1414号01719
Email: tappan@cisco.com
Email: tappan@cisco.com
Toby Smith Google 6425 Penn Ave. #700 Pittsburgh, PA 15206 United States of America
托比·史密斯谷歌美国宾夕法尼亚州匹兹堡宾夕法尼亚大道6425号，邮编15206
Email: tob@google.com
Email: tob@google.com
Dimitri Vlachos Riverbed Technology
Dimitri Vlachos河床技术
Email: dimitri@riverbed.com
Email: dimitri@riverbed.com
Jayakumar Jayakumar Cisco Systems Inc. 3800 Zanker Road, MS-SJ02/2 San Jose, CA 95134 United States of America
美国加利福尼亚州圣何塞市赞克路3800号，邮编：95134
Email: jjayakum@cisco.com
Email: jjayakum@cisco.com
Alex Hamilton, Cisco Systems Inc. 485 East Tasman Drive, MS-SJC07/3 San Jose, CA 95134 United States of America
亚历克斯·汉密尔顿，思科系统公司，美国加利福尼亚州圣何塞市东塔斯曼大道485号，邮编：95134
Email: tahamilt@cisco.com
Email: tahamilt@cisco.com
Steve Vogelsang ECI Telecom Omega Corporate Center 1300 Omega Drive Pittsburgh, PA 15205 United States of America
Steve Vogelsang ECI电信欧米茄公司中心美国宾夕法尼亚州匹兹堡欧米茄大道1300号，邮编15205
Email: stephen.vogelsang@ecitele.com
Email: stephen.vogelsang@ecitele.com
John Shirron ECI Telecom Omega Corporate Center 1300 Omega Drive Pittsburgh, PA 15205 United States of America
美国宾夕法尼亚州匹兹堡欧米茄大道1300号，邮编15205
Email: john.shirron@ecitele.com
Email: john.shirron@ecitele.com
Andrew G. Malis Verizon 60 Sylvan Rd. Waltham, MA 02451 United States of America
美国马萨诸塞州沃尔瑟姆西尔文路60号安德鲁·G·马里斯威瑞森02451
Email: andrew.g.malis@verizon.com
Email: andrew.g.malis@verizon.com
Vinai Sirkay Reliance Infocomm Dhirubai Ambani Knowledge City Navi Mumbai 400 709 India
Vinai Sirkay Reliance Infocomm Dhirubai Ambani知识城纳维孟买400 709印度
Email: vinai@sirkay.com
Email: vinai@sirkay.com
Vasile Radoaca Nortel Networks 600 Technology Park Billerica MA 01821 United States of America
瓦西里·拉多阿卡北电网络600技术园美国马里兰州比尔里卡01821
Email: vasile@nortelnetworks.com
Email: vasile@nortelnetworks.com
Chris Liljenstolpe 149 Santa Monica Way San Francisco, CA 94127 United States of America
Chris Liljenstolpe 149圣莫尼卡路旧金山，CA 94127美利坚合众国
Email: ietf@cdl.asgaard.org
Email: ietf@cdl.asgaard.org
Dave Cooper Global Crossing 960 Hamlin Court Sunnyvale, CA 94089 United States of America
美国加利福尼亚州桑尼维尔哈姆林法院960号戴夫·库珀环球交叉路口，邮编94089
Email: dcooper@gblx.net
Email: dcooper@gblx.net
Kireeti Kompella Juniper Networks 1194 N. Mathilda Ave Sunnyvale, CA 94089 United States of America
Kireeti Kompella Juniper Networks 1194 N.Mathilda Ave Sunnyvale，CA 94089美利坚合众国
Email: kireeti@juniper.net
Email: kireeti@juniper.net
Authors' Addresses
作者地址
Luca Martini (editor) Cisco Systems, Inc. 1899 Wynkoop Street, Suite 600 Denver, CO 80202 United States of America
卢卡·马蒂尼（编辑）思科系统公司，美国丹佛市温库普街1899号600室，邮编：80202
Email: lmartini@monoski.com
Email: lmartini@monoski.com
Giles Heron (editor) Cisco Systems 10 New Square Bedfont Lakes Feltham Middlesex TW14 8HA United Kingdom
Giles Heron（编辑）Cisco Systems 10 New Square Bedfont Lakes Feltham Middlesex TW14 8HA英国
Email: giheron@cisco.com
Email: giheron@cisco.com