Network Working Group N. McGill
Request for Comments: 5641 C. Pignataro
Updates: 3931, 4349, 4454, 4591, 4719 Cisco Systems
Category: Standards Track August 2009
Network Working Group N. McGill
Request for Comments: 5641 C. Pignataro
Updates: 3931, 4349, 4454, 4591, 4719 Cisco Systems
Category: Standards Track August 2009
Layer 2 Tunneling Protocol Version 3 (L2TPv3) Extended Circuit Status Values
第2层隧道协议版本3（L2TPv3）扩展电路状态值
Abstract
摘要
This document defines additional Layer 2 Tunneling Protocol Version 3 (L2TPv3) bit values to be used within the "Circuit Status" Attribute Value Pair (AVP) to communicate finer-grained error states for Attachment Circuits (ACs) and pseudowires (PWs). It also generalizes the Active bit and deprecates the use of the New bit in the Circuit Status AVP, updating RFC 3931, RFC 4349, RFC 4454, RFC 4591, and RFC 4719.
本文档定义了附加的第2层隧道协议版本3（L2TPv3）位值，用于“电路状态”属性值对（AVP）内，以传递连接电路（ACs）和伪线（PW）的更细粒度错误状态。它还概括了活动位，并反对在电路状态AVP中使用新位，更新RFC 3931、RFC 4349、RFC 4454、RFC 4591和RFC 4719。
Status of This Memo
关于下段备忘
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
本文件规定了互联网社区的互联网标准跟踪协议，并要求进行讨论和提出改进建议。有关本协议的标准化状态和状态，请参考当前版本的“互联网官方协议标准”（STD 1）。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document.
本文件受BCP 78和IETF信托在本文件出版之日生效的与IETF文件有关的法律规定的约束(http://trustee.ietf.org/license-info). 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。
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 . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Specification of Requirements . . . . . . . . . . . . . . 2
1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2. L2TPv3 Extended Circuit Status Values . . . . . . . . . . . . 3
3. Circuit Status Usage and Clarifications . . . . . . . . . . . 7
4. Updates to Existing RFCs . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . . 10
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Specification of Requirements . . . . . . . . . . . . . . 2
1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2. L2TPv3 Extended Circuit Status Values . . . . . . . . . . . . 3
3. Circuit Status Usage and Clarifications . . . . . . . . . . . 7
4. Updates to Existing RFCs . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . . 10
Currently, the L2TPv3 Circuit Status AVP [RFC3931] is able to convey the UP/DOWN status of an access circuit. However, a finer granularity is often useful to determine the direction of the fault, as has been added for MPLS-based pseudowires and is used in the pseudowire control protocol using the Label Distribution Protocol (LDP); see Section 3.5 of [RFC4446] and Section 5.4.2 of [RFC4447].
目前，L2TPv3电路状态AVP[RFC3931]能够传送接入电路的上升/下降状态。然而，更细的粒度通常有助于确定故障的方向，这是为基于MPLS的伪线添加的，并在使用标签分发协议（LDP）的伪线控制协议中使用；参见[RFC4446]第3.5节和[RFC4447]第5.4.2节。
Additionally, it is useful (in session-level redundancy scenarios) to be able to indicate if a pseudowire is in a standby state, where it is fully established by signaling and allows Operations, Administration, and Maintenance, but is not switching data. Again, such functionality is available for MPLS-based pseudowires using LDP, see [PREF-FWD].
此外，能够指示伪线是否处于待机状态是有用的（在会话级冗余场景中），其中伪线通过信令完全建立，允许操作、管理和维护，但不交换数据。同样，这种功能也可用于使用LDP的基于MPLS的伪线，请参见[PREF-FWD]。
This document provides extended circuit status bit values for L2TPv3 and adds them in a manner such that it is backwards compatible with the current Circuit Status AVP. These new bits are applicable to all pseudowire types that use the Circuit Status AVP.
本文档提供L2TPv3的扩展电路状态位值，并以与当前电路状态AVP向后兼容的方式添加它们。这些新位适用于使用电路状态AVP的所有伪线类型。
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。
The following abbreviations are used in this document and in the documents that it updates. L2TPv3 Control Message Types are listed in Section 6 of [RFC3931].
本文件及其更新的文件中使用了以下缩写。L2TPv3控制消息类型在[RFC3931]的第6节中列出。
AC Attachment Circuit AVP Attribute Value Pair LCCE L2TP Control Connection Endpoint NNI Network-Network Interface PE Provider Edge PSN Packet Switched Network PW Pseudowire
交流连接电路AVP属性值对LCCE L2TP控制连接端点NNI网络接口PE提供程序边缘PSN分组交换网络PW伪线
The Circuit Status AVP (ICRQ, ICRP, ICCN, OCRQ, OCRP, OCCN, SLI), Attribute Type 71, indicates the initial status of, or a status change in, the circuit to which the session is bound.
电路状态AVP（ICRQ、ICRP、ICCN、OCRQ、OCRP、OCCN、SLI）属性类型71表示会话绑定到的电路的初始状态或状态更改。
The Attribute Value field for this AVP, currently defined in [RFC3931], has the following format:
[RFC3931]中当前定义的该AVP的属性值字段具有以下格式：
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |N|A|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |N|A|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Bit Bit-Value Name
----------------------------------------------------------------
(A) 15 0x0001 Active
(N) 14 0x0002 New
Bit Bit-Value Name
----------------------------------------------------------------
(A) 15 0x0001 Active
(N) 14 0x0002 New
As currently defined in [RFC3931] and replicated in [RFC4349], [RFC4454], [RFC4591], and [RFC4719], the two bits have the following meanings:
如[RFC3931]中当前定义并在[RFC4349]、[RFC4454]、[RFC4591]和[RFC4719]中复制的，这两个位具有以下含义：
o The A (Active) bit indicates whether the circuit is up/active/ ready (1) or down/inactive/not-ready (0).
o A（活动）位指示电路是向上/活动/就绪（1）还是向下/非活动/未就绪（0）。
o The N (New) bit indicates whether the circuit status indication is for a new circuit (1) or an existing circuit (0).
o N（新）位表示电路状态指示是针对新电路（1）还是针对现有电路（0）。
This document updates the semantics of the A and N bits as follows (see also Section 4):
本文件更新了A和N位的语义，如下所示（另见第4节）：
The A (Active) bit indicates whether the local pseudowire endpoint (including the local Attachment Circuit (AC) and local Packet Switched Network (PSN)-facing pseudowire termination) has no faults present and is up/active/ready (1) or has faults present and is down/ inactive/not-ready (0).
A（活动）位指示本地伪线端点（包括本地连接电路（AC）和面向本地分组交换网络（PSN）的伪线终端）是否不存在故障且处于启动/活动/就绪状态（1），或者是否存在故障且处于关闭/非活动/未就绪状态（0）。
The N (New) bit indicates if the notification is for a new circuit (1) or an existing circuit (0), and is provided to emulate Network-Network Interface (NNI) signaling between Provider Edge (PE) routers, e.g., Frame Relay NNI. It MAY be used to convey that a circuit has been re-provisioned or newly provisioned at the PE, which can already be inferred from the L2TP control message type. It is therefore uncertain as to what use the receiving PE can make of this bit, although it MAY include logging. This document deprecates this bit as it is of little or no use, hence this bit SHOULD be ignored on receipt and is OPTIONAL to set on sending. For reference, see Section 3.4 of [RFC4591], which does not specify any additional usage beyond the setting of the N bit in the ICRQ, ICRP (and OCRQ, OCRP) and the clearing of it in all other control messages.
N（新）位指示通知是针对新电路（1）还是现有电路（0），并用于模拟提供商边缘（PE）路由器（例如帧中继NNI）之间的网络接口（NNI）信令。它可用于表示已在PE处重新配置或新配置了电路，这已经可以从L2TP控制消息类型推断出来。因此，虽然接收PE可能包括日志记录，但接收PE如何利用该位还不确定。此文档不推荐此位，因为它几乎没有用处或没有用处，因此在接收时应忽略此位，并且在发送时可选择设置此位。参考请参见[RFC4591]第3.4节，该节未规定除ICRQ、ICRP（和OCRQ、OCRP）中的N位设置和所有其他控制消息中的清除之外的任何其他用途。
This document also extends this bitmap of values to allow for finer granularity of local pseudowire (i.e., Attachment Circuit or PSN-facing endpoint) status reporting.
本文档还扩展了该值位图，以允许更细粒度的本地伪线（即，连接电路或面向PSN的端点）状态报告。
The Attribute Value field for the Circuit Status AVP, including the new values, has the following format:
电路状态AVP的属性值字段（包括新值）具有以下格式：
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |S|E|I|T|R|N|A|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |S|E|I|T|R|N|A|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Bit Bit-Value Name
-----------------------------------------------------------------
(A) 15 0x0001 Active: Pseudowire has no faults
(N) 14 0x0002 New [use deprecated]
(R) 13 0x0004 Local Attachment Circuit (ingress) Receive Fault
(T) 12 0x0008 Local Attachment Circuit (egress) Transmit Fault
(I) 11 0x0010 Local PSN-facing PW (ingress) Receive Fault
(E) 10 0x0020 Local PSN-facing PW (egress) Transmit Fault
(S) 9 0x0040 Pseudowire is in Standby mode
Bit Bit-Value Name
-----------------------------------------------------------------
(A) 15 0x0001 Active: Pseudowire has no faults
(N) 14 0x0002 New [use deprecated]
(R) 13 0x0004 Local Attachment Circuit (ingress) Receive Fault
(T) 12 0x0008 Local Attachment Circuit (egress) Transmit Fault
(I) 11 0x0010 Local PSN-facing PW (ingress) Receive Fault
(E) 10 0x0020 Local PSN-facing PW (egress) Transmit Fault
(S) 9 0x0040 Pseudowire is in Standby mode
The new bit values have the following meanings:
新的位值具有以下含义：
(R), Local Attachment Circuit (ingress) Receive Fault
（R） ，本地连接电路（入口）接收故障
Fault Here
|
|
| +----------------------+ +----------------------+
| Rx| LCCE |Egress | Peer LCCE |
--X-->| |-------->| |
| L2TPv3 | [PSN] | L2TPv3 |
Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit |
<-----| |<--------| |
+----------------------+ +----------------------+
Fault Here
|
|
| +----------------------+ +----------------------+
| Rx| LCCE |Egress | Peer LCCE |
--X-->| |-------->| |
| L2TPv3 | [PSN] | L2TPv3 |
Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit |
<-----| |<--------| |
+----------------------+ +----------------------+
An alarm or fault has occurred at the local Attachment Circuit such that it is unable to receive traffic. It can still transmit traffic.
本地连接电路发生警报或故障，无法接收通信。它仍然可以传输流量。
(T), Local Attachment Circuit (egress) Transmit Fault
（T） ，本地连接电路（出口）传输故障
+----------------------+ +----------------------+
Rx| LCCE |Egress | Peer LCCE |
----->| |-------->| |
| L2TPv3 | [PSN] | L2TPv3 |
Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit |
<--X--| |<--------| |
| +----------------------+ +----------------------+
|
|
Fault Here
+----------------------+ +----------------------+
Rx| LCCE |Egress | Peer LCCE |
----->| |-------->| |
| L2TPv3 | [PSN] | L2TPv3 |
Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit |
<--X--| |<--------| |
| +----------------------+ +----------------------+
|
|
Fault Here
A fault has occurred at the local Attachment Circuit such that it is unable to transmit traffic. It can still receive traffic.
本地连接电路发生故障，无法传输通信量。它仍然可以接收流量。
(I), Local PSN-facing PW (ingress) Receive Fault
（一） ，面向PW（入口）的本地PSN接收故障
+----------------------+ +----------------------+
Rx| LCCE |Egress | Peer LCCE |
----->| |-------->| |
| L2TPv3 | [PSN] | L2TPv3 |
Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit |
<-----| |<---X----| |
+----------------------+ | +----------------------+
|
|
Fault Here
+----------------------+ +----------------------+
Rx| LCCE |Egress | Peer LCCE |
----->| |-------->| |
| L2TPv3 | [PSN] | L2TPv3 |
Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit |
<-----| |<---X----| |
+----------------------+ | +----------------------+
|
|
Fault Here
A fault has occurred in the receive direction between the local endpoint and the remote L2TP endpoint.
本地终结点和远程L2TP终结点之间的接收方向发生故障。
Note that a fault at the session level would not necessarily trigger an L2TP control connection timeout. The means of detecting this fault are outside the scope of this document; as an example, detection may be via PW Type-specific means, Bidirectional Forwarding Detection (BFD), or other methods.
请注意，会话级别的故障不一定会触发L2TP控制连接超时。检测该故障的方法不在本文件范围内；例如，检测可经由PW类型特定装置、双向转发检测（BFD）或其它方法。
(E), Local PSN-facing PW (egress) Transmit Fault
（E） ，本地PSN面对PW（出口）传输故障
Fault Here
|
|
+----------------------+ | +----------------------+
Rx| LCCE |Egress| | Peer LCCE |
----->| |------X->| |
| L2TPv3 | [PSN] | L2TPv3 |
Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit |
<-----| |<--------| |
+----------------------+ +----------------------+
Fault Here
|
|
+----------------------+ | +----------------------+
Rx| LCCE |Egress| | Peer LCCE |
----->| |------X->| |
| L2TPv3 | [PSN] | L2TPv3 |
Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit |
<-----| |<--------| |
+----------------------+ +----------------------+
A fault has occurred in the transmit direction between the local endpoint and the remote L2TP endpoint.
本地端点和远程L2TP端点之间的传输方向发生故障。
Note that a fault at the session level would not necessarily trigger an L2TP control connection timeout. The means of detecting this fault are outside the scope of this document; as an example, detection may be via PW Type-specific means, BFD, or other methods.
请注意，会话级别的故障不一定会触发L2TP控制连接超时。检测该故障的方法不在本文件范围内；例如，可通过PW类型特定手段、BFD或其他方法进行检测。
(S), Pseudowire is in Standby mode
（S） ，伪线处于待机模式
Standby
|
|
+----------------------+ | +----------------------+
Rx| LCCE |Egress | Peer LCCE |
----->| |---X---->| |
| L2TPv3 | [PSN] | L2TPv3 |
Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit |
<-----| |<--X-----| |
+----------------------+ | +----------------------+
|
|
Standby
Standby
|
|
+----------------------+ | +----------------------+
Rx| LCCE |Egress | Peer LCCE |
----->| |---X---->| |
| L2TPv3 | [PSN] | L2TPv3 |
Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit |
<-----| |<--X-----| |
+----------------------+ | +----------------------+
|
|
Standby
The pseudowire has been placed into a Standby mode, which means that although it was signaled (during setup of the PW) and is operational, it is NOT switching user traffic. Any received user traffic SHOULD be dropped. User traffic MUST NOT be transmitted.
伪线已被置于待机模式，这意味着尽管它已发出信号（在PW设置期间）且处于运行状态，但它并未切换用户通信量。应丢弃任何接收到的用户流量。不得传输用户流量。
A standby pseudowire also allows for means to check its data plane liveness in order to ensure its ability to switch data packets end-to-end. This is achieved, for example, as detailed in [RFC5085] or [VCCV-BFD]. However, data is not forwarded from an Attachment Circuit (AC) into the L2TPv3 session, or from the L2TPv3 session out to the AC.
备用伪线还允许检查其数据平面活动性，以确保其端到端交换数据包的能力。例如，如[RFC5085]或[VCCV-BFD]中所述，可以实现这一点。但是，数据不会从连接电路（AC）转发到L2TPv3会话，也不会从L2TPv3会话转发到AC。
In implementations prior to this specification, bits 0-13 MUST be set to zero (see Section 5.4.5 of [RFC3931]). This allows for legacy implementations to interwork properly with new implementations.
在本规范之前的实施中，位0-13必须设置为零（见[RFC3931]第5.4.5节）。这允许遗留实现与新实现正常交互。
The following are clarifications regarding the usage of the Circuit Status AVP bits as defined in this specification:
以下是关于本规范中定义的电路状态AVP位使用的澄清：
o The (R), (T), (I), and (E) bits are collectively referred to as "fault status bits".
o （R）、（T）、（I）和（E）位统称为“故障状态位”。
o [RFC3931] defined the (A) bit as pertaining to local access circuit state only. This document redefines it as meaning that "no faults are present on the local pseudowire endpoint."
o [RFC3931]将（A）位定义为仅与本地访问电路状态有关。本文档将其重新定义为“本地伪线端点上不存在故障”
o If multiple faults occur, all the fault status bits corresponding to each fault MUST be set (i.e., they MUST be bitwise ORed together).
o 如果发生多个故障，则必须设置与每个故障对应的所有故障状态位（即，它们必须按位或在一起）。
o The (A) bit MUST NOT be set until all fault status bits are cleared. This behavior allows an endpoint to be backwards compatible with a remote endpoint that does not understand these new status bits.
o 在清除所有故障状态位之前，不得设置（A）位。此行为允许端点与不了解这些新状态位的远程端点向后兼容。
o If any of the fault status bits are set, then the (A) bit MUST be cleared. That is, the fault status bits (R, T, I, E) are a more granular definition of (A), such that ORing the bits provides an inverted (A).
o 如果设置了任何故障状态位，则必须清除（A）位。也就是说，故障状态位（R，T，I，E）是（a）的更精细的定义，使得对位进行ORing提供了一个反向（a）。
o If (A) is clear and the fault status bits (R, T, I, E) are clear, it means that there is no extended circuit status. That is, the circuit is down/inactive/not-ready (from the (A) bit), without a more granular (extended) indication.
o 如果（A）清除且故障状态位（R、T、I、E）清除，则表示不存在扩展电路状态。也就是说，电路关闭/不活动/未准备就绪（从（A）位开始），没有更精细的（扩展）指示。
o The (S) bit can be set in conjunction with any other bit, including (A). A pseudowire endpoint in Standby (S bit set) can be up/active/ready (A bit set) or experiencing a fault (A bit cleared and one or more of the fault status bits (R, T, I, E) set.
o 位可以与任何其他位一起设置，包括（A）。备用（S位集）中的伪线端点可以是启动/活动/就绪（位集）或遇到故障（位清除和一个或多个故障状态位（R、T、I、E）集。
o Leaving Standby mode is indicated by the clearing of the (S) bit.
o 通过清除（S）位指示退出待机模式。
o The usage of the (N) bit has been deprecated.
o （N）位的用法已被弃用。
This document updates existing RFCs that define (either generically or in the context of a specific set of PW Types) the Active and New bits of the Circuit Status AVP. The Active and New bits of the Circuit Status AVP are specified in Section 5.4.5 of [RFC3931]. Those definitions are adapted to specific Attachment Circuits and replicated in Section 3.4 of [RFC4349] (High-Level Data Link Control Frames over L2TPv3), Section 8 of [RFC4454] (Asynchronous Transfer Mode over L2TPv3), Section 3.4 of [RFC4591] (Frame Relay over L2TPv3), and Section 2.3.3 of [RFC4719] (Ethernet Frames over L2TPv3). This document updates the definitions in all five of these references to say:
本文件更新了现有的RFC，这些RFC定义（一般或在特定PW类型集的上下文中）电路状态AVP的活动位和新位。[RFC3931]第5.4.5节规定了电路状态AVP的激活位和新位。这些定义适用于特定的连接电路，并在[RFC4349]第3.4节（L2TPv3上的高电平数据链路控制帧）、[RFC4454]第8节（L2TPv3上的异步传输模式）、[RFC4591]第3.4节（L2TPv3上的帧中继）和[RFC4719]第2.3.3节（L2TPv3上的以太网帧）中复制。本文件更新了所有五个参考文献中的定义，即：
The A (Active) bit indicates whether the local pseudowire endpoint (including the local Attachment Circuit and local PSN-facing pseudowire termination) has no faults present and is up/active/ ready (1) or has faults present and is down/inactive/not-ready (0).
A（活动）位指示本地伪线端点（包括本地连接电路和面向伪线终端的本地PSN）是否不存在故障，是否为up/Active/ready（1）或是否存在故障，是否为down/Active/not ready（0）。
The N (New) bit usage is deprecated; it SHOULD be ignored on receipt and is OPTIONAL to set on sending.
N（新）位用法已弃用；在接收时应忽略它，并且在发送时设置它是可选的。
This document also updates Section 2.2 (bullet c) of [RFC4719], removing the following two sentences:
本文件还更新了[RFC4719]第2.2节（项目符号c），删除了以下两句话：
For ICRQ and ICRP, the Circuit Status AVP MUST indicate that the circuit status is for a new circuit (refer to N bit in Section 2.3.3).
对于ICRQ和ICRP，电路状态AVP必须表明电路状态为新电路（参考第2.3.3节中的N位）。
For ICCN and SLI (refer to Section 2.3.2), the Circuit Status AVP MUST indicate that the circuit status is for an existing circuit (refer to N bit in Section 2.3.3) and reflect the current status of the link (refer to A bit in Section 2.3.3).
对于ICCN和SLI（参考第2.3.2节），电路状态AVP必须表明电路状态是针对现有电路的（参考第2.3.3节中的N位），并反映链路的当前状态（参考第2.3.3节中的位）。
And finally, this document updates Section 3.1 of [RFC4349], Section 3.1 of [RFC4454], Section 3.1 of [RFC4591], and Section 2.2 of [RFC4719] with the following paragraph addition:
最后，本文件更新了[RFC4349]第3.1节、[RFC4454]第3.1节、[RFC4591]第3.1节和[RFC4719]第2.2节，增加了以下段落：
The usage of the N bit in the Circuit Status AVP is deprecated. Therefore, for ICRQ and ICRP, the Circuit Status AVP need not indicate on sending (nor check on receipt) that the circuit status is for a new circuit, and for ICCN and SLI, the Circuit Status AVP need not indicate on sending (nor check on receipt) that the circuit status is for an existing circuit.
不推荐在电路状态AVP中使用N位。因此，对于ICRQ和ICRP，电路状态AVP无需在发送时指示（或在接收时检查）电路状态为新电路，对于ICCN和SLI，电路状态AVP无需在发送时指示（或在接收时检查）电路状态为现有电路。
Security considerations for the Circuit Status AVP are covered in the base L2TPv3 specification (see Section 8 of [RFC3931]). No additional security considerations exist with extending this attribute.
基本L2TPv3规范中涵盖了电路状态AVP的安全注意事项（参见[RFC3931]第8节）。扩展此属性时不存在其他安全注意事项。
The Circuit Status Bits number space [IANA-l2tp] is managed by IANA as per Section 10.7 of [RFC3931]. Five new bits (bits 9 through 13) and one updated bit (bit 14) have been assigned as follows:
电路状态位号空间[IANA-l2tp]由IANA根据[RFC3931]第10.7节进行管理。已分配五个新位（位9至13）和一个更新位（位14），如下所示：
Circuit Status Bits - per [RFC3931]
-------------------
Circuit Status Bits - per [RFC3931]
-------------------
Bit 9 - S (Standby) bit Bit 10 - E (Local PSN-facing PW (egress) Tx Fault) bit Bit 11 - I (Local PSN-facing PW (ingress) Rx Fault) bit Bit 12 - T (Local AC (egress) Tx Fault) bit Bit 13 - R (Local AC (ingress) Rx Fault) bit Bit 14 - N (New) bit [use deprecated]
位9-S（备用）位10-E（本地PSN面对PW（出口）发送故障）位11-I（本地PSN面对PW（入口）接收故障）位12-T（本地AC（出口）发送故障）位13-R（本地AC（入口）接收故障）位14-N（新）位[使用弃用]
The authors wish to thank Muhammad Yousuf, Mark Townsley, George Wilkie, Prashant Jhingran, Pawel Sowinski, and Ignacio Goyret for useful comments received.
作者希望感谢穆罕默德·优素福、马克·汤斯利、乔治·威尔基、普拉尚特·金兰、帕维尔·索温斯基和伊格纳西奥·戈雷特收到的有用评论。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.
[RFC3931]Lau，J.，Townsley，M.，和I.Goyret，“第二层隧道协议-版本3（L2TPv3）”，RFC 39312005年3月。
[RFC4349] Pignataro, C. and M. Townsley, "High-Level Data Link Control (HDLC) Frames over Layer 2 Tunneling Protocol, Version 3 (L2TPv3)", RFC 4349, February 2006.
[RFC4349]Pignataro，C.和M.Townsley，“第2层隧道协议上的高级数据链路控制（HDLC）帧，第3版（L2TPv3）”，RFC 4349，2006年2月。
[RFC4454] Singh, S., Townsley, M., and C. Pignataro, "Asynchronous Transfer Mode (ATM) over Layer 2 Tunneling Protocol Version 3 (L2TPv3)", RFC 4454, May 2006.
[RFC4454]Singh，S.，Townsley，M.，和C.Pignataro，“第2层隧道协议第3版（L2TPv3）上的异步传输模式（ATM）”，RFC 4454，2006年5月。
[RFC4591] Townsley, M., Wilkie, G., Booth, S., Bryant, S., and J. Lau, "Frame Relay over Layer 2 Tunneling Protocol Version 3 (L2TPv3)", RFC 4591, August 2006.
[RFC4591]Townsley，M.，Wilkie，G.，Booth，S.，Bryant，S.，和J.Lau，“第2层隧道协议第3版（L2TPv3）上的帧中继”，RFC 45912006年8月。
[RFC4719] Aggarwal, R., Townsley, M., and M. Dos Santos, "Transport of Ethernet Frames over Layer 2 Tunneling Protocol Version 3 (L2TPv3)", RFC 4719, November 2006.
[RFC4719]Aggarwal，R.，Townsley，M.和M.Dos Santos，“通过第2层隧道协议版本3（L2TPv3）传输以太网帧”，RFC 4719，2006年11月。
[IANA-l2tp] Internet Assigned Numbers Authority, "Layer Two Tunneling Protocol 'L2TP'", <http://www.iana.org>.
[IANA-l2tp]互联网分配号码管理局，“第二层隧道协议‘l2tp’”<http://www.iana.org>.
[PREF-FWD] Muley, P., Bocci, M., and L. Martini, "Preferential Forwarding Status bit definition", Work in Progress, September 2008.
[PREF-FWD]Muley，P.，Bocci，M.，和L.Martini，“优先转发状态位定义”，正在进行的工作，2008年9月。
[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)", BCP 116, RFC 4446, April 2006.
[RFC4446]Martini，L.，“伪线边到边仿真（PWE3）的IANA分配”，BCP 116，RFC 4446，2006年4月。
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4447]Martini，L.，Rosen，E.，El Aawar，N.，Smith，T.，和G.Heron，“使用标签分发协议（LDP）的伪线设置和维护”，RFC 4447，2006年4月。
[RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, December 2007.
[RFC5085]Nadeau，T.和C.Pignataro，“伪线虚拟电路连接验证（VCCV）：伪线的控制通道”，RFC 5085，2007年12月。
[VCCV-BFD] Nadeau, T. and C. Pignataro, "Bidirectional Forwarding Detection (BFD) for the Pseudowire Virtual Circuit Connectivity Verification (VCCV)", Work in Progress, July 2009.
[VCCV-BFD]Nadeau，T.和C.Pignataro，“伪线虚拟电路连接验证（VCCV）的双向转发检测（BFD）”，正在进行的工作，2009年7月。
Authors' Addresses
作者地址
Neil McGill Cisco Systems 7025-4 Kit Creek Road PO Box 14987 Research Triangle Park, NC 27709 USA
Neil McGill Cisco Systems 7025-4 Kit Creek Road邮政信箱14987美国北卡罗来纳州三角研究公园27709
EMail: nmcgill@cisco.com
EMail: nmcgill@cisco.com
Carlos Pignataro Cisco Systems 7200-12 Kit Creek Road PO Box 14987 Research Triangle Park, NC 27709 USA
Carlos Pignataro Cisco Systems 7200-12 Kit Creek Road邮政信箱14987美国北卡罗来纳州三角研究公园27709
EMail: cpignata@cisco.com
EMail: cpignata@cisco.com