Internet Engineering Task Force (IETF) H. Chen
Request for Comments: 8400 Huawei Technologies
Category: Standards Track A. Liu
ISSN: 2070-1721 Ciena
T. Saad
Cisco Systems
F. Xu
Verizon
L. Huang
China Mobile
June 2018
Internet Engineering Task Force (IETF) H. Chen
Request for Comments: 8400 Huawei Technologies
Category: Standards Track A. Liu
ISSN: 2070-1721 Ciena
T. Saad
Cisco Systems
F. Xu
Verizon
L. Huang
China Mobile
June 2018
Extensions to RSVP-TE for Label Switched Path (LSP) Egress Protection
用于标签交换路径（LSP）出口保护的RSVP-TE扩展
Abstract
摘要
This document describes extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for locally protecting the egress node(s) of a Point-to-Point (P2P) or Point-to-Multipoint (P2MP) Traffic Engineered (TE) Label Switched Path (LSP).
本文档描述了资源预留协议-流量工程（RSVP-TE）的扩展，用于本地保护点对点（P2P）或点对多点（P2MP）流量工程（TE）标签交换路径（LSP）的出口节点。
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 https://www.rfc-editor.org/info/rfc8400.
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https://www.rfc-editor.org/info/rfc8400.
Copyright Notice
版权公告
Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2018 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 (https://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.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(https://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。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Local Protection of Egress Nodes . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 5
4.1. Extensions to SERO . . . . . . . . . . . . . . . . . . . 5
4.1.1. Primary Egress Subobject . . . . . . . . . . . . . . 7
4.1.2. P2P LSP ID Subobject . . . . . . . . . . . . . . . . 8
5. Egress Protection Behaviors . . . . . . . . . . . . . . . . . 9
5.1. Ingress Behavior . . . . . . . . . . . . . . . . . . . . 9
5.2. Primary Egress Behavior . . . . . . . . . . . . . . . . . 10
5.3. Backup Egress Behavior . . . . . . . . . . . . . . . . . 10
5.4. Transit Node and PLR Behavior . . . . . . . . . . . . . . 11
5.4.1. Signaling for One-to-One Protection . . . . . . . . . 12
5.4.2. Signaling for Facility Protection . . . . . . . . . . 12
5.4.3. Signaling for S2L Sub-LSP Protection . . . . . . . . 13
5.4.4. PLR Procedures during Local Repair . . . . . . . . . 14
6. Application Traffic Considerations . . . . . . . . . . . . . 14
6.1. A Typical Application . . . . . . . . . . . . . . . . . . 14
6.2. PLR Procedure for Applications . . . . . . . . . . . . . 17
6.3. Egress Procedures for Applications . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
9.1. Normative References . . . . . . . . . . . . . . . . . . 18
9.2. Informative References . . . . . . . . . . . . . . . . . 19
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 19
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Local Protection of Egress Nodes . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 5
4.1. Extensions to SERO . . . . . . . . . . . . . . . . . . . 5
4.1.1. Primary Egress Subobject . . . . . . . . . . . . . . 7
4.1.2. P2P LSP ID Subobject . . . . . . . . . . . . . . . . 8
5. Egress Protection Behaviors . . . . . . . . . . . . . . . . . 9
5.1. Ingress Behavior . . . . . . . . . . . . . . . . . . . . 9
5.2. Primary Egress Behavior . . . . . . . . . . . . . . . . . 10
5.3. Backup Egress Behavior . . . . . . . . . . . . . . . . . 10
5.4. Transit Node and PLR Behavior . . . . . . . . . . . . . . 11
5.4.1. Signaling for One-to-One Protection . . . . . . . . . 12
5.4.2. Signaling for Facility Protection . . . . . . . . . . 12
5.4.3. Signaling for S2L Sub-LSP Protection . . . . . . . . 13
5.4.4. PLR Procedures during Local Repair . . . . . . . . . 14
6. Application Traffic Considerations . . . . . . . . . . . . . 14
6.1. A Typical Application . . . . . . . . . . . . . . . . . . 14
6.2. PLR Procedure for Applications . . . . . . . . . . . . . 17
6.3. Egress Procedures for Applications . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
9.1. Normative References . . . . . . . . . . . . . . . . . . 18
9.2. Informative References . . . . . . . . . . . . . . . . . 19
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 19
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
[RFC4090] describes two methods for locally protecting the transit nodes of a P2P LSP: one-to-one and facility protection. [RFC4875] specifies how these methods can be used to protect the transit nodes of a P2MP LSP. These documents do not discuss the procedures for locally protecting the egress node(s) of an LSP.
[RFC4090]描述了两种本地保护P2P LSP传输节点的方法：一对一和设施保护。[RFC4875]指定如何使用这些方法来保护P2MP LSP的传输节点。这些文件不讨论本地保护LSP出口节点的程序。
This document fills that void and specifies extensions to RSVP-TE for local protection of the egress node(s) of an LSP. "Egress node" and "egress" are used interchangeably.
本文档填补了这一空白，并指定了对RSVP-TE的扩展，用于本地保护LSP的出口节点。“出口节点”和“出口”互换使用。
In general, locally protecting an egress node of an LSP means that when the egress node fails, the traffic that the LSP carries will be delivered to its destination by the direct upstream node of the egress node to a backup egress node. Without protecting the egress node of the LSP, when the egress node fails, the traffic will be lost (i.e., the traffic will not be delivered to its destination).
通常，本地保护LSP的出口节点意味着当出口节点失败时，LSP承载的业务将由出口节点的直接上游节点传送到其目的地，并传送到备用出口节点。在不保护LSP的出口节点的情况下，当出口节点发生故障时，通信量将丢失（即，通信量将不会传送到其目的地）。
Figure 1 shows an example of using backup LSPs to locally protect egress nodes L1 and L2 of a primary P2MP LSP starting from ingress node R1. La and Lb are the designated backup egress nodes for primary egress nodes L1 and L2, respectively. The backup LSP for protecting L1 is from its upstream node R3 to backup egress node La, and the backup LSP for protecting L2 is from R5 to Lb.
图1显示了使用备份LSP从入口节点R1开始本地保护主P2MP LSP的出口节点L1和L2的示例。La和Lb分别是主出口节点L1和L2的指定备份出口节点。用于保护L1的备份LSP从其上游节点R3到备份出口节点La，用于保护L2的备份LSP从R5到Lb。
******* ******* S Source
[R2]-----[R3]-----[L1] CEx Customer Edge
*/ &\ \ Rx Non-Egress
*/ &\ \ Lx Egress
*/ &\ [CE1] *** Primary LSP
*/ &\ / &&& Backup LSP
*/ &\ /
*/ [La]
*/
*/
*/
*/ ******** ******** *******
[S]---[R1]------[R4]------[R5]-----[L2]
&\ \
&\ \
&\ [CE2]
&\ /
&\ /
[Lb]
******* ******* S Source
[R2]-----[R3]-----[L1] CEx Customer Edge
*/ &\ \ Rx Non-Egress
*/ &\ \ Lx Egress
*/ &\ [CE1] *** Primary LSP
*/ &\ / &&& Backup LSP
*/ &\ /
*/ [La]
*/
*/
*/
*/ ******** ******** *******
[S]---[R1]------[R4]------[R5]-----[L2]
&\ \
&\ \
&\ [CE2]
&\ /
&\ /
[Lb]
Figure 1: Backup LSP for Locally Protecting Egress
图1：用于本地保护出口的备份LSP
During normal operations, the traffic carried by the P2MP LSP is sent through R3 to L1, which delivers the traffic to its destination CE1. When R3 detects the failure of L1, R3 switches the traffic to the backup LSP to backup egress node La, which delivers the traffic to CE1. The time for switching the traffic is within tens of milliseconds.
在正常操作期间，P2MP LSP承载的流量通过R3发送到L1，L1将流量发送到其目的地CE1。当R3检测到L1故障时，R3将流量切换到备份LSP以备份出口节点La，后者将流量发送到CE1。切换流量的时间在几十毫秒之内。
The exact mechanism by which the failure of the primary egress node is detected by the upstream node R3 is out of the scope of this document.
上游节点R3检测主出口节点故障的确切机制不在本文档的范围内。
In the beginning, the primary P2MP LSP from ingress node R1 to primary egress nodes L1 and L2 is configured. It may be used to transport the traffic from source S, which is connected to R1, to destinations CE1 and CE2, which are connected to L1 and L2, respectively.
首先，配置从入口节点R1到主出口节点L1和L2的主P2MP LSP。它可用于将业务从连接到R1的源S传输到分别连接到L1和L2的目的地CE1和CE2。
To protect the primary egress nodes L1 and L2, one configures on the ingress node R1 a backup egress node for L1, another backup egress node for L2, and other options. After the configuration, the ingress node sends a Path message for the LSP with information such as the Secondary Explicit Route Objects (SEROs), refer to Section 4.1, containing the backup egress nodes for protecting the primary egress nodes.
为了保护主出口节点L1和L2，在入口节点R1上配置用于L1的备份出口节点、用于L2的另一备份出口节点和其他选项。配置完成后，入口节点向LSP发送一条路径消息，其中包含辅助显式路由对象（SERO）等信息，参见第4.1节，其中包含用于保护主出口节点的备份出口节点。
After receiving the Path message with the information, the upstream node of a primary egress node sets up a backup LSP to the corresponding backup egress node for protecting the primary egress node.
在接收到带有该信息的路径消息之后，主出口节点的上游节点建立到相应的备份出口节点的备份LSP以保护主出口节点。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“建议”、“不建议”、“可”和“可选”在所有大写字母出现时（如图所示）应按照BCP 14[RFC2119][RFC8174]所述进行解释。
The following terminology is used in this document.
本文件使用以下术语。
LSP: Label Switched Path
标签交换路径
TE: Traffic Engineering
交通工程
P2MP: Point-to-Multipoint
P2MP：点对多点
P2P: Point-to-Point
P2P：点对点
LSR: Label Switching Router
标签交换路由器
RSVP: Resource Reservation Protocol
资源预留协议
S2L: Source-to-Leaf
S2L：源到叶
SERO: Secondary Explicit Route Object
SERO：次显式路由对象
RRO: Record Route Object
记录路由对象
BFD: Bidirectional Forwarding Detection
双向转发检测
VPN: Virtual Private Network
虚拟专用网
L3VPN: Layer 3 VPN
L3VPN：第三层VPN
VRF: Virtual Routing and Forwarding
虚拟路由和转发
LFIB: Label Forwarding Information Base
LFIB：标签转发信息库
UA: Upstream Assigned
UA：上游分配
PLR: Point of Local Repair
PLR：局部维修点
BGP: Border Gateway Protocol
边界网关协议
CE: Customer Edge
行政长官：顾客优势
PE: Provider Edge
PE：提供程序边缘
The Secondary Explicit Route Object (SERO) is defined in [RFC4873]. The format of the SERO is reused.
第二显式路由对象（SERO）在[RFC4873]中定义。SERO的格式被重用。
The SERO used for protecting a primary egress node of a primary LSP may be added into the Path messages for the LSP and sent from the ingress node of the LSP to the upstream node of the egress node. It contains three subobjects.
用于保护主LSP的主出口节点的SERO可以添加到LSP的路径消息中，并从LSP的入口节点发送到出口节点的上游节点。它包含三个子对象。
The first subobject (refer to Section 4.2 of [RFC4873]) indicates the branch node that is to originate the backup LSP (to a backup egress node). The branch node is typically the direct upstream node of the primary egress node of the primary LSP. If the direct upstream node does not support local protection against the failure of the primary egress node, the branch node can be any (upstream) node on the primary LSP. In this case, the backup LSP from the branch node to the backup egress node protects against failures on the segment of the primary LSP from the branch node to, and including, the primary egress node.
第一个子对象（参考[RFC4873]第4.2节）表示将发起备份LSP（到备份出口节点）的分支节点。分支节点通常是主LSP的主出口节点的直接上游节点。如果直接上游节点不支持针对主出口节点故障的本地保护，则分支节点可以是主LSP上的任何（上游）节点。在这种情况下，从分支节点到备份出口节点的备份LSP保护从分支节点到（包括）主出口节点的主LSP段上的故障。
The second subobject is an Egress Protection subobject, which is a PROTECTION object with a new C-Type (3). The format of the Egress Protection subobject is defined as follows:
第二个子对象是出口保护子对象，它是具有新C类型（3）的保护对象。出口保护子对象的格式定义如下：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Reserved | C-Type (3) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |E-Flags|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Subobjects |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Reserved | C-Type (3) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |E-Flags|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Subobjects |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E-Flags are defined for local protection of egress nodes.
为出口节点的本地保护定义了E标志。
Bit 31 ("egress local protection" flag): It is the least significant bit of the 32-bit word and is set to 1, which indicates that local protection of egress nodes is desired.
位31（“出口本地保护”标志）：它是32位字的最低有效位，设置为1，表示需要出口节点的本地保护。
Bit 30 ("S2L sub-LSP backup desired" flag): It is the second least significant bit of the 32-bit word and is set to 1, which indicates an S2L sub-LSP (refer to [RFC4875]) is desired for protecting an egress node of a P2MP LSP.
位30（“S2L子LSP备份所需”标志）：它是32位字的第二个最低有效位，设置为1，表示需要S2L子LSP（参考[RFC4875]）来保护P2MP LSP的出口节点。
The Reserved parts MUST be set to zero on transmission and MUST be ignored on receipt.
传输时必须将保留零件设置为零，接收时必须忽略。
Four optional subobjects are defined: they are IPv4 and IPv6 primary egress node subobjects as well as IPv4 and IPv6 P2P LSP ID subobjects. IPv4 and IPv6 primary egress node subobjects indicate the IPv4 and IPv6 address of the primary egress node, respectively. IPv4 and IPv6 P2P LSP ID subobjects contain the information for identifying IPv4 and IPv6 backup P2P LSP tunnels, respectively. Their contents are described in Sections 4.1.1 through 4.1.2.2. They have the following format:
定义了四个可选子对象：它们是IPv4和IPv6主出口节点子对象以及IPv4和IPv6 P2P LSP ID子对象。IPv4和IPv6主出口节点子对象分别表示主出口节点的IPv4和IPv6地址。IPv4和IPv6 P2P LSP ID子对象分别包含用于标识IPv4和IPv6备份P2P LSP隧道的信息。其内容见第4.1.1节至第4.1.2.2节。它们的格式如下：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved (zero) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Contents / Body of Subobject |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved (zero) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Contents / Body of Subobject |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where Type is the type of a subobject and Length is the total size of the subobject in bytes, including Type, Length, and Contents fields. The Reserved field MUST be set to zero on transmission and MUST be ignored on receipt.
其中，Type是子对象的类型，Length是子对象的总大小（以字节为单位），包括Type、Length和Contents字段。传输时必须将保留字段设置为零，接收时必须忽略该字段。
The third (final) subobject (refer to Section 4.2 of [RFC4873]) in the SERO contains the egress node of the backup LSP, i.e., the address of the backup egress node in the place of the merge node.
SERO中的第三（最终）子对象（参考[RFC4873]的第4.2节）包含备份LSP的出口节点，即备份出口节点的地址代替合并节点。
After the upstream node of the primary egress node (a.k.a. the branch node) receives the SERO and determines a backup egress node for the primary egress node, it computes a path from itself to the backup egress node and sets up a backup LSP along the path for protecting the primary egress node according to the information in the FAST_REROUTE object in the Path message. For example, if facility protection is desired, it is provided for the primary egress node.
在主出口节点的上游节点（也称为分支节点）接收SERO并确定主出口节点的备用出口节点之后，它计算从自身到备份出口节点的路径，并根据路径消息中的FAST_REROUTE对象中的信息沿路径建立备份LSP以保护主出口节点。例如，如果需要设施保护，则为主出口节点提供设施保护。
The upstream node constructs a new SERO based on the SERO received and adds the new SERO into the Path message for the backup LSP. The new SERO also contains three subobjects as the SERO for the primary LSP. The first subobject in the new SERO indicates the upstream node, which may be copied from the first subobject in the SERO received. The second subobject in the new SERO includes a primary egress node, which indicates the address of the primary egress node. The third one contains the backup egress node.
上游节点基于接收到的SERO构造新的SERO，并将新的SERO添加到备份LSP的路径消息中。新的血清还包含三个子对象作为主要LSP的血清。新SERO中的第一个子对象表示上游节点，该节点可以从接收到的SERO中的第一个子对象复制。新SERO中的第二个子对象包括主出口节点，其指示主出口节点的地址。第三个包含备份出口节点。
The upstream node updates the SERO in the Path message for the primary LSP. The Egress Protection subobject in the SERO contains a subobject called a P2P LSP ID subobject, which contains the information for identifying the backup LSP. The final subobject in the SERO indicates the address of the backup egress node.
上游节点更新主LSP路径消息中的SERO。SERO中的出口保护子对象包含一个称为P2P LSP ID子对象的子对象，该子对象包含用于标识备份LSP的信息。SERO中的最后一个子对象指示备份出口节点的地址。
There are two primary egress subobjects: the IPv4 primary egress subobject and the IPv6 primary egress subobject.
有两个主出口子对象：IPv4主出口子对象和IPv6主出口子对象。
The Type of an IPv4 primary egress subobject is 1, and the body of the subobject is given below:
IPv4主出口子对象的类型为1，子对象的主体如下所示：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o IPv4 Address: The IPv4 address of the primary egress node.
o IPv4地址：主出口节点的IPv4地址。
The Type of an IPv6 primary egress subobject is 2, and the body of the subobject is shown below:
IPv6主出口子对象的类型为2，子对象的主体如下所示：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Address (16 bytes) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Address (16 bytes) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o IPv6 Address: The IPv6 address of the primary egress node.
o IPv6地址：主出口节点的IPv6地址。
A P2P LSP ID subobject contains the information for identifying a backup P2P LSP tunnel.
P2P LSP ID子对象包含用于标识备份P2P LSP隧道的信息。
The Type of an IPv4 P2P LSP ID subobject is 3, and the body of the subobject is shown below:
IPv4 P2P LSP ID子对象的类型为3，子对象的主体如下所示：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P2P LSP Tunnel Egress IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (MUST be zero) | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P2P LSP Tunnel Egress IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (MUST be zero) | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o P2P LSP Tunnel Egress IPv4 Address: The IPv4 address of the egress node of the tunnel.
o P2P LSP隧道出口IPv4地址：隧道出口节点的IPv4地址。
o Tunnel ID (refer to [RFC4875] and [RFC3209]): A 16-bit identifier that remains constant over the life of the tunnel and occupies the least significant 16 bits of the 32-bit word.
o 隧道ID（参考[RFC4875]和[RFC3209]）：在隧道寿命期间保持不变的16位标识符，占据32位字的最低有效16位。
o Extended Tunnel ID (refer to [RFC4875] and [RFC3209]): A 4-byte identifier that remains constant over the life of the tunnel.
o 扩展隧道ID（请参阅[RFC4875]和[RFC3209]）：在隧道寿命期间保持不变的4字节标识符。
The Type of an IPv6 P2P LSP ID subobject is 4, and the body of the subobject is illustrated below:
IPv6 P2P LSP ID子对象的类型为4，子对象的主体如下图所示：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ P2P LSP Tunnel Egress IPv6 Address (16 bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (MUST be zero) | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Extended Tunnel ID (16 bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ P2P LSP Tunnel Egress IPv6 Address (16 bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (MUST be zero) | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Extended Tunnel ID (16 bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o P2P LSP Tunnel Egress IPv6 Address: The IPv6 address of the egress node of the tunnel.
o P2P LSP隧道出口IPv6地址：隧道出口节点的IPv6地址。
o Tunnel ID (refer to [RFC4875] and [RFC3209]): A 16-bit identifier that remains constant over the life of the tunnel and occupies the least significant 16 bits of the 32-bit word.
o 隧道ID（参考[RFC4875]和[RFC3209]）：在隧道寿命期间保持不变的16位标识符，占据32位字的最低有效16位。
o Extended Tunnel ID (refer to [RFC4875] and [RFC3209]): A 16-byte identifier that remains constant over the life of the tunnel.
o 扩展隧道ID（请参阅[RFC4875]和[RFC3209]）：在隧道寿命期间保持不变的16字节标识符。
To protect a primary egress node of an LSP, the ingress node MUST set the "label recording desired" flag and the "node protection desired" flag in the SESSION_ATTRIBUTE object.
为了保护LSP的主出口节点，入口节点必须在会话_属性对象中设置“标签记录所需”标志和“节点保护所需”标志。
If one-to-one backup or facility backup is desired to protect a primary egress node of an LSP, the ingress node MUST include a FAST_REROUTE object and set the "one-to-one backup desired" or "facility backup desired" flag, respectively.
如果需要一对一备份或设施备份来保护LSP的主出口节点，则入口节点必须包括快速重新路由对象，并分别设置“需要一对一备份”或“需要设施备份”标志。
If S2L sub-LSP backup is desired to protect a primary egress node of a P2MP LSP, the ingress node MUST set the "S2L sub-LSP backup desired" flag in an SERO object.
如果需要S2L子LSP备份来保护P2MP LSP的主出口节点，则入口节点必须在SERO对象中设置“S2L子LSP备份所需”标志。
The decision to instantiate a backup egress node for protecting the primary egress node of an LSP can be initiated by either the ingress node or the primary egress node of that LSP, but not both.
实例化备份出口节点以保护LSP的主出口节点的决定可以由该LSP的入口节点或主出口节点发起，但不能同时由两者发起。
A backup egress node MUST be configured on the ingress node of an LSP to protect a primary egress node of the LSP if and only if the backup egress node is not configured on the primary egress node (refer to Section 5.2).
当且仅当主出口节点上未配置备份出口节点时，必须在LSP的入口节点上配置备份出口节点，以保护LSP的主出口节点（参考第5.2节）。
The ingress node MUST send a Path message for the LSP with the objects above and the SEROs for protecting egress nodes of the LSP if protection of the egress nodes is desired. For each primary egress node of the LSP to be protected, the ingress node MUST add an SERO object into the Path message if the backup egress node, or some options, are given. If the backup egress node is given, then the final subobject in the SERO contains it; otherwise, the address in the final subobject is zero.
如果需要保护出口节点，则入口节点必须发送带有上述对象的LSP路径消息和用于保护LSP出口节点的SEROs。对于要保护的LSP的每个主出口节点，如果提供了备份出口节点或某些选项，则入口节点必须在路径消息中添加一个SERO对象。如果给定了备份出口节点，那么SERO中的最终子对象包含它；否则，最后一个子对象中的地址为零。
To protect a primary egress node of an LSP, a backup egress node MUST be configured on the primary egress node of the LSP to protect the primary egress node if and only if the backup egress node is not configured on the ingress node of the LSP (refer to Section 5.1).
为了保护LSP的主出口节点，必须在LSP的主出口节点上配置一个备份出口节点，以在且仅在LSP的入口节点上未配置备份出口节点时保护主出口节点（参考第5.1节）。
If the backup egress node is configured on the primary egress node of the LSP, the primary egress node MUST send its upstream node a Resv message for the LSP with an SERO for protecting the primary egress node. It sets the flags in the SERO in the same way as an ingress node.
如果在LSP的主出口节点上配置了备份出口节点，则主出口节点必须向其上游节点发送用于LSP的Resv消息，其中SERO用于保护主出口节点。它以与入口节点相同的方式设置SERO中的标志。
If the LSP carries the service traffic with a service label, the primary egress node sends its corresponding backup egress node the information about the service label as a UA label (refer to [RFC5331]) and the related forwarding.
如果LSP携带带有服务标签的服务通信量，则主出口节点向其相应的备份出口节点发送关于服务标签的信息作为UA标签（参考[RFC5331]）和相关转发。
When a backup egress node receives a Path message for an LSP, it determines whether the LSP is used for egress local protection by checking the SERO with an Egress Protection subobject in the message. If there is an Egress Protection subobject in the Path message for the LSP and the "egress local protection" flag in the object is set to 1, the LSP is the backup LSP for local protection of an egress node. The primary egress node to be protected is in the primary egress subobject in the SERO.
当备份出口节点接收到LSP的路径消息时，它通过检查消息中带有出口保护子对象的SERO来确定LSP是否用于出口本地保护。如果在LSP的路径消息中存在出口保护子对象，并且该对象中的“出口本地保护”标志设置为1，则LSP是用于出口节点的本地保护的备份LSP。要保护的主出口节点位于SERO中的主出口子对象中。
When the backup egress node receives the information about a UA label and its related forwarding from the primary egress node, it uses the backup LSP label as a context label and creates a forwarding entry using the information about the UA label and the related forwarding.
当备份出口节点从主出口节点接收到关于UA标签及其相关转发的信息时，它使用备份LSP标签作为上下文标签，并使用关于UA标签和相关转发的信息创建转发条目。
This forwarding entry is in a forwarding table for the primary egress node.
此转发条目位于主出口节点的转发表中。
When the primary egress node fails, its upstream node switches the traffic from the primary LSP to the backup LSP to the backup egress node, which delivers the traffic to its receiver, such as a CE, using the backup LSP label as a context label to get the forwarding table for the primary egress node and using the service label as a UA label to find the forwarding entry in the table to forward the traffic to the receiver.
当主出口节点发生故障时，其上游节点将流量从主LSP切换到备用LSP，再切换到备用出口节点，备用出口节点将流量传送到其接收器，例如CE，使用备份LSP标签作为上下文标签来获取主出口节点的转发表，并使用服务标签作为UA标签来查找表中的转发条目，以将流量转发给接收方。
If a transit node of an LSP receives the Path message with the SEROs and it is not an upstream node of any primary egress node of the LSP as a branch node, it MUST forward them unchanged.
如果LSP的传输节点接收到带有SEROs的Path消息，并且它不是作为分支节点的LSP的任何主出口节点的上游节点，则它必须原封不动地转发它们。
If the transit node is the upstream node of a primary egress node to be protected as a branch node, it determines the backup egress node, obtains a path for the backup LSP, and sets up the backup LSP along the path. If the upstream node receives the Resv message with an SERO object, it MUST send its upstream node the Resv message without the object.
如果传输节点是要作为分支节点进行保护的主出口节点的上游节点，则它确定备份出口节点，获取备份LSP的路径，并沿该路径设置备份LSP。如果上游节点接收到带有SERO对象的Resv消息，则必须向其上游节点发送不带该对象的Resv消息。
The PLR (which is the upstream node of the primary egress node a.k.a. the branch node) MUST extract the backup egress node from the respective SERO object in either a Path or a Resv message. If no matching SERO object is found, the PLR tries to find the backup egress node, which is not the primary egress node but has the same IP address as the destination IP address of the LSP.
PLR（即主出口节点a.k.a.分支节点的上游节点）必须在路径或Resv消息中从相应的SERO对象提取备份出口节点。如果未找到匹配的SERO对象，PLR将尝试查找备份出口节点，该节点不是主出口节点，但具有与LSP的目标IP地址相同的IP地址。
Note that if a backup egress node is not configured explicitly for protecting a primary egress node, the primary egress node and the backup egress node SHOULD have the same local address configured, and the cost to the local address on the backup egress node SHOULD be much bigger than the cost to the local address on the primary egress node. Thus, the primary egress node and backup egress node are considered as a "virtual node". Note that the backup egress node is different from this local address (e.g., from the primary egress node's point of view). In other words, it is identified by an address different from this local address.
注意，如果没有明确配置备份出口节点以保护主出口节点，则主出口节点和备份出口节点应具有相同的本地地址配置，并且备份出口节点上的本地地址的成本应远大于主出口节点上的本地地址的成本。因此，主出口节点和备份出口节点被视为“虚拟节点”。注意，备份出口节点不同于该本地地址（例如，从主出口节点的角度）。换句话说，它由一个不同于本地地址的地址标识。
After obtaining the backup egress node, the PLR computes a backup path from itself to the backup egress node and sets up a backup LSP along the path. It excludes the segment including the primary egress node to be protected when computing the path. The PLR sends the primary egress node a Path message with an SERO for the primary LSP,
在获得备份出口节点之后，PLR计算从其自身到备份出口节点的备份路径，并沿该路径建立备份LSP。在计算路径时，它排除了包括要保护的主出口节点的段。PLR向主出口节点发送带有用于主LSP的SERO的路径消息，
which indicates the backup egress node by the final subobject in the SERO. The PLR puts an SERO into the Path messages for the backup LSP, which indicates the primary egress node.
它通过SERO中的最终子对象指示备份出口节点。PLR将一个SERO放入备份LSP的路径消息中，该消息指示主出口节点。
The PLR MUST provide one-to-one backup protection for the primary egress node if the "one-to-one backup desired" flag is set in the message; otherwise, it MUST provide facility backup protection if the "facility backup desired" flag is set.
如果消息中设置了“一对一备份所需”标志，则PLR必须为主出口节点提供一对一备份保护；否则，如果设置了“需要设施备份”标志，则必须提供设施备份保护。
The PLR MUST set the protection flags in the RRO subobject for the primary egress node in the Resv message according to the status of the primary egress node and the backup LSP protecting the primary egress node. For example, it sets the "local protection available" flag and the "node protection" flag, which indicate that the primary egress node is protected when the backup LSP is up and ready to protect the primary egress node.
PLR必须根据主出口节点和保护主出口节点的备份LSP的状态，在Resv消息中为主出口节点的RRO子对象中设置保护标志。例如，它设置“local protection available”（本地保护可用）标志和“node protection”（节点保护）标志，这表明当备份LSP启动并准备好保护主出口节点时，主出口节点受到保护。
The behavior of the upstream node of a primary egress node of an LSP (as a PLR) is the same as that of a PLR for one-to-one backup described in [RFC4090], except that the upstream node (as a PLR) creates a backup LSP from itself to a backup egress node in a session different from the primary LSP.
LSP的主出口节点（作为PLR）的上游节点的行为与[RFC4090]中描述的一对一备份的PLR的行为相同，只是上游节点（作为PLR）在与主LSP不同的会话中创建从自身到备份出口节点的备份LSP。
If the LSP is a P2MP LSP and a primary egress node of the LSP is also a transit node (i.e., bud node), the upstream node of the primary egress node (as a PLR) creates a backup LSP from itself to each of the next hops of the primary egress node.
如果LSP是P2MP LSP并且LSP的主出口节点也是传输节点（即，bud节点），则主出口节点的上游节点（作为PLR）创建从其自身到主出口节点的每个下一跳的备份LSP。
When the PLR detects the failure of the primary egress node, it switches the packets from the primary LSP to the backup LSP to the backup egress node. For the failure of the bud node of a P2MP LSP, the PLR also switches the packets to the backup LSPs to the bud node's next hops, where the packets are merged into the primary LSP.
当PLR检测到主出口节点的故障时，它将数据包从主LSP切换到备份LSP，再切换到备份出口节点。对于P2MP LSP的bud节点的故障，PLR还将分组切换到备份LSP到bud节点的下一跳，其中分组合并到主LSP中。
Except for backup LSP and downstream label, the behavior of the upstream node of the primary egress node of a primary LSP (as a PLR) follows the PLR behavior for facility backup, which is described in [RFC4090].
除备用LSP和下游标签外，主LSP的主出口节点的上游节点的行为（作为PLR）遵循设施备份的PLR行为，如[RFC4090]所述。
For a number of primary P2P LSPs going through the same PLR to the same primary egress node, the primary egress node of these LSPs MAY be protected by one backup LSP from the PLR to the backup egress node designated for protecting the primary egress node.
对于通过相同PLR到达相同主出口节点的多个主P2P LSP，这些LSP的主出口节点可以由从PLR到指定用于保护主出口节点的备份出口节点的一个备份LSP来保护。
The PLR selects or creates a backup LSP from itself to the backup egress node. If there is a backup LSP that satisfies the constraints given in the Path message, then this one is selected; otherwise, a new backup LSP to the backup egress node is created.
PLR选择或创建从自身到备份出口节点的备份LSP。如果存在满足路径消息中给定约束的备份LSP，则选择该LSP；否则，将创建备份出口节点的新备份LSP。
After getting the backup LSP, the PLR associates the backup LSP with a primary LSP for protecting its primary egress node. The PLR records that the backup LSP is used to protect the primary LSP against its primary egress node failure and MUST include an SERO object in the Path message for the primary LSP. The object MUST contain the backup LSP ID. It indicates that the primary egress node MUST send the backup egress node the service label as a UA label and also send the information about forwarding the traffic to its destination using the label if there is a service carried by the LSP and the primary LSP label as a UA label (if the label is not implicit null). How a UA label is sent is out of scope for this document (refer to [FRAMEWK]).
获取备份LSP后，PLR将备份LSP与主LSP关联，以保护其主出口节点。PLR记录备份LSP用于保护主LSP不受其主出口节点故障的影响，并且必须在主LSP的路径消息中包含一个SERO对象。该对象必须包含备份LSP ID。它指示主出口节点必须将服务标签作为UA标签发送给备份出口节点，并且如果LSP承载服务，并且主LSP标签作为UA标签，则还必须使用标签发送关于将流量转发到其目的地的信息（如果标签不是隐式null）。如何发送UA标签超出了本文档的范围（请参阅[FRAMEWK]）。
When the PLR detects the failure of the primary egress node, it redirects the packets from the primary LSP into the backup LSP to the backup egress node and keeps the primary LSP label from the primary egress node in the label stack if the label is not implicit null. The backup egress node delivers the packets to the same destinations as the primary egress node using the backup LSP label as a context label and the labels under as UA labels.
当PLR检测到主出口节点的故障时，它将数据包从主LSP重定向到备份LSP到备份出口节点，并且如果标签不是隐式空的，则在标签堆栈中保留来自主出口节点的主LSP标签。备份出口节点使用备份LSP标签作为上下文标签，将分组发送到与主出口节点相同的目的地，并将备份LSP标签下的标签作为UA标签。
The S2L sub-LSP protection uses an S2L sub-LSP (refer to [RFC4875]) as a backup LSP to protect a primary egress node of a P2MP LSP. The PLR MUST determine to protect a primary egress node of a P2MP LSP via S2L sub-LSP protection when it receives a Path message with the "S2L sub-LSP backup desired" flag set.
S2L子LSP保护使用S2L子LSP（参考[RFC4875]）作为备份LSP，以保护P2MP LSP的主出口节点。当PLR接收到设置了“S2L子LSP备份所需”标志的Path消息时，必须确定通过S2L子LSP保护来保护P2MP LSP的主出口节点。
The PLR MUST set up the backup S2L sub-LSP to the backup egress node and create and maintain its state in the same way as if setting up a S2L sub-LSP defined in [RFC4875] from the signaling's point of view. It computes a path for the backup LSP from itself to the backup egress node, constructs and sends a Path message along the path, and receives and processes a Resv message responding to the Path message.
PLR必须为备份出口节点设置备份S2L子LSP，并以与从信令角度设置[RFC4875]中定义的S2L子LSP相同的方式创建和维护其状态。它计算备份LSP从自身到备份出口节点的路径，沿着该路径构造和发送路径消息，并接收和处理响应路径消息的Resv消息。
After receiving the Resv message for the backup LSP, the PLR creates a forwarding entry with an inactive state or flag called "inactive forwarding entry". This inactive forwarding entry is not used to forward any data traffic during normal operations.
在接收到备份LSP的Resv消息后，PLR创建一个具有非活动状态或标记的转发条目，称为“非活动转发条目”。此非活动转发条目不用于在正常操作期间转发任何数据流量。
When the PLR detects the failure of the primary egress node, it changes the forwarding entry for the backup LSP to "active". Thus, the PLR forwards the traffic to the backup egress through the backup LSP, which sends the traffic to its destination.
当PLR检测到主出口节点故障时，它将备份LSP的转发条目更改为“活动”。因此，PLR通过备份LSP将业务转发到备份出口，备份LSP将业务发送到其目的地。
When the upstream node of a primary egress node of an LSP (as a PLR) detects the failure of the primary egress node, it follows the procedures defined in Section 6.5 of [RFC4090]. It SHOULD notify the ingress node about the failure of the primary egress node in the same way as a PLR notifies the ingress node about the failure of a transit node.
当LSP（作为PLR）主出口节点的上游节点检测到主出口节点故障时，它遵循[RFC4090]第6.5节中定义的程序。它应该以PLR通知入口节点中转节点故障的相同方式通知入口节点主出口节点故障。
Moreover, the PLR MUST let the upstream part of the primary LSP stay alive after the primary egress node fails by sending the Resv message to its upstream node along the primary LSP. The downstream part of the primary LSP from the PLR to the primary egress node SHOULD be removed. When a bypass LSP from the PLR to a backup egress node protects the primary egress node, the PLR MUST NOT send any Path message for the primary LSP through the bypass LSP to the backup egress node.
此外，PLR必须通过沿主LSP向其上游节点发送Resv消息，使主LSP的上游部分在主出口节点失败后保持活动。应移除从PLR到主出口节点的主LSP的下游部分。当从PLR到备用出口节点的旁路LSP保护主出口节点时，PLR不得通过旁路LSP向备用出口节点发送主LSP的任何路径消息。
In the local revertive mode, the PLR will re-signal each of the primary LSPs that were routed over the restored resource once it detects that the resource is restored. Every primary LSP successfully re-signaled along the restored resource will be switched back.
在本地恢复模式下，一旦PLR检测到资源已恢复，PLR将重新发送通过已恢复资源路由的每个主LSP的信号。沿恢复的资源成功重新发送信号的每个主LSP都将切换回。
Note that the procedure for protecting the primary egress node is triggered on the PLR if the primary egress node failure is determined. If link (from PLR to primary egress node) failure and primary egress node alive are determined, then the link protection procedure is triggered on the PLR. How to determine these is out of scope for this document.
注意，如果确定主出口节点故障，则在PLR上触发保护主出口节点的过程。如果确定链路（从PLR到主出口节点）故障且主出口节点活动，则在PLR上触发链路保护程序。如何确定这些超出了本文档的范围。
This section focuses on an example with application traffic carried by P2P LSPs.
本节重点介绍P2P LSP承载的应用程序流量示例。
L3VPN is a typical application. Figure 2 below shows a simple VPN
that consists of two CEs, CE1 and CE2, connected to two PEs, R1 and
L1, respectively. There is a P2P LSP from R1 to L1, which is
represented by stars (****). This LSP is called the primary LSP. R1
is the ingress node of the LSP and L1 is the (primary) egress node of
L3VPN is a typical application. Figure 2 below shows a simple VPN
that consists of two CEs, CE1 and CE2, connected to two PEs, R1 and
L1, respectively. There is a P2P LSP from R1 to L1, which is
represented by stars (****). This LSP is called the primary LSP. R1
is the ingress node of the LSP and L1 is the (primary) egress node of
the LSP. R1 sends the VPN traffic received from CE1 through the P2P LSP to L1, which delivers the traffic to CE2. R1 sends the VPN traffic with an LSP label and a VPN label via the LSP. When the traffic reaches the egress node L1 of the LSP, L1 pops the LSP label and uses the VPN label to deliver the traffic to CE2.
LSP。R1通过P2P LSP将从CE1接收到的VPN流量发送到L1，L1将流量发送到CE2。R1通过LSP发送带有LSP标签和VPN标签的VPN流量。当流量到达LSP的出口节点L1时，L1弹出LSP标签，并使用VPN标签将流量传送到CE2。
In previous solutions based on ingress protection to protect the VPN traffic against failure of the egress node L1 of the LSP, when the egress node fails, the ingress node R1 of the LSP does the reroute (refer to Figure 2). This solution entailed:
在以前的基于入口保护的解决方案中，保护VPN流量不受LSP出口节点L1故障的影响，当出口节点故障时，LSP的入口节点R1进行重新路由（参见图2）。这一解决办法包括：
1. A multi-hop BFD session between ingress node R1 and egress node L1 of the primary LSP. The BFD session is represented by dots (....).
1. 主LSP的入口节点R1和出口节点L1之间的多跳BFD会话。BFD会话由点（..）表示。
2. A backup LSP from ingress node R1 to backup egress node La, which is indicated by ampersands (&&&&).
2. 从入口节点R1到备份出口节点La的备份LSP，由符号（&&&&&&）表示。
3. La sends R1 a VPN backup label and related information via BGP.
3. La通过BGP向R1发送VPN备份标签和相关信息。
4. R1 has a VRF with two sets of routes for CE2: one set uses the primary LSP and L1 as the next hop; the other uses the backup LSP and La as the next hop.
4. R1有一个VRF，有两组CE2路由：一组使用主LSP和L1作为下一跳；另一个使用备份LSP和La作为下一跳。
***** *****
CE1,CE2 in [R2]-----[R3]-----[L1] **** Primary LSP
one VPN */ : \ &&&& Backup LSP
*/ .................: \ .... BFD Session
[CE1]--[R1] ..: [CE2]
&\ /
&\ /
[R4]-----[R5]-----[La](BGP sends R1 VPN backup label)
&&&&& &&&&&
***** *****
CE1,CE2 in [R2]-----[R3]-----[L1] **** Primary LSP
one VPN */ : \ &&&& Backup LSP
*/ .................: \ .... BFD Session
[CE1]--[R1] ..: [CE2]
&\ /
&\ /
[R4]-----[R5]-----[La](BGP sends R1 VPN backup label)
&&&&& &&&&&
Figure 2: Protect Egress for L3VPN Traffic
图2：保护L3VPN流量的出口
In normal operations, R1 sends the VPN traffic from CE1 through the primary LSP with the VPN label received from L1 as the inner label to L1, which delivers the traffic to CE2 using the VPN label.
在正常操作中，R1通过主LSP将来自CE1的VPN流量发送到L1，其中从L1接收的VPN标签作为内部标签，L1使用VPN标签将流量发送到CE2。
When R1 detects the failure of L1, R1 sends the traffic from CE1 via the backup LSP with the VPN backup label received from La as the inner label to La, which delivers the traffic to CE2 using the VPN backup label.
当R1检测到L1的故障时，R1通过备份LSP将来自CE1的流量发送给La，其中从La接收的VPN备份标签作为内部标签，La使用VPN备份标签将流量发送给CE2。
The solution defined in this document that uses egress local protection for protecting L3VPN traffic entails (refer to Figure 3):
本文档中定义的使用出口本地保护来保护L3VPN流量的解决方案包括（参见图3）：
1. A BFD session between R3 (i.e., upstream node of L1) and egress node L1 of the primary LSP. This is different from the BFD session in Figure 2, which is a multi-hop between ingress node R1 and egress node L1. The PLR R3 is closer to L1 than the ingress node R1. It may detect the failure of the egress node L1 faster and more reliably. Therefore, this solution can provide faster protection for failure of an egress node.
1. R3（即，L1的上游节点）和主LSP的出口节点L1之间的BFD会话。这与图2中的BFD会话不同，BFD会话是入口节点R1和出口节点L1之间的多跳。PLR R3比入口节点R1更接近L1。它可以更快、更可靠地检测出口节点L1的故障。因此，该解决方案可以为出口节点的故障提供更快的保护。
2. A backup LSP from R3 to backup egress node La. This is different from the backup LSP in Figure 2, which is an end-to-end LSP from ingress node R1 to backup egress node La.
2. 从R3到备份出口节点La的备份LSP。这与图2中的备份LSP不同，后者是从入口节点R1到备份出口节点La的端到端LSP。
3. Primary egress node L1 sends backup egress node La the VPN label as a UA label and also sends related information. The backup egress node La uses the backup LSP label as a context label and creates a forwarding entry using the VPN label in an LFIB for the primary egress node L1.
3. 主出口节点L1将VPN标签作为UA标签发送给备份出口节点La，并发送相关信息。备份出口节点La使用备份LSP标签作为上下文标签，并使用LFIB中的VPN标签为主出口节点L1创建转发条目。
4. L1 and La are virtualized as one node (or address). R1 has a VRF with one set of routes for CE2, using the primary LSP from R1 to L1 and a virtualized node as the next hop. This can be achieved by configuring the same local address on L1 and La using the address as a destination of the LSP and BGP next hop for the VPN traffic. The cost to L1 is configured to be less than the cost to La.
4. L1和La被虚拟化为一个节点（或地址）。R1有一个VRF，其中有一组用于CE2的路由，使用从R1到L1的主LSP和一个虚拟化节点作为下一跳。这可以通过在L1和La上配置相同的本地地址来实现，使用该地址作为VPN流量的LSP和BGP下一跳的目的地。L1的成本配置为小于La的成本。
***** *****
CE1,CE2 in [R2]-----[R3]-----[L1] **** Primary LSP
one VPN */ &\:.....: \ &&&& Backup LSP
*/ &\ \ .... BFD Session
[CE1]--[R1] &\ [CE2]
&\ /
&\ /
[La](VPN label from L1 as a UA label)
***** *****
CE1,CE2 in [R2]-----[R3]-----[L1] **** Primary LSP
one VPN */ &\:.....: \ &&&& Backup LSP
*/ &\ \ .... BFD Session
[CE1]--[R1] &\ [CE2]
&\ /
&\ /
[La](VPN label from L1 as a UA label)
Figure 3: Locally Protect Egress for L3VPN Traffic
图3：L3VPN流量的本地保护出口
In normal operations, R1 sends the VPN traffic from CE1 via the primary LSP with the VPN label as an inner label to L1, which delivers the traffic to CE2 using the VPN label.
在正常操作中，R1通过主LSP将VPN标签作为内部标签从CE1发送VPN流量到L1，L1使用VPN标签将流量发送到CE2。
When the primary egress node L1 fails, its upstream node R3 detects it and switches the VPN traffic from the primary LSP to the backup LSP to La, which delivers the traffic to CE2 using the backup LSP
当主出口节点L1发生故障时，其上游节点R3检测到它并将VPN流量从主LSP切换到备份LSP到La，后者使用备份LSP将流量传送到CE2
label as a context label to get the LFIB for L1 and the VPN label as a UA label to find the forwarding entry in the LFIB to forward the traffic to CE2.
标签作为上下文标签，用于获取L1的LFIB，VPN标签作为UA标签，用于查找LFIB中的转发条目，以将流量转发到CE2。
When the PLR gets a backup LSP from itself to a backup egress node for protecting a primary egress node of a primary LSP, it includes an SERO object in the Path message for the primary LSP. The object contains the ID information of the backup LSP and indicates that the primary egress node sends the backup egress node the application traffic label (e.g., the VPN label) as a UA label when needed.
当PLR从其自身获得备份LSP到备份出口节点以保护主LSP的主出口节点时，它在主LSP的路径消息中包括SERO对象。该对象包含备份LSP的ID信息，并指示主出口节点在需要时将应用流量标签（例如VPN标签）作为UA标签发送给备份出口节点。
When a primary egress node of an LSP sends the ingress node of the LSP a label for an application such as a VPN label, it sends the label (as a UA label) to the backup egress node for protecting the primary egress node. Exactly how the label is sent is out of scope for this document.
当LSP的主出口节点向LSP的入口节点发送诸如VPN标签之类的应用标签时，它将标签（作为UA标签）发送到备份出口节点以保护主出口节点。标签的确切发送方式超出了本文档的范围。
When the backup egress node receives a UA label from the primary egress node, it adds a forwarding entry with the label into the LFIB for the primary egress node. When the backup egress node receives a packet from the backup LSP, it uses the top label as a context label to find the LFIB for the primary egress node and uses the inner label to deliver the packet to the same destination as the primary egress node according to the LFIB.
当备份出口节点从主出口节点接收到UA标签时，它将带有标签的转发条目添加到主出口节点的LFIB中。当备份出口节点从备份LSP接收到分组时，它使用顶部标签作为上下文标签来查找主出口节点的LFIB，并使用内部标签根据LFIB将分组传送到与主出口节点相同的目的地。
This document builds upon existing work, specifically, the security considerations of [RFC4090], [RFC4875], [RFC3209], and [RFC2205] continue to apply. Additionally, protecting a primary egress node of a P2P LSP carrying service traffic through a backup egress node requires out-of-band communication between the primary egress node and the backup egress node in order for the primary egress node to convey a service label as a UA label and also convey its related forwarding information to the backup egress node. It is important to confirm that the identifiers used to identify the primary and backup egress nodes in the LSP are verified to match with the identifiers used in the out-of-band protocol (such as BGP).
本文件以现有工作为基础，具体而言，[RFC4090]、[RFC4875]、[RFC3209]和[RFC2205]的安全注意事项继续适用。另外,，保护通过备份出口节点承载服务流量的P2P LSP的主出口节点需要主出口节点和备份出口节点之间的带外通信，以便主出口节点将服务标签作为UA标签传送，并且还将其相关转发信息传送到备份出口节点。确认用于标识LSP中的主出口节点和备份出口节点的标识符已验证为与带外协议（例如BGP）中使用的标识符匹配，这一点很重要。
IANA maintains a registry called "Class Names, Class Numbers, and Class Types" under "Resource Reservation Protocol (RSVP) Parameters". IANA has assigned a new C-Type under the PROTECTION object class, Class Number 37:
IANA在“资源预留协议（RSVP）参数”下维护一个名为“类名、类号和类类型”的注册表。IANA已在保护对象类别下分配了一个新的C型，类别编号37：
Value Description Definition
----- ----------- ----------
3 Egress Protection Section 4.1
Value Description Definition
----- ----------- ----------
3 Egress Protection Section 4.1
IANA has created and now maintains a registry under the PROTECTION object class (Class Number 37) and Egress Protection (C-Type 3). Initial values for the registry are given below. Future assignments are to be made through IETF Review [RFC8216].
IANA已经在保护对象类（类编号37）和出口保护（C-Type 3）下创建并维护了一个注册表。注册表的初始值如下所示。未来的任务将通过IETF审查[RFC8216]进行。
Value Description Definition
----- ----------- ----------
0 Reserved
1 IPv4_PRIMARY_EGRESS Section 4.1.1
2 IPv6_PRIMARY_EGRESS Section 4.1.1
3 IPv4_P2P_LSP_ID Section 4.1.2
4 IPv6_P2P_LSP_ID Section 4.1.2
5-127 Unassigned
128-255 Reserved
Value Description Definition
----- ----------- ----------
0 Reserved
1 IPv4_PRIMARY_EGRESS Section 4.1.1
2 IPv6_PRIMARY_EGRESS Section 4.1.1
3 IPv4_P2P_LSP_ID Section 4.1.2
4 IPv6_P2P_LSP_ID Section 4.1.2
5-127 Unassigned
128-255 Reserved
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://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<https://www.rfc-editor.org/info/rfc2119>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, <https://www.rfc-editor.org/info/rfc3209>.
[RFC3209]Awduche，D.，Berger，L.，Gan，D.，Li，T.，Srinivasan，V.，和G.Swallow，“RSVP-TE：LSP隧道RSVP的扩展”，RFC 3209，DOI 10.17487/RFC3209，2001年12月<https://www.rfc-editor.org/info/rfc3209>.
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090, DOI 10.17487/RFC4090, May 2005, <https://www.rfc-editor.org/info/rfc4090>.
[RFC4090]Pan，P.，Ed.，Swallow，G.，Ed.，和A.Atlas，Ed.，“LSP隧道RSVP-TE的快速重路由扩展”，RFC 4090，DOI 10.17487/RFC4090，2005年5月<https://www.rfc-editor.org/info/rfc4090>.
[RFC4873] Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel, "GMPLS Segment Recovery", RFC 4873, DOI 10.17487/RFC4873, May 2007, <https://www.rfc-editor.org/info/rfc4873>.
[RFC4873]Berger，L.，Bryskin，I.，Papadimitriou，D.，和A.Farrel，“GMPLS段恢复”，RFC 4873，DOI 10.17487/RFC4873，2007年5月<https://www.rfc-editor.org/info/rfc4873>.
[RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S. Yasukawa, Ed., "Extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for Point-to-Multipoint TE Label Switched Paths (LSPs)", RFC 4875, DOI 10.17487/RFC4875, May 2007, <https://www.rfc-editor.org/info/rfc4875>.
[RFC4875]Aggarwal，R.，Ed.，Papadimitriou，D.，Ed.，和S.Yasukawa，Ed.，“资源预留协议的扩展-点对多点TE标签交换路径（LSP）的流量工程（RSVP-TE）”，RFC 4875，DOI 10.17487/RFC4875，2007年5月<https://www.rfc-editor.org/info/rfc4875>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8174]Leiba，B.，“RFC 2119关键词中大写与小写的歧义”，BCP 14，RFC 8174，DOI 10.17487/RFC8174，2017年5月<https://www.rfc-editor.org/info/rfc8174>.
[RFC8216] Pantos, R., Ed. and W. May, "HTTP Live Streaming", RFC 8216, DOI 10.17487/RFC8216, August 2017, <https://www.rfc-editor.org/info/rfc8216>.
[RFC8216]Pantos，R.，Ed.和W.May，“HTTP直播”，RFC 8216，DOI 10.17487/RFC82162017年8月<https://www.rfc-editor.org/info/rfc8216>.
[FRAMEWK] Shen, Y., Jeganathan, J., Decraene, B., Gredler, H., Michel, C., Chen, H., and Y. Jiang, "MPLS Egress Protection Framework", Work in Progress, draft-ietf-mpls-egress-protection-framework-00, January 2018.
[FRAMEWK]Shen，Y.，Jeganathan，J.，DeClaene，B.，Gredler，H.，Michel，C.，Chen，H.，和Y.Jiang，“MPLS出口保护框架”，正在进行的工作，草案-ietf-MPLS-出口保护框架-00，2018年1月。
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, DOI 10.17487/RFC2205, September 1997, <https://www.rfc-editor.org/info/rfc2205>.
[RFC2205]Braden，R.，Ed.，Zhang，L.，Berson，S.，Herzog，S.，和S.Jamin，“资源保留协议（RSVP）——版本1功能规范”，RFC 2205，DOI 10.17487/RFC2205，1997年9月<https://www.rfc-editor.org/info/rfc2205>.
[RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream Label Assignment and Context-Specific Label Space", RFC 5331, DOI 10.17487/RFC5331, August 2008, <https://www.rfc-editor.org/info/rfc5331>.
[RFC5331]Aggarwal，R.，Rekhter，Y.，和E.Rosen，“MPLS上游标签分配和上下文特定标签空间”，RFC 5331，DOI 10.17487/RFC5331，2008年8月<https://www.rfc-editor.org/info/rfc5331>.
Acknowledgements
致谢
The authors would like to thank Richard Li, Nobo Akiya, Lou Berger, Jeffrey Zhang, Lizhong Jin, Ravi Torvi, Eric Gray, Olufemi Komolafe, Michael Yue, Daniel King, Rob Rennison, Neil Harrison, Kannan Sampath, Yimin Shen, Ronhazli Adam, and Quintin Zhao for their valuable comments and suggestions on this document.
作者要感谢李泽楷、秋叶信孝、娄伯杰、张杰弗里、金立中、拉维·托维、埃里克·格雷、奥卢菲米·科莫拉菲、迈克尔·岳、丹尼尔·金、罗布·雷尼森、尼尔·哈里森、坎南·桑帕斯、沈一民、罗哈兹利·亚当和昆廷·赵对本文件提出的宝贵意见和建议。
Contributors
贡献者
The following people contributed significantly to the content of this document and should be considered coauthors:
以下人员对本文件的内容做出了重大贡献，应被视为共同作者：
Ning So Tata Email: ningso01@gmail.com
Ning So Tata电子邮件：ningso01@gmail.com
Mehmet Toy Verizon Email: mehmet.toy@verizon.com
Mehmet Toy Verizon电子邮件：Mehmet。toy@verizon.com
Lei Liu Fujitsu Email: lliu@us.fujitsu.com
刘磊富士通电子邮件：lliu@us.fujitsu.com
Zhenbin Li Huawei Technologies Email: lizhenbin@huawei.com
李振斌华为技术电子邮件：lizhenbin@huawei.com
We also acknowledge the contributions of the following individuals:
我们还感谢以下个人的贡献：
Boris Zhang Telus Communications Email: Boris.Zhang@telus.com
Boris Zhang Telus通信电子邮件：Boris。Zhang@telus.com
Nan Meng Huawei Technologies Email: mengnan@huawei.com
南盟华为技术电子邮件：mengnan@huawei.com
Prejeeth Kaladharan Huawei Technologies Email: prejeeth@gmail.com
Prejeeth Kaladharan华为技术公司电子邮件：prejeeth@gmail.com
Vic Liu China Mobile Email: liu.cmri@gmail.com
Vic Liu中国移动电子邮件：Liu。cmri@gmail.com
Authors' Addresses
作者地址
Huaimo Chen Huawei Technologies Boston, MA United States of America
美国马萨诸塞州波士顿华为技术有限公司
Email: huaimo.chen@huawei.com
Email: huaimo.chen@huawei.com
Autumn Liu Ciena United States of America
美利坚合众国的秋天
Email: hliu@ciena.com
Email: hliu@ciena.com
Tarek Saad Cisco Systems
塔瑞克萨阿德思科系统公司
Email: tsaad@cisco.com
Email: tsaad@cisco.com
Fengman Xu Verizon 2400 N. Glenville Dr Richardson, TX 75082 United States of America
Fengman Xu Verizon 2400 N.Glenville Richardson博士，德克萨斯州75082美利坚合众国
Email: fengman.xu@verizon.com
Email: fengman.xu@verizon.com
Lu Huang China Mobile No.32 Xuanwumen West Street, Xicheng District Beijing 100053 China
中国移动北京市西城区宣武门西街32号路黄100053
Email: huanglu@chinamobile.com
Email: huanglu@chinamobile.com