Internet Engineering Task Force (IETF) H. Chen
Request for Comments: 8099 R. Li
Category: Experimental Huawei Technologies
ISSN: 2070-1721 A. Retana
Cisco Systems, Inc.
Y. Yang
Sockrate
Z. Liu
China Mobile
February 2017
Internet Engineering Task Force (IETF) H. Chen
Request for Comments: 8099 R. Li
Category: Experimental Huawei Technologies
ISSN: 2070-1721 A. Retana
Cisco Systems, Inc.
Y. Yang
Sockrate
Z. Liu
China Mobile
February 2017
OSPF Topology-Transparent Zone
OSPF拓扑透明区
Abstract
摘要
This document presents a Topology-Transparent Zone (TTZ) in an OSPF area. A TTZ comprises a group of routers and a number of links connecting these routers. Any router outside of the zone is not aware of the zone. A TTZ hides the internal topology of the TTZ from the outside. It does not directly advertise any internal information about the TTZ to a router outside of the TTZ. The information about the links and routers such as a link down inside the TTZ is not advertised to any router outside of the TTZ.
本文档介绍OSPF区域中的拓扑透明区（TTZ）。TTZ包括一组路由器和连接这些路由器的多个链路。区域外的任何路由器都不知道该区域。TTZ从外部隐藏TTZ的内部拓扑。它不会直接向TTZ外部的路由器公布任何关于TTZ的内部信息。关于链路和路由器的信息（如TTZ内的链路断开）不会播发给TTZ外的任何路由器。
Status of This Memo
关于下段备忘
This document is not an Internet Standards Track specification; it is published for examination, experimental implementation, and evaluation.
本文件不是互联网标准跟踪规范；它是为检查、实验实施和评估而发布的。
This document defines an Experimental Protocol for the Internet community. 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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 7841.
本文档为互联网社区定义了一个实验协议。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。并非IESG批准的所有文件都适用于任何级别的互联网标准；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/rfc8099.
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/rfc8099.
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。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Conventions Used in This Document . . . . . . . . . . . . . . 5
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Topology-Transparent Zone . . . . . . . . . . . . . . . . . . 5
5.1. Overview of Topology-Transparent Zone . . . . . . . . . . 5
5.2. TTZ Example . . . . . . . . . . . . . . . . . . . . . . . 6
6. Extensions to OSPF Protocols . . . . . . . . . . . . . . . . 8
6.1. General Format of TTZ LSA . . . . . . . . . . . . . . . . 8
6.2. TTZ ID TLV . . . . . . . . . . . . . . . . . . . . . . . 9
6.3. TTZ Router TLV . . . . . . . . . . . . . . . . . . . . . 9
6.4. TTZ Options TLV . . . . . . . . . . . . . . . . . . . . . 10
6.5. Link Scope TTZ LSA . . . . . . . . . . . . . . . . . . . 12
7. Constructing LSAs for TTZ . . . . . . . . . . . . . . . . . . 12
7.1. TTZ Migration Process . . . . . . . . . . . . . . . . . . 13
8. Establishing Adjacencies . . . . . . . . . . . . . . . . . . 14
8.1. Discovery of TTZ Neighbors . . . . . . . . . . . . . . . 14
8.2. Adjacency between TTZ Edge and TTZ-External Router . . . 17
9. Advertisement of LSAs . . . . . . . . . . . . . . . . . . . . 17
9.1. Advertisement of LSAs within TTZ . . . . . . . . . . . . 17
9.2. Advertisement of LSAs through TTZ . . . . . . . . . . . . 18
10. Computation of Routing Table . . . . . . . . . . . . . . . . 18
11. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Configuring TTZ . . . . . . . . . . . . . . . . . . . . 18
11.2. Migration to TTZ . . . . . . . . . . . . . . . . . . . . 19
11.3. Adding a Router into TTZ . . . . . . . . . . . . . . . . 21
12. Manageability Considerations . . . . . . . . . . . . . . . . 22
13. Security Considerations . . . . . . . . . . . . . . . . . . . 22
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
15.1. Normative References . . . . . . . . . . . . . . . . . . 23
15.2. Informative References . . . . . . . . . . . . . . . . . 23
Appendix A. Prototype Implementation . . . . . . . . . . . . . . 24
A.1. What Is Implemented and Tested . . . . . . . . . . . . . 24
A.2. Implementation Experience . . . . . . . . . . . . . . . . 25
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 26
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Conventions Used in This Document . . . . . . . . . . . . . . 5
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Topology-Transparent Zone . . . . . . . . . . . . . . . . . . 5
5.1. Overview of Topology-Transparent Zone . . . . . . . . . . 5
5.2. TTZ Example . . . . . . . . . . . . . . . . . . . . . . . 6
6. Extensions to OSPF Protocols . . . . . . . . . . . . . . . . 8
6.1. General Format of TTZ LSA . . . . . . . . . . . . . . . . 8
6.2. TTZ ID TLV . . . . . . . . . . . . . . . . . . . . . . . 9
6.3. TTZ Router TLV . . . . . . . . . . . . . . . . . . . . . 9
6.4. TTZ Options TLV . . . . . . . . . . . . . . . . . . . . . 10
6.5. Link Scope TTZ LSA . . . . . . . . . . . . . . . . . . . 12
7. Constructing LSAs for TTZ . . . . . . . . . . . . . . . . . . 12
7.1. TTZ Migration Process . . . . . . . . . . . . . . . . . . 13
8. Establishing Adjacencies . . . . . . . . . . . . . . . . . . 14
8.1. Discovery of TTZ Neighbors . . . . . . . . . . . . . . . 14
8.2. Adjacency between TTZ Edge and TTZ-External Router . . . 17
9. Advertisement of LSAs . . . . . . . . . . . . . . . . . . . . 17
9.1. Advertisement of LSAs within TTZ . . . . . . . . . . . . 17
9.2. Advertisement of LSAs through TTZ . . . . . . . . . . . . 18
10. Computation of Routing Table . . . . . . . . . . . . . . . . 18
11. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Configuring TTZ . . . . . . . . . . . . . . . . . . . . 18
11.2. Migration to TTZ . . . . . . . . . . . . . . . . . . . . 19
11.3. Adding a Router into TTZ . . . . . . . . . . . . . . . . 21
12. Manageability Considerations . . . . . . . . . . . . . . . . 22
13. Security Considerations . . . . . . . . . . . . . . . . . . . 22
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
15.1. Normative References . . . . . . . . . . . . . . . . . . 23
15.2. Informative References . . . . . . . . . . . . . . . . . 23
Appendix A. Prototype Implementation . . . . . . . . . . . . . . 24
A.1. What Is Implemented and Tested . . . . . . . . . . . . . 24
A.2. Implementation Experience . . . . . . . . . . . . . . . . 25
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 26
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
Networks expand as business grows and traffic increases. For scalability and manageability, a hierarchical network architecture is usually deployed in OSPF networks by regrouping routers into areas, which is often challenging and causes service interruptions.
网络随着业务增长和流量增加而扩展。为了实现可扩展性和可管理性，OSPF网络中通常会部署分层网络体系结构，将路由器重新分组到多个区域，这通常会带来挑战并导致服务中断。
At first, reorganizing a network from one area into multiple areas or from a number of existing areas into even more areas is a very challenging and time-consuming task since it involves significant network architecture changes. Considering the one area case, originally the network has only one area, which is the backbone. This original backbone area will be reorganized into a new backbone and a number of non-backbone areas. In general, each of the non-backbone areas is connected to the new backbone area through the Area Border Routers (ABRs) between the non-backbone and the backbone area (refer to RFC 2328, Section 3). It demands careful redesigning of network topology in advance to guarantee backbone area continuity and non-backbone-area reachability, and it requires significant modifications of configurations on many routers to ensure consistent routing.
首先，将一个网络从一个区域重新组织为多个区域，或从多个现有区域重新组织为更多区域是一项非常具有挑战性和耗时的任务，因为它涉及到重大的网络架构更改。考虑到一个区域的情况，最初网络只有一个区域，即主干。原有的主干区将被重组为一个新的主干区和一些非主干区。通常，每个非主干区域通过非主干和主干区域之间的区域边界路由器（ABR）连接到新的主干区域（参考RFC 2328，第3节）。它需要事先仔细地重新设计网络拓扑，以保证主干区域的连续性和非主干区域的可达性，并且需要对许多路由器上的配置进行重大修改，以确保一致的路由。
Second, the services carried by the network may be interrupted while the network is being reorganized from one area into multiple areas or from a number of existing areas into even more areas since every OSPF interface with an area change is going down with its old area and then up with a new area.
第二，当网络从一个区域重组为多个区域，或从多个现有区域重组为更多区域时，网络承载的服务可能会中断，因为每个发生区域变化的OSPF接口都会随着其旧区域下降，然后随着新区域上升。
This document presents a Topology-Transparent Zone (TTZ) in an OSPF area and describes extensions to OSPFv2 for supporting the TTZ, which is scalable and resolves the issues above. A TTZ hides the internal topology of the TTZ from the outside. It does not directly advertise any internal information about the TTZ to any router outside of the TTZ.
本文档介绍了OSPF区域中的拓扑透明区（TTZ），并描述了支持TTZ的OSPFv2扩展，TTZ可扩展并解决了上述问题。TTZ从外部隐藏TTZ的内部拓扑。它不会直接向TTZ之外的任何路由器公布关于TTZ的任何内部信息。
TTZ link or TTZ-internal link: A link whose ends are within a single TTZ.
TTZ链路或TTZ内部链路：其端部在单个TTZ内的链路。
TTZ-internal router: A router whose links are TTZ-internal links inside a single TTZ.
TTZ内部路由器：其链路为单个TTZ内的TTZ内部链路的路由器。
TTZ-external router: A router outside of a TTZ that has no TTZ-internal links.
TTZ外部路由器：TTZ外部没有TTZ内部链路的路由器。
TTZ-external link: A link not configured to be within a TTZ.
TTZ外部链路：未配置为在TTZ内的链路。
TTZ edge router: A router is called a TTZ edge router if some, but not all, of its links are within a single TTZ.
TTZ边缘路由器：如果一个路由器的部分（但不是全部）链路位于一个TTZ内，则称之为TTZ边缘路由器。
TTZ router: A TTZ-internal router or a TTZ edge router.
TTZ路由器：TTZ内部路由器或TTZ边缘路由器。
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。
A Topology-Transparent Zone may be deployed to resolve some critical issues in existing networks and future networks. The requirements for a TTZ are listed as follows:
可以部署拓扑透明区域来解决现有网络和未来网络中的一些关键问题。TTZ的要求如下所示：
o Routers outside a TTZ MUST NOT require any changes to operate with the TTZ.
o TTZ外的路由器不得要求任何更改才能使用TTZ运行。
o A TTZ MUST be enclosed in a single area.
o TTZ必须封闭在单个区域内。
o A TTZ MUST hide the topology of the TTZ from any router outside of the TTZ.
o TTZ必须对TTZ之外的任何路由器隐藏TTZ的拓扑。
A Topology-Transparent Zone is identified by a TTZ identifier (ID), and it consists of a group of routers and a number of links connecting the routers. A TTZ MUST be contained within an OSPF area.
拓扑透明区由TTZ标识符（ID）标识，它由一组路由器和连接路由器的多个链路组成。TTZ必须包含在OSPF区域内。
A TTZ ID is a 32-bit number that is unique for identifying a TTZ. The TTZ ID SHOULD NOT be 0 in order to avoid confusion with Area 0. The same TTZ ID MUST be configured on the routers and/or links that make up a specific instance of a TTZ. All TTZ instances in an OSPF area MUST be unique.
TTZ ID是用于标识TTZ的唯一32位数字。TTZ ID不应为0，以避免与区域0混淆。组成TTZ特定实例的路由器和/或链路上必须配置相同的TTZ ID。OSPF区域中的所有TTZ实例必须是唯一的。
In addition to having similar functions of an OSPF area, an OSPF TTZ makes some improvements on an OSPF area, which include:
除了具有OSPF区域的类似功能外，OSPF TTZ还对OSPF区域进行了一些改进，包括：
o An OSPF TTZ represents a set of TTZ edge routers, connected by a full mesh of virtual connections between them.
o OSPF TTZ表示一组TTZ边缘路由器，通过它们之间的完整虚拟连接网进行连接。
o Non-TTZ link-state information is handled as normal. TTZ routers receive the link-state information about the topology outside of the TTZ, store the information, and flood the information through the TTZ to the routers outside of the TTZ.
o 非TTZ链路状态信息按正常方式处理。TTZ路由器接收关于TTZ外部拓扑的链路状态信息，存储该信息，并通过TTZ将该信息发送到TTZ外部的路由器。
The figure below shows an area containing a TTZ: TTZ 600.
下图显示了包含TTZ:TTZ 600的区域。
TTZ 600 ---- TTZ-Internal Link
\ ==== Normal Link
Area X \ ^~^~^~^~^~^~^~^~^~^~^~^~
( )
===[R15]========(==[T61]----[T81]---[T63]==)======[R29]===
|| ( | \ / | ) ||
|| ( | \ / | ) ||
|| ( [T75] \ / | ) ||
|| ( | ___\ / | ) ||
|| ( | / [T71] [T79] ) ||
|| ( | [T73] / \ | ) ||
|| ( | / \ | ) ||
|| ( | / \ | ) ||
|| ( | / \ | ) ||
===[R17]========(==[T65]---[T77]----[T67]==)======[R31]===
\\ (// \\) //
|| //v~v~v~v~v~v~v~v~v~v~v~\\ ||
|| // \\ ||
|| // \\ ||
\\ // \\ //
======[R23]==============================[R25]=====
// \\
// \\
TTZ 600 ---- TTZ-Internal Link
\ ==== Normal Link
Area X \ ^~^~^~^~^~^~^~^~^~^~^~^~
( )
===[R15]========(==[T61]----[T81]---[T63]==)======[R29]===
|| ( | \ / | ) ||
|| ( | \ / | ) ||
|| ( [T75] \ / | ) ||
|| ( | ___\ / | ) ||
|| ( | / [T71] [T79] ) ||
|| ( | [T73] / \ | ) ||
|| ( | / \ | ) ||
|| ( | / \ | ) ||
|| ( | / \ | ) ||
===[R17]========(==[T65]---[T77]----[T67]==)======[R31]===
\\ (// \\) //
|| //v~v~v~v~v~v~v~v~v~v~v~\\ ||
|| // \\ ||
|| // \\ ||
\\ // \\ //
======[R23]==============================[R25]=====
// \\
// \\
All the routers in the figure are in area X. Routers with T (i.e., T61, T63, T65, T67, T71, T73, T75, T77, T79, and T81) are also in TTZ 600, which contains the TTZ-internal links connecting them. To create a TTZ, we need to configure it (refer to Section 11).
图中的所有路由器都位于区域X中。带有T（即T61、T63、T65、T67、T71、T73、T75、T77、T79和T81）的路由器也位于TTZ 600中，其中包含连接它们的TTZ内部链路。要创建TTZ，我们需要对其进行配置（请参阅第11节）。
There are two types of routers in a TTZ: TTZ-internal and TTZ edge routers. TTZ 600 has four TTZ edge routers: T61, T63, T65, and T67. Each of them has at least one adjacent router in TTZ 600 and one adjacent router outside of TTZ 600. For instance, router T61 is a TTZ edge router since it has an adjacent router, R15, outside of TTZ 600 and three adjacent routers T71, T75, and T81 in TTZ 600.
TTZ中有两种类型的路由器：TTZ内部路由器和TTZ边缘路由器。TTZ 600有四个TTZ边缘路由器：T61、T63、T65和T67。它们中的每一个在TTZ 600中具有至少一个相邻路由器，并且在TTZ 600之外具有一个相邻路由器。例如，路由器T61是TTZ边缘路由器，因为它在TTZ 600之外有一个相邻的路由器R15，并且在TTZ 600中有三个相邻的路由器T71、T75和T81。
In addition, TTZ 600 comprises six TTZ-internal routers: T71, T73, T75, T77, T79, and T81. Each of them has all its adjacent routers in TTZ 600. For instance, router T71 is a TTZ-internal router since its
此外，TTZ 600包括六个TTZ内部路由器：T71、T73、T75、T77、T79和T81。它们中的每一个都有其在TTZ 600中的所有相邻路由器。例如，路由器T71是TTZ内部路由器，因为其
adjacent routers, T61, T63, T65, T67, and T73, are all in TTZ 600. It should be noted that, by definition, a TTZ-internal router cannot also be an ABR.
相邻路由器T61、T63、T65、T67和T73都在TTZ 600中。应该注意的是，根据定义，TTZ内部路由器也不能是ABR。
A TTZ hides the internal topology of the TTZ from the outside. It does not directly advertise any internal information about the TTZ to any router outside of the TTZ.
TTZ从外部隐藏TTZ的内部拓扑。它不会直接向TTZ之外的任何路由器公布关于TTZ的任何内部信息。
For instance, TTZ 600 does not send the information about TTZ-internal router T71 to any router outside of TTZ 600; it does not send the information about the link between TTZ routers T61 and T71 to any router outside of TTZ 600.
例如，TTZ 600不向TTZ 600之外的任何路由器发送关于TTZ内部路由器T71的信息；它不会将关于TTZ路由器T61和T71之间的链路的信息发送到TTZ 600之外的任何路由器。
The figure below illustrates area X from the point of view of a router outside of TTZ 600 after TTZ 600 is created.
下图从创建TTZ 600后TTZ 600外部路由器的角度说明了区域X。
Area X ==== Normal Link
Area X ==== Normal Link
===[R15]===========[T61]=========[T63]=========[R29]===
|| || \\ // || ||
|| || \\ // || ||
|| || \\ // || ||
|| || \\// || ||
|| || //\ || ||
|| || // \\ || ||
|| || // \\ || ||
|| || // \\ || ||
|| || // \\ || ||
===[R17]===========[T65]=========[T67]=========[R31]===
\\ // \\ //
|| // \\ ||
|| // \\ ||
|| // \\ ||
\\ // \\ //
======[R23]============================[R25]=====
// \\
// \\
===[R15]===========[T61]=========[T63]=========[R29]===
|| || \\ // || ||
|| || \\ // || ||
|| || \\ // || ||
|| || \\// || ||
|| || //\ || ||
|| || // \\ || ||
|| || // \\ || ||
|| || // \\ || ||
|| || // \\ || ||
===[R17]===========[T65]=========[T67]=========[R31]===
\\ // \\ //
|| // \\ ||
|| // \\ ||
|| // \\ ||
\\ // \\ //
======[R23]============================[R25]=====
// \\
// \\
From a router outside of the TTZ, a TTZ is seen as the TTZ edge routers connected to each other. For instance, router R15 sees that T61, T63, T65, and T67 are connected to each other.
从TTZ外部的路由器，TTZ被视为相互连接的TTZ边缘路由器。例如，路由器R15看到T61、T63、T65和T67彼此连接。
In addition, a router outside of the TTZ sees TTZ edge routers having normal connections to the routers outside of the TTZ. For example, router R15 sees that T61, T63, T65, and T67 have the normal connections to R15; R29; R17 and R23; and R25 and R31, respectively.
此外，TTZ外部的路由器看到TTZ边缘路由器与TTZ外部的路由器具有正常连接。例如，路由器R15看到T61、T63、T65和T67具有到R15的正常连接；R29；R17和R23；以及R25和R31。
The link-state information about a TTZ includes router Link-State Advertisements (LSAs), which can be contained and advertised in opaque LSAs [RFC5250] within the TTZ. Some control information regarding a TTZ can also be contained and advertised in opaque LSAs within the TTZ. These opaque LSAs are called TTZ opaque LSAs or TTZ LSAs for short.
关于TTZ的链路状态信息包括路由器链路状态通告（lsa），其可包含在TTZ内的不透明lsa[RFC5250]中并通告。关于TTZ的一些控制信息也可以包含在TTZ内的不透明LSA中并发布。这些不透明LSA简称为TTZ不透明LSA或TTZ LSA。
The following is the general format of a TTZ LSA. It has a Link-State (LS) Type = 10/9 and TTZ LSA Type, and it contains a number of TLVs.
以下是TTZ LSA的一般格式。它有一个链路状态（LS）类型=10/9和TTZ LSA类型，并且它包含许多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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | LS Type = 10/9|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TTZ LSA Type(9)| Instance ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | LS Type = 10/9|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TTZ LSA Type(9)| Instance ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
There are three TTZ LSAs of LS Type 10 defined:
定义了三个LS类型10的TTZ LSA：
o TTZ router LSA: a TTZ LSA containing a TTZ ID TLV and a TTZ Router TLV.
o TTZ路由器LSA：包含TTZ ID TLV和TTZ路由器TLV的TTZ LSA。
o TTZ control LSA: a TTZ LSA containing a TTZ ID TLV and a TTZ Options TLV.
o TTZ控制LSA：包含TTZ ID TLV和TTZ选项TLV的TTZ LSA。
o TTZ indication LSA: a TTZ LSA containing a TTZ ID TLV with E = 0, which indicates that the router originating this LSA is a TTZ-internal router.
o TTZ指示LSA：包含TTZ ID TLV且E=0的TTZ LSA，表示发起此LSA的路由器是TTZ内部路由器。
There is one TTZ LSA of LS Type 9:
有一个LS类型9的TTZ LSA：
o TTZ discovery LSA: a TTZ LSA containing a TTZ ID TLV and an optional TTZ Options TLV.
o TTZ发现LSA：包含TTZ ID TLV和可选TTZ选项TLV的TTZ LSA。
A TTZ ID TLV has the following format. It contains a TTZ ID (refer to Section 5.1) and some flags. It has the TLV-Length of 8 octets.
TTZ ID TLV具有以下格式。它包含一个TTZ ID（参考第5.1节）和一些标志。它的TLV长度为8个八位字节。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTZ ID TLV Type (1) | TLV-Length (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTZ ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (MUST be zero) |E|Z|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTZ ID TLV Type (1) | TLV-Length (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTZ ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (MUST be zero) |E|Z|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E = 1: Indicating a router is a TTZ edge router
Z = 1: Indicating a router has migrated to TTZ
E = 1: Indicating a router is a TTZ edge router
Z = 1: Indicating a router has migrated to TTZ
When a TTZ router originates a TTZ LSA containing a TTZ ID TLV, it MUST set flag E to 1 in the TTZ ID TLV if it is a TTZ edge router and to 0 if it is a TTZ-internal router. It MUST set flag Z to 1 after it has migrated to TTZ and to 0 before it migrates to TTZ or after it rolls back from TTZ (refer to Section 6.4).
当TTZ路由器发起包含TTZ ID TLV的TTZ LSA时，如果是TTZ边缘路由器，则必须在TTZ ID TLV中将标志E设置为1，如果是TTZ内部路由器，则必须将标志E设置为0。它必须在迁移到TTZ后将标志Z设置为1，在迁移到TTZ前或从TTZ回滚后将标志Z设置为0（参考第6.4节）。
The format of a TTZ Router TLV is as follows. It has the same content as a standard OSPF router LSA (RFC 2328) with the following modifications.
TTZ路由器TLV的格式如下所示。它的内容与标准OSPF路由器LSA（RFC 2328）相同，但有以下修改。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTZ RT TLV Type (2) | TLV-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 |V|E|B| 0 | # links |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | # TOS | metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTZ RT TLV Type (2) | TLV-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 |V|E|B| 0 | # links |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | # TOS | metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
Note: TOS = Type of Service
注：TOS=服务类型
For a router link, the existing 8-bit Link Type field for a router link is split into two fields as follows:
对于路由器链路，路由器链路的现有8位链路类型字段分为两个字段，如下所示：
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| I | Type-1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| I | Type-1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
I bit flag: 1: Router link is a TTZ-internal link. 0: Router link is a TTZ-external link. Type-1: The kind of the link. The values for Type-1 are the same as those for Type defined in RFC 2328, Section 12.4.1.
I位标志：1：路由器链路是TTZ内部链路。0:路由器链路是TTZ外部链路。类型1：链接的类型。类型-1的值与RFC 2328第12.4.1节中定义的类型值相同。
The Link Type field is 8 bits and the values 128-255 of the field are reserved (refer to [RFC4940]), which allows the reuse of the bottom 7 bits to indicate the type of TTZ-internal or external link.
链路类型字段为8位，字段的值128-255保留（参考[RFC4940]），这允许重用底部7位来指示TTZ内部或外部链路的类型。
The format of a TTZ Options TLV is as follows.
TTZ选项TLV的格式如下所示。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTZ OP TLV Type (3) | TLV-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OP | Reserved (MUST be zero) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTZ OP TLV Type (3) | TLV-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OP | Reserved (MUST be zero) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OP Value Meaning (Operation) 0x001 (T): Advertising TTZ Topology Information for Migration 0x010 (M): Migrating to TTZ 0x011 (N): Advertising Normal Topology Information for Rollback 0x100 (R): Rolling Back from TTZ
OP值含义（操作）0x001（T）：为迁移播发TTZ拓扑信息0x010（M）：迁移到TTZ 0x011（N）：为回滚播发正常拓扑信息0x100（R）：从TTZ回滚
An OP field of 3 bits is defined. It may have a value of 0x001 for T, 0x010 for M, 0x011 for N, or 0x100 for R, which indicates one of the four operations above. When any of the other values is received, it is ignored.
定义了一个3位的运算字段。它的值可能为0x001表示T，0x010表示M，0x011表示N，或0x100表示R，这表示上述四种操作之一。当接收到任何其他值时，将忽略该值。
Advertising TTZ Topology Information for Migration (T): After a user configures a TTZ router to advertise TTZ topology information, advertising TTZ topology information for migration is triggered. The TTZ router originates a TTZ control LSA having a TTZ Options TLV with OP for T. It also originates its other
为迁移播发TTZ拓扑信息（T）：用户将TTZ路由器配置为播发TTZ拓扑信息后，触发为迁移播发TTZ拓扑信息。TTZ路由器发起一个TTZ控制LSA，该LSA具有TTZ选项TLV，OP代表T。它还发起另一个TTZ控制LSA
TTZ LSA such as a TTZ router LSA or TTZ indication LSA. When another TTZ router receives the LSA with OP for T, it originates its TTZ LSA as described in Section 7.
TTZ LSA，如TTZ路由器LSA或TTZ指示LSA。当另一个TTZ路由器接收到带有OP for T的LSA时，它按照第7节中的描述发起其TTZ LSA。
Migrating to TTZ (M): After a user configures a TTZ router to migrate to TTZ, migrating to TTZ is triggered. The TTZ router originates a TTZ control LSA having a TTZ Options TLV with OP for M and migrates to TTZ. When another TTZ router receives the LSA with OP for M, it also migrates to TTZ. When a router migrates to TTZ, it computes routes using the TTZ topology and the topology outside of the TTZ. For a TTZ-internal router, it also updates its TTZ indication LSA with Z = 1. For a TTZ edge router, it updates its TTZ router LSA with Z = 1 and its router LSA for virtualizing the TTZ. A TTZ router determines whether it is internal or edge based on configurations (refer to Section 11.1).
迁移到TTZ（M）：用户将TTZ路由器配置为迁移到TTZ后，将触发迁移到TTZ。TTZ路由器发起一个TTZ控制LSA，该LSA具有TTZ选项TLV和OP for M，并迁移到TTZ。当另一个TTZ路由器接收到带有OP for M的LSA时，它也会迁移到TTZ。当路由器迁移到TTZ时，它使用TTZ拓扑和TTZ之外的拓扑计算路由。对于TTZ内部路由器，它还将其TTZ指示LSA更新为Z=1。对于TTZ边缘路由器，它将其TTZ路由器LSA更新为Z=1，并将其路由器LSA更新为虚拟化TTZ。TTZ路由器根据配置确定是内部路由器还是边缘路由器（请参阅第11.1节）。
Advertising Normal Topology Information for Rollback (N): After a user configures a TTZ router to advertise normal topology information, advertising Normal topology information for rollback is triggered. The TTZ router originates a TTZ control LSA having a TTZ Options TLV with OP for N. It also advertises its normal LSAs such as its normal router LSA and stops advertising its other TTZ LSAs. When another TTZ router receives the LSA with OP for N, it forwards the LSA, advertises its normal LSAs, and stops advertising its TTZ LSAs.
用于回滚的播发正常拓扑信息（N）：用户将TTZ路由器配置为播发正常拓扑信息后，将触发用于回滚的播发正常拓扑信息。TTZ路由器发起一个TTZ控制LSA，该LSA具有TTZ选项TLV，OP代表N。它还播发其正常LSA，如其正常路由器LSA，并停止播发其其他TTZ LSA。当另一个TTZ路由器接收到OP为N的LSA时，它转发LSA，播发其正常LSA，并停止播发其TTZ LSA。
Rolling back from TTZ (R): After a user configures a TTZ router to roll back from TTZ, rolling back from TTZ is triggered. The TTZ router originates a TTZ control LSA having a TTZ Options TLV with OP for R and rolls back from TTZ. When another TTZ router receives the LSA with OP for R, it also rolls back from TTZ.
从TTZ回滚（R）：用户将TTZ路由器配置为从TTZ回滚后，触发从TTZ回滚。TTZ路由器发起一个TTZ控制LSA，该LSA具有TTZ选项TLV，OP代表R，并从TTZ回滚。当另一个TTZ路由器接收到带有OP for R的LSA时，它也会从TTZ回滚。
After a TTZ router originates a TTZ control LSA in response to a configuration described above to control TTZ, it flushes the TTZ control LSA if OP in the LSA is set for the configuration and the configuration is removed.
在TTZ路由器响应于上述控制TTZ的配置而发起TTZ控制LSA之后，如果LSA中的OP被设置为该配置并且该配置被移除，则TTZ路由器将刷新TTZ控制LSA。
A TTZ LSA of LS Type 9 has the following format.
LS类型9的TTZ LSA具有以下格式。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | LS Type = 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TTZ LSA Type(9)| Instance ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TTZ ID TLV ~
+---------------------------------------------------------------+
| |
~ (TTZ Options 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | LS Type = 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TTZ LSA Type(9)| Instance ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TTZ ID TLV ~
+---------------------------------------------------------------+
| |
~ (TTZ Options TLV) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
It contains a mandatory TTZ ID TLV, which may be followed by an optional TTZ Options TLV. It is used to discover a TTZ neighbor.
它包含一个强制的TTZ ID TLV，后面可能跟一个可选的TTZ选项TLV。它用于发现TTZ邻居。
For a TTZ, its topology is represented by the LSAs generated by its TTZ routers for the link states in the TTZ, which include TTZ router LSAs by TTZ edge routers, TTZ indication LSAs by TTZ-internal routers, normal router LSAs, and network LSAs. The TTZ router LSAs and TTZ indication LSAs MUST be generated after advertising TTZ topology information for migration is triggered.
对于TTZ，其拓扑由TTZ路由器为TTZ中的链路状态生成的LSA表示，包括TTZ边缘路由器生成的TTZ路由器LSA、TTZ内部路由器生成的TTZ指示LSA、正常路由器LSA和网络LSA。TTZ路由器LSA和TTZ指示LSA必须在触发用于迁移的公布TTZ拓扑信息后生成。
A TTZ edge router generates a TTZ router LSA that has a TTZ ID TLV and a TTZ Router TLV. The former includes the ID of the TTZ to which the router belongs and flag E is set to 1, which indicates the originator of the LSA is a TTZ edge router. The TTZ Router TLV contains the TTZ-external links to the routers outside of the TTZ and the TTZ-internal links to the routers inside of the TTZ as described in Section 6. The TTZ router LSA containing this TLV is constructed and advertised within the TTZ.
TTZ边缘路由器生成具有TTZ ID TLV和TTZ路由器TLV的TTZ路由器LSA。前者包括路由器所属的TTZ的ID，标志E设置为1，表示LSA的发起者是TTZ边缘路由器。TTZ路由器TLV包含到TTZ外部路由器的TTZ外部链路和到TTZ内部路由器的TTZ内部链路，如第6节所述。包含此TLV的TTZ路由器LSA在TTZ内构造和公布。
A TTZ-internal router generates a TTZ indication LSA that has a TTZ ID TLV containing the ID of the TTZ to which the router belongs and flag E is set to 0, which indicates the originator of the LSA is a
TTZ内部路由器生成TTZ指示LSA，其TTZ ID TLV包含路由器所属TTZ的ID，且标志E设置为0，表示LSA的发起人是
TTZ-internal router. For a TTZ-internal router, its regular router LSA is still generated. If a TTZ router is a Designated Router (DR), it originates its regular network LSA.
TTZ内部路由器。对于TTZ内部路由器，其常规路由器LSA仍然生成。如果TTZ路由器是指定路由器（DR），则它发起其常规网络LSA。
After receiving a trigger to migrate to TTZ such as a TTZ control LSA with OP for M, a TTZ edge router MUST originate its normal router LSA for virtualizing a TTZ, which comprises three groups of links in general.
在接收到迁移到TTZ的触发器（例如带有OP for M的TTZ控制LSA）后，TTZ边缘路由器必须发起其用于虚拟化TTZ的普通路由器LSA，TTZ通常包括三组链路。
The first group is the router links connecting the TTZ-external routers. These router links are normal router links. There is a router link for every adjacency between this TTZ edge router and a TTZ-external router.
第一组是连接TTZ外部路由器的路由器链路。这些路由器链路是正常的路由器链路。这个TTZ边缘路由器和一个TTZ外部路由器之间的每个邻接都有一个路由器链路。
The second group is the "virtual" router links connecting to the other TTZ edge routers. For each of the other TTZ edge routers, there is a corresponding point-to-point (P2P) router link to it from this TTZ edge router. The cost of the link is the cost of the shortest path from this TTZ edge router to the other TTZ edge router within the TTZ.
第二组是连接到其他TTZ边缘路由器的“虚拟”路由器链路。对于其他每个TTZ边缘路由器，都有一个相应的点到点（P2P）路由器链接从该TTZ边缘路由器连接到它。链路成本是从该TTZ边缘路由器到TTZ内其他TTZ边缘路由器的最短路径的成本。
In addition, the LSA may contain a third group of links, which are the stub links for the loopback addresses inside the TTZ to be accessed by nodes outside of the TTZ.
此外，LSA可以包含第三组链路，它们是TTZ内的环回地址的存根链路，供TTZ外的节点访问。
After migration to TTZ is triggered, a TTZ router computes routes using its TTZ topology (refer to Section 10), and a TTZ edge router originates its normal router LSA for virtualizing the TTZ in two steps:
触发到TTZ的迁移后，TTZ路由器使用其TTZ拓扑计算路由（参考第10节），TTZ边缘路由器通过两个步骤启动其正常路由器LSA以虚拟化TTZ：
Step 1: The router updates its router LSA by adding a P2P link to each of the other known edge routers in the TTZ and also by adding the stub links for the loopback addresses in the TTZ to be accessed outside of the TTZ according to configuration policies of operators.
步骤1：路由器通过向TTZ中的每个其他已知边缘路由器添加P2P链路，以及根据运营商的配置策略，为TTZ中要在TTZ之外访问的环回地址添加存根链路，来更新其路由器LSA。
Step 2: After MaxLSAGenAdvTime (0.3 s) or sr-time + MaxLSAAdvTime (0.1 s), it removes the TTZ links from its router LSA, where sr-time is the time from updating its router LSA to receiving the ack for its router LSA and receiving the updated router LSAs originated by the other TTZ edge routers. In other words, it removes the TTZ links from its router LSA after sending its updated router LSA and receiving the updated router LSAs originated by the other TTZ edge routers for MaxLSAAdvTime or after sending its updated router LSA for MaxLSAGenAdvTime. MaxLSAAdvTime and MaxLSAGenAdvTime SHOULD be set to 100 ms and 300
步骤2：在MaxLSAGenAdvTime（0.3 s）或sr time+MaxLSAAdvTime（0.1 s）之后，它从其路由器LSA移除TTZ链路，其中sr time是从更新其路由器LSA到接收其路由器LSA的ack以及接收由其他TTZ边缘路由器发起的更新路由器LSA的时间。换言之，在发送其更新的路由器LSA并接收由其他TTZ边缘路由器针对MaxLSAAdvTime发起的更新的路由器LSA之后，或在发送其更新的路由器LSA针对MaxLSAAdvTime之后，它从其路由器LSA移除TTZ链路。MaxLSAAdvTime和MaxLSAGenAdvTime应分别设置为100 ms和300 ms
ms, respectively, but MAY be configurable. The former is the maximum time for an LSA to be advertised to all the routers in an area. The latter is the maximum time for all TTZ router LSAs to be generated by all TTZ edge routers and advertised to all the routers in an area after a first TTZ router LSA is generated.
ms，但可能是可配置的。前者是向一个区域内的所有路由器通告LSA的最长时间。后者是在生成第一个TTZ路由器LSA之后，所有TTZ边缘路由器生成所有TTZ路由器LSA并向区域中的所有路由器通告的最长时间。
This is to avoid a possible route down or change in a TTZ-external router while the TTZ is being virtualized. If each TTZ edge router originates its router LSA by adding its P2P links to the other TTZ edge routers and removing its TTZ links in one step, a route taking a path through the TTZ in the TTZ-external router may be down or changed before all the router LSAs generated by the TTZ edge routers reach the TTZ-external router. When the TTZ-external router computes routes with some router LSAs originated by the TTZ edge routers, bidirectional checks for some of the P2P links will fail. Thus, the route taking the path through the shortest path for the P2P link failing the bidirectional check will be down or changed.
这是为了在虚拟化TTZ时避免TTZ外部路由器中可能的路由下降或更改。如果每个TTZ边缘路由器通过将其P2P链路添加到其他TTZ边缘路由器并在一步中移除其TTZ链路来发起其路由器LSA，则在TTZ边缘路由器生成的所有路由器LSA到达TTZ外部路由器之前，通过TTZ外部路由器中TTZ的路径的路由可能会关闭或更改。当TTZ外部路由器使用TTZ边缘路由器发起的某些路由器LSA计算路由时，对某些P2P链路的双向检查将失败。因此，对于未通过双向检查的P2P链路，采用通过最短路径的路径的路由将被关闭或更改。
To roll back from a TTZ smoothly after receiving a trigger to roll back from TTZ, a TTZ edge router MUST originate its normal router LSA in the above two steps in a reverse way.
为了在收到从TTZ回滚的触发器后顺利从TTZ回滚，TTZ边缘路由器必须以相反的方式在上述两个步骤中发起其正常路由器LSA。
Step 1: Initially, it updates its normal router LSA by adding the normal links for the links configured as TTZ links into the LSA.
步骤1：最初，它通过将配置为TTZ链路的链路的正常链路添加到LSA中来更新其正常路由器LSA。
Step 2: It then removes the P2P links to the other edge routers of the TTZ for virtualizing the TTZ and the stub links for the loopback addresses from its updated router LSA after sending its updated router LSA and receiving the updated router LSAs originated by the other TTZ edge routers for MaxLSAAdvTime or after sending its updated router LSA for MaxLSAGenAdvTime.
步骤2：然后，在发送其更新的路由器LSA并接收由其他TTZ边缘路由器针对MaxLSAAdvTime发起的更新的路由器LSA后，或在发送其更新的路由器LSA后，删除到TTZ其他边缘路由器的P2P链路，以虚拟化TTZ，并从其更新的路由器LSA删除环回地址的存根链路对于MaxLSAGenAdvTime。
This section describes the TTZ adjacencies.
本节介绍TTZ邻接。
When two routers A and B are connected by a P2P link and have a normal adjacency, they TTZ discover each other through a TTZ LSA of LS Type 9 with a TTZ ID TLV. We call this LSA D-LSA for short.
当两个路由器A和B通过P2P链路连接并且具有正常邻接时，它们TTZ通过具有TTZ ID TLV的LS类型9的TTZ LSA相互发现。我们简称为LSA D-LSA。
If two ends of the link have different TTZ IDs or only one end is configured with a TTZ ID, TTZ adjacency over the link MUST NOT be "formed".
如果链路的两端具有不同的TTZ ID，或者只有一端配置了TTZ ID，则链路上的TTZ邻接不得“形成”。
If two ends of the link have the same TTZ ID and Z flag value, A and B are TTZ neighbors. The following is a sequence of events related to TTZ for this case.
如果链路的两端具有相同的TTZ ID和Z标志值，则A和B是TTZ邻居。以下是与本案例中的TTZ相关的一系列事件。
A B
Configure TTZ Configure TTZ
D-LSA (TTZ ID=100)
----------------------> Same TTZ ID and Z
A is B's TTZ Neighbor
D-LSA (TTZ ID=100)
Same TTZ ID and Z <----------------------
B is A's TTZ Neighbor
A B
Configure TTZ Configure TTZ
D-LSA (TTZ ID=100)
----------------------> Same TTZ ID and Z
A is B's TTZ Neighbor
D-LSA (TTZ ID=100)
Same TTZ ID and Z <----------------------
B is A's TTZ Neighbor
A sends B a D-LSA with TTZ ID after the TTZ is configured on it. B sends A a D-LSA with TTZ ID after the TTZ is configured on it.
在配置TTZ后，A向B发送带有TTZ ID的D-LSA。B在其上配置TTZ后，发送带有TTZ ID的D-LSA。
When A receives the D-LSA from B and determines they have the same TTZ ID and Z flag value, B is A's TTZ neighbor. A also sends B all the TTZ LSAs it has and originates its TTZ LSA when one of the following conditions is met.
当A从B接收到D-LSA并确定它们具有相同的TTZ ID和Z标志值时，B是A的TTZ邻居。A还向B发送其拥有的所有TTZ LSA，并在满足以下条件之一时发起其TTZ LSA。
o Z = 0 and there is a TTZ LSA with OP for T.
o Z=0，并且有一个TTZ LSA，其中OP代表T。
o Z = 1.
o Z=1。
B is symmetric to A and acts similarly to A.
B与A对称，其作用类似于A。
If two ends of the link have the same TTZ ID but the Z flags are different, a TTZ adjacency over the link MUST be "formed" in the following steps. Suppose that A has migrated to TTZ and B has not (i.e., flag Z in A's D-LSA is 1, and flag Z in B's D-LSA is 0).
如果链路的两端具有相同的TTZ ID，但Z标志不同，则必须在以下步骤中“形成”链路上的TTZ邻接。假设A已迁移到TTZ，而B尚未迁移（即，A的D-LSA中的标志Z为1，B的D-LSA中的标志Z为0）。
A B
Configure TTZ Configure TTZ
D-LSA(TTZ ID=100,Z=1)
----------------------> Same TTZ ID, but
different Z
A is B's TTZ Neighbor
D-LSA(TTZ ID=100,Z=0)
Same TTZ ID, but <----------------------
different Z
B is A's TTZ Neighbor
TTZ LSAs
----------------------->
TTZ LSAs
<-----------------------
A B
Configure TTZ Configure TTZ
D-LSA(TTZ ID=100,Z=1)
----------------------> Same TTZ ID, but
different Z
A is B's TTZ Neighbor
D-LSA(TTZ ID=100,Z=0)
Same TTZ ID, but <----------------------
different Z
B is A's TTZ Neighbor
TTZ LSAs
----------------------->
TTZ LSAs
<-----------------------
When A receives the D-LSA from B and determines they have the same TTZ ID but its Z = 1 and B's Z = 0, A sends B all the TTZ LSAs it has and triggers B to migrate to TTZ. A updates and sends B its D-LSA by adding a TTZ Options TLV with OP for M after sending B all the TTZ LSAs.
当A从B接收到D-LSA并确定它们具有相同的TTZ ID，但其Z=1和B的Z=0时，A向B发送其所有的TTZ LSA，并触发B迁移到TTZ。A在向B发送所有TTZ LSA后，通过添加带有OP for M的TTZ选项TLV更新并向B发送其D-LSA。
D-LSA(TTZ ID=100,OP=M)
Add TTZ Options -----------------------> Migrate to TTZ
TLV with OP for M
D-LSA(TTZ ID=100,Z=1) Migrated to TTZ
<----------------------- Set Z=1
D-LSA(TTZ ID=100,OP=M)
Add TTZ Options -----------------------> Migrate to TTZ
TLV with OP for M
D-LSA(TTZ ID=100,Z=1) Migrated to TTZ
<----------------------- Set Z=1
D-LSA(TTZ ID=100,Z=1)
Remove ----------------------->
TTZ Options TLV
D-LSA(TTZ ID=100,Z=1)
Remove ----------------------->
TTZ Options TLV
When B receives the D-LSA from A and determines they have the same TTZ ID but its Z = 0 and A's Z = 1, B sends A all the TTZ LSAs it has.
当B从A接收到D-LSA并确定它们具有相同的TTZ ID，但其Z=0且A的Z=1时，B向A发送其具有的所有TTZ LSA。
When B receives the D-LSA from A with OP for M, it starts to migrate to TTZ. B updates and advertises its LSAs as needed.
当B从A接收到D-LSA，其中OP代表M时，它开始迁移到TTZ。B根据需要更新和宣传其LSA。
After receiving B's D-LSA with Z = 1, A updates and sends B its D-LSA by removing the TTZ Options TLV. It also updates and advertises its LSAs as needed.
在接收到B的D-LSA且Z=1后，A通过删除TTZ选项TLV更新并发送B的D-LSA。它还根据需要更新和宣传其LSA。
When a number of routers connected through a broadcast link have normal adjacencies among them, they also TTZ discover each other through D-LSAs. The Designated Router (DR) for the link MUST "form" TTZ adjacencies with the other routers if all the routers attached to the link have the same TTZ ID configured on the connections to the link. Otherwise, the DR MUST NOT "form" any TTZ adjacency with any router attached to the link.
当通过广播链路连接的多个路由器之间具有正常的邻接时，它们也会通过D-LSA相互发现。如果连接到该链路的所有路由器在与该链路的连接上配置了相同的TTZ ID，则该链路的指定路由器（DR）必须与其他路由器“形成”TTZ邻接。否则，DR不得与连接到链路的任何路由器“形成”任何TTZ邻接。
When a number of routers connected through a broadcast link have TTZ adjacencies among them, if a misconfigured router is introduced on the broadcast link, the DR for the link MUST NOT "form" any TTZ adjacency with this misconfigured router.
当通过广播链路连接的多个路由器之间存在TTZ邻接时，如果在广播链路上引入了配置错误的路由器，则链路的DR不得与该配置错误的路由器“形成”任何TTZ邻接。
For routers connected via a link without any adjacency among them, they TTZ discover each other through D-LSAs in the same way as described above after they form a normal adjacency.
对于通过链路连接的路由器，它们之间没有任何邻接，在形成正常邻接后，它们通过D-lsa以如上所述的相同方式相互发现。
A TTZ adjacency over a link MUST be removed when one of the following events happens.
发生下列事件之一时，必须删除链接上的TTZ邻接。
o TTZ ID on one end of the link is changed to a different one.
o 链接一端的TTZ ID已更改为另一个。
o TTZ ID on one end of the link is removed.
o 链路一端的TTZ ID已删除。
o The D-LSA is not received after the D-LSA-MAX-RETRANSMIT-TIME or is explicitly flushed. The D-LSA-MAX-RETRANSMIT-TIME SHOULD be set to 60 minutes, but MAY be configurable.
o 在D-LSA-MAX-RETRANSMIT-TIME之后未接收到D-LSA，或者显式刷新了D-LSA。D-LSA-MAX-RETRANSMIT-TIME应设置为60分钟，但可以配置。
o Normal adjacency over the link is down.
o 链接上的正常邻接已关闭。
When the TTZ ID on one end of the link is removed, the corresponding D-LSA is flushed.
当链路一端的TTZ ID被删除时，相应的D-LSA被刷新。
A TTZ edge router forms an adjacency with any TTZ-external router to which it is connected.
TTZ边缘路由器与其连接的任何TTZ外部路由器形成邻接。
When the TTZ edge router synchronizes its link-state database with the TTZ-external router, it sends the TTZ-external router the information about all the LSAs except for the LSAs belonging to the TTZ that are hidden from any router outside of the TTZ.
当TTZ边缘路由器将其链路状态数据库与TTZ外部路由器同步时，它向TTZ外部路由器发送关于所有LSA的信息，但属于TTZ的LSA除外，这些LSA对TTZ外部的任何路由器都是隐藏的。
At the end of the link-state database synchronization, the TTZ edge router originates its own router LSA for virtualizing the TTZ and sends this LSA to its adjacent routers, including the TTZ-external router.
在链路状态数据库同步结束时，TTZ边缘路由器发起其自己的路由器LSA，用于虚拟化TTZ，并将此LSA发送到其相邻路由器，包括TTZ外部路由器。
LSAs can be divided into a couple of classes according to their Advertisements. The first class of LSAs is advertised within a TTZ. The second is advertised through a TTZ.
LSA可以根据其广告分为两类。第一类LSA在TTZ中发布。第二种是通过TTZ进行广告。
Any LSA about a link state in a TTZ is advertised only within the TTZ. It is not advertised to any router outside of the TTZ. For example, a router LSA generated for a TTZ-internal router is advertised only within the TTZ.
关于TTZ中的链路状态的任何LSA仅在TTZ中公布。它不会向TTZ之外的任何路由器播发。例如，为TTZ内部路由器生成的路由器LSA仅在TTZ内播发。
Any network LSA generated for a broadcast or Non-Broadcast Multi-Access (NBMA) network in a TTZ is advertised only within the TTZ. It is not advertised outside of the TTZ.
为TTZ中的广播或非广播多址（NBMA）网络生成的任何网络LSA仅在TTZ内通告。它不会在TTZ之外发布广告。
Any opaque LSA generated for a TTZ-internal TE link is advertised only within the TTZ.
为TTZ内部TE链路生成的任何不透明LSA仅在TTZ内公布。
After migrating to TTZ, every edge router of a TTZ MUST NOT advertise any LSA about a link state in the TTZ to any router outside of the TTZ. The TTZ edge router determines whether an LSA is about a TTZ-internal link state by checking if the advertising router of the LSA is a TTZ-internal router (i.e., there is a TTZ indication LSA generated by the TTZ-internal router that has the same advertising router).
迁移到TTZ后，TTZ的每个边缘路由器不得向TTZ之外的任何路由器播发关于TTZ中链路状态的任何LSA。TTZ边缘路由器通过检查LSA的广告路由器是否是TTZ内部路由器（即，存在由具有相同广告路由器的TTZ内部路由器生成的TTZ指示LSA）来确定LSA是否关于TTZ内部链路状态。
For any TTZ LSA originated by a router within the TTZ, every edge router of the TTZ MUST NOT advertise it to any router outside of the TTZ.
对于由TTZ内的路由器发起的任何TTZ LSA，TTZ的每个边缘路由器不得向TTZ外的任何路由器播发。
Any LSA about a link state outside of a TTZ received by an edge router of the TTZ is advertised using the TTZ as transit. For example, when an edge router of a TTZ receives an LSA from a router outside of the TTZ, it floods it to its neighboring routers both inside and outside of the TTZ. This LSA may be any LSA such as a router LSA that is advertised within an OSPF area.
由TTZ的边缘路由器接收的关于TTZ之外的链路状态的任何LSA使用TTZ作为传输来播发。例如，当TTZ的边缘路由器从TTZ外部的路由器接收LSA时，它会将LSA洪泛到TTZ内部和外部的相邻路由器。该LSA可以是任何LSA，例如在OSPF区域内通告的路由器LSA。
The routers in the TTZ continue to flood the LSA. When another edge router of the TTZ receives the LSA, it floods the LSA to its neighboring routers both inside and outside of the TTZ.
TTZ中的路由器继续淹没LSA。当TTZ的另一个边缘路由器接收到LSA时，它将LSA洪泛到其TTZ内外的相邻路由器。
After a router migrates to TTZ, the computation of the routing table on the router is the same as that described in RFC 2328, Section 16 with one exception. The router in a TTZ ignores the router LSAs generated by the TTZ edge routers for virtualizing the TTZ. It computes routes using the TTZ router LSAs and the regular LSAs, excluding the router LSAs for virtualizing the TTZ. That is, it computes routes using the TTZ topology and the topology outside of the TTZ, excluding the links for virtualizing the TTZ.
路由器迁移到TTZ后，路由器上路由表的计算与RFC 2328第16节中描述的相同，但有一个例外。TTZ中的路由器忽略TTZ边缘路由器为虚拟化TTZ而生成的路由器LSA。它使用TTZ路由器LSA和常规LSA计算路由，不包括用于虚拟化TTZ的路由器LSA。也就是说，它使用TTZ拓扑和TTZ外部的拓扑计算路由，不包括用于虚拟化TTZ的链路。
This section proposes some options for configuring a TTZ.
本节介绍了一些配置TTZ的选项。
1. Configuring TTZ on Every Link in TTZ
1. 在TTZ中的每个链路上配置TTZ
If every link in a TTZ is configured with the same TTZ ID as a TTZ link, the TTZ is determined. A router with some links in a TTZ and some links not in this TTZ is a TTZ edge router. A router with all its links in a TTZ is a TTZ-internal router.
如果TTZ中的每个链路都配置了与TTZ链路相同的TTZ ID，则确定TTZ。在TTZ中有一些链路，而在这个TTZ中没有一些链路的路由器是TTZ边缘路由器。在TTZ中具有所有链路的路由器是TTZ内部路由器。
2. Configuring TTZ on Routers in TTZ
2. 在TTZ中的路由器上配置TTZ
A same TTZ ID is configured on every TTZ-internal router in a TTZ and on every TTZ edge router's links connecting to the routers in the TTZ.
在TTZ中的每个TTZ内部路由器和连接到TTZ中路由器的每个TTZ边缘路由器链路上配置相同的TTZ ID。
A router configured with the TTZ ID on some of its links is a TTZ edge router. A router configured with the TTZ ID only is a TTZ-internal router. All the links on a TTZ-internal router are TTZ links. This option is simpler than option 1 above.
在某些链路上配置TTZ ID的路由器是TTZ边缘路由器。仅配置TTZ ID的路由器是TTZ内部路由器。TTZ内部路由器上的所有链路都是TTZ链路。此选项比上面的选项1简单。
For a TTZ edge router X with different TTZ IDs on its different links, router X connects two or more different TTZs. In this case, router X originates its router LSA for virtualizing the TTZs. This LSA includes the normal links connecting to routers outside of these TTZs and the virtual links to the other edge routers of each of these TTZs. Router X also originates its TTZ router LSA for each of the TTZs. The TTZ router LSA for TTZ N includes the links to the routers outside of these TTZs, the virtual links to the other edge routers of the other TTZs, and the TTZ links to the routers in TTZ N.
对于在不同链路上具有不同TTZ ID的TTZ边缘路由器X，路由器X连接两个或多个不同的TTZ。在这种情况下，路由器X启动其路由器LSA以虚拟化TTZ。此LSA包括连接到这些TTZ外部路由器的正常链路和到每个TTZ的其他边缘路由器的虚拟链路。路由器X还为每个TTZ发起其TTZ路由器LSA。TTZ N的TTZ路由器LSA包括到这些TTZ之外的路由器的链路、到其他TTZ的其他边缘路由器的虚拟链路以及到TTZ N中的路由器的TTZ链路。
For a group of routers and a number of links connecting the routers in an area, making them transfer to work as a TTZ without any service interruption takes a few steps or stages.
对于一组路由器和连接一个区域内路由器的多个链路，使它们在不中断任何服务的情况下作为TTZ传输需要几个步骤或阶段。
At first, a user configures the TTZ feature on every router in the TTZ. In this stage, a router does not originate or advertise its TTZ topology information. It will discover its TTZ neighbors.
首先，用户在TTZ中的每个路由器上配置TTZ功能。在此阶段中，路由器不发起或公布其TTZ拓扑信息。它将发现它的TTZ邻居。
Second, after configuring the TTZ, a user issues a configuration on one router in the TTZ, which triggers every router in the TTZ to generate and advertise TTZ information among the routers in the TTZ. When the router receives the configuration, it originates a TTZ control LSA with OP for T (indicating TTZ information generation and advertisement for migration). It also originates its TTZ LSA, such as TTZ router LSA or TTZ indication LSA, and advertises the LSA to its TTZ neighbors. When another router in the TTZ receives the LSA with OP for T, it originates its TTZ LSA. In this stage, every router in the TTZ has dual roles. One is to function as a normal router. The other is to generate and advertise TTZ information.
其次，在配置TTZ之后，用户在TTZ中的一个路由器上发布配置，该配置触发TTZ中的每个路由器，以在TTZ中的路由器之间生成和公布TTZ信息。当路由器接收到配置时，它发起一个TTZ控制LSA，其中OP代表T（表示TTZ信息生成和迁移广告）。它还发起其TTZ LSA，例如TTZ路由器LSA或TTZ指示LSA，并向其TTZ邻居播发LSA。当TTZ中的另一个路由器接收到带有OP for T的LSA时，它将发起其TTZ LSA。在此阶段，TTZ中的每个路由器都具有双重角色。一个是作为一个普通的路由器。另一个是生成和公布TTZ信息。
Third, a user checks whether a router in the TTZ is ready for migration to TTZ. A router in the TTZ is ready after it has received all the TTZ LSAs, including TTZ router LSAs from TTZ edge routers and TTZ indication LSAs from TTZ-internal routers. This information may be displayed on a router through a configuration.
第三，用户检查TTZ中的路由器是否准备好迁移到TTZ。TTZ中的路由器在接收到所有TTZ LSA（包括来自TTZ边缘路由器的TTZ路由器LSA和来自TTZ内部路由器的TTZ指示LSA）后准备就绪。此信息可通过配置显示在路由器上。
Then, a user activates the TTZ through using a configuration such as migrate to TTZ on one router in the TTZ. The router migrates to TTZ, generates and advertises a TTZ control LSA with OP for M (indicating Migrating to TTZ) after it receives the configuration. After another router in the TTZ receives the TTZ control LSA with OP for M, it also migrates to TTZ. Thus, activating the TTZ on one TTZ router propagates to every router in the TTZ, which migrates to TTZ.
然后，用户通过在TTZ中的一个路由器上使用诸如迁移到TTZ的配置来激活TTZ。路由器迁移到TTZ，在收到配置后生成并播发带有OP for M（表示迁移到TTZ）的TTZ控制LSA。TTZ中的另一个路由器接收到带有OP for M的TTZ控制LSA后，它也迁移到TTZ。因此，在一个TTZ路由器上激活TTZ会传播到TTZ中的每个路由器，并迁移到TTZ。
For an edge router of the TTZ, migrating to work as a TTZ router comprises generating a router LSA to virtualize the TTZ and flooding this LSA to all its neighboring routers in two steps as described in Section 7.
对于TTZ的边缘路由器，迁移以用作TTZ路由器包括生成路由器LSA以虚拟化TTZ，并在第7节中描述的两个步骤中将该LSA泛洪到其所有相邻路由器。
In normal operations for migration to TTZ and rollback from TTZ, a user issues a series of configurations according to certain procedures. In an abnormal case, for example, two conflicting configurations are issued on two TTZ routers in a TTZ at the same time, and a TTZ router issues an error and logs the error when it detects a conflict.
在迁移到TTZ和从TTZ回滚的正常操作中，用户根据特定的过程发布一系列配置。在异常情况下，例如，在TTZ中的两个TTZ路由器上同时发出两个冲突的配置，并且TTZ路由器在检测到冲突时发出错误并记录错误。
A conflicting configuration may be detected on a router on which the configuration is issued. Thus, some abnormal cases may be prevented. When a configuration for migration/rollback is issued on a router, the router checks whether it is in a correct sequence of configurations for migration/rollback through using the information it has. For migrating a part of an area to a TTZ, the correct sequence of configurations is in general as follows:
可能在发布配置的路由器上检测到冲突配置。因此，可以防止一些异常情况。当在路由器上发布迁移/回滚配置时，路由器使用其拥有的信息检查其是否处于迁移/回滚配置的正确序列中。要将一部分区域迁移到TTZ，正确的配置顺序通常如下所示：
1) configure TTZ on every router in the part of the area to be migrated to TTZ;
1) 在要迁移到TTZ的区域的每个路由器上配置TTZ；
2) configure on one router in the TTZ to trigger every router in the TTZ to generate and advertise TTZ information for migration; and
2) 在TTZ中的一个路由器上进行配置，以触发TTZ中的每个路由器生成并公布TTZ信息以进行迁移；和
3) configure on one router in the TTZ to trigger every router in the TTZ to migrate to TTZ.
3) 在TTZ中的一个路由器上进行配置，以触发TTZ中的每个路由器迁移到TTZ。
After receiving a configuration on a router to migrate to TTZ, which is for 3), the router determines whether 2) is performed by checking if it has received/originated TTZ LSAs. If it has not, it issues an error to an operator (generation and advertisement of TTZ information for migration to TTZ is not done yet) and rejects the configuration at this time.
在路由器上接收到要迁移到TTZ的配置（即3）后，路由器通过检查是否已接收/发起TTZ LSA来确定是否执行2）。如果没有，它将向操作员发出错误（尚未生成和公布用于迁移到TTZ的TTZ信息），并在此时拒绝配置。
After a router receives a TTZ LSA with OP for M for 3) from another router, it determines whether 2) is performed by checking if it has received/originated TTZ LSAs. If it has not, it issues an error and logs the error, and it does not migrate to TTZ. In this case, it
路由器从另一个路由器接收到带有OP for M for 3）的TTZ LSA后，它通过检查是否已接收/发起TTZ LSA来确定是否执行了2）。如果没有，则会发出错误并记录错误，并且不会迁移到TTZ。在这种情况下，它
does not originate its router LSA for virtualizing the TTZ if it is a TTZ edge router.
如果是TTZ边缘路由器，则不发起其用于虚拟化TTZ的路由器LSA。
After receiving a configuration on a router to generate and advertise TTZ information, which is for 2), the router determines whether 1) is performed by checking if TTZ is configured on it. If it is not, it issues an error to an operator (TTZ is not configured on it yet) and rejects the configuration at this time.
在路由器上接收到生成和播发TTZ信息的配置（用于2）后，路由器通过检查其上是否配置了TTZ来确定是否执行1）。如果不是，则向操作员发出错误（尚未在其上配置TTZ），并在此时拒绝配置。
For rolling back from TTZ, the correct sequence of configurations is below.
对于从TTZ回滚，正确的配置顺序如下所示。
1) configure on one router in the TTZ to trigger every router in the TTZ to advertise normal LSAs and stop advertising TTZ LSAs; and
1) 在TTZ中的一个路由器上进行配置，以触发TTZ中的每个路由器播发正常LSA并停止播发TTZ LSA；和
2) configure on one router in the TTZ to trigger every router in the TTZ to roll back from TTZ.
2) 在TTZ中的一个路由器上进行配置，以触发TTZ中的每个路由器从TTZ回滚。
After receiving a configuration on a router to roll back from TTZ, which is for 2), the router determines whether 1) is performed by checking if it has received TTZ LSA with OP for N. If it has not, it issues an error to an operator (advertise normal LSAs and stop advertising TTZ LSAs as rolling back from TTZ is not done yet) and rejects the configuration at this time.
在路由器上接收到要从TTZ回滚的配置（用于2）后，路由器通过检查是否已接收到OP为N的TTZ LSA来确定是否执行1）。如果未接收到，则向操作员发出错误（播发正常LSA并停止播发TTZ LSA，因为尚未从TTZ回滚）并在此时拒绝配置。
After a router receives a TTZ LSA with OP for R for 2) from another router, it determines whether 1) is performed by checking if it has received TTZ LSA with OP for N. If it has not, it issues an error and logs the error, and it does not roll back from TTZ.
路由器从另一个路由器接收到带有OP的TTZ LSA（对于R为2）后，通过检查是否已收到带有OP的TTZ LSA（对于N为2），确定是否执行了1）。如果未收到，则发出错误并记录错误，并且不会从TTZ回滚。
After receiving a configuration on a router to advertise normal LSAs and stop advertising TTZ LSAs for rolling back from TTZ, which is for 1), the router checks whether it has any TTZ LSAs. If it does not, it issues an error to an operator (no TTZ to be rolled back) and rejects the configuration at this time.
在路由器上接收到用于播发正常LSA并停止播发TTZ LSA以从TTZ（即1）回滚）的配置后，路由器检查是否有任何TTZ LSA。如果没有，它将向操作员发出错误（没有要回滚的TTZ），并在此时拒绝配置。
When a non-TTZ router (say R1) is connected via a P2P link to a migrated TTZ router (say T1), and there is a normal adjacency between them over the link, a user can configure TTZ on both ends of the link to add R1 into the TTZ to which T1 belongs. They TTZ discover each other as described in Section 8.
当非TTZ路由器（比如R1）通过P2P链路连接到迁移的TTZ路由器（比如T1），并且它们之间通过链路存在正常的邻接时，用户可以在链路的两端配置TTZ，以将R1添加到T1所属的TTZ中。如第8节所述，它们相互发现。
When a number of non-TTZ routers are connected via a broadcast or NBMA link to a migrated TTZ router (say T1), and there are normal adjacencies among them, a user configures TTZ on the connection to the link on every router to add the non-TTZ routers into the TTZ to
当多个非TTZ路由器通过广播或NBMA链路连接到迁移的TTZ路由器（例如T1），并且它们之间存在正常的邻接时，用户在每个路由器上的链路连接上配置TTZ，以将非TTZ路由器添加到TTZ路由器中
which T1 belongs. The DR for the link "forms" TTZ adjacencies with the other routers connected to the link if they all have the same TTZ ID configured for the link. This is determined through the TTZ discovery process described in Section 8.
T1属于哪一个。链路的DR与连接到链路的其他路由器“形成”TTZ邻接，前提是它们都具有为链路配置的相同TTZ ID。这是通过第8节中描述的TTZ发现过程确定的。
Section 11 ("Operations") outlines the configuration process and deployment scenarios for a TTZ. The configurable item is enabling a TTZ on a router and/or an interface on a router. The TTZ function may be controlled by a policy module and assigned a suitable user privilege level to enable. A suitable model may be required to verify the TTZ status on routers participating in the TTZ, including their role as an internal or edge TTZ router. The mechanisms defined in this document do not imply any new liveness detection and monitoring requirements in addition to those indicated in [RFC2328].
第11节（“操作”）概述了TTZ的配置过程和部署场景。可配置项是启用路由器上的TTZ和/或路由器上的接口。TTZ功能可由策略模块控制，并分配适当的用户权限级别以启用。可能需要合适的模型来验证参与TTZ的路由器上的TTZ状态，包括其作为内部或边缘TTZ路由器的角色。除了[RFC2328]中指出的机制外，本文件中定义的机制并不意味着任何新的活性检测和监测要求。
A notable beneficial security aspect of TTZ is that the TTZ is enclosed in a single area, and TTZ could be used to mask the internal topology. External routers that are not participating in the TTZ will not be aware of the internal TTZ topology. It should be noted that a malicious node could inject TTZ LSAs with the OP field set to M or R, which could trigger the migration into/from a TTZ and may result in the isolation of some routers in the network. Good security practice might reuse the OSPF authentication and other security mechanisms described in [RFC2328] and [RFC7474] to mitigate this type of risk.
TTZ的一个显著的有益安全方面是，TTZ被封闭在单个区域中，并且TTZ可以用来屏蔽内部拓扑。不参与TTZ的外部路由器将不知道内部TTZ拓扑。应该注意的是，恶意节点可能会将OP字段设置为M或R注入TTZ LSA，这可能会触发TTZ的迁移，并可能导致网络中某些路由器的隔离。良好的安全实践可能会重用[RFC2328]和[RFC7474]中描述的OSPF身份验证和其他安全机制，以减轻此类风险。
Under the registry name "Opaque Link-State Advertisements (LSA) Option Types" [RFC5250], IANA has assigned a new Opaque Type registry value for TTZ LSA as follows:
在注册表名“不透明链接状态播发（LSA）选项类型”[RFC5250]下，IANA为TTZ LSA分配了一个新的不透明类型注册表值，如下所示：
+====================+===============+=======================+
| Registry Value | Opaque Type | reference |
+====================+===============+=======================+
| 9 | TTZ LSA | This document |
+--------------------+---------------+-----------------------+
+====================+===============+=======================+
| Registry Value | Opaque Type | reference |
+====================+===============+=======================+
| 9 | TTZ LSA | This document |
+--------------------+---------------+-----------------------+
IANA has created and will maintain a new registry:
IANA已创建并将维护一个新的注册表：
o OSPFv2 TTZ LSA TLVs
o OSPFv2 TTZ LSA TLV
Initial values for the registry are given below. The future assignments are to be made through IETF Review [RFC5226].
注册表的初始值如下所示。未来的任务将通过IETF审查[RFC5226]进行。
Value OSPFv2 TTZ LSA TLV Name Definition
----- ----------------------- ----------
0 Reserved
1 TTZ ID TLV see Section 6.2
2 TTZ Router TLV see Section 6.3
3 TTZ Options TLV see Section 6.4
4-32767 Unassigned
32768-65535 Reserved
Value OSPFv2 TTZ LSA TLV Name Definition
----- ----------------------- ----------
0 Reserved
1 TTZ ID TLV see Section 6.2
2 TTZ Router TLV see Section 6.3
3 TTZ Options TLV see Section 6.4
4-32767 Unassigned
32768-65535 Reserved
[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>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998, <http://www.rfc-editor.org/info/rfc2328>.
[RFC2328]Moy，J.，“OSPF版本2”，STD 54，RFC 2328，DOI 10.17487/RFC2328，1998年4月<http://www.rfc-editor.org/info/rfc2328>.
[RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250, July 2008, <http://www.rfc-editor.org/info/rfc5250>.
[RFC5250]Berger，L.，Bryskin，I.，Zinin，A.，和R.Coltun，“OSPF不透明LSA选项”，RFC 5250，DOI 10.17487/RFC5250，2008年7月<http://www.rfc-editor.org/info/rfc5250>.
[RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed., "Security Extension for OSPFv2 When Using Manual Key Management", RFC 7474, DOI 10.17487/RFC7474, April 2015, <http://www.rfc-editor.org/info/rfc7474>.
[RFC7474]Bhatia，M.，Hartman，S.，Zhang，D.，和A.Lindem，Ed.，“使用手动密钥管理时OSPFv2的安全扩展”，RFC 7474，DOI 10.17487/RFC7474，2015年4月<http://www.rfc-editor.org/info/rfc7474>.
[RFC4940] Kompella, K. and B. Fenner, "IANA Considerations for OSPF", BCP 130, RFC 4940, DOI 10.17487/RFC4940, July 2007, <http://www.rfc-editor.org/info/rfc4940>.
[RFC4940]Kompella，K.和B.Fenner，“OSPF的IANA考虑”，BCP 130，RFC 4940，DOI 10.17487/RFC4940，2007年7月<http://www.rfc-editor.org/info/rfc4940>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI 10.17487/RFC5226, May 2008, <http://www.rfc-editor.org/info/rfc5226>.
[RFC5226]Narten，T.和H.Alvestrand，“在RFCs中编写IANA注意事项部分的指南”，BCP 26，RFC 5226，DOI 10.17487/RFC5226，2008年5月<http://www.rfc-editor.org/info/rfc5226>.
1. Command-Line Interface (CLI) Commands for TTZ
1. 用于TTZ的命令行界面（CLI）命令
The CLIs implemented and tested include:
实施和测试的CLI包括：
o the CLIs of the simpler option for configuring TTZ, and
o 用于配置TTZ的更简单选项的CLI，以及
o the CLIs for controlling migration to TTZ.
o 用于控制迁移到TTZ的CLI。
2. Extensions to OSPF Protocols for TTZ
2. 用于TTZ的OSPF协议扩展
All the extensions defined in "Extensions to OSPF Protocols" (Section 6) are implemented and tested except for rolling back from TTZ. The testing results illustrate:
除了从TTZ回滚之外，“OSPF协议扩展”（第6节）中定义的所有扩展都已实现和测试。测试结果表明：
o As seen from the outside, a TTZ is virtualized as its edge routers connected to each other. Any router outside of the TTZ sees the edge routers (as normal routers) connecting to each other and to some other routers.
o 从外部看，TTZ是虚拟化的，因为它的边缘路由器相互连接。TTZ之外的任何路由器都可以看到边缘路由器（作为普通路由器）相互连接以及与其他一些路由器连接。
o The link-state information about the routers and links inside the TTZ is contained within the TTZ. It is not advertised to any router outside of the TTZ.
o 关于TTZ内路由器和链路的链路状态信息包含在TTZ内。它不会向TTZ之外的任何路由器播发。
o TTZ is transparent. From a router inside a TTZ, it sees the topology (link state) outside of the TTZ. From a router outside of the TTZ, it sees the topology beyond the TTZ. The link-state information outside of the TTZ is advertised through the TTZ.
o TTZ是透明的。从TTZ内部的路由器，它可以看到TTZ外部的拓扑（链路状态）。从TTZ之外的路由器，它可以看到TTZ之外的拓扑。TTZ之外的链路状态信息通过TTZ播发。
o TTZ is backward compatible. Any router outside of a TTZ does not need to support or know TTZ.
o TTZ是向后兼容的。TTZ之外的任何路由器都不需要支持或了解TTZ。
3. Smooth Migration to TTZ
3. 平滑迁移到TTZ
The procedures and related protocol extensions for smooth migration to TTZ are implemented and tested. The testing results show:
实现并测试了顺利迁移到TTZ的过程和相关协议扩展。测试结果表明：
o A part of an OSPF area is smoothly migrated to a TTZ without any routing disruptions. The routes on every router are stable while the part of the area is being migrated to the TTZ.
o OSPF区域的一部分被平滑地迁移到TTZ，而没有任何路由中断。当部分区域迁移到TTZ时，每个路由器上的路由都是稳定的。
o Migration to TTZ is very easy to operate.
o 迁移到TTZ非常容易操作。
4. Add a Router to TTZ
4. 将路由器添加到TTZ
Adding a router into TTZ is implemented and tested. The testing results illustrate:
实现并测试了在TTZ中添加一个路由器。测试结果表明：
o A router can be easily added into a TTZ to become a TTZ router.
o 路由器可以很容易地添加到TTZ中，成为TTZ路由器。
o The router added into the TTZ is not seen on any router outside of the TTZ, but it is a part of the TTZ.
o 添加到TTZ中的路由器在TTZ之外的任何路由器上都看不到，但它是TTZ的一部分。
5. Leak TTZ Loopbacks Outside
5. 向外泄漏TTZ环回
Leaking loopback addresses in a TTZ to routers outside of the TTZ is implemented and tested. The testing results illustrate:
实现并测试了将TTZ中的环回地址泄漏到TTZ之外的路由器。测试结果表明：
o The loopback addresses inside the TTZ are advertised to the routers outside of the TTZ.
o TTZ内的环回地址将通告给TTZ外的路由器。
o The loopback addresses are accessible from a router outside of the TTZ.
o 环回地址可从TTZ外部的路由器访问。
The implementation of TTZ reuses the existing OSPF code along with additional simple logic. A couple of engineers started to work on implementing the TTZ from the middle of June 2014 and finished coding it just before the end of July 2014. After some testing and bug fixes, it works as expected.
TTZ的实现重用了现有的OSPF代码和附加的简单逻辑。一些工程师从2014年6月中旬开始实施TTZ，并在2014年7月底之前完成了编码。经过一些测试和错误修复后，它可以正常工作。
In our implementation, the link-state information in a TTZ opaque LSA is stored in the same link-state database as the link-state information in a normal LSA. For each TTZ link in the TTZ opaque LSA, there is an additional flag, which is used to differentiate between a TTZ link and a normal link.
在我们的实现中，TTZ不透明LSA中的链路状态信息存储在与普通LSA中的链路状态信息相同的链路状态数据库中。对于TTZ不透明LSA中的每个TTZ链路，都有一个附加标志，用于区分TTZ链路和正常链路。
Before migration to TTZ, every router in the TTZ computes its routing table using the normal links. After migration to TTZ, every router in the TTZ computes its routing table using the TTZ links and normal links. In the case where both the TTZ link and the normal link exist, the TTZ link is used.
在迁移到TTZ之前，TTZ中的每个路由器都使用普通链路计算其路由表。迁移到TTZ后，TTZ中的每个路由器使用TTZ链路和普通链路计算其路由表。在同时存在TTZ链路和正常链路的情况下，使用TTZ链路。
Acknowledgements
致谢
The authors would like to thank Acee Lindem, Abhay Roy, Christian Hopps, Dean Cheng, Russ White, Tony Przygienda, Wenhu Lu, Lin Han, Kiran Makhijani, Padmadevi Pillay Esnault, and Yang Yu for their valuable comments on this specification.
作者感谢Acee Lindem、Abhay Roy、Christian Hopps、Cheng院长、Russ White、Tony Przygienda、Lu文虎、Lin Han、Kiran Makhijani、Padmadevi Pillay Esnault和Yang Yu对本规范的宝贵意见。
Contributors
贡献者
The following people contributed significantly to the content of this document and should be considered co-authors:
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：
Mehmet Toy United States of America Email: mehmet.toy@verizon.com
Mehmet玩具美国电子邮件：Mehmet。toy@verizon.com
Gregory Cauchie France Email: greg.cauchie@gmail.com
Gregory Cauchie法国电子邮件：greg。cauchie@gmail.com
Anil Kumar SN India Email: anil.sn@huawei.com
Anil Kumar SN India电子邮件：Anil。sn@huawei.com
Ning So United States of America Email: ningso01@gmail.com
Ning So美利坚合众国电子邮件：ningso01@gmail.com
Lei Liu United States of America Email: lliu@us.fujitsu.com
刘磊美利坚合众国电子邮件：lliu@us.fujitsu.com
We also acknowledge the contribution of the following individuals:
我们还感谢以下个人的贡献：
Veerendranatha Reddy Vallem India Email: veerendranatharv@huawei.com
Veerendranatha Reddy Vallem印度电子邮件：veerendranatharv@huawei.com
William McCall United States of America will.mccall@rightside.co
美利坚合众国威廉·麦考尔将。mccall@rightside.co
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
Renwei Li Huawei Technologies 2330 Central expressway Santa Clara, CA United States of America
美国加利福尼亚州圣克拉拉中央高速公路2330号华为技术公司
Email: renwei.li@huawei.com
Email: renwei.li@huawei.com
Alvaro Retana Cisco Systems, Inc. 7025 Kit Creek Rd. Raleigh, NC 27709 United States of America
Alvaro Retana Cisco Systems，Inc.美国北卡罗来纳州罗利基特克里克路7025号，邮编：27709
Email: aretana@cisco.com
Email: aretana@cisco.com
Yi Yang Sockrate Cary, NC United States of America
美国北卡罗来纳州益阳市
Email: yyang1998@gmail.com
Email: yyang1998@gmail.com
Zhiheng Liu 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号刘志恒100053
Email: liu.cmri@gmail.com
Email: liu.cmri@gmail.com