Network Working Group D. McPherson, Ed.
Request for Comments: 5311 Arbor Networks
Obsoletes: 3786 L. Ginsberg
S. Previdi
M. Shand
Cisco Systems
February 2009
Network Working Group D. McPherson, Ed.
Request for Comments: 5311 Arbor Networks
Obsoletes: 3786 L. Ginsberg
S. Previdi
M. Shand
Cisco Systems
February 2009
Simplified Extension of Link State PDU (LSP) Space for IS-IS
IS-IS链路状态PDU（LSP）空间的简化扩展
Status of This Memo
关于下段备忘
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
本文件规定了互联网社区的互联网标准跟踪协议，并要求进行讨论和提出改进建议。有关本协议的标准化状态和状态，请参考当前版本的“互联网官方协议标准”（STD 1）。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2009 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (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.
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/ 许可证信息）在本文件发布之日生效。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。
Abstract
摘要
This document describes a simplified method for extending the Link State PDU (LSP) space beyond the 256 LSP limit. This method is intended as a preferred replacement for the method defined in RFC 3786.
本文档描述了一种将链路状态PDU（LSP）空间扩展到256 LSP限制之外的简化方法。该方法旨在作为RFC 3786中定义的方法的首选替代方法。
Table of Contents
目录
1. Overview ........................................................2
2. Specification of Requirements ...................................3
3. Definition of Commonly Used Terms ...............................3
4. Utilizing Additional System IDs .................................4
4.1. Additional Information in Extended LSPs ....................4
4.2. Extended LSP Restrictions ..................................4
4.2.1. TLVs That MUST NOT Appear ...........................4
4.2.2. Leaf Advertisements in Extended LSPs ................5
4.2.3. IS Neighbor Advertisement Restrictions ..............5
4.2.4. Area Addresses ......................................6
4.2.5. Overload, Attached, Partition Repair Bits ...........6
4.3. Originating LSP Requirements ...............................6
4.4. IS Alias ID TLV (IS Alias ID) ..............................7
4.5. New TLVs in Support of IS Neighbor Attributes ..............7
5. Comparison with the RFC 3786 Solution ...........................8
6. Deployment Considerations .......................................8
6.1. Advertising New TLVs in Extended LSPs ......................9
6.2. Reachability and Non-SPF TLV Staleness .....................9
6.3. Normal LSP OL State and Use of Extended LSPs ...............9
6.4. Moving Neighbor Attribute INFO LSPs ........................9
6.5. Advertising Leaf INFO Extended LSPs .......................10
7. Security Considerations ........................................10
8. IANA Considerations ............................................10
9. References .....................................................11
9.1. Normative References ......................................11
9.2. Informative References ....................................11
1. Overview ........................................................2
2. Specification of Requirements ...................................3
3. Definition of Commonly Used Terms ...............................3
4. Utilizing Additional System IDs .................................4
4.1. Additional Information in Extended LSPs ....................4
4.2. Extended LSP Restrictions ..................................4
4.2.1. TLVs That MUST NOT Appear ...........................4
4.2.2. Leaf Advertisements in Extended LSPs ................5
4.2.3. IS Neighbor Advertisement Restrictions ..............5
4.2.4. Area Addresses ......................................6
4.2.5. Overload, Attached, Partition Repair Bits ...........6
4.3. Originating LSP Requirements ...............................6
4.4. IS Alias ID TLV (IS Alias ID) ..............................7
4.5. New TLVs in Support of IS Neighbor Attributes ..............7
5. Comparison with the RFC 3786 Solution ...........................8
6. Deployment Considerations .......................................8
6.1. Advertising New TLVs in Extended LSPs ......................9
6.2. Reachability and Non-SPF TLV Staleness .....................9
6.3. Normal LSP OL State and Use of Extended LSPs ...............9
6.4. Moving Neighbor Attribute INFO LSPs ........................9
6.5. Advertising Leaf INFO Extended LSPs .......................10
7. Security Considerations ........................................10
8. IANA Considerations ............................................10
9. References .....................................................11
9.1. Normative References ......................................11
9.2. Informative References ....................................11
[IS-IS] defines the set of LSPs that may be originated by a system at each level. This set is limited to 256 LSPs. [IS-IS] also defines a maximum value for an LSP (originatingLxLSPBufferSize) as 1492 bytes. The carrying capacity of an LSP set, while bounded, has thus far been sufficient for advertisements associated with an area/domain in existing deployment scenarios. However, the definition of additional information to be included in LSPs (e.g., multi-topology support, traffic engineering information, router capabilities, etc.) has the potential to exceed the carrying capacity of an LSP set.
[IS-IS]定义了可能由系统在每个级别发起的LSP集。此设置限制为256个LSP。[IS-IS]还将LSP（原始LXLSPBufferSize）的最大值定义为1492字节。LSP集的承载能力虽然有限制，但到目前为止已足以在现有部署场景中发布与区域/域关联的广告。然而，要包含在LSP中的附加信息的定义（例如，多拓扑支持、流量工程信息、路由器能力等）有可能超过LSP集的承载能力。
This issue first drew interest when traffic engineering extensions were introduced. This interest resulted in the solution defined in [RFC3786]. However, that solution suffers from restrictions required to maintain interoperability with systems that do not support the extensions.
当引入交通工程扩展时，这个问题首先引起了人们的兴趣。这种兴趣导致了[RFC3786]中定义的解决方案。但是，该解决方案受到与不支持扩展的系统保持互操作性所需的限制。
This document defines extensions that allow a system to exceed the 256 LSP limit and do so in a way that has no interoperability issues with systems that do not support the extension. It is seen as a simpler, and therefore preferred, solution to the problem.
本文档定义了允许系统超过256 LSP限制的扩展，并且扩展方式与不支持扩展的系统没有互操作性问题。它被视为一种更简单的、因此更可取的解决方案。
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 RFC 2119 [BCP14].
本文件中的关键词“必须”、“不得”、“要求”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照RFC 2119[BCP14]中所述进行解释。
This section provides definitions for terms that are used throughout the text. The terminology is consistent with that used in RFC 3786.
本节提供全文中使用的术语的定义。该术语与RFC 3786中使用的术语一致。
Originating System: A physical IS running the IS-IS protocol. As this document describes a method that allows a single physical IS to originate LSPs on behalf of multiple virtual ISs, the Originating System represents the single physical IS.
发起系统：物理系统正在运行IS-IS协议。由于本文档描述了允许单个物理IS代表多个虚拟ISs发起LSP的方法，发起系统表示单个物理IS。
Normal system-id: The system-id of an Originating System as defined by [IS-IS].
正常系统id:[IS-IS]定义的原始系统的系统id。
Additional system-id: A system-id other than the "Normal system-id" that is assigned by the network administrator to an Originating System in order to allow the generation of Extended LSPs. The Additional system-id, like the Normal system-id, must be unique throughout the routing area (Level-1) or domain (Level-2).
附加系统id：网络管理员为允许生成扩展LSP而分配给发起系统的“正常系统id”以外的系统id。额外的系统id与普通系统id一样，在整个路由区域（级别1）或域（级别2）中必须是唯一的。
Original LSP: An LSP using the Normal system-id in its LSP ID.
原始LSP：在其LSP id中使用正常系统id的LSP。
Extended LSP: An LSP using an Additional system-id in its LSP ID.
扩展LSP：在其LSP id中使用附加系统id的LSP。
LSP set: All LSPs of a given level having the same system ID and Pseudonode ID. (The LSPID field then only varies in the LSP number octet.) This constitutes the complete set of link state information at a given level originated using that system ID/Pseudonode ID. This term is defined to resolve the ambiguity between a logical LSP and a single Link State PDU -- which is sometimes called an LSP fragment. The latter is the unit of information handled by the update process.
LSP集合：具有相同系统ID和伪节点ID的给定级别的所有LSP。（LSPID字段仅在LSP编号八位字节中变化。）这构成了使用该系统ID/伪节点ID生成的给定级别上的完整链路状态信息集。定义该术语是为了解决逻辑LSP和单个链路状态PDU（有时称为LSP片段）之间的歧义。后者是更新过程处理的信息单元。
Extended LSP set: An LSP set consisting of LSPs using an Additional system-id.
扩展LSP集：由使用附加系统id的LSP组成的LSP集。
Extension-capable IS: An IS implementing the mechanisms described in this document.
支持扩展的IS:An正在实现本文档中描述的机制。
Virtual IS: The system, identified by an Additional system-id, advertised as originating the Extended LSPs. These LSPs specify the Additional system-id in their LSP IDs.
虚拟IS：由附加系统id标识的系统，公告为发起扩展LSP。这些LSP在其LSP id中指定附加的系统id。
This extension allows an Originating System to be assigned additional system-ids that may be used to generate additional LSP sets. The additional system-ids are subject to the same restrictions as normal system-ids, i.e., when used at Level-1, the additional system-id MUST be unique within the Level-1 area. When used at Level-2, the additional system-id MUST be unique within the domain.
此扩展允许为原始系统分配额外的系统ID，这些系统ID可用于生成额外的LSP集。附加系统id受到与正常系统id相同的限制，即当在1级使用时，附加系统id在1级区域内必须是唯一的。在2级使用时，附加系统id在域中必须是唯一的。
Extended LSPs are treated by the IS-IS Update Process in the same manner as normal LSPs, i.e., the same rules as to generation, flooding, purging, etc. apply. In particular, if the Extended LSP with LSP number zero and remaining lifetime > 0 is not present for a particular additional system-id, then none of the Extended LSPs in that Extended LSP set shall be processed.
IS-IS更新过程以与正常LSP相同的方式处理扩展LSP，即适用与生成、泛洪、清除等相同的规则。特别是，如果LSP编号为零且剩余寿命>0的扩展LSP对于特定的附加系统id不存在，则该扩展LSP集中的任何扩展LSP都不应被处理。
The LSP number zero of an Extended LSP set MUST include the new IS alias ID TLV defined in Section 4.4. This allows the Extended LSP set to be associated with the Originating System that generated the LSP(s).
扩展LSP集的LSP编号0必须包括第4.4节中定义的新IS别名ID TLV。这允许扩展LSP集与生成LSP的原始系统相关联。
The following restrictions on the information that may appear in an Extended LSP are defined in order to avoid interoperability issues with systems that do not support the extensions defined in this document. All TLV references are based on the current definitions in the IANA IS-IS TLV Codepoints Registry.
对扩展LSP中可能出现的信息定义了以下限制，以避免与不支持本文档中定义的扩展的系统的互操作性问题。所有TLV参考均基于IANA IS-IS TLV代码点注册表中的当前定义。
The following TLVs MUST NOT appear in an Extended LSP:
以下TLV不得出现在扩展LSP中：
TLV Name (#)
-----------
ES Neighbors (3)
Part. DIS (4)
Prefix Neighbors (5)
TLV Name (#)
-----------
ES Neighbors (3)
Part. DIS (4)
Prefix Neighbors (5)
If any of the TLVs listed above appear in an Extended LSP, an Extension Capable IS MUST ignore those TLVs on receipt and SHOULD report an error. Other TLVs in that Extended LSP set MUST be processed normally.
如果上面列出的任何TLV出现在扩展LSP中，具有扩展能力的IS必须在收到时忽略这些TLV，并应报告错误。必须正常处理扩展LSP集中的其他TLV。
Advertisement of leaf information in Extended LSPs is allowed. Inclusion of such information requires the advertisement of a neighbor between the Originating System and the Virtual IS associated with the Extended LSP set in which the leaf advertisements appear. See Section 4.2.3.
允许在扩展LSP中发布叶信息。包含这样的信息需要在发起系统和虚拟机之间通告邻居，该邻居与叶通告出现在其中的扩展LSP集相关联。见第4.2.3节。
When leaf advertisements for multiple topologies (see [RFC5120]) are included in an Extended LSP set, the multi-topology TLV (229) MUST include all topologies for which a leaf advertisement is included.
当扩展LSP集合中包括多个拓扑（参见[RFC5120]）的叶广告时，多拓扑TLV（229）必须包括包含叶广告的所有拓扑。
The following TLVs fall into this category:
以下TLV属于此类：
TLV Name (#)
-----------
IP Int. Reach (128)
IP Ext. Address (130)
The extended IP reachability TLV (135)
MT IP Reach (235)
IPv6 IP Reach (236)
MT IPv6 IP Reach (237)
TLV Name (#)
-----------
IP Int. Reach (128)
IP Ext. Address (130)
The extended IP reachability TLV (135)
MT IP Reach (235)
IPv6 IP Reach (236)
MT IPv6 IP Reach (237)
Advertisement of IS Neighbor Reachability in an Extended LSP is restricted to advertisement of neighbor reachability to the Originating System. A neighbor to the Originating System MUST be advertised in Extended LSPs. If multi-topology capability [RFC5120] is supported, an MT IS Neighbor advertisement to the Originating System IS MUST be included for every topology advertised in the Extended LSP set. Neighbor advertisement(s) to the Originating System in an Extended LSP MUST use a non-zero metric and SHOULD use a metric of MaxLinkMetric-1.
扩展LSP中的IS邻居可达性通告仅限于向发起系统通告邻居可达性。必须在扩展LSP中通告发起系统的邻居。如果支持多拓扑功能[RFC5120]，则对于扩展LSP集中播发的每个拓扑，必须包括到原始系统的MT is邻居播发。扩展LSP中发送到发起系统的邻居播发必须使用非零度量，并且应使用MaxLinkMetric-1度量。
The restrictions defined here apply to all TLVs used to advertise neighbor reachability. These include the following TLVs:
此处定义的限制适用于用于通告邻居可达性的所有TLV。其中包括以下TLV：
TLV Name (#)
-----------
IIS Neighbors (2)
The extended IS reachability TLV (22)
MT-ISN (222)
TLV Name (#)
-----------
IIS Neighbors (2)
The extended IS reachability TLV (22)
MT-ISN (222)
LSP number zero of an Extended LSP set MUST include an Area Address TLV. The set of area addresses advertised MUST be a subset of the set of Area Addresses advertised in the normal LSP number zero at the corresponding level. Preferably, the advertisement SHOULD be syntactically identical to that included in the normal LSP number zero at the corresponding level.
扩展LSP集的LSP编号0必须包含区域地址TLV。播发的区域地址集必须是在相应级别的正常LSP编号0中播发的区域地址集的子集。优选地，广告在语法上应与对应级别的正常LSP编号0中包括的广告相同。
The Overload (OL), Attached (ATT), and Partition Repair (P) bits MUST be set to 0 in all Extended LSPs.
在所有扩展LSP中，重载（OL）、附加（ATT）和分区修复（P）位必须设置为0。
Note that ISs NOT supporting these extensions will interpret these bits normally in Extended LSPs they receive. If the ATT bit were set in an Extended LSP, this could indicate that the Virtual IS is attached to other areas when the Originating System is not. This might cause legacy systems to use the Virtual IS as a default exit point from the area.
请注意，不支持这些扩展的ISs通常会在接收到的扩展LSP中解释这些位。如果在扩展LSP中设置了ATT位，则这可能表示当原始系统未连接时，虚拟机已连接到其他区域。这可能会导致遗留系统将虚拟IS用作该区域的默认退出点。
The Original LSP set MUST include a neighbor to the Virtual IS associated with each Extended LSP set generated. If multi-topology capability [RFC5120] is supported, an MT IS Neighbor advertisement to the Virtual IS MUST be included for every topology advertised in the Extended LSP set. The neighbor advertisement(s) in the Original LSP MUST specify a metric of zero. This guarantees that the two-way connectivity check between Originating System and Virtual IS will succeed and that the cost of reaching the Virtual IS is the same as the cost to reach the Originating System.
原始LSP集必须包含与生成的每个扩展LSP集关联的虚拟机的邻居。如果支持多拓扑功能[RFC5120]，则对于扩展LSP集中播发的每个拓扑，必须包括到虚拟is的MT is邻居播发。原始LSP中的相邻播发必须指定零的度量。这保证了发起系统和虚拟IS之间的双向连接检查将成功，并且到达虚拟IS的成本与到达发起系统的成本相同。
The IS-Alias TLV allows extension-capable ISs to recognize the Originating System of an Extended LSP set. It identifies the Normal system-id of the Originating System.
IS别名TLV允许支持扩展的ISs识别扩展LSP集的原始系统。它标识发起系统的正常系统id。
Type 24 Length # of octets in the value field (7 to 255) Value
在值字段（7到255）值中键入八位字节的24长度
No. of octets
+-----------------------+
| Normal System-id | 6
+-----------------------+
| Sub-TLV length | 1
+-----------------------+
| Sub-TLVs (optional) | 0 to 248
+-----------------------+
No. of octets
+-----------------------+
| Normal System-id | 6
+-----------------------+
| Sub-TLV length | 1
+-----------------------+
| Sub-TLVs (optional) | 0 to 248
+-----------------------+
Normal system-id
正常系统id
The Normal system-id of the Originating System.
发起系统的正常系统id。
Sub-TLVs length
子TLV长度
Total length of all sub-TLVs.
所有子TLV的总长度。
Sub-TLVs
子TLV
No sub-TLVs are defined in this document. Should future extensions define sub-TLVs, the sub-TLVs MUST be formatted as described in [RFC5305].
本文件中未定义子TLV。如果将来的扩展定义了子TLV，则子TLV必须按照[RFC5305]中的说明进行格式化。
One of the major sources of additional information in LSPs is the sub-TLV information associated with the extended IS reachability TLV (22) and MT-ISN TLV (222). This includes (but is not limited to) information required in support of Traffic Engineering (TE) as defined in [RFC5305] and [RFC5307]. The restrictions defined in this document prohibit the presence of TLV 22 and/or TLV 222 in Extended LSPs except to advertise the neighbor relationship to the Originating System. In the event that there is a need to advertise in Extended LSPs such information associated with neighbors of the Originating System, it is necessary to define new TLVs to carry the sub-TLV information.
LSP中附加信息的主要来源之一是与扩展is可达性TLV（22）和MT-ISN TLV（222）相关联的子TLV信息。这包括（但不限于）支持[RFC5305]和[RFC5307]中定义的交通工程（TE）所需的信息。本文件中定义的限制禁止在扩展LSP中存在TLV 22和/或TLV 222，但向发起系统通告邻居关系除外。如果需要在扩展LSP中公布与发起系统的邻居相关联的此类信息，则有必要定义新的TLV以承载子TLV信息。
Two new TLVs are therefore defined.
因此，定义了两个新的TLV。
1) IS Neighbor Attribute TLV (23). It is identical in format to the extended IS reachability TLV (22).
1) 是邻居属性TLV（23）。它在格式上与扩展is可达性TLV（22）相同。
2) MT IS Neighbor Attribute TLV (223). It is identical in format to the MT-ISN TLV (222).
2) MT是邻居属性TLV（223）。其格式与MT-ISN TLV（222）相同。
These new TLVs MAY be included in Original LSPs or Extended LSPs. Regardless of the type of LSP in which the TLVs appear, the information pertains to the neighbor relationship between the Originating System and the IS identified in the TLV.
这些新的TLV可能包含在原始LSP或扩展LSP中。无论TLV出现在哪种LSP类型中，该信息都与原始系统和TLV中标识的LSP之间的邻居关系有关。
These TLVs MUST NOT be used to infer that a neighbor relationship exists in the absence of TLV 22 or TLV 222 (whichever applies) in the Originating LSP set for the specified neighbor. This restriction is necessary in order to maintain compatibility with systems that do not support these extensions.
这些TLV不得用于推断在指定邻居的原始LSP集中不存在TLV 22或TLV 222（以适用者为准）的情况下存在邻居关系。为了保持与不支持这些扩展的系统的兼容性，此限制是必需的。
This document utilizes the same basic mechanism (additional system-ids) as RFC 3786 to allow an originating system to generate more than 256 LSPs. It differs from RFC 3786 in that it restricts the content of Extended LSPs to information that does NOT impact the building of a Shortest Path Tree (SPT).
本文档使用与RFC 3786相同的基本机制（附加系统ID），以允许原始系统生成256个以上的LSP。它与RFC 3786的不同之处在于，它将扩展LSP的内容限制为不影响最短路径树（SPT）构建的信息。
Legacy IS-IS implementations which do not support the extensions defined in this document see the Extended LSPs as information associated with a system that is reachable only via the Originating System. As no other systems are reachable via the Virtual ISs, the Shortest Path First (SPF) calculation in legacy ISs is therefore consistent with that performed by extension-capable ISs. There is therefore no need for the two different operating modes defined in RFC 3786.
不支持本文档中定义的扩展的传统IS-IS实现将扩展LSP视为与系统相关的信息，该系统只能通过原始系统访问。由于没有其他系统可以通过虚拟ISs访问，因此传统ISs中的最短路径优先（SPF）计算与支持扩展的ISs执行的计算是一致的。因此，不需要RFC 3786中定义的两种不同操作模式。
There is also no need for the special handling of the original LSP set and the Extended LSP set(s) as a single Logical LSP during the SPF as specified in Section 5 of RFC 3786.
按照RFC 3786第5节的规定，在SPF期间，也不需要将原始LSP集和扩展LSP集作为单个逻辑LSP进行特殊处理。
There are a number of deployment considerations that limit the usefulness of Extended LSPs unless all systems are extension-capable ISs.
除非所有系统都具有扩展能力，否则有许多部署考虑因素限制了扩展LSP的用途。
As Extended LSPs MAY be utilized to advertise TLVs associated with other protocol extensions (definition of which is outside the scope of this document) and/or the extensions defined in Section 4.4 of this document, it is obvious that the utilization of the information in Extended LSPs by legacy IS-IS implementations will be limited. The implication of this is that as implementations are revised to support the protocol extensions that define new TLVs/sub-TLVs that MAY be advertised in Extended LSPs; the implementation SHOULD also be revised to support the extensions defined in this document so that it is capable of processing the new information whether it appears in normal or Extended LSPs.
由于扩展LSP可用于公布与其他协议扩展（其定义不在本文件范围内）和/或本文件第4.4节中定义的扩展相关的TLV，很明显，传统is-is实现对扩展LSP中信息的利用将受到限制。这意味着as实现被修改以支持协议扩展，协议扩展定义了新的TLV/子TLV，这些TLV可能在扩展LSP中发布；还应修改实施，以支持本文件中定义的扩展，以便能够处理新信息，无论其出现在正常LSP还是扩展LSP中。
In cases where non-SPF information is advertised in LSPs, it is necessary to determine whether the system that originated the advertisement is reachable in order to guarantee that a receiving IS does not use or leak stale information. As long as the OL bit is NOT set by the Originating System in normal LSPs, reachability to the Virtual IS will be consistent with reachability to the Originating System. Therefore, no special rules are required in this case.
在LSP中发布非SPF信息的情况下，有必要确定发起发布的系统是否可访问，以确保接收不使用或泄漏过时信息。只要发起系统未在正常LSP中设置OL位，虚拟is的可达性将与发起系统的可达性一致。因此，在这种情况下不需要特殊规则。
If the Originating System sets the OL bit in a normal LSP, legacy systems will see the Virtual ISs associated with that Originating System as unreachable and therefore will not use the information in the corresponding Extended LSPs. Under these circumstances, Extension-capable ISs MUST also see the Virtual ISs as unreachable. This avoids potential routing loops in cases where leaf information is advertised in Extended LSPs.
如果始发系统在正常LSP中设置OL位，传统系统将看到与该始发系统关联的虚拟ISs不可访问，因此不会使用相应扩展LSP中的信息。在这种情况下，支持扩展的ISs也必须将虚拟ISs视为无法访问。这避免了在扩展LSP中公布叶信息的情况下可能出现的路由循环。
Section 4.4 defines new TLVs that MAY be used to advertise neighbor attribute information in Extended LSPs. In cases where neighbor attribute information associated with the same context (e.g., the same link) appears in both an Original LSP and in one or more Extended LSP sets, the following rules apply for each attribute:
第4.4节定义了可用于在扩展LSP中公布邻居属性信息的新TLV。如果在原始LSP和一个或多个扩展LSP集中同时出现与相同上下文（例如，相同链接）关联的邻居属性信息，则以下规则适用于每个属性：
o If the attribute information does not conflict, it MUST be considered additive.
o 如果属性信息不冲突，则必须将其视为附加信息。
o If the attribute information conflicts, then the information in the Original LSP, if present, MUST be used. If no information is
o 如果属性信息冲突，则必须使用原始LSP中的信息（如果存在）。如果没有提供任何信息
in the Original LSP, then the information from the Extended LSP with the lowest system-id SHALL be preferred.
在原始LSP中，则应优先使用来自具有最低系统id的扩展LSP的信息。
o In cases where information about the same neighbor/link/attribute appears in both TLV 22 and TLV 23 (or TLV 222 and TLV 223 for the same MTID) then the information in TLV 22 (or TLV 222) MUST be used and the information in TLV 23 (or TLV 223) MUST be ignored.
o 如果关于相同邻居/链路/属性的信息同时出现在TLV 22和TLV 23中（或针对相同MTID的TLV 222和TLV 223），则必须使用TLV 22（或TLV 222）中的信息，并且必须忽略TLV 23（或TLV 223）中的信息。
Utilization of the new TLVs for neighbor attribute information would provide additional benefits that include:
将新TLV用于邻居属性信息将带来其他好处，包括：
o Elimination of the need for redundant IS neighbor TLVs to be processed as part of the SPF.
o 消除了作为SPF一部分处理的冗余IS相邻TLV的需要。
o Easier support for a set of TE information associated with a single link that exceeds the 255-byte TLV limit by allowing the interpretation of multiple TLVs to be considered additive rather than mutually exclusive.
o 通过允许将多个TLV的解释视为相加而不是互斥，更容易支持与超过255字节TLV限制的单个链路相关联的一组TE信息。
The need to advertise leaf information in Extended LSPs may arise because of extensive leaking of inter-level information or because of the support of multiple topologies as described in [RFC5120]. When leaf information is advertised in Extended LSPs, these LSPs now contain information that MUST be processed in order to correctly update the forwarding plane of an IS. This may increase the frequency of events that trigger forwarding plane updates by ISs in the network. It is therefore recommended that, when possible, leaf information be restricted to the normal LSP set.
由于层间信息的大量泄漏或[RFC5120]中所述的支持多种拓扑，可能需要在扩展LSP中公布叶信息。在扩展LSP中播发叶信息时，这些LSP现在包含必须处理的信息，以便正确更新is的转发平面。这可能会增加触发网络中ISs转发平面更新的事件频率。因此，建议尽可能将叶信息限制为正常LSP集。
This document raises no new security issues for IS-IS. For general security considerations for IS-IS, see [RFC5304].
本文档没有为IS-IS提出新的安全问题。有关IS-IS的一般安全注意事项，请参阅[RFC5304]。
This document defines the following new ISIS TLVs that are reflected in the ISIS TLV codepoint registry:
本文件定义了以下反映在ISIS TLV代码点注册表中的新ISIS TLV：
Type Description IIH LSP SNP
---- ----------------------------------- --- --- ---
23 IS Neighbor Attribute n y n
24 IS Alias ID n y n
223 MT IS Neighbor Attribute n y n
Type Description IIH LSP SNP
---- ----------------------------------- --- --- ---
23 IS Neighbor Attribute n y n
24 IS Alias ID n y n
223 MT IS Neighbor Attribute n y n
[IS-IS] ISO, "Intermediate system to Intermediate system routeing information exchange protocol for use in conjunction with the Protocol for providing the Connectionless-mode Network Service (ISO 8473)," ISO/IEC 10589:2002, Second Edition.
[IS-IS]ISO，“与提供无连接模式网络服务的协议一起使用的中间系统到中间系统路由信息交换协议（ISO 8473）”，ISO/IEC 10589:2002，第二版。
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, October 2008.
[RFC5305]Li，T.和H.Smit，“交通工程的IS-IS扩展”，RFC 5305，2008年10月。
[RFC5307] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 5307, October 2008.
[RFC5307]Kompella，K.，Ed.，和Y.Rekhter，Ed.，“支持通用多协议标签交换（GMPLS）的IS-IS扩展”，RFC 5307，2008年10月。
[BCP14] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[BCP14]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, February 2008.
[RFC5120]Przygienda，T.，Shen，N.，和N.Sheth，“M-ISIS：中间系统到中间系统（IS-ISs）的多拓扑（MT）路由”，RFC 5120，2008年2月。
[RFC3786] Hermelin, A., Previdi, S., and M. Shand, "Extending the Number of Intermediate System to Intermediate System (IS-IS) Link State PDU (LSP) Fragments Beyond the 256 Limit", RFC 3786, May 2004.
[RFC3786]Hermelin，A.，Previdi，S.，和M.Shand，“将中间系统到中间系统（IS-IS）链路状态PDU（LSP）片段的数量扩展到256个限制之外”，RFC 3786，2004年5月。
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic Authentication", RFC 5304, October 2008.
[RFC5304]Li，T.和R.Atkinson，“IS-IS加密认证”，RFC 5304，2008年10月。
Authors' Addresses
作者地址
Danny McPherson (editor) Arbor Networks, Inc. EMail: danny@arbor.net
Danny McPherson（编辑）Arbor Networks，Inc.电子邮件：danny@arbor.net
Les Ginsberg Cisco Systems EMail: ginsberg@cisco.com
Les Ginsberg Cisco Systems电子邮件：ginsberg@cisco.com
Stefano Previdi Cisco Systems EMail: sprevidi@cisco.com
Stefano Previdi Cisco Systems电子邮件：sprevidi@cisco.com
Mike Shand Cisco Systems EMail: mshand@cisco.com
Mike Shand Cisco Systems电子邮件：mshand@cisco.com