Internet Engineering Task Force (IETF) C. Dearlove
Request for Comments: 7185 BAE Systems ATC
Category: Informational T. Clausen
ISSN: 2070-1721 LIX, Ecole Polytechnique
P. Jacquet
Alcatel-Lucent Bell Labs
April 2014
Internet Engineering Task Force (IETF) C. Dearlove
Request for Comments: 7185 BAE Systems ATC
Category: Informational T. Clausen
ISSN: 2070-1721 LIX, Ecole Polytechnique
P. Jacquet
Alcatel-Lucent Bell Labs
April 2014
Rationale for the Use of Link Metrics in the Optimized Link State Routing Protocol Version 2 (OLSRv2)
优化链路状态路由协议版本2（OLSRv2）中使用链路度量的基本原理
Abstract
摘要
The Optimized Link State Routing Protocol version 2 (OLSRv2) includes the ability to assign metrics to links and to use those metrics to allow routing by other than minimum hop count routes. This document provides a historic record of the rationale for, and design considerations behind, how link metrics were included in OLSRv2.
优化链路状态路由协议版本2（OLSRv2）包括为链路分配指标的能力，以及使用这些指标允许通过最小跳数路由以外的其他路由进行路由的能力。本文件提供了链接度量如何包含在OLSRv2中的基本原理和设计注意事项的历史记录。
Status of This Memo
关于下段备忘
This document is not an Internet Standards Track specification; it is published for informational purposes.
本文件不是互联网标准跟踪规范；它是为了提供信息而发布的。
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 5741.
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 5741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/rfc7185.
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/rfc7185.
Copyright Notice
版权公告
Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2014 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
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。从该文档中提取的代码组件必须
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.
包括信托法律条款第4.e节中所述的简化BSD许可证文本，且不提供简化BSD许可证中所述的担保。
This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English.
本文件可能包含2008年11月10日之前发布或公开的IETF文件或IETF贡献中的材料。控制某些材料版权的人员可能未授予IETF信托允许在IETF标准流程之外修改此类材料的权利。在未从控制此类材料版权的人员处获得充分许可的情况下，不得在IETF标准流程之外修改本文件，也不得在IETF标准流程之外创建其衍生作品，除了将其格式化以RFC形式发布或将其翻译成英语以外的其他语言。
Table of Contents
目录
1. Introduction ....................................................3
2. Terminology .....................................................5
3. Applicability ...................................................5
4. Motivational Scenarios ..........................................5
5. Link Metrics ....................................................7
5.1. Link Metric Properties .....................................7
5.2. Link Metric Types ..........................................8
5.3. Directional Link Metrics ..................................10
5.4. Reporting Link and Neighbor Metrics .......................10
5.5. Defining Incoming Link Metrics ............................12
5.6. Link Metric Values ........................................12
6. MPRs with Link Metrics .........................................14
6.1. Flooding MPRs .............................................14
6.2. Routing MPRs ..............................................16
6.3. Relationship between MPR Sets .............................19
7. Security Considerations ........................................21
8. Acknowledgements ...............................................21
9. Informative References .........................................21
Appendix A. MPR Routing Property .................................23
1. Introduction ....................................................3
2. Terminology .....................................................5
3. Applicability ...................................................5
4. Motivational Scenarios ..........................................5
5. Link Metrics ....................................................7
5.1. Link Metric Properties .....................................7
5.2. Link Metric Types ..........................................8
5.3. Directional Link Metrics ..................................10
5.4. Reporting Link and Neighbor Metrics .......................10
5.5. Defining Incoming Link Metrics ............................12
5.6. Link Metric Values ........................................12
6. MPRs with Link Metrics .........................................14
6.1. Flooding MPRs .............................................14
6.2. Routing MPRs ..............................................16
6.3. Relationship between MPR Sets .............................19
7. Security Considerations ........................................21
8. Acknowledgements ...............................................21
9. Informative References .........................................21
Appendix A. MPR Routing Property .................................23
The Optimized Link State Routing Protocol version 1 (OLSRv1) [RFC3626] is a proactive routing protocol for mobile ad hoc networks (MANETs) [RFC2501]. OLSRv1 finds the shortest, defined as minimum number of hops, routes from a router to all possible destinations.
优化链路状态路由协议版本1（OLSRv1）[RFC3626]是移动自组织网络（MANET）[RFC2501]的主动式路由协议。OLSRv1查找从路由器到所有可能目的地的最短路由（定义为最小跳数）。
Using only minimum hop routes may result in what are, in practice, inferior routes. Some examples are given in Section 4. Thus, one of the distinguishing features of the Optimized Link State Routing Protocol version 2 (OLSRv2) [RFC7181] is the introduction of the ability to select routes using link metrics other than the number of hops.
仅使用最小跳数路由可能会导致实际上的劣质路由。第4节给出了一些示例。因此，优化链路状态路由协议版本2（OLSRv2）[RFC7181]的一个显著特征是引入了使用链路度量而不是跳数来选择路由的能力。
During the development of OLSRv2, the working group and authors repeatedly discussed how and why some choices were made in the protocol specification, particularly at the metric integration level. Some of the issues may be non-intuitive, and this document is presented as a record of the considerations and decisions to provide informational discussion about motivation and historic design choices. This document is intended to be useful as a reference if those questions arise again.
在OLSRv2的开发过程中，工作组和作者反复讨论了在协议规范中如何以及为什么做出一些选择，特别是在度量集成级别。一些问题可能是非直观的，本文档作为考虑事项和决策的记录，提供关于动机和历史设计选择的信息性讨论。如果这些问题再次出现，本文件可作为参考。
Use of the extensible message format [RFC5444] by OLSRv2 has allowed the addition, by OLSRv2, of link metric information to the HELLO messages defined in the MANET Neighborhood Discovery Protocol (NHDP) [RFC6130] as well as inclusion in the Topology Control (TC) messages defined in [RFC7181].
OLSRv2使用可扩展消息格式[RFC5444]允许OLSRv2将链路度量信息添加到MANET邻域发现协议（NHDP）[RFC6130]中定义的HELLO消息中，并包含在[RFC7181]中定义的拓扑控制（TC）消息中。
OLSRv2 essentially first determines local link metrics from 1-hop neighbors, these being defined by a process outside OLSRv2, then distributes required link metric values in HELLO messages and TC messages, and then finally forms routes with minimum total link metric. Using a definition of route metric other than number of hops is a natural extension that is commonly used in link state protocols.
OLSRv2基本上首先确定来自1跳邻居的本地链路度量，这些度量由OLSRv2外部的进程定义，然后在HELLO消息和TC消息中分配所需的链路度量值，最后形成具有最小总链路度量的路由。使用路由度量而不是跳数的定义是链路状态协议中常用的一种自然扩展。
A metric-based route selection process for OLSRv2 could have been handled as an extension to OLSRv2. However, were this to have been done, OLSRv2 routers that did not implement this extension would not recognize any link metric information and would attempt to use minimum hop-count routes. This would have meant that, in effect, routers that did implement and routers that did not implement this extension would differ over their valuation of links and routes. This would have led to the fundamental routing problem of "looping". Thus, if metric-based route selection were to have been considered only as an extension to OLSRv2, then routers that did implement and routers that did not implement this extension would not have been
OLSRv2基于度量的路由选择过程可以作为OLSRv2的扩展处理。然而，如果这样做，未实现此扩展的OLSRv2路由器将无法识别任何链路度量信息，并将尝试使用最小跳数路由。这就意味着，实际上，实现了该扩展的路由器和未实现该扩展的路由器在链路和路由的估值上会有所不同。这将导致根本的路由问题“循环”。因此，如果基于度量的路由选择仅被视为OLSRv2的一个扩展，那么实现此扩展的路由器和未实现此扩展的路由器将不会被考虑
able to interoperate. This would have been a significant limitation of such an extension. Link metrics were therefore included as standard in OLSRv2.
能够进行互操作。这将是这种扩展的一个重大限制。因此，链接度量作为标准包含在OLSRv2中。
This document discusses the motivation and design rationale behind how link metrics were included in OLSRv2. The principal issues involved when including link metrics in OLSRv2 were:
本文档讨论链接度量如何包含在OLSRv2中的动机和设计原理。在OLSRv2中包含链接度量时涉及的主要问题是：
o Assigning metrics to links involved considering separate metrics for the two directions of a link, with the receiving router determining the metric from transmitter to receiver. A metric used by OLSRv2 may be either of:
o 考虑链路两个方向的单独度量，将度量分配给链路，接收路由器确定从发射机到接收机的度量。OLSRv2使用的度量可以是：
* A link metric, the metric of a specific link from an OLSRv2 interface of the transmitting router to an OLSRv2 interface of the receiving router.
* 链路度量，从发送路由器的OLSRv2接口到接收路由器的OLSRv2接口的特定链路的度量。
* A neighbor metric, the minimum of the link metrics between two OLSRv2 routers, in the indicated direction.
* 指示方向上两个OLSRv2路由器之间链路度量的最小值，即邻居度量。
These metrics are necessarily the same when these routers each have a single OLSRv2 interface but may differ when either has more. HELLO messages may include both link metrics and neighbor metrics. TC messages include only neighbor metrics.
当这些路由器都有一个OLSRv2接口时，这些指标必然相同，但当其中一个有更多接口时，这些指标可能不同。HELLO消息可能包括链路度量和邻居度量。TC消息仅包括邻居度量。
o Metrics as used in OLSRv2 are defined to be dimensionless and additive. The assignment of metrics, including their relationship to real parameters such as data rate, loss rate, and delay, and the management of the choice of metric, is outside the scope of [RFC7181], which simply uses these metrics in a consistent manner. Within a single MANET, including all components of a temporarily fragmented MANET, a single choice of link metric is used. By use of a registry of metric types (employing extended types of a single Address Block TLV type), routers can be configured to use only a subset of the available metric types.
o OLSRv2中使用的度量定义为无量纲和可加性。指标的分配，包括它们与真实参数（如数据速率、丢失率和延迟）的关系，以及指标选择的管理，不在[RFC7181]的范围内，RFC7181只是以一致的方式使用这些指标。在单个MANET中，包括临时分段MANET的所有组件，使用单一的链路度量选择。通过使用度量类型注册表（使用单个地址块TLV类型的扩展类型），路由器可以配置为仅使用可用度量类型的子集。
o Node metrics were not included in OLSRv2. Node metrics can be implemented by the addition of the corresponding value to all incoming link metrics by the corresponding router.
o OLSRv2中未包含节点度量。节点度量可以通过相应路由器向所有传入链路度量添加相应的值来实现。
o The separation of the two functions performed by multipoint relays (MPRs) in OLSRv1, optimized flooding and reduced topology advertisement for routing, into separate sets of MPRs in OLSRv2 [RFC7181], denoted "flooding MPRs" and "routing MPRs". Flooding MPRs can be calculated as in [RFC3626], but the use of link metrics in OLSRv2 can improve the MPR selection. Routing MPRs need a metric-aware selection algorithm. The selection of routing MPRs guarantees the use of minimum distance routes using the
o 将OLSRv1中的多点继电器（MPR）执行的两个功能分离为OLSRv2[RFC7181]中的独立MPR集，表示为“泛洪MPR”和“路由MPR”。泛洪MPR可以按照[RFC3626]中的方法计算，但是在OLSRv2中使用链路度量可以改进MPR选择。路由MPR需要一个度量感知的选择算法。路由MPR的选择保证了使用
chosen metric, while using only symmetric 2-hop neighborhood information from HELLO messages and routing MPR selector information from TC messages.
选择度量，同时仅使用HELLO消息中的对称2跳邻居信息和TC消息中的路由MPR选择器信息。
o The protocol Information Bases defined in OLSRv2 include required metric values. This has included additions to the protocol Information Bases defined in NHDP [RFC6130] when used by OLSRv2.
o OLSRv2中定义的协议信息库包括所需的度量值。这包括在OLSRv2使用时，对NHDP[RFC6130]中定义的协议信息库进行补充。
All terms introduced in [RFC5444], including "message" and "TLV" (type-length-value), are to be interpreted as described there.
[RFC5444]中引入的所有术语，包括“消息”和“TLV”（类型长度值），均应按照此处所述进行解释。
All terms introduced in [RFC6130], including "MANET interface", "HELLO message", "heard", "link", "symmetric link", "1-hop neighbor", "symmetric 1-hop neighbor", "2-hop neighbor", "symmetric 2-hop neighbor", "symmetric 2-hop neighborhood", and the symbolic constants SYMMETRIC and HEARD, are to be interpreted as described there.
[RFC6130]中引入的所有术语，包括“MANET接口”、“HELLO消息”、“heard”、“链路”、“对称链路”、“1跳邻居”、“对称1跳邻居”、“2跳邻居”、“对称2跳邻居”、“对称2跳邻居”以及符号常数symmetric and heard，均应按照此处所述进行解释。
All terms introduced in [RFC7181], including "router", "OLSRv2 interface", "willingness", "multipoint relay (MPR)", "MPR selector", "MPR flooding", and the TLV type LINK_METRIC, are to be interpreted as described there.
[RFC7181]中介绍的所有术语，包括“路由器”、“OLSRv2接口”、“意愿”、“多点中继（MPR）”、“MPR选择器”、“MPR泛洪”和TLV型链路度量，均应按照此处所述进行解释。
The objective of this document is to retain the design considerations behind how link metrics were included in [RFC7181]. This document does not prescribe any behavior but explains some aspects of the operation of OLSRv2.
本文件的目的是保留[RFC7181]中如何包含链接度量的设计考虑因素。本文件未规定任何行为，但解释了OLSRv2操作的某些方面。
The basic situation that suggests the desirability of use of routes other than minimum hop routes is shown in Figure 1.
图1显示了使用最小跳数路由以外的路由的可取性的基本情况。
A ----- X ----- B
\ /
\ /
Y ------- Z
A ----- X ----- B
\ /
\ /
Y ------- Z
Figure 1
图1
The minimum hop route from A to B is via X. However, if the links A to X and X to B are poor (e.g., have low data rate or are unreliable) but the links A to Y, Y to Z, and Z to B are better (e.g., have reliable high data rate), then the route A to B via Y and Z may be preferred to that via X.
从A到B的最小跳路由是经由X。然而，如果链路A到X和X到B较差（例如，数据速率低或不可靠），但是链路A到Y、Y到Z和Z到B较好（例如，具有可靠的高数据速率），则经由Y和Z的路由A到B可能优于经由X的路由。
There are other situations where the use of some links should be discouraged, even if the avoidance of them does not show immediately obvious benefits to users. Consider a network with many short-range links and a few long-range links. Use of minimum hop routes will immediately lead to heavy use of the long-range links. This will be particularly undesirable if those links achieve their longer range through reduced data rate or through being less reliable. However, even if the long-range links have the same characteristics as the short-range links, it may be better to reserve usage of the long-range links for when this usage is particularly valuable -- for example, when the use of one long-range link saves several short-range links, rather than the single link saving that is needed for a minimum hop route.
在其他情况下，即使避免使用某些链接不会立即给用户带来明显的好处，也不应鼓励使用这些链接。考虑一个具有许多短距离链路和一些远程链路的网络。使用最小跳数路由将立即导致大量使用远程链路。如果这些链路通过降低数据速率或降低可靠性来实现其更长的范围，则这将是特别不可取的。然而，即使远程链路具有与短程链路相同的特性，也最好将远程链路的使用保留到这种使用特别有价值的时候——例如，当一条远程链路的使用节省了几个短程链路时，而不是最小跳数路由所需的单链路节省。
A related case is that of a privileged relay. An example is an aerial router in an otherwise ground-based network. The aerial router may have a link to many, or even all, other routers. That would lead to all routers attempting to send all their traffic (other than to symmetric 1-hop neighbors and some symmetric 2-hop neighbors) via the aerial router. It may, however, be important to reserve that capacity for cases where the aerial router is actually essential, such as if the ground-based portion of the network is not connected.
一个相关的例子是特权中继。例如，地面网络中的空中路由器。空中路由器可能与许多甚至所有其他路由器有链接。这将导致所有路由器试图通过空中路由器发送其所有流量（除了对称1跳邻居和一些对称2跳邻居）。然而，在空中路由器实际上至关重要的情况下，例如如果网络的地面部分未连接，则保留该容量可能很重要。
Link metrics provide a possible solution to these scenarios. For example, in Figure 1, the route A to Y to Z to B could be preferred to A to X to B by making the metrics on the former path 1 and those on the latter path 2. The aerial privileged relay could be used only when necessary by giving its links maximal metric values, with much smaller other metric values or, if the aerial link is to be preferred to N ground links, by giving the ground links metric values of 1 while making the sum of the aerial node uplink and downlink metrics equal to N.
链接度量为这些场景提供了一个可能的解决方案。例如，在图1中，通过在前一条路径1和后一条路径2上生成度量，路径A到Y到Z到B可能比路径A到X到B更可取。只有在必要时，通过给出其链路的最大度量值，以及更小的其他度量值，或者，如果空中链路要优于N个地面链路，则通过给出地面链路度量值1，同时使空中节点上行链路和下行链路度量之和等于N，才能使用空中特权中继。
Other cases may involve attempts to avoid areas of congestion, attempts to route around insecure routers, and attempts by routers to discourage being used as relays due to, for example, limited battery power. OLSRv2 does have another mechanism to aid in this: a router's willingness to act as an MPR. However, there are cases where that cannot help but where use of non-minimum hop routes could.
其他情况可能涉及避免拥塞区域的尝试、绕过不安全路由器的尝试，以及由于例如电池功率有限而被路由器阻止用作中继的尝试。OLSRv2确实有另一种机制来帮助实现这一点：路由器愿意充当MPR。然而，在某些情况下，这并没有帮助，但使用非最小跳数路由可能会有所帮助。
Similarly, note that OLSRv2's optional use of link quality (through its use of [RFC6130]) is not a solution to these problems. Use of link quality as specified in [RFC6130] allows a router to decline to use a link, not only on its own, but on all routers' behalf. It does not, for example, allow the use of a link otherwise determined to be too low quality to be generally useful as part of a route where no better links exist. These mechanisms (link quality and link metrics) solve distinctly different problems.
同样，请注意，OLSRv2对链路质量的可选使用（通过使用[RFC6130]）并不能解决这些问题。[RFC6130]中规定的链路质量的使用允许路由器拒绝使用链路，不仅是为了它自己，而且是为了所有路由器。例如，它不允许在没有更好链路的情况下，使用质量太低而不能作为路由的一部分使用的链路。这些机制（链接质量和链接度量）解决了截然不同的问题。
It should also be noted that the loop-free property of OLSRv2 applies strictly only in the static state. When the network topology is changing and when messages can be lost, it is possible for transient loops to form. However, with update rates appropriate to the rate of topology change, such loops will be sufficiently rare. Changing link metrics is a form of network topology change and should be limited to a rate slower than the message information update rate (defined by the parameters HELLO_INTERVAL, HELLO_MIN_INTERVAL, REFRESH_INTERVAL, TC_INTERVAL, and TC_MIN_INTERVAL).
还应注意，OLSRv2的无循环特性仅严格适用于静态。当网络拓扑发生变化且消息可能丢失时，可能会形成瞬态环路。然而，随着更新速率与拓扑变化速率相适应，这样的循环将非常罕见。更改链路度量是网络拓扑更改的一种形式，应限制为低于消息信息更新速率的速率（由参数HELLO_INTERVAL、HELLO_MIN_INTERVAL、REFRESH_INTERVAL、TC_INTERVAL和TC_MIN_INTERVAL定义）。
This section describes the required and selected properties of the link metrics used in OLSRv2, followed by implementation details achieving those properties.
本节介绍OLSRv2中使用的链路度量的必需和选定属性，然后介绍实现这些属性的实现细节。
Link metrics in OLSRv2 are:
OLSRv2中的链路指标包括：
o Dimensionless. While they may, directly or indirectly, correspond to specific physical information (such as delay, loss rate, or data rate), this knowledge is not used by OLSRv2. Instead, generating the metric value is the responsibility of a mechanism external to OLSRv2.
o 无量纲的。虽然它们可能直接或间接地对应于特定的物理信息（如延迟、丢失率或数据速率），但OLSRv2不使用这些知识。相反，生成度量值是OLSRv2外部机制的责任。
o Additive, so that the metric of a route is the sum of the metrics of the links forming that route. Note that this requires a metric where a low value of a link metric indicates a "good" link and a high value of a link metric indicates a "bad" link, and the former will be preferred to the latter.
o 加法，因此路由的度量是构成该路由的链路的度量之和。注意，这需要一个度量，其中链路度量的低值表示“好”链路，而链路度量的高值表示“坏”链路，前者将优先于后者。
o Directional, the metric from router A to router B need not be the same as the metric from router B to router A, even when using the same OLSRv2 interfaces. At router A, a link metric from router B to router A is referred to as an incoming link metric, while a link metric from router A to router B is referred to as an outgoing link metric. (These are, of course, reversed at router B.)
o 定向，从路由器A到路由器B的度量不需要与从路由器B到路由器A的度量相同，即使使用相同的OLSRv2接口。在路由器A，从路由器B到路由器A的链路度量称为传入链路度量，而从路由器A到路由器B的链路度量称为传出链路度量。（当然，这些在路由器B上是反向的。）
o Specific to a pair of OLSRv2 interfaces, so that if there is more than one link from router A to router B, each has its own link metric in that direction. There is also an overall metric, a "neighbor metric", from router A to router B (its 1-hop neighbor). This is the minimum value of the link metrics from router A to router B, considering symmetric links only; it is undefined if there are no such symmetric links. A neighbor metric from one router to another is always equal to a link metric in the same
o 特定于一对OLSRv2接口，因此，如果从路由器a到路由器B有多条链路，则每个链路在该方向上都有自己的链路度量。从路由器a到路由器B（其1跳邻居）还有一个整体度量，即“邻居度量”。这是从路由器A到路由器B的链路度量的最小值，仅考虑对称链路；如果没有这样的对称链接，它是未定义的。从一个路由器到另一个路由器的邻居度量总是等于同一路由器中的链路度量
direction between OLSRv2 interfaces of those routers. When referring to a specific OLSRv2 interface (for example, in a Link Tuple or a HELLO message sent on that OLSRv2 interface), a link metric always refers to a link on that OLSRv2 interface to or from the indicated 1-hop neighbor OLSRv2 interface, while a neighbor metric may be equal to a link metric to and/or from another OLSRv2 interface.
这些路由器的OLSRv2接口之间的方向。当引用特定的OLSRv2接口（例如，在该OLSRv2接口上发送的链路元组或HELLO消息中）时，链路度量总是指该OLSRv2接口上到或来自所指示的1跳邻居OLSRv2接口的链路，而邻居度量可能等于到和/或来自另一OLSRv2接口的链路度量。
There are various physical characteristics that may be used to define a link metric. Some examples, which also illustrate some characteristics of metrics that result, are:
有各种物理特性可用于定义链路度量。以下示例也说明了结果指标的一些特征：
o Delay is a straightforward metric; as it is naturally additive, the delay of a multi-link route is the sum of the delays of the links. This does not directly take into account delays due to routers (such as due to router queues or transition of packets between router interfaces) rather than links, but these delays can be divided among incoming and outgoing links.
o 延迟是一个简单的指标；由于它是自然相加的，因此多链路路由的延迟是链路延迟的总和。这并不直接考虑由于路由器（例如由于路由器队列或路由器接口之间的数据包转换）而不是链路引起的延迟，但这些延迟可以在传入和传出链路之间划分。
o Probability of loss on a link is, as long as probabilities of loss are small and independent, approximately additive. (A slightly more accurate approach is using a negatively scaled logarithm of the probability of not losing a packet.) If losses are not independent, then this will be pessimistic.
o 只要链路上的丢失概率较小且独立，则链路上的丢失概率近似为加法。（更准确的方法是使用不丢失数据包概率的负比例对数。）如果丢失不是独立的，那么这将是悲观的。
o Data rates are not additive. They even have the wrong characteristic of being good when high and bad when low; thus, a mapping that inverts the ordering must be applied. Such a mapping can, at best, only produce a metric that is acceptable to treat as additive. Consider, for example, a preference for a route that maximizes the minimum data rate link on the route and then prefers a route with the fewest links of each data rate from the lowest. If links may be of three discrete data rates, "high", "medium", and "low", then this preference can be achieved, on the assumption that no route will have more than 10 links, with metric values of 1, 10, and 100 for the three data rates.
o 数据速率不是累加的。他们甚至有一个错误的特征，那就是高的时候好，低的时候坏；因此，必须应用反转顺序的映射。这样的映射最多只能生成一个可接受的可作为加法处理的度量。例如，考虑对路由上的最小数据速率链路最大化的路由的偏好，然后优先考虑每个数据速率与最低数据链路最少的路由。如果链路可能具有三个离散数据速率，“高”、“中”和“低”，则可以实现此偏好，前提是没有路由具有超过10个链路，三个数据速率的度量值为1、10和100。
If routes can have more than 10 links, the range of metrics must be increased; this was one reason for a preference for a wide "dynamic range" of link metric values. Depending on the ratios of the numerical values of the three data rates, the same effect may be achieved by using a scaling of an inverse power of the numerical values of the data rates. For example, if the three data rates were 2, 5, and 10 Mbit/s, then a possible mapping would be the fourth power of 10 Mbit/s divided by the data rate, giving metric values of 625, 16, and 1 (good for up to 16 links in a
如果路由可以有10条以上的链路，则必须增加度量范围；这是一个偏好广泛的链接度量值“动态范围”的原因。根据三个数据速率的数值的比率，可以通过使用数据速率的数值的逆幂的缩放来实现相同的效果。例如，如果三个数据速率分别为2、5和10 Mbit/s，则可能的映射将是10 Mbit/s的四次方除以数据速率，给出625、16和1的度量值（适用于一个网络中最多16个链路）
route). This mapping can be extended to a system with more data rate values, for example, giving a 4 Mbit/s data rate a metric value of about 39. This may lose the capability to produce an absolutely maximal minimum data rate route but will usually produce either that, or something close (and at times maybe better, is a route of three 5 Mbit/s links really better than one of a single 4 Mbit/s link?). Specific metrics will need to define the mapping.
路线）。该映射可以扩展到具有更多数据速率值的系统，例如，为4Mbit/s数据速率提供大约39的度量值。这可能会失去生成绝对最大最小数据速率路由的能力，但通常会生成绝对最大最小数据速率路由或接近的路由（有时可能更好，三条5 Mbit/s链路的路由真的比一条4 Mbit/s链路的路由好吗？）。具体指标将需要定义映射。
There are also many other possible metrics, including using physical-layer information (such as signal-to-noise ratio and error-control statistics) and information such as packet-queuing statistics.
还有许多其他可能的度量，包括使用物理层信息（如信噪比和差错控制统计）和信息（如分组队列统计）。
In a well-designed network, all routers will use the same metric type. It will not produce good routes if, for example, some link metrics are based on data rate and some on path loss (except to the extent that these may be correlated). How to achieve this is an administrative matter, outside the scope of OLSRv2. In fact, even the actual physical meanings of the metrics is outside the scope of OLSRv2. This is because new metrics may be added in the future, for example, as data rates increase, and may be based on new, possibly non-physical, considerations, for example, financial cost. Each such type will have a metric type number. Initially, a single link metric type zero is defined as indicating a dimensionless metric with no predefined physical meaning.
在设计良好的网络中，所有路由器将使用相同的度量类型。例如，如果某些链路指标基于数据速率，而某些链路指标基于路径损耗（除非这些指标可能相互关联），则不会产生良好的路由。如何实现这一点是一个管理问题，超出了OLSRv2的范围。事实上，即使度量的实际物理意义也超出了OLSRv2的范围。这是因为将来可能会添加新的度量，例如，随着数据速率的增加，并且可能基于新的、可能是非物理的考虑，例如，财务成本。每种类型都有一个公制类型编号。最初，单链路度量类型零被定义为表示没有预定义物理意义的无量纲度量。
An OLSRv2 router is instructed which single link metric type to use and recognize, without knowing whether it represents delay, probability of loss, data rate, cost, or any other quantity. This recognized link metric type number is a router parameter and subject to change in case of reconfiguration or possibly the use of a protocol (outside the scope of OLSRv2) permitting a process of link metric type agreement between routers.
OLSRv2路由器被指示使用和识别哪种单链路度量类型，而不知道它是否表示延迟、丢失概率、数据速率、成本或任何其他数量。该识别的链路度量类型号是路由器参数，在重新配置或可能使用允许路由器之间链路度量类型协议过程的协议（在OLSRv2范围之外）的情况下会发生变化。
The use of link metric type numbers also suggests the possibility of use of multiple link metric types and multiple network topologies. This is a possible future extension to OLSRv2. To allow for that future possibility, the sending of more than one metric of different physical types, which should otherwise not be done for reasons of efficiency, is not prohibited, but types other than that configured will be ignored.
链路度量类型编号的使用也表明了使用多个链路度量类型和多个网络拓扑的可能性。这是OLSRv2未来可能的扩展。考虑到未来的可能性，不禁止发送不同物理类型的一个以上度量，否则出于效率原因不应发送，但将忽略配置的类型以外的类型。
The following three sections assume a chosen single link metric type, of unspecified physical nature.
以下三个部分假设选择了一种未指定物理性质的单链路度量类型。
OLSRv2 uses only "symmetric" (bidirectional) links, which may carry traffic in either direction. A key decision was whether these links should each be assigned a single metric, used in both directions, or a metric in each direction, noting that:
OLSRv2仅使用“对称”（双向）链路，该链路可在任一方向承载流量。一个关键决定是，是否应为这些链接分配一个单独的度量，在两个方向上使用，还是在每个方向上分配一个度量，注意：
o Links can have different characteristics in each direction. Use of directional link metrics recognizes this.
o 链接在每个方向上可以具有不同的特性。使用定向链路度量可以认识到这一点。
o In many (possibly most) cases, the two ends of a link will naturally form different views as to what the link metric should be. To use a single link metric requires a coordination between the two that can be avoided if using directional metrics. Note that if using a single metric, it would be essential that the two ends agree as to its value; otherwise, it is possible for looping to occur. This problem does not occur for directional metrics.
o 在许多（可能是大多数）情况下，链路的两端自然会就链路度量应该是什么形成不同的视图。要使用单个链路度量，需要在两者之间进行协调，如果使用定向度量，则可以避免这种协调。注意，如果使用单一度量，则两端必须就其值达成一致；否则，可能会发生循环。定向度量不会出现此问题。
Based on these considerations, directional metrics are used in OLSRv2. Each router must thus be responsible for defining the metric in one direction only. This could have been in either direction, i.e., a router is responsible for either incoming or outgoing link metrics, as long as the choice is universal. The former (incoming) case is used in OLSRv2 because, in general, receiving routers have more information available to determine link metrics (for example, received signal strength, interference levels, and error-control coding statistics).
基于这些考虑，OLSRv2中使用了方向度量。因此，每个路由器必须只负责在一个方向上定义度量。这可能是在两个方向，即路由器负责传入或传出链路度量，只要选择是通用的。前一种（传入）情况用于OLSRv2，因为通常情况下，接收路由器具有更多可用信息来确定链路度量（例如，接收信号强度、干扰级别和差错控制编码统计）。
Note that, using directional metrics, if router A defines the metric of the link from router B to router A, then router B must use router A's definition of that metric on that link in that direction. (Router B could, if appropriate, use a bad mismatch between directional metrics as a reason to discontinue use of this link, using the link quality mechanism defined in [RFC6130]; note that this is a distinct mechanism from the use of link metrics.)
注意，使用方向度量，如果路由器A定义了从路由器B到路由器A的链路的度量，那么路由器B必须在该方向上使用路由器A对该链路的该度量的定义。（如果合适，路由器B可以使用[RFC6130]中定义的链路质量机制，将定向度量之间的严重不匹配作为停止使用该链路的理由；注意，这是一种不同于使用链路度量的机制。）
Links, and hence link metrics, are reported in HELLO messages. A router must report incoming link metrics in its HELLO messages in order for these link metrics to be available at the other end of the link. This means that, for a symmetric link, both ends of the link will know both of the incoming and outgoing link metrics.
链接和链接度量在HELLO消息中报告。路由器必须在其HELLO消息中报告传入的链路度量，以便这些链路度量在链路的另一端可用。这意味着，对于对称链路，链路的两端都将知道传入和传出链路度量。
As well as advertising incoming link metrics, HELLO messages also advertise incoming neighbor metrics. These are used for routing MPR selection (see Section 6.2), which requires use of the lowest metric
除了公布传入的链接度量，HELLO消息还公布传入的邻居度量。这些用于路由MPR选择（见第6.2节），这需要使用最低度量
link between two routers when more than one link exists. This neighbor metric may be using another OLSRv2 interface, and hence, the link metric alone is insufficient.
当存在多个链路时，两个路由器之间的链路。该邻居度量可能正在使用另一个OLSRv2接口，因此，仅链路度量是不够的。
Metrics are also reported in TC messages. It can be shown that these need to be outgoing metrics:
指标也会在TC消息中报告。可以看出，这些需要是传出的度量：
o Router A must be responsible for advertising a metric from router A to router B in TC messages. This can be seen by considering a route connecting single OLSRv2 interface routers P to Q to R to S. Router P receives its only information about the link from R to S in the TC messages transmitted by router R, which is an MPR of router S (assuming that only MPR selectors are reported in TC messages). Router S may not even transmit TC messages (if no routers have selected it as an MPR and it has no attached networks to report). So any information about the metric of the link from R to S must also be included in the TC messages sent by router R; hence, router R is responsible for reporting the metric for the link from R to S.
o 路由器A必须负责在TC消息中公布从路由器A到路由器B的度量。这可以通过考虑将单个OLSRv2接口路由器P连接到Q到R到S的路由来看出。路由器P在路由器R传输的TC消息中只接收关于从R到S的链路的信息，这是路由器S的MPR（假设在TC消息中只报告MPR选择器）。路由器S甚至可能不发送TC消息（如果没有路由器选择它作为MPR，并且它没有要报告的连接网络）。因此，关于从R到S的链路的度量的任何信息也必须包含在路由器R发送的TC消息中；因此，路由器R负责报告从R到S的链路的度量。
o In a more general case, where there may be more than one link from R to S, the TC message must, so that minimum metric routes can be constructed (e.g., by router P), report the minimum of these outgoing link metrics, i.e., the outgoing neighbor metric from R to S.
o 在更一般的情况下，在从R到S可能存在多个链路的情况下，TC消息必须报告这些传出链路度量的最小值，即从R到S的传出邻居度量，以便可以构造最小度量路由（例如，由路由器P）。
In this example, router P also receives information about the existence of a link between Q and R in the HELLO messages sent by router Q. Without the use of metrics, this link could be used by OLSRv2 for 2-hop routing to router R, using just HELLO messages sent by router Q. For this property (which accelerates local route formation) to be retained (from OLSRv1), router P must receive the metric from Q to R in HELLO messages sent by router Q. This indicates that router Q must be responsible for reporting the metric for the outgoing link from Q to R. This is in addition to the incoming link metric information that a HELLO message must report. Again, in general, this must be the outgoing neighbor metric, rather than the outgoing link metric.
在本例中，路由器P还接收关于路由器Q发送的HELLO消息中Q和R之间存在链路的信息。在不使用度量的情况下，OLSRv2可以使用该链路，仅使用路由器Q发送的HELLO消息，进行到路由器R的2跳路由。对于该属性（加速本地路由形成）要保留（从OLSRv1），路由器P必须在路由器Q发送的HELLO消息中接收从Q到R的度量。这表示路由器Q必须负责报告从Q到R的传出链路的度量。这是HELLO消息必须报告的传入链路度量信息之外的信息。同样，一般来说，这必须是传出邻居度量，而不是传出链路度量。
In addition, Section 6.1 offers an additional reason for reporting outgoing neighbor metrics in HELLO messages, without which metrics can properly affect only routing, not flooding.
此外，第6.1节还提供了在HELLO消息中报告传出邻居度量的另一个原因，如果没有这些度量，这些度量只能正确地影响路由，而不会影响泛洪。
Note that there is no need to report an outgoing link metric in a HELLO message. The corresponding 1-hop neighbor knows that value; it specified it. Furthermore, for 2-hop neighborhood use, neighbor metrics are required (as these will, in general, not use the same OLSRv2 interface).
请注意，无需在HELLO消息中报告传出链接度量。对应的1跳邻居知道该值；它具体说明了这一点。此外，对于2跳邻居使用，需要邻居度量（因为这些度量通常不会使用相同的OLSRv2接口）。
When a router reports a 1-hop neighbor in a HELLO message, it may do so for the first time with link status HEARD. As the router is responsible for defining and reporting incoming link metrics, it must evaluate that metric and attach that link metric to the appropriate address (which will have link status HEARD) in the next HELLO message reporting that address on that OLSRv2 interface. There will, at this time, be no outgoing link metric available to report, but a router must be able to immediately decide on an incoming link metric once it has heard a 1-hop neighbor on an OLSRv2 interface for the first time.
当路由器在HELLO消息中报告1跳邻居时，它可能会在听到链路状态的情况下第一次报告。由于路由器负责定义和报告传入链路度量，因此它必须评估该度量，并在报告OLSRv2接口上地址的下一条HELLO消息中将该链路度量附加到适当的地址（将听到链路状态）。此时将没有可报告的传出链路度量，但路由器必须能够在第一次听到OLSRv2接口上的1跳邻居后立即决定传入链路度量。
This is because, when receiving a HELLO message from this router, the 1-hop neighbor seeing its own address listed with link status HEARD will (unless the separate link quality mechanism indicates otherwise) immediately consider that link to be SYMMETRIC, advertise it with that link status in future HELLO messages, and use it (for MPR selection and data traffic forwarding).
这是因为，当从该路由器接收到hello消息时，看到其具有链路状态所列出的自己的地址的1-跳邻居将（除非单独的链路质量机制指示其他）立即考虑链路是对称的，在未来的hello消息中用该链路状态对其进行广告，并使用它。（用于MPR选择和数据流量转发）。
It may, depending on the physical nature of the link metric, be too early for an ideal decision as to that metric; however, a choice must be made. The metric value may later be refined based on further observation of HELLO messages, other message transmissions between the routers, or other observations of the environment. It will probably be best to over-estimate the metric if initially uncertain as to its value, to discourage, rather than over-encourage, its use. If no information other than the receipt of the HELLO message is available, then a conservative maximum link metric value, denoted MAXIMUM_METRIC in [RFC7181], should be used.
取决于链路度量的物理性质，对于该度量的理想决策来说可能为时过早；然而，必须作出选择。稍后可基于对HELLO消息的进一步观察、路由器之间的其他消息传输或对环境的其他观察来细化度量值。如果最初不确定指标的价值，最好是高估指标，以阻止而不是过度鼓励其使用。如果除了接收HELLO消息之外没有其他信息可用，则应使用保守的最大链路度量值，在[RFC7181]中表示为最大_度量。
Link metric values are recorded in LINK_METRIC TLVs, defined in [RFC7181], using a compressed (lossy) representation that occupies 12 bits. The use of 12 bits is convenient because, when combined with 4 flag bits of additional information, described below, this results in a 2-octet value field. However, the use of 12 bits, and thus the availability of 4 flag bits, was a consequence of a design to use a modified exponent/mantissa form with the following characteristics:
链路度量值记录在[RFC7181]中定义的链路度量TLV中，使用占12位的压缩（有损）表示。12位的使用是方便的，因为当与下面描述的附加信息的4个标志位组合时，这将产生2个八位值字段。然而，12位的使用，以及4个标志位的可用性，是使用具有以下特征的修改指数/尾数形式的设计的结果：
o The values represented are to be positive integers starting 1, 2, ...
o 表示的值是从1、2、….开始的正整数。。。
o The maximum value represented should be close to, but less than 2^24 (^ denotes exponentiation in this section). This is so that with a route limited to no more than 255 hops, the maximum route metric is less than 2^32, i.e., can be stored in 32 bits. (The link metric value can be stored in 24 bits.)
o 表示的最大值应接近但小于2^24（^表示本节中的幂运算）。这使得当路由限制为不超过255跳时，最大路由度量小于2^32，即可以存储在32位中。（链路度量值可存储为24位。）
A representation that is modified from an exponent/mantissa form with e bits of exponent and m bits of mantissa and that has the first of these properties is one that starts at 1, then is incremented by 1 up to 2^m, then has a further 2^m increments by 2, then a further 2^m increments by 4, and so on for 2^e sets of increments. This means that the represented value is never in error by more than a half (if rounding) or one (if truncating) part in 2^m, usually less.
从指数/尾数形式修改而来的一种表示形式，具有指数的e位和尾数的m位，并且具有这些属性中的第一个，即从1开始，然后递增1到2^m，然后再递增2^m，然后再递增2^m，再递增2^m，再递增4^m，依此类推。这意味着表示的值的误差不会超过2^m中的一半（如果舍入）或一部分（如果截断），通常小于一半。
The position in the increment sequence, from 0 to 2^m-1, is considered as a form of mantissa and denoted a. The increment sequence number, from 0 to 2^e-1, is considered as a form of exponent and denoted b.
增量序列中从0到2^m-1的位置被视为尾数的一种形式，并表示为a。从0到2^e-1的增量序列号被视为指数形式，表示为b。
The value represented by (b,a) can then be shown to be equal to (2^m+a+1)2^b-2^m. To verify this, note that:
（b，a）表示的值可以显示为等于（2^m+a+1）2^b-2^m。要验证这一点，请注意：
o With fixed b, the difference between two values with consecutive values of a is 2^b, as expected.
o 对于固定b，两个连续值为a的值之间的差值为2^b，如预期的那样。
o The value represented by (b,2^m-1) is (2^m+2^m)2^b-2^m. The value represented by (b+1,0) is (2^m+1)(2^(b+1))-2^m. The difference between these two values is 2^(b+1), as expected.
o 由（b，2^m-1）表示的值是（2^m+2^m）2^b-2^m。（b+1,0）表示的值是（2^m+1）（2^（b+1））-2^m。这两个值之间的差值为2^（b+1），如预期的那样。
The maximum represented value has b = 2^e-1 and a = 2^m-1 and is (2^m+2^m)(2^(2^e-1))-2^m = 2^(2^e+m)-2^m. This is slightly less than 2^(2^e+m). The required 24-bit limit can be achieved if 2^e+m = 24. Of the possible (e,m) pairs that satisfy this equation, the pair e = 4, m = 8 was selected as most appropriate and is that used by OLSRv2. It uses the previously indicated e+m = 12 bits. An algorithm for converting from a 24-bit value v to a 12-bit pair (b,a) is given in Section 6.2 of [RFC7181].
表示的最大值为b=2^e-1和a=2^m-1，为（2^m+2^m）（2^（2^e-1））-2^m=2^（2^e+m）-2^m。这略小于2^（2^e+m）。如果2^e+m=24，则可以达到所需的24位限制。在满足该方程的可能（e，m）对中，选择了最合适的对e=4，m=8，这是OLSRv2使用的对。它使用先前指示的e+m=12位。[RFC7181]第6.2节给出了将24位值v转换为12位对（b，a）的算法。
As noted above, the 12-bit representation then shares two octets with 4 flag bits. Putting the flag bits first, it is then natural to put the exponent bits in the last four bits of the first octet and to put the mantissa bits in the second octet. The 12 consecutive bits, using network byte order (most significant octet first), then represent 256b+a. Note that the ordering of these 12-bit representation values is the same as the ordering of the 24-bit metric values. In other words, two 12-bit metrics fields can be compared for equality/ordering as if they were unsigned integers.
如上所述，12位表示然后与4个标志位共享两个八位字节。将标志位放在第一位，然后自然地将指数位放在第一个八位字节的最后四位，并将尾数位放在第二个八位字节。使用网络字节顺序（首先是最高有效八位字节）的12个连续位表示256b+a。请注意，这些12位表示值的顺序与24位度量值的顺序相同。换句话说，两个12位度量字段可以进行相等/排序比较，就像它们是无符号整数一样。
The four flag bits each represent one kind of metric, defined by its direction (incoming or outgoing) and whether the metric is a link metric or a neighbor metric. As indicated by the flag bits set, a metric value may be of any combination of these four kinds of metric.
四个标志位各自表示一种度量，由其方向（传入或传出）以及该度量是链路度量还是邻居度量定义。如标志位集所示，度量值可以是这四种度量的任意组合。
MPRs are used for two purposes in OLSRv2. In both cases, it is MPR selectors that are actually used, MPR selectors being determined from MPRs advertised in HELLO messages.
在OLSRv2中，MPR有两个用途。在这两种情况下，实际使用的都是MPR选择器，MPR选择器由HELLO消息中广告的MPR确定。
o Optimized Flooding. This uses the MPR selector status of symmetric 1-hop neighbor routers from which messages are received in order to determine if these messages are to be forwarded. MPR selector status is recorded in the Neighbor Set (defined in [RFC6130] and extended in [RFC7181]) and determined from received HELLO messages.
o 优化洪水。这使用接收消息的对称1跳邻居路由器的MPR选择器状态来确定是否转发这些消息。MPR选择器状态记录在邻居集中（在[RFC6130]中定义，在[RFC7181]中扩展），并根据收到的HELLO消息确定。
o Routing. Non-local link information is based on information recorded in this router's Topology Information Base. That information is based on received TC messages. The neighbor information in these TC messages consists of addresses of the originating router's advertised (1-hop) neighbors, as recorded in that router's Neighbor Set (defined in [RFC6130] and extended in [RFC7181]). These advertised neighbors include all of the MPR selectors of the originating router.
o 路由。非本地链路信息基于此路由器拓扑信息库中记录的信息。该信息基于收到的TC消息。这些TC消息中的邻居信息由原始路由器的通告（1跳）邻居的地址组成，记录在该路由器的邻居集中（在[RFC6130]中定义，在[RFC7181]中扩展）。这些广告邻居包括发起路由器的所有MPR选择器。
Metrics interact with these two uses of MPRs differently, as described in the following two sections. This leads to the requirement for two separate sets of MPRs for these two uses when using metrics. The relationship between these two sets of MPRs is considered in Section 6.3.
度量与MPR的这两种使用之间的交互方式不同，如下两节所述。这导致在使用度量时，这两种用途需要两套独立的MPR。第6.3节考虑了这两组MPR之间的关系。
The essential detail of the "flooding MPR" selection specification is that a router must select a set of MPRs such that a message transmitted by a router and retransmitted by all its flooding MPRs will reach all of the selecting router's symmetric 2-hop neighbors.
“泛洪MPR”选择规范的基本细节是，路由器必须选择一组MPR，以便由路由器传输并由其所有泛洪MPR重新传输的消息将到达选择路由器的所有对称2跳邻居。
Flooding MPR selection can ignore metrics and produce a solution that meets the required specification. However, that does not mean that metrics cannot be usefully considered in selecting flooding MPRs. Consider the network in Figure 2, where numbers are metrics of links in the direction away from router A, towards router D.
泛洪MPR选择可以忽略指标并生成满足所需规范的解决方案。然而，这并不意味着在选择泛洪MPR时不能有效地考虑指标。考虑图2中的网络，其中数字是远离路由器A的方向的链路度量，指向路由器D。
3
A ----- B
| |
1 | | 1
| |
C ----- D
4
3
A ----- B
| |
1 | | 1
| |
C ----- D
4
Figure 2
图2
Which is the better flooding MPR selection by router A: B or C? If the metric represents probability of message loss, then clearly choosing B maximizes the probability of a message sent by A reaching D. This is despite C having a lower metric in its connection to A than B does. (Similar arguments about a preference for B can be made if, for example, the metric represents data rate or delay rather than probability of loss.)
路由器A:B或C的泛洪MPR选择哪个更好？如果度量表示消息丢失的概率，那么显然选择B将使a发送的消息到达D的概率最大化。尽管C在与a的连接中的度量比B低。（例如，如果度量表示数据速率或延迟而不是丢失概率，则可以对B的偏好进行类似的论证。）
However, neither should only the second hop be considered. If this example is modified to that in Figure 3, where the numbers still are metrics of links in the direction away from router A, towards router D, then it is possible that, when A is selecting flooding MPRs, selecting C is preferable to selecting B.
但是，也不应只考虑第二跳。如果将该示例修改为图3中的示例，其中数字仍然是远离路由器A、朝向路由器D的方向上的链路的度量，则当A选择泛洪MPR时，选择C比选择B更可取。
3
A ----- B
| |
1 | | 3
| |
C ----- D
4
3
A ----- B
| |
1 | | 3
| |
C ----- D
4
Figure 3
图3
If the metrics represent scaled values of delay or the probability of loss, then selecting C is clearly better. This indicates that the sum of metrics is an appropriate measure to use to choose between B and C.
如果度量值表示延迟或损失概率的标度值，那么选择C显然更好。这表明度量的总和是在B和C之间选择的合适度量。
However, this is a particularly simple example. Usually, it is not a simple choice between two routers as a flooding MPR, each only adding one router coverage. When considering which router to next add as a flooding MPR, a more general process should incorporate the metric to that router and the metric from that router to each symmetric 2-hop neighbor as well as the number of newly covered symmetric 2-hop neighbors. Other factors may also be included.
然而，这是一个特别简单的例子。通常，作为泛洪MPR，在两个路由器之间进行选择并不简单，每个路由器只增加一个路由器覆盖范围。当考虑下一个添加哪个路由器作为泛洪MPR时，更一般的过程应该包括该路由器的度量、该路由器到每个对称2跳邻居的度量以及新覆盖的对称2跳邻居的数量。其他因素也可能包括在内。
The required specification for flooding MPR selection is in Section 18.4 (also using Section 18.3) of [RFC7181], which may use the example MPR selection algorithm in Appendix B of [RFC7181]. However, note that (as in [RFC3626]) each router can make its own independent choice of flooding MPRs, and flooding MPR selection algorithm, and still interoperate.
[RFC7181]第18.4节（也使用第18.3节）中规定了泛洪MPR选择所需的规范，可使用[RFC7181]附录B中的示例MPR选择算法。但是，请注意（如[RFC3626]中所述），每个路由器都可以独立选择泛洪MPR和泛洪MPR选择算法，并且仍然可以互操作。
Also note that the references above to the direction of the metrics is correct: for flooding, directional metrics outward from a router are appropriate, i.e., metrics in the direction of the flooding. This is an additional reason for including outward metrics in HELLO messages, as otherwise a metric-aware MPR selection for flooding is not possible. The second-hop metrics are outgoing neighbor metrics because the OLSRv2 interface used for a second-hop transmission may not be the same as that used for the first-hop reception.
还请注意，上面对度量方向的引用是正确的：对于泛洪，从路由器向外的定向度量是合适的，即泛洪方向的度量。这是在HELLO消息中包含向外度量的另一个原因，否则不可能为泛洪选择度量感知的MPR。第二跳度量是传出邻居度量，因为用于第二跳传输的OLSRv2接口可能与用于第一跳接收的接口不同。
The essential detail of the "routing MPR" selection specification is that a router must, per OLSRv2 interface, select a set of MPRs such that there is a 2-hop route from each symmetric 2-hop neighbor of the selecting router to the selecting router, with the intermediate router on each such route being a routing MPR of the selecting router.
“路由MPR”选择规范的基本细节是，路由器必须根据OLSRv2接口选择一组MPR，以便从选择路由器的每个对称2跳邻居到选择路由器有一个2跳路由，每个这样的路由上的中间路由器是选择路由器的路由MPR。
It is sufficient, when using an additive link metric rather than a hop count, to require that these routing MPRs provide not just a 2-hop route but a minimum distance 2-hop route. In addition, a router is a symmetric 2-hop neighbor even if it is a symmetric 1-hop neighbor, as long as there is a 2-hop route from it that is shorter than the 1-hop link from it. (The property that no routes go through routers with willingness WILL_NEVER is retained. Examples below assume that all routers are equally willing, with none having willingness WILL_NEVER.)
当使用附加链路度量而不是跳数时，要求这些路由MPR不仅提供2跳路由，而且提供最小距离2跳路由就足够了。此外，路由器是对称的2-hop邻居，即使它是对称的1-hop邻居，只要它的2-hop路由比它的1-hop链路短。（不会保留任何路由通过自愿路由器的属性。下面的示例假设所有路由器都同样愿意，没有自愿路由器将永远不会。）
For example, consider the network in Figure 4. Numbers are metrics of links in the direction towards router A, away from router D. Router A must pick router B as a routing MPR, whereas for minimum hop count routing, it could alternatively pick router C. Note that the use of incoming neighbor metrics in this case follows the same reasoning as for the directionality of metrics in TC messages, as described in Section 5.4.
例如，考虑图4中的网络。数字是朝向路由器A、远离路由器D的链路的度量。路由器A必须选择路由器B作为路由MPR，而对于最小跳数路由，它也可以选择路由器C。请注意，在这种情况下，使用传入邻居度量遵循与TC消息中度量方向性相同的推理，如第5.4节所述。
2
A ----- B
| |
1 | | 1
| |
C ----- D
3
2
A ----- B
| |
1 | | 1
| |
C ----- D
3
Figure 4
图4
In Figure 5, where numbers are metrics of links in the direction towards router A and away from router C, router A must pick router B as a routing MPR, but for minimum hop count routing, it would not need to pick any MPRs.
在图5中，数字是朝向路由器A和远离路由器C的链路的度量，路由器A必须选择路由器B作为路由MPR，但对于最小跳数路由，它不需要选择任何MPR。
1
A - B
\ |
4 \ | 2
\|
C
1
A - B
\ |
4 \ | 2
\|
C
Figure 5
图5
In Figure 6, where numbers are metrics of links in the direction towards router A and away from routers D and E, router A must pick both routers B and C as routing MPRs, but for minimum hop count routing, it could pick either.
在图6中，数字是朝向路由器A和远离路由器D和E的链路的度量，路由器A必须选择路由器B和C作为路由MPR，但对于最小跳数路由，它可以选择其中一个。
D E
|\ /|
| \ 3 / |
| \ / |
1 | \/ | 1
| /\ |
| / \ |
| / 2 \ |
|/ \|
B C
\ |
\ /
3 \ / 2
\ /
A
D E
|\ /|
| \ 3 / |
| \ / |
1 | \/ | 1
| /\ |
| / \ |
| / 2 \ |
|/ \|
B C
\ |
\ /
3 \ / 2
\ /
A
Figure 6
图6
It is shown in Appendix A that selecting routing MPRs according to this definition and advertising only such links (plus knowledge of local links from HELLO messages) will result in selection of lowest total metric routes, even if all links (advertised or not) are considered in the definition of a shortest route.
附录A中显示，根据此定义选择路由MPR并仅公布此类链接（加上来自HELLO消息的本地链接知识）将导致选择最低总度量路由，即使在最短路由定义中考虑了所有链接（公布或未公布）。
However, the definition noted above as sufficient for routing MPR selection is not necessary. For example, consider the network in Figure 7, where numbers are metrics of links in the direction towards router A, away from other routers; the metrics from B to C and C to B are both assumed to be 2.
然而，上述定义对于路由MPR选择来说是足够的，这是不必要的。例如，考虑图7中的网络，其中数字是指向路由器A的链路的度量，远离其他路由器；从B到C和C到B的度量都假定为2。
1
A ----- B
\ /
4 \ / 2
\ /
C ----- D ----- E
3 5
1
A ----- B
\ /
4 \ / 2
\ /
C ----- D ----- E
3 5
Figure 7
图7
Using the above definition, A must pick both B and C as routing MPRs, in order to cover the symmetric 2-hop neighbors C and D, respectively. (C is a symmetric 2-hop neighbor because the route length via B is shorter than the 1-hop link.)
使用上述定义，A必须选择B和C作为路由mpr，以便分别覆盖对称的2跳邻居C和D。（C是对称的2跳邻居，因为通过B的路由长度比1跳链路短。）
However, A only needs to pick B as a routing MPR, because the only reason to pick C as a routing MPR would be so that C can advertise the link to A for routing -- to be used by, for example, E. However, A knows that no other router should use the link C to A in a shortest route because routing via B is shorter. So, if there is no need to advertise the link from C to A, then there is no reason for A to select C as a routing MPR.
然而，A只需要选择B作为路由MPR，因为选择C作为路由MPR的唯一原因是C可以公布到A的链路以进行路由——例如，供E使用。然而，A知道没有其他路由器应该在最短的路由中使用到A的链路C，因为通过B的路由更短。因此，如果不需要公布从C到A的链接，那么A没有理由选择C作为路由MPR。
This process of "thinning out" the routing MPR selection uses only local information from HELLO messages. Using any minimum distance algorithm, the router identifies shortest routes, whether one, two, or more hops, from all routers in its symmetric 2-hop neighborhood. It then selects as MPRs all symmetric 1-hop neighbors that are the last router (before the selecting router itself) on any such route. Where there is more than one shortest distance route from a router, only one such route is required. Alternative routes may be selected so as to minimize the number of last routers -- this is the equivalent to the selection of a minimal set of MPRs in the non-metric case.
这个“细化”路由MPR选择的过程只使用来自HELLO消息的本地信息。使用任何最小距离算法，路由器从其对称2跳邻居中的所有路由器识别最短路由，无论是一个、两个或更多跳。然后，它选择任何此类路由上的最后一个路由器（在选择路由器之前）的所有对称1跳邻居作为MPR。如果一个路由器有多条最短距离路由，则只需要一条这样的路由。可选择替代路由以最小化最后路由器的数量——这相当于在非度量情况下选择最小MPR集。
Note that this only removes routing MPRs whose selection can be directly seen to be unnecessary. Consequently, if (as is shown in Appendix A) the first approach creates minimum distance routes, then so does this process.
请注意，这仅删除可直接看到其选择不必要的路由MPR。因此，如果（如附录A所示）第一种方法产生最小距离路线，则该过程也会产生最小距离路线。
The examples in Figures 5 and 6 show that use of link metrics may require a router to select more routing MPRs than when not using metrics and even require a router to select routing MPRs when, without metrics, it would not need any routing MPRs. This may result in more, and larger, messages being generated and forwarded more often. Thus, the use of link metrics is not without cost, even excluding the cost of link metric signaling.
图5和图6中的示例表明，使用链路度量可能需要路由器选择比不使用度量时更多的路由MPR，甚至需要路由器选择路由MPR，如果没有度量，它将不需要任何路由MPR。这可能导致更频繁地生成和转发更多、更大的消息。因此，链路度量的使用并非没有成本，甚至不包括链路度量信令的成本。
These examples consider only single OLSRv2 interface routers. However, if routers have more than one OLSRv2 interface, then the process is unchanged; other than that, if there is more than one known metric between two routers (on different OLSRv2 interfaces), then, considering symmetric links only (as only these are used for routing) the smallest link metric, i.e., the neighbor metric, is used. There is no need to calculate routing MPRs per OLSRv2 interface. That requirement results from the consideration of flooding and the need to avoid certain "race" conditions, which are not relevant to routing, only to flooding.
这些示例只考虑单个OLSRv2接口路由器。但是，如果路由器具有多个OLSRv2接口，则该过程不变；除此之外，如果两个路由器之间（在不同的OLSRv2接口上）存在多个已知度量，则仅考虑对称链路（因为只有这些链路用于路由），使用最小链路度量，即邻居度量。不需要计算每个OLSRv2接口的路由MPR。该要求源于对洪水的考虑以及避免某些“竞争”条件的需要，这些条件与路由无关，只与洪水有关。
The required specification for routing MPR selection is in Section 18.5 (also using Section 18.3) of [RFC7181], which may use the example MPR selection algorithm in Appendix B of [RFC7181]. However, note that (as in [RFC3626]) each router can make its own independent choice of routing MPRs, and routing MPR selection algorithm, and still interoperate.
[RFC7181]第18.5节（也使用第18.3节）中规定了路由MPR选择所需的规范，可使用[RFC7181]附录B中的示例MPR选择算法。但是，请注意（如[RFC3626]中所述），每个路由器都可以独立选择路由MPR和路由MPR选择算法，并且仍然可以互操作。
It would be convenient if the two sets of flooding and routing MPRs were the same. This can be the case if all metrics are equal, but in general, for "good" sets of MPRs, they are not. (A reasonable definition of this is that there is no common minimal set of MPRs.) If metrics are asymmetrically valued (the two sets of MPRs use opposite direction metrics) or routers have multiple OLSRv2 interfaces (where routing MPRs can ignore this but flooding MPRs cannot), this is particularly unlikely. However, even using a symmetrically valued metric with a single OLSRv2 interface on each router, the ideal sets need not be equal, nor is one always a subset of the other. To show this, consider these examples, where all lettered routers are assumed equally willing to be MPRs, and numbers are bidirectional metrics for links.
如果两套泛洪和路由MPR是相同的，这将很方便。如果所有指标都相等，则可能出现这种情况，但通常情况下，对于“良好”的MPR集，它们并不相等。（合理的定义是不存在公共最小MPR集。）如果度量值不对称（两组MPR使用相反方向的度量值）或路由器具有多个OLSRv2接口（其中路由MPR可以忽略这一点，但泛洪MPR不能），则这种可能性尤其小。然而，即使在每个路由器上使用具有单个OLSRv2接口的对称值度量，理想集也不一定相等，也不一定总是另一个的子集。为了说明这一点，考虑这些例子，其中所有字母路由器都同样愿意成为MPR，并且数字是链路的双向度量。
In Figure 8, A does not require any flooding MPRs. However, A must select B as a routing MPR.
在图8中，A不需要任何泛洪MPR。但是，A必须选择B作为路由MPR。
1
A - B
\ |
4 \ | 2
\|
C
1
A - B
\ |
4 \ | 2
\|
C
Figure 8
图8
In Figure 9, A must select C and D as routing MPRs. However, A's minimal set of flooding MPRs is just B. In this example, the set of routing MPRs serves as a set of flooding MPRs, but a non-minimal one (although one that might be better, depending on the relative importance of number of MPRs and flooding link metrics).
在图9中，A必须选择C和D作为路由MPR。然而，A的最小泛洪MPR集只是B。在本例中，路由MPR集用作一组泛洪MPR，但不是最小MPR（尽管可能更好，这取决于MPR数量和泛洪链路度量的相对重要性）。
2
C --- E
/ /
1 / / 1
/ 4 /
A --- B
\ \
1 \ \ 1
\ \
D --- F
2
2
C --- E
/ /
1 / / 1
/ 4 /
A --- B
\ \
1 \ \ 1
\ \
D --- F
2
Figure 9
图9
However, this is not always the case. In Figure 10, A's set of routing MPRs must contain B but need not contain C. A's set of flooding MPRs need not contain B but must contain C. (In this case, flooding with A selecting B rather than C as a flooding MPR will reach D but in three hops rather than the minimum two that MPR flooding guarantees.)
然而，情况并非总是如此。在图10中，A的路由MPR集必须包含B，但不必包含C。A的泛洪MPR集不必包含B，但必须包含C。（在这种情况下，选择B而不是C作为泛洪MPR的泛洪将达到D，但只需三个跃点，而不是MPR泛洪保证的最小两个跃点。）
2 1
B - C - D
| /
1 | / 4
|/
A
2 1
B - C - D
| /
1 | / 4
|/
A
Figure 10
图10
An attacker can have an adverse impact on an OLSRv2 network by creating apparently valid messages that contain incorrect link metrics. This could take the form of influencing the choice of routes or, in some cases, producing routing loops. This is a more subtle, and likely to be less effective, attack than other forms of invalid message injection. These can add and remove other and more basic forms of network information, such as the existence of some routers and links.
攻击者可以通过创建包含不正确链接度量的明显有效消息，对OLSRv2网络产生不利影响。这可能会影响路由的选择，或者在某些情况下，产生路由循环。与其他形式的无效消息注入相比，这是一种更微妙的攻击，而且可能不太有效。这些可以添加和删除其他和更基本形式的网络信息，例如某些路由器和链路的存在。
As such, no significantly new security issues arose from the inclusion of metrics in OLSRv2. Defenses to the injection of invalid link metrics are the same as to other forms of invalid message injection, as discussed in the Security Considerations section of [RFC7181].
因此，在OLSRv2中包含指标不会产生显著的新安全问题。无效链路度量注入的防御措施与其他形式的无效消息注入的防御措施相同，如[RFC7181]的安全注意事项部分所述。
There are possible uses for link metrics in the creation of security countermeasures to prefer the use of links that have better security properties, including better availability, to those with poorer security properties. This, however, is beyond the scope of both this document and [RFC7181].
在创建安全对策时，链接度量可能会使用具有更好安全属性（包括更好的可用性）的链接，而不是具有较差安全属性的链接。然而，这超出了本文件和[RFC7181]的范围。
The authors would like to gratefully acknowledge the following people (listed alphabetically) for intense technical discussions, early reviews, and comments on the documents and its components: Brian Adamson (NRL), Alan Cullen (BAE Systems), Justin Dean (NRL), Ulrich Herberg (Fujitsu), Charles Perkins (Huawei), Stan Ratliff (Cisco), and Henning Rogge (FGAN).
作者衷心感谢以下人员（按字母顺序排列）对文件及其组件进行了深入的技术讨论、早期审查和评论：布赖恩·亚当森（NRL）、艾伦·卡伦（BAE Systems）、贾斯汀·迪恩（NRL）、乌尔里希·赫伯格（富士通）、查尔斯·珀金斯（华为）、斯坦·拉特利夫（思科），和亨宁·罗格（FGAN）。
Finally, the authors would like to express their gratitude to (listed alphabetically) Benoit Claise, Adrian Farrel, Stephen Farrell, and Suresh Krishnan for their reviews and comments on the later draft versions of this document.
最后，作者要感谢（按字母顺序排列）Benoit Claise、Adrian Farrell、Stephen Farrell和Suresh Krishnan对本文件后期草案版本的审查和评论。
[RFC2501] Corson, S. and J. Macker, "Mobile Ad hoc Networking (MANET): Routing Protocol Performance Issues and Evaluation Considerations", RFC 2501, January 1999.
[RFC2501]Corson，S.和J.Macker，“移动自组网（MANET）：路由协议性能问题和评估考虑”，RFC 2501，1999年1月。
[RFC3626] Clausen, T. and P. Jacquet, "Optimized Link State Routing Protocol (OLSR)", RFC 3626, October 2003.
[RFC3626]Clausen，T.和P.Jacquet，“优化链路状态路由协议（OLSR）”，RFC 3626，2003年10月。
[RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih, "Generalized Mobile Ad Hoc Network (MANET) Packet/Message Format", RFC 5444, February 2009.
[RFC5444]Clausen，T.，Dearlove，C.，Dean，J.，和C.Adjih，“通用移动自组网（MANET）数据包/消息格式”，RFC 54442009年2月。
[RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc Network (MANET) Neighborhood Discovery Protocol (NHDP)", RFC 6130, April 2011.
[RFC6130]Clausen，T.，Dearlove，C.，和J.Dean，“移动自组织网络（MANET）邻域发现协议（NHDP）”，RFC6130，2011年4月。
[RFC7181] Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg, "The Optimized Link State Routing Protocol Version 2", RFC 7181, April 2014.
[RFC7181]Clausen，T.，Dearlove，C.，Jacquet，P.，和U.Herberg，“优化链路状态路由协议版本2”，RFC 7181，2014年4月。
In order for routers to find and use shortest routes in a network while using the minimum reduced topology supported by OLSRv2 (that a router only advertises its MPR selectors in TC messages), routing MPR selection must result in the property that there are shortest routes with all intermediate routers being routing MPRs.
为了使路由器在使用OLSRv2支持的最小简化拓扑（即路由器仅在TC消息中公布其MPR选择器）的同时查找和使用网络中的最短路由，路由MPR选择必须导致存在所有中间路由器都是路由MPR的最短路由的属性。
This appendix uses the following terminology and assumptions:
本附录使用以下术语和假设：
o The network is a graph of nodes connected by arcs, where nodes correspond to routers with willingness not equal to WILL_NEVER (except possibly at the ends of routes). An arc corresponds to the set of symmetric links connecting those routers; the OLSRv2 interfaces used by those links are not relevant.
o 网络是由弧连接的节点图，其中节点对应于意愿不等于WILL_NEVER的路由器（可能在路由末端除外）。弧对应于连接这些路由器的一组对称链路；这些链接使用的OLSRv2接口不相关。
o Each arc has a metric in each direction, being the minimum of the corresponding link metrics in that direction, i.e., the corresponding neighbor metric. This metric must be positive.
o 每个弧在每个方向上都有一个度量，它是该方向上对应链路度量的最小值，即对应的邻居度量。该指标必须为正。
o A sequence of arcs joining two nodes is referred to as a path.
o 连接两个节点的弧序列称为路径。
o Node A is an MPR of node B if corresponding router A is a routing MPR of router B.
o 如果相应的路由器A是路由器B的路由MPR，则节点A是节点B的MPR。
The required property (of using shortest routes with reduced topology) is equivalent to the following property: for any pair of distinct nodes X and Z, there is a shortest path from X to Z, X - Y1 - Y2 - ... - Ym - Z such that Y1 is an MPR of Y2, ..., Ym is an MPR of Z. Call such a path a routable path, and call this property the routable path property.
所需的属性（使用简化拓扑的最短路径）等效于以下属性：对于任何一对不同的节点X和Z，存在从X到Z的最短路径，X-Y1-Y2-Ym-Z，使得Y1是Y2的MPR，…，Ym是Z的MPR。将这样的路径称为可路由路径，并将此属性称为可路由路径属性。
The required definition for a node X selecting MPRs is that for each distinct node Z from which there is a two-arc path, there is a shorter, or equally short, path that is either Z - Y - X where Y is an MPR of X or is the one-arc path Z - X. Note that the existence of locally known, shorter paths that have more than two arcs, which can be used to reduce the numbers of MPRs, is not considered here. (Such reductions are only when the remaining MPRs can be seen to retain all necessary shortest paths and therefore retain the required property.)
选择MPR的节点X所需的定义是，对于存在两条弧路径的每个不同节点Z，存在一条较短或同样短的路径，即Z-Y-X，其中Y是X的MPR，或是一条弧路径Z-X。请注意，存在局部已知的较短路径，该路径具有两条以上的弧，此处不考虑可用于减少MPR数量的。（只有当剩余的MPR能够保留所有必要的最短路径，从而保留所需的属性时，才会出现这种减少。）
Although this appendix is concerned with paths with minimum total metric, not number of arcs (hop count), it proceeds by induction on the number of arcs in a path. Although it considers minimum metric routes with a bounded number of arcs, it then allows that number of arcs to increase so that overall minimum metric paths, regardless of the number of arcs, are considered.
虽然本附录涉及的是具有最小总度量的路径，而不是弧数（跃点计数），但它通过归纳路径中的弧数来进行。尽管它考虑弧数有界的最小度量路径，但它允许弧数增加，以便考虑整体最小度量路径，而不考虑弧数。
Specifically, the routable path property is a corollary of the property that for all positive integers n and all distinct nodes X and Z, if there is any path from X to Z of n arcs or fewer, then there is a shortest path, from among those of n arcs or fewer, that is a routable path. This may be called the n-arc routable path property.
具体而言，可路由路径属性是该属性的推论，即对于所有正整数n和所有不同的节点X和Z，如果存在从X到Z的任意路径，且该路径的弧数为n或更少，则在这些弧数中存在最短路径，即可路由路径。这可以称为n弧可路由路径属性。
The n-arc routable path property is trivial for n = 1 and directly follows from the definition of the MPRs of Z for n = 2.
n-arc可路由路径属性对于n=1来说是微不足道的，并且直接遵循n=2时Z的MPR的定义。
Proceeding by induction, assuming the n-arc routable path property is true for n = k, consider the case that n = k+1.
通过归纳，假设n-弧可路由路径属性对于n=k是真的，考虑n＝k+ 1的情况。
Suppose that X - V1 - V2 - ... - Vk - Z is a shortest k+1 arc path from X to Z. We construct a path that has no more than k+1 arcs, has the same or shorter length (hence has the same, shortest, length considering only paths of up to k+1 arcs, by assumption), and is a routable path.
假设X-V1-V2-Vk-Z是从X到Z的最短k+1弧路径。我们构造的路径不超过k+1弧，具有相同或更短的长度（因此，假设仅考虑最多k+1弧的路径，具有相同、最短的长度），并且是一条可路由路径。
First, consider whether Vk is an MPR of Z. If it is not, then consider the two-arc path Vk-1 - Vk - Z. This can be replaced either by a one-arc path Vk-1 - Z or by a two-arc path Vk-1 - Wk - Z, where Wk is an MPR of Z, such that the metric from Vk-1 to Z by the replacement path is no longer. In the former case (replacement one-arc path), this now produces a path of length k, and the previous inductive step may be applied. In the latter case, we have replaced Vk by Wk, where Wk is an MPR of Z. Thus, we need only consider the case that Vk is an MPR of Z.
首先，考虑Vk是否是Z的MPR。如果不是，则考虑两个圆弧路径VK1-VK-Z。这可以由一个圆弧路径VK1-Z或由两个圆弧路径VK1-WK-Z代替，其中WK是Z的MPR，使得由替换路径从VK-1到Z的度量不再是。在前一种情况下（替换一条弧路径），现在产生长度为k的路径，并且可以应用前一个感应步骤。在后一种情况下，我们用WK代替了VK，WK是Z的MPR。因此，我们只需要考虑Vk是Z的MPR的情况。
We now apply the previous inductive step to the path X - V1 - ... - Vk-1 - Vk, replacing it by an equal length path X - W1 - ... Wm-1 - Vk, where m <= k, where this path is a routable path. Then, because Vk is an MPR of Z, the path X - W1 - ... - Wm-1 - Vk - Z is a routable path and demonstrates the n-arc routable path property for n = k+1.
现在我们将前面的归纳步骤应用于路径X-V1-Vk-1-Vk，将其替换为等长路径X-W1-。。。Wm-1-Vk，其中m<=k，其中该路径为可路由路径。然后，因为Vk是Z的MPR，路径X-W1-Wm-1-Vk-Z是一条可路由路径，它演示了n=k+1的n弧可路由路径属性。
This thus shows that for any distinct nodes X and Z, there is a routable path using the MPR-reduced topology from X to Z, i.e., that OLSRv2 finds minimum length paths (minimum total metric routes).
因此，这表明对于任何不同的节点X和Z，存在使用MPR简化拓扑从X到Z的可路由路径，即OLSRv2找到最小长度路径（最小总度量路由）。
Authors' Addresses
作者地址
Christopher Dearlove BAE Systems Advanced Technology Centre West Hanningfield Road Great Baddow, Chelmsford United Kingdom
克里斯托弗·迪尔洛夫英国切姆斯福德大巴德西汉宁菲尔德路BAE系统先进技术中心
Phone: +44 1245 242194
EMail: chris.dearlove@baesystems.com
URI: http://www.baesystems.com/
Phone: +44 1245 242194
EMail: chris.dearlove@baesystems.com
URI: http://www.baesystems.com/
Thomas Heide Clausen LIX, Ecole Polytechnique 91128 Palaiseau Cedex France
托马斯·海德·克劳森·利克斯，法国塞德克斯宫91128理工学院
Phone: +33 6 6058 9349
EMail: T.Clausen@computer.org
URI: http://www.thomasclausen.org/
Phone: +33 6 6058 9349
EMail: T.Clausen@computer.org
URI: http://www.thomasclausen.org/
Philippe Jacquet Alcatel-Lucent Bell Labs
菲利普雅克阿尔卡特朗讯贝尔实验室
Phone: +33 6 7337 1880
EMail: philippe.jacquet@alcatel-lucent.com
Phone: +33 6 7337 1880
EMail: philippe.jacquet@alcatel-lucent.com