Network Working Group M. Handley
Request for Comments: 5015 UCL
Category: Standards Track I. Kouvelas
T. Speakman
Cisco
L. Vicisano
Digital Fountain
October 2007
Network Working Group M. Handley
Request for Comments: 5015 UCL
Category: Standards Track I. Kouvelas
T. Speakman
Cisco
L. Vicisano
Digital Fountain
October 2007
Bidirectional Protocol Independent Multicast (BIDIR-PIM)
双向协议独立多播（BIDIR-PIM）
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。
Abstract
摘要
This document discusses Bidirectional PIM (BIDIR-PIM), a variant of PIM Sparse-Mode that builds bidirectional shared trees connecting multicast sources and receivers. Bidirectional trees are built using a fail-safe Designated Forwarder (DF) election mechanism operating on each link of a multicast topology. With the assistance of the DF, multicast data is natively forwarded from sources to the Rendezvous-Point (RP) and hence along the shared tree to receivers without requiring source-specific state. The DF election takes place at RP discovery time and provides the route to the RP, thus eliminating the requirement for data-driven protocol events.
本文档讨论双向PIM（BIDIR-PIM），这是PIM稀疏模式的一种变体，用于构建连接多播源和接收器的双向共享树。双向树是使用在多播拓扑的每个链路上运行的故障安全指定转发器（DF）选择机制构建的。在DF的帮助下，多播数据从源本地转发到集合点（RP），从而沿着共享树转发到接收器，而不需要特定于源的状态。DF选择在RP发现时进行，并提供到RP的路由，从而消除了数据驱动协议事件的要求。
Table of Contents
目录
1. Introduction ....................................................3
2. Terminology .....................................................4
2.1. Definitions ................................................4
2.2. Pseudocode Notation ........................................6
3. Protocol Specification ..........................................6
3.1. BIDIR-PIM Protocol State ...................................7
3.1.1. General Purpose State ...............................8
3.1.2. RPA State ...........................................8
3.1.3. Group State .........................................9
3.1.4. State Summarization Macros .........................10
3.2. PIM Neighbor Discovery ....................................11
3.3. Data Packet Forwarding Rules ..............................11
3.3.1. Upstream Forwarding at RP ..........................12
3.3.2. Source-Only Branches ...............................12
3.3.3. Directly Connected Sources .........................13
3.4. PIM Join/Prune Messages ...................................13
3.4.1. Receiving (*,G) Join/Prune Messages ................13
3.4.2. Sending Join/Prune Messages ........................16
3.5. Designated Forwarder (DF) Election ........................18
3.5.1. DF Requirements ....................................18
3.5.2. DF Election Description ............................19
3.5.2.1. Bootstrap Election ........................20
3.5.2.2. Loser Metric Changes ......................20
3.5.2.3. Winner Metric Changes .....................21
3.5.2.4. Winner Loses Path .........................22
3.5.2.5. Late Router Starting Up ...................22
3.5.2.6. Winner Dies ...............................22
3.5.3. Election Protocol Specification ....................22
3.5.3.1. Election State ............................22
3.5.3.2. Election Messages .........................23
3.5.3.3. Election Events ...........................24
3.5.3.4. Election Actions ..........................25
3.5.3.5. Election State Transitions ................26
3.5.4. Election Reliability Enhancements ..................30
3.5.5. Missing Pass .......................................30
3.5.6. Periodic Winner Announcement .......................30
3.6. Timers, Counters, and Constants ...........................31
3.7. BIDIR-PIM Packet Formats ..................................34
3.7.1. DF Election Packet Formats .........................34
3.7.2. Backoff Message ....................................36
3.7.3. Pass Message .......................................36
3.7.4. Bidirectional Capable PIM-Hello Option .............37
4. RP Discovery ...................................................37
5. Security Considerations ........................................38
5.1. Attacks Based on Forged Messages ..........................38
5.1.1. Election of an Incorrect DF ........................38
1. Introduction ....................................................3
2. Terminology .....................................................4
2.1. Definitions ................................................4
2.2. Pseudocode Notation ........................................6
3. Protocol Specification ..........................................6
3.1. BIDIR-PIM Protocol State ...................................7
3.1.1. General Purpose State ...............................8
3.1.2. RPA State ...........................................8
3.1.3. Group State .........................................9
3.1.4. State Summarization Macros .........................10
3.2. PIM Neighbor Discovery ....................................11
3.3. Data Packet Forwarding Rules ..............................11
3.3.1. Upstream Forwarding at RP ..........................12
3.3.2. Source-Only Branches ...............................12
3.3.3. Directly Connected Sources .........................13
3.4. PIM Join/Prune Messages ...................................13
3.4.1. Receiving (*,G) Join/Prune Messages ................13
3.4.2. Sending Join/Prune Messages ........................16
3.5. Designated Forwarder (DF) Election ........................18
3.5.1. DF Requirements ....................................18
3.5.2. DF Election Description ............................19
3.5.2.1. Bootstrap Election ........................20
3.5.2.2. Loser Metric Changes ......................20
3.5.2.3. Winner Metric Changes .....................21
3.5.2.4. Winner Loses Path .........................22
3.5.2.5. Late Router Starting Up ...................22
3.5.2.6. Winner Dies ...............................22
3.5.3. Election Protocol Specification ....................22
3.5.3.1. Election State ............................22
3.5.3.2. Election Messages .........................23
3.5.3.3. Election Events ...........................24
3.5.3.4. Election Actions ..........................25
3.5.3.5. Election State Transitions ................26
3.5.4. Election Reliability Enhancements ..................30
3.5.5. Missing Pass .......................................30
3.5.6. Periodic Winner Announcement .......................30
3.6. Timers, Counters, and Constants ...........................31
3.7. BIDIR-PIM Packet Formats ..................................34
3.7.1. DF Election Packet Formats .........................34
3.7.2. Backoff Message ....................................36
3.7.3. Pass Message .......................................36
3.7.4. Bidirectional Capable PIM-Hello Option .............37
4. RP Discovery ...................................................37
5. Security Considerations ........................................38
5.1. Attacks Based on Forged Messages ..........................38
5.1.1. Election of an Incorrect DF ........................38
5.1.2. Preventing Election Convergence ....................39
5.2. Non-Cryptographic Authentication Mechanisms ...............39
5.2.1. Basic Access Control ...............................39
5.3. Authentication Using IPsec ................................40
5.4. Denial-of-Service Attacks .................................40
6. IANA Considerations ............................................40
7. Acknowledgments ................................................40
8. Normative References ...........................................40
9. Informative References .........................................41
List of Figures
Figure 1. Downstream group per-interface state machine ............15
Figure 2. Upstream group state machine ............................17
Figure 3. Designated Forwarder election state machine .............27
5.1.2. Preventing Election Convergence ....................39
5.2. Non-Cryptographic Authentication Mechanisms ...............39
5.2.1. Basic Access Control ...............................39
5.3. Authentication Using IPsec ................................40
5.4. Denial-of-Service Attacks .................................40
6. IANA Considerations ............................................40
7. Acknowledgments ................................................40
8. Normative References ...........................................40
9. Informative References .........................................41
List of Figures
Figure 1. Downstream group per-interface state machine ............15
Figure 2. Upstream group state machine ............................17
Figure 3. Designated Forwarder election state machine .............27
This document specifies Bidirectional PIM (BIDIR-PIM), a variant of PIM Sparse-Mode (PIM-SM) [4] that builds bidirectional shared trees connecting multicast sources and receivers.
本文档指定了双向PIM（BIDIR-PIM），这是PIM稀疏模式（PIM-SM）[4]的一种变体，用于构建连接多播源和接收器的双向共享树。
PIM-SM constructs unidirectional shared trees that are used to forward data from senders to receivers of a multicast group. PIM-SM also allows the construction of source-specific trees, but this capability is not related to the protocol described in this document.
PIM-SM构造单向共享树，用于将数据从发送方转发到多播组的接收方。PIM-SM还允许构建特定于源代码的树，但此功能与本文档中描述的协议无关。
The shared tree for each multicast group is rooted at a multicast router called the Rendezvous Point (RP). Different multicast groups can use separate RPs within a PIM domain.
每个多播组的共享树都植根于称为集合点（RP）的多播路由器。不同的多播组可以在PIM域中使用不同的RPs。
In unidirectional PIM-SM, there are two possible methods for distributing data packets on the shared tree. These differ in the way packets are forwarded from a source to the RP:
在单向PIM-SM中，有两种可能的方法在共享树上分发数据包。数据包从源转发到RP的方式不同：
o Initially, when a source starts transmitting, its first hop router encapsulates data packets in special control messages (Registers) that are unicast to the RP. After reaching the RP, the packets are decapsulated and distributed on the shared tree.
o 最初，当源开始传输时，其第一跳路由器将数据包封装在特殊控制消息（寄存器）中，该消息单播到RP。到达RP后，数据包被解除封装并分布在共享树上。
o A transition from the above distribution mode can be made at a later stage. This is achieved by building source-specific state on all routers along the path between the source and the RP. This state is then used to natively forward packets from that source.
o 可在稍后阶段从上述分配模式过渡。这是通过在源和RP之间的路径上的所有路由器上建立特定于源的状态来实现的。然后使用该状态以本机方式转发来自该源的数据包。
Both of these mechanisms suffer from problems. Encapsulation results in significant processing, bandwidth, and delay overheads. Forwarding using source-specific state has additional protocol and memory requirements.
这两种机制都存在问题。封装会导致显著的处理、带宽和延迟开销。使用源特定状态的转发具有附加的协议和内存要求。
Bidirectional PIM dispenses with both encapsulation and source state by allowing packets to be natively forwarded from a source to the RP using shared tree state. In contrast to PIM-SM, this mode of forwarding does not require any data-driven events.
双向PIM通过允许使用共享树状态将数据包从源本地转发到RP，从而免除了封装和源状态。与PIM-SM不同，这种转发模式不需要任何数据驱动事件。
The protocol specification in this document assumes familiarity with the PIM-SM specification in [4]. Portions of the BIDIR-PIM protocol operation that are identical to that of PIM-SM are only defined by reference.
本文件中的协议规范假定熟悉[4]中的PIM-SM规范。BIDIR-PIM协议操作中与PIM-SM相同的部分仅通过引用定义。
In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and indicate requirement levels for compliant BIDIR-PIM implementations.
在本文件中，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[1]中的描述进行解释，并表示符合BIDIR-PIM实施的要求级别。
This specification uses a number of terms to refer to the roles of routers participating in BIDIR-PIM. The following terms have special significance for BIDIR-PIM:
本规范使用许多术语来表示参与BIDIR-PIM的路由器的角色。以下术语对BIDIR-PIM具有特殊意义：
Multicast Routing Information Base (MRIB) The multicast topology table, which is typically derived from the unicast routing table, or routing protocols such as Multiprotocol BGP (MBGP) [8] that carry multicast-specific topology information. It is used by PIM for establishing the RPF interface (used in the forwarding rules). In PIM-SM, the MRIB is also used to make decisions regarding where to forward Join/Prune messages, whereas in BIDIR-PIM, it is used as a source for routing metrics for the DF election process.
多播路由信息库（MRIB）：多播拓扑表，通常源自单播路由表，或承载多播特定拓扑信息的路由协议，如多协议BGP（MBGP）[8]。PIM使用它来建立RPF接口（在转发规则中使用）。在PIM-SM中，MRIB还用于决定在何处转发加入/删减消息，而在BIDIR-PIM中，它用作DF选举过程的路由度量的来源。
Rendezvous Point Address (RPA) An RPA is an address that is used as the root of the distribution tree for a range of multicast groups. The RPA must be routable from all routers in the PIM domain. The RPA does not need to correspond to an address for an interface of a real router. In this respect, BIDIR-PIM differs from PIM-SM, which requires an actual router to be configured as the Rendezvous Point (RP). Join messages from receivers for a BIDIR-PIM group propagate hop-by-hop towards the RPA.
集合点地址（RPA）RPA是用作一系列多播组的分发树的根的地址。RPA必须可从PIM域中的所有路由器路由。RPA不需要对应于实际路由器接口的地址。在这方面，BIDIR-PIM不同于PIM-SM，后者要求将实际路由器配置为集合点（RP）。加入来自BIDIR-PIM组接收器的消息，逐跳向RPA传播。
Rendezvous Point Link (RPL) An RPL for a particular RPA is the physical link to which the RPA belongs. In BIDIR-PIM, all multicast traffic to groups mapping to a specific RPA is forwarded on the RPL of that RPA. The RPL is special within a BIDIR-PIM domain as it is the only link on which
交会点链路（RPL）特定RPA的RPL是RPA所属的物理链路。在BIDIR-PIM中，映射到特定RPA的组的所有多播流量都在该RPA的RPL上转发。RPL在BIDIR-PIM域中是特殊的，因为它是唯一一个
a Designated Forwarder election does not take place (see DF definition below).
未进行指定货运代理选举（见下文DF定义）。
Upstream Towards the root (RPA) of the tree. The direction used by packets traveling from sources to the RPL.
向树根（RPA）上游。数据包从源传输到RPL的方向。
Downstream Away from the root of the tree. The direction on which packets travel from the RPL to receivers.
远离树根的下游。数据包从RPL传输到接收器的方向。
Designated Forwarder (DF) The protocol presented in this document is largely based on the concept of a Designated Forwarder (DF). A single DF exists for each RPA on every link within a BIDIR-PIM domain (this includes both multi-access and point-to-point links). The only exception is the RPL on which no DF exists. The DF is the router on the link with the best route to the RPA (determined by comparing MRIB provided metrics). A DF for a given RPA is in charge of forwarding downstream traffic onto its link, and forwarding upstream traffic from its link towards the RPL. It does this for all the bidirectional groups that map to the RPA. The DF on a link is also responsible for processing Join messages from downstream routers on the link as well as ensuring that packets are forwarded to local receivers (discovered through a local membership mechanism such as MLD [3] or IGMP [2]).
指定转发器（DF）本文件中提出的协议主要基于指定转发器（DF）的概念。BIDIR-PIM域内每个链路上的每个RPA都有一个DF（包括多址和点到点链路）。唯一的例外是不存在DF的RPL。DF是链路上的路由器，具有到RPA的最佳路由（通过比较MRIB提供的指标确定）。给定RPA的DF负责将下游流量转发到其链路上，并将上游流量从其链路转发到RPL。它对映射到RPA的所有双向组执行此操作。链路上的DF还负责处理来自链路上下游路由器的加入消息，并确保将数据包转发给本地接收器（通过本地成员机制（如MLD[3]或IGMP[2]）。
RPF Interface RPF stands for "Reverse Path Forwarding". The RPF Interface of a router with respect to an address is the interface that the MRIB indicates should be used to reach that address. In the case of a BIDIR-PIM multicast group, the RPF interface is determined by looking up the RPA in the MRIB. The RPF information determines the interface of the router that would be used to send packets towards the RPL for the group.
RPF接口RPF代表“反向路径转发”。路由器与地址相关的RPF接口是MRIB指示用于到达该地址的接口。对于BIDIR-PIM多播组，通过在MRIB中查找RPA来确定RPF接口。RPF信息确定将用于向组的RPL发送数据包的路由器接口。
RPF Neighbor The RPF Neighbor of a router with respect to an address is the neighbor that the MRIB indicates should be used to reach that address. Note that in BIDIR-PIM, the RPF neighbor for a group is not necessarily the router on the RPF interface that Join messages for that group would be directed to (Join messages are only directed to the DF on the RPF interface for the group).
RPF邻居路由器相对于地址的RPF邻居是MRIB指示应用于到达该地址的邻居。请注意，在BIDIR-PIM中，组的RPF邻居不一定是RPF接口上的路由器，该组的加入消息将定向到该路由器（加入消息仅定向到该组RPF接口上的DF）。
Tree Information Base (TIB) This is the collection of state at a PIM router that has been created by receiving PIM Join/Prune messages, PIM DF election messages, and IGMP or MLD information from local hosts. It
树信息库（TIB）这是通过从本地主机接收PIM加入/删除消息、PIM DF选择消息和IGMP或MLD信息而创建的PIM路由器上的状态集合。信息技术
essentially stores the state of all multicast distribution trees at that router.
本质上存储该路由器上所有多播分发树的状态。
Multicast Forwarding Information Base (MFIB) The TIB holds all the state that is necessary to forward multicast packets at a router. However, although this specification defines forwarding in terms of the TIB, to actually forward packets using the TIB is very inefficient. Instead, a real router implementation will normally build an efficient MFIB from the TIB state to perform forwarding. How this is done is implementation-specific, and is not discussed in this document.
多播转发信息库（MFIB）TIB保存在路由器上转发多播数据包所需的所有状态。然而，尽管该规范根据TIB定义了转发，但使用TIB实际转发数据包是非常低效的。相反，真正的路由器实现通常会从TIB状态构建一个高效的MFIB来执行转发。如何做到这一点是特定于实现的，本文档中没有讨论。
We use set notation in several places in this specification.
在本规范中，我们在几个地方使用集合表示法。
A (+) B is the union of two sets, A and B.
A（+）B是两个集合A和B的并集。
A (-) B is the elements of set A that are not in set B.
A（-）B是集合A中不在集合B中的元素。
NULL is the empty set or list.
NULL是空的集合或列表。
In addition, we use C-like syntax:
此外，我们使用类似C的语法：
= denotes assignment of a variable.
=表示变量的赋值。
== denotes a comparison for equality.
==表示相等的比较。
!= denotes a comparison for inequality.
!= 表示不等式的比较。
Braces { and } are used for grouping.
大括号{和}用于分组。
The specification of BIDIR-PIM is broken into several parts:
BIDIR-PIM的规范分为几个部分：
o Section 3.1 details the protocol state stored.
o 第3.1节详细说明了存储的协议状态。
o Section 3.2 defines the BIDIR-PIM extensions to the PIM-SM [4] neighbor discovery mechanism.
o 第3.2节定义了PIM-SM[4]邻居发现机制的BIDIR-PIM扩展。
o Section 3.3 specifies the data packet forwarding rules.
o 第3.3节规定了数据包转发规则。
o Section 3.4 specifies the BIDIR-PIM Join/Prune generation and processing rules.
o 第3.4节规定了BIDIR-PIM连接/修剪生成和处理规则。
o Section 3.5 specifies the Designated Forwarder (DF) election.
o 第3.5节规定了指定货代（DF）的选择。
o Section 3.7 specifies the PIM packet formats.
o 第3.7节规定了PIM数据包格式。
o Section 3.6 summarizes BIDIR-PIM timers and gives their default values.
o 第3.6节总结了BIDIR-PIM定时器，并给出了其默认值。
This section specifies all the protocol state that a BIDIR-PIM implementation should maintain in order to function correctly. We term this state the Tree Information Base or TIB, as it holds the state of all the multicast distribution trees at this router. In this specification, we define PIM mechanisms in terms of the TIB. However, only a very simple implementation would actually implement packet forwarding operations in terms of this state. Most implementations will use this state to build a multicast forwarding table, which would then be updated when the relevant state in the TIB changes.
本节指定BIDIR-PIM实现为正常运行应保持的所有协议状态。我们将此状态称为树信息库或TIB，因为它保存此路由器上所有多播分发树的状态。在本规范中，我们根据TIB定义PIM机制。然而，只有一个非常简单的实现才能真正实现这种状态下的包转发操作。大多数实现将使用此状态来构建多播转发表，当TIB中的相关状态发生更改时，将更新该表。
Although we specify precisely the state to be kept, this does not mean that an implementation of BIDIR-PIM needs to hold the state in this form. This is actually an abstract state definition, which is needed in order to specify the router's behavior. A BIDIR-PIM implementation is free to hold whatever internal state it requires, and will still be conformant with this specification so long as it results in the same externally visible protocol behavior as an abstract router that holds the following state.
尽管我们精确地指定了要保持的状态，但这并不意味着BIDIR-PIM的实现需要以这种形式保持状态。这实际上是一个抽象的状态定义，需要它来指定路由器的行为。BIDIR-PIM实现可以自由地保持其所需的任何内部状态，并且只要其产生与保持以下状态的抽象路由器相同的外部可见协议行为，则仍然符合本规范。
We divide TIB state into two sections:
我们将TIB状态分为两部分：
RPA state State that maintains the DF election information for each RPA.
RPA状态维护每个RPA的DF选择信息的状态。
Group state State that maintains a group-specific tree for groups that map to a given RPA.
组状态为映射到给定RPA的组维护组特定树的状态。
The state that should be kept is described below. Of course, implementations will only maintain state when it is relevant to forwarding operations - for example, the "NoInfo" state might be assumed from the lack of other state information, rather than being held explicitly.
应保持的状态如下所述。当然，实现只会在与转发操作相关时维护状态——例如，“NoInfo”状态可能是由于缺少其他状态信息而假定的，而不是显式地保持。
A router holds the following state that is not specific to an RPA or group:
路由器具有以下非特定于RPA或组的状态：
Neighbor State:
邻国：
For each neighbor:
对于每个邻居：
o Neighbor's Gen ID
o 邻居的Gen ID
o Neighbor liveness timer (NLT)
o 邻居活跃度计时器（NLT）
o Other information from neighbor's Hello
o 邻居的其他信息你好
For more information on Hello information, look at Section 3.2 as well as the PIM-SM specification in [4].
有关Hello信息的更多信息，请参阅第3.2节以及[4]中的PIM-SM规范。
A router maintains a multicast-group to RPA mapping, which is built through static configuration or by using an automatic RP discovery mechanism like BSR or AUTO-RP (see Section 4). For each BIDIR-PIM RPA, a router holds the following state:
路由器维护多播组到RPA的映射，该映射通过静态配置或使用自动RP发现机制（如BSR或AUTO-RP）构建（参见第4节）。对于每个BIDIR-PIM RPA，路由器保持以下状态：
o RPA (actual address)
o RPA（实际地址）
Designated Forwarder (DF) State:
Designated Forwarder (DF) State:translate error, please retry
For each router interface:
对于每个路由器接口：
Acting DF information:
代理DF信息：
o DF IP Address
o DF IP地址
o DF metric
o 测向度量
Election information:
选举资料：
o Election State
o 选举国
o DF election-Timer (DFT)
o DF选择计时器（DFT）
o Message-Count (MC)
o 消息计数（MC）
Current best offer:
当前最佳报价：
o IP address of best offering router
o 最佳路由器的IP地址
o Best offering router metric
o 最佳路由器指标
Designated Forwarder state is described in Section 3.5.
第3.5节描述了指定的转发器状态。
For every group G, a router keeps the following state:
对于每个G组，路由器保持以下状态：
Group state:
组状态：
For each interface:
对于每个接口：
Local Membership:
本地会员：
o State: One of {"NoInfo", "Include"}
o 国家{“NoInfo”，“Include”}之一
PIM Join/Prune State:
PIM连接/删除状态：
o State: One of {"NoInfo" (NI), "Join" (J), "PrunePending" (PP)}
o 国家：其中一个{“NoInfo”（NI），“Join”（J），“PrunePending”（PP）}
o PrunePendingTimer (PPT)
o PrunePendingTimer（PPT）
o Join/Prune Expiry Timer (ET)
o 加入/删除到期计时器（ET）
Not interface specific:
不特定于接口：
o Upstream Join/Prune Timer (JT)
o 上游连接/删除计时器（JT）
o Last RPA Used
o 最后使用的RPA
Local membership is the result of the local membership mechanism (such as IGMP [2]) running on that interface. This information is used by the pim_include(*,G) macro described in Section 3.1.4.
本地成员身份是在该接口上运行的本地成员身份机制（如IGMP[2]）的结果。该信息由第3.1.4节所述的pim_include（*，G）宏使用。
PIM Join/Prune state is the result of receiving PIM (*,G) Join/Prune messages on this interface, and is specified in Section 3.4.1. The state is used by the macros that calculate the outgoing interface list in Section 3.1.4, and in the JoinDesired(G) macro (defined in Section 3.4.2) that is used in deciding whether a Join(*,G) should be sent upstream.
PIM加入/删减状态是在该接口上接收PIM（*，G）加入/删减消息的结果，在第3.4.1节中有规定。该状态由第3.1.4节中计算传出接口列表的宏和用于决定是否应向上游发送连接（*，G）的JoinDesired（G）宏（定义见第3.4.2节）使用。
The upstream Join/Prune timer is used to send out periodic Join(*,G) messages, and to override Prune(*,G) messages from peers on an upstream LAN interface.
上游加入/修剪计时器用于发送定期加入（*，G）消息，并覆盖上游LAN接口上对等方的修剪（*，G）消息。
The last RPA used must be stored because if the group to RPA mapping changes (see RP Set changes in [4]), then state must be torn down and rebuilt for groups whose RPA changes.
必须存储最后使用的RPA，因为如果组到RPA的映射发生更改（请参见[4]中的RP集更改），则必须为RPA发生更改的组拆除并重建状态。
Using this state, we define the following "macro" definitions that we will use in the descriptions of the state machines and pseudocode in the following sections.
使用此状态，我们将定义以下“宏”定义，我们将在以下部分的状态机和伪代码描述中使用这些定义。
olist(G) =
RPF_interface(RPA(G)) (+) joins(G) (+) pim_include(G)
olist(G) =
RPF_interface(RPA(G)) (+) joins(G) (+) pim_include(G)
RPF_interface(RPA) is the interface the MRIB indicates would be used to route packets to RPA. The olist(G) is the list of interfaces on which packets to group G must be forwarded.
RPF_接口（RPA）是MRIB指示用于将数据包路由到RPA的接口。olist（G）是必须将数据包转发到组G的接口列表。
The macro pim_include(G) indicates the interfaces to which traffic might be forwarded because of hosts that are local members on that interface.
宏pim_include（G）指示由于主机是该接口上的本地成员而可能将流量转发到的接口。
pim_include(G) =
{ all interfaces I such that:
I_am_DF(RPA(G),I) AND local_receiver_include(G,I) }
pim_include(G) =
{ all interfaces I such that:
I_am_DF(RPA(G),I) AND local_receiver_include(G,I) }
The clause "I_am_DF(RPA,I)" is TRUE if the router is in the Win or Backoff states in the DF election state machine (described in Section 3.5) for the given RPA on interface I. Otherwise, it is FALSE.
如果路由器在接口I上给定RPA的DF选择状态机（如第3.5节所述）中处于赢或退避状态，则“I_am_DF（RPA，I）”条款为真。否则为假。
The clause "local_receiver_include(G,I)" is true if the IGMP module, MLD module, or other local membership mechanism has determined that there are local members on interface I that desire to receive traffic sent to group G.
如果IGMP模块、MLD模块或其他本地成员机制已确定接口I上存在希望接收发送到组G的流量的本地成员，则“本地接收器包括（G，I）”条款为真。
The set "joins(G)" is the set of all interfaces on which the router has received (*,G) Joins:
集合“连接（G）”是路由器接收（*，G）连接的所有接口的集合：
joins(G) =
{ all interfaces I such that
I_am_DF(RPA(G),I) AND
DownstreamJPState(G,I) is either Joined or PrunePending }
joins(G) =
{ all interfaces I such that
I_am_DF(RPA(G),I) AND
DownstreamJPState(G,I) is either Joined or PrunePending }
DownstreamJPState(G,I) is the state of the finite state machine in Section 3.4.1.
下游状态（G，I）是第3.4.1节中有限状态机的状态。
RPF_DF(RPA) is the neighbor that Join messages must be sent to in order to build the group shared tree rooted at the RPL for the given RPA. This is the Designated-Forwarder on the RPF_interface(RPA).
RPF_DF（RPA）是连接消息必须发送到的邻居，以便为给定RPA构建以RPL为根的组共享树。这是RPF_接口（RPA）上的指定转发器。
PIM routers exchange PIM-Hello messages with their neighboring PIM routers. These messages are used to update the Neighbor State described in Section 3.1. The procedures for generating and processing Hello messages as well as maintaining Neighbor State are specified in the PIM-SM [4] documentation.
PIM路由器与其相邻的PIM路由器交换PIM Hello消息。这些消息用于更新第3.1节所述的邻居状态。PIM-SM[4]文档中规定了生成和处理Hello消息以及维护邻居状态的过程。
BIDIR-PIM introduces the Bidirectional Capable PIM-Hello option that MUST be included in all Hello messages from a BIDIR-PIM capable router. The Bidirectional Capable option advertises the router's ability to participate in the BIDIR-PIM protocol. The format of the Bidirectional Capable option is described in Section 3.7.
BIDIR-PIM引入了双向PIM Hello选项，该选项必须包含在所有来自BIDIR-PIM路由器的Hello消息中。双向功能选项宣传路由器参与BIDIR-PIM协议的能力。第3.7节描述了双向功能选项的格式。
If a BIDIR-PIM router receives a PIM-Hello message that does not contain the Bidirectional Capable option from one of its neighbors, the error must be logged to the router administrator in a rate-limited manner.
如果BIDIR-PIM路由器从其一个邻居接收到不包含双向功能选项的PIM Hello消息，则必须以速率受限的方式将错误记录给路由器管理员。
For groups mapping to a given RPA, the following responsibilities are uniquely assigned to the DF for that RPA on each link:
对于映射到给定RPA的组，每个链路上该RPA的DF将唯一分配以下职责：
o The DF is the only router that forwards packets traveling downstream onto the link.
o DF是唯一一个将下行数据包转发到链路上的路由器。
o The DF is the only router that picks-up upstream traveling packets off the link to forward towards the RPL.
o DF是唯一一个从链路上拾取上行移动数据包并向RPL转发的路由器。
Non-DF routers on a link, which use that link as their RPF interface to reach the RPA, may perform the following forwarding actions for bidirectional groups:
链路上的非DF路由器使用该链路作为其RPF接口来到达RPA，可对双向组执行以下转发操作：
o Forward packets from the link towards downstream receivers.
o 将数据包从链路转发到下游接收器。
o Forward packets from downstream sources onto the link (provided they are the DF for the downstream link from which the packet was picked-up).
o 将数据包从下游源转发到链路上（前提是它们是从中拾取数据包的下游链路的DF）。
The BIDIR-PIM packet forwarding rules are defined below in pseudocode.
BIDIR-PIM数据包转发规则在下面的伪代码中定义。
iif is the incoming interface of the packet. G is the destination address of the packet (group address). RPA is the Rendezvous Point Address for this group.
iif是数据包的传入接口。G是数据包的目标地址（组地址）。RPA是此组的集合点地址。
First we check to see whether the packet should be accepted based on TIB state and the interface that the packet arrived on. A packet is accepted if it arrives on the RPF interface to reach the RPA (downstream traveling packet) or if the router is the DF on the interface the packet arrives (upstream traveling packet).
首先，我们根据TIB状态和数据包到达的接口检查数据包是否应该被接受。如果数据包到达RPF接口以到达RPA（下游移动数据包），或者如果路由器是数据包到达的接口（上游移动数据包）上的DF，则接受该数据包。
If the packet should be forwarded, we build an outgoing interface list for the packet.
如果包应该被转发，我们为包建立一个传出接口列表。
Finally, we remove the incoming interface from the outgoing interface list we've created, and if the resulting outgoing interface list is not empty, we forward the packet out of those interfaces.
最后，我们从我们创建的传出接口列表中删除传入接口，如果生成的传出接口列表不是空的，我们将数据包转发出这些接口。
On receipt of data to G on interface iif:
if( iif == RPF_interface(RPA) || I_am_DF(RPA,iif) ) {
oiflist = olist(G) (-) iif
forward packet on all interfaces in oiflist
}
On receipt of data to G on interface iif:
if( iif == RPF_interface(RPA) || I_am_DF(RPA,iif) ) {
oiflist = olist(G) (-) iif
forward packet on all interfaces in oiflist
}
When configuring a BIDIR-PIM domain, it is possible to assign the Rendezvous Point Address (RPA) such that it does not belong to a physical box but instead is simply a routable address. Routers that have interfaces on the RPL that the RPA belongs to will upstream forward traffic onto the link. Joins from receivers in the domain will propagate hop-by-hop till they reach one of the routers connected to the RPL where they will terminate (as there will be no DF elected on the RPL).
配置BIDIR-PIM域时，可以分配集合点地址（RPA），使其不属于物理框，而只是一个可路由地址。在RPA所属的RPL上具有接口的路由器将向上游将流量转发到链路上。来自域中接收器的连接将逐跳传播，直到它们到达连接到RPL的其中一个路由器，在那里它们将终止（因为在RPL上不会选择DF）。
If instead the administrator chooses to configure the RPA to be the address of a physical interface of a specific router, then nothing changes. That router must still upstream forward traffic on to the RPL and behave no differently than any other router with an interface on the RPL.
如果管理员选择将RPA配置为特定路由器的物理接口地址，则不会发生任何更改。该路由器必须仍然向上游转发RPL上的流量，并且其行为与RPL上具有接口的任何其他路由器没有任何区别。
To configure a BIDIR-PIM network to operate in a mode similar to that of PIM-SM where a single router (the RP) is acting as the root of the distribution tree, the RPA can be configured to be the loopback interface of a router.
为了将BIDIR-PIM网络配置为在类似于PIM-SM的模式下运行，其中单个路由器（RP）充当分发树的根，可以将RPA配置为路由器的环回接口。
Source-only branches of the distribution tree for a group G are branches that do not lead to any receivers, but that are used to forward packets traveling upstream from sources towards the RPL. Routers along source-only branches only have the RPF interface to the RPA in their olist for G, and hence do not need to maintain any group
组G的分发树的仅源分支是不通向任何接收器的分支，但用于转发从源向RPL上游移动的数据包。仅源分支上的路由器在其olist for G中只具有与RPA的RPF接口，因此不需要维护任何组
specific state. Upstream forwarding can be performed using only RPA specific state. An implementation may decide to maintain group state for source-only branches for accounting or performance reasons. However, doing so requires data-driven events (to discover the groups with active sources), thus sacrificing one of the main benefits of BIDIR-PIM.
特定状态。只能使用RPA特定状态执行上行转发。出于会计或性能原因，实现可能决定维护仅源分支的组状态。但是，这样做需要数据驱动的事件（以发现具有活动源的组），因此牺牲了BIDIR-PIM的主要优点之一。
A major advantage of using a Designated Forwarder in BIDIR-PIM compared to PIM-SM is that special treatment is no longer required for sources that are directly connected to a router. Data from such sources does not need to be differentiated from other multicast traffic and will automatically be picked up by the DF and forwarded upstream. This removes the need for performing a directly-connected-source check for data to groups that do not have existing state.
与PIM-SM相比，在BIDIR-PIM中使用指定转发器的一个主要优点是，直接连接到路由器的源不再需要特殊处理。来自这些来源的数据不需要与其他多播流量区分开来，DF将自动拾取并向上游转发。这样就不需要对不具有现有状态的组的数据执行直接连接的源代码检查。
BIDIR-PIM Join/Prune messages are used to construct group-specific distribution trees between receivers and the RPL. Joins are originated by last-hop routers that are elected as the DF on an interface with directly connected receivers. The Joins propagate hop-by-hop towards the RPA until they reach a router connected to the RPL.
BIDIR-PIM连接/删除消息用于在接收方和RPL之间构建特定于组的分发树。连接由最后一跳路由器发起，该路由器在与直接连接的接收器的接口上被选为DF。连接逐跳向RPA传播，直到它们到达连接到RPL的路由器。
A BIDIR-PIM Join/Prune message consists of a list of Joined and Pruned Groups. When processing a received Join/Prune message, each Joined or Pruned Group is effectively considered individually by applying the following state machines. When considering a Join/Prune message whose PIM Destination field addresses this router, (*,G) Joins and Prunes can affect the downstream state machine. When considering a Join/Prune message whose PIM Destination field addresses another router, most Join or Prune entries could affect the upstream state machine.
BIDIR-PIM加入/删减消息由已加入和删减组的列表组成。在处理接收到的加入/删减消息时，通过应用以下状态机，每个加入或删减的组都被有效地单独考虑。当考虑其PIM目的地字段寻址此路由器的加入/删减消息时，（*，G）加入和删减会影响下游状态机。当考虑其PIM目的地字段寻址另一路由器的加入/删减消息时，大多数加入或删减条目可能会影响上游状态机。
When a router receives a Join(*,G) or Prune(*,G), it MUST first check to see whether the RP address in the message matches RPA(G) (the router's idea of what the Rendezvous Point Address is). If the RP address in the message does not match RPA(G), the Join or Prune MUST be silently dropped.
当路由器收到连接（*，G）或删除（*，G）时，它必须首先检查消息中的RP地址是否与RPA（G）（路由器对集合点地址的理解）匹配。如果消息中的RP地址与RPA（G）不匹配，则必须以静默方式删除联接或修剪。
If a router has no RPA information for the group (e.g., has not recently received a BSR message), then it MAY choose to accept Join(*,G) or Prune(*,G) and treat the RP address in the message as
如果路由器没有组的RPA信息（例如，最近没有收到BSR消息），那么它可以选择接受加入（*，g）或删减（*，g），并将消息中的RP地址视为
RPA(G). If the newly discovered RPA did not previously exist for any other group, a DF election has to be initiated.
RPA（G）。如果新发现的RPA之前不存在于任何其他团体，则必须启动DF选举。
Note that a router will process a Join(*,G) targeted to itself even if it is not the DF for RP(G) on the interface on which the message was received. This is an optimisation to eliminate the Join delay of one Join period (t_periodic) in the case where a new DF processes the received Pass and Join messages in reverse order. The BIDIR-PIM forwarding logic will ensure that data packets are not forwarded on such an interface while the router is not the DF (unless it is the RPF interface towards the RPA).
请注意，路由器将处理以自身为目标的连接（*，G），即使它不是接收消息的接口上RP（G）的DF。这是一种优化，用于在新DF以相反顺序处理接收到的Pass和Join消息的情况下，消除一个连接周期（t_周期）的连接延迟。BIDIR-PIM转发逻辑将确保当路由器不是DF时，数据包不会在此类接口上转发（除非它是指向RPA的RPF接口）。
The per-interface state machine for receiving (*,G) Join/Prune Messages is given below. There are three states:
下面给出了用于接收（*，G）连接/删除消息的每个接口状态机。有三个州：
NoInfo (NI) The interface has no (*,G) Join state and no timers running.
NoInfo（NI）接口没有（*，G）连接状态，也没有运行计时器。
Join (J) The interface has (*,G) Join state. If the router is the DF on this interface (I_am_DF(RPA(G),I) is TRUE), the Join state will cause us to forward packets destined for G on this interface.
Join（J）接口具有（*，G）连接状态。如果路由器是这个接口上的DF（I_am_DF（RPA（G），I）为TRUE），那么连接状态将导致我们转发这个接口上目的地为G的数据包。
PrunePending (PP) The router has received a Prune(*,G) on this interface from a downstream neighbor and is waiting to see whether the Prune will be overridden by another downstream router. For forwarding purposes, the PrunePending state functions exactly like the Join state.
剪枝结束（PP）路由器已在此接口上收到来自下游邻居的剪枝（*，G），并等待查看该剪枝是否将被另一个下游路由器覆盖。出于转发目的，prunepend状态的功能与Join状态完全相同。
In addition, the state machine uses two timers:
此外，状态机使用两个计时器：
ExpiryTimer (ET) This timer is restarted when a valid Join(*,G) is received. Expiry of the ExpiryTimer causes the interface state to revert to NoInfo for this group.
ExpiryTimer（ET）当接收到有效的连接（*，G）时，此计时器将重新启动。ExpiryTimer的过期将导致此组的接口状态恢复为NoInfo。
PrunePendingTimer (PPT) This timer is set when a valid Prune(*,G) is received. Expiry of the PrunePendingTimer causes the interface state to revert to NoInfo for this group.
PrunePendingTimer（PPT）此计时器在收到有效的修剪（*，G）时设置。PrunePendingTimer的过期将导致此组的接口状态恢复为NoInfo。
Figure 1: Downstream group per-interface state machine in tabular form
图1：表格形式的每个接口状态机的下游组
+---------------++---------------------------------------------------+
| || Prev State |
|Event ++---------------+-----------------+-----------------+
| || NoInfo (NI) | Join (J) | PrunePending |
| || | | (PP) |
+---------------++---------------+-----------------+-----------------+
| || -> J state | -> J state | -> J state |
|Receive || start Expiry | restart Expiry | restart Expiry |
|Join(*,G) || Timer | Timer | Timer; stop |
| || | | PrunePending- |
| || | | Timer |
+---------------++---------------+-----------------+-----------------+
|Receive || - | -> PP state | -> PP state |
|Prune(*,G) || | start Prune- | |
| || | PendingTimer | |
+---------------++---------------+-----------------+-----------------+
|PrunePending- || - | - | -> NI state |
|Timer Expires || | | Send Prune- |
| || | | Echo(*,G) |
+---------------++---------------+-----------------+-----------------+
|Expiry Timer || - | -> NI state | -> NI state |
|Expires || | | |
+---------------++---------------+-----------------+-----------------+
|Stop Being DF || - | -> NI state | -> NI state |
|on I || | | |
+---------------++---------------+-----------------+-----------------+
+---------------++---------------------------------------------------+
| || Prev State |
|Event ++---------------+-----------------+-----------------+
| || NoInfo (NI) | Join (J) | PrunePending |
| || | | (PP) |
+---------------++---------------+-----------------+-----------------+
| || -> J state | -> J state | -> J state |
|Receive || start Expiry | restart Expiry | restart Expiry |
|Join(*,G) || Timer | Timer | Timer; stop |
| || | | PrunePending- |
| || | | Timer |
+---------------++---------------+-----------------+-----------------+
|Receive || - | -> PP state | -> PP state |
|Prune(*,G) || | start Prune- | |
| || | PendingTimer | |
+---------------++---------------+-----------------+-----------------+
|PrunePending- || - | - | -> NI state |
|Timer Expires || | | Send Prune- |
| || | | Echo(*,G) |
+---------------++---------------+-----------------+-----------------+
|Expiry Timer || - | -> NI state | -> NI state |
|Expires || | | |
+---------------++---------------+-----------------+-----------------+
|Stop Being DF || - | -> NI state | -> NI state |
|on I || | | |
+---------------++---------------+-----------------+-----------------+
The transition events "Receive Join(*,G)" and "Receive Prune(*,G)" imply receiving a Join or Prune targeted to this router's address on the received interface. If the destination address is not correct, these state transitions in this state machine must not occur, although seeing such a packet may cause state transitions in other state machines.
转换事件“Receive Join（*，G）”和“Receive Prune（*，G）”意味着在接收到的接口上接收针对该路由器地址的连接或修剪。如果目标地址不正确，则此状态机中的这些状态转换不得发生，尽管看到这样的数据包可能会导致其他状态机中的状态转换。
On unnumbered interfaces on point-to-point links, the router's address should be the same as the source address it chose for the Hello packet it sent over that interface. However, on point-to-point links, we also RECOMMEND that PIM messages with a destination address of all zeros also be accepted.
在点到点链路上的无编号接口上，路由器的地址应与它为通过该接口发送的Hello数据包选择的源地址相同。但是，在点到点链路上，我们还建议也接受目标地址为全零的PIM消息。
The transition event "Stop Being DF" implies a DF re-election taking place on this router interface for RPA(G) and the router changing status from being the active DF to being a non-DF router (the value of the I_am_DF macro changing to FALSE).
转换事件“Stop BE DF”意味着RPA（G）和路由器状态从活动DF更改为非DF路由器（I_am_DF宏的值更改为FALSE）的路由器接口上发生的DF重新选择。
When ExpiryTimer is started or restarted, it is set to the HoldTime from the Join/Prune message that triggered the timer.
当ExpiryTimer启动或重新启动时，它会从触发计时器的Join/Prune消息中设置为HoldTime。
When PrunePendingTimer is started, it is set to the J/P_Override_Interval if the router has more than one neighbor on that interface; otherwise, it is set to zero causing it to expire immediately.
当PrunePendingTimer启动时，如果路由器在该接口上有多个邻居，则将其设置为J/P_覆盖_间隔；否则，它将设置为零，导致它立即过期。
The action "Send PruneEcho(*,G)" is triggered when the router stops forwarding on an interface as a result of a Prune. A PruneEcho(*,G) is simply a Prune(*,G) message sent by the upstream router to itself on a LAN. Its purpose is to add additional reliability so that if a Prune that should have been overridden by another router is lost locally on the LAN, then the PruneEcho may be received and cause the override to happen. A PruneEcho(*,G) need not be sent when the router has only one neighbor on the link.
当路由器由于修剪而停止在接口上的转发时，将触发操作“发送prueecho（*，G）”。PruneEcho（*，G）只是上游路由器在局域网上发送给自身的一条Prune（*，G）消息。它的目的是增加额外的可靠性，以便如果本应由另一路由器覆盖的修剪在LAN上本地丢失，则可能会接收到该修剪并导致发生覆盖。当路由器在链路上只有一个邻居时，不需要发送prueecho（*，G）。
The downstream per-interface state machines described above hold Join state from downstream PIM routers. This state then determines whether a router needs to propagate a Join(*,G) upstream towards the RPA. Such Join(*,G) messages are sent on the RPF interface towards the RPA and are targeted at the DF on that interface.
上述下游每接口状态机保持来自下游PIM路由器的连接状态。然后，该状态确定路由器是否需要向RPA上游传播连接（*，G）。此类Join（*，G）消息通过RPF接口发送到RPA，并以该接口上的DF为目标。
If a router wishes to propagate a Join(*,G) upstream, it must also watch for messages on its upstream interface from other routers on that subnet, and these may modify its behavior. If it sees a Join(*,G) to the correct upstream neighbor, it should suppress its own Join(*,G). If it sees a Prune(*,G) to the correct upstream neighbor, it should be prepared to override that Prune by sending a Join(*,G) almost immediately. Finally, if it sees the Generation ID (see PIM-SM specification [4]) of the correct upstream neighbor change, it knows that the upstream neighbor has lost state, and it should be prepared to refresh the state by sending a Join(*,G) almost immediately.
如果路由器希望向上游传播连接（*，G），它还必须在其上游接口上监视来自该子网上其他路由器的消息，这些消息可能会修改其行为。如果它看到一个连接（*，G）到正确的上游邻居，它应该抑制自己的连接（*，G）。如果它看到对正确的上游邻居进行了修剪（*，G），它应该准备通过几乎立即发送连接（*，G）来覆盖该修剪。最后，如果它看到正确的上游邻居的生成ID（参见PIM-SM规范[4]）发生变化，它就知道上游邻居已丢失状态，并且它应该准备通过几乎立即发送连接（*，G）来刷新状态。
In addition, changes in the next hop towards the RPA trigger a Prune off from the old next hop and join towards the new next hop. Such a change can be caused by the following two events:
此外，对RPA的下一个跃点的更改会触发对旧的下一个跃点的修剪，并向新的下一个跃点加入。这种变化可能由以下两个事件引起：
o The MRIB indicates that the RPF Interface towards the RPA has changed. In this case the DF on the new RPF interface becomes the new RPF Neighbor.
o MRIB表示指向RPA的RPF接口已更改。在这种情况下，新RPF接口上的DF成为新RPF邻居。
o There is a DF re-election on the RPF interface and a new router emerges as the DF.
o 在RPF接口上有一个DF重新选择，一个新的路由器作为DF出现。
The upstream (*,G) state machine only contains two states:
上游（*，G）状态机仅包含两种状态：
Not Joined The downstream state machines indicate that the router does not need to join the RPA tree for this group.
未加入下游状态机表示路由器不需要加入此组的RPA树。
Joined The downstream state machines indicate that the router would like to join the RPA tree for this group.
已加入下游状态机表示路由器要加入此组的RPA树。
In addition, one timer JT(G) is kept, which is used to trigger the sending of a Join(*,G) to the upstream next hop towards the RPA (the DF on the RPF interface for RPA(G)).
此外，保留一个计时器JT（G），用于触发向RPA（RPA（G）的RPF接口上的DF）的上游下一跳发送连接（*，G）。
Figure 2: Upstream group state machine in tabular form
图2：表格形式的上游组状态机
+---------------------+----------------------------------------------+
| | Event |
| Prev State +-----------------------+----------------------+
| | JoinDesired(G) | JoinDesired(G) |
| | ->True | ->False |
+---------------------+-----------------------+----------------------+
| | -> J state | - |
| NotJoined (NJ) | Send Join(*,G); | |
| | Set Timer to | |
| | t_periodic | |
+---------------------+-----------------------+----------------------+
| Joined (J) | - | -> NJ state |
| | | Send Prune(*,G) |
+---------------------+-----------------------+----------------------+
+---------------------+----------------------------------------------+
| | Event |
| Prev State +-----------------------+----------------------+
| | JoinDesired(G) | JoinDesired(G) |
| | ->True | ->False |
+---------------------+-----------------------+----------------------+
| | -> J state | - |
| NotJoined (NJ) | Send Join(*,G); | |
| | Set Timer to | |
| | t_periodic | |
+---------------------+-----------------------+----------------------+
| Joined (J) | - | -> NJ state |
| | | Send Prune(*,G) |
+---------------------+-----------------------+----------------------+
In addition, we have the following transitions that occur within the Joined state:
此外，我们在连接状态中有以下转换：
+--------------------------------------------------------------------+
| In Joined (J) State |
+----------------+----------------+-----------------+----------------+
|Timer Expires | See Join(*,G) | See Prune(*,G) | RPF_DF(RPA(G)) |
| | to | to | GenID changes |
| | RPF_DF(RPA(G)) | RPF_DF(RPA(G)) | |
+----------------+----------------+-----------------+----------------+
|Send | Increase Timer | Decrease Timer | Decrease Timer |
|Join(*,G); Set | to | to t_override | to t_override |
|Timer to | t_suppressed | | |
|t_periodic | | | |
+----------------+----------------+-----------------+----------------+
+--------------------------------------------------------------------+
| In Joined (J) State |
+----------------+----------------+-----------------+----------------+
|Timer Expires | See Join(*,G) | See Prune(*,G) | RPF_DF(RPA(G)) |
| | to | to | GenID changes |
| | RPF_DF(RPA(G)) | RPF_DF(RPA(G)) | |
+----------------+----------------+-----------------+----------------+
|Send | Increase Timer | Decrease Timer | Decrease Timer |
|Join(*,G); Set | to | to t_override | to t_override |
|Timer to | t_suppressed | | |
|t_periodic | | | |
+----------------+----------------+-----------------+----------------+
+--------------------------------------------------------------------+
| In Joined (J) State |
+-----------------------------------+--------------------------------+
| Change of RPF_DF(RPA(G)) | RPF_DF(RPA(G)) GenID |
| | changes |
+-----------------------------------+--------------------------------+
| Send Join(*,G) to new | Decrease Timer to |
| DF; Send Prune(*,G) to | t_override |
| old DF; set Timer to | |
| t_periodic | |
+-----------------------------------+--------------------------------+
+--------------------------------------------------------------------+
| In Joined (J) State |
+-----------------------------------+--------------------------------+
| Change of RPF_DF(RPA(G)) | RPF_DF(RPA(G)) GenID |
| | changes |
+-----------------------------------+--------------------------------+
| Send Join(*,G) to new | Decrease Timer to |
| DF; Send Prune(*,G) to | t_override |
| old DF; set Timer to | |
| t_periodic | |
+-----------------------------------+--------------------------------+
This state machine uses the following macro:
此状态机使用以下宏：
bool JoinDesired(G) {
if (olist(G) (-) RPF_interface(RPA(G))) != NULL
return TRUE
else
return FALSE
}
bool JoinDesired(G) {
if (olist(G) (-) RPF_interface(RPA(G))) != NULL
return TRUE
else
return FALSE
}
This section presents a fail-safe mechanism for electing a per-RPA designated router on each link in a BIDIR-PIM domain. We call this router the Designated Forwarder (DF). The DF election does not take place on the RPL for an RPA.
本节介绍一种故障安全机制，用于在BIDIR-PIM域中的每个链路上选择每个RPA指定的路由器。我们称此路由器为指定转发器（DF）。国防军选举不是在爱国阵线上举行的爱国阵线选举。
The DF election chooses the best router on a link to assume responsibility for forwarding traffic between the RPL and the link for the range of multicast groups served by the RPA. Different multicast groups that share a common RPA share the same upstream direction. Hence, the election of an upstream forwarder on each link does not have to be a group-specific decision but instead can be RPA-specific. As the number of RPAs is typically small, the number of elections that have to be performed is significantly reduced by this observation.
DF选择选择链路上的最佳路由器，以承担在RPL和链路之间转发RPA服务的多播组范围内的流量的责任。共享公共RPA的不同多播组共享相同的上行方向。因此，在每个链路上选择上游转发器不必是特定于组的决策，而是可以是特定于RPA的决策。由于RPA的数量通常很小，因此必须进行的选举数量会因这一观察而显著减少。
To optimise tree creation, it is desirable that the winner of the election process should be the router on the link with the "best" unicast routing metric (as reported by the MRIB) to reach the RPA. When comparing metrics from different unicast routing protocols, we use the same comparison rules used by the PIM-SM assert process [4].
为了优化树的创建，选举过程的获胜者应该是链路上具有“最佳”单播路由度量（如MRIB所报告）以达到RPA的路由器。当比较来自不同单播路由协议的度量时，我们使用PIM-SM断言过程使用的相同比较规则[4]。
The election process needs to take place when information on a new RPA initially becomes available. The result can be re-used as new
选举过程需要在新的RPA信息最初可用时进行。结果可以作为新的重复使用
bidir groups that map to the same RPA are encountered. However, there are some conditions under which an update to the election is required:
遇到映射到相同RPA的bidir组。但是，在某些情况下，需要更新选举：
o There is a change in unicast metric to reach the RPA for any of the routers on the link.
o 单播度量发生变化，以达到链路上任何路由器的RPA。
o The interface on which the RPA is reachable (RPF Interface) changes to an interface for which the router was previously the DF.
o 可访问RPA的接口（RPF接口）更改为路由器以前是DF的接口。
o A new PIM neighbor starts up on a link that must participate in the elections and be informed of the current outcome.
o 一个新的PIM邻居在一条必须参加选举并被告知当前结果的链路上启动。
o The elected DF fails (detected through neighbor information timeout or MRIB RPF change at downstream router).
o 选择的DF失败（通过邻居信息超时或下游路由器的MRIB RPF更改检测到）。
The election process has to be robust enough to ensure with very high probability that all routers on the link have a consistent view of the DF. Given the forwarding rules described in Section 3.3, loops may result if multiple routers end-up thinking that they should be responsible for forwarding. To minimize the possibility of this occurrence, the election algorithm has been biased towards discarding DF information and suspending forwarding during periods of ambiguity.
选举过程必须足够稳健，以确保链路上的所有路由器都有一致的DF视图。根据第3.3节中描述的转发规则，如果多个路由器最终认为它们应该负责转发，则可能会导致循环。为了最大限度地减少这种情况发生的可能性，选举算法倾向于丢弃测向信息，并在模糊期间暂停转发。
This section gives an outline of the DF election process. It does not provide the definitive specification for the DF election. If any discrepancy exists between Section 3.5.3 and this section, the specification in Section 3.5.3 is to be assumed correct.
本节概述了民主阵线选举过程。它没有提供DF选举的最终规范。如果第3.5.3节与本节之间存在任何差异，则假定第3.5.3节中的规范正确。
To perform the election of the DF for a particular RPA, routers on a link need to exchange their unicast routing metric information for reaching the RPA. Routers advertise their own metrics in Offer, Winner, Backoff, and Pass messages. The advertised metric is calculated using the RPF Interface and metric to reach the RPA available through the MRIB. When a router is participating in a DF election for an RPA on the interface that its MRIB indicates as the RPF Interface, then that router MUST always advertise an infinite metric in its election messages. When a router is participating in a DF election on an interface other than the MRIB-indicated RPF Interface then it MUST advertise the MRIB-provided metrics in its election messages.
要为特定RPA选择DF，链路上的路由器需要交换其单播路由度量信息以到达RPA。路由器在提供、赢家、退避和传递消息中宣传自己的指标。使用RPF接口和指标计算公布的指标，以达到通过MRIB可用的RPA。当路由器在其MRIB指示为RPF接口的接口上参与RPA的DF选择时，该路由器必须始终在其选择消息中公布无限度量。当路由器在MRIB指示的RPF接口以外的接口上参与DF选择时，它必须在其选择消息中公布MRIB提供的度量。
In the election protocol described below, many message exchanges are repeated Election_Robustness times for reliability. In all those cases, the message retransmissions are spaced in time by a small
在下面描述的选择协议中，为了可靠性，许多消息交换被重复选择一次。在所有这些情况下，消息重传在时间上间隔很小
random interval. All of the following description is specific to the election on a single link for a single RPA.
随机间隔。以下所有描述均特定于单个RPA的单个链接上的选择。
Initially, when no DF has been elected, routers finding out about a new RPA start participating in the election by sending Offer messages. Offer messages include the router's metric to reach the RPA. Offers are periodically retransmitted with a period of Offer_Interval.
最初，当没有DF当选时，发现新RPA的路由器通过发送Offer消息开始参与选举。报价信息包括路由器达到RPA的指标。要约以要约间隔周期性地重新传输。
If a router hears a better offer than its own from a neighbor, it stops participating in the election for a period of Election_Robustness * Offer_Interval, thus giving a chance to the neighbor with the better metric to be elected DF. If during this period no winner is elected, the router restarts the election from the beginning. If at any point during the initial election a router receives an out of order offer with worse metrics than its own, then it restarts the election from the beginning.
如果一个路由器从邻居那里听到比它自己更好的提议，它将在一段选举时间内停止参与选举，从而给具有更好度量的邻居一个当选的机会。如果在此期间未选出获胜者，路由器将从头开始重新启动选举。如果在初始选择期间的任何时间点，路由器收到一个无序的报价，其指标比其自身的更差，那么它将从一开始重新启动选择。
The result should be that all routers except the best candidate stop advertising their offers.
结果应该是，除最佳候选路由器外，所有路由器都停止宣传其产品。
A router assumes the role of the DF after having advertised its metrics Election_Robustness times without receiving any offer from any other neighbor. At that point, it transmits a Winner message that declares to every other router on the link the identity of the winner and the metrics it is using.
路由器在未收到任何其他邻居的任何报价的情况下，在多次公布其度量后，承担DF的角色。在这一点上，它将发送一条Winner消息，向链路上的其他每一个路由器声明Winner的身份及其使用的度量。
Routers receiving a Winner message stop participating in the election and record the identity and metrics of the winner. If the local metrics are better than those of the winner, then the router records the identity of the winner (accepting it as the acting DF) but re-initiates the election to try and take over.
收到赢家消息的路由器停止参与选举，并记录赢家的身份和指标。如果本地指标优于获胜者的指标，则路由器会记录获胜者的身份（接受它作为代理DF），但会重新启动选举以尝试接管。
Whenever the unicast metric to an RPA changes at a non-DF router to a value that is better than that previously advertised by the acting DF, the router with the new better metric should take action to eventually assume forwarding responsibility. When the metric change is detected, the non-DF router with the now better metric restarts the DF election process by sending Offer messages with this new metric. Note that at any point during an election if no response is received after Election_Robustness retransmissions of an offer, a router assumes the role of the DF following the usual Winner announcement procedure.
每当在非DF路由器上对RPA的单播度量改变为比代理DF先前公布的更好的值时，具有新的更好度量的路由器应采取行动以最终承担转发责任。当检测到度量变化时，具有现在更好度量的非DF路由器通过发送具有此新度量的提供消息来重新启动DF选择过程。请注意，在选举期间的任何时候，如果在重新传输报价后没有收到响应，路由器将按照通常的获胜者公告程序承担DF的角色。
Upon receipt of an offer that is worse than its current metric, the DF will respond with a Winner message declaring its status and advertising its better metric. Upon receiving the Winner message, the originator of the Offer records the identity of the DF and aborts the election.
在收到比其当前指标更差的报价后，DF将以一条赢家消息作为回应，声明其状态并宣传其更好的指标。收到赢家消息后，要约的发起人记录DF的身份并中止选举。
Upon receipt of an offer that is better than its current metric, the DF records the identity and metrics of the offering router and responds with a Backoff message. This instructs the offering router to hold off for a short period of time while the unicast routing stabilizes and other routers get a chance to put in their offers. The Backoff message includes the offering router's new metric and address. All routers on the link that have pending offers with metrics worse than those in the Backoff message (including the original offering router) will hold further offers for a period of time defined in the Backoff message.
在收到优于其当前指标的报价后，DF记录报价路由器的标识和指标，并用退避消息进行响应。这将指示提供服务的路由器在单播路由稳定且其他路由器有机会提供服务时暂停一小段时间。退避消息包括产品路由器的新度量和地址。链路上所有具有比退避消息中的指标更差的待定报价的路由器（包括原始报价路由器）将在退避消息中定义的一段时间内持有更多报价。
If a third router sends a better offer during the Backoff_Period, the Backoff message is repeated for the new offer and the Backoff_Period is restarted.
如果第三个路由器在退避_期间发送更好的报价，则退避消息将针对新报价重复，并且退避_期间将重新启动。
Before the Backoff_Period expires, the acting DF nominates the router having made the best offer as the new DF using a Pass message. This message includes the IDs and metrics of both the old and new DFs. The old DF stops performing its tasks at the time the Pass message transmission is made. The new DF assumes the role of the DF as soon as it receives the Pass message. All other routers on the link take note of the new DF and its metric. Note that this event constitutes an RPF Neighbor change, which may trigger Join messages to the new DF (see Section 3.4).
在退避周期到期之前，代理DF使用Pass消息将提供最佳报价的路由器指定为新DF。此消息包括旧DFs和新DFs的ID和度量。在进行Pass消息传输时，旧DF停止执行其任务。新的DF一收到Pass消息就承担DF的角色。链路上的所有其他路由器都会注意到新的DF及其度量。请注意，此事件构成RPF邻居更改，这可能会触发新DF的加入消息（请参阅第3.4节）。
If the DF's routing metric to reach the RPA changes to a worse value, it sends a set of Election_Robustness randomly spaced Winner messages on the link, advertising the new metric. Routers that receive this announcement but have a better metric may respond with an Offer message that results in the same handoff procedure described above. All routers assume the DF has not changed until they see a Pass or Winner message indicating the change.
如果DF达到RPA的路由度量更改为更差的值，它将在链路上发送一组随机间隔的获胜者消息，宣传新的度量。收到此公告但具有更好度量的路由器可能会响应一条Offer消息，该消息将导致上述相同的切换过程。所有路由器都假定DF没有改变，直到它们看到一条表明改变的通过或获胜消息。
There is no pressure to make this handoff quickly if the acting DF still has a path to the RPL. The old path may now be suboptimal, but it will still work while the re-election is in progress.
如果代理DF仍然有到RPL的路径，则没有压力快速进行切换。旧的道路现在可能不太理想，但在连任过程中仍然有效。
If a router's RPF Interface to the RPA switches to be on a link for which it is acting as the DF, then it can no longer provide forwarding services for that link. It therefore immediately stops being the DF and restarts the election. As its path to the RPA is through the link, an infinite metric is used in the Offer message it sends.
如果路由器到RPA的RPF接口切换到它作为DF的链路上，那么它就不能再为该链路提供转发服务。因此，它立即停止担任国防军，重新开始选举。由于它到RPA的路径是通过链接的，所以在它发送的Offer消息中使用了一个无限度量。
A late router starting up after the DF election process has completed will have no immediate knowledge of the election outcome. As a result, it will start advertising its metric in Offer messages. As soon as this happens, the currently elected DF will respond with a Winner message if its metric is better than the metric in the Offer message, or with a Backoff message if its metric is worse than the metric in the Offer message.
DF选举过程完成后启动的延迟路由器将无法立即了解选举结果。因此，它将开始在报价信息中宣传其指标。一旦发生这种情况，如果当前选择的DF的度量值优于要约消息中的度量值，则该DF将以赢家消息响应，如果其度量值低于要约消息中的度量值，则该DF将以退避消息响应。
Whenever the DF dies, a new DF has to be elected. The speed at which this can be achieved depends on whether there are any downstream routers on the link.
每当DF死亡时，必须选出新的DF。实现这一点的速度取决于链路上是否有任何下游路由器。
If there are downstream routers, typically their MRIB reported next-hop before the DF dies will be the DF itself. They will therefore notice either a change in the metric for the route to the RPA or a change in next-hop away from the DF and can restart the election by transmitting Offer messages. If according to the MRIB the RPA is now reachable through the same link via another upstream router, an infinite metric will be used in the Offer.
如果存在下游路由器，通常在DF死亡之前，它们的MRIB报告的下一跳将是DF本身。因此，他们将注意到到到RPA的路由度量的变化，或者距离DF的下一个跃点的变化，并且可以通过传输Offer消息来重新开始选择。如果根据MRIB，RPA现在可以通过另一个上游路由器通过同一链路访问，则将在报价中使用无限度量。
If no downstream routers are present, the only way for other upstream routers to detect a DF failure is by the timeout of the PIM neighbor information, which will take significantly longer.
如果没有下游路由器，其他上游路由器检测DF故障的唯一方法是通过PIM邻居信息超时，这将花费更长的时间。
This section provides the definitive specification for the DF election process. If any discrepancy exists between Section 3.5.2 and this section, the specification in this section is to be assumed correct.
本节提供了DF选择过程的最终规范。如果第3.5.2节和本节之间存在任何差异，则假定本节中的规范正确。
The DF election state is maintained per RPA for each multicast enabled interface I on the router as introduced in Section 3.1.
如第3.1节所述，对于路由器上的每个启用多播的接口I，按照RPA维护DF选择状态。
The state machine has the following four states:
状态机具有以下四种状态：
Offer Initial election state. When in the Offer state, a router thinks it can eventually become the winner and periodically generates Offer messages.
提供初始选举状态。当处于提供状态时，路由器认为它最终可以成为赢家，并定期生成提供消息。
Lose In this state, the router knows that there either is a different election winner or that no router on the link has a path to the RPA.
在这种状态下，路由器知道有不同的选举获胜者，或者链路上没有路由器有到RPA的路径。
Win The router is the acting DF without any contest.
赢得路由器是没有任何竞争的代理DF。
Backoff The router is the acting DF but another router has made a bid to take over.
退让路由器是代理DF，但另一个路由器已出价接管。
In the state machine, a router is considered to be an acting DF if it is in the Win or Backoff states.
在状态机中，如果路由器处于赢或退避状态，则将其视为代理DF。
The operation of the election protocol makes use of the variables and timers described below:
选择协议的操作使用以下描述的变量和计时器：
Acting DF information Used to store the identity and advertised metrics of the election winner that is the currently acting DF.
代理DF信息，用于存储当前代理DF的选举获胜者的身份和广告指标。
DF election-Timer (DFT) Used to schedule transmission of Offer, Winner, and Pass messages.
DF选举计时器（DFT），用于计划发送要约、获胜者和传递消息。
Message-Count (MC) Used to maintain the number of times an Offer or Winner message has been transmitted.
消息计数（MC），用于保持发送报价或中标消息的次数。
Best-Offer Used by the DF to record the identity and advertised metrics of the router that has made the last offer, for use when sending the Path message.
DF用于记录发出最后一个报价的路由器的身份和广告度量的最佳报价，以供发送路径消息时使用。
The election process uses the following PIM control messages. The packet format is described in Section 3.7:
选择过程使用以下PIM控制消息。数据包格式见第3.7节：
Offer (OfferingID, Metric) Sent by routers that believe they have a better metric to the RPA than the metric that has been on offer so far.
路由器发送的Offer（OfferingID，Metric），这些路由器认为它们对RPA的度量比目前提供的度量更好。
Winner (DF-ID, DF-Metric) Sent by a router when assuming the role of the DF or when re-asserting in response to worse offers.
当承担DF角色或响应更差的报价重新断言时，路由器发送的赢家（DF-ID，DF度量）。
Backoff (DF-ID, DF-Metric, OfferingID, OfferMetric, BackoffInterval) Used by the DF to acknowledge better offers. It instructs other routers with equal or worse offers to wait until the DF passes responsibility to the sender of the offer.
退避（DF-ID、DF度量、OfferingID、OfferMetric、BackoffInterval）由DF用于确认更好的报价。它指示具有相同或更差报价的其他路由器等待，直到DF将责任传递给报价的发送方。
Pass (Old-DF-ID, Old-DF-Metric, New-DF-ID, New-DF-Metric) Used by the old DF to pass forwarding responsibility to a router that has previously made an offer. The Old-DF-Metric is the current metric of the DF at the time the pass is sent.
Pass（旧DF ID、旧DF度量、新DF ID、新DF度量）由旧DF用于将转发责任传递给先前发出报价的路由器。旧DF度量是发送过程时DF的当前度量。
Note that when a router is participating in a DF election for an RPA on the interface that its MRIB indicates as the RPF Interface, then that router MUST always advertise an infinite metric in its election messages. When a router is participating in a DF election on an interface other than the MRIB-indicated RPF Interface, then it MUST advertise the MRIB-provided metrics in its election messages.
请注意，当路由器在其MRIB指示为RPF接口的接口上参与RPA的DF选择时，该路由器必须始终在其选择消息中公布无限度量。当路由器在MRIB指示的RPF接口以外的接口上参与DF选择时，它必须在其选择消息中公布MRIB提供的度量。
During protocol operation, the following events can take place:
在协议操作期间，可能发生以下事件：
Control message reception Reception of one of the four control DF election messages (Offer, Winner, Backoff, and Pass). When a control message is received and actions are specified on a condition that metrics are Better or Worse, the comparison must be performed as follows:
控制信息接收四条控制DF选举信息（提供、获胜者、退避和通过）中的一条。当接收到控制消息并且在指标更好或更差的情况下指定了操作时，必须按照以下方式执行比较：
o On receipt of an Offer or Winner message, compare the current metrics for the RPA with the metrics advertised for the sender of the message.
o 在收到要约或获奖者消息后，将RPA的当前指标与消息发送者公布的指标进行比较。
o On receipt of a Backoff or Pass message, compare the current metrics for the RPA with the metrics advertised for the target of the message.
o 收到退避或通过消息后，将RPA的当前度量与消息目标的公布度量进行比较。
Path to RPA lost Losing the path to the RPA can happen in two ways. The first happens when the route learned through the MRIB is withdrawn and the MRIB no longer reports an available route to reach the RPA. The second case happens when the next-hop information reported by the MRIB changes to indicate a next-hop that is reachable through the router interface under consideration. Clearly, as the router is using the interface as its RPF Interface, it cannot offer forwarding services towards the RPL to other routers on that link.
RPA路径丢失丢失RPA路径有两种情况。第一种情况发生在通过MRIB学习的路线被撤回，并且MRIB不再报告到达RPA的可用路线时。第二种情况发生在MRIB报告的下一跳信息改变以指示可通过所考虑的路由器接口到达的下一跳时。显然，由于路由器使用该接口作为其RPF接口，因此它无法向该链路上的其他路由器提供指向RPL的转发服务。
Metric reported by the MRIB to reach the RPA changes This event is triggered when the MRIB supplied information for the RPA changes and the new information provides a path to the RPA. If the new MRIB information either reports no route or reports a next-hop interface through the interface for which the DF election is taking place, then the "Path to RPA lost" event triggers instead. In specific states, the event may be further filtered by specifying whether it is expected of the metric to become better or worse and which of the stored metrics the new MRIB information must be compared against. The new information must be compared with either the router's old metric, the stored DF metric, or the stored Best Offer metric.
MRIB报告的到达RPA的指标发生变化。当MRIB提供的RPA信息发生变化且新信息提供了RPA的路径时，会触发此事件。如果新的MRIB信息报告没有路由或通过正在进行DF选择的接口报告下一跳接口，则会触发“RPA丢失路径”事件。在特定状态下，可通过指定是否期望度量变得更好或更差以及必须将新MRIB信息与哪个存储度量进行比较来进一步过滤事件。新信息必须与路由器的旧指标、存储的DF指标或存储的最佳报价指标进行比较。
Election-Timer (DFT) expiration Expiration of the DFT election timer can cause message transmission and state transitions. The event might be further qualified by specifying the value of the Message Count (MC) as well as the current existence of a path to the RPA (as defined above).
选举计时器（DFT）DFT选举计时器的过期可能导致消息传输和状态转换。可以通过指定消息计数（MC）的值以及RPA路径（如上定义）的当前存在来进一步限定事件。
Detection of DF failure Detection of DF failure can occur through the timeout of PIM neighbor state.
DF故障检测DF故障检测可通过PIM邻居状态超时来实现。
The DF election state machine action descriptions use the following notation in addition to the pseudocode notation described earlier in this specification:
除了本规范前面描述的伪代码表示法外，DF选举状态机操作描述还使用以下表示法：
?= denotes the operation of lowering a timer to a new value. If the timer is not running, then it is started using the new value. If the timer is running with an expiration lower than the new value, then the timer is not altered.
？=表示将计时器降低到新值的操作。如果计时器未运行，则使用新值启动计时器。如果计时器运行时过期时间低于新值，则不会更改计时器。
When an action of "set DF to Sender or Target" is encountered during receipt of a Winner, Pass, or Backoff message, it means the following:
当在收到赢家、通过或退避消息期间遇到“将DF设置为发送者或目标”操作时，表示以下情况：
o On receipt of a Winner message, set the DF to be the originator of the message and record its metrics.
o 收到赢家消息后，将DF设置为消息的发起人，并记录其指标。
o On receipt of a Pass message, set the DF to be the target of the message and record its metrics.
o 收到Pass消息后，将DF设置为消息的目标并记录其度量。
o On receipt of a Backoff message, set the DF to be the originator of the message and record its metrics.
o 收到退避消息后，将DF设置为消息的发起人，并记录其度量。
When a Designated Forwarder election is initiated, the starting state is the Offer state, the message counter (MC) is set to zero, and the DF election Timer (DFT) is set to OPlow (see Section 3.6 for a definition of timer values).
当启动指定的转发器选择时，开始状态为提供状态，消息计数器（MC）设置为零，DF选择计时器（DFT）设置为OPlow（计时器值定义见第3.6节）。
Figure 3: Designated Forwarder election state machine in tabular form
图3：表格形式的指定转发器选择状态机
+-------------+------------------------------------------------------+
| | Event |
| Prev State +-----------------+------------------+-----------------+
| | Recv better | Recv better | Recv better |
| | Pass / Win | Backoff | Offer |
+-------------+-----------------+------------------+-----------------+
| | -> Lose | - | - |
| Offer | DF = Sender or | DFT = BOperiod | DFT = OPhigh; |
| | Target; Stop | + OPlow; MC = | MC = 0 |
| | DFT | 0 | |
+-------------+-----------------+------------------+-----------------+
| | - | - | -> Offer |
| Lose | DF = Sender or | DF = Sender | DFT = OPhigh; |
| | Target | | MC = 0 |
+-------------+-----------------+------------------+-----------------+
| | -> Lose | -> Lose | -> Backoff |
| | DF = Sender or | DF = Sender; | Set Best to |
| Win | Target; Stop | Stop DFT | Sender; Send |
| | DFT | | Backoff; DFT = |
| | | | BOperiod |
+-------------+-----------------+------------------+-----------------+
| | -> Lose | -> Lose | - |
| | DF = Sender or | DF = Sender; | Set Best to |
| Backoff | Target; Stop | Stop DFT | Sender; Send |
| | DFT | | Backoff; DFT = |
| | | | BOperiod |
+-------------+-----------------+------------------+-----------------+
+-------------+------------------------------------------------------+
| | Event |
| Prev State +-----------------+------------------+-----------------+
| | Recv better | Recv better | Recv better |
| | Pass / Win | Backoff | Offer |
+-------------+-----------------+------------------+-----------------+
| | -> Lose | - | - |
| Offer | DF = Sender or | DFT = BOperiod | DFT = OPhigh; |
| | Target; Stop | + OPlow; MC = | MC = 0 |
| | DFT | 0 | |
+-------------+-----------------+------------------+-----------------+
| | - | - | -> Offer |
| Lose | DF = Sender or | DF = Sender | DFT = OPhigh; |
| | Target | | MC = 0 |
+-------------+-----------------+------------------+-----------------+
| | -> Lose | -> Lose | -> Backoff |
| | DF = Sender or | DF = Sender; | Set Best to |
| Win | Target; Stop | Stop DFT | Sender; Send |
| | DFT | | Backoff; DFT = |
| | | | BOperiod |
+-------------+-----------------+------------------+-----------------+
| | -> Lose | -> Lose | - |
| | DF = Sender or | DF = Sender; | Set Best to |
| Backoff | Target; Stop | Stop DFT | Sender; Send |
| | DFT | | Backoff; DFT = |
| | | | BOperiod |
+-------------+-----------------+------------------+-----------------+
+-----------+-------------------------------------------------------+
| | Event |
| +-------------+-------------+--------------+------------+
|Prev State |Recv Backoff |Recv Pass |Recv Worse |Recv worse |
| |for us |for us |Pass / Win / |Offer |
| | | |Backoff | |
+-----------+-------------+-------------+--------------+------------+
| |- |-> Win |- |- |
| |DFT = |Stop DFT |Set DF to |DFT ?= |
|Offer |BOperiod + | |Sender or |OPlow; MC = |
| |OPlow; MC = | |Target; DFT |0 |
| |0 | |?= OPlow; MC | |
| | | |= 0 | |
+-----------+-------------+-------------+--------------+------------+
| |-> Offer |-> Offer |-> Offer |-> Offer |
| |DF = Sender; |DF = Sender; |DF = Sender |DFT = OPlow;|
|Lose |DFT = OPlow; |DFT = OPlow; |or Target; |MC = 0 |
| |MC = 0 |MC = 0 |DFT = OPlow; | |
| | | |MC = 0 | |
+-----------+-------------+-------------+--------------+------------+
| |-> Offer |-> Offer |-> Offer |- |
| |DF = Sender; |DF = Sender; |DF = Sender |Send Winner |
|Win |DFT = OPlow; |DFT = OPlow; |or Target; | |
| |MC = 0 |MC = 0 |DFT = OPlow; | |
| | | |MC = 0 | |
+-----------+-------------+-------------+--------------+------------+
| |-> Offer |-> Offer |-> Offer |-> Win |
| |DF = Sender; |DF = Sender; |DF = Sender |Send Winner;|
|Backoff |DFT = OPlow; |DFT = OPlow; |or Target; |Stop DFT |
| |MC = 0 |MC = 0 |DFT = OPlow; | |
| | | |MC = 0 | |
+-----------+-------------+-------------+--------------+------------+
+-----------+-------------------------------------------------------+
| | Event |
| +-------------+-------------+--------------+------------+
|Prev State |Recv Backoff |Recv Pass |Recv Worse |Recv worse |
| |for us |for us |Pass / Win / |Offer |
| | | |Backoff | |
+-----------+-------------+-------------+--------------+------------+
| |- |-> Win |- |- |
| |DFT = |Stop DFT |Set DF to |DFT ?= |
|Offer |BOperiod + | |Sender or |OPlow; MC = |
| |OPlow; MC = | |Target; DFT |0 |
| |0 | |?= OPlow; MC | |
| | | |= 0 | |
+-----------+-------------+-------------+--------------+------------+
| |-> Offer |-> Offer |-> Offer |-> Offer |
| |DF = Sender; |DF = Sender; |DF = Sender |DFT = OPlow;|
|Lose |DFT = OPlow; |DFT = OPlow; |or Target; |MC = 0 |
| |MC = 0 |MC = 0 |DFT = OPlow; | |
| | | |MC = 0 | |
+-----------+-------------+-------------+--------------+------------+
| |-> Offer |-> Offer |-> Offer |- |
| |DF = Sender; |DF = Sender; |DF = Sender |Send Winner |
|Win |DFT = OPlow; |DFT = OPlow; |or Target; | |
| |MC = 0 |MC = 0 |DFT = OPlow; | |
| | | |MC = 0 | |
+-----------+-------------+-------------+--------------+------------+
| |-> Offer |-> Offer |-> Offer |-> Win |
| |DF = Sender; |DF = Sender; |DF = Sender |Send Winner;|
|Backoff |DFT = OPlow; |DFT = OPlow; |or Target; |Stop DFT |
| |MC = 0 |MC = 0 |DFT = OPlow; | |
| | | |MC = 0 | |
+-----------+-------------+-------------+--------------+------------+
+--------------------------------------------------------------------+
| In Offer State |
+----------------------+----------------------+----------------------+
| DFT Expires and MC | DFT Expires and MC | DFT Expires and MC |
| is less than | is equal to | is equal to |
| Robustness | Robustness and we | Robustness and |
| | have path to RPA | there is no path |
| | | to RPA |
+----------------------+----------------------+----------------------+
| - | -> Win | -> Lose |
| Send Offer; DFT = | Send Winner | Set DF to None |
| OPlow; MC = MC + 1 | | |
+----------------------+----------------------+----------------------+
+--------------------------------------------------------------------+
| In Offer State |
+--------------------------------------------------------------------+
| Metric changes and is now worse |
+--------------------------------------------------------------------+
| DFT ?= OPlow |
| MC = 0 |
+--------------------------------------------------------------------+
+--------------------------------------------------------------------+
| In Offer State |
+----------------------+----------------------+----------------------+
| DFT Expires and MC | DFT Expires and MC | DFT Expires and MC |
| is less than | is equal to | is equal to |
| Robustness | Robustness and we | Robustness and |
| | have path to RPA | there is no path |
| | | to RPA |
+----------------------+----------------------+----------------------+
| - | -> Win | -> Lose |
| Send Offer; DFT = | Send Winner | Set DF to None |
| OPlow; MC = MC + 1 | | |
+----------------------+----------------------+----------------------+
+--------------------------------------------------------------------+
| In Offer State |
+--------------------------------------------------------------------+
| Metric changes and is now worse |
+--------------------------------------------------------------------+
| DFT ?= OPlow |
| MC = 0 |
+--------------------------------------------------------------------+
+--------------------------------------------------------------------+
| In Lose State |
+------------------------------+-------------------------------------+
| Detect DF Failure | Metric changes and now |
| | is better than DF |
+------------------------------+-------------------------------------+
| -> Offer | -> Offer |
| DF = None; DFT = | DFT = OPlow_int; MC = 0 |
| OPlow_int; MC = 0 | |
+------------------------------+-------------------------------------+
+--------------------------------------------------------------------+
| In Lose State |
+------------------------------+-------------------------------------+
| Detect DF Failure | Metric changes and now |
| | is better than DF |
+------------------------------+-------------------------------------+
| -> Offer | -> Offer |
| DF = None; DFT = | DFT = OPlow_int; MC = 0 |
| OPlow_int; MC = 0 | |
+------------------------------+-------------------------------------+
+--------------------------------------------------------------------+
| In Win State |
+----------------------+-----------------------+---------------------+
| Metric changes and | Timer Expires and | Path to RPA lost |
| is now worse | MC is less than | |
| | Robustness | |
+----------------------+-----------------------+---------------------+
| - | - | -> Offer |
| DFT = OPlow; MC = | Send Winner; DFT = | Set DF to None; |
| 0 | OPlow; MC = MC + 1 | DFT = OPlow; MC = |
| | | 0 |
+----------------------+-----------------------+---------------------+
+--------------------------------------------------------------------+
| In Win State |
+----------------------+-----------------------+---------------------+
| Metric changes and | Timer Expires and | Path to RPA lost |
| is now worse | MC is less than | |
| | Robustness | |
+----------------------+-----------------------+---------------------+
| - | - | -> Offer |
| DFT = OPlow; MC = | Send Winner; DFT = | Set DF to None; |
| 0 | OPlow; MC = MC + 1 | DFT = OPlow; MC = |
| | | 0 |
+----------------------+-----------------------+---------------------+
+--------------------------------------------------------------------+
| In Backoff State |
+----------------------+-----------------------+---------------------+
| Metric changes and | Timer Expires | Path to RPA lost |
| is now better than | | |
| Best | | |
+----------------------+-----------------------+---------------------+
| -> Win | -> Lose | -> Offer |
| Stop Timer | Send Pass; Set DF | Set DF to None; |
| | to stored Best | DFT = OPlow; MC = |
| | | 0 |
+----------------------+-----------------------+---------------------+
+--------------------------------------------------------------------+
| In Backoff State |
+----------------------+-----------------------+---------------------+
| Metric changes and | Timer Expires | Path to RPA lost |
| is now better than | | |
| Best | | |
+----------------------+-----------------------+---------------------+
| -> Win | -> Lose | -> Offer |
| Stop Timer | Send Pass; Set DF | Set DF to None; |
| | to stored Best | DFT = OPlow; MC = |
| | | 0 |
+----------------------+-----------------------+---------------------+
For the correct operation of BIDIR-PIM, it is very important to avoid situations where two routers consider themselves to be Designated Forwarders for the same link. The two precautions below are not required for correct operation but can help diagnose and correct anomalies.
对于BIDE-PIM的正确操作，避免两个路由器认为自己是同一链路的转发器是非常重要的。以下两项预防措施不是正确操作所必需的，但有助于诊断和纠正异常。
After a DF has been elected, a router whose metrics change to become better than the DF will attempt to take over. If during the re-election the acting DF has a condition that causes it to lose all of the election messages (like a CPU overload), the new candidate will transmit three offers and assume the role of the forwarder resulting in two DFs on the link. This situation is pathological and should be corrected by fixing the overloaded router. It is desirable that such an event can be detected by a network administrator.
在一个DF被选出来后，一个路由器的指标变化会比DF更好，它将试图接管。如果在重新选举期间，代理DF出现导致其丢失所有选举消息的情况（如CPU过载），则新候选人将发送三个报价，并担任转发器的角色，从而在链路上产生两个DF。这种情况是病态的，应该通过修复过载的路由器来纠正。希望网络管理员能够检测到这样的事件。
When a router becomes the DF for a link without receiving a Pass message from the known old DF, the PIM neighbor information for the old DF can be marked to this effect. Upon receiving the next PIM Hello message from the old DF, the router can retransmit Winner messages for all the RPAs for which it is acting as the DF. The anomaly may also be logged by the router in a rate-limited manner to alert the operator.
当路由器成为链路的DF而没有从已知的旧DF接收Pass消息时，旧DF的PIM邻居信息可以标记为这种效果。当从旧DF接收到下一条PIM Hello消息时，路由器可以为其作为DF的所有RPA重新传输赢家消息。路由器也可能以速率受限的方式记录异常，以提醒操作员。
An additional degree of safety can be achieved by having the DF for each RPA periodically announce its status in a Winner message. Transmission of the periodic Winner message can be restricted to occur only for RPAs that have active groups, thus avoiding the periodic control traffic in areas of the network without senders or receivers for a particular RPA.
通过让每个RPA的DF在赢家消息中定期宣布其状态，可以实现额外的安全度。周期性赢家消息的传输可以被限制为仅针对具有活动组的RPA发生，从而避免在没有特定RPA的发送者或接收者的网络区域中的周期性控制通信量。
BIDIR-PIM maintains the following timers, as discussed in Section 3.1. All timers are countdown timers - they are set to a value and count down to zero, at which point they typically trigger an action. Of course they can just as easily be implemented as count-up timers, where the absolute expiry time is stored and compared against a real-time clock, but the language in this specification assumes that they count downwards to zero.
BIDIR-PIM维护以下计时器，如第3.1节所述。所有计时器都是倒计时计时器-它们被设置为一个值并倒计时到零，在这一点上它们通常触发一个动作。当然，它们可以像计数计时器一样轻松实现，其中存储绝对到期时间并与实时时钟进行比较，但本规范中的语言假设它们向下计数为零。
Per Rendezvous-Point Address (RPA):
每个集合点地址（RPA）：
Per interface (I):
每个接口（I）：
DF Election Timer: DFT(RPA,I)
DF选择计时器：DFT（RPA，I）
Per Group (G):
每组（G）：
Upstream Join Timer: JT(G)
上游加入计时器：JT（G）
Per interface (I):
每个接口（I）：
Join Expiry Timer: ET(G,I)
加入到期计时器：ET（G，I）
PrunePendingTimer: PPT(G,I)
剪枝时间：PPT（G，I）
When timers are started or restarted, they are set to default values. This section summarizes those default values.
启动或重新启动计时器时，将其设置为默认值。本节总结了这些默认值。
Timer Name: DF Election Timer (DFT)
计时器名称：DF选择计时器（DFT）
+-------------------+------------------------+-----------------------+
| Value Name | Value | Explanation |
+-------------------+------------------------+-----------------------+
| Offer_Period | 100 ms | Interval to wait |
| | | between repeated |
| | | Offer and Winner |
| | | messages. |
+-------------------+------------------------+-----------------------+
| Backoff_Period | 1 sec | Period that acting |
| | | DF waits between |
| | | receiving a better |
| | | Offer and sending |
| | | the Pass message |
| | | to transfer DF |
| | | responsibility. |
+-------------------+------------------------+-----------------------+
| OPlow | rand(0.5, 1) * | Range of actual |
| | Offer_Period | randomised value |
| | | used between |
| | | repeated messages. |
+-------------------+------------------------+-----------------------+
| OPhigh | Election_Robustness | Interval to wait |
| | * Offer_Period | in order to give a |
| | | chance to a router |
| | | with a better |
| | | Offer to become |
| | | the DF. |
+-------------------+------------------------+-----------------------+
+-------------------+------------------------+-----------------------+
| Value Name | Value | Explanation |
+-------------------+------------------------+-----------------------+
| Offer_Period | 100 ms | Interval to wait |
| | | between repeated |
| | | Offer and Winner |
| | | messages. |
+-------------------+------------------------+-----------------------+
| Backoff_Period | 1 sec | Period that acting |
| | | DF waits between |
| | | receiving a better |
| | | Offer and sending |
| | | the Pass message |
| | | to transfer DF |
| | | responsibility. |
+-------------------+------------------------+-----------------------+
| OPlow | rand(0.5, 1) * | Range of actual |
| | Offer_Period | randomised value |
| | | used between |
| | | repeated messages. |
+-------------------+------------------------+-----------------------+
| OPhigh | Election_Robustness | Interval to wait |
| | * Offer_Period | in order to give a |
| | | chance to a router |
| | | with a better |
| | | Offer to become |
| | | the DF. |
+-------------------+------------------------+-----------------------+
Timer Names: Join Expiry Timer (ET(G,I))
计时器名称：加入到期计时器（ET（G，I））
+---------------+---------------+------------------------------------+
|Value Name | Value | Explanation |
+---------------+---------------+------------------------------------+
|J/P HoldTime | from message | Hold Time from Join/Prune Message |
+---------------+---------------+------------------------------------+
+---------------+---------------+------------------------------------+
|Value Name | Value | Explanation |
+---------------+---------------+------------------------------------+
|J/P HoldTime | from message | Hold Time from Join/Prune Message |
+---------------+---------------+------------------------------------+
Timer Names: PrunePendingTimer (PPT(G,I))
计时器名称：PrunePendingTimer（PPT（G，I））
+-------------------------+-------------------+----------------------+
| Value Name | Value | Explanation |
+-------------------------+-------------------+----------------------+
| J/P Override Interval | Default: 3 secs | Short period after |
| | | a Join or Prune to |
| | | allow other |
| | | routers on the LAN |
| | | to override the |
| | | Join or Prune |
+-------------------------+-------------------+----------------------+
+-------------------------+-------------------+----------------------+
| Value Name | Value | Explanation |
+-------------------------+-------------------+----------------------+
| J/P Override Interval | Default: 3 secs | Short period after |
| | | a Join or Prune to |
| | | allow other |
| | | routers on the LAN |
| | | to override the |
| | | Join or Prune |
+-------------------------+-------------------+----------------------+
Note that the value of the J/P Override Interval is interface specific and depends on both the Propagation_Delay and the Override_Interval values that may change when Hello messages are received [4].
请注意，J/P覆盖间隔的值是特定于接口的，取决于传播延迟和覆盖间隔值，当接收到Hello消息时，覆盖间隔值可能会改变[4]。
Timer Names: Upstream Join Timer (JT(G))
定时器名称：上游连接定时器（JT（G））
+------------+-------------------+-----------------------------------+
Value Name |Value Explanation |
+------------+-------------------+-----------------------------------+
t_periodic |Default: 60 secs Period between Join/Prune Messages |
+------------+-------------------+-----------------------------------+
t_suppressed |rand(1.1 * Suppression period when someone |
| |t_periodic, 1.4 * else sends a J/P message so we |
| |t_periodic) don't need to do so. |
+------------+-------------------+-----------------------------------+
t_override |rand(0, 0.9 * J/P Randomized delay to prevent |
| |Override Interval) response implosion when sending a |
| | Join message to override someone |
| | else's Prune message. |
+------------+-------------------+-----------------------------------+
+------------+-------------------+-----------------------------------+
Value Name |Value Explanation |
+------------+-------------------+-----------------------------------+
t_periodic |Default: 60 secs Period between Join/Prune Messages |
+------------+-------------------+-----------------------------------+
t_suppressed |rand(1.1 * Suppression period when someone |
| |t_periodic, 1.4 * else sends a J/P message so we |
| |t_periodic) don't need to do so. |
+------------+-------------------+-----------------------------------+
t_override |rand(0, 0.9 * J/P Randomized delay to prevent |
| |Override Interval) response implosion when sending a |
| | Join message to override someone |
| | else's Prune message. |
+------------+-------------------+-----------------------------------+
For more information about these values, refer to the PIM-SM [4] documentation.
有关这些值的更多信息，请参阅PIM-SM[4]文档。
Constant Name: DF Election Robustness
常量名称：DF
+-------------------------+------------------+-----------------------+
| Constant Name | Value | Explanation |
+-------------------------+------------------+-----------------------+
| Election_Robustness | Default: 3 | Minimum number of |
| | | election messages |
| | | that must be lost |
| | | in order for |
| | | election to fail. |
+-------------------------+------------------+-----------------------+
+-------------------------+------------------+-----------------------+
| Constant Name | Value | Explanation |
+-------------------------+------------------+-----------------------+
| Election_Robustness | Default: 3 | Minimum number of |
| | | election messages |
| | | that must be lost |
| | | in order for |
| | | election to fail. |
+-------------------------+------------------+-----------------------+
This section describes the details of the packet formats for BIDIR-PIM control messages. BIDIR-PIM shares a number of control messages in common with PIM-SM [4]. These include the Hello and Join/Prune messages as well as the format for the Encoded-Unicast address. For details on the format of these packets, please refer to the PIM-SM documentation. Here we will only define the additional packets that are introduced by BIDIR-PIM. These are the packets used in the DF election process as well as the Bidirectional Capable PIM-Hello option.
本节介绍BIDIR-PIM控制消息的数据包格式的详细信息。BIDIR-PIM与PIM-SM共享许多控制消息[4]。其中包括Hello和Join/Prune消息以及编码单播地址的格式。有关这些数据包格式的详细信息，请参阅PIM-SM文档。这里我们只定义BIDIR-PIM引入的附加数据包。这些是DF选择过程中使用的数据包以及双向PIM Hello选项。
All PIM control messages have IP protocol number 103.
所有PIM控制消息的IP协议号均为103。
BIDIR-PIM messages are multicast with TTL 1 to the `ALL-PIM-ROUTERS' group. The IPv4 `ALL-PIM-ROUTERS' group is `224.0.0.13'. The IPv6 `ALL-PIM-ROUTERS' group is `ff02::d'.
BIDIR-PIM消息通过TTL 1多播到“ALL-PIM-ROUTERS”组。IPv4“ALL-PIM-ROUTERS”组为“224.0.0.13”。IPv6“ALL-PIM-ROUTERS”组是“ff02:：d”。
All DF election BIDIR-PIM control messages share the common header below:
所有DF REFECTION BIDIR-PIM控制消息共享以下公共标头：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PIM Ver| Type |Subtype| Rsvd | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RP Address (Encoded-Unicast format) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Metric Preference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PIM Ver| Type |Subtype| Rsvd | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RP Address (Encoded-Unicast format) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Metric Preference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PIM Ver PIM Version number is 2.
PIM版本号为2。
Type All DF-Election PIM control messages share the PIM message Type of 10.
键入所有PIM控制消息共享PIM消息类型10。
Subtype Subtypes for DF election messages are:
DF选举消息的子类型为：
1 = Offer 2 = Winner 3 = Backoff 4 = Pass
1=报价2=获胜者3=退避4=通过
Rsvd Set to zero on transmission. Ignored on receipt.
传输时Rsvd设置为零。收到时忽略。
Checksum A standard checksum IP checksum is used, i.e., the 16-bit one's complement of the one's complement sum of the entire PIM message. For computing the checksum, the checksum field is zeroed.
校验和使用标准校验和IP校验和，即整个PIM消息的16位一的补码和。为了计算校验和，校验和字段被置零。
RP Address The bidirectional RPA for which the election is taking place. The format is described in [4], Section 4.9.1.
RP地址正在进行选举的双向RPA。格式见[4]第4.9.1节。
Sender Metric Preference Preference value assigned to the unicast routing protocol that the message sender used to obtain the route to the RPA.
指定给单播路由协议的发送方度量首选项值，消息发送方用于获取到RPA的路由。
Sender Metric The unicast routing table metric used by the message sender to reach the RPA. The metric is in units applicable to the unicast routing protocol used.
发送方度量消息发送方用于到达RPA的单播路由表度量。度量单位适用于所使用的单播路由协议。
In addition to the fields defined above, the Backoff and Pass messages have the extra fields described below.
除了上面定义的字段外，退避和传递消息还有下面描述的额外字段。
The Backoff message uses the following fields in addition to the common election message format described above.
退避消息除了使用上述通用选举消息格式外，还使用以下字段。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offering Address (Encoded-Unicast format) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offering Metric Preference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offering Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offering Address (Encoded-Unicast format) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offering Metric Preference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offering Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Offering Address The address of the router that made the last (best) Offer. The format is described in [4], Section 4.9.1.
提供地址发出最后（最佳）报价的路由器的地址。格式见[4]第4.9.1节。
Offering Metric Preference Preference value assigned to the unicast routing protocol that the offering router used to obtain the route to the RPA.
提供路由器用于获取到RPA的路由的单播路由协议的提供度量首选项值。
Offering Metric The unicast routing table metric used by the offering router to reach the RPA. The metric is in units applicable to the unicast routing protocol used.
提供度量提供路由器用于到达RPA的单播路由表度量。度量单位适用于所使用的单播路由协议。
Interval The backoff interval in milliseconds to be used by routers with worse metrics than the offering router.
Interval路由器使用的退避间隔（毫秒），其度量比提供的路由器更差。
The Pass message uses the following fields in addition to the common election fields described above.
除了上述常用选择字段外，Pass消息还使用以下字段。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New Winner Address (Encoded-Unicast format) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New Winner Metric Preference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New Winner Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New Winner Address (Encoded-Unicast format) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New Winner Metric Preference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New Winner Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
New Winner Address The address of the router that made the last (best) Offer. The format is described in [4], Section 4.9.1.
New Winner Address提供最后（最佳）报价的路由器的地址。格式见[4]第4.9.1节。
New Winner Metric Preference Preference value assigned to the unicast routing protocol that the offering router used to obtain the route to the RPA.
分配给提供路由器用于获取到RPA的路由的单播路由协议的新Winner度量首选项值。
New Winner Metric The unicast routing table metric used by the offering router to reach the RPA. The metric is in units applicable to the unicast routing protocol used.
New Winner Metric提供路由器用于到达RPA的单播路由表指标。度量单位适用于所使用的单播路由协议。
BIDIR-PIM introduces one new PIM-Hello option.
BIDIR-PIM引入了一个新的PIM Hello选项。
o OptionType 22: Bidirectional Capable
o OptionType 22：双向功能
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 22 | Length = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 22 | Length = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Routers discover that a range of multicast group addresses operates in bidirectional mode, and that the address of the Rendezvous-Point address (RPA) is serving the group range either through static configuration or using an automatic RP discovery mechanism like the PIM Bootstrap mechanism (BSR) [7] or Auto-RP.
路由器发现一系列多播组地址以双向模式运行，并且集合点地址（RPA）的地址通过静态配置或使用自动RP发现机制（如PIM引导机制（BSR）[7]或自动RP）服务于组范围。
The IPsec [5] authentication header MAY be used to provide data integrity protection and group-wise data origin authentication of BIDIR-PIM protocol messages. Authentication of BIDIR-PIM messages can protect against unwanted behaviour caused by unauthorized or altered BIDIR-PIM messages.
IPsec[5]认证报头可用于提供BIDIR-PIM协议消息的数据完整性保护和分组数据源认证。BIDIR-PIM消息的身份验证可以防止未经授权或更改的BIDIR-PIM消息导致的不必要行为。
As in PIM Sparse-Mode, the extent of possible damage depends on the type of counterfeit messages accepted. BIDIR-PIM only uses link-local multicast messages sent to the ALL_PIM_ROUTERS address, hence attacks can only be carried out by directly connected nodes, or with the complicity of directly connected routers.
与PIM稀疏模式一样，可能的损坏程度取决于接受的伪造消息的类型。BIDIR-PIM仅使用发送到ALL_PIM_路由器地址的链路本地多播消息，因此攻击只能由直接连接的节点执行，或者由直接连接的路由器共同执行。
Some of the BIDIR-PIM protocol messages (Join/Prune and Hello) are identical, both in format and functionality, to the respective messages used in PIM-SM. Security considerations for these messages are to be found in [4]. Other messages (DF-election messages) are specific to BIDIR-PIM and will be discussed in the following paragraphs.
一些BIDIR-PIM协议消息（Join/Prune和Hello）在格式和功能上与PIM-SM中使用的相应消息相同。这些消息的安全注意事项见[4]。其他消息（DF选举消息）特定于BIDIR-PIM，将在以下段落中讨论。
By forging DF-election messages, an attacker can disrupt the election of the Designated Forwarder on a link in two different ways:
通过伪造DF选择消息，攻击者可以通过两种不同的方式破坏链路上指定转发器的选择：
An attacker can force its election as DF by participating in a regular election and advertising the best metric to reach the RPA. An attacker can also try to force the election of another router as DF by sending an Offer, Winner, or Pass message and impersonating another router. In some cases (e.g., the Offer), multiple messages might be needed to carry out an attack.
攻击者可以通过参加常规选举并宣传达到RPA的最佳指标来强制其当选为DF。攻击者还可以通过发送要约、获胜者或通过消息并模拟另一路由器，尝试强制选择另一路由器作为DF。在某些情况下（例如，要约），可能需要多条消息来执行攻击。
In the case of Offer or Winner messages, the attacker will have to impersonate the node that it wants to have become the DF. In the case of the Pass, it will have to impersonate the current DF. This type of attack causes the wrong DF to be recorded in all nodes apart from the one that is being impersonated. This node typically will be able to detect the anomaly and, possibly, restart a new election.
在提供或赢家消息的情况下，攻击者必须模拟它希望成为DF的节点。在Pass的情况下，它必须模拟当前DF。这种类型的攻击会导致在除正在模拟的节点之外的所有节点中记录错误的DF。该节点通常能够检测异常，并可能重新启动新的选举。
A more sophisticated attacker might carry out a concurrent DoS attack on the node being impersonated, so that it will not be able to detect the forged packets and/or take countermeasures.
更复杂的攻击者可能会对被模拟的节点执行并发DoS攻击，因此无法检测伪造的数据包和/或采取对策。
All attacks based on impersonation can be detected by all routers and avoided if the source of DF-election messages can be authenticated. When authentication is available, spoofed messages MUST be discarded and a rate-limited warning message SHOULD be logged.
所有路由器都可以检测到所有基于模拟的攻击，如果可以验证DF选举消息的来源，则可以避免这些攻击。当身份验证可用时，必须丢弃伪造的消息，并记录速率受限的警告消息。
A more subtle attacker could use MAC-level addresses to partition the set of recipients of DF-election messages and create an inconsistent DF view on the link. For example, the attacker could use unicast MAC addresses for its forged DF-election messages. To prevent this type of attack, BIDIR-PIM routers SHOULD check the destination MAC address of received DF-election messages. This however is ineffective on links that do not support layer-2 multicast delivery.
更狡猾的攻击者可以使用MAC级地址对DF选举消息的收件人集进行分区，并在链接上创建不一致的DF视图。例如，攻击者可以将单播MAC地址用于伪造的DF选举消息。为了防止这种类型的攻击，BIDIR-PIM路由器应该检查接收到的DF选举消息的目标MAC地址。但是，这在不支持第2层多播传送的链路上是无效的。
Source authentication is also sufficient to prevent this kind of attack.
源身份验证也足以防止此类攻击。
By forging DF election messages, an attacker can prevent the election from converging, thus disrupting the establishment of multicast forwarding trees. There are many ways to achieve this. The simplest is by sending an infinite sequence of Offer messages (the metric used in the messages is not important).
通过伪造DF选举消息，攻击者可以阻止选举聚合，从而中断多播转发树的建立。实现这一点的方法有很多。最简单的方法是发送无限序列的Offer消息（消息中使用的度量并不重要）。
A BIDIR-PIM router SHOULD provide an option to limit the set of neighbors from which it will accept Join/Prune, Assert, and DF-election messages. Either static configuration of IP addresses or an IPsec security association may be used. Furthermore, a PIM router SHOULD NOT accept protocol messages from a router from which it has not yet received a valid Hello message.
BIDIR-PIM路由器应提供一个选项，以限制其将从中接受加入/删减、断言和DF选择消息的邻居集。可以使用IP地址的静态配置或IPsec安全关联。此外，PIM路由器不应接受来自尚未收到有效Hello消息的路由器的协议消息。
In a PIM-SM domain, when all routers are trusted, it is possible to implement a basic form of access control for both sources and receivers: Receivers can be validated by the last-hop DR and sources can be validated by the first-hop DR and/or the RP.
在PIM-SM域中，当所有路由器都受信任时，可以对源和接收器实施基本形式的访问控制：接收器可以由最后一跳DR验证，源可以由第一跳DR和/或RP验证。
In BIDIR-PIM, this is generally feasible only for receivers, as sources can send to the multicast group without the need for routers to detect their activity and create source-specific state. However, it is possible to modify the standard BIDIR-PIM behaviour, in a backward compatible way, to allow per-source access control. The tradeoff would be protocol simplicity, memory, and processing requirements.
在BIDIR-PIM中，这通常仅适用于接收器，因为源可以发送到多播组，而无需路由器检测其活动并创建源特定状态。但是，可以以向后兼容的方式修改标准BIDIR-PIM行为，以允许每个源访问控制。权衡将是协议的简单性、内存和处理要求。
Just as with PIM-SM, the IPsec [5] transport mode using the Authentication Header (AH) is the recommended method to prevent the above attacks against BIDIR-PIM.
与PIM-SM一样，使用身份验证头（AH）的IPsec[5]传输模式是防止上述针对BIDIR-PIM的攻击的推荐方法。
It is recommended that IPsec authentication be applied to all BIDIR-PIM protocol messages. The specification on how this is done is found in [4]. Specifically, the authentication of PIM-SM link-local messages, described in [4], applies to all BIDIR-PIM messages as well.
建议对所有BIDIR-PIM协议消息应用IPsec身份验证。关于如何实现这一点的规范见[4]。具体而言，[4]中描述的PIM-SM链路本地消息的认证也适用于所有BIDIR-PIM消息。
The denial-of-service attack based on forged Join messages, described in [4], also applies to BIDIR-PIM.
[4]中描述的基于伪造连接消息的拒绝服务攻击也适用于BIDIR-PIM。
IANA has assigned OptionType 22 to the "Bidirectional Capable" option.
IANA已将OptionType 22分配给“双向功能”选项。
The bidirectional proposal in this document is heavily based on the ideas and text presented by Estrin and Farinacci in [6]. The main difference between the two proposals is in the method chosen for upstream forwarding.
本文件中的双向提案主要基于Estrin和Farinaci在[6]中提出的观点和文本。这两个方案之间的主要区别在于为上游转发选择的方法。
We would also like to thank John Zwiebel at Cisco, Deborah Estrin at ISI/USC, Bill Fenner at AT&T Research, as well as Nidhi Bhaskar, Yiqun Cai, Toerless Eckert, Apoorva Karan, Rajitha Sumanasekera, and Beau Williamson at Cisco for their contributions and comments to this document.
我们还要感谢思科的John Zwiebel、ISI/USC的Deborah Estrin、at&T Research的Bill Fenner，以及思科的Nidhi Bhaskar、Yiqun Cai、Toerless Eckert、Apoorva Karan、Rajitha Sumanasekera和Beau Williamson对本文件的贡献和评论。
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[1] Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[2] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. Thyagarajan, "Internet Group Management Protocol, Version 3", RFC 3376, October 2002.
[2] Cain，B.，Deering，S.，Kouvelas，I.，Fenner，B.，和A.Thyagarajan，“互联网组管理协议，第3版”，RFC 3376，2002年10月。
[3] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener Discovery (MLD) for IPv6", RFC 2710, October 1999.
[3] Deering，S.，Fenner，W.和B.Haberman，“IPv6的多播侦听器发现（MLD）”，RFC 2710，1999年10月。
[4] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, August 2006.
[4] Fenner，B.，Handley，M.，Holbrook，H.，和I.Kouvelas，“协议独立多播-稀疏模式（PIM-SM）：协议规范（修订版）”，RFC 4601，2006年8月。
[5] Kent, S. and R. Atkinson, "Security Architecture for the Internet Protocol", RFC 2401, November 1998.
[5] Kent，S.和R.Atkinson，“互联网协议的安全架构”，RFC 2401，1998年11月。
[6] Estrin, D. and D. Farinacci, "Bi-directional Shared Trees in PIM-SM", Work in Progress, May 1999.
[6] Estrin，D.和D.Farinaci，“PIM-SM中的双向共享树”，正在进行的工作，1999年5月。
[7] Bhaskar, N., Gall, A., Lingard, J., and S. Venaas, "Bootstrap Router (BSR) Mechanism for PIM", Work in Progress, February 2007.
[7] Bhaskar，N.，Gall，A.，Lingard，J.，和S.Venaas，“PIM引导路由器（BSR）机制”，正在进行的工作，2007年2月。
[8] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, January 2007.
[8] Bates，T.，Chandra，R.，Katz，D.，和Y.Rekhter，“BGP-4的多协议扩展”，RFC 4760，2007年1月。
Index
指数
DF. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5,18
Downstream. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
DownstreamJPState(G,I). . . . . . . . . . . . . . . . . . . . . . 10
ET(G,I) . . . . . . . . . . . . . . . . . . . . . . . . . . . 9,14,33
ET(RPA,I) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
I_am_DF(RPA,I). . . . . . . . . . . . . . . . . . . . . . . .10,12,14
J/P_HoldTime. . . . . . . . . . . . . . . . . . . . . . . . . . . 33
J/P_Override_Interval . . . . . . . . . . . . . . . . . . . . . 16,33
JoinDesired(G). . . . . . . . . . . . . . . . . . . . . . . . . . 18
joins(G). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
JT(*,G) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
JT(G) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9,33
local_receiver_include(G,I) . . . . . . . . . . . . . . . . . . . 10
MFIB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
NLT(N,I). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Offer_Period. . . . . . . . . . . . . . . . . . . . . . . . . . . 32
olist(G). . . . . . . . . . . . . . . . . . . . . . . . . . .10,12,18
Bidirectional Capable OptionType . . . . . . . . . . . . . . . . 37
pim_include(G). . . . . . . . . . . . . . . . . . . . . . . . . . 10
PPT(G,I). . . . . . . . . . . . . . . . . . . . . . . . . . . 9,14,33
RPA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
RPF_interface(RPA). . . . . . . . . . . . . . . . . . . . . . . 10,12
RPL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
TIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
t_override. . . . . . . . . . . . . . . . . . . . . . . . . . . 17,33
t_periodic. . . . . . . . . . . . . . . . . . . . . . . . . . . 17,33
t_suppressed. . . . . . . . . . . . . . . . . . . . . . . . . . 17,33
Upstream. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
DF. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5,18
Downstream. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
DownstreamJPState(G,I). . . . . . . . . . . . . . . . . . . . . . 10
ET(G,I) . . . . . . . . . . . . . . . . . . . . . . . . . . . 9,14,33
ET(RPA,I) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
I_am_DF(RPA,I). . . . . . . . . . . . . . . . . . . . . . . .10,12,14
J/P_HoldTime. . . . . . . . . . . . . . . . . . . . . . . . . . . 33
J/P_Override_Interval . . . . . . . . . . . . . . . . . . . . . 16,33
JoinDesired(G). . . . . . . . . . . . . . . . . . . . . . . . . . 18
joins(G). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
JT(*,G) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
JT(G) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9,33
local_receiver_include(G,I) . . . . . . . . . . . . . . . . . . . 10
MFIB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
NLT(N,I). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Offer_Period. . . . . . . . . . . . . . . . . . . . . . . . . . . 32
olist(G). . . . . . . . . . . . . . . . . . . . . . . . . . .10,12,18
Bidirectional Capable OptionType . . . . . . . . . . . . . . . . 37
pim_include(G). . . . . . . . . . . . . . . . . . . . . . . . . . 10
PPT(G,I). . . . . . . . . . . . . . . . . . . . . . . . . . . 9,14,33
RPA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
RPF_interface(RPA). . . . . . . . . . . . . . . . . . . . . . . 10,12
RPL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
TIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
t_override. . . . . . . . . . . . . . . . . . . . . . . . . . . 17,33
t_periodic. . . . . . . . . . . . . . . . . . . . . . . . . . . 17,33
t_suppressed. . . . . . . . . . . . . . . . . . . . . . . . . . 17,33
Upstream. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses
Authors' Addressestranslate error, please retry
Mark Handley Computer Science Department University College London EMail: M.Handley@cs.ucl.ac.uk
马克·汉德利计算机科学系伦敦大学学院电子邮件：M。Handley@cs.ucl.ac.uk
Isidor Kouvelas Cisco Systems EMail: kouvelas@cisco.com
Isidor Kouvelas Cisco Systems电子邮件：kouvelas@cisco.com
Tony Speakman Cisco Systems EMail: speakman@cisco.com
Tony Speakman Cisco Systems电子邮件：speakman@cisco.com
Lorenzo Vicisano Digital Fountain EMail: lorenzo@digitalfountain.com
Lorenzo Vicisano数字喷泉电子邮件：lorenzo@digitalfountain.com
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