Network Working Group                                      T. Morin, Ed.
Request for Comments: 4834                            France Telecom R&D
Category: Informational                                       April 2007
Network Working Group                                      T. Morin, Ed.
Request for Comments: 4834                            France Telecom R&D
Category: Informational                                       April 2007

Requirements for Multicast in Layer 3 Provider-Provisioned Virtual Private Networks (PPVPNs)


Status of This Memo


This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.


Copyright Notice


Copyright (C) The IETF Trust (2007).




This document presents a set of functional requirements for network solutions that allow the deployment of IP multicast within Layer 3 (L3) Provider-Provisioned Virtual Private Networks (PPVPNs). It specifies requirements both from the end user and service provider standpoints. It is intended that potential solutions specifying the support of IP multicast within such VPNs will use these requirements as guidelines.


Table of Contents


   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  5
     2.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  5
     2.2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Problem Statement  . . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  Motivations  . . . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  General Requirements . . . . . . . . . . . . . . . . . . .  7
     3.3.  Scaling vs. Optimizing Resource Utilization  . . . . . . .  8
   4.  Use Cases  . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Scenarios  . . . . . . . . . . . . . . . . . . . . . . . .  8
       4.1.1.  Live Content Broadcast . . . . . . . . . . . . . . . .  9
       4.1.2.  Symmetric Applications . . . . . . . . . . . . . . . . 10
       4.1.3.  Data Distribution  . . . . . . . . . . . . . . . . . . 10
       4.1.4.  Generic Multicast VPN Offer  . . . . . . . . . . . . . 11
     4.2.  Scalability Orders of Magnitude  . . . . . . . . . . . . . 11
       4.2.1.  Number of VPNs with Multicast Enabled  . . . . . . . . 11
       4.2.2.  Number of Multicast VPNs per PE  . . . . . . . . . . . 12
       4.2.3.  Number of CEs per Multicast VPN per PE . . . . . . . . 12
       4.2.4.  PEs per Multicast VPN  . . . . . . . . . . . . . . . . 12
       4.2.5.  PEs with Multicast VRFs  . . . . . . . . . . . . . . . 13
       4.2.6.  Number of Streams Sourced  . . . . . . . . . . . . . . 13
   5.  Requirements for Supporting IP Multicast within L3 PPVPNs  . . 13
     5.1.  End User/Customer Standpoint . . . . . . . . . . . . . . . 13
       5.1.1.  Service Definition . . . . . . . . . . . . . . . . . . 13
       5.1.2.  CE-PE Multicast Routing and Group Management
               Protocols  . . . . . . . . . . . . . . . . . . . . . . 14
       5.1.3.  Quality of Service (QoS) . . . . . . . . . . . . . . . 14
       5.1.4.  Operations and Management  . . . . . . . . . . . . . . 15
       5.1.5.  Security Requirements  . . . . . . . . . . . . . . . . 16
       5.1.6.  Extranet . . . . . . . . . . . . . . . . . . . . . . . 17
       5.1.7.  Internet Multicast . . . . . . . . . . . . . . . . . . 18
       5.1.8.  Carrier's Carrier  . . . . . . . . . . . . . . . . . . 18
       5.1.9.  Multi-Homing, Load Balancing, and Resiliency . . . . . 19
       5.1.10. RP Engineering . . . . . . . . . . . . . . . . . . . . 19
       5.1.11. Addressing . . . . . . . . . . . . . . . . . . . . . . 20
       5.1.12. Minimum MTU  . . . . . . . . . . . . . . . . . . . . . 20
     5.2.  Service Provider Standpoint  . . . . . . . . . . . . . . . 21
       5.2.1.  General Requirement  . . . . . . . . . . . . . . . . . 21
       5.2.2.  Scalability  . . . . . . . . . . . . . . . . . . . . . 21
       5.2.3.  Resource Optimization  . . . . . . . . . . . . . . . . 23
       5.2.4.  Tunneling Requirements . . . . . . . . . . . . . . . . 24
       5.2.5.  Control Mechanisms . . . . . . . . . . . . . . . . . . 26
       5.2.6.  Support of Inter-AS, Inter-Provider Deployments  . . . 26
       5.2.7.  Quality-of-Service Differentiation . . . . . . . . . . 27
       5.2.8.  Infrastructure security  . . . . . . . . . . . . . . . 27
       5.2.9.  Robustness . . . . . . . . . . . . . . . . . . . . . . 28
   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  5
     2.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  5
     2.2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Problem Statement  . . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  Motivations  . . . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  General Requirements . . . . . . . . . . . . . . . . . . .  7
     3.3.  Scaling vs. Optimizing Resource Utilization  . . . . . . .  8
   4.  Use Cases  . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Scenarios  . . . . . . . . . . . . . . . . . . . . . . . .  8
       4.1.1.  Live Content Broadcast . . . . . . . . . . . . . . . .  9
       4.1.2.  Symmetric Applications . . . . . . . . . . . . . . . . 10
       4.1.3.  Data Distribution  . . . . . . . . . . . . . . . . . . 10
       4.1.4.  Generic Multicast VPN Offer  . . . . . . . . . . . . . 11
     4.2.  Scalability Orders of Magnitude  . . . . . . . . . . . . . 11
       4.2.1.  Number of VPNs with Multicast Enabled  . . . . . . . . 11
       4.2.2.  Number of Multicast VPNs per PE  . . . . . . . . . . . 12
       4.2.3.  Number of CEs per Multicast VPN per PE . . . . . . . . 12
       4.2.4.  PEs per Multicast VPN  . . . . . . . . . . . . . . . . 12
       4.2.5.  PEs with Multicast VRFs  . . . . . . . . . . . . . . . 13
       4.2.6.  Number of Streams Sourced  . . . . . . . . . . . . . . 13
   5.  Requirements for Supporting IP Multicast within L3 PPVPNs  . . 13
     5.1.  End User/Customer Standpoint . . . . . . . . . . . . . . . 13
       5.1.1.  Service Definition . . . . . . . . . . . . . . . . . . 13
       5.1.2.  CE-PE Multicast Routing and Group Management
               Protocols  . . . . . . . . . . . . . . . . . . . . . . 14
       5.1.3.  Quality of Service (QoS) . . . . . . . . . . . . . . . 14
       5.1.4.  Operations and Management  . . . . . . . . . . . . . . 15
       5.1.5.  Security Requirements  . . . . . . . . . . . . . . . . 16
       5.1.6.  Extranet . . . . . . . . . . . . . . . . . . . . . . . 17
       5.1.7.  Internet Multicast . . . . . . . . . . . . . . . . . . 18
       5.1.8.  Carrier's Carrier  . . . . . . . . . . . . . . . . . . 18
       5.1.9.  Multi-Homing, Load Balancing, and Resiliency . . . . . 19
       5.1.10. RP Engineering . . . . . . . . . . . . . . . . . . . . 19
       5.1.11. Addressing . . . . . . . . . . . . . . . . . . . . . . 20
       5.1.12. Minimum MTU  . . . . . . . . . . . . . . . . . . . . . 20
     5.2.  Service Provider Standpoint  . . . . . . . . . . . . . . . 21
       5.2.1.  General Requirement  . . . . . . . . . . . . . . . . . 21
       5.2.2.  Scalability  . . . . . . . . . . . . . . . . . . . . . 21
       5.2.3.  Resource Optimization  . . . . . . . . . . . . . . . . 23
       5.2.4.  Tunneling Requirements . . . . . . . . . . . . . . . . 24
       5.2.5.  Control Mechanisms . . . . . . . . . . . . . . . . . . 26
       5.2.6.  Support of Inter-AS, Inter-Provider Deployments  . . . 26
       5.2.7.  Quality-of-Service Differentiation . . . . . . . . . . 27
       5.2.8.  Infrastructure security  . . . . . . . . . . . . . . . 27
       5.2.9.  Robustness . . . . . . . . . . . . . . . . . . . . . . 28
       5.2.10. Operation, Administration, and Maintenance . . . . . . 28
       5.2.11. Compatibility and Migration Issues . . . . . . . . . . 29
       5.2.12. Troubleshooting  . . . . . . . . . . . . . . . . . . . 30
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 30
   7.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 31
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 31
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 32
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 33
       5.2.10. Operation, Administration, and Maintenance . . . . . . 28
       5.2.11. Compatibility and Migration Issues . . . . . . . . . . 29
       5.2.12. Troubleshooting  . . . . . . . . . . . . . . . . . . . 30
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 30
   7.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 31
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 31
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 32
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 33
1. Introduction
1. 介绍

Virtual Private Network (VPN) services satisfying the requirements defined in [RFC4031] are now being offered by many service providers throughout the world. VPN services are popular because customers need not be aware of the VPN technologies deployed in the provider network. They scale well for the following reasons:


o because P routers (Provider Routers) need not be aware of VPN service details

o 因为P路由器(提供商路由器)不需要知道VPN服务的详细信息

o because the addition of a new VPN member requires only limited configuration effort

o 因为添加新的VPN成员只需要有限的配置工作

There is also a growing need for support of IP multicast-based services. Efforts to provide efficient IP multicast routing protocols and multicast group management have been made in standardization bodies which has led, in particular, to the definition of Protocol Independent Multicast (PIM) and Internet Group Management Protocol (IGMP).


However, multicast traffic is not natively supported within existing L3 PPVPN solutions. Deploying multicast over an L3VPN today, with only currently standardized solutions, requires designing customized solutions which will be inherently limited in terms of scalability, operational efficiency, and bandwidth usage.

但是,现有L3 PPVPN解决方案不支持本地多播通信。在目前只有标准化解决方案的L3VPN上部署多播需要设计定制的解决方案,而定制的解决方案在可扩展性、操作效率和带宽使用方面都会受到固有的限制。

This document complements the generic L3VPN requirements [RFC4031] document, by specifying additional requirements specific to the deployment within PPVPNs of services based on IP multicast. It clarifies the needs of both VPN clients and providers and formulates the problems that should be addressed by technical solutions with the key objective being to remain solution agnostic. There is no intent in this document to specify either solution-specific details or application-specific requirements. Also, this document does NOT aim at expressing multicast-related requirements that are not specific to L3 PPVPNs.

本文件补充了通用L3VPN要求[RFC4031]文件,具体规定了PPVPN内基于IP多播的服务部署的额外要求。它阐明了VPN客户端和提供商的需求,并阐述了技术解决方案应解决的问题,其主要目标是保持解决方案不可知性。本文档无意指定特定于解决方案的详细信息或特定于应用程序的要求。此外,本文档的目的并不是表达与多播相关的要求,这些要求并非特定于L3 PPVPN。

It is expected that solutions that specify procedures and protocol extensions for multicast in L3 PPVPNs SHOULD satisfy these requirements.

预计在L3 PPVPN中指定多播过程和协议扩展的解决方案应满足这些要求。

2. Conventions Used in This Document
2. 本文件中使用的公约
2.1. Terminology
2.1. 术语

Although the reader is assumed to be familiar with the terminology defined in [RFC4031], [RFC4364], [RFC4601], and [RFC4607], the following glossary of terms may be worthwhile.


We also propose here generic terms for concepts that naturally appear when multicast in VPNs is discussed.


ASM: Any Source Multicast. One of the two multicast service models, in which a terminal subscribes to a multicast group to receive data sent to the group by any source.


Multicast-enabled VPN, multicast VPN, or mVPN: A VPN that supports IP multicast capabilities, i.e., for which some PE devices (if not all) are multicast-enabled and whose core architecture supports multicast VPN routing and forwarding.


PPVPN: Provider-Provisioned Virtual Private Network.


PE, CE: "Provider Edge", "Customer Edge" (as defined in [RFC4026]). As suggested in [RFC4026], we will use these notations to refer to the equipments/routers/devices themselves. Thus, "PE" will refer to the router on the provider's edge, which faces the "CE", the router on the customer's edge.


VRF or VR: By these terms, we refer to the entity defined in a PE dedicated to a specific VPN instance. "VRF" refers to "VPN Routing and Forwarding table" as defined in [RFC4364], and "VR" to "Virtual Router" as defined in [VRs] terminology.


MDTunnel: Multicast Distribution Tunnel. The means by which the customer's multicast traffic will be transported across the SP network. This is meant in a generic way: such tunnels can be either point-to-point or point-to-multipoint. Although this definition may seem to assume that distribution tunnels are unidirectional, the wording also encompasses bidirectional tunnels.


S: Denotes a multicast source.


G: Denotes a multicast group.


Multicast channel: In the multicast SSM model [RFC4607], a "multicast channel" designates traffic from a specific source S to a multicast group G. Also denominated as "(S,G)".


SP: Service provider.


SSM: Source Specific Multicast. One of the two multicast service models, where a terminal subscribes to a multicast group to receive data sent to the group by a specific source.


RP: Rendezvous Point (Protocol Independent Multicast - Sparse Mode (PIM-SM) [RFC4601]).


P2MP, MP2MP: Designate "Point-to-Multipoint" and "Multipoint-to-Multipoint" replication trees.


L3VPN, VPN: Throughout this document, "L3VPN" or even just "VPN" will refer to "Provider-Provisioned Layer 3 Virtual Private Network" (PP L3VPNs), and will be preferred for readability.

L3VPN、VPN:在本文档中,“L3VPN”甚至只是“VPN”将指的是“提供商提供的第3层虚拟专用网络”(PP L3VPN),并且出于可读性考虑,将优先考虑。

Please refer to [RFC4026] for details about terminology specifically relevant to VPN aspects, and to [RFC2432] for multicast performance or quality of service (QoS)-related terms.


2.2. Conventions
2.2. 习俗

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].


3. Problem Statement
3. 问题陈述
3.1. Motivations
3.1. 动机

More and more L3VPN customers use IP multicast services within their private infrastructures. Naturally, they want to extend these multicast services to remote sites that are connected via a VPN.


For instance, the customer could be a national TV channel with several geographical locations that wants to broadcast a TV program from a central point to several regional locations within its VPN.


A solution to support multicast traffic could consist of point-to-point tunnels across the provider network and requires the PEs (Provider Edge routers) to replicate traffic. This would obviously be sub-optimal as it would place the replication burden on the PE and hence would have very poor scaling characteristics. It would also probably waste bandwidth and control plane resources in the provider's network.


Thus, to provide multicast services for L3VPN networks in an efficient manner (that is, with a scalable impact on signaling and protocol state as well as bandwidth usage), in a large-scale environment, new mechanisms are required to enhance existing L3VPN solutions for proper support of multicast-based services.


3.2. General Requirements
3.2. 一般要求

This document sets out requirements for L3 provider-provisioned VPN solutions designed to carry customers' multicast traffic. The main requirement is that a solution SHOULD first satisfy the requirements documented in [RFC4031]: as far as possible, a multicast service should have the same characteristics as the unicast equivalent, including the same simplicity (technology unaware), the same quality of service (if any), the same management (e.g., performance monitoring), etc.


Moreover, it also has to be clear that a multicast VPN solution MUST interoperate seamlessly with current unicast VPN solutions. It would also make sense that multicast VPN solutions define themselves as extensions to existing L3 provider-provisioned VPN solutions (such as for instance, [RFC4364] or [VRs]) and retain consistency with those, although this is not a core requirement.


The requirements in this document are equally applicable to IPv4 and IPv6, for both customer- and provider-related matters.


3.3. Scaling vs. Optimizing Resource Utilization
3.3. 扩展与优化资源利用率

When transporting multicast VPN traffic over a service provider network, there intrinsically is tension between scalability and resource optimization, since the latter is likely to require the maintenance of control plane states related to replication trees in the core network [RFC3353].


Consequently, any deployment will require a trade-off to be made. This document will express some requirements related to this trade-off.


4. Use Cases
4. 用例

The goal of this section is to highlight how different applications and network contexts may have a different impact on how a multicast VPN solution is designed, deployed, and tuned. For this purpose, we describe some typical use case scenarios and express expectations in terms of deployment orders of magnitude.


Most of the content of these sections originates from a survey done in summer 2005, among institutions and providers that expect to deploy such solutions. The full survey text and raw results (13 responses) were published separately, and we only present here the most relevant facts and expectations that the survey exposed.


For scalability figures, we considered that it was relevant to highlight the highest expectations, those that are expected to have the greatest impact on solution design. For balance, we do also mention cases where such high expectations were expressed in only a few answers.


4.1. Scenarios
4.1. 情节

We don't provide here an exhaustive set of scenarios that a multicast VPN solution is expected to support -- no solution should restrict the scope of multicast applications and deployments that can be done over a multicast VPN.


Hence, we only give here a short list of scenarios that are expected to have a large impact on the design of a multicast VPN solution.


4.1.1. Live Content Broadcast
4.1.1. 直播

Under this label, we group all applications that distribute content (audio, video, or other content) with the property that this content is expected to be consulted at once ("live") by the receiver. Typical applications are broadcast TV, production studio connectivity, and distribution of market data feeds.


The characteristics of such applications are the following:


o one or few sources to many receivers

o 从一个或几个源到多个接收器

o sources are often in known locations; receivers are in less predictable locations (this latter point may depend on applications)

o 来源通常位于已知位置;接收器位于不太可预测的位置(后一点可能取决于应用程序)

o in some cases, it is expected that the regularity of audience patterns may help improve how the bandwidth/state trade-off is handled

o 在某些情况下,预期受众模式的规律性可能有助于改进带宽/状态权衡的处理方式

o the number of streams can be as high as hundreds, or even thousands, of streams

o 流的数量可以高达数百条,甚至数千条

o bandwidth will depend on the application, but may vary between a few tens/hundreds of Kb/s (e.g., audio or low-quality video media) and tens of Mb/s (high-quality video), with some demanding professional applications requiring as much as hundreds of Mb/s.

o 带宽将取决于应用程序,但可能在几十/数百Kb/s(例如音频或低质量视频媒体)和几十Mb/s(高质量视频)之间变化,一些要求苛刻的专业应用程序需要数百Mb/s。

o QoS requirements include, in many cases, a low multicast group join delay

o 在许多情况下,QoS要求包括较低的多播组加入延迟

o QoS of these applications is likely to be impacted by packet loss (some applications may be robust to low packet loss) and to have low robustness against jitter

o 这些应用程序的QoS可能会受到数据包丢失的影响(一些应用程序可能对低数据包丢失具有鲁棒性),并且对抖动具有较低的鲁棒性

o delay sensitivity will depend on the application: some applications are not so delay sensitive (e.g., broadcast TV), whereas others may require very low delay (professional studio applications)

o 延迟敏感度取决于应用:一些应用程序对延迟不敏感(例如广播电视),而其他应用程序可能需要非常低的延迟(专业演播室应用程序)

o some of these applications may involve rapid changes in customer multicast memberships as seen by the PE, but this will depend on audience patterns and on the amount of provider equipments deployed close to VPN customers

o 这些应用中的一些可能涉及到PE所看到的客户多播成员身份的快速变化,但这将取决于受众模式和部署在VPN客户附近的提供商设备的数量

4.1.2. Symmetric Applications
4.1.2. 对称应用

Some use cases exposed by the survey can be grouped under this label, and include many-to-many applications such as conferencing and server cluster monitoring.


They are characterized by the relatively high number of streams that they can produce, which has a direct impact on scalability expectations.


A sub-case of this scenario is the case of symmetric applications with small groups, when the number of receivers is low compared to the number of sites in the VPNs (e.g., video conferencing and e-learning applications).


This latter case is expected to be an important input to solution design, since it may significantly impact how the bandwidth/state is managed.


Optimizing bandwidth may require introducing dedicated states in the core network (typically as much as the number of groups) for the following reasons:


o small groups, and low predictability of the location of participants ("sparse groups")

o 小群体,参与者位置的可预测性低(“稀疏群体”)

o possibly significantly high bandwidth (a few Mb/s per participant)

o 带宽可能非常高(每个参与者几Mb/s)

Lastly, some of these applications may involve real-time interactions and will be highly sensitive to packet loss, jitter, and delay.


4.1.3. Data Distribution
4.1.3. 数据分布

Some applications that are expected to be deployed on multicast VPNs are non-real-time applications aimed at distributing data from few sources to many receivers.


Such applications may be considered to have lower expectations than their counterparts proposed in this document, since they would not necessarily involve more data streams and are more likely to adapt to the available bandwidth and to be robust to packet loss, jitter, and delay.


One important property is that such applications may involve higher bandwidths (hundreds of Mb/s).


4.1.4. Generic Multicast VPN Offer
4.1.4. 通用多播VPN服务

This ISP scenario is a deployment scenario where IP-multicast connectivity is proposed for every VPN: if a customer requests a VPN, then this VPN will support IP multicast by default. In this case, the number of multicast VPNs equals the number of VPNs. This implies a quite important scalability requirement (e.g., hundreds of PEs, hundreds of VPNs per PE, with a potential increase by one order of magnitude in the future).


The per-mVPN traffic behavior is not predictable because how the service is used is completely up to the customer. This results in a traffic mix of the scenarios mentioned in Section 4.1. QoS requirements are similar to typical unicast scenarios, with the need for different classes. Also, in such a context, a reasonably large range of protocols should be made available to the customer for use at the PE-CE level.


Also, in such a scenario, customers may want to deploy multicast connectivity between two or more multicast VPNs as well as access to Internet Multicast.


4.2. Scalability Orders of Magnitude
4.2. 可伸缩性数量级

This section proposes orders of magnitude for different scalability metrics relevant for multicast VPN issues. It should be noted that the scalability figures proposed here relate to scalability expectations of future deployments of multicast VPN solutions, as the authors chose to not restrict the scope to only currently known deployments.


4.2.1. Number of VPNs with Multicast Enabled
4.2.1. 启用多播的VPN数量

From the survey results, we see a broad range of expectations. There are extreme answers: from 5 VPNs (1 answer) to 10k VPNs (1 answer), but more typical answers are split between the low range of tens of VPNs (7 answers) and the higher range of hundreds or thousands of VPNs (2 + 4 answers).

从调查结果中,我们看到了广泛的期望。有一些极端的答案:从5个VPN(1个答案)到10k VPN(1个答案),但更典型的答案分为低范围的数十个VPN(7个答案)和高范围的数百或数千个VPN(2+4个答案)。

A solution SHOULD support a number of multicast VPNs ranging from one to several thousands.


A solution SHOULD NOT limit the proportion of multicast VPNs among all (unicast) VPNs.


4.2.2. Number of Multicast VPNs per PE
4.2.2. 每个PE的多播VPN数

The majority of survey answers express a number of multicast VPNs per PE of around tens (8 responses between 5 and 50); a significant number of them (4) expect deployments with hundreds or thousands (1 response) of multicast VPNs per PE.


A solution SHOULD support a number of multicast VPNs per PE of several hundreds, and may have to scale up to thousands of VPNs per PE.


4.2.3. Number of CEs per Multicast VPN per PE
4.2.3. 每个PE的每个多播VPN的CE数

Survey responses span from 1 to 2000 CEs per multicast VPN per PE. Most typical responses are between tens (6 answers) and hundreds (4 responses).

调查响应范围为每个多播VPN每个PE 1到2000个CE。最典型的回答介于十(6个答案)和数百(4个答案)之间。

A solution SHOULD support a number of CEs per multicast VPN per PE going up to several hundreds (and may target the support of thousands of CEs).


4.2.4. PEs per Multicast VPN
4.2.4. 每多播VPN的PEs

People who answered the survey typically expect deployments with the number of PEs per multicast VPN in the range of hundreds of PEs (6 responses) or tens of PEs (4 responses). Two responses were in the range of thousands (one mentioned a 10k figure).


A multicast VPN solution SHOULD support several hundreds of PEs per multicast VPN, and MAY usefully scale up to thousands.

多播VPN解决方案应该支持每个多播VPN数百个PE,并且可以有效地扩展到数千个。 ... with Sources ... 有消息来源

The number of PEs (per VPN) that would be connected to sources seems to be significantly lower than the number of PEs per VPN. This is obviously related to the fact that many respondents mentioned deployments related to content broadcast applications (one to many).


Typical numbers are tens (6 responses) or hundreds (4 responses) of source-connected PEs. One respondent expected a higher number of several thousands.


A solution SHOULD support hundreds of source-connected PEs per VPN, and some deployment scenarios involving many-to-many applications may require supporting a number of source-connected PEs equal to the number of PEs (hundreds or thousands).

一个解决方案应该支持每个VPN数百个源连接的PE,一些涉及多对多应用程序的部署场景可能需要支持与PE数量相等的源连接的PE数量(数百或数千)。 ... with Receivers ... 带接收器

The survey showed that the number of PEs with receivers is expected to be of the same order of magnitude as the number of PEs in a multicast VPN. This is consistent with the intrinsic nature of most multicast applications, which have few source-only participants.


4.2.5. PEs with Multicast VRFs
4.2.5. 具有多播VRFs的PEs

A solution SHOULD scale up to thousands of PEs having multicast service enabled.


4.2.6. Number of Streams Sourced
4.2.6. 来源的流数

Survey responses led us to retain the following orders of magnitude for the number of streams that a solution SHOULD support:


per VPN: hundreds or thousands of streams


per PE: hundreds of streams


5. Requirements for Supporting IP Multicast within L3 PPVPNs
5. 在L3 PPVPN中支持IP多播的要求

Again, the aim of this document is not to specify solutions but to give requirements for supporting IP multicast within L3 PPVPNs.

同样,本文档的目的不是指定解决方案,而是给出在L3 PPVPN中支持IP多播的要求。

In order to list these requirements, we have taken the standpoint of two different important entities: the end user (the customer using the VPN) and the service provider.


In the rest of the document, by "a solution" or "a multicast VPN solution", we mean a solution that allows multicast in an L3 provider-provisioned VPN, and which addresses the requirements listed in this document.


5.1. End User/Customer Standpoint
5.1. 最终用户/客户立场
5.1.1. Service Definition
5.1.1. 服务定义

As for unicast, the multicast service MUST be provider provisioned and SHALL NOT require customer devices (CEs) to support any extra features compared to those required for multicast in a non-VPN context. Enabling a VPN for multicast support SHOULD be possible with no impact (or very limited impact) on existing multicast protocols possibly already deployed on the CE devices.


5.1.2. CE-PE Multicast Routing and Group Management Protocols
5.1.2. CE-PE多播路由和组管理协议

Consequently to Section 5.1.1, multicast-related protocol exchanges between a CE and its directly connected PE SHOULD happen via existing multicast protocols.


Such protocols include: PIM-SM [RFC4601], bidirectional-PIM [BIDIR-PIM], PIM - Dense Mode (DM) [RFC3973], and IGMPv3 [RFC3376] (this version implicitly supports hosts that only implement IGMPv1 [RFC1112] or IGMPv2 [RFC2236]).


Among those protocols, the support of PIM-SM (which includes the SSM model) and either IGMPv3 (for IPv4 solutions) and/or Multicast Listener Discovery Version 2 (MLDv2) [RFC3810] (for IPv6 solutions) is REQUIRED. Bidir-PIM support at the PE-CE interface is RECOMMENDED. And considering deployments, PIM-DM is considered OPTIONAL.

在这些协议中,需要PIM-SM(包括SSM模型)和IGMPv3(用于IPv4解决方案)和/或多播侦听器发现版本2(MLDv2)[RFC3810](用于IPv6解决方案)的支持。建议在PE-CE接口上支持Bidir PIM。考虑到部署,PIM-DM被认为是可选的。

When a multicast VPN solution is built on a VPN solution supporting IPv6 unicast, it MUST also support v6 variants of the above protocols, including MLDv2, and PIM-SM IPv6-specific procedures. For a multicast VPN solution built on a unicast VPN solution supporting only IPv4, it is RECOMMENDED that the design favors the definition of procedures and encodings that will provide an easy adaptation to IPv6.

当多播VPN解决方案构建在支持IPv6单播的VPN解决方案上时,它还必须支持上述协议的v6变体,包括MLDv2和PIM-SM IPv6特定过程。对于基于仅支持IPv4的单播VPN解决方案构建的多播VPN解决方案,建议该设计有利于定义可轻松适应IPv6的过程和编码。

5.1.3. Quality of Service (QoS)
5.1.3. 服务质量(QoS)

Firstly, general considerations regarding QoS in L3VPNs expressed in Section 5.5 of [RFC4031] are also relevant to this section.


QoS is measured in terms of delay, jitter, packet loss, and availability. These metrics are already defined for the current unicast PPVPN services and are included in Service Level Agreements (SLAs). In some cases, the agreed SLA may be different between unicast and multicast, and that will require differentiation mechanisms in order to monitor both SLAs.


The level of availability for the multicast service SHOULD be on par with what exists for unicast traffic. For instance, comparable traffic protection mechanisms SHOULD be available for customer multicast traffic when it is carried over the service provider's network.


A multicast VPN solution SHALL allow a service provider to define at least the same level of quality of service as exists for unicast, and as exists for multicast in a non-VPN context. From this perspective, the deployment of multicast-based services within an L3VPN


environment SHALL benefit from Diffserv [RFC2475] mechanisms that include multicast traffic identification, classification, and marking capabilities, as well as multicast traffic policing, scheduling, and conditioning capabilities. Such capabilities MUST therefore be supported by any participating device in the establishment and the maintenance of the multicast distribution tunnel within the VPN.


As multicast is often used to deliver high-quality services such as TV broadcast, a multicast VPN solution MAY provide additional features to support high QoS such as bandwidth reservation and admission control.


Also, considering that multicast reception is receiver-triggered, group join delay (as defined in [RFC2432]) is also considered one important QoS parameter. It is thus RECOMMENDED that a multicast VPN solution be designed appropriately in this regard.


The group leave delay (as defined in [RFC2432]) may also be important on the CE-PE link for some usage scenarios: in cases where the typical bandwidth of multicast streams is close to the bandwidth of a PE-CE link, it will be important to have the ability to stop the emission of a stream on the PE-CE link as soon as it stops being requested by the CE, to allow for fast switching between two different high-throughput multicast streams. This implies that it SHOULD be possible to tune the multicast routing or group management protocols (e.g., IGMP/MLD or PIM) used on the PE-CE adjacency to reduce the group leave delay to the minimum.


Lastly, a multicast VPN solution SHOULD as much as possible ensure that client multicast traffic packets are neither lost nor duplicated, even when changes occur in the way a client multicast data stream is carried over the provider network. Packet loss issues also have to be considered when a new source starts to send traffic to a group: any receiver interested in receiving such traffic SHOULD be serviced accordingly.


5.1.4. Operations and Management
5.1.4. 业务和管理

The requirements and definitions for operations and management (OAM) of L3VPNs that are defined in [RFC4176] equally apply to multicast, and are not extensively repeated in this document. This sub-section mentions the most important guidelines and details points of particular relevance in the context of multicast in L3VPNs.


A multicast VPN solution SHOULD allow a multicast VPN customer to manage the capabilities and characteristics of their multicast VPN services.


A multicast VPN solution MUST support SLA monitoring capabilities, which SHOULD rely upon techniques similar to those used for the unicast service for the same monitoring purposes. Multicast SLA-related metrics SHOULD be available through means similar to the ones already used for unicast-related monitoring, such as Simple Network Management Protocol (SNMP) [RFC3411] or IPFIX [IPFIX-PROT].


Multicast-specific characteristics that may be monitored include: multicast statistics per stream, end-to-end delay, and group join/ leave delay (time to start/stop receiving a multicast group's traffic across the VPN, as defined in [RFC2432], Section 3).


The monitoring of multicast-specific parameters and statistics MUST include multicast traffic statistics: total/incoming/outgoing/dropped traffic, by period of time. It MAY include IP Performance Metrics related information (IPPM, [RFC2330]) that is relevant to the multicast traffic usage: such information includes the one-way packet delay, the inter-packet delay variation, etc. See [MULTIMETRICS].


A generic discussion of SLAs is provided in [RFC3809].


Apart from statistics on multicast traffic, customers of a multicast VPN will need information concerning the status of their multicast resource usage (multicast routing states and bandwidth). Indeed, as mentioned in Section 5.2.5, for scalability purposes, a service provider may limit the number (and/or throughput) of multicast streams that are received/sent to/from a client site. In such a case, a multicast VPN solution SHOULD allow customers to find out their current resource usage (multicast routing states and throughput), and to receive some kind of feedback if their usage exceeds the agreed bounds. Whether this issue will be better handled at the protocol level at the PE-CE interface or at the Service Management Level interface [RFC4176] is left for further discussion.


It is RECOMMENDED that any OAM mechanism designed to trigger alarms in relation to performance or resource usage metrics integrate the ability to limit the rate at which such alarms are generated (e.g., some form of a hysteresis mechanism based on low/high thresholds defined for the metrics).


5.1.5. Security Requirements
5.1.5. 安全要求

Security is a key point for a customer who uses a VPN service. For instance, the [RFC4364] model offers some guarantees concerning the security level of data transmission within the VPN.


A multicast VPN solution MUST provide an architecture with the same level of security for both unicast and multicast traffic.


Moreover, the activation of multicast features SHOULD be possible:


o per VRF / per VR

o 每VRF/每VR

o per CE interface (when multiple CEs of a VPN are connected to a common VRF/VR)

o 每个CE接口(当VPN的多个CE连接到公共VRF/VR时)

o per multicast group and/or per channel

o 每个多播组和/或每个通道

o with a distinction between multicast reception and emission

o 区分多播接收和发射

A multicast VPN solution may choose to make the optimality/ scalability trade-off stated in Section 3.3 by sometimes distributing multicast traffic of a client group to a larger set of PE routers that may include PEs that are not part of the VPN. From a security standpoint, this may be a problem for some VPN customers; thus, a multicast VPN solution using such a scheme MAY offer ways to avoid this for specific customers (and/or specific customer multicast streams).


5.1.6. Extranet
5.1.6. 外联网

In current PP L3VPN models, a customer site may be set up to be part of multiple VPNs, and this should still be possible when a VPN is multicast-enabled. In practice, it means that a VRF or VR can be part of more than one VPN.

在当前的PP L3VPN模型中,可以将客户站点设置为多个VPN的一部分,并且当VPN启用多播时,这仍然是可能的。实际上,这意味着VRF或VR可以是多个VPN的一部分。

A multicast VPN solution MUST support such deployments.


For instance, it must be possible to configure a VRF so that an enterprise site participating in a BGP/MPLS multicast-enabled VPN and connected to that VRF can receive a multicast stream from (or originate a multicast stream towards) another VPN that would be associated to that VRF.


This means that a multicast VPN solution MUST offer means for a VRF to be configured so that multicast connectivity can be set up for a chosen set of extranet VPNs. More precisely, it MUST be possible to configure a VRF so that:


o receivers behind attached CEs can receive multicast traffic sourced in the configured set of extranet VPNs

o 连接的CEs后面的接收器可以接收源于配置的外部网络VPN集中的多播流量

o sources behind attached CEs can reach multicast traffic receivers located in the configured set of extranet VPNs

o 连接的CEs后面的源可以到达位于配置的外部网VPN集中的多播流量接收器

o multicast reception and emission can be independently enabled for each of the extranet VPNs

o 可以为每个外部网VPN独立启用多播接收和发射

Moreover, a solution MUST allow service providers to control an extranet's multicast connectivity independently from the extranet's unicast connectivity. More specifically:


o enabling unicast connectivity to another VPN MUST be possible without activating multicast connectivity with that VPN

o 必须能够启用到另一个VPN的单播连接,而无需激活与该VPN的多播连接

o enabling multicast connectivity with another VPN SHOULD NOT require more than the strict minimal unicast routing. Sending multicast to a VPN SHOULD NOT require having unicast routes to that VPN; receiving multicast from a VPN SHOULD be possible with nothing more than unicast routes to the relevant multicast sources of that VPN

o 启用与另一个VPN的多播连接不应要求严格的最小单播路由。向VPN发送多播不应要求具有到该VPN的单播路由;从VPN接收多播应该只需要单播路由就可以到达该VPN的相关多播源

o when unicast routes from another VPN are imported into a VR/VRF, for multicast Reverse Path Forwarding (RPF) resolution, this SHOULD be possible without making those routes available for unicast routing

o 当来自另一个VPN的单播路由导入到VR/VRF中时,对于多播反向路径转发(RPF)解决方案,这应该是可能的,而无需使这些路由可用于单播路由

Proper support for this feature SHOULD NOT require replicating multicast traffic on a PE-CE link, whether it is a physical or logical link.


5.1.7. Internet Multicast
5.1.7. 因特网多播

Connectivity with Internet Multicast is a particular case of the previous section, where sites attached to a VR/VRF would need to receive/send multicast traffic from/to the Internet.


This should be considered OPTIONAL given the additional considerations, such as security, needed to fulfill the requirements for providing Internet Multicast.


5.1.8. Carrier's Carrier
5.1.8. 承运人的承运人

Many L3 PPVPN solutions, such as [RFC4364] and [VRs], define the "Carrier's Carrier" model, where a "carrier's carrier" service provider supports one or more customer ISPs, or "sub-carriers". A multicast VPN solution SHOULD support the carrier's carrier model in a scalable and efficient manner.

许多L3 PPVPN解决方案,如[RFC4364]和[VRs],定义了“运营商运营商”模式,其中“运营商运营商”服务提供商支持一个或多个客户ISP或“子运营商”。多播VPN解决方案应以可扩展和高效的方式支持运营商的运营商模型。

Ideally, the range of tunneling protocols available for the sub-carrier ISP should be the same as those available for the carrier's carrier ISP. This implies that the protocols that may be used at the PE-CE level SHOULD NOT be restricted to protocols required as per Section 5.1.2 and SHOULD include some of the protocols listed in Section 5.2.4, such as for instance P2MP MPLS signaling protocols.

理想情况下,子载波ISP可用的隧道协议范围应与载波ISP可用的隧道协议范围相同。这意味着可在PE-CE级别使用的协议不应限于第5.1.2节要求的协议,并且应包括第5.2.4节中列出的一些协议,例如P2MP MPLS信令协议。

In the context of MPLS-based L3VPN deployments, such as BGP/MPLS VPNs [RFC4364], this means that MPLS label distribution SHOULD happen at the PE-CE level, giving the ability to the sub-carrier to use multipoint LSPs as a tunneling mechanism.

在基于MPLS的L3VPN部署环境中,如BGP/MPLS VPN[RFC4364],这意味着MPLS标签分发应在PE-CE级别进行,使子载波能够使用多点LSP作为隧道机制。

5.1.9. Multi-Homing, Load Balancing, and Resiliency
5.1.9. 多宿主、负载平衡和恢复能力

A multicast VPN solution SHOULD be compatible with current solutions that aim at improving the service robustness for customers such as multi-homing, CE-PE link load balancing, and fail-over. A multicast VPN solution SHOULD also be able to offer those same features for multicast traffic.


Any solution SHOULD support redundant topology of CE-PE links. It SHOULD minimize multicast traffic disruption and fail-over.


5.1.10. RP Engineering
5.1.10. RP工程

When PIM-SM (or bidir-PIM) is used in ASM mode on the VPN customer side, the RP function (or RP-address in the case of bidir-PIM) has to be associated to a node running PIM, and configured on this node.

当在VPN客户端的ASM模式下使用PIM-SM(或bidir PIM)时,RP功能(或bidir PIM情况下的RP地址)必须与运行PIM的节点相关联,并在此节点上进行配置。 RP Outsourcing RP外包

In the case of PIM-SM in ASM mode, engineering of the RP function requires the deployment of specific protocols and associated configurations. A service provider may offer to manage customers' multicast protocol operation on their behalf. This implies that it is necessary to consider cases where a customer's RPs are outsourced (e.g., on PEs). Consequently, a VPN solution MAY support the hosting of the RP function in a VR or VRF.

对于ASM模式下的PIM-SM,RP功能的工程设计需要部署特定协议和相关配置。服务提供商可以代表客户管理其多播协议操作。这意味着有必要考虑客户的RPS外包的情况(例如,在PES上)。因此,VPN解决方案可支持在VR或VRF中托管RP功能。 RP Availability RP可用性

Availability of the RP function (or address) is required for proper operation of PIM-SM (ASM mode) and bidir-PIM. Loss of connectivity to the RP from a receiver or source will impact the multicast service. For this reason, different mechanisms exist, such as BSR [PIM-BSR] or anycast-RP (Multicast Source Discovery Protocol (MSDP)- based [RFC3446] or PIM-based [RFC4610]).

正确操作PIM-SM(ASM模式)和bidir PIM需要RP功能(或地址)的可用性。接收器或源与RP的连接中断将影响多播服务。因此,存在不同的机制,例如BSR[PIM-BSR]或基于多播源发现协议(MSDP)的[RFC3446]或基于PIM的[RFC4610])。

These protocols and procedures SHOULD work transparently through a multicast VPN, and MAY if relevant, be implemented in a VRF/VR.


Moreover, a multicast VPN solution MAY improve the robustness of the ASM multicast service regarding loss of connectivity to the RP, by providing specific features that help:


a) maintain ASM multicast service among all the sites within an MVPN that maintain connectivity among themselves, even when the site(s) hosting the RP lose their connectivity to the MVPN

a) 在MVPN内所有站点之间维护ASM多播服务,这些站点之间保持连接,即使承载RP的站点失去与MVPN的连接

b) maintain ASM multicast service within any site that loses connectivity to the service provider

b) 在与服务提供商失去连接的任何站点内维护ASM多播服务 RP Location RP定位

In the case of PIM-SM, when a source starts to emit traffic toward a group (in ASM mode), if sources and receivers are located in VPN sites that are different than that of the RP, then traffic may transiently flow twice through the SP network and the CE-PE link of the RP (from source to RP, and then from RP to receivers). This traffic peak, even short, may not be convenient depending on the traffic and link bandwidth.


Thus, a VPN solution MAY provide features that solve or help mitigate this potential issue.


5.1.11. Addressing
5.1.11. 寻址

A multicast provider-provisioned L3VPN SHOULD NOT impose restrictions on multicast group addresses used by VPN customers.


In particular, like unicast traffic, an overlap of multicast group address sets used by different VPN customers MUST be supported.


The use of globally unique means of multicast-based service identification at the scale of the domain where such services are provided SHOULD be recommended. For IPv4 multicast, this implies the use of the multicast administratively scoped range (239/8 as defined by [RFC2365]) for services that are to be used only inside the VPN, and of either SSM-range addresses (232/8 as defined by [RFC4607]) or globally assigned group addresses (e.g., GLOP [RFC3180], 233/8) for services for which traffic may be transmitted outside the VPN.


5.1.12. Minimum MTU
5.1.12. 最小MTU

For customers, it is often a serious issue whether or not transmitted packets will be fragmented. In particular, some multicast applications might have different requirements than those that make use of unicast, and they may expect services that guarantee available packet length not to be fragmented.


Therefore, a multicast VPN solution SHOULD be designed with these considerations in mind. In practice:


o the encapsulation overhead of a multicast VPN solution SHOULD be minimized, so that customer devices can be free of fragmentation and reassembly activity as much as possible

o 应尽量减少多播VPN解决方案的封装开销,以便客户设备尽可能避免碎片和重组活动

o a multicast VPN solution SHOULD enable the service provider to commit to a minimum path MTU usable by multicast VPN customers

o 多播VPN解决方案应使服务提供商能够提交多播VPN客户可用的最小路径MTU

o a multicast VPN solution SHOULD be compatible with path MTU discovery mechanisms (see [RFC1191] and [RFC4459]), and particular care SHOULD be given to means to help troubleshoot MTU issues

o 多播VPN解决方案应与路径MTU发现机制兼容(请参阅[RFC1191]和[RFC4459]),并且应特别注意帮助解决MTU问题的方法

Moreover, since Ethernet LAN segments are often located at first and last hops, a multicast VPN solution SHOULD be designed to allow for a minimum 1500-byte IP MTU for VPN customers multicast packet, when the provider backbone design allows it.

此外,由于以太网LAN段通常位于第一个和最后一个跃点,因此应设计多播VPN解决方案,以便在提供商主干网设计允许的情况下,为VPN客户多播数据包提供至少1500字节的IP MTU。

5.2. Service Provider Standpoint
5.2. 服务提供者立场

Note: To avoid repetition and confusion with terms used in solution specifications, we introduced in Section 2.1 the term MDTunnel (for Multicast Distribution Tunnel), which designates the data plane means used by the service provider to forward customer multicast traffic over the core network.


5.2.1. General Requirement
5.2.1. 一般要求

The deployment of a multicast VPN solution SHOULD be possible with no (or very limited) impact on existing deployments of standardized multicast-related protocols on P and PE routers.


5.2.2. Scalability
5.2.2. 可伸缩性

Some currently standardized and deployed L3VPN solutions have the major advantage of being scalable in the core regarding the number of customers and the number of customer routes. For instance, in the [RFC4364] and Virtual Router [VRs] models, a P router sees a number of MPLS tunnels that is only linked to the number of PEs and not to the number of VPNs, or customer sites.


As far as possible, this independence in the core, with respect to the number of customers and to customer activity, is recommended. Yet, it is recognized that in our context scalability and resource usage optimality are competing goals, so this requirement may be reduced to giving the possibility of bounding the quantity of states that the service provider needs to maintain in the core for MDTunnels, with a bound being independent of the multicast activity of VPN customers.


It is expected that multicast VPN solutions will use some kind of point-to-multipoint technology to efficiently carry multicast VPN traffic, and because such technologies require maintaining state information, this will use resources in the control plane of P and PE routers (memory and processing, and possibly address space).


Scalability is a key requirement for multicast VPN solutions. Solutions MUST be designed to scale well with an increase in any of the following:


o the number of PEs

o PEs的数量

o the number of customer VPNs (total and per PE)

o 客户VPN的数量(总数和每个PE)

o the number of PEs and sites in any VPN

o 任何VPN中的PE和站点数

o the number of client multicast channels (groups or source-groups)

o 客户端多播通道数(组或源组)

Please consult Section 4.2 for typical orders of magnitude up to which a multicast VPN solution is expected to scale.


Scalability of both performance and operation MUST be considered.


Key considerations SHOULD include:


o the processing resources required by the control plane (neighborhood or session maintenance messages, keep-alives, timers, etc.)

o 控制平面所需的处理资源(邻居或会话维护消息、保持生命、计时器等)

o the memory resources needed for the control plane

o 控制平面所需的内存资源

o the amount of protocol information transmitted to manage a multicast VPN (e.g., signaling throughput)

o 为管理多播VPN而传输的协议信息量(例如,信令吞吐量)

o the amount of control plane processing required on PE and P routers to add or remove a customer site (or a customer from a multicast session)

o 在PE和P路由器上添加或删除客户站点(或从多播会话中删除客户)所需的控制平面处理量

o the number of multicast IP addresses used (if IP multicast in ASM mode is proposed as a multicast distribution tunnel)

o 使用的多播IP地址数(如果ASM模式下的IP多播被建议作为多播分发隧道)

o other particular elements inherent to each solution that impact scalability (e.g., if a solution uses some distribution tree inside the core, topology of the tree and number of leaf nodes may be some of them)

o 每个解决方案固有的影响可伸缩性的其他特定元素(例如,如果解决方案在核心内使用某个分发树,则树的拓扑和叶节点的数量可能是其中的一部分)

It is expected that the applicability of each solution will be evaluated with regards to the aforementioned scalability criteria.


These considerations naturally lead us to believe that proposed solutions SHOULD offer the possibility of sharing such resources between different multicast streams (between different VPNs, between different multicast streams of the same or of different VPNs). This means, for instance, if MDTunnels are trees, being able to share an MDTunnel between several customers.


Those scalability issues are expected to be more significant on P routers, but a multicast VPN solution SHOULD address both P and PE routers as far as scalability is concerned.


5.2.3. Resource Optimization
5.2.3. 资源优化 General Goals 总体目标

One of the aims of the use of multicast instead of unicast is resource optimization in the network.


The two obvious suboptimal behaviors that a multicast VPN solution would want to avoid are needless duplication (when the same data travels twice or more on a link, e.g., when doing ingress PE replication) and needless reception (e.g., a PE receiving traffic that it does not need because there are no downstream receivers).

多播VPN解决方案想要避免的两个明显的次优行为是不必要的复制(当相同的数据在链路上传输两次或两次以上时,例如,在进行入口PE复制时)和不必要的接收(例如,PE接收由于没有下游接收器而不需要的流量)。 Trade-off and Tuning 权衡与调整

As previously stated in this document, designing a scalable solution that makes an optimal use of resources is considered difficult. Thus, what is expected from a multicast VPN solution is that it addresses the resource optimization issue while taking into account the fact that some trade-off has to be made.


Moreover, it seems that a "one size fits all" trade-off probably does not exist either. Thus, a multicast VPN solution SHOULD offer service providers appropriate configuration settings that let them tune the trade-off according to their particular constraints (network topology, platforms, customer applications, level of service offered etc.).


As an illustration, here are some example bounds of the trade-off space:


Bandwidth optimization: setting up optimized core MDTunnels whose topology (PIM or P2MP LSP trees, etc.) precisely follows a customer's multicast routing changes. This requires managing a large amount of state in the core, and also quick reactions of the core to customer multicast routing changes. This approach can be advantageous in terms of bandwidth, but it is poor in terms of state management.

带宽优化:设置优化的核心MDT隧道,其拓扑结构(PIM或P2MP LSP树等)精确跟踪客户的多播路由更改。这需要管理内核中的大量状态,还需要内核对客户多播路由更改做出快速反应。这种方法在带宽方面是有利的,但在状态管理方面却很差。

State optimization: setting up MDTunnels that aggregate multiple customer multicast streams (all or some of them, across different VPNs or not). This will have better scalability properties, but at the expense of bandwidth since some MDTunnel leaves will very likely receive traffic they don't need, and because increased constraints will make it harder to find optimal MDTunnels.

状态优化:设置聚合多个客户多播流的MDTunnel(所有或部分,是否跨不同的VPN)。这将具有更好的可伸缩性属性,但会以带宽为代价,因为一些MDTunnel叶子很可能会接收到它们不需要的流量,并且因为约束的增加会使找到最佳MDTunnel变得更加困难。 Traffic Engineering 交通工程

If the VPN service provides traffic engineering (TE) features for the connection used between PEs for unicast traffic in the VPN service, the solution SHOULD provide equivalent features for multicast traffic.


A solution SHOULD offer means to support key TE objectives as defined in [RFC3272], for the multicast service.


A solution MAY also usefully support means to address multicast-specific traffic engineering issues: it is known that bandwidth resource optimization in the point-to-multipoint case is an NP-hard problem, and that techniques used for unicast TE may not be applicable to multicast traffic.


Also, it has been identified that managing the trade-off between resource usage and scalability may incur uselessly sending traffic to some PEs participating in a multicast VPN. For this reason, a multicast VPN solution MAY permit that the bandwidth/state tuning take into account the relative cost or availability of bandwidth toward each PE.


5.2.4. Tunneling Requirements
5.2.4. 隧道要求 Tunneling Technologies 隧道技术

Following the principle of separation between the control plane and the forwarding plane, a multicast VPN solution SHOULD be designed so that control and forwarding planes are not interdependent: the control plane SHALL NOT depend on which forwarding plane is used (and vice versa), and the choice of forwarding plane SHOULD NOT be limited


by the design of the solution. Also, the solution SHOULD NOT be tied to a specific tunneling technology.


In a multicast VPN solution extending a unicast L3 PPVPN solution, consistency in the tunneling technology has to be favored: such a solution SHOULD allow the use of the same tunneling technology for multicast as for unicast. Deployment consistency, ease of operation, and potential migrations are the main motivations behind this requirement.

在扩展单播L3 PPVPN解决方案的多播VPN解决方案中,必须有利于隧道技术的一致性:这种解决方案应允许对多播使用与单播相同的隧道技术。部署一致性、易操作性和潜在的迁移是这一需求背后的主要动机。

For MDTunnels, a solution SHOULD be able to use a range of tunneling technologies, including point-to-point and point-to-multipoint, such as:


o Generic Routing Encapsulation (GRE) [RFC2784] (including GRE in multicast IP trees),

o 通用路由封装(GRE)[RFC2784](包括多播IP树中的GRE),

o MPLS [RFC3031] (including P2P or MP2P tunnels, and multipoint tunnels signaled with MPLS P2MP extensions to the Resource Reservation Protocol (RSVP) [P2MP-RSVP-TE] or Label Distribution Protocol (LDP) [P2MP-LDP-REQS] [P2MP-LDP]),

o MPLS[RFC3031](包括P2P或MP2P隧道,以及通过资源预留协议(RSVP)[P2MP-RSVP-TE]或标签分发协议(LDP)[P2MP-LDP-REQS][P2MP-LDP]的MPLS P2MP扩展发送信号的多点隧道),

o Layer-2 Tunneling Protocol (L2TP) (including L2TP for multicast [RFC4045]),

o 第二层隧道协议(L2TP)(包括用于多播的L2TP[RFC4045]),

o IPsec [RFC4031]

o IPsec[RFC4031]

o IP-in-IP [RFC2003], etc.

o IP[RFC2003]中的IP等。

Naturally, it is RECOMMENDED that a solution is built so that it can leverage the point-to-multipoint variants of these techniques. These variants allow for packet replications to happen along a tree in the provider core network, and they may help improve bandwidth efficiency in a multicast VPN context.

当然,建议构建一个解决方案,以便能够利用这些技术的点对多点变体。这些变体允许沿提供商核心网络中的树进行数据包复制,并且它们可能有助于提高多播VPN上下文中的带宽效率。 MTU and Fragmentation MTU与碎片化

A solution SHOULD support a method that provides the minimum MTU of the MDTunnel (e.g., to discover MTU, to communicate MTU via signaling, etc.) so that:


o fragmentation inside the MDTunnel does not happen, even when allowed by the underlying tunneling technology

o MDTunnel内部不会发生碎片,即使底层隧道技术允许

o proper troubleshooting can be performed if packets that are too big for the MDTunnel happen to be encapsulated in the MDTunnel

o 如果对MDTunnel来说太大的数据包恰好被封装在MDTunnel中,则可以执行适当的故障排除

5.2.5. Control Mechanisms
5.2.5. 控制机制

The solution MUST provide some mechanisms to control the sources within a VPN. This control includes the number of sources that are entitled to send traffic on the VPN, and/or the total bit rate of all the sources.


At the reception level, the solution MUST also provide mechanisms to control the number of multicast groups or channels VPN users are entitled to subscribe to and/or the total bit rate represented by the corresponding multicast traffic.


All these mechanisms MUST be configurable by the service provider in order to control the amount of multicast traffic and state within a VPN.


Moreover, it MAY be desirable to be able to impose some bound on the quantity of state used by a VPN in the core network for its multicast traffic, whether on each P or PE router, or globally. The motivation is that it may be needed to avoid out-of-resources situations (e.g., out of memory to maintain PIM state if IP multicast is used in the core for multicast VPN traffic, or out of memory to maintain RSVP state if MPLS P2MP is used, etc.).

此外,可能希望能够对核心网络中VPN用于其多播业务的状态量施加某种限制,无论是在每个P或PE路由器上,还是在全球范围内。其动机是,可能需要避免资源不足的情况(例如,如果在多播VPN流量的核心中使用IP多播,则内存不足以保持PIM状态;如果使用MPLS P2MP,则内存不足以保持RSVP状态,等等)。

5.2.6. Support of Inter-AS, Inter-Provider Deployments
5.2.6. 支持跨AS、跨提供商部署

A solution MUST support inter-AS (Autonomous System) multicast VPNs, and SHOULD support inter-provider multicast VPNs. Considerations about coexistence with unicast inter-AS VPN Options A, B, and C (as described in Section 10 of [RFC4364]) are strongly encouraged.

解决方案必须支持跨AS(自治系统)多播VPN,并应支持跨提供商多播VPN。强烈鼓励考虑与单播inter AS VPN选项A、B和C共存(如[RFC4364]第10节所述)。

A multicast VPN solution SHOULD provide inter-AS mechanisms requiring the least possible coordination between providers, and keep the need for detailed knowledge of providers' networks to a minimum -- all this being in comparison with corresponding unicast VPN options.


o Within each service provider, the service provider SHOULD be able on its own to pick the most appropriate tunneling mechanism to carry (multicast) traffic among PEs (just like what is done today for unicast)

o 在每个服务提供商内部,服务提供商应能够自行选择最合适的隧道机制,以在PEs之间传输(多播)流量(就像现在单播所做的那样)

o If a solution does require a single tunnel to span P routers in multiple ASs, the solution SHOULD provide mechanisms to ensure that the inter-provider coordination to set up such a tunnel is minimized

o 如果一个解决方案确实需要一个隧道来跨越多个ASs中的P个路由器,那么该解决方案应该提供机制,以确保设置这样一个隧道的提供商间协调最小化

Moreover, such support SHOULD be possible without compromising other requirements expressed in this requirement document, and SHALL NOT incur penalties on scalability and bandwidth-related efficiency.


5.2.7. Quality-of-Service Differentiation
5.2.7. 服务质量差异化

A multicast VPN solution SHOULD give a VPN service provider the ability to offer, guarantee and enforce differentiated levels of QoS for its different customers.


5.2.8. Infrastructure security
5.2.8. 基础设施安全

The solution SHOULD provide the same level of security for the service provider as what currently exists for unicast VPNs (for instance, as developed in the Security sections of [RFC4364] and [VRs]). For instance, traffic segregation and intrinsic protection against DoS (Denial of Service) and DDoS (Distributed Denial of Service) attacks of the BGP/MPLS VPN solution must be supported by the multicast solution.

该解决方案应为服务提供商提供与当前单播VPN相同的安全级别(例如,在[RFC4364]和[VRs]的安全部分中开发)。例如,多播解决方案必须支持流量隔离和针对BGP/MPLS VPN解决方案的DoS(拒绝服务)和DDoS(分布式拒绝服务)攻击的内在保护。

Moreover, since multicast traffic and routing are intrinsically dynamic (receiver-initiated), some mechanism SHOULD be proposed so that the frequency of changes in the way client traffic is carried over the core can be bounded and not tightly coupled to dynamic changes of multicast traffic in the customer network. For example, multicast route dampening functions would be one possible mechanism.


Network devices that participate in the deployment and the maintenance of a given L3VPN MAY represent a superset of the participating devices that are also involved in the establishment and maintenance of the multicast distribution tunnels. As such, the activation of IP multicast capabilities within a VPN SHOULD be device-specific, not only to make sure that only the relevant devices will be multicast-enabled, but also to make sure that multicast (routing) information will be disseminated to the multicast-enabled devices only, hence limiting the risk of multicast-inferred DOS attacks.


Traffic of a multicast channel for which there are no members in a given multicast VPN MUST NOT be propagated within the multicast VPN, most particularly if the traffic comes from another VPN or from the Internet.


Security considerations are particularly important for inter-AS and inter-provider deployments. In such cases, it is RECOMMENDED that a multicast VPN solution support means to ensure the integrity and authenticity of multicast-related exchanges across inter-AS or inter-provider borders. It is RECOMMENDED that corresponding procedures


require the least possible coordination between providers; more precisely, when specific configurations or cryptographic keys have to be deployed, this shall be limited to ASBRs (Autonomous System Border Routers) or a subset of them, and optionally BGP Route Reflectors (or a subset of them).


Lastly, control mechanisms described in Section 5.2.5 are also to be considered from this infrastructure security point of view.


5.2.9. Robustness
5.2.9. 健壮性

Resiliency is also crucial to infrastructure security; thus, a multicast VPN solution SHOULD either avoid single points of failures or propose some technical solution making it possible to implement a fail-over mechanism.


As an illustration, one can consider the case of a solution that would use PIM-SM as a means to set up MDTunnels. In such a case, the PIM RP might be a single point of failure. Such a solution SHOULD be compatible with a solution implementing RP resiliency, such as anycast-RP [RFC4610] or BSR [PIM-BSR].

作为一个例子,可以考虑使用PIM-SM作为设置MDTunnels的方法的解决方案的情况。在这种情况下,PIM RP可能是单点故障。此类解决方案应与实现RP弹性的解决方案兼容,如选播RP[RFC4610]或BSR[PIM-BSR]。

5.2.10. Operation, Administration, and Maintenance
5.2.10. 操作、管理和维护

The operation of a multicast VPN solution SHALL be as light as possible, and providing automatic configuration and discovery SHOULD be a priority when designing a multicast VPN solution. Particularly, the operational burden of setting up multicast on a PE or for a VR/ VRF SHOULD be as low as possible.


Also, as far as possible, the design of a solution SHOULD carefully consider the number of protocols within the core network: if any additional protocols are introduced compared with the unicast VPN service, the balance between their advantage and operational burden SHOULD be examined thoroughly.


Moreover, monitoring of multicast-specific parameters and statistics SHOULD be offered to the service provider, following the requirements expressed in [RFC4176].


Most notably, the provider SHOULD have access to:


o Multicast traffic statistics (incoming/outgoing/dropped/total traffic conveyed, by period of time)

o 多播流量统计(传入/传出/丢弃/传输的总流量,按时间段)

o Information about client multicast resource usage (multicast routing state and bandwidth usage)

o 有关客户端多播资源使用情况(多播路由状态和带宽使用情况)的信息

o Alarms when limits are reached on such resources

o 达到此类资源限制时发出警报

o The IPPM (IP Performance Metrics [RFC2330])-related information that is relevant to the multicast traffic usage: such information includes the one-way packet delay, the inter-packet delay variation, etc.

o IPPM(IP性能度量[RFC2330])与多播通信量使用相关的信息:此类信息包括单向分组延迟、分组间延迟变化等。

o Statistics on decisions related to how client traffic is carried on distribution tunnels (e.g., "traffic switched onto a multicast tree dedicated to such groups or channels")

o 有关如何在分发隧道中承载客户端流量的决策的统计信息(例如,“切换到专用于此类组或通道的多播树上的流量”)

o Statistics on parameters that could help the provider to evaluate its optimality/state trade-off

o 有助于供应商评估其最佳性/状态权衡的参数统计数据

This information SHOULD be made available through standardized SMIv2 [RFC2578] Management Information Base (MIB) modules to be used with SNMP [RFC3411], or through IPFIX [IPFIX-PROT]. For instance, in the context of BGP/MPLS VPNs [RFC4364], multicast extensions to MIBs defined in [RFC4382] SHOULD be proposed, with proper integration with [RFC3811], [RFC3812], [RFC3813], and [RFC3814] when applicable.

该信息应通过与SNMP[RFC3411]一起使用的标准化SMIv2[RFC2578]管理信息库(MIB)模块或IPFIX[IPFIX-PROT]提供。例如,在BGP/MPLS VPN[RFC4364]的上下文中,应建议对[RFC4382]中定义的MIB进行多播扩展,并在适用时与[RFC3811]、[RFC3812]、[RFC3813]和[RFC3814]进行适当集成。

Mechanisms similar to those described in Section 5.2.12 SHOULD also exist for proactive monitoring of the MDTunnels.


Proposed OAM mechanisms and procedures for multicast VPNs SHOULD be scalable with respect to the parameters mentioned in Section 5.2.2. In particular, it is RECOMMENDED that particular attention is given to the impact of monitoring mechanisms on performances and QoS.


Moreover, it is RECOMMENDED that any OAM mechanism designed to trigger alarms in relation to performance or resource usage metrics integrate the ability to limit the rate at which such alarms are generated (e.g., some form of a hysteresis mechanism based on low/ high thresholds defined for the metrics).


5.2.11. Compatibility and Migration Issues
5.2.11. 兼容性和迁移问题

It is a requirement that unicast and multicast services MUST be able to coexist within the same VPN.


Likewise, a multicast VPN solution SHOULD be designed so that its activation in devices that participate in the deployment and maintenance of a multicast VPN SHOULD be as smooth as possible, i.e., without affecting the overall quality of the services that are already supported by the underlying infrastructure.


A multicast VPN solution SHOULD prevent compatibility and migration issues, for instance, by focusing on providing mechanisms


facilitating forward compatibility. Most notably, a solution supporting only a subset of the requirements expressed in this document SHOULD be designed to allow compatibility to be introduced in further revisions.


It SHOULD be an aim of any multicast VPN solution to offer as much backward compatibility as possible. Ideally, a solution would have the ability to offer multicast VPN services across a network containing some legacy routers that do not support any multicast VPN-specific features.


In any case, a solution SHOULD state a migration policy from possibly existing deployments.


5.2.12. Troubleshooting
5.2.12. 故障排除

A multicast VPN solution that dynamically adapts the way some client multicast traffic is carried over the provider's network may incur the disadvantage of being hard to troubleshoot. In such a case, to help diagnose multicast network issues, a multicast VPN solution SHOULD provide monitoring information describing how client traffic is carried over the network (e.g., if a solution uses multicast-based MDTunnels, which provider multicast group is used for a given client multicast stream). A solution MAY also provide configuration options to avoid any dynamic changes, for multicast traffic of a particular VPN or a particular multicast stream.


Moreover, a solution MAY provide mechanisms that allow network operators to check that all VPN sites that advertised interest in a particular customer multicast stream are properly associated with the corresponding MDTunnel. Providing operators with means to check the proper setup and operation of MDTunnels MAY also be provided (e.g., when P2MP MPLS is used for MDTunnels, troubleshooting functionalities SHOULD integrate mechanisms compliant with [RFC4687], such as LSP Ping [RFC4379][LSP-PING]). Depending on the implementation, such verification could be initiated by a source-PE or a receiver-PE.

此外,解决方案可以提供允许网络运营商检查在特定客户多播流中广告感兴趣的所有VPN站点是否与相应的MDTunnel正确关联的机制。还可向操作员提供检查MDTunnel正确设置和操作的方法(例如,当P2MP MPLS用于MDTunnel时,故障排除功能应集成符合[RFC4687]的机制,如LSP Ping[RFC4379][LSP-Ping])。根据实现,此类验证可由源PE或接收器PE发起。

6. Security Considerations
6. 安全考虑

This document does not by itself raise any particular security issue.


A set of security issues has been identified that MUST be addressed when considering the design and deployment of multicast-enabled L3 PPVPNs. Such issues have been described in Section 5.1.5 and Section 5.2.8.

在考虑设计和部署支持多播的L3 PPVPN时,已经确定了一组必须解决的安全问题。此类问题已在第5.1.5节和第5.2.8节中描述。

7. Contributors
7. 贡献者

The main contributors to this document are listed below, in alphabetical order:


o Christian Jacquenet France Telecom 3, avenue Francois Chateau CS 36901 35069 RENNES Cedex, France Email:

o Christian Jacquenet法国电信3号,法国弗朗索瓦城堡大道CS 36901 35069雷恩塞德斯,法国电子邮件:Christian。

o Yuji Kamite NTT Communications Corporation Tokyo Opera City Tower 3-20-2 Nishi Shinjuku, Shinjuku-ku Tokyo 163-1421, Japan Email:

o Yuji Kamite NTT通信公司东京歌剧城3-20-2号楼,新宿,新宿东京163-1421电子邮件:y。

o Jean-Louis Le Roux France Telecom R&D 2, avenue Pierre-Marzin 22307 Lannion Cedex, France Email:

o Jean-Louis Le Roux法国电信研发2号,Pierre Marzin大街22307号,法国Lannion Cedex电子邮件:jeanlouis。

o Nicolai Leymann Deutsch Telecom Engineering Networks, Products & Services Goslarer Ufer 3510589 Berlin, Germany Email:

o Nicolai Leymann Deutsch电信工程网络、产品和服务德国柏林Goslarer Ufer 3510589电子邮件:Nicolai。leymann@t-系统网

o Renaud Moignard France Telecom R&D 2, avenue Pierre-Marzin 22307 Lannion Cedex, France Email:

o 雷诺·莫格纳德法国电信研发2号,皮埃尔·马津大街22307,法国拉尼翁·塞德克斯,电子邮件:雷诺。

o Thomas Morin France Telecom R&D 2, avenue Pierre-Marzin 22307 Lannion Cedex, France Email:

o Thomas Morin法国电信研发2号,Pierre Marzin大街22307,法国Lannion Cedex电子邮件:Thomas。

8. Acknowledgments
8. 致谢

The authors would like to thank, in rough chronological order, Vincent Parfait, Zubair Ahmad, Elodie Hemon-Larreur, Sebastien Loye, Rahul Aggarwal, Hitoshi Fukuda, Luyuan Fang, Adrian Farrel, Daniel King, Yiqun Cai, Ronald Bonica, Len Nieman, Satoru Matsushima, Netzahualcoyotl Ornelas, Yakov Rekhter, Marshall Eubanks, Pekka


Savola, Benjamin Niven-Jenkins, and Thomas Nadeau, for their review, valuable input, and feedback.


We also thank the people who kindly answered the survey, and Daniel King, who took care of gathering and anonymizing its results.


9. References
9. 工具书类
9.1. Normative References
9.1. 规范性引用文件

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2119]Bradner,S.,“RFC中用于表示需求水平的关键词”,BCP 14,RFC 2119,1997年3月。

[RFC4031] Carugi, M. and D. McDysan, "Service Requirements for Layer 3 Provider-Provisioned Virtual Private Networks (PPVPNs)", RFC 4031, April 2005.

[RFC4031]Carugi,M.和D.McDysan,“第3层提供商提供的虚拟专用网络(PPVPN)的服务要求”,RFC 4031,2005年4月。

[RFC4026] Andersson, L. and T. Madsen, "Provider-Provisioned Virtual Private Network (VPN) Terminology", RFC 4026, March 2005.

[RFC4026]Andersson,L.和T.Madsen,“提供商提供的虚拟专用网络(VPN)术语”,RFC 4026,2005年3月。

[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, August 2006.

[RFC4601]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 46012006年8月。

[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP", RFC 4607, August 2006.


[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. Thyagarajan, "Internet Group Management Protocol, Version 3", RFC 3376, October 2002.

[RFC3376]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。

[RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.

[RFC3810]Vida,R.和L.Costa,“IPv6多播侦听器发现版本2(MLDv2)”,RFC 3810,2004年6月。

[RFC4176] El Mghazli, Y., Nadeau, T., Boucadair, M., Chan, K., and A. Gonguet, "Framework for Layer 3 Virtual Private Networks (L3VPN) Operations and Management", RFC 4176, October 2005.

[RFC4176]El Mghazli,Y.,Nadeau,T.,Boucadair,M.,Chan,K.,和A.Gonguet,“第三层虚拟专用网络(L3VPN)运营和管理框架”,RFC 41762005年10月。

[RFC3973] Adams, A., Nicholas, J., and W. Siadak, "Protocol Independent Multicast - Dense Mode (PIM-DM): Protocol Specification (Revised)", RFC 3973, January 2005.

[RFC3973]Adams,A.,Nicholas,J.,和W.Siadak,“协议独立多播-密集模式(PIM-DM):协议规范(修订版)”,RFC 3973,2005年1月。

9.2. Informative References
9.2. 资料性引用

[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, February 2006.

[RFC4364]Rosen,E.和Y.Rekhter,“BGP/MPLS IP虚拟专用网络(VPN)”,RFC 4364,2006年2月。

[VRs] Ould-Brahim, H., "Network based IP VPN Architecture Using Virtual Routers", Work in Progress, March 2006.

[VRs]Ould Brahim,H.,“使用虚拟路由器的基于网络的IP VPN架构”,正在进行的工作,2006年3月。

[RFC2432] Dubray, K., "Terminology for IP Multicast Benchmarking", RFC 2432, October 1998.

[RFC2432]Dubrey,K.,“IP多播基准测试术语”,RFC 2432,1998年10月。

[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001.

[RFC3031]Rosen,E.,Viswanathan,A.,和R.Callon,“多协议标签交换体系结构”,RFC 30312001年1月。

[RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5, RFC 1112, August 1989.

[RFC1112]Deering,S.,“IP多播的主机扩展”,STD 5,RFC11121989年8月。

[RFC2236] Fenner, W., "Internet Group Management Protocol, Version 2", RFC 2236, November 1997.

[RFC2236]Fenner,W.,“互联网组管理协议,第2版”,RFC 2236,1997年11月。

[P2MP-RSVP-TE] Aggarwal, R., "Extensions to RSVP-TE for Point-to-Multipoint TE LSPs", Work in Progress, August 2006.

[P2MP-RSVP-TE]Aggarwal,R.,“点对多点TE LSP的RSVP-TE扩展”,正在进行的工作,2006年8月。

[PIM-BSR] Bhaskar, N., "Bootstrap Router (BSR) Mechanism for PIM", Work in Progress, June 2006.


[RFC4610] Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol Independent Multicast (PIM)", RFC 4610, August 2006.

[RFC4610]Farinaci,D.和Y.Cai,“使用协议独立多播(PIM)的任意广播RP”,RFC 46102006年8月。

[RFC3446] Kim, D., Meyer, D., Kilmer, H., and D. Farinacci, "Anycast Rendevous Point (RP) mechanism using Protocol Independent Multicast (PIM) and Multicast Source Discovery Protocol (MSDP)", RFC 3446, January 2003.

[RFC3446]Kim,D.,Meyer,D.,Kilmer,H.,和D.Farinaci,“使用协议独立多播(PIM)和多播源发现协议(MSDP)的任意广播呈现点(RP)机制”,RFC 3446,2003年1月。

[P2MP-LDP] Minei, I., "Label Distribution Protocol Extensions for Point-to-Multipoint and Multipoint-to-Multipoint Label Switched Paths", Work in Progress, October 2006.


[P2MP-LDP-REQS] Roux, J., "Requirements for point-to-multipoint extensions to the Label Distribution Protocol", Work in Progress, June 2006.


[RFC4687] Yasukawa, S., Farrel, A., King, D., and T. Nadeau, "Operations and Management (OAM) Requirements for Point-to-Multipoint MPLS Networks", RFC 4687, September 2006.

[RFC4687]Yasukawa,S.,Farrel,A.,King,D.,和T.Nadeau,“点对多点MPLS网络的运营和管理(OAM)要求”,RFC 4687,2006年9月。

[BIDIR-PIM] Handley, M., "Bi-directional Protocol Independent Multicast (BIDIR-PIM)", Work in Progress, October 2005.


[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003, October 1996.

[RFC2003]Perkins,C.,“IP内的IP封装”,RFC 2003,1996年10月。

[RFC3353] Ooms, D., Sales, B., Livens, W., Acharya, A., Griffoul, F., and F. Ansari, "Overview of IP Multicast in a Multi-Protocol Label Switching (MPLS) Environment", RFC 3353, August 2002.

[RFC3353]Ooms,D.,Sales,B.,Livens,W.,Acharya,A.,Griffoul,F.,和F.Ansari,“多协议标签交换(MPLS)环境中的IP多播概述”,RFC 33532002年8月。

[RFC3272] Awduche, D., Chiu, A., Elwalid, A., Widjaja, I., and X. Xiao, "Overview and Principles of Internet Traffic Engineering", RFC 3272, May 2002.

[RFC3272]Awduche,D.,Chiu,A.,Elwalid,A.,Widjaja,I.,和X.Xiao,“互联网流量工程概述和原则”,RFC 3272,2002年5月。

[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, March 2000.

[RFC2784]Farinaci,D.,Li,T.,Hanks,S.,Meyer,D.,和P.Traina,“通用路由封装(GRE)”,RFC 27842000年3月。

[IPFIX-PROT] Claise, B., "Specification of the IPFIX Protocol for the Exchange", Work in Progress, November 2006.


[RFC4045] Bourdon, G., "Extensions to Support Efficient Carrying of Multicast Traffic in Layer-2 Tunneling Protocol (L2TP)", RFC 4045, April 2005.

[RFC4045]Bourdon,G.“支持在第二层隧道协议(L2TP)中高效承载多播流量的扩展”,RFC 4045,2005年4月。

[RFC3809] Nagarajan, A., "Generic Requirements for Provider-Provisioned Virtual Private Networks (PPVPN)", RFC 3809, June 2004.

[RFC3809]Nagarajan,A.,“提供商提供的虚拟专用网络(PPVPN)的一般要求”,RFC 3809,2004年6月。

[RFC3811] Nadeau, T. and J. Cucchiara, "Definitions of Textual Conventions (TCs) for Multiprotocol Label Switching (MPLS) Management", RFC 3811, June 2004.

[RFC3811]Nadeau,T.和J.Cucchiara,“多协议标签交换(MPLS)管理的文本约定(TC)定义”,RFC 3811,2004年6月。

[RFC3812] Srinivasan, C., Viswanathan, A., and T. Nadeau, "Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) Management Information Base (MIB)", RFC 3812, June 2004.

[RFC3812]Srinivasan,C.,Viswanathan,A.,和T.Nadeau,“多协议标签交换(MPLS)流量工程(TE)管理信息库(MIB)”,RFC 3812,2004年6月。

[RFC3813] Srinivasan, C., Viswanathan, A., and T. Nadeau, "Multiprotocol Label Switching (MPLS) Label Switching Router (LSR) Management Information Base (MIB)", RFC 3813, June 2004.

[RFC3813]Srinivasan,C.,Viswanathan,A.,和T.Nadeau,“多协议标签交换(MPLS)标签交换路由器(LSR)管理信息库(MIB)”,RFC 38132004年6月。

[RFC3814] Nadeau, T., Srinivasan, C., and A. Viswanathan, "Multiprotocol Label Switching (MPLS) Forwarding Equivalence Class To Next Hop Label Forwarding Entry (FEC-To-NHLFE) Management Information Base (MIB)", RFC 3814, June 2004.

[RFC3814]Nadeau,T.,Srinivasan,C.,和A.Viswanathan,“多协议标签交换(MPLS)转发等价类到下一跳标签转发条目(FEC到NHLFE)管理信息库(MIB)”,RFC 3814,2004年6月。

[RFC2365] Meyer, D., "Administratively Scoped IP Multicast", BCP 23, RFC 2365, July 1998.

[RFC2365]Meyer,D.,“管理范围的IP多播”,BCP 23,RFC 2365,1998年7月。

[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, "Framework for IP Performance Metrics", RFC 2330, May 1998.

[RFC2330]Paxson,V.,Almes,G.,Mahdavi,J.,和M.Mathis,“IP性能度量框架”,RFC 2330,1998年5月。

[MULTIMETRICS] Stephan, E., "IP Performance Metrics (IPPM) for spatial and multicast", Work in Progress, October 2006.


[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998.

[RFC2475]Blake,S.,Black,D.,Carlson,M.,Davies,E.,Wang,Z.,和W.Weiss,“差异化服务架构”,RFC 24751998年12月。

[RFC3180] Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8", BCP 53, RFC 3180, September 2001.

[RFC3180]Meyer,D.和P.Lothberg,“233/8中的GLOP寻址”,BCP 53,RFC 31802001年9月。

[RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An Architecture for Describing Simple Network Management Protocol (SNMP) Management Frameworks", STD 62, RFC 3411, December 2002.

[RFC3411]Harrington,D.,Presohn,R.,和B.Wijnen,“描述简单网络管理协议(SNMP)管理框架的体系结构”,STD 62,RFC 3411,2002年12月。

[RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J. Schoenwaelder, Ed., "Structure of Management Information Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.

[RFC2578]McCloghrie,K.,Ed.,Perkins,D.,Ed.,和J.Schoenwaeld,Ed.“管理信息的结构版本2(SMIv2)”,STD 58,RFC 2578,1999年4月。

[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, November 1990.


[RFC4382] Nadeau, T. and H. van der Linde, "MPLS/BGP Layer 3 Virtual Private Network (VPN) Management Information Base", RFC 4382, February 2006.

[RFC4382]Nadeau,T.和H.van der Linde,“MPLS/BGP第3层虚拟专用网络(VPN)管理信息库”,RFC 4382,2006年2月。

[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures", RFC 4379, February 2006.

[RFC4379]Kompella,K.和G.Swallow,“检测多协议标签交换(MPLS)数据平面故障”,RFC 4379,2006年2月。

[LSP-PING] Farrel, A. and S. Yasukawa, "Detecting Data Plane Failures in Point-to-Multipoint Multiprotocol", Work in Progress, September 2006.


[RFC4459] Savola, P., "MTU and Fragmentation Issues with In-the-Network Tunneling", RFC 4459, April 2006.

[RFC4459]Savola,P.,“网络隧道中的MTU和碎片问题”,RFC 4459,2006年4月。

Author's Address


Thomas Morin (editor) France Telecom R&D 2, avenue Pierre Marzin Lannion 22307 France



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