Network Working Group                                  A. Nagarajan, Ed.
Request for Comments: 3809                              Juniper Networks
Category: Informational                                        June 2004
Network Working Group                                  A. Nagarajan, Ed.
Request for Comments: 3809                              Juniper Networks
Category: Informational                                        June 2004

Generic Requirements for Provider Provisioned Virtual Private Networks (PPVPN)


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 Internet Society (2004).




This document describes generic requirements for Provider Provisioned Virtual Private Networks (PPVPN). The requirements are categorized into service requirements, provider requirements and engineering requirements. These requirements are not specific to any particular type of PPVPN technology, but rather apply to all PPVPN technologies. All PPVPN technologies are expected to meet the umbrella set of requirements described in this document.


Table of Contents


   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
       1.1. Problem Statement . . . . . . . . . . . . . . . . . . . .  3
       1.2. Deployment Scenarios. . . . . . . . . . . . . . . . . . .  4
       1.3. Outline of this document. . . . . . . . . . . . . . . . .  5
   2.  Contributing Authors . . . . . . . . . . . . . . . . . . . . .  6
   3.  Definitions and Taxonomy . . . . . . . . . . . . . . . . . . .  7
   4.  Service Requirements . . . . . . . . . . . . . . . . . . . . .  7
       4.1. Availability  . . . . . . . . . . . . . . . . . . . . . .  7
       4.2. Stability . . . . . . . . . . . . . . . . . . . . . . . .  8
       4.3. Traffic types . . . . . . . . . . . . . . . . . . . . . .  8
       4.4. Data Isolation. . . . . . . . . . . . . . . . . . . . . .  9
       4.5. Security  . . . . . . . . . . . . . . . . . . . . . . . .  9
            4.5.1. User data security . . . . . . . . . . . . . . . . 10
            4.5.2. Access Control . . . . . . . . . . . . . . . . . . 10
            4.5.3. Site authentication and authorization. . . . . . . 10
            4.5.4. Inter domain security. . . . . . . . . . . . . . . 10
       4.6. Topology  . . . . . . . . . . . . . . . . . . . . . . . . 11
       4.7. Addressing. . . . . . . . . . . . . . . . . . . . . . . . 11
       4.8. Quality of Service  . . . . . . . . . . . . . . . . . . . 11
       4.9. Service Level Agreement and Service Level Specification
            Monitoring and Reporting. . . . . . . . . . . . . . . . . 13
       4.10.Network Resource Partitioning and Sharing between VPNs. . 14
   5.  Provider requirements. . . . . . . . . . . . . . . . . . . . . 14
       5.1. Scalability . . . . . . . . . . . . . . . . . . . . . . . 14
            5.1.1. Service Provider Capacity Sizing Projections . . . 15
            5.1.2. VPN Scalability aspects. . . . . . . . . . . . . . 15
            5.1.3. Solution-Specific Metrics. . . . . . . . . . . . . 17
       5.2. Management  . . . . . . . . . . . . . . . . . . . . . . . 18
            5.2.1. Customer Management of a VPN . . . . . . . . . . . 18
   6.  Engineering requirements . . . . . . . . . . . . . . . . . . . 19
       6.1. Forwarding plane requirements . . . . . . . . . . . . . . 19
       6.2. Control plane requirements. . . . . . . . . . . . . . . . 20
       6.3. Control Plane Containment . . . . . . . . . . . . . . . . 20
       6.4. Requirements related to commonality of PPVPN mechanisms
            with each other and with generic Internet mechanisms. . . 21
       6.5. Interoperability  . . . . . . . . . . . . . . . . . . . . 21
   7.  Security Considerations. . . . . . . . . . . . . . . . . . . . 22
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
       8.1. Normative References. . . . . . . . . . . . . . . . . . . 23
       8.2. Informative References. . . . . . . . . . . . . . . . . . 23
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 24
   10. Editor's Address . . . . . . . . . . . . . . . . . . . . . . . 24
   11. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 25
   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
       1.1. Problem Statement . . . . . . . . . . . . . . . . . . . .  3
       1.2. Deployment Scenarios. . . . . . . . . . . . . . . . . . .  4
       1.3. Outline of this document. . . . . . . . . . . . . . . . .  5
   2.  Contributing Authors . . . . . . . . . . . . . . . . . . . . .  6
   3.  Definitions and Taxonomy . . . . . . . . . . . . . . . . . . .  7
   4.  Service Requirements . . . . . . . . . . . . . . . . . . . . .  7
       4.1. Availability  . . . . . . . . . . . . . . . . . . . . . .  7
       4.2. Stability . . . . . . . . . . . . . . . . . . . . . . . .  8
       4.3. Traffic types . . . . . . . . . . . . . . . . . . . . . .  8
       4.4. Data Isolation. . . . . . . . . . . . . . . . . . . . . .  9
       4.5. Security  . . . . . . . . . . . . . . . . . . . . . . . .  9
            4.5.1. User data security . . . . . . . . . . . . . . . . 10
            4.5.2. Access Control . . . . . . . . . . . . . . . . . . 10
            4.5.3. Site authentication and authorization. . . . . . . 10
            4.5.4. Inter domain security. . . . . . . . . . . . . . . 10
       4.6. Topology  . . . . . . . . . . . . . . . . . . . . . . . . 11
       4.7. Addressing. . . . . . . . . . . . . . . . . . . . . . . . 11
       4.8. Quality of Service  . . . . . . . . . . . . . . . . . . . 11
       4.9. Service Level Agreement and Service Level Specification
            Monitoring and Reporting. . . . . . . . . . . . . . . . . 13
       4.10.Network Resource Partitioning and Sharing between VPNs. . 14
   5.  Provider requirements. . . . . . . . . . . . . . . . . . . . . 14
       5.1. Scalability . . . . . . . . . . . . . . . . . . . . . . . 14
            5.1.1. Service Provider Capacity Sizing Projections . . . 15
            5.1.2. VPN Scalability aspects. . . . . . . . . . . . . . 15
            5.1.3. Solution-Specific Metrics. . . . . . . . . . . . . 17
       5.2. Management  . . . . . . . . . . . . . . . . . . . . . . . 18
            5.2.1. Customer Management of a VPN . . . . . . . . . . . 18
   6.  Engineering requirements . . . . . . . . . . . . . . . . . . . 19
       6.1. Forwarding plane requirements . . . . . . . . . . . . . . 19
       6.2. Control plane requirements. . . . . . . . . . . . . . . . 20
       6.3. Control Plane Containment . . . . . . . . . . . . . . . . 20
       6.4. Requirements related to commonality of PPVPN mechanisms
            with each other and with generic Internet mechanisms. . . 21
       6.5. Interoperability  . . . . . . . . . . . . . . . . . . . . 21
   7.  Security Considerations. . . . . . . . . . . . . . . . . . . . 22
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
       8.1. Normative References. . . . . . . . . . . . . . . . . . . 23
       8.2. Informative References. . . . . . . . . . . . . . . . . . 23
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 24
   10. Editor's Address . . . . . . . . . . . . . . . . . . . . . . . 24
   11. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 25
1. Introduction
1. 介绍

This document is an output of the design team formed to develop requirements for PPVPNs in the Provider Provisioned Virtual Private Networks (PPVPN) working group and provides requirements that are generic to both Layer 2 Virtual Private Networks (L2VPN) and Layer 3 Virtual Private Networks (L3VPN). This document discusses generic PPVPN requirements categorized as service, provider and engineering requirements. These are independent of any particular type of PPVPN technology. In other words, all PPVPN technologies are expected to meet the umbrella set of requirements described in this document. PPVPNs may be constructed across single or multiple provider networks and/or Autonomous Systems (ASes). In most cases the generic requirements described in this document are independent of the deployment scenario. However, specific requirements that differ based on whether the PPVPN is deployed across single or multiple providers (and/or ASes) will be pointed out in the document. Specific requirements related to Layer 3 PPVPNs are described in [L3REQTS]. Similarly, requirements that are specific to layer 2 PPVPNs are described in [L2REQTS].


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].


1.1. Problem Statement
1.1. 问题陈述

Corporations and other organizations have become increasingly dependent on their networks for telecommunications and data communication. The data communication networks were originally built as Local Area Networks (LAN). Over time the possibility to interconnect the networks on different sites has become more and more important. The connectivity for corporate networks has been supplied by service providers, mainly as Frame Relay (FR) or Asynchronous Transfer Mode (ATM) connections, and more recently as Ethernet and IP-based tunnels. This type of network, interconnecting a number of sites over a shared network infrastructure is called Virtual Private Network (VPN). If the sites belong to the same organization, the VPN is called an Intranet. If the sites belong to different organizations that share a common interest, the VPN is called an Extranet.


Customers are looking for service providers to deliver data and telecom connectivity over one or more shared networks, with service level assurances in the form of security, QoS and other parameters.


In order to provide isolation between the traffic belonging to different customers, mechanisms such as Layer 2 connections or Layer 2/3 tunnels are necessary. When the shared infrastructure is an IP network, the tunneling technologies that are typically used are IPsec, MPLS, L2TP, GRE, IP-in-IP etc.


Traditional Internet VPNs have been based on IPsec to provide security over the Internet. Service providers are now beginning to deploy enhanced VPN services that provide features such as service differentiation, traffic management, Layer 2 and Layer 3 connectivity, etc. in addition to security. Newer tunneling mechanisms have certain features that allow the service providers to provide these enhanced VPN services.

传统的Internet VPN基于IPsec来提供Internet上的安全性。服务提供商现在开始部署增强的VPN服务,除了安全性之外,还提供服务差异化、流量管理、第2层和第3层连接等功能。较新的隧道机制具有某些特性,允许服务提供商提供这些增强的VPN服务。

The VPN solutions we define now MUST be able to accommodate the traditional types of VPNs as well as the enhanced services now being deployed. They need to be able to run in a single service provider's network, as well as between a set of service providers and across the Internet. In doing so the VPNs SHOULD NOT be allowed to violate basic Internet design principles or overload the Internet core routers or accelerate the growths of the Internet routing tables. Specifically, Internet core routers SHALL NOT be required to maintain VPN-related information, regardless of whether the Internet routing protocols are used to distribute this information or not. In order to achieve this, the mechanisms used to develop various PPVPN solutions SHALL be as common as possible with generic Internet infrastructure mechanisms like discovery, signaling, routing and management. At the same time, existing Internet infrastructure mechanisms SHALL NOT be overloaded.


Another generic requirement from a standardization perspective is to limit the number of different solution approaches. For example, for service providers that need to support multiple types of VPN services, it may be undesirable to require a completely different solution approach for each type of VPN service.


1.2. Deployment Scenarios
1.2. 部署场景

There are three different deployment scenarios that need to be considered for PPVPN services:


1. Single-provider, single-AS: This is the least complex scenario, where the PPVPN service is offered across a single service provider network spanning a single Autonomous System.

1. 单一提供商,单一AS:这是最不复杂的场景,PPVPN服务通过跨越单一自治系统的单一服务提供商网络提供。

2. Single-provider, multi-AS: In this scenario, a single provider may have multiple Autonomous Systems (for e.g., a global Tier-1 ISP with different ASes depending on the global location, or an ISP

2. 单个提供商,多AS:在这种情况下,单个提供商可能有多个自治系统(例如,根据全球位置,具有不同ASE的全球一级ISP或ISP)

that has been created by mergers and acquisitions of multiple networks). This scenario involves the constrained distribution of routing information across multiple Autonomous Systems.


3. Multi-provider: This scenario is the most complex, wherein trust negotiations need to be made across multiple service provider backbones in order to meet the security and service level agreements for the PPVPN customer. This scenario can be generalized to cover the Internet, which comprises of multiple service provider networks. It should be noted that customers can construct their own VPNs across multiple providers. However such VPNs are not considered here as they would not be "Provider-provisioned".

3. 多提供商:此场景最为复杂,需要跨多个服务提供商主干网进行信任协商,以满足PPVPN客户的安全和服务级别协议。这种情况可以推广到包括由多个服务提供商网络组成的互联网。应该注意的是,客户可以跨多个提供商构建自己的VPN。但是,此处不考虑此类VPN,因为它们不是“提供商配置的”。

A fourth scenario, "Carrier's carrier" VPN may also be considered. In this scenario, a service provider (for example, a Tier 1 service provider) provides VPN service to another service provider (for example, a Tier 2 service provider), which in turn provides VPN service on its VPN to its customers. In the example given above, the Tier 2 provider's customers are contained within the Tier 2 provider's network, and the Tier 2 provider itself is a customer of the Tier 1 provider's network. Thus, this scenario is not treated separately in the document, because all of the single provider requirements would apply equally to this case.


It is expected that many of the generic requirements described in this document are independent of the three deployment scenarios listed above. However, specific requirements that are indeed dependent on the deployment scenario will be pointed out in this document.


1.3. Outline of this document
1.3. 本文件大纲

This document describes generic requirements for Provider Provisioned Virtual Private Networks (PPVPN). The document contains several sections, with each set representing a significant aspect of PPVPN requirements.


Section 2 lists authors who contributed to this document. Section 3 defines terminology and presents a taxonomy of PPVPN technologies. The taxonomy contains two broad classes, representing Layer 2 and Layer 3 VPNs. Each top level VPN class contains subordinate classes. For example, the Layer 3 VPN class contains a subordinate class of PE-based Layer 3 VPNs.


Sections 4, 5, 6 describe generic PPVPN requirements.


The requirements are broadly classified under the following categories:


1) Service requirements - Service attributes that the customer can observe or measure. For example, does the service forward frames or route datagrams? What security guarantees does the service provide? Availability and stability are key requirements in this category.

1) 服务要求-客户可以观察或测量的服务属性。例如,服务是否转发帧或路由数据报?该服务提供哪些安全保证?可用性和稳定性是该类别的关键要求。

2) Provider requirements - Characteristics that Service Providers use to determine the cost-effectiveness of a PPVPN service. Scaling and management are examples of Provider requirements.

2) 提供商要求-服务提供商用于确定PPVPN服务成本效益的特征。扩展和管理是提供者需求的示例。

3) Engineering requirements - Implementation characteristics that make service and provider requirements achievable. These can be further classified as:

3) 工程需求-使服务和提供商需求可实现的实施特征。这些可进一步分类为:

3a) Forwarding plane requirements - e.g., requirements related to router forwarding behavior.


3b) Control plane requirements - e.g., requirements related to reachability and distribution of reachability information.


3c) Requirements related to the commonality of PPVPN mechanisms with each other and with generic Internet mechanisms.


2. Contributing Authors
2. 撰稿人

This document was the combined effort of several individuals that were part of the Service Provider focus group whose intentions were to present Service Provider view on the general requirements for PPVPN. A significant set of requirements were directly taken from previous work by the PPVPN WG to develop requirements for Layer 3 PPVPN [L3REQTS]. The existing work in the L2 requirements area has also influenced the contents of this document [L2REQTS].


Besides the editor, the following are the authors that contributed to this document:


Loa Andersson ( Ron Bonica ( Dave McDysan ( Junichi Sumimoto ( Muneyoshi Suzuki ( David Meyer ( Marco Carugi (


Yetik Serbest ( Luyuan Fang ( Javier Achirica (


3. Definitions and Taxonomy
3. 定义和分类

The terminology used in this document is defined in [TERMINOLOGY]. In addition the following terminology is used:


Site: a geographical location with one or more users or one or more servers or a combination of servers and users.


User: the end user equipment (hosts), e.g., a workstation.


          |                                 |
       Layer 2 (L2)                     Layer 3 (L3)
    ______|_____                      ______|________
    |          |                      |             |
   PE-based   CE-based             PE-based       CE-based
    |          |
   P2P        P2MP
          |                                 |
       Layer 2 (L2)                     Layer 3 (L3)
    ______|_____                      ______|________
    |          |                      |             |
   PE-based   CE-based             PE-based       CE-based
    |          |
   P2P        P2MP

The figure above presents a taxonomy of PPVPN technologies. PE-based and CE-based Layer 2 VPNs may also be further classified as point-to-point (P2P) or point-to-multipoint (P2MP). It is also the intention of the working group to have a limited number of solutions, and this goal must be kept in mind when proposing solutions that meet the requirements specified in this document. Definitions for CE-based and PE-based PPVPNs can be obtained from [L3FRAMEWORK]. Layer 2 specific definitions can be obtained from [L2FRAMEWORK].


4. Service requirements
4. 服务要求

These are the requirements that a customer can observe or measure, in order to verify if the PPVPN service that the Service Provider (SP) provides is satisfactory. As mentioned before, each of these requirements apply equally across each of the three deployment scenarios unless stated otherwise.


4.1. Availability
4.1. 可利用性

VPN services MUST have high availability. VPNs that are distributed over several sites require connectivity to be maintained even in the event of network failures or degraded service.


This can be achieved via various redundancy techniques such as:


1. Physical Diversity

1. 物理多样性

A single site connected to multiple CEs (for CE-based PPVPNs) or PEs (for PE-based PPVPNs), or different POPs, or even different service providers.


2. Tunnel redundancy

2. 隧道冗余

Redundant tunnels may be set up between the PEs (in a PE-based PPVPN) or the CEs (in a CE-based PPVPN) so that if one tunnel fails, VPN traffic can continue to flow across the other tunnel that has already been set-up in advance.


Tunnel redundancy may be provided over and above physical diversity. For example, a single site may be connected to two CEs (for CE-based PPVPNs) or two PEs (for PE-based PPVPNs). Tunnels may be set up between each of the CEs (or PEs as the case may be) across different sites.


Of course, redundancy means additional resources being used, and consequently, management of additional resources, which would impact the overall scaling of the service.


It should be noted that it is difficult to guarantee high availability when the VPN service is across multiple providers, unless there is a negotiation between the different service providers to maintain the service level agreement for the VPN customer.


4.2. Stability
4.2. 稳定性

In addition to availability, VPN services MUST also be stable. Stability is a function of several components such as VPN routing, signaling and discovery mechanisms, in addition to tunnel stability. For example, in the case of routing, route flapping or routing loops MUST be avoided in order to ensure stability. Stability of the VPN service is directly related to the stability of the mechanisms and protocols used to establish the service. It SHOULD also be possible to allow network upgrades and maintenance procedures without impacting the VPN service.


4.3. Traffic types
4.3. 交通类型

VPN services MUST support unicast (or point to point) traffic and SHOULD support any-to-any or point-to-multipoint traffic including multicast and broadcast traffic. In the broadcast model, the network


delivers a stream to all members of a subnetwork, regardless of their interest in that stream. In the multicast model, the network delivers a stream to a set of destinations that have registered interest in the stream. All destinations need not belong to the same subnetwork. Multicast is more applicable to L3 VPNs while broadcast is more applicable to L2VPNs. It is desirable to support multicast limited in scope to an intranet or extranet. The solution SHOULD be able to support a large number of such intranet or extranet specific multicast groups in a scalable manner.

将流传递给子网的所有成员,而不管他们对该流感兴趣。在多播模型中,网络将流传送到一组对该流感兴趣的目的地。所有目的地不必属于同一子网。组播更适用于L3 VPN,而广播更适用于L2VPN。希望支持范围限于内联网或外联网的多播。该解决方案应该能够以可伸缩的方式支持大量此类特定于内联网或外联网的多播组。

All PPVPN approaches SHALL support both IPv4 and IPv6 traffic. Specific L2 traffic types (e.g., ATM, Frame Relay and Ethernet) SHALL be supported via encapsulation in IP or MPLS tunnels in the case of L2VPNs.


4.4. Data isolation
4.4. 数据隔离

The PPVPN MUST support forwarding plane isolation. The network MUST never deliver user data across VPN boundaries unless the two VPNs participate in an intranet or extranet.


Furthermore, if the provider network receives signaling or routing information from one VPN, it MUST NOT reveal that information to another VPN unless the two VPNs participate in an intranet or extranet. It should be noted that the disclosure of any signaling/routing information across an extranet MUST be filtered per the extranet agreement between the organizations participating in the extranet.


4.5. Security
4.5. 安全

A range of security features SHOULD be supported by the suite of PPVPN solutions in the form of securing customer flows, providing authentication services for temporary, remote or mobile users, and the need to protect service provider resources involved in supporting a PPVPN. These security features SHOULD be implemented based on the framework outlined in [VPN-SEC]. Each PPVPN solution SHOULD state which security features it supports and how such features can be configured on a per customer basis. Protection against Denial of Service (DoS) attacks is a key component of security mechanisms. Examples of DoS attacks include attacks to the PE or CE CPUs, access connection congestion, TCP SYN attacks and ping attacks.

PPVPN解决方案套件应支持一系列安全功能,包括保护客户流,为临时、远程或移动用户提供身份验证服务,以及保护支持PPVPN所涉及的服务提供商资源的需要。这些安全功能应基于[VPN-SEC]中概述的框架实施。每个PPVPN解决方案应说明其支持哪些安全功能,以及如何根据每个客户配置这些功能。防止拒绝服务(DoS)攻击是安全机制的关键组成部分。DoS攻击的示例包括对PE或CE CPU的攻击、访问连接拥塞、TCP SYN攻击和ping攻击。

Some security mechanisms (such as use of IPsec on a CE-to-CE basis) may be equally useful regardless of the scope of the VPN. Other mechanisms may be more applicable in some scopes than in others. For example, in some cases of single-provider single-AS VPNs, the VPN service may be isolated from some forms of attack by isolating the


infrastructure used for supporting VPNs from the infrastructure used for other services. However, the requirements for security are common regardless of the scope of the VPN service.


4.5.1. User data security
4.5.1. 用户数据安全

PPVPN solutions that support user data security SHOULD use standard methods (e.g., IPsec) to achieve confidentiality, integrity, authentication and replay attack prevention. Such security methods MUST be configurable between different end points, such as CE-CE, PE-PE, and CE-PE. It is also desirable to configure security on a per-route or per-VPN basis. User data security using encryption is especially desirable in the multi-provider scenario.


4.5.2. Access control
4.5.2. 访问控制

A PPVPN solution may also have the ability to activate the appropriate filtering capabilities upon request of a customer. A filter provides a mechanism so that access control can be invoked at the point(s) of communication between different organizations involved in an extranet. Access control can be implemented by a firewall, access control lists on routers, cryptographic mechanisms or similar mechanisms to apply policy-based access control. Access control MUST also be applicable between CE-CE, PE-PE and CE-PE. Such access control mechanisms are desirable in the multi-provider scenario.


4.5.3. Site authentication and authorization
4.5.3. 站点身份验证和授权

A PPVPN solution requires authentication and authorization of the following:


- temporary and permanent access for users connecting to sites (authentication and authorization BY the site)

- 连接到站点的用户的临时和永久访问(站点的身份验证和授权)

- the site itself (authentication and authorization FOR the site)

- 站点本身(站点的身份验证和授权)

4.5.4. Inter domain security
4.5.4. 域间安全

The VPN solution MUST have appropriate security mechanisms to prevent the different kinds of Distributed Denial of Service (DDoS) attacks mentioned earlier, misconfiguration or unauthorized accesses in inter domain PPVPN connections. This is particularly important for multi-service provider deployment scenarios. However, this will also be important in single-provider multi-AS scenarios.


4.6. Topology
4.6. 拓扑学

A VPN SHOULD support arbitrary, customer-defined inter-site connectivity, ranging, for example, from hub-and-spoke, partial mesh to full mesh topology. These can actually be different from the topology used by the service provider. To the extent possible, a PPVPN service SHOULD be independent of the geographic extent of the deployment.


Multiple VPNs per customer site SHOULD be supported without requiring additional hardware resources per VPN. This SHOULD also include a free mix of L2 and L3 VPNs.

每个客户站点应支持多个VPN,而不需要每个VPN额外的硬件资源。这还应包括L2和L3 VPN的免费混合。

To the extent possible, the PPVPN services SHOULD be independent of access network technology.


4.7. Addressing
4.7. 寻址

Each customer resource MUST be identified by an address that is unique within its VPN. It need not be identified by a globally unique address.


Support for private addresses as described in [RFC1918], as well as overlapping customer addresses SHALL be supported. One or more VPNs for each customer can be built over the same infrastructure without requiring any of them to renumber. The solution MUST NOT use NAT on the customer traffic to achieve that goal. Interconnection of two networks with overlapping IP addresses is outside the scope of this document.


A VPN service SHALL be capable of supporting non-IP customer addresses via encapsulation techniques, if it is a Layer 2 VPN (e.g., Frame Relay, ATM, Ethernet). Support for non-IP Layer 3 addresses may be desirable in some cases, but is beyond the scope of VPN solutions developed in the IETF, and therefore, this document.


4.8. Quality of Service
4.8. 服务质量

A technical approach for supporting VPNs SHALL be able to support QoS via IETF standardized mechanisms such as Diffserv. Support for best-effort traffic SHALL be mandatory for all PPVPN types. The extent to which any specific VPN service will support QoS is up to the service provider. In many cases single-provider single-AS VPNs will offer QoS guarantees. Support of QoS guarantees in the multi-service-provider case will require cooperation between the various service providers involved in offering the service.


It should be noted that QoS mechanisms in the multi-provider scenario REQUIRES each of the participating providers to support the mechanisms being used, and as such, this is difficult to achieve.


Note that all cases involving QoS may require that the CE and/or PE perform shaping and/or policing.


The need to provide QoS will occur primarily in the access network, since that will often be the bottleneck. This is likely to occur since the backbone effectively statistically multiplexes many users, and is traffic engineered or includes capacity for restoration and growth. Hence in most cases PE-PE QoS is not a major issue. As far as access QoS is concerned, there are two directions of QoS management that may be considered in any PPVPN service regarding QoS:

提供QoS的需求将主要发生在接入网络中,因为这通常是瓶颈。这很可能发生,因为主干网在统计上有效地多路复用了许多用户,并且是经过流量设计的,或者包括用于恢复和增长的容量。因此,在大多数情况下,PE-PE QoS不是主要问题。就访问QoS而言,在任何PPVPN服务中都可以考虑两个方向的QoS管理,即QoS:

- From the CE across the access network to the PE - From the PE across the access network to CE

- 从接入网络的CE到PE-从接入网络的PE到CE

PPVPN CE and PE devices SHOULD be capable of supporting QoS across at least the following subset of access networks, as applicable to the specific type of PPVPN (L2 or L3). However, to the extent possible, the QoS capability of a PPVPN SHOULD be independent of the access network technology:

PPVPN CE和PE设备应能够支持至少以下接入网络子集的QoS,适用于特定类型的PPVPN(L2或L3)。然而,PPVPN的QoS能力应尽可能独立于接入网络技术:

- ATM Virtual Connections (VCs) - Frame Relay Data Link Connection Identifiers (DLCIs) - 802.1d Prioritized Ethernet - MPLS-based access - Multilink Multiclass PPP - QoS-enabled wireless (e.g., LMDS, MMDS) - Cable modem - QoS-enabled Digital Subscriber Line (DSL)

- ATM虚拟连接(VCs)-帧中继数据链路连接标识符(DLCI)-802.1d优先以太网-基于MPLS的访问-多链路多类PPP-支持QoS的无线(如LMDS、MMDS)-电缆调制解调器-支持QoS的数字用户线(DSL)

Different service models for QoS may be supported. Examples of PPVPN QoS service models are:

可能支持不同的QoS服务模型。PPVPN QoS服务模型的示例包括:

- Managed access service: Provides QoS on the access connection between CE and the customer facing ports of the PE. No QoS support is required in the provider core network in this case.

- 托管访问服务:在CE和PE面向客户的端口之间的访问连接上提供QoS。在这种情况下,提供商核心网络不需要QoS支持。

- Edge-to-edge QoS: Provides QoS across the provider core, either between CE pairs or PE pairs, depending on the tunnel demarcation points. This scenario requires QoS support in the provider core network. As mentioned above, this is difficult to achieve in a multi-provider VPN offering.

- 边缘到边缘QoS:根据隧道分界点,跨提供程序核心在CE对或PE对之间提供QoS。此场景需要提供商核心网络中的QoS支持。如上所述,在多提供商VPN产品中很难实现这一点。

4.9. Service Level Agreement and Service Level Specification Monitoring and Reporting

4.9. 服务级别协议和服务级别规范监控和报告

A Service Level Specification (SLS) may be defined per access network connection, per VPN, per VPN site, and/or per VPN route. The service provider may define objectives and the measurement interval for at least the SLS using the following Service Level Objective (SLO) parameters:


- QoS and traffic parameters for the Intserv flow or Diffserv class [Y.1541]

- Intserv流或Diffserv类的QoS和流量参数[Y.1541]

- Availability for the site, VPN, or access connection

- 站点、VPN或访问连接的可用性

- Duration of outage intervals per site, route or VPN

- 每个站点、路由或VPN的停机间隔持续时间

- Service activation interval (e.g., time to turn up a new site)

- 服务激活间隔(例如,打开新站点的时间)

- Trouble report response time interval

- 故障报告响应时间间隔

- Time to repair interval

- 维修间隔时间

- Total traffic offered to the site, route or VPN

- 提供给站点、路由或VPN的总流量

- Measure of non-conforming traffic for the site, route or VPN

- 站点、路由或VPN的不合格流量测量

- Delay and delay variation (jitter) bounds

- 延迟和延迟变化(抖动)界限

- Packet ordering, at least when transporting L2 services sensitive to reordering (e.g., ATM).

- 数据包排序,至少在传输对重新排序敏感的L2服务时(如ATM)。

The above list contains items from [Y.1241], as well as other items typically part of SLAs for currently deployed VPN services [FRF.13]. See [RFC3198] for generic definitions of SLS, SLA, and SLO.


The provider network management system SHALL measure, and report as necessary, whether measured performance meets or fails to meet the above SLS objectives.


In many cases the guaranteed levels for Service Level Objective (SLO) parameters may depend upon the scope of the VPN. For example, one level of guarantee might be provided for service within a single AS. A different (generally less stringent) guarantee might be provided within multiple ASs within a single service provider. At the current time, in most cases specific guarantees are not offered for multi-provider VPNs, and if guarantees were offered they might be expected to be less stringent still.


The service provider and the customer may negotiate a contractual arrangement that includes a Service Level Agreement (SLA) regarding compensation if the provider does not meet an SLS performance objective. Details of such compensation are outside the scope of this document.


4.10. Network Resource Partitioning and Sharing between VPNs
4.10. VPN之间的网络资源分区和共享

Network resources such as memory space, FIB table, bandwidth and CPU processing SHALL be shared between VPNs and, where applicable, with non-VPN Internet traffic. Mechanisms SHOULD be provided to prevent any specific VPN from taking up available network resources and causing others to fail. SLAs to this effect SHOULD be provided to the customer.


Similarly, resources used for control plane mechanisms are also shared. When the service provider's control plane is used to distribute VPN specific information and provide other control mechanisms for VPNs, there SHALL be mechanisms to ensure that control plane performance is not degraded below acceptable limits when scaling the VPN service, or during network events such as failure, routing instabilities etc. Since a service provider's network would also be used to provide Internet service, in addition to VPNs, mechanisms to ensure the stable operation of Internet services and other VPNs SHALL be made in order to avoid adverse effects of resource hogging by large VPN customers.


5. Provider requirements
5. 供应商要求

This section describes operational requirements for a cost-effective, profitable VPN service offering.


5.1. Scalability
5.1. 可伸缩性

The scalability for VPN solutions has many aspects. The list below is intended to comprise of the aspects that PPVPN solutions SHOULD address. Clearly these aspects in absolute figures are very different for different types of VPNs - i.e., a point to point service has only two sites, while a VPLS or L3VPN may have a larger number of sites. It is also important to verify that PPVPN solutions not only scales on the high end, but also on the low end - i.e., a VPN with three sites and three users should be as viable as a VPN with hundreds of sites and thousands of users.


5.1.1. Service Provider Capacity Sizing Projections
5.1.1. 服务提供商能力规模预测

A PPVPN solution SHOULD be scalable to support a very large number of VPNs per Service Provider network. The estimate is that a large service provider will require support for O(10^4) VPNs within four years.


A PPVPN solution SHOULD be scalable to support a wide range of number of site interfaces per VPN, depending on the size and/or structure of the customer organization. The number of site interfaces SHOULD range from a few site interfaces to over 50,000 site interfaces per VPN.


A PPVPN solution SHOULD be scalable to support of a wide range of number of routes per VPN. The number of routes per VPN may range from just a few to the number of routes exchanged between ISPs (O(10^5)), with typical values being in the O(10^3) range. The high end number is especially true considering the fact that many large ISPs may provide VPN services to smaller ISPs or large corporations. Typically, the number of routes per VPN is at least twice the number of site interfaces.


A PPVPN solution SHOULD support high values of the frequency of configuration setup and change, e.g., for real-time provisioning of an on-demand videoconferencing VPN or addition/deletion of sites.


Approaches SHOULD articulate scaling and performance limits for more complex deployment scenarios, such as single-provider multi-AS VPNs, multi-provider VPNs and carriers' carrier. Approaches SHOULD also describe other dimensions of interest, such as capacity requirements or limits, number of interworking instances supported as well as any scalability implications on management systems.


A PPVPN solution SHOULD support a large number of customer interfaces on a single PE (for PE-based PPVPN) or CE (for CE-based PPVPN) with current Internet protocols.


5.1.2. VPN Scalability aspects
5.1.2. VPN可扩展性方面

This section describes the metrics for scaling PPVPN solutions, points out some of the scaling differences between L2 and L3 VPNs. It should be noted that the scaling numbers used in this document must be treated as typical examples as seen by the authors of this document. These numbers are only representative and different service providers may have different requirements for scaling. Further discussion on service provider sizing projections is in Section 5.1.1. Please note that the terms "user" and "site" are as defined in Section 3. It should also be noted that the numbers given

本节介绍扩展PPVPN解决方案的指标,指出L2和L3 VPN之间的一些扩展差异。应注意的是,本文件中使用的标度数必须视为本文件作者看到的典型示例。这些数字仅具有代表性,不同的服务提供商可能对扩展有不同的要求。关于服务提供商规模预测的进一步讨论见第5.1.1节。请注意,术语“用户”和“站点”的定义见第3节。还应注意的是,给出的数字

below would be different depending on whether the scope of the VPN is single-provider single-AS, single-provider multi-AS, or multi-provider. Clearly, the larger the scope, the larger the numbers that may need to be supported. However, this also means more management issues. The numbers below may be treated as representative of the single-provider case.

根据VPN的范围是单提供商单AS、单提供商多AS还是多提供商,以下内容可能有所不同。显然,范围越大,可能需要支持的数字就越大。然而,这也意味着更多的管理问题。以下数字可被视为单一供应商案例的代表。 Number of users per site 每个站点的用户数

The number of users per site follows the same logic as for users per VPN. Further, it must be possible to have single user sites connected to the same VPN as very large sites are connected to.


L3 VPNs SHOULD scale from 1 user per site to O(10^4) per site. L2 VPNs SHOULD scale from 1 user to O(10^3) per site for point-to-point VPNs and to O(10^4) for point-to-multipoint VPNs.

L3 VPN应从每个站点1个用户扩展到每个站点0(10^4)。对于点到点VPN,L2 VPN应从每个站点1个用户扩展到O(10^3),对于点到多点VPN,应扩展到O(10^4)。 Number of sites per VPN 每个VPN的站点数

The number of sites per VPN clearly depends on the number of users per site. VPNs SHOULD scale from 2 to O(10^3) sites per VPN. These numbers are usually limited by device memory.

每个VPN的站点数显然取决于每个站点的用户数。VPN应在每个VPN上从2个扩展到0个(10^3)站点。这些数字通常受到设备内存的限制。 Number of PEs and CEs PEs和CE的数量

The number of PEs that supports the same set of VPNs, i.e., the number of PEs that needs to directly exchange information on VPN de-multiplexing information is clearly a scaling factor in a PE-based VPN. Similarly, in a CE-based VPN, the number of CEs is a scaling factor. This number is driven by the type of VPN service, and also by whether the service is within a single AS/domain or involves a multi-SP or multi-AS network. Typically, this number SHOULD be as low as possible in order to make the VPN cost effective and manageable.

支持同一组VPN的PE数量,即需要直接交换VPN解复用信息的PE数量显然是基于PE的VPN中的一个比例因子。类似地,在基于CE的VPN中,CE的数量是一个比例因子。这个数字取决于VPN服务的类型,也取决于该服务是在单个AS/域内还是涉及多SP或多AS网络。通常,该数字应尽可能低,以使VPN经济高效且易于管理。 Number of sites per PE 每个PE的站点数

The number of sites per PE needs to be discussed based on several different scenarios. On the one hand there is a limitation to the number of customer facing interfaces that the PE can support. On the other hand the access network may aggregate several sites connected on comparatively low bandwidth on to one single high bandwidth interface on the PE. The scaling point here is that the PE SHOULD be able to support a few or even a single site on the low end and O(10^4) sites on the high end. This number is also limited by device memory. Implementations of PPVPN solutions may be evaluated based on this requirement, because it directly impacts cost and manageability of a VPN.

每个PE的站点数量需要根据几个不同的场景进行讨论。一方面,PE可以支持的面向客户的接口数量有限。另一方面,接入网络可以将在相对低带宽上连接的多个站点聚合到PE上的单个高带宽接口上。这里的扩展点是,PE应该能够在低端支持几个甚至单个站点,在高端支持O(10^4)站点。这个数字也受到设备内存的限制。PPVPN解决方案的实施可以基于此需求进行评估,因为它直接影响VPN的成本和可管理性。 Number of VPNs in the network 网络中的VPN数量

The number of VPNs SHOULD scale linearly with the size of the access network and with the number of PEs. As mentioned in Section 5.1.1, the number of VPNs in the network SHOULD be O(10^4). This requirement also effectively places a requirement on the number of tunnels that SHOULD be supported in the network. For a PE-based VPN, the number of tunnels is of the same order as the number of VPNs. For a CE-based VPN, the number of tunnels in the core network may be fewer, because of the possibility of tunnel aggregation or multiplexing across the core.

VPN的数量应与接入网络的大小和PE的数量成线性比例。如第5.1.1节所述,网络中的VPN数量应为O(10^4)。该要求还有效地对网络中应支持的隧道数量提出了要求。对于基于PE的VPN,隧道的数量与VPN的数量顺序相同。对于基于CE的VPN,核心网络中的隧道数量可能会更少,因为可能会跨核心进行隧道聚合或多路复用。 Number of VPNs per customer 每个客户的VPN数量

In some cases a service provider may support multiple VPNs for the same customer of that service provider. For example, this may occur due to differences in services offered per VPN (e.g., different QoS, security levels, or reachability) as well as due to the presence of multiple workgroups per customer. It is possible that one customer will run up to O(100) VPNs.

在某些情况下,服务提供商可能为该服务提供商的同一客户支持多个VPN。例如,这可能是由于每个VPN提供的服务不同(例如,不同的QoS、安全级别或可达性)以及每个客户存在多个工作组造成的。一个客户可能运行多达O(100)个VPN。 Number of addresses and address prefixes per VPN 每个VPN的地址数和地址前缀

Since any VPN solution SHALL support private customer addresses, the number of addresses and address prefixes are important in evaluating the scaling requirements. The number of address prefixes used in routing protocols and in forwarding tables specific to the VPN needs to scale from very few (for smaller customers) to very large numbers seen in typical Service Provider backbones. The high end is especially true considering that many Tier 1 SPs may provide VPN services to Tier 2 SPs or to large corporations. For a L2 VPN this number would be on the order of addresses supported in typical native Layer 2 backbones.

由于任何VPN解决方案都应支持私有客户地址,因此地址数量和地址前缀在评估扩展需求时非常重要。在路由协议和专用于VPN的转发表中使用的地址前缀的数量需要从很少(对于较小的客户)扩展到非常大的数量,这在典型的服务提供商主干网中可以看到。考虑到许多第1层SP可能向第2层SP或大公司提供VPN服务,高端尤其如此。对于L2 VPN,此数字将按照典型的本机第2层主干中支持的地址顺序排列。

5.1.3. Solution-Specific Metrics
5.1.3. 解决方案特定指标

Each PPVPN solution SHALL document its scalability characteristics in quantitative terms. A VPN solution SHOULD quantify the amount of state that a PE and P device has to support. This SHOULD be stated in terms of the order of magnitude of the number of VPNs and site interfaces supported by the service provider. Ideally, all VPN-specific state SHOULD be contained in the PE device for a PE-based VPN. Similarly, all VPN-specific state SHOULD be contained in the CE device for a CE-based VPN. In all cases, the backbone routers (P devices) SHALL NOT maintain VPN-specific state as far as possible.


Another metric is that of complexity. In a PE-based solution the PE is more complex in that it has to maintain tunnel-specific information for each VPN, but the CE is simpler since it does not need to support tunnels. On the other hand, in a CE-based solution, the CE is more complex since it has to implement routing across a number of tunnels to other CEs in the VPN, but the PE is simpler since it has only one routing and forwarding instance. Thus, the complexity of the PE or CE SHOULD be noted in terms of their processing and management functions.


5.2. Management
5.2. 经营

A service provider MUST have a means to view the topology, operational state, service order status, and other parameters associated with each customer's VPN. Furthermore, the service provider MUST have a means to view the underlying logical and physical topology, operational state, provisioning status, and other parameters associated with the equipment providing the VPN service(s) to its customers.


In the multi-provider scenario, it is unlikely that participating providers would provide each other a view to the network topology and other parameters mentioned above. However, each provider MUST ensure via management of their own networks that the overall VPN service offered to the customers are properly managed. In general the support of a single VPN spanning multiple service providers requires close cooperation between the service providers. One aspect of this cooperation involves agreement on what information about the VPN will be visible across providers, and what network management protocols will be used between providers.


VPN devices SHOULD provide standards-based management interfaces wherever feasible.


5.2.1. Customer Management of a VPN
5.2.1. VPN的客户管理

A customer SHOULD have a means to view the topology, operational state, service order status, and other parameters associated with his or her VPN.


All aspects of management information about CE devices and customer attributes of a PPVPN manageable by an SP SHOULD be capable of being configured and maintained by the customer after being authenticated and authorized.


A customer SHOULD be able to make dynamic requests for changes to traffic parameters. A customer SHOULD be able to receive real-time response from the SP network in response to these requests. One


example of such as service is a "Dynamic Bandwidth management" capability, that enables real-time response to customer requests for changes of allocated bandwidth allocated to their VPN(s). A possible outcome of giving customers such capabilities is Denial of Service attacks on other VPN customers or Internet users. This possibility is documented in the Security Considerations section.


6. Engineering requirements
6. 工程要求

These requirements are driven by implementation characteristics that make service and provider requirements achievable.


6.1. Forwarding plane requirements
6.1. 转运飞机要求

VPN solutions SHOULD NOT pre-suppose or preclude the use of IETF developed tunneling techniques such as IP-in-IP, L2TP, GRE, MPLS or IPsec. The separation of VPN solution and tunnels will facilitate adaptability with extensions to current tunneling techniques or development of new tunneling techniques. It should be noted that the choice of the tunneling techniques may impact the service and scaling capabilities of the VPN solution.


It should also be noted that specific tunneling techniques may not be feasible depending on the deployment scenario. In particular, there is currently very little use of MPLS in the inter-provider scenario. Thus, native MPLS support may be needed between the service providers, or it would be necessary to run MPLS over IP or GRE. It should be noted that if MPLS is run over IP or GRE, some of the other capabilities of MPLS, such as Traffic Engineering, would be impacted. Also note that a service provider MAY optionally choose to use a different encapsulation for multi-AS VPNs than is used for single AS VPNs. Similarly, a group of service providers may choose to use a different encapsulation for multi-service provider VPNs than for VPNs within a single service provider.

还应注意,根据部署场景,特定的隧道技术可能不可行。特别是,目前在提供商间场景中很少使用MPLS。因此,服务提供商之间可能需要本机MPLS支持,或者需要在IP或GRE上运行MPLS。应该注意的是,如果MPLS在IP或GRE上运行,MPLS的一些其他功能(如流量工程)将受到影响。还请注意,服务提供商可以选择对多AS VPN使用不同于单AS VPN的封装。类似地,一组服务提供商可以选择对多个服务提供商VPN使用与对单个服务提供商内的VPN不同的封装。

For Layer 2 VPNs, solutions SHOULD utilize the encapsulation techniques defined by the Pseudo-Wire Emulation Edge-to-Edge (PWE3) Working Group, and SHOULD NOT impose any new requirements on these techniques.


PPVPN solutions MUST NOT impose any restrictions on the backbone traffic engineering and management techniques. Conversely, backbone engineering and management techniques MUST NOT affect the basic operation of a PPVPN, apart from influencing the SLA/SLS guarantees associated with the service. The SP SHOULD, however, be REQUIRED to provide per-VPN management, tunnel maintenance and other maintenance required in order to meet the SLA/SLS.


By definition, VPN traffic SHOULD be segregated from each other, and from non-VPN traffic in the network. After all, VPNs are a means of dividing a physical network into several logical (virtual) networks. VPN traffic separation SHOULD be done in a scalable fashion. However, safeguards SHOULD be made available against misbehaving VPNs to not affect the network and other VPNs.


A VPN solution SHOULD NOT impose any hard limit on the number of VPNs provided in the network.


6.2. Control plane requirements
6.2. 控制平面要求

The plug and play feature of a VPN solution with minimum configuration requirements is an important consideration. The VPN solutions SHOULD have mechanisms for protection against customer interface and/or routing instabilities so that they do not impact other customers' services or impact general Internet traffic handling in any way.


A VPN SHOULD be provisioned with minimum number of steps. For instance, a VPN need not be configured in every PE. For this to be accomplished, an auto-configuration and an auto-discovery protocol, which SHOULD be as common as possible to all VPN solutions, SHOULD be defined. However, these mechanisms SHOULD NOT adversely affect the cost, scalability or stability of a service by being overly complex, or by increasing layers in the protocol stack.


Mechanisms to protect the SP network from effects of misconfiguration of VPNs SHOULD be provided. This is especially of importance in the multi-provider case, where misconfiguration could possibly impact more than one network.


6.3. Control Plane Containment
6.3. 控制平面安全壳

The PPVPN control plane MUST include a mechanism through which the service provider can filter PPVPN related control plane information as it passes between Autonomous Systems. For example, if a service provider supports a PPVPN offering, but the service provider's neighbors do not participate in that offering, the service provider SHOULD NOT leak PPVPN control information into neighboring networks. Neighboring networks MUST be equipped with mechanisms that filter this information should the service provider leak it. This is important in the case of multi-provider VPNs as well as single-provider multi-AS VPNs.


6.4. Requirements related to commonality of PPVPN mechanisms with each other and with generic Internet mechanisms

6.4. 与PPVPN机制之间以及与通用互联网机制之间的通用性相关的要求

As far as possible, the mechanisms used to establish a VPN service SHOULD re-use well-known IETF protocols, limiting the need to define new protocols from scratch. It should, however, be noted that the use of Internet mechanisms for the establishment and running of an Internet-based VPN service, SHALL NOT affect the stability, robustness, and scalability of the Internet or Internet services. In other words, these mechanisms SHOULD NOT conflict with the architectural principles of the Internet, nor SHOULD it put at risk the existing Internet systems. For example, IETF-developed routing protocols SHOULD be used for routing of L3 PPVPN traffic, without adding VPN-specific state to the Internet core routers. Similarly, well-known L2 technologies SHOULD be used in VPNs offering L2 services, without imposing risks to the Internet routers. A solution MUST be implementable without requiring additional functionality to the P devices in a network, and minimal functionality to the PE in a PE-based VPN and CE in a CE-based VPN.

用于建立VPN服务的机制应尽可能重复使用众所周知的IETF协议,从而限制从头定义新协议的需要。但是,应注意,使用互联网机制建立和运行基于互联网的VPN服务,不得影响互联网或互联网服务的稳定性、健壮性和可扩展性。换句话说,这些机制不应与互联网的架构原则相冲突,也不应使现有的互联网系统处于危险之中。例如,IETF开发的路由协议应用于L3 PPVPN流量的路由,而不向Internet核心路由器添加VPN特定状态。类似地,在提供L2服务的VPN中应使用众所周知的L2技术,而不会给Internet路由器带来风险。解决方案必须是可实施的,而不需要网络中的P设备的附加功能,以及基于PE的VPN中的PE和基于CE的VPN中的CE的最小功能。

In addition to commonality with generic Internet mechanisms, infrastructure mechanisms used in different PPVPN solutions (both L2 and L3), e.g., discovery, signaling, routing and management, SHOULD be as common as possible.


6.5. Interoperability
6.5. 互操作性

Each technical solution is expected to be based on interoperable Internet standards.


Multi-vendor interoperability at network element, network and service levels among different implementations of the same technical solution SHOULD be ensured (that will likely rely on the completeness of the corresponding standard). This is a central requirement for SPs and customers.


The technical solution MUST be multi-vendor interoperable not only within the SP network infrastructure, but also with the customer's network equipment and services making usage of the PPVPN service.


Customer access connections to a PPVPN solution may be different at different sites (e.g., Frame Relay on one site and Ethernet on another).


Interconnection of a L2VPN over an L3VPN as if it were a customer site SHALL be supported. However, interworking of Layer 2 technologies is not required, and is outside the scope of the working group, and therefore, of this document.


Inter-domain interoperability - It SHOULD be possible to deploy a PPVPN solution across domains, Autonomous Systems, or the Internet.


7. Security Considerations
7. 安全考虑

Security requirements for Provider Provisioned VPNs have been described in Section 4.5. In addition, the following considerations need to be kept in mind when a provider provisioned VPN service is provided across a public network infrastructure that is also used to provide Internet connectivity. In general, the security framework described in [VPN-SEC] SHOULD be used as far as it is applicable to the given type of PPVPN service.


The PE device has a lot of functionality required for the successful operation of the VPN service. The PE device is frequently also part of the backbone providing Internet services, and is therefore susceptible to security and denial of service attacks. The PE control plane CPU is vulnerable from this point of view, and it may impact not only VPN services but also general Internet services if not adequately protected. In addition to VPN configuration, if mechanisms such as QoS are provisioned on the PE, it is possible for attackers to recognize the highest priority traffic or customers and launch directed attacks. Care SHOULD be taken to prevent such attacks whenever any value added services such as QoS are offered.


When a service such as "Dynamic Bandwidth Management" as described in Section 5.2.1 is provided, it allows customers to dynamically request for changes to their bandwidth allocation. The provider MUST take care to authenticate such requests and detect and prevent possible Denial-of-Service attacks. These DoS attacks are possible when a customer maliciously or accidentally may cause a change in bandwidth allocation that may impact the bandwidth allocated to other VPN customers or Internet users.


Different choices of VPN technology have different assurance levels of the privacy of a customer's network. For example, CE-based solutions may enjoy more privacy than PE-based VPNs by virtue of tunnels extending from CE to CE, even if the tunnels are not encrypted. In a PE-based VPN, a PE has many more sites than those attached to a CE in a CE-based VPN. A large number of these sites may use [RFC1918] addresses. Provisioning mistakes and PE software bugs may make traffic more prone to being misdirected as opposed to a CE-based VPN. Care MUST be taken to prevent misconfiguration in all kinds of PPVPNs, but more care MUST be taken in the case of PE-based VPNs, as this could impact other customers and Internet services. Similarly, there SHOULD be mechanisms to prevent the flooding of


Internet routing tables whenever there is a misconfiguration or failure of PPVPN control mechanisms that use Internet routing protocols for relay of VPN-specific information.


Different deployment scenarios also dictate the level of security that may be needed for a VPN. For example, it is easier to control security in a single provider, single AS VPN and therefore, expensive encryption techniques may not be used in this case, as long as VPN traffic is isolated from the Internet. There is a reasonable amount of control possible in the single provider, multi AS case, although care SHOULD be taken to ensure the constrained distribution of VPN route information across the ASes. Security is more of a challenge in the multi-provider case, where it may be necessary to adopt encryption techniques in order to provide the highest level of security.


8. References
8. 工具书类
8.1. Normative References
8.1. 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。

8.2. Informative References
8.2. 资料性引用

[TERMINOLOGY] Andersson, L., Madsen, T., "Terminology for Provider Provisioned Virtual Private Networks", Work in Progress.


[L3FRAMEWORK] Callon, R., Suzuki, M., et al. "A Framework for Layer 3 Provider Provisioned Virtual Private Networks", Work in Progress, March 2003.


[L2FRAMEWORK] Andersson, L., et al. "Framework for Layer 2 Virtual Private Networks (L2VPNs)", Work in Progress, March 2004.


[L3REQTS] Carugi, M., McDysan, D. et al., "Service Requirements for Layer 3 Provider Provisioned Virtual Private Networks", Work in Progress, April 2003.


[L2REQTS] Augustyn, W., Serbest, Y., et al., "Service Requirements for Layer 2 Provider Provisioned Virtual Private Networks", Work in Progress, April 2003.


[Y.1241] "IP Transfer Capability for the support of IP based Services", Y.1241 ITU-T Draft Recommendation, March 2000.

[Y.1241]“支持基于IP的服务的IP传输能力”,Y.1241 ITU-T建议草案,2000年3月。

[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G. and E. Lear, "Address Allocation for Private Internets", BCP 5, RFC 1918, February 1996.

[RFC1918]Rekhter,Y.,Moskowitz,B.,Karrenberg,D.,de Groot,G.和E.Lear,“私人互联网地址分配”,BCP 5,RFC 1918,1996年2月。

[RFC3198] Westerinen, A., Schnizlein, J., Strassner, J., Scherling, M., Quinn, B., Herzog, S., Huynh, A., Carlson, M., Perry, J. and S. Waldbusser, "Terminology for Policy-Based Management", RFC 3198, November 2001.

[RFC3198]Westerinen,A.,Schnizlein,J.,Strassner,J.,Scherling,M.,Quinn,B.,Herzog,S.,Huynh,A.,Carlson,M.,Perry,J.和S.Waldbusser,“基于政策的管理术语”,RFC 3198,2001年11月。

[VPN-SEC] Fang, L., et al., "Security Framework for Provider Provisioned Virtual Private Networks", Work in Progress, February 2004.


[FRF.13] Frame Relay Forum, "Service Level Definitions Implementation Agreement", August 1998.


[Y.1541] "Network Performance Objectives for IP-based Services", Y.1541, ITU-T Recommendation.


9. Acknowledgements
9. 致谢

This work was done in consultation with the entire design team for PPVPN requirements. A lot of the text was adapted from the Layer 3 requirements document produced by the Layer 3 requirements design team. The authors would also like to acknowledge the constructive feedback from Scott Bradner, Alex Zinin, Steve Bellovin, Thomas Narten and other IESG members, and the detailed comments from Ross Callon.

这项工作是在与整个设计团队协商PPVPN要求后完成的。很多文本都是从第三层需求设计团队制作的第三层需求文档中改编而来的。作者还要感谢Scott Bradner、Alex Zinin、Steve Bellovin、Thomas Narten和IESG其他成员的建设性反馈,以及Ross Callon的详细评论。

10. Editor's Address
10. 编辑地址

Ananth Nagarajan Juniper Networks

Ananth Nagarajan Juniper网络

11. Full Copyright Statement
11. 完整版权声明

Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.

版权所有(C)互联网协会(2004年)。本文件受BCP 78中包含的权利、许可和限制的约束,除其中规定外,作者保留其所有权利。



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