path: root/doc/rfc/rfc4031.txt

Network Working Group                                     M. Carugi, Ed.
Request for Comments: 4031                               Nortel Networks
Category: Informational                                  D. McDysan, Ed.
                                                                     MCI
                                                              April 2005


                    Service Requirements for 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 Internet Society (2005).

Abstract

   This document provides requirements for Layer 3 Virtual Private
   Networks (L3VPNs).  It identifies requirements applicable to a number
   of individual approaches that a Service Provider may use to provision
   a Virtual Private Network (VPN) service.  This document expresses a
   service provider perspective, based upon past experience with IP-
   based service offerings and the ever-evolving needs of the customers
   of such services.  Toward this end, it first defines terminology and
   states general requirements.  Detailed requirements are expressed
   from a customer perspective as well as that of a service provider.

Table of Contents

   1.   Introduction. . . . . . . . . . . . . . . . . . . . . . . . .  3
        1.1.  Scope of This Document. . . . . . . . . . . . . . . . .  4
        1.2.  Outline . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.   Contributing Authors. . . . . . . . . . . . . . . . . . . . .  5
   3.   Definitions . . . . . . . . . . . . . . . . . . . . . . . . .  5
        3.1.  Virtual Private Network . . . . . . . . . . . . . . . .  6
        3.2.  Users, Sites, Customers, and Agents . . . . . . . . . .  6
        3.3.  Intranets, Extranets, and VPNs. . . . . . . . . . . . .  6
        3.4.  Networks of Customer and Provider Devices . . . . . . .  7
        3.5.  Access Networks, Tunnels, and Hierarchical Tunnels. . .  7
        3.6.  Use of Tunnels and Roles of CE and PE in L3VPNs . . . .  8
              3.6.1.  PE-Based L3VPNs and Virtual Forwarding
                      Instances . . . . . . . . . . . . . . . . . . .  8
              3.6.2.  CE-Based L3VPN Tunnel Endpoints and Functions . 10



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        3.7.  Customer and Provider Network Management. . . . . . . . 10
   4.   Service Requirements Common to Customers and Service
        Providers . . . . . . . . . . . . . . . . . . . . . . . . . . 11
        4.1.  Isolated Exchange of Data and Routing Information . . . 11
        4.2.  Addressing. . . . . . . . . . . . . . . . . . . . . . . 12
        4.3.  Quality of Service. . . . . . . . . . . . . . . . . . . 12
              4.3.1.  QoS Standards . . . . . . . . . . . . . . . . . 12
              4.3.2.  Service Models. . . . . . . . . . . . . . . . . 13
        4.4.  Service Level Specification and Agreements. . . . . . . 14
        4.5.  Management. . . . . . . . . . . . . . . . . . . . . . . 14
        4.6.  Interworking. . . . . . . . . . . . . . . . . . . . . . 15
   5.   Customer Requirements . . . . . . . . . . . . . . . . . . . . 15
        5.1.  VPN Membership (Intranet/Extranet). . . . . . . . . . . 15
        5.2.  Service Provider Independence . . . . . . . . . . . . . 16
        5.3.  Addressing. . . . . . . . . . . . . . . . . . . . . . . 16
        5.4.  Routing Protocol Support. . . . . . . . . . . . . . . . 16
        5.5.  Quality of Service and Traffic Parameters . . . . . . . 16
              5.5.1.  Application Level QoS Objectives. . . . . . . . 17
              5.5.2.  DSCP Transparency . . . . . . . . . . . . . . . 17
        5.6.  Service Level Specification/Agreement . . . . . . . . . 18
        5.7.  Customer Management of a VPN. . . . . . . . . . . . . . 18
        5.8.  Isolation . . . . . . . . . . . . . . . . . . . . . . . 18
        5.9.  Security. . . . . . . . . . . . . . . . . . . . . . . . 19
        5.10. Migration Impact. . . . . . . . . . . . . . . . . . . . 19
        5.11. Network Access. . . . . . . . . . . . . . . . . . . . . 19
              5.11.1. Physical/Link Layer Technology. . . . . . . . . 20
              5.11.2. Temporary Access. . . . . . . . . . . . . . . . 20
              5.11.3. Sharing of the Access Network . . . . . . . . . 20
              5.11.4. Access Connectivity . . . . . . . . . . . . . . 20
        5.12. Service Access. . . . . . . . . . . . . . . . . . . . . 23
              5.12.1. Internet Access . . . . . . . . . . . . . . . . 23
              5.12.2. Hosting, Application Service Provider . . . . . 24
              5.12.3. Other Services. . . . . . . . . . . . . . . . . 24
        5.13. Hybrid VPN Service Scenarios. . . . . . . . . . . . . . 24
   6.   Service Provider Network Requirements . . . . . . . . . . . . 24
        6.1.  Scalability . . . . . . . . . . . . . . . . . . . . . . 24
        6.2.  Addressing. . . . . . . . . . . . . . . . . . . . . . . 25
        6.3.  Identifiers . . . . . . . . . . . . . . . . . . . . . . 25
        6.4.  Discovering VPN Related Information . . . . . . . . . . 26
        6.5.  SLA and SLS Support . . . . . . . . . . . . . . . . . . 26
        6.6.  Quality of Service (QoS) and Traffic Engineering. . . . 27
        6.7.  Routing . . . . . . . . . . . . . . . . . . . . . . . . 27
        6.8.  Isolation of Traffic and Routing. . . . . . . . . . . . 28
        6.9.  Security. . . . . . . . . . . . . . . . . . . . . . . . 28
              6.9.1.  Support for Securing Customer Flows . . . . . . 28
              6.9.2.  Authentication Services . . . . . . . . . . . . 29
              6.9.3.  Resource Protection . . . . . . . . . . . . . . 30
        6.10. Inter-AS (SP)VPNs . . . . . . . . . . . . . . . . . . . 30



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              6.10.1. Routing Protocols . . . . . . . . . . . . . . . 31
              6.10.2. Management. . . . . . . . . . . . . . . . . . . 31
              6.10.3. Bandwidth and QoS Brokering . . . . . . . . . . 31
              6.10.4. Security Considerations . . . . . . . . . . . . 32
        6.11. L3VPN Wholesale . . . . . . . . . . . . . . . . . . . . 32
        6.12. Tunneling Requirements. . . . . . . . . . . . . . . . . 33
        6.13. Support for Access and Backbone Technologies. . . . . . 33
              6.13.1. Dedicated Access Networks . . . . . . . . . . . 34
              6.13.2. On-Demand Access Networks . . . . . . . . . . . 34
              6.13.3. Backbone Networks . . . . . . . . . . . . . . . 35
        6.14. Protection, Restoration . . . . . . . . . . . . . . . . 35
        6.15. Interoperability. . . . . . . . . . . . . . . . . . . . 35
        6.16. Migration Support . . . . . . . . . . . . . . . . . . . 36
   7.   Service Provider Management Requirements. . . . . . . . . . . 36
        7.1.  Fault Management. . . . . . . . . . . . . . . . . . . . 37
        7.2.  Configuration Management. . . . . . . . . . . . . . . . 37
              7.2.1.  Configuration Management for PE-Based VPNs. . . 38
              7.2.2.  Configuration Management for CE-Based VPNs. . . 39
              7.2.3.  Provisioning Routing. . . . . . . . . . . . . . 39
              7.2.4.  Provisioning Network Access . . . . . . . . . . 39
              7.2.5.  Provisioning Security Services. . . . . . . . . 40
              7.2.6.  Provisioning VPN Resource Parameters. . . . . . 40
              7.2.7.  Provisioning Value-Added Service Access . . . . 40
              7.2.8.  Provisioning Hybrid VPN Services. . . . . . . . 41
        7.3.  Accounting. . . . . . . . . . . . . . . . . . . . . . . 41
        7.4.  Performance Management. . . . . . . . . . . . . . . . . 42
              7.4.1.  Performance Monitoring. . . . . . . . . . . . . 42
              7.4.2.  SLA and QoS Management Features . . . . . . . . 42
        7.5.  Security Management . . . . . . . . . . . . . . . . . . 43
              7.5.1.  Resource Access Control . . . . . . . . . . . . 43
              7.5.2.  Authentication. . . . . . . . . . . . . . . . . 43
        7.6.  Network Management Techniques . . . . . . . . . . . . . 44
   8.   Security Considerations . . . . . . . . . . . . . . . . . . . 44
   9.   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 45
   10.  References. . . . . . . . . . . . . . . . . . . . . . . . . . 45
        10.1. Normative References. . . . . . . . . . . . . . . . . . 45
        10.2. Informative References. . . . . . . . . . . . . . . . . 46
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 49
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 50

1.  Introduction

   This section describes the scope and outline of the document.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 ([RFC2119]).




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1.1.  Scope of This Document

   This document provides requirements specific to Layer 3 Virtual
   Private Networks (L3VPN). (Requirements that are generic to L2 and L3
   VPNs are contained in [RFC3809].)

   This document identifies requirements that may apply to one or more
   individual approaches that a Service Provider may use to provision a
   Layer 3 (e.g., IP) VPN service.  It makes use of the terminology and
   common components for Layer 3 VPNs as defined in [L3VPN-FR] and of
   the generic VPN terminology defined in
   [PPVPN-TERM].

   The specification of technical means to provide L3VPN services is
   outside the scope of this document.  Other documents are intended to
   cover this aspect, such as the L3 VPN framework document [L3VPN-FR]
   and several sets of documents, one for each technical approach for
   providing L3VPN services.

   Technical approaches targeted by this document include the network-
   based (PE-based) L3VPN category (aggregated routing VPNs [2547bis]
   and virtual routers [PPVPN-VR]) and the CE-based L3VPNs category
   [CE-PPVPN][IPSEC-PPVPN].  The document distinguishes L3VPN categories
   as to where the endpoints of tunnels exist, as detailed in the L3VPN
   framework document [L3VPN-FR].  Terminology describing whether
   equipment faces a customer or the service provider network is used to
   define the various types of L3VPN solutions.

   This document is intended as a "checklist" of requirements, providing
   a consistent way to evaluate and document how well each approach
   satisfies specific requirements.  The applicability statement
   documents for each approach should present the results of this
   evaluation.  This document is not intended to compare one approach to
   another.

   This document provides requirements from several points of view.  It
   begins with some considerations from a point of view common to
   customers and service providers not covered in the generic provider
   provisioned VPN requirement document [RFC3809], continues with a
   customer perspective, and concludes with specific needs of a Service
   Provider (SP).

   The following L3VPN deployment scenarios are considered within this
   document:

   1.  Internet-wide: VPN sites attached to arbitrary points in the
       Internet.




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   2.  Single SP/single AS: VPN sites attached to the network of a
       single provider within the scope of a single AS.

   3.  Single SP/multiple ASes: VPN sites attached to the network of a
       single provider consisting of multiple ASes.

   4.  Cooperating SPs: VPN sites attached to networks of different
       providers that cooperate with each other to provide the VPN
       service.

   The above deployment scenarios have many requirements in common.
   These include SP requirements for security, privacy, manageability,
   interoperability, and scalability, including service provider
   projections for number, complexity, and rate of change of customer
   VPNs over the next several years.  When requirements apply to a
   specific deployment scenario, the above terminology is used to state
   the context of those particular requirements.

1.2.  Outline

   The outline of the rest of the document is as follows:  Section 2
   lists the contributing authors.  Section 3 provides definitions of
   terms and concepts.  Section 4 provides requirements common to both
   customers and service providers that are not covered in the generic
   provider provisioned VPN requirement document [RFC3809].  Section 5
   states requirements from a customer perspective.  Section 6 states
   network requirements from a service provider perspective.  Section 7
   states service provider management requirements.  Section 8 describes
   security considerations.  Section 9 lists acknowledgments.  Section
   10 provides a list of references cited herein.  Section 11 lists the
   authors' addresses.

2.  Contributing Authors

   This document is the combined effort of the two co-editors and the
   following contributing authors:

      Luyuan Fang
      Ananth Nagarajan
      Junichi Sumimoto
      Rick Wilder

3.  Definitions

   This section provides the definition of terms and concepts used
   throughout the document.  Terminology used herein is taken from
   [PPVPN-TERM] and [L3VPN-FR].




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3.1.  Virtual Private Network

   "L3 Virtual Private Network" (L3VPN) refers to the L3 communication
   between a set of sites making use of a shared network infrastructure.

   "Provider Provisioned VPN" (PPVPN) refers to VPNs for which the
   service provider participates in management and provisioning of the
   VPN.

3.2.  Users, Sites, Customers, and Agents

   User: A user is an entity (e.g., a human being using a host, a
   server, or a system) authorized to use a VPN service.

   Site: A site is a set of users that have mutual L3 (i.e., IP)
   reachability without use of a specific service provider network.  A
   site may consist of a set of users that are in geographic proximity.
   Note that a topological definition of a site (e.g., all users at a
   specific geographic location) may not always conform to this
   definition.  For example, two geographic locations connected via
   another provider's network would also constitute a single site as
   communication between the two locations does not involve the use of
   the service provider offering the L3 VPN service.

   Customer: A single organization, corporation, or enterprise that
   administratively controls a set of sites.

   Agent: A set of users designated by a customer who has the
   authorization to manage a customer's VPN service offering.

3.3.  Intranets, Extranets, and VPNs

   Intranet: An intranet restricts communication to a set of sites that
   belong to one customer.  An example is branch offices at different
   sites that require communication with a headquarters site.

   Extranet: An extranet allows the specification of communication
   between a set of sites that belong to different customers.  In other
   words, two or more organizations have access to a specified set of
   each other's sites.  Examples of extranets include multiple companies
   cooperating in joint software development, a service provider having
   access to information from the vendors' corporate sites, different
   companies, or universities participating in a consortium.  An
   extranet often has further restrictions on reachability, for example,
   at a host and individual transport level.






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   Note that an intranet or extranet can exist across a single service
   provider network with one or more ASes, or across multiple service
   provider networks.

   L3 Virtual Private Network (L3VPN): An alternative definition of VPN
   refers to a specific set of sites that have been configured to allow
   communication as either an intranet or an extranet.  Note that a site
   is a member of at least one VPN and may be a member of many VPNs.

3.4.  Networks of Customer and Provider Devices

   L3VPNs are composed of the following types of devices.

   Customer Edge (CE) device: A CE device faces the users at a customer
   site.  The CE has an access connection to a PE device.  It may be a
   router or a switch that allows users at a customer site to
   communicate over the access network with other sites in the VPN.  In
   a CE-based L3VPN, as intended in this document (provider-provisioned
   CE-based VPN), the service provider manages (at least partially) the
   CE device.

   Provider Edge (PE) device: A PE device faces the provider network on
   one side and attaches via an access connection over one or more
   access networks to one or more CE devices.  It participates in the
   Packet Switched Network (PSN) in performing routing and forwarding
   functions.

   Note that the definitions of Customer Edge and Provider Edge do not
   necessarily describe the physical deployment of equipment on customer
   premises or a provider point of presence.

   Provider (P) device: A device within a provider network that
   interconnects PE (or other P) devices but does not have any direct
   attachment to CE devices.  The P router does not keep VPN state and
   is VPN unaware [PPVPN-TERM].

   Packet Switched Network (PSN): A (IP or MPLS [RFC3031]) network
   through which the tunnels supporting the VPN services are set up
   [PPVPN-TERM].

   Service Provider (SP) network: An SP network is a set of
   interconnected PE and P devices administered by a single service
   provider in one or more ASes.

3.5.  Access Networks, Tunnels, and Hierarchical Tunnels

   VPNs are built between CEs by using access networks, tunnels, and
   hierarchical tunnels across a PSN.



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   Access connection: An access connection provides connectivity between
   a CE and a PE.  This includes dedicated physical circuits, virtual
   circuits (such as Frame Relay), ATM, Ethernet (V)LAN, or IP tunnels
   (e.g., IPsec, L2TP [RFC2661]).

   Access network: An access network provides access connections between
   CE and PE devices.  It may be a TDM network, an L2 network (e.g., FR,
   ATM, and Ethernet), or an IP network over which access is tunneled
   (e.g., by using L2TP).

   Tunnel: A tunnel between two entities is formed by encapsulating
   packets within another encapsulating header for the purposes of
   transmission between those two entities in support of a VPN
   application.  Examples of protocols commonly used for tunneling are
   GRE, IPsec, IP-in-IP tunnels, and MPLS.

   Hierarchical Tunnel: Encapsulating one tunnel within another forms a
   hierarchical tunnel.  The innermost tunnel protocol header defines a
   logical association between two entities (e.g., between CEs or PEs)
   [VPNTUNNEL].  Note that the tunneling protocols need not be the same
   at different levels in a hierarchical tunnel.

3.6.  Use of Tunnels and Roles of CE and PE in L3 VPNs

   This section summarizes the points where tunnels terminate and the
   functions implemented in the CE and PE devices that differentiate the
   two major categories of L3VPNs for which requirements are stated,
   namely PE-based and CE-based L3VPNs.  See the L3VPN framework
   document for more detail [L3VPN-FR].

3.6.1.  PE-Based L3VPNs and Virtual Forwarding Instances

   In a PE-based L3VPN service, a customer site receives IP layer (i.e.,
   layer 3) service from the SP.  The PE is attached via an access
   connection to one or more CEs.  The PE forwards user data packets
   based on information in the IP layer header, such as an IPv4 or IPv6
   destination address.  The CE sees the PE as a layer 3 device such as
   an IPv4 or IPv6 router.

   Virtual Forwarding Instance (VFI): In a PE-based L3VPN service, the
   PE contains a VFI for each L3 VPN that it serves.  The VFI terminates
   tunnels for interconnection with other VFIs and also terminates
   access connections for accommodating CEs.  VFI contains information
   regarding how to forward data received over the CE-PE access
   connection to VFIs in other PEs supporting the same L3VPN.  The VFI
   includes the router information base and the forwarding information
   base for an L3VPN [L3VPN-FR].  A VFI enables router functions
   dedicated to serving a particular VPN, such as separation of



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   forwarding and routing and support for overlapping address spaces.
   Routing protocols in the PEs and the CEs interact to populate the
   VFI.

   The following narrative and figures provide further explanation of
   the way PE devices use tunnels and hierarchical tunnels.  Figure 1.1
   illustrates the case where a PE uses a separate tunnel for each VPN.
   As shown in the figure, the tunnels provide communication between the
   VFIs in each of the PE devices.

                  +----------+              +----------+
   +-----+        |PE device |              |PE device |        +-----+
   | CE  |        |          |              |          |        | CE  |
   | dev | Access | +------+ |              | +------+ | Access | dev |
   | of  |  conn. | |VFI of| |    Tunnel    | |VFI of| |  conn. | of  |
   |VPN A|----------|VPN A |==================|VPN A |----------|VPN A|
   +-----+        | +------+ |              | +------+ |        +-----+
                  |          |              |          |
   +-----+ Access | +------+ |              | +------+ | Access +-----+
   |CE   |  conn. | |VFI of| |    Tunnel    | |VFI of| |  conn. | CE  |
   | dev |----------|VPN B |==================|VPN B |----------| dev |
   | of  |        | +------+ |              | +------+ |        | of  |
   |VPN B|        |          |              |          |        |VPN B|
   +-----+        +----------+              +----------+        +-----+

        Figure 1.1.  PE Usage of Separate Tunnels to Support VPNs

   Figure 1.2 illustrates the case where a single hierarchical tunnel is
   used between PE devices to support communication for VPNs.  The
   innermost encapsulating protocol header provides the means for the PE
   to determine the VPN for which the packet is directed.

                  +----------+              +----------+
   +-----+        |PE device |              |PE device |        +-----+
   | CE  |        |          |              |          |        | CE  |
   | dev | Access | +------+ |              | +------+ | Access | dev |
   | of  |  conn. | |VFI of| |              | |VFI of| |  conn. | of  |
   |VPN A|----------|VPN A | | Hierarchical | |VPN A |----------|VPN A|
   +-----+        | +------+\|   Tunnel     |/+------+ |        +-----+
                  |          >==============<          |
   +-----+ Access | +------+/|              |\+------+ | Access +-----+
   | CE  |  conn. | |VFI of| |              | |VFI of| |  conn. | CE  |
   | dev |----------|VPN B | |              | |VPN B |----------| dev |
   | of  |        | +------+ |              | +------+ |        | of  |
   |VPN B|        |          |              |          |        |VPN B|
   +-----+        +----------+              +----------+        +-----+

   Figure 1.2. PE Usage of Shared Hierarchical Tunnels to Support VPNs



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3.6.2.  CE-Based L3VPN Tunnel Endpoints and Functions

   Figure 1.3 illustrates the CE-based L3VPN reference model.  In this
   configuration, typically a single level of tunnel (e.g., IPsec)
   terminates at pairs of CEs.  Usually, a CE serves a single customer
   site, and therefore the forwarding and routing is physically separate
   from all other customers.  Furthermore, the PE is not aware of the
   membership of specific CE devices to a particular VPN.  Hence, the
   VPN functions are implemented with provisioned configurations on the
   CE devices, and the shared PE and P network is used to only provide
   the routing and forwarding that supports the tunnel endpoints on
   between CE devices.  The tunnel topology connecting the CE devices
   may be a full or partial mesh, depending on VPN customer requirements
   and traffic patterns.

       +---------+  +--------------------------------+  +---------+
       |         |  |                                |  |         |
       |         |  |                 +------+     +------+  : +------+
   +------+ :    |  |                 |      |     |      |  : |  CE  |
   |  CE  | :    |  |                 |  P   |     |  PE  |  : |device|
   |device| :  +------+    Tunnel     |router|     |device|  : |  of  |
   |  of  |=:================================================:=|VPN  A|
   |VPN  A| :  |      |               +------+     +------+  : +------+
   +------+ :  |  PE  |                              |  |    :    |
   +------+ :  |device|                              |  |    :    |
   |  CE  | :  |      |           Tunnel           +------+  : +------+
   |device|=:================================================:=|  CE  |
   |  of  | :  +------+                            |  PE  |  : |device|
   |VPN  B| :    |  |                              |device|  : |  of  |
   +------+ :    |  |  +----------+   +----------+ |      |  : |VPN  B|
       |    :    |  |  | Customer |   | Network  | +------+  : +------+
       |Customer |  |  |management|   |management|   |  |    :    |
       |interface|  |  | function |   | function |   |  |Customer |
       |         |  |  +----------+   +----------+   |  |interface|
       |         |  |                                |  |         |
       +---------+  +--------------------------------+  +---------+
       | Access  |  |<-------- SP network(s) ------->|  | Access  |
       | network |  |                                |  | network |

                        Figure 1.3. CE-Based L3VPN

3.7.  Customer and Provider Network Management

   Customer Network Management Function: A customer network management
   function provides the means for a customer agent to query or
   configure customer-specific information, or to receive alarms
   regarding his or her VPN.  Customer-specific information includes
   data related to contact, billing, site, access network, IP address,



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   and routing protocol parameters.  It may use a combination of
   proprietary network management system, SNMP manager, or directory
   service (e.g., LDAP [RFC3377] [RFC2251]).

   Provider Network Management Function: A provider network management
   function provides many of the same capabilities as a customer network
   management system across all customers.  This would not include
   customer confidential information, such as keying material.  The
   intent of giving the provider a view comparable to that of the
   customer is to aid in troubleshooting and problem resolution.  Such a
   system also provides the means to query, configure, or receive alarms
   regarding any infrastructure supporting the L3VPN service.  It may
   use a combination of proprietary network management system, SNMP
   manager, or directory service (e.g., LDAP [RFC3377] [RFC2251]).

4.  Service Requirements Common to Customers and Service Providers

   Many of the requirements that apply to both the customer and the
   provider and are of an otherwise general nature, or that apply to
   both L2 and L3VPNs, are described in [RFC3809].  This section
   contains requirements that are not covered in [RFC3809] and that are
   specific to L3VPNs.

4.1.  Isolated Exchange of Data and Routing Information

   A mechanism must be provided for isolating the distribution of
   reachability information to only those sites associated with a VPN.

   L3VPN solutions shall define means that prevent routers in a VPN from
   interacting with unauthorized entities and that avoid introducing
   undesired routing information that could corrupt the VPN routing
   information base [VPN-CRIT].

   A means must be provided to constrain or isolate the distribution of
   addressed data to only those VPN sites determined by either routing
   data and/or configuration.

   A single site shall be capable of being in multiple VPNs.  The VPN
   solution must ensure that traffic is exchanged only with sites in the
   same VPN.

   The internal structure of a VPN should not be advertised or
   discoverable from outside that VPN.

   Note that isolation of forwarded data or exchange of reachability
   information to only those sites that are part of a VPN may be viewed
   as a form of security - for example, [Y.1311.1], [MPLSSEC].




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4.2.  Addressing

   IP addresses must be unique within the set of sites reachable from
   the VPNs of which a particular site is a member.

   A VPN solution must support IPv4 and IPv6 as both the encapsulating
   and encapsulated protocol.

   If a customer has private or non-unique IP addresses, then a VPN
   service SHOULD be capable of translating such customer private or
   non-unique IP addresses for communicating with IP systems having
   public addresses.

4.3.  Quality of Service

   To the extent possible, L3VPN QoS should be independent of the access
   network technology.

4.3.1.  QoS Standards

   A non-goal of the L3VPN WG effort (as chartered) is the development
   of new protocols or extension of existing ones.  An L3VPN shall be
   able to support QoS in one or more of the following already defined
   modes:

      - Best Effort  (mandatory support for all L3VPN types)
      - Aggregate CE Interface Level QoS ("hose" level QoS)
      - Site-to-site ("pipe" level QoS)
      - Intserv (i.e., RSVP) signaled
      - Diffserv marked
      - Across packet-switched access networks

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

   L3VPN CEs should be capable of supporting integrated services
   (Intserv) for certain customers in support of session applications,
   such as switched voice or video.  Intserv-capable CE devices shall
   support the following Internet standards:

   -  Resource reSerVation Protocol (RSVP) [RFC2205]
   -  Guaranteed Quality of Service providing a strict delay bound
      [RFC2212]
   -  Controlled Load Service providing performance equivalent to that
      of an unloaded network [RFC2211]






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   L3VPN CE and PE should be capable of supporting differentiated
   service (Diffserv).  Diffserv-capable L3VPN CE and PE shall support
   the following per hop behavior (PHB) [RFC2475] types:

   -  Expedited Forwarding (EF) - The departure rate of an aggregate
      class of traffic from a device that must equal or exceed a
      configured rate [RFC3246].

   -  Assured Forwarding (AF) - A means for a provider Diffserv (DS)
      domain to offer different levels of forwarding assurances for IP
      packets received from a customer DS domain.  Four AF classes are
      defined, where each AF class implies allocation in each DS node of
      a certain amount of forwarding resources (e.g., buffer space and
      bandwidth) [RFC2597].

   A CE or PE device supporting an L3VPN service may classify a packet
   for a particular Intserv or Diffserv service based on one or more of
   the following IP header fields: protocol ID, source port number,
   destination port number, destination address, or source address.

   For a specifiable set of Internet traffic, L3VPN devices should
   support Random Early Detection (RED) to provide graceful degradation
   in the event of network congestion.

4.3.2.  Service Models

   A service provider must be able to offer QoS service to a customer
   for at least the following generic service types: managed-access VPN
   service or edge-to-edge QoS VPN service [RFC3809].  More detail
   specific to L3VPNs is provided below.

   A managed-access L3VPN service provides QoS on the access connection
   between the CE and the PE.  For example, diffserv would be enabled
   only on the CE router and the customer-facing ports of the PE router.
   Note that this service would not require Diffserv implementation in
   the SP backbone.  The SP may use policing for inbound traffic at the
   PE.  The CE may perform shaping for outbound traffic.  Another
   example of a managed-access L3VPN service is when the SP performs the
   packet classification and diffserv marking.  An SP may provide
   several packet classification profiles that customers may select or
   may offer custom profiles based on customer specific requirements.
   In general, more complex QoS policies should be left to the customer
   for implementation.

   An edge-to-edge QoS VPN service provides QoS from edge device to edge
   device.  The edge device may be either PE or CE, depending on the
   service demarcation point between the provider and the customer.
   Such a service may be provided across one or more provider backbones.



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   The CE requirements for this service model are the same as the
   managed access VPN service.  However, in this service QoS is provided
   from one edge of the SP network(s) to the other.

4.4.  Service-Level Specification and Agreements

   A generic discussion of SLAs is provided in [RFC3809].  Additionally,
   SLS measurements for quality based on the DiffServ scheme SHOULD be
   based on the following classification:

       -  A Point-to-Point SLS [Y.1311.1], sometimes also referred to as
          the "Pipe" model, defines traffic parameters in conjunction
          with the QoS objectives for traffic exchanged between a pair
          of VPN sites (i.e., points).  A Point-to-Point SLS is
          analogous to the SLS typically supported over point-to-point
          Frame Relay or ATM PVCs or an edge-to-edge MPLS tunnel.  The
          set of SLS specifications to all other reachable VPN sites
          would define the overall Point-to-Point SLS for a specific
          site.

       -  A Point-to-Cloud SLS [Y.1311.1], sometimes also referred to as
          the "Hose" model, defines traffic parameters in conjunction
          with the QoS objectives for traffic exchanged between a CE and
          a PE for traffic destined to a set (either all or a subset) of
          other sites in the VPN (i.e., the cloud), as applicable.  In
          other words, a point-to-cloud SLS defines compliance in terms
          of all packets transmitted from a given VPN site toward the SP
          network on an aggregate basis (i.e., regardless of the
          destination VPN site of each packet).

       -  A Cloud-to-Point SLS (a case not covered by this SLS is where
          flows originating from multiple sources may congest the
          interface toward a specific site).

   Traffic parameters and actions SHOULD be defined for packets to and
   from the demarcation between the service provider and the site.  For
   example, policing may be defined on ingress, and shaping on egress.

4.5.  Management

   An SP and its customers MUST be able to manage the capabilities and
   characteristics of their VPN services.  To the extent possible,
   automated operations and interoperability with standard management
   platforms SHOULD be supported.







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   The ITU-T Telecommunications Management Network (TMN) model has the
   following generic requirements structure:

   O  Engineer, deploy, and manage the switching, routing, and
      transmission resources supporting the service, from a network
      perspective (network element management).

   O  Manage the VPN networks deployed over these resources (network
      management).

      o  Manage the VPN service (service management).
      o  Manage the VPN business, mainly provisioning administrative and
         accounting information related to the VPN service customers
         (business management).

   Service management should include the TMN 'FCAPS' functionalities, as
   follows: Fault, Configuration, Accounting, Provisioning, and
   Security, as detailed in section 7.

4.6.  Interworking

   Interworking scenarios among different solutions providing L3VPN
   services is highly desirable.  See the L3VPN framework document for
   more details on interworking scenarios [L3VPN-FR].  Interworking
   SHOULD be supported in a scalable manner.

   Interworking scenarios MUST at least consider traffic and routing
   isolation, security, QoS, access, and management aspects.  This
   requirement is essential of network migration, to ensure service
   continuity among sites belonging to different portions of the
   network.

5.  Customer Requirements

   This section captures additional requirements from a customer
   perspective.

5.1.  VPN Membership (Intranet/Extranet)

   When an extranet is formed, a customer agent from each of the
   organizations first approves addition of a site to an extranet VPN as
   a business decision between the parties involved.  The solution
   SHOULD provide a means for these organizations to control extranet
   communication involving the L3VPN exchange of traffic and routing
   information.






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5.2.  Service Provider Independence

   Customers MAY require VPN service that spans multiple administrative
   domains or service provider networks.  Therefore, a VPN service MUST
   be able to span multiple AS and SP networks, but still act and appear
   as a single, homogeneous VPN from a customer point of view.

   A customer might also start with a VPN provided in a single AS with a
   certain SLA but then ask for an expansion of the service, spanning
   multiple ASes/SPs.  In this case, as well as for all kinds of multi-
   AS/SP VPNs, VPN service SHOULD be able to deliver the same SLA to all
   sites in a VPN regardless of the AS/SP to which it homes.

5.3.  Addressing

   A customer requires support from an L3VPN for the following
   addressing IP assignment schemes:

   o  Customer-assigned, non-unique, or [RFC1918] private addresses
   o  Globally unique addresses obtained by the customer
   o  Globally unique addresses statically assigned by the L3VPN service
      provider
   o  On-demand, dynamically assigned IP addresses (e.g., DHCP),
      irrespective of whether the access is temporary (e.g., remote) or
      permanent (e.g., dedicated)

   In the case of combined L3VPN service with non-unique or private
   addresses and Internet access, mechanisms that permit the exchange of
   traffic between the customer's address space and the global unique
   Internet address space MAY be supported.  For example, NAT is
   employed by many customers and by some service providers today to
   meet this need.  A preferred solution would be to assign unique
   addresses, either IPv4 or IPv6; however, some customers do not want
   to renumber their networks.

5.4.  Routing Protocol Support

   There SHOULD be no restriction on the routing protocols used between
   CE and PE routers, or between CE routers.  At least the following
   protocols MUST be supported: static routing, IGP protocols such as
   RIP, OSPF, IS-IS, and BGP [L3VPN-FR].

5.5.  Quality of Service and Traffic Parameters

   QoS is expected to be an important aspect of an L3VPN service for
   some customers.  QoS requirements cover scenarios involving an
   intranet, an extranet, and shared access between a VPN site and the
   Internet.



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5.5.1.  Application-Level QoS Objectives

   A customer is concerned primarily that the L3VPN service provides his
   or her applications with the QoS and level of traffic so that the
   applications perform acceptably.  Voice, interactive video, and
   multimedia applications are expected to require the most stringent
   QoS.  These real-time applications are sensitive to delay, delay
   variation, loss, availability, and/or reliability.  Another set of
   applications, including some multimedia and interactive video
   applications, high-performance web browsing, and file transfer
   intensive applications, requires near real time performance.
   Finally, best effort applications are not sensitive to degradation,
   that is they are elastic and can adapt to conditions of degraded
   performance.

   The selection of appropriate QoS and service type to meet specific
   application requirements is particularly important to deal with
   periods of congestion in an SP network.  Sensitive applications will
   likely select per-flow Integrated service (Intserv) with precise SLA
   guarantees measured on a per-flow basis.  On the other hand, non-
   sensitive applications will likely rely on a Diffserv class-based
   QoS.

   The fundamental customer application requirement is that an L3VPN
   solution MUST support both the Intserv QoS model for selected
   individual flows and Diffserv for aggregated flows.

   A customer application SHOULD experience consistent QoS independent
   of the access network technology used at different sites connected to
   the same VPN.

5.5.2.  DSCP Transparency

   The Diffserv Code Point (DSCP) set by a user as received by the
   ingress CE SHOULD be capable of being relayed transparently to the
   egress CE (see section 2.6.2 of [RFC3270] and [Y.1311.1]).  Although
   RFC 2475 states that interior or boundary nodes within a DS domain
   can change the DSCP, customer VPNs MAY have other requirements, such
   as

   o  applications that use the DSCP in a manner differently from the
      DSCP solution supported by the SP network(s),
   o  customers using more DSCPs within their sites than the SP
      network(s) supports,
   o  support for a carrier's carrier service in which one SP is the
      customer of another L3VPN SP.  Such an SP should be able to resell
      VPN service to his or her VPN customers independently of the DSCP
      mapping solution supported by the carrier's carrier SP.



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   Note that support for DSCP transparency has no implication on the QoS
   or SLA requirements.  If an SP supports DSCP transparency, then that
   SP needs to carry only the DSCP values across its domain but MAY map
   the received DSCP to some other value for QoS support across its
   domain.

5.6.  Service-Level Specification/Agreement

   Most customers simply want their applications to perform well.  An
   SLA is a vehicle for customer recourse in the event that SP(s) do not
   perform or manage a VPN service well in a measurable sense.
   Therefore, when purchasing service under an SLA, a customer agent

   MUST have access to the measures from the SP(s) that support the SLA.

5.7.  Customer Management of a VPN

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

   Most aspects of management information about CE devices and customer
   attributes of an L3VPN manageable by an SP SHOULD be capable of being
   configured and maintained by an authenticated, authorized customer
   agent.  However, some aspects, such as encryption keys, SHALL NOT be
   readable nor writable by management systems.

   A customer agent 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 service is a "Dynamic Bandwidth management"
   capability that enables real-time response to customer requests for
   changes of allocated bandwidth allocated to his or her VPN
   [Y.1311.1].

   A customer who may not be able to afford the resources to manage his
   own sites SHOULD be able to outsource the management of the entire
   VPN to the SP(s) supporting the VPN network.

5.8.  Isolation

   These features include traffic and routing information exchange
   isolation, similar to that obtained in VPNs based on Layer 1 and
   Layer 2 (e.g., private lines, FR, or ATM) [MPLSSEC].








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5.9.  Security

   The suite of L3VPN solutions SHOULD support a range of security
   related features.  Higher levels of security services, such as edge-
   to-edge encryption, authentication, or replay attack, should be
   supported.  More details on customer requirements for security are
   described in [VPNSEC].

   Security in an L3VPN service SHOULD be as transparent as possible to
   the customer, with the obvious exception of support for remote or
   temporary user access, as detailed in section 5.11.2.

   L3VPN customers MUST be able to deploy their own internal security
   mechanisms in addition to those deployed by the SP, in order to
   secure specific applications or traffic at a granularity finer than
   that on a site-to-site basis.

   If a customer requires QoS support in an L3VPN, then this request
   MUST be communicated to the SP either by using unencrypted fields or
   via an agreed security association.  For example, applications could
   send RSVP messages in support of Intserv either in the clear or
   encrypted with a key negotiated with the SP.  Another case is that
   where applications using an IPsec tunnel could copy the DSCP from the
   encrypted IP header to the header of the tunnel's IP header.

5.10.  Migration Impact

   Often, customers are migrating from an already deployed private
   network toward one or more L3VPN solutions.  A typical private
   network scenario is CE routers connected via real or virtual
   circuits.  Ideally, minimal incremental cost SHOULD result during the
   migration period.  Furthermore, if necessary, any disruption of
   service SHOULD also be minimized.

   A range of scenarios of customer migration MUST be supported.  Full
   migration of all sites MUST be supported.  Support for cases of
   partial migration is highly desirable [Y.1311.1] -  that is, legacy
   private network sites that belong to the L3VPN service SHOULD still
   have L3 reachability to the sites that migrate to the L3VPN service.

5.11.  Network Access

   Every L3 packet exchanged between the customer and the SP over the
   access connection MUST appear as it would on a private network
   providing an equivalent service to that offered by the L3VPN.






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5.11.1.  Physical/Link Layer Technology

   L3VPNs SHOULD support a broad range of physical and link-layer access
   technologies, such as PSTN, ISDN, xDSL, cable modem, leased line,
   Ethernet, Ethernet VLAN, ATM, Frame Relay, Wireless local loop, and
   mobile radio access.  The capacity and QoS achievable may be
   dependent on the specific access technology in use.

5.11.2.  Temporary Access

   The VPN service offering SHOULD allow both permanent and temporary
   access to one or more L3VPNs for authenticated users across a broad
   range of access technologies.  Support for remote or temporary VPN
   access SHOULD include ISDN, PSTN dial-in, xDSL, or access via another
   SP network.  The customer SHOULD be able to choose from alternatives
   for authentication of temporary access users.  Choices for access
   authentication are SP-provided, third-party, or customer-provided
   authentication.

   A significant number of VPN users may not be permanently attached to
   one VPN site: in order to limit access to a VPN to authorized users,
   it is first necessary to authenticate them.  Authentication SHALL
   apply as configured by the customer agent and/or SP where a specific
   user may be part of one or more VPNs.  The authentication function
   SHOULD be used to invoke all actions necessary to join a user to the
   VPN automatically.

   A user SHOULD be able to access an L3VPN via a network having generic
   Internet access.

   Mobile users may move within an L3VPN site.  Mobile users may also
   have temporary connections to different L3VPN sites within the same
   VPN.  Authentication SHOULD be provided in both of these cases.

5.11.3.  Sharing of the Access Network

   In a PE-based L3VPN, if the site shares the access network with other
   traffic (e.g., access to the Internet), then data security in the
   access network is the responsibility of the L3VPN customer.

5.11.4.  Access Connectivity

   Various types of physical connectivity scenarios MUST be supported,
   such as multi-homed sites, backdoor links between customer sites, and
   devices homed to two or more SP networks.  L3VPN solutions SHOULD
   support at least the types of physical or link-layer connectivity
   arrangements shown in Figure 2.1.  Support for other physical
   connectivity scenarios with arbitrary topology is desirable.



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   Access arrangements with multiple physical or logical paths from a CE
   to other CEs and PEs MUST support redundancy and SHOULD support load
   balancing.  Resiliency uses redundancy to provide connectivity
   between a CE site and other CE sites and, optionally, other services.
   Load balancing provides a means to perform traffic engineering so
   that capacity on redundant links is used to achieve improved
   performance during periods when the redundant component(s) are
   available.

   For multi-homing to a single SP, load balancing capability SHOULD be
   supported by the PE across the CE to PE links.  For example, in case
   (a), load balancing SHOULD be provided by the two PEs over the two
   links connecting to the single CE.  In case (c), load balancing
   SHOULD be provided by the two PEs over the two links connecting to
   the two CEs.

   In addition, the load-balancing parameters (e.g., the ratio of
   traffic on the multiple load-balanced links, or the preferred link)
   SHOULD be provisionable based on customer's requirements.  The load-
   balancing capability may also be used to achieve resiliency in the
   event of access connectivity failures.  For example, in case (b) a CE
   may connect to two different SPs via diverse access networks.
   Resiliency MAY be further enhanced as shown in case (d), where CEs
   connected via a "back door" connection connect to different SPs.
   Furthermore, arbitrary combinations of the above methods, with a few
   examples shown in cases (e) and (f), should be supportable by any
   L3VPN approach.

   For multi-homing to multiple SPs, load balancing capability MAY also
   be supported by the PEs in the different SPs (clearly, this is a more
   complex type of load balancing to realize, requiring policy and
   service agreements between the SPs to interoperate).



















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                   +----------------                    +---------------
                   |                                    |
                +------+                            +------+
      +---------|  PE  |                  +---------|  PE  |
      |         |router|                  |         |router| SP network
      |         +------+                  |         +------+
   +------+         |                  +------+         |
   |  CE  |         |                  |  CE  |         +---------------
   |device|         |   SP network     |device|         +---------------
   +------+         |                  +------+         |
      |         +------+                  |         +------+
      |         |  PE  |                  |         |  PE  |
      +---------|router|                  +---------|router| SP network
                +------+                            +------+
                    |                                   |
                    +----------------                   +---------------
                   (a)                                 (b)
                    +----------------                  +---------------
                    |                                  |
   +------+     +------+               +------+     +------+
   |  CE  |-----|  PE  |               |  CE  |-----|  PE  |
   |device|     |router|               |device|     |router| SP network
   +------+     +------+               +------+     +------+
      |             |                     |             |
      | Backdoor    |                     | Backdoor    +---------------
      | link        |   SP network        | link        +---------------
      |             |                     |             |
   +------+     +------+               +------+     +------+
   |  CE  |     |  PE  |               |  CE  |     |  PE  |
   |device|-----|router|               |device|-----|router| SP network
   +------+     +------+               +------+     +------+
                    |                                   |
                    +----------------                   +---------------
                   (c)                                  (d)

















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                   +----------------                    +---------------
                   |                                    |
  +------+     +------+                +------+     +------+
  |  CE  |-----|  PE  |                |  CE  |-----|  PE  |
  |device|     |router|                |device|     |router| SP network
  +------+\\   +------+                +------+\\   +------+
     |     \\       |                     |     \\       |
     |Back  \\      |                     |Back  \\
  +---------------
     |door   \\     |   SP network        |door   \\
  +---------------
     |link    \\    |                     |link    \\    |
  +------+     +------+               +------+     +------+
  |  CE  |     |  PE  |               |  CE  |     |  PE  |
  |device|-----|router|               |device|-----|router| SP network
  +------+     +------+               +------+     +------+
                   |                                   |
                   +----------------                   +---------------
                  (e)                                 (f)

         Figure 2.1.  Representative types of access arrangements

5.12.  Service Access

   Customers MAY also require access to other services, as described in
   this section.

5.12.1.  Internet Access

   Customers SHOULD be able to have L3VPN and Internet access across the
   same access network for one or more of the customer's sites.

   Customers SHOULD be able to direct Internet traffic from the set of
   sites in the L3VPN to one or more customer sites that have firewalls,
   other security-oriented devices, and/or NATs that process all traffic
   between the Internet and the customer's VPN.

   L3 VPN Customers SHOULD be able to receive traffic from the Internet
   addressed to a publicly accessible resource that is not part of the
   VPN, such as an enterprise's public web server.

   As stated in section 5.3, if a customer L3VPN employs private or
   non-unique IP addresses, then network address translation (NAT) or a
   similar mechanism MUST be provided either by the customer or the SP
   in order to allow traffic exchange with devices outside the
   customer's L3VPN.





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5.12.2.  Hosting, Application Service Provider

   A customer SHOULD be able to access hosting, other application
   services, or other Application Service Providers (ASP) over an L3
   L3VPN service.  This MAY require that an ASP participate in one or
   more VPNs with the customers that use such a service.

5.12.3.  Other Services

   In conjunction with a VPN service, a customer MAY also wish to have
   access to other services, such as DNS, FTP, HTTP, NNTP, SMTP, LDAP,
   VoIP, NAT, LDAP, Videoconferencing, Application sharing, E-business,
   Streaming, E-commerce, Directory, Firewall, etc.  The resources that
   implement these services could be physically dedicated to each VPN.
   If the resources are logically shared, then they MUST have access
   separated and isolated between VPNs in a manner consistent with the
   L3VPN solution to meet this requirement.

5.13.  Hybrid VPN Service Scenarios

   Intranet or extranet customers have a number of reasons for wanting
   hybrid networks that involve more than one VPN solution type.  These
   include migration, mergers, extranet customers with different VPN
   types, the need for different capabilities between different sets of
   sites, temporary access, and different availability of VPN solutions
   as provided by different service providers.

   The framework and solution approaches SHOULD include provisions for
   interworking, interconnection, and/or reachability between different

   L3VPN solutions in a way that does not overly complicate
   provisioning, management, scalability, or performance.

6.  Service Provider Network Requirements

   This section describes requirements from a service provider
   perspective.

6.1.  Scalability

   [RFC3809] lists projections of L3VPN sizing and scalability
   requirements and metrics related to specific solutions.









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6.2.  Addressing

   As described in section 4.2, SPs MUST have support for public and
   private IP addresses, IPv4 and IPv6, for both unicast and multicast.
   In order to support this range of addressing schemes, SPs require the
   following support from L3VPN solutions.

   An L3VPN solution MUST be able to assign blocks of addresses from its
   own public IP address space to L3VPN customer sites so that
   advertisement of routes to other SPs and other sites aggregates
   efficiently.

   An L3VPN solution MUST be able to use address assignments made by a
   customer.  These customer-assigned addresses may be public or
   private.

   If private IP addresses are used, an L3VPN solution MUST provide a
   means for an SP to translate such addresses to public IP addresses
   for communication with other VPNs by using overlapping addresses or
   the Internet.

6.3.  Identifiers

   A number of identifiers MAY be necessary for SP use in management,
   control, and routing protocols.  Requirements for at least the
   following identifiers are known.

   An SP domain MUST be uniquely identified at least within the set of
   all interconnected SP networks when supporting a VPN that spans
   multiple SPs.  Ideally, this identifier should be globally unique
   (e.g., an AS number).

   An identifier for each VPN SHOULD be unique, at least within each
   SP's network.  Ideally, the VPN identifier SHOULD be globally unique
   to support the case where a VPN spans multiple SPs (e.g., [RFC2685]).

   A CE device SHOULD have a unique identifier, at least within each
   SP's network.

   A PE device SHOULD have a unique identifier, at least within each
   SP's network.

   The identifier of a device interconnecting SP networks MUST be unique
   within the set of aforementioned networks.

   Each site interface SHOULD have a unique identifier, at least within
   each PE router supporting such an interface.




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   Each tunnel SHOULD have a unique identifier, at least within each
   router supporting the tunnel.

6.4.  Discovering VPN Related Information

   Configuration of CE and PE devices is a significant task for a
   service provider.  Solutions SHOULD strive to contain methods that
   dynamically allow VPN information to be discovered (or learned) by
   the PE and/or CE to reduce configuration complexity.  The following
   specific requirements apply to intra- and inter-provider VPNs
   [VPNDISC].

   Every device involved in a VPN SHALL be able to identify and
   authenticate itself to other devices in the VPN.  After learning the
   VPN membership, the devices SHOULD be able to exchange configuration
   information securely.  The VPN information MUST include at least the
   IP address of the PE and may be extensible to provide additional
   information.

   Each device in a VPN SHOULD be able to determine which other devices
   belong to the same VPN.  Such a membership discovery scheme MUST
   prevent unauthorized access and allow authentication of the source.

   Distribution of VPN information SHOULD be limited to those devices
   involved in that VPN.

   In the case of a PE-based VPN, a solution SHOULD support the means
   for attached CEs to authenticate each other and verify that the SP's
   VPN network is correctly configured.

   The mechanism SHOULD respond to VPN membership changes in a timely
   manner.  This is no longer than the provisioning timeframe, typically
   on the order of minutes, and could be as short as the timeframe
   required for "rerouting", typically on the order of seconds.

   Dynamically creating, changing, and managing multiple VPN assignments
   to sites and/or customers is another aspect of membership that MUST
   be addressed in an L3VPN solution.

6.5.  SLA and SLS Support

   Typically, a Service Provider offering an L3VPN service commits to
   specific Service Level Specifications (SLS) as part of a contract
   with the customer, as described in section 4.4 and [RFC3809].  Such a
   Service Level Agreement (SLA) implies SP requirements for measuring
   Specific Service Level Specifications (SLS) for quality,
   availability, response time, and configuration intervals.




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6.6.  Quality of Service (QoS) and Traffic Engineering

   A significant aspect of an L3VPN is support for QoS.  Since an SP has
   control over the provisioning of resources and configuration of
   parameters in at least the PE and P devices and, in some cases, in
   the CE device as well, the onus is on the SP to provide either
   managed QoS access service, or edge-to-edge QoS service, as defined
   in section 4.3.2.

   Each L3VPN approach MUST describe the traffic engineering techniques
   available for an SP to meet the QoS objectives.  These descriptions
   of traffic engineering techniques SHOULD quantify scalability and
   achievable efficiency.  Traffic engineering support MAY be on an
   aggregate or per-VPN basis.

   QoS policies MUST not be impacted by security mechanisms.  For
   example, Diffserv policies MUST not be impacted by the use of IPSec
   tunnels using the mechanisms explained in RFC 2983 [RFC2983].

   As stated in RFC 2475, a mapping function from customer provided
   Diffserv marking to marking used in an SP network should be provided
   for L3 VPN services.

   If a customer requires DSCP transparency, as described in section
   5.5.2, an L3VPN service MUST deliver the same value of DSCP field in
   the IP header received from the customer to the egress demarcation of
   the destination.

6.7.  Routing

   The distribution of reachability and routing policy SHOULD be
   constrained to the sites that are members of the VPN.

   Optionally, the exchange of such information MAY use some form of
   authentication (e.g., MD5).

   Functions to isolate the SP network and customer VPNs from anomalous
   routing behavior from a specific set of customer sites SHOULD be
   provided.  Examples of such functions are controls for route flap
   dampening, filters that accept only prefixes configured for a
   specific CE, a maximum number of routes accepted for each CE, or a
   maximum rate at which route updates can be received from a CE.

   When VPN customers use overlapping non-unique IP addresses, the
   solution MUST define a means to distinguish between such overlapping
   addresses on a per-VPN basis.





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   Furthermore, the solution SHOULD provide an option that either allows
   or prevents advertisement of VPN routes to the Internet.

   Ideally, the choice of an SP's IGP SHOULD not depend on the routing
   protocol(s) used between PE and CE routers in a PE-based VPN.

   Furthermore, it is desirable that an SP SHOULD have a choice
   regarding the IGP routing protocol.

   The additional routing burden that an SP must carry should be
   articulated in each specific L3VPN solution.

6.8.  Isolation of Traffic and Routing

   The internal structure of an L3VPN network SHOULD not be visible to
   outside networks (e.g., the Internet or any connected VPN).

   From a high-level SP perspective, a PE-based L3VPN MUST isolate the
   exchange of traffic and routing information to only those sites that
   are authenticated and authorized members of a VPN.

   In a CE-based VPN, the tunnels that connect the sites effectively
   meet this isolation requirement if both traffic and routing
   information flow over the tunnels.

   An L3VPN solution SHOULD provide a means to meet L3VPN QoS SLA
   requirements that isolates VPN traffic from the effects of traffic
   offered by non-VPN customers.  Also, L3VPN solutions SHOULD provide a
   means to isolate the effects that traffic congestion produced by
   sites as part of one VPN can have on another VPN.

6.9.  Security

   This section contains requirements related to securing customer
   flows; providing authentication services for temporary, remote, or
   mobile users; and protecting service provider resources involved in
   supporting an L3VPN.  More detailed security requirements are
   provided in [VPNSEC].

6.9.1.  Support for Securing Customer Flows

   In order to meet the general requirement for providing a range of
   security options to a customer, each L3VPN solution MUST clearly
   spell out the configuration options that can work together and how
   they can do so.






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   When a VPN solution operates over a part of the Internet, it should
   support a configurable option to support one or more of the following
   standard IPsec methods for securing a flow for a specified subset of
   a customer's VPN traffic:

   o  Confidentiality, so that only authorized devices can decrypt it
   o  Integrity, to ensure that the data has not been altered
   o  Authentication, to ensure that the sender is indeed who he or she
      claims to be
   o  Replay attack prevention.

   The above functions SHOULD be applicable to "data traffic" of the
   customer, which includes the traffic exchanged between sites between
   temporary users and sites, and even between temporary users.  It
   SHOULD also be possible to apply these functions to "control
   traffic", such as routing protocol exchanges, that are not
   necessarily perceived by the customer but are nevertheless essential
   to maintain his or her VPN.

   Furthermore, 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
   [VPNSEC].

   A VPN solution MAY support one or more encryption schemes, including
   AES, and 3DES.  Encryption, decryption, and key management SHOULD be
   included in profiles as part of the security management system.

6.9.2.  Authentication Services

   A service provider MUST provide authentication services in support of
   temporary user access requirements, as described in section 5.11.2.

   Furthermore, traffic exchanged within the scope of VPN MAY involve
   several categories of equipment that must cooperate to provide the
   service [Y.1311.1].  These network elements can be CE, PE, firewalls,
   backbone routers, servers, management stations, etc.  These network
   elements learn about each other's identity, either via manual
   configuration or via discovery protocols, as described in section
   6.4. When network elements must cooperate, these network elements
   SHALL authenticate peers before providing the requested service.
   This authentication function MAY also be used to control access to
   network resources.

   The peer identification and authentication function described above
   applies only to network elements participating in the VPN.  Examples
   include:




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   -  traffic between a CE and a PE,
   -  traffic between CEs belonging to the same VPN,
   -  CE or PE routers dealing with route announcements for a VPN,
   -  policy decision point [RFC3198] and a network element, and
   -  management station and an SNMP agent.

   For a peer authentication function, each L3VPN solution SHOULD
   describe where necessary, how it shall be implemented, how secure it
   must be, and the way to deploy and maintain identification and
   authentication information necessary to operate the service.

6.9.3.  Resource Protection

   Recall from the definitions in section 3.3 that a site can be part of
   an intranet with sites from the only same organization, can be part
   of an extranet involving sites from other organizations, can have
   access to the Internet, or can have any combination of these scopes
   of communication.  Within these contexts, a site might be subject to
   various attacks coming from different sources.  Potential sources of
   attack include:

   -  users connected to the supporting public IP backbone,
   -  users from the Internet, and
   -  users from temporary sites belonging to the intranet and/or
      extranet VPN the site is part of.

   Security threats and risks that a site may encounter include the
   following:

   -  Denial of service, for example mail spamming, access connection
      congestion, TCP SYN attacks, and ping attacks
   -  Intrusion attempts, which may eventually lead to denial of service
      (e.g., a Trojan horse attack).

   Additional threat scenarios are defined in [VPNSEC].  An L3VPN
   solution MUST state how it addresses each potential threat scenario.

   The devices in the L3VPN network must provide some means of reporting
   intrusion attempts to the service provider resources.

6.10.  Inter-AS (SP)VPNs

   The scenario for VPNs spanning multiple Autonomous Systems (AS) or
   Service Providers (SP) requires standard solutions.  The scenario
   where multiple ASes are involved is the most general case and is
   therefore the one described here.  The scenarios of concern are the
   CE-based and PE-based L3VPNs defined in section 3.




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   In each scenario, all applicable SP requirements, such as traffic and
   routing isolation, SLAs, management, security, and provisioning.
   MUST be preserved across adjacent ASes.  The solutions MUST describe
   the inter-SP network interface, encapsulation method(s), routing
   protocol(s), and all applicable parameters [VPNIW].

   An essential pre-condition for an inter-AS VPN is an agreement
   between the ASes involved that spells out at least trust, economic,
   and management responsibilities.

   The overall scalability of the VPN service MUST allow the L3VPN
   service to be offered across potentially hundreds of SPs, with the
   overall scaling parameters per SP given in [RFC3809].

6.10.1.  Routing Protocols

   If the link between ASes is not trusted, routing protocols running
   between those ASes MUST support some form of authentication.  For
   example, the TCP option for carrying an MD5 digest may be used to
   enhance security for BGP [RFC2385].

   BGP MUST be supported as the standard inter-AS routing protocol to
   control the path taken by L3VPN traffic.

6.10.2.  Management

   The general requirements for managing a single AS apply to a
   concatenation of ASes.  A minimum subset of such capabilities as
   follows:

   - Diagnostic tools (e.g., ping, traceroute)
   - Secured access to one AS management system by another
   - Configuration request and status query tools
   - Fault notification and trouble-tracking tools

6.10.3.  Bandwidth and QoS Brokering

   When a VPN spans multiple ASes, a brokering mechanism is desired that
   requests certain SLA parameters, such as bandwidth and QoS, from the
   other domains and/or networks involved in transferring traffic to
   various sites.  Although bandwidth and QoS brokering across multiple
   ASes is not common in today's networks, these may be desirable for
   maintaining SLAs in inter-AS VPNs.  This section describes
   requirements for features that would facilitate these mechanisms.
   The objective is that a solution SHOULD be able to determine whether
   a set of ASes can establish and guarantee uniform QoS in support of
   an L3VPN.




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   The brokering mechanism can be a manual one, for example, in which
   one provider requests from another a specific set of bandwidth and
   QoS parameters for traffic going to and from a specific set of sites.
   The mechanism could also be an automated one where a device
   dynamically requests and receives certain bandwidth and SLA/QoS
   parameters.  For instance, in the case of an L3VPN over MPLS, a PE
   may negotiate the label for different traffic classes to reach a PE
   residing in a neighboring AS.  Or, it might be a combination of both.
   For additional detailed requirements on the automated approach, see
   [TE-INTERAS].

   Brokering on a per VPN basis is not desirable as this approach would
   not scale.  A solution MUST provide some means to aggregate QoS and
   bandwidth brokering requests between ASes.  One method could be for
   SPs to make an agreement specifying the maximum amount of bandwidth
   for specific QoS parameters for all VPN customers using the SP
   network.  Alternatively, such aggregation might be on a per
   hierarchical tunnel basis between PE routers in different ASes
   supporting an L3VPN service [TE-INTERAS].

6.10.4.  Security Considerations

   If a tunnel traverses multiple SP networks and passes through an
   unsecured SP, POP, NAP, or IX, then security mechanisms MUST be
   employed.  These security mechanisms include encryption,
   authentication, and resource protection, as described in section 6.9,
   and security management, as covered in section 7.5.  For example, a
   provider should consider using both authentication and encryption for
   a tunnel used as part of an L3VPN that traverses another service
   provider's network.

6.11.  L3VPN Wholesale

   The architecture MUST support the possibility of one service provider
   offering VPN service to another service provider.  Another example is
   when one service provider sells L3VPN service at wholesale to another
   service provider, who then resells that VPN service to his or her
   customers.

   The wholesaler's VPN MUST be transparent to the addressing and
   routing used by the reseller.

   Support for additional levels of hierarchy (for example, three levels
   at which a reseller can again resell the VPN service to yet another
   VPN provider) SHOULD be provided.

   The Carrier's Carrier scenario is the term used in this document for
   this category of L3VPN wholesale (although some scenarios of Inter-



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   AS/Inter-Provider VPN could possibly fall in this L3VPN wholesale
   category, too).  Various carrier's carrier scenarios should be
   supported, such as when

   -  the customer carriers do not operate L3VPN services for their
      clients;
   -  the customer carriers operate L3VPN services for their clients,
      but these services are not linked with the L3VPN service offered
      by the Carrier's Carrier and
   -  the customer carriers operate L3VPN services for their clients,
      and these services are linked with the L3VPN service offered by
      the Carrier's Carrier ("Hierarchical VPNs" scenario).

6.12.  Tunneling Requirements

   Connectivity between CE sites or PE devices in the backbone SHOULD
   use a range of tunneling technologies, such as L2TP, IPSEC, GRE, IP-
   in-IP, and MPLS.

   To set up tunnels between routers, every router MUST support static
   configuration for tunneling and MAY support a tunnel setup protocol.
   If employed, a tunnel establishment protocol SHOULD be capable of
   conveying information such as the following:

     - Relevant identifiers
     - QoS/SLA parameters
     - Restoration parameters
     - Multiplexing identifiers
     - Security parameters

   There MUST be a means to monitor the following aspects of tunnels:

   -  Statistics, such as amount of time spent in the up and down state.
   -  Count of transitions between the up and down state.
   -  Events, such as transitions between the up and down states.

   The tunneling technology used by the VPN Service Provider and its
   associated mechanisms for tunnel establishment, multiplexing, and
   maintenance MUST meet the requirements on scaling, isolation,
   security, QoS, manageability, etc.

6.13.  Support for Access and Backbone Technologies

   This section describes requirements for aspects of access and
   backbone network technologies from an SP point of view.






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   Some SPs MAY desire that a single network infrastructure suffices for
   all services, public IP, VPNs, traffic engineering, and
   differentiated services [L2VPN].

6.13.1.  Dedicated Access Networks

   Ideally, the L3VPN service SHOULD be independent of physical, link
   layer, or even network technology of the access network.  However,
   the characteristics of access networks MUST be accounted for when the
   QoS aspects of SLAs for VPN service offerings are specified.

6.13.2.  On-Demand Access Networks

   Service providers SHOULD be able to support temporary user access, as
   described in section 5.11.2, by using dedicated or dial-in access
   network technology.

   L3VPN solutions MUST support the case where a VPN user directly
   accesses the VPN service through an access network connected to the
   service provider.  They MUST also describe how they can support the
   case where one or more other service provider networks are used for
   access to the service provider supporting the L3VPN service.

   Ideally, all information necessary to identify and authenticate users
   for an intranet SHOULD be stored and maintained by the customer.  In
   an extranet, one customer SHOULD be able to maintain the
   authentication server, or the customers involved in the extranet MAY
   choose to outsource the function to a service provider.

   Identification and authentication information could be made available
   to the service provider for controlling access, or the service
   provider may query a customer maintained server.  Furthermore, one SP
   may act as access for the SP providing the VPN service.  If the
   access SP performs identification and authentication on behalf of the
   VPN SP, an agreement MUST be reached on a common specification.

   Support for at least the following authentication protocols SHALL be
   supported: PAP, CHAP, and EAP, as they are currently used in a wide
   range of equipment and services.












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6.13.3.  Backbone Networks

   Ideally, the backbone interconnecting SP, PE, and P devices SHOULD be
   independent of physical and link layer technology.  Nevertheless, the
   characteristics of backbone technology MUST be taken into account
   when specifying the QoS aspects of SLAs for VPN service offerings.

6.14.  Protection, Restoration

   When primary and secondary access connections are available, an L3VPN
   solution MUST provide restoration of access connectivity whenever the
   primary access link from a CE site to a PE fails.  This capability
   SHOULD be as automatic as possible, that is, the traffic should be
   directed over the secondary link soon after failure of the primary
   access link is detected.  Furthermore, reversion to the primary link
   SHOULD be dynamic, if configured to do so [VPN-NEEDS].

   As mentioned in section 5.11.4, in the case of multi-homing, the load
   balancing capability MAY be used to achieve a degree of redundancy in
   the network.  In the case of failure of one or more (but not all) of
   the multi-homed links, the load balancing parameters MAY be
   dynamically adjusted to redirect the traffic rapidly from the failed
   link(s) to the surviving links.  Once the failed link(s) is (are)
   restored, the original provisioned load balancing ratio SHOULD be
   restored to its value prior to the failure.

   An SP SHOULD be able to deploy protection and restoration mechanisms
   within his or her backbone infrastructure to increase reliability and
   fault tolerance of the VPN service offering.  These techniques SHOULD
   be scalable, and therefore should strive not to perform such function
   in the backbone on a per-VPN basis.

   Appropriate measurements and alarms that indicate how well network
   protection and restoration mechanisms are performing MUST be
   supported.

6.15.  Interoperability

   Service providers are interested in interoperability in at least the
   following scenarios:

   -  Facilitating use of PE and managed CE devices within a single SP
      network.
   -  Implementing L3VPN services across two or more interconnected SP
      networks.






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   -  Achieving interworking or interconnection between customer sites
      using different L3VPN approaches or different implementations of
      the same approach.

   Each approach MUST describe whether any of the above objectives can
   be met.  If an objective can be met, the approach MUST describe how
   such interoperability could be achieved.  In particular, the approach
   MUST describe the inter-solution network interface, encapsulation
   method(s), routing protocol(s), security, isolation, management, and
   all other applicable aspects of the overall VPN solution provided
   [VPNIW].

6.16.  Migration Support

   Service providers MUST have a graceful means to migrate a customer
   with minimal service disruption on a site-by-site basis to an L3VPN
   approach.

   If L3VPN approaches can interwork or interconnect, then service
   providers MUST have a graceful means to migrate a customer with
   minimal service disruption on a site-by-site basis whenever
   interworking or interconnection is changed.

7.  Service Provider Management Requirements

   A service provider MUST have a means to view the topology,
   operational state, order status, and other parameters associated with
   each customer's VPN.  Furthermore, an SP 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.

   Currently, proprietary methods are often used to manage VPNs.  The
   additional expense associated with operators using multiple
   proprietary management methods (e.g., command line interface (CLI)
   languages) to access such systems is undesirable.  Therefore, devices
   SHOULD provide standards-based interfaces wherever feasible.

   The remainder of this section presents detailed SP management
   requirements for a Network Management System (NMS) in the traditional
   fault, configuration, accounting, performance, and security (FCAPS)
   management categories.  Much of this text was adapted from ITU-T
   Y.1311.1.








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7.1.  Fault Management

   Support for fault management includes:

   -  indication of customers impacted by failure,
   -  fault detection (incidents reports, alarms and failure
      visualization),
   -  fault localization (analysis of alarms reports and diagnostics),
   -  incident recording or logs (creation and follow-through of trouble
      tickets), and
   -  corrective actions (traffic, routing, and resource allocation).

   As PE-based VPNs rely on a common network infrastructure, the NMS
   MUST provide a means to inform the provider of the VPN customers
   impacted by a failure in the infrastructure.  The NMS SHOULD provide
   pointers to the related customer configuration information to aid in
   fault isolation and determining corrective action.

   Detecting faults caused by configuration errors is desirable, because
   these may cause VPN service failure or may disrupt other requirements
   (e.g., traffic and routing isolation).  This is a likely case of
   compromised security [VPNSEC].  Detection of such errors is
   inherently difficult because the problem involves more than one node
   and may reach across a global perspective.  One approach could be a
   protocol that systematically checks whether all constraints and
   consistency checks hold among tunnel configuration parameters at the
   various end points.

   A capability to verify L3 reachability within a VPN MUST be provided
   for diagnostic purposes.

   A capability to verify the parameter configuration of a device
   supporting an L3VPN MUST be provided for diagnostic purposes.

7.2.  Configuration Management

   Overall, the NMS must support a configuration necessary to realize
   the desired L3-reachability of an L3VPN.  Toward this end, an NMS
   MUST provide configuration management to provision at least the
   following L3VPN components: PE,CE, hierarchical tunnels, access
   connections, routing, and QoS, as detailed in this section.  If
   shared access to the Internet is provided, then this option MUST also
   be configurable.

   As VPN configuration and topology are highly dependent on a
   customer's organization, provisioning systems MUST address a broad
   range of customer-specific requirements.  The NMS MUST ensure that




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   these devices and protocols are provisioned consistently and
   correctly.

   Provisioning for adding or removing sites SHOULD be as localized and
   automated as possible.

   Configuration management for VPNs, according to service templates
   defined by the provider MUST be supported.  A service template
   contains fields that, when used, yield a definite service requirement
   or policy.  For example, a template for an IPSec tunnel would contain
   fields such as tunnel end points, authentication modes, encryption
   and authentication algorithms, pre-shared keys (if any), and traffic
   filters.  An SLA template would contain fields such as delay, jitter,
   and throughput and packet loss thresholds, as well as end points over
   which the SLA has to be satisfied.  In general, a customer's service
   order can be regarded as a set of instantiated service templates.
   This set can, in turn, be regarded as the logical service
   architecture of the customer's VPN.

   Service templates can also be used by the provider to define the
   service architecture of the provider's own network.  For example,
   OSPF templates could contain fields such as the subnets that form a
   particular area, the area identifier, and the area type.  BGP service
   template could contain fields that, when used, would yield a BGP
   policy, such as for expressing a preference about an exit router for
   a particular destination.

   The set of service templates SHOULD be comprehensive in that it can
   capture all service orders in some meaningful sense.

   The provider SHOULD provide means to translate service templates into
   device configurations so that associated services can be provisioned.

   Finally, the approach SHOULD provide means to check whether a service
   order is correctly provisioned.  This would represent one method of
   diagnosing configuration errors.  Configuration errors can arise due
   to a variety of reasons: manual configuration, intruder attacks, and
   conflicting service requirements.

7.2.1.  Configuration Management for PE-Based VPNs

   Requirements for configuration management unique to a PE-based VPN
   are as follows:

   o  The NMS MUST support configuration of at least the following
      aspects of L3 PE routers: intranet and extranet membership, CE
      routing protocol for each access connection, routing metrics, and
      tunnels.



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   o  The NMS SHOULD use identifiers for SPs, L3VPNs, PEs, CEs,
      hierarchical tunnels, and access connections, as described in
      section 6.3.

   o  Tunnels MUST be configured between PE and P devices.  This
      requires coordination of identifiers of tunnels, hierarchical
      tunnels, VPNs, and any associated service information, for
      example, a QoS/SLA service.

   o  Routing protocols running between PE routers and CE devices MUST
      be configured per VPN.

   o  For multicast service, multicast routing protocols MUST also be
      configurable.

   o  Routing protocols running between PE routers and between PE and P
      routers MUST also be configured.

   o  The configuration of a PE-based L3VPN MUST be coordinated with the
      configuration of the underlying infrastructure, including Layer 1
      and 2 networks interconnecting components of an L3VPN.

7.2.2.  Configuration Management for CE-Based VPN

   Requirements for configuration management unique to a CE-based VPN
   are as follows:

   o  Tunnels MUST be configured between CE devices.  This requires
      coordination of identifiers of tunnels, VPNs, and any associated
      service information, for example, a QoS/SLA service.

   o  Routing protocols running between PE routers and CE devices MUST
      be configured.  For multicast service, multicast routing protocols
      MUST also be configurable.

7.2.3.  Provisioning Routing

   A means for a service provider to provision parameters for the IGP
   for an L3VPN MUST be provided.  This includes link level metrics,
   capacity, QoS capability, and restoration parameters.

7.2.4.  Provisioning Network Access

   A service provider MUST have the means to provision network access
   between SP-managed PE and CE, as well as the case where the customer
   manages the CE.





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7.2.5.  Provisioning Security Services

   When a security service is requested, an SP MUST have the means to
   provision the entities and associated parameters involved with the
   service.  For example, for IPsec service, tunnels, options, keys, and
   other parameters must be provisioned at either the CE or the PE.  In
   the case of an intrusion detection service, the filtering and
   detection rules must be provisioned on a VPN basis.

7.2.6.  Provisioning VPN Resource Parameters

   A service provider MUST have a means to provision resources
   associated with VPN services dynamically.  For example, in a PE-based
   service, the number and size of virtual switching and forwarding
   table instances must be provisionable.

   Dynamic VPN resource assignment is crucial for coping with the
   frequent change requests from customers (e.g., sites joining or
   leaving a VPN), as well as for achieving scalability.  The PEs SHOULD
   be able to dynamically assign the VPN resources dynamically.  This
   capability is especially important for dial and wireless VPN
   services.

   If an SP supports a "Dynamic Bandwidth management" service, then the
   provisioning system MUST be able to make requested changes within the
   ranges and bounds specified in the SLA.  Examples of SLA parameters
   are response time and probability of being able to service such a
   request.

7.2.7.  Provisioning Value-Added Service Access

   An L3VPN service provides controlled access between a set of sites
   over a common backbone.  However, many service providers also offer a
   range of value-added services. (for example, Internet access,
   firewall services, intrusion protection, IP telephony and IP Centrex,
   application hosting, and backup).  It is outside of the scope of this
   document to define whether and how these different services interact
   with the VPN to solve issues such as addressing, integrity, and
   security.  However, the VPN service MUST be able to provide access to
   these various types of value-added services.

   A VPN service SHOULD allow the SP to supply the customer with
   different kinds of standard IP services, such as DNS, NTP, and
   RADIUS, that are needed for ordinary network operation and
   management.  The provider SHOULD be able to provide IP services to
   multiple VPN customers.





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   A firewall function MAY be required to restrict access to the L3VPN
   from the Internet [Y.1311].

   A managed firewall service MUST be carrier grade.  For redundancy and
   failure recovery, a means for firewall fail-over should be provided.
   Managed firewall services that may be provided include dropping
   specified protocol types, intrusion protection, and traffic-rate
   limiting against malicious attacks.

   Managed firewalls MUST be supported on a per-VPN basis, although
   multiple VPNs may be supported by the same physical device (e.g., in
   a PE-based solution).  Managed firewalls SHOULD be provided at the
   major access point(s) for the L3VPN.  Managed firewall services may
   be embedded in CE or PE device or implemented in standalone devices.

   The NMS SHOULD allow a customer to outsource the management of an IP
   networking service to the SP providing the VPN or to a third party.

   The NMS SHOULD support collection of information necessary for
   optimal allocation of IP services in response to customer orders.

   Reachability to and from the Internet to sites within a VPN MUST be
   configurable by an SP.  This could be controlled by configuring
   routing policy to control distribution of VPN routes advertised to
   the Internet.

7.2.8.  Provisioning Hybrid VPN Services

   Configuration of interworking or interconnection between L3VPN
   solutions SHOULD be also supported.  Ensuring that security and
   end-to-end QoS issues are provided consistently SHOULD be addressed.

7.3.  Accounting

   Many service providers require collection of measurements regarding
   resource usage for accounting purposes.  The NMS MAY need to
   correlate accounting information with performance and fault
   management information to produce billing that takes into account SLA
   provisions for periods of time when the SLS is not met.

   An L3VPN solution MUST describe how the following accounting
   functions can be provided:

   - Measurements of resource utilization.
   - collection of accounting information.
   - storage and administration of measurements.





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   Some providers may require near - real time reporting of measurement
   information and may offer this as part of a customer network
   management service.

   If an SP supports a "Dynamic Bandwidth management" service, then the
   dates, times, amounts, and interval required to perform requested
   bandwidth allocation change(s) MUST be traceable for monitoring and
   accounting purposes.

   Solutions should state compliance with accounting requirements, as
   described in section 1.7 of RFC 2975 [RFC2975].

7.4.  Performance Management

   Performance management MUST support functions involved with
   monitoring and collecting performance data for devices, facilities,
   and services, as well as determining conformance to SLS, such as QoS
   and availability measurements.

   Performance management SHOULD also support analysis of important
   aspects of an L3VPN, such as bandwidth utilization, response time,
   availability, QoS statistics, and trends based on collected data.

7.4.1.  Performance Monitoring

   The NMS MUST monitor device behavior to evaluate performance metrics
   associated with an SLA.  Different measurement techniques may be
   necessary depending on the service for which an SLA is provided.
   Example services are QoS, security, multicast, and temporary access.
   These techniques MAY be either intrusive or non-intrusive depending
   on the parameters being monitored.

   The NMS MUST also monitor aspects of the VPN not directly associated
   with an SLA, such as resource utilization, state of devices, and
   transmission facilities, as well as control of monitoring resources
   such as probes and remote agents at network access points used by
   customers and mobile users.

7.4.2.  SLA and QoS Management Features

   The NMS SHOULD support SLAs between an SP and the various VPN
   customers according to the corresponding SLSes by measurement of the
   indicators defined within the context of the SLA, on a regular basis.

   The NMS SHOULD use the QoS parameter measurement definitions,
   techniques, and methods as defined by the IETF IP Performance Metrics
   (IPPM) working group for delay, loss, and delay variation.




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   The NMS SHOULD support allocation and measurement of end-to-end QoS
   requirements to QoS parameters for one or more VPN network(s).

   Devices supporting L3VPN SLAs SHOULD have real-time performance
   measurements that have indicators and threshold crossing alerts.
   Such thresholds should be configurable.

7.5.  Security Management

   The security management function of the NMS MUST include management
   features to guarantee the security of devices, access connections,
   and protocols within the L3VPN network(s), as well as the security of
   customer data and control as described in section 6.9.

7.5.1.  Resource Access Control

   Resource access control determines the privileges that a user has to
   access particular applications and VPN network resources.  Without
   such control, only the security of the data and control traffic is
   protected, leaving the devices providing the L3VPN network
   unprotected.  Access control capabilities protect these devices to
   ensure that users have access only to the resources and applications
   they are authorized to use.

   In particular, access to the routing and switching resources managed
   by the SP MUST be tightly controlled to prevent and/or effectively
   mitigate a malicious attack.  More detailed requirements in this area
   are described in [VPNSEC].

7.5.2.  Authentication

   Authentication is the process of verifying that the sender is
   actually who he or she claims to be.  The NMS MUST support standard
   methods for authenticating users attempting to access management
   services.

   Scalability is critical, as the number of nomadic/mobile clients is
   increasing rapidly.  The authentication scheme implemented for such
   deployments MUST be manageable for large numbers of users and VPN
   access points.

   Strong authentication schemes SHALL be supported to ensure the
   security of both VPN access point-to-VPN access point  (e.g., PE to
   PE in a PE-based case) and client-to-VPN access point (e.g., CE-to-PE
   in a PE-based case) communications.  This is particularly important
   for preventing VPN access point spoofing, a situation where an
   attacker tries to convince a PE or CE that the attacker is the VPN
   access point.  If an attacker can convince a PE or CE device of this,



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   then that device will send VPN traffic to the attacker (who could
   forward it to the true access point after compromising
   confidentiality or integrity).  In other words, a non-authenticated
   VPN AP can be spoofed with a man-in-the-middle attack, because the
   endpoints never verify each other.  A weakly authenticated VPN AP may
   be subject to such an attack.  Strongly authenticated VPN APs are not
   subject to such attacks, because the man-in-the-middle cannot be
   authenticated as the real AP due to the strong authentication
   algorithms.

7.6.  Basis and Presentation Techniques of Management Information

   Each L3VPN solution approach MUST specify the management information
   bases (MIB) modules for the network elements involved in L3VPN
   services.  This is an essential requirement in network provisioning.
   The approach SHOULD identify any information not contained in a
   standard MIB related to FCAPS that is necessary to meet a generic
   requirement.

   An IP VPN (Policy) Information model, when available, SHOULD reuse
   the policy information models being developed in parallel for
   specific IP network capabilities [IM-REQ].  This includes the QoS
   Policy Information Model [QPIM] and the IPSEC Configuration Policy
   Model [IPSECIM].  The IP VPN Information model SHOULD provide the OSS
   with adequate "hooks" to correlate service level specifications with
   traffic data collected from network elements.  The use of policies
   includes rules that control corrective actions taken by OSS
   components responsible for monitoring the network and ensuring that
   it meets service requirements.

   Additional requirements on VPN information models are given in
   reference [IM-PPVPN].  In particular, an information model MUST allow
   an SP to change VPN network dimensions with minimal influence on
   provisioning issues.  The adopted model SHOULD be applicable to both
   small/medium size and large-scale L3VPN scenarios.

   Some service providers MAY require systems that visually, audibly, or
   logically present FCAPS information to internal operators and/or
   customers.

8.  Security Considerations

   Security considerations occur at several levels and dimensions within
   L3VPNs, as detailed within this document.  This section provides a
   summary with references to detailed supporting information
   [L3VPN-SEC] [VPNSEC].





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   The requirements in this document separate traditional notions of
   security requirements, such as integrity, confidentiality, and
   authentication, from issues such as isolating (or separating) the
   exchange of VPN data and control traffic between specific sets of
   sites (as defined in sections 3.3 and 4.1).  Further detail on
   security requirements is given from the customer and service provider
   perspectives in sections 5.9 and 6.9, respectively.  Further detail
   on data and control traffic isolation requirements are given from the
   customer and service provider perspectives in sections 5.1 and 6.8,
   respectively.

   Furthermore, requirements regarding management of security from a
   service provider perspective are described in section 7.5.

9.  Acknowledgements

   The authors of this document would like to acknowledge the
   contributions from the people who launched the work on VPN
   requirements inside ITU-T SG13 and the authors of the original IP VPN
   requirements and framework document [RFC2764], as well as Tom
   Worster, Ron Bonica, Sanjai Narain, Muneyoshi Suzuki, Tom Nadeau,
   Nail Akar, Derek Atkins, Bryan Gleeson, Greg Burns, and Frederic Le
   Garrec.  The authors are also grateful to the helpful suggestions and
   direction provided by the technical advisors, Alex Zinin, Scott
   Bradner, Bert Wijnen, and Rob Coltun.  Finally, the authors wish to
   acknowledge the insights and requirements gleaned from the many
   documents listed in the references section.  Citations to these
   documents were made only where the authors believed that additional
   insight could be obtained from reading the source document.

10.  References

10.1.  Normative References

   [RFC3377]     Hodges, J. and R. Morgan, "Lightweight Directory Access
                 Protocol (v3): Technical Specification", RFC 3377,
                 September 2002.

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

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

   [RFC2205]     Braden, R., Zhang, L., Berson, S., Herzog, S., and S.
                 Jamin, "Resource ReSerVation Protocol (RSVP) -- Version
                 1 Functional Specification", RFC 2205, September 1997.



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   [RFC2211]     Wroclawski, J., "Specification of the Controlled-Load
                 Network Element Service", RFC 2211, September 1997.

   [RFC2212]     Shenker, S., Partridge, C., and R. Guerin,
                 "Specification of Guaranteed Quality of Service", RFC
                 2212, September 1997.

   [RFC2251]     Wahl, M., Howes, T., and S. Kille, "Lightweight
                 Directory Access Protocol (v3)", RFC 2251, December
                 1997.

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

   [RFC2597]     Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski,
                 "Assured Forwarding PHB Group", RFC 2597, June 1999.

   [RFC2661]     Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn,
                 G., and B. Palter, "Layer Two Tunneling Protocol
                 "L2TP"", RFC 2661, August 1999.

   [RFC2685]     Fox, B. and B. Gleeson, "Virtual Private Networks
                 Identifier", RFC 2685, September 1999.

   [RFC3246]     Davie, B., Charny, A., Bennet, J.C., Benson, K., Le
                 Boudec, J., Courtney, W., Davari, S., Firoiu, V., and
                 D. Stiliadis, "An Expedited Forwarding PHB (Per-Hop
                 Behavior)", RFC 3246, March 2002.

   [RFC3270]     Le Faucheur, F., Wu, L., Davie, B., Davari, S.,
                 Vaananen, P., Krishnan, R., Cheval, P., and J.
                 Heinanen, "Multi-Protocol Label Switching (MPLS)
                 Support of Differentiated Services", RFC 3270, May
                 2002.

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

10.2.  Informative References

   [2547bis]     Rosen, E., Rekhter, Y. et al., "BGP/MPLS VPNs", Work in
                 Progress.

   [IM-PPVPN]    Lago, P., et al., "An Information Model for Provider
                 Provisioned Virtual Private Networks", Work in
                 Progress.



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   [IM-REQ]      Iyer, M., et al., "Requirements for an IP VPN Policy
                 Information Model", Work in Progress.

   [IPSECIM]     Jason, J., "IPsec Configuration Policy Model", Work in
                 Progress.

   [CE-PPVPN]    De Clercq, J., Paridaens, O., Krywaniuk, A., Wang, C.,
                 "An Architecture for Provider Provisioned CE-based
                 Virtual Private Networks using IPsec", Work in
                 Progress.

   [IPSEC-PPVPN] Gleeson, B., "Uses of IPsec with Provider Provisioned
                 VPNs", Work in Progress.

   [L2VPN]       Rosen, E., et al., "An Architecture for L2VPNs", Work
                 in Progress.

   [MPLSSEC]     Behringer, M., "Analysis of the Security of the MPLS
                 Architecture", Work in Progress.

   [PPVPN-TERM]  Andersson, L., Madsen, T., "PPVPN Terminology", Work in
                 Progress.

   [L3VPN-SEC]   Fang, L., et al., "Security Framework for Provider
                 Provisioned Virtual Private Networks", Work in
                 Progress.

   [L3VPN-FR]    Callon, R., Suzuki, M., et al. "A Framework for Layer 3
                 Provider Provisioned Virtual Private Networks", Work in
                 Progress.

   [PPVPN-VR]    Knight, P., Ould-Brahim, H., Gleeson, B., "Network
                 based IP VPN Architecture using Virtual Routers", Work
                 in Progress.

   [QPIM]        Snir, Ramberg, Strassner, Cohen and Moore, "Policy QoS
                 Information Model", Work in Progress.

   [RFC2385]     Heffernan, A., "Protection of BGP Sessions via the TCP
                 MD5 Signature Option", RFC 2385, August 1998.

   [RFC2764]     Gleeson, B., Lin, A., Heinanen, J., Armitage, G., and
                 A. Malis, "A Framework for IP Based Virtual Private
                 Networks", RFC 2764, February 2000.

   [RFC2975]     Aboba, B., Arkko, J., and D. Harrington, "Introduction
                 to Accounting Management", RFC 2975, October 2000.




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   [RFC2983]     Black, D., "Differentiated Services and Tunnels", RFC
                 2983, October 2000.

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

   [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.

   [TE-INTERAS]  Zhang, R., Vasseur, J.P., "MPLS Inter-AS Traffic
                 Engineering requirements", Work in Progress.

   [VPNDISC]     Squire, M. et al., "VPN Discovery Discussions and
                 Options", Work in Progress.

   [VPNIW]       Kurakami, H., et al., "Provider-Provisioned VPNs
                 Interworking", Work in Progress.

   [VPNSEC]      De Clercq, J., et al., "Considerations about possible
                 security extensions to BGP/MPLS VPN", Work in Progress.

   [VPNTUNNEL]   Worster, T., et al., "A PPVPN Layer Separation: VPN
                 Tunnels and Core Connectivity", Work in Progress.

   [VPN-CRIT]    Yu, J., Jou, L., Matthews, A ., Srinivasan, V.,
                 "Criteria for Evaluating VPN Implementation
                 Mechanisms", Work in Progress.

   [VPN-NEEDS]   Jacquenet, C., "Functional needs for the deployment of
                 an IP VPN service offering : a service provider
                 perspective", Work in Progress.

   [Y.1311.1]    Carugi, M. (editor), "Network Based IP VPN over MPLS
                 architecture", Y.1311.1 ITU-T Recommendation, July
                 2001.

   [Y.1311]      Knightson, K. (editor), "Network based VPNs  - Generic
                 Architecture and Service Requirements", Y.1311 ITU-T
                 Recommendation, March 2002.









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Authors' Addresses

   Marco Carugi (co-editor)
   Nortel Networks
   Parc d'activites de Magny-Chateaufort
   Les Jeunes Bois - MS CTF 32B5 - Chateaufort
   78928 YVELINES Cedex 9  - FRANCE

   EMail: marco.carugi@nortel.com


   Dave McDysan (co-editor)
   MCI
   22001 Loudoun County Parkway
   Ashburn, VA 20147, USA

   EMail: dave.mcdysan@mci.com


   Luyuan Fang
   AT&T
   200 Laurel Ave - Room C2-3B35
   Middletown, NJ 07748 USA

   EMail: Luyuanfang@att.com


   Ananth Nagarajan
   Juniper Networks

   EMail: ananth@juniper.net


   Junichi Sumimoto
   NTT Communications Corporation
   3-20-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-1421, Japan

   EMail: j.sumimoto@ntt.com


   Rick Wilder
   Alcatel

   EMail: rick.wilder@alcatel.com







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Full Copyright Statement

   Copyright (C) The Internet Society (2005).

   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.

   This document and the information contained herein are provided on an
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   The IETF invites any interested party to bring to its attention any
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.







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