GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools

Problem, Formatting or Query -  Send Feedback

Was this page helpful?-10+1


rfc:rfc4031

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

Carugi & McDysan Standards Track [Page 1] RFC 4031 Service Requirements for L3 PPVPNs April 2005

      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

Carugi & McDysan Standards Track [Page 2] RFC 4031 Service Requirements for L3 PPVPNs April 2005

            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]).

Carugi & McDysan Standards Track [Page 3] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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.

Carugi & McDysan Standards Track [Page 4] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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].

Carugi & McDysan Standards Track [Page 5] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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.

Carugi & McDysan Standards Track [Page 6] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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.

Carugi & McDysan Standards Track [Page 7] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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

Carugi & McDysan Standards Track [Page 8] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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

Carugi & McDysan Standards Track [Page 9] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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,

Carugi & McDysan Standards Track [Page 10] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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].

Carugi & McDysan Standards Track [Page 11] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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:
  1. Best Effort (mandatory support for all L3VPN types)
  2. Aggregate CE Interface Level QoS ("hose" level QoS)
  3. Site-to-site ("pipe" level QoS)
  4. Intserv (i.e., RSVP) signaled
  5. Diffserv marked
  6. 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:
  1. Resource reSerVation Protocol (RSVP) [RFC2205]
  2. Guaranteed Quality of Service providing a strict delay bound

[RFC2212]

  1. Controlled Load Service providing performance equivalent to that

of an unloaded network [RFC2211]

Carugi & McDysan Standards Track [Page 12] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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:
  1. Expedited Forwarding (EF) - The departure rate of an aggregate

class of traffic from a device that must equal or exceed a

    configured rate [RFC3246].
  1. 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.

Carugi & McDysan Standards Track [Page 13] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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:
  1. 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.
  1. 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).
  1. 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.

Carugi & McDysan Standards Track [Page 14] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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.

Carugi & McDysan Standards Track [Page 15] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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.

Carugi & McDysan Standards Track [Page 16] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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.

Carugi & McDysan Standards Track [Page 17] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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].

Carugi & McDysan Standards Track [Page 18] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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.

Carugi & McDysan Standards Track [Page 19] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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.

Carugi & McDysan Standards Track [Page 20] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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).

Carugi & McDysan Standards Track [Page 21] RFC 4031 Service Requirements for L3 PPVPNs April 2005

                 +----------------                    +---------------
                 |                                    |
              +------+                            +------+
    +---------|  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)

Carugi & McDysan Standards Track [Page 22] RFC 4031 Service Requirements for L3 PPVPNs April 2005

                 +----------------                    +---------------
                 |                                    |
+------+     +------+                +------+     +------+
|  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.

Carugi & McDysan Standards Track [Page 23] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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.

Carugi & McDysan Standards Track [Page 24] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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.

Carugi & McDysan Standards Track [Page 25] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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.

Carugi & McDysan Standards Track [Page 26] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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.

Carugi & McDysan Standards Track [Page 27] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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.

Carugi & McDysan Standards Track [Page 28] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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:

Carugi & McDysan Standards Track [Page 29] RFC 4031 Service Requirements for L3 PPVPNs April 2005

  1. traffic between a CE and a PE,
  2. traffic between CEs belonging to the same VPN,
  3. CE or PE routers dealing with route announcements for a VPN,
  4. policy decision point [RFC3198] and a network element, and
  5. 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:
  1. users connected to the supporting public IP backbone,
  2. users from the Internet, and
  3. 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:
  1. Denial of service, for example mail spamming, access connection

congestion, TCP SYN attacks, and ping attacks

  1. 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.

Carugi & McDysan Standards Track [Page 30] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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:
  1. Diagnostic tools (e.g., ping, traceroute)
  2. Secured access to one AS management system by another
  3. Configuration request and status query tools
  4. 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.

Carugi & McDysan Standards Track [Page 31] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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-

Carugi & McDysan Standards Track [Page 32] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 AS/Inter-Provider VPN could possibly fall in this L3VPN wholesale
 category, too).  Various carrier's carrier scenarios should be
 supported, such as when
  1. the customer carriers do not operate L3VPN services for their

clients;

  1. 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:
  1. Relevant identifiers
  2. QoS/SLA parameters
  3. Restoration parameters
  4. Multiplexing identifiers
  5. Security parameters
 There MUST be a means to monitor the following aspects of tunnels:
  1. Statistics, such as amount of time spent in the up and down state.
  2. Count of transitions between the up and down state.
  3. 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.

Carugi & McDysan Standards Track [Page 33] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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.

Carugi & McDysan Standards Track [Page 34] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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:
  1. Facilitating use of PE and managed CE devices within a single SP

network.

  1. Implementing L3VPN services across two or more interconnected SP

networks.

Carugi & McDysan Standards Track [Page 35] RFC 4031 Service Requirements for L3 PPVPNs April 2005

  1. 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.

Carugi & McDysan Standards Track [Page 36] RFC 4031 Service Requirements for L3 PPVPNs April 2005

7.1. Fault Management

 Support for fault management includes:
  1. indication of customers impacted by failure,
  2. fault detection (incidents reports, alarms and failure

visualization),

  1. fault localization (analysis of alarms reports and diagnostics),
  2. incident recording or logs (creation and follow-through of trouble

tickets), and

  1. 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

Carugi & McDysan Standards Track [Page 37] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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.

Carugi & McDysan Standards Track [Page 38] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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.

Carugi & McDysan Standards Track [Page 39] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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.

Carugi & McDysan Standards Track [Page 40] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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:
  1. Measurements of resource utilization.
  2. collection of accounting information.
  3. storage and administration of measurements.

Carugi & McDysan Standards Track [Page 41] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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.

Carugi & McDysan Standards Track [Page 42] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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,

Carugi & McDysan Standards Track [Page 43] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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].

Carugi & McDysan Standards Track [Page 44] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 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.

Carugi & McDysan Standards Track [Page 45] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 [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.

Carugi & McDysan Standards Track [Page 46] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 [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.

Carugi & McDysan Standards Track [Page 47] RFC 4031 Service Requirements for L3 PPVPNs April 2005

 [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.

Carugi & McDysan Standards Track [Page 48] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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

Carugi & McDysan Standards Track [Page 49] RFC 4031 Service Requirements for L3 PPVPNs April 2005

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
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at ietf-
 ipr@ietf.org.

Acknowledgement

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

Carugi & McDysan Standards Track [Page 50]

/data/webs/external/dokuwiki/data/pages/rfc/rfc4031.txt · Last modified: 2005/04/12 18:41 (external edit)