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Versions: 00 01 02 RFC 4031

   INTERNET DRAFT                                             M. Carugi
   Internet Engineering Task Force                      Nortel Networks
   Document:                                                 D. McDysan
   draft-ietf-l3vpn-requirements-01.txt                             MCI
   June 2004                                               (Co-Editors)
   Category: Informational
   Expires: December 2004
   Service requirements for Layer 3 Virtual Private Networks:
   Status of this memo
   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC 2026 ([RFC-2026]).
   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as Internet-
   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents
   at any time.  It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than as "work in progress."
   The list of current Internet-Drafts can be accessed at
   The list of Internet-Draft Shadow Directories can be accessed at
   This document is a product of the IETF's Layer 3 Virtual Private
   Network (l3vpn) working group. Comments should be addressed to WG's
   mailing list at l3vpn@ietf.org. The charter for l3vpn may be found
   at http://www.ietf.org/html.charters/l3vpn-charter.html
   Copyright (C) The Internet Society (2000). All Rights Reserved.
   Distribution of this memo is unlimited.
   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 for the
   provisioning of a VPN service. This document expresses a service
   provider perspective, based upon past experience of 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 as well as a service provider perspective.
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               Service requirements for Layer 3 PPVPNs     June, 2004
   Conventions used in this document
   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   this document are to be interpreted as described in RFC 2119 ([RFC-
   Table of Contents
   1 Introduction....................................................5
 1.1  Scope of this document.........................................5
 1.2  Outline........................................................6
   2 Contributing Authors............................................6
   3 Definitions.....................................................6
 3.1  Virtual Private Network........................................6
 3.2  Users, Sites, Customers and Agents.............................7
 3.3  Intranets, Extranets, and VPNs.................................7
 3.4  Networks of Customer and Provider Devices......................7
 3.5  Access Networks, Tunnels, and Hierarchical Tunnels.............8
 3.6  Use of Tunnels and roles of CE and PE in L3 VPNs...............9
   3.6.1   PE-Based Layer 3 VPNs and Virtual Forwarding Instances....9
   3.6.2   CE-Based L3VPN Tunnel Endpoints and Functions............10
 3.7  Customer and Provider Network Management......................11
   4 Service Requirements Common to Customers and Service Providers.12
 4.1  Isolated Exchange of Data and Routing Information.............12
 4.2  Addressing....................................................12
 4.3  Quality of Service............................................12
   4.3.1   QoS Standards............................................13
   4.3.2   Service Models...........................................14
 4.4  Service Level Specification and Agreements....................14
 4.5  Management....................................................15
 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.........................16
   5.5.2   DSCP Transparency........................................17
 5.6  Service Level Specification/Agreement.........................17
 5.7  Customer Management of a VPN..................................18
 5.8  Isolation.....................................................18
 5.9  Security......................................................18
 5.10 Migration Impact..............................................19
 5.11 Network Access................................................19
   5.11.1  Physical/Link Layer Technology...........................19
   5.11.2  Temporary Access.........................................19
   5.11.3  Sharing of the Access Network............................20
   5.11.4  Access Connectivity......................................20
 5.12 Service Access................................................22
   5.12.1  Internet Access..........................................22
   5.12.2  Hosting, Application Service Provider....................22
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   5.12.3  Other Services...........................................22
 5.13 Hybrid VPN Service Scenarios..................................22
   6 Service Provider Network Requirements..........................23
 6.1  Scalability...................................................23
 6.2  Addressing....................................................23
 6.3  Identifiers...................................................23
 6.4  Discovering VPN Related Information...........................24
 6.5  SLA and SLS Support...........................................24
 6.6  Quality of Service (QoS) and Traffic Engineering..............25
 6.7  Routing.......................................................25
 6.8  Isolation of Traffic and Routing..............................26
 6.9  Security......................................................26
   6.9.1   Support for Securing Customer Flows......................26
   6.9.2   Authentication Services..................................27
   6.9.3   Resource Protection......................................27
 6.10 Inter-AS (SP)VPNs.............................................28
   6.10.1  Routing Protocols........................................28
   6.10.2  Management...............................................28
   6.10.3  Bandwidth and QoS Brokering..............................29
   6.10.4  Security Considerations..................................29
 6.11 L3VPN Wholesale...............................................29
 6.12 Tunneling Requirements........................................30
 6.13 Support for Access and Backbone Technologies..................31
   6.13.1  Dedicated Access Networks................................31
   6.13.2  On-Demand Access Networks................................31
   6.13.3  Backbone Networks........................................31
 6.14 Protection, Restoration.......................................31
 6.15 Interoperability..............................................32
 6.16 Migration Support.............................................32
   7 Service Provider Management Requirements.......................33
 7.1  Fault management..............................................33
 7.2  Configuration Management......................................34
   7.2.1   Configuration Management for PE-Based VPNs...............35
   7.2.2   Configuration management for CE-based VPN................35
   7.2.3   Provisioning Routing.....................................36
   7.2.4   Provisioning Network Access..............................36
   7.2.5   Provisioning Security Services...........................36
   7.2.6   Provisioning VPN Resource Parameters.....................36
   7.2.7   Provisioning Value-Added Service Access..................36
   7.2.8   Provisioning Hybrid VPN Services.........................37
 7.3  Accounting....................................................37
 7.4  Performance Management........................................38
   7.4.1   Performance Monitoring...................................38
   7.4.2   SLA and QoS management features..........................38
 7.5  Security Management...........................................39
   7.5.1   Resource Access Control....................................39
   7.5.2   Authentication...........................................39
 7.6  Network Management Techniques.................................39
   8 Security Considerations........................................40
   9 Acknowledgements...............................................40
   10 References.....................................................41
 10.1 Normative References..........................................41
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 10.2 Non-normative References......................................42
   11 Authors' address...............................................43
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   1 Introduction
   This section describes the scope and outline of the document.
   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 [PPVPN-GR]).
   This document identifies requirements that may apply to one or more
   individual approaches that a Service Provider may use for the
   provisioning of a Layer 3 (e.g., IP) VPN service. It makes use of
   the terminology and common components for Layer 3 VPNs defined in
   [L3VPN-FR] and of the generic VPN terminology defined in [PPVPN-
   The specification of technical means to provide L3VPN services is
   outside the scope of this document. Other documents, such as the L3
   VPN framework document [L3VPN-FR] and several sets of documents, one
   set per each individual technical approach for providing L3VPN
   services, are intended to cover this aspect.
   Technical approaches targeted by this document include the network-
   based (PE-based) L3 VPN category (aggregated routing VPNs
   [RFC2547bis] and virtual routers [PPVPN-VR]) and the CE-based L3
   VPNs 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
   regarding whether equipment faces a customer or the service provider
   network is used to define the various types of L3 VPN solutions.>
   This document is intended as a "checklist" of requirements providing
   a consistent way to evaluate and document how well each individual
   approach satisfies specific requirements. The applicability
   statement documents for each individual approach should present the
   results of this evaluation. It is not the intent of this document to
   state a comparison of one approach versus another.
   This document provides requirements from several points of view. It
   begins with some considerations from a common customer and service
   provider point of view not covered in the generic provider
   provisioned VPN requirement document [PPVPN-GR], followed by a
   customer perspective, and concludes with specific needs of a Service
   Provider (SP).
   The following L3VPN deployment scenarios are considered within this
       1. Internet-wide: VPN sites attached to arbitrary points in
         the Internet
       2. Single SP/single AS: VPN sites attached to the network of a
         single provider within the scope of a single AS
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       3.Single SP/multiple AS'es: VPN sites attached to the network
         of a single provider consisting of multiple AS'es
       4.Cooperating SPs: VPN sites attached to networks of different
         providers that cooperate with each other to provide the VPN
   The above deployment scenarios have many requirements in  common.
   These common requirements 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
   1.2 Outline
   The outline of the rest of the document is as follows. Section 2
   mentions the contributing authors. Section 3 provides definitions of
   terms and concepts. Section 4 provides requirements that are common
   to both customers and service providers and are not covered in the
   generic provider provisioned VPN requirement document [PPVPN-GR].
   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 acknowledgements.
   Section 10 provides a list of references cited herein. Section 11
   lists the authorsÆ 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].
   3.1 Virtual Private Network
   "L3 Virtual Private Network" (L3 VPN) refers to the L3 communication
   between a set of sites, making use of a shared network
   ôProvider Provisioned VPNö (PPVPN) refers to VPNs for which the
   service provider participates in management and provisioning of the
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   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) that has been 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 since
   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 to 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 an extranet scenario 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.
   Note that an intranet or extranet can exist across a single service
   provider network with one or more ASÆs, or across multiple service
   provider networks.
   L3 Virtual Private Network (L3 VPN): An alternative definition of
   VPN refers to a specific set of sites as either an intranet or an
   extranet that have been configured to allow communication. Note that
   a site is a member of at least one VPN, and may be a member of many
   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
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   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
   Note that the definitions of Customer Edge and Provider Edge do not
   necessarily map to 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 un-aware [PPVPN-TERM].
   Packet Switched Network (PSN): A (IP or MPLS) 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 ASÆs.
   3.5 Access Networks, Tunnels, and Hierarchical Tunnels
   VPNs are built between CEs using access networks, tunnels, and
   hierarchical tunnels across a PSN.
   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).
   Access network: An access network provides access connections
   between CE and PE devices.  It may be a TDM network, L2 network
   (e.g. FR, ATM, and Ethernet), or an IP network over which access is
   tunneled (e.g., using L2TP]).
   Tunnel: A tunnel between two entities is formed by encapsulating
   packets within another encapsulating header for purpose 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)
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   [VPN TUNNEL]. 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 point where tunnels terminate and the
   functions implemented in the CE and PE devices that differentiate
   the two major categories of L3 VPNs for which requirements are
   stated, namely PE-based and CE-based L3 VPNs. See the L3VPN
   framework document for more detail [L3VPN-FR].
   3.6.1 PE-Based Layer 3 VPNs and Virtual Forwarding Instances
   In a PE-based layer 3 VPN 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 performs forwarding of
   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 layer 3 VPN
   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 L3 VPN.
   The VFI includes the router information base and the forwarding
   information base for a L3 VPN [L3VPN-FR]. A VFI enables router
   functions dedicated to serving a particular VPN, such as separation
   of 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 3.1
   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 3.1 PE Usage of Separate Tunnels to Support VPNs
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   Figure 3.2 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 3.2 PE Usage of Shared Hierarchical Tunnels to Support VPNs
   3.6.2 CE-Based L3VPN Tunnel Endpoints and Functions
   Figure 3.3 illustrates the CE-based L3 VPN 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 using 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 upon VPN
   customer requirements and traffic patterns.
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       +---------+  +--------------------------------+  +---------+
       |         |  |                                |  |         |
       |         |  |                 +------+     +------+  : +------+
   +------+ :    |  |                 |      |     |      |  : |  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 3.3 CE-based L3 VPN
   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 receive alarms regarding
   his or her VPN. Customer specific information includes data related
   to contact, billing, site, access network, IP address, routing
   protocol parameters, etc. It may also include confidential data,
   such as encryption keys. 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]).
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   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 apply to both L2
   and L3 VPNs, are described in [PPVPN-GR]. This section contains
   requirements specific to L3 VPNs which are not covered in [PPVPN-
   4.1 Isolated Exchange of Data and Routing Information
   A mechanism for isolating the distribution of reachability
   information to only those sites associated with a VPN must be
   L3VPN solutions shall define means that prevent routers in a VPN
   from interaction with unauthorized entities and avoid introducing
   undesired routing information that could corrupt the VPN
   routing information base [VPN-CRIT].
   A means to constrain, or isolate, the distribution of addressed data
   to only those VPN sites determined either by routing data and/or
   configuration must be provided.
   A single site shall be capable of being in multiple VPNs. The VPN
   solution must ensure that traffic is exchanged only with those sites
   that are in the same VPN.
   The internal structure of a VPN should not be advertised nor
   discoverable from outside that VPN.
   Note that isolation of forwarded data and/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],[MPLS
   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, L3 VPN QoS should be independent of the
   access network technology.
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   4.3.1 QoS Standards
   A non-goal of the L3 VPN WG effort (as chartered) is the development
   of new protocols or extension of existing ones. With regards to QoS
   support, a L3 VPN shall be able to support QoS in one or more of the
   following already defined modes:
     - Best Effort  (mandatory support for all L3VPN types)
     - Aggregate CE Interface Level QoS (ôhoseö level QoS)
     - Site-to-site (ôpipeö level QoS)
     - Intserv (i.e., RSVP) signaled
     - Diffserv marked
     - Across packet-switched access networks
   Note that all cases involving QoS may require that the CE and/or PE
   perform shaping and/or policing.
   L3VPN CEs should be capable of supporting integrated services
   (Intserv) for certain customers in support of session applications,
   such as switched voice or video. Intserv-capable CE devices shall
   support the following Internet standards:
     - Resource reSerVation Protocol (RSVP) [RFC 2205]
     - Guaranteed Quality of Service providing a strict delay bound
       [RFC 2212]
     - Controlled Load Service providing performance equivalent to that
   of an unloaded network [RFC 2211]
   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) [RFC 2475] types:
     - Expedited Forwarding (EF) - the departure rate of an aggregate
   class of traffic from a device that must equal or exceed a
   configured rate [RFC 3246].
     - 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) [RFC 2597].
   A CE or PE device supporting a L3 VPN service may classify a packet
   for a particular Intserv or Diffserv service based on upon one or
   more of the following IP header fields: protocol ID, source port
   number, destination port number, destination address, or source
   For a specifiable set of Internet traffic, L3 VPN devices should
   support Random Early Detection (RED) to provide graceful degradation
   in the event of network congestion.
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   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 [PPVPN-GR]. More detail
   specific to L3 VPNs is provided below.
   A managed access L3 VPN 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 L3 VPN service is where
   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 upon 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 upon
   the service demarcation point between the provider and the customer.
   Such a service may be provided across one or more provider
   backbones. 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 edge.
   4.4 Service Level Specification and Agreements
   A generic discussion of SLAs is provided in [PPVPN-GR].
   Additionally, SLS measurements for quality based on the DiffServ
   scheme SHOULD be based upon the following classification:
       . A Point-to-Point SLS [Y.1311.1], sometimes also referred to as
          the "Pipe" model, defines traffic parameters in conjunction
          with the QoS objectives for traffic exchanged between a pair
          of VPN sites (i.e., points). A Point-to-Point SLS is analogous
          to the SLS typically supported over point-to-point Frame Relay
          or ATM PVCs or an edge-to-edge MPLS tunnel. The set of SLS
          specifications to all other reachable VPN sites would define
          the overall Point-to-Point SLS for a specific site.
       . A Point-to-Cloud SLS [Y.1311.1], sometimes also referred 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).
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       . A Cloud-to-Point SLS (a case not covered by this SLS is where
          flows originating from multiple sources may congest the
          interface from the network 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.
   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
     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 consider at least traffic and routing
   isolation, security, QoS, access, and management aspects. This
   requirement is essential in the case 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
   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. When one or
   more SPs are involved, the solution SHALL allow SPs to ensure that
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   both organizations approve extranet communication before the L3VPN
   allows exchange of traffic and routing information.
   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, homogenous 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 ASs/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 a L3 VPN for the following
   addressing IP assignment schemes:
     o customer assigned, non-unique, or RFC 1918 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 (i.e., dedicated)
   In the case of combined L3 VPN 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 MUST be supported, for example NAT.
   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 a L3VPN service for
   some customers. QoS requirements cover scenarios involving an
   intranet, an extranet, as well as shared access between a VPN site
   and the Internet.
   5.5.1 Application Level QoS Objectives
   A customer is concerned primarily that the L3VPN service provide his
   or her applications with the QoS and level of traffic such that the
   applications perform acceptably. Voice and 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
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   intensive applications, requires near real time performance.
   Finally, best effort applications are not sensitive to degradation,
   that is are elastic and can adapt to conditions of degraded
   The selection of appropriate QoS and service type to meet specific
   application requirements is particularly important to deal with
   periods of congestion in a 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
   The fundamental customer application requirement is that a 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 RFC 3270 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 than 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 where 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 carrierÆs carrier SP.
   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 only carry 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
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   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
   Most aspects of management information about CE devices and customer
   attributes of a 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
   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) [MPLS SEC].
   5.9 Security
   The suite of L3VPN solutions SHOULD support a range of security
   related features.  Higher levels of security services, like edge-to-
   edge encryption, authentication, or replay attack should be
   supported. More details on customer requirements for security are
   described in [VPNSEC].
   Security in a 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
   a site-to-site basis.
   If a a customer requires QoS support in a L3 VPN, then this request
   MUST be communicated to the SP either using unencrypted fields or
   else via an agreed  security association. For example, applications
   could send RSVP messages in support of Intserv either in the clear
   or encrypted using a key negotiated with the SP. Another case is
   where applications using an IPsec tunnel could copy the DSCP from
   the encrypted IP header to the header of the tunnelÆs IP header.
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   5.10  Migration Impact
   Often, customers are migrating from an already deployed private
   network toward one or more L3 VPN 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.
   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, mobile radio access, etc. 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
   A significant number of VPN users may not be permanently attached to
   one VPN site : in order to limit access to a VPN to only 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 automatically invoke all actions
   necessary to join a user to the VPN.
   A user SHOULD be able to access a L3VPN via a network having generic
   Internet access.
   Mobile users may move within a L3VPN site. Mobile users may also
   have temporary connections to different L3VPN site within the same
   VPN. Authentication SHOULD be provided for both of these cases.
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   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,
   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 5.1. Support for other physical
   connectivity scenarios with arbitrary topology is desirable.
   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 such 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 customerÆs requirements. The load
   balancing capability may also be used to achieve resiliency in the
   event of access connectivity failures. For example, in cases (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, and requires policy
   and service agreements between the SPs to interoperate).
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                  +----------------                    +---------------
                  |                                    |
               +------+                            +------+
     +---------|  PE  |                  +---------|  PE  |
     |         |router|                  |         |router| SP network
     |         +------+                  |         +------+
  +------+         |                  +------+         |
  |  CE  |         |                  |  CE  |         +---------------
  |device|         |   SP network     |device|         +---------------
  +------+         |                  +------+         |
     |         +------+                  |         +------+
     |         |  PE  |                  |         |  PE  |
     +---------|router|                  +---------|router| SP network
               +------+                            +------+
                   |                                   |
                   +----------------                   +---------------
                  (a)                                 (b)
                   +----------------                  +---------------
                   |                                  |
  +------+     +------+               +------+     +------+
  |  CE  |-----|  PE  |               |  CE  |-----|  PE  |
  |device|     |router|               |device|     |router| SP network
  +------+     +------+               +------+     +------+
     |             |                     |             |
     | Backdoor    |                     | Backdoor    +---------------
     | link        |   SP network        | link        +---------------
     |             |                     |             |
  +------+     +------+               +------+     +------+
  |  CE  |     |  PE  |               |  CE  |     |  PE  |
  |device|-----|router|               |device|-----|router| SP network
  +------+     +------+               +------+     +------+
                   |                                   |
                   +----------------                   +---------------
                  (c)                                  (d)
                   +----------------                   +---------------
                   |                                   |
  +------+     +------+               +------+     +------+
  |  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 5.1 Representative types of access arrangements.
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               Service requirements for Layer 3 PPVPNs     June, 2004
   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 L3 VPN 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 NAT 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 L3 VPN 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 be able to exchange traffic with devices outside the
   customerÆs L3 VPN.
   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 a L3
   L3VPN service. This MAY require that an ASP participates 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, 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
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   L3VPN solutions in such 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
   6.1 Scalability
   [PPVPN-GR} lists projections regarding L3VPN sizing  and scalability
   requirements and metrics related to specific solutions.
   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.
   A L3VPN solution MUST be able to assign blocks of addresses from its
   own public IP address space to L3VPN customer sites in such a way
   that advertisement of routes to other SPs and other sites aggregates
   A L3VPN solution MUST be able to use address assignments made by a
   customer. These customer assigned addresses may be public, or
   In the case where private IP addresses are used, a L3VPN solution
   MUST provide a means for an SP to translate such addresses to public
   IP addresses for communication with other VPNs 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., [RFC
   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.
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   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.
   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 [VPN
   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 securely exchange
   configuration information. The VPN information MUST include at least
   the IP address of the PE and may be extensible to provide additional
   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 SPÆs
   VPN network is correctly configured.
   The mechanism SHOULD respond to VPN membership changes in a timely
   manner. A "timely manner" 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
   Dynamically creating, changing, and managing multiple VPN
   assignments to sites and/or customers is another aspect of
   membership that MUST be addressed in a L3 VPN solution.
   6.5 SLA and SLS Support
   Typically, a Service Provider offering a L3VPN service commits to
   specific Service Level Specifications (SLS) as part of a contract
   with the customer, as described in section 4.4 and [PPVPN-GR]. Such
   a Service Level Agreement (SLA) implies SP requirements for
   measuring Specific Service Level Specifications (SLS) for quality,
   availability, response time, and configuration intervals.
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   6.6 Quality of Service (QoS) and Traffic Engineering
   A significant aspect of a 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, 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 a 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.
   As stated in RFC 2475, a mapping function from customer provided
   Diffserv marking to marking used in a SP network should be provided
   for L3 VPN services.
   In the case where a customer requires DSCP transparency, as
   described in section 5.5.2, a L3 VPN 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.
   Furthermore, the solution SHOULD provide an option that either
   allows, or prevents advertisement of VPN routes to the Internet.
   Ideally, the choice of a SP's IGP SHOULD not depend on the routing
   protocol(s) used between PE and CE routers in a PE-based VPN.
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   Furthermore, it is desirable that an SP SHOULD have a choice with
   regards to the IGP routing protocol.
   The additional routing burden that an SP must carry should be
   articulated in each specific L3 VPN solution.
   6.8 Isolation of Traffic and Routing
   The internal structure of a L3VPN network SHOULD not be visible to
   outside networks (i.e., 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.
   A L3VPN solution SHOULD provide a means for meeting L3VPN QoS SLA
   requirements that isolates VPN traffic from the affects 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 the need to protect service provider resources
   involved in supporting a 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
   the can do so.
   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 customerÆs 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 capable of being applied 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
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   not necessarily perceived by the customer but 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 [VPN
   A VPN solution MAY support one or more encryption schemes, including
   AES, 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
   Furthermore, traffic exchanged within the scope of VPN MAY involve
   several categories of equipment that must cooperate together 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 others 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
   - traffic between a CE and a PE,
   - traffic between CEs belonging to the same VPN,
   - CE or PE routers dealing with route announcements for a VPN,
   - policy decision point [RFC 3198] and a network element,
   - management station and an SNMP agent.
   Each L3VPN solution SHOULD describe for a peer authentication
   function: where it is 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, part of
   an extranet involving sites from other organizations, have access to
   the Internet, or any combination of these scopes of communication.
   Within these contexts, a site might be subject to various attacks
   coming from different sources. Potential sources of attack include:
   - users connected to the supporting public IP backbone,
   - users from the Internet,
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   - users from temporary sites belonging to the intranet and/or
   extranet VPN that the site is part of.
   Security threats and risks that a site may encounter include the
     - denial of service, for example mail spamming, access connection
     congestion, TCP SYN attacks, ping attacks, etc.
     - intrusion attempts, which may eventually lead to denial of
     service (e.g. a Trojan horse attack).
   Additional threat scenarios are defined in [VPNSEC]. A L3 VPN
   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 ASÆs 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 L3 VPNs defined in section 3.
   In each scenario, all applicable SP requirements, such as traffic
   and routing isolation, SLA's, management, security, provisioning,
   etc. MUST be preserved across adjacent ASÆs. The solutions MUST
   describe the inter-SP network interface, encapsulation method(s),
   routing protocol(s), and all applicable parameters [VPN IW].
   An essential pre-condition for an inter-AS VPN is an agreement
   between the AS's 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 [PPVPN-GR].
   6.10.1 Routing Protocols
   If the link between AS's is not trusted, routing protocols running
   between those AS's 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 AS's. A minimum subset of such capabilities is the
     - Diagnostic tools (e.g., ping, traceroute)
     - Secured access to one AS management system by another
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     - Configuration request and status query tools
     - Fault notification and trouble tracking tools
   6.10.3 Bandwidth and QoS Brokering
   When a VPN spans multiple AS's, there is a need for a brokering
   mechanism that requests certain SLA parameters, such as bandwidth
   and QoS, from the other domains and/or networks involved in
   transferring traffic to various sites. The essential requirement is
   that a solution MUST be able to determine whether a set of AS's can
   establish and guarantee uniform QoS in support of a L3VPN.
   The brokering mechanism can be a manual one, for example, where one
   provider requests from another provider a specific set of 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 SLA/QoS parameters. For
   instance, in the case of a L3 VPN 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-
   In the case of an automated function, which is desirable, the
   functionality supported SHOULD dynamically request and reserve
   certain QoS parameters such as bandwidth and priority, and then to
   classify, mark and handle the packets as agreed in the negotiation.
   Observe that as traffic might traverse multiple AS's, the brokering
   method should also allow this.
   It is not desirable to perform brokering on a per VPN basis since
   such an approach would not scale. A solution MUST provide some means
   of aggregating QoS and bandwidth brokering requests between AS's.
   One method could be for SP's 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 AS's supporting a L3 VPN service.
   6.10.4 Security Considerations
   If a tunnel traverses multiple SP networks and it 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 of section 7.5. For example, a provider
   should consider use of both authentication and encryption for a
   tunnel used as part of a 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
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   wholesale to another service provider, who then resells that VPN
   service to his or her customers.
   The wholesalerÆs VPN MUST be transparent to the addressing and
   routing used by the reseller.
   Support for additional levels of hierarchy, for example three levels
   where a reseller can again resell the VPN service to yet another VPN
   provider, SHOULD be provided.
   The CarrierÆs Carrier scenario is the name used in this document for
   this category of L3VPN wholesale (although some scenarios of Inter-
   AS/Inter-Provider VPN could possibly fall in this L3VPN wholesale
   category too). Various carrierÆs carrier scenarios should be
   supported, such as:
  - the customer Carriers do not operate L3VPN services for their
  - the customer Carriers operate L3VPN services for their clients,
     but these services are not linked with the L3VPN service offered
     by the CarriersÆ Carrier;
  - the customer Carriers operate L3VPN services for their clients and
     these services are linked with the L3VPN service offered by the
     CarriersÆ Carrier ("Hierarchical VPNs" scenario)
   6.12  Tunneling Requirements
   Connectivity between CE sites or PE devices in the backbone SHOULD
   be able to use a range of tunneling technologies, such as L2TP,
   IPSEC, GRE, IP-in-IP, MPLS, etc.
   To set up tunnels between routers, every router MUST support static
   configuration for tunneling and MAY support a tunnel setup protocol.
   If employed, a tunnel establishment protocol SHOULD be capable of
   conveying information, such as the following:
     - Relevant identifiers
     - QoS/SLA parameters
     - Restoration parameters
     - Multiplexing identifiers
     - Security parameters
   There MUST be a means to monitor the following aspects of tunnels:
     - Statistics, such as amount of time spent in the up and down
     - Count of transitions between the up and down state
     - Events, such as transitions between the up and down states
   The tunneling technology used by the VPN Service Provider and its
   associated mechanisms for tunnel establishment, multiplexing, and
   maintenance MUST meet the requirements on scaling, isolation,
   security, QoS, manageability, etc.
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   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.
   Some SPs MAY desire that a single network infrastructure should
   suffice for all services, public IP, VPNs, traffic engineering, and
   differentiated services [L2 VPN].
   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
   specifying the QoS aspects of SLAs for VPN service offerings.
   6.13.2 On-Demand Access Networks
   Service providers SHOULD be able to support temporary user access,
   as described in section 5.11.2 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 as
   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. In the case where 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, since they are currently used in a
   wide range of equipment and services.
   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, a L3VPN
   solution MUST provide restoration of access connectivity whenever
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   the primary access link from a CE site to a PE fails. This
   restoration 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 above, 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 rapidly redirect the
   traffic 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
   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 to not 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
   6.15  Interoperability
   Service providers are interested in interoperability in at least the
   following scenarios:
     - To facilitate use of PE and managed CE devices within a single SP
     - To implement L3VPN services across two or more interconnected SP
     - To achieve 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
   [VPN IW].
   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 a L3VPN
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   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 changing
   interworking or interconnection.
   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 having to use 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.
   7.1 Fault management
   Support for fault management includes:
   - indication of customers impacted by failure,
   - fault detection (incidents reports, alarms, failure
   - fault localization (analysis of alarms reports, diagnostics),
   - incident recording or logs, creation and follow through of trouble
   - corrective actions (traffic, routing, resource allocation).
   Since PE-based VPNs rely on a common network infrastructure, the NMS
   MUST provide a means to inform the provider on 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 the determination of corrective action.
   It is desirable to detect faults caused by configuration errors,
   because these may cause VPN service to fail, or not meet 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 that all
   constraints and consistency checks hold among tunnel configuration
   parameters at the various end points.
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   A capability to verify L3 reachability within a VPN MUST beprovided
   for diagnostic purposes.
   A capability to verify the parameter configuration of a device
   supporting a L3VPN MUST be provided for diagnostic purposes.
   7.2 Configuration Management
   Overall, the NMS must support configuration necessary to realize
   desired L3 reachability of a 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
   Since VPN configuration and topology are highly dependent upon a
   customer's organization, provisioning systems MUST address a broad
   range of customer specific requirements. The NMS MUST ensure that
   these devices and protocols are provisioned consistently and
   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 which, when instantiated, 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, 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
   or 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 which when instantiated 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 they
   can capture all service orders in some meaningful sense.
   The provider SHOULD provide means for translating instantiated
   service templates into device configurations so that associated
   services can be provisioned.
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   Finally, the approach SHOULD provide means for checking if 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,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 a L3 PE routers: intranet and extranet membership, CE
   routing protocol for each access connection, routing metrics,
   tunnels, etc.
   o The NMS SHOULD use identifiers for SPs, L3VPNs, PEs, CEs,
   hierarchical tunnels and access connections as described in section
   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
   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 a 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.
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   7.2.3 Provisioning Routing
   A means for a service provider to provision parameters for the IGP
   for a 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.
   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 and/or 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 dynamically provision
   resources associated with VPN services. 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 to cope with the frequent
   changes requests from customerÆs (e.g., sites joining or leaving a
   VPN), as well as to achieve scalability. The PEs SHOULD be able to
   dynamically assign the VPN resources. 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 Service Level Agreement
   (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
   A 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, backup, etc. It is outside of the
   scope of this document to define if and how these different services
   interact with the VPN in order 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, like DNS, NTP and RADIUS
   needed for ordinary network operation and management. The provider
   SHOULD be able to provide IP services to multiple VPN customers.
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   A firewall function MAY be required to restrict access to the L3VPN
   from the Internet [Y.1311].
   A managed firewall service MUST be carrier grade. For redundancy and
   failure recovery, a means for firewall fail-over should be provided.
   Managed firewall services that may be provided include dropping
   specified protocol types, intrusion protection, traffic-rate
   limiting against malicious attacks, etc.
   Managed firewalls MUST be supported on a per-VPN basis, although
   multiple VPNs may be supported by the same physical device (e.g., in
   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
   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 where the SLS is not met.
   A L3VPN solution MUST describe how the following accounting
   functions can be provided:
   - measurements of resource utilization,
   - collection of accounting information,
   - storage and administration of measurements.
   Some providers may require near-real time reporting of measurement
   information, and may offer this as part of a customer network
   management service.
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   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 to accounting requirements, as
   described in section 1.7 of RFC 2975.
   7.4 Performance Management
   Performance management MUST support functions involved with
   monitoring and collecting performance data regarding devices,
   facilities, and services, as well as determination of conformance to
   Service Level Specifications (SLS), such as QoS and availability
   Performance management SHOULD also support analysis of important
   aspects of a 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
   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.
   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.
   Carugi, McDysan et al Informational - Expires December 2004     38
               Service requirements for Layer 3 PPVPNs     June, 2004
   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 to only the resources and applications
   to which 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
   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 to prevent VPN access point spoofing.  VPN Access Point
   Spoofing is the 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 that, 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.
   Carugi, McDysan et al Informational - Expires December 2004     39
               Service requirements for Layer 3 PPVPNs     June, 2004
   The approach SHOULD identify any information not contained in a
   standard MIB related to FCAPS that is necessary to meet a generic
   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
   8 Security Considerations
   Security considerations occur at several levels and dimensions
   within L3 VPNs, as detailed within this document. This section
   provides a summary with references to supporting detailed
   The requirements in this document separate the notion of traditional
   security requirements, such as integrity, confidentiality, and
   authentication (as detailed in section Error! Reference source not
   found.) from that of 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 Error! Reference source not found. and 5.9, respectively.
   In an analogous manner, further detail on data and control traffic
   isolation requirements are given from the customer and service
   provider perspectives in sections 4.1 and 5.8, respectively.
   Additionally, references to a document [VPNSEC] specifically
   addressing security requirements are made where appropriate.
   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, the authors of the original IP VPN
   Carugi, McDysan et al Informational - Expires December 2004     40
               Service requirements for Layer 3 PPVPNs     June, 2004
   requirements and framework document [RFC 2764], 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 also 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 to the requirement could be obtained by reading the source
   10 References
   10.1  Normative References
    [PPVPN-GR]     Nagarajan, A., "Generic Requirements for Provider
                   Provisioned VPN," Work in Progress.
    [RFC 3377]     Hodges, J., Morgan, R. ôLightweight Directory Access
                   Protocol (v3): Technical Specification,ö RFC 3377,
                   September 2002
    [RFC 1918]     Rekhter, Y., et al., "Address Allocation for Private
                   Internets," RFC 1918, February 1996.
    [RFC 2026]     Bradner, S., "The Internet Standards Process --
                   Revision 3", BCP 9, RFC 2026, October 1996.
    [RFC 2119]     Bradner, S., "Key words for use in RFCs to Indicate
                   Requirement Levels", BCP 14, RFC 2119, March 1997
    [RFC 2205]     Braden, R., Ed., Zhang, L., Berson, S.,  Herzog, S.,
                   Jamin, S. "Resource ReSerVation Protocol (RSVP) --
                   Version 1 Functional Specification," September 1997.
    [RFC 2211]     Wroclawski, J., Specification of the Controlled-Load
                   Network Element Service, RFC 2211, IETF, September
    [RFC 2212]     Shenker, S., Partridge, C., Guerin, R., Specification
                   of Guaranteed Quality of Service, RFC 2212, IETF,
                   September 1997.
    [RFC 2251]     Wahl, M. et al., "Lightweight Directory Access
                   Protocol (v3)," RFC 2251, December 1997.
    [RFC 2475]     Blake, S., Black, D., Carlson, M., Davies, E., Wang,
                   Z., Weiss, W.  "An Architecture for Differentiated
                   Services", RFC  2475, Dec. 1998.
    [RFC 2597]     Baker, F., Heinanen, J., Weiss, W., Wroclawski, J.
                   "Assured Forwarding PHB Group", RFC 2597, June 1999.
    [RFC 2661]     Townsley, W. et al., "Layer Two Tunneling Protocol
                   "L2TP"," RFC 2661, August 1999.
    [RFC 2685]     Fox B., et al, "Virtual Private Networks Identifier",
                   RFC 2685, September 1999.
    [RFC 2983]     Black, D. ôDifferentiated Services and Tunnelsö,
                   RFC2983, October 2000
    [RFC 3031]     Rosen, E., Viswanathan, A., Callon, R.  "Multiprotocol
                   Label Switching Architecture," January 2001.
   Carugi, McDysan et al Informational - Expires December 2004     41
               Service requirements for Layer 3 PPVPNs     June, 2004
    [RFC 3246]     Davie, B., et al., "An Expedited Forwarding PHB", RFC
                   3246, March 2002.
    [RFC 3270]     Le Faucheur, F., et al., ôMulti-Protocol Label
                   Switching (MPLS) Support of Differentiated Services,ö
                   RFC 3270, May 2002
   10.2  Non-normative References
    [2547bis]      Rosen, E., Rekhter, Y. et al., "BGP/MPLS VPNs", work
                   in progress.
    [2917bis]      Muthukrishnan, K., et al., ô A Core MPLS IP VPN
                   Architectureö, work in progress
    [DOCSIS 1.1]   Data Over Cable Service Interface Specification
                   (DOCSIS), Cable Labs,
    [FRF.13]       Frame Relay Forum, "Service Level Definitions
                   Implementation Agreement," August, 1998.
    [IM-PPVPN]     Lago, P., et al., "An Information Model for Provider
                   Provisioned Virtual Private Networks," work in
    [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., ôAn Architecture for Provider Provisioned CE-
                   based Virtual Private Networks using IPsec,ö work in
    [IPSEC-PPVPN]  Gleeson, B., "Uses of IPsec with Provider
                   Provisioned VPNs," work in progress.
    [L2 MPLS]      Martini, L., et al., ôTransport of Layer 2 Frames
                   Over MPLS,ö work in progress.
    [L2 VPN]       Rosen, E., et al., "An Architecture for L2VPNs,"
                   work in progress.
    [L2 VPN]       Kompella, K., Bonica, R., "Whither Layer 2 VPNs?,"
                   work in progress.
    [MPLS SEC]     Behringer, M., "Analysis of the Security of the MPLS
                   Architecture," work in progress
    [PPVPN-TERM]   Andersson, L., Madsen, T., ôPPVPN Terminology,ö work
                   in progress
    [L3VPN-SEC]    Fang, L., et al., ôSecurity Framework for Provider
                   Provisioned Virtual Private Networks,ö work in
    [NBVPN-FR]     Suzuki, M. and Sumimoto, J. (editors), "A framework
                   for Network-based VPNs", 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.
   Carugi, McDysan et al Informational - Expires December 2004     42
               Service requirements for Layer 3 PPVPNs     June, 2004
    [RFC 2547]     Rosen, E., Rekhter, Y., ôBGP/MPLS VPNs,ö RFC 2547,
                   March 1999.
    [RFC 2764]     Gleeson, B., et al., "A Framework for IP based Virtual
                   Private Networks", RFC 2764, February 2000.
    [RFC 2975]     Aboba, B., et al., "Introduction to Accounting
                   Management," October 2000.
    [RFC 3198]     Westerinen, A., et al., "Terminology for Policy-Based
                   Management," November, 2001.
    [TE-INTERAS]   Le Roux, JL., Boyle, J., et al., ôRequirements for
                   Inter-area MPLS Traffic Engineering,ö work in
    [VPN DISC]     Squire, M. et al., "VPN Discovery Discussions and
                   Options," work in progress.
    [VPN IW]       Kurakami, H., et al., "Provider-Provisioned VPNs
                   Interworking," work in progress.
    [VPN SEC]      De Clercq, J., et al., "Considerations about
                   possible security extensions to BGP/MPLS VPN," work
                   in progress.
    [VPN TUNNEL]   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.1241]       "IP Transfer Capability for the support of IP based
                   Services", Y.1241 ITU-T  Recommendation, January 2001.
    [Y.1311.1]     Carugi, M. (editor), "Network Based IP VPN over MPLS
                   architecture",Y.1311.1 ITU-T Recommendation, July2001.
    [Y.1311]       Knightson, K. (editor), " Network based VPNs  -
                   Generic Architectureand Service Requirements ", Y.1311
                   ITU-T Recommendation, March 2002.
   11 Authors' address
   Marco Carugi (Co-editor)
   Nortel Networks
   Parc d'activit‰s de Magny-Les Jeunes Bois  CHATEAUFORT
   78928 YVELINES Cedex 9  - FRANCE
   EMail: marco.carugi@nortelnetworks.com
   Dave McDysan (Co-editor)
   22001 Loudoun County Parkway
   Ashburn, VA 20147, USA
   EMail: dave.mcdysan@mci.com
   Luyuan Fang
   Carugi, McDysan et al Informational - Expires December 2004     43
               Service requirements for Layer 3 PPVPNs     June, 2004
   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
   EMail: rick.wilder@alcatel.com
   Full copyright statement
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   Carugi, McDysan et al Informational - Expires December 2004     44

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