





Network Working Group                                   W. Augustyn, Ed.
Request for Comments: 4665                               Y. Serbest, Ed.
Category: Informational                                             AT&T
                                                          September 2006


                   Service Requirements for Layer 2
             Provider-Provisioned Virtual Private Networks

Status of This Memo

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

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document provides requirements for Layer 2 Provider-Provisioned
   Virtual Private Networks (L2VPNs).  It first provides taxonomy and
   terminology and states generic and general service requirements.  It
   covers point-to-point VPNs, referred to as Virtual Private Wire
   Service (VPWS), as well as multipoint-to-multipoint VPNs, also known
   as Virtual Private LAN Service (VPLS).  Detailed requirements are
   expressed from both a customer as well as a service provider
   perspectives.






















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Table of Contents

   1. Introduction ....................................................4
      1.1. Scope of This Document .....................................4
      1.2. Outline ....................................................5
   2. Conventions used in this document ...............................5
   3. Contributing Authors ............................................5
   4. Definitions and Taxonomy ........................................5
      4.1. Definitions ................................................5
      4.2. Taxonomy of L2VPN Types ....................................6
      4.3. VPWS .......................................................6
      4.4. VPLS .......................................................7
   5. Service Requirements Common to Customers and Service Providers ..7
      5.1. Scope of emulation .........................................8
      5.2. Traffic Types ..............................................8
      5.3. Topology ...................................................8
      5.4. Isolated Exchange of Data and Forwarding Information .......9
      5.5. Security ...................................................9
           5.5.1. User Data Security .................................10
           5.5.2. Access Control .....................................10
      5.6. Addressing ................................................11
      5.7. Quality of Service ........................................11
           5.7.1. QoS Standards ......................................11
           5.7.2. Service Models .....................................11
      5.8. Service Level Specifications ..............................12
      5.9. Protection and Restoration ................................12
      5.10. CE-to-PE and PE-to-PE Link Requirements ..................12
      5.11. Management ...............................................12
      5.12. Interoperability .........................................12
      5.13. Inter-working ............................................13
   6. Customer Requirements ..........................................13
      6.1. Service Provider Independence .............................13
      6.2. Layer 3 Support ...........................................13
      6.3. Quality of Service and Traffic Parameters .................14
      6.4. Service Level Specification ...............................14
      6.5. Security ..................................................14
           6.5.1. Isolation ..........................................14
           6.5.2. Access Control .....................................14
           6.5.3. Value-Added Security Services ......................15
      6.6. Network Access ............................................15
           6.6.1. Physical/Link Layer Technology .....................15
           6.6.2. Access Connectivity ................................15
      6.7. Customer Traffic ..........................................17
           6.7.1. Unicast, Unknown Unicast, Multicast, and
                  Broadcast forwarding ...............................17
           6.7.2. Packet Re-ordering .................................17
           6.7.3. Minimum MTU ........................................17
           6.7.4. End-point VLAN Tag Translation .....................18



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           6.7.5. Transparency .......................................18
      6.8. Support for Layer 2 Control Protocols .....................18
      6.9. CE Provisioning ...........................................19
   7. Service Provider Network Requirements ..........................19
      7.1. Scalability ...............................................19
           7.1.1. Service Provider Capacity Sizing Projections .......19
           7.1.2. Solution-Specific Metrics ..........................19
      7.2. Identifiers ...............................................19
      7.3. Discovering L2VPN Related Information .....................19
      7.4. Quality of Service (QoS) ..................................20
      7.5. Isolation of Traffic and Forwarding Information ...........20
      7.6. Security ..................................................21
      7.7. Inter-AS/SP L2VPNs ........................................22
           7.7.1. Management .........................................22
           7.7.2. Bandwidth and QoS Brokering ........................22
      7.8. L2VPN Wholesale ...........................................23
      7.9. Tunneling Requirements ....................................23
      7.10. Support for Access Technologies ..........................23
      7.11. Backbone Networks ........................................24
      7.12. Network Resource Partitioning and Sharing Between
            L2VPNs ...................................................24
      7.13. Interoperability .........................................24
      7.14. Testing ..................................................25
      7.15. Support on Existing PEs ..................................25
   8. Service Provider Management Requirements .......................26
   9. Engineering Requirements .......................................26
      9.1. Control Plane Requirements ................................26
      9.2. Data Plane Requirements ...................................27
           9.2.1. Encapsulation ......................................27
           9.2.2. Responsiveness to Congestion .......................27
           9.2.3. Broadcast Domain ...................................27
           9.2.4. Virtual Switching Instance .........................27
           9.2.5. MAC Address Learning ...............................27
   10. Security Considerations .......................................28
   11. Acknowledgements ..............................................28
   12. References ....................................................29
      12.1. Normative References .....................................29
      12.2. Informative References ...................................29













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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 for provider-provisioned Layer 2
   Virtual Private Networks (L2VPN).  It identifies requirements that
   MAY apply to one or more individual approaches that a Service
   Provider (SP) may use for the provisioning of a Layer 2 VPN service.
   The content of this document makes use of the terminology defined in
   [RFC4026] and common components for deploying L2VPNs described in
   [RFC4664].

   The technical specifications to provide L2VPN services are outside
   the scope of this document.  The framework document [RFC4664] and
   several other documents, which explain technical approaches providing
   L2VPN services, such as [VPLS_LDP], [VPLS_BGP], and [IPLS], are
   available to cover this aspect.

   This document describes requirements for two types of L2VPNs: (1)
   Virtual Private Wire Service (VPWS), and (2) Virtual Private LAN
   Service (VPLS).  The approach followed in this document distinguishes
   L2VPN types as to how the connectivity is provided (point-point or
   multipoint-multipoint), as detailed in [RFC4664].

   This document is intended as a "checklist" of requirements that will
   provide a consistent way to evaluate and document how well each
   individual approach satisfies specific requirements.  The
   applicability statement document for each individual approach should
   document the results of this evaluation.

   In the context of provider-provisioned VPNs, there are two entities
   involved in operation of such services, the Provider and the
   Customer.  The Provider engages in a binding agreement with the
   Customer as to the behavior of the service in a normal situation as
   well as in exceptional situations.  Such agreement is known as
   Service Level Specification (SLS), which is part of the Service Level
   Agreement (SLA) established between the Provider and the Customer.

   A proper design of L2VPNs aids formulation of SLSes in that it
   provides means for proper separation between Customer Edge (CE) and
   Provider Edge (PE), allows proper execution of the SLS offer, and
   supports a flexible and rich set of capabilities.

   This document provides requirements from both the Provider's and the
   Customer's point of view.  It begins with common customer's and
   service provider's point of view, followed by a customer's



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   perspective, and concludes with specific needs of an SP.  These
   requirements provide high-level L2VPN features expected by an SP in
   provisioning L2VPNs, which include SP requirements for security,
   privacy, manageability, interoperability, and scalability.

1.2.  Outline

   The outline of the rest of this document is as follows.  Section 4
   provides definitions and taxonomy.  Section 5 provides common
   requirements that apply to both customer and SP, respectively.
   Section 6 states requirements from a customer perspective.  Section 7
   states network requirements from an SP perspective.  Section 8 states
   SP management requirements.  Section 9 describes the engineering
   requirements, particularly control and data plane requirements.
   Section 10 provides security considerations.  Section 11 lists
   acknowledgements.  Section 12 provides a list of references cited
   herein.

2.  Conventions used in this document

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

3.  Contributing Authors

   This document was the combined effort of several individuals.  The
   following are the authors that contributed to this document:

   Waldemar Augustyn
   Marco Carugi
   Giles Heron
   Vach Kompella
   Marc Lasserre
   Pascal Menezes
   Hamid Ould-Brahim
   Tissa Senevirathne
   Yetik Serbest

4.  Definitions and Taxonomy

4.1.  Definitions

   The terminology used in this document is defined in [RFC4026].  The
   L2VPN framework document [RFC4664] further describes these concepts
   in the context of a reference model that defines layered service
   relationships between devices and one or more levels of tunnels.




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4.2.  Taxonomy of L2VPN Types

   The requirements distinguish two major L2VPN models, a Virtual
   Private Wire Service (VPWS), and a Virtual Private LAN Service
   (VPLS).

   The following diagram shows an L2VPN reference model.

   +-----+                                       +-----+
   + CE1 +--+                                +---| CE2 |
   +-----+  |    ........................    |   +-----+
   L2VPN A  |  +----+                +----+  |   L2VPN A
            +--| PE |--- Service  ---| PE |--+
               +----+    Provider    +----+
              /  .       Backbone       .  \     -   /\-_
   +-----+   /   .          |           .   \   / \ /   \     +-----+
   + CE4 +--+    .          |           .    +--\ Access \----| CE5 |
   +-----+       .        +----+        .       | Network |   +-----+
   L2VPN B       .........| PE |.........        \       /    L2VPN B
                          +----+     ^            -------
                            |        |
                            |        |
                         +-----+     |
                         | CE3 |     +-- Logical switching instance
                         +-----+
                         L2VPN A

                     Figure 1.  L2VPN Reference Model

4.3.  VPWS

   The PE devices provide a logical interconnect such that a pair of CE
   devices appears to be connected by a single logical Layer 2 circuit.
   PE devices act as Layer 2 circuit switches.  Layer 2 circuits are
   then mapped onto tunnels in the SP network.  These tunnels can either
   be specific to a particular VPWS, or be shared among several
   services.  VPWS applies for all services, including Ethernet, ATM,
   Frame Relay, etc.  In Figure 1, L2VPN B represents a VPWS case.

   Each PE device is responsible for allocating customer Layer 2 frames
   to the appropriate VPWS and for proper forwarding to the intended
   destinations.









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4.4.  VPLS

   In case of VPLS, the PE devices provide a logical interconnect such
   that CE devices belonging to a specific VPLS appear to be connected
   by a single LAN.  End-to-end VPLS consists of a bridge module and a
   LAN emulation module ([RFC4664]).  A VPLS can contain a single VLAN
   or multiple VLANs ([IEEE_802.1Q]).  A variation of this service is
   IPLS ([RFC4664]), which is limited to supporting only customer IP
   traffic.

   In a VPLS, a customer site receives Layer 2 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
   Layer 2 header, such as a MAC destination address.  In Figure 1,
   L2VPN A represents a VPLS case.

   The details of VPLS reference model, which we summarize here, can be
   found in [RFC4664].  In VPLS, the PE can be viewed as containing a
   Virtual Switching Instance (VSI) for each L2VPN that it serves.  A CE
   device attaches, possibly through an access network, to a bridge
   module of a PE.  Within the PE, the bridge module attaches, through
   an Emulated LAN Interface to an Emulated LAN.  For each VPLS, there
   is an Emulated LAN instance.  The Emulated LAN consists of VPLS
   Forwarder module (one per PE per VPLS service instance) connected by
   pseudo wires (PW), where the PWs may be traveling through Packet
   Switched Network (PSN) tunnels over a routed backbone.  VSI is a
   logical entity that contains a VPLS forwarder module and part of the
   bridge module relevant to the VPLS service instance [RFC4664].
   Hence, the VSI terminates PWs for interconnection with other VSIs and
   also terminates Attachment Circuits (ACs) (see [RFC3985] for
   definition) for accommodating CEs.  A VSI includes the forwarding
   information base for an L2VPN [RFC4664] which is the set of
   information regarding how to forward Layer 2 frames received over the
   AC from the CE to VSIs in other PEs supporting the same L2VPN service
   (and/or to other ACs), and it contains information regarding how to
   forward Layer 2 frames received from PWs to ACs.  Forwarding
   information bases can be populated dynamically (such as by source MAC
   address learning) or statically (e.g., by configuration).  Each PE
   device is responsible for proper forwarding of the customer traffic
   to the appropriate destination(s) based on the forwarding information
   base of the corresponding VSI.

5.  Service Requirements Common to Customers and Service Providers

   This section contains requirements that apply to both the customer
   and the provider, or that are of an otherwise general nature.





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5.1.  Scope of emulation

   L2VPN protocols SHOULD NOT interfere with existing Layer 2 protocols
   and standards of the Layer 2 network the customer is managing.  If
   they impact customer Layer 2 protocols that are sent over the VPLS,
   then these impacts MUST be documented.

   Some possibly salient differences between VPLS and a real LAN are:

   - The reliability may likely be less, i.e., the probability that a
     message broadcast over the VPLS is not seen by one of the bridge
     modules in PEs is higher than in a true Ethernet.

   - VPLS frames can get duplicated if the PW sequencing option isn't
     turned on.  The data frames on the PWs are sent in IP datagrams,
     and under certain failure scenarios, IP networks can duplicate
     packets.  If the PW data transmission protocol does not ensure
     sequence of data packets, frames can be duplicated or received out
     of sequence.  If the customer's Bridge Protocol Data Unit (BPDU)
     frames are sent as data packets, then BPDU frames can be duplicated
     or mis-sequenced, although this may not create any problems for
     Real-Time Streaming Protocol (RSTP).

   - Delayed delivery of packets (e.g., more than half a second), rather
     than dropping them, could have adverse effect on the performance of
     the service.

   - 802.3x Pause frames will not be transported over a VPLS, as the
     bridge module ([RFC4664]) in the PE terminates them.

   - Since the IPLS solution aims at transporting encapsulated traffic
     (rather than Layer 2 frames themselves), the IPLS solution is NOT
     REQUIRED to preserve the Layer 2 Header transparently from CE to
     CE.  For example, Source MAC address will probably not be preserved
     by the IPLS solution.

5.2.  Traffic Types

   A VPLS MUST support unicast, multicast, and broadcast traffic.
   Support for efficient replication of broadcast and multicast traffic
   is highly desirable.

5.3.  Topology

   A SP network may be realized using one or more network tunnel
   topologies to interconnect PEs, ranging from simple point-to-point to
   distributed hierarchical arrangements.  The typical topologies
   include:



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      - Point-to-point
      - Point-to-multipoint, a.k.a. hub and spoke
      - Any-to-any, a.k.a. full mesh
      - Mixed, a.k.a. partial mesh
      - Hierarchical

   Regardless of the SP topology employed, the service to the customers
   MUST retain the connectivity type implied by the type of L2VPN.  For
   example, a VPLS MUST allow multipoint-to-multipoint connectivity even
   if it is implemented with point-to-point circuits.  This requirement
   does not imply that all traffic characteristics (such as bandwidth,
   QoS, delay, etc.) necessarily be the same between any two end points
   of an L2VPN.  It is important to note that SLS requirements of a
   service have a bearing on the type of topology that can be used.

   To the extent possible, an L2VPN service SHOULD be capable of
   crossing multiple administrative boundaries.

   To the extent possible, the L2VPN services SHOULD be independent of
   access network technology.

5.4.  Isolated Exchange of Data and Forwarding Information

   L2VPN solutions SHALL define means that prevent CEs in an L2VPN from
   interaction with unauthorized entities.

   L2VPN solutions SHALL avoid introducing undesired forwarding
   information that could corrupt the L2VPN forwarding information base.

   A means to constrain or isolate the distribution of addressed data to
   only those VPLS sites determined either by MAC learning and/or
   configuration MUST be provided.

   The internal structure of an L2VPN SHOULD not be advertised or
   discoverable from outside that L2VPN.

5.5.  Security

   A range of security features MUST be supported by the suite of L2VPN
   solutions.  Each L2VPN solution MUST state which security features it
   supports and how such features can be configured on a per-customer
   basis.

   A number of security concerns arise in the setup and operation of an
   L2VPN, ranging from misconfigurations to attacks that can be launched
   on an L2VPN and can strain network resources such as memory space,
   forwarding information base table, bandwidth, and CPU processing.




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   This section lists some potential security hazards that can result
   due to mis-configurations and/or malicious attacks.  There MUST be
   methods available to protect against the following situations.

   - Protocol attacks
     o Excessive protocol adjacency setup/teardown
     o Excessive protocol signaling/withdrawal

   - Resource Utilization
     o Forwarding plane replication (VPLS)
     o Looping (VPLS primarily)
     o MAC learning table size limit (VPLS)

   - Unauthorized access
     o Unauthorized member of VPN
     o Incorrect customer interface
     o Incorrect service delimiting VLAN tag
     o Unauthorized access to PE

   - Tampering with signaling
     o Incorrect FEC signaling
     o Incorrect PW label assignment
     o Incorrect signaled VPN parameters (e.g., QoS, MTU, etc.)

   - Tampering with data forwarding
     o Incorrect MAC learning entry
     o Incorrect PW label
     o Incorrect AC identifier
     o Incorrect customer facing encapsulation
     o Incorrect PW encapsulation
     o Hijacking PWs using the wrong tunnel
     o Incorrect tunnel encapsulation

5.5.1.  User Data Security

   An L2VPN solution MUST provide traffic separation between different
   L2VPNs.

   In case of VPLS, VLAN Ids MAY be used as service delimiters.  When
   used in this manner, they MUST be honored and traffic separation MUST
   be provided.

5.5.2.  Access Control

   An L2VPN solution MAY also have the ability to activate the
   appropriate filtering capabilities upon request of a customer.





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5.6.  Addressing

   An L2VPN solution MUST support overlapping addresses of different
   L2VPNs.  For instance, customers MUST NOT be prevented from using the
   same MAC addresses with different L2VPNs.  If a service provider uses
   VLANs as service delimiters, the L2VPN solution MUST ensure that VLAN
   Ids cannot overlap.  If VLANs are not used as service delimiters,
   L2VPN solutions MAY allow VLAN Ids to overlap.

5.7.  Quality of Service

   To the extent possible, L2VPN QoS SHOULD be independent of the access
   network technology.

5.7.1.  QoS Standards

   As provided in [RFC3809], an L2VPN SHALL be able to support QoS in
   one or more of the following already standardized modes:

   - Best Effort  (support mandatory for all provider-provisioned
                  VPN types)

   - Aggregate CE Interface Level QoS (i.e., 'hose' level)

   - Site-to-site, or 'pipe' level QoS

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

   Mappings or translations of Layer 2 QoS parameters into PSN QoS
   (e.g., DSCPs or MPLS EXP field) as well as QoS mapping based on VC
   (e.g., FR/ATM or VLAN) MAY be performed in order to provide QoS
   transparency.  The actual mechanisms for these mappings or
   translations are outside the scope of this document.  In addition,
   the Diffserv support of underlying tunneling technologies (e.g.,
   [RFC3270] or [RFC3308]) and the Intserv model ([RFC2205]) MAY be
   used.  As such, the L2VPN SLS requirements SHOULD be supported by
   appropriate core mechanisms.

5.7.2.  Service Models

   A service provider may desire to offer QoS service to a customer for
   at least the following generic service types: managed access VPN
   service or an edge-to-edge QoS service.  The details of the service
   models can be found in [RFC3809] and in [RFC4031].

   In L2VPN service, both DSCP ([RFC2474]) and 802.1p ([IEEE_802.1D])
   fields may be used for this purpose.



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5.8.  Service Level Specifications

   For an L2VPN service, the capabilities for Service Level
   Specification (SLS) monitoring and reporting stated in [RFC3809]
   SHOULD be provided.

5.9.  Protection and Restoration

   The L2VPN service infrastructure SHOULD provide redundant paths to
   ensure high availability.  The reaction to failures SHOULD result in
   an attempt to restore the service using alternative paths.

   The intention is to keep the restoration time small.  The restoration
   time MUST be less than the time it takes the CE devices, or customer
   Layer 2 control protocols as well as Layer 3 routing protocols, to
   detect a failure in the L2VPN.

5.10.  CE-to-PE and PE-to-PE Link Requirements

   The CE-to-PE links MAY be

   - direct physical links (e.g., 100BaseTX, and T1/E1 TDM),
   - logical links (e.g., ATM PVC, and RFC2427-encapsulated link),
   - transport networks carrying Ethernet,
   - a Layer 2 tunnel that goes through a Layer 3 network (e.g., L2TP
     sessions).

   Layer 2 frames MAY be tunneled through a Layer 3 backbone from PE to
   PE, using one of a variety of tunneling technologies (e.g., IP-in-IP,
   GRE, MPLS, L2TP, etc.).

5.11.  Management

   Standard interfaces to manage L2VPN services MUST be provided (e.g.,
   standard SNMP MIB Modules).  These interfaces SHOULD provide access
   to configuration, verification and runtime monitoring protocols.

   Service management MAY include the TMN 'FCAPS' functionalities, as
   follows: Fault, Configuration, Accounting, Performance, and Security,
   as detailed in [ITU_Y.1311.1].

5.12.  Interoperability

   Multi-vendor interoperability, which corresponds to similar network
   and service levels among different implementations, at the network
   element SHOULD be guaranteed.  This will likely rely on the
   completeness of the corresponding standard.




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   The technical solution MUST be multi-vendor interoperable, not only
   within the SP network infrastructure, but also with the customer's
   network equipment and services making use of the L2VPN service.

   A L2VPN solution SHOULD NOT preclude different access technologies.
   For instance, customer access connections to an L2VPN service MAY be
   different at different CE devices (e.g., Frame Relay, ATM, 802.1D,
   MPLS).

5.13.  Inter-working

   Inter-working scenarios among different solutions providing L2VPN
   services are highly desirable.  It is possible to have cases that
   require inter-working or interconnection between customer sites,
   which span network domains with different L2VPN solutions or
   different implementations of the same approach.  Inter-working SHOULD
   be supported in a scalable manner.

   Inter-working scenarios MUST consider at least traffic 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.

6.  Customer Requirements

   This section captures requirements from a customer perspective.

6.1.  Service Provider Independence

   Customers MAY require L2VPN service that spans multiple
   administrative domains or SP networks.  Therefore, an L2VPN service
   MUST be able to span multiple AS and SP networks but still to act and
   to appear as a single, homogeneous L2VPN from a customer point of
   view.

   A customer might also start with an L2VPN provided in a single AS
   with a certain SLS but then ask for an expansion of the service
   spanning multiple ASes and/or multiple-SPs.  In this case, as well as
   for all kinds of multi-AS and multiple-SP L2VPNs, L2VPN service
   SHOULD be able to deliver the same SLS to all sites in a VPN
   regardless of the AS/SP to which it homes.

6.2.  Layer 3 Support

   With the exception of IPLS, an L2VPN service SHOULD be agnostic to
   customer's Layer 3 traffic (e.g., IP, IPX, Appletalk) encapsulated
   within Layer 2 frames.



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   IPLS MUST allow transport of customer's IPv4 and IPv6 traffic
   encapsulated within Layer 2 frames.  IPLS SHOULD also allow CEs to
   run ISIS and MPLS protocols transparently among them when those are
   used in conjunction with IP.

6.3.  Quality of Service and Traffic Parameters

   QoS is expected to be an important aspect of an L2VPN service for
   some customers.

   A customer requires that the L2VPN service provide the QoS applicable
   to his or her application, which can range from PWs (e.g., SONET
   emulation) to voice, interactive video, and multimedia applications.
   Hence, best-effort as well as delay and loss sensitive traffic MUST
   be supported over an L2VPN service.  A customer application SHOULD
   experience consistent QoS independent of the access network
   technology used at different sites connected to the same L2VPN.

6.4.  Service Level Specification

   Most customers simply want their applications to perform well.  A SLS
   is a vehicle for a customer to measure the quality of the service
   that SP(s) provide.  Therefore, when purchasing a service, a customer
   requires access to the measures from the SP(s) that support the SLS.

   Standard interfaces to monitor usage of L2VPN services SHOULD be
   provided (e.g., standard SNMP MIB Modules).

6.5.  Security

6.5.1.  Isolation

   An L2VPN solution MUST provide traffic as well as forwarding
   information base isolation for customers similar to that obtained in
   private lines, FR, or ATM services.

   An L2VPN service MAY use customer VLAN Ids as service delimiters.  In
   that case, they MUST be honored, and traffic separation MUST be
   provided.

6.5.2.  Access Control

   An L2VPN solution MAY have the mechanisms to activate the appropriate
   filtering capabilities upon request of a customer.  For instance, MAC
   and/or VLAN filtering MAY be considered between CE and PE for a VPLS.






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6.5.3.  Value-Added Security Services

   An L2VPN solution MAY provide value-added security services such as
   encryption and/or authentication of customer packets, certificate
   management, and similar services.

   L2VPN services MUST NOT interfere with the security mechanisms
   employed at Layer 3 and higher layers by customers.  Layer 2 security
   mechanisms, such as 802.10b ([IEEE_802.10]) and 802.1AE
   ([IEEE_802.1AE]), MAY inhibit L2VPN services, when the service
   delimiting VLAN Ids are encrypted.

6.6.  Network Access

   Every 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 L2VPN.

6.6.1.  Physical/Link Layer Technology

   L2VPN solutions 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.

6.6.2.  Access Connectivity

   Various types of physical connectivity scenarios MUST be supported,
   such as multi-homed sites, backdoor links between customer sites, and
   devices homed to two or more SP networks.  In case of VPLS, IEEE
   802.3ad-2000 link aggregation SHOULD be supported.  L2VPN solutions
   SHOULD support at least the types of physical or link-layer
   connectivity arrangements shown in Figures 2 - 4 (in addition to the
   case shown in Figure 1).  As in Figure 2, a CE can be dual-homed to
   an SP or to two different SPs via diverse access networks.















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RFC 4665            Service Requirements for L2VPNs       September 2006


                   +----------------                    +---------------
                   |                                    |
                +------+                            +------+
      +---------|  PE  |                  +---------|  PE  |
      |         |device|                  |         |device| SP network
      |         +------+                  |         +------+
   +------+         |                  +------+         |
   |  CE  |         |                  |  CE  |         +---------------
   |device|         |   SP network     |device|         +---------------
   +------+         |                  +------+         |
      |         +------+                  |         +------+
      |         |  PE  |                  |         |  PE  |
      +---------|device|                  +---------|device| SP network
                +------+                            +------+
                    |                                   |
                    +----------------                   +---------------
                   (a)                                 (b)

                Figure 2.  Dual-Homed Access of CE Devices

   Resiliency of the L2VPN service can be further enhanced as shown in
   Figure 3, where CE's connected via a "back door" connection, connect
   to the same SP or to different SPs.

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

               Figure 3.  Backdoor Links Between CE Devices

   Arbitrary combinations of the above methods, with a few examples
   shown in Figure 4, SHOULD be supported by any L2VPN solution.





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                    +----------------                   +---------------
                    |                                   |
   +------+     +------+               +------+     +------+
   |  CE  |-----|  PE  |               |  CE  |-----|  PE  |
   |device|     |device|               |device|     |device| SP network
   +------+\    +------+               +------+\    +------+
      |     \       |                     |     \       |
      |Back  \      |                     |Back  \      +-------------
      |door   \     |   SP network        |door   \     +-------------
      |link    \    |                     |link    \    |
   +------+     +------+               +------+     +------+
   |  CE  |     |  PE  |               |  CE  |     |  PE  |
   |device|-----|device|               |device|-----|device| SP network
   +------+     +------+               +------+     +------+
                    |                                   |
                    +----------------                   +---------------
                   (a)                                 (b)

                Figure 4.  Combination of Dual-Homing and
                           Backdoor Links for CE Devices

6.7.  Customer Traffic

6.7.1.  Unicast, Unknown Unicast, Multicast, and Broadcast forwarding

   A VPLS MUST deliver every packet at least to its intended
   destination(s) within the scope of the VPLS, subject to the ingress
   policing and security policies.

6.7.2.  Packet Re-ordering

   During normal operation, the queuing and forwarding policies SHOULD
   preserve packet order for packets with the same QoS parameters.

6.7.3.  Minimum MTU

   A VPLS MUST support the theoretical MTU of the offered service.

   The committed minimum MTU size MUST be the same for a given VPLS
   instance.  Different L2VPN services MAY have different committed MTU
   sizes.  If the customer VLANs are used as service delimiters, all
   VLANs within a given VPLS MUST inherit the same MTU size.

   A VPLS MAY use IP fragmentation if it presents reassembled packets at
   VPLS customer edge devices.






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6.7.4.  End-point VLAN Tag Translation

   The L2VPN service MAY support translation of customers' AC
   identifiers (e.g., VLAN tags, if the customer VLANs are used as
   service delimiters).  Such service simplifies connectivity of sites
   that want to keep their AC assignments or sites that belong to
   different administrative domains.  In the latter case, the
   connectivity is sometimes referred to as Layer 2 extranet.  On the
   other hand, it should be noted that VLAN tag translation affects the
   support for multiple spanning trees (i.e., 802.1s [IEEE_802.1s]) and
   can break the proper operation.

6.7.5.  Transparency

   The L2VPN service is intended to be transparent to Layer 2 customer
   networks.  An L2VPN solution SHOULD NOT require any special packet
   processing by the end users before sending packets to the provider's
   network.

   If VLAN Ids are assigned by the SP, then VLANs are not transparent.
   Transparency does not apply in this case, as it is the same as FR/ATM
   service model.

   Since the IPLS solution aims at transporting encapsulated traffic
   (rather than Layer 2 frames themselves), the IPLS solution MUST not
   alter the packets encapsulated inside Layer 2 frames that are
   transported by the IPLS.  However, the IPLS solution is NOT REQUIRED
   to preserve the Layer 2 header transparently from CE to CE.  For
   example, Source MAC address might not be preserved by the IPLS
   solution.  The IPLS solution MAY remove Layer 2 headers for transport
   over the backbone when those can be reconstructed on egress without
   compromising transport of encapsulated traffic.

6.8.  Support for Layer 2 Control Protocols

   The L2VPN solution SHOULD allow transparent operation of Layer 2
   control protocols employed by customers.

   In case of VPLS, the L2VPN service MUST ensure that loops be
   prevented.  This can be accomplished with a loop-free topology or
   appropriate forwarding rules.  Control protocols such as Spanning
   Tree (STP) or similar protocols could be employed.  The L2VPN
   solution MAY use indications from customer Layer 2 control protocols,
   e.g., STP BPDU snooping, to improve the operation of a VPLS.







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6.9.  CE Provisioning

   The L2VPN solution MUST require only minimal or no configuration on
   the CE devices, depending on the type of CE device that connects into
   the infrastructure.

7.  Service Provider Network Requirements

   This section describes requirements from an SP perspective.

7.1.  Scalability

   This section contains projections regarding L2VPN sizing and
   scalability requirements and metrics specific to particular
   solutions.

7.1.1.  Service Provider Capacity Sizing Projections

   [RFC3809] lists projections regarding L2VPN sizing and scalability
   requirements and metrics.  The examples are provided in [RFC3809].

7.1.2.  Solution-Specific Metrics

   Each L2VPN solution SHALL document its scalability characteristics in
   quantitative terms.

7.2.  Identifiers

   An SP domain MUST be uniquely identified at least within the set of
   all interconnected SP networks when supporting an L2VPN that spans
   multiple SPs.  Ideally, this identifier SHOULD be globally unique
   (e.g., an AS number).

   An identifier for each L2VPN SHOULD be unique, at least within each
   SP's network, as it MAY be used in auto-discovery, management (e.g.,
   alarm and service correlation, troubleshooting, performance
   statistics collection), and signaling.  Ideally, the L2VPN identifier
   SHOULD be globally unique to support the case, where an L2VPN spans
   multiple SPs (e.g., [RFC2685]).  Globally unique identifiers
   facilitate the support of inter-AS/SP L2VPNs.

7.3.  Discovering L2VPN Related Information

   Configuration of PE devices (i.e., U-PE and N-PE [RFC4664]) is a
   significant task for an SP.  Solutions SHOULD provide methods that
   dynamically allow L2VPN information to be discovered by the PEs to
   minimize the configuration steps.




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   Each device in an L2VPN SHOULD be able to determine which other
   devices belong to the same L2VPN.  Such a membership discovery scheme
   MUST prevent unauthorized access, and it allows authentication of the
   source.

   Distribution of L2VPN information SHOULD be limited to those devices
   involved in that L2VPN.  An L2VPN solution SHOULD employ discovery
   mechanisms to minimize the amount of operational information
   maintained by the SPs.  For example, if an SP adds or removes a
   customer port on a given PE, the remaining PEs SHOULD determine the
   necessary actions to take without the SP's having to explicitly
   reconfigure those PEs.

   A L2VPN solution SHOULD support the means for attached CEs to
   authenticate each other and to verify that the SP L2VPN is correctly
   connected.

   The mechanism SHOULD respond to L2VPN membership changes in a timely
   manner.  A "timely manner" is no longer than the provisioning
   timeframe, typically on the order of minutes, and MAY be as short as
   the timeframe required for "rerouting," typically on the order of
   seconds.

   Dynamically creating, changing, and managing multiple L2VPN
   assignments to sites and/or customers is another aspect of membership
   that MUST be addressed in an L2VPN solution.

7.4.  Quality of Service (QoS)

   A significant aspect of a provider-provisioned VPN is support for
   QoS.  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 devices as well.  Therefore, the SP is to provide
   either managed QoS access service, or edge-to-edge QoS service, as
   defined in [RFC4031].

7.5.  Isolation of Traffic and Forwarding Information

   From a high level SP perspective, an L2VPN MUST isolate the exchange
   of traffic and forwarding information to only those sites that are
   authenticated and authorized members of an L2VPN.

   An L2VPN solution SHOULD provide a means for meeting provider-
   provisioned VPN QoS SLS requirements that isolates L2VPN traffic from
   the affects of traffic offered by non-VPN customers.  Also, L2VPN
   solutions SHOULD provide a means so that traffic congestion produced
   by sites as part of one L2VPN does not affect another L2VPN.




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7.6.  Security

   The security requirements are stated in Section 6.5.  The security
   requirements provided in [RFC3809] SHOULD be met.  The security
   requirements, except Layer 3 and higher-layer dependent ones,
   specified in [RFC4031], SHOULD be met.

   In addition, an SP network MUST be protected against malformed or
   maliciously constructed customer traffic.  This includes but is not
   limited to duplicate or invalid Layer 2 addresses, customer side
   loops, short/long packets, spoofed management packets, spoofed VLAN
   tags, high volume traffic.

   The SP network devices MUST NOT be accessible from any L2VPN, unless
   specifically authorized.  The devices in the SP network SHOULD
   provide some means of reporting intrusion attempts to the SP, if the
   intrusion is detected.

   When an L2VPN 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 customer's VPN
   traffic:

   - Confidentiality, so that only authorized devices can decrypt it

   - Integrity, to ensure that the data has not been altered

   - Authentication, to ensure that the sender is indeed who he or she
     claims to be

   - Replay attack prevention.

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

   Furthermore, such security methods MUST be configurable between
   different end-points, such as PE-PE and PE-MTU, only in the case
   where L2VPN data traffic is carried over IP [RFC4023].  Methods to
   secure data flows at the native service layer (Layer-2), from CE-CE,
   CE-MTU and CE-PE, are outside the scope of this document.  It is also
   desirable to configure security on a per-VPN basis.






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

7.7.  Inter-AS/SP L2VPNs

   All applicable SP requirements, such as traffic and forwarding
   information isolation, SLSes, management, security, provisioning,
   etc.  MUST be preserved across adjacent ASes.  The solution MUST
   describe the inter-SP network interface, encapsulation method(s),
   routing protocol(s), and all applicable parameters.

   An L2VPN solution MUST provide the specifics of offering L2VPN
   services spanning multiple ASes and/or SPs.

   An L2VPN solution MUST support proper dissemination of operational
   parameters to all elements of an L2VPN service in the presence of
   multiple ASes and/or SPs.  A L2VPN solution MUST employ mechanisms
   for sharing operational parameters between different ASes.

   An L2VPN solution SHOULD support policies for proper selection of
   operational parameters coming from different ASes.  Similarly, an
   L2VPN solution SHOULD support policies for selecting information to
   be disseminated to different ASes.

7.7.1.  Management

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

   - Diagnostic tools

   - Secured access to one AS management system by another

   - Configuration request and status query tools

   - Fault notification and trouble tracking tools

7.7.2.  Bandwidth and QoS Brokering

   When an L2VPN spans multiple ASes, there is a need for a brokering
   mechanism that requests certain SLS 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 ASes can
   establish and guarantee uniform QoS in support of a provider-
   provisioned VPN.



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7.8.  L2VPN Wholesale

   The architecture MUST support the possibility of one SP's offering
   L2VPN service to another SP.  One example is when one SP sells L2VPN
   service at wholesale to another SP, who then resells that L2VPN
   service to his or her customers.

7.9.  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, GRE,
   IP-in-IP, MPLS, etc.

   Every PE MUST support a tunnel setup protocol, if tunneling is used.
   A PE MAY support static configuration.  If employed, a tunnel
   establishment protocol SHOULD be capable of conveying information,
   such as the following:

   - Relevant identifiers

   - QoS/SLS parameters

   - Restoration parameters

   - Multiplexing identifiers

   - Security parameters

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

   - Statistics, such as amount of time spent in the up and down state

   - Count of transitions between the up and down state

   - Events, such as transitions between the up and down states

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

   Regardless of the tunneling choice, the existence of the tunnels and
   their operations MUST be transparent to the customers.

7.10.  Support for Access Technologies

   The connectivity between PE and CE devices is referred to as an AC.
   ACs MAY span networks of other providers or public networks.



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   There are several choices for implementing ACs.  Some popular choices
   include Ethernet, ATM (DSL), Frame Relay, MPLS-based virtual circuits
   etc.

   In case of VPLS, the AC MUST use Ethernet frames as the Service
   Protocol Data Unit (SPDU).

   A CE access connection over an AC MUST be bi-directional.

   PE devices MAY support multiple ACs on a single physical interface.
   In such cases, PE devices MUST NOT rely on customer controlled
   parameters for distinguishing between different access connections.
   For example, if VLAN tags were used for that purpose, the provider
   would be controlling the assignment of the VLAN tag values and would
   strictly enforce compliance by the CEs.

   An AC, whether direct or virtual, MUST maintain all committed
   characteristics of the customer traffic, such as QoS, priorities etc.
   The characteristics of an AC are only applicable to that connection.

7.11.  Backbone Networks

   Ideally, the backbone interconnecting the SP's 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 SLSes for VPN
   service offerings.

7.12.  Network Resource Partitioning and Sharing Between L2VPNs

   In case network resources such as memory space, forwarding
   information base table, bandwidth, and CPU processing are shared
   between L2VPNs, the solution SHOULD guarantee availability of
   resources necessary to prevent any specific L2VPN service instance
   from taking up available network resources and causing others to
   fail.  The solution SHOULD be able to limit the resources consumed by
   an L2VPN service instance.  The solution SHOULD guarantee
   availability of resources necessary to fulfill the obligation of
   committed SLSes.

7.13.  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
     network




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   - To implement L2VPN services across two or more interconnected SP
     networks

   - To achieve inter-working or interconnection between customer sites
     using different L2VPN solutions 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.

7.14.  Testing

   The L2VPN solution SHOULD provide the ability to test and verify
   operational and maintenance activities on a per L2VPN service basis,
   and, in case of VPLS, on a per-VLAN basis if customer VLANs are used
   as service delimiters.

   The L2VPN solution SHOULD provide mechanisms for connectivity
   verification, and for detecting and locating faults.

   Examples of testing mechanisms are as follows:

   - Checking connectivity between "service-aware" network nodes

   - Verifying data plane and control plane integrity

   - Verifying service membership

   The provided mechanisms MUST satisfy the following: the connectivity
   checking for a given customer MUST enable the end-to-end testing of
   the data path used by that of customer's data packets, and the test
   packets MUST not propagate beyond the boundary of the SP network.

7.15.  Support on Existing PEs

   To the extent possible, the IPLS solution SHOULD facilitate support
   of IPLS on existing PE devices that may be already deployed by the SP
   and MAY have been designed primarily for Layer 3 services.












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8.  Service Provider Management Requirements

   An SP desires to have a means to view the topology, operational
   state, and other parameters associated with each customer's L2VPN.
   Furthermore, the SP requires a means to view the underlying logical
   and physical topology, operational state, provisioning status, and
   other parameters associated with the equipment providing the L2VPN
   service(s) to its customers.  Therefore, the devices SHOULD provide
   standards-based interfaces (e.g., L2VPN MIB Modules), wherever
   feasible.

   The details of service provider management requirements for a Network
   Management System (NMS) in the traditional fault, configuration,
   accounting, performance, and security (FCAPS) management categories
   can be found in [ITU_Y.1311.1].

9.  Engineering Requirements

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

9.1.  Control Plane Requirements

   An L2VPN service SHOULD be provisioned with minimum number of steps.
   Therefore, the control protocols SHOULD provide methods for signaling
   between PEs.  The signaling SHOULD inform of membership, tunneling
   information, and other relevant parameters.

   The infrastructure MAY employ manual configuration methods to provide
   this type of information.

   The infrastructure SHOULD use policies to scope the membership and
   reachability advertisements for a particular L2VPN service.  A
   mechanism for isolating the distribution of reachability information
   to only those sites associated with an L2VPN MUST be provided.

   The control plane traffic increases with the growth of L2VPN
   membership.  Similarly, the control plane traffic increases with the
   number of supported L2VPN services.  The use of control plane
   resources MAY increase as the number of hosts connected to an L2VPN
   service grows.

   An L2VPN solution SHOULD minimize control plane traffic and the
   consumption of control plane resources.  The control plane MAY offer
   means for enforcing a limit on the number of customer hosts attached
   to an L2VPN service.





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9.2.  Data Plane Requirements

9.2.1.  Encapsulation

   An L2VPN solution SHOULD utilize the encapsulation techniques defined
   by PWE3 ([RFC3985]), and SHOULD not impose any new requirements on
   these techniques.

9.2.2.  Responsiveness to Congestion

   An L2VPN solution SHOULD utilize the congestion avoidance techniques
   defined by PWE3 ([RFC3985]).

9.2.3.  Broadcast Domain

   A separate Broadcast Domain MUST be maintained for each VPLS.

   In addition to VPLS Broadcast Domains, an L2VPN service MAY honor
   customer VLAN Broadcast Domains, if customer VLANs are used as
   service delimiters.  In that case, the L2VPN solution SHOULD maintain
   a separate VLAN Broadcast Domain for each customer VLAN.

9.2.4.  Virtual Switching Instance

   L2VPN PE devices MUST maintain a separate VSI per VPLS.  Each VSI
   MUST have capabilities to forward traffic based on customer's traffic
   parameters, such as MAC addresses, VLAN tags (if supported), etc. as
   well as local policies.

   L2VPN PE devices MUST have capabilities to classify incoming customer
   traffic into the appropriate VSI.

   Each VSI MUST have flooding capabilities for its Broadcast Domain to
   facilitate proper forwarding of Broadcast, Multicast, and Unknown
   Unicast customer traffic.

9.2.5.  MAC Address Learning

   A VPLS SHOULD derive all topology and forwarding information from
   packets originating at customer sites.  Typically, MAC address
   learning mechanisms are used for this purpose.  With IPLS, snooping
   of particular packets originating at customer sites and signaling
   might also be used.

   Dynamic population of the forwarding information base (e.g., via MAC
   address learning) MUST take place on a per VSI basis; i.e., in the
   context of a VPLS and, if supported, in the context of VLANs therein.




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10.  Security Considerations

   Security considerations occur at several levels and dimensions within
   L2VPNs, as detailed within this document.

   The requirements based on security concerns and potential security
   hazards are detailed in Section 6.5.  Further details on security
   requirements are given from the customer and service provider
   perspectives in Sections 6.5 and 7.6, respectively.  In an analogous
   manner, further detail on traffic and routing isolation requirements
   are given from the customer and service provider perspectives in
   Sections 5.4 and 7.5, respectively.  Safeguards to protect network
   resources such as CPU, memory, and bandwidth are required in Section
   7.12.

   IPsec can also be applied after tunneling Layer 2 traffic to provide
   additional security.

   In the case where an L2VPN service is carried over IP [RFC4023],
   traverses multiple SP networks and passes through an unsecured SP,
   POP, NAP, or IX, then security mechanisms MUST be employed.  These
   security mechanisms include encryption, authentication, and resource
   protection, as described in section 5.5.  For example, a provider
   should consider using both authentication and encryption for a tunnel
   used as part of an L2VPN that traverses another service provider's
   network.

11.  Acknowledgements

   The authors would like to acknowledge extensive comments and
   contributions provided by Loa Andersson, Joel Halpern, Eric Rosen,
   Ali Sajassi, Muneyoshi Suzuki, Ananth Nagarajan, Dinesh Mohan, Yakov
   Rekhter, Matt Squire, Norm Finn, Scott Bradner, and Francois Le
   Faucheur.  The authors also wish to extend their appreciation to
   their respective employers and various other people who volunteered
   to review this work and provided feedback.  This work was done in
   consultation with the entire Layer 2 PPVPN design team.  A lot of the
   text was adapted from the Layer 3 VPN requirements document produced
   by the Layer 3 VPN requirements design team.












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12.  References

12.1.  Normative References

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

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

12.2.  Informative References

   [VPLS_LDP]      Lasserre, M., Kompella, V. "Virtual Private LAN
                   Services over MPLS", Work in Progress.

   [VPLS_BGP]      Kompella, K., Rekhter, Y. "Virtual Private LAN
                   Service", Work in Progress.

   [IPLS]          Shah, H., et al. "IP-Only LAN Service (IPLS)", Work
                   in Progress.

   [IEEE_802.1Q]   IEEE Std 802.1Q-1998, "Virtual Bridged Local Area
                   Networks", 1998

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

   [RFC2474]       Nichols, K., Blake, S., Baker, F., and D. Black,
                   "Definition of the Differentiated Services Field (DS
                   Field) in the IPv4 and IPv6 Headers", RFC 2474,
                   December 1998.

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

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

   [RFC3308]       Calhoun, P., Luo, W., McPherson, D., and K. Peirce,
                   "Layer Two Tunneling Protocol (L2TP) Differentiated
                   Services Extension", RFC 3308, November 2002.




Augustyn & Serbest           Informational                     [Page 29]

RFC 4665            Service Requirements for L2VPNs       September 2006


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

   [RFC3985]       Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-
                   to-Edge (PWE3) Architecture", RFC 3985, March 2005.

   [RFC4023]       Worster, T., Rekhter, Y., and E. Rosen,
                   "Encapsulating MPLS in IP or Generic Routing
                   Encapsulation (GRE)", RFC 4023, March 2005.

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

   [RFC4664]       Andersson, L. and E. Rosen, "Framework for Layer 2
                   Virtual Private Networks (L2VPNs)", RFC 4664,
                   September 2006.

   [IEEE_802.1D]   ISO/IEC 15802-3: 1998 ANSI/IEEE Std 802.1D, 1998
                   Edition (Revision and redesignation of ISO/IEC
                   10038:98), "Part 3: Media Access Control (MAC)
                   Bridges", 1998.

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

   [IEEE_802.10]   IEEE Std 802.10-1998 Edition (Revision IEEE Std
                   802.10-1992, incorporating IEEE Std 802.10b-1992,
                   802.10e-1993, 802.10f-1993, 802.10g-1995, and
                   802.10h-1997), "Standard for Interoperable LAN/MAN
                   Security (SILS)", 1998.

   [IEEE_802.1AE]  IEEE 802.1AE/D5.1, "Draft Standard for Local and
                   Metropolitan Area Networks - Media Access Control
                   (MAC) Security", P802.1AE/D5.1, January 19, 2006.

   [IEEE_802.1s]   IEEE Std 802.1s-2002, "Virtual Bridged Local Area
                   Networks-Amendment 3: Multiple Spanning Trees", 2002.











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RFC 4665            Service Requirements for L2VPNs       September 2006


Editors' Addresses

   Waldemar Augustyn

   EMail: waldemar@wdmsys.com


   Yetik Serbest
   AT&T Labs
   9505 Arboretum Blvd.
   Austin, TX 78759

   EMail: yetik_serbest@labs.att.com






































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RFC 4665            Service Requirements for L2VPNs       September 2006


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