





Network Working Group                                     T. Takeda, Ed.
Request for Comments: 4847                                           NTT
Category: Informational                                       April 2007


    Framework and Requirements for Layer 1 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 IETF Trust (2007).

Abstract

   This document provides a framework and service level requirements for
   Layer 1 Virtual Private Networks (L1VPNs).  This framework is
   intended to aid in developing and standardizing protocols and
   mechanisms to support interoperable L1VPNs.

   The document examines motivations for L1VPNs, high level (service
   level) requirements, and outlines some of the architectural models
   that might be used to build L1VPNs.

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................3
   3. Overview ........................................................5
      3.1. Network Topology ...........................................5
      3.2. Introducing Layer 1 VPNs ...................................5
      3.3. Current Technologies for Dynamic Layer 1 Provisioning ......6
      3.4. Relationship with ITU-T ....................................7
   4. Motivations .....................................................8
      4.1. Basic Layer 1 Services .....................................8
           4.1.1. L1VPN for Dynamic Layer 1 Provisioning ..............9
      4.2. Merits of L1VPN ............................................9
           4.2.1. Customer Merits .....................................9
           4.2.2. Provider Merits ....................................10
      4.3. L1VPN Deployment Scenarios ................................10
           4.3.1. Multi-Service Backbone .............................11
           4.3.2. Carrier's Carrier ..................................11
           4.3.3. Layer 1 Resource Trading ...........................12
           4.3.4. Inter-AS and Inter-SP L1VPNs .......................12



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           4.3.5. Scheduling Service .................................13
   5. Reference Model ................................................14
      5.1. Management Systems ........................................15
   6. Generic Service Description ....................................15
      6.1. CE Construct ..............................................15
      6.2. Generic Service Features ..................................16
   7. Service Models .................................................16
      7.1. Management-Based Service Model ............................17
      7.2. Signaling-Based Service Model (Basic Mode) ................17
           7.2.1. Overlay Service Model ..............................18
      7.3. Signaling and Routing Service Model (Enhanced Mode) .......19
           7.3.1. Overlay Extension Service Model ....................20
           7.3.2. Virtual Node Service Model .........................20
           7.3.3. Virtual Link Service Model .........................21
           7.3.4. Per-VPN Peer Service Model .........................22
   8. Service Models and Service Requirements ........................22
      8.1. Detailed Service Level Requirements .......................24
   9. Recovery Aspects ...............................................25
      9.1. Recovery Scope ............................................25
      9.2. Recovery Resource Sharing Schemes .........................26
   10. Control Plane Connectivity ....................................27
      10.1. Control Plane Connectivity between a CE and a PE .........27
      10.2. Control Plane Connectivity between CEs ...................28
   11. Manageability Considerations ..................................29
   12. Security Considerations .......................................31
      12.1. Types of Information .....................................32
      12.2. Security Features ........................................32
      12.3. Scenarios ................................................33
   13. Acknowledgements ..............................................34
   14. Contributors ..................................................34
   15. Normative References ..........................................35
   16. Informative References ........................................35



















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1.  Introduction

   This document examines motivations for Layer 1 Virtual Private
   Networks (L1VPNs), provides high-level (service-level) requirements,
   and outlines some of the architectural models that might be used to
   build L1VPNs.

   The objective of the document is mainly to present the requirements
   and architecture based on the work undertaken within Question 11 of
   Study Group 13 of the ITU-T.

   L1VPNs provide services over layer 1 networks.  This document
   provides a framework for L1VPNs and the realization of the framework
   by those networks being controlled by Generalized Multi-Protocol
   Label Switching (GMPLS) protocols.

   Use of GMPLS protocols for providing L1VPN services has several
   advantages, such as:

   - Flexible network operation.

   - Use of standardized protocols.

   - Use of common control and measurement plane protocols applicable to
     various layer 1 networks, including Time Division Multiplexing
     (TDM) networks and optical networks.

2.  Terminology

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

   The reader is assumed to be familiar with the terminology in
   [RFC3031], [RFC3209], [RFC3471], [RFC3473], [RFC4202], [RFC3945],
   [RFC4208], and [RFC4026].

   In this context, a Layer 1 Network is any transport network that has
   connectivity and/or switching using spatial switching (e.g., incoming
   port or fiber to outgoing port or fiber), lambda-switching, or time-
   division-multiplex-switching.

   A Layer 1 VPN (L1VPN) is a service offered by a core layer 1 network
   to provide layer 1 connectivity between two or more customer sites,
   and where the customer has some control over the establishment and
   type of the connectivity.  An alternative definition is simply to say
   that an L1VPN is a VPN whose data plane operates at layer 1.  Further
   details of the essence of an L1VPN are provided in Section 3.



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   In addition, the following new terms are used within this document:

   - Virtual link: A provider network Traffic Engineering (TE) link
     advertised to customers in routing information for purposes that
     include path computation.  A direct data link may or may not exist
     between the two end points of a virtual link.

   - Virtual node: A provider network logical node advertised to
     customers in routing information.  A virtual node may represent a
     single physical node, or multiple physical nodes and the links
     between them.

   - VPN end point: A Customer Edge (CE) device's data plane interface,
     which is connected to a Provider Edge (PE) device, and which is
     part of the VPN membership.  Note that a data plane interface is
     associated with a TE link end point.  For example, if a CE router's
     interface is a channelized interface (defined in SONET/SDH), a
     channel in the channelized interface can be a data plane interface.

   - VPN connection (or connection in the L1VPN context): A connection
     between a pair of VPN end points.  Note that in some scenarios a
     connection may be established between a pair of C (Customer)
     devices using this CE-CE VPN connection as a segment or forwarding
     adjacency defined in [RFC4206].

   Note that the following terms are aligned with Provider Provisioned
   VPN (PPVPN) terminology [RFC4026], and in this document, have a
   meaning in the context of L1VPNs, unless otherwise specified.

   - CE device: A CE device is a customer device that receives L1VPN
     service from the provider.  A CE device is connected to at least
     one PE device.  A CE device can be a variety of devices, for
     example, Time Division Multiplexing (TDM) switch, router, and layer
     2 switch.  A CE device does not have to have the capability to
     switch at layer 1, but it is capable of receiving a layer 1 signal
     and either switching it or terminating it with adaptation.  A CE
     device may be attached to one or more C devices on the customer
     site, and it may be a host using a layer 1 connection directly.

   - PE device: A PE device is a provider device that provides L1VPN
     service to the customer.  A PE device is connected to at least one
     CE device.  A layer 1 PE device is a TDM switch, an Optical Cross-
     Connect (OXC) (see [RFC3945]), or a Photonic Cross-Connect (PXC)
     (see [RFC3945]).  Alternatively, a PE device may be an Ethernet
     Private Line (EPL) type of device that maps Ethernet frames onto
     layer 1 connections (by means of Ethernet over TDM etc.).





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   - P (Provider) device: A P device is a provider device that is
     connected only to other provider devices (P or PE devices).  A
     layer 1 P is a TDM switch, OXC, or PXC.

   - Customer: A customer has authority over a set of CE devices within
     the same VPN (e.g., the owner of CE devices).  Note that a customer
     may outsource the management of CE devices to other organizations,
     including to the provider itself.

   - Provider: A provider has authority over the management of the
     provider network.

   - Membership information: A list of CE-PE TE link addresses belonging
     to the same VPN.  Membership information contains the association
     of a CE, a PE, and a VPN.

3.  Overview

3.1.  Network Topology

   The layer 1 network, made of OXCs, TDM switches, or PXCs may be seen
   as consisting of PE devices that give access from outside of the
   network, and P devices that operate only within the core of the
   network.  Similarly, outside the layer 1 network is the customer
   network consisting of C devices with access to the layer 1 network
   made through CE devices.

   A CE and PE are connected by one or more links.  A CE may also be
   connected to more than one PE, and a PE may have more than one CE
   connected to it.

   A layer 1 connection is provided between a pair of CEs.  Such a
   connection follows the hierarchy defined in [RFC4206].  That is, a
   CE-CE connection may be nested in a lower layer connection (e.g., VC3
   connection over STM1 connection).  Likewise, the switching
   capabilities of the interfaces of the CEs, PEs, and Ps on which a
   connection is routed, follow the hierarchy defined in [RFC4206].

3.2.  Introducing Layer 1 VPNs

   The concept of a PPVPN has been established through many previous
   documents such as [RFC4664] and [RFC4110].  Terminology for PPVPNs is
   set out in [RFC4026] with special reference to layer 2 and layer 3
   VPNs.

   The realization of L1VPNs can be based on extensions of the concepts
   of the PPVPN to the layer 1 network.  It must be understood that
   meeting the requirements set out in this document may necessitate



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   extensions to the existing mechanisms both for the control plane
   within the layer 1 network and for service provisioning at the edge
   of the network (CE and PE devices).  It is at the interface between
   CE and PE devices that the L1VPN service is provided.

   Note that the fundamental difference between L1VPNs and L2/L3 VPNs is
   that in L1VPNs, data plane connectivity does not guarantee control
   plane connectivity (and vice versa).  But CE-PE control plane
   connectivity is required for L1VPN services provisioned through the
   control plane, and CE-CE data plane connectivity is maintained by
   signaling mechanisms based on this control plane connectivity.
   Furthermore, the provision of CE-CE control plane connectivity over
   the provider network is also required for certain levels of L1VPN
   service, and this can be achieved by the exchange of control packets
   between CEs over the control plane of the provider network.  This
   aspect is discussed further in Section 10.2.

3.3.  Current Technologies for Dynamic Layer 1 Provisioning

   Pre-existing efforts at standardization have focused on the provision
   of dynamic connections within the layer 1 network (signaling and
   routing) and the definition of interfaces for requesting services
   between the user and the layer 1 network over the User-Network
   Interface (UNI), and between networks across the External Network-
   Network Interface (E-NNI) (see [RFC3945], [RFC4208], [RFC4139], and
   [RFC4258]).

   Current UNIs include features to facilitate requests for end-to-end
   (that is, CE to CE) services that include the specification of
   constraints such as explicit paths, bandwidth requirements,
   protection needs, and (of course) destinations.

   Current E-NNIs include features to exchange routing information, as
   well as to facilitate requests for end-to-end services.

   The UNIs and E-NNIs may be applied in the context of L1VPNs.  For
   example, the UNI may be applied between the CE and the PE, and the
   E-NNI may be applied between PEs (inter-AS/SP L1VPNs), or between the
   CE and the PE.

   However, the existing UNI and E-NNI specifications do not provide
   sufficient parameters to support VPNs without some additions.  For
   example, there is no way to distinguish between control messages
   received over a shared control link (i.e., a control link shared by
   multiple VPNs) at a UNI/E-NNI, and these messages must be
   disambiguated to determine the L1VPN to which they apply.  A control
   link is an IP link used for establishing a control channel between
   nodes.



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   Another example is that there is no clearly defined way of
   distributing membership information to be used in combination with
   UNI/E-NNI.  This function is necessary in order to discover the
   existence and location of the CEs to be connected by L1 connections.
   Distribution of membership information is typically done by the
   provider, and may be realized by mechanisms such as static
   provisioning, or by piggybacking on routing protocols (e.g., see
   Section 4.2.1 of [RFC4110]).  Note that the method chosen for
   distribution of membership information depends on the solution used
   for supporting L1VPNs, which is outside of the scope of this
   document.

   Furthermore, customer addressing realms may overlap with each other,
   and may also overlap with the service provider addressing realm.
   This requires address mapping mechanisms, but such mechanisms are not
   well defined in existing UNI/E-NNI specifications.

   Lastly, there is no clearly defined way to restrict connectivity
   among CEs (or over a UNI/E-NNI).  In addition, E-NNIs allow routing
   information exchange, but there is no clearly defined way to allow
   limited routing information exchange (i.e., a specific set of routing
   information is distributed to a specific set of CEs).

   In order for L1VPNs to be supported in a fully functional manner,
   these additional capabilities and other requirements set out later in
   this document must be addressed.

   Note that inter-AS/SP L1VPNs require additional analysis beyond the
   focus of this document.

3.4.  Relationship with ITU-T

   The foundation of this document is based on the work of the ITU-T
   Study Group 13, Question 11, such as [Y.1312] and [Y.1313].  This
   group has been researching and specifying both the requirements and
   the architecture of L1VPNs for some time.  In this context, the
   foundation of this document is a representation of the findings of
   the ITU-T, and a presentation of those findings in terms and format
   that are familiar to the IETF.

   In particular, this document is limited to the areas of concern of
   the IETF.  That is, it is limited to layer 1 networks that utilize IP
   as the underlying support for their control plane.

   The foundation of this document presents the requirements and
   architectures developed within the ITU-T for better understanding
   within the IETF and to further cooperation between the two bodies.




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   Some work related to the L1VPN solution space has already been done
   within the IETF.

4.  Motivations

   The general benefits and desirability of VPNs have been described
   many times and in many places ([RFC4110] and [RFC4664]).  This
   document does not dwell on the merits of VPNs as such, but focuses
   entirely on the applicability of the VPN concept to layer 1 networks.

   Similarly, the utility and value of a control plane for the
   configuration, management, and operation of a layer 1 network is
   well-rehearsed [RFC3945].

4.1.  Basic Layer 1 Services

   Basic layer 1 services may be characterized in terms that include:

   - Connectivity: Between a pair of CEs.

   - Capacity: For example, the bit rate for a TDM service or the
     capacity of a lambda.

   - Transparency: For example, for an SDH network, overhead
     transparency.

   - Availability: The percentage of time that the offered service meets
     the criteria that the provider defines, possibly agreed with each
     customer.  To achieve the required level of availability for the
     customer connections the service provider's network may use
     restoration or protected resources [RFC4427].

   - Performance: The quality of the service delivered to customers,
     e.g., the number of error-seconds per month.

   The layer 1 services may be categorized based on the combination of
   connectivity features (data plane) and service control capability
   features (control plane) available to the customer.  A CE is
   associated with the service interface between a customer site and the
   provider network, and the categorization can be seen in the context
   of this service interface as follows.

   1.  A single connection between a pair of CEs.

     - Static Service:
       The classic private line service achieved through a permanent
       connection.




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     - Dynamic Service:
       Either a switched connection service, or a customer-controlled
       soft permanent connection service (i.e., the customer is in
       control of when the signaled part is established).

   2.  Multiple connections among a set of CEs.

     - Static Service:
       A private network service consisting of a mesh of permanent
       connections.

     - Dynamic Service:
       A dynamic private network service consisting of any combination
       of switched connection services and customer-controlled soft
       permanent connection services.

   For service types 1 and 2, connections are point-to-point, and can be
   permanent, soft-permanent, or switched.  For a static service, the
   management plane of the provider network is responsible for the
   management of both the network infrastructure and the end-user
   connections.  For dynamic services, the management plane of the
   provider network is only responsible for the configuration of the
   infrastructure; end-user connections are established dynamically via
   the control plane of the provider network upon customer request.

   This document does not preclude other advanced services and topology
   support, such as point-to-multipoint (P2MP) services, as part of the
   layer 1 services, but these are for further study.

4.1.1.  L1VPN for Dynamic Layer 1 Provisioning

   Private network services in the second category in Section 4.1 can be
   enhanced so that multiple private networks are supported across the
   layer 1 network as virtual private networks.  These are Layer 1
   Virtual Private Networks (L1VPNs).  Note that the first category in
   Section 4.1 would include L1VPNs with only two CEs as a special case.

   Compared to the first category of service, the L1VPN service has
   features such as connectivity restriction, a separate policy, and
   distribution of membership information applied to a specific group.

4.2.  Merits of L1VPN

4.2.1.  Customer Merits

   From the customer's perspective, there are two main benefits to a
   L1VPN.  These benefits apply over and above the advantages of access
   to a dynamically provisioned network.



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   - The customer can outsource the direct management of a layer 1
     network by placing the VPN management in the control of a third
     party.  This frees the customer from the need to configure and
     manage the connectivity information for the CEs that participate in
     the VPN.

   - The customer can make small-scale use of a layer 1 network.  So,
     for example, by sharing the layer 1 network infrastructure with
     many other users, the customer sites can be connected together
     across the layer 1 network without bearing the full cost of
     deploying and managing the layer 1 network.

   To some extent, the customer may also gain from the provider's
   benefits (see below).  That is, if the provider is able to extract
   more value from the layer 1 network, the customer will benefit from
   lower priced services that are better tailored to the customer's
   needs.

4.2.2.  Provider Merits

   The provider benefits from the customer's perception of benefits.

   In particular, the provider can build on dynamic, on-demand services
   by offering new VPN services and off-loading the CE-to-CE
   configuration requirements from the customers.

   Additionally, a more flexible VPN structure applied to the layer 1
   network allows the provider to make more comprehensive use of the
   spare (that is, previously unused) resources within the network.
   This could be achieved by applying a network model where the provider
   is responsible for deciding how resources are used and for
   provisioning of the connection through the layer 1 network.

4.3.  L1VPN Deployment Scenarios

   In large carrier networks providing various kinds of service, it is
   often the case that multiple service networks are supported over a
   shared transport network.  By applying L1VPNs, multiple internal
   service networks (which may be managed and operated separately) can
   be supported over a shared layer 1 transport network controlled and
   managed using GMPLS.  In addition, L1VPNs can support capabilities to
   offer innovative services to external clients.

   Some more specific deployment scenarios are as follows.







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4.3.1.  Multi-Service Backbone

   A multi-service backbone is characterized such that each service
   department of a carrier that receives the carrier's L1VPN service
   provides a different kind of higher-layer service.  The customer
   receiving the L1VPN service (i.e., each service department) can offer
   its own services, whose payloads can be any layer (e.g., ATM, IP,
   TDM).  The layer 1 transport network and each service network belong
   to the same organization, but may be managed separately.  From the
   L1VPN service provider's point of view, these services are not
   visible and are not part of the L1VPN service.  That is, the type of
   service being carried within the layer 1 payload is not known by the
   service provider.

   The benefit is that the same layer 1 transport network resources are
   shared by multiple services.  A large capacity backbone network (data
   plane) can be built economically by having the resources shared by
   multiple services usually with flexibility to modify topologies,
   while separating the control functions for each service department.
   Thus, each customer can select a specific set of features that are
   needed to provide their own service.

   Note that it is also possible to control and manage these service
   networks and the layer 1 transport network by using GMPLS in the
   integrated model [RFC3945] instead of using L1VPNs.  However, using
   L1VPNs is beneficial in the following points:

   - Independent address space for each of the service networks.

   - Network isolation (topology information isolation, fault isolation
     among service networks).

   - Independent layer 1 resource view for each of the service networks.

   - Independent policies that could be applied for each of the service
     networks.

   These points may apply to the management plane functionalities as
   well as to the control plane functionalities.

4.3.2. Carrier's Carrier

   A carrier's carrier is characterized such that one carrier that
   receives another carrier's L1VPN service provides its own services.
   In this scenario, two carriers are in different organizations.  It
   is, therefore, expected that the information provided at the service
   demarcation points is more limited than in the multi-service backbone
   case.  Similarly, less control of the L1VPN service is given at the



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   service demarcation points.  For example, customers of an L1VPN
   service receive:

   - A more limited view of the L1VPN service provider network.

   - More limited control over the L1VPN service provider network.

   One of the merits is that each carrier can concentrate on a specific
   service.  For example, the customer of the L1VPN service may focus on
   L3 services, e.g., providing secure access to the Internet, leaving
   the L1VPN provider to focus on the layer 1 service, e.g., providing a
   long-haul bandwidth between cities.  The L1VPN customer can construct
   its own network using layer 1 resources supplied by the L1VPN
   provider, usually with flexibility to modify topologies, while
   separating the control functions for each customer carrier.

4.3.3.  Layer 1 Resource Trading

   In addition to the scenarios where the second tier service provider
   is using a single core service provider as mentioned in Section
   4.3.2, it is possible for the second tier provider to receive
   services from more than one core service provider.  In this scenario,
   there are some benefits for the second tier service provider such as
   route redundancy and dynamic carrier selection based on the price.

   The second tier service provider can support a function that enables
   a layer 1 resource trading service.  Using resource information
   published by its core service providers, a second tier service
   provider can decide how to best use the core providers.  For example,
   if one core service provider is no longer able to satisfy requests
   for service, an alternate service provider can be used.  Or the
   second tier service provider could choose to respond to price changes
   of service over time.

   Another example of second tier service provider use is to reduce
   exposure to failures in each provider (i.e., to improve
   availability).

4.3.4.  Inter-AS and Inter-SP L1VPNs

   In addition to the scenarios where a single connection between two
   CEs is routed over a single service provider as mentioned in Section
   4.3.2, it is possible that a connection is routed over multiple ASes
   within a service provider (called inter-AS L1VPN) or over multiple
   service providers (called inter-SP L1VPN).

   The inter-AS L1VPN scenario can be used to construct a single L1VPN
   from network resources administered by different domains of a single



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   service provider.  These administrative domains might not usually
   have a collaborative relationship at layer 1, and so the inter-AS
   L1VPN offers a new business model for joint delivery of services to a
   customer.  Consideration of inter-AS L1VPNs requires further analysis
   beyond the scope of this document.

   The inter-SP scenario can be used to construct a single L1VPN from
   services provided by multiple regional providers.  There could be a
   variety of business relationships among providers and customers, and
   this scenario contains many more manageability, security, privacy,
   policy, and commercial issues than the more simple inter-AS L1VPN
   case.  Consideration of inter-SP L1VPN requires further analysis
   beyond the scope of this document.

4.3.5.  Scheduling Service

   In some deployment scenarios, customers of L1VPN services may wish to
   set up layer 1 connections not on-demand, but at a planned time in
   the future.  Or, even though customers of L1VPN services may wish to
   use layer 1 connections on-demand, they can tolerate some delay, for
   example, due to lack of resources at that moment.

   In those scenarios, the provider can reserve bandwidth at a specified
   time in the future, and can establish the VPN connections according
   to a schedule.  This makes it possible to use bandwidth more
   efficiently over time (i.e., support more demand).  This service, the
   scheduling service, may be used to support customers who use layer 1
   connections for data backup applications, content delivery
   applications, and some other applications.

   Furthermore, customers may be able to specify when to release layer 1
   connections in advance.  By considering this information, the
   provider may be able to further engineer scheduling, which leads to
   still more efficient bandwidth usage.

   Note that scheduling of L1VPN services requires time-scoped resource
   management, which is not well considered in current GMPLS protocols
   and requires the support of the management plane.  In addition,
   offering scheduling service and on-demand service on the same
   infrastructure needs careful consideration.











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5.  Reference Model

      Figure 5.1 describes the L1VPN reference model.

                     :    +--------------------+    :
                     :    |   +------------+   |    :
                     :    |   | Management |   |    :
            +------+ :    |   |  system(s) |   |    : +------+
            |  C   | :    |   +------------+   |    : |  CE  |  +------+
            |device| :    |                    |    : |device|--|  C   |
            +------+ :    |                +------+ : |  of  |  |device|
                |    :    |                |      |=:=|VPN  A|  +------+
                |    :    |                |      | : +------+
            +------+ :    |                |  PE  | : +------+
  +------+  |  CE  | :    |                |device| : |  CE  |  +------+
  |  C   |  |device| : +------+  +------+  |      | : |device|  |  C   |
  |device|--|  of  |=:=|      |==|      |==|      |-:-|  of  |--|device|
  +------+  |VPN  A| : |      |  |      |  +------+ : |VPN  B|  +------+
            +------+ : |  PE  |  |  P   |      |    : +------+
            +------+ : |device|  |device|      |    : +------+
  +------+  | CE   | : |      |  |      |  +------+ : |  CE  |  +------+
  |  C   |--|device|=:=|      |==|      |==|      |-:-|device|--|  C   |
  |device|  | of   | : +------+  +------+  |      | : |  of  |  |device|
  +------+  |VPN  B| :    |                |  PE  | : |VPN  A|  +------+
            +------+ :    |                |device| : +------+
               |     :    |                |      | : +------+
               |     :    |                |      |=:=|  CE  |  +------+
            +------+ :    |                +------+ : |device|  |  C   |
            |  C   | :    |                    |    : |  of  |--|device|
            |device| :    |                    |    : |VPN  B|  +------+
            +------+ :    |                    |    : +------+
                     :    |                    |    :
                Customer  |                    |  Customer
                interface |                    |  interface
                          +--------------------+
                          |<---- Provider ---->|
                          |      network       |

     Key:   ==== Layer 1 Connection     -- link

                    Figure 5.1: L1VPN Reference Model

   In an L1VPN, layer 1 connections are provided between CEs' data plane
   interfaces within the same VPN.  In Figure 5.1, a connection is
   provided between the left-hand CE of VPN A and the upper right-hand
   CE of VPN A, and another connection is provided between the left-hand
   CE of VPN B and lower right-hand CE of VPN B (shown as "=" mark).
   These layer 1 connections are called VPN connections.



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   Note that as mentioned in Section 3.1, these VPN connections follow
   the hierarchy defined in [RFC4206].

5.1.  Management Systems

   As shown in the reference model, a provider network may contain one
   or more management systems.  A management system may support
   functions including provisioning, monitoring, billing, and recording.
   Provider management systems may also communicate with customer
   management systems in order to provide services.  Sections 7 and 11
   provide more detail.

6.  Generic Service Description

   This section describes generic L1VPN services.  Detailed descriptions
   are provided through specific service models in Section 7.

6.1.  CE Construct

   - The CE device may support more than one customer VPN.

   - CE-PE data plane links (between data plane interfaces) may be
     shared by multiple VPNs.

   Note that it is necessary to disambiguate control plane messages
   exchanged between CE and PE if the CE-PE relationship is applicable
   to more than one VPN.  This makes it possible to determine to which
   VPN such control plane messages apply.  Such disambiguation might be
   achieved by allocating a separate control channel to each VPN (either
   using a separate physical channel, a separate logical channel such as
   IP tunnel, or using separate addressing).

   A customer addressing realm consists of CE-PE TE link addresses and
   CE-PE control channel addresses as well as customer site addresses (C
   and CE addresses).  Customer addressing realms may overlap, and may
   also overlap with the service provider addressing realm.

   NATs or firewalls might reasonably be placed at customer interfaces,
   or between administrative domains within the core network.
   Addressing in the L1VPN model must handle such eventualities.
   Traversal of NATs and firewalls within the customer network might
   have implications for L1VPN services that connect C devices, and is
   for further study.








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6.2.  Generic Service Features

   L1VPN has the following two generic service features.

   - Connectivity restriction: Layer 1 connectivity is provided to a
     limited set of CEs' data plane interfaces, called VPN end points.
     (This set forms the L1VPN membership.)

   - Per VPN control and management: Some level of control and
     management capability is provided to the customer.  Details differ
     depending on service models described in Section 7.

7.  Service Models

   This section describes Layer 1 VPN service models that can be
   supported by GMPLS protocols enabled networks.  These models are
   derived from the generic service description presented above.

   Such layer 1 networks are managed and controlled using GMPLS
   signaling as described in [RFC3471] and [RFC3473], and GMPLS routing
   as described in [RFC4202].  It must be understood that meeting the
   requirements set out in this document may necessitate extensions to
   the existing GMPLS protocols both for the control plane within the
   layer 1 network and for service provisioning at the edge of the
   network (CE and PE devices).  A CE and a PE are connected by one or
   more data links.  The ends of each link are usually represented as
   GMPLS-capable interfaces.

   Note that in this document, service models are classified by the
   semantics of information exchanged over the customer interface.  The
   customer interface may be instantiated by the CE-PE control plane
   communication and/or the management plane communication between the
   customer management systems(s) and the provider management system(s).
   Note that how to realize a CE-PE control channel is discussed in
   Section 10.1.  Customer management system(s) and provider management
   systems(s) may communicate by utilizing the CE-PE control channel(s).















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7.1.  Management-Based Service Model

   Figure 7.1 describes the Management-based service model.

                        +--------------------+
                  :     |                    |
     +----------+ :     |    +----------+    |
     | Customer | :     |    | Provider |    |
     |Management| :     |    |Management|    |
     | system(s)|-:-----+----| system(s)|    |
     +----------+ :     |    +----------+    |
                  :     |                    |     :
                  :     |                    |     :
        +----+    :   +----+    +----+    +----+   :   +----+
        | CE |----:---| PE |----| P  |----| PE |---:---| CE |
        +----+    :   +----+    +----+    +----+   :   +----+
                  :     |                    |     :
                  :     |                    |     :
                  :     +--------------------+     :
                  :     |                    |     :
                  :     |<-Provider network->|     :
             Customer                           Customer
             interface                          interface

              Figure 7.1: Management-Based Service Model

   In this service model, customer management systems and provider
   management systems communicate with each other.  Customer management
   systems access provider management systems to request layer 1
   connection setup/deletion between a pair of CEs.  Customer management
   systems may obtain additional information, such as resource
   availability information and monitoring information, from provider
   management systems.  There is no control message exchange between a
   CE and PE.

   The provider network may be based on GMPLS.  In this case, mechanisms
   to support soft permanent connections can be applied.  However,
   interfaces between management systems are not within the scope of
   this document.

7.2.  Signaling-Based Service Model (Basic Mode)

   In this service model, the CE-PE interface's functional repertoire is
   limited to path setup signaling only.  The provider's network is not
   involved in distribution of customer network's routing information.






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   Note in addition that there may be communication between customer
   management system(s) and provider management system(s) in order to
   provide customers with detailed monitoring, fault information, etc.

7.2.1.  Overlay Service Model

   Figure 7.2 describes the Overlay service model.

                        +--------------------+
                  :     |                    |     :
                  :     |                    |     :
         +----+   :   +----+              +----+   :   +----+
         | CE |---:---| PE |              | PE |---:---| CE |
         +----+   :   +----+              +----+   :   +----+
                  :     |                    |     :
                  :     |                    |     :
                  :     +--------------------+     :
                  :     |                    |     :
                  :     |<-Provider network->|     :
             Customer                           Customer
             interface                          interface

                  Figure 7.2: Overlay Service Model

   In this service model, the customer interface is based on the GMPLS
   UNI Overlay [RFC4208].  The CE requests layer 1 connection
   setup/deletion to a remote CE.  There is no routing protocol running
   (i.e., no routing neighbor/peering relationship) between a CE and a
   PE.  The CE does not receive routing information from remote customer
   sites, nor routing information about the provider network.

   The CE's interface may be assigned a public or private address, that
   designates VPN end points.

   In this model, membership information needs to be configured on PEs,
   so that the PE that receives a Path message from the ingress CE can
   identify the remote PE connected to the egress CE.  Distribution of
   membership information between PEs is typically done by the provider,
   and may be realized by mechanisms such as static provisioning, or by
   piggybacking on routing protocols (auto-discovery).

   There are various ways that customers perceive the provider network.
   In one example, the whole provider network may be considered as one
   node -- the path specified and recorded in signaling messages
   reflects this.  Note that this is distinct from the Virtual Node
   service model described in Section 7.3.2 because such a model
   requires that the network is represented to the VPN sites as a
   virtual node -- that is, some form of routing advertisement is



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   implied, and this is not in scope for the Signaling-based service
   model.

7.3.  Signaling and Routing Service Model (Enhanced Mode)

   In this service model, the CE-PE interface provides the signaling
   capabilities as in the Basic Mode, plus permits limited exchange of
   information between the control planes of the provider and the
   customer to help such functions as discovery of customer network
   routing information (i.e., reachability or TE information in remote
   customer sites), or parameters of the part of the provider's network
   dedicated to the customer.

   By allowing CEs to obtain customer network routing information, a
   so-called N-square routing problem could be solved.

   In addition, by using the received traffic engineering-based routing
   information, a customer can use traffic engineering capabilities.
   For example, a customer can set up two disjoint connections between a
   pair of CEs.  Another example is that a customer can request a
   connection between a pair of devices within customer sites, and not
   necessarily between CEs, with more effective traffic engineering.

   As such, the customer interface is based on GMPLS signaling and
   mechanisms to exchange reachability/TE information.  Typically, a
   routing protocol is used between a CE and PE, or more precisely
   between a CE and the VPN routing context instantiated on the PE.
   Link state routing information would be needed to implement the above
   two example scenarios.  Some scenarios may be satisfied with
   reachability routing information only.

   Note that this service model does not preclude the use of mechanisms
   other than routing protocols to exchange reachability/TE information.

   As with the Signaling-based service model, there may be communication
   between customer management system(s) and provider management
   system(s) in order to provide detailed monitoring, fault information
   etc. to customers.

   Four specific types of the Signaling and Routing service model are
   the Overlay Extension service model, the Virtual Node service model,
   the Virtual Link service model and the Per-VPN Peer service model,
   depending on how customers perceive the provider network in routing
   and signaling (i.e., the level of information details that a customer
   is allowed to receive in routing and signaling).






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7.3.1.  Overlay Extension Service Model

   This service model complements the Overlay service model.  In this
   service model, a CE receives a list of CE-PE TE link addresses to
   which it can request a VPN connection (i.e., membership information).
   This may include additional information concerning these TE links
   (e.g., switching type).  Mechanisms other than routing could be used
   to exchange reachability/TE information between the CE and the PE.

7.3.2.  Virtual Node Service Model

   Figure 7.3 describes the Virtual Node service model.

                        +--------------------+
                    :   |                    |   :
           +----+   :   |                    |   :   +----+
           | CE |---:---|    Virtual Node    |---:---| CE |
           +----+   :   |                    |   :   +----+
                    :   |                    |   :
                    :   +--------------------+   :
                    :   |                    |   :
                    :   |<-Provider network->|   :
              Customer                          Customer
              interface                         interface

                Figure 7.3: Virtual Node Service Model

   In this type of service model, the whole provider network is
   represented as a virtual node (defined in Section 2).  The customer
   perceives the provider network as one single node.  The CE receives
   routing information about CE-PE links and the customer network (i.e.,
   remote customer sites).

   Note that in this service model, there must be one single virtual
   node, and this virtual node must be connected with every CE in the
   VPN.















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7.3.3.  Virtual Link Service Model

   Figure 7.4 describes the Virtual Link service model.

                        +--------------------+
                  :     |                    |     :
                  :     |       Virtual      |     :
         +----+   :   +----+     link     +----+   :   +----+
         | CE |---:---| PE |**************| PE |---:---| CE |
         +----+   :   +----+              +----+   :   +----+
                  :     |                    |     :
                  :     +--------------------+     :
                  :     |                    |     :
                  :     |<-Provider network->|     :
             Customer                           Customer
             interface                          interface

                Figure 7.4: Virtual Link Service Model

   In this service model, a virtual link is constructed between PEs.
   For the definition of a virtual link, please refer to terminology in
   Section 2.  A virtual link is assigned to each VPN and disclosed to
   the corresponding CEs.  As such, the CE receives routing information
   about CE-PE links, customer network (i.e., remote customer sites), as
   well as virtual links assigned to each VPN.  A special property of
   the virtual links used in this service model is that the provider
   network allocates data plane link resources for the exclusive use of
   each virtual link.  The TE attributes of a virtual link are
   determined according to data plane link resources allocated to this
   virtual link.  Virtual links are an abstraction of the provider
   network to customers for administrative purposes as well as to
   exclude "unnecessary information".

   Note that in this service model, both end points of each virtual link
   must be a PE device.
















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7.3.4.  Per-VPN Peer Service Model

   Figure 7.5 describes the Per-VPN Peer service model.

                        +--------------------+
                  :     |                    |     :
         +----+   :   +----+    +----+    +----+   :   +----+
         | CE |---:---| PE |----| P  |----| PE |---:---| CE |
         +----+   :   +----+    +----+    +----+   :   +----+
                  :     |                    |     :
                  :     +--------------------+     :
                  :     |                    |     :
                  :     |<-Provider network->|     :
             Customer                           Customer
             interface                          interface

               Figure 7.5: Per-VPN Peer Service Model

   This service model is a generalization and combination of the Virtual
   Link service model and the Virtual Node service model mentioned in
   Sections 7.3.2 and 7.3.3 respectively.

   In this service model, the provider partitions the TE links within
   the provider network per VPN, and discloses per-VPN TE link
   information to corresponding CEs.  As such, a CE receives routing
   information about CE-PE links, customer network (i.e., remote
   customer sites), as well as partitioned portions of the provider
   network.

   Note that PEs may advertise abstracted routing information about the
   provider network to CEs for administrative purpose as well as to
   exclude "unnecessary information".  In other words, virtual links may
   be constructed between two nodes where direct data links do not
   exist, or virtual nodes may be constructed to represent multiple
   physical nodes and links between them.

   In the Per-VPN Peer service model, at least one virtual node
   corresponding to P devices (one single P or a set of Ps) must be
   visible to customers.

8.  Service Models and Service Requirements

   The service models mentioned in Section 7 are related to what
   information is exchanged between CE and PE.  In addition, service
   models differ in how data plane resources are allocated for each VPN.

   Note that in the ITU-T documents, the term "U-Plane" is used instead
   of "data plane".



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   o Data plane resource allocation

     - Shared or dedicated:

       Shared means that provider network data plane links are shared by
       multiple (i.e., any or a specific set of) VPNs.  (Data plane
       links are dynamically allocated to a VPN when a VPN connection is
       requested, and data plane links allocated to one VPN at one time
       can be allocated to another VPN at another time.)

       Dedicated means that provider network data plane links are
       partitioned per VPN.  (Data plane links are statically allocated
       to one VPN and can not be used by other VPNs.)

   o Information exchanged between CE and PE

     - Signaling

     - Membership information (optionally includes TE information of the
       associated CE-PE TE links)

     - Customer network routing information (reachability only, or may
       include TE information)

     - Provider network routing information (TE information)

     Note that link management information (e.g., LMP [RFC4204]) may be
     exchanged between a CE and a PE, but this is orthogonal to the
     definition of the service models.

     Table 1 shows combination of service requirements and service
     models.



















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                               |    Data plane    |    Data plane
                               |      shared      |     dedicated
    ---------------------------+------------------+-------------------
      Signaling                |     Overlay      |     Overlay
    ---------------------------+------------------+-------------------
      Signaling +              |     Overlay      |     Overlay
      Membership information   |    Extension     |    Extension
    ---------------------------+------------------+-------------------
      Signaling +              |                  |
      Membership information + |   Virtual Node   |   Virtual Node
      Customer network routing |                  |
      information              |                  |
    ---------------------------+------------------+-------------------
      Signaling +              |                  |
      Membership information + |                  |   Virtual Link
      Customer network routing |  Not applicable  |
      information +            |                  |   Per-VPN Peer
      Provider network routing |                  |
      information              |                  |

       Table 1: Combination of service requirements and service models

   As described in previous sections, the difference between the Virtual
   Link service model and the Per-VPN Peer service model is whether
   customers have visibility of P devices.  In the Virtual Link service
   model, the end points of virtual links must be PE devices, thus P
   devices are not visible to customers.  In the Per-VPN Peer service
   model, at least one virtual node corresponding to P devices (one
   single P, or a set of Ps) is visible to customers.

   Note that when customers receive provider network routing information
   in the form of virtual link, customers must be able to specify such
   links for a VPN connection over the provider network in signaling.

8.1.  Detailed Service Level Requirements

   In addition to the requirements set out in table 1, more detailed
   service requirements are provided below.  They are generally common
   to the various service models, except where indicated.

   - Selection of layer 1 service class: Customers MAY be allowed to
     specify a layer 1 service class (e.g., availability level) for a
     VPN connection.  Further details are described in Section 9.








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   - Reception of performance information: Customers MAY be allowed to
     receive performance information for their VPN connections (e.g.,
     performance monitoring data).  When data plane links are dedicated,
     customers MAY be allowed to receive performance information for
     links dedicated to them.

   - Reception of fault information: Customers MAY be allowed to receive
     fault information for their VPN connections (e.g., failure
     notification by RSVP-TE, data plane alarm notification through the
     management plane, notification of connection setup rejection
     causes).  Note that this does not prevent customers from using
     Operations and Management (OAM) mechanisms for, or on, their VPN
     connections.  When data plane links are dedicated, customers MAY be
     allowed to receive fault information for links dedicated to them.

   - Reception of connection information: Customers MAY be allowed to
     receive information for current VPN connections (through the
     management plane).

   - Reception of accounting information: Customers MUST be able to
     receive accounting information for each VPN.

   - Specification of policy: Customers MAY be allowed to specify
     policies (e.g., path computation policies, recovery policies
     including parameters) for each VPN.

   - Security: The communication between the customer and the provider
     MUST be secure.  Further details are described in Section 12.

   - Filtering: Unnecessary information (e.g., information concerning
     other VPNs) MUST NOT be provided to each customer.  This applies
     particularly to the Signaling and Routing service model, but is
     also relevant to the Signaling-based service model and to the
     Management-based service model.  Further details are described in
     Section 12.

9.  Recovery Aspects

9.1.  Recovery Scope

   GMPLS provides various recovery techniques for use in different
   recovery scenarios [RFC4427].  The provider network may apply these
   recovery techniques to protect VPN connections as part of the L1VPN
   service, for example as follows:







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   o PE-PE recovery

     The provider network constitutes a recovery domain, and the
     recovery scope is the PE-PE part of the CE-CE VPN connection.

     It should be possible for the provider network to hide the provider
     network recovery operation from the customer.  Namely, it should be
     possible to configure the provider network to not notify the
     customer when a failure occurs and a PE-PE recovery operation
     successfully repairs the failure.  Further, when PE-PE recovery
     fails and the failure should be notified to the customer, it should
     be possible for the provider network to hide its internal topology.

   o CE-PE recovery

     The recovery scope is either or both of the ingress and egress
     CE-PE links of the CE-CE VPN connection.

   o CE-CE recovery

     The recovery scope is the entire CE-CE VPN connection.

     When a failure needs to be notified to a customer so that the
     customer can initiate recovery operation, it should be possible for
     the provider network to hide its internal topology.

   These recovery schemes may be applied in combination.

   Customers may be allowed to specify the desired recovery level in a
   connection setup request.  Furthermore, the customer may be allowed
   to specify the desired recovery level in a way that is agnostic of
   the recovery technique (e.g., when the recovery operation does not
   require cooperation between the provider network and the customer
   network).  In such cases, the provider network must translate the
   specified recovery level into specific recovery techniques, based on
   operational policies.  This allows enhanced recovery techniques above
   and beyond the GMPLS specifications to be used in the provider
   network.

9.2.  Recovery Resource Sharing Schemes

   The provider network may support various recovery resource sharing
   schemes, such as the following:

   o Shared recovery

     When the provider network supports shared recovery (e.g., shared
     mesh restoration [RFC4427]), the provider network may provide



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     sharing recovery resources between VPN connections that serve with
     only the same VPN, a specific set of VPNs, or any VPN.  The default
     mode is sharing recovery resources with any VPN.

   o Extra traffic

     GMPLS recovery mechanisms support extra traffic.  Extra traffic
     allows the transfer of preemptable traffic on the recovery
     resources when these resources are not being used for the recovery
     of protected normal traffic [RFC4427].

     In the context of L1VPNs, extra traffic is applied for CE-CE VPN
     connections, or PE-PE part of CE-CE VPN connections.  The latter
     case may be applied only when there is hierarchy (i.e., CE-CE VPN
     connection is nested on top of PE-PE connection).  In this section,
     the latter aspect is analyzed.

     When the provider network allows a CE-CE VPN connection to be set
     up as "extra traffic", it means that the VPN connection may use a
     PE-PE connection that protects some other CE-CE VPN connection.  In
     such a case the provider network may restrict extra traffic CE-CE
     VPN connection to use resources (i.e., the PE-PE connections) that:

     - protect VPN connections from the same VPN as the extra traffic
       connection.

     - are used for a specific set of VPNs.

     - are available for any VPN.

   The default mode is to support preemptable traffic on recovery
   resources reserved for any VPN.

10.  Control Plane Connectivity

10.1.  Control Plane Connectivity between a CE and a PE

   In the Signaling-based service model and the Signaling and Routing
   service model, there must be a control channel (IP-level
   connectivity) between a CE and its PE.  The instantiation of the
   control channel may differ depending on addressing and security.

   As stated in Section 6.1, it is necessary to disambiguate control
   plane messages exchanged between the CE and PE if the CE-PE
   relationship is applicable to more than one VPN.  Furthermore,
   private addresses may be assigned to CE-PE control channels.





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   Security aspects of the CE-PE control channel are discussed in
   Section 12.

10.2.  Control Plane Connectivity between CEs

   A customer network connected by VPN connections may be controlled by
   MPLS or GMPLS, and the VPN connections may be treated as TE links
   within the customer network.  In such cases, there must be control
   plane (IP-level) connectivity between the CEs, so that control
   messages, such as signaling and routing messages, can be exchanged
   between the CEs.  Furthermore, in some recovery techniques, Notify
   message exchange is needed between the ingress and egress of the VPN
   connection, which requires control plane connectivity between the
   CEs.  There are several potential ways to achieve this.

   o Use of VPN connections as in-band control channels

     If the CEs have the ability to inject control messages into the VPN
     connections and to extract the messages at the far end of the VPN
     connections, then control messages can be exchanged in-band.  For
     example, when a VPN connection is a Packet Switch Capable (PSC) TE
     link in the customer network, this operation is transparent to the
     L1VPN service provider.

   o Use of overhead associated with the VPN connections

     If the VPN connection provides connectivity in the customer network
     at a different switching capability (implying network technology
     layer) from that used by the provider network to support the CE-PE
     and PE-PE connectivity, then the customer network can utilize any
     overhead available within the VPN connection as a control channel
     to connect the CEs.  For example, if a VPN connection provides a
     TDM TE link in the customer network but is supported by a
     technology such as lambda or fiber, then the CEs may utilize the
     overhead (DCC) as a control channel, if the network supports
     transparent transfer of such overhead.  This operation is
     transparent to the L1VPN service provider.

   o Use of control-channel-specific VPN connections

     A customer establishes VPN connections dedicated as control
     channels.  This operation is transparent to the L1VPN service
     provider, but since control plane traffic is likely to be
     relatively low compared with the capacity of VPN connections, this
     may be an expensive solution for the customer.






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   o Use of separate network

     A customer may utilize another network and network service, such as
     private line service, L3VPN service, L2VPN service, or Internet
     access service, to establish CE-CE control channel connectivity.
     This operation is transparent to the L1VPN service provider.

   o Use of CE-PE control channels

     In the Signaling-based service model, and the Signaling and Routing
     service model, there must be control plane (IP-level) connectivity
     between the CE and PE, as described in Section 10.1.

     By utilizing this, CE-CE control message exchange could be realized
     as part of the service provided by the L1VPN service provider.
     Namely, the provider network transfers control messages received
     over the CE-PE control channel to the other side of the provider
     network and delivers them through the PE-CE control channel.  The
     realization of this within the provider network is up to the
     operator, but where the provider network uses a GMPLS control
     plane, the customer control plane messages could be forwarded
     through the provider control plane, perhaps using IP tunnels.

     Care must be taken to protect the provider network and other
     customers from Denial of Service (DoS) attack.  Traffic saturation
     over the control plane network needs to be carefully managed as
     well.  Note that if private addresses are assigned to the CE-PE
     control channels, the provider network must support VPN-scoped
     routing and forwarding for control messages.

11.  Manageability Considerations

   Manageability considerations for GMPLS are described in existing
   documents, such as [RFC3945].  Also, manageability considerations for
   L3VPN are described in existing documents, such as [RFC4176].  These
   manageability considerations should also be applied in L1VPNs, and
   these aspects are described in this section.  In addition, there are
   some specific manageability considerations for L1VPNs, such as
   configuration and accounting.

   o Fault management

   The provider network MUST support fault management.  It MUST support
   liveness detection, and monitoring and verification of correct
   operation.






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   When a failure occurs, the provider network SHOULD correlate the
   failure.  Also, it SHOULD be able to detect which customer is
   affected by the failure.

   If the provider network can resolve failures without intervention
   from the customer network, it MUST be possible to configure the
   provider network to not report failures to the customers.  However,
   it MAY be part of an agreement between a customer and provider that
   failures are reported to the customer, regardless.

   o Configuration management

   The provider network MUST support configuration management, such as
   the following.

     - Service mode/model configuration.

     - Network representation configuration: Configuration of virtual
       node and virtual link.

     - Resource allocation configuration: Dedicated, shared.  See
       Section 8 for more detail.

     - Recovery policy configuration: For example, recovery resource
       sharing schemes, such as shared recovery, extra traffic.  See
       Section 9 for more detail.

     - Membership configuration.

     - Network/Element level configuration: For example, TE link
       configuration.

     It SHOULD be possible for the provider network to verify that
     configuration is correctly made.

   o Accounting management

     The provider network MUST support accounting management.  It MUST
     be able to record usage of VPN connections for each customer.

   o Performance management

     The provider network MUST support performance management.

     In particular, it MUST support performance monitoring of parameters
     associated with the Service Level Agreement (SLA), such as bit
     error rate per VPN connection, and SLA verification.




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     In addition, it MUST support performance monitoring and analysis of
     parameters related to the network and equipment not directly
     associated with the SLA, such as network resource utilization.

   o Security management

     The provider network MUST support security management.  See Section
     12 for details.

   o Management systems

     In order to support various management functionalities, the
     provider network relies on management systems and related tools.
     GMPLS protocols and potential extensions of GMPLS MUST be able to
     work with management systems and related tools to provide such
     functionalities.

     In particular, MIB modules for GMPLS protocols and potential
     extensions MUST be supported.

   o Management of customer networks

     Customers MAY outsource management of their network (especially CEs
     and CE-CE links) to the provider network.  In such case, the
     provider MUST be able to manage the customer network, as well as
     the provider network.

12.  Security Considerations

   Security is clearly one of the essential requirements in L1VPNs.  In
   this section, key security requirements are highlighted.  Security
   considerations for L3VPNs and L2VPNs are described in existing
   documents, such as [RFC4110], [RFC4111], and [RFC4664].  These
   security considerations should also be applied in L1VPNs, and these
   aspects are described in this section.  In addition, there are some
   specific security considerations for L1VPNs, such as connectivity
   restriction and shared control links.

   This section first describes types of information to be secured.
   Then, security features or aspects are described.  Finally, some
   considerations concerning scenarios where security mechanisms are
   applied is described.









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12.1.  Types of Information

   It MUST be possible to secure the information exchanged between the
   customer and the provider.  This includes data plane information,
   control plane information, and management plane information.

   At layer 1, data plane information is normally assumed to be secured
   once connections are established, since those connections are
   dedicated to each VPN.  That is, it is not possible to communicate
   unless there is a connection.  Therefore, in L1VPNs, the main concern
   of data plane security is restricting VPN connections to be used only
   within the same VPN, as described in Section 6.2.  Note that a
   customer may wish to assure data plane information security against
   not only other customers, but also the provider.  In such case, the
   customer may wish to apply their own security mechanisms for data
   plane information (CE-CE security), as later described.

   In addition, information contained in the provider network MUST be
   secured.  This includes VPN service contract information, current VPN
   connection information, VPN membership information, and system
   information.  Note these types of information MAY be accessible to
   authorized entities.

12.2.  Security Features

   Security features include the following:

   o Data integrity

     The information exchanged between the customer and the provider
     MUST be delivered unchanged.

   o Confidentiality

     The information exchanged between the customer and the provider
     MUST NOT be disclosed to a third party.

   o Authentication

     The entity requesting the service to the provider MUST be
     identified and have its identity authenticated, and the provider
     providing the service MUST also be identified and have its identify
     authenticated.








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   o Access control

     Access to the information contained in the provider network, which
     may be information about the customer networks or the existence of
     customers, as well as about the provider network, MUST be
     restricted to the authorized entity.

   o DoS attack detection and protection

     The provider network MUST have mechanisms to detect DoS attack and
     to protect against it reactively and proactively.

12.3.  Scenarios

   There are two scenarios (or occasions) in which security mechanisms
   are applied.  One is the service contract phase, where security
   mechanisms are applied once.  The other is the service access phase,
   where security mechanisms are applied every time the service is
   requested.

   o Service contract scenario (static)

     This scenario includes the addition of new physical devices, such
     as CE devices, data links and control links.  It MUST be guaranteed
     that these physical devices are connected to the right entity.  In
     addition, authority to access specific information MAY be given to
     each customer as a part of service contract.

   o Service access scenario (dynamic)

     This scenario includes the reception of connection requests,
     routing information exchange requests (e.g., attempts to establish
     a neighbor relationship in routing protocols, or command request
     via the management plane interface), and management information
     retrieval requests.  If a communication channel between the
     customer and the provider (control channel, management interface)
     is physically separate per customer, and the entity connected over
     this communication channel is identified in the service contract
     phase, the provider can ensure who is requesting the service.
     Also, the communication channel could be considered as secure.
     However, when communication channel is physically shared among
     customers, security mechanisms MUST be available and SHOULD be
     enforced.  Examples of such security mechanisms include IPsec
     [RFC4302] and [RFC4303].  Note that even in the case of physically
     separate communication channels, customers may wish to apply
     security mechanisms to assure higher security, and such mechanisms
     MUST be available.




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     When the entity requesting the service is identified, the provider
     MUST ensure that the request is authorized for that entity.  This
     includes assuring that connection request is between VPN end points
     belonging to the same VPN.

     Also note that customers may wish to apply their own security
     mechanisms for data plane information (CE-CE security).  This
     includes IPsec [RFC4302] and [RFC4303] for IP traffic.

13.  Acknowledgements

   The material in this document is based on the work of the ITU-T Study
   Group 13.

   We would like to thank Dimitri Papadimitriou, Deborah Brungard, Yakov
   Rekhter, Alex Zinin, Igor Bryskin, Adrian Farrel, and Ross Callon for
   their useful comments and suggestions.

   Thanks to Mark Townsley, Dan Romascanu, and Cullen Jennings for
   helpful input during IESG review.

14.  Contributors

   The foundation of this document is based heavily on the work of ITU-T
   Study Group 13, Question 11.  SG13/Q11 has been investigating the
   service requirements and architecture for Layer 1 VPNs for some time,
   and the foundation of this document is a summary and development of
   the conclusions they have reached.  Based on such material, the IETF
   and the L1VPN WG in particular have developed this framework and
   requirements for the support of L1VPNs by use of GMPLS protocols.

   The details of this document are the result of contributions from
   several authors who are listed here in alphabetic order.  Contact
   details for these authors can be found in a separate section near the
   end of this document.

   Raymond Aubin (Nortel)
   Marco Carugi (Nortel)
   Ichiro Inoue (NTT)
   Hamid Ould-Brahim (Nortel)
   Tomonori Takeda (NTT)










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15.  Normative References

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

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

   [RFC3209]   Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
               and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
               Tunnels", RFC 3209, December 2001.

   [RFC3471]   Berger, L., Ed., "Generalized Multi-Protocol Label
               Switching (GMPLS) Signaling Functional Description", RFC
               3471, January 2003.

   [RFC3473]   Berger, L., Ed., "Generalized Multi-Protocol Label
               Switching (GMPLS) Signaling Resource ReserVation
               Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
               3473, January 2003.

   [RFC3945]   Mannie, E., Ed., "Generalized Multi-Protocol Label
               Switching (GMPLS) Architecture", RFC 3945, October 2004.

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

   [RFC4202]   Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
               Extensions in Support of Generalized Multi-Protocol Label
               Switching (GMPLS)", RFC 4202, October 2005.

   [RFC4208]   Swallow, G., Drake, J., Ishimatsu, H., and Y. Rekhter,
               "Generalized Multiprotocol Label Switching (GMPLS) User-
               Network Interface (UNI): Resource ReserVation Protocol-
               Traffic Engineering (RSVP-TE) Support for the Overlay
               Model", RFC 4208, October 2005.

   [Y.1312]    Y.1312 - Layer 1 Virtual Private Network Generic
               requirements and architecture elements, ITU-T
               Recommendation, September 2003, available from
               <http://www.itu.int>.

16.  Informative References

   [Y.1313]    Y.1313 - Layer 1 Virtual Private Network service and
               network architectures, ITU-T Recommendation, July 2004,
               available from <http://www.itu.int>.



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   [RFC4110]   Callon, R. and M. Suzuki, "A Framework for Layer 3
               Provider-Provisioned Virtual Private Networks (PPVPNs)",
               RFC 4110, July 2005.

   [RFC4111]   Fang, L., Ed., "Security Framework for Provider-
               Provisioned Virtual Private Networks (PPVPNs)", RFC 4111,
               July 2005.

   [RFC4139]   Papadimitriou, D., Drake, J., Ash, J., Farrel, A., and L.
               Ong, "Requirements for Generalized MPLS (GMPLS) Signaling
               Usage and Extensions for Automatically Switched Optical
               Network (ASON)", RFC 4139, July 2005.

   [RFC4176]   El Mghazli, Y., Ed., Nadeau, T., Boucadair, M., Chan, K.,
               and A. Gonguet, "Framework for Layer 3 Virtual Private
               Networks (L3VPN) Operations and Management", RFC 4176,
               October 2005.

   [RFC4204]   Lang, J., Ed., "Link Management Protocol (LMP)", RFC
               4204, October 2005.

   [RFC4206]   Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
               Hierarchy with Generalized Multi-Protocol Label Switching
               (GMPLS) Traffic Engineering (TE)", RFC 4206, October
               2005.

   [RFC4258]   Brungard, D., Ed., "Requirements for Generalized Multi-
               Protocol Label Switching (GMPLS) Routing for the
               Automatically Switched Optical Network (ASON)", RFC 4258,
               November 2005.

   [RFC4302]   Kent, S., "IP Authentication Header", RFC 4302, December
               2005

   [RFC4303]   Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
               4303, December 2005.

   [RFC4427]   Mannie, E., Ed., and D. Papadimitriou, Ed., "Recovery
               (Protection and Restoration) Terminology for Generalized
               Multi-Protocol Label Switching (GMPLS)", RFC 4427, March
               2006.

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






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Authors' Addresses

   Raymond Aubin
   Nortel Networks
   P O Box 3511 Station C
   Ottawa, ON K1Y 4H7 Canada
   Phone: +1 (613) 763 2208
   EMail: aubin@nortel.com


   Marco Carugi
   Nortel Networks S.A.
   Parc d'activites de Magny-Chateaufort
   Les Jeunes Bois - MS CTF 32B5 - Chateaufort
   78928 YVELINES Cedex 9  - FRANCE
   Phone: +33 1 6955 7027
   EMail: marco.carugi@nortel.com


   Ichiro Inoue
   NTT Network Service Systems Laboratories, NTT Corporation
   3-9-11, Midori-Cho
   Musashino-Shi, Tokyo 180-8585 Japan
   Phone: +81 422 59 6076
   EMail: inoue.ichiro@lab.ntt.co.jp


   Hamid Ould-Brahim
   Nortel Networks
   P O Box 3511 Station C
   Ottawa, ON K1Y 4H7 Canada
   Phone: +1 (613) 765 3418
   EMail: hbrahim@nortel.com


   Tomonori Takeda, Editor
   NTT Network Service Systems Laboratories, NTT Corporation
   3-9-11, Midori-Cho
   Musashino-Shi, Tokyo 180-8585 Japan
   Phone: +81 422 59 7434
   EMail : takeda.tomonori@lab.ntt.co.jp










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Full Copyright Statement

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