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RFC 5253 - Applicability Statement for Layer 1 Virtual Private N


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Network Working Group                                     T. Takeda, Ed.
Request for Comments: 5253                                           NTT
Category: Informational                                        July 2008

                      Applicability Statement for
           Layer 1 Virtual Private Network (L1VPN) Basic Mode

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.

Abstract

   This document provides an applicability statement on the use of
   Generalized Multiprotocol Label Switching (GMPLS) protocols and
   mechanisms to support Basic Mode Layer 1 Virtual Private Networks
   (L1VPNs).

   L1VPNs provide customer services and connectivity at Layer 1 over
   Layer 1 networks.  The operation of L1VPNs is divided into the Basic
   Mode and the Enhanced Mode, where the Basic Mode of operation does
   not feature any exchange of routing information between the Layer 1
   network and the customer domain.  This document examines how GMPLS
   protocols can be used to satisfy the requirements of a Basic Mode
   L1VPN.

Table of Contents

   1. Introduction ....................................................3
      1.1. Terminology ................................................3
   2. Basic Mode Overview .............................................3
   3. Supported Network Types .........................................4
      3.1. Data Plane .................................................4
      3.2. Control Plane ..............................................4
   4. Addressing ......................................................5
   5. Provider Control of Its Infrastructure ..........................5
      5.1. Provisioning Model .........................................5
      5.2. PE-to-PE Segment Control ...................................6
           5.2.1. Path Computation and Establishment ..................6
           5.2.2. Resource Management .................................7
           5.2.3. Consideration of CE-to-PE Traffic Engineering
                  Information .........................................8
      5.3. Connectivity Restriction ...................................8
   6. Customer Control of Its L1VPN ...................................8
      6.1. Topology Control ...........................................8
      6.2. Note on Routing ............................................9
   7. Scalability and Resiliency .....................................10
      7.1. Scalability ...............................................10
      7.2. Data Plane Resiliency .....................................11
      7.3. Control Plane Resiliency ..................................12
   8. Security Considerations ........................................12
      8.1. Topology Confidentiality ..................................12
      8.2. External Control of the Provider Network ..................13
      8.3. Data Plane Security .......................................13
      8.4. Control Plane Security ....................................14
   9. Manageability Considerations ...................................15
   10. References ....................................................15
      10.1. Normative References .....................................15
      10.2. Informative References ...................................16
   11. Acknowledgments ...............................................17

1.  Introduction

   This document provides an applicability statement on the use of
   Generalized Multiprotocol Label Switching (GMPLS) protocols and
   mechanisms to Basic Mode Layer 1 Virtual Private Networks (L1VPNs) as
   specified in [RFC4847].

   The operation of L1VPNs is divided into the Basic Mode and the
   Enhanced Mode.  The Basic Mode of operation does not feature any
   exchange of routing information between the Layer 1 network and the
   customer domain, while the Enhanced Mode of operation features
   exchange of routing information between the Layer 1 network and the
   customer domain.

   The main GMPLS protocols and mechanisms applicable to the L1VPN Basic
   Mode are described in [RFC5251], [RFC5195], and [RFC5252], along with
   several other documents referenced within this document.

   Note that discussion in this document is focused on areas where GMPLS
   protocols and mechanisms are relevant.

1.1.  Terminology

   The reader is assumed to be familiar with the terminology in
   [RFC3031], [RFC3209], [RFC3471], [RFC3473], [RFC4202], [RFC4026], and
   [RFC4847].

2.  Basic Mode Overview

   As described in [RFC4847], in the Basic Mode service model, there is
   no routing exchange between the Customer Edge (CE) and the Provider
   Edge (PE).  CE-to-CE L1VPN connections (i.e., the CE-to-CE VPN
   connection in RFC 4847) are set up by GMPLS signaling between the CE
   and the PE, and then across the provider network.  A L1VPN connection
   is limited to the connection between CEs belonging to the same L1VPN.

   Note that in L1VPNs, routing operates within the provider network.
   Also note that routing may be used by PEs to exchange information
   specific to the L1VPNs supported by the provider network (e.g.,
   membership information).

   In the L1VPN Basic Mode, the provider network is completely under the
   control of the provider.  This includes the PE-to-PE segment of the
   CE-to-CE L1VPN connection that is controlled and computed by the
   provider (PE-to-PE segment control).  On the other hand, the L1VPN
   itself, constructed from a set of CEs and the L1VPN connections
   provided by the provider, is under the control of each customer.
   This control includes that a customer can request between which CEs a

   connection is to be established (topology control).  Note that a
   customer may outsource the management of its L1VPN to a third party,
   including to the provider itself.  There is a confidentiality
   requirement between the provider and each customer.

   [RFC5251], which extends [RFC4208], specifies GMPLS signaling to
   establish CE-to-CE L1VPN connections.

   [RFC5195] and [RFC5252] specify alternative mechanisms to exchange
   L1VPN membership information between PEs, based on BGP and OSPF,
   respectively.

3.  Supported Network Types

3.1.  Data Plane

   The provider network can be constructed from any type of Layer 1
   switches, such as Time Division Multiplexing (TDM) switches, Optical
   Cross-Connects (OXCs), or Photonic Cross-Connects (PXCs).
   Furthermore, a PE 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.).  The provider network may be constructed
   from switches providing a single switching granularity (e.g., only
   VC3 switches), or from switches providing multiple switching
   granularities (e.g., from VC3/VC4 switches, or from VC3 switches and
   OXCs).  The provider network may provide a single type of L1VPN
   connection (e.g., VC3 connections only), or multiple types of
   connection (e.g., VC3/VC4 connections, or VC3 connections and
   wavelength connections).

   A CE does not have to have the capability to switch at Layer 1, but
   it must be capable of receiving a Layer 1 signal and either switching
   it or terminating it with adaptation.

   As described in [RFC4847] and [RFC5251], a CE and a 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 CE may belong to a single L1VPN, or to multiple L1VPNs, and a PE
   may support one or more L1VPNs through a single CE or through
   multiple CEs.

3.2.  Control Plane

   The provider network is controlled by GMPLS.  L1VPN Basic Mode
   provider networks are limited to a single AS within the scope of this
   document.  Multi-AS Basic Mode L1VPNs are for future study.

   As described in [RFC4847] and [RFC5251], a CE and a PE need to be
   connected by at least one control channel.  It is necessary to
   disambiguate control plane messages exchanged between a CE and a PE
   if the CE-to-PE relationship is applicable to more than one L1VPN.
   This makes it possible to determine to which L1VPN such control plane
   messages apply.  Such disambiguation can be achieved by allocating a
   separate control channel to each L1VPN (either using a separate
   physical channel, a separate logical channel such as an IP tunnel, or
   using separate addressing).

   GMPLS allows any type of control channel to be used, as long as there
   is IP level reachability.  In the L1VPN context, instantiation of a
   control channel between a CE and a PE may differ depending on
   security requirements, etc.  This is discussed in Section 8.

4.  Addressing

   As described in [RFC5251], the L1VPN Basic Mode allows that customer
   addressing realms overlap with each other, and also overlap with the
   service provider addressing realm.  That is, a customer network may
   reuse addresses used by the provider network, and may reuse addresses
   used in another customer network supported by the same provider
   network.  This is the same as in any other VPN model.

   In addition, the L1VPN Basic Mode allows CE-to-PE control channel
   addressing realms to overlap.  That is, a CE-to-PE control channel
   address (CE's address of this control channel and PE's address of
   this control channel) is unique within the L1VPN that the CE-to-PE
   control channel belongs to, but not necessarily unique across
   multiple L1VPNs.

   Furthermore, once a L1VPN connection has been established, the L1VPN
   Basic Mode does not enforce any restriction on address assignment for
   this L1VPN connection (treated as a link) for customer network
   operation (e.g., IP network, MPLS network).

5.  Provider Control of Its Infrastructure

5.1.  Provisioning Model

   As described in [RFC5251], for each L1VPN that has at least one
   customer-facing port on a given PE, the PE maintains a Port
   Information Table (PIT) associated with that L1VPN.  A PIT provides a
   cross-reference between Customer Port Indices (CPIs) and Provider
   Port Indices (PPIs) and contains a list of <CPI, PPI> tuples for all
   the ports within the L1VPN.  In addition, for local PE ports of a
   given L1VPN, the PE retains an identifier known as the VPN-PPI, and
   this is stored in the PIT with the <CPI, PPI> tuples.

   When a new CE belonging to one or more L1VPNs is added to a PE, PIT
   entries associated to those L1VPNs need to be configured on the PE.
   Section 4 of [RFC5251] specifies such procedures:

   - If no PIT exists for the L1VPN on the PE, a new PIT is created by
     the provider and associated with the VPN identifier.

   - The PIT (new or pre-existing) is updated to include information
     related to the newly added CE.  The VPN-PPI, PPI, and CPI are
     installed in the PIT.  Note that the PPI is well-known by the PE,
     but the CPI must be discovered either through manual configuration
     or automatically by mechanisms such as the Link Management Protocol
     (LMP) [RFC4204].  In addition, a CE-to-PE control channel needs to
     be configured.

   - The updated PIT information needs to be configured in the PITs on
     the remote PE associated with the L1VPN.  For such purposes, manual
     configuration or some sort of auto-discovery mechanisms can be
     used.  [RFC5195] and [RFC5252] specify alternative auto-discovery
     mechanisms.

   - In addition, remote PIT information associated with the L1VPN needs
     to be configured on this PE if the PIT has been newly created.
     Again, this can be achieved through manual configuration or through
     auto-discovery; see [RFC5195] and [RFC5252].

   When L1VPN membership of an existing CE changes, or when a CE is
   removed from a PE, similar procedures need to be applied to update
   the local and remote PITs.

5.2.  PE-to-PE Segment Control

   In the L1VPN Basic Mode, a PE-to-PE segment of a CE-to-CE L1VPN
   connection is completely under the control of the provider network.

5.2.1.  Path Computation and Establishment

   A PE-to-PE segment of a CE-to-CE L1VPN connection may be established
   based on various policies.  Those policies can be applied per L1VPN
   or per L1VPN connection.  The policy is configured by the provider,
   possibly based on the contracts with each customer.

   Examples of PE-to-PE segment connection establishment polices
   supported in the L1VPN Basic Mode are as follows.

   - Policy 1: On-demand establishment, on-demand path computation
   - Policy 2: On-demand establishment, pre-computed path
   - Policy 3: Pre-establishment, pre-computed path

   In each policy, the PE-to-PE path may be computed by the local PE or
   by a path computation entity outside of the local PE (e.g., a Path
   Computation Element (PCE) [RFC4655] or a management system).

   In policies 2 and 3, pre-computation of paths (and pre-establishment
   if applicable) can be done at the network planning phase, or just
   before signaling (e.g., triggered by an off-line customer request).
   As the result of pre-computation (and pre-establishment), there could
   be multiple PE-to-PE segments for a specific pair of PEs.  When a PE
   receives a Path message from a CE for a L1VPN connection, a PE needs
   to determine which PE-to-PE segment to use.  In such cases, the
   provider may want to control:

   - Which L1VPN uses which PE-to-PE L1VPN segment.
   - Which CE-to-CE L1VPN connection uses which PE-to-PE L1VPN segment.

   The former requires mapping between the PIT and the PE-to-PE segment.
   The latter requires some more sophisticated mapping method, for
   example:

   - Mapping between individual PIT entries and PE-to-PE segments.
   - Use of a Path Key ID [CONF-SEG] supplied by the provider to the CE,
     and signaled by the CE as part of the L1VPN connection request.

   The L1VPN Basic Mode does not preclude usage of other methods, if
   applicable.

   In policy 3, stitching or nesting is necessary in order to map the
   CE-to-CE L1VPN connection to a pre-established PE-to-PE segment.

5.2.2.  Resource Management

   The provider network may operate resource management based on various
   policies.  These policies can be applied per L1VPN or per L1VPN
   connection.  The policy is configured by the provider, possibly based
   on the contracts with each customer.

   For example, a provider may choose to partition the resources of the
   provider network for limited use by different L1VPNs or customers.
   Such a function might be achieved within the scope of the Basic Mode
   using resource affinities [RFC3209], but the details of per-L1VPN
   resource models (especially in terms of CE-to-PE routing) are
   considered as part of the Enhanced Mode.

5.2.3.  Consideration of CE-to-PE Traffic Engineering Information

   [RFC5252] and [BGP-TE] allow CE-to-PE Traffic Engineering (TE) link
   information to be injected into the provider network, and in
   particular to be exchanged between PEs.  This may be helpful for the
   ingress PE to prevent connection setup failure due to lack of
   resources or incompatible switching capabilities on remote CE-to-PE
   TE links.

   Furthermore, the L1VPN Basic Mode allows a remote CE to be reached
   through more than one TE link connected to the same PE (single-homed)
   or to different PEs (dual-homed).  In such cases, to facilitate route
   choice, the ingress CE needs to initiate signaling by specifying the
   egress CE's router ID, not the egress CPI, in the Session Object and
   the Explicit Route Object (ERO), if present, so as to not constrain
   the choice of route within the provider network.  Therefore, the CE's
   router ID needs to be configured in the PITs.

   Note that, as described in Section 7.2, consideration of the full
   feature set enabled by dual-homing (such as resiliency) is out of
   scope of the L1VPN Basic Mode.

5.3.  Connectivity Restriction

   The L1VPN Basic Mode allows restricting connection establishment
   between CEs belonging to the same L1VPN for policy reasons (including
   L1VPN security).  Since the PIT at each PE is associated with a
   L1VPN, this function can be easily supported.  The restriction can be
   applied at the ingress PE or at the egress PE according to the
   applicable restriction policy, but note that applying the policy at
   the egress may waste signaling effort within the network as L1VPN
   connections are pointlessly attempted.

   In addition, the L1VPN Basic Mode does not restrict use of any
   advanced admission control based on various policies.

6.  Customer Control of Its L1VPN

6.1.  Topology Control

   In the L1VPN Basic Mode, L1VPN connection topology is controlled by
   the customer.  That is, a customer can request
   setup/deletion/modification of L1VPN connections using signaling
   mechanisms specified in [RFC5251].

   Also note that if there are multiple CE-to-PE TE links (single-homed
   or multi-homed), a customer can specify which CE-to-PE TE link to use
   to support any L1VPN connection.  Alternatively, a customer may let
   the provider choose the CE-to-PE TE link at the egress side, as
   described in Section 5.2.3.

6.2.  Note on Routing

   A CE needs to obtain the remote CPI to which it wishes to request a
   connection.  Since, in the L1VPN Basic Mode, there is no routing
   information exchange between a CE and a PE, there is no dynamic
   mechanism supported as part of the Basic Mode L1VPN service, and the
   knowledge of remote CPIs must be acquired in a L1VPN-specific way,
   perhaps through configuration or through a directory server.

   If an L1VPN is used by a customer to operate a private IP network,
   the customer may wish to form routing adjacencies over the CE-to-CE
   L1VPN connections.  The L1VPN Basic Mode does not enforce any
   restriction on such operation by a customer, and the use made of the
   L1VPN connections is transparent to the provider network.

   Furthermore, if an L1VPN is used by a customer to operate a private
   Multiprotocol Label Switching (MPLS) or GMPLS network, the customer
   may wish to treat a L1VPN connection as a TE link, and this requires
   a CE-to-CE control channel.  Note that a Forwarding Adjacency
   [RFC4206] cannot be formed from the CE-to-CE L1VPN connection in the
   Basic Mode because there is no routing exchange between CE and PE.
   That is, the customer network and the provider network do not share a
   routing instance, and the customer control channel cannot be carried
   within the provider control plane.  But where the CE provides
   suitable adaptation (for example, where the customer network is a
   packet- switched MPLS or GMPLS network), the customer control channel
   may be in-band and a routing adjacency may be formed between the CEs
   using the L1VPN connection.  Otherwise, CE-to-CE control plane
   connectivity may form part of the L1VPN service provided to the
   customer by the provider and may be achieved within the L1VPN
   connection (for example, through the use of overhead bytes) or
   through a dedicated control channel connection or tunnel.  The
   options available are discussed further in Section 10.2 of [RFC4847].

7.  Scalability and Resiliency

7.1.  Scalability

   There are several factors that impact scalability.

   o Number of L1VPNs (PITs) configured on each PE

     With the increase of this number, information to be maintained on
     the PE increases.  Theoretically, the upper limit of the number of
     L1VPNs supported in a provider network is governed by how the ID
     associated with a L1VPN is allocated, and the number of PITs
     configured on each PE is limited by this number.  However,
     implementations may impose arbitrary limits on the number of PITs
     supported by any one PE.

   o Number of CE-to-PE TE links for each L1VPN

     With the increase of this number, information to be maintained in
     each PIT increases.  When auto-discovery mechanisms are used, the
     amount of information that an auto-discovery mechanism can support
     may restrict this number.

     Note that [RFC5252] floods membership information not only among
     PEs, but also to all P nodes.  This may lead to scalability
     concerns, compared to [RFC5195], which distributes membership
     information only among PEs.  Alternatively, a separate instance of
     the OSPF protocol can be used just between PEs for distributing
     membership information.  In such a case, Ps do not participate in
     flooding.

     Note that in the L1VPN Basic Mode, a PE needs to obtain only CE-
     to-PE TE link information, and not customer routing information,
     which is quite different from the mode of operation of an L3VPN.
     Therefore, the scalability concern is considered to be less
     problematic.

   o Number of L1VPN connections

     With the increase of this number, information to be maintained on
     each PE/P increases.  When stitching or nesting is used, the state
     to be maintained at each PE increases compared to when connectivity
     is achieved without stitching or nesting.

     However, in a Layer 1 core, this number is always bounded by the
     available physical resource because each LSP uses a separate label
     which is directly bound to a physical, switchable resource

     (timeslot, lambda, or fiber).  Thus, it can be safely assumed that
     the PEs/Ps can comfortably handle the number of LSPs that they may
     be called on to switch for a L1VPN.

7.2.  Data Plane Resiliency

   The L1VPN Basic Mode supports the following data plane recovery
   techniques [RFC5251].

   o PE-to-PE segment recovery

     The CE indicates to protect the PE-to-PE segment by including
     Protection Object specified in [RFC4873] in the Path message and
     setting Segment Recovery Flags.  The CE may also indicate the
     branch and merge nodes by including a Secondary Explicit Route
     Object.

     Depending on the signaling mechanisms used within the provider
     network, details on how to protect the PE-to-PE segment may differ
     as follows.

     - If LSP stitching or LSP hierarchy are used to provision the PE-
       to-PE segment, then the PE-to-PE LSP may be protected using end-
       to-end recovery within the provider network.

     - If the CE-to-CE L1VPN connection is a single end-to-end LSP
       (including if session shuffling is used), then the PE-to-PE LSP
       segment may be protected using segment protection [RFC4873].

   o CE-to-PE recovery and PE-to-PE recovery via link protection

     The CE indicates to protect ingress and egress CE-to-PE links as
     well as links within the provider network by including the
     Protection Object specified in [RFC3473] and setting Link Flags in
     the Path message.

     - The ingress and egress CE-to-PE link may be protected at a lower
       layer.

     Depending on the signaling mechanisms used within the provider
     network, details on how to protect links within the provider
     network may differ as follows.

     - If the PE-to-PE segment is provided as a single TE link
       (stitching or hierarchy) so that the provider network can perform
       simple PE-to-PE routing, then the TE link may offer link-level
       protection through the instantiation of multiple PE-to-PE LSPs.

     - The PE-to-PE segment may be provisioned using only link-protected
       links within the core network.

   Note that it is not possible to protect only the CE-to-PE portion or
   the PE-to-PE portion by link protection because the CE-to-CE
   signaling request asks for a certain level of link protection on all
   links used by the LSP.  Also, it is not possible to protect the CE-
   to-PE portion by link recovery and the PE-to-PE portion by segment
   recovery at the same time.

   CE-to-CE recovery through the use of connections from one CE to
   diverse PEs (i.e., dual-homing) is not supported in the L1VPN Basic
   Mode.

7.3.  Control Plane Resiliency

   The L1VPN Basic Mode allows use of GMPLS control plane resiliency
   mechanisms.  This includes, but is not limited to, control channel
   management in LMP [RFC4204] and fault handling in RSVP-TE ([RFC3473]
   and [RFC5063]) between a CE and a PE, as well as within the provider
   network.

8.  Security Considerations

   Security considerations are described in [RFC4847], and this section
   describes how these considerations are addressed in the L1VPN Basic
   Mode.

   Additional discussion of GMPLS security can be found in [GMPLS-SEC].

8.1.  Topology Confidentiality

   As specified in [RFC5251], a provider's topology confidentiality is
   preserved by the Basic Mode.  Since there is no routing exchange
   between PE and CE, the customer network can gather no information
   about the provider network.  Further, as described in Section 4 of
   [RFC4208], a PE may filter the information present in a Record Route
   Object (RRO) that is signaled from the provider network to the
   customer network.  In addition, as described in Section 5 of
   [RFC4208] and Section 4.4 of [RFC5251], when a Notify message is sent
   to a CE, it is possible to hide the provider internal address.  This
   is accomplished by a PE updating the Notify Node Address with its own
   address when the PE receives a NOTIFY_REQUEST object from the CE.

   Even in the case of pre-computed and/or pre-signaled PE-to-PE
   segments, provider topology confidentiality may be preserved through
   the use of path key IDs [CONF-SEG].

   The customer's topology confidentiality cannot be completely hidden
   from the provider network.  At the least, the provider network will
   know about the addresses and locations of CEs.  Other customer
   topology information will remain hidden from the provider in the
   Basic Mode, although care may be needed to protect the customer
   control channel as described in Section 8.4.

   The provider network is responsible for maintaining confidentiality
   of topology information between customers and across L1VPNs.  Since
   there is no distribution of routing information from PE to CE in the
   Basic Mode, there is no mechanism by which the provider could
   accidentally, or deliberately but automatically, distribute this
   information.

8.2.  External Control of the Provider Network

   The provider network is protected from direct control from within
   customer networks through policy and through filtering of signaling
   messages.

   There is a service-based policy installed at each PE that directs how
   a PE should react to a L1VPN connection request received from any CE.
   Each CE is configured at the PE (or through a policy server) for its
   membership of a L1VPN, and so CEs cannot dynamically bind to a PE or
   join a L1VPN.  With this configuration comes the policy that tells
   the PE how to react to a L1VPN connection request (for example,
   whether to allow dynamic establishment of PE-to-PE connections).
   Thus, the provider network is protected against spurious L1VPN
   connection requests and can charge for all L1VPN connections
   according to the service agreement with the customers.  Hence, the
   provider network is substantially protected against denial-of-service
   (DoS) attacks.

   At the same time, if a Path message from a CE contains an Explicit
   Route Object (ERO) specifying the route within provider network, it
   is rejected by the PE.  Thus, the customer network has no control
   over the resources in the provider network.

8.3.  Data Plane Security

   As described in [RFC4847], at Layer 1, data plane information is
   normally assumed to be secure once connections are established since
   the optical signals themselves are normally considered to be hard to
   intercept or modify, and it is considered difficult to insert data
   into an optical stream.  The very use of an optical signal may be
   considered to provide confidentiality and integrity to the payload
   data.  Furthermore, as indicated in [RFC4847], L1VPN connections are

   each dedicated to a specific L1VPN by which an additional element of
   security for the payload data is provided.

   Misconnection remains a security vulnerability for user data.  If a
   L1VPN connection were to be misconnected to the wrong destination,
   user data would be delivered to the wrong consumers.  In order to
   protect against mis-delivery, each L1VPN connection is restricted to
   use only within a single L1VPN.  That is, a L1VPN connection does not
   connect CEs that are in different L1VPNs.  In order to realize this,
   the identity of CEs is assured as part of the service contract.  And
   upon receipt of a request for connection setup, the provider network
   assures that the connection is requested between CEs belonging to the
   same L1VPN.  This is achieved as described in Section 5.3.

   Furthermore, users with greater sensitivity to the security of their
   payload data should apply appropriate security measures within their
   own network layer.  For example, a customer exchanging IP traffic
   over a L1VPN connection may choose to use IPsec to secure that
   traffic (i.e., to operate IPsec on the CE-to-CE exchange of IP
   traffic).

8.4 Control Plane Security

   There are two aspects for control plane security.

   First, the entity connected over a CE-to-PE control channel must be
   identified.  This is done when a new CE is added as part of the
   service contract and the necessary control channel is established.
   This identification can use authentication procedures available in
   RSVP-TE [RFC3209].  That is, control plane entities are identified
   within the core protocols used for signaling, but are not
   authenticated unless the authentication procedures of [RFC3209] are
   used.

   Second, it must be possible to secure communication over a CE-to-PE
   control channel.  If a communication channel between the customer and
   the provider (control channel, management interface) is physically
   separate per customer, the communication channel could be considered
   as secure.  However, when the communication channel is physically
   shared among customers, security mechanisms need to be available and
   should be enforced.  RSVP-TE [RFC3209] provides for tamper-protection
   of signaling message exchanges through the optional Integrity object.
   IPsec tunnels can be used to carry the control plane messages to
   further ensure the integrity of the signaling messages.

   Note that even in the case of physically separate communication
   channels, customers may wish to apply security mechanisms, such as

   IPsec, to assure higher security, and such mechanisms must be
   available.

   Furthermore, the provider network needs mechanisms to detect DoS
   attacks and to protect against them reactively and proactively.  In
   the Basic Mode, this relies on management systems.  For example,
   management systems collect and analyze statistics on signaling
   requests from CEs, and protect against malicious behaviors where
   necessary.

   Lastly, it should be noted that customer control plane traffic
   carried over the provider network between CEs needs to be protected.
   Such protection is normally the responsibility of the customer
   network and can use the security mechanisms of the customer signaling
   and routing protocols (for example, RSVP-TE [RFC3209]) or may use
   IPsec tunnels between CEs.  CE-to-CE control plane security may form
   part of the data plane protection where the control plane traffic is
   carried in-band in the L1VPN connection.  Where the CE-to-CE control
   plane connectivity is provided as an explicit part of the L1VPN
   service by the provider, control plane security should form part of
   the service agreement between the provider and customer.

9.  Manageability Considerations

   Manageability considerations are described in [RFC4847].  In the
   L1VPN Basic Mode, we rely on management systems for various aspects
   of the different service functions, such as fault management,
   configuration and policy management, accounting management,
   performance management, and security management (as described in
   Section 8).

   In order to support various management functionalities, MIB modules
   need to be supported.  In particular, the GMPLS TE MIB (GMPLS-TE-STD-
   MIB) [RFC4802] can be used for GMPLS-based traffic engineering
   configuration and management, while the TE Link MIB (TE-LINK-STD-MIB)
   [RFC4220] can be used for configuration and management of TE links.

10.  References

10.1.  Normative References

   [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.

   [RFC4026]    Anderssion, L. and Madsen, T., "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.

   [RFC4847]    Takeda, T., Ed., "Framework and Requirements for Layer 1
                Virtual Private Networks", RFC 4847, April 2007.

   [RFC4873]    Berger, L., Bryskin, I., Papadimitriou, D., and A.
                Farrel, "GMPLS Segment Recovery", RFC 4873, May 2007.

   [RFC5195]    Ould-Brahim, H., Fedyk, D., and Y. Rekhter, "BGP-Based
                Auto-Discovery for Layer-1 VPNs", RFC 5195, June 2008.

   [RFC5251]   Fedyk, D., Ed., Rekhter, Y., Ed., Papadimitriou, D.,
                Rabbat, R., and L. Berger, "Layer 1 VPN Basic Mode", RFC
                5251, July 2008.

   [RFC5252]  Bryskin, I. and Berger, L., "OSPF-Based Layer 1 VPN Auto-
                Discovery", RFC 5252, July 2008.

10.2.  Informative References

   [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.

   [RFC4220]    Dubuc, M., Nadeau, T., and J. Lang, "Traffic Engineering
                Link Management Information Base", RFC 4220, November
                2005.

   [RFC4655]    Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
                Computation Element (PCE)-Based Architecture", RFC 4655,
                August 2006.

   [RFC4802]    Nadeau, T., Ed., and A. Farrel, Ed., "Generalized
                Multiprotocol Label Switching (GMPLS) Traffic
                Engineering Management Information Base", RFC 4802,
                February 2007.

   [RFC5063]    Satyanarayana, A., Ed., and R. Rahman, Ed., "Extensions
                to GMPLS Resource Reservation Protocol (RSVP) Graceful
                Restart", RFC 5063, October 2007.

   [BGP-TE]     Ould-Brahim, H., Fedyk, D., and Y. Rekhter, "Traffic
                Engineering Attribute", Work in Progress, January 2008.

   [CONF-SEG]   Bradford, R., Ed., Vasseur, JP., and A. Farrel,
                "Preserving Topology Confidentiality in Inter-Domain
                Path Computation Using a Key-Based Mechanism", Work in
                Progress, May 2008.

   [GMPLS-SEC]  Fang, L., Ed., " Security Framework for MPLS and GMPLS
                Networks", Work in Progress, February 2008.

11.  Acknowledgments

   The authors would like to thank Ichiro Inoue for valuable comments.
   In addition, the authors would like to thank Marco Carugi and Takumi
   Ohba for valuable comments in the early development of this document.

   Thanks to Tim Polk and Mark Townsley for comments during IESG review.

Authors' Addresses

   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

   Deborah Brungard
   AT&T
   Rm. D1-3C22 - 200 S. Laurel Ave.
   Middletown, NJ 07748, USA
   Phone: +1 732 4201573
   EMail: dbrungard@att.com

   Adrian Farrel
   Old Dog Consulting
   Phone:  +44 (0) 1978 860944
   EMail:  adrian@olddog.co.uk

   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

   Dimitri Papadimitriou
   Alcatel-Lucent
   Francis Wellensplein 1,
   B-2018 Antwerpen, Belgium
   Phone: +32 3 2408491
   EMail: dimitri.papadimitriou@alcatel-lucent.be

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