RFC 5523

Network Working Group                                          L. Berger
Request for Comment: 5523                           LabN Consulting, LLC
Category: Experimental                                        April 2009

                OSPFv3-Based Layer 1 VPN Auto-Discovery

Status of This Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.


   This document defines an OSPFv3-based (Open Shortest Path First
   version 3) Layer 1 Virtual Private Network (L1VPN) auto-discovery
   mechanism.  This document parallels the existing OSPF version 2 L1VPN
   auto-discovery mechanism.  The notable functional difference is the
   support of IPv6.

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Table of Contents

   1. Introduction ....................................................2
      1.1. Terminology ................................................2
      1.2. Conventions Used in This Document ..........................3
      1.3. Overview ...................................................3
   2. OSPFv3 L1VPN LSA and Its TLVs ...................................5
      2.1. OSPFv3 L1VPN LSA ...........................................5
      2.2. L1VPN IPv6 INFO TLV ........................................7
   3. OSPFv3 L1VPN LSA Advertising and Processing .....................8
   4. Backward Compatibility ..........................................9
   5. Manageability Considerations ....................................9
      5.1. Coexistence with and Migration from OSPFv2 .................9
   6. Security Considerations ........................................10
   7. IANA Considerations ............................................11
   8. Acknowledgment .................................................11
   9. References .....................................................11
      9.1. Normative References ......................................11
      9.2. Informative References ....................................12

1.  Introduction

   This document defines an OSPFv3-based (Open Shortest Path First
   version 3) Layer 1 Virtual Private Network (L1VPN) auto-discovery
   mechanism.  This document parallels the existing OSPF version 2 L1VPN
   auto-discovery mechanism.  The notable functional difference is the
   support of IPv6.

1.1.  Terminology

   The reader of this document should be familiar with the terms used in
   [RFC4847] and [RFC5251].  The reader of this document should also be
   familiar with [RFC5340], [RFC5329], and [RFC5252].  In particular,
   the following terms:

      L1VPN   Layer 1 Virtual Private Network

      CE      Customer (edge) network element directly connected to the
              Provider network (terminates one or more links to one or
              more PEs); it is also connected to one or more Cs and/or
              other CEs.

      C       Customer network element that is not connected to the
              Provider network but is connected to one or more other Cs
              and/or CEs.

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      PE      Provider (edge) network element directly connected to one
              or more Customer networks (terminates one or more links to
              one or more CEs associated with the same or different
              L1VPNs); it is also connected to one or more Ps and/or
              other PEs.

      P       Provider (core) network element that is not directly
              connected to any of Customer networks; P is connected to
              one or more other Ps and/or PEs.

      LSA     OSPF Link State Advertisement.

      LSDB    Link State Database: a data structure supported by an IGP

      PIT     Port Information Table.

      CPI     Customer Port Identifier.

      PPI     Provider Port Identifier.

1.2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

1.3.  Overview

   The framework for Layer 1 VPNs is described in [RFC4847].  Basic mode
   operation is further defined in [RFC5251].  [RFC5251] identifies the
   information that is necessary to map customer information (port
   identifiers) to provider information (identifiers).  It also states
   that this mapping information may be provided via provisioning or via
   an auto-discovery mechanism.  [RFC5252] provides such an auto-
   discovery mechanism using Open Shortest Path First (OSPF) version 2.
   This document provides the same functionality using OSPF version 3
   and adds support for IPv6.

   Figure 1 shows the L1VPN basic service being supported using OSPF-
   based L1VPN auto-discovery.  This figure shows two PE routers
   interconnected over a GMPLS backbone.  Each PE is attached to three
   CE devices belonging to three different Layer 1 VPNs.  In this
   network, OSPF is used to provide the VPN membership, port mapping,
   and related information required to support basic mode operation.

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                  PE                        PE
               +---------+             +--------------+
   +--------+  | +------+|             | +----------+ | +--------+
   |  VPN-A |  | |VPN-A ||             | |  VPN-A   | | |  VPN-A |
   |   CE1  |--| |PIT   ||  OSPF LSAs  | |  PIT     | |-|   CE2  |
   +--------+  | |      ||<----------->| |          | | +--------+
               | +------+| Distribution| +----------+ |
               |         |             |              |
   +--------+  | +------+|             | +----------+ | +--------+
   | VPN-B  |  | |VPN-B ||   -------   | |   VPN-B  | | |  VPN-B |
   |  CE1   |--| |PIT   ||--( GMPLS )--| |   PIT    | |-|   CE2  |
   +--------+  | |      ||  (Backbone) | |          | | +--------+
               | +------+|   --------  | +----------+ |
               |         |             |              |
   +--------+  | +-----+ |             | +----------+ | +--------+
   | VPN-C  |  | |VPN-C| |             | |   VPN-C  | | |  VPN-C |
   |  CE1   |--| |PIT  | |             | |   PIT    | |-|   CE2  |
   +--------+  | |     | |             | |          | | +--------+
               | +-----+ |             | +----------+ |
               +---------+             +--------------+

                 Figure 1: OSPF Auto-Discovery for L1VPNs

   The approach used in this document to provide OSPFv3-based L1VPN
   auto-discovery uses a new type of Link State Advertisement (LSA),
   which is referred to as an OSPFv3 L1VPN LSA.  The OSPFv3 L1VPN LSA
   carries information in TLV (type, length, value) structures.  An
   L1VPN-specific TLV is defined below to propagate VPN membership and
   port information.  This TLV is referred to as the L1VPN Info TLV.

   The OSPFv3 L1VPN LSA may also carry Traffic Engineering (TE) TLVs;
   see [RFC3630], [RFC4203], and [RFC5329].

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RFC 5523         OSPV3-Based Layer 1 VPN Auto-Discovery       April 2009

2.  OSPFv3 L1VPN LSA and Its TLVs

   This section defines the OSPFv3 L1VPN LSA and its TLVs.


   The format of a OSPFv3 L1VPN LSA is as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   |           LS age              |          LS type              |
   |                       Link State ID                           |
   |                    Advertising Router                         |
   |                    LS sequence number                         |
   |        LS checksum            |            length             |
   |                           L1VPN Info TLV                      |
   |                             ...                               |
   |                            TE Link TLV                        |
   |                             ...                               |

   LS age

      As defined in [RFC5340].

   LS type

      As defined in [RFC5340].  The U-bit MUST be set to 1, and the S1
      and S2 bits MUST be set to indicate either area or Autonomous
      System (AS) scoping.  The LSA Function Code portion of this field
      MUST be set to 14, i.e., the OSPFv3 L1VPN LSA.

   Advertising Router

      As defined in [RFC5340].

   LS Sequence Number

      As defined in [RFC5340].

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RFC 5523         OSPV3-Based Layer 1 VPN Auto-Discovery       April 2009

   LS checksum

      As defined in [RFC5340].


      As defined in [RFC5340].

   L1VPN Info TLV

      A single L1VPN Info TLV, as defined in Section 2.2 of [RFC5252] or
      Section 2.2 of this document, MUST be present.  If more than one
      L1VPN Info TLV is present, only the first TLV is processed and the
      others MUST be ignored on receipt.  If no L1VPN Info TLV is
      present, the LSA is processed (and flooded) as normal, but the
      L1VPN PIT table MUST NOT be modified in any way.

   TE Link TLV

      A single TE Link TLV MAY be included in an OSPFv3 L1VPN LSA.  When
      an L1VPN IPv4 Info TLV is present, a single TE Link TLV as defined
      in [RFC3630] and [RFC4203] MAY be included.  When an L1VPN IPv6
      Info TLV is present, a single TE Link TLV as defined in [RFC5329]
      MAY be included.

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RFC 5523         OSPV3-Based Layer 1 VPN Auto-Discovery       April 2009


   The following TLV is introduced:

   Name: L1VPN IPv6 Info
   Type: 32768
   Length: Variable

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   |           L1VPN TLV Type      |         L1VPN TLV Length      |
   |                 L1VPN Globally Unique Identifier              |
   |                              ...                              |
   |                          PE TE Address                        |
   |                              ...                              |
   |                              ...                              |
   |                              ...                              |
   |                       Link-Local Identifier                   |
   |                              ...                              |
   |                 L1VPN Auto-Discovery Information              |
   +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              .|           Padding             |

   L1VPN TLV Type

      The type of the TLV (see above).

   TLV Length

      The length of the TLV in bytes, excluding the four (4) bytes of
      the TLV header and, if present, the length of the Padding field.

   L1VPN Globally Unique Identifier

      As defined in [RFC5251].

   PE TE Address

      This field MUST carry an address that has been advertised by the
      LSA originator per [RFC5329] and is either the Router IPv6 Address
      TLV or Local Interface IPv6 Address link sub-TLV.  It will
      typically carry the TE Router Address.

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RFC 5523         OSPV3-Based Layer 1 VPN Auto-Discovery       April 2009

   Link-Local Identifier

      This field is used to support unnumbered links.  When an
      unnumbered PE TE link is represented, this field MUST contain a
      value advertised by the LSA originator per [RFC5340] in a Router
      LSA.  When a numbered link is represented, this field MUST be set
      to zero (0).

   L1VPN Auto-Discovery Information

      As defined in [RFC5251].


      A field of variable length and of sufficient size to ensure that
      the TLV is aligned on a 4-byte boundary.  This field is only
      required when the L1VPN Auto-Discovery Information field is not
      4-byte aligned.  This field MUST be less than 4 bytes long, and
      MUST NOT be present when the size of L1VPN Auto-Discovery
      Information field is 4-byte aligned.

3.  OSPFv3 L1VPN LSA Advertising and Processing

   PEs advertise local <CPI, PPI> tuples in OSPFv3 L1VPN LSAs containing
   L1VPN Info TLVs.  Each PE MUST originate a separate OSPFv3 L1VPN LSA
   with area or AS flooding scope, based on configuration, for each
   local CE-PE link.  The LSA MUST be originated each time a PE restarts
   and every time there is a change in the PIT entry associated with a
   local CE-PE link.  The LSA MUST include a single L1VPN Info TLV and
   MAY include a single TE Link TLV.  The TE Link TLV carries TE
   attributes of the associated CE-PE link.  Note that because CEs are
   outside of the provider TE domain, the attributes of CE-PE links are
   not advertised via normal OSPF-TE procedures as described in
   [RFC5329].  If more than one L1VPN Info TLVs and/or TE Link TLVs are
   found in the LSA, the subsequent TLVs SHOULD be ignored by the
   receiving PEs.

   Every time a PE receives a new, removed, or modified OSPFv3 L1VPN
   LSA, the PE MUST check whether it maintains a PIT associated with the
   L1VPN specified in the L1VPN Globally Unique Identifier field.  If
   this is the case (the appropriate PIT will be found if one or more
   local CE-PE links that belong to the L1VPN are configured), the PE
   SHOULD add, remove, or modify the PIT entry associated with each of
   the advertised CE-PE links accordingly.  (An implementation MAY
   choose to not remove or modify the PIT according to local policy or
   management directives.)  Thus, in the normal steady-state case, all
   PEs associated with a particular L1VPN will have identical local PITs
   for an L1VPN.

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4.  Backward Compatibility

   Neither the TLV nor the LSA introduced in this document present any
   interoperability issues.  Per [RFC5340], and due to the U-bit being
   set, OSPFv3 speakers that do not support the OSPFv3 L1VPN LSA (Ps for
   example) just participate in the LSA's flooding process but should
   ignore the LSA's contents.

5.  Manageability Considerations

   The principal concern in operating an auto-discovery mechanism for an
   L1VPN is that the PE needs to be configured with information about
   which VPNs it supports.  This information can be discovered from the
   CEs using some form of membership negotiation, but is more likely to
   be directly configured by the operator as described in [RFC4847],
   [RFC5251], and [RFC5253].  No standardized mechanisms to configure
   this information have been defined, and it is a matter for individual
   implementations with input from operator policy how a PE is told
   which L1VPNs it supports.  It is probable that configuration of this
   information is closely tied to the configuration of CE-facing ports
   on the PE, which in turn causes PITs to be established in the PE.

   Additionally, it may be of value to an operator to view the L1VPN
   membership information that has been learned by a PE.  An
   implementation may supply this information through a proprietary
   interface, or may allow it to be inspected through the OSPFv3 MIB
   module [OSPFv3-MIB] or the Traffic Engineering Database MIB

   Note that the operation of the control plane has no impact on IP
   network traffic because all of the user data is in Layer 1, while the
   control plane is necessarily out of band in a Data Communications
   Network (DCN).

5.1.  Coexistence with and Migration from OSPFv2

   It is expected that only a single routing protocol instance will be
   used to operate auto-discovery within an L1VPN at any time.  Thus,
   coexistence issues only apply to the migration from OSPFv2 to OSPFv3
   and can be expected to be transient.

   Migration from OSPFv2 to OSPFv3 would be a once-only event for any
   network and would probably depend on the migration of the routing
   protocol used within the network for normal GMPLS procedures.  The
   migration process would not be any different from the process used to
   migrate the normal GMPLS routing protocol.  The steps to follow are

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   clearly a matter for the operator of the network and are not a matter
   for standardization, but the following sequence is provided to
   illustrate the potential actions:

   1. Assign IPv6 addresses to all control plane and data plane

   2. Install and enable OSPFv3 on all controllers.

   3. Use OSPFv3 to advertise IPv4 and IPv6 resource identifiers.

   4. Manually verify the advertised membership and topology information
      from the OSPFv2 and OSPFv3 databases.

   5. Start a maintenance window where data continues to flow, but no
      L1VPN connections can be changed.

   6. Cut over to the OSPFv3 membership and topology information.

   7. Close the maintenance window.

   8. Turn off OSPFv2.

   9. Remove/disable the IPv4 address for all control plane and data
      plane resources.

6.  Security Considerations

   The approach presented in this document describes how PEs dynamically
   learn L1VPN specific information.  Mechanisms to deliver the VPN
   membership information to CEs are explicitly out of scope of this
   document.  Therefore, the security issues raised in this document are
   limited to within the OSPF domain.

   This defined approach reuses mechanisms defined in [RFC5340].
   Therefore, the same security approaches and considerations apply to
   this approach.  OSPF provides several security mechanisms that can be
   applied.  Specifically, OSPF supports multiple types of
   authentication, limits the frequency of LSA origination and
   acceptance, and provides techniques to avoid and limit the impact of
   database overflow.  In cases were end-to-end authentication is
   desired, OSPF's neighbor-to-neighbor authentication approach can be
   augmented with an approach similar to the experimental extension to
   OSPF, see [RFC2154], which supports the signing and authentication of

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RFC 5523         OSPV3-Based Layer 1 VPN Auto-Discovery       April 2009

7.  IANA Considerations

   IANA has assigned an OSPFv3 LSA Function Code as described in Section
   2.1 of this document.  IANA has made an assignment in the form:

       Value   OSPFv3 LSA type function Type            Reference
      -------  -----------------------------            ---------
           14  OSPFv3 L1VPN LSA                         [RFC5523]

8.  Acknowledgment

   This document was created at the request of Pasi Eronen.  Adrian
   Farrel and Acee Lindem provided valuable reviews of this document.
   Adrian also provided the text for Section 5.

9.  References

9.1.  Normative References

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

   [RFC5340]    Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
                for IPv6", RFC 5340, July 2008.

   [RFC3630]    Katz, D., Kompella, K., and D. Yeung, "Traffic
                Engineering (TE) Extensions to OSPF Version 2", RFC
                3630, September 2003.

   [RFC4203]    Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions
                in Support of Generalized Multi-Protocol Label Switching
                (GMPLS)", RFC 4203, October 2005.

   [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 L. Berger, "OSPF-Based Layer 1 VPN
                Auto-Discovery", RFC 5252, July 2008.

   [RFC5329]    Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
                "Traffic Engineering Extensions to OSPF Version 3", RFC
                5329, September 2008.

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RFC 5523         OSPV3-Based Layer 1 VPN Auto-Discovery       April 2009

9.2.  Informative References

   [OSPFv3-MIB] Joyal, D., Ed. and V. Manral, Ed., "Management
                Information Base for OSPFv3", Work in Progress, November

   [RFC2154]    Murphy, S., Badger, M., and B. Wellington, "OSPF with
                Digital Signatures", RFC 2154, June 1997.

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

   [RFC5253]    Takeda, T., Ed., "Applicability Statement for Layer 1
                Virtual Private Network (L1VPN) Basic Mode", RFC 5253,
                July 2008.

   [TED-MIB]    Miyazawa, M., Otani, T., Nadeau, T., and K. Kumaki,
                "Traffic Engineering Database Management Information
                Base in support of MPLS-TE/GMPLS", Work in Progress,
                January 2009.

Author's Address

   Lou Berger
   LabN Consulting, LLC
   EMail: lberger@labn.net

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