OSPFv3-Based Layer 1 VPN Auto-Discovery
draft-ietf-l1vpn-ospfv3-auto-discovery-03

Internet Draft                         Lou Berger (LabN Consulting, LLC)
Category: Experimental
Expiration Date: July 12, 2009

                                                        January 12, 2009

                OSPFv3 Based Layer 1 VPN Auto-Discovery

             draft-ietf-l1vpn-ospfv3-auto-discovery-03.txt

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Abstract

   This document defines an Open Shortest Path First (OSPF) version 3
   based 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  ..............................................   3
 1.1    Terminology  ...............................................   3
 1.2    Overview  ..................................................   4
 2      OSPFv3 L1VPN LSA and its TLVs  .............................   5
 2.1    OSPFv3 L1VPN LSA  ..........................................   5
 2.2    L1VPN IPv6 INFO TLV  .......................................   6
 3      OSPFv3 L1VPN LSA Advertising and Processing  ...............   8
 4      Backward Compatibility  ....................................   8
 5      Manageability Considerations  ..............................   9
 5.1    Coexistence with and Migration from OSPFv2  ................   9
 6      Security Considerations  ...................................  10
 7      IANA Considerations  .......................................  10
 8      Acknowledgment  ............................................  11
 9      References  ................................................  11
 9.1    Normative References  ......................................  11
 9.2    Informative References  ....................................  11
10      Authors' Addresses  ........................................  12

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Conventions used in this document

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

1. Introduction

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 One 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

     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
             speaker

     PIT -  Port Information Table

     CPI -  Customer Port Identifier

     PPI -  Provider Port Identifier

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1.2. 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 of 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.

                  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 is referred to as the L1VPN Info TLV.

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

2. OSPFv3 L1VPN LSA and its TLVs

   This section defines the OSPFv3 L1VPN LSA and its TLVs.

2.1. OSPFv3 L1VPN LSA

   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 AS scoping.
      The LSA Function Code portion of this field MUST be set to TBA
      (by IANA), i.e., the OSPFv3 L1VPN LSA.

   Advertising Router
      As defined in [RFC5340].

   LS Sequence Number
      As defined in [RFC5340].

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   LS checksum
      As defined in [RFC5340].

   Length
      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.

2.2. L1VPN IPv6 INFO TLV

   The following TLV is introduced:

   Name: L1VPN IPv6 Info
   Type: 32768
   Length: Variable

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    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.

   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].

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

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 LSAs flooding process but should
   ignore the LSAs contents.

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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 [TED-
   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 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
   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
         resources.
      2. Install and enable OSPFv3 on all controllers.

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      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 impact
   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
   LSAs.

7. IANA Considerations

   Section 2.1 of this document requests the assignment of an OSPFv3 LSA
   Function Code, see http://www.iana.org/assignments/ospfv3-parameters.
   IANA is requested to make an assignment in the form:

       Value   OSPFv3 LSA type function Type            Reference
      -------  -----------------------------            ---------
          TBA  OSPFv3 L1VPN LSA                         [this document]

      A value of 13 is suggested for TBA.

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8. Acknowledgment

   This document was created at the request of Pasi Eronen.  Adrian
   Farrel and Acee Lindem provided valuable reviews of this draft.
   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
             requirements levels", RFC 2119, March 1997.

   [RFC5340] R. Coltun, D. Ferguson, J. Moy, "OSPF for IPv6",
             RFC 5340.

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

   [RFC4203] Kompela, K., Rekhter, Y. "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, June 2008.

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

   [RFC5329]  K. Ishiguro, T. Takada, "Traffic Engineering
              Extensions to OSPF version 3", RFC 5328,
              September 2008.

9.2. Informative References

   [OSPFv3-MIB] Joyal, D., Manral, V., Eds., "Management Information
                Base for OSPFv3", draft-ietf-ospf-ospfv3-mib, Work in
                Progress, November 2008.

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

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   [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., Kumaki, K.,
                "Traffic Engineering Database Management Information
                Base in support of MPLS-TE/GMPLS", Work in Progress,
                draft-ietf-ccamp-gmpls-ted-mib, July 2008.

10. Authors' Addresses

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

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