Internet Draft                    Igor Bryskin (ADVA Optical Networking)
Category: Standards Track              Lou Berger (LabN Consulting, LLC)
Expiration Date: March 26, 2008

                                                      September 26, 2007

                    OSPF Based L1VPN Auto-Discovery


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Copyright Notice

   Copyright (C) The IETF Trust (2007).


   This document defines an OSPF based layer-1 VPN auto-discovery
   mechanism.  This mechanism enables PEs using the OSPF IGP to
   dynamically learn about existence of each other, and attributes of
   currently configured CE-PE links and their associations with L1VPNs.
   This document builds on [RFC4847] and provides an auto-discovery
   mechanism as discussed in [L1VPN-BM].

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 1      Terminology  ...............................................   3
 2      Introduction  ..............................................   4
 3      L1VPN LSA and its TLVs  ....................................   5
 3.1    L1VPN LSA  .................................................   5
 3.2    L1VPN INFO TLV  ............................................   6
 4      L1VPN LSA Advertising and Processing  ......................   7
 4.1    Discussion and Example  ....................................   7
 5      Backward compatibility  ....................................   8
 6      Security Considerations  ...................................   9
 7      IANA Considerations  .......................................   9
 8      Acknowledgment  ............................................   9
 9      References  ................................................   9
 9.1    Normative References  ......................................   9
 9.2    Informative References  ....................................  10
10      Authors' Addresses  ........................................  10
11      Full Copyright Statement  ..................................  10
12      Intellectual Property  .....................................  11

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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. Terminology

   The reader of this document should be familiar with the terms used in
   [RFC4847] and [L1VPN-BM].  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

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

   PIT - Port Information Table

   CPI - Customer Port Identifier

   PPI - Provider Port Identifier

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2. Introduction

   The framework for Layer 1 VPNs is described in [RFC4847].  Basic mode
   operation is further defined in [L1VPN-BM].  [L1VPN-BM] document
   identifies the information that is necessary to map customer
   information (ports identifiers) to provider information
   (identifiers).  It also states that this mapping information may be
   provided via provisioning or via an auto-discovery mechanism.  This
   document provides such an auto-discovery mechanism using the OSPF
   IGP.  Figure 1 shows the L1VPN basic service being supported using
   OSPF based L1VPN auto-discovery.  See [L1VPN-BGP] for a parallel
   L1VPN auto-discovery that uses BGP.  The IGP approach described in
   this document is particularly useful in networks where BGP is not
   typically used.

                  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 OSPF based L1VPN auto-
   discovery uses an Opaque LSA of a new Opaque Type (referred as a
   L1VPN LSA).

   There is a TLV type defined for use within a L1VPN LSA. The TLV,
   which is referred to as L1VPN Info TLV, is used to propagate <CPI,
   PPI> tuple and VPN ID mappings.

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3. L1VPN LSA and its TLVs

   This section defines the L1VPN LSA and its TLVs.

3.1. L1VPN LSA

   The format of a 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             |     Options   |  LS Type      |
   |  Opaque Type  |               Opaque ID                       |
   |                      Advertising Router                       |
   |                      LS Sequence Number                       |
   |         LS checksum           |           Length              |
   |                           L1VPN Info TLV                      |
   |                             ...                               |
   |                            TE Link TLV                        |
   |                             ...                               |

   LS age
      As defined in [RFC2328]

      As defined in [RFC2328].

   LS Type
      This field MUST be set to 11.

   Opaque Type
      The value of this field MUST be set to TBA (by IANA).

   Opaque ID
      As defined in [RFC2370]

   Advertising Router
      As defined in [RFC2328].

   LS Sequence Number

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      As defined in [RFC2328].

   LS checksum
      As defined in [RFC2328].

      As defined in [RFC2328].

   L1VPN Info TLV
      A single TLV, as defined in section 3.2

   TE Link TLV
      A single TE Link TLV (as defined in [RFC3630] and [RFC4203])
      MAY be included in a L1VPN LSA


   The following TLV is introduced:

   Name: L1VPN IPv4 Info
   Type: 1
   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 length      |           L1VPN TLV Type      |
   |                 L1VPN Globally unique identifier              |
   |                                                               |
   |                        PE TE Address                          |
   |                              ...                              |
   |                 L1VPN Auto-Discovery Information              |
   |                              ...                              |

   TLV length
      The length of the TLV in bytes, including the 4 bytes of
      the TLV header.

   L1VPN TLV Type
      The type of the TLV.

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   L1VPN Globally unique identifier
      As defined in [L1VPN-BM].

   PE TE Address
      Valid PE TE address: either TE Router ID specified in the
      Router Address TLV or local numbered TE link ID specified in
      the Local interface IP address sub-TLV of the TE Link TLV of the
      TE LSA originated by the PE

   L1VPN Auto-discovery information
      As defined in [L1VPN-BM].

4. L1VPN LSA Advertising and Processing

   PEs advertise local <CPI, PPI> tuples in L1VPN LSAs containing L1VPN
   Info TLVs. Each PE MUST originate a separate L1VPN LSA with AS
   flooding scope for each local CE-PE link. The LSA MUST be originated
   once on the PE restart and every time when 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 as per
   [RFC3630] and [RFC4203].

   L1VPN LSAs are flooded to all PEs within the AS according to
   [RFC2370] or [2370BIS]. Every time a PE receives a new, removed or
   modified such 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. Thus,
   in the steady mode all PEs associated with a particular L1VPN
   maintain identical local PITs for the L1VPN.

4.1. Discussion and Example

   The L1VPN auto-discovery mechanism described in this document does
   not prevent a PE from applying any local policy with respect to PIT
   management. For example, it should be possible to configure permanent
   (static) PIT entries, blocking information carried in L1VPN LSAs that
   are advertised by some remote PEs from making it to the PITs and so

   The reason why it is required that the value specified in the PE TE
   Address field of the L1VPN Info TLV matches a valid PE TE Router ID
   or numbered TE Link ID is to ensure that CEs attached to this PE

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   could be resolved to the PE as it is known to the Traffic Engineering
   Database (TED) and hence TE paths towards the CEs across the Provider
   domain could be computed.

   Let us consider example presented on Figure 2.

                            CE11               CE13
                              |                 |
                              |         |
                             CE15      PE3

                    Figure 2: Single area configuration

   Let us assume that PE1 is connected to CE11 and CE15 in L1VPN1 and to
   CE22 in L1VPN2; PE2 is connected to CE13 in L1VPN1; PE3 is connected
   to CE24 in L1VPN2. In this configuration PE1 manages two PITs: PIT1
   for L1VPN1 and PIT2 for L1VPN2; PE2 manages only PIT1, and PE3
   manages only PIT2. PE1 originates three L1VPN LSAs, each containing a
   L1VPN Info TLV advertising links PE1-CE11, PE1-CE22 and PE1-CE15
   respectively. PE2 originates a single L1VPN LSA for link PE2-CE13 and
   PE3 originates a single L1VPN LSA for link PE3-CE24. In the steady
   mode PIT1 on PE1 and PE3 will contain information on links PE1-CE11,
   PE1-CE15 and PE2-CE13; PIT2 on PE1 and PE2 will contain entries for
   links PE1-CE22 and PE3-CE24. Thus, all PEs will learn about all
   remote PE-CE links for all L1VPNs supported by PEs.

   Note that P in this configuration does not have links connecting it
   to any of L1VPNs. It neither originates L1VPN LSAs nor maintains any
   PITs. However, it does participate in the flooding of all of the
   L1VPN LSA and hence maintains the LSAs in its LSDB. This is a cause
   for scalability concerns and could prove to be problematic on large

5. Backward compatibility

   Neither the TLV nor the LSA introduced in this document present any
   interoperability issues. OSPF speakers that do not support L1VPN
   auto-discovery application (Ps for example) just participate in the
   L1VPN LSAs flooding process but should ignore the LSAs contents.

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6. Security Considerations

   The solution 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, no new security issues are raised in this

7. IANA Considerations

   This document requests the assignment of an OSPF Opaque LSA type, see  IANA is requested
   to make an assignment in the form:

       Value   Opaque Type                              Reference
      -------  -----------                              ---------
          TBA  L1VPN LSA                                [this document]

      A value of 4 is suggested for TBA.

8. Acknowledgment

   We would like to thank Adrian Farrel for his useful comments.

9. References

9.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to indicate
             requirements levels", RFC 2119, March 1997.

   [RFC2328] Moy, J., " OSPF Version 2 ", RFC 2328, April 1998.

   [RFC2370] Coltun, R., " The OSPF Opaque LSA Option ", RFC 2730,
             July 1998.

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

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

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   [L1VPN-BM] Fedyk, D., Rekhter, Y. (Eds.), "Layer 1 VPN Basic
              Mode", draft-fedyk-l1vpn-basic-mode, March
              2006, work in progress.

9.2. Informative References

   [2370BIS] Berger, L., Bryskin, I., Zinin, A., "The OSPF Opaque LSA
             Option", work in progress, draft-ietf-ospf-rfc2370bis,
             December, 2006.

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

   [L1VPN-BGP] Ould-Brahim H.,  Fedyk D., Rekhter, Y., "BGP-based Auto-
               Discovery for L1VPNs ",
               work in progress, March 2006

10. Authors' Addresses

   Igor Bryskin
   ADVA Optical Networking Inc
   7926 Jones Branch Drive
   Suite 615
   McLean, VA - 22102

   Lou Berger
   LabN Consulting, LLC

11. Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an

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12. Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

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   specification can be obtained from the IETF on-line IPR repository at

   The IETF invites any interested party to bring to its attention any
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   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at ietf-


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   Administrative Support Activity (IASA).

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