GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools

Problem, Formatting or Query -  Send Feedback

Was this page helpful?-10+1


rfc:rfc5523

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.

Abstract

 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.

Berger Experimental [Page 1] RFC 5523 OSPV3-Based Layer 1 VPN Auto-Discovery April 2009

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.

Berger Experimental [Page 2] RFC 5523 OSPV3-Based Layer 1 VPN Auto-Discovery April 2009

    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.

1.2. 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].

1.3. 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.

Berger Experimental [Page 3] RFC 5523 OSPV3-Based Layer 1 VPN Auto-Discovery April 2009

                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].

Berger Experimental [Page 4] 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.

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 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].

Berger Experimental [Page 5] RFC 5523 OSPV3-Based Layer 1 VPN Auto-Discovery April 2009

 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.

Berger Experimental [Page 6] RFC 5523 OSPV3-Based Layer 1 VPN Auto-Discovery April 2009

2.2. L1VPN IPv6 INFO TLV

 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.

Berger Experimental [Page 7] 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].
 Padding
    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.

Berger Experimental [Page 8] RFC 5523 OSPV3-Based Layer 1 VPN Auto-Discovery April 2009

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
 [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 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

Berger Experimental [Page 9] RFC 5523 OSPV3-Based Layer 1 VPN Auto-Discovery April 2009

 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.
 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
 LSAs.

Berger Experimental [Page 10] 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.

Berger Experimental [Page 11] 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
              2008.
 [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

Berger Experimental [Page 12]

/data/webs/external/dokuwiki/data/pages/rfc/rfc5523.txt · Last modified: 2009/04/08 23:39 (external edit)