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Versions: 00 01 02 draft-ietf-ospf-multi-instance

Network Working Group                                          A. Lindem
Internet-Draft                                          Redback Networks
Intended status: Standards Track                                  A. Roy
Expires: March 12, 2008                                    Cisco Systems
                                                            S. Mirtorabi
                                                        Force10 Networks
                                                       September 9, 2007


                     OSPF Multi-Instance Extensions
                   draft-acee-ospf-multi-instance-00.txt

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Copyright Notice

   Copyright (C) The IETF Trust (2007).











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Abstract

   OSPFv3 includes a mechanism for supporting multiple instances on the
   same link.  OSPFv2 could benefit from such a mechanism in order to
   support multiple routing domains on the same subnet.  The OSPFv2
   instance ID is reserved for support of separate OSPFv2 protocol
   instances.  This is different from OSPFv3 where it could be used for
   other purposes such as putting the same link in multiple areas.
   OSPFv2 supports this capability using a separate subnet or the OSPF
   multi-area adjacency capability.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements notation  . . . . . . . . . . . . . . . . . .  3
   2.  OSPFv2 Instance Packet Encoding  . . . . . . . . . . . . . . .  4
   3.  OSPF Interface Instance ID . . . . . . . . . . . . . . . . . .  6
     3.1.  Sending and Receiving OSPF packets . . . . . . . . . . . .  6
   4.  Backward Compatibility and Deployment Considerations . . . . .  7
     4.1.  Separate Multicast Addresses for Backward Compatibility  .  7
     4.2.  Separate Protocol ID for Backward Compatibility  . . . . .  7
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   7.  Normative References . . . . . . . . . . . . . . . . . . . . . 10
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
   Intellectual Property and Copyright Statements . . . . . . . . . . 13























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1.  Introduction

   OSPFv3 [OSPFV3] includes a mechanism for supporting multiple
   instances on the same link.  OSPFv2 [OSPFV2] could benefit from such
   a mechanism in order to support multiple routing domains on the same
   subnet.  The OSPFv2 instance ID is reserved for support of separate
   OSPFv2 protocol instances.  This is different from OSPFv3 where it
   could be used for other purposes such as putting the same link in
   multiple areas.  OSPFv2 supports this capability using a separate
   subnet or the OSPF multi-area adjacency capability [MULTI-AREA].

1.1.  Requirements notation

   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 [RFC-KEYWORDS].



































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2.  OSPFv2 Instance Packet Encoding

   OSPFv2 currently doesn't offer a mechanism to differentiate packets
   for different instances sent and received on the same interface.  In
   support of this capability, this document introduces a modified
   packet header format when the Authentication Type field is split into
   an instance ID and type.


       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Version #   |     Type      |         Packet length         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Router ID                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Area ID                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Checksum             |  Instance ID  |  AuType       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Authentication                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Authentication                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         The OSPFv2 Packet Header


   Version #
      The OSPFv2 version number - 2

   Type
      The OSPFv2 packet type as specified [OSPFV2].

   Packet length
      The length of the OSPF protocol packet in bytes.  This length
      includes the standard OSPF header.

   Router ID
      The Router ID of the packet's source.

   Area ID
      A 32-bit number identifying the area corresponding the packet as
      specified in [OSPFV2].







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   Checksum
      OSPFv2 standard checksum calculation as specified in specified in
      [OSPFV2].

   Instance ID
      Enables multiple instances of OSPF to be run over a single link.
      Each protocol instance would be assigned a separate Instance ID;
      the Instance ID has local subnet significance only.  Received
      packets whose Instance ID is not equal to the receiving
      interface's Instance ID are discarded.

   AuType
      OSPFv2 authentication type as specified in specified in [OSPFV2].

   Authentication
      A 64-bit field for Authentication type dependent authentication
      data.


































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3.  OSPF Interface Instance ID

   OSPF [OSPFV2] describes the conceptual interface data structure in
   section 9.  The OSPF Interface ID will be added to this structure.
   The Interface Instance ID will default to 0.  Its setting to a non-
   zero value may be accomplished through configuration or implied by
   some usage beyond the scope of this document.

3.1.  Sending and Receiving OSPF packets

   When sending OSPF packets, if the interface instance ID has a non-
   zero value, it will be set in the OSPF packet header.  When receiving
   OSPF packets, the OSPFv2 Header Instance ID will be used to aid in
   demultiplexing the packet and routing it to the correct OSPFv2
   instance.




































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4.  Backward Compatibility and Deployment Considerations

   When there are OSPF routers that support this capability on the same
   broadcast capable link as those that do not, packets with non-zero
   Instance IDs will be received by those legacy routers.  Since the
   authentication type will be unknown to them they will not process the
   packet.  This is what is desired.  However, the impact varies by
   implementation and some implementations may log every single
   authentication type mismatch.

4.1.  Separate Multicast Addresses for Backward Compatibility

   Another way to avoid the backward compatibility problem would be to
   use new IPv4 multicast addresses for OSPF multicast packets with non-
   zero instance IDs.  We would need to reserve two, one for
   AllSPFRouters and another for ALLDRouters.  This would have the added
   benefit that the OSPF routers not supporting this specification would
   not receive the packet or at least drop it silently at an earlier
   junction.  However, it isn't clear whether this is justified simply
   for migration.

4.2.  Separate Protocol ID for Backward Compatibility

   Another way to avoid the backward compatibility problem would be to
   use a different IPv4 header protocol ID for OSPF packets with non-
   zero instance IDs.  This approach would have the added benefit of
   allowing all packets associated with a non-zero Instance ID to be
   identified at the IP layer.  This may be desirable for some
   applications utilizing multiple instances.






















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5.  Security Considerations

   The enhancement described herein doesn't add any additional security
   considerations to OSPFv2.  Security considerations for OSPFv2 are
   described in [OSPFV2].

   Given that only three OSPFv2 authentication types have been
   standardized, it seems reasonable to reduce the OSPF packet header
   field to 8 bits.










































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6.  IANA Considerations

   A new registry will be added for OSPF Instance IDs.  The allocation
   is TBD.

   Dependent on the approach, two new multicast addresses from the IPv4
   Multicast Addresses registry would need to be allocated.

   Dependent on the approach, a new protocol ID may need to be allocated
   from the Protocol Numbers registry.









































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7.  Normative References

   [MULTI-AREA]
              Mirtorabi, S., Psenak, P., Lindem, A., and A. Oswal, "OSPF
              Multi-Area Adjacency",
              draft-ietf-ospf-multi-area-adj-08.txt (work in progress).

   [OSPFV2]   Moy, J., "OSPF Version 2", RFC 2328, April 1998.

   [OSPFV3]   Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6",
              RFC 2740, April 2007.

   [RFC-KEYWORDS]
              Bradner, S., "Key words for use in RFC's to Indicate
              Requirement Levels", RFC 2119, March 1997.




































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Appendix A.  Acknowledgments

   The RFC text was produced using Marshall Rose's xml2rfc tool.
















































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Authors' Addresses

   Acee Lindem
   Redback Networks
   102 Carric Bend Court
   Cary, NC  27519
   USA

   Email: acee@redback.com


   Abhay Roy
   Cisco Systems
   225 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: akr@cisco.com


   Sina Mirtorabi
   Force10 Networks
   350 Holger Way
   San Jose, CA  95134
   USA

   Email: sina@force10networks.com
























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Full Copyright Statement

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