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Internet Engineering Task Force (IETF)                         A. LindemRequest for Comments: 6549                                      EricssonUpdates:2328                                                     A. RoyCategory: Standards Track                                   S. MirtorabiISSN: 2070-1721                                            Cisco Systems                                                              March 2012OSPFv2 Multi-Instance ExtensionsAbstract   OSPFv3 includes a mechanism to support multiple instances of the   protocol running on the same interface.  OSPFv2 can utilize such a   mechanism in order to support multiple routing domains on the same   subnet.   This document defines the OSPFv2 Instance ID to enable separate   OSPFv2 protocol instances on the same interface.  Unlike OSPFv3 where   the Instance ID can be used for multiple purposes, such as putting   the same interface in multiple areas, the OSPFv2 Instance ID is   reserved for identifying protocol instances.   This document updatesRFC 2328.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by   the Internet Engineering Steering Group (IESG).  Further   information on Internet Standards is available inSection 2 of   RFC 5741.   Information about the current status of this document, any   errata, and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6549.Lindem, et al.               Standards Track                    [Page 1]

RFC 6549            OSPFv2 Multi-Instance Extensions          March 2012Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Table of Contents1. Introduction ....................................................21.1. Requirements Notation ......................................32. OSPFv2 Instance Packet Encoding .................................33. OSPFv2 Interface Instance ID ....................................43.1. Sending and Receiving OSPFv2 Packets .......................43.2. Interface Instance ID Values ...............................44. State Sharing Optimizations between OSPFv2 Instances ............55. OSPFv2 Authentication Impacts ...................................56. Backward Compatibility and Deployment Considerations ............57. Security Considerations .........................................68. IANA Considerations .............................................69. References ......................................................79.1. Normative References .......................................79.2. Informative References .....................................7Appendix A. Acknowledgments.... ....................................81.  Introduction   OSPFv3 [OSPFV3] includes a mechanism to support multiple instances of   a protocol running on the same interface.  OSPFv2 [OSPFV2] can   utilize such a mechanism in order to support multiple routing domains   on the same subnet.   This document defines the OSPFv2 Instance ID to enable separate   OSPFv2 protocol instances on the same interface.  Unlike OSPFv3 where   the Instance ID can be used for multiple purposes, such as putting   the same interface in multiple areas, the OSPFv2 Instance ID is   reserved for identifying protocol instances.Lindem, et al.               Standards Track                    [Page 2]

RFC 6549            OSPFv2 Multi-Instance Extensions          March 20121.1.  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].2.  OSPFv2 Instance Packet Encoding   This document extends OSPFv2 with a mechanism to differentiate   packets for different instances sent and received on the same   interface.  In support of this capability, a modified packet header   format with the Authentication Type field split into an Instance ID   and AuType.       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   All fields are as defined in [OSPFV2] except that the Instance ID   field is new, and the AuType field is reduced to 8 bits from 16 bits   without any change in meaning.  The Instance ID field is defined as   follows:   Instance ID      Enables multiple instances of OSPFv2 to be used on a single      interface.  Each protocol instance would be assigned a separate      Instance ID; the Instance ID has local subnet significance only.      Received packets with an Instance ID not equal to one of the      Instance IDs corresponding to one of the configured OSPFv2      Instances for the receiving interface MUST be discarded.Lindem, et al.               Standards Track                    [Page 3]

RFC 6549            OSPFv2 Multi-Instance Extensions          March 20123.  OSPFv2 Interface Instance ID   Section 9 of [OSPFV2] describes the conceptual interface data   structure.  The OSPFv2 Interface Instance ID is added to this   structure.  The OSPFv2 Interface Instance ID has a default value of   0.  Setting it to a non-zero value may be accomplished through   configuration.3.1.  Sending and Receiving OSPFv2 Packets   When sending OSPFv2 packets, the OSPFv2 Interface Instance ID is set   in the OSPFv2 packet header.  When receiving OSPFv2 packets, the   OSPFv2 Header Instance ID is used to aid in demultiplexing the packet   and associating it with the correct OSPFv2 instance.  Received   packets with an Instance ID not equal to one of the configured OSPFv2   Instance IDs on the receiving interface MUST be discarded.3.2.  Interface Instance ID Values   The following OSPFv2 Instance IDs have been defined:   0      Base IPv4 Instance - This is the default IPv4 routing instance          corresponding to default IPv4 unicast routing and the          attendant IPv4 routing table.  Use of this Instance ID          provides backward compatibility with the base OSPF          specification [OSPFV2].   1      Base IPv4 Multicast Instance - This IPv4 instance corresponds          to the separate IPv4 routing table used for the Reverse Path          Forwarding (RPF) checking performed on IPv4 multicast traffic.   2      Base IPv4 In-band Management Instance - This IPv4 instance          corresponds to a separate IPv4 routing table used for network          management applications.   3-127  Private Use - These Instance IDs are reserved for definition          and semantics defined by the local network administrator.  For          example, separate Interface Instance IDs and their          corresponding OSPFv2 instances could be used to support          independent non-congruent topologies for different classes of          IPv4 unicast traffic.  The details of such deployments are          beyond the scope of this document.   The first three Interface Instance IDs are analogous to the topology   IDs defined in [RFC4915].Lindem, et al.               Standards Track                    [Page 4]

RFC 6549            OSPFv2 Multi-Instance Extensions          March 20124.  State-Sharing Optimizations between OSPFv2 Instances   This is beyond the scope of this document and is an area for further   study.5.  OSPFv2 Authentication Impacts   Now that the AuType OSPFv2 header field has been reduced from 2   octets to 1 octet, OSPFv2 routers not supporting this specification   will fail packet authentication for any instance other than the   default (i.e., the Base IPv4 Unicast Instance).  This is solely due   to the difference in field definition as opposed to any explicit   change to OSPFv2 authentication, as described inAppendix D ofRFC2328 [OSPFV2] andRFC 5709 [RFC5709].  However, this is exactly what   is desired since OSPFv2 routers not supporting this specification   should only support the default instance (refer toSection 6).6.  Backward Compatibility and Deployment Considerations   When there are OSPFv2 routers that support OSPFv2 Multi-Instance   extensions on the same broadcast-capable interface as OSPFv2 routers   that do not, packets with non-zero OSPFv2 header Instance IDs are   received by those legacy OSPFv2 routers.  Since the non-zero Instance   ID is included in the AuType by these legacy OSPFv2 routers, it is   misinterpreted as a mismatched authentication type and the packet is   dropped.  This is exactly what is expected and desired.   Previously, there was concern that certain implementations would log   every single authentication type mismatch.  However, discussions with   implementers have led us to the conclusion that this is not as severe   a problem as we'd first thought, and it will be even less of a   problem by the time the mechanism described herein is standardized,   implemented, and deployed.  Most implementations will dampen the   logging of errors.  Hence, the more drastic mechanisms to avoid   legacy OSPFv2 routers from receiving multicast OSPFv2 packets with   non-zero Instance IDs have been removed.   If the OSPF MIB as specified in [OSPF-MIB] is implemented, even the   damped generation of the ospfIfAuthFailure or ospfVirtIfAuthFailure   Simple Network Management Protocol (SNMP) notifications would be   undesirable in situations where legacy OSPFv2 routers are deployed on   the same subnet as OSPFv2 routers supporting this specification.   Consequently, it is recommended that implementations that implement   this specification and the OSPF MIB also implement SNMP Notification   filtering as specified inSection 6 of [RFC3413].Lindem, et al.               Standards Track                    [Page 5]

RFC 6549            OSPFv2 Multi-Instance Extensions          March 20127.  Security Considerations   The enhancement described herein doesn't include 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 OSPFv2 packet header   field to 8 bits.8.  IANA Considerations   The size of the AuType field is reduced from 16 octets to 8 octets.   This changes the OSPF Authentication Codes registry in that the   values 256-65535 are no longer defined and are therefore deprecated.   There is no backward compatibility issue since this range of values   was previously defined as "Reserved and should not be assigned".   A new registry has been created for OSPFv2 Instance IDs.  The initial   allocation of OSPFv2 Instance IDs is described below.  Refer toSection 3.2 for more information.      +-------------+----------------------+--------------------+      | Value/Range | Designation          | Assignment Policy  |      +-------------+----------------------+--------------------+      | 0           | Base IPv4 Unicast    | Assigned           |      |             | Instance             |                    |      |             |                      |                    |      | 1           | Base IPv4 Multicast  | Assigned           |      |             | Instance             |                    |      |             |                      |                    |      | 2           | Base IPv4 In-band    | Assigned           |      |             | Management Instance  |                    |      |             |                      |                    |      | 3-127       | Private Use          | Reserved for local |      |             |                      | policy assignment  |      |             |                      |                    |      | 128-255     | Unassigned           | Standards Action   |      +-------------+----------------------+--------------------+                      OSPFv2 Instance IDLindem, et al.               Standards Track                    [Page 6]

RFC 6549            OSPFv2 Multi-Instance Extensions          March 20129.  References9.1.  Normative References   [OSPFV2]   Moy, J., "OSPF Version 2", STD 54,RFC 2328, April 1998.   [OSPFV3]   Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF              for IPv6",RFC 5340, July 2008.   [RFC-KEYWORDS]              Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.9.2.  Informative References   [OSPF-MIB] Joyal, D., Ed., Galecki, P., Ed., Giacalone, S., Ed.,              Coltun, R., and F. Baker, "OSPF Version 2 Management              Information Base",RFC 4750, December 2006.   [RFC3413]  Levi, D., Meyer, P., and B. Stewart, "Simple Network              Management Protocol (SNMP) Applications", STD 62,RFC3413, December 2002.   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",RFC4915, June 2007.   [RFC5709]  Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,              Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic              Authentication",RFC 5709, October 2009.Lindem, et al.               Standards Track                    [Page 7]

RFC 6549            OSPFv2 Multi-Instance Extensions          March 2012Appendix A.  Acknowledgments   Thanks to Adrian Farrel for reviewing and providing some suggested   improvements during the IESG review.   Thanks to Paul Wells for commenting on the backward compatibility   issues.   Thanks to Paul Wells and Vladica Stanisic for commenting during the   OSPF WG last call.   Thanks to Manav Bhatia for comments and for being the document   shepherd.   Thanks to Magnus Nystrom for comments under the auspices of the   Security Directorate review.   Thanks to Dan Romascanu for comments during the IESG review.   Thanks to Pete McCann for comments under the auspices of the Gen-ART   review.Lindem, et al.               Standards Track                    [Page 8]

RFC 6549            OSPFv2 Multi-Instance Extensions          March 2012Authors' Addresses   Acee Lindem   Ericsson   102 Carric Bend Court   Cary, NC 27519   USA   EMail: acee.lindem@ericsson.com   Abhay Roy   Cisco Systems   225 West Tasman Drive   San Jose, CA 95134   USA   EMail: akr@cisco.com   Sina Mirtorabi   Cisco Systems   3 West Plumeria Drive   San Jose, CA 95134   USA   EMail: sina@cisco.comLindem, et al.               Standards Track                    [Page 9]