Network Working Group A. Lindem Internet-Draft Ericsson Updates: 2328 (if approved) A. Roy Intended status: Standards Track S. Mirtorabi Expires: May 1, 2012 Cisco Systems October 29, 2011 OSPF Multi-Instance Extensions draft-ietf-ospf-multi-instance-06.txt Abstract OSPFv3 includes a mechanism for supporting multiple instances on the same interface. 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 interface in multiple areas. OSPFv2 supports this capability using a separate subnet or the OSPF multi-area adjacency capability. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on May 1, 2012. Copyright Notice Copyright (c) 2011 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents Lindem, et al. Expires May 1, 2012 [Page 1] Internet-Draft OSPF Multi-Instance Extensions October 2011 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 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. State Sharing Optimizations between OSPF instances . . . . . . 7 5. OSPFv2 Authentication Impacts . . . . . . . . . . . . . . . . 8 6. Backward Compatibility and Deployment Considerations . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. Normative References . . . . . . . . . . . . . . . . . . . 12 9.2. Informative References . . . . . . . . . . . . . . . . . . 12 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Lindem, et al. Expires May 1, 2012 [Page 2] Internet-Draft OSPF Multi-Instance Extensions October 2011 1. Introduction OSPFv3 [OSPFV3] includes a mechanism for supporting multiple instances on the same interface. OSPFv2 [OSPFV2] could benefit from such a mechanism in order to support multiple routing domains on the same subnet. The OSPFv2 Interface 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 interface 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]. Lindem, et al. Expires May 1, 2012 [Page 3] Internet-Draft OSPF Multi-Instance Extensions October 2011 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 with the Authentication Type field is 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 Version # The OSPF version number - 2 Type The OSPF 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]. Lindem, et al. Expires May 1, 2012 [Page 4] Internet-Draft OSPF Multi-Instance Extensions October 2011 Checksum OSPF standard checksum calculation as specified in specified in [OSPFV2]. Instance ID Enables multiple instances of OSPF 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 OSPF Instances for the receiving interface MUST be discarded. AuType OSPF authentication type as specified in specified in [OSPFV2]. Authentication A 64-bit field for authentication data (dependent on the Authentication Type as specified in the AuType field). Lindem, et al. Expires May 1, 2012 [Page 5] Internet-Draft OSPF Multi-Instance Extensions October 2011 3. OSPF Interface Instance ID OSPF [OSPFV2] describes the conceptual interface data structure in section 9. The OSPF Interface Instance ID will be added to this structure. The OSPF 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 OSPF Interface Instance ID has a non-zero value, it will be set in the OSPF packet header. When receiving OSPF packets, the OSPF Header Instance ID will be used to aid in demultiplexing the packet and routing it to the correct OSPF instance. Received packets with an Instance ID not equal to one of the configured OSPF Instance IDs on the receiving interface MUST be discarded. Lindem, et al. Expires May 1, 2012 [Page 6] Internet-Draft OSPF Multi-Instance Extensions October 2011 4. State Sharing Optimizations between OSPF instances This is beyond the scope of this draft and is an area for further study. Lindem, et al. Expires May 1, 2012 [Page 7] Internet-Draft OSPF Multi-Instance Extensions October 2011 5. OSPFv2 Authentication Impacts Now that the AuType OSPFv2 header field has been reduced from 2 octets to 1 octet, OSPF 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 Appendix D, [OSPFV2] or [RFC5709]. However, this is exactly what is desired since OSPF routers not supporting this specification should only support the default instance (Refer to Section 6). Lindem, et al. Expires May 1, 2012 [Page 8] Internet-Draft OSPF Multi-Instance Extensions October 2011 6. Backward Compatibility and Deployment Considerations When there are OSPF routers that support OSPF Multi-Instance extensions on the same broadcast capable interface as OSPF routers that do not, packets with non-zero OSPF header Instance IDs will be received by those legacy OSPF routers. Since the non-zero Instance ID will be included in the AuType by these legacy OSPF routers, it will be misinterpreted as a mismatched authentication type and the packet will be dropped. This is exactly what is expected and desired. Previously, there was concern that certain implementations would log every single authentication type mismatch. Additionally, if ospfIfAuthFailure SNMP generation is enabled as specified in [OSPF-MIB], a separate trap would be generated for each received OSPF packet with a non-zero Instance ID. 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 in this draft is standardized, implemented, and deployed. Most implementations will dampen both the logging of errors and the generation of identical SNMP traps. Hence, the more drastic mechanisms to avoid legacy OSPF routers from receiving multicast OSPF packets with non-zero Instance IDs have been removed. Lindem, et al. Expires May 1, 2012 [Page 9] Internet-Draft OSPF Multi-Instance Extensions October 2011 7. 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. Lindem, et al. Expires May 1, 2012 [Page 10] Internet-Draft OSPF Multi-Instance Extensions October 2011 8. IANA Considerations A new registry will be added for OSPF Instance IDs. The allocation of OSPF Instance IDs is described below. +-------------+----------------------+--------------------+ | 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 | Local Policy | Reserved for local | | | | policy assignment | | | | | | 128-255 | Unassigned | Standards Action | +-------------+----------------------+--------------------+ OSPFv2 Instance ID Lindem, et al. Expires May 1, 2012 [Page 11] Internet-Draft OSPF Multi-Instance Extensions October 2011 9. References 9.1. Normative References [OSPFV2] Moy, J., "OSPF Version 2", 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", RFC 2119, March 1997. 9.2. Informative References [MULTI-AREA] Mirtorabi, S., Psenak, P., Lindem, A., and A. Oswal, "OSPF Multi-Area Adjacency", RFC 5185, May 2008. [OSPF-MIB] Joyal, D., Galecki, P., Giacalone, S., Baker, F., and R. Coltun, "OSPF Version 2 Management Information Base", RFC 4750, December 2006. [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. Expires May 1, 2012 [Page 12] Internet-Draft OSPF Multi-Instance Extensions October 2011 Appendix A. Acknowledgments The RFC text was produced using Marshall Rose's xml2rfc tool. 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 being the document shepherd. Lindem, et al. Expires May 1, 2012 [Page 13] Internet-Draft OSPF Multi-Instance Extensions October 2011 Authors' 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.com Lindem, et al. Expires May 1, 2012 [Page 14]