Network Working Group Sina Mirtorabi Internet Draft Abhay Roy Document: draft-ietf-ospfv3-af-alt-01.txt Michael Barnes Expiration Date: April 2005 Cisco Systems Acee Lindem Redback Networks Quaizar Vohra Rahul Aggarwal Juniper Networks October 2004 Support of address families in OSPFv3 draft-ietf-ospf-af-alt-01.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Mirtorabi et al. [Page 1]
Internet Draft Address Families in OSPFv3 October 2004 Copyright Notice Copyright (C) The Internet Society (2004). Abstract This document describes a mechanism for supporting multiple address families in OSPFv3 using multiple instances. It maps an address family (AF) to an OSPFv3 instance using the Instance ID field in the OSPFv3 packet header. This approach is fairly simple and minimizes extensions to OSPFv3 for supporting multiple AF's. 1. Motivation OSPFv3 has been defined to support IPv6 unicast AF. There is a need to carry other AFs in OSPFv3 such as multicast IPv6, unicast or multicast IPv4. This document introduces these other AFs in OSPFv3 by reserving Instance IDs and using one OSPFv3 instance for one AF. 2. Proposed Solution Currently the entire Instance ID number space is used for IPv6 unicast. We propose to assign different ranges to different AF's in order to support other AF's in OSPFv3. Each AF will establish different adjacency, have different link state database and compute different shortest path tree. Additionally, the current LSAs that are defined to carry IPv6 unicast prefix can be used without any modification in different instances to carry different AF's prefixes. It should be noted that OSPFv3 is running on the top of IPv6 and uses IPv6 link local address for OSPFv3 control packet and next hop calculation. Therefore, it is required that IPv6 be enabled on a link, although the link may not be participating in IPv6 unicast AF. 3. Instance ID values for new AF's Instance ID zero is already used by default for IPv6 unicast AF. We define the following ranges for different AF's. The first value of each range is considered as the default value for the corresponding AF. Mirtorabi et al. [Page 2]
Internet Draft Address Families in OSPFv3 October 2004 Instance ID # 0 - # 31 IPv6 unicast AF Instance ID # 32 - # 63 IPv6 multicast AF Instance ID # 64 - # 95 IPv4 unicast AF Instance ID # 96 - # 127 IPv4 multicast AF Instance ID # 128 - # 255 Reserved 4. New bit in Options field A new bit is defined in the Options field for AF support. 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---+--+--+--+--+--+--+ | | | | | | | | | | | | | | | | | AF|DC| R| N|MC| E|V6| -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---+--+--+--+--+--+--+ AF-bit When a router supports AF, it MUST set this bit in the Options field of Hello Packets, DD packets and LSAs. 5. Changes to the Hello processing When a router does not support an AF but it is configured with an Instance ID in the same range, packets could be blackholed. This could happen due to misconfiguration or router downgrade to a previous code level. Blackholing is possible because the router which doesn't support the AF can still be included in the SPF calculated path as long as it establishes adjacencies using the Instance ID corresponding to the AF. Note that router and network LSAs are AF independent. In order to avoid the above situation, hello processing is changed in order to only establish adjacency with the routers that have the AF-bit set in their Options field. Receiving Hello Packets is specified in section 3.2.2.1 of [Ref1]. The following check is added to Hello reception: When a router participate in an AF (sets the AF-bit in Options field) it MUST discard Hello packets having the AF-bit clear in the Options field. The only exception is IPv6 unicast AF, where this check MUST NOT be done (to help backward compatibility). Mirtorabi et al. [Page 3]
Internet Draft Address Families in OSPFv3 October 2004 6. Modification to some of the bits defined in [Ref1] Some of the bits defined in OSPFv3 are relevant to IPv6 unicast AF, and are not needed in other AF's. Some may be applicable only to a certain AF. Below is the list of changes to those bits: o Options Field 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+--+--+--+--+--+ | | | | | | | | | | | | | | | | | |DC| R| N|* | E|* | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+--+--+--+--+--+ o V6-bit The V6 bit is used in OSPFv3 to exclude a node from IPv6 unicast route calculation but allow it in the SPF calculation for other address families. Since Instance ID now denotes the AF explicitly, this bit is ignored in AF's other than IPv6 unicast. o MC-bit This bit is not used in other AF's introduced in this document. o Prefix Options Field 0 1 2 3 4 5 6 7 +--+--+--+--+--+--+--+--+ | | | | | P|* |LA|NU| +--+--+--+--+--+--+--+--+ o MC bit in the Prefix Options field This bit is not used in other AF's introduced in this document. o NU bit usage in the Prefix Options field The NU bit must be clear in all unicast AF's and it must be set in all multicast AF's. Note that all bits unused in a given AF could be redefined later. Mirtorabi et al. [Page 4]
Internet Draft Address Families in OSPFv3 October 2004 7. Carrying Prefixes in new AF's Each Prefix defined in OSPFv3 has a prefix length field. This facilitate advertising prefixes of different lengths in different AF's. The existing LSAs defined in OSPFv3 are used for this purpose and there is no need to define new LSAs. 8. Next hop for IPv4 unicast and multicast AF's OSPFv3 runs on the top of IPv6 and uses IPv6 link local addresses for OSPFv3 control packets and next hop calculations. Although IPV6 link local addresses could be used as next hops for IPv4 address families, it is desirable to have IPv4 next hop addresses. For example, in IPv4 multicast having the nexthop address the same as the PIM neighbor address (IPv4 address) makes it easier to know to which upstream neighbor to send a PIM join when doing a RPF lookup for a source. It is also easier for troubleshooting purposes to have a next hop with the same semantics as the AF. In order to achieve this, the link's IPv4 address will be advertised in the "link local address" field of the IPv4 instance's Link-LSA. This address is placed in the first 32 bit of "link local address" field and used for IPv4 next hop calculations. We call direct interface address (DIA) the address that is reachable directly via the link provided that a layer 3 to layer 2 mapping is available. Note that there is no explicit need for the IPv4 link addresses to be on the same subnet. An implementation should resolve layer 3 to layer 2 mappings via ARP or ND for a DIA even if the IPv4 address is not on the same subnet as the router's interface IP address. 9. Virtual Link (VL) OSPFv3 control packets sent over a virtual link are IPv6 packets and may traverse multiples hops. Therefore, there must be a global IPv6 address associated with the virtual link so that the control packet is forwarded correctly by the intermediate hops between VL end points. Although this requirement can be satisfied in IPv6 unicast AF, this will not function in other AFs as there cannot be a multihop forwarding based on global IPv6 address or such a path may not exist. Therefore virtual link are not currently supported in other AF's. Mirtorabi et al. [Page 5]
Internet Draft Address Families in OSPFv3 October 2004 10. Backward compatibility issues Each new AF will have their corresponding Instance ID and can operate with the existing non-capable routers in IPv6 unicast topology. Further, when a non-capable router uses an Instance ID which is reserved for a given AF, since the non-capable router will not have the AF-bit set in the Hello an adjacency will not be established with an AF capable router. Therefore, there are no backward compatibility issues. AF's can be gradually deployed without disturbing networks with current non-capable routers. 11. Address-family design Considerations This section describes the rationale for adopting the multiple instance ID approach for supporting multiple address families in OSPFv3. As described earlier, OSPFv3 is designed to support multiple instances. Hence mapping an instance to an address family doesn't introduce new mechanisms in the protocol. It minimizes the protocol extensions required and it simplifies the implementation. The presence of a separate link state database per address family is also easier to debug and operate. Additionally, it doesn't change the existing instance, area and interface based configuration model in most OSPF implementations. 12. Security Considerations The technique described in this document does not introduce any new security issues to the OSPFv3 protocol. 13. References [Ref1] R. Coltun, D. Ferguson and J. Moy, "OSPF for IPv6", RFC 2740, December 1999. 14. Authors address Sina Mirtorabi Acee Lindem Cisco Systems Redback Networks 170 W. Tasman Dr. 102 Carric Bend Court San Jose, CA 95134 Cary, NC 27519 Email: sina@cisco.com Email: acee@redback.com Mirtorabi et al. [Page 6]
Internet Draft Address Families in OSPFv3 October 2004 Abhay Roy Quaizar Vohra Cisco Systems Juniper Networks 170 W. Tasman Dr. 1194 North Mathilda Ave. San Jose, CA 95134 Sunnyvale, CA 94089 Email: akr@cisco.com Email: qv@juniper.net Michael Barnes Rahul Aggarwal Cisco Systems Juniper Networks 170 W. Tasman Dr. 1194 North Mathilda Ave. San Jose, CA 95134 Sunnyvale, CA 94089 Email: mjbarnes@cisco.com Email: rahul@juniper.net Intellectual Property Statement 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. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Mirtorabi et al. [Page 7]
Internet Draft Address Families in OSPFv3 October 2004 Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2004). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Mirtorabi et al. [Page 8]
