Network Working Group A. Lindem (Editor) Internet-Draft Ericsson Intended status: Standards Track S. Mirtorabi Expires: June 18, 2010 A. Roy M. Barnes Cisco Systems R. Aggarwal Juniper Networks December 15, 2009 Support of address families in OSPFv3 draft-ietf-ospf-af-alt-10.txt 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 AFs. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. 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. This Internet-Draft will expire on June 18, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the Lindem (Editor), et al. Expires June 18, 2010 [Page 1] Internet-Draft OSPFv3 AF December 2009 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 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 BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Design Considerations . . . . . . . . . . . . . . . . . . 3 1.2. Requirements notation . . . . . . . . . . . . . . . . . . 3 2. Protocol Details . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Instance ID values for new AFs . . . . . . . . . . . . . . 4 2.2. OSPFv3 Options Changes . . . . . . . . . . . . . . . . . . 4 2.3. Advertising Prefixes in AFs other than IPv6 . . . . . . . 5 2.4. Changes to the Hello processing . . . . . . . . . . . . . 5 2.5. Next-Hop Calculation for IPv4 unicast and multicast AFs . 6 2.6. AS External LSA Forwarding Address for IPv4 Unicast and IPv4 Multicast AFs . . . . . . . . . . . . . . . . . . 6 2.7. Database Description Maximum Transmission Unit (MTU) Specification for Non-IPv6 AFs . . . . . . . . . . . . . . 6 2.8. Operation over Virtual Links . . . . . . . . . . . . . . . 8 3. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 9 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.1. Normative References . . . . . . . . . . . . . . . . . . . 13 6.2. Informative References . . . . . . . . . . . . . . . . . . 13 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Lindem (Editor), et al. Expires June 18, 2010 [Page 2] Internet-Draft OSPFv3 AF December 2009 1. Introduction OSPFv3 [OSPFV3] has been defined to support the base IPv6 unicast Address Family (AF). There are requirements to advertise other AFs in OSPFv3 including multicast IPv6, unicast IPv4, and multicast IPv4. This document supports these other AFs in OSPFv3 by mapping each AF to a separate Instance ID and OSPFv3 instance. 1.1. Design Considerations This section describes the rationale for using the multiple instance ID approach to support 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 any new mechanisms to 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 OSPFv3 implementations. 1.2. 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 (Editor), et al. Expires June 18, 2010 [Page 3] Internet-Draft OSPFv3 AF December 2009 2. Protocol Details Currently the entire Instance ID number space is used for IPv6 unicast. This specification assigns different Instance ID ranges to different AFs in order to support other AFs in OSPFv3. Each Instance ID implies a separate OSPFv3 instance with its own neighbor adjacencies, link state database, protocol data structures, and shortest path first (SPF) computation. Additionally, the current Link State Advertisements (LSAs) defined to advertise IPv6 unicast prefixes can be used to advertise prefixes from other AFs without modification. It should be noted that OSPFv3 runs on top of IPv6 and uses IPv6 link local addresses for OSPFv3 control packets. Therefore, it is required that IPv6 be enabled on an OSPFv3 link, although the link may not be participating in any IPv6 AFs. 2.1. Instance ID values for new AFs Instance ID zero is already defined by default for the IPv6 unicast AF. When this specification is used to support multiple AFs, we define the following ranges for different AFs. The first value of each range is the default value for the corresponding AF. 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 Unassigned OSPFv3 Instance IDs 2.2. OSPFv3 Options Changes A new AF-bit is added to the OSPFv3 options field. The V6-bit is only applicable to the IPv6 unicast AF. 1 2 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|x | E|V6| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+--+-+-+--+--+--+ The Options field OSPFv3 Options Lindem (Editor), et al. Expires June 18, 2010 [Page 4] Internet-Draft OSPFv3 AF December 2009 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 AFs other than IPv6 unicast. AF-bit When an OSPFv3 router is supporting AFs as described in this specification, it MUST set the AF-bit in the OSPFv3 Options field of Hello Packets, Database Description packets, and LSAs. 2.3. Advertising Prefixes in AFs other than IPv6 Each Prefix defined in OSPFv3 has a prefix length field. This facilitates advertising prefixes of different lengths in different AFs. The existing LSAs defined in OSPFv3 are used for this purpose and there is no need to define new LSAs. Prefixes which don't conform to OSPFv3 instance AF MUST be not be used in the route computation for the instance. 2.4. Changes to the Hello processing When an OSPFv3 router does not support this specification and it is configured with the corresponding Instance ID, packets could be black holed. This could happen due to misconfiguration or a router software downgrade. Black holing 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-LSAs and Network-LSAs are AF independent. In order to avoid the above situation, hello processing is changed in order to only establish adjacencies with routers that have the AF-bit set in their Options field. Receiving Hello Packets is specified in section 3.2.2.1 of [OSPFV3]. The following check is added to Hello reception: o When an OSPFv3 router participates 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 the Base IPv6 unicast AF, where this check MUST NOT be done (for backward compatibility). Lindem (Editor), et al. Expires June 18, 2010 [Page 5] Internet-Draft OSPFv3 AF December 2009 2.5. Next-Hop Calculation for IPv4 unicast and multicast AFs OSPFv3 runs on 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 the IPv4 multicast AF, the Protocol Independent Multicast (PIM) [PIM] neighbor address and the next-hop address should both be IPv4 addresses in order for the Reverse Path Forwarding (RPF) lookup to work correctly. Troubleshooting is also easier when the prefix address and next-hop address are in the same 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 is used for IPv4 next-hop calculations. The remaining bits MUST be set to zero. We call the 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 Address Resolution Protocol (ARP) [ARP] or Neighbor Discovery (ND) [ND] for a DIA even if the IPv4 address is not on the same subnet as the router's interface IP address. 2.6. AS External LSA Forwarding Address for IPv4 Unicast and IPv4 Multicast AFs For OSPFv3, this address is an IPv6 host address (128 bits). If included, data traffic for the advertised destination will be forwarded to this address. For IPv4 unicast and IPv4 multicast AFs, the Forwarding Address in AS-external-LSAs MUST encode an IPv4 address. To achieve this, the IPv4 Forwarding Address is advertised by placing it in the first 32 bits of the Forwarding Address field in the AS-external-LSAs. The remaining bits MUST be set to zero. 2.7. Database Description Maximum Transmission Unit (MTU) Specification for Non-IPv6 AFs For address families other than IPv6, both the MTU for the instance address family and IPv6 MTU used for OSPFv3 maximum packet determination MUST be considered. The MTU in the Database Description packet MUST always contain the MTU corresponding to the advertised address family. For example, if the instance corresponds to an IPv4 address family, the IPv4 MTU for the interface MUST be specified in the interface MTU field. As specified section 10.6 of Lindem (Editor), et al. Expires June 18, 2010 [Page 6] Internet-Draft OSPFv3 AF December 2009 [OSPFV2], the Database Description packet will be rejected if the MTU is greater than the receiving interface's MTU for the address family corresponding to the instance. This behavior will assure an adjacency is not formed and address family specific routes are not installed over a path with conflicting MTUs. The value used for OSPFv3 maximum packet size determination MUST also be compatible for an adjacency to be established. Since only a single MTU field is specified, the M6-bit is defined by this specification. If the M6-bit is clear, the specified MTU SHOULD also be checked against the IPv6 MTU and the Database Description packet SHOULD be rejected if the MTU is larger than the receiving interface's IPv6 MTU. An OSPFv3 router SHOULD NOT set the M6-bit if its IPv6 MTU and address family specific MTU are the same. If the IPv6 and IPv4 MTUs differ, the M6-bit MUST be set for non-IPv6 address families. If the M6-bit is set, the IPv6 MTU is decided by the presence or absence of an IPv6 MTU TLV in the LLS [LLS] block. If this TLV is present, it carries the IPv6 MTU that SHOULD be compared with local IPv6 MTU. If this TLV is absent, the minimum IPv6 MTU of 1280 octets SHOULD be used for the comparison (refer to [IPV6]). If the M6-bit is set in a received Database Description packet for a non-IPv6 address family, the receiving router MUST NOT check the Interface MTU in the Database Description packet against the receiving interface's IPv6 MTU. The figure below graphically depicts the changed fields in the octets 20-23 of the OSPFv3 Database Description Packet: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+-+--+ | Interface MTU | 0 |0|0|0|M6|0|I|M|MS| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+-+--+ OSPFv3 Database Description Packet Changes The changed fields in the Database Description packet are described below. The remaining fields are unchanged from [OSPFV3]. Interface MTU The size in octets of the largest AF specific datagram that can be sent on the associated interface without fragmentation. The MTUs of common Internet link types can be found in Table 7-1 of [MTUDISC]. Interface MTU SHOULD be set to 0 in Database Lindem (Editor), et al. Expires June 18, 2010 [Page 7] Internet-Draft OSPFv3 AF December 2009 Description packets sent over virtual links. M6-bit The IPv6 MTU bit - this bit indicates the sender is using a different IPv6 MTU than the MTU for the AF. An IPv6 MTU TLV can be optionally carried in LLS block as described above. This TLV carries the IPv6 MTU for the interface. The length field of the TLV is set to 4 bytes. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 6 (TBD) | 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 MTU | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Format of IPv6 MTU TLV Only one instance of the IPv6 MTU TLV MAY appear in the LLS block. Instances subsequent to the first are not processed and the LLS inconsistency SHOULD be logged. 2.8. Operation over Virtual Links 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 OSPFv3 control packets are forwarded correctly by the intermediate hops between virtual link endpoints. Although this requirement can be satisfied in IPv6 unicast AFs, it will not function in other AFs as there will not be a routable global IPv6 address or forwarding path. Therefore, virtual links are not supported in AFs other than IPv6 Unicast. Lindem (Editor), et al. Expires June 18, 2010 [Page 8] Internet-Draft OSPFv3 AF December 2009 3. Backward Compatibility All modifications to OSPFv3 apply exclusively to the support address families other than IPv6 unicast using multiple OSPFv3 instances as described in this specification. They are not applicable to IPv6 unicast topologies and do not preclude future single instance mechanisms for supporting multiple address families. In this section, we will define a non-capable OSPFv3 router as one not supporting this specification. When multiple AFs are supported as defined herein, each new AF will have a corresponding Instance ID and can interoperate with the existing non-capable OSPFv3 routers in an IPv6 unicast topology. Furthermore, when a non-capable OSPFv3 router uses an Instance ID that is reserved for a given AF, no adjacency will be formed with this router since the AF-bit in the Options field will be clear in its OSPFv3 Hello packets. Therefore, there are no backward compatibility issues. AFs can be gradually deployed without disturbing OSPFv3 routing domains with non-capable OSPFv3 routers. Lindem (Editor), et al. Expires June 18, 2010 [Page 9] Internet-Draft OSPFv3 AF December 2009 4. Security Considerations IPsec [IPsec] can be used for OSPFv3 authentication and confidentiality as described in [OSPFV3-AUTH]. When multiple OSPFv3 instances use the same interface, they all MUST use the same Security Association (SA), since the SA selectors do not provide selection based on OSPFv3 header fields, such as the Instance ID. This restriction is documented in section 8 of [OSPFV3-AUTH]. Security considerations for the OSPFv3 are covered in [OSPFV3]. Lindem (Editor), et al. Expires June 18, 2010 [Page 10] Internet-Draft OSPFv3 AF December 2009 5. IANA Considerations The following IANA assignments are to be made from existing registries: The AF-bit is assigned from OSPFv3 Options field as defined in Section 2.2. IANA is requested to create a new registry, "OSPFv3 Instance ID Address Family Values", for assignment of the mapping of OSPFv3 Instance ID to address families when this specification is used to support multiple address families. Note that the Instance ID field MAY be used for applications other than the support of multiple address families. However, if it is being used for address families as described in this specification, the assignments herein SHOULD be honored. +-------------+----------------------+--------------------+ | Value/Range | Designation | Assignment Policy | +-------------+----------------------+--------------------+ | 0 | Base IPv6 Unicast AF | Already assigned | | | | | | 1-31 | IPv6 Unicast AFs | Already assigned | | | dependent on local | | | | policy | | | | | | | 32 | Base IPv6 Multicast | Already assigned | | | | | | 33-63 | IPv6 Multicast AFs | Already assigned | | | dependent on local | | | | policy | | | | | | | 64 | Base IPv4 Unicast AF | Already assigned | | | | | | 65-95 | IPv4 Unicast AFs | Already assigned | | | dependent on local | | | | policy | | | | | | | 96 | Base IPv4 Multicast | Already assigned | | | | | | 97-127 | IPv4 Multicast AFs | Already assigned | | | dependent on local | | | | policy | | | | | | | 128-255 | Unassigned | Standards Action | +-------------+----------------------+--------------------+ OSPFv3 Address Family Use of Instance IDs Lindem (Editor), et al. Expires June 18, 2010 [Page 11] Internet-Draft OSPFv3 AF December 2009 o Instance IDs 0-127 are assigned by this specification. o Instance IDs in the range 128-255 are not assigned at this time. Before any assignments can be made in this range, there MUST be a Standards Track RFC including IANA Considerations explicitly specifying the AF Instance IDs being assigned. M6-Bit is assigned as defined in Section 2.7. A TLV type for IPv6 MTU TLV is assigned from OSPF LLS TLVs registry. Lindem (Editor), et al. Expires June 18, 2010 [Page 12] Internet-Draft OSPFv3 AF December 2009 6. References 6.1. Normative References [IPV6] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. [IPsec] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005. [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. [OSPFV3-AUTH] Gupta, M. and S. Melam, "Authentication/Confidentiality for OSPFv3", RFC 4552, June 2006. [RFC-KEYWORDS] Bradner, S., "Key words for use in RFC's to Indicate Requirement Levels", RFC 2119, March 1997. 6.2. Informative References [ARP] Plummer, D., "An Ethernet Address Resolution Protocol", RFC 826, November 1982. [LLS] Zinin, A., Roy, A., Nguyen, L., Friedman, B., and D. Young, "OSPF Link-local Signaling", RFC 5613, August 2009. [MTUDISC] Mogul, J. and S. Deering, "Path MTU Discovery", RFC 1191, November 1990. [ND] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 4861, September 2007. [PIM] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, August 2006. Lindem (Editor), et al. Expires June 18, 2010 [Page 13] Internet-Draft OSPFv3 AF December 2009 Appendix A. Acknowledgments The RFC text was produced using Marshall Rose's xml2rfc tool. Thanks to Tom Henderson and the folks at Boeing for implementing in the Quagga routing suite, http:www.quagga.net. Thanks to Nischal Sheth for review and comments. Thanks to Christian Vogt for comments during the Gen-ART review. Thanks to Adrian Farrel for comments during the IESG review. Lindem (Editor), et al. Expires June 18, 2010 [Page 14] Internet-Draft OSPFv3 AF December 2009 Authors' Addresses Acee Lindem Ericsson 102 Carric Bend Court Cary, NC 27519 USA Email: acee.lindem@ericsson.com Sina Mirtorabi Cisco Systems 3 West Plumeria Drive San Jose, CA 95134 USA Email: smirtora@cisco.com Abhay Roy Cisco Systems 225 West Tasman Drive San Jose, CA 95134 USA Email: akr@cisco.com Michael Barnes Cisco Systems 225 West Tasman Drive San Jose, CA 95134 USA Email: mjbarnes@cisco.com Rahul Aggarwal Juniper Networks 1194 N. Mathilda Ave. Sunnyvale, CA 94089 USA Email: rahul@juniper.net Lindem (Editor), et al. 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