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'Ref1') (Obsoleted by RFC 5340) Summary: 12 errors (**), 0 flaws (~~), 5 warnings (==), 6 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Sina Mirtorabi 3 Internet Draft Abhay Roy 4 Document: draft-ietf-ospfv3-af-alt-01.txt Michael Barnes 5 Expiration Date: April 2005 Cisco Systems 7 Acee Lindem 8 Redback Networks 10 Quaizar Vohra 11 Rahul Aggarwal 12 Juniper Networks 14 October 2004 16 Support of address families in OSPFv3 17 draft-ietf-ospf-af-alt-01.txt 19 Status of this Memo 21 This document is an Internet-Draft and is subject to all provisions 22 of section 3 of RFC 3667. By submitting this Internet-Draft, each 23 author represents that any applicable patent or other IPR claims of 24 which he or she is aware have been or will be disclosed, and any of 25 which he or she become aware will be disclosed, in accordance with 26 RFC 3668. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF), its areas, and its working groups. Note that 30 other groups may also distribute working documents as 31 Internet-Drafts. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 The list of current Internet-Drafts can be accessed at 39 http://www.ietf.org/ietf/1id-abstracts.txt. 41 The list of Internet-Draft Shadow Directories can be accessed at 42 http://www.ietf.org/shadow.html. 44 Copyright Notice 46 Copyright (C) The Internet Society (2004). 48 Abstract 50 This document describes a mechanism for supporting multiple address 51 families in OSPFv3 using multiple instances. It maps an address 52 family (AF) to an OSPFv3 instance using the Instance ID field in the 53 OSPFv3 packet header. This approach is fairly simple and minimizes 54 extensions to OSPFv3 for supporting multiple AF's. 56 1. Motivation 58 OSPFv3 has been defined to support IPv6 unicast AF. There is a need 59 to carry other AFs in OSPFv3 such as multicast IPv6, unicast or 60 multicast IPv4. This document introduces these other AFs in OSPFv3 61 by reserving Instance IDs and using one OSPFv3 instance for one AF. 63 2. Proposed Solution 65 Currently the entire Instance ID number space is used for IPv6 66 unicast. We propose to assign different ranges to different AF's in 67 order to support other AF's in OSPFv3. Each AF will establish 68 different adjacency, have different link state database and compute 69 different shortest path tree. Additionally, the current LSAs that are 70 defined to carry IPv6 unicast prefix can be used without any 71 modification in different instances to carry different AF's prefixes. 73 It should be noted that OSPFv3 is running on the top of IPv6 and uses 74 IPv6 link local address for OSPFv3 control packet and next hop 75 calculation. Therefore, it is required that IPv6 be enabled on a link, 76 although the link may not be participating in IPv6 unicast AF. 78 3. Instance ID values for new AF's 80 Instance ID zero is already used by default for IPv6 unicast AF. 81 We define the following ranges for different AF's. The first value 82 of each range is considered as the default value for the 83 corresponding AF. 85 Instance ID # 0 - # 31 IPv6 unicast AF 86 Instance ID # 32 - # 63 IPv6 multicast AF 87 Instance ID # 64 - # 95 IPv4 unicast AF 88 Instance ID # 96 - # 127 IPv4 multicast AF 89 Instance ID # 128 - # 255 Reserved 91 4. New bit in Options field 93 A new bit is defined in the Options field for AF support. 95 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 96 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---+--+--+--+--+--+--+ 97 | | | | | | | | | | | | | | | | | AF|DC| R| N|MC| E|V6| 98 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---+--+--+--+--+--+--+ 100 AF-bit 102 When a router supports AF, it MUST set this bit in the Options 103 field of Hello Packets, DD packets and LSAs. 105 5. Changes to the Hello processing 107 When a router does not support an AF but it is configured with an 108 Instance ID in the same range, packets could be blackholed. This 109 could happen due to misconfiguration or router downgrade to a 110 previous code level. Blackholing is possible because the router which 111 doesn't support the AF can still be included in the SPF calculated 112 path as long as it establishes adjacencies using the Instance ID 113 corresponding to the AF. Note that router and network LSAs are AF 114 independent. 116 In order to avoid the above situation, hello processing is changed in 117 order to only establish adjacency with the routers that have the 118 AF-bit set in their Options field. 120 Receiving Hello Packets is specified in section 3.2.2.1 of [Ref1]. 121 The following check is added to Hello reception: 123 When a router participate in an AF (sets the AF-bit in Options field) 124 it MUST discard Hello packets having the AF-bit clear in the Options 125 field. The only exception is IPv6 unicast AF, where this check MUST 126 NOT be done (to help backward compatibility). 128 6. Modification to some of the bits defined in [Ref1] 130 Some of the bits defined in OSPFv3 are relevant to IPv6 unicast 131 AF, and are not needed in other AF's. Some may be applicable only 132 to a certain AF. Below is the list of changes to those bits: 134 o Options Field 136 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 137 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+--+--+--+--+--+ 138 | | | | | | | | | | | | | | | | | |DC| R| N|* | E|* | 139 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+--+--+--+--+--+ 141 o V6-bit 143 The V6 bit is used in OSPFv3 to exclude a node from IPv6 unicast 144 route calculation but allow it in the SPF calculation for 145 other address families. Since Instance ID now denotes the AF 146 explicitly, this bit is ignored in AF's other than IPv6 unicast. 148 o MC-bit 150 This bit is not used in other AF's introduced in this document. 152 o Prefix Options Field 154 0 1 2 3 4 5 6 7 155 +--+--+--+--+--+--+--+--+ 156 | | | | | P|* |LA|NU| 157 +--+--+--+--+--+--+--+--+ 159 o MC bit in the Prefix Options field 161 This bit is not used in other AF's introduced in this document. 163 o NU bit usage in the Prefix Options field 165 The NU bit must be clear in all unicast AF's and it must be set 166 in all multicast AF's. 168 Note that all bits unused in a given AF could be redefined later. 170 7. Carrying Prefixes in new AF's 172 Each Prefix defined in OSPFv3 has a prefix length field. This 173 facilitate advertising prefixes of different lengths in different 174 AF's. The existing LSAs defined in OSPFv3 are used for this 175 purpose and there is no need to define new LSAs. 177 8. Next hop for IPv4 unicast and multicast AF's 179 OSPFv3 runs on the top of IPv6 and uses IPv6 link local addresses 180 for OSPFv3 control packets and next hop calculations. Although IPV6 181 link local addresses could be used as next hops for IPv4 address 182 families, it is desirable to have IPv4 next hop addresses. For 183 example, in IPv4 multicast having the nexthop address the same as 184 the PIM neighbor address (IPv4 address) makes it easier to know to 185 which upstream neighbor to send a PIM join when doing a RPF lookup 186 for a source. It is also easier for troubleshooting purposes to have 187 a next hop with the same semantics as the AF. 189 In order to achieve this, the link's IPv4 address will be advertised 190 in the "link local address" field of the IPv4 instance's Link-LSA. 191 This address is placed in the first 32 bit of "link local address" 192 field and used for IPv4 next hop calculations. 194 We call direct interface address (DIA) the address that is reachable 195 directly via the link provided that a layer 3 to layer 2 mapping is 196 available. Note that there is no explicit need for the IPv4 link 197 addresses to be on the same subnet. An implementation should resolve 198 layer 3 to layer 2 mappings via ARP or ND for a DIA even if the IPv4 199 address is not on the same subnet as the router's interface IP address. 201 9. Virtual Link (VL) 203 OSPFv3 control packets sent over a virtual link are IPv6 packets and 204 may traverse multiples hops. Therefore, there must be a global IPv6 205 address associated with the virtual link so that the control packet 206 is forwarded correctly by the intermediate hops between VL end 207 points. Although this requirement can be satisfied in IPv6 unicast 208 AF, this will not function in other AFs as there cannot be a multihop 209 forwarding based on global IPv6 address or such a path may not exist. 210 Therefore virtual link are not currently supported in other AF's. 212 10. Backward compatibility issues 214 Each new AF will have their corresponding Instance ID and can 215 operate with the existing non-capable routers in IPv6 unicast 216 topology. Further, when a non-capable router uses an Instance ID which 217 is reserved for a given AF, since the non-capable router will not have 218 the AF-bit set in the Hello an adjacency will not be established with 219 an AF capable router. Therefore, there are no backward compatibility 220 issues. AF's can be gradually deployed without disturbing networks with 221 current non-capable routers. 223 11. Address-family design Considerations 225 This section describes the rationale for adopting the multiple 226 instance ID approach for supporting multiple address families in 227 OSPFv3. As described earlier, OSPFv3 is designed to support multiple 228 instances. Hence mapping an instance to an address family doesn't 229 introduce new mechanisms in the protocol. It minimizes the protocol 230 extensions required and it simplifies the implementation. The 231 presence of a separate link state database per address family is 232 also easier to debug and operate. Additionally, it doesn't change 233 the existing instance, area and interface based configuration model 234 in most OSPF implementations. 236 12. Security Considerations 238 The technique described in this document does not introduce any new 239 security issues to the OSPFv3 protocol. 241 13. References 243 [Ref1] R. Coltun, D. Ferguson and J. Moy, "OSPF for IPv6", 244 RFC 2740, December 1999. 246 14. Authors address 248 Sina Mirtorabi Acee Lindem 249 Cisco Systems Redback Networks 250 170 W. Tasman Dr. 102 Carric Bend Court 251 San Jose, CA 95134 Cary, NC 27519 252 Email: sina@cisco.com Email: acee@redback.com 253 Abhay Roy Quaizar Vohra 254 Cisco Systems Juniper Networks 255 170 W. Tasman Dr. 1194 North Mathilda Ave. 256 San Jose, CA 95134 Sunnyvale, CA 94089 257 Email: akr@cisco.com Email: qv@juniper.net 259 Michael Barnes Rahul Aggarwal 260 Cisco Systems Juniper Networks 261 170 W. 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