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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Source Address Selection for IPv6 FUJIKAWA Kenji 3 Internet-Draft ROOT Inc. 4 Expires: August 25, 2008 February 2007 6 Source Address Selection Using Just Routing Information for IPv6 7 draft-fujikawa-ipv6-src-addr-selection-03.txt 9 Status of this Memo 11 By submitting this Internet-Draft, each author represents that any 12 applicable patent or other IPR claims of which he or she is aware 13 have been or will be disclosed, and any of which he or she becomes 14 aware will be disclosed, in accordance with Section 6 of BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on May 19, 2008. 34 Copyright Notice 36 Copyright (C) The IETF Trust (2008). 38 Abstract 40 This document describes a problem of source address selection Rule 8. 41 stated in RFC3484[RFC3484], and shows one solution, which is based 42 just on the destination based address routing and does not require 43 policy routing such as source address based routing. 45 1. A Problem of at Source Address Selection Rule 8. in RFC3484 47 In RFC3484[RFC3404], the source address selection guidelines are 48 shown in the case of multihoming. However, according to them, a 49 problem occurs that a host cannot select the best path. 51 Rule 8 in 5. Source Address Selection in RFC3484 says: 53 Rule 8: Use longest matching prefix. If CommonPrefixLen(SA, D) > 54 CommonPrefixLen(SB, D), then prefer SA. Similarly, if 55 CommonPrefixLen(SB, D) > CommonPrefixLen(SA,D), then prefer SB. 57 Here, consider a network shown in Fig. 1. 59 +---+ 60 |CN | 61 +-+-+ 62 | 2001:db8:2001::CN 63 | 64 +---+---+2001:db8:2000:/36 65 | | 66 +---------+ ISP2 | 67 | | | 68 | +-------+ 69 | 70 +---+---+2001:db8:1000:/36 +-------+2001:db8:3000::/36 71 | | | | 72 | ISP1 +-------------------+ ISP3 | 73 | | | | 74 +---+---+ +---+---+ 75 | | 76 | | 77 +----------+ +---------+ 78 2001:db8:1000:R | |2001:db8:3000:R 79 +-+-+ +-+-+ 80 2001:db8:1001::/48|R1 | |R3 |2001:db8:3001::/48 81 +-+-+ +-+-+ 82 fe80::R1| |fe80:R3 83 | | 84 --+---+---+-- 85 2001:db8:1001:1:EN | 2001:db8:3001:1:EN 86 +-+-+ 87 |EN | 88 +---+ 90 Fig. 1 92 In Fig. 1, 93 - Each of ISP1, ISP2, and ISP3 is assigned an address space, 94 2001:db8:1000::/36, 2001:db8:2000::/36, and 2001:db8:3000::/36, 95 respectively. 97 - Correspondent node CN belongs to ISP2, and is assigned an 98 address 2001:db8:2001::CN. 100 - The site is multihomed to ISP1 and ISP3, and the routers R1 and 101 R2 distributes address spaces to downstream nodes such as 102 2001:db8:1001::/48 and 2001:db8:3001::/48. 104 - End node EN is assigned two addresses, 2001:db8:1001:1:EN and 105 2001:db8:3001:1:EN. 107 Here, in the above IPv6 address notation, CN, R1, R2, and EN 108 indicates 64bit Interface ID's. 110 According to Rule 8, by means of the longest match method, 111 2001:db8:3001:EN is selected as the source address of a packet 112 directed from CN to EN. Therefore, 114 - For the purpose of avoiding the source address filtering, 115 policy routing or etc. is required in order to direct a packet to 116 ISP3. 118 - The route becomes roundabout passing through ISP3. 120 2. A Solution Using Just the Information of the Destination Address of 121 Packets 123 Here, one of the solutions of the above problem is shown, which is 124 based on the traditional destination address based routing, that is, 125 does not require policy routing such as source address based routing. 126 This approach is separated into two issues, an management issue and 127 implementation issue. 129 2.1 Management Issue 131 +---+ 132 |CN | 133 +-+-+ 134 | 2001:db8:2001::CN 135 | 136 +---+---+2001:db8:2000:/36 137 | | 138 +---------+ ISP2 | 139 | | | 140 | +-------+ 141 | 142 +---+---+2001:db8:1000:/36 +-------+2001:db8:3000::/36 143 | | | | 144 | ISP1 +-------------------+ ISP3 | 145 | | | | 146 +---+---+ +---+---+ 147 | | 148 | | 149 +----------+ +---------+ 150 2001:db8:1000:R | |2001:db8:3000:R 151 +-+-+ +-+-+ 152 2001:db8:1001::/48|R1 | |R3 |2001:db8:3001::/48 153 +-+-+ +-+-+ 154 2001:db8:1001:1:R1| |2001:db8:3001:1:R3 <- Change from Fig.1 155 | | 156 --+---+---+-- 157 2001:db8:1001:1:EN | 2001:db8:3001:1:EN 158 +-+-+ 159 |EN | 160 +---+ 162 Routing Tables: 163 R1: 164 Destination Next Hop 165 2001:db8:1000::/36 address_of_ISP1's_router 166 2001:db8:2000::/36 address_of_ISP1's_router 167 R3: 168 2001:db8:3000::/36 address_of_ISP3's_router 169 EN: 170 Destination Next Hop 171 2001:db8:1000::/36 2001:db8:1001:1:R1 172 2001:db8:2000::/36 2001:db8:1001:1:R1 173 2001:db8:3000::/36 2001:db8:3001:1:R3 175 Fig.2 177 First, mange a network such as shown in Fig. 2. Here: 179 - The global addresses 2001:db8:1001:R1 and 2001:db8:3001:R3 is 180 respectively assigned to the downstream interfaces of R1 and R3, 181 in addition to the link local addresses. 183 - Each of R1, R3 and EN keeps the traditional routing table 184 shown in Fig.2, respectively. 186 2.2 Implementation Issue 188 When an entry of a routing table is hit, a source address is selected 189 which longest-matches the next hop in the entry. 191 In the above example, on end node EN, when the entry 192 "2001:db8:2000::/36 2001:db8:1001:1:R" is hit for the destination 193 "2001:db8:2001::CN", the next hop becomes "2001:db8:1001::R", as a 194 result, the address "2001:db8:1001:1:EN" is selected, because it 195 longest-matches the next hop. 197 3. Modification to RFC3484 199 Before Rule 8 (Use longest matching prefix) in section 5. (Source 200 Address Selection) in RFC3484, the rule using longest-matching prefix 201 to the next hop is to be added. 203 4. How to distribute the routing information 205 Any intra-domain routing protocol can be adaptable. In order to 206 deliver the routing information to be used with this rule, employing 207 ND may not be suitable. Delivering destination and next-hop pairs 208 with routing protocols such as RIPng is the way to go. 210 5. Relations to [I-D.ietf-6man-addr-select-sol] 212 This method is categorized into the most proactive approach in [I- 213 D.ietf-6man-addr-select-sol]. 215 In order to select a precise source address for any destination at 216 any time, the full routing table is required to the host. This is an 217 unavoidable issue for all the most proactive approaches, if one of 218 those approaches is solely adopted. It is also the same to the issue 219 that in order to select the best path for any destination at any 220 time, the full routing table is required. 222 6. Adaptation to a Single Router Multihomed Site. 224 +---+ 225 |CN | 226 +-+-+ 227 | 2001:db8:2001::CN 228 | 229 +---+---+2001:db8:2000:/36 230 | | 231 +---------+ ISP2 | 232 | | | 233 | +-------+ 234 | 235 +---+---+2001:db8:1000:/36 +-------+2001:db8:3000::/36 236 | | | | 237 | ISP1 +-------------------+ ISP3 | 238 | | | | 239 +---+---+ +---+---+ 240 | | 241 | | 242 +------------+ +------------+ 243 2001:db8:1000:R| |2001:db8:3000:R 244 ++-++ 245 2001:db8:1001::/48| R |2001:db8:3001::/48 246 +-+-+ 247 2001:db8:1001:1:R | 2001:db8:3001:1:R 248 | 249 2001:db8:1001:1:EN | 2001:db8:3001:1:EN 250 +-+-+ 251 |EN | 252 +---+ 254 Routing Tables: 255 R: 256 Destination Next Hop 257 2001:db8:1000::/36 address_of_ISP1's_router 258 2001:db8:2000::/36 address_of_ISP1's_router 259 2001:db8:3000::/36 address_of_ISP3's_router 260 EN: 261 Destination Next Hop 262 2001:db8:1000::/36 2001:db8:1001:1:R 263 2001:db8:2000::/36 2001:db8:1001:1:R 264 2001:db8:3000::/36 2001:db8:3001:1:R 266 Fig.3 268 This method is also adaptable to a single router multihomed site. In 269 the site, the single router should be assigned multiple address 270 spaces, and it assigns multiple addresses to the downstream 271 interfaces. This is required when it has only a single downstream 272 interface. (see Fig. 3) 274 Author's Address 276 FUJIKAWA Kenji 277 ROOT Inc., Kyoto Information Laboratory 278 59 Minami-yonnotsubo-cho, Iwakura, Sakyo-ku, Kyoto 606-0033, Japan 279 Phone: +81-3-5436-8380 (Ext. 1593) 280 Email: fujikawa@root-hq.com 282 References 284 [RFC3484] Draves, R., "Default Address Selection for Internet 285 Protocol version 6 (IPv6)", RFC 3484, February 2003. 287 [I-D.ietf-6man-addr-select-sol] 288 Matsumoto, A., at el., Solution approaches for 289 address-selection problems, 290 draft-ietf-6man-addr-select-sol-00.txt (work in progress), 291 January 2007. 293 Full Copyright Statement 295 Copyright (C) The IETF Trust (2007). 297 This document is subject to the rights, licenses and restrictions 298 contained in BCP 78, and except as set forth therein, the authors 299 retain all their rights. 301 This document and the information contained herein are provided on an 302 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 303 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 304 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 305 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 306 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 307 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 309 Intellectual Property 311 The IETF takes no position regarding the validity or scope of any 312 Intellectual Property Rights or other rights that might be claimed to 313 pertain to the implementation or use of the technology described in 314 this document or the extent to which any license under such rights 315 might or might not be available; nor does it represent that it has 316 made any independent effort to identify any such rights. 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