Source Address Selection for IPv6 FUJIKAWA Kenji Internet-Draft ROOT Inc. Expires: August 25, 2008 February 2007 Source Address Selection Using Just Routing Information for IPv6 draft-fujikawa-ipv6-src-addr-selection-03.txt Status of this Memo 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 becomes aware will be disclosed, in accordance with Section 6 of 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 May 19, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract This document describes a problem of source address selection Rule 8. stated in RFC3484[RFC3484], and shows one solution, which is based just on the destination based address routing and does not require policy routing such as source address based routing. FUJIKAWA Expires August 25, 2008 [Page 1] Internet-Draft Source Address Selection for IPv6 July 2007 1. A Problem of at Source Address Selection Rule 8. in RFC3484 In RFC3484[RFC3404], the source address selection guidelines are shown in the case of multihoming. However, according to them, a problem occurs that a host cannot select the best path. Rule 8 in 5. Source Address Selection in RFC3484 says: Rule 8: Use longest matching prefix. If CommonPrefixLen(SA, D) > CommonPrefixLen(SB, D), then prefer SA. Similarly, if CommonPrefixLen(SB, D) > CommonPrefixLen(SA,D), then prefer SB. Here, consider a network shown in Fig. 1. +---+ |CN | +-+-+ | 2001:db8:2001::CN | +---+---+2001:db8:2000:/36 | | +---------+ ISP2 | | | | | +-------+ | +---+---+2001:db8:1000:/36 +-------+2001:db8:3000::/36 | | | | | ISP1 +-------------------+ ISP3 | | | | | +---+---+ +---+---+ | | | | +----------+ +---------+ 2001:db8:1000:R | |2001:db8:3000:R +-+-+ +-+-+ 2001:db8:1001::/48|R1 | |R3 |2001:db8:3001::/48 +-+-+ +-+-+ fe80::R1| |fe80:R3 | | --+---+---+-- 2001:db8:1001:1:EN | 2001:db8:3001:1:EN +-+-+ |EN | +---+ Fig. 1 In Fig. 1, FUJIKAWA Expires August 25, 2008 [Page 2] Internet-Draft Source Address Selection for IPv6 July 2007 - Each of ISP1, ISP2, and ISP3 is assigned an address space, 2001:db8:1000::/36, 2001:db8:2000::/36, and 2001:db8:3000::/36, respectively. - Correspondent node CN belongs to ISP2, and is assigned an address 2001:db8:2001::CN. - The site is multihomed to ISP1 and ISP3, and the routers R1 and R2 distributes address spaces to downstream nodes such as 2001:db8:1001::/48 and 2001:db8:3001::/48. - End node EN is assigned two addresses, 2001:db8:1001:1:EN and 2001:db8:3001:1:EN. Here, in the above IPv6 address notation, CN, R1, R2, and EN indicates 64bit Interface ID's. According to Rule 8, by means of the longest match method, 2001:db8:3001:EN is selected as the source address of a packet directed from CN to EN. Therefore, - For the purpose of avoiding the source address filtering, policy routing or etc. is required in order to direct a packet to ISP3. - The route becomes roundabout passing through ISP3. 2. A Solution Using Just the Information of the Destination Address of Packets Here, one of the solutions of the above problem is shown, which is based on the traditional destination address based routing, that is, does not require policy routing such as source address based routing. This approach is separated into two issues, an management issue and implementation issue. FUJIKAWA Expires August 25, 2008 [Page 3] Internet-Draft Source Address Selection for IPv6 July 2007 2.1 Management Issue +---+ |CN | +-+-+ | 2001:db8:2001::CN | +---+---+2001:db8:2000:/36 | | +---------+ ISP2 | | | | | +-------+ | +---+---+2001:db8:1000:/36 +-------+2001:db8:3000::/36 | | | | | ISP1 +-------------------+ ISP3 | | | | | +---+---+ +---+---+ | | | | +----------+ +---------+ 2001:db8:1000:R | |2001:db8:3000:R +-+-+ +-+-+ 2001:db8:1001::/48|R1 | |R3 |2001:db8:3001::/48 +-+-+ +-+-+ 2001:db8:1001:1:R1| |2001:db8:3001:1:R3 <- Change from Fig.1 | | --+---+---+-- 2001:db8:1001:1:EN | 2001:db8:3001:1:EN +-+-+ |EN | +---+ Routing Tables: R1: Destination Next Hop 2001:db8:1000::/36 address_of_ISP1's_router 2001:db8:2000::/36 address_of_ISP1's_router R3: 2001:db8:3000::/36 address_of_ISP3's_router EN: Destination Next Hop 2001:db8:1000::/36 2001:db8:1001:1:R1 2001:db8:2000::/36 2001:db8:1001:1:R1 2001:db8:3000::/36 2001:db8:3001:1:R3 Fig.2 FUJIKAWA Expires August 25, 2008 [Page 4] Internet-Draft Source Address Selection for IPv6 July 2007 First, mange a network such as shown in Fig. 2. Here: - The global addresses 2001:db8:1001:R1 and 2001:db8:3001:R3 is respectively assigned to the downstream interfaces of R1 and R3, in addition to the link local addresses. - Each of R1, R3 and EN keeps the traditional routing table shown in Fig.2, respectively. 2.2 Implementation Issue When an entry of a routing table is hit, a source address is selected which longest-matches the next hop in the entry. In the above example, on end node EN, when the entry "2001:db8:2000::/36 2001:db8:1001:1:R" is hit for the destination "2001:db8:2001::CN", the next hop becomes "2001:db8:1001::R", as a result, the address "2001:db8:1001:1:EN" is selected, because it longest-matches the next hop. 3. Modification to RFC3484 Before Rule 8 (Use longest matching prefix) in section 5. (Source Address Selection) in RFC3484, the rule using longest-matching prefix to the next hop is to be added. 4. How to distribute the routing information Any intra-domain routing protocol can be adaptable. In order to deliver the routing information to be used with this rule, employing ND may not be suitable. Delivering destination and next-hop pairs with routing protocols such as RIPng is the way to go. 5. Relations to [I-D.ietf-6man-addr-select-sol] This method is categorized into the most proactive approach in [I- D.ietf-6man-addr-select-sol]. In order to select a precise source address for any destination at any time, the full routing table is required to the host. This is an unavoidable issue for all the most proactive approaches, if one of those approaches is solely adopted. It is also the same to the issue that in order to select the best path for any destination at any time, the full routing table is required. FUJIKAWA Expires August 25, 2008 [Page 5] Internet-Draft Source Address Selection for IPv6 July 2007 6. Adaptation to a Single Router Multihomed Site. +---+ |CN | +-+-+ | 2001:db8:2001::CN | +---+---+2001:db8:2000:/36 | | +---------+ ISP2 | | | | | +-------+ | +---+---+2001:db8:1000:/36 +-------+2001:db8:3000::/36 | | | | | ISP1 +-------------------+ ISP3 | | | | | +---+---+ +---+---+ | | | | +------------+ +------------+ 2001:db8:1000:R| |2001:db8:3000:R ++-++ 2001:db8:1001::/48| R |2001:db8:3001::/48 +-+-+ 2001:db8:1001:1:R | 2001:db8:3001:1:R | 2001:db8:1001:1:EN | 2001:db8:3001:1:EN +-+-+ |EN | +---+ Routing Tables: R: Destination Next Hop 2001:db8:1000::/36 address_of_ISP1's_router 2001:db8:2000::/36 address_of_ISP1's_router 2001:db8:3000::/36 address_of_ISP3's_router EN: Destination Next Hop 2001:db8:1000::/36 2001:db8:1001:1:R 2001:db8:2000::/36 2001:db8:1001:1:R 2001:db8:3000::/36 2001:db8:3001:1:R Fig.3 This method is also adaptable to a single router multihomed site. In FUJIKAWA Expires August 25, 2008 [Page 6] Internet-Draft Source Address Selection for IPv6 July 2007 the site, the single router should be assigned multiple address spaces, and it assigns multiple addresses to the downstream interfaces. This is required when it has only a single downstream interface. (see Fig. 3) Author's Address FUJIKAWA Kenji ROOT Inc., Kyoto Information Laboratory 59 Minami-yonnotsubo-cho, Iwakura, Sakyo-ku, Kyoto 606-0033, Japan Phone: +81-3-5436-8380 (Ext. 1593) Email: fujikawa@root-hq.com References [RFC3484] Draves, R., "Default Address Selection for Internet Protocol version 6 (IPv6)", RFC 3484, February 2003. [I-D.ietf-6man-addr-select-sol] Matsumoto, A., at el., Solution approaches for address-selection problems, draft-ietf-6man-addr-select-sol-00.txt (work in progress), January 2007. FUJIKAWA Expires August 25, 2008 [Page 7] Internet-Draft Source Address Selection for IPv6 July 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). 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