IPv6 Maintenance Working Group A. Matsumoto Internet-Draft T. Fujisaki Intended status: Informational NTT Expires: January 3, 2010 R. Hiromi Intec Netcore July 6, 2009 Considerations of address selection policy conflicts draft-arifumi-6man-addr-select-conflict-00.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. 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The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 3, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. Matsumoto, et al. Expires January 3, 2010 [Page 1] Internet-Draft Address-Selection Confliction July 2009 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract This document tries to speculate how policy conflicts happen, and how to address the conflicts. After classifying address selection policies, we proposed how to solve the merging conflicting policies for each classes. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Address Selection Control . . . . . . . . . . . . . . . . . . . 3 3. Source Address Selection Conflicts and Solution . . . . . . . . 4 4. Destination Address Selection Conflicts and Solution . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 7. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Matsumoto, et al. Expires January 3, 2010 [Page 2] Internet-Draft Address-Selection Confliction July 2009 1. Introduction As mentioned in RFC 5220 [RFC5220], a host and a site can belong to multiple upstream networks. For example, a host with multiple interfaces, such as wireless and wired interfaces, can easily belong to multiple networks. A site may have connectivity to ISP and a corporate network through a VPN link. In these cases, if two or more of the upstream networks want to control address selection behavior of his network's customer host, those address selection policies have to be merged at the host, and they may collide there. Some of the problems described in RFC 5220 are specific to and resulted from the address selection mechanism defined in RFC 3484. [RFC3484] However, above mentioned policy collision is an intrinsic problem of address selection policy merging, and not specific to the RFC 3484 mechanism. This document tries to speculate how policy conflicts happen, and how to address the conflicts. However, this document does not aim to examine a concrete mechanism for solving conflicts, nor assume the address selection mechanism defined in RFC 3484. [RFC3484] This document focuses on identifying what kind of conflict related problems we have, and in what kind of manner we can solve them. 2. Address Selection Control As in RFC 5220, there are various motivations for network administrator to control address selection behavior of his customers' hosts. However, we can summarize them into two following kinds of controls. - Source address selection behavior control: "When accessing to PREFIX-1, use ADDRESS-1 as the source address." A lot of ISPs have this policy and they usually implement it by adopting ingress filtering to incoming packets from their customers. Another case where this policy is used is a network that makes use of multiple address blocks in the network and assigns multiple addresses/prefixes to its customers and use them for different purpose, such as the Internet access use and telephone call use. - Destination address selection behavior control: Matsumoto, et al. Expires January 3, 2010 [Page 3] Internet-Draft Address-Selection Confliction July 2009 "When accessing to PREFIX-1 or PREFIX-2, prefer PREFIX-1 rather than PREFIX-2." This control is rather intended for optimization of the customers' traffic. This kind of control is not intended for on-off switch, but rather a preference degree. For example, this is useful when a destination site has both PREFIX-1 and PREFIX-2, and the network administrator knows connectivity to PREFIX-1 is better than PREFIX-2. The typical case of this is IPv4 and IPv6 prioritization as mentioned in RFC 5220. On-off switch manner of control is not in scope of address selection behavior, but it should be implemented some other mechanism, such as routing table manipulation and DNS resolution. As this is intrinsiclly intended for optimization, it should not be used for any other purpose like security . Here, PREFIX-* is used to denote both IPv4 and IPv6 prefixes. In the following part, policy conflict and solution for these two patterns above are examined separately. 3. Source Address Selection Conflicts and Solution As mentioned above, source address selection policy have following meaning: "When accessing to PREFIX-1, use ADDRESS-1 as the source address." The upstream network that has this kind of policy usually assigns an address block that includes ADDRESS-1, and also provides reachability to the network that is specified by PREFIX-1. Source address selection policy conflict can happen when different network have a policy for the same prefix. For example, in the following figure, Network-1 have a policy: "To PREFIX-1, use ADDRESS-1", and Network-2: "To PREFIX-1 and PREFIX-2, use ADDRESS-2". PREFIX-1 -----+ PREFIX-2 | \ | | \ | +-----+-----+ +-+---+-----+ | Network-1 | | Network-2 | +------+----+ +----+------+ \ / \ / ADDRESS-1 \ / ADDRESS-2 +---+----+---+ | Host/Site | +------------+ Matsumoto, et al. Expires January 3, 2010 [Page 4] Internet-Draft Address-Selection Confliction July 2009 In this case, the solution is straightforward. The destination address is determined before source address selection policy is used. Thus, the outgoing route, such as the next-hop node and the network interface, is determined by looking up the routing table at a host. That is, the outgoing network that carries the packet to the destination is fixed without source address selection policy. So, the bottom line is that the source address selection policy that matches routing table's behavior should be chosen. There is no point adopting the source address selection policy of a network where a packet does not go through. In other words, if the routing table is fixed before the source address selection policy, then the source address selection policy should be implemented avoiding contradiction with the routing table. If not, the routing table should be coordinated to match the source address selection policy. 4. Destination Address Selection Conflicts and Solution As mentioned in section 2, destination address selection policy have following meaning: "When accessing to a destination site that has PREFIX-1 and PREFIX-2, prefer PREFIX-1 rather than PREFIX-2." The upstream network that has this kind of policy should provides reachability to both networks that are specified by PREFIX-1 and PREFIX-2. Destination address selection policy conflict can happen when a network has a policy that has inverse effect of another network's policy. That is, in the figure below, Network-1 prefers PREFIX-1 rather than PREFIX-2, and Network-2 prefers PREFIX-2 rather than PREFIX-1. bad bad PREFIX-1 ---- ---- PREFIX-2 | X | good | / \ | good +-----+-----+ +-----+-----+ | Network-1 | | Network-2 | +------+----+ +----+------+ \ / \ / ADDRESS-1 \ / ADDRESS-2 +---+---+---+ | Host/Site | +-----------+ Matsumoto, et al. Expires January 3, 2010 [Page 5] Internet-Draft Address-Selection Confliction July 2009 This problem is very similar to routing protocol's route selection. In any routing protocols, a router advertises a route with the cost, in the form of AS path length or metric, that have to be paid when accessing to the route via the router. In routing protocols, for example, Network-1 router advertises the following routes to customers: to PREFIX-1, cost 10 via Network-1 to PREFIX-2, cost 20 via Network-1 Network-2 advertises: to PREFIX-1, cost 20 via Network-2 to PREFIX-2, cost 10 via Network-2 Then, the receiving host will have the following merged routing table: to PREFIX-1, cost 10 via Network-1 to PREFIX-2, cost 10 via Network-2 Going back to address selection, almost the same goes for it. That is, in address selection, a network advertises prefixes A, B to reach a destination FQDN, and each prefix has a cost. For example, Network-1 router advertises the following policy to the customers: to PREFIX-1, cost 10 to PREFIX-2, cost 20 Network-2 advertises: to PREFIX-1, cost 20 to PREFIX-2, cost 10 Then, the receiving host should have the following merged address selection policy: to PREFIX-1, cost 10 via Network-1 to PREFIX-2, cost 10 via Network-2 Here, it should be noted that the resulting address selection policy is combined with routing table nature. It does not mean that the database schema for address selection policy has to be extended, but that address selection policy has to be coordinated with routing table when merging these kind of policies. 5. IANA Considerations This document has no actions for IANA. Matsumoto, et al. Expires January 3, 2010 [Page 6] Internet-Draft Address-Selection Confliction July 2009 6. Security Considerations TBD 7. Conclusions In this document, we examined and classified address selection policies. For each class, we proposed how to solve the merging conflicting policies. 8. References 8.1. Normative References [RFC3484] Draves, R., "Default Address Selection for Internet Protocol version 6 (IPv6)", RFC 3484, February 2003. [RFC5220] Matsumoto, A., Fujisaki, T., Hiromi, R., and K. Kanayama, "Problem Statement for Default Address Selection in Multi- Prefix Environments: Operational Issues of RFC 3484 Default Rules", RFC 5220, July 2008. 8.2. Informative References Authors' Addresses Arifumi Matsumoto NTT PF Lab Midori-Cho 3-9-11 Musashino-shi, Tokyo 180-8585 Japan Phone: +81 422 59 3334 Email: arifumi@nttv6.net Tomohiro Fujisaki NTT PF Lab Midori-Cho 3-9-11 Musashino-shi, Tokyo 180-8585 Japan Phone: +81 422 59 7351 Email: fujisaki@syce.net Matsumoto, et al. Expires January 3, 2010 [Page 7] Internet-Draft Address-Selection Confliction July 2009 Ruri Hiromi Intec Netcore, Inc. Shinsuna 1-3-3 Koto-ku, Tokyo 136-0075 Japan Phone: +81 3 5665 5069 Email: hiromi@inetcore.com Matsumoto, et al. Expires January 3, 2010 [Page 8]