Arifumi Matsumoto Internet-Draft Tomohiro Fujisaki Expires: April 21, 2005 Hirotaka Matsuoka Jun-ya Kato NTT PF Lab. October 21, 2004 Configuring Source Address Selection Policy by Neighbor Discovery Protocol for IPv6 draft-arifumi-ipv6-nd-source-address-select-01 Status of this Memo By submitting this Internet-Draft, we certify that any applicable patent or other IPR claims of which we are aware have been disclosed, or will be disclosed, and any of which we become aware will be disclosed, in accordance with RFC 3668. 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 made obsolete 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. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document describes a Neighbor Discovery IPv6 Source Address Selection(SAS) Policy option for distributing of source address selection policies to end nodes. This option is particularly effective when a consumer site has multiple address blocks. Every end node is guided by such a policy in selecting an appropriate source address for each destination address. This makes it possible Arifumi Expires April 21, 2005 [Page 1] Internet-Draft October 2004 for an end node to set up a connection without concern for transfer failures due to ingress filtering by ISPs, for ISP operators to manage user behavior and networking policy, and for consumers to be provided with networks that are almost automatically robust and reliable. 1. Introduction An IPv6 multihoming site has multiple nodes, each of which is assigned multiple IPv6 addresses by up stream ISPs. When there are multiple up stream ISPs, the current means of selecting the ISP for an outgoing packet is based on the destination address. Actually, in general, each packet should have a source address that has been allocated by the selected up stream ISP. This is because the routers of ISPs may be configured to perform ingress filtering with the aim of blocking packets with illegal source addresses. In another Internet-Draft [1], we propose a technique that can be used both to distribute policy information for source address selection(SAS) at end nodes and to establish a method for packet- forwarding by routers. This enables ISPs to control incoming traffic from customer sites and the end nodes to select appropriate source addresses. It also enables the selection of outgoing ISPs in a way that is almost certain to produce successful connection setups. In this document, we propose an extension to the Neighbor Discovery Router Advertisement Message [2]. In another draft, we propose a new option [5] for DHCPv6 [3,4] to handle delivery of address selection policies end nodes. An address selection policy delivered to an end node is stored in the form of a policy table, as defined in RFC 3484 [6]. These two drafts are protocol specifications implementing the multihome network technique proposed previously [1]. 2. Terminology 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 [7]. 3. Message formats 3.1. Changes to Prefix Information option of Router Advertisement Message The change from Neighbor Discovery [2] section 4.6 is as follows: Arifumi Expires April 21, 2005 [Page 2] Internet-Draft October 2004 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Prefix Length |L|A| SASID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Valid Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Preferred Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Prefix + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Fields: SASID A 6-bit unsigned integer; the identifier of the Source Address Selection (SAS) Policy option related to this Prefix Information option. Each Prefix Information option can be linked with one SAS Policy option, as mentioned in the next paragraph. If this Prefix Information option isn't bound with any SAS Policy option, the value of this field must be zero. Otherwise, it will be the identifier of the corresponding SAS option. Arifumi Expires April 21, 2005 [Page 3] Internet-Draft October 2004 3.2 Source Address Selection (SAS) Policy option 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | SASID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix Length | | +-+-+-+-+-+-+-+-+ Prefix (Variable Length) | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Prefix Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Prefix (Variable Length) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . Prefix ... . . +-+-+-+-+-+-+-+-+ | | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Fields: Type TBD Length An 8-bit unsigned integer; the length of the option (including the Type and Length fields) in units of 4 octets. Reserved A 10-bit unused field. This field MUST be initialized to zero by the sender and ignored by the receiver. SASID A 6-bit unsigned integer; the identifier of the SAS Policy option. A Router Advertisement Message cannot contain multiple SAS Policy options with the same SASID. With this identifier, the SAS Policy options are linked with the Prefix Information option. An SAS Policy option with no linked Prefix Information option will be discarded. Prefix Length An 8-bit unsigned integer; the number of leading bits in the prefix that are valid. The value ranges from 0 to 128. The Prefix field is 0, 4, 8, 12, or 16 octets, depending on the length. Prefix A variable-length field containing an IP address or the prefix of an IP address. The Prefix Length field contains the number of valid leading bits in the prefix. The bits in the prefix after the Prefix Length (if any) are reserved and Arifumi Expires April 21, 2005 [Page 4] Internet-Draft October 2004 MUST be initialized to zero by the sender and ignored by the receiver. Padding A variable-length field for 32-bit alignment. This field MUST be initialized to 1 by the sender and ignored by the receiver. This option appears only in Router Advertisement Message and has to have corresponding Prefix Information option within the same Router Advertisement Message. Otherwise, this option MUST be ignored. 3.3 Discussion The SASID, mentioned above, is used to link the Prefix Information and a SAS Policy option. This field occupies as much space as 6-bit reserved field in the Prefix Information option. Instead of the SASID, an alternative method of linking is to copy the prefix of the corresponding Prefix Information option into the SAS Policy option, as shown in the figure below. This method, however, is expected to consume more option space. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Prefix Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | Prefix | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix Length | | +-+-+-+-+-+-+-+-+ Prefix (Variable Length) | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Prefix Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Prefix (Variable Length) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . Prefix ... . . +-+-+-+-+-+-+-+-+ | | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Arifumi Expires April 21, 2005 [Page 5] Internet-Draft October 2004 4. Specifications 4.1 Router Specification - The SAS Policy option MUST NOT appear in anything other than a Neighbor Discovery Router Advertisement Message. - Multiple Prefix Information options can share the same SASID. - When a router has too much information to make into one packet (1280 bytes), the incident SHOULD be reported or logged. 4.2 Host Specification - An SAS Policy option in anything other than a Neighbor Distribution Router Advertisement Message MUST be ignored. - Each SAS Policy option is linked with one or more Prefix Information options. This tuple will be kept in a policy table, as defined in RFC 3484, Section 2.1 [6]. Assume that a host receives the following tuples: Prefix SAS 2001:1:1:1::/64 - SAS1 (2001:1::/16, 2001:2::/16) 2001:2:2:2::/64 - SAS1 (2001:1::/16, 2001:2::/16) 2002:3:3:3::/64 - SAS2 (::/0) Table 1 Then, these tuples are stored in a policy table like that shown below. Prefix Precedence Label 2001:1:1:1::/64 undefined 10 2001:2:2:2::/64 undefined 10 2001:1::/16 undefined 10 2001:2::/16 undefined 10 2002:3:3:3::/64 undefined 20 ::/0 undefined 20 Table 2 The first two tuples in Table 1 are linked with the same SAS Policy option (SAS1), so they are also linked with each other, and thus, they have the same Label value in Table 2. Arifumi Expires April 21, 2005 [Page 6] Internet-Draft October 2004 - When two Prefixes contained in different SAS Policy options are the same, the Prefixes will be ignored. - Each SAS Policy option has a lifetime, which is the valid lifetime of the corresponding Prefix Information option. When an SAS Policy option is related to multiple Prefix Information options, its lifetime will be the maximum lifetime among those of all the Prefix Information options. 5. Security Considerations With regard to the possibility of traffic abduction by announcing a bogus policy, this scheme seems to neither lower nor raise the security level obtained with the existing base protocol, namely, Neighbor Discovery Router Advertisement. It does, however, raise the possibility of a new form of DoS attack on routers and hosts, in which large numbers of address selection policies are generated by different source addresses. We will have to discuss this and take precautionary measures in designing the protocol specification. 6. Normative References [1] Matsumoto, A., Fujisaki, T., Matsuoka. H and J. Kato, "Source Address Selection Policy Distribution for Multihoming", Internet-Draft, October 2004, draft-arifumi-multi6-sas-policy- dist-00.txt. [2] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)," RFC 2461, December 1998. [3] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)," RFC 3315, July 2003. [4] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6" RFC 3633, December 2003. [5] Matsuoka, H., Fujisaki, T., Kato, J. and A. Matsumoto, "Source Address Selection Option DHCPv6," Internet-Draft, October 2004, draft-hirotaka-dhcp6-sas-option-00.txt. [6] R. Draves, "Default Address Selection for Internet Protocol version 6 (IPv6)," RFC 3484, February 2003. [7] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Arifumi Expires April 21, 2005 [Page 7] Internet-Draft October 2004 Authors' Addresses Arifumi Matsumoto Nippon Telegraph and Telephone Corporation Information Sharing Platform Laboratories 3-9-11 Midori-cho Musashino-shi, Tokyo 180-8585 Japan Phone: +81-422-59-3334 E-Mail: matsumoto.arifumi@lab.ntt.co.jp Tomohiro Fujisaki Nippon Telegraph and Telephone Corporation Information Sharing Platform Laboratories 3-9-11 Midori-cho Musashino-shi, Tokyo 180-8585 Japan Phone: +81-422-59-7351 E-Mail: fujisaki.tomohiro@lab.ntt.co.jp Hirotaka Matsuoka Nippon Telegraph and Telephone Corporation Information Sharing Platform Laboratories 3-9-11 Midori-cho Musashino-shi, Tokyo 180-8585 Japan Phone: +81-422-59-4949 E-Mail: matsuoka.hirotaka@lab.ntt.co.jp Jun-ya Kato Nippon Telegraph and Telephone Corporation Information Sharing Platform Laboratories 3-9-11 Midori-cho Musashino-shi, Tokyo 180-8585 Japan Phone: +81-422-59-2939 E-Mail: kato.junya@lab.ntt.co.jp Full Copyright Statement Copyright (C) The Internet Society (2004). 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