Behave Working Group J. Kato Internet-Draft A. Matsumoto Intended status: Standards Track T. Fujisaki Expires: September 6, 2010 NTT March 5, 2010 Checksum-Neutral Prefix NAT for IPv6 draft-kato-behave-prefix-nat-01.txt Abstract This document describes a use-case of IPv6-to-IPv6 network address translation, and a translation mechanism for smaller network. To be used typically in a network where IPv6 /64 prefix is advertiesed, a network address translation mechanism is proposed that is based on Interface Identifier rewriting to be checksum neutral. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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 September 6, 2010. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents Kato, et al. Expires September 6, 2010 [Page 1] Internet-Draft Checksum-Neutral Prefix NAT March 2010 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. 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. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Kato, et al. Expires September 6, 2010 [Page 2] Internet-Draft Checksum-Neutral Prefix NAT March 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Proposal of Address Translation using Interface Identifier . . 4 2.1. Address Translation Example . . . . . . . . . . . . . . . . 4 3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. Normative References . . . . . . . . . . . . . . . . . . . 6 6.2. Informative References . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Kato, et al. Expires September 6, 2010 [Page 3] Internet-Draft Checksum-Neutral Prefix NAT March 2010 1. Introduction The IPv6-to-IPv6 translation mechanism proposed in NAT66 document. NAT66 document [I-D.mrw-behave-nat66]. This assumes that a network is assigned /48 or larger address block. This is because the mechanism uses 16 bits of IPv6 address for subnetting to make the translation neutral to address translation. However, in some environment, a network cannot get such a large address space. Then, we propose another IPv6-to-IPv6 translation mechanism that can be used in a network with /48 or smaller address block and that is neutral to transport layer checksum. This mechanism also has a characteristics of one-to-one mapping, to keep the end-to-end transparency as much as possible. 2. Proposal of Address Translation using Interface Identifier A IPv6 address translation mechanism for smaller network is proposed in this section. This translation mechiansm is one-to-one mapping based, and is Interface Identifier rewriting based, to make it checksum neutral. Regarding the prefix part of an IPv6 address, it is simply replaced with the predefined external/internal prefix value. Regarding the Interface Identifier part, the modified value is chosen so that the address translation does not have an impact on transport layer checksum, which is almost the same technique adopted in NAT66 [I-D.mrw-behave-nat66]. 2.1. Address Translation Example Example network structure is described below. Kato, et al. Expires September 6, 2010 [Page 4] Internet-Draft Checksum-Neutral Prefix NAT March 2010 external network: 2001:0DB8:1111:0001::/64 ------+---------------------- | | o eth0 2001:0DB8:1111:0001::1 +----+-----+ | NAT66BOX | +----+-----+ o eth1 FD00:0203:1111:0405::1 | | ---+--+---------------------- | internal network: FD00:0203:1111:0405::/64 | | o eth0 FD00:0203:1111:0405:0200:1111:1011:1234 +-----+-----+ | IPv6 host | +-----+-----+ example network When IPv6 host sends a packet destined to external network, NAT66BOX receives the following IPv6 packet. dst IPv6 address: (somewhere in external network) src IPv6 address: fd00:0203:1111:0405:0200:1111:1011:1234 NAT66BOX performs the following address translation to the source address of the IPv6 packet, and forward the packet to the upstream. Here, it is assumed that the function cksum(x) calculates the 16-bit one's complement sum as defined in RFC1071 [RFC1071]. 1. Calculates the difference between to-be-translated prefix checksum and translated prefix checksum. cksum(FD01:0203:1111:0405) => 0x141B cksum(2001:0DB8:1111:0001) => 0x3ECB 2. Gets the difference of the two prefixes based on one's complement sum. 0x3ECB - 0x141B = 0x2AB0 Kato, et al. Expires September 6, 2010 [Page 5] Internet-Draft Checksum-Neutral Prefix NAT March 2010 3. Gets the difference of the least significant 16 bits of the to-be-translated IPv6 address and the difference of the prefixes' checksums calculated at 2. 0x1234 - 0x2AB0 = 0xE783 4. Puts the value of 3 to the least significant 16 bits of the translated address Interface Identifier, and gets the translated address. 2001:0DB8:1111:0001:0200:1111:1011:E783 In the same way, translation of incoming packet from external network can be processed. 3. Discussion The mechanism describes here ignores the meaning U/L bit described in [RFC4291]. As the Interface Identifier part of the translated address is not assured of uniqueness, the U/L bit should not be set to 1. The workarounds for this issue are to have per-session translation table, to administrate the addresses of hosts in local network and make all of them use addresses with U/L bit 0. 4. IANA Considerations This document has no actions for IANA. 5. Security Considerations TBD 6. References 6.1. Normative References [I-D.mrw-behave-nat66] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Address Translation (NAT66)", draft-mrw-behave-nat66-02 (work in progress), March 2009. Kato, et al. Expires September 6, 2010 [Page 6] Internet-Draft Checksum-Neutral Prefix NAT March 2010 [RFC1071] Braden, R., Borman, D., Partridge, C., and W. Plummer, "Computing the Internet checksum", RFC 1071, September 1988. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. 6.2. Informative References Authors' Addresses Jun-ya Kato NTT PF Lab Midori-Cho 3-9-11 Musashino-shi, Tokyo 180-8585 Japan Phone: +81 422 59 2939 Email: kato@nttv6.net 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 Kato, et al. Expires September 6, 2010 [Page 7]