IPv6 Maintenance L. Colitti Internet-Draft E. Kline Intended status: Standards Track J. Linkova Expires: January 21, 2019 Google July 20, 2018 Discovering PREF64 in Router Advertisements draft-pref64folks-6man-ra-pref64-01 Abstract This document specifies a Router Advertisement option to configure the NAT64 prefix. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on January 21, 2019. Copyright Notice Copyright (c) 2018 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 (https://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 Simplified BSD License. Colitti, et al. Expires January 21, 2019 [Page 1] Internet-Draft Discovering PREF64 in Router Advertisements July 2018 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 2. Why include the NAT64 prefix in Router Advertisements . . . . 2 3. Semantics . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Option format . . . . . . . . . . . . . . . . . . . . . . . . 3 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 5 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction NAT64 [RFC6146] with DNS64 [RFC6147] is a widely-deployed mechanism to provide IPv4 access on IPv6-only networks. In order to support functions such as local validation of DNSSEC [RFC4033] responses, 464xlat [RFC6877], and local IPv4 address synthesis [RFC8305], the host must be aware of the NAT64 prefix in use by the network. This document specifies a Router Advertisement [RFC4861] option to communicate the NAT64 prefix to hosts. 1.1. Requirements Language 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 RFC 2119 [RFC2119]. 2. Why include the NAT64 prefix in Router Advertisements Fate sharing. NAT64 requires a routing to be configured. IPv6 routing configuration requires receiving an IPv6 Router Advertisement [RFC4861]. Compared to currently-deployed NAT64 prefix discovery methods such as [RFC7050], including the NAT64 prefix in the Router Advertisement minimizes the number of packets required to configure a host. This speeds up the process of connecting to a network that supports NAT64/DNS64, and simplifies host implementation by removing the possibility that the a can have an incomplete layer 3 configuration (e.g., IPv6 addresses and prefixes, but no NAT64 prefix). Deployability. All IPv6 hosts and networks are required to support [RFC4861]. Other options such as [RFC7225] require implementing other protocols. Colitti, et al. Expires January 21, 2019 [Page 2] Internet-Draft Discovering PREF64 in Router Advertisements July 2018 3. Semantics This option specifies exactly one NAT64 prefix for all IPv4 destinations. If the network operator desires to route different parts of the IPv4 address space to different NAT64 devices, this can be accomplished by routing more specifics of the NAT64 prefix to those devices. For example, if the operator would like to route 10.0.0.0/8 through NAT64 device A and the rest of the IPv4 space through NAT64 device B, and the operator's NAT64 prefix is 2001:db8:a:b::/96, then the operator can route 2001:db8:a:b::a00:0/104 to NAT64 A and 2001:db8:a:b::/64 to NAT64 B. This option may appear more than once in a Router Advertisement. Host behaviour with regards to synthesizing IPv6 addresses from IPv4 addresses SHOULD follow the recommendations given in Section 5.1 of [RFC7050], limited to the NAT64 prefixes that have non-zero lifetime. In a network that provides both IPv4 and NAT64, it may be desirable for certain IPv4 addresses not to be translated. An example might be private address ranges that are local to the network and should not be reached through the NAT64. This type of configuration cannot be conveyed to hosts using this option, or through other NAT64 prefix provisioning mechanisms such as [RFC7050] or [RFC7225]. This problem does not apply in IPv6-only networks, because in such networks, the host does not have an IPv4 address and cannot reach any IPv4 destinations without the NAT64. For simplicity, this option only supports a NAT64 prefix length of 96 bits, as this is by the most common configuration used by hosts. Networks using one of the other prefix lengths supported in ([RFC6052]) can use other mechanisms such as [RFC7050] or [RFC7225]. If different prefix lengths become common, another RA option could be created to configure them. 4. Option format Colitti, et al. Expires January 21, 2019 [Page 3] Internet-Draft Discovering PREF64 in Router Advertisements July 2018 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 | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Prefix + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: NAT64 Prefix Option Format Fields: Type 8-bit identifier of the RDNSS option type as assigned by IANA: TBD Length 8-bit unsigned integer. The length of the option (including the Type and Length fields) is in units of 8 octets. The sender MUST set the Length to 2. A host MUST ignore the NAT64 prefix option if the length field value is 1. If the Length field value exceeds 2, the host MUST utilize the first 16 octets and ignore the rest of the option. Lifetime 16-bit unsigned integer. The maximum time in seconds over which this NAT64 prefix MAY be used. The value of Lifetime SHOULD by default be set to lesser of 3 x MaxRtrAdvInterval or 65535 seconds. A value of zero means that the prefix MUST no longer be used. Prefix The highest 96-bits of the NAT64 prefix. 5. IANA Considerations The IANA is requested to assign a new IPv6 Neighbor Discovery Option type for the PREF64 option defined in this document. +---------------+-------+ | Option Name | Type | +---------------+-------+ | PREF64 option | (TBD) | +---------------+-------+ Table 1 The IANA registry for these options is: https://www.iana.org/assignments/icmpv6-parameters [1] Colitti, et al. Expires January 21, 2019 [Page 4] Internet-Draft Discovering PREF64 in Router Advertisements July 2018 6. Security Considerations Because Router Advertisements are required in all IPv6 configuration scenarios, on IPv6-only networks, Router Advertisements must already be secured, e.g., by deploying RA guard [RFC6105]. Providing all configuration in Router Advertisements increases security by ensuring that no other protocols can be abused by malicious attackers to provide hosts with invalid configuration. The security measures that must already be in place to ensure that Router Advertisements are only received from legitimate sources eliminate the problem of NAT64 prefix validation described in section 3.1 of [RFC7050]. 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, DOI 10.17487/RFC6052, October 2010, . 7.2. Informative References [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS Security Introduction and Requirements", RFC 4033, DOI 10.17487/RFC4033, March 2005, . [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, . [RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J. Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105, DOI 10.17487/RFC6105, February 2011, . Colitti, et al. Expires January 21, 2019 [Page 5] Internet-Draft Discovering PREF64 in Router Advertisements July 2018 [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146, April 2011, . [RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van Beijnum, "DNS64: DNS Extensions for Network Address Translation from IPv6 Clients to IPv4 Servers", RFC 6147, DOI 10.17487/RFC6147, April 2011, . [RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT: Combination of Stateful and Stateless Translation", RFC 6877, DOI 10.17487/RFC6877, April 2013, . [RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis", RFC 7050, DOI 10.17487/RFC7050, November 2013, . [RFC7225] Boucadair, M., "Discovering NAT64 IPv6 Prefixes Using the Port Control Protocol (PCP)", RFC 7225, DOI 10.17487/RFC7225, May 2014, . [RFC8305] Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2: Better Connectivity Using Concurrency", RFC 8305, DOI 10.17487/RFC8305, December 2017, . 7.3. URIs [1] https://www.iana.org/assignments/icmpv6-parameters Authors' Addresses Lorenzo Colitti Google Roppongi 6-10-1 Minato, Tokyo 106-6126 JP Email: lorenzo@google.com Colitti, et al. Expires January 21, 2019 [Page 6] Internet-Draft Discovering PREF64 in Router Advertisements July 2018 Erik Kline Google Roppongi 6-10-1 Minato, Tokyo 106-6126 JP Email: ek@google.com Jen Linkova Google 1 Darling Island Rd Pyrmont, NSW 2009 AU Email: furry@google.com Colitti, et al. Expires January 21, 2019 [Page 7]