--- 1/draft-ietf-6man-ra-pref64-00.txt 2019-06-28 01:13:09.856973309 -0700 +++ 2/draft-ietf-6man-ra-pref64-01.txt 2019-06-28 01:13:09.880973915 -0700 @@ -1,19 +1,18 @@ IPv6 Maintenance L. Colitti -Internet-Draft E. Kline -Intended status: Standards Track J. Linkova -Expires: September 25, 2019 Google - March 24, 2019 +Internet-Draft J. Linkova +Intended status: Standards Track Google +Expires: December 30, 2019 June 28, 2019 Discovering PREF64 in Router Advertisements - draft-ietf-6man-ra-pref64-00 + draft-ietf-6man-ra-pref64-01 Abstract This document specifies a Router Advertisement option to communicate NAT64 prefixes to clients. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. @@ -21,21 +20,21 @@ 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 September 25, 2019. + This Internet-Draft will expire on December 30, 2019. Copyright Notice Copyright (c) 2019 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 @@ -47,60 +46,60 @@ Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 2. Use cases for communicating the NAT64 prefix to hosts . . . . 3 3. Why include the NAT64 prefix in Router Advertisements . . . . 3 4. Semantics . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Option format . . . . . . . . . . . . . . . . . . . . . . . . 4 - 6. Handling Multiple NAT64 Prefixes . . . . . . . . . . . . . . 5 - 7. Multihoming . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 7 - 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 11.1. Normative References . . . . . . . . . . . . . . . . . . 7 - 11.2. Informative References . . . . . . . . . . . . . . . . . 8 - 11.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 + 6. Handling Multiple NAT64 Prefixes . . . . . . . . . . . . . . 6 + 7. Multihoming . . . . . . . . . . . . . . . . . . . . . . . . . 7 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 + 9. Security Considerations . . . . . . . . . . . . . . . . . . . 8 + 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 + 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 + 11.1. Normative References . . . . . . . . . . . . . . . . . . 8 + 11.2. Informative References . . . . . . . . . . . . . . . . . 9 + 11.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 10 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction NAT64 [RFC6146] with DNS64 [RFC6147] is a widely-deployed mechanism to provide IPv4 access on IPv6-only networks. In various scenarios, 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]. 1.2. Terminology - Pref64: an IPv6 prefix used for IPv6 address synthesis [RFC6146]; - - PvD: Provisioning Domain, a set of network configuration information; - for more information, see [RFC7556]. + Pref64 (or NAT64 prefix): an IPv6 prefix used for IPv6 address + synthesis [RFC6146]; - PvD-aware host A host that supports the association of network - configuration information into PvDs and the use of these PvDs. Also - named PvD-aware node in [RFC7556]. + NAT64: Network Address and Protocol Translation from IPv6 Clients to + IPv4 Servers ([RFC6146]); RA: Router Advertisement, a message used by IPv6 routers to advertise their presence together with various link and Internet parameters ([RFC4861]); + DNS64: a mechanism for synthesizing AAAA records from A records + ([RFC6147]); + 2. Use cases for communicating the NAT64 prefix to hosts On networks employing NAT64, it is useful for hosts to know the NAT64 prefix for several reasons, including the following: o Local DNSSEC validation. As discussed in [RFC6147] section 2, the stub resolver in the host "will try to obtain (real) AAAA RRs, and in case they are not available, the DNS64 function will synthesize AAAA RRs for internal usage." This is required in order to use DNSSEC on a NAT64 network. @@ -137,86 +136,115 @@ Updatability: it is possible to change the NAT64 prefix at any time, because when it changes, it is possible to notify hosts by sending a new Router Advertisement. Deployability: all IPv6 hosts and networks are required to support [RFC4861]. Other options such as [RFC7225] require implementing other protocols. 4. Semantics - This option only supports a NAT64 prefix length of 96 bits, as this - is by the most common configuration used by hosts and supporting - variable prefix length would significantly increase the option size. - 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 can be - created to configure them. + To support prefix lengths defined in ([RFC6052]) this option contains + the prefix length field. However as /96 prefix is considered to be + the most common usecase, the prefix length field is optional and only + presents for non-/96 prefixes. It allows to keep the option length + to a minimum (16 bytes) for the most common case and increase it to + 20 bytes for non-/96 prefixes only (see Section 5 below for more + details). 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 (e.g. in case of graceful renumbering the network from one NAT64 prefix to another). Host behaviour with regards to synthesizing IPv6 addresses from IPv4 addresses SHOULD follow the recommendations given in Section 3 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. + In a network (or a provisioning domain) 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/provisioning domain 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. The multihoming and multiple provisioning domains + scenarios are discussed in Section 7. 5. Option format 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 + - | | + + + + | Highest 96 bits of the Prefix | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Lowest bits (96-127) of the prefix (optional, if Length > 2) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Prefix Length | Reserved | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: NAT64 Prefix Option Format Fields: - Type 8-bit identifier of the RDNSS option type as assigned by + Type 8-bit identifier of the Pref64 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. + the Type and Length fields) is in units of 8 octets. If the + prefix length is 96 bits the sender MUST set the Length to 2 + and include the 96 bits of the prefix in the option. If the + prefix length is not 96 bits then the sender MUST set the + length to 3 and include all 128 bits of the prefix in the + Prefix field and set the Prefix Length field to the prefix + length. The receiver MUST ignore the Pref64 option if the + length field value is 1. If the Length field value exceeds + 3, the receiver MUST utilize the first 21 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 96-bit NAT64 prefix. + + Highest 96-bit unsigned integer. Contains bits 0 - 95 of the NAT64 + 96 bits prefix. + of the + prefix + + Lowest 32-bit unsigned integer. Contains bits 96 - 127 of the NAT64 + bits of prefix. + the + prefix + + Prefix 8-bit unsigned integer. The sender MUST set it only to one + Length of the following values: 32, 40, 48, 56, 64 ([RFC6052]. The + receiver MUST ignore the Pref64 option if the prefix length + value is not set to one of those numbers. + + Reserved A 3-byte unused field. It MUST be initialized to zero by + the sender and MUST be ignored by the receiver. 6. Handling Multiple NAT64 Prefixes In some cases a host may receive multiple NAT64 prefixes from different sources. Possible scenarios include (but are not limited to): o the host is using multiple mechanisms to discover Pref64 prefixes (e.g. by using PCP ([RFC7225]) and/or by resolving IPv4-only fully qualified domain name ([RFC7050]) in addition to receiving the @@ -254,21 +282,23 @@ Like most IPv6 configuration information, the Pref64 option is specific to the network on which it is received. For example, a Pref64 option received on a particular wireless network may not be usable unless the traffic is also sourced on that network. Similarly, a host connected to a cellular network that povides NAT64 generally cannot use that NAT64 for destinations reached through a VPN tunnel that terminates outside that network. Thus, correct use of this option on a multihomed host generally - requires the host to be PVD-aware. + requires the host to support the concept of multiple Provisioning + Domains (PvD, a set of configuration information associated with a + network, [RFC7556]) and to be able to use these PvDs. This issue is not specific to the Pref64 RA option and, for example, is quite typical for DNS resolving on multihomed hosts (e.g. a host might resolve a destination name by using the corporate DNS server via the VPN tunnel but then send the traffic via its Internet-facing interface). 8. IANA Considerations The IANA is requested to assign a new IPv6 Neighbor Discovery Option @@ -296,44 +326,45 @@ 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]. 10. Acknowledgements Thanks to the following people (in alphabetical order) for their - review and feedback: Mikael Abrahamsson, Brian E Carpenter, Nick - Heatley, Tatuya Jinmei, David Schinazi. + review and feedback: Mikael Abrahamsson, Mark Andrews, Brian E + Carpenter, Nick Heatley, Martin Hunek, Tatuya Jinmei, Erik Kline, + Michael Richardson, David Schinazi. 11. References 11.1. 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, . 11.2. Informative References [I-D.ietf-intarea-provisioning-domains] Pfister, P., Vyncke, E., Pauly, T., Schinazi, D., and W. Shao, "Discovering Provisioning Domain Names and Data", - draft-ietf-intarea-provisioning-domains-04 (work in - progress), March 2019. + draft-ietf-intarea-provisioning-domains-05 (work in + progress), June 2019. [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, . @@ -390,25 +421,17 @@ Authors' Addresses Lorenzo Colitti Google Roppongi 6-10-1 Minato, Tokyo 106-6126 JP Email: lorenzo@google.com - 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