Network Working Group S. Cheshire Internet-Draft D. Schinazi Updates: 7050 (if approved) Apple Inc. Intended status: Standards Track May 19, 2016 Expires: November 20, 2016 Special Use Domain Name 'ipv4only.arpa' draft-cheshire-sudn-ipv4only-dot-arpa-01 Abstract The document "Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis" [RFC7050] specifies the Special Use Domain Name 'ipv4only.arpa', with certain precise special properties, but, perversely, the Domain Name Reservation Considerations section [RFC6761] in that document then goes on to deny the specialness of that name, and (as of May 2016) the name 'ipv4only.arpa' does not appear in the Special-Use Domain Names registry. This document updates RFC 7050 with a more appropriate summary of the legitimate and useful special properties of the name ipv4only.arpa. 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 http://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 November 20, 2016. Copyright Notice Copyright (c) 2016 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 (http://trustee.ietf.org/license-info) in effect on the date of Cheshire & Schinazi Expires November 20, 2016 [Page 1] Internet-Draft Dot Home May 2016 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. 1. Introduction The document "Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis" [RFC7050] specifies the Special Use Domain Name 'ipv4only.arpa', with certain precise special properties, but, perversely, the Domain Name Reservation Considerations section [RFC6761] in that document denies the specialness of that name, and (as of May 2016) the name 'ipv4only.arpa' does not appear in the Special-Use Domain Names registry [SUDN]. As a result of the name 'ipv4only.arpa' being formally declared to have no special properties, there was no mandate for software to treat this name specially. Consequently, queries for this name have to be handled normally, and result in a large volume of unnecessary queries to the 'arpa' name servers. At times, for reasons that are as yet unclear, the 'arpa' name servers have been observed to be slow or unresponsive. The failures of these 'ipv4only.arpa' queries result in failures of software that depends on them for NAT64 address synthesis. Having millions of devices around the world issue these queries generates pointless additional load on the 'arpa' name servers, which is completely unnecessary when this name is defined, by Internet Standard, to have only two address records, 192.0.0.170 and 192.0.0.171, and no other records. To remedy this situation, this document updates RFC 7050 with a more appropriate Domain Name Reservation Considerations section [RFC6761] that properly lists the desirable and beneficial special handling for ipv4only.arpa. 2. Conventions and Terminology Used in this Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in "Key words for use in RFCs to Indicate Requirement Levels" [RFC2119]. Cheshire & Schinazi Expires November 20, 2016 [Page 2] Internet-Draft Dot Home May 2016 3. Security Considerations Hard-coding the answers for ipv4only.arpa queries avoids the risk of malicious devices intercepting those queries and returning incorrect answers. DNSSEC signing issues for the ipv4only.arpa address records don't apply, since the only use of the ipv4only.arpa name is to trigger synthesis of NAT64 AAAA records, which aren't signed by arpa anyway. 4. IANA Considerations [Once published, this should say] IANA has recorded the name 'ipv4only.arpa' in the Special-Use Domain Names registry [SUDN]. 4.1. Domain Name Reservation Considerations The name 'ipv4only.arpa' is special only to (a) client software wishing to perform NAT64 address synthesis, and (b) the DNS64 server responding to such requests. These two considerations are listed in items 2 and 4 below: 1. Normal users should never have reason to encounter the ipv4only.arpa domain name. If they do, queries for ipv4only.arpa should result in the answers specified in RFC 7050. Normal users have no need to know that ipv4only.arpa is special. 2. Application software may explicitly use the name ipv4only.arpa for NAT64 address synthesis, and expect to get the answers specified in RFC 7050. If application software encounters the name ipv4only.arpa in the normal course of handling user input, the application software should resolve that name as usual and need not treat it in any special way. 3. Name resolution APIs and libraries SHOULD NOT recognize ipv4only.arpa as special and SHOULD NOT treat it differently. Name resolution APIs SHOULD send queries for this name to their configured recursive/caching DNS server(s). Cheshire & Schinazi Expires November 20, 2016 [Page 3] Internet-Draft Dot Home May 2016 4. Recursive/caching DNS servers SHOULD recognize ipv4only.arpa as special and SHOULD NOT, by default, attempt to look up NS records for it, or otherwise query authoritative DNS servers in an attempt to resolve this name. Instead, recursive/caching DNS servers SHOULD, by default, act as authoritative and generate immediate responses for all such queries. Traditional recursive/caching DNS servers that act as authoritative for this name MUST generate only the 192.0.0.170 and 192.0.0.171 responses for these queries, and no others. All DNS64 recursive/caching DNS servers MUST generate the 192.0.0.170 and 192.0.0.171 address record responses for these queries, and MUST generate the appropriate synthesized IPv6 address record responses for all AAAA queries. This local self-contained generation of these responses is to avoid placing unnecessary load on the 'arpa' name servers. 5. Traditional authoritative DNS server software need not recognize ipv4only.arpa as special or handle it in any special way. As a practical matter, only the administrators of the 'arpa' namespace will configure their name servers to be authoritative for this name and to generate the appropriate answers; all other authoritative name servers will not be configured to know anything about this name and will reject queries for it as they would reject queries for any other name about which they have no information. 6. Generally speaking, operators of authoritative DNS servers need not know anything about the name ipv4only.arpa, just as they don't need to know anything about any other names they are not responsible for. Operators of authoritative DNS servers who are configuring their name servers to be authoritative for this name MUST understand that ipv4only.arpa is a special name, with answers specified by Internet Standard (generally this applies only to the administrators of the 'arpa' namespace). 7. DNS Registries/Registrars need not know anything about the name ipv4only.arpa, just as they don't need to know anything about any other name they are not responsible for. Only the administrators of the 'arpa' namespace need to be aware of this name's purpose and how it should be configured. Cheshire & Schinazi Expires November 20, 2016 [Page 4] Internet-Draft Dot Home May 2016 5. References 5.1. 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, . [RFC6761] Cheshire, S. and M. Krochmal, "Special-Use Domain Names", RFC 6761, DOI 10.17487/RFC6761, February 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, . 5.2. Informative References [SUDN] "Special-Use Domain Names Registry", . Authors' Addresses Stuart Cheshire Apple Inc. 1 Infinite Loop Cupertino, California 95014 USA Phone: +1 408 974 3207 Email: cheshire@apple.com David Schinazi Apple Inc. 1 Infinite Loop Cupertino, California 95014 USA Phone: +1 669 227 9921 Email: dschinazi@apple.com Cheshire & Schinazi Expires November 20, 2016 [Page 5]