Internet Engineering Task Force S. Cheshire Internet-Draft M. Krochmal Intended status: Standards Track Apple Inc. Expires: June 15, 2011 Dec 12, 2010 Special-Use Domain Names draft-cheshire-dnsext-special-names-00 Abstract This document describes what it means to say that a DNS name is reserved for special use, when reserving such a name is appropriate, and the procedure for doing so. 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 June 15, 2011. 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 (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 Simplified BSD License. Cheshire & Krochmal Expires June 15, 2011 [Page 1] Internet-Draft Special-Use Domain Names Dec 2010 1. Introduction Certain individual IP addresses and IP address ranges are treated specially by network implementations, and consequently are not suitable for use as unicast addresses. For example, IPv4 addresses 224.0.0.0 to 239.255.255.255 are multicast addresses [RFC2606], with 224.0.0.1 being the "all hosts" multicast address [RFC1112] [RFC3171]. Another example is 127.0.0.1, the IPv4 "local host" address [RFC3330]. Analogous to Special-Use IPv4 Addresses [RFC3330], DNS has its own concept of reserved names, such as "example.com", "example.net", and "example.org", or any name falling under the top level pseudo-domain "invalid" [RFC2606]. However, "Reserved Top Level DNS Names" [RFC2606] does not state whether implementations are expected to treat such names differently, and if so, in what way. 2. Applicability When IP multicast was created [RFC1112], implementations had to be updated to understand what a multicast address means and what to do with it. Adding IP multicast to a networking stack entailed more than merely adding the right routing table entries for those addresses. Moreover, supporting IP multicast entails some level of commonality that is consistent across all conformant hosts, independent of what networks those hosts may be connected to. While it is possible to build a private isolated network using whatever valid unicast IP addresses and routing topology you choose (regardless of whether those unicast IP addresses are already in use by other hosts on the public Internet) the IPv4 multicast address 224.0.0.1 is always the "all hosts" multicast address and that's not a local decision. Similarly, if a domain name has special properties that affect the way hardware and software implementations handle the name, which apply universally regardless of what network the implementation may be connected to, then that may be a candidate for having the IETF declare the name to be a Special-Use Domain Name and specify what special treatment implementations should give to that name. If declaring a given name to be special would result in no change to any implementations, then that suggests that the name may not be special in any material way, and it may be more appropriate to use the existing DNS mechanisms [RFC1034] to provide the desired delegation, data, or lack-of-data for the name in question. Where the desired behaviour can be achieved via the existing domain name registration processes, that process should be used. Reservation of a Special-Use Domain Names is not a mechanism for circumventing normal domain name registration processes. Cheshire & Krochmal Expires June 15, 2011 [Page 2] Internet-Draft Special-Use Domain Names Dec 2010 3. Procedure If it is determined that special handling of a name is required in order to implement some desired new functionality, then an IETF "Standards Action" RFC [RFC5226] needs to be published describing the new functionality, and: o The RFC needs to state how implementations determine that the special handling is required for any given name. This is typically done by stating that any fully-qualified domain names ending in a certain suffix (i.e. falling within a specified parent pseudo- domain) will receive the special behaviour. In effect this carves off a sub-tree of the DNS namespace in which the modified name treatment rules apply, analogous to how IP multicast [RFC1112] or IP link-local addresses [RFC2462] [RFC3927] carve off chunks of the IP address space in which their respective modified address treatment rules apply. o The RFC needs to state, in each of the seven categories below, what special treatment, if any, is to be applied. If the answer in all seven categories is "none", then possibly no special treatment is required and requesting reservation of a Special-Use Domain Name may not be appropriate. 4. Domain Name Reservation Considerations An IETF "Standards Action" RFC specifying some new naming behaviour, which requires a Special-Use Domain Name be reserved to implement this desired new behaviour, needs to contain a "Domain Name Reservation Considerations" section giving answers in the following seven categories: 1. Users: Are human users expected to recognize these names as special and use them differently? In what way? 2. Application Software: Are writers of application software expected to make their software recognize these names as special and treat them differently? In what way? (e.g. if a human users enters such a name, should the application software reject it with an error message?) Cheshire & Krochmal Expires June 15, 2011 [Page 3] Internet-Draft Special-Use Domain Names Dec 2010 3. Name Resolution APIs and libraries: Are writers of name resolution APIs and libraries expected to make their software recognize these names as special and treat them differently? If so, how? 4. Caching DNS Servers: Are developers of caching DNS name servers expected to make their implementations recognize these names as special and treat them differently? If so, how? 5. Authoritative DNS Servers: Are developers of authoritative DNS name servers expected to make their implementations recognize these names as special and treat them differently? If so, how? 6. DNS Server Operators: Does this reserved Special-Use Domain Name have any potential impact on DNS server operators? If they try to configure their authoritative DNS server as authoritative for this reserved name will compliant name server software reject it as invalid? Do DNS server operators need to know about that and understand why? Even if the name server software doesn't prevent them from using this reserved name, are there other ways that it may not work as expected, which the DNS server operator should be aware of? 7. DNS Registrars: How should DNS Registrars treat requests to register this reserved domain name? Should such requests be denied? Should such requests be allowed, but only to a specially-designated entity? (For example, the name "www.example.org" is reserved for documentation examples and is not available for registration; however, the name is in fact registered; and there is even a web site at that name, which states circularly that the name is reserved for use in documentation and cannot be registered!) Cheshire & Krochmal Expires June 15, 2011 [Page 4] Internet-Draft Special-Use Domain Names Dec 2010 5. Security Considerations This document outlines the circumstances in which reserving a domain name for special-use is appropriate, and the procedure for having that Special-Use Domain Name recorded by IANA. Any document requesting such a Special-Use Domain Name needs to contain an appropriate "Security Considerations" section which describes any security issues relevant to that special use. 6. IANA Considerations IANA needs to create a new registry of Special-Use Domain Names. When IANA receives a request to record a new "Special-Use Domain Name" it should verify that the IETF "Standards Action" RFC [RFC5226] includes the required "Domain Name Reservation Considerations" section stating how the special meaning of this name affects the behaviour of hardware, software, and humans in the seven categories, and if so, record in the registry the Special-Use Domain Name and a reference to the RFC that documents it. 7. Informative References [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987. [RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5, RFC 1112, August 1989. [RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998. [RFC2606] Eastlake, D. and A. Panitz, "Reserved Top Level DNS Names", BCP 32, RFC 2606, June 1999. [RFC3171] Albanna, Z., Almeroth, K., Meyer, D., and M. Schipper, "IANA Guidelines for IPv4 Multicast Address Assignments", RFC 3171, August 2001. [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330, September 2002. [RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic Configuration of IPv4 Link-Local Addresses", RFC 3927, May 2005. Cheshire & Krochmal Expires June 15, 2011 [Page 5] Internet-Draft Special-Use Domain Names Dec 2010 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Authors' Addresses Stuart Cheshire Apple Inc. 1 Infinite Loop Cupertino, California 95014 USA Phone: +1 408 974 3207 Email: cheshire@apple.com Marc Krochmal Apple Inc. 1 Infinite Loop Cupertino, California 95014 USA Phone: +1 408 974 4368 Email: marc@apple.com Cheshire & Krochmal Expires June 15, 2011 [Page 6]