Network Working Group D. Crocker Internet-Draft Brandenburg InternetWorking Expires: December 21, 2006 June 19, 2006 DNS Scoped Data Through Attribute Leaves draft-crocker-dns-attrleaf-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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 December 21, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract Historically, any DNS RR may occur for any name. Recent additions have defined DNS leaf nodes that contain a reserved node name, beginning with an underscore. With the underscore construct, the choice of valid RRs is limited to a defined set. The underscore construct is a basic paradigm modification to the DNS, because it defines a scope-constrained attribute space for the containing domain name. This note defines the nature of this DNS usage and defines the procedures for registering new "underscore names" with IANA. Crocker Expires December 21, 2006 [Page 1] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 4. Informative . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Appendix A. IANA Registration Procedures . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 Intellectual Property and Copyright Statements . . . . . . . . . . 8 Crocker Expires December 21, 2006 [Page 2] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 1. Introduction Historically, any DNS RR may occur for any name. Recent additions have defined DNS leaf nodes that contain a reserved node name, beginning with an underscore. With the underscore construct, the choice of valid RRs is limited to a defined set. The underscore construct is a basic paradigm modification to the DNS, because it defines a scope-constrained attribute space for the containing domain name. The DNS technical specification defines no semantics to domain names and no constraints upon which resource records may be associated with a particular name. This freedom in the basic technology has permitted a wide range of administrative and semantic policies to be used -- in parallel -- with the DNS. In the DNS specifications, data semantics have been limited to the specifications for precise resource records, on the expectation that new ones would be added as needed. Although there remains an expectation that this method of enhancement is to be preferred, alternative approaches have been explored. One uses a special class of DNS node name uses a leading underscore character to define special contexts for specific resource records. An established example is the SRV record, which generalizes concepts long-used for email routing, with the MX record.[3][2] The use of special DNS names has significant benefits and detriments. Some of these are explored in [1]. One that has perhaps not been noticed is that the use of the underscore construct substantially changes possible concerns for scaling effects, when there are different uses for the same RR, notably the free-form TXT record. Within the scope of a defined underscore leaf, the specific uses of specific resource records is formally constrained. The purpose of this note is to attempt to provide an explicit definition of this type of DNS naming, and to establish an IANA registry for the reserved names beginning with underscore. NOTE: Apologies for the incomplete state of this note. It will be revised, shortly, to provide more detail. Given the DNS-related activities in the DKIM working group, I thought it worth marking the established nature and the significant meaning of the underscore construct. Crocker Expires December 21, 2006 [Page 3] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 2. Security Considerations This memo raises no security issues Crocker Expires December 21, 2006 [Page 4] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 3. IANA Considerations Domain node names that begin with an underscore MUST be registered with IANA. The procedures will be specified in a later version of this note. 4. Informative [1] "IAB Discussion about alternative methods of adding information to the DNS". [2] "Definition of MX record". [3] "Definition of SRV record". Crocker Expires December 21, 2006 [Page 5] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 Appendix A. IANA Registration Procedures TBD Crocker Expires December 21, 2006 [Page 6] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 Author's Address Dave Crocker Brandenburg InternetWorking 675 Spruce Dr. Sunnyvale, CA 94086 US Phone: +1.408.246.8253 Email: dcrocker@bbiw.net URI: http://bbiw.net/ Crocker Expires December 21, 2006 [Page 7] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Crocker Expires December 21, 2006 [Page 8]