Network Working Group D. Crocker Internet-Draft Brandenburg InternetWorking Expires: December 27, 2006 June 25, 2006 DNS Scoped Data Through Attribute Leaves draft-crocker-dns-attrleaf-01 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 27, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract Historically, any DNS RR may occur for any domain name. Recent additions have defined DNS leaf nodes that contain a reserved node name, beginning with an underscore. The underscore construct is used to define a semantic scope for the name, within which the choice of valid RRs is limited to a defined set. Hence the underscore construct defines a basic paradigm modification to the DNS. This note explores the nature of this DNS usage and defines the procedures for registering new "underscore names" with IANA. Crocker Expires December 27, 2006 [Page 1] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 5. References -- Informative . . . . . . . . . . . . . . . . . . . 4 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 7 Crocker Expires December 27, 2006 [Page 2] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 1. Introduction Historically, any DNS RR may occur for any domain name. The DNS technical specification assigns no semantics to domain names and no constraints upon which resource records may be associated with a particular name. Over time, some leaf node names, such as "www" and "ftp" have come to imply support for particular services, but this is a matter of operational convention, rather than defined semantics. 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 data semantics have been limited to specifications for specific resource records, on the expectation that new ones would be added as needed. Although there remains an expectation that this method of enhancement is preferred, alternative approaches have been explored. Recent additions have defined DNS leaves that contain a reserved leaf node name, beginning with an underscore. The underscore construct is used to define a semantic scope for the name, within which the choice of valid RRs is limited to a defined set. Hence the underscore construct defines a basic paradigm modification to the DNS. Within the scope of a defined underscore leaf, the specific uses of specific resource records can be formally defined and constrained. An established example is the SRV record,[RFC2782] which generalizes concepts long-used for email routing in the MX record.[RFC0974][RFC2821] The use of special DNS names has significant benefits and detriments. Some of these are explored in [I-D.iab-dns-choices]. One use that has perhaps not been noticed is that the underscore construct substantially changes possible concerns for scaling effects. For example, different uses for the same RR, such as the free-form TXT record, become manageable when those are defined to be within different, scoped leaf nodes. This note disusses this enhancement, provides an explicit definition of it, and establishes an IANA registry for the reserved names beginning with underscore. 2. Procedure NOTE: This procedure is modeled after that specified in [RFC2489] The author of a new DHCP option will follow these steps to obtain approval for the option and publication of the specification of the option as an RFC: Crocker Expires December 27, 2006 [Page 3] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 1. The author devises the new option. 2. The author documents the new option as an Internet Draft, choosing a node name that has not yet been registered. 3. The author submits the Internet Draft for publication as an RFC, either as an independent submission or as an IETF-approved document. 4. The specification of the new option is reviewed for publication by the appropriate bodies. 5. At the time of publication as an RFC, IANA formally lists the node name. 3. Security Considerations This memo raises no security issues 4. IANA Considerations IANA is requested to establish the DNS Underscore Name Registry, for DNS node names that begin with the underscore character and have been specified in any published RFC. Initial entries in the registry comprise: NAME RFC ============== ======== _ rfc2782 _ rfc2782 NOTE: In the case of RFC2782, the set of names is defined in terms of other IANA tables, namely any table with symbolic names. Even more problematic is that the set of names is not explicitly defined, except in vague terms. This makes it essentially impossible to guarantee that a new underscore name is unambiguous! 5. References -- Informative [I-D.iab-dns-choices] Faltstrom, P., "Design Choices When Expanding DNS", draft-iab-dns-choices-03 (work in progress), April 2006. Crocker Expires December 27, 2006 [Page 4] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 [RFC0974] Partridge, C., "Mail routing and the domain system", RFC 974, January 1986. [RFC2489] Droms, R., "Procedure for Defining New DHCP Options", BCP 29, RFC 2489, January 1999. [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782, February 2000. [RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, April 2001. Appendix A. Acknowledgements Thanks go to Tony Hansen for diligent review. Crocker Expires December 27, 2006 [Page 5] Internet-Draft DNS Scoped Data Through Attribute Leaves June 2006 Author's Address Dave Crocker Brandenburg InternetWorking 675 Spruce Dr. Sunnyvale, CA 94086 USA Phone: +1.408.246.8253 Email: dcrocker@bbiw.net URI: http://bbiw.net/ Crocker Expires December 27, 2006 [Page 6] 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. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. 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 27, 2006 [Page 7]