Network Working Group M. Mealling
Request for Comments: 3401 VeriSign
Updates: 2276 October 2002
Obsoletes: 2915, 2168
Category: Informational
 Dynamic Delegation Discovery System (DDDS)
 Part One: The Comprehensive DDDS
Status of this Memo
 This memo provides information for the Internet community. It does
 not specify an Internet standard of any kind. Distribution of this
 memo is unlimited.
Copyright Notice
 Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
 This document specifies the exact documents that make up the complete
 Dynamic Delegation Discovery System (DDDS). DDDS is an abstract
 algorithm for applying dynamically retrieved string transformation
 rules to an application-unique string.
 This document along with RFC 3402, RFC 3403 and RFC 3404 obsolete RFC
 2168 and RFC 2915, as well as updates RFC 2276.
1. Intended Audience
 This document and the documents that it references are intended for
 anyone attempting to implement or understand the generic DDDS
 algorithm, URI Resolution, ENUM telephone number to URI resolution,
 and the NAPTR DNS resource record. The reader is warned that reading
 one of the documents in this series without reading the others will
 probably lead to misunderstandings and interoperability problems.
2. Introduction
 The Dynamic Delegation Discovery System is used to implement lazy
 binding of strings to data, in order to support dynamically
 configured delegation systems. The DDDS functions by mapping some
 unique string to data stored within a DDDS Database by iteratively
 applying string transformation rules until a terminal condition is
 reached. This document defines the entire DDDS by listing the
 documents that make up the complete specification at this time.
 This document along with RFC 3402, RFC 3403 and RFC 3404 obsoletes
 RFC 2168 [8] and RFC 2915 [6], as well as updates RFC 2276 [5]. This
 document will be updated and or obsoleted when changes are made to
 the DDDS specifications. Thus the reader is strongly encouraged to
 check the IETF RFC repository for any documents that obsoletes or
 updates this one.
3. The Algorithm
 The DDDS algorithm is defined by RFC 3402 [1]. That document defines
 the following DDDS concepts:
 o The basic DDDS vocabulary.
 o The algorithm.
 o The requirements on applications using the algorithm.
 o The requirements on databases that store DDDS rules.
 RFC 3402 is the actual DDDS Algorithm specification. But the
 specification by itself is useless without some additional document
 that defines how and why the algorithm is used. These documents are
 called Applications and do not actually make up part of the DDDS core
 specification. Applications require databases in which to store
 their Rules. These databases are called DDDS Databases and are
 usually specified in separate documents. But again, these Database
 specifications are not included in the DDDS core specification
 itself.
4. DDDS Applications
 No implementation can begin without an Application specification, as
 this is what provides the concrete instantiation details for the DDDS
 Algorithm. Without them the DDDS is nothing more than a general
 algorithm. Application documents define the following:
 o the Application Unique String (the thing the delegation rules act
 on).
 o the First Well Known Rule (the Rule that says where the process
 starts).
 o the list of valid Databases (you can't just use any Database).
 o the final expected output.
 Some sample Applications are documented in:
 o "E.164 number and DNS" (RFC 2916) [7]. This Application uses the
 DDDS to map a telephone number to service endpoints such as SIP or
 email.
 o "Dynamic Delegation Discovery System (DDDS) Part Four: The Uniform
 Resource Identifiers (URI) Resolution Application" (RFC 3404) [3].
 This Application uses the DDDS to resolve any URI to a set of
 endpoints or 'resolvers' that can give additional information
 about the URI independent of its particular URI scheme.
5. Currently Standardized Databases
 Any DDDS Application must use some type of DDDS Database. Database
 documents define the following:
 o the general spec for how the Database works.
 o formats for Keys.
 o formats for Rules.
 o Key lookup process.
 o rule insertion procedures.
 o collision avoidance measures.
 A Database cannot be used on its own; there must be at least one
 Application that uses it. Multiple Databases and Applications are
 defined, and some Databases will support multiple Applications.
 However, not every Application uses each Database, and vice versa.
 Thus, compliance is defined by the combination of a Database and
 Application specification.
 One sample Database specification is documented in:
 o "Dynamic Delegation Discovery System (DDDS) Part Three: The Domain
 Name System (DNS) Database" (RFC 3402) [1]. (This document is the
 official specification for the NAPTR DNS Resource Record.)
6. Security Considerations
 Any known security issues that arise from the use of algorithms and
 databases must be specified in the respective specifications. They
 must be completely and fully described. It is not required that the
 database and algorithms be secure or that it be free from risks, but
 that the known risks be identified. Publication of a new database
 type or algorithm does require a security review, and the security
 considerations section should be subject to continuing evaluation.
 Additional security considerations should be addressed by publishing
 revised versions of the database and algorithm specifications.
7. IANA Considerations
 While this document itself does not create any new requirements for
 the IANA, the documents in this series create many varied
 requirements. The IANA Considerations sections in those documents
 should be reviewed by the IANA to determine the complete set of new
 registries and requirements. Any new algorithms, databases or
 applications should take great care in what they require the IANA to
 do in the future.
References
 [1] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
 Two: The Algorithm", RFC 3402, October 2002.
 [2] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
 Three: The Doman Name System (DNS) Database", RFC 3403, October
 2002.
 [3] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
 Four: The Uniform Resource Identifiers (URI) Resolution
 Application", RFC 3404, October 2002.
 [4] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
 Five: URI.ARPA Assignment Procedures", RFC 3405, October 2002.
 [5] Sollins, K., "Architectural Principles of Uniform Resource Name
 Resolution", RFC 2276, January 1998.
 [6] Mealling, M. and R. Daniel, "The Naming Authority Pointer (NAPTR)
 DNS Resource Record", RFC 2915, August 2000.
 [7] Faltstrom, P., "E.164 number and DNS", RFC 2916, September 2000.
 [8] Daniel, R. and M. Mealling, "Resolution of Uniform Resource
 Identifiers using the Domain Name System", RFC 2168, June 1997.
Author's Address
 Michael Mealling
 VeriSign
 21345 Ridgetop Circle
 Sterling, VA 20166
 US
 EMail: michael@neonym.net
 URI: http://www.verisignlabs.com
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