DDDS overview: Dynamic Delegation Discovery System (DDDS) Part One: The Comprehensive DDDS
The document map for the Dynamic Delegation Discovery System.
Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part One: The Comprehensive DDDS", RFC 3401, DOI 10.17487/RFC3401, October 2002, <https://www.rfc-editor.org/info/rfc3401>.
@misc{rfc3401,
series = {Request for Comments},
number = 3401,
howpublished = {RFC 3401},
publisher = {RFC Editor},
doi = {10.17487/RFC3401},
url = {https://www.rfc-editor.org/info/rfc3401},
author = {M. Mealling},
title = {{Dynamic Delegation Discovery System (DDDS) Part One: The Comprehensive DDDS}},
pagetotal = 6,
year = 2002,
month = oct,
} RFC text
Contents
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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ISO Plain Language
On this page
§2What DDDS Does
DDDS maps an application-specific unique string to data in a DDDS Database. It repeatedly applies string transformation rules until it reaches a terminal condition. RFC 3401 is an overview that lists the documents making up the complete specification.
The RFC is intended for people implementing or studying the generic algorithm, URI resolution, ENUM telephone-number resolution, or the NAPTR DNS resource record. It warns that reading only one document in the series can cause misunderstandings and interoperability problems.
DDDS starts with a unique string, looks up a rule, and applies the rule to find the next value. RFC 3401 identifies the documents needed to understand that process.
§3The Algorithm and the Core Documents
RFC 3402 defines the generic algorithm, its vocabulary, and requirements for applications and databases. The algorithm by itself does not say what task to perform or where to store its rules.
Application documents provide the task-specific details. DDDS Database documents define how a database works, including key and rule formats, lookup, rule insertion, and collision avoidance. Applications and database specifications are outside the DDDS core specification, but an implementation needs both.
The algorithm gives general steps. An application says what those steps should accomplish, and a database specification explains where and how the rules are stored.
- ApplicationDefines the unique string, starting rule, valid databases, and final output.
- DDDS algorithmDefines the vocabulary, algorithm, and requirements. RFC 3402.
- DatabaseDefines how keys and rules are stored, found, and added.
§4What an Application Defines
An Application specification gives the concrete details needed to use DDDS. It defines the Application Unique String, the First Well Known Rule that starts the process, the valid databases, and the expected final output.
The RFC names two application examples. RFC 2916 maps E.164 telephone numbers to service endpoints such as SIP or email. RFC 3404 describes an application for resolving URIs to endpoints or resolvers that can provide further information.
An application specifies the starting string, the first rule, which databases can be used, and what final result is expected. The RFC gives telephone-number and URI resolution as examples.
§5DDDS Databases
Every DDDS Application must use a DDDS Database. A database specification defines its operation, the formats of its keys and rules, how a key is looked up, how rules are inserted, and how collisions are avoided.
A database cannot be used on its own; at least one application must use it. A database may support multiple applications, and an application may use only selected databases. Compliance therefore depends on the combination of an application specification and a database specification. RFC 3403 specifies the DNS database and the NAPTR DNS resource record.
A DDDS database stores rules for an application. To know whether a system follows DDDS, consider both the application and database specifications it uses.
§6Security and IANA Considerations
Known security issues related to an algorithm or database must be described in its specification. New database types and algorithms require security review, and their security considerations should continue to be evaluated.
RFC 3401 creates no new IANA requirements. Other documents in the series do have IANA considerations, so the RFC asks the IANA to review those documents for the complete set of registries and requirements.
Specifications for new algorithms and databases must describe known security risks and receive security review. RFC 3401 itself adds no IANA requirements.