Discussion Papers

Dieter Elixmann, Annette Hillebrand, Ralf G. Schäfer, Martin O. Wengler

Zusammenwachsen von Telefonie und Internet – Marktentwicklungen und Herausforderungen der Implementierung von ENUM
Nr. 253 / Mai 2004


ENUM is mainly defined by a technical specification of the Internet Engineering Task Force (IETF) (RFC 2916). It represents a procedure to map uniquely an E.164-(telephone) number onto an Internet domain. Thus, communication is enabled between PSTN- and IP-phones or other services like voice-mail, e-mail, websites and unified messaging services, which use Uniform Resource Identifiers (URI). ENUM is based on the Domain Name Systems (DNS), which rests on a system of hierachically structured servers. DNS itself forms a logical link and transformation, respectively, between domains and the associated IP-adresses of the internet devices.

Until now, the implementation of ENUM takes place only as field trials. Usually these trials are initiated and performed on a national level. Sometimes, however, single companies arrange ENUM field trials.

The objective of the present study is to illuminate the complex challenges of implementing an ENUM-solution, to condense the experiences of the field trials and to derive implications regarding a final implementation of ENUM. The study focuses on the national field trials in Austria, Germany, France, Sweden, the U.K., and the USA. Moreover, the available information on field trials in Taiwan and South Korea has been evaluated and assessed.

The field trials are addressing several issues relevant for the implementation of ENUM. First and foremost the objectives of the field trials comprise the following aspects: (1) assessing the interest of telcos and ISP’s in ENUM and gaining experience in running ENUM under test conditions, (2) assessing pros and cons of different ENUM implementations, particularly with respect to the role of registries and registrars, (3) evaluating processes, interfaces and protocols governing the relationships between the involved parties, (4) testing ENUM and associated applications from a technical and user oriented perspective, (5) assessing the economics of ENUM, especially identifying profit and operational costs, (6) evaluating possible business models, (7) handling user data in the ENUM processes against the backdrop of security standards, (8) discussing issues involved with ENUM which are relevant for competition policy and regulation.

Our analysis shows that in particular the following four topics are vital for a successful implementation of ENUM: Securing integrity of the E.164-numbering scheme (validation procedures), data security issues (subscriber data, NAPTR-resource records, DoS attacs), privacy issues (use of the whois-data bank and of NAPTR-resource records) and competitively neutral institutional arrangements between the players.[Only German language version available.]

Diskussion Paper is available for download.

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