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Contirbution by Douglas Ranalli

Is “” The Only Answer For
Tier-1 ENUM Registry Services?


By Douglas Ranalli, Founder


Author’s Bias: As the Founder and Chief Strategy Officer of, a provider of commercial ENUM services under the “” domain, I believe in the value of competition in ENUM services at both the Tier-1 (Registry) and Tier-2 (NAPTR services) levels.   Given this underlying belief, I support the efforts of the International Telecommunication Union (ITU) in defining a public ENUM Registry under the “” domain as a viable competitive option for the delivery of global ENUM services.   Furthermore, NetNumber plans to participate actively in winning contracts at the ITU Member State level to provide Registry services under the public ENUM structure.  However, while I support “” as one viable competitive option, I do not believe that the industry is best served by viewing a public ENUM implementation as the exclusive Tier-1 Registry option. 


This paper addresses three key questions relating to the deployment of global ENUM services: 


(1)     Is the IP-communications industry best served by utilizing “” as the exclusive ENUM Registry implementation?


(2)     What is the competitive alternative?


(3)     Can the competitive model meet the unique operational demands of the emerging IP-Communications industry?


Is the emerging IP-Communications industry best served by utilizing “” as the exclusive Tier-1 ENUM Registry implementation?

The “” public ENUM registry implementation is based on asking 200+ ITU Member States to each define a structure for operating ENUM Registry services for the subset of E.164 numbers that fall under their control at the country code level.  For example, France will define a structure for the registration of E.164 numbers under country code 33, Germany under country code 49, and so on.  A perceived strength of the “” model is that it derives authority from the existing PSTN regulatory model.  By comparison, a potential weakness of the model is the widely distributed nature of the solution.   For example:


Time to market: will be slow to develop.  It is simply time consuming and difficult to coordinate the selection of Tier-1 ENUM service providers across 200+ ITU Member States.


Pricing: Pricing policies, billing policies, payment terms, etc. are likely to vary from Member State to Member State.  Complexity never comes for free.  In an environment without a competitive alternative, will “” achieve a pricing model that reflects the needs of the emerging industry? 


Creativity: Restricting ENUM to one public Tier-1 implementation imposes an artificial limit on the creative process.  In a competitive market the focus of Tier-1 service providers will be to “develop services that drive the utilization of ENUM services”.  In an exclusive public implementation a major driving force becomes: “win contracts for providing services under".  Given the fact that the market has little practical experience with ENUM to date, are we prepared to artificially limit investment and creativity at this early stage in the process?    


Policy consistency: The 200+ Tier-1 service providers under “” may never achieve consistent policies regarding registration procedures, conflict resolution, disclosure of registrant information, etc.  Given the potential for policy inconsistency, what impact will this have on early adopters of ENUM services?  How will a multi-national corporation with 10,000 employees located in 47 offices across 22 countries register for global ENUM services under the exclusive model?  Will it be practical to register for global ENUM services under the “” model in the near term or even medium term?  How long are we willing to wait?


Given the concerns raised above, are we absolutely certain that limiting ENUM Registry services to a single public implementation under “” is in the best interests of the emerging IP-Communications industry? 



What is the competition based alternative model?


Introducing competition to Tier-1 ENUM services has the potential to address many of the risks associated with an exclusive public ENUM model as described above.  Outlined below is one view of how a competitive ENUM Registry model might develop: 

Private/Enterprise ENUM Services:  Example: “”:  Large enterprise customers may find value in deploying private ENUM services to provide closed user group functionality, in addition to participating in a public ENUM service.  As such, the communications systems deployed within these closed user group environments will be required to query more than one Tier-1 ENUM service.  Example:  "” for private user group information and “” or "" for external/shared information.

Commercial ENUM Services: Example: “”:  NetNumber has deployed a commercial ENUM service under "" and we are currently working with a large number of IP-communications vendors to incorporate NetNumber’s ENUM services into their applications.  As part of ENUM integration process, NetNumber provides an ENUM resolver that can be configured to simultaneously query several customer defined ENUM services and return prioritized results. 

Public ENUM Service:  “”:  The efforts to advance a public ENUM implementation under “” are well documented and require no further explanation. 

Can the competitive model meet the unique operational demands of the IP-Communications industry?

Outlined below is an analysis of several issues that have been raised by industry participants over the past few months regarding the introduction of competition in Tier-1 Registry services:

Too many competitive ENUM services will make queries ineffective: The concern has been raised that a competitive market place will produce hundreds or even thousands of ENUM services that might all need to be queried by a communications application to obtain complete information.  I see three reasons why a more likely outcome will be a limited number of Tier-1 ENUM providers:


I.                     Market evidence:  To date, there is no evidence of the market deployment of hundreds or thousands of ENUM services.  There is however evidence of an effort to create one public implementation and a limited number of commercial implementations. 


II.                   Underlying Economics Of Directory Services:  The natural economies of scale in providing DNS Registry services tend to favor a limited number of Registry providers, not a widely distributed market.


III.                  Underlying Customer Behavior:  Customer's aren't likely to be interested in configuring their communications platforms to query a large number of Tier-1 ENUM services.  This natural desire for simplicity will stimulate the market to achieve balance with a limited number of competitive providers.


Query Delay From Searching Multiple ENUM Services: The issue has been raised that too much delay might be introduced by sequentially querying multiple ENUM services to obtain accurate addressing information.  Under a model of a limited number of viable ENUM services, I propose that a more likely outcome is that ENUM resolvers will be designed to simultaneously query a set of ENUM services defined by the customer.  NetNumber's publicly available ENUM resolver has already been deployed with this flexibility. 

Cost and Complexity With Users Registering In Multiple ENUM services: The issue has been raised that a competitive market might cause E.164 Subscribers to feel compelled to register their E164 names in multiple ENUM services.  Or similarly, we might end up with confusion over conflicting registrations in different services.  Both of these concerns would be true if a Subscriber felt a need to “protect their numbers” against unauthorized registrations in alternate ENUM Registries.  NetNumber has always approached the industry with the vision that registration validation is a requirement for an ENUM service provider.  In a world where Subscriber rights are protected, no incentive exists to register with more than one ENUM service.  Subscribers and Service Providers will select the ENUM service that best meets their needs and register accordingly.  The assumption I'm making is that a validation structure can be defined for or by the ENUM industry to protect the rights of Subscribers.  Clarification of the role that government regulatory agencies might be willing to play in defining acceptable ENUM validation mechanisms represents a topic for further discussion.   


While I support “” as one viable competitive option for the delivery of global ENUM Registry services, I do not believe that the Internet-Telephony industry is best served by viewing a single public ENUM implementation as the exclusive Registry option.  Given agreement on an ENUM registration validation structure, competition can play an important role in advancing the use of the newly defined ENUM standard. 





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Updated : 2011-04-04