NEWS: Number Portability & ENUM

Even in 2017 the telephone number remains the most universal identifier for real-time communication. And as the word is moving to be All-IP, we have to be able to translate the number into something more meaningful for routing in IP networks. The GSMA organization selected for this purpose the Electronic Number Mapping System (ENUM) and in 2007 released the first version of PRD IR.67.

ENUM based Routing

Moreover Mobile Operators in over 50 countries have to support Mobile Number Portability (MNP). Although for MNP is a great feature for end subscribers, it makes the signalling more complex and costly for the Operators. The MNP is not just a problem for signalling (routing) but also for billing and management of interconnect agreements. Last but not least it can be a significant issue for content and application providers who may not be aware of the change of the operator for a particular user.


The best candidate for the MNP service implementation is again the ENUM. For both the services we ideally need a trusted world-wide database. The GSMA provides the Root DNS service for global roaming and it’s ideally placed to provide the same service for ENUM.

So in 2008 the GSMA came with a pilot called GSMA PathFinder. Since 2009 it is commercially available. To this date the GSMA PathFinder covers 240 countries and territories and thus powers access to 95 % of world’s phone numbers. The service itself is managed by Neustar.

GSMA PathFinder

From the technical point of view the the Query service uses ENUM as an open, standards-based, lightweight mechanism to resolve E.164 telephone numbers to the true Service Provider Network. MNP Discovery allows its users to customize the information returned in the query response, including:

  • PSTN or Tel URI (user@domain format)
  • E.212 MCC/MNC
  • Service Provider Network (SPN)
  • Alternate SPN
  • Number Portability Dip Indicator

This year in March the GSMA released a first version of NG.105 ENUM Guidelines for Service Providers and IPX Providers. The document provides recommendations for configuration of ENUM servers, GSMA processes and procedures relating to formats, usage of domain names and sub-domain names, and guidelines and recommendations on GSMA Carrier ENUM.

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