The VoIP Peering Puzzle�Part 11: VeriSign ENUM Data Access Service

If you have sent an e-mail to a user with a .com or .net domain suffix recently, you have been interacting with address processing technology from VeriSign, Inc. The Mountain View, California-based company has a daily workload that is on the verge of mind-boggling: authoritative routing support for every web address ending with .com or .net, as many as 18 billion Domain Name System (DNS) queries every day; daily delivery of 100 million mobile-originated intercarrier SMS messages—plus over 600,000 multimedia messages; delivery of over 4.5 million ringtones, pictures, videos, and games to mobile telephone customers every day; monitoring 300 million retail transactions; and delivering over 150 million headline links. This adds up to quite a portfolio of accomplishments for a firm that was only founded in 1995, but has since grown to include 4,000 employees and, in 2005, boasted revenues of $1.66 billon.

VeriSign developed the Advanced Transaction Look-Up and Signaling, or ATLAS, platform to support the Internet’s DNS, as well as the convergence of voice and data networks. ATLAS is a real-time, distributed directory system that can support a number of business and technical applications, based upon a variety of protocols and database applications. This software platform, which has been operational for several years, processes over 15 billion interactions daily, has the capacity for 200 billion queries, and is slated to go beyond these capacities in the future. The ATLAS platform forms the basis for a number of VeriSign services, including the global resolution of the .com and .net, the Online Certificate Status Protocol (OCSP)—a part of their public key infrastructure (def.)—and telecom applications such as ENUM, local number portability (LNP), and VoIP directory services.

VeriSign’s ENUM Data Access Service is based upon the ATLAS architecture, and provides telephone number registration information, thus enabling communication between users in different communities. This registration information can then be used to route voice calls, text, or multimedia messages to other telecommunications service providers, and, optionally, map a telephone number to the uniform resource identifier (URI) associated with a service provider. The registration information is determined by associating the address either with a globally unique service-provider identifier (SPID), or with a pseudo-service-provider identifier (or pseudo-SPID). A pseudo-SPID identifies a service provider that has registered a telephone number that does not possess a globally unique SPID, and applies within the context of an ENUM service.

VeriSign’s ENUM Data Access Service architecture consists of two elements: an ENUM Client, and an ENUM Server. Examples of ENUM Clients would be carriers, content providers, and related services that need access to the ENUM Server information, with the ENUM Client typically colocated with the voice, messaging or content application. The ENUM Server maintains and regulates access to the E.164 telephone address information and the SPIDs associated with those telephone numbers. Additionally, it may also host the functions for mapping the E.164 address or SPID/Pseudo-SPID to a URI.

Two types of data are stored in the ENUM Server: public data and private data. Public ENUM data is global in scope and may be viewed by all ENUM clients. This information arrives at the server from industry sources, and could be either of two types: Local Number Portability (LNP) data, for ported and pooled telephone numbers; and Industry Data Source data that identifies number blocks within the North American Numbering Plan (NANP) that are assigned to a particular service provider. The Private ENUM data that comes from an ENUM client presents that client’s view of the Public data, and provides the opportunity to override or augment Public data with authoritative data. There are three types of Private data: white list, in which an ENUM client can create a list of E.164 numbers that are viewable by only specific clients; override data, which apply for a limited period of time and supercede all sources of Public data; and authoritative lists, which list all E.164 numbers allocated to a given network operator.

The ENUM Data Access Service also features secure IP connectivity, either through a virtual private network (VPN) or through Transport Layer Security (TLS); interoperability between ENUM and the Session Initiation Protocol (SIP) redirect function; and a secure web portal that allows service providers to manage their private ENUM data such as white lists.

Further details on the VeriSign addressing services architecture are available at Our next peering tutorial will continue our examination of some of the commercial enterprises that are offering ENUM and other directory services.

Copyright Acknowledgement: © 2007 DigiNet Corporation ®, All Rights Reserved

Author’s Biography
Mark A. Miller, P.E. is President of DigiNet ® Corporation, a Denver-based consulting engineering firm. He is the author of many books on networking technologies, including Voice over IP Technologies, and Internet Technologies Handbook, both published by John Wiley & Sons.

Latest Articles

Follow Us On Social Media

Explore More