The VoIP Peering Puzzle – Part 12: Neustar’s SIP-IX

Neustar, Inc., with corporate headquarters in Sterling, Virginia, is a company whose services you have almost certainly used—most likely without knowing it. It began as an independent unit of Lockheed-Martin, spinning off as a separate entity in 1999. Today, Neustar is in the clearinghouse business, providing specialized addressing-related services to the North American telecommunications industry.

Specifically, Neustar operates the authoritative directories that manage virtually all telephone area codes and numbers that enable the dynamic routing of calls among thousands of service providers in the United States and Canada. Since 1997, NeuStar has served as the FCC-appointed administrator of the North American Numbering Plan (NANP)—an integrated telephone numbering plan serving 19 countries across North America and the Caribbean—with the overall responsibility for neutrally overseeing the assignment and use of NANP numbering resources. In addition, they manage the authoritative directories for the .us and .biz Internet domains—as well as the Common Short Codes, part of the short messaging service (or SMS) that is used extensively within the U.S. cellular telephone industry.

Neustar generated $252 million in revenue in 2005 and has satellite offices in London, Singapore, and Taiwan.

Considering its expertise in addressing-related technologies, it should come as no surprise that Neustar is involved with Electronic Numbering (ENUM) technology. Neustar’s SIP-IX offering is a comprehensive suite of services designed to enable direct network-to-network peering between trading partners for voice, video, and content services. The service embraces a number of industry standards, including the Session Initiation Protocol (SIP), Electronic Numbering (ENUM) and Simple Object Access Protocol (SOAP/XML) technologies, to enable Voice Over IP (VoIP) and IP Multimedia Subsystems (IMS) applications. SIP-IX builds upon the company’s successful private ENUM routing service, which has been used by major mobile service providers since 2003.

SIP-IX’s architecture is based upon a high-availability master database, which is replicated out to six partner Internet Exchange Provider (IXP) locations in North America, Europe, and the Far East. At these sites, SIP-IX is directly connected to the high-speed switch that serves as a traffic exchange for major telecommunication carriers, Internet Service Providers, and content providers.

This architecture includes three key functions: Registrar, Telephone Number Registry, and ENUM and SIP Server Location. The Registrar function includes the Publish interface, which allows registrants such as service providers to input records and to add, delete, modify, and associate related information. A related policy management capability lets service providers publish their data only to—and trade traffic only with—trading partners that they designate. The Telephone Number Registry function includes a Subscribe interface, which allows data from the SIP-IX registry to be downloaded to a local ENUM cache via a non-proprietary web services interface. The ENUM and SIP Server Location function includes the Query interface, which is the conduit through which the registry responds to ENUM and/or SIP queries, and through which Naming Authority Pointer (NAPTR) or SIP Redirect responses are returned, based upon the input and previously defined rules and policies in place.

Thus, SIP-IX can accept data into from two sources: the Number Portability Administration Center (NPAC), which provides the routing information for non-IP calls; or from the SIP-IX Publish interface, which is used by carriers to publish their routes for an IP call. IP routing information can be obtained from the registry in two ways: from the SIP-IX Subscribe interface, where service providers can download the relevant portion of the database into their network; or from the Query interface, which allows equipment to use either ENUM or SIP Redirect queries to request a database lookup each time a call needs to be routed.

Further details on the SIP-IX architecture and other Neustar services are available at Our next 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