The VoIP Peering Puzzle�Part 17: XConnect ENUM Exchange

XConnect Global Networks Ltd., headquartered in London, and with offices and facilities in the USA, Europe and Asia, provides ENUM and peering services to over 400 VoIP operators in more than 35 countries. XConnect also claims to be the world’s first and largest provider of what they call Plug and Peer VoIP federation-based interconnection and ENUM services, dedicated to connecting VoIP operators and enabling rich multimedia, end-to-end IP communication. XConnect was founded in 2005 by Eli Katz, previously Managing Director of TelcoGlobal in the UK, as well as founder and interim Chairman of the UK’s Internet Telephony Service Provider’s Association (ITSPA).

XConnect has also led the industry in consolidation, with the acquisition of European provider in May 2006 (see and IPeerX, in September 2006 (see German-based service serves over 30 member carriers, with over 120 million telephone numbers in its directory. XConnect expanded into North America with their acquisition of IPeerX, the ENUM services and peering provider founded by Jeff Pulver, and based upon the Free World Dialup network. IPeerX serves over 140 member service providers, representing over 4.5 million end users world wide.

In addition, XConnect was recently selected by the cable industry in the Netherlands to operate that country’s first nationwide VoIP peering solution, called the SIP Exchange, which is the first of several private (national) federations powered by XConnect’s infrastructure.

XConnect takes what they call a ‘holistic approach’ to ENUM and peering, allowing service providers to define their own policies via a portfolio of services that combine ENUM, signaling, and security. This approach is the cornerstone of all their federations, including their Global Alliance service, which is 100 percent ENUM driven, and also their strategic federations, such as the SIP Exchange for the Dutch multiple system operators (MSOs). XConnect recognizes that federations can address some or all of the addressing, routing, and security issues posed by VoIP interconnection; but the key is to give service providers maximum flexibility in determining how their data is distributed and/or utilized.

The XConnect services allow each service provider to define and control their peering policies in four ways:

  • Access to the ENUM data: Should the service provider data be exchanged directly with peers, or made available on a query-only basis?
  • Privacy/Anonymity of ENUM data: Should peers be able to determine which ENUM records belong to the service provider, or should data only reveal the identity of the federation via which the service provider can be reached?
  • Signaling path: Should a peer establish signaling bilaterally with the service provider, or should signaling be via XConnect’s central signaling proxy which guarantees interoperability and supports security and other features?
  • Security: Should calls be accepted from any party, or only where Caller ID can be fully validated?

Xconnect’s ENUM Exchange is based upon the acquired service, and offers a federated registry/addressing service that is used by service providers to exchange ENUM data. Participating carriers synchronize their databases with the central registry, downloading data to and from approved peers, and store data from their peers in third-party ENUM or DNS servers, such as Nominum’s Navitas or NetNumber’s Titan, that can then be queried locally. The XConnect ENUM Exchange contains over 121 million VoIP numbers in the fully expanded ranges owned by the carrier participants.

The XConnect Alliance is a VoIP Peering Federation, which combines an ENUM Registry with federated SIP signaling, robust security features, and a settlement-free commercial model. The Alliance has over 60 service provider members from 30 countries, all of which are peered with each other.

Because the service providers don’t necessarily all know and trust one another, XConnect’s role as the Federation operator is to deliver trust. Access to the ENUM data is on a query-only basis, and results are anonymized, so no service provider can harvest the subscriber list of another or determine how many subscribers another member has. The query can be remote to XConnect’s hosted servers (using the ENUM protocol or via SIP), or to enhance throughput and reduce latency, locally to an instance of XConnect’s Local Directory Server (LDS). The LDS is a dedicated Query server containing a synchronized and encrypted copy of the Registry data, has both ENUM and SIP query interfaces, and prevents data harvesting. Because the LDS data is also anonymized, signaling between Alliance peers is via XConnect’s secure signaling proxy. XConnect then uses ENUM in its core network to resolve the true identity of the terminating service providers, while also implementing security measures to prevent Caller ID spoofing and Spam over Internet Telephony, or SPIT.

Further details on XConnect’s ENUM and peering services are available at Our next tutorial will return to our investigation of session border controllers.

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.

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