November/December 2001

ENUM -- A Key Enabler For IP-based Communications In Service Provider Networks

BY MARK NEIDER

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Communications Application Service Providers (CASPs) are rapidly expanding their capabilities to provide users many new and effective ways of communicating, including real-time voice communication across IP and PSTN networks. Serving as a lightening rod for industry, CASPs are developing services that bridge the methodologies of the last 100 years and today's next-generation broadband IP-based communication technology. They are taking advantage of the exponential build-out of large-scale IP backbone networks that have created a virtual tidal wave of available bandwidth. Leveraging bandwidth has the effect of eliminating the physical distances across networks for the hosted CASP -- building a virtual community by bringing subscribers and new applications closer to home.

CASPs that have implemented IP-based platforms that leverage VoiceXML and advanced speech recognition technologies are offering many new services that have been unavailable until now, including unified messaging, IP Centrex with Web-based subscriber provisioning, speech-to-text services, voice-enabled Web sites, and call center services. Gartner Group analyst Eric Paulak believes that CASP providers will see continued robust growth in this market space, fueled by IP convergence, capital investment restraint, and global outsourcing trends.

As this convergence of the telephone network and the Internet has advanced, a well-defined addressing challenge has emerged.

ENUM -- A STANDARDS-BASED SOLUTION
Telephone services like real-time voice, voice mail, and fax are based on using standard telephone numbers for addressing. Unfortunately, Internet-based communications services use a completely different addressing format. In order for the convergence of telephone services and the Internet to continue, a mechanism needs to exist to translate standard telephone numbers into Internet addresses.

In response to this addressing challenge, the Internet Engineering Task Force (IETF) launched a working group to define a technical standard for translating telephone numbers into Internet addresses. The result of this effort, RFC 2916, is commonly referred to as electronic numbering (ENUM).

CASE STUDY: THE NEED FOR AN ENUM-BASED DIRECTORY
Webley, a recognized leader of unified communications services using a PSTN transport, has recently extended its service by hosting its applications on its native SIP Media Switching Platform (MSP). Webley's MSP extends the potential of its unified communications application by capitalizing on the ubiquity of the Internet. This places Webley at the cutting edge of defining and employing innovative new services by using soft phones and IP phones in a virtual PBX context, based on technology such as SIP, XML, and VoiceXML.

Webley is utilizing ENUM services that allow them to provision multiple phone numbers within the ENUM service. This circumvents traditional PSTN networks, enabling calls to reach specific IP endpoints, such as IP-PBXs, IP phones, SIP proxy servers, PDAs, and other IP-capable devices provisioned by other service providers and carriers. "ENUM services are a vital link enabling peer-to-peer IP communications and IP-to-PSTN communications," according to Michael Poremba, Webley senior architect of product management and engineering.

By implementing ENUM, leading CASPs have found an effective way to discover IP-based endpoint addresses so that calls originating through either the PSTN or IP can be routed to IP destinations across multiple service provider domains. The impact to the CASP community of ENUM-enabled cross-domain IP calling can be significant. For voice calls between subscribers of different CASPs domains, transport costs over the IP network are based on bandwidth usage, not the traditional per-minute billing model. End-to-end IP routing of calls across service provider domains can lead, in some cases, to reduction in transport costs of more than 50 percent.

For voice portal companies, a significant advantage occurs when PSTN calls are terminated to an IP endpoint such as a portal's IP-based application platform. This termination model can give the CASP improved flexibility to manage calls, provide additional services, and lower overall costs, according to Don Jackson, vice president of advanced telephony at Tellme Networks. ENUM enables calls to well known phone numbers to be routed directly over IP to Tellme's SIP-based voice application network. When a Tellme customer's VoiceXML application makes an outbound call, ENUM enables Tellme to determine if this call can be connected over IP, or if it needs to be converted via a VoIP gateway into a legacy PSTN call. When calls are delivered to Tellme via IP, SIP proxy servers allow fine-grained control of call distribution to TellMe's VoiceXML server, far more so than being on the user side of an inter-exchange carrier's Class 4 switch, Jackson adds.

Tellme works with enterprise customers to reduce telecom costs and improve how they interact with callers by providing a network-based solution for building, running and managing VoiceXML applications. Tellme also hosts the world's largest voice portal, 1-800-555-TELL.

A NEW INTERCONNECT MODEL
Carriers are also getting into the act by viewing the adoption of ENUM as a means to enable a new type of interconnect model. ENUM provides service discovery for cross-domain routing of voice sessions and represents a fundamental shift in the network architecture. Long-distance voice calls that were destined for termination on the PSTN can be converted to IP and directed to IP endpoints using ENUM for discovery of the IP address. Additionally IP originated calls can be terminated to IP endpoints in the same manner, all on a global scale.

Jay Sayers, chief technologist of the Williams Communications voice architecture group, believes that as carriers begin to interconnect and to exchange IP- based voice traffic, the limitations of current peering methods with regard to scale, security, and manageability will become problematic. Clearly a dynamic directory service can help solve these issues. ENUM has the opportunity to be a key enabler in the convergence of existing PSTN-based infrastructure and next-generation softswitch-based VoIP networks.

With carriers and CASPs deploying IP-based services worldwide, a global ENUM directory is required to support the dramatic growth of IP endpoints. This new interconnect model is based on an open architecture where a cross-carrier federation of IP-based voice calls will become as common as traditional voice calls today.

ENUM will be an enabling infrastructure component in the creation of a new interconnect model among various service providers, and between service providers and transport carriers. IP application-enabled endpoints become more valuable as they increase in volume. In the ENUM-enabled interconnect model, CASPs will be empowered to benefit from the value of the IP-enabled endpoints they deploy, and transport carriers will benefit by leveraging their backbone infrastructure

Mark Neider is director of business development at NetNumber. NetNumber is a leading provider of Global ENUM directory services.

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Transport carriers and CASPs have specific requirements that must be supported by the global ENUM directory service provider. Security is a critical component and must be both physical and network based. Network access to the ENUM service must be available worldwide and should provide significant operational support for high query volumes. As IP communications expand, the amount of traffic between PSTN and IP domains will grow significantly and will require massive storage capability and rapid access speeds. The ENUM service provider will need to support a carrier class environment required by carriers and service providers. A seamless infrastructure must also be in place between the ENUM provider and the CASP or transport carrier to provide subscriber registration and validation. Billing based on transaction must support usage and type. Control and management of subscriber information and billing is important in making the service reliable and easy to use.

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