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Feature Article
May 2002

Calling All Endpoints: ENUM Will Play Key Role In Enabling IP-Based Communications Services


Softswitch-based VoIP deployments are accelerating in both core and edge networks even as the telecom market as a whole is experiencing a difficult environment. Market research firm InfoTech recently released a study claiming that more than 40 percent of U.S. companies employing 500 or more people are in the process of converting to VoIP systems. Large carriers are continuing to evolve away from traditional tandem switches in favor of softswitch platforms that are much more scalable, require less footprint, and ultimately serve to lower costs.

On the services side, history has shown that new telecommunications services typically originate in the enterprise and expand into the network over time. Communications Application Service Providers (CASPs) such as Webley, Tellme, Voxeo, and others are driving toward these new services using Session Initiation Protocol (SIP) and VoiceXML programming. CASPs are providing these new services by using a hosted solution, as well as a direct software and services approach to the enterprise. The large incumbents have been successful in deploying these solutions for wireline and wireless networks. Microsoft�s XP strategy, starting initially with its existing MSN subscriber base, will eventually extend into the enterprise market, when the timing is right. These developments will lead to an ensuing rapid growth of IP endpoints, which will further the convergence of IP and PSTN, thus creating the need for a global directory service to discover these millions of IP endpoints and translate them into numbers the converged networks can understand.

Translating PSTN Numbers to IP
PSTN services, such as real-time voice � and unified communications applications such as voice mail and conferencing � use standard telephone numbers for addressing endpoints. IP communications services use a completely different addressing format. In order for the convergence of the PSTN and IP services to progress, the market needs a mechanism that translates standard telephone numbers into Internet addresses.

Responding to this convergence challenge, the Internet Engineering Task Force (IETF) defined a technical standard for translating telephone numbers into Internet addresses � RFC 2916, commonly referred to as telephone number mapping or ENUM.

DataVoN, a next-generation IP-based carrier maintains that ENUM is critical to the evolution of IP networks. �IP is here today but will continue to evolve, making the discovery of IP endpoints a necessary requirement,� stated Hugh Simpson, DataVoN CEO. Simpson goes on to state that IP products over and beyond VoIP such as IP conferencing (both audio/video) will require IP endpoint discovery making a seamless transition for the consumer, which is ideal for ENUM.

ENUM Directory: Discovering IP Endpoints
CASPs have found that ENUM provides an effective way to discover IP-based endpoint addresses so that calls originating on either PSTN or IP can be routed to IP destinations across multiple service provider domains. ENUM-enabled cross-domain IP calling can have a significant cost advantage for CASPs, is some cases reducing transport costs by more than 50 percent. For voice calls between subscribers of different CASP�s domains, transport costs over the IP network are based on bandwidth usage, not the traditional per-minute billing model common to PSTN. Thus, end-to-end IP routing of calls across service provider domains can lead to major cost savings.

Webley, a recognized leader in providing unified communications services using a PSTN transport, recently extended its service by hosting applications on its native SIP Media Switching Platform (MSP). Webley�s MSP extends the potential of its unified communications application by taking advantage of the Internet�s worldwide capabilities. Webley is at the cutting edge of defining and employing innovative new services by using �soft phones� and �IP phones� in a virtual PBX context, using SIP, XML, and VoiceXML.

Webley uses ENUM services that allow provisioning of multiple phone numbers within the ENUM service. This bypasses 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,� said Michael Poremba, senior architect of product management and engineering at Webley.

ENUM Enables New Interconnect Model
Carriers see the adoption of ENUM enabling a new type of interconnect model where long-distance voice calls, previously destined for termination on the PSTN, can be converted to IP and directed to IP endpoints. ENUM, which provides services for discovery of IP addresses and for cross-domain routing of voice sessions, represents a fundamental shift in the network architecture. Both PSTN-originated and IP originated calls can be terminated to IP endpoints in the same manner, all on a global scale.

Identification of IP endpoints and the implications related to number portability requires that LNP be incorporated in the architecture discussions and ultimate deployment of global ENUM services. Additionally new network intelligence is required to inform the PSTN switching and signaling infrastructure that traffic destined to the IP networks is routed to IP-based media or signaling infrastructure components. As IP networks draw increasing traffic from the PSTN the need to access legacy AIN data elements, and new application such as presence becomes quite clear.

Timothy Jasionowski, director of IP Product Incubation at Qwest Communications, believes that ENUM will be important to the deployment of large-scale networks that will require cross-carrier and cross-technology interworking. �This type of technology is integral to interworking between existing SS7 and next-generation VoIP networks,� Jasionowski said.

More Than A New Number: A New Model
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 PSTN voice calls are today. A global ENUM directory that can keep pace with the dramatic growth of IP endpoints will be necessary to support carriers and CASPs deploying IP-based services worldwide. ENUM will play a key role in enabling the creation of this new interconnect model among various service providers and between service providers and transport carriers. Just as the telephone became a necessity as more businesses and homes installed them, the more IP application-enabled endpoints are deployed, the more valuable they become. As service providers deploy IP-enabled endpoints, their markets for value-added communications services will grow, and transport carriers will benefit by increased use of their backbone infrastructure.

Mark Neider is director of business development at NetNumber, a leading provider of Global ENUM directory services. For more information, visit the company online at www.netnumber.com.

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