The Fundamentals of IP Telephony

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Internet protocol (IP) has been the subject of much talk and speculation over the past few years. The hype is turning into a reality as major carriers enter the IP market, cable operators roll out new services and pure-play voice over Internet protocol (VoIP) providers gain subscribers. Total IP revenues are expected to grow in 2004 by 7.8 percent, achieving a total of $14.9 billion, according to the Telecommunications Industry Association’s (TIA’s) 2004 Telecommunications Market Review and Forecast.

What’s driving this growth? More organizations are exploring IP options because the technology enables institutions of all sizes to deploy revenue-generating services quickly and cheaply by leveraging existing packet-switched networks. This solution isn’t just for Fortune 1000 companies anymore—the audience for IP telephony has expanded. There are applications, equipment and cost factors that can be scaled to size. Companies can benefit from managing just a single network, as opposed to managing as many as four networks for voice, video, data and wireless.

The rapid growth of IP traffic on the network–75 percent in 2003–clearly indicates that the migration to IP is in full swing. Yet there are lingering issues with respect to VoIP quality, and its status with respect to regulatory supervision remains unclear. The FCC is currently clarifying the regulatory issues around IP applications, such as VoIP, to help address this issue. Nevertheless, VoIP forces are advancing. IP-PBX shipments are surging, and VoIP is beginning to penetrate the residential market. TIA expects that by the end of 2004, there will be more than 6 million VoIP access lines, a figure the association anticipates will rise to more than 19 million by 2007. (See Figure 1.)

What’s Driving IP?
One of the key factors driving IP is that it enables companies to bring geographically dispersed facilities (remote facilities as well as distributed networks) together under a single converged network umbrella.

IP allows the creation of new business solutions via voice-enabling applications. Typical computer-telephony applications, such as interactive voice response (IVR), calling card, prepaid services and automatic call distributor (ACD), can be reinvented by adding IP connectivity or making it an option. Newer enhanced services, such as unified messaging, find-me/follow-me, call management, privacy and calendar settings, family- or community-integrated features and parental controls, are attracting new customers.

“Messaging has become an anchor application and a vital revenue stream for carriers,” said Arun Sobti, CEO and chairman of IP Unity. “In North America alone, there are more than 24 million subscribers on first-generation ILEC voice messaging. Now carriers can migrate message content and features from legacy voicemail platforms to all-IP messaging platforms in a completely non-disruptive fashion.”

There are many other features and options that haven’t yet reached the market, but service providers are beginning to introduce these advanced services, layered over feature sets that offer parity with traditional PSTN (public switched telephone network) offerings. Different carriers are making the move to IP at different stages based on their business strategy. No single solution applies to all parties.

“VocalData has supported a wide variety of VoIP deployments, ranging from residential and enterprise to wholesale and cable IP networks,” said Mark Whittier, vice president of VocalData. “VocalData’s per-subscriber revenue model not only minimizes service providers’ upfront costs, it links their success directly to ours. That’s why we offer programs designed to help our wholesale partners and their customers succeed in maximizing the return on VoIP investments.”

So, what are the hottest trends in the VoIP developer area?



  • Hottest Markets: Both the banking and retail markets are showing tremendous growth in VoIP technology applications. The services and education industries are also key markets.
  • Contact Centers: Many contact centers are using VoIP as both a cost-saving and a profit-generating enabler. IP-based call centers, for example, are using VoIP for local and remote agents and providing rich support for caller self-service; for example, Web VoIP-based IVR, e-mail, short message service (SMS) or wireless application protocol (WAP).
  • Eliminating the Need for Wiring: Companies can eliminate the need for analog/digital wiring by implementing IP/VoIP networks and using IP phones to utilize existing data networks for voice, thereby reducing the cost.
  • Deployment of Mobile Telephony: Wireless telephony for the workplace, using VoIP and Wi-Fi, enables rapid, cost-effective deployment of mobile telephony.
  • New Applications: Applications that simplify the ownership of VoIP itself are becoming more popular.


Tools to Help You Serve Your Customers
IT professionals have opportunities to create new and improved solutions for telcos, service providers, systems integrators, telecommunications and network equipment manufacturers, contact center equipment manufacturers and enterprises. You might capitalize on certain opportunities using a customer’s existing network. In order to take advantage of these opportunities, it’s essential to highlight the benefits that the end user cares about rather than discussing the technology itself, or why IP is better than traditional networks. You also need to consider where the solutions will be deployed–home, office or network–since that will impact reliability requirements, the scale of deployment and even the choice of operating system.

Whether your background is in data and Web-oriented programming or purely telecom-related, you can easily learn new voice protocols such as session initiation protocol (SIP), and today’s application development tools are similar to the ones many are already using.

A Balancing Act
Implementing IP can be a balancing act because you may be challenged to balance efficiency with quality. Telephony networks are always changing, and the management complexity of the network increases proportionately to the number of converged applications that run on the same network, especially if the carrier needs to migrate gradually from a circuit-switched to an IP-centric network infrastructure.

A critical factor to a successful implementation is the amount of time dedicated to production environment simulation and migration testing prior to the recommended pilot implementation. This is especially critical for larger projects where the design validation phase will make or break the final deployment.

Key functions of migration and integration include the following, as related to a specific legacy application such as voicemail:



  • Conversion of subscribers’ stored messages.
  • Replication/porting of user prompts, greetings and message waiting indicators from legacy to all-IP platforms.
  • Mapping of mailbox types and profile attributes.
  • Audio-recording tool and SIPserver module, SIP/MGCP bridging.
  • A servlet engine to generate voice-extensible markup language (VXML) dialogs.
  • Conversion of OAM&P features from command-line interface to GUI-based support screens, including operator tools for live scheduling, executing, monitoring and obtaining reports.
  • Back-end tools, including pre-process/post-process tools and migration progress-monitoring interfaces.


So, what’s out there that can help you implement a balanced approach? To help ease your burden, there are a number of tools/techniques, such as:



  • Developer Kits: There is a robust market for application developer kits (ADKs) for both telephony and traditional programming facilities t
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