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Practical VoIP Using VOCAL

Speaking About VoIP

by Bruce Stewart

Bruce Stewart recently sat down for a roundtable discussion with the authors of Practical VoIP Using VOCAL. In this interview Luan Dang, cofounder of Vovida Networks, Cullen Jennings, and David G. Kelly explain why VoIP is on the verge of taking off, and how their book and VOCAL, the open source software that enables a core network to support VoIP, are helping the community to grow and build practical VoIP applications.

Stewart: What is VoIP?

Dang: VoIP is a set of rules (also known as protocols) and devices that enable users to make phone calls over the Internet. VoIP systems transmit signals to set up and tear down calls and media to make it possible for users to hear each other talk. These signals and media are sent over networks as packets just like other forms of data. Another term for VoIP is "packet telephony."

More and more organizations are installing VoIP systems to make better use of their networks. If you are already using a large network for sharing text and images, it is not a large technical leap to deploy a VoIP system on the same network. Open source systems, such as VOCAL, help make setting up VoIP networks cost effective.

Kelly: Manufacturers of traditional phone equipment, also known as time division multiplexing (TDM) equipment, are offering VoIP solutions to help their customers switch from the older technology to the new Internet-based technology. Some VoIP architectures offer smart phones that are capable of doing much more than traditional home or office phones. We anticipate many new developments in the features and functionality available on IP phones in the coming years.

Stewart: What hurdles have to be overcome for VoIP to be widely used?

Dang: Compared to the traditional phone system, which is over 100 years old, VoIP is new and it takes time for many organizations to make large investments in new technologies. We are starting to see major banks, manufacturing companies, and other "old economy" organizations installing VoIP phone systems.

Kelly: There are several quality-of-service issues that still need to be addressed, although sometimes when I make a long-distance call over the public Internet, the quality is as good as what I would expect from a traditional land-line phone. Security is another concern. However, there are many people in the Internet Engineering Task Force (IETF) who are coming up with new proposals and standards to make VoIP secure enough to assure privacy and protection for end users.

VoIP equipment is still expensive, as much of it is in the early stages of product development. However, just as the cost of PCs and other electronic equipment has come down in price, soon VoIP equipment will be considered as a viable alternative to traditional systems by many more individuals and organizations.

Stewart: What is VOCAL?

Dang: VOCAL is the Vovida Open Communication Application Library, which is open source software that enables a core network to support VoIP. In 1999, Alan Knitowski and I founded a company called Vovida Networks (think about VOice, VIdeo and DAta) to kick-start VoIP application development by offering free open source protocol stacks to the public. Eventually, we sold Vovida Networks to Cisco Systems and made the VOCAL system open source and available from a community Web site called Vovida.org.

VOCAL is governed by a BSD-style license that enables developers to download the code without paying any royalties or fees, make changes without having to send the changes back to our code repository, and use the code within new proprietary applications with our full permission. VOCAL was written primarily in C++ with a Java-based provisioning system. VOCAL runs on many flavors of Linux as well as Sun Solaris. VOCAL uses Session Initiation Protocol (SIP) to set up and tear down phone calls. You can download a copy of our SIP stack from Vovida.org. It is also open source.

Kelly: Even though we don't require developers in the community to share their code changes with us, many people have sent us bug fixes, minor enhancements, and fully fledged open source applications. The Vovida.org community is growing and we are constantly surprised by the volume of email we receive and the diversity of the people contributing code and helpful information. The Vovida.org community has become truly international.

Stewart: Why did you decide to write Practical VoIP Using VOCAL?

Dang: VOCAL is cool and by providing useful documentation, we have helped our community grow and build practical VoIP applications.

Jennings: VOCAL empowers the end user with control over feature development and customized integration with legacy systems. Along with all other VoIP applications, VOCAL is actively inverting the way that telephony is deployed by allowing an Internet-style anarchy that was never possible in the traditional PSTN. It has been a fun area to work in.

Kelly: The book provides a parallel channel for documentation distribution and awareness of VOCAL. Writing an O'Reilly book has provided us with a valuable companion to our Web site, www.vovida.org, our mailing lists, and our participation in different trade shows such as LinuxWorld, ISPCon, and ASPCon.

Stewart: Why is your book especially important now?

Kelly: VoIP is on the verge of taking off and becoming part of the public consciousness. Our current stage of development is analogous to where the Internet was in the late 1980s to early 1990s.

Jennings: VoIP is gaining support through its ability to provide viable services. In many cases, calling over the Internet from here to China offers a quality of service that rivals the PSTN. To the average end user, the difference in quality between a circuit switched call (PSTN) and a packet switched call (VoIP) is imperceptible.

Stewart: What is the single most important thing readers will be able to do after finishing your book that they couldn't do before?

Kelly: For many, mostly those who have no prior knowledge of VOCAL or Vovida.org, it will provide them with their first opportunity to download, test, and analyze the software. For those who have already worked with VOCAL, this book provides much greater detail about the data structures found within the code than any other material available on the Web site or elsewhere.

Jennings: Those advanced users will be able to gain a better understanding about the code and its functionality by referencing the book.

Stewart: Who is your intended audience?

Jennings: Essentially, those who have the wherewithal to download open source applications from the Internet and run them from a Linux server. These people may be hobbyists, students, or professional engineers, including those who make their living developing VoIP applications and solutions.

Dang: Although we attempt to expand our community by being inclusive, this is not beginner's software and it does require the user to have some sophistication with Linux to install and operate it.

Stewart: Tell us a little bit about the history of VoIP and how this book came to be.

Related Reading

Practical VoIP Using VOCAL
By David G. Kelly, Cullen Jennings, Luan Dang

Dang: Vovida Networks was founded in 1999 by Alan Knitowski and myself as an expression of our dissatisfaction with the status quo. Both of us came from a major telecom manufacturer that endeavored to maintain control over their customer's installations through building proprietary systems. Alan and I considered the Internet model of open standards and open source implementations as a better way to bring VoIP to the end users.

Kelly: During this time, Silicon Valley was booming and many talented engineers and business people were flocking to fledgling startups and the alternative culture being fostered therein. Vovida was a fun place to work and, like all small ventures, a place where each individual could see the impact of his or her work on the development effort. As we approached our first delivery milestones, Dang (Vovida's CTO) and Jennings (Vovida's VP of Engineering), while knowing nothing about writing books, agreed to terms with O'Reilly and soon found that their technical expertise in voice technology was not enough to bring this work to life. As any good executives would do, they delegated the responsibility of vitalizing this project to myself, Vovida's technical writer. I didn't know anything about VoIP, but managed to transform Luan's and Cullen's knowledge into something readable.

Jennings: While the material was being put together, the Silicon Valley economy turned from an all-time high to a devastating low and now appears to be bouncing back. At the same time, the Internet has shifted in the public's imagination from being a curiosity to a novelty to its present state of being a practical tool. VoIP is part of the practical tool-set for future Internet development and, from this point of view, the timing of the book's release could not be better.

Stewart: How important is VoIP? What is on the horizon for VoIP and VOCAL?

Jennings: VoIP will dramatically change the telephony landscape and voice will be treated like any other kind of data package. VoIP will be leading development of voice services into countries where installing traditional phone systems would be prohibitively expensive. VoIP is the wave of the future because of convergence, everything coming together, voice, video, and data (the source of the startup's name, Vovida), when applications in the same place, and the same time create a sum greater than its parts. For example, presence has helped instant messaging become much more useful that it would have been otherwise.

Dang: In the U.S., it took 80 years to create the PSTN and it is excellent. However, in China the requirement is to build the system in one-tenth the time, to serve ten times the number of customers at one-tenth the cost. That adds up to many constraints to meet at the same time, and we believe that VoIP is the only way to accomplish those goals.

Kelly: There is also the change towards flat-rate billing for long distance that can be traced to the emergence of VoIP. This has become most evident in the cellular phone packages being offered by service providers in the U.S. The cost of long distance has collapsed in the past ten years. The fact that you can make an excellent, free phone call over the Internet is a big reason why it will continue collapsing.

Stewart: Do you think the recent problems many of the large telcos are experiencing, like the bankruptcy of WorldCom, will have any effect on the acceptance of VoIP?

Dang: Our primary concern with the failure of these large companies, and the general slowdown in the service provider market, is that funding for new VoIP applications is becoming harder to find. In the long run, new companies will take the place of those that have failed, and what happened to WorldCom, Global Crossing, and others will be interesting history but not important to the day-to-day business of VoIP.

Kelly: We have noticed a sharp decline in the number of small companies at trade shows and the variety of open source projects available on the Internet. It seems that people are really concerned about keeping their jobs or finding jobs if they have been laid off. Soon, when companies start hiring more people and the fears of a downward-spiraling economy are abated, we believe that many developers will start where they left off and there will once again be a rich new world of ideas and products.

If you want to be a contrarian, you could say that this is an excellent time to start a small service provider organization and to slowly grow the business into sustainability. This type of venture would require a great deal of patience and may take a long time before it attracted substantial financial backing, but once the dust settles, there will be new opportunities for growth. Conrad Hilton started his hotel chain during the 1930s; who knows what exciting new markets may open up a few years from now.

Bruce Stewart is a freelance technology writer and editor.

O'Reilly & Associates recently released (July 2002) Practical VoIP Using VOCAL.