September 1998

BY RICK PIERSON

Interoperability between the PSTN and IP networks has taken on tremendous importance as of late, primarily because the PSTN has been providing voice service for over 125 years and happens to own over 99.8 percent of the market. From the beginning, the PSTN was designed to carry voice with reasonable sound quality. From their inception, IP networks were created to transport data as efficiently as possible. Because of these different roles, there are issues that must be resolved between the PSTN (circuit-switched world) and IP networks (packet-based world) in order for IP Telephony devices to be as ubiquitous as your telephone.

The PSTN allows the phone, a dumb 125-year-old end device, to be connected to hundreds of millions of other phones throughout the world. This is over a network with five nines (99.999 percent) of reliability, fast call setup times, a robust feature set, and a sophisticated billing and settlement system. That sounds like magic, but remember, this technology has been evolving since the last century. So how does this dumb device, the telephone, do all of these functions while we have such a hard time with an intelligent device such as a PC, which is vastly more expensive than a phone?

INTELLIGENCE IN THE NETWORK
The answer is an intelligent control network with strictly enforced national (ANSI) and international (ITU) standards often referred to as the Signaling System 7 (SS7) network. In essence, a very smart network, properly referred to as the Intelligent Network (IN), controls your dumb telephone. This intelligent network is getting smarter all the time as new SS7-based features emerge to offer more enhanced services such as central office voice mail, follow-me services, voice recognition dialing, and the like.

INTELLIGENCE AT THE ENDPOINTS
The IP network is the exact opposite of the PSTN. It is a very stupid network with intelligent endpoints (e.g., servers, PCs, and such). It uses fast packet routers and switches, which are essentially dumb devices with just enough intelligence to determine where to send packets. The stupid network is growing fast because it can do things that the PSTN cannot do. The networking equipment is inexpensive (compared to PSTN switches) and it's mostly free due to the interconnection agreements of the Internet.

Because of the phenomenal growth of the Internet, it was only natural to find ways to use packet networks to offer voice services - thus, the birth of a new industry, Internet telephony. In 1998, we anticipate two-tenths of one percent of domestic voice traffic will be carried over IP networks. By the year 2002, some analysts (such as Probe Research) believe that we should see numbers in the range of 18 percent.

In many ways, the emerging IP telephony industry is undergoing the same type of growth problems that the original PSTN had, albeit in "Internet time." There were major interoperability problems for over fifty years in the PSTN; until a gentleman named Vail convinced the U.S. government that telecommunications was vital to economic growth and national security. Regulations where passed that forced standards on the public phone system. These regulations made the PSTN a truly national and eventually an international communications medium that most of us take for granted today.

For IP telephony to succeed, IP networks need to carry voice with the same Quality of Services (QoS) and with functionality that meets or exceeds the current PSTN. IP telephony networks must offer enhanced services such as call waiting, caller ID, as well as other such services. It has to offer a global reach that is easy to use and it must have the same reliability that is synonymous with those three little words: The dial tone. And of course, it needs to interoperate with today's PSTN.

BUILDING ON THE PAST
So how do we create this new future in IP telephony? Do we reinvent all of the features of the PSTN into an IP world? Or do we find ways to leverage the infrastructure already in place and add only what we need? Certain vendors believe that we should create new services with IP telephony while building upon the core infrastructure of the PSTN. After all, it took us thirty years to create a worldwide intelligent network that makes our telephone work everywhere, all of the time. Let's take advantage of it.

By interfacing into the SS7 network, one can build IP Telephony access devices, which offer features to satisfy our most basic needs in telephony: Features such as one-stage dialing, fast call setup times, many enhanced SS7 services, and the use of legacy billing and settlement services. Thanks to the Telecommunications Act of 1996, anyone can have access to the SS7 network. From here, technology vendors can tackle the challenges of H.323 video conferencing, Web telephony, and phone-to-anything communications.

A JETSON-LIKE FUTURE
Let's go back in time. Some of you may remember a cartoon called the Jetsons. This cartoon was about the future where man travels around the planet and across outer space much like we go for a ride down the highway today. The one thing about this TV show that really impressed me was the ability to communicate with anyone (global), at anytime (reliable), over any distance (scalable), from any place (portable). The Jetsons could even see each other (video) and talk to inanimate objects like their car, house, or office (data).

Some believe that for Jetson-style communication, the PSTN must go the way of the dinosaur (Flintstone technology). As a Bell-head and ex-AT&T/MCI alumni, I'll go so far as to say the PSTN will be here long after I have left this world. There are 1,000 billion dollars of PSTN infrastructure built around this world. If the PSTN is here to stay, however, how is it going to evolve to meet the needs of the Jetsons?

The future is not just about IP telephony, it's about offering global universal services which run on a variety of networks including cable, satellite, Internet, and who know what else. There is no doubt that the PSTN alone cannot deliver the futuristic Jetsons type of communications for a number of reasons. Lack of bandwidth, last mile termination, technology immaturity, government regulations, lack of standards, and interoperability are just a few good reasons. The PSTN needs to interwork with packet networks to make universal access possible, and the carriers will be offering this kind of service in the near future.

The circuit-switched network isn't going to go away anytime soon. There will be a transition from circuit to packet, and long term co-existence is likely. There are plenty of circuit-switched carriers that want to get into IP services above and beyond basic Internet connectivity. AT&T, MCI, US West, and others have already announced investments and ventures in the IP telephony realm. For example, AT&T is backing ITXC, while US West and Bell Atlantic have invested in IP phone and videoconferencing technology developer VDONet.

These carriers already have legacy billing systems and business processes in place, plus they have billions invested in their circuit-switched networks. They don't want to create new billing and OSS networks just for IP telephony. They need to find ways to interface their 30-year-old COBOL billing networks to their IP telephony gateways.

CONCLUSION
The integration between SS7 and remote access is about the simple transition of a PSTN circuit to an IP packet seamlessly. Voice or data - it makes no difference. Leave SS7 on the PSTN alone, it works great, and discover what services are important to the customer and innovate with new IP signaling systems and advanced feature/functionality over time. Remember, when it comes to voice, quality and simplicity are more important than the fact that it's being carried on an IP network.

IP services, and especially IP telephony, have caught Wall Street's attention and investment dollars are flowing to IP carriers by the billions. The next investment wave for these IP carriers will be in billing, customer care systems, and telecom class services. This spells opportunity for innovative software and hardware vendors looking to enter new markets. Carriers, whether they're circuit-switched or IP, can rest assured that they'll have plenty of solutions to choose from. Your future in IP telephony is high-quality service built upon legacy PSTN infrastructure, with a whole new class of services that none of us have even dreamed about.

Jane? I'm home!

Rick Pierson is director of business development and strategic alliances for Mockingbird Networks. Prior to joining Mockingbird Networks, Mr. Pierson was a Bell-head working as director of IP telephony engineering at AT&T Bell Labs, and a co-author of the MSAF IP Telephony Manifesto. Mockingbird Networks develops solutions, which integrate data communications and computer telephony technology with SS7 enhanced services to create world-class, open systems platforms that can be integrated into the telecom networking infrastructure. For more information, visit the company's Web site at www.mockingbirdnet.com.