It seems like an attractive and logical conclusion to aggressive price wars between long-distance service providers. It seems too good to be true, and in many ways, it probably is. The catch is that part of the call is carried over the Internet or some other data network. It's never completely free, and the quality of the conversation will almost certainly not be what the customer is used to -- but it may still make sense in certain situations.
When a long-distance phone call is placed, an electronic circuit is created -- the same way that plugging in a vacuum cleaner creates a new circuit to that appliance. The long-distance carrier measures the connection in time and distance and shares the customer's eventual payment with everyone involved in creating that circuit. The greater the distance and the longer the call, the more the user pays.
Computer calling shifts part or all of that long-distance connection off the metered circuit and replaces it with data packets racing across a data network. At the end of the network, those packets can be converted back to a regular phone call, or delivered directly to a multimedia PC for playback through a sound card. Since local calls to an Internet service provider (ISP) or a departmental location are charged at a flat rate, the entire connection can appear to be toll free. Unfortunately, it's not entirely true, and the connection usually has all the quality of a conversation with a lunar lander.
First, local calls are not free. They are simply billed at a monthly flat rate. The same is true for data network connections, whether they are part of an internal private network or provided by an ISP. The flat rate provides the ability to connect and transmit data. So a voice call over a data network is not "free," but it may still be significantly less expensive than the price of a long-distance toll call.
However, there still must be some method of converting voice signals into data packets. Either inexpensive software for a multimedia PC or a hardware/software gateway connects an existing phone system to a wide-area data network. In either case, the hardware and software have to be acquired, configured and managed at some expense. Still, those relatively minor capital and management costs can easily pale compared to a long-distance telephone bill, especially if they get the job done.
Data networks are designed for reliable -- as opposed to timely -- delivery of information. Packets of information that include a destination address are fed into a data network, where different devices read the address and route the packet along whatever path seems best at the moment. Packets get out of order, bump into each other, slow down and speed up, all depending on how they are routed and the state of the data network. While that is not usually a problem for electronic mail or text or pictures, it can be unacceptable for a realtime, interactive voice conversation.
Chris Hughes is the director of Information Delivery Services for Public Works and Government Services Canada. His department manages the primary government Web site and tends to handle Internet requirements for smaller departments and unexpected peaks in customer demand from across the country. He also manages a 300-person telephone call center that handles well over 1 million calls a year.
"Our challenge is to combine many sources of information and many vehicles of delivery into a consistent information package. We have to adapt technology to meet business needs," he said.
Hughes says new technology may not be needed for some services, like clicking on a button in a Web page to create a voice connection.
"We are encouraging users to examine the Web as a collaborative tool, in conjunction with the telephone. I'm not sure we need more technology to do that," he said.
John A. MacDonald, executive vice president and chief technology officer for Bell Canada, is well aware of the possibility of sending voice calls over a data network, but he does not seem overly concerned about lost revenues. "We are used to doing deterministic planning over a 10-year cycle for our circuit-switched voice network," he explained. "On the data side, customer demand is chaotic and fractal in the load it places on the data network. The demand is similarly uneven, moment-to-moment, hour-to-hour and day-to-day. On the voice side, we have a well-established infrastructure for signaling and billing, amongst other things. Should we mix the two?"
MacDonald sees the need to bifurcate the network -- split voice and data into two separate networks. In specific terms, that means ISDN or ADSL technology, which provide both kinds of service to a subscriber.
ISDN
Integrated Services Digital Network (ISDN) is the older of the two technologies, dating back to a much-hyped announcement in 1985. Superficially, the service looks like two phone lines stuck together with high-speed data modems at either end. Each Bearer (or B channel) has a separate dial number associated with it and provides 64Kbps (kilobits per second) of throughput -- the same as a standard telephone circuit. A separate Delta (or D channel) handles call set-up and progress information, providing an unhindered aggregate of 128Kbps throughput through the two B channels of the modem. The B channels can also be split apart to allow a voice call on one and data on the other, or two separate data calls at 64 Kbps.
ISDN modems, unfortunately, are limited in distance to about 10,000 feet, so deployment tends to cluster around central office locations. They are also notoriously complex to set up, and not cheap to operate. One specification outlines 29 possible configurations.
ADSL
Asymmetrical Digital Subscriber Line (ADSL), the newer hybrid data-and-voice technology, uses portions of the audio spectrum -- not required for voice -- to create an end-to-end digital connection. This "passband" spectrum can provide seven different channels with as much as 10 times the throughput of an ISDN modem for downloads, a separate upload channel and a regular telephone connection, all using the same copper wire used for voice today. Subscription costs are likely to be similar.
In a September 1996 speech on ADSL, MacDonald said, "Right now, your telephone line uses less than 1 percent of its capacity. With this new service, we will make use of the remaining 99 percent."
If the quality of a voice call is less important than the cost, it may make sense to take advantage of voice calling over a data network. But how can the quality of voice over a data network become as good as the current circuit-based voice network?
One solution is more bandwidth. If data packets arrive in a timely, uninterrupted fashion, voice quality would be perfect. Another approach is the ReSerVation Protocol (RSVP), now nearing formalization by the Internet Engineering Task Force. Essentially, RSVP will reserve and guarantee a certain amount of data network bandwidth so voice packets can be delivered in a timely fashion.
It certainly seems possible for voice calls over data networks to provide good quality, if the packets carrying voice have a guaranteed, timely path between subscribers. There is a certain irony here, because the circuit-based voice network has, for almost a decade, converted voice signals into digital data as soon as it reached the telephone company's equipment.
Ultimately, both voice and data traffic travels across the same fiber-optic backbones. Carried to its logical conclusion, the data network should have almost identical quality to the current circuit-switched voice network, but then it would probably cost about the same to use.
Michael Grishko -- a consultant, writer and sometime futurist -- is president of Nulogic Computer Solutions Inc. in Ottawa.
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