Pacific Connection(英語)

On the Internet: Voice Packets Now Compete with Data

I "phoned" my cousin Bob in Southern California the other day. Except, there wasn't any phone: just two PCs linked to the Internet via broadband cable connections. I had plugged a Plantronics headset into my sound card, then pulled up Microsoft NetMeeting, which has come bundled with every version of Windows since Windows 95. I "dialed" Bob's IP address, and, after some adjusting of the controls, we were talking.

"Can you hear me?" I asked.

"Can you hear me?," I heard myself say over his speakers. Bob wasn't using a headphone, and the echo from the delay in the Internet voice transmission was driving me nuts.

"You'll get used it," he said without a trace of compassion. Bob is my mothers' first cousin, a retired attorney who moved with his wife to the desert, where he hangs out with the lizards, revels in the blazing summer heat, and makes fun of people who hate telephone echoes. He regularly uses NetMeeting to link a three-way conversation with his son in Los Angeles and his grandson in Baltimore, on the East Coast. This is the techno-nerd side of my family. They even use webcams to see each other.

We opened up NetMeeting's whiteboard: I drew a circle in yellow; he drew a bigger one in purple. I opened up a mapping program, and he could see it. He opened up an Excel spreadsheet, and I could see it. We opened up the chat window and typed messages to each other. We talked for nearly an hour. The cost of the call: free.

NetMeeting and other PC-to-PC voice programs are the most rudimentary, and cheapest form of Internet telephony, otherwise known as "voice over IP", or VoIP. While people have been making calls over the Internet since 1995, the technology's biggest push is still ahead. VoIP has taken off among businesses and telephone companies and is changing how ordinary telephone calls are routed. The primary reason is cost-the lower cost of the connection, easier maintenance, and the convenience of managing data and voice over the same network.

From a network perspective, VoIP is more efficient because of its use of packet switching. Conventional voice traffic employs circuit switching, in which a single point-to-point connection is maintained for the duration of the call-whether or not someone is speaking. With packet switching, no circuit is held in reserve throughout the call. Packets can be sent by multiple routes and recombined at the receiving end. As with email and chat, voice callers only consume bandwidth when they are sending information, that is, when they are speaking.

Back in 1993, telecom expert Harry Newton wrote that "packet switching is a very efficient way of moving digital data around. It is not very useful for voice, yet, though experiments are underway." Ten years later, VoIP is no longer experimental. Many international calls go over it. Companies are reconfiguring their telephone networks to support it. In Japan, people are bypassing NTT with it. While there are still some glitches, VoIP has gone from a hobbyist toy to a serious business, one that could eventually overtake circuit switching for voice transmission.

The predominant standard for moving voice traffic over the Web is the H.323 protocol, which was ratified by the International Telecommunications Union in May 1996, H.323 defines how voice, data, and video traffic are transported over IP-based local area networks. An open source version of H.323 called the OpenH323 Project can be found at A rival protocol called SIP--Session Initiation Protocol-has been around since the late 1990s. Some vendors, like Cisco, support both.

VoIP is not problem-free. It is subject to latency, the source of the delayed echo I heard over NetMail. It is subject to "jitter," caused by the uneven transmission speed of consecutive packets. And it is subject to packet loss. Unlike data transmissions, voice packets are not recovered-they either arrive on time or are discarded. VoIP proponents argue that these problems can be minimized by reserving bandwidth, prioritizing voice packets, and-within an office-separating voice from data over the local area network. VoIP requires new equpment, which companies will purchase only when they see an economic payback. The VoIP revolution, if there is to be one, will take place only gradually.

According to Christine Hartman of Probe Research, 13 percent of international calls were routed over an IP network in 2002-including the public Internet, corporate intranets, and telephone carriers' private IP facilities. The New Jersey-based firm predicts the number will rise to 20 percent by end of this year. "VoIP is also being used for long distance and local calls, which go over the Internet at the premises, though the percentages are lower."

In Japan, by contrast, VoIP is primarily used to make domestic calls, says Hartman's colleague, Alan Mosher, who analyzes the small office/home office (SOHO) market for Probe Research. The reason is NTT's relatively high cost-per-minute charges, especially for local calls. (In the U.S., local calls are unmetered.) At the same time, Japan is ahead of the U.S. in its adoption of broadband services. "In Japan, broadband connections are much faster and cheaper than in the U.S.," Mosher says. While the going rate in the U.S. for DSL and cable services is about $50/month for 648Kbps service, Moser estimates that 8MB service in Japan costs only $20 to $25, with 12 Mbps for just slightly more. VoIP in Japan is becoming even more attractive as VoIP providers offer free calls between subscribers. Yahoo!Japan has done that for its own subscribers, as have five other ISPs on a reciprocal basis.

As a result , an increasing number of broadband subscribers are using VoIP services. Back in July 2001, says Moser, Yahoo!Japan had 660,000 DSL subscribers, of whom 200,000 also subscribed to voice. More recently, the service had 1.97 million DSL subscribers, 1.58 million subscribing to voice. "The gap is closing," he says, and NTT is under pressure. "Like telephone carriers throughout the world, NTT is seeing declining numbers of people using conventional circuit services. Wireless has already cut a huge chunk out of conventional telephone services, and VoIP will continue the trend." Moser thinks Japanese-style VoIP service could succeed in other countries, as well, including the United Kingdom, Germany, and France. "Any place with metered local service and widely available broadband connections is a good candidate."

PC-to-Phone: cheap international calls

The Japanese model-in which the household telephone is connected to the Internet via a small gateway-is not very common in the U.S. But I was able to test out a PC-to-Phone service offered by Net2Phone since 1996. These days, corporate calls to satellite offices represents the bulk of Net2Phone's business, but the company still offers the service, which enables you to make a call from your PC to someone else's phone. To use it, you download the Net2Phone CommCenter software and put some money in your account. The software, which includes a dialpad and advertising, simulates the sound of a real telephone phone going off-hook and the beep-beep sound of the DTMF tones. You specify a country, enter the local number, and click "dial."

I placed calls to friends in Japan and Europe. The quality and delay varied, but all went through. A call to an old college buddy now living in Belgium was clearer than an ordinary phone call. Another to Holland had a slight echo. The Japanese connection had a low tonal range, but all three calls were understandable. The cost was about 7 yen per minute, about half of what I would have paid if I had used my phone, though comparable to what it would have cost me using a prepaid calling card, such as the one offered in the U.S. by Net2Phone, itself.

A PC-to-Phone Net2Phone call is routed over the Internet to the company's network, which converts it to a circuit-switched signal and sends it via the public telephone switched network (PTSN). At the receiving end, the telephone rings and the call goes through, just as with any other call. Most Net2Phone's customers making calls this way are outside the U.S, because the pricing for international calls in the U.S. is so competitive that the savings are minimal. "People won't use their computer to make a call if they only save a penny a minute," said Sarah Hofstetter, Net2Phone's senior vice president of corporate communications. "For the most part, we offer these services in countries that have recently opened up the telephone market to competition and the pricing structure doesn't yet reflect it. Typical savings for Net2Phone customers ranges from 50-75 percent."

A "carrier's carrier" transports international calls by VoIP

You don't need a PC to place a VoIP call. Most calls going over the Internet are phone-to-phone. Consider ITXC, which was founded in 1997 by Tom Evslin, who previously headed AT&T's WorldNet Internet service. ITXC is a carrier's carrier of international long-distance; it sells transport services to telephone companies on a wholesale basis. "Voice over IP is a well-proven technology," says John Landau, IXTC's executive vice president of product management. "It's not flawless: you can get bad quality if you have too much packet loss, latency, or jitter. The very edge of the consumer networks are at most risk for that, especially if you have a dial-up network. If you have a broadband connection, the data compressed rates are 8-12 Kbps per voice channel-which is sufficient to make it work.

ITXC peers up to the Internet with companies like UUNET, Genuity, British Telecom and AT&T. "Our agreements give us significant bandwidth pipes," Landau says. "And once we are on those big bandwidth highways, traffic flows very nicely." Calls begin with an international long distance carrier or prepaid service provider. The call is then routed over ITXC's network, which sends it over the Internet to an overseas carrier, which delivers the call. ITXC is paid by the originating carrier to take the call, and pays the receiving carrier to deliver it. Capital costs are low-IXTC doesn't lay cable or need to do so. Its network is a logical network within the Internet, and its service, strictly speaking, is an Internet application.

Landau says the quality of ITXC-routed calls it is at least as good as PSTN; sometimes better. "The key is to have enough capacity, whether on a switched network or an IP network." Calls are monitored for quality at the company's headquarters in New Jersey. "The process resembles an air traffic control facility. We may push traffic onto a different route or, more rarely, will move calls to PSTN." The company monitors traffic at the IP level, looking at the jitter, loss packets, and latency-and it monitors traffic at the voice level, checking for quality. "If we randomly shot traffic over the Internet, there would randomly be periods of congestion that wouldn't be resolved," says Landau. " But we're not random-we have a sophisticated set of routing and management software that we've developed over the last five years."

ITXC has steadily expanded its service, which began in the U.S. and has spread to Europe, China, and South Africa. While the company has no publicly announced relationships with carriers in Japan, Landau says it handles calls in and out of the country. The company has also gone into the domestic call transport business. "Telecom Italia and China Unicom use VoIP inside their existing networks-and it's extremely cost effective," says Landau. "They lay out new data backbones and instead of maintaining a separate, parallel network for voice, they run VoIP over the data backbones." In Bolivia, the company worked with COTAS/Teledata to create a national long distance network. "To their surprise and our pleasure, the quality of our calls was better than the competition's-the former monopoly carrier."

I asked Landau whether he thought conventional voice circuit switching was headed for extinction. "Not overnight. When something's working you don't throw it away. But circuit switching has a limited future. As the cost of ownership of the switching equipment gets high, it will eventually be phased out. Instead, we'll see big data networks continue to be built, with voice offered as a service over those networks.

NEC's IP-enabled PBXs

Corporations are also moving to VoIP, either by adding IP cards to their PBXs-creating so-called IP-enabled PBXs-or by eliminating the conventional PBX entirely. Not surprisingly, PBX manufacturers favor the first method, arguing that it preserves customer equipment and software investment. For the vendor, of course, it also preserves the customer. The second approach, much less conventional, is being pushed primarily by Cisco, which has slowly but convincingly moved into the VoIP market. In both cases, the typical customer is a company with smaller offices, such as a bank with branch offices surrounding a regional ones. Traditionally, the bank would install a low-volume key system to direct calls at each location, perhaps with a leased lines back to the main office. The data network would be entirely separate. With VoIP, the two networks are combined and the switching equipment might be off-premises.

Paul Weismantel, director of enterprise solutions for NEC America, describes a Florida customer who opened a call center on the island of Jamaica to take advantage of lower labor costs. "Ordinarily, they would have installed and managed a separate voice system-but there were no local staff people to do that. Instead, we installed IP telephones and ran them off of an NEAX 2000 IPS switch in Miami." The advantage, says Weismantel, is that you can make the transition to VoIP gradually, in whatever ratio needed, whether you need five IP phones or 500. You can also use your existing digital phone with an adapter.

NEC has added IP switching capability to other PBXs, as well as to its Electra Elite IPK key system. Weismantel argues that its approach of retaining existing equipment makes sense because most companies will never go entirely VoIP-unless they move to new facilities. "If you already have copper [the medium used for circuit switching], the payback for transitioning everybody to IP is much more difficult than if you are starting from scratch." Moving voice to the data network puts additional burden on that network. Some network managers have been shocked to find that their 'robust' network is suddenly starved for bandwidth," Weismantel says. The problem is amplified because voice traffic flows peer-to-peer, rather than to a central mainframe or server farm.

NECs strategy is to move its conventional telephony applications over to IP. "The end-user experience has to be identical, otherwise, IP telephony simply won't be adopted. It becomes disruptive to the business. Some other PBX companies have offered IP in a hybrid environment. But they've built a new set of terminals and a whole new switching architecture, forcing the customer to make a major choice. It's a choice they shouldn't be forced to make."

Despite all the attention, IP remains a " small sliver of NEC America's total business," Weismantel says. And although most of the development work for NEC IP products is being done in Japan, America has been quicker to deploy it. "Japan is more conservative in their adoption of IP telephony, especially in larger corporations. Most movement has been among smaller companies, especially retailers. Larger Japanese companies already have their infrastructure in place."

LAN telephony: Cisco banishes the PBX

No company has been more vocal about the benefits of VoIP than Cisco. The company that made its name as the pipe-and-router provider for data networks would like to do the same thing for voice. Cisco doesn't even like the term "PBX" for the kind of VoIP it does, preferring "LAN telephony" instead. "If I put an IP trunk card into a conventional TDM [time division multiplex] PBX to make it compatible with IP phones, the dirty little secret is that it's still a TDM PBX," says Craig Cotton, manager, product marketing for enterprise voice and video business unit. "The PBX companies are not our friends, and did not like us entering the market. The one I used to work for has seen nine straight quarters of declining revenues. Cisco has largely driven IP telephony, and we've forced many PBX manufacturers to embrace it. For Cisco, telecommunications represents a growth market in which it has a 50 percent share."

Cisco has now shipped more than 1.4 million phones to some 6,000 customers. Among the largest deployments are financial services companies, like Merrill Lynch. Some banks with many branch offices are putting in clusters of call manager servers in their data service centers where they would have used a small PBX. At the branches, they are just putting in IP phones, using the data network to have the phones register. Cisco has customers with hundreds of sites running off the centralized cluster.

Smaller installations are doing the same. "It's awesome," says Mike Luter, Chief Technology Officer of the Cancer Therapy and Research Center, in San Antonio, Texas. "We put the Cisco system in 1.5 years ago: 800 IP phones spread over three locations, that all tie back into the medical center." Luter says the advantages of VoIP would be apparent even within a single building, because the LAN infrastructure can be used for voice. "When we expanded the medical building from 80,000 to 200,000 square feet, we saved $58,000 on the cabling alone."

Installation was also simpler. "With a classical PBX, if you want to add a phone, you need a line card to establish a point-to-point connection. With Cisco, they're not needed. Call agent software runs on Compaq servers managing all call traffic. If you want redundancy, you can get two of them. I plug an RJ45 jack into an Ethernet connection, plug a phone into the other end, and plug the computer into the phone-and I'm set."

Cisco itself has the world largest corporate IP network. The company has 35,000 phones sending voice over the Internet-about 22,000 in the San Jose, California campus, alone. The transition took about 2.5 years. "During the transition period, some users had PBX phones, others had IP phones, and you couldn't tell the difference," says Cisco's Craig Cotton. He argues that Cisco is not new to VoIP. The company started doing voice over IP when it acquired a company called StrataCom-putting voice over frame relay and ATM. In 1997, the company started doing toll bypass, sending voice traffic from a PBX to a router, which compresses and transports the signal, reversing the process at the other end. Cisco started selling IP phones in 1999, and the following year, launched a new release of CallManager in which, if a server goes down, the phone will find another one.

The case in favor of IP-enabled PBXs is that the transition is easier. You use your existing PBXs, add IP cards, and gradually shift over. But Cotton [?] argues that the transition costs are comparable with LAN telephony, that adding a call server to the network is no more expensive than adding line cards. In a conventional business configuration, phones are plugged into PBXs, PCs into the local area network. In Cisco's universe, the PBX goes away and one or more Ethernet switches are used for both voice and data. Each IP phone is plugged into a Cisco Catalyst Switch, and the user's PC is plugged into the back of the phone, thereby eliminating the cost of the PBX phone port. Cisco still segregates voice from data traffic using a separate "VLAN" to maintain quality, while providing additional security for the voice traffic. The VLAN also eliminates the need to change the IP scheme within the company. The PCs still get the IP addresses, while the phones use an internal, non-registered address.

The phones, in turn, get their instructions from the call manager server sitting on the network. If the call is within the campus, the routing server translates the extension number into an IP address and rings the called phone. When the Ethernet switches connect the call, the routing server drops out. By contrast, in a conventional voice network, all calls get routed through the PBX. "At least an order of magnitude less gear is required," Cotton [?] says. "We can register 7,500 phones on a 3.5-inch tall server."

A call outside Cisco is routed through a gateway, also on the network, with phone trunks connected to it. The gateway routes the calling information over the circuit network. Calls to other Cisco locations are routed like email, over the wide-area-network, with the voice packets given priority to help assure quality. That's critical over a WAN, Cotton [?] says. On a LAN, calls can go out uncompressed-consuming about 80K of bandwidth including the voice packets and overhead. "80 Kbps of traffic on a 100baseT connection represents .1 percent of the bandwidth on that link. For that reason, some customers who have a well-architected LAN see no reason to do quality-of-service on it, although we always recommend it. Contention is always a possibility."

Cotton says that the main advantage of LAN telephony is a lower cost of ownership. Voice and data can be managed from a single network. Maintenance costs are lower. "Servers are a fraction of the cost of PBXs, even if you put two in and use one for backup. Moves and changes are easier. I've been at Cisco five years and have moved offices at least five times, and people here are moving constantly. When we had a PBX, we paid a contractor a $150 a move. With IP phones, Call Manager tracks employees not by IP address, but by MAC address. That means when I plug a phone in to a new port, it automatically registers and gets an IP address assigned to it via DHCP [Dynamic Host Configuration Protocol]." And, of course, fewer T1 lines are needed to carry voice. "Our customers are saving an average of 20 percent on telephone and facilities cost."

Cotton says that LAN telephony has created a new niche for software developers. "What was missing for the last 25 years in the PBX world was a lot of innovation around third-party developers. We've facilitated that by adopting open APIs, including TAPI, JTapi, XML and SOAP." Phones are even more common than PCs, and IP phones, like any other network node, can access network data. "Companies are using the IP capability and the XML capabilities of the screen space on the phone to tie in to dozens of different back-end database systems. High-end hotels, for example, are putting IT phones in rooms to help guests order room service and check out. The U.S. Department of Commerce, which operates out of a massive building in Washington D.C. was looking at an analog paging system for $1.5 million to help with emergency evacuations. One of our partners came up with a system that plays pre-canned emergency messages stored on a server And flashes information on the displays of the IP phones. It cost $150,000-an order of magnitude less than the analog solution."