Review: Voice over IP routers

Voice and data together? Not on my network.

That's what many network managers said just a few years ago. They worried that voice traffic would suck up bandwidth and interfere with vital data transmissions. And early Internet telephony suffered from poor-quality voice communications, difficulty with directory assistance and an inability to integrate with applications such as voice mail.

Our tests of four IP telephony gateways show that's no longer the case. With the four products we tested, the quality was better than cell phone calls. We liked Oki Network Technologies' Internet Voice Gateway BS1200 the best for its easy installation and low price. At $7,395 for four channels, this device can show a quick return on investment for a company with multiple geographically dispersed branches.

But large companies with extensive investment in IP-based frame relay networks might benefit with highly scalable server-based products, such as Inter-Tel, Inc.'s Vocal'Net and NeTrue Communications, Inc.'s NeTruePhone. For a company simply trying to connect two offices together over the Internet, V/IP, a product from Micom, a division of Nortel, might be the better choice.

We invited many more vendors than the four we tested, but we found that the vast majority of companies were still in early beta testing and preferred not to submit a first-version product for review.

On the other hand, one company's product was so large (about the size of a refrigerator) the firm said it would need weeks to prepare to ship the product to us.

The products prove the Internet has emerged as a cost-effective alternative to the public switched telephone network (PSTN). The new generation of Internet telephony systems are gateways that connect to TCP/IP networks - the Internet or private IP-based frame relay networks. A company that maintains a dedicated IP backbone or high-speed connection to the Internet can set up a voice-over-IP gateway on the network in the same fashion as an e-mail or Web server.

Despite the enthusiasm, it is important to note that while private networks can offer a reliable voice-over-IP service, any product deployed over the Internet is at the mercy of available bandwidth resources. Peak traffic periods on the Internet could result in a poor-quality conversation.

Dozens of companies are releasing Internet telephony systems that provide real-time voice communications over the Internet. These products don't require you to use a microphone attached to a sound card on your computer. You use your telephone as usual, but instead of dialing 9 to get a telco dial tone, you dial a 6 or a 5 to get an Internet dial tone. Surprisingly, call quality across the 'Net is comparable to calls made over the PSTN.

Call handling

Perhaps the most important factor in voice-over-IP products is call handling, or the ability to emulate and integrate with existing phone systems. The ideal is 100% transparent integration; in this scenario, you dial 8 or 9 to get a dial tone and your PBX automatically chooses the least costly route, be it an IP connection or a more traditional one.

None of these voice-over-IP products approaches the ideal. At best, callers are required to enter access codes akin to those used with traditional tie lines, especially for the products aimed at service providers looking to offer Internet telephony services.

For example, in order to get access to the NeTruePhone and Vocal'Net systems you have to dial user ID information, much like you do with a voice messaging or calling card service. The Inter-Tel, and especially the NeTrue system, appear best suited for service providers such as ISPs, though both can be set up and configured for businesses.

Call quality, however, is as good as a standard telephone conversation, even on networks loaded with data. That's due in part to the fact that all the products we tested support a small 8K bit/sec packet (as the ITU G.729 standard requires); such systems don't suffer when bandwidth is limited.

In-band integration with call processing systems worked well all around. Under load, however, we found a tendency to receive packets late, resulting in a small echo known as jitter. Jitter suppression technology is a clear requirement for these systems. Of all our participants, the Oki system controlled jitter best and provided a lot of documentation on understanding the cause of jitter.

Manageability

Voice-over-IP systems are administration-intensive, forcing you to designate which ports can be configured for voice and which for fax, as well as ways to integrate the voice-over-IP system with phone systems. Thus easy administration is a big plus.

Inter-Tel's Vocal'Net leads this field with the ability to manage its databases, line interface cards, network interface cards (T-1s, E-1s and more) and quality-of-service (QoS) options. Inter-Tel also has an impressive call accounting and call management package called Inside Track.

Oki's Internet Voice Gateway is managed through a serial interface, much like a router. The remaining products are managed through dialog boxes in Windows 95 (Micom's V/IP cards) and Windows NT (Inter-Tel's Vocal'Net and NeTrue's NeTruePhone).

The graphical user interface-based applications use simple data entry screens, not unlike the dialog boxes that abound in the Windows Control Panel. SNMP management is a prerequisite for these systems. SNMP allows the devices to be managed along with other TCP/IP systems as a unified collection of Internet services. According to the vendors who supplied the information in our Buyer's Guide Chart on page 72, all these products support SNMP.

PBX integration, reliability, scalability

All the products we tested let you plug in standard telephone lines and have a range of digital and analog options. Inter-Tel's Vocal'Net provides more sophisticated and advanced PBX integration options than the rest of the products, letting you set up lines for a variety of telephone system integration options. With Vocal'Net we could connect directly to the telephone company (gateway ports) or to a PBX or key system.

While the voice-over-IP systems we tested were not running for long periods, the hardware architecture we inspected was impressive and clearly designed to run for long stretches without failure. All the systems remained stable during tests, and all but Micom's can be clustered using third-party redundancy tools for Windows NT.

However, to illustrate just how vulnerable the technology still is, we were able to shut down every system we tested by simply dropping User Datagram Protocol (UDP) packets at our firewall. This left us wondering how we could reconcile our voice-over-IP plans and security concerns.

Like reliability, it's hard to test scalability, especially with only a single unit from each vendor. There was not much information in any product's documentation detailing how to tie systems together as a single cluster. Vocal'Net's and NeTruePhone's software could clearly accommodate hundreds, if not thousands, of users. All the systems except Micom's run under Windows NT. While Micom is working on an NT version, the Micom cards under Windows 95 currently are a difficult sell for scalability.

Oki's solution integrates with the Internet Domain Name System (DNS). Oki's DNS feature maps IP addresses to an Internet telephone "numbering plan," using IP addresses of the units as gateways or routers of Internet voice traffic. The Oki system allows you to resolve up to a maximum of 2,045 such host gateways using DNS.

Without using DNS, you would have to enter host or gateway lookup information. It was unclear how the other products we tested find gateways on the Internet (other than implicit linking of systems over point-to-point virtual circuit) to patch a call through. We could thus initiate conversations only between two identical systems. (Proponents of Internet telephony are working on standards to allow gateways to interoperate and communicate with each other, just as the switches on the PSTN do.)

Documentation

No matter how good a product's features, it can be difficult to use without good documentation and support. The manuals from Oki and Micom provide extensive insight into their respective architectures, adherence to standards, technology used, network planning and more. Oki goes to great lengths to cover diagnostics, network planning, QoS and technology limitations. Oki's manuals suffer a little from inelegant translation from Japanese but are organized the best - comprehensive in scope and attentive to detail.

Inter-Tel's documentation, on the other hand, is aimed at computer telephony and network engineers and technicians, rather than at MIS and IT administrators. Inter-Tel's Vocal'Net manuals are thorough, detailed and clear for installation and setup tasks. We were overjoyed at the extensive coverage of phone, central office and PBX integration options. However, we would have liked more detail on technology behind the scenes and philosophy of operation.

The NeTruePhone documentation is limited; we read the entire manual in 10 minutes. It offers inadequate phone system integration information and virtually no product background.

Installation and setup

Oki's Internet Voice Gateway was the easiest of the four products to install and fire up. The entire unit is built into a small case that can fit into a briefcase. Setting up and connecting lines and settings takes about 15 minutes.

The NeTruePhone is also easy to install. The thin manual briefly covers assembling a system, but the boxes we received were all ready to go. Connecting cables is a bit tricky. Without the knowledge of what a Dialogic Corp. voice card is, you would have a hard time trying to guess where to plug in the telephone lines and where to put the network cables.

Also strange is the requirement to hard-code a specific Internet routable IP address into the system prior to shipping, presumably to protect the system against unauthorized use. This makes the system more suitable for service providers rather than corporations, which might prefer a system that was not bound to a legal InterNIC-allocated IP network ID.

Micom's V/IP gateway relies on proprietary adapter cards that plug in to any Windows 95 machine. The whole effort is not unlike setting up a sophisticated modem or fax card. There are various DIP switches and settings with which to play. We spent a solid day on the setup of the product.

But Inter-Tel's Vocal'Net is the most time-consuming to set up and install. It comes as a kit that includes two Hewlett-Packard Co. Internet Server machines. Software setup and configuration under Windows NT is a lengthy process, as complex as setting up Microsoft Exchange Server or an advanced voice/fax messaging system.

Voice-over-IP technology shows exceptional promise, with solutions ready to be fired up now. Emerging standards, such as Resource Reservation Protocol that can reserve bandwidth for voice communications, and support from heavyweights such as AT&T, will add to the promise. Still, we have a long way to go before the borders of the 'Net and the PSTN become indistinguishable. RELATED LINKS

Shapiro is president and CEO of TekMatix, Inc., a systems integrator in Coconut Creek, Fla. He is the author of Computer Telephony Strategies, among other titles. He can be reached at jeffreys@ tekmatix.com.