IP telephony: A cost-effective call

Although most network managers have long been familiar with the potential cost benefits of consolidating voice and data, few IP telephony products were ready for deployment in the enterprise.

All that has changed in the past few months, as several vendors began shipping voice-over-IP gateways designed for corporate use.

The recent entry of major network hardware vendors has helped legitimize the nascent IP telephony market. For example, several Cisco Systems, Inc. products now accommodate IP voice cards, eliminating the need for PC-based gateways. Managers can add IP voice capabilities when they upgrade their routers.

Several other vendors offer voice-over-IP gateways that run on Windows NT Pentium-class PCs. These platforms host call-processing software and accommodate voice cards with powerful Digital Signal Processors for rapid analog/ digital conversions.

A PC-based voice-over-IP gateway typically fits between a PBX or key system and a router. Many gateways rely on the PBX for some functionality, while products from PBX vendors such as Lucent Technologies, Inc. or Nortel tend to be more tightly integrated. Some IP voice gateways can even replace a PBX by providing similar functionality.

Naturally, voice quality should be a top priority. You can't save money if employees won't use the system. Although there is considerable variance among suppliers, most voice-over-IP gateways deliver acceptable voice quality on intranets with only minor network tweaking. However, business-quality voice over the Internet is still a distant goal.

As you'll see in the accompanying Buyer's Guide Database, prices range from just over $1,000 to hundreds of thousands of dollars, depending on capacity and features.

Ask vendors to give you estimates for the specific configuration you need. Although you may pay more attention to pricing a voice-over-IP gateway with high-capacity, digital interfaces for use in corporate headquarters, the bulk of your IP telephony investment will probably go toward smaller systems with two to eight analog channels for all your branch offices.

Be sure to also think about a gateway's life-cycle cost. Installation can be relatively complex, and ongoing maintenance expenses are significant. Today, most buyers expect a payback in one year or less. A return on investment is often achievable in just a few months if your company makes lots of international calls.

As the info in the database indicates, most voice-over-IP gateways supply at least one T-1/E-1 connection to the PBX, while a few also support ISDN lines. The few products in the chart that support analog lines are designed for small offices that only use a few phone lines. Regardless of line type, the majority of voice-over-IP gateways support Ethernet or Fast Ethernet.

While product reliability isn't yet up to traditional telephony standards, many voice-over-IP gateways provide some level of redundancy. For instance, nine products in the Buyer's Guide offer backup power supplies, several feature hot-swappable gateways and/or cards, and a few provide redundant disk drives.

More than half of the gateways also feature automatic public switched telephone network fallback. The very need for such phone network backup highlights the comparative frailty of IP telephony systems.

All vendors offer remote management of multiple gateways from a central location. Because remote sites often lack appropriate technical expertise, this capability merits close examination. Remote diagnostic testing and error-logging capabilities are other important requirements.

Look for ease of use and automation as well as comprehensive management capabilities. For example, automatic updating of phone directories throughout the network greatly simplifies the ongoing administration of changes in users and sites. Consider choosing a product with support for SNMP, which is emerging as a de facto standard to facilitate interoperability with other network management systems and devices.

Thorough and clear documentation is a must, and online help features are a plus. Graphical user interfaces are helpful.

Most voice-over-IP gateways support several compression schemes, such as G. 711 and G. 729. A selection of choices lets you tailor compression to meet your unique network conditions and performance requirements. Support for International Telecommunication Union standard compression methods will eventually help vendors' equipment operate with their competitors. On the other hand, proprietary methods can provide important performance advantages.

For now, you'll need to buy your entire IP telephony system from a single supplier. Although standards work is steadily progressing, it will be some time before you can confidently mix voice-over-IP gateways from multiple vendors. In addition to voice compression and call setup, common approaches are needed for such critical features as numbering, remote configuration and fault diagnosis.

To diminish some of the risk of relying on a single vendor, favor vendors that have made commitments to implementing standards such as the International Multimedia Teleconferencing Consortium's recently approved Version 1.0 voice-over-IP interoperability implementation agreement. But formal conformance testing and certification processes are still lacking, so you'll need to rely on informal testing between individual suppliers. RELATED LINKS

Review of VoIP gateways

Interactive buyer's guide
Find a gateway based on your specific criteria, or download a spreadsheet containing specs for 26 of them.

The Virtual Voice
The site for IP telephony novices. It includes a very basic Internet telephony tutorial, as well as a newsletter, product listing, FAQ, and news listing.

Voice over IP
Another intro to the field.

Pulver.com
This site is loaded with research materials, transcripts of VOIP conferences and speeches and vendor listings.

Telecommunications Tutorials and Articles
Tutorials on connecting PBXs to the Internet and a descriptive introduction to 'Net telephony, plus a comparative analysis of Internet telephony gateways.

Internet Telephony Consortium
Group of vendors and service providers working to advance IP telephony as it relates to standards and technology developments.

More IP telephony links

Hall is the vice president of research at telecom consultancy Action Information Services and the principal author of a comprehensive Internet telephony market study. He can be reached at shall@ actioninfo.com.