SIP breathes new life into voice over IP

A new class of flexible, instantaneous, multimedia applications enabled by Session Initiation Protocol could well be the impetus for more companies to deploy converged networks.

Despite years of hype, the convergence of voice and data networks onto a single IP-based platform has failed to gain much traction. According to Gartner, voice-over-IP migration actually slowed a bit in 2001. InfoTech estimates that only 6% of U.S. companies have scheduled volume rollouts of IP LAN telephony.

Still, with all the PBX vendors now shipping IP-based PBXs, there's not much doubt that eventually converged networks will become the norm. "It's no longer a question of if, but when," says Gartner analyst Kathleen Simpson. But if there's plenty of life left in your PBX, you aren't likely to scrap your circuit-switched, TDM voice network unless there's a compelling reason to do so. And that's where SIP-based applications come in.

"TDM is the world's sturdiest, most ubiquitous network, and you need sound business reasons for replacing it," says Dave Moore, director of Nortel's enterprise marketing team. "Finally, here are the applications you cannot do in the TDM world. Once companies see how they can marry these technologies to their businesses, you will see VoIP adoption rates go up."

SIP is a simple, lightweight protocol that lets end users instantly set up interactive communication sessions. These sessions can include any combination of voice, video and data, and SIP-enabled gear will automatically recognize the type of presence each participant maintains. This would let businesses respond quickly to crises by pulling people into sessions over whatever connectivity method is available to them. During these sessions, people can send files or Web pages to one another and browse or use applications together.

Image problems

However, some major hurdles must be cleared first -- even if they involve perception more than reality:

Reliability is still regarded as a major issue, and data network infrastructures might need costly upgrades to provide the stability and redundancy required for 99.999% uptime. Routers and switches have to be voice-capable, all traffic to desktops must be switched, and cabling might need to be replaced or terminated again. The voice quality problem largely has been licked, but only if there is plenty of bandwidth from end to end. Also, there is still work to be done on a standard for delivering electrical power to phones over Ethernet.

However, some early VoIP adopters say experience has put their reliability concerns to rest.

"Our [Cisco AVVID] IP PBX has been more reliable" than a traditional TDM switch, says Byron Vielehr, CTO in charge of Merrill Lynch's 5,000-user VoIP installation in Hopewell, N.J. "We put in [universal power supplies] when we were building the network out, so when we lost power to the facility, the IP PBX stayed up and running beyond what a legacy system would have been able to do."

The distributed nature of IP infrastructures also provides some inherent fault tolerance that centralized PBX switches don't have. When the Sept. 11 terrorist attacks took down the local public phone network, Merrill Lynch restored phone service to employees in New York City by connecting them to the VoIP network in New Jersey.

The feature gap between VoIP and TDM switches also has been narrowing.

"Many of the 500-odd features in legacy PBX systems were not available in any IP-based voice switches until recently," says Mark Straton, a senior vice president in Siemens' enterprise networks division. "You paid more and got less." Today, Cisco's pure IP PBX platform offers about 300 features, and most users will never miss those that are absent.

Also, because the IP PBX is an open platform, "you can add such features yourself by writing a little code, and you can deal with it on the application side," Vielehr says.

The softswitch foundation of IP PBXs also creates some image problems. While traditional PBXs have separate physical ports for each end station and switch calls on physical circuits, IP PBXs are software-based and use virtual ports. This makes them seem less solid, but it conveys a huge advantage.

"We can leverage the packet and server and [operating system] technologies to produce triple the performance of our largest Definity PBX," says Jorge Blanco, director of planning and strategy for converged enterprise systems at Avaya. "You can support more users and more calls."

Softswitches are inherently more flexible and can carry voice, video and data traffic more efficiently than platforms using traditional hardware switching, making it easier to implement new features and applications.

However, superior scalability and performance are not the current perception people have of them. "The sweet spot for VoIP is still environments with less than 100 lines," Simpson says.

Where's the ROI?

Return on investment (ROI) is probably the biggest single stumbling block for VoIP. "That's what customers ask first," Blanco says. "�Show me the ROI.'"

One problem is that existing PBXs have a lot of life left in them, in part to Y2K-driven upgrades. And most early adopters of VoIP agree that instant savings are not what you should be sought.

"We expected VoIP to cost more," says Christopher Roth, IT manager for Digirad, a San Diego medical-device manufacturer that has implemented a VoIP network based on Avaya technology.

In early 2000, Digirad was outgrowing a Norstar key system and decided to replace it with an IP-based platform. Nortel didn't have one yet, and Roth and his staff rejected a pure IP player in favor of Lucent (now Avaya). "When I need voice support, I want to call Bell Labs," Roth says.

On the plus side, VoIP has reduced the cost of moves, adds and changes. Also, going with a softswitch eliminated the need to put a separate switch on each of the company's two locations that spans seven buildings. There is money to be saved via toll bypass, especially on intrastate long-distance traffic.

However, the cost of additional bandwidth and bandwidth management have more than offset the savings. "Bandwidth is fine on the LAN links," Roth says. "The problems always occur over the T-3 WAN links. During peak times, voice occasionally degrades a bit. But for the most part, people don't notice." He says he occasionally maxes out three T-3 connections with the voice and data traffic generated by 200-plus users.

A trade-off between easier administration and harder management is typical in VoIP environments, although vendors say they are addressing the issue of VoIP packet monitoring.

Roth expects the real VoIP payoff to come in the near future, when integrated voice/data applications start to appear.

"Entire call centers will move to SIP to erase the seam between voice communication and CRM applications. And SIP will change the way businesses do [video teleconferencing], and put this very rich mode of communication within the reach of more people," he says.

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SIP breathes new life into voice over IP

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