Six Things You Need to Know About VoIP

Courtesy of Networking Pipeline

Do you think you know VoIP? Think again. There are plenty of myths and misunderstandings about the technology making the rounds. To help separate the truth from facts, we contacted more than 30 experts, and asked them to dispel the most common myths, and give you the straight truth. Here's what they told us.

Is VoIP just about voice?

The clear consensus of our experts is that the future of VoIP is more about a broad, new landscape that brings messaging, services, and apps to the desktop than simply about voice. Phil Edholm, VP of network architecture for Nortel Networks' Optical Ethernet and Enterprise Product Portfolio business units, suggests that an appropriate term for this converged networking is IP Multimedia.

Like other experts, Doug Fink, VP of IP communications for Calence, notes that SIP and presence likely will lead the way, with multichannel requests such as email and the Web looking more and more like real-time requests. Greg Welch, president and CEO of GlobalTouch Telecom, points to VoIP services and applications that listen to an e-mail on a handheld device or forwards voicemail as an email attachment. Telephone, fax, e-mail, and video conferencing no longer are fixed to locations. "Click a contact in Outlook or say a name to locate that person no matter where or on what device," adds Welch.

Jon Doyle of CommuniGate Systems chimes in with the convergence charge: "Call my email address? The long-term view is for users to have one data and voice address for all [IP-based] interactions." Meanwhile, Ray Prescott, CEO of VoxBox World Telecom, says that PDAs soon will have the same functionality as cellular in a WiFi hot spot through VoIP.

Does VoIP provide quality conversations?

The jury is still out on the question of VoIP quality compared to traditional phone systems. Mike Grieb, project manager for Technisource, says VoIP got a bad reputation largely from poorly engineered data networks when introduced, but adds that, properly engineered, VoIP is equal to or better than toll-quality voice. Grieb notes that the most common voice encoding scheme, G.711, is designed to be exactly equal to the public voice network in terms of quality, with a frequency spectrum of 300-3000hz.

As Grieb points out, while voice doesn't require much bandwidth, it requires error-free delivery. Networks designed to work well for data can tolerate occasional errors, but those errors may manifest themselves as pops, static, or worse in voice transmissions. Grieb further observes that the average Internet connection often has 2-5 seconds or more of delay to compensate for best-effort transmission. The problem comes when you want interactive audio. Imagine, suggests Grieb, having a discussion and you must wait for 5 seconds before responding. Too late, the other party has started again.

Eric Bear, VP of product management and global business development at Viola Networks, comments on a common VoIP complaint: "VoIP sometimes makes you hear things twice, makes you hear things twice. VoIP does not create the echo. Point your screwdriver at the PSTN equipment. VoIP can actually offer richer sound quality."

How secure is VoIP?

Our experts mostly concur that VoIP security isn't yet where we need it. Andrew Graydon, chair of the Security Requirements Committee of the Voice over Internet Protocol Security Alliance and CTO of BorderWare, observes that traditional firewalls don't protect VoIP calls due to the dynamic nature of real-time SIP communications. "Voice traffic raises technology challenges because voice packets must be encrypted and traverse a firewall without undue latency." Graydon adds that network threats are becoming more common. A VoIP attack could bring down an entire network. "Security problems include voicemail spam, identity theft, impersonation, session eavesdropping, voicemail bombing, hijacking, and redirection."

Grieb adds that a hacker who can access your data stream can decode the voice protocol. The good news is that whatever is deployed for data security also is applicable to voice packets.

How does VoIP affect network bandwidth?

The experts diverge about the effects of VoIP on bandwidth, though most express significant concerns. Bear observes frustration when he says, "Bandwidth, bandwidth everywhere, and I still can't make a call. Capacity isn't enough for voice; configuration and connectivity must be considered." Michael Mullaley, director of enterprise marketing at Ciena Corporation, adds that when VoIP traffic exceeds 100 gigs per day, an IP-routed WAN begins to drop packets, which easily can exceed the capacity of even mid-sized businesses. Telemarketing spam, phishing attacks, and other nasties can consume more network bandwidth than traditional messaging threats and can slow down network performance, says Graydon.

Advantages of VoIP come from a network infrastructure that carries both voice and traditional data traffic, but that can lead to potential contention for bandwidth and performance degradation, such as jitter and delay due to congestion, say experts such as Myles Falvella, director of product manufacturing and corporate communications for TelCove.

Meanwhile, Grieb observes that voice bandwidth is "very thin," with the most common encoding schemes requiring about 100kbs per conversation at most. Compared to even a 10Mbs connection to the desktop, that represents 0.1 of a percent of the bandwidth. But he argues that "the trick is to not let too many conversations on the network." In legacy voice, this is not a problem because of a finite number of lines off the network. If you need an outside line and all of them are used, you get a busy tone. The VoIP limited bandwidth segments must be engineered to do the same thing. If you need 60% of your bandwidth for data, then when 40% of bandwidth is used for voice, you must refuse the call attempt.

What are some of VoIP's installation and implementation issues?

More than any other subject, our experts expressed views about the installation and implementation of VoIP. Eileen Haggerty, director of solutions marketing at NetScout Systems, emphasizes that managing VoIP rollouts should include a predeployment network audit of applications and their priority. She adds that your existing WAN infrastructure may not support VoIP services the way you need it to do and you should consider WAN technologies, such as MPLS, designed to handle multimedia traffic according to priority levels.

Matt Sines, COO of Fonix Teleco, observes that some IT contractors block some SIP ports and FTP traffic in the name of securing a LAN. Customer configurations must be tested prior to installation. "Who knew Tivo didn't interface well to VoIP?"

Viola Networks' Bear notes that, "while IP PBX vendors have done a great job building feature parity into IP PBXs, they aren't fully there yet. VoIP is functionally richer." Jorge Blanco, VP of strategic marketing for Avaya, expands that point. "Enterprise survivability can be better supported today by IP telephony than by traditional PBXs. VoIP implementations can give you a more survivable infrastructure for the distributed nature of today's businesses. If you had two locations supporting communications and B drops out, B would be lost. Under VoIP, B can remain running since it can reregister to location A."

Latency-related issues of course are a key VoIP issue. NetQoS CEO Joel Trammell says that "the number one killer of voice traffic is network latency and jitter. Latency, jitter, and packet loss causes poor audio quality and dropped calls. Latency caused by overloaded call managers or network congestion can be a major cause of poor VoIP performance." According to a VoIP network best practices list provided by Network Instruments, metrics to assess VoIP call quality include jitter, MOS, R-Factor, gap density, burst density, quality of service prioritization, and compression techniques. That list encourages you to consider whether you're mostly concerned about monitoring VoIP traffic locally, over WAN links, or both, and placing your analysis tools to ensure optimal visibility of VoIP communications. The list also suggests that "if jitter becomes a problem, look at the big picture. If there is a correlation between jitter and bandwidth usage, the problem is overall network usage. If there is not a direct correlation, then excessive jitter may require further investigation."

Are the promises of cost savings real?

Our experts offer varying thoughts about cost savings through VoIP. Some argue that cost savings are significant and reduced deployment expenses are resulting in mainstream VoIP deployment.

On the other hand, deployment savings may not be all they seem at first glance. Be sure to consider hardware, training, and other costs. Jeff Lewis, BellSouth's director of advanced voice services, says that the average costs of enterprise VoIP implementation are nearly $1,000 per user.

Two experts offer concluding sagely advice. Greg Brahier, VP of marketing at Virtual PBX, a hosted PBX firm, notes that "as businesses demand more services and federal regulations kick in, VoIP pricing won't be so attractive." And Sun Microsystems' VoIP lead Ronald Lott reminds us that, as with so many technologies, VoIP won't get cheaper, but better.

J.W. Olsen has been a full-time author, editor, and freelance book project manager with more than 1000 editorial credits for IT publishers since 1990, and has provided computer, Web site, and editorial services to other clients since 1985. He welcomes feedback via the e-mail response form at