Network Physics Delivers Insight on VoIP Performance

Since 1999, Mountain View, Calif.-based Network Physics has been attending to the needs of IT managers—from mid-size to very large enterprises—to understand what in the world is going on in their networks, from a performance point of view.

To that end, the company has developed the NetSensory family of hardware/software appliances that sit on the network and gather traffic data in real time. The NetSensory applicance tracks more than 60 performance metrics, and, by means of a variety of correlations and analytic models, turns the data into a bewildering array of performance analysis tools. Network Physics has packaged these tools into a group of specialized software modules it calls Solution Insights that address particular management needs, such as auditing, optimizing, troubleshooting, etc.

This week the company introduced a new Insights package aimed at voice over IP, and called, appropriately, NetSensory Solution Insight for VoIP.

In a sense, voice is just another application on the IP network. However, in another, obvious, sense, it’s not like other applications on the network. As Network Physics vice president of marketing, Scott Safe, put it to, “Because of the sensitivity of the VoIP application to extreme network conditions, anything that changes in the slightest context—things like latency, packet loss, jitter, etc.—degrades voice. Voice is a binary application: it’s either on or it’s off—not like email, where if it’s delayed a couple of minutes, it’s not a problem; with voice it’s a problem,” he pointed out.

And while there are a number of IP network management products available that address traditional applications, and a number of voice over IP management packages that only look at the voice piece, Network Physics believes that its Solution Insight for VoIP is the first tool available that looks at the total network application picture, with special tools for assessing VoIP performance.

“The unique value that we’re bringing is a real-time view of integrated performance management of both VoIP and data applications,” Safe asserted. “It’s the first app on the market that will do this in real time—managing all the calls on the network, giving an accurate picture of call setup and the actual call itself, plus the ability to understand the data traffic on that same network—and give you that unified view.”

Furthermore, most performance management systems focused on voice require instrumentation on both ends of a call. Insight for VoIP, by contrast, uses a “single arm” deployment model. The appliance gathers traffic data by means of a SPAN ]Switched Port Analyzer Tap [Test Access Port] directly off the net.

“We look at all the traffic—real traffic, not synthetic—not reports from routers or call managers,” Safe said. “With our “single arm” deployment, we can sit near the data center side and derive the same kinds of voice statistics that network managers are used to. MOS scores, jitter, R-factors, etc.”

In terms of VoIP data monitoring, the system can track the signaling exchanged involved in setting up a call, and “once that call setup is done, channels are allocated for the actual conversation and that’s where we get into inspecting the actual RTP packets going across the network,” Safe explained. One result is that when trouble arises, there is a clear, detailed picture of what was going on—both on the voice call or calls and with regard to other applications on the network.

Safe illustrated with an anecdote about a problem that had been isolated and fixed in one of their early installations: It seems that one group was experiencing VoIP degradation at about the same time every day. “We went in and looked at what was going on on the network at that particular time. Because we discover all the other applications, we noticed that a particular FTP job—a backup job—was kicked off at this time every day. It took up a significant portion of the bandwidth available to that network. Because of that, voice over IP suffered. You began to see a delay in the actual packets being transmitted across the network, and that resulted in the calls having jitter.”

This required that both voice and data traffic were being monitored from a management point of view, which, again, Network Physics considers to be its unique contribution.

“You have the luxury of concentrating on voice alone,” Scott Safe pointed out to “The poor network managers out there don’t have that luxury.”

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