Friday, May 05, 2006

VoIP Quality of Service

So how do you keep from getting dropped VoIP calls in a buisness place where there is demand for bandwidth for email, large data transfers and VoIP calls. By protecting your VoIP bandwidth with QoS (Quality of Service) Mae Kowalke, of TMCnet explains in a recent article:

You may know that Quality of Service, or QoS, is an important part of keeping your networking running smoothly. But do you know what types of applications benefit most from QoS?

In a recent application note, Kentrox provides an answer to that very question: “QoS becomes necessary when Voice over IP (VoIP) capable phones are to be added to what is currently a data only network infrastructure.”

Sounds simple enough. Here’s why that’s true.

Without VoIP, networks are used to send data using IP packets. Some networks now support server-based infrastructures that require access to the Internet.

Supporting e-mail, Internet access, file transfers, server backups, streaming video, video conferencing, and other applications takes quite a bit of bandwidth.

So, what happens when VoIP is added to the mix?

Kentrox’s answer: “A few data packets carrying a voice conversation will probably be lost among those large data applications running on a network originally designed for data. The end result is a scrambled or difficult to hear conversation.”

The human ear is a very sensitive instrument, and will quickly pick up on the loss of quality.

Luckily, there’s a way to prevent that quality loss. And it’s called, you guess it, Quality of Service.

In the application note, Kentrox explains that modern networks are designed to handle both voice and data traffic. “These networks also have the ability to prioritize traffic streams based on QoS parameters.”

Now we’re getting down to the nitty-gritty of how Quality of Service works. In a nutshell, it’s all about prioritization.

“QoS is a set of algorithms or policies that are created by a network administrator to assign different levels of quality (or priority) to different types of network traffic,” Kentrox explains.

Anything that interferes with the timely delivery of voice or video packets can cause problematic losses in quality. A QoS policy marks these packets as high priority, allowing them to be delivered prior to unmarked data traffic.

This concept is illustrated in Figures 1 and 2 below.

There’s more to Quality of Service than that, of course, but it’s all you need to know. Kentrox’s Quality of Service products, like the Q1300 QoS Appliance, make it easy to ensure high-quality VoIP on your network.

To learn more, visit


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