Optimization ensures high-quality VOIP

Communications News, March, 2008 by Stan Schreyer, Dale Tesch

One of the biggest challenges organizations face when implementing voice-over-IP (VoIP) systems is matching the high quality of service that employees are accustomed to from the traditional voice network. VoIP is an application that does not tolerate any disruptions or delays. When the application performs poorly, end-users experience crackling on the lines, delays in hearing a caller's voice and possibly dropped calls.

Two issues can cause VoIP to perform poorly-latency and network congestion. Latency is the inherent delay for voice traffic to travel long distances over the wide-area network (WAN). Network congestion occurs when a high volume of network traffic competes for a fixed amount of bandwidth. Network traffic spikes can wreak havoc with call quality because less bandwidth is available for VoIP calls.

WAN optimization technology can address both latency and network congestion. WAN optimization appliances can be used to get a clear picture of how network bandwidth is being used and how the network traffic patterns vary over time. The appliances can generate a variety of graphs to show top applications and URLs being accessed by network users, as well as top users of the network. Traffic spikes can be identified quickly based on the time of day, day of the week or month.

After identifying the top applications consuming bandwidth, the WAN optimization appliance can be used to control network traffic, including VoIP. A portion of network bandwidth can be reserved for VoIP calls. The appliance can also classify, compress and accelerate other applications (e.g., HTTP, FTP, CIFS) to free additional bandwidth for VoIP traffic.

Ideally, WAN optimization appliances should be installed at each location where VoIP will be implemented. This enables two-way prioritization of traffic between the data center and a branch office or between two branch offices.

Some customers prefer to work with a network integrator that specializes in WAN optimization. Network integrators can install an evaluation appliance, provide immediate feedback on network usage and recommend how much bandwidth to reserve for VoIP calls. They can also set all network policies to classify, prioritize and accelerate non-VoIP traffic.

Whether keeping the work in-house or using an integrator, look for a WAN optimization solution that is easy to install and use.

Some WAN optimization appliances come with a preconfigured default policy to begin optimizing and accelerating traffic on the network immediately. The default policy helps network administers bypass some preliminary configuration steps and can be modified to suit the changing needs of the business over time.

This feature allows the appliance to automatically discover other WAN optimization appliances in the network. This feature is important for accelerating applications between corporate locations, which helps free bandwidth for VoIP calls.

Peer-to-peer applications for downloading of videos and audio files can consume large amounts of bandwidth, negatively impacting VoIP call quality. Ideally, a WAN optimization solution should have the ability to limit or block this type of Internet traffic.

WAN optimization appliances do require some level of maintenance. Ongoing monitoring of VoIP performance is recommended. Monitoring the impact that adding more network users, applications and traffic may have on VoIP call quality also is important.

Network policies can be fine-tuned accordingly to ensure consistent high-quality VoIP calls. This may involve reserving a larger percentage of bandwidth for VoIP, reprioritizing network traffic or accelerating new applications.

WAN optimization technology plays a key role in ensuring high-quality VoIP. Optimization can also reduce overall network operating costs and ensure proper priofitization of all networktraffic. Furthermore, optimization helps companies take a proactive stance on capacity planning for VoIP systems and the underlying Internet communications links that support it.

Stan Schreyer is a vice president of Exinda Networks, Boston, and Dale Tesch is director of sales for Invercence Corp., Portsmouth, H.H.

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