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Avoiding VoIP surprises with WAN emulation

How can you determine how well VoIP will perform on your production network? The answer could be WAN emulation.

Yigal Gafni

Surprises are fun on birthdays and other special occasions. But they're the last thing you want when you're deploying VoIP on your network.

Unfortunately, VoIP roll-outs are often full of surprises. That's because, despite vendor claims to the contrary, most networks aren't really ready to support VoIP. Some networks only require minor modification to deliver reliable, high-quality voice service. Others require more significant overhauls. But that's something you want to know before you start your roll-out -- not three-quarters of the way into it, when you've already burned most of your budget and your deadline is looming.

How can you determine how well VoIP will perform on your production network before you actually implement it on your production network? And how can you keep VoIP performance up to par even as your network changes? The answer is WAN emulation.

WAN emulation lets you capture and accurately duplicate your existing network infrastructure in a test lab setting. Every network characteristic that can impact voice quality (latency, jitter, packet loss, etc.) is faithfully reproduced in the test environment. It allows you to pinpoint and troubleshoot potential problems while they're still easily addressed, rather than after you've bought and installed expensive equipment all across your far-flung network.

WAN emulation also lets you ensure that changing conditions on your network don't threaten voice quality over time. VoIP can be affected by all kinds of changes: the introduction of new applications, increased traffic for existing ones, modifications in hardware configurations, etc. With WAN emulation, you can proactively assess the impact of these changes on VoIP performance by creating "what if" testing scenarios that replicate planned or potential changes in your network environment.

This kind of proactive testing isn't something you can do on your production network, unless, of course, you enjoy the sound of your end-users cursing vociferously after you've flooded your corporate WAN with artificial test traffic and crashed their critical systems!

Of course, it is possible to run certain types of rudimentary VoIP tests on the production network itself. However, this can get time-consuming and complicated. Test end-points have to be installed on remote PCs. Tests have to be run at various times throughout the week or month to ensure that VoIP service is evaluated under both average and peak loads. In some organizations, you may have to get approval from IT management staff to install testing software on desktop end-points at each location.

Performing tests in your production environment can also create security problems, because you have to change your firewall settings to support the application being tested -- and then remember to roll back your settings after the test is complete. So managing your tests can become almost as much of a project as your VoIP deployment itself.

With an emulated environment, none of these hassles raise their ugly heads. All testing takes place on an easily managed, conveniently located test environment. You don't have to worry about disrupting someone's work environment or negotiating with IT managers. Plus, as noted above, you can freely modify the testing environment to prepare for a full range of worst-case scenarios.

Better yet, you can repeatedly recreate those scenarios to see if any "fixes" you've made to the configuration of your VoIP equipment or overall VoIP architecture in fact yield improved results. This repetitive testing can become enormously expensive and time-consuming if you try to do it on your production network.

WAN emulation is obviously applicable to all kinds of applications. While VoIP is very sensitive to a variety of network conditions and attributes, all networked applications should really be tested before deployment on the WAN. This is especially true for overseas/offshore implementations, where WAN links may provide limited bandwidth and exhibit high latency. In other words, the more geographically dispersed your network is, the more essential WAN emulation becomes for all of your critical applications.

But WAN emulation has become particularly popular for VoIP. The International Telecommunications Union, for example, has embraced WAN emulation in their efforts to measure and optimize voice quality over IP data networks. So have top-tier service providers, hardware manufacturers and VoIP integrators. These organizations have determined that it's simply too risky to deploy VoIP without thorough emulation-based testing. If you're similarly averse to risk -- and if you're intent on ensuring the quality, stability and longevity of your VoIP implementation -- you'll want to adopt WAN emulation, too.


About the author:
Yigal Gafni is the Director of Customer Services for Shunra Software. He can be reached at Shunra is a leading provider of WAN emulation solutions that empower companies to build and maintain reliable, high-quality voice services and data applications over the network. More on Shunra can be found at


This was last published in April 2004

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