SD-WANs lost my voice | Network World

If there’s one application that brings chills to the hearts of SD-WAN implementers it’s providing a predictable real-time voice service. So let’s talk about how SD-WANs might help.

The problem with voice

We need to separate from the theory of voice and the reality of voice. The theory goes something like this. The Internet is fine for email and web browsing. It’s even pretty good for personal voice. But if I want to deliver a voice service, day-in-day out without a hiccup, then I run into a problem. Voice is a real-time protocol with strict tolerances around latency, loss and jitter. Exceed those tolerances and symptoms common to a poor voice service set in. Increased delays from traffic routing or lost packets disrupt voice calls. Outages and brownouts can cause calls to drop.

With a story like that the only answer would seem to be MPLS or some other SLA-backed backbone from companies such as Aryaka or Cato Networks. The reality of voice is more complex. It’s not that you can’t run voice over the public Internet, services like Skype proved that’s possible, it’s just more challenging with business-class voice. Some Internet routes are in fact very predictable, particularly within North America. At the same time, MPLS availability is high, but not necessarily for the local loops where there is usually only one active connection per office.

How SD-WANs help

SD-WANs use a number of techniques to improve voice. Application-based routing allows SD-WANs to steer voice traffic across the optimum path. Alone this is a big improvement over the general Internet. By running two active connections, SD-WANs can switch active calls to the secondary connection fast enough to preserve the call.

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