Where WANs Fall Short in Supporting VoIP and How SD-WAN Can Help

February 1st, 2019 by · Leave a Comment

This Industry Viewpoint was authored by Bruce Wirt, E.V.P, Chief Development Officer of Telesystem

If you travel frequently, you’ve probably relied more than once on the likes of Google Maps, Apple Maps and Waze. These tools provide unique utility, insofar as they can both predefine an optimal route for you and re-configure it as needed if you get lost or encounter previously unexpected conditions such as roadwork.

Traditional wide area networks (WANs) are a lot like pre-map apps navigation, i.e. writing down or printing out directions and stopping to ask for help on occasion. They are inflexible in the face of changing external conditions, plus they require a lot of legwork if any course correction is required.

That’s bad news for performance-sensitive applications such as hosted VoIP. Even slight fluctuations in packet loss, latency or jitter on a WAN path can degrade the experience of using modern real-time communications platforms. Their traffic can end up like vehicles stuck in a long line of cars that would have been avoidable with better route planning.

Why legacy WAN architectures fall short for today’s apps

A WAN is series of connections between sites, typically remote and branch offices along with data centers. It may utilize different modes of network transport, with highly reliable Multi Protocol Label Switching (MPLS) historically the most popular option.

However, these architectures are not optimized for cloud computing or for the responsiveness and security required by today’s apps. They struggle with:


Have you ever driven past your intended destination and needed to do some serious backtracking to reach it? That’s basically how many hub-and-spoke apps handle cloud-bound traffic (e.g., apps such as Office 365, Salesforce, VoIP and many others). It gets forwarded over WAN links and then again over the internet, for a double hop that sends it to the right place but at the cost of significant delay. This backhauling will negatively impact how end users perceive crucial cloud-connected services, including VoIP and unified communications systems.

Traffic prioritization

Mapping services are powerful in large part because they continuously look for the best available route in light of current traffic, closures, detours, etc. That way, you can often get to your destination as quickly as possible. Many WANs struggle to do the same for applications, since they don’t offer full visibility of network activity and can’t efficiently route traffic over the best available links in accordance with an organization’s specific policies. This shortcoming creates delays, sort of like a set of directions that always sends you down the same congested expressway.


Traditional WANs have some degree of Quality of Service (QoS), thanks to the presence of MPLS links that provide superior service guarantees to standard broadband. At the same time, this QoS comes only at a great expense. MPLS can cost hundreds of times more per Mbps per month than internet service. Plus, adding extra bandwidth and locations is complex and costly, meaning that a WAN can prevent an organization from reaching its full growth potential. Compared to the cloud and hosted services today’s companies routinely depend on, an old-fashioned MPLS-only WAN is a major outlier in terms of both its cost and flexibility.

SD-WAN: Smarter navigation for your applications

SD-WANs address all of these issues and more by implementing a software layer that dynamically and securely manages multiple link types. In addition to MPLS, it can incorporate broadband, 4G LTE, dedicated internet access and satellite connectivity, which together allow for a much more cost-effective, sustainable WAN.

On the performance side, it constantly monitors all paths across the network to determine the optimal route for current policy requirements. As a result, you can virtually eliminate outages and significant performance degradation affecting your most important software. Traffic can be seamlessly sent over alternative links without having to wrangle with complex backup infrastructure. For sensitive apps like hosted VoIP, SD-WAN is essential. It’s a natural fit for their particular requirements, while also being a prime way to trim your MPLS-related costs.

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Categories: Industry Viewpoint · SDN · VoIP

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