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SD-WAN technology: A primer for what you need to know

Software-defined WAN is poised to take the wide area network by storm, simplifying operations and reducing costs. Here's what you should know about the new SDN-based approach.

Today's traditional corporate WAN is a rigid and complex space, with private lines offering dedicated bandwidth,...

but at a high cost from both a Capex and Opex perspective. Viable alternative WAN landscapes have emerged, however, growing from the SDN trend in the data center. Software-defined WAN, or SD-WAN, can change the way enterprise networks connect to each other by reducing the cost and complexity involved.

The basics of SD-WAN technology

Specific software-defined WAN products and services vary. Speaking in general terms, however, SD-WAN technology consists of two main components: the control plane and the data plane. The control plane refers to the controller, normally a software component that runs on a cloud-based or locally based machine. The controller manages all device profiles and configurations, and offers a single-pane-of-glass view of the WAN and its devices. The data plane consists of all the WAN edge devices deployed to the sites that handle traffic.

Traditional and hybrid WANs

Now, think about your current WAN setup. Are you using a commercial broadband connection for your Internet connectivity? Broadband is not as feature-rich as an MPLS cloud, but you get a lot more bang for your buck when it comes to bandwidth. High-definition video streaming and audio calls -- nearly unimaginable just a few years ago -- are now the new normal in homes around the world.

The resulting increased demand for bandwidth has prompted a new trend: Many companies today want to take advantage of a broadband connection for Internet connectivity, as well as multiprotocol label switching (MPLS) or a private line connection for mission-critical applications or intra-company traffic. The downside of this kind of hybrid WAN approach, when it is not software-defined: The configuration is complex and sometimes time-consuming to maintain, as application trends change and usage fluctuates. Components like Cisco's Performance Routing (PfR), quality of service and dynamic multipoint VPN just add to the myriad levels of complexity.

With SD-WAN technology you can expect to reduce complexity, because the software does virtually all of the work for you.

Other models that companies use for WAN connectivity include expensive backup circuits that just sit there eating money until they're needed. In some cases there's even a third LTE backup for worst-case scenarios. What if, instead, you could make use of the circuits you're already paying for?

Another problem is the issue of provisioning these edge devices once they arrive on-site. Most companies have to not only ship equipment to sites but also either hire knowledge contractors or send employees to perform installations. Wouldn't it be nice to have a device that you could just plug into the network, and that's it?

How SD-WAN technology is different

SD-WAN has the power to change the landscape and cut the time required for the upkeep of these multifarious network challenges. SD-WAN devices automate the configuration, monitoring and maintenance of the WAN.

With SD-WAN technology you can expect to reduce complexity, because the software does virtually all of the work for you. A software-defined, hybrid WAN constantly monitors all connections and chooses the best path available for the type of traffic crossing the network. Again, you could devise a similar scheme with a hybrid WAN on normal network routers, but that setup does not provide an effective way to measure things like jitter, congestion or packet loss without using tools like Cisco's IP SLA (Internet protocol service-level agreement) or PfR. Even using such tools, the WAN requires constant management on the part of the engineer to keep these things up to date. SD-WAN, in contrast, does all the work necessary on the back end and you just feed the metrics into the system.

SD-WAN can also reduce the cost associated with access, by relying more heavily on broadband connectivity than on expensive, private MPLS lines. Some companies have even shunned private lines altogether. That's not entirely advisable, however, as broadband providers typically don't guarantee uptime or quality.

In short, depending on the depreciation of your equipment, vendor contracts and particular SD-WAN product requirements, you can normally expect a fairly good ROI on switching to SD-WAN.

Zero-touch provisioning is another big plus when it comes to SD-WAN technology. In most cases, you only need someone on-site to plug in the edge device, which then pulls down all the configurations necessary to get you up and running. This reduces the need to send engineers out to branch locations, thus saving more money in the process. Security is also addressed, as the overlays created by the devices themselves encrypt traffic so it can pass safely over any connection.

Implementing SD-WAN technology also provides you with a flexible network. It reacts to different network conditions and shunts traffic or makes tweaks as needed, all with little to no intervention on the part of the engineer. It's astounding how much time engineers can save using this technology, which in turn frees them up for other tasks.

Getting started: The basics

Currently, there are quite a few players in the SD-WAN field, and more seem to pop up all the time. Several to consider: Cisco IWAN, Silver Peak, VeloCloud and Viptela. All have slightly different requirements when it comes to infrastructure and access, and sadly none are interoperable -- so an SD-WAN product or service needs to remain consistent across the wide area network. Before you jump in with both feet, make sure to do a good test deployment so you can get a true handle on challenges you may find in the switchover.

Next Steps

Is software-defined WAN right for you?

Providers begin to offer managed SD-WAN services

Are hybrid, virtual and software-defined WAN all the same?

This was last published in February 2016

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