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The Pros and Cons of Over the Top SD-WAN

In 2019, the WAN connectivity debate isn’t raging as hard as it was just a few years earlier. There isn’t much of an argument when it comes to SD-WAN vs MPLS anymore. SD-WAN has proven itself and is entering the mass adoption stages while MPLS popularity has leveled off.

However, there isn’t just one single “SD-WAN” solution but rather a variety of SD-WAN offerings that take different approaches. Organizations looking to make a decision on an SD-WAN vendor need to be aware of the pros and cons of these different approaches, and how each can impact performance and cost.

At a high-level, there are two main flavors of SD-WAN: Over the Top (OTT) SD-WAN and SD-WAN bundled with underlying network infrastructure. In this piece, we’ll review the pros and cons of OTT SD-WAN and explore how SDWaaS (SD-WAN as a Service) helps address the downsides of OTT without sacrificing the upsides.

What is OTT SD-WAN?

Before we dive in, let’s define OTT SD-WAN. Simply put, OTT SD-WAN is a WAN overlay that uses third-party transport methods like MPLS, xDSL, or cable. There is no underlying network, no SLA from the SD-WAN provider – simply an overlay that enables SD-WAN functionality and the use of network services from different vendors.

The pros

The main upside of OTT SD-WAN is flexibility. Being able to select the ISP or network provider that makes the most sense for a given region is a major upside. It can also greatly reduce bandwidth costs when compared with MPLS. Generally speaking, public Internet bandwidth is significantly cheaper than MPLS bandwidth.

Additionally, OTT SD-WAN helps enterprises add redundancy and resilience to their WANs. Since there is no vendor-lock in, OTT SD-WAN users can leverage links from multiple ISPs to avoid single points of failure.

The cons

As OTT SD-WAN is simply a WAN overlay, there are some inherent downsides as well. One of the bigger downsides is: the public Internet isn’t reliable enough for enterprise WAN connectivity. This was one of the go-to arguments for MPLS proponents back when the MPLS vs SD-WAN argument was still going on. No SLA can be a deal-breaker for some enterprises. Additionally, when packets have to traverse long distances, latency create performance degradation to the point of making some services (videoconferencing for example) unusable.

The easy answer to this would be to couple MPLS with OTT SD-WAN, but that approach limits the upsides of going with SD-WAN in the first place. Some of the main reasons enterprises look to replace MPLS with SD-WAN are increased flexibility and reduced cost. Adding MPLS back to the equation decreases those benefits.

OTT SD-WAN has a few other downsides as well. Mobile users, which almost all enterprises must be able to accommodate, generally cannot be serviced by OOT SD-WAN solutions. Further, even integrations with cloud service providers can be a challenge. If enterprises want to connect directly to cloud service providers, a discrete appliance is needed for each business-critical service. Not only does this increase cost (deploying an appliance at a remote datacenter isn’t cheap), it increases network complexity and makes scalability a challenge.

How SDWaaS helps address the downsides of OTT SD-WAN

While the downsides of OTT SD-WAN create real challenges for enterprises, going back to MPLS isn’t the answer. The flexibility, particularly in the last-mile, of OTT SD-WAN is important and MPLS has drawbacks of its own that make it inefficient for modern enterprises. This is where SDWaaS comes in.

SDWaaS offers all the flexibility and functionality of OTT SD-WAN, while also addressing the cons of OTT SD-WAN. This is possible because SDWaaS includes a robust underlying network and is capable of efficiently integrating mobile users and cloud services at scale.

SDWaaS gives enterprises access to an SLA-backed global private backbone. This backbone is supported by PoPs (Points of Presence) all over the world. This global backbone resolves the SLA issue enterprises struggle with when dealing with OOT SD-WAN, and, along with cloud-native software, helps ensure enterprise-grade network performance. For example, SDWaaS includes features like Packet Loss Compensation to help boost last mile performance, is able to minimize middle mile performance using its own private backbone, and offers functionality like Dynamic Path Selection to ensure optimized routing of packets in real time.

Since many of the PoPs are in or near the same data centers as major cloud service providers, SDWaaS providers are able to provide integrations at scale without the need for enterprises to deploy costly appliances. This means low-latency connectivity to providers like AWS and Azure is possible without any additional hardware.

Finally, mobile clients and the cloud-native nature of SDWaaS make mobile integrations simple and secure. While mobile with OTT SD-WAN was generally out of reach, with SDWaaS enterprises can support mobile users (even BYOD users) easily while implementing the same level of auditing and security they do for on-premises employees.

SDWaaS provides enterprises with a complete WAN connectivity solution

OTT SD-WAN has a number of benefits and does a great job at providing flexibility and redundancy when it comes to network providers. However, on its own OTT SD-WAN is an incomplete solution. To meet all the challenges of a modern WAN, OTT SD-WAN must be supplemented by a variety of additional appliances and services, driving up cost and complexity and creating a less than ideal WAN architecture.

SDWaaS fills the gaps OTT SD-WAN fails to address, such as providing an SLA, integration with cloud services, and support for mobile users, while still delivering flexibility and redundancy that enterprises demand.

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