Software-defined WAN caveats Perhaps the greatest challenge when evaluating SD-WAN technologies is the ROI calculation. The capex and opex of the SD-WAN solution will need to be compared to the overall cost of the WAN itself. The idea is that a hybrid WAN that makes heavier use of cheap broadband should allow for smaller private links; some offices might not require private links at all.

As a result, this ROI calculation could reveal that an SD-WAN purchase will pay for itself or even save money. The catch in downsizing or eliminating private circuits is that most carriers lock their enterprise customers in with a multi-year contract. Thus, penalties for early termination or service-level changes could further impact ROI.

Another consideration when evaluating SD-WAN technology is that of vendor lock-in. There are several SD-WAN products, and they are all different and incompatible. Some layer on to a WAN; some replace WAN hardware with their own. An evaluation process should carefully consider the long-term commitment to the vendor.

Closely tied to this is the notion that an SD-WAN solution must be integrated into an organization’s WAN. If the product requires hardware replacement, has that hardware already been depreciated? This could be a hidden cost that needs to be considered, beyond the practical operational costs of implementing a new IT solution.