While evaluating SD WAN solutions currently available in different forms from several vendors, please realize that all are proprietary. Whichever vendor you choose will supply products that are incompatible and may not even be completely interoperable with another vendor’s offerings. So, once you choose one, you are committed to it, and any idiosyncrasies or limitations it presents.
Some solutions require you to replace your WAN hardware with units they supply. Therefore, it is very important to know the vendor’s repair and replacement policy. Other packages only layer software on top of your existing WAN. Depreciation of hardware replacements could add unnoticed costs, above and beyond any costs associated with setting up a new IT solution.
On the funding side of things, calculating an accurate ROI for SD WAN changes can be a challenge. When working as designed, SD WANs make much more use of cheaper broadband connections, enabling reducing private link usage, in some situations to zero. These savings may not be real, if your carrier has you locked-in with a multi-year contract on your private networking resources. There may be penalties from the carrier you must pay if you terminate their service.