SD-WAN is an overlay to the existing network – essentially a network running on top of a network. This is accomplished by using tunneling technology to differentiate the physical network from the logical network.

SD-WAN implements a centralized controller, acting as a single pane of glass for managing the entire solution. It is used to set and maintain policy. This policy is used to control traffic paths, SLAs, failover, monitoring, etc. The SLAs are written based on application-specific information. Once policies are defined, they are pushed from that centralized controller to each SD-WAN node for more "hands-off" configuration.

Know more @ advantages of SDN

Once the policy is pushed, it intelligently monitors the performance on a link, migrating traffic based on that particular SLA. At this point, we are no longer dependent on a circuit outage to swing traffic to a backup or redundant link.

Where do we go from here?
SD-WAN brings new agility and speed of provisioning to the WAN, while driving down the total cost of the WAN solution. As new technologies emerge, the capabilities and definitions around SD-WAN solutions will shift over time. At minimum, you should be aware of SD-WAN’s potential to positively impact you business needs. And if these benefits resonate with your current goals, consider starting with a SD-WAN proof-of-concept to evaluate the technology’s value to your organization. 
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