Most enterprises need reliable connectivity between remote branches and the corporate Headquarters or data center. MPLS (Multi-Protocol label switching) is the Cadillac of private secure data connectivity and is found in most enterprise WAN (wide area network) environments. With the ever growing popularity of cloud based computing and the increasingly cheap bandwidth available most enterprises are consistently upgrading those MPLS networks to handle the increased demand.
Sometimes what happens however is one of those branch offices is located in a more remote region of the state and there are not a lot of tier 1 providers there making upgrades unreasonably expensive and difficult. Most metro areas now offer fiber and high speeds for very competitive rates but in remote areas that just isn't the case. However often times there is a provider that can offer high speed internet via cable, DSL etc. Normally those would not be ideal choices because they require customers to traverse a public network rather than a private one.
The solution for these instances can be SD WAN (software Defined wide area networking). SD WAN allows for multiple carrier circuits from any provider and allows you to manage the VPN in the cloud. None of the system brains exist at the branch level, they are moved to a controller in the cloud that IT can manage from anywhere.
SD WAN allows for multiple connecting types and load balances, prioritizes etc. between connection types to maintain solid connectivity and performance. It is also if desired reasonable to keep the lower bandwidth MPLS for the most critical traffic such as voice and send all other traffic across the broadband connection.
Lastly SD WAN also solves the need for disaster recovery. Two or more varying carrier connections and connection types (ie wireless, cable, etc) from redundant carriers call all be terminated in a single SD WAN box. That means if provider A gets cut or goes down then provider B still has connectivity and all traffic will re-route maintaining business integrity.
While I would never advocate for replacing all MPLS with SD WAN just to save money there are some great uses and benefits to SD WAN. Upgrading a remote office is a huge win for the corporate network using this new technology.