A software-defined wide area network, or SD-WAN, is a virtualized service that connects and extends enterprise networks over large geographical distances. WANs use links such as multiprotocol label switching (MPLS), wireless, broadband, virtual private networks (VPNs) and the Internet to give users in remote offices access to corporate applications, services and resources, allowing them to carry out daily functions regardless of location. SD-WAN monitors the performance of WAN connections and manages traffic in an effort to maintain strong speeds as well as optimize connectivity.