White-boxes usually work with a simplified operating system (usually Linux-based), which provides basic interfaces between hardware and SDN controller (or other management system). Network protocols (BGP, IP/MPLS stack, etc.) and other intelligence traditionally embedded in routers are implemented as applications on top of the controllers. The main barrier to adopt white-boxes in transport network is that these applications mainly come from less-known innovative vendors, which are not often invited in tenders. Limited number and functionality of these applications is also a barrier, but as industry develops more of them appear and mature.
Traditional protocols like, for example BGP and RSVP, implemented in SDN applications, might decide how to manage traffic, but it does not imply that BGP or RSVP related commands are forced to the device level. Traffic management decisions might be translated into other protocol’s logic, for example OpenFlow-based rules, by SDN controller or another application. This is the approach making the transition much smoother.