Synchronizers are the components of CORD that map the abstract declarative state about how the system is suppose to behave (as defined by the XOS data model) into the concrete operational state of the backend components that implement the system (e.g., VNFs, micro-services, SDN control applications).
Writing a Synchronizer is half of the work required to on-board a service into CORD. First a model for the service is written as an xproto specification, and then you implement a synchronizer that translates that model onto some backend component.
To implement a Synchronizer, it is important to first understand the role they play in CORD and the assumptions made about their behavior. The next section describes a set of design guidelines and the following one presents the implementation details.